Atomistic understanding of capacity loss in LiNiO_(2)for high-nickel Li-ion batteries:First-principles study

Combining the first-principles calculations and structural enumeration with recognition,the delithiation process of LiNiO_(2)is investigated,where various supercell shapes are considered in order to obtain the formation energy of Li_(x)NiO_(2).Meanwhile,the voltage profile is simulated and the ordered phases of lithium vacancies corresponding to concentrations of 1/4,2/5,3/7,1/2,2/3,3/4,5/6,and 6/7 are predicted.To understand the capacity decay in the experiment during the charge/discharge cycles,deoxygenation and Li/Ni antisite defects are calculated,revealing that the chains of oxygen vacancies will be energetically preferrable.It can be inferred that in the absence of oxygen atom in high delithiate state,the diffusion of Ni atoms is facilitated and the formation of Li/Ni antisite is induced.

Recovery of cadmium by high-temperature vaccum evaporation from Ni-Cd batteries

High temperature vaccum evaporation is a recycling technology that includes a selective material recovering process. The fundamental research on a process of disassembling and recovering selected materials from Ni Cd batteries was conducted using self designed experimental apparatus. An effective recycling technology based on the evaporation phenomenon of batteries and the elements of cadmium under the laboratory condition was studied. The results show that: (1)Ni/Cd can be effectively recovered by vacuum distillation at appropriate temperature, pressure and time, and high purity cadmium (>99%) can be obtained through the process; (2)the effective distillatory temperature should be at the range of 5731 173 K; (3)the higher the evaporation temperature, the lower the purity of cadmium in condensate

Separation of cadmium and nickel from waste Ni-Cd batteries

To separate the cadmium and nickel resources in waste Ni-Cd batteries, aself-designed vacuum distillation recycling system was studied under laboratory conditions. Theeffects of system temperature, operating pressure, and time on the separation of Ni and Cd werestudied respectively. The mechanism of vacuum thermal recycling was also discussed. Results showthat vacuum distillation is a very effective separation method for waste Ni-Cd batteries. At aconstant pressure, the increase of temperature can improve the separating efficiency of Cd. When thetemperature is 1 173 K, cadmium can evaporate completely from the samples during 3 h at 10 Pa. Thereduction of pressure in a certain range is effective to the separating of Cd from Ni-Cd batteriesby vacuum distillation.

Vacuum-Aided Recovery Technology of Spent Ni-Cd Batteries

Recovery of Ni-Cd batteries was studied by a self-designed vacuum-aided recovering system under laboratory conditions. The fundamental research on a process of disassembling and recovering selected materials from Ni-Cd batterieswas conducted. The impacts of temperature, pressure and time were studied respectively. The mechanism of vacuum thermal recovering was also discussed. The results show that: Ni-Cd batteries can be recovered effectively byvacuum-aided recovering system at 573~1173 K. At constant pressure, the increase of temperature can improve theseparating efficiency of cadmium. When the temperature is 1173 K, the cadmium can evaporate completely fromthe residue during 3 h at 10 Pa. The reduction of pressure in the certain range is effective to separate cadmium byvacuum distillation. Distillation time is a very important factor affecting separation of cadmium.

Enhanced electrochemical properties of LaFeO_3 with Ni modification for MH–Ni batteries

In this work,we synthesized LaFeO_3–xwt%Ni(x=0,5,10,15)composites via a solid-state reaction method by adding Ni to the reactants,La_2O_3 and Fe_2O_3.Field-emission scanning electron microscopy(FE-SEM)and energy-dispersive X-ray spectroscopy(EDS)results revealed that Ni powders evenly dispersed among the LaFeO_3 particles and apparently reduced their aggregation,which imparted the composites with a loose structure.Moreover,the Ni formed a conductive network,thus improving the conductivity of the composites.The maximum discharge capacity of the LaFeO_3 electrodes remarkably increased from 266.8 mAh·g^(–1)(x=0)to 339.7 mAh·g^(–1)(x=10).In particular,the high-rate dischargeability of the LaFeO_3–10wt%Ni electrode at a discharge current density of 1500 mA·g^(-1) reached 54.6%,which was approximately 1.5 times higher than that of the pure LaFeO_3.Such a Ni-modified loose structure not only increased the charge transfer rate on the surface of the LaFeO_3 particles but also enhanced the hydrogen diffusion rate in the bulk LaFeO_3.

Graphene-immobilized flower-like Ni3S2 nanoflakes as a stable binder-free anode material for sodium-ion batteries

A binder-free Ni3S2 electrode was prepared directly on a graphene-coated Ni foam （G/Ni） substrate through surface sulfiding of substrate using thiourea as the sulfur source in this work. The Ni3S2 showed a flower-like morphology and was uniformly distributed on the G/Ni surface. The flower-like Ni3S2 was composed of cross-arrayed nanoflakes with a diameter and a thickness of 1-2 μm and -50 nm, re- spectively. The free space in the flowers and the thin feature of Ni3S2 buffered the volume changes and relieved mechanical strain during re- peated cycling. The intimate contact with the Ni substrate and the fixing effect of graphene maintained the structural stability of the Ni3S2 electrode during cycling. The G/Ni-supported Ni3S2 maintained a reversible capacity of 250 mAh·g^-1 after 100 cycles at 50 mA·g^-1, demon- strating the good cycling stability as a result of the unique microstructure of this electrode material.

Bifunctional Oxygen Electrocatalyst of Mesoporous Ni/NiO Nanosheets for Flexible Rechargeable Zn–Air Batteries

One approach to accelerate the stagnant kinetics of both the oxygen reduction and evolution reactions(ORR/OER)is to develop a rationally designed multiphase nanocomposite,where the functions arising from each of the constituent phases,their interfaces,and the overall structure are properly controlled.Herein,we successfully synthesized an oxygen electrocatalyst consisting of Ni nanoparticles purposely interpenetrated into mesoporous NiO nanosheets(porous Ni/NiO).Benefiting from the contributions of the Ni and NiO phases,the well-established pore channels for charge transport at the interface between the phases,and the enhanced conductivity due to oxygen-deficiency at the pore edges,the porous Ni/NiO nanosheets show a potential of 1.49 V(10 mA cm^-2)for the OER and a half-wave potential of 0.76 V for the ORR,outperforming their noble metal counterparts.More significantly,a Zn-air battery employing the porous Ni/NiO nanosheets exhibits an initial charging-discharging voltage gap of 0.83 V(2 mA cm^-2),specific capacity of 853 mAh gZn^-1 at 20 mA cm^-2,and long-time cycling stability(120 h).In addition,the porous Ni/NiO-based solid-like Zn-air battery shows excellent electrochemical performance and flexibility,illustrating its great potential as a next-generation rechargeable power source for flexible electronics.

Preparation and Electrochemical Performances of Nickel Metal Hydride Batteries with High Specific Volume Capacity

Cylindrical nickel metal hydride （Ni-MH） battery with high specific volume capacity was prepared by using the oxyhydroxide Ni（OH）2 and AB5 type hydrogen storage alloy and adjusting the designing parameters of positive and negative electrodes. The oxyhydroxide Ni（OH）2 was synthesized by oxidizing spherical β-Ni（OH）2 with chemical method. The X-ray diffraction （XRD） patterns and the Fourier transform infrared （PT-IR） spectra indicated that 7-NiOOH was formed on the oxyhydroxide Ni（OH）2 powders, and some H2O molecules were inserted into their crystal lattice spacing. The battery capacity could not be improved when the oxyhydroxide Ni（OH）2 sample was directly used as the positive active materials. However, based on the conductance and residual capacity of the oxyhydroxide Ni（OH）2 powders, AA size Ni-MH battery with 2560 mA.h capacity and 407 W·h·L^-1 specific volume energy at 0.2C was obtained by using the commercial spherical β-Ni（OH）2 and AB5-type hydrogen-storage alloy powders as the active materials when 10% mass amount of the oxyhydroxide Ni（OH）2 with 2.50 valence was added to the positive active materials and subsequently the battery designing parameters were adjusted as well. The as-prepared battery showed 70% initial capacity after 80 cycles at 0.5C. The possibility for adjusting the capacity ratio of positive and negative electrodes from 1 ： 1.35 to 1 ： 1.22 was demonstrated preliminarily. It is considered the as-prepared battery can meet the requirement of some special portable electrical instruments.

The design and fabrication of Co3O4/Co3V2O8/Ni nanocomposites as high-performance anodes for Li-ion batteries

The CoO/CoVO/Ni nanocomposites were rationally designed and prepared by a two-step hydrothermal synthesis and subsequent annealing treatment. The one-dimensional（1D） CoOnanowire arrays directly grew on Ni foam, whereas the 1D CoVOnanowires adhered to parts of CoOnanowires.Most of the hybrid nanowires were inlayed with each other, forming a 3D hybrid nanowires network.As a result, the discharge capacity of CoO/CoVO/Ni nanocomposites could reach 1201.8 mAh/g after100 cycles at 100 mA/g. After 600 cycles at 1 A/g, the discharge capacity was maintained at 828.1 mAh/g.Moreover, even though the charge/discharge rates were increased to 10 A/g, it rendered reversible capacity of 491.2 mAh/g. The superior electrochemical properties of nanocomposites were probably ascribed to their unique 3D architecture and the synergistic effects of two active materials. Therefore, such CoO/CoVO/Ni nanocomposites could potentially be used as anode materials for high-performance Li-ion batteries.

Improved electrochemical performances of yttrium oxyfluoride-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 for lithium ion batteries

The Li-rich layered oxides show a higher discharge capacity over 250 mAh/g and have been developed into a promising positive material for lithium ion batteries. A rare earth metal oxyfluoride YOF-coated Li[Lio.2Mno.54Ni0.13Co0.13]O2 composites have been synthesized by a simple wet chem- ical method. Crystal structure, micro-morphology and element valence of the pristine and YOF-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 materials are characterized by XRD, SEM, TEM, and XPS. The results indicate that all materials exhibit a typical layered structure, and are made up of small and homogenous parti- cles ranging from 100 nm to 200 nm. In addition, YOF layer with a thickness of approximately 3-8 nm is precisely coated on the surface of the Li[Li0.2Mn0.54Ni0.13Co0.13]02. Constant current charge/discharge tests at various current densities show that the electrochemical performance of 2 wt% YOF-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 has been improved significantly. 2 wt% YOF-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 delivers the highest discharge capacity of 250.4 mAh/g at 20 mA/g among all the samples, and capacity retention of 87% after 100 charge/discharge cycles at 200 mA/g while that of the pristine one is only 81.6%. The superior electrochemical performance of 2wt% YOF-coated sample is ascribed to YOF coating layer, which could not only reduce side reactions between the electrode and liquid electrolyte, but also promote lithium ion migration.

The Bacteria Absorption-based Yolk-Shell Ni3P-Carbon @ Reduced Graphene Oxides for Lithium-Ion Batteries

Traditional carbon layer enwrapping active materials cannot easily realize perfect cladding.Therefore,it still cannot prevent the pulverization of active materials during the course of charging/discharging.In this paper,we utilize natural bacteria to absorb nickel acetate,the active materials Ni3P nanoparticles are well enwrapped,as a natural organisms surviving for billions of years,their cell walls have a perfect carbon structure,and the cell walls become carbon layer through high annealing temperature.Based on this,the yolk-shell Ni3P–carbon@reduced graphene oxides paper is prepared,through a proper annealing temperature,the Ni3P particles disperse in the inner surface or both ends,so the active materials were prevented from dissolving into the electrolyte,so it may keep from invalidity during charging/discharging.The electrochemical performances display that it has stable and high capacities as Li-ion batteries(LIBs)anode.Its capacity can keep 200 cycles without any decrease,and especially its rate performance exhibits an excellent peculiarity,with the current density increasing from 400 to 1000 mA g^(−1) every 200 mA g^(−1),its capacities decrease only 9.8%,2.9%and 6.4%,and its can recover the same capacity when the current density comes back to 200 mA g^(−1).It may be a fine choice for LIBs.

Application of Nanocrystalline LaNi_5-type Hydrogen Absorbing Alloys in Ni-MH_x Batteries

The structure and electrochemical properties of nanocrystalline LaNi_5-type alloys were studied. These materials were prepared by mechanical alloying (MA) followed by annealing. The properties of hydrogen host materials can be modified substantially by alloying to obtain the desired storage characteristics. It was found that the partial substitution of Ni by Al or Mn in LaNi_(5-x)M_x alloy leads to an increase in discharge capacity. The alloying elements such as Al, Mn and Co greatly improved the cycle life of LaNi_5 material. For example, in the nanocrystalline LaNi_(3.75)Mn_(0.75)Al_(0.25)Co_(0.25) powder, discharge capacity up to 258 mAh·g^(-1) was measured (at 40 mA·g^(-1) discharge current). Furthermore, the effect of the graphite coating on the structure of some nanocrystalline alloys and the electrodes characteristics were investigated. The mechanical coating with graphite effectively reduced the degradation rate of the studied electrode materials. The combination of a nanocrystalline LaNi_5-type hydride electrodes and a nickel positive electrode to form a Ni-MH battery, was successful.

Research of heat treatment of low-Co AB_5 type hydrogen storage alloys for MH-Ni batteries

The effects of low-Co AB_5 type hydrogen storage alloys prepared by quenchingand annealing on the performances of MH-Ni batteries were investigated, and the characteristics ofthe low-Co AB_5 type hydrogen storage alloys were compared with those of the high-Co AB_5 typehydrogen storage alloy as well. The results showed that the faster the cooling of the low-Cohydrogen storage alloy is, the better homogeneity of the chemical composition for the alloy and thelonger cycle life of the battery are, but the electrochemical discharge capacity and high-ratedischarge ability are reduced. The high-rate discharge ability and charge retention of MH-Nibatteries for the conventional as-cast annealed low-Co hydrogen storage alloy were superior to thosefor the rapidly quenched low-Co hydrogen storage alloy and the high-Co hydrogen storage alloy, buta little inferior in the cycle life.

Characteristics and electrochemical performance of cathode material Co-coated LiNiO_2 for Li-ion batteries

Spherical Ni(OH)2 powder coated with Co(OH)2 as raw material was mixed with LiOH to synthesize cathode material for lithium ion battery by using solid-state reaction. After sintered at temperature above 600 ℃, a solid solution with layer structure was formed. The result of XPS shows that it is a concentration gradient material with higher cobalt content at the surface, and the gradient decreases with increasing sintering temperature from 650 to 750 ℃. This new gradient material, called as Co-coated LiNiO2, exhibits excellent electrochemical performances for the cathode of Li-ion batteries in comparison with LiNiO2 and Co-doping LiNiO2. The discharge capacity of Co-coated LiNiO2 is over 180 mA·h/g and capacity decay per cycle is less than 0.07% when Co-coated LiNiO2 consisting of 92% nickel and 8% cobalt was sintered at the temperatures between 650-670 ℃. Though initial discharge capacity could be increased with higher sintering temperature, the cycle life would be reduced.

Effect of lithium content on electrochemical property of Li_(1+x)(Mn_(0.6)Ni_(0.2)Co_(0.2))_(1-x)O_2(0≤x≤0.3) composite cathode materials for rechargeable lithium-ion batteries

In order to confirm the optimal Li content of Li-rich Mn-based cathode materials(a fixed mole ratio of Mn to Ni to Co is0.6:0.2:0.2),Li1+x(Mn0.6Ni0.2Co0.2)1-xO2(x=0,0.1,0.2,0.3)composites were obtained,which had a typical layered structure with R3m and C2/m space group observed from X-ray powder diffraction(XRD).Electron microscopy micrograph(SEM)reveals that the particle sizes in the range of0.4-1.1μm increase with an increase of x value.Li1.2(Mn0.6Ni0.2Co0.2)0.8O2sample delivers a larger initial discharge capacity of275.7mA·h/g at the current density of20mA/g in the potential range of2.0-4.8V,while Li1.1(Mn0.6Ni0.2Co0.2)0.9O2shows a better cycle performance with a capacity retention of93.8%at0.2C after50cycles,showing better reaction kinetics of lithium ion insertion and extraction.

Effect of surface modification of metal hydride electrode on performance of MH/Ni batteries

A novel method was applied to the surface modification of the metal hydride(MH)electrode of MH/Ni batteries.Both sides of the electrode were plated with a thin silver film about 0.1μm thick using vacuum evaporation plating technology,and the effect of the electrode on the performance of MH/Ni batteries was examined.It is found that the surface modification can enhance the electrode conductivity and decrease the battery ohimic resistance.After surface modification,the discharge capacity at 5C(7.5A)is increased by 212 mA.h and the discharge voltage is increased by 0.11 V,the resistance of the batteries is also decreased by 32%.The batteries with modified electrode exhibit satisfactory durability.The remaining capacity of the modified batteries is 89%of the initial capacity even after 500 cycles.The inner pressure of the batteries during overcharging is lowered and the charging efficiency of the batteries is improved.

Electrochemical performance of nickel/metal hydride batteries under unconventional conditions and degradation analysis

The charge discharge performance and cycle stability of D size Ni/MH batteries at -20 ℃, 25 ℃ and 55 ℃ were examined. The results show that the decline rate of Ni/MH battery discharge capacity at -20 ℃ and 55 ℃ are 12.1% and 13.6%,and the average discharge voltage decreases by a value of 0.13 V and 0.06 V respectively, cycling stability declines obviously at various temperatures. The capacity degradation of Ni/MH batteries under low temperature is reversible, belonging to transient degradation and that of high and normal temperatures are not reversible, belonging to permanent degradation. Electrochemical impedance spectroscopy, scanning electron microscope and energy dispersive X ray analyzer were introduced to study the main causes of cycling deterioration of Ni/MH batteries.

Microstructure and electrochemical properties of low-temperature hydrogen storage alloy used in Ni/MH batteries

AB5 hydrogen storage alloys La0.54Ce0.28Pr0.18Ni4-xCo0.6Mn0.35Alx(x=0.1,0.2,0.3) were prepared by arc melting method under an Ar atmosphere. The results show that the contents of Ni and Al have obvious influences on the microstructure and electrochemical properties of the alloys. Both the lattice parameters and the cell volumes decrease with decreasing x value. Moreover,the discharge capacity at different temperatures,the high rate discharge property,and the cycling life of the alloy electrode are also in close relationship with the x value. When x value increases from 0.1 to 0.3,the discharge capacities with a discharge current density of 60 mA/g slightly decreases at 25 ℃,but evidently deteriorates at -40 ℃,the high-rate property gravely decreases,and the cycle life of the alloy electrode is improved in some extent. Therefore,it is meaningful to control Al content for the AB5 hydrogen storage alloys used in Ni/MH batteries.

High-rate capability of spinel LiNi_(0.05)Mn_(1.95)O_4 cathode for Li-ion batteries prepared via coprecipitated precursor

Spinel LiNi0.05Mn1.95O4 cathode material for lithium ion batteries was synthesized by solid-state reaction from coprecipitated Ni-Mn hydroxide precursors and characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and galvanostatic charge-discharge tests. It is found that LiNi0.05Mn1.95O4 powder has an ordered cubic spinel phase(space group Fd 3m) and exhibits superior rate capability. After 450 cycles,the LiNi0.05Mn1.95O4/carbonaceous mesophase spheres(CMS) Li-ion batteries can retain 96.0% and 93.3% capacity at 5C and 10C charge/discharge rate,respectively,compared with 85.3%(5C) and 80.5%(10C) retention for LiMn2O4 batteries. However,the initial discharge capacity of LiNi0.05Mn1.95O4/CMS batteries at 1C charge/discharge rate(96.20 mA·h/g) is slightly lower than that of the LiMn2O4 batteries(100.98 mA·h/g) due to the increased average oxidation state of Mn in LiNi0.05Mn1.95O4.

Study on Degradation and Recovery of AB_5-Type Hydrogen Storage Alloy Used in Ni-MH Batteries

The influences of deeply overdischarge on the negative electrode alloy of Ni/MH battery were studied. After overdischarge, La(OH) 3 and Al(OH) 3 are found to form in the negative electrode through XRD analysis. The hydrogen storage alloy powder from spent Ni/MH batteries was recovered by chemical and melting method according to degradation mechanism. The structure of recovered alloy was measured by XRD. The experimental results demonstrate that the alloy structure is CaCu 5 type. The constant current charge/discharge test was carried out to the original alloy and the recovered alloy. It is found that their discharge capacities are almost the same, but the discharge potential of the recovered alloy is higher than that of the original alloy. The results of cyclic lifetime test demonstrate that the capacity degradation of the recovered alloy is slower than that of the original one.