Research on Preparation and Electrochemical Performance of the High Compacted Density Ni-Co-Mn Ternary Cathode Materials

The high compacted density LiNi0.5-xCo0.2Mn0.3MgxO2 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 Ni0.5Co0.2Mn0.3 (OH)2, Li2CO3 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 LiNi0.4985Co0.2Mn0.3 Mg0.0015O2 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/cm3. 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.

Influence of Cathode Modification by Chitosan and Fe^(3+)on the Electrochemical Performance of Marine Sediment Microbial Fuel Cell

The electrochemical performances of cathode play a key role in the marine sediment microbial fuel cells(MSMFCs)as a long lasting power source to drive instruments,especially when the dissolved oxygen concentration is very low in seawater.A CTS-Fe^(3+)modified cathode is prepared here by grafting chitosan(CTS)on a carbon fiber surface and then chelating Fe^(3+)through the coordination process.The electrochemical performance in seawater and the output power of the assembled MSMFCs are both studied.The results show that the exchange current densities of CTS and the CTS-Fe^(3+)group are 5.5 and 6.2 times higher than that of the blank group,respectively.The potential of the CTS-Fe^(3+)modified cathode increases by 138 mV.The output power of the fuel cell(613.0 mW m^(-2))assembled with CTS-Fe^(3+)is 54 times larger than that of the blank group(11.4 mW m^(-2))and the current output corresponding with the maximum power output also increases by 56 times.Due to the valence conversion between Fe^(3+)and Fe^(2+)on the modified cathode,the kinetic activity of the dissolved oxygen reduction is accelerated and the depolarization capability of the cathode is enhanced,resulting higher cell power.On the basis of this study,the new cathode materials will be encouraged to design with the complex of iron ion in natural seawater as the catalysis for oxygen reduction to improve the cell power in deep sea.

Enhanced Electrochemical Performances of Ni Doped Cr_(8)O_(21)Cathode Materials for Lithium-ion Batteries

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.

Ce&F multifunctional modification improves the electrochemical performance of LiCoO_(2)at 4.60 V

Lithium cobalt oxide(LiCoO_(2))is proverbially employed as cathode materials of lithium-ion batteries attributed to the high theoretical capacity,and currently,it is developing towards higher cut-off voltages in the pursuit of higher energy density.However,it suffers from serious structural degradation and surface side reactions,in particular,at the voltage above 4.60 V,leading to rapid decay of the battery life.Taking into account the desirable oxygen buffering property and the fast ion mobility characteristic of cerium oxide fluoride,in this work,we prepared Ce&F co-modified LiCoO_(2)by using the precursors of Ce(NO_(3))_(3)·6H_(2)O and NH_(4)F,and evaluated the electrochemical performance under voltages exceeding 4.60 V.The results indicated that the modified samples have multiphase heterostructure of surface CeO_(2-x)and unique Ce-O-F solid solution phase.At 3.0–4.60 V and 25℃,the preferred sample LCO-0.5Ce-0.3F has a high initial discharge specific capacity of 221.9 mA h g^(-1)at 0.1 C,with the retention of 80.3%and 89.6%after 300 cycles at 1 and 5 C,comparing with the pristine LCO(56.4%and 22.6%).And at 3.0–4.65 V,its retention is 64.0%after 300 cycles at 1 C,versus 8.5%of the pristine LCO.Through structural characterizations and DFT calculations,it suggests that Ce^(4+)&F^(-)co-doping suppresses the H3 to H1/3 irreversible phase transition,stabilizes the lattice structure,and reduces the redox activity of the lattice oxygen by modulating the Co 3d–O 2p energy band,consequently improving the electrochemical performance of LiCoO_(2)at high voltages.

Influence of Mg and Ti on the microstructure and electrochemical performance of aluminum alloy sacrificial anodes

The experiments focused on the influence of magnesium and titanium as additional alloying elements on the microstructure and electro-chemical behavior of Al-Zn-In sacrificial anodes. The electrochemical behavior of the aluminum sacrificial anode with 3 wt.% sodium chloride solution was studied by electrochemical impedance spectroscopy (EIS) tests. It was found that a microstructure with few precipitates and refined grains could be achieved by adding 1 wt.% Mg and 0.05 wt.% Ti to the Al-Zn-In alloy,resulting in the improved current capacity and efficiency of the alloy. The equivalent circuit based on the EIS experimental data revealed less corrosion and lower adsorbed corrosion production on the surface of the aluminum alloy with a combination of 1 wt.% Mg and 0.05 wt.% Ti,which suggested that the corrosion behavior seemed to be strongly related to the presence of precipitate particles in the aluminum alloy,and moderate amounts of precipitate particles could be beneficial to the electrochemical performance of the aluminum alloy sacrificial anode.

Amorphous Zr(OH)4 coated LiNi0.915Co0.075Al0.01O2 cathode material with enhanced electrochemical performance for lithium ion batteries

LiNi_(0.915)Co_(0.075)Al_(0.01)O_2(NCA) with Zr(OH)_4 coating is demonstrated as high performance cathode material for lithium ion batteries(LIBs). The coated materials are synthesized via a simple dry coating method of NCA with Zr(OH)_4 powders, and then characterized with scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS). Experimental results show that amorphous Zr(OH)_4 powders have been successfully coated on the surface of spherical NCA particles, exhibiting improved electrochemical performance. 0.50 wt% Zr(OH)_4 coated NCA delivers a capacity of 197.6 mAh/g at the first cycle and 154.3 mAh/g after 100 cycles with a capacity retention of 78.1% at 1 C rate. In comparison, the pure NCA shows a capacity of 194.6 mAh/g at the first cycle and 142.5 mAh/g after 100 cycles with a capacity retention of 73.2% at 1 C rate. Electrochemical impedance spectroscopy(EIS) results show that the coated material exhibits a lower resistance, indicating that the coating layer can efficiently suppress transition metals dissolution and decrease the side reactions at the surface between the electrode and electrolyte. Therefore, surface coating with amorphous Zr(OH)_4 is a simple and useful method to enhance the electrochemical performance of NCA-based materials for the cathode of LIBs.

Modified carbon cloth as positive electrode with high electrochemical performance for vanadium redox flow batteries

Carbon cloth modified by hydrothermal treatment in ammonia water is developed as the positive electrode with high electrochemical performance for vanadium redox flow batteries.The SEM shows that the treatment has no obvious influence on the morphology of carbon cloth.XPS measurements indicate that the nitrogenous functional groups can be introduced on the surface of carbon cloth successfully.The electrochemical performance of V(IV)/V(V) redox couple on the prepared electrode is evaluated with cyclic voltammetry and linear sweep voltammetry measurements.The N-doped carbon cloth exhibits outstanding electrochemical activity and reversibility toward V(IV)/V(V) redox couple.The rate constant of V(IV)/V(V) redox reaction on carbon cloth can increase to 2.27 × 10^(-4)cm/s from 1.47 × 10^(-4)cm/s after nitrogen doping.The cell using N-doped carbon cloth as positive electrode has larger discharge capacity and higher energy efficiency compared with the cell using pristine carbon cloth.The average energy efficiency of the cell using N-doped carbon cloth for 50 cycles at 30 m A/cm^2 is 87.8%,4.3% larger than that of the cell using pristine carbon cloth.It indicates that the N-doped carbon cloth has a promise application prospect in vanadium redox flow batteries.

Electrochemical performance of C-La^(3+) codoped LiFePO_4 synthesized by microwave heating

La3+ was selected to elevate the lattice electronic conductivity of LiFePO4,and LiFePO4/(C+La3+) cathode powders were synthesized by microwave heating using a domestic microwave oven for 35 min. The microstructures and morphologies of the synthesized materials were investigated by XRD and SEM. The electrochemical performances were evaluated by galvanostatic charge-discharge. The electrochemical performance of LiFePO4 with different La3+ contents was studied. Results indicated that the initial specific discharge capacity of LiFePO4/(C+La3+) composites with 2% La3+ (116.3 mAh/g) was better than that of LiFePO4/C (105.4 mAh/g). The addition of La3+ further improved the electrochemical properties. So the codoping is an effective method to improve the electrochemical performance.

Electrochemical performance of Al-substituted Li_3V_2(PO_4)_3 cathode materials synthesized by sol-gel method

The effect of Al-substitution on the electrochemical performances of Li3V2(PO4)3 cathode materials was studied.Samples with stoichiometric proportion of Li3AlxV2-x(PO4)3(x=0,0.05,0.10)were prepared by adding Al(NO3)3 in the raw materials of Li3V2(PO4)3.The XRD analysis shows that the Al-substituted Li3V2(PO4)3 has the same monoclinic structure as the un-substituted Li3V2(PO4)3.The SEM images show that Al-substituted Li3V2(PO4)3 has regular and uniform particles.The electrochemical measurements show that Al-substitution can improve the rate capability of cathode materials.The Li3Al0.05V1.95(PO4)3 sample shows the best high-rate performance.The discharge capacity at 1C rate is 119 mA·h/g with 30th capacity retention rate about 92.97%.The electrode reaction reversibility and electronic conductivity are enhanced,and the charge transfer resistance decreases through Al-substitution.The improved electrochemical performances of Al-substituted Li3V2(PO4)3 cathode materials offer some favorable properties for their commercial application.

Influence of graphene oxide on electrochemical performance of Si anode material for lithium-ion batteries

We have developed a Si/graphene oxide electrode synthesized via ultrasonication-stirring method under alkaline condition. Scanning electron microscopy(SEM), transmission electron microscope(TEM), EDS dot-mapping and high-resolution transmission electron microscopy(HRTEM) results show that Si particles are evenly dispersed on the graphene oxide sheets. The electrochemical performance was investigated by galvanostatic charge/discharge tests at room temperature. The results revealed that Si/graphene oxide electrode exhibited a high reversible capacity of 2825 mAh/g with a coulombic efficiency of 94.6%at 100 mA/g after 15 cycles and a capacity retention of 70.8% after 105 cycles at 4000 mA/g. These performance parameters show a great potential in the high-performance batteries application for portable electronics, electric vehicles and renewable energy storage.

Selective adsorption-involved formation of NMC532/PANI microparticles with high ageing resistance and improved electrochemical performance

Surface modification offers an alternative strategy to improve both ageing resistance and electrochemical performance of cathode materials for lithium-ion batteries.From the viewpoint of real application,surface modification of the cathode materials should be designed with scientificity,effectiveness,low cost,less Li+leaching,and remained tap density.In this contribution,a selective adsorption-involved in-situ growth of polyaniline(PANI)nanoparticles on LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(2)(NMC532)has been designed through a room-temperature-and-pressure chemical vapor deposition technique.The selective growth of PANTI on NMC532 is based on theoretical computation results that multivalent Ni,Mn,and Co are capable of specifically conjugating and activating aniline molecules and,hence,initiating in-situ oxidation polymerization.With only trace amount of aniline monomer,the resulting PANI nanoparticles-inlaid NMC532 microparticles can endure four-month ageing in ambient atmosphere and exhibit improved electrochemical performance at both room temperature and 55℃ compared with pristine NMC532.The improved electrochemical performance of NMC532/PANI is attributed to the enhanced structural stability of NMC532 and inhibited side reactions related to Li_(2)CO_(3) formation,PVDF degradation,electrolyte decomposition,and transition-metal dissolution,owing to PANI modification.

Structures and electrochemical performances of La_(0.75-x)Zr_xMg_(0.25)Ni_(3.2)Co_(0.2)Al_(0.1) (x=0-0.2) electrode alloys prepared by melt spinning

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.

Sandwich-like structure C/SiO_(x)@graphene anode material with high electrochemical performance for lithium ion batteries

Silicon suboxide(SiO_(x),0<x<2)is recognized as one of the next-generation anode materials for high-energy-density lithium ion batteries(LIBs)due to its high theoretical specific capacity and abundant resource.However,the severe mechanical instability arising from large volume variation upon charge/discharge cycles frustrates its electrochemical performance.Here we propose a well-designed sandwich-like structure with sandwiched SiO_(x) nanoparticles between graphene sheets and amorphous carbon-coating layer so as to improve the structural stability of SiO_(x) anode materials during cycling.Graphene sheets and carbon layer together construct a three-dimensional conductive network around SiO_(x) particles,which not only improves the electrode reactions kinetics,but also homogenizes local current density and thus volume variation on SiO_(x) surface.Moreover,Si-O-C bonds between SiO_(x) and graphene endow the strong particle adhesion on graphene sheets,which prevents SiO_(x) peeling from graphene sheets.Owing to the synergetic effects of the structural advantages,the C/SiO_(x)@graphene material exhib-its an excellent cyclic performance such as 890 mAh/g at 0.1 C rate and 73.7%capacity retention after 100 cycles.In addition,it also delivers superior rate capability with a capacity recovery of 886 mAh/g(93.7%recovery rate)after 35 cycles of ascending steps at current range of 0.1-5 C and finally back to 0.1 C.This study provides a novel strategy to improve the structural stability of high-capacity anode materials for lithium/sodium ion batteries.

One-time sintering process to modify xLi2MnO3(1-x)LiMO2 hollow architecture and studying their enhanced electrochemical performances

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.

Boosting the Electrochemical Performance of Li-and Mn-Rich Cathodes by a Three-in-One Strategy

There are plenty of issues need to be solved before the practi-cal application of Li-and Mn-rich cathodes,including the detrimental voltage decay and mediocre rate capability,etc.Element doping can e ectively solve the above problems,but cause the loss of capacity.The introduction of appropriate defects can compensate the capacity loss;however,it will lead to structural mismatch and stress accumulation.Herein,a three-in-one method that combines cation–polyanion co-doping,defect construction,and stress engineering is pro-posed.The co-doped Na^(+)/SO_(4)^(2-)can stabilize the layer framework and enhance the capacity and voltage stability.The induced defects would activate more reac-tion sites and promote the electrochemical performance.Meanwhile,the unique alternately distributed defect bands and crystal bands structure can alleviate the stress accumulation caused by changes of cell parameters upon cycling.Consequently,the modified sample retains a capacity of 273 mAh g^(-1)with a high-capacity retention of 94.1%after 100 cycles at 0.2 C,and 152 mAh g^(-1)after 1000 cycles at 2 C,the corresponding voltage attenuation is less than 0.907 mV per cycle.

Preparation of Large-Scale Double-Side BDD Electrodes and Their Electrochemical Performances

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.

High-temperature electrochemical performance and phase composition of Ti_(0.7) Zr_(0.5) V_(0.2) Mn_(1.8-x)Ni_x hydrogen storage electrode alloys

The rapid development of electric vehicles demands the development of high performance nickel metal hydride battery that is able to endure high temperature. The discharge properties of Ti 0.7 Zr 0.5 V 0.2 Mn 1.8- x Ni x ( x =0.4, 0.8, 1.1, 1.4, 1.7)hydrogen storage alloys was investigated and its phase composition was analyzed using X ray diffraction. The results show that the cycling life was improved as the content of nickel increases. When x =0.4, 0.8, 1.1 and 1.4, the main phase is MgZn 2 type C14 Laves phase and the second one is cubic TiNi phase. When x =1.7, the Laves phase structure disappears. EDAS analysis shows that the increase of nickel content is effective in suppressing the dissolution of vanadium component in alloys. [

Improving Electrochemical Performance of Cellulose Fiber-based Supercapacitor Electrode Using Polypyrrole-wrapped Iron Oxyhydroxide

Polypyrrole(PPy)@cellulose fiber-based composites have been widely investigated as electrode materials for use in flexible supercapacitors.However,they cannot readily provide high specific capacitance and cyclic stability owing to their inherent drawbacks,such as high resistance,Weber impedance,and volume expansion or collapse during charging/discharging.In this study,iron oxyhydroxide(FeOOH)is incorporated in the abovementioned composite to decrease the equivalent series resistance,charge transfer resistance,and Weber impedance,thereby enhancing electron transfer and ion diffusion,which results in superior electrochemical performance.The PPy-wrapped FeOOH@cellulose fiber-based composite electrode with the molar ratio of FeSO_(4) to NaBH4 of 1∶1 exhibits a high specific capacitance of 513.8 F/g at a current density of 0.2 A/g,as well as an excellent capacitance retention of 89.4% after 1000 cycles.

Humic Acid and Iron Chelation Modified Anode Improves the Electrochemical Performance of Marine Sediment Microbial Fuel Cell

Marine sediment microbial fuel cell(MSMFCs)can be utilized as a long lasting power source to drive small instruments to work for long time on ocean floor and its higher power has a significant meaning for practical application.Anode modification can greatly improve the performance of MSMFCs.Herein,humic acid(HA)and humic acid-iron ion complex(HA-Fe)were used to modify the anode for constructing a better MSMFCs.The results indicated that HA-Fe modified anode,better than HA modification,significantly improved the MSMFCs cell power output.The maximum power density of HA-Fe modified MSMFCs is 165.3 mW m−2,which are 6.5-folds of blank MSMFCs.The number of microorganisms on anode,redox activity,and relative kinetic activity were 1.8-,6.1-,and 13.1-folds of blank MSMFCs,respectively.The MSMFCs improvement would be attributed to the electron transfer media of HA and the valence conversion of Fe ions.A synergistic interaction between the naturally occurring HA and Fe ions on the anodic surface in marine sediments would make the modified anodes have‘renewable’characteristics,which is beneficial for the MSMFCs to maintain its long-term higher power.

Synthesis and Characterization of Polyaniline/MgTiO_(3) Composite with Excellent Thermal and Electrochemical Performance

This article explores the effects of doping ferroelectric materials MgTiO_(3) with different proportions on the properties of polyaniline(PANI).PANI/MgTiO_(3) composites were prepared by in-situ composite method.Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD)were used to characterize the structure of the composites.Scanning electron microscope(SEM)was used to characterize the morphology of the composites.The thermal stability of the composites was investigated by thermogravimetry(TG)and derivative thermogravimetry(DTG).Electrochemical methods(cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS),and constant current charge-discharge test)were used to compare and analyze the electrochemical performance of the composites.TG-DTG analysis and electrochemical experiments all show that the thermal stability and electrochemical properties of the PANI/MgTiO_(3) composite with a mass ratio of 82/18(w/w)are the best.The results indicate that there is a synergistic effect between PANI and MgTiO_(3),which improves the performances of the PANI when the appropriate amount of MgTiO_(3) is added.