Synthesis and electrochemical characterization of a new Se-doped spinel material for lithium secondary batteries

A new Se-doped spinel material, LiAl_0.18Se_0.02Mn_1.8O₄ powder with a phase-pure polycrystalline was synthesized by a sol–gel method. The material in the 3 V region (2.4 3.5 V) and both the 3 and 4 V region (2.4 4.4 V) initially deliver a discharge capacity of 81 and 178 mA h g^–1 which increase with cycling to reach 110 and 204 after 50 cycles, respectively. The material shows excellent cycleability in the 4 V region (3.0 4.4 V) with almost no capacity loss. The structural integrity of the Se-doped spinel was characterized by charge–discharge cycling tests and X-;ray diffraction.     

Binder effect on cycling performance of silicon/carbon composite anodes for lithium ion batteries

The cycling performance of a silicon/carbon composite anode has been significantly enhanced by using acrylic adhesive and modified acrylic adhesive as binder to fabricate the electrodes for lithium ion batteries. The capacity retentions of Si/C composite electrodes bound by acrylic adhesive and modified acrylic adhesive are 79% and 90% after 50 cycles, respectively. These two binders are electrochemically stable in the organic electrolyte in the working window. They also show larger adhesion strength between the coating and the Cu current collector as well as smaller solvent absorption in the electrolyte solvent than polyvinylidene fluoride (PVDF). Furthermore, sodium carboxyl methyl cellulose (CMC) plays an important role on improving the properties of acrylic adhesive, which increases the adhesive strength of acrylic adhesive and improves the activation of the electrodes.     

废旧锂电池中有价金属回收及三元正极材料的再制备

探讨了磷酸体系下不同因素对废旧锂电池正极材料中有价金属浸出效率的影响，结果表明：在浸出时间60min，反应温度60℃，磷酸浓度2mol/L，液固比20mL/g，还原剂(H₂O₂)体积分数为4%时，可得最佳浸出效果，Co、Li、Mn、Ni浸出效率分别可达96.3%、100%、98.8%和99.5%；浸出液添加相应比例金属离子，采用草酸共沉淀法制备前体材料(Ni_1/3Co_1/3Mn_1/3)C₂O₄，并得到相应再生磷酸溶液。再生磷酸进行循环浸出实验，实验研究结果表明：循环浸出5次之后Li的浸出率仍可保持在90.1%，而Co、Mn和Ni的浸出率在75.0%以上。前体添加锂源Li₂CO₃煅烧合成Li(Ni_1/3Co_1/3Mn_1/3)O₂材料，考察了不同温度对Li(Ni_1/3Co_1/3Mn_1/3)O₂材料合成的影响，结果显示，当合成温度为800℃时，得到的材料性能最优良，初次放电容量可达136.4mA·h/g。在0.2C下经过50圈循环后容量保持率为97.2%。     

Possible use of methylbenzenes as electrolyte additives for improving the overcharge tolerances of Li-ion batteries

Based on the voltammetric behaviour of a series of methyl-substituted benzenes in 1M LiPF₆/EC-DMC electrolyte, xylene was selected and tested as an electrolyte additive for overcharge protection of Li-ion batteries. From the overcharge curves, CV behaviour and SEM observations of the cells in the presence of xylene, it was found that the additive can polymerize at the overcharged voltage to form a dense layer of isolating polymer film at the cathode surface, which blocks off further oxidation of the electroactive material and electrolyte and, therefore, improves the overcharge tolerance of the Li-ion battery. In addition, the xylene additive has shown only a slight influence on the cycling behaviour.     

磷酸铁锂锂离子电池正极材料的研究

锂离子电池是绿色高能可充电池，具有工作电压高、比能量大、自放电小、循环寿命长、无记忆效应、无环境污染等突出优点。本文从磷酸铁锂的结构与性能、材料的制备方法、改性、粒径控制等几方面综述了近年来对橄榄石型磷酸铁锂（LiFePO4）锂离子电池正极材料的研究进展。材料的粒度大小及其分布、离子和电子的传导能力对产品的电化学性能影响很大。在制备时，采用惰性气氛、掺杂导电材料和控制晶粒生长制备粉体是获得性能优良的LiFePO4的有效方法。     

Electrochemical performance of nanocrystalline Li3V2(PO4)3/carbon composite material synthesized by a novel sol–gel method

A novel sol–gel method based on V₂O₅·nH₂O hydro-gel was developed to synthesize nanocrystalline Li₃V₂(PO₄)₃/carbon composite material. In this route, V₂O₅·nH₂O hydro-gel, NH₄H₂PO₄, Li₂CO₃ and high-surface-area carbon were used as starting materials to prepare precursor, and the Li₃V₂(PO₄)₃/carbon was obtained by sintering precursor at 750 °C for 4 h in flowing argon. The sol–gel synthesis ensures homogeneity of the precursors and improved reactivity. The sample was characterized by XRD, SEM and TEM. X-ray diffraction results show Li₃V₂(PO₄)₃ sample is monoclinic structure with the space group of P2₁/n. The TEM image indicates that the Li₃V₂(PO₄)₃ particles modified by conductive carbon are about 70 nm in diameter. The Li₃V₂(PO₄)₃/carbon system showed that the discharge capacities in the first and 50th cycle are about 155.3 and 143.6 mAh/g, respectively, in the range of 3.0–4.8 V. The sol–gel method is fit for the preparation of Li₃V₂(PO₄)₃/carbon composite material which may offer some favorable properties for commercial application.     

Structural, electrochemical and thermal properties of LiNi0.8−yTiyCo0.2O2 as cathode materials for lithium ion battery

Multiple substitution compounds with the formula LiNi_0.8−yTi_yCo_0.2O₂ (0≤y≤0.1) were synthesized by sol-gel method using citric acid as a chelating agent. The effects of titanium substitution on the structural, electrochemical and thermal properties of the cathode materials are investigated. A solid solution phase (R-3m) is observed in the range of 0≤y≤0.1 for the titanium-doped materials. X-ray photoelectron spectroscopy (XPS) shows that there are Ni³⁺, Ni²⁺, Co³⁺, Co²⁺ and Ti⁴⁺ five transition metal ions in titanium-doped materials. Rietveld refinement of X-ray diffraction (XRD) patterns indicates that titanium substitution changes the materials’ structure with different cationic distribution. An increase of the Ni/Co amount in the 3a Li site is found with the addition of titanium amount. An improved cycling performance is observed for titanium-doped cathode materials, which is interpreted to a significant suppression of phase transitions and lattice changes during cycling. The thermal stability of titanium-doped materials is also improved, which can be attributed to its lower oxidation ability and enhanced structural stability at delithiated state.     

In situ composite of nano SiO2-P(VDF-HFP) porous polymer electrolytes for Li-ion batteries

Nano SiO₂-P(VDF-HFP) composite porous membranes were prepared as the matrix of porous polymer electrolytes through in situ composite method based on hydrolysis of tetraethoxysilane and phase inversion. SEM, TEM, DSC and AC impedance analysis were carried out. It is found that the in situ prepared nano silica was homogeneously dispersed in the polymeric matrix, enhanced conductivity and electrochemical stability of porous polymer electrolytes, and improved the stability of the electrolytes against lithium metal electrodes. The in situ composite method was found to be much better than the direct composite method in lowering the interfacial resistance between electrolyte and lithium metal electrode. Moreover, cycle test of lithium batteries using lithium metal as anode and sulfur composite material as cathode showed that the electrolyte based on in situ composite of silica presented stable charge-discharge behavior and little capacity loss of battery.     

球形磷酸铁锂材料的制备及其18650电池的测试

采用高能球磨和喷雾干燥法制备了球形磷酸铁锂材料LFP-1,并制作18650实装电池,测试电极片的压实密度,同时选择一种商业化磷酸铁锂材料LFP-2作为对比。测试结果显示,2种LFP材料均由平均粒径为300~500 nm的一次颗粒组成,比表面积为13~15 m²/g,碳质量分数为1.5%左右。通过CR2032纽扣型电池充放电测试表明,在0.2C时,LFP-1的比放电容量约为165 mA·h/g,与商业化磷酸铁锂材料LFP-2相近。制备18650电池的结果表明,商业化磷酸铁锂LFP-2材料制备的电极片的最高压实密度可以达到2.52 g/cm³,显著高于实验室制得的磷酸铁锂材料LFP-1的最高压实密度2.25 g/cm³,这可能与材料的颗粒粒度分布不同有关。     

A novel lithium intercalation compound based on the layered structure of lithium nitridonickelates Li3−2xNixN

New lithium nickel nitrides Li_3−2xNi_xN (0.20 ≤ x ≤ 0.60) have been prepared and investigated as negative electrode in the 0.85/0.02 V potential window. These materials are prepared from a Ni/Li₃N mixture at 700 °C under a nitrogen flow. Their structural characteristics as well as their electrochemical behaviour are investigated as a function of the nickel content. For the first time are reported here the electrochemical properties of a lithium intercalation compound based on a layered nitride structure. The Li_3−2xNi_xN compounds can be reversibly reduced and oxidized around 0.5 V versus Li/Li⁺ leading to specific capacities in the range 120-160 mAh/g depending on the nickel content and the C rate. Due to a large number of lithium vacancies, the structural stability provides an excellent capacity retention of the specific capacity upon cycling.