高倍率性能锂离子电池Li[Ni1/3Co1/3Mn1/3]O2正极材料的制备及其电化学性能

采用改进的碳酸盐共沉淀与高温固相法相结合的方法制备出了高倍率性能的锂离子电池正极材料Li[Ni_1/3Co_1/3Mn_1/3]O₂, 通过X射线衍射(XRD)、扫描电镜(SEM)、循环伏安扫描(CV)、电化学阻抗谱(EIS)和电化学性能测试等手段对材料进行表征. 结果表明, 该方法制备的材料具有良好的α-NaFeO₂型层状结构(R3m(166)), 一次粒径平均大小为157 nm, 二次颗粒成球形. 同传统碳酸盐制备得到的材料相比, 该材料具备良好的倍率性能和循环性能, 在2.7-4.3 V 电压范围内, 0.1C (1.0C=180 mA·g^-1)倍率下, 首次放电比容量为156.4mAh·g^-1, 库仑效率为81.9%. 在较高倍率下, 即0.5C、5.0C和20C时, 其放电比容量分别为136.9、111.3、81.3mAh·g^-1. 在1C倍率下100次循环容量保持率为92.9%, 高于传统共沉淀法得到的材料(87.0%).     

锂离子电池Sn-Al薄膜电极的制备及电化学性能研究

采用磁控溅射沉积技术制备了纳米级Sn-Al合金薄膜电极材料,并用X射线衍射和扫描电子显微镜进行表征,用高精度电池测试系统进行充放电和循环伏安测试.结果表明直流DC与射频RF两种不同的溅射方法制备的Sn-Al薄膜电极具有很大的性能差异,前者DC法制备的材料颗粒细小,表现出稳定的循环性能,其首次放电容量为1060 mAh/g,首次效率为71.7％,电极经过50次循环后比容量保持在700 mAh/g以上.后者RF法制备的材料颗粒较大,放电比容量开始上升,第五次循环后接着逐渐衰减,表现出较差的循环性能. 关键词： 锂离子电池 磁控溅射 Sn-Al合金 电化学性能     

Interaction of Li ions with ethylene carbonate (EC): Density functional theory calculations

Electronic structures of Li⁺ ion-ethylene carbonate (EC) complexes were studied by density functional theory. The structural, electronic and dynamical properties of Li⁺-EC complexes were studied for both an isolated EC molecule and clusters including Li⁺ ion. Our structural analysis showed only one type of Li⁺ coordination with EC through Li⁺?OC which was supported by the vibration spectral analysis for interaction between Li⁺ ion and a solvent (EC) molecule. It was analyzed that the solvation energy and Mulliken charge of Li+ ion solvated by EC molecule decrease with increase in number of EC molecule. However, electron affinity shows the opposite change. This analysis with solvation energy, electron affinity and Mulliken charge supported the stabilization of 4-coordinated solvation shell among [Li⁺(EC)_n]_n=1-5 complexes.     

Enhanced Corrosion Resistance and Discharge Performance of Mg-MnO2 Battery by Na2SiO3 Additive

Corrosion resistance and delayed action are major obstacles that severely limit the practical application of Mg alloy in battery fields. In this work, the effects of Na2SiO3 on the electrochemical behavior of the AZ31B Mg alloy in MgSO4-Mg(NO3)2 composite solution[0.14 mol/L MgSO4,1.86 mol/L Mg(NO3)2] were investigated. Electrochemical tests were carried out using electrochemical impedance spectroscopy, galvanostatic discharge, and linear sweep voltammograms. The results indicate that the impedance value increases by nearly fourfold, and the delayed time decreases from 2.1 s to 0.6s. Battery perfoniiance test reveals that the addition of Na2SiO3 significantly improves the discharge specific capacity of Mg-MnO2. The surface morphology and composition of corrosion products from Mg alloys were studied by scanning electron microscopy(SEM) and Fourier translonn infrared spectroscopy(FTIR), respectively. The SEM images of the AZ31B Mg alloys in composite solution with or without Na2SiO3 additive have an evident distinction due to the ionnation of new insoluble compound.FTIR result confirms that the corrosion products accumulated on the alloy surface in the electrolyte containing Na2SiO3 are mainly composed of Mg(OH)2, MgCO3, and MgSiO3.     

The synergic effects of Ca and Sm co-doping on the crystal structure and electrochemical performances of Li4-xCaxTi5-xSmxO12 anode material

Li₄Ti₅O₁₂ as the well-known “zero strain” anode material for lithium ion batteries (LIBs) suffers from low intrinsic ionic and electronic conductivity. The strategy of lattice doping has been widely taken to relieve the intrinsic issues. But the roles of the dopants are poorly understood. Herein, we propose to modulate the crystal structure and improve the electrochemical performance of Li₄Ti₅O₁₂ by substituting Li and Ti with Ca and Sm, respectively. The roles of Ca and Sm on the crystal structure and electrochemical performances have been comprehensively investigated by means of X-ray diffraction (XRD), neutron diffraction (ND) and electrochemical analysis. The Rietveld refinement of ND data indicate that Ca and Sm prefer to take 8a site (tetrahedral site) and 16d site (octahedral site), respectively. Li_3.98Ca_0.02Ti_4.98Sm_0.02O₁₂ has the longer Li1-O bond and shorter Ti-O bond length which reduces Li⁺ migration barrier as well as enhances the structure stability. Ca-Sm co-doping also alleviates the electrode polarization and enhances the reversibility of oxidation and reduction. In compared to bare Li₄Ti₅O₁₂ and Li_3.95Ca_0.05Ti_4.95Sm_0.05O₁₂, Li_3.98Ca_0.02Ti_4.98Sm_0.02O₁₂ electrode shows the lower charge transfer resistance, higher Li⁺ diffusion coefficient, better rate capability and cycling performance. The proposed insights on the roles of dopants are also instructive to design high performance electrode materials by lattice doping.     

Polyanionic Compounds for Potassium‐Ion Batteries

Lithium‐ion batteries have the highest energy density among practical secondary batteries and are widely used for electronic devices, electric vehicles, and even stationary energy‐storage systems. Along with the expansion of demand and applications, the concern about resources of lithium and cobalt is growing. Therefore, secondary batteries composed of abundant elements are required to complement lithium‐ion batteries. In recent years, the development of potassium‐ion batteries has attracted much attention, especially for large‐scale energy storage. In order to realize potassium‐ion batteries, various compounds are proposed and investigated as positive electrode materials, including layered transition‐metal oxides, Prussian blue analogues, and polyanionic compounds. This article offers a review of polyanionic compounds which are typically composed of abundant elements and expected high operating potential. Furthermore, we deliver our new results to partially compensate for lack of studies and provide a future perspective.     

First‐Principles Study of Na‐Ion Battery Performance and Reaction Mechanism of Tin Sulfide as Negative Electrode

We study the Na‐ion battery characteristics of SnS as a negative electrode by first‐principles calculations. From energy analyses, we clarify the discharge reaction process of the Na/SnS half‐cell system. We show a phase diagram of Na?Sn?S ternary systems by constructing convex‐hull curves, and show a possible reaction route considering intermediate products in discharge reactions. Voltage‐capacity curves are calculated based on the Na?SnS reaction path that is obtained from the ternary phase diagram. It is found that the conversion reactions and subsequently the alloying reactions proceed in the SnS electrode, contributing to its high capacity compared with the metallic Sn electrode, in which only the alloying reactions progresses stepwise. To verify the calculated reaction process, x‐ray absorption spectra (XAS) are calculated and compared with experimental XAS at S K‐edge, showing meaningful XAS changes associated with Na₂S and SnS in discharged and charged states, respectively.     

Role of Nickel Nanoparticles in High‐Performance TiO2/Ni/Carbon Nanohybrid Lithium/Sodium‐Ion Battery Anodes

Super‐small sized TiO₂ nanoparticles are in situ co‐composited with carbon and nickel nanoparticles in a facile scalable way, using difunctional methacrylate monomers as solvent and carbon source. Good control over crystallinity, morphology, and dispersion of the nanohybrid is achieved because of the thermosetting nature of the resin polymer. The effects of the nickel nanoparticle on the composition, crystallographic phase, structure, morphology, tap density, specific surface area, and electrochemical performance as both lithium‐ion and sodium‐ion battery anodes are systematically investigated. It is found that the incorporation of the in situ formed nickel nanoparticles with certain content effectively enhances the electrochemical performance including reversible capacities, cyclic stability and rate performance as both lithium‐ion and sodium‐ion battery anodes. The experimental I‐V profiles at different temperatures and theoretical calculations reveal that the charge carriers are accumulated in the amorphous carbon regions, which act as scattering centers to the carriers and lower the carrier mobility for the composite. With increasing nickel content, the mobility of the charge carriers is significantly increased, while the number of the charge carriers maintains almost constant. The nickel nanoparticles provide extra pathways for the accumulated charge, leading to reduced scatterings among the charge carriers and enhanced charge‐carrier transportation.     

包含液相扩散方程简化的锂离子电池电化学模型

锂离子电池的电化学模型对于电池特性分析和电池管理具有重要意义,但是准二维(P2D)模型复杂度太高,为了在保证模型精度的基础上尽量降低复杂度,本文提出了一种包含液相简化的P2D (LSP2D)模型,该模型首先基于电化学平均动力学将电池端电压化简成为仅耦合固相Li+浓度c_s和液相Li+浓度c_e的方程,然后进一步对表达c_s和c_e演化规律的偏微分方程进行抛物线近似化简,使得最终的模型由多项式组成.COMSOL仿真表明在放电倍率为1C时该模型与单粒子(SP)模型的估算精度和速度相当,但在放电倍率为3C时,该模型的估算时间比P2D模型减少了99.73%,与SP模型相当,估算精度相比SP模型有大幅度提升.     

三(2-羧乙基)膦阻隔层对锂硫电池穿梭效应的抑制

为了抑制热力学穿梭效应, 改善锂硫电池的电化学性能. 将三(2-羧乙基)膦芳纶纸中间层(TCEP-AP)嵌在锂硫电池正极和隔膜之间. 通过透射电子显微镜(TEM)、 扫描电子显微镜(SEM)、 红外光谱和元素能谱分析(EDS)等对材料进行结构和性能表征. 电化学实验表明, TCEP是一种特别有效的多硫化物剪切剂, 在0.1C倍率时, S-TCEP-AP 锂硫电池的初始放电容量达到1544 mA·h·g ^-1. 在1C倍率下循环400次后, 比放电容量仍维持在609 mA·h·g ^-1, 衰减率极低(每周衰减0.029%), 展现出良好的倍率和循环性能.