富镍锂离子电池三元材料NCM的研究进展

锂离子电池作为新能源电池符合时代要求，具有良好的应用前景。电池容量、倍率性能与循环性能是电池性能的重要评价指标，在选取高能量密度电极材料的同时要充分考虑电池结构稳定性及其安全性能，三元材料基于这种思路进行设计。目前，针对电池中锂离子导通率与结构不可逆坍塌问题，通过包覆涂层、离子掺杂等手段改善锂离子电池性能已经常态化，实际需求要求有更有效的改性方法。因此，本文综述了富镍锂离子电池三元材料LiNi_0.4Co_0.2Mn_0.4O₂（NCM424）、LiNi_0.5Co_0.2Mn_0.3O₂(NCM523)、LiNi_0.6Co_0.2Mn_0.2O₂(NCM622)和LiNi_0.8Co_0.1Mn_0.1O₂(NCM811)的研究现状与发展导向，认为简单的单一材料改性已遇到瓶颈，改性方法复合、设计材料多元结构是提升电池性能的一大发展方向；从改性材料的合成和运行路径入手，研究分子水平上的作用机制，建立统一理论模型，通过计算模拟手段设计电极结构，实现锂离子电池突破性的发展。     

Ni3(PO4)2-coated Li[Ni0.8Co0.15Al0.05]O2 lithium battery electrode with improved cycling performance at 55 °C

To improve the cycling performance of LiNi_0.8Co_0.15Al_0.05O₂ at 55 °C, a thin Ni₃(PO₄) layer was homogeneously coated onto the cathode particle via simple ball milling. The morphology of the Ni₃(PO₄)₂-coated LiNi_0.8Co_0.15Al_0.05O₂ particle was characterized using SEM and TEM analysis, and the coating thickness was found to be approximately 10-20 nm. The Ni₃(PO₄)₂-coated LiNi_0.8Co_0.15Al_0.05O₂ cell showed improved lithium intercalation stability and rate capability especially at high C rates. This improved cycling performance was ascribed to the presence of Ni₃(PO₄)₂ on the LiNi_0.8Co_0.15Al_0.05O₂ particle, which protected the cathode from chemical attack by HF and thus suppressed an increase in charge transfer resistance. Transmission electron microscopy of extensively cycled particles confirmed that the particle surface of the Ni₃(PO₄)₂-coated LiNi_0.8Co_0.15Al_0.05O₂ remained almost undamaged, whereas pristine particles were severely serrated. The stabilization of the host structure by Ni₃(PO₄)₂ coating was also verified using X-ray diffraction.     

高镍三元正极材料表面碱性物质研究进展

高镍三元正极材料表面形成的碱性物质容易导致电池容量衰减加快、寿命缩短,因而调控三元材料表面碱性物质对于提高锂离子二次电池的功能和安全性至关重要。综述了高镍锂离子电池三元正极材料表面碱性物质的形成机理及处理手段,从不同角度阐述了环境中的水、二氧化碳对表面碱性物质形成的影响。探讨了表面碱性物质形成过程中,由于锂离子和过渡金属的迁移与固化引发的表面结构的相变现象,造成了三元正极材料的加工储存性能的恶化。还对降碱工艺中的洗涤、干燥、低温烧结等过程进行了重点说明,阐述了洗涤工艺对三元材料表面碱性物质降低及对材料性质的影响,指出需选择合适的洗涤、干燥条件,减小材料表面发生的变异。最后结合目前降碱工艺对后续研究方向提出了建议。     

An Intrinsically Nonflammable Electrolyte for Prominent-Safety Lithium Metal Batteries with High Energy Density and Cycling Stability

Nex-generation high-energy-density storage battery, assembled with lithium (Li)-metal anode and nickel-rich cathode, puts forward urgent demand for advanced electrolytes that simultaneously possess high security, wide electrochemical window, and good compatibility with electrode materials. Herein an intrinsically nonflammable electrolyte is designed by using 1 M lithium difluoro(oxalato)borate (LiDFOB) in triethyl phosphate (TEP) and N-methyl-N-propyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [Pyr₁₃][TFSI] ionic liquid (IL) solvents. The introduction of IL can bring plentiful organic cations and anions, which provides a cation shielding effect and regulates the Li⁺ solvation structure with plentiful Li⁺-DFOB⁻ and Li⁺-TFSI⁻ complexes. The unique Li⁺ solvation structure can induce stable anion-derived electrolyte/electrode interphases, which effectively inhibit Li dendrite growth and suppress side reactions between TEP and electrodes. Therefore, the LiNi_0.9Co_0.05Mn_0.05O₂ (NCM90)/Li coin cell with this electrolyte can deliver stable cycling even under 4.5 V and 60 °C. Moreover, a Li-metal battery with thick NCM90 cathode (≈ 15 mg cm⁻²) and thin Li-metal anode (≈ 50 µm) (N/P ≈ 3), also reveals stable cycling performance under 4.4 V. And a 2.2 Ah NCM90/Li pouch cell can simultaneously possess prominent safety with stably passing the nail penetration test, and high gravimetric energy density of 470 Wh kg⁻¹ at 4.4 V.     

高镍锂离子电池三元材料NCM电解质的应用

高镍三元正极材料成本低、比容量高,符合锂离子电池可持续发展的理念,被认为是下一代的主流正极材料。但是,高镍材料需搭配合适的电解质才能有效发挥其性能,而这一研究很少被关注。因此,总结并选择适配的电解质对于高镍锂离子电池来说格外重要。本文简述了锂离子电池电解质的一般组成及其产生的电解质类型,重点综述了有机液体电解质、固体电解质及离子液体基电解质在高镍三元材料电池中的应用,并通过电解质的量化计算进行了验证总结。分析表明,离子液体-有机溶剂混合电解质在高镍三元材料（NCM）电池中具备更好的循环效果,同时满足了电池安全稳定的要求,更适合作为高镍材料电池的电解质。最后,针对混合电解质各溶剂间的相互作用机理及Li⁺传输等分子动力学研究进行了展望。     

Enhanced cycling stability of La modified LiNi0.8–xCo0.1Mn0.1LaxO2 for Li-ion battery

A series of layered LiNi_0.8–xCo_0.1Mn_0.1La_xO₂ (x=0, 0.01, 0.03) cathode materials were synthesized by combining co-precipitation and high temperature solid state reaction to investigate the effect of La-doping on LiNi_0.8Co_0.1Mn_0.1O₂. A new phase La₂Li_0.5Co_0.5O₄ was observed by XRD, and the content of the new phase could be determined by Retiveld refinement and calculation. The cycle stability of the material is obviously increased from 74.3% to 95.2% after La-doping, while the initial capacity exhibits a decline trend from 202 mA·h/g to 192 mA·h/g. The enhanced cycle stability comes from both of the decrease of impurity and the protection of newly formed La₂Li_0.5Co_0.5O₄, which prevents the electrolytic corrosion to the active material. The CV measurement confirms that La-doped material exhibits better reversibility compared with the pristine material.     

层状富镍过渡金属氧化物正极材料衰减机理研究进展

层状富镍过渡金属氧化物正极材料因具有比容量高、价格低廉以及对环境友好等特性而受到广泛关注,并已在产品中应用。但其本身固有的一些缺陷,如在循环过程中结构稳定性较差、高温循环衰减过快、导电系数较低及储存性能不佳等,极大地限制了其在各个领域的广泛应用。本文对近年来高镍层状过渡金属氧化物正极材料在循环过程中容量衰减有关机理进行概括总结,并针对不同衰减机理给出简要改进方法。     

一种链箅机箅板抗高温氧化膜的微观分析

采用XRD,SEM和EDS等方法对一种使用寿命超过18个月箅板的抗高温氧化膜进行了微观分析和研究。结果发现,该箅板具有优异抗氧化性能,使用寿命明显高于同类产品的原因是该箅板的氧化膜的外层和内层分别是SiO2膜和Cr2O3膜,加上对氧化膜起补充作用的高温下化学性质稳定的富镍层,使得氧化膜的致密性和连续性好,氧化膜薄且嵌入在箅板基材中,使得氧化膜的粘附性好,不易剥落,保护了基材,提高了箅板的抗高温氧化性能。     

锂离子电池高镍三元材料的研究进展

用于锂离子电池的高镍三元材料由于成本低、能量密度高、可逆容量高、环境友好等优点,是现在以及未来车用动力电池首选正极材料。本文在综述了高镍三元材料的晶体结构特性和电化学特性的基础上,介绍了国内外主要制备方法、掺杂以及包覆等改性措施,重点讨论了不同种类包覆材料对高镍三元倍率性能、循环性能和高温稳定性能的影响。最后,针对高镍三元电解液、安全性、压实密度及循环寿命等问题进行分析与展望。     

Boosting Reaction Homogeneity in High-Energy Lithium-Ion Battery Cathode Materials

Conventional nickel-rich cathode materials suffer from reaction heterogeneity during electrochemical cycling particularly at high temperature, because of their polycrystalline properties and secondary particle morphology. Despite intensive research on the morphological evolution of polycrystalline nickel-rich materials, its practical investigation at the electrode and cell levels is still rarely discussed. Herein, an intrinsic limitation of polycrystalline nickel-rich cathode materials in high-energy full-cells is discovered under industrial electrode-fabrication conditions. Owing to their highly unstable chemo-mechanical properties, even after the first cycle, nickel-rich materials are degraded in the longitudinal direction of the high-energy electrode. This inhomogeneous degradation behavior of nickel-rich materials at the electrode level originates from the overutilization of active materials on the surface side, causing a severe non-uniform potential distribution during long-term cycling. In addition, this phenomenon continuously lowers the reversibility of lithium ions. Consequently, considering the degradation of polycrystalline nickel-rich materials, this study suggests the adoption of a robust single-crystalline LiNi_0.8Co_0.1Mn_0.1O₂ as a feasible alternative, to effectively suppress the localized overutilization of active materials. Such an adoption can stabilize the electrochemical performance of high-energy lithium-ion cells, in which superior capacity retention above ≈80% after 1000 cycles at 45 °C is demonstrated.