Research progress in blending modification cathode materials for lithium ion batteries

本文简述了国内外锂离子电池正极材料共混改性的研究进展。正极材料是锂离子电池重要组成部分，是决定锂离子电池能量密度和成本的关键因素。共混改性具有制备工艺简单、材料性能一致性容易控制、综合成本较低等优点，在钴酸锂、锰酸锂、磷酸铁锂和三元材料电池制造中得到应用。国内外通过对正极材料共混改性机理研究，发现共混改性是材料改善电化学性能、降低成本、提升安全性能的有效途径，并有望发展成为依据材料特性指导锂离子电池高性能电极设计的重要方法。同时在正极材料共混改性方面亟需加强共混材料物性匹配、充放电机制选取、共混工艺研究，该方法也为高镍、富锂锰基等新一代正极材料工业化应用提供了工艺参考。     

Research progress on the Li-excess Mn-based cathode materials with high capacity for lithium-ion battery

富锂锰基正极材料因具有高的放电比容量,有望成为下一代400 W·h/kg动力电池最有前景的正极材料。本文简要介绍了本研究团队在富锂锰基正极材料方面的研究进展。通过团队多年研发,材料的首次不可逆容量、倍率性能、循环稳定性得到明显的改善,而且,电压衰减被有效的抑制。同时,研制出基于富锂锰基正极材料和纳米硅碳负极材料的新型24A·h高容量锂离子电池,其质量能量密度达到374 W·h/kg,体积能量密度达到  577 W·h/L。     

Surface homogenizing heterostructure coatings induced by Ti3C2Tx MXene for enhanced cycle performance of lithium-rich cathode materials

The layered lithium-rich manganese-based cathode material (Li_1.2Mn_0.54Co_0.13Ni_0.13) has the significant advantage of high specific capacity, but this material also suffers serious defects, including severe capacity attenuation and voltage attenuation during the cycle. At present, most researchers have been working to optimize the cycle performance of lithium-rich materials. In this work, we propose a surface homogenizing heterostructure coating induced by MXene modification to reduce capacity reduction and voltage decay. It can be found that the initial Coulombic efficiency (ICE) increases from 77.2% for the bare electrode Li_1.2Mn_0.54Co_0.13Ni_0.13 (LMO) to 85.5% for 1.4 wt% MXene (Ti₃C₂T_x, T_x represents the surface terminations: OH, O, F) modified lithium-rich (TO2). Furthermore, the discharge specific capacity of the electrode at 5 C rate increased from 160.7 mAh g⁻¹ for LMO to 200.6 mAh g⁻¹ for TO2. More prominently, the outstanding cycle stability with capacity retention rate is 82.1% for TO2 after 200 cycles, while only 64.7% for LMO, and the average discharge voltage dropped from 0.788 to 0.468 V. In addition, the mechanism for improving the electrochemical performance is systematically studied.     

Interpretation of cathode material standards for lithium ion batteries

随着应用领域的不断拓宽,近年来锂离子电池行业呈现稳步快速增长态势,其正极材料迎来了前所未有的发展机遇。我国在锂离子电池正极材料的开发和产业化方面具有得天独厚的优势,拥有完善的产业链和可持续发展的良好势头,市场上出现了越来越多的正极种类和产品类型。本文介绍了国内锂离子电池正极材料标准的现状,对比分析了不同类别正极材料的关键技术指标要求,解读了指标出现差异的原因,并指出了个别标准的不足之处,对今后的标准化工作提出了建议。     

Failure mechanism of Li1+x(NCM)1-xO2 layered oxide cathode material during capacity degradation

镍钴锰三元层状氧化物（NCM）正极材料由于其优越的综合性能在动力/储能电池系统（ESS）领域得到广泛应用。虽然Ni含量的增加可提高三元材料的比容量及电池的能量密度,但相关电池体系的容量保持率和安全性将会变差。如何有效解决该矛盾是此类NCM电池所面临的关键问题。本文从NCM电池体系循环过程中常见的体相结构破坏和正极-电解液界面组成改变两方面失效现象出发,结合近年来国内外对NCM失效模式研究中所提出的新理论、方法、应用,从机械破坏、结构演变、电化学极化、化学副反应、正负极协同效应等多个角度对NCM材料的衰退机理提出见解,对指导电池用户合理制定充放电协议、缓解电动汽车（EV）里程焦虑乃至材料设计本身均有重要的指导及借鉴意义。     

Preparation and electrochemical performances of Ni-rich LiNi0.91Co0.06Mn0.03O2 cathode for high-energy LIBs

One important challenge of lithium ion batteries is to improve the energy density while maintaining long-term cyclability. The energy density is strongly dependent on the Ni content in LiNi_1-x-yCo_xMn_yO₂. Herein, Ni-rich LiNi_0.91Co_0.06Mn_0.03O₂ has been synthesized as a high energy cathode material by co-precipitation method and the electrochemical performance of the LiNi_0.91Co_0.06Mn_0.03O₂ has been investigated. The granule morphology LiNi_0.91Co_0.06Mn_0.03O₂ with high crystallinity is obtained and which delivers a discharge capacity of 208.3 mA h g⁻¹ with cyclability of 61.9%, after 100 cycles and rate performance of 85.6%, at 2 C. These findings indicate that LiNi_0.91Co_0.06Mn_0.03O₂ is one of the promising candidate cathode for high-energy lithium ion batteries.     

Mo doping of layered Li (NixMnyCo1‐x‐y‐zMz)O2 cathode materials for lithium‐ion batteries

We systematically investigated the effects of Mo doping on the structure, morphology, and the electrochemical performance of Li (Ni_xMn_yCo_{1‐x‐y‐z}M_z)O₂ (NMC) cathode materials for Li‐ion batteries. Layered NMC cathodes were synthesized with the ratio of 111, 622, and 226 via spray pyrolysis yielding submicron‐sized aggregates in the shape of hollow spherical particles. We performed X‐ray diffraction analyses to determine the present phases and the ordering in structure. X‐ray diffraction pattern of Mo‐doped 111, 226, and 622 cathodes showed well‐defined [006]/[102] and [108]/[110] doublets, indicating the layered structure, and good hexagonal ordering. Galvanostatic charge/discharge and electrical impedance spectroscopy measurements were carried out to reveal the effect of Mo doping on the electrochemical performance of the cathodes. Charge/discharge measurements after 20 cycles indicated that the Mo‐doped 111 and 622 NMC cathodes performed a capacity retention of 80% and 81% respectively. Present findings reveal the stabilization effect of Mo in layered NMC structure, especially in the case of Ni‐rich NMC cathodes.     

Preparation and electrochemical performance of LiFePO4/S composite cathode materials

以提高磷酸铁锂体系动力电池的能量密度为目的,在LiFePO₄正极材料中加入少量S材料球磨制得LiFePO₄/S复合正极材料。使用X射线衍射（XRD）和扫描电子显微镜（SEM）表征了结构和形貌,并分别组装扣式电池和软包电池测试其电化学性能。结果表明,磷酸铁锂纳米颗粒致密均匀附着在硫材料表面,构成具有包覆性结构的复合材料。在不同比例的LiFePO₄/S复合材料中,硫的添加量为15%的LiFePO₄/S复合正极材料表现出最优异的电化学性能,0.1 C下的初始容量为251.5mA·h/g,循环100周之后容量保持率达94.9%。以该比例的复合材料为正极的0.5A·h软包电池,循环100周后容量保持率为86.7%。LiFePO₄作为一种极性载体,对多硫化物有一定的吸附能力,少量硫的加入可以在大幅度提高LiFePO₄材料放电容量的同时,维持优异的循环稳定性。LiFePO₄/S复合材料可为磷酸铁锂体系动力电池的发展提供新的思路。     

Preparation of LiNi0.80Co0.15Al0.05O2 cathode material via Li-rich method

本文采用共沉淀法制备球形Ni_0.80Co_0.15Al_0.05(OH)_2.05前驱体,经预氧化后,采用富锂配比在氧气和空气气氛下烧结合成LiNi_0.80Co_0.15Al_0.05O₂正极材料.用X射线衍射,扫描电镜和恒电流充放电测试等方法对该材料的结构,形貌及电化学性能进行表征.结果表明:当锂配比为1.15时,氧气和空气中烧结合成的LiNi_0.80Co_0.15Al_0.05O₂正极材料的形貌,结构和电化学性能相当.富锂配比方法可在空气气氛下制备出电化学性能优异的LiNi_0.80Co_0.15Al_0.05O₂正极材料.0.1 C放电克比容量在200 mA·h/g以上,首次效率在87%左右;1 C放电克比容量在168 mA·h/g以上;800周循环容量保持率在80%以上.     

Preparation and electrochemical performance of F-doped SiO@C composite material

本工作以SiO、沥青和聚四氟乙烯为原料,通过机械融合和加热包覆,制备出了氟元素掺杂的硅碳复合材料。采用SEM、TEM、XRD、红外碳硫分析、激光粒度分析、粉末电阻率和比表面积测试仪等对样品进行了微观形貌表征和物相结构分析。电化学测试表明：当聚四氟乙烯用量为20%（质量百分数）时,SiO@C-F材料具有优异的电化学性能,可逆比容量为1426.8 mA·h/g,首次效率为77.01%,20圈容量保持率83.95%。     

Sulfur encapsulated in nitrogen-doped graphene aerogel as a cathode material for high performance lithium-sulfur batteries

Lithium-sulfur batteries are considered to be an ideal high-performance rechargeable lithium battery. However, some problems have seriously hindered the practical application of lithium-sulfur batteries. A simple one-step hydrothermal method has been applied to design nitrogen-doped graphene aerogel (N-GA) with three different nitrogen sources. Subsequently, sulfur was encapsulated in N-GA by chemical deposition method to synthesize sulfur encapsulated in N-GA (N-GA/S) composites. Among them, the N-GA1/S composite with sulfur content reaching 75.5 wt% has a discharge specific capacity of 723.9 mAh g^?1 after 100 cycles at 0.7 C, and the capacity retention rate is up to 87.4% while the coulombic efficiency still remains 98%. The outstanding electrochemical performance is owing to the good coating of sulfur by nitrogen-doped graphene aerogel, the improvement of the conductivity of the graphene skeleton by nitrogen doping, and the strong adsorption capacity of the doped nitrogen atom to lithium polysulfide. The graphene skeleton also helps to reduce the volume effect while charging and discharging. Furthermore, the proportion of pyridinic-N in N-GA1/S composites is higher than that in the two other composites, and it has a better adsorption capacity for lithium polysulfide.     

Improvement of elevated temperature performance of LiMn1·5Ni0·5O4 cathode material by surface modification with LiCoO2

The surface-modified LiMn_1·5Ni_0·5O₄ materials by LiCoO₂ were prepared by a sol-gel method to improve the electrochemical performance of LiMn_1·5Ni_0·5O₄ and were characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and transmission electron microscopy (TEM)-EDS. X-ray diffraction results indicate that all the samples (modified and pristine samples) have cubic spinel structures, and XRD, FTIR and TEM-EDS data reveal the formation of a solid solution contained Li–Co–Mn–Ni–O on the surface of particles. For the electrochemical properties, the modified material demonstrated dramatically enhanced reversibility and stability at elevated temperature. These improvements are attributed to the formation of the solid solution, and thus-formed solid-solution phase on the surface of LiMn_1·5Ni_0·5O₄ particle reduces the dissolution of Mn ion and stabilises the structure of the cathode material during the charge–discharge process.     

Fabrication of layered structure VS4 anchor in 3D graphene aerogels as a new cathode material for lithium ion batteries

VS₄ has gained more and more attention for its high theoretical capacity (449 mAh/g with 3e⁻ transfer) in lithium ion batteries (LIBs). Herein, a layered structure VS₄ anchored in graphene aerogels is prepared and first reported as cathode material for LIBs. VS₄@GAs composite exhibits an exceptional high initial reversible capacity (511 mAh/g), an excellent high-rate capability (191 mAh/g at the 5 C), and an excellent cyclic stability (239 mAh/g after 15 cycles).     

Li2MnO3 based Li-rich cathode materials: towards a better tomorrow of high energy lithium ion batteries

Abstract

Li₂MnO₃ based layered Li-rich materials as promising cathode candidates of Li ion batteries (LIBs) have attracted much recent attention mainly owing to their superior high specific capacity and high working voltage. To date, although researchers have put much effort to this family of materials, there are still a number of issues under debates in the fundamental understanding of the crystal structures and the electrochemical reaction mechanisms, before the materials can be ready for practical applications. In this review article, we address the recent progress of this group of Li-rich cathode materials with a good hope to better understanding of the relationships among composition, crystal structure and electrochemical reaction mechanisms. In addition, the use of advanced microscopic characterisation and the strategies of novel material designs will also be discussed for better cathode design for LIBs.     

Technology progress of cathode materials for lithium ion batteries

本文针对商业化锂离子电池正极材料,介绍了钴酸锂、镍钴锰三元材料、尖晶石锰酸锂、磷酸铁锂等正极材料的优缺点、市场现状,以及我国正极材料的技术和产业现状。对行业存在的共性问题,如产品品质差,技术实力不足进行了分析。展望了产业未来发展趋势,并提出了增加技术投入、加强产学研协同和高端装备应用等建议。     

Applications of atomic force microscopy in lithium ion batteries research

锂离子电池由于具有高能量密度、高循环寿命、安全等诸多优点,是现代生活中最受欢迎的便携式电源,有着广阔的应用前景。为了充分发挥锂离子电池的潜力,推进其实用化进程,需要深入研究电极反应历程。作为锂离子电池研究的得力助手,原子力显微镜（AFM）能通过其针尖原子与电极表面原子之间的相互作用,实时检测电极表面的微观形貌,在纳米尺度上提供电极表面的物理化学信息,为电极材料和电解液的优化改性提供实验依据。本文综述了AFM在锂离子电池研究中的最新应用进展,包括电化学反应条件下电极材料的形貌变化、纳米力学性能和电学性能等,说明AFM将会进一步推动锂离子电池的研究进展。     

Microstructure and energy storage properties of Li1.2[Mn0.52-0.5xNi0.20-0.5xCo0.08+x]O2 cathode materials

以碳酸钠为沉淀剂,乳酸钠为络合剂合成碳酸盐前驱体,950℃烧结制备了Li_1.2[Mn_0.52-0.5xNi_0.20-0.5xCo_0.08+x]O₂（x=0, 0.02, 0.04, 0.06）系列材料,探讨元素含量变化对材料的结构、形貌、充放电性能的影响。研究结果表明：随着x的增大,材料的晶格常数c/a比值增加,层状结构更加完整。当x=0.02时,该材料的充放电性能最优,其首次放电容量为261.0 mA·h/g,0.5C下循环100次后的放电容量仍有189.9 mA·h/g,容量保持率高达98.85%,2C倍率下放电容量最高达到157.6 mA·h/g。进一步增大x值时,由于Co含量的上升,使得更多的Co^3+/4+ 2g轨道与O^2- 2p轨道发生带隙重叠,从而使得材料的比容量和循环性能下降。     

Research progress of cycle phosphazenes applied in lithium ion batteries

本文回顾了环三磷腈及其衍生物的合成,阐述了其在锂离子电池电解液,正负极材料等关键材料方面的应用研究进展,并进行了相应的展望.随着锂离子电池在高容量动力及储能领域中的广泛应用,电池的安全性问题日益凸显,材料安全性是电池安全性的基本保证.磷腈化合物由于其特殊的组成和结构,具有高效阻燃与电化学稳定性,在用于改善锂离子电池安全性方面受到越来越广泛的关注.在锂离子电池电解液添加剂和共溶剂的研究中发现,磷腈化合物不仅可以改善电解液的热稳定性和阻燃性能,还可以提高电池的充放电电压和循环稳定性;同时,也可以作为正负极材料的重要组分,改善电极材料的安全性.在锂离子电池安全性领域中具有较好的研究价值和实用意义.     

Highly active cluster structure manganese-based metal organic frameworks (Mn-MOFs) like corals in the sea synthesized by facile solvothermal method as gas electrode catalyst for lithium-oxygen batteries

Lithium-oxygen batteries are promising energy storage systems for electric vehicles owing to their very high specific capacity. In all of their components, the catalysts in the air electrode have a profound influence on its electrochemical performances, especially cycle life and specific energy. In this paper, a type of cluster structure manganese-based metal organic frameworks (Mn-MOFs) material is synthesized by facile solvothermal method. Through X-ray diffraction (XRD), scanning electron microscope (SEM), and Raman spectrum tests, it shows that the Mn-MOFs materials with the 1.3:1 molar ratio (Mn: p-phthalic acid) have high crystallinity and orientation and show obvious cluster structure like corals in the sea. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests demonstrate that this MOFs material as the gas electrode catalyst has more excellent reversibility and the oxidation process. Furthermore, the air electrode has quick electronic and lithium ion transfer rate. In addition, the lithium-oxygen batteries with this Mn-based MOFs material as the air electrode catalyst have longer cycle life. After 35 times charge and discharge cycles, the specific discharge capacity can still be maintained over 500 mAh·g⁻¹, and it has the much higher discharge voltage platform.     

Electrochemical thermal stability of the LiFePO4/LiNi0.8Co0.15Al0.05O2 blend cathode material for lithium ion batteries

为了改善LiNi_0.8Co_0.15Al_0.05O₂正极材料的电化学热稳定性能,加入LiFePO₄共混制成了LiFePO₄/LiNi_0.8Co_0.15Al_0.05O₂锂离子电池用混合正极材料。使用X射线衍射（XRD）和扫描电子显微镜（SEM）表征了结构和形貌,测试了电化学性能。结果显示,简单球磨的混合LiFePO₄/LiNi_0.8Co_0.15Al_0.05O₂正极材料中,纳米LiFePO₄粒子包覆在LiNi_0.8Co_0.15Al_0.05O₂粒子表面提高了混合正极材料在充放电过程中的电化学稳定性和结构稳定性。LiFePO₄/LiNi_0.8Co_0.15Al_0.05O₂混合正极材料在50 ℃下循环100周容量保持率为82.0%,明显地优于单一LiNi_0.8Co_0.15Al_0.05O₂材料的72.9%。