Cathode materials,nickel doped Cr_(8)O_(21),were synthesized by a solid-state method.The effects of Ni doping on the electrochemical performances of Cr_(8)O_(21) were investigated.The experimental results show that th...Cathode materials,nickel doped Cr_(8)O_(21),were synthesized by a solid-state method.The effects of Ni doping on the electrochemical performances of Cr_(8)O_(21) were investigated.The experimental results show that the discharge capacities of the samples depend on the nickel contents,which increases firstly and then decreases with increasing Ni contents.Optimized Ni_(0.5)Cr_(7.5)O_(21)delivers a first capacity up to 392.6 m Ah·g^(-1)at 0.1C.In addition,Ni doped sample also demonstrates enhanced cycling stability and rate capability compared with that of the bare Cr_(8)O_(21).At 1 C,an initial discharge capacity of 348.7 m Ah·g^(-1)was achieved for Ni_(0.5)Cr_(7.5)O_(21),much higher than 271.4 m Ah·g^(-1)of the un-doped sample,with an increase of more than 28%.Electrochemical impedance spectroscopy results confirm that Ni doping reduces the growth of interface resistance and charge transfer resistance,which is conducive to the electrochemical kinetic behaviors during charge-discharge.展开更多
To solve the critical problems of lithium rich cathode materials, e.g., structure instability and short cycle life, we have successfully prepared a ZrO2-coated and Zr-doping xLi2MnO3·(1–x)LiMO2 hollow architectu...To solve the critical problems of lithium rich cathode materials, e.g., structure instability and short cycle life, we have successfully prepared a ZrO2-coated and Zr-doping xLi2MnO3·(1–x)LiMO2 hollow architecture via one-time sintering process. The modified structural materials as lithium-ion cathodes present good structural stability and superior cycle performance in LIBs. The discharge capacity of the ZrO2-coated and Zr-doped hollow pristine is 220 mAh g-1 at the 20th cycle at 0.2 C(discharge capacity loss, 2.7%)and 150 m Ah g-1 at the 100 th cycle at 1 C(discharge capacity loss, 17.7%), respectively. However, hollow pristine electrode only delivers 203 m Ah g-1 at the 20 th cycle at 0.2 C and 124 mAh g-1 at the 100 th cycle at 1 C, respectively, and the corresponding to capacity retention is 92.2% and 72.8%, respectively.Diffusion coefficients of modified hollow pristine electrode are much higher than that of hollow pristine electrode after 100 cycles(approach to 1.4 times). In addition, we simulate the adsorption reaction of HF on the surface of ZrO2-coated layer by the first-principles theory. The calculations prove that the adsorption energy of HF on the surface of ZrO2-coated layer is about-1.699 e V, and the ZrO2-coated layer could protect the hollow spherical xLi2MnO3·(1–x)LiMO2 from erosion by HF. Our results would be applicable for systematic amelioration of high-performance lithium rich material for anode with the respect of practical application.展开更多
Boron doped diamond(BDD)performs well in electrochemical oxidation for organic pollutants thanks to its wide electrochemical window and superior chemical stability.We presented a method to obtain well-adherent large-s...Boron doped diamond(BDD)performs well in electrochemical oxidation for organic pollutants thanks to its wide electrochemical window and superior chemical stability.We presented a method to obtain well-adherent large-scale BDD/Nb electrode by the modified hot filament chemical vapor deposition system(HFCVD).SiC particles were sand blasted to enhance the adhesion of BDD coating.The BDD coating was then deposited on both sides of Nb which was placed vertically and closely with filament grids on both sides.The BDD/Nb electrodes had no deformation because the thermal deformations of the BDD films on both sides of the Nb substrate conteracted each other during cooling process after deposition.The surface morphology and purity of the BDD/Nb electrode were analyzed by Raman and scanning elestron microscope(SEM)techniques.Scratch test was used to investigate the adhesion of BDD films.The electrochemical performances were measured by cyclic voltammetry test.The BDD electrode at the B/C ratio of 2 000×10^(-6) held a higher oxygen evolution potential thanks to its high sp3 carbon content.Accelerated life test illustrated that the sandblasting pretreatment obviously enhanced the adhesion of BDD coating which resulted in a longer service duration than the un-sandblasted one.展开更多
The element Ni in the Mg2Ni alloy is partially substituted by M(M = Cu, Co, Mn) in order to ameliorate the electrochemical hydrogen storage performances of Mg2Ni-type electrode alloys. The nanocrystalline and amorph...The element Ni in the Mg2Ni alloy is partially substituted by M(M = Cu, Co, Mn) in order to ameliorate the electrochemical hydrogen storage performances of Mg2Ni-type electrode alloys. The nanocrystalline and amorphous Mg20Ni10-xMx(M = None, Cu, Co, Mn; x = 0-4) alloys were prepared by melt spinning. The effects of the M(M = Cu, Co, Mn) content on the structures and electrochemical hydrogen storage characteristics of the as-cast and spun alloys were comparatively studied. The analyses by XRD, SEM and HRTEM reveal that all the as-cast alloys have a major phase of Mg2Ni but the M(M = Co, Mn) substitution brings on the formation of some secondary phases, MgCo2 and Mg for the(M = Co) alloy, and Mn Ni and Mg for the(M = Mn) alloy. Besides, the as-spun(M = None, Cu) alloys display an entirely nanocrystalline structure, whereas the as-spun(M = Co, Mn) alloys hold a nanocrystalline/amorphous structure, suggesting that the substitution of M(M = Co, Mn) for Ni facilitates the glass formation in the Mg2Ni-type alloys. The electrochemical measurements indicate that the variation of M(M = Cu, Co, Mn) content engenders an obvious effect on the electrochemical performances of the as-cast and spun alloys. To be specific, the cyclic stabilities of the alloys augment monotonously with increasing M(M = Cu, Co, Mn) content, and the capacity retaining rate(S20) is in an order of(M = Cu) 〉(M = Co) 〉(M = Mn) 〉(M = None) for x≤1 but changes to(M = Co) 〉(M = Mn) 〉(M = Cu) 〉(M = None) for x≥2. The discharge capacities of the as-cast and spun alloys always grow with the rising of M(M = Co, Mn) content but first mount up and then go down with increasing M(M = Cu) content. Whatever the M content is, the discharge capacities are in sequence:(M = Co) 〉(M = Mn) 〉(M = Cu) 〉(M = None). The high rate discharge abilities(HRDs) of all the alloys grow clearly with rising M(M = Cu, Co) content except for(M = Mn) alloy, whose HRD has a maximum value with varying M(M = Mn) content. Furthermore, for the as-cast alloys, the HRD is in order of(M = Co) 〉(M = Mn) 〉(M = Cu) 〉(M = None), while for the as-spun(20 m·s^-1) alloys, it changes from(M = Co) 〉(M = Mn) 〉(M = Cu) 〉(M = None) for x = 1 to(M = Cu) 〉(M = Co) 〉(M = None) 〉(M = Mn) for x = 4.展开更多
The La-Mg-Ni-based A2B7-type Lao.8_xNdx Mgo.2Ni3.35Alo.lSio.o5 (x = 0, 0.1, 0.2, 0.3, and 0.4) electrode alloys were prepared by casting and annealing. The influence of the partial substitution of Nd for La on the s...The La-Mg-Ni-based A2B7-type Lao.8_xNdx Mgo.2Ni3.35Alo.lSio.o5 (x = 0, 0.1, 0.2, 0.3, and 0.4) electrode alloys were prepared by casting and annealing. The influence of the partial substitution of Nd for La on the structure and electrochemical performances of the alloys was investigated. The structural analysis of X-ray diffraction and scanning electron microscopy reveals that the experimental alloys consist of two major phases: (La,Mg)2Ni7 with the hexagonal Ce2Ni7-type structure and LaNi5 with the hexagonal CaCus-type structure as well as some residual phases of LaNi3 and NdNis. The electrochemical measurements indicate that an evident change of the electrochemical performance of the alloys is associated with the substitution of Nd for La. The discharge capacity of the alloy first increases then decreases with the growing Nd content, whereas their cycle stability clearly grows all the time. Furthermore, the measurements of the high rate discharge ability, the limiting current density, and hydrogen diffusion coefficient all demonstrate that the electrochemical kinetic properties of the alloy electrodes first augment then decline with the rising amount of Nd substitution.展开更多
The La-Mg-Ni-system (PuNi3-type) La2Mg (Ni0.85 Co0.15 )9M0.1 ( M = B, Cr) hydrogen storage etectrode alloys were prepared by casting and rapid quenching. The electrochemical performances and microstructures of t...The La-Mg-Ni-system (PuNi3-type) La2Mg (Ni0.85 Co0.15 )9M0.1 ( M = B, Cr) hydrogen storage etectrode alloys were prepared by casting and rapid quenching. The electrochemical performances and microstructures of the as-cast and quenched alloys were determined and measured. The effects of rapid quenching on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the alloys are composed of the (La, Mg) Ni3 phase (PuNi3-type structure) and the LaNi5 phase, as well as the small amount of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloy containing boron, and the Ni2B phase in the alloy nearly disappears after rapid quenching. The relative amount of each phase in the alloys depends on the quenching rate. The rapid quenching technique can greatly improve the electrochemical performance of the alloy, and the effect of rapid quenching on the activation performances of the alloys is minor. Rapid quenching enhances the cycle stability of the alloy, and the cycle life of the alloy increases with the increase of the quenching rate.展开更多
The La-Mg-Ni-Mn-based AB_2-type La_(1-x)Ce_xMgNi_(3.5)Mn_(0.5)(x = 0, 0.1, 0.2, 0.3, and 0.4) alloys were fabricated by melt spinning technology. The effects of Ce content on the structures and electrochemical...The La-Mg-Ni-Mn-based AB_2-type La_(1-x)Ce_xMgNi_(3.5)Mn_(0.5)(x = 0, 0.1, 0.2, 0.3, and 0.4) alloys were fabricated by melt spinning technology. The effects of Ce content on the structures and electrochemical hydrogen storage performances of the alloys were studied systematically. The XRD and SEM analyses proved that the experimental alloys consist of a major phase LaMgNi_4 and a secondary phase LaNi_5. The variation of Ce content causes an obvious change in the phase abundance of the alloys without changing the phase composition. Namely, with the increase of Ce content, the LaMgNi_4 phase augments and the LaNi_5 phase declines. The lattice constants and cell volumes of the alloys clearly shrink with increasing Ce content. Moreover, the Ce substitution for La results in the grains of the alloys clearly refined. The electrochemical tests showed that the substitution of Ce for La obviously improves the cycle stability of the as-spun alloys. The analyses on the capacity degradation mechanism demonstrate that the improvement can be attributed to the ameliorated anti-corrosion and antioxidation ability originating from substituting partial La with Ce. The as-spun alloys exhibit excellent activation capability, reaching the maximum discharge capacities just at the first cycling without any activation treatment. The substitution of Ce for La evidently improves the discharge potential characteristics of the as-spun alloys. The discharge capacity of the alloys first increases and then decreases with growing Ce content. Furthermore, a similar trend also exists in the electrochemical kinetics of the alloys, including the high rate discharge ability(HRD), hydrogen diffusion coefficient(D), limiting current density(IL) and charge transfer rate.展开更多
The La-Mg-Ni system A2B7-type electrode alloys with nominal composition La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1(x=0,0.05, 0.1,0.15,0.2)were prepared by casting and melt-spinning.The influences of melt spinning on the electro...The La-Mg-Ni system A2B7-type electrode alloys with nominal composition La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1(x=0,0.05, 0.1,0.15,0.2)were prepared by casting and melt-spinning.The influences of melt spinning on the electrochemical performances as well as the structures of the alloys were investigated.The results obtained by XRD,SEM and TEM show that the as-cast and spun alloys have a multiphase structure,consisting of two main phases(La,Mg)Ni3 and LaNi5 as well as a residual phase LaNi2.The melt spinning leads to an obvious increase of the LaNi5 phase and a decrease of the(La,Mg)Ni3 phase in the alloys.The results of the electrochemical measurement indicate that the discharge capacity of the alloys(x≤0.1)first increases and then decreases with the increase of spinning rate,whereas for x>0.1,the discharge capacity of the alloys monotonously falls.The melt spinning slightly impairs the activation capability of the alloys,but it significantly enhances the cycle stability of the alloys.展开更多
A new self-made additive of amidocyanogen-acetic salt was used in wet ball-grind technique (WBGT) for preparing hydrogen storage alloys, and the effect on the electrochemical performance of the alloy electrode was i...A new self-made additive of amidocyanogen-acetic salt was used in wet ball-grind technique (WBGT) for preparing hydrogen storage alloys, and the effect on the electrochemical performance of the alloy electrode was investigated in detail. It was found that the prepared electrode had perfect electrochemical performances, such as rapid activation, high capability, high-rate discharge (HRD) ability, and good stability. The first discharge capacitance at 0.2 C (throughout this study, n C rate means that the rated capacity of a hydrogen storage alloy (full capacity) is charged or discharged completely in 1/n h) reached 278 mAh·g^-1 and the discharge capacitance reached the maximum of 322 mAh·g^-1 only after two charge-discharge cycles. For the dry method, wet method, and WBGT, the high rate discharge (HRD) values (C5 c/C0.2c ratio) were approximately 0.59, 0.76, and 0.83, respectively. The stable discharge capacity at 3 C increased from 275 mAh·g^-1 (dry method)to 295 mAh·g^-1 (WBGT).展开更多
In view of the higher temperature of large-size NilMH battery in electric vehicle, the effect of temperature on electrochemical performances of hydrogen storage alloy Ml ( NiCoMnTi )5 was investigated systematically...In view of the higher temperature of large-size NilMH battery in electric vehicle, the effect of temperature on electrochemical performances of hydrogen storage alloy Ml ( NiCoMnTi )5 was investigated systematically. The results show that the electrochemical performances of alloy vary drastically with temperature changing. As temperature rises, the hydrogen equilibrium pressure increases, the width of hydrogen desorption plateau decreases and the gradient increases, leading to a decline of capacity. When temperature rises from 20 ℃ to 80 ℃ , the discharge capacity of the alloy decreases from 309.11 mA· h· g^-1 to 227.64 mA· h· g^-1 , but the high rate dischargeability is improved markedly. Higher temperatures also bring about a significant decrease in the cycling stability and self-discharge property. X-ray diffraction analysis indicates that the alloy has a single phase with CaCu5-type LaNi5 structure.展开更多
The high compacted density LiNi<sub>0.5-x</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub>Mg<sub>x</sub>O<sub>2</sub> cathode material for lithium-ion batteries was syn...The high compacted density LiNi<sub>0.5-x</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub>Mg<sub>x</sub>O<sub>2</sub> cathode material for lithium-ion batteries was synthesized by high temperature solid-state method, taking the Mg element as a doping element and the spherical Ni<sub>0.5</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub> (OH)<sub>2</sub>, Li<sub>2</sub>CO<sub>3</sub> as raw materials. The effects of calcination temperature on the structure and properties of the products were investigated. The structure and morphology of cathode materials powder were analyzed by X-ray diffraction spectroscopy (XRD) and scanning electronmicroscopy (SEM). The electrochemical properties of the cathode materials were studied by charge-discharge test and cyclic properties test. The results show that LiNi<sub>0.4985</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub> Mg<sub>0.0015</sub>O<sub>2</sub> cathode material prepared at calcination temperature 930°C has a good layered structure, and the compacted density of the electrode sheet is above 3.68 g/cm<sup>3</sup>. The discharge capacity retention rate is more than 97.5% after 100 cycles at a charge-discharge rate of 1C, displaying a good cyclic performance.展开更多
The casting and annealing technologies were applied to fabricate the La0.8Mg0.2Ni3.3Co0.2Six (x = 0-0.2) electrode alloys. The effects of Si content and annealing temperature on the structure and electrochemical per...The casting and annealing technologies were applied to fabricate the La0.8Mg0.2Ni3.3Co0.2Six (x = 0-0.2) electrode alloys. The effects of Si content and annealing temperature on the structure and electrochemical performances of the alloys were investigated systematically. The analyses of XRD and SEM show that all the alloys possess a multiphase structure, involving two main phases (La, Mg)2Ni7 and LaNi5 as well as a residual phase LaNi3. The addition of Si brings on an evident increase in the LaNi5 phase and a decrease in the (La, Mg)2Ni7 phase, without altering the main phase component of the alloy, which also makes the lattice constants and cell volumes of the alloy enlarged. Likewise, the annealing treatment engenders the same action on the lattice constants and cell volumes as adding Si. Simultaneously, it gives rise to the variation of the phase abundance and the coarsening of the alloy grains. The electrochemical measurements indicate that the addition of Si ameliorates the cycle stability of the as-cast and annealed alloys significantly, but impairs their discharge capacities clearly. Similarly, the annealing treatment makes a positive contribution to the cycle stability of the alloy evidently, and the discharge capacity of the alloy shows a maximum value with annealing temperature rising. Furthermore, the high rate discharge ability (HR) first augments and then declines with the rising of Si content and annealing temperature.展开更多
Lithium ion batteries using Ni-Co-Mn ternary oxide materials(NCMs)and Ni-Co-Al materials(NCAs)as the cathode materials are dominantly employed to power the electric vehicles(EVs).Increasing the driving range of EVs ne...Lithium ion batteries using Ni-Co-Mn ternary oxide materials(NCMs)and Ni-Co-Al materials(NCAs)as the cathode materials are dominantly employed to power the electric vehicles(EVs).Increasing the driving range of EVs necessitates an increase of Ni content to improve the energy densities,which,however,degrades the cycle stability.Here we review the doping/coating of tungsten and related elements to improve the electrochemical performance of these cathodes especially the cycle stability.The selection of tungsten and related elements is based on their special properties including the high valence state,strong bonding with oxygen and the large ionic radius.The improvement of cycle stability mainly results from two features:(1)the enhancement of bulk structure stability upon doping(Mo,W,Ta,Nb)and(2)the resistance of side reactions of electrode/electrolyte by the surficial layer induced by direct coating(V,W,Nb)or bulk doping.For the recent high Ni materials,the formation of Ni2+and its migration to the Li layer induced by these doped/coated tungsten-related elements,and the presence of spinel or rock-salt phase before cycling contributes to improving the cycle stability.The key challenges are the selection of an optimized additive concentration and the fundamental understanding of the reaction mechanism,which will provide insightful guidance for maximizing the electrochemical performance of the state-of-the-art lithium-ion batteries at minimal additional process costs.展开更多
Orthorhombic LiMnO_(2)nanoparticles and LiMnO_(2)nanorods have been synthesized by hydrothermal methods.LiMnO_(2)nanoparticles were synthesized by simple one-step hydrothermal method.To obtain rod-like LiMnO_(2),γ-Mn...Orthorhombic LiMnO_(2)nanoparticles and LiMnO_(2)nanorods have been synthesized by hydrothermal methods.LiMnO_(2)nanoparticles were synthesized by simple one-step hydrothermal method.To obtain rod-like LiMnO_(2),γ-MnOOH nanorods were first synthesized and then the H+ions were completely replaced by Li+resulting in LiMnO_(2)nanorods.Their electrochemical performances were thoroughly investigated by galvanostatic tests.Although the LiMnO_(2)nanoparticles have smaller size than LiMnO_(2)nanorods,the latter exhibited higher discharge capacity and better cyclability.For example,the discharge capacities of LiMnO_(2)nanorods reached 200 mA·h/g over many cycles and remained above 180 mA·h/g after 30 cycles.However,the maximum capacity of LiMnO_(2)nanoparticles was only 170 mA·h/g and quickly decreased to 110 mA·h/g after 30 cycles.Nanorods with one-dimensional electronic pathways favor the transport of electrons along the length direction and accommodate volume changes resulting from charge/discharge processes.Thus the morphology of LiMnO_(2)may play an important role in electrochemical performance.展开更多
La-Mg-Ni-Mn-based AB2-type La(1–x)CexMgNi(3.5)Mn(0.5)(x=0–0.4) alloys were prepared by melt spinning technology. The detections of X-ray diffraction(XRD) and scanning electron microscopy(SEM) indicated t...La-Mg-Ni-Mn-based AB2-type La(1–x)CexMgNi(3.5)Mn(0.5)(x=0–0.4) alloys were prepared by melt spinning technology. The detections of X-ray diffraction(XRD) and scanning electron microscopy(SEM) indicated that the experimental alloys consisted of a major phase LaMgNi4 and a secondary phase LaNi5. With spinning rate growing, the abundance of LaMgNi4 phase increased and that of LaNi5 phase decreased. Moreover, with the melt spinning rate increasing, both the lattice constants and cell volumes increased, and further accelerated the grains refinement of the alloys. The electrochemical tests showed that the as-spun alloys possessed excellent capability of activation, achieving the maximum discharge capacities just at the first cycling without any activation needed. As for the as-spun alloys, its discharge potential characteristics could be improved obviously by adopting the technology of melt spinning. In addition, the melt spinning raised electrochemical cycle stability of the alloys, the main reason was that the melt spinning enhanced the anti-pulverization ability of the alloys. With spinning rate increasing, the discharge capacity of the alloys presented a tendency to increase firstly then decrease. Moreover, the electrochemical kinetics of the alloys showed the same trend under fixed condition.展开更多
Spherical cathode material LiNi_0.5Mn_1.5O_4 for lithium-ion batteries was synthesized by hydroxide co- precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical mea- su...Spherical cathode material LiNi_0.5Mn_1.5O_4 for lithium-ion batteries was synthesized by hydroxide co- precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical mea- surements were carried out to characterize prepared LiNi_0.5Mn_1.5O_4 cathode material. SEM images show that the LiNi_0.5Mn_1.5O_4 cathode material is constituted by micro-sized spherical particles (with a diameter of around 8 μm). XRD patterns reveal that the structure of prepared LiNi_0.5Mn_1.5O_4 cathode material belongs to Fd3m space group. Electrochemical tests at 25℃show that the LiNi_0.5Mn_1.5O_4 cathode material prepared after annealing at 600 ℃ has the best electrochemical performances. The initial discharge capacity of prepared cathode material delivers 113.5 mAh·g-1 at 1C rate in the range of 3.50-4.95 V, and the sample retains 96.2% (1.0C) of the initial capacity after 50 cycles. Under different rates with a cutoff voltage range of 3.50-4.95 V at 25℃, the dis- charge capacities of obtained cathode material can be kept at about 145.0 (0.1C), 126.8 (0.5C), 113.5 (1.0C) and 112.4mAh·g-1 (2.0C), the corresponding initial coulomb efficiencies retain above 95.2% (0.1C), 95.0% (0.5C), 92.5% (1.0C) and 94.8% (2.0C), respectively.展开更多
A method of ultrasonic treatment (UST) was first used to modify the structure and electrochemical performance of nickel hydroxide for the active material of nickel series alkaline batteries. The experimental results...A method of ultrasonic treatment (UST) was first used to modify the structure and electrochemical performance of nickel hydroxide for the active material of nickel series alkaline batteries. The experimental results showed that UST was an effective method to improve the electrochemical performance of β-Ni(OH)2 such as specific discharge capacity, discharge potential, electrochemical reversibility and oxygen evolution over-potential. The results of electrochemical impedance spectroscopy, powder X-ray diffraction and particle size distribution indicated that the improvement of the performance of β-Ni(OH)2 through UST was attributed to the reduction of the charge-transfer resistance (Rt) and the diffusion impedance (Zw), which resulted from the decrease of the crystallite and particle size and the increase of interlayer spacing. Diffusion coefficient of proton DH of ultrasonic treated β-Ni(OH)2 gained by CV tests was 1.13 × 10^-11 cm^2/s, and the average discharge specific capacity of ultrasonic treated β-Ni(OH)2 electrode was 301 mAh/g.展开更多
Further application of organic quinone cathodes is restricted because they are inherent in poor conductivity and tend to dissolve in aprotic electrolytes.Salinization can work on the strong solubility of quinones.Here...Further application of organic quinone cathodes is restricted because they are inherent in poor conductivity and tend to dissolve in aprotic electrolytes.Salinization can work on the strong solubility of quinones.Herein,the ortho-disodium salt of tetrahydroxyquinone(o-Na_(2)THBQ)was selected to promote the electrochemical properties of tetrahydroxyquinone(THBQ).Reduced dissolution of o-Na_(2)THBQ in electrolyte after salinization(replacement of two H with two Na)contributed to enhanced electrochemical performance.In sodium-ion batteries(SIBs)in ester-based electrolyte,o-Na2THBQ cathodes at 50 mA·g^(-1)exhibited a reversible discharge capacity of 107 mAh·g^(-1)after 200 cycles.Ulteriorly,in ether-based electrolyte,reversible discharge capacities of 200.4,102.2,99.5 and 88 mAh·g^(-1)were obtained at 800,1600,3200 and 4800 mA·g^(-1)after 1000,2000,5000 and 8000 cycles,respectively.The ultraviolet absorption spectra and ex situ dissolution experiments of THBQ and o-Na_(2)THBQ showed that o-Na_(2)THBQ hardly dissolved in ether-based electrolyte.In lithium-ion batteries(LIBs),graphene was selected to further enhance the conductivity of o-Na2THBQ.At 50 mA·g^(-1),o-Na_(2)THBQ and o-Na_(2)THBQ/Gr cathodes exhibited reversible discharge capacities of 124 and 131.5 mAh·g^(-1)after 200 cycles in ester-based electrolyte,respectively.At 50 mA·g^(-1),PTPAn/o-Na_(2)THBQ electrodes in an all-organic Na/Li-ion battery showed reversible charge/discharge capacities of 51/50.3 and 33.8/33.1 mAh·g^(-1)after 200 cycles.展开更多
Despite the high specific capacities,the practical application of transition metal oxides as the lithium ion battery(LIB)anode is hindered by their low cycling stability,severe polarization,low initial coulombic effic...Despite the high specific capacities,the practical application of transition metal oxides as the lithium ion battery(LIB)anode is hindered by their low cycling stability,severe polarization,low initial coulombic efficiency,etc.Here,we report the synthesis of the NiO/Ni2N nanocomposite thin film by reactive magnetron sputtering with a Ni metal target in an atmosphere of 1 vol.% O2 and 99 vol.%N2.The existence of homogeneously dispersed nano Ni2N phase not only improves charge transfer kinetics,but also contributes to the one-off formation of a stable solid electrolyte interphase(SEI).In comparison with the NiO electrode,the NiO/Ni2N electrode exhibits significantly enhanced cycling stability with retention rate of 98.8%(85.6%for the NiO electrode)after 50 cycles,initial coulombic efficiency of 76.6%(65.0%for the NiO electrode)and rate capability with 515.3 mA·h·g^−1(340.1 mA·h·g^−1 for the NiO electrode)at 1.6 A·g^−1.展开更多
Developing new electrode materials with a high specific capacity for excellent lithium-ion storage properties is very desirable.The MnCO_(3)/Mn_(3)O_(4)nanoparticles with uniform size(about 50 nm)and shape which are w...Developing new electrode materials with a high specific capacity for excellent lithium-ion storage properties is very desirable.The MnCO_(3)/Mn_(3)O_(4)nanoparticles with uniform size(about 50 nm)and shape which are wrapped with graphene have been successfully synthesized via the one-step method for anode material of lithium-ion batteries.The as-prepared graphene-wrapped MnCO_(3)/Mn_(3)O_(4)nanocomposite exhibits remarkable electrochemical performance,including high reversible specific capacity,outstanding cycling stability,and excellent rate capability in comparison with the bare MnCO_(3)and MnCO_(3)/Mn_(3)O_(4)nanocomposite.This is because the synergistic effect of MnCO_(3)and Mn_(3)O_(4)nanoparticles and graphene nanosheets act as both electron conductors and volume buffer layers.From the scanning electron microscopy(SEM)analysis,we confirmed that the morphology and structure of the composite are preserved after 200 cycles.This further confirms that graphene-wrapped MnCO_(3)/Mn_(3)O_(4)nanocomposite acts as a stable template for reversible lithium-ion intercalation/deintercalation.展开更多
基金National Natural Science Foundation of China(No.51790490)。
文摘Cathode materials,nickel doped Cr_(8)O_(21),were synthesized by a solid-state method.The effects of Ni doping on the electrochemical performances of Cr_(8)O_(21) were investigated.The experimental results show that the discharge capacities of the samples depend on the nickel contents,which increases firstly and then decreases with increasing Ni contents.Optimized Ni_(0.5)Cr_(7.5)O_(21)delivers a first capacity up to 392.6 m Ah·g^(-1)at 0.1C.In addition,Ni doped sample also demonstrates enhanced cycling stability and rate capability compared with that of the bare Cr_(8)O_(21).At 1 C,an initial discharge capacity of 348.7 m Ah·g^(-1)was achieved for Ni_(0.5)Cr_(7.5)O_(21),much higher than 271.4 m Ah·g^(-1)of the un-doped sample,with an increase of more than 28%.Electrochemical impedance spectroscopy results confirm that Ni doping reduces the growth of interface resistance and charge transfer resistance,which is conducive to the electrochemical kinetic behaviors during charge-discharge.
基金the financial support by the Natural Science Foundation of Guangdong Province(2019A1515012111)the National Natural Science Foundation of China(51804199 and 51604081)+2 种基金the Science and Technology Innovation Commission of Shenzhen(JCYJ20190808173815205 and 20180123)the Shenzhen Science and Technology Program(KQTD20180412181422399)“Chenguang Program”supported by Shanghai Education Development Foundation and Shanghai Municipal Education Commission(16CG40)。
文摘To solve the critical problems of lithium rich cathode materials, e.g., structure instability and short cycle life, we have successfully prepared a ZrO2-coated and Zr-doping xLi2MnO3·(1–x)LiMO2 hollow architecture via one-time sintering process. The modified structural materials as lithium-ion cathodes present good structural stability and superior cycle performance in LIBs. The discharge capacity of the ZrO2-coated and Zr-doped hollow pristine is 220 mAh g-1 at the 20th cycle at 0.2 C(discharge capacity loss, 2.7%)and 150 m Ah g-1 at the 100 th cycle at 1 C(discharge capacity loss, 17.7%), respectively. However, hollow pristine electrode only delivers 203 m Ah g-1 at the 20 th cycle at 0.2 C and 124 mAh g-1 at the 100 th cycle at 1 C, respectively, and the corresponding to capacity retention is 92.2% and 72.8%, respectively.Diffusion coefficients of modified hollow pristine electrode are much higher than that of hollow pristine electrode after 100 cycles(approach to 1.4 times). In addition, we simulate the adsorption reaction of HF on the surface of ZrO2-coated layer by the first-principles theory. The calculations prove that the adsorption energy of HF on the surface of ZrO2-coated layer is about-1.699 e V, and the ZrO2-coated layer could protect the hollow spherical xLi2MnO3·(1–x)LiMO2 from erosion by HF. Our results would be applicable for systematic amelioration of high-performance lithium rich material for anode with the respect of practical application.
基金supported by the National Natural Science Foundation of China(Nos.51575269,51275232)the Six Talent Peaks Project in Jiangsu Province(No.ZBZZ005)the Zhejiang Provincial Key Laboratory for Cutting Tools(No.ZD201305)
文摘Boron doped diamond(BDD)performs well in electrochemical oxidation for organic pollutants thanks to its wide electrochemical window and superior chemical stability.We presented a method to obtain well-adherent large-scale BDD/Nb electrode by the modified hot filament chemical vapor deposition system(HFCVD).SiC particles were sand blasted to enhance the adhesion of BDD coating.The BDD coating was then deposited on both sides of Nb which was placed vertically and closely with filament grids on both sides.The BDD/Nb electrodes had no deformation because the thermal deformations of the BDD films on both sides of the Nb substrate conteracted each other during cooling process after deposition.The surface morphology and purity of the BDD/Nb electrode were analyzed by Raman and scanning elestron microscope(SEM)techniques.Scratch test was used to investigate the adhesion of BDD films.The electrochemical performances were measured by cyclic voltammetry test.The BDD electrode at the B/C ratio of 2 000×10^(-6) held a higher oxygen evolution potential thanks to its high sp3 carbon content.Accelerated life test illustrated that the sandblasting pretreatment obviously enhanced the adhesion of BDD coating which resulted in a longer service duration than the un-sandblasted one.
基金Funded by the National Natural Science Foundations of China(Nos.51161015,51371094)Natural Science Foundation of Inner Mongolia,China(No.2011ZD10)
文摘The element Ni in the Mg2Ni alloy is partially substituted by M(M = Cu, Co, Mn) in order to ameliorate the electrochemical hydrogen storage performances of Mg2Ni-type electrode alloys. The nanocrystalline and amorphous Mg20Ni10-xMx(M = None, Cu, Co, Mn; x = 0-4) alloys were prepared by melt spinning. The effects of the M(M = Cu, Co, Mn) content on the structures and electrochemical hydrogen storage characteristics of the as-cast and spun alloys were comparatively studied. The analyses by XRD, SEM and HRTEM reveal that all the as-cast alloys have a major phase of Mg2Ni but the M(M = Co, Mn) substitution brings on the formation of some secondary phases, MgCo2 and Mg for the(M = Co) alloy, and Mn Ni and Mg for the(M = Mn) alloy. Besides, the as-spun(M = None, Cu) alloys display an entirely nanocrystalline structure, whereas the as-spun(M = Co, Mn) alloys hold a nanocrystalline/amorphous structure, suggesting that the substitution of M(M = Co, Mn) for Ni facilitates the glass formation in the Mg2Ni-type alloys. The electrochemical measurements indicate that the variation of M(M = Cu, Co, Mn) content engenders an obvious effect on the electrochemical performances of the as-cast and spun alloys. To be specific, the cyclic stabilities of the alloys augment monotonously with increasing M(M = Cu, Co, Mn) content, and the capacity retaining rate(S20) is in an order of(M = Cu) 〉(M = Co) 〉(M = Mn) 〉(M = None) for x≤1 but changes to(M = Co) 〉(M = Mn) 〉(M = Cu) 〉(M = None) for x≥2. The discharge capacities of the as-cast and spun alloys always grow with the rising of M(M = Co, Mn) content but first mount up and then go down with increasing M(M = Cu) content. Whatever the M content is, the discharge capacities are in sequence:(M = Co) 〉(M = Mn) 〉(M = Cu) 〉(M = None). The high rate discharge abilities(HRDs) of all the alloys grow clearly with rising M(M = Cu, Co) content except for(M = Mn) alloy, whose HRD has a maximum value with varying M(M = Mn) content. Furthermore, for the as-cast alloys, the HRD is in order of(M = Co) 〉(M = Mn) 〉(M = Cu) 〉(M = None), while for the as-spun(20 m·s^-1) alloys, it changes from(M = Co) 〉(M = Mn) 〉(M = Cu) 〉(M = None) for x = 1 to(M = Cu) 〉(M = Co) 〉(M = None) 〉(M = Mn) for x = 4.
基金supported by the National Natural Science Foundation of China(Nos.51161015 and 50961009)the National High Technology Research and Development Program of China(No.2011AA03A408)the Natural Science Foundation of Inner Mongolia(Nos.2011ZD10 and 2010ZD05)
文摘The La-Mg-Ni-based A2B7-type Lao.8_xNdx Mgo.2Ni3.35Alo.lSio.o5 (x = 0, 0.1, 0.2, 0.3, and 0.4) electrode alloys were prepared by casting and annealing. The influence of the partial substitution of Nd for La on the structure and electrochemical performances of the alloys was investigated. The structural analysis of X-ray diffraction and scanning electron microscopy reveals that the experimental alloys consist of two major phases: (La,Mg)2Ni7 with the hexagonal Ce2Ni7-type structure and LaNi5 with the hexagonal CaCus-type structure as well as some residual phases of LaNi3 and NdNis. The electrochemical measurements indicate that an evident change of the electrochemical performance of the alloys is associated with the substitution of Nd for La. The discharge capacity of the alloy first increases then decreases with the growing Nd content, whereas their cycle stability clearly grows all the time. Furthermore, the measurements of the high rate discharge ability, the limiting current density, and hydrogen diffusion coefficient all demonstrate that the electrochemical kinetic properties of the alloy electrodes first augment then decline with the rising amount of Nd substitution.
基金Project supported by National Natural Science Foundation of China (50131040) and Natural Science Foundation of Inner Mon-golia (200408020706)
文摘The La-Mg-Ni-system (PuNi3-type) La2Mg (Ni0.85 Co0.15 )9M0.1 ( M = B, Cr) hydrogen storage etectrode alloys were prepared by casting and rapid quenching. The electrochemical performances and microstructures of the as-cast and quenched alloys were determined and measured. The effects of rapid quenching on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the alloys are composed of the (La, Mg) Ni3 phase (PuNi3-type structure) and the LaNi5 phase, as well as the small amount of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloy containing boron, and the Ni2B phase in the alloy nearly disappears after rapid quenching. The relative amount of each phase in the alloys depends on the quenching rate. The rapid quenching technique can greatly improve the electrochemical performance of the alloy, and the effect of rapid quenching on the activation performances of the alloys is minor. Rapid quenching enhances the cycle stability of the alloy, and the cycle life of the alloy increases with the increase of the quenching rate.
基金the National Natural Science Foundation of China(Nos.51761032 and 51471054)the Natural Science Foundation of Inner Mongolia,China(No.2015MS0558)
文摘The La-Mg-Ni-Mn-based AB_2-type La_(1-x)Ce_xMgNi_(3.5)Mn_(0.5)(x = 0, 0.1, 0.2, 0.3, and 0.4) alloys were fabricated by melt spinning technology. The effects of Ce content on the structures and electrochemical hydrogen storage performances of the alloys were studied systematically. The XRD and SEM analyses proved that the experimental alloys consist of a major phase LaMgNi_4 and a secondary phase LaNi_5. The variation of Ce content causes an obvious change in the phase abundance of the alloys without changing the phase composition. Namely, with the increase of Ce content, the LaMgNi_4 phase augments and the LaNi_5 phase declines. The lattice constants and cell volumes of the alloys clearly shrink with increasing Ce content. Moreover, the Ce substitution for La results in the grains of the alloys clearly refined. The electrochemical tests showed that the substitution of Ce for La obviously improves the cycle stability of the as-spun alloys. The analyses on the capacity degradation mechanism demonstrate that the improvement can be attributed to the ameliorated anti-corrosion and antioxidation ability originating from substituting partial La with Ce. The as-spun alloys exhibit excellent activation capability, reaching the maximum discharge capacities just at the first cycling without any activation treatment. The substitution of Ce for La evidently improves the discharge potential characteristics of the as-spun alloys. The discharge capacity of the alloys first increases and then decreases with growing Ce content. Furthermore, a similar trend also exists in the electrochemical kinetics of the alloys, including the high rate discharge ability(HRD), hydrogen diffusion coefficient(D), limiting current density(IL) and charge transfer rate.
基金Project(2007AA03Z227)supported by High-tech Research and Development Program of ChinaProjects(50871050,50701011)supported by the National Natural Science Foundation of China+1 种基金Project(200711020703)supported by the Natural Science Foundation of Inner Mongolia,ChinaProject(NJzy08071)supported by High Education Science Research Project of Inner Mongolia,China
文摘The La-Mg-Ni system A2B7-type electrode alloys with nominal composition La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1(x=0,0.05, 0.1,0.15,0.2)were prepared by casting and melt-spinning.The influences of melt spinning on the electrochemical performances as well as the structures of the alloys were investigated.The results obtained by XRD,SEM and TEM show that the as-cast and spun alloys have a multiphase structure,consisting of two main phases(La,Mg)Ni3 and LaNi5 as well as a residual phase LaNi2.The melt spinning leads to an obvious increase of the LaNi5 phase and a decrease of the(La,Mg)Ni3 phase in the alloys.The results of the electrochemical measurement indicate that the discharge capacity of the alloys(x≤0.1)first increases and then decreases with the increase of spinning rate,whereas for x>0.1,the discharge capacity of the alloys monotonously falls.The melt spinning slightly impairs the activation capability of the alloys,but it significantly enhances the cycle stability of the alloys.
文摘A new self-made additive of amidocyanogen-acetic salt was used in wet ball-grind technique (WBGT) for preparing hydrogen storage alloys, and the effect on the electrochemical performance of the alloy electrode was investigated in detail. It was found that the prepared electrode had perfect electrochemical performances, such as rapid activation, high capability, high-rate discharge (HRD) ability, and good stability. The first discharge capacitance at 0.2 C (throughout this study, n C rate means that the rated capacity of a hydrogen storage alloy (full capacity) is charged or discharged completely in 1/n h) reached 278 mAh·g^-1 and the discharge capacitance reached the maximum of 322 mAh·g^-1 only after two charge-discharge cycles. For the dry method, wet method, and WBGT, the high rate discharge (HRD) values (C5 c/C0.2c ratio) were approximately 0.59, 0.76, and 0.83, respectively. The stable discharge capacity at 3 C increased from 275 mAh·g^-1 (dry method)to 295 mAh·g^-1 (WBGT).
基金Funded by the Science Research Foundation of Ordnance Engi-neering College(No.yjjxm0006)
文摘In view of the higher temperature of large-size NilMH battery in electric vehicle, the effect of temperature on electrochemical performances of hydrogen storage alloy Ml ( NiCoMnTi )5 was investigated systematically. The results show that the electrochemical performances of alloy vary drastically with temperature changing. As temperature rises, the hydrogen equilibrium pressure increases, the width of hydrogen desorption plateau decreases and the gradient increases, leading to a decline of capacity. When temperature rises from 20 ℃ to 80 ℃ , the discharge capacity of the alloy decreases from 309.11 mA· h· g^-1 to 227.64 mA· h· g^-1 , but the high rate dischargeability is improved markedly. Higher temperatures also bring about a significant decrease in the cycling stability and self-discharge property. X-ray diffraction analysis indicates that the alloy has a single phase with CaCu5-type LaNi5 structure.
文摘The high compacted density LiNi<sub>0.5-x</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub>Mg<sub>x</sub>O<sub>2</sub> cathode material for lithium-ion batteries was synthesized by high temperature solid-state method, taking the Mg element as a doping element and the spherical Ni<sub>0.5</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub> (OH)<sub>2</sub>, Li<sub>2</sub>CO<sub>3</sub> as raw materials. The effects of calcination temperature on the structure and properties of the products were investigated. The structure and morphology of cathode materials powder were analyzed by X-ray diffraction spectroscopy (XRD) and scanning electronmicroscopy (SEM). The electrochemical properties of the cathode materials were studied by charge-discharge test and cyclic properties test. The results show that LiNi<sub>0.4985</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub> Mg<sub>0.0015</sub>O<sub>2</sub> cathode material prepared at calcination temperature 930°C has a good layered structure, and the compacted density of the electrode sheet is above 3.68 g/cm<sup>3</sup>. The discharge capacity retention rate is more than 97.5% after 100 cycles at a charge-discharge rate of 1C, displaying a good cyclic performance.
基金Funded by National Natural Science Foundations of China(Nos.51161015 and 51371094)National 863 Plans Projects of China(No.2011AA03A408)
文摘The casting and annealing technologies were applied to fabricate the La0.8Mg0.2Ni3.3Co0.2Six (x = 0-0.2) electrode alloys. The effects of Si content and annealing temperature on the structure and electrochemical performances of the alloys were investigated systematically. The analyses of XRD and SEM show that all the alloys possess a multiphase structure, involving two main phases (La, Mg)2Ni7 and LaNi5 as well as a residual phase LaNi3. The addition of Si brings on an evident increase in the LaNi5 phase and a decrease in the (La, Mg)2Ni7 phase, without altering the main phase component of the alloy, which also makes the lattice constants and cell volumes of the alloy enlarged. Likewise, the annealing treatment engenders the same action on the lattice constants and cell volumes as adding Si. Simultaneously, it gives rise to the variation of the phase abundance and the coarsening of the alloy grains. The electrochemical measurements indicate that the addition of Si ameliorates the cycle stability of the as-cast and annealed alloys significantly, but impairs their discharge capacities clearly. Similarly, the annealing treatment makes a positive contribution to the cycle stability of the alloy evidently, and the discharge capacity of the alloy shows a maximum value with annealing temperature rising. Furthermore, the high rate discharge ability (HR) first augments and then declines with the rising of Si content and annealing temperature.
基金financially supported by the Australian CRC-P project“Value-added cobalt refining technologies powering advanced batteries”,administered by Pure Battery Technologies Pty LtdAustralian Research Council through its Laureate Fellowship and Linkage Projects
文摘Lithium ion batteries using Ni-Co-Mn ternary oxide materials(NCMs)and Ni-Co-Al materials(NCAs)as the cathode materials are dominantly employed to power the electric vehicles(EVs).Increasing the driving range of EVs necessitates an increase of Ni content to improve the energy densities,which,however,degrades the cycle stability.Here we review the doping/coating of tungsten and related elements to improve the electrochemical performance of these cathodes especially the cycle stability.The selection of tungsten and related elements is based on their special properties including the high valence state,strong bonding with oxygen and the large ionic radius.The improvement of cycle stability mainly results from two features:(1)the enhancement of bulk structure stability upon doping(Mo,W,Ta,Nb)and(2)the resistance of side reactions of electrode/electrolyte by the surficial layer induced by direct coating(V,W,Nb)or bulk doping.For the recent high Ni materials,the formation of Ni2+and its migration to the Li layer induced by these doped/coated tungsten-related elements,and the presence of spinel or rock-salt phase before cycling contributes to improving the cycle stability.The key challenges are the selection of an optimized additive concentration and the fundamental understanding of the reaction mechanism,which will provide insightful guidance for maximizing the electrochemical performance of the state-of-the-art lithium-ion batteries at minimal additional process costs.
基金the National Natural Science Foundation of China(No.90606006)the State Key Project of Fundamental Research for Nanoscience and Nanotechnology(No.2006CB932300).
文摘Orthorhombic LiMnO_(2)nanoparticles and LiMnO_(2)nanorods have been synthesized by hydrothermal methods.LiMnO_(2)nanoparticles were synthesized by simple one-step hydrothermal method.To obtain rod-like LiMnO_(2),γ-MnOOH nanorods were first synthesized and then the H+ions were completely replaced by Li+resulting in LiMnO_(2)nanorods.Their electrochemical performances were thoroughly investigated by galvanostatic tests.Although the LiMnO_(2)nanoparticles have smaller size than LiMnO_(2)nanorods,the latter exhibited higher discharge capacity and better cyclability.For example,the discharge capacities of LiMnO_(2)nanorods reached 200 mA·h/g over many cycles and remained above 180 mA·h/g after 30 cycles.However,the maximum capacity of LiMnO_(2)nanoparticles was only 170 mA·h/g and quickly decreased to 110 mA·h/g after 30 cycles.Nanorods with one-dimensional electronic pathways favor the transport of electrons along the length direction and accommodate volume changes resulting from charge/discharge processes.Thus the morphology of LiMnO_(2)may play an important role in electrochemical performance.
基金Project supported by National Natural Science Foundation of China(51161015,51371094,51471054)
文摘La-Mg-Ni-Mn-based AB2-type La(1–x)CexMgNi(3.5)Mn(0.5)(x=0–0.4) alloys were prepared by melt spinning technology. The detections of X-ray diffraction(XRD) and scanning electron microscopy(SEM) indicated that the experimental alloys consisted of a major phase LaMgNi4 and a secondary phase LaNi5. With spinning rate growing, the abundance of LaMgNi4 phase increased and that of LaNi5 phase decreased. Moreover, with the melt spinning rate increasing, both the lattice constants and cell volumes increased, and further accelerated the grains refinement of the alloys. The electrochemical tests showed that the as-spun alloys possessed excellent capability of activation, achieving the maximum discharge capacities just at the first cycling without any activation needed. As for the as-spun alloys, its discharge potential characteristics could be improved obviously by adopting the technology of melt spinning. In addition, the melt spinning raised electrochemical cycle stability of the alloys, the main reason was that the melt spinning enhanced the anti-pulverization ability of the alloys. With spinning rate increasing, the discharge capacity of the alloys presented a tendency to increase firstly then decrease. Moreover, the electrochemical kinetics of the alloys showed the same trend under fixed condition.
基金financially supported by the funding from the State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals (No. SKL-SPM201211)the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT13026)
文摘Spherical cathode material LiNi_0.5Mn_1.5O_4 for lithium-ion batteries was synthesized by hydroxide co- precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical mea- surements were carried out to characterize prepared LiNi_0.5Mn_1.5O_4 cathode material. SEM images show that the LiNi_0.5Mn_1.5O_4 cathode material is constituted by micro-sized spherical particles (with a diameter of around 8 μm). XRD patterns reveal that the structure of prepared LiNi_0.5Mn_1.5O_4 cathode material belongs to Fd3m space group. Electrochemical tests at 25℃show that the LiNi_0.5Mn_1.5O_4 cathode material prepared after annealing at 600 ℃ has the best electrochemical performances. The initial discharge capacity of prepared cathode material delivers 113.5 mAh·g-1 at 1C rate in the range of 3.50-4.95 V, and the sample retains 96.2% (1.0C) of the initial capacity after 50 cycles. Under different rates with a cutoff voltage range of 3.50-4.95 V at 25℃, the dis- charge capacities of obtained cathode material can be kept at about 145.0 (0.1C), 126.8 (0.5C), 113.5 (1.0C) and 112.4mAh·g-1 (2.0C), the corresponding initial coulomb efficiencies retain above 95.2% (0.1C), 95.0% (0.5C), 92.5% (1.0C) and 94.8% (2.0C), respectively.
文摘A method of ultrasonic treatment (UST) was first used to modify the structure and electrochemical performance of nickel hydroxide for the active material of nickel series alkaline batteries. The experimental results showed that UST was an effective method to improve the electrochemical performance of β-Ni(OH)2 such as specific discharge capacity, discharge potential, electrochemical reversibility and oxygen evolution over-potential. The results of electrochemical impedance spectroscopy, powder X-ray diffraction and particle size distribution indicated that the improvement of the performance of β-Ni(OH)2 through UST was attributed to the reduction of the charge-transfer resistance (Rt) and the diffusion impedance (Zw), which resulted from the decrease of the crystallite and particle size and the increase of interlayer spacing. Diffusion coefficient of proton DH of ultrasonic treated β-Ni(OH)2 gained by CV tests was 1.13 × 10^-11 cm^2/s, and the average discharge specific capacity of ultrasonic treated β-Ni(OH)2 electrode was 301 mAh/g.
基金This study was financially supported by the National Natural Science Foundation,China(Nos.21773057,21773057,52071132 and U1904216)Zhongyuan Thousand People Plan-Zhongyuan Youth Talent Support Program(in Science and Technology)+3 种基金China(No.ZYQR201810139)the Innovative Funds Plan of Henan University of Technology,China(No.2020ZKCJ04)Fundamental Research Funds for Henan Provincial Colleges and Universities in Henan University of Technology,China(No.2018RCJH01)the Science and Technology Research Project of Henan Province,China(No.212102210215).
文摘Further application of organic quinone cathodes is restricted because they are inherent in poor conductivity and tend to dissolve in aprotic electrolytes.Salinization can work on the strong solubility of quinones.Herein,the ortho-disodium salt of tetrahydroxyquinone(o-Na_(2)THBQ)was selected to promote the electrochemical properties of tetrahydroxyquinone(THBQ).Reduced dissolution of o-Na_(2)THBQ in electrolyte after salinization(replacement of two H with two Na)contributed to enhanced electrochemical performance.In sodium-ion batteries(SIBs)in ester-based electrolyte,o-Na2THBQ cathodes at 50 mA·g^(-1)exhibited a reversible discharge capacity of 107 mAh·g^(-1)after 200 cycles.Ulteriorly,in ether-based electrolyte,reversible discharge capacities of 200.4,102.2,99.5 and 88 mAh·g^(-1)were obtained at 800,1600,3200 and 4800 mA·g^(-1)after 1000,2000,5000 and 8000 cycles,respectively.The ultraviolet absorption spectra and ex situ dissolution experiments of THBQ and o-Na_(2)THBQ showed that o-Na_(2)THBQ hardly dissolved in ether-based electrolyte.In lithium-ion batteries(LIBs),graphene was selected to further enhance the conductivity of o-Na2THBQ.At 50 mA·g^(-1),o-Na_(2)THBQ and o-Na_(2)THBQ/Gr cathodes exhibited reversible discharge capacities of 124 and 131.5 mAh·g^(-1)after 200 cycles in ester-based electrolyte,respectively.At 50 mA·g^(-1),PTPAn/o-Na_(2)THBQ electrodes in an all-organic Na/Li-ion battery showed reversible charge/discharge capacities of 51/50.3 and 33.8/33.1 mAh·g^(-1)after 200 cycles.
基金The authors acknowledge the support by the National Natural Science Foundation of China(Grant No.51767021)the Jiangxi Yunjia High Tech Co.,Ltd.(Grant No.738010128).
文摘Despite the high specific capacities,the practical application of transition metal oxides as the lithium ion battery(LIB)anode is hindered by their low cycling stability,severe polarization,low initial coulombic efficiency,etc.Here,we report the synthesis of the NiO/Ni2N nanocomposite thin film by reactive magnetron sputtering with a Ni metal target in an atmosphere of 1 vol.% O2 and 99 vol.%N2.The existence of homogeneously dispersed nano Ni2N phase not only improves charge transfer kinetics,but also contributes to the one-off formation of a stable solid electrolyte interphase(SEI).In comparison with the NiO electrode,the NiO/Ni2N electrode exhibits significantly enhanced cycling stability with retention rate of 98.8%(85.6%for the NiO electrode)after 50 cycles,initial coulombic efficiency of 76.6%(65.0%for the NiO electrode)and rate capability with 515.3 mA·h·g^−1(340.1 mA·h·g^−1 for the NiO electrode)at 1.6 A·g^−1.
基金financially supported by the 111 Project(B16009)the National Natural Science Foundation of China(Nos.51704065 and 51804219)+1 种基金the Fundamental Research Funds for the Central Universities of China(No.N2002022)the Natural Science Foundation of Anhui Province,China(No.1808085QE161)
文摘Developing new electrode materials with a high specific capacity for excellent lithium-ion storage properties is very desirable.The MnCO_(3)/Mn_(3)O_(4)nanoparticles with uniform size(about 50 nm)and shape which are wrapped with graphene have been successfully synthesized via the one-step method for anode material of lithium-ion batteries.The as-prepared graphene-wrapped MnCO_(3)/Mn_(3)O_(4)nanocomposite exhibits remarkable electrochemical performance,including high reversible specific capacity,outstanding cycling stability,and excellent rate capability in comparison with the bare MnCO_(3)and MnCO_(3)/Mn_(3)O_(4)nanocomposite.This is because the synergistic effect of MnCO_(3)and Mn_(3)O_(4)nanoparticles and graphene nanosheets act as both electron conductors and volume buffer layers.From the scanning electron microscopy(SEM)analysis,we confirmed that the morphology and structure of the composite are preserved after 200 cycles.This further confirms that graphene-wrapped MnCO_(3)/Mn_(3)O_(4)nanocomposite acts as a stable template for reversible lithium-ion intercalation/deintercalation.