Low-strain Co-free Li-rich layered cathode with excellent voltage and capacity stability

Owing to the inherent advantages of low cost and high capacity, cobalt(Co)-free lithium(Li)-rich layered oxides have become one of the most promising cathodes for next-generation high-energy lithium-ion batteries. However, these familial cathodes suffer from serious voltage decay due to many reasons, such as oxygen release and transition metal(TM) migration, which are closely related to nanoscale strain evolution. Here, by combining the synergistic effects of surface integration, bulk doping, an...     

Improvement of electrochemical properties of lithium-rich manganese-based cathode materials by Ta2O5

Journal of Solid State Electrochemistry - As one of the most promising cathodes for next-generation lithium-ion batteries, lithium-rich materials have been widely studied because of their excellent...     

Distinctive electrochemical performance of novel Fe-based Li-rich cathode material prepared by molten salt method for lithium-ion batteries

For constructing next-generation lithium-ion batteries with advanced performances,pursuit of highcapacity Li-rich cathodes has caused considerable attention.So far,the low discharge specific capacity and serious capacity fading are strangling the development of Fe-based Li-rich materials.To activate the extra-capacity of Fe-based Li-rich cathode materials,a facile molten salt method is exploited using an alkaline mixture of LiOH–LiNO_3–Li_2O_2 in this work.The prepared Li_(1.09)(Fe_(0.2)Ni_(0.3)Mn_(0.5))_(0.91)O_2 material yields high discharge specific capacity and good cycling stability.The discharge specific capacity shows an upward tendency at 0.1 C.After 60 cycles,a high reversible specific capacity of ～250 m Ah g~(-1)is delivered.The redox of Fe~(3+)/Fe~(4+)and Mn~(3+)/Mn~(4+)are gradually activated during cycling.Notably,the redox reaction of Fe~(2+)/Fe~(3+)can be observed reversibly below 2 V,which is quite different from the material prepared by a traditional co-precipitation method.The stable morphology of fine nanoparticles(100–300 nm)is considered benefiting for the distinctive electrochemical performances of Li_(1.09)(Fe_(0.2)Ni_(0.3)Mn_(0.5))_(0.91)O_2.This study demonstrates that molten salt method is an inexpensive and effective approach to activate the extra capacity of Fe-based Li-rich cathode material for high-performance lithium-ion batteries.     

One-pot electrosynthesis and physicochemical properties of multifunctional material based on graphene oxide,poly-o-phenylenediamine,and silicotungstic acid

Journal of Solid State Electrochemistry - The methods of silicotungstic acid (SiW) immobilization on conducting substrates were studied. For SiW immobilization by codeposition,...     

LiPO2F2 electrolyte additive for high-performance Li-rich cathode material

Li-rich layered oxide cathodes have received considerable attention because of the high operating poten-tial and specific capacity.However,the structural instab...     

Effects of microwave irradiation on the electrochemical performance of manganese-based cathode materials for lithium-ion batteries

Microwave-assisted synthesis has continued to be adopted for the preparation of high-performance manganese-based cathode materials for lithium-ion batteries. The technique is fast, energy-efficient and has significant positive impacts on the general physico-chemical properties of the cathode materials: LiMn₂O₄, LiMn_1.5Ni_0.5O₄, and lithium nickel manganese cobalt oxides. Despite the advantages of microwave-assisted synthesis, this review reveals that the application is still limited. In our opinion, increased basic knowledge of the microwave process and availability of safe and reliable instrumentation could be a great opportunity for the commercial realization of low-cost and energy-dense Mn-based cathode materials for the next-generation lithium-ion batteries.     

Structural evolution and the capacity fade mechanism upon long-term cycling in Li-rich cathode material

High capacity Li-rich layered cathode Li(Li(0.2)Mn(0.54)Ni(0.13)Co(0.13))O(2) and doped one are investigated to understand mechanisms of capacity fade as well as voltage decrease upon long-term cycling. Detailed electrochemical analysis reveals a phase-separation-like behavior with increase in the cycle number, which is responsible for gradual reduction in discharge voltage. X-ray photoelectron spectroscopy (XPS), transmission electron microscope coupled with energy dispersive X-ray spectroscopy (TEM-EDS) and inductively coupled plasma emission spectrometry (ICP) analysis results show increase in valence of transition metals on the surface of powder at a fully discharged state in addition to surface dissolution of Ni, leading to rapid capacity loss. High resolution transmission electron microscopy (HR-TEM) shows a phase transformation from original layered structure into spinel-like nano-domains in local structure. Though such an unexpected structural change is unfavorable because of lower output voltage, it is observed to be beneficial for high-rate performance.     

Synthesis,microstructure, and electrochemical performance of Li-rich layered oxide cathode materials for Li-ion batteries

Russian Chemical Bulletin - Li-rich layered oxides Li1.2Mn0.54Ni0.13Co0.13O2 were synthesized by modified Pechini method using various compositions of the reaction mixture. Difference in the...     

Morphology regulation and electrochemical properties of cathode material V6O13 for lithium-ion battery

Journal of Solid State Electrochemistry - A V6O13 micro-flower was synthesized via a facial hydrothermal method using ammonium metavanadate and oxalic acid dihydrate and combined with subsequent...     

PVDF-HFP composite polymer electrolyte with excellent electrochemical properties for Li-ion batteries

Poly (vinylidene fluoride-co-hexafluoropropylene)-based composite polymer electrolyte (CPE) was prepared by phase inversion technique. In this work, we first applied a novel surface-modified sub-micro-sized alumina, PC-401, as ceramic filler. Various electrochemical methods were applied to investigate the electrochemical properties of the polymer electrolytes. We found that the CPE with 10 wt.% PC-401 has excellent electrochemical properties, including the ionic conductivity as high as 0.89 mS cm⁻¹ and the Li-ion transference number of 0.46. Polymer Li-ion batteries using LiFePO₄ as cathode active material exhibited excellent cycling and high-temperature performances. PC-401 shows a promising applicability in the preparation of polymer electrolyte with high electrochemical properties.     

V2O5@TiO2 composite as cathode material for lithium-ion storage with excellent performance

Journal of Solid State Electrochemistry - V2O5 is a promising candidate for cathode active material for Li-ion batteries due to its high theoretical specific capacity but suffers from poor rate...     

A bi-component polyoxometalate-derivative cathode material showed impressive electrochemical performance for the aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries are recently gaining incremental attention because of low cost and material abundance, but their development is plagued by limited choices of cathode materials with satisfactory cycling performance. The polyoxometalates perform formidable redox stability and able to participate in multi-electron transfer, which was well-suited for energy storage. Herein, a bi-component polyoxometalate-derivative KNiVO (K₂[Ni(H₂O)₆]₂[V₁₀O₂₈]·4H₂O polyoxometalates after annealing) is firstly demonstrated as a cathode material for aqueous ZIBs. The layered KV₃O₈ (KVO) In the bi-component material constitutes Zn²⁺ migration and storage channels (K⁺ were substantially replaced by Zn²⁺ in the activation phase), and the three-dimensional NiV₃O₈ (NiVO) part acts as skeleton to stabilize the ion channels, which assist the cell to demonstrate a high-rate capacity and specific energy of 229.4 mAh/g and satisfactory cyclability (capacity retention of 99.1% after 4500 cycles at a current density of 4 A/g). These results prove the feasibility of POM as cathode materials precursor and put forward a novel pattern of the Zn²⁺ storage mechanism in the activated-KNiVO clusters, which also provide a new route for selecting or designing high-performance cathode for aqueous ZIBs and other advanced battery systems.     

Synthesis and electrochemical properties of Li1-xVxCryFe1-xPO4/C as a cathode material

Composites Li_(1-x)V_xCr_yFe_(1-y)PO_4/C (x=0.01,0.02;y=0.01,0.02) were synthesized by solid-state reaction method.The influence of the content of doping vanadium and chromium on the structure of Li_(1-x)V_xCr_yFe_(1-y)PO_4/C was investigated by XRD, while the morphology of powders was observed by SEM.The investigation of the electrochemical performances showed that the Li_(0.99)V_(0.02)Cr_(0.02)Fe_(0.98)PO_4/C material has a higher capacity.At 0.1 C discharging rate,it is capable of delivering reversible specific capacity of 163.8 mAh/g with fairly stable cycleability.     

Synthesis and electrochemical properties of K-doped LiFePO4/C composite as cathode material for lithium-ion batteries

Li_1 − x K _x FePO₄/C (x = 0, 0.03, 0.05, and 0.07) composites were synthesized at 700 °C in an argon atmosphere by carbon thermal reduction method. Based on X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analysis, the composite was ultrafine sphere-like particles with 100–300 nm size, and the lattice structure of LiFePO₄ was not destroyed by K doping, while the lattice volume was enlarged. The electrochemical properties were investigated by four-point probe conductivity measurements, galvanostatic charge and discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The results indicated that the capacity performance at high rate and cyclic stability were improved by doping an appropriate amount of K, which might be ascribed to the fact that the doped K ion expands Li ion diffusion pathway. Among the doped materials, the Li_0.97K_0.03FePO₄/C samples exhibited the best electrochemical activity, with the initial discharge capacity of 153.7 mAh g⁻¹ at 0.1 C and the capacity retention rate of about 92% after 50 cycles at above 1 C, 11% higher than undoped sample. Remarkably, it still showed good cycle retention at a high current rate of 10 C.     

Synthesis and electrochemical properties of Li1-xVxCryFe1-yPO4/C as a cathode material

Composites Li1-xVxCryFe1-yPO4/C（x=0.01, 0.02; y = 0.01, 0.02） were synthesized by solid-state reaction method. The influence of the content of doping vanadium and chromium on the structure of Li1-xVxCryFe1-yPO4/C was investigated by XRD, while the morphology of powders was observed by SEM. The investigation of the electrochemical performances showed that the Li0.99V0.01Cr0.02Fe0.98PO4/C material has a higher capacity. At 0.1 C discharging rate, it is capable of delivering reversible specific capacity of 163.8 mAh/g with fairly stable cycleability.     

Effects of carbon sources and carbon contents on the electrochemical properties of LiFePO4/C cathode material

LiFePO₄/C composites are prepared by using two types of carbon source: one using polymer (PAALi) and the other using sucrose. The physical characteristics of LiFePO₄/C composites are investigated by X-ray diffraction), scanning electron microscopy, BET, laser particle analyzer, and Raman spectroscopy. Their electrochemical properties are characterized by cyclic voltammograms, constant current charge–discharge, and electrochemical impedance spectra. These analyses indicate that the carbon source and carbon content have a great effect on the physical and electrochemical performances of LiFePO₄/C composites. An ideal carbon source and appropriate carbon content can effectively increase the lithium-ion diffusion coefficient and exchange current density, decrease the charge transfer resistance (R _ct), and enhance the electrochemical performances of LiFePO₄/C composite. The results show that PAALi is a better carbon source for the synthesis of LiFePO₄/C composites. When the carbon content is 4.11 wt.% (the molar ratio of PAALi/Li₂C₂O₄ was 2:1), as-prepared LiFePO₄/C composite shows the best combination between electrochemical performances and tap density.     

Electronic structure theory investigation on the electrochemical properties of cyclohexanone derivatives as organic carbonyl-based cathode material for lithium-ion batteries

Organic carbonyl-based compounds with redox-active site have recently gained full attention as organic cathode material in lithium-ion batteries (LIBs) owing to its high cyclability, low cost, high abundance, tunability of their chemical structure compared to traditionally used inorganic material. However, the utilization of organic carbonyl-based compounds in LIBs is limited to its poor charge capacity and dissolution of lower molecular weight species in electrolytes. In this study, we theoretically investigated five set of cyclohexanone derivatives (denoted as: H₁, H₂, H₃, H₄, and H₅) and influence of functional groups (-F and -NH₂) on their electrochemical properties using advanced level density functional theory (DFT) with the Perdew-Burke-Ernzenhof hybrid functional (PBE0) at 6-31+G(d,p) basis set. In line with the result gotten, the HOMO-LUMO results revealed that compound H₅ is the most reactive among the studied cyclohexanone derivatives exhibiting energy gap values of 0.552, 0.532, 0.772 eV for free optimized structures and structurally engineered structures with electron withdrawing group (EWG) and electron donating group (EDG) respectively. Also, results from electrochemical properties of the studied compounds lithiated with only one lithium atom displayed that compound H₂ exhibited interesting redox potential and energy density for all the studied structures in free optimized state (1108.28 W h kg^?1, 4.92 V vs Li/Li⁺), with EWG (648.22 W h kg^?1, 3.313 V Li/Li⁺), and with EDG (1002.4 W h kg^?1, 5.011 V vs Li/Li⁺). From our result, we can infer that compound H₂ and H₃ with corresponding redox potential, energy density and theoretical charge capacity value of 4.92 V vs Li/Li⁺, 1108.28 W h kg^?1, 225.26 mA h g^?1 and 5.168 V, 1041.61 W h kg^?1, 201.55 mA h g^?1 lithiated with only one lithium atom in free optimized state are the most suitable compounds to be employed as organic cathode material in lithium-ion batteries among all the investigated cyclohexanone derivatives.     

正极材料LiNi0.5C0.5O2的电化学性能研究

以聚丙烯酰胺（PAM）为分散剂用微波—固相复合加热技术合成了层状锂离子电池正极材料LiNi0.5C0.5O2。通过扫描电子显微镜（SEM）和X—射线粉末衍射（XRD）分析技术对材料的微观形貌和相结构进行了表征。恒电流充放电循环测试表明：材料的放电比容量高达154mAh／g，且有良好的循环性能。重点利用循环扫描伏安、计时电量和电化学交流阻抗测试技术，对材料在循环前后的电化学性能变化规律进行了探讨。结果表明，经过循环后材料的导电能力以及锂离子扩散能力都有了很大的提高。另外，材料中的锂含量对材料的导电能力也有很大的影响。