复合正极材料及其在锂离子电池中的应用

发布时间：2018-06-10 02:22

本文选题：锂离子电池 + 锂电池正极材料　；参考：《浙江大学》2017年硕士论文

【摘要】：目前,商业上广泛应用的锂离子正极材料主要有LiCoO_2(LCO)层状材料、尖晶石型LiMn204(LMO)材料、橄榄石型LiFeP04(LFP)材料和Li[NiCoMn]02(NCM)三元层状材料。它们有各自的优点,但也存在相应的缺点。LMO具有三维锂离子通道,工作电压较高,资源丰富成本较低,环境友好污染小,尤其是安全性较好,是理想的锂离子动力电池正极材料。然而,LMO可逆循环容量(110～120mAh/g)偏低,且充放电循环过程中由于锰的溶解、电解液分解以及Jahn-Teller效应等原因,容量衰减较快。为此,论文引入高容量的第二正极材料,在正极中形成微电池,减少了LMO材料颗粒表面Li+的富集,抑制Jahn-Teller效应以保持LMO晶体结构的完整,从而获得比容量高、长循环寿命的锂离子电池正极材料。研究结果表明,由高电位LMO与低电位LFP、LCO、NCM材料组成的复合材料,具有比LMO更高的比容量和更好的循环寿命。复合材料放电时Li+先嵌入高电位LMO,再向低电位材料迁移,LMO颗粒表面富集的Li+嵌入低电位材料,减少了 LMO材料颗粒表面Li+的富集,稳定材料结构,抑制其产生畸形应变。充电过程中,Li+从低电位材料脱嵌,高电位LMO的Li+,再向低电位材料迁移,形成一种“阶段脱锂”过程,达到充电缓冲的目的,从而提升材料的充放电循环性能。优化后的LMO-NCM复合材料表现出比容量高、倍率性能好、长循环寿命的优异综合性能。经过放大实际生产出了电池模块,其安全性能和电化学性能都达到了国家标准。市场化应用表明,LMO-NCM电池模块完全达到预期性能指标。
[Abstract]:At present, LiCoO2LCO-layered materials, spinel LiMn204LMO-based materials, olivine LiFeP04LFP-based materials and Li [NiCoMn] 02NCM-ternary laminated materials are widely used in commercial applications. They have their own advantages, but they also have some disadvantages. LMO has three dimensional lithium ion channels, high operating voltage, low cost of rich resources, less environmental friendly pollution, especially better safety. It is an ideal cathode material for lithium ion power battery. However, the reversible cycle capacity of LMO is low, and the capacity decreases rapidly due to the dissolution of manganese, decomposition of electrolyte and Jahn-Teller effect during charge-discharge cycle. Therefore, a high capacity second cathode material is introduced to form a microcell in the positive electrode, which reduces the concentration of Li on the surface of the LMO particles and suppresses the Jahn-Teller effect to maintain the integrity of the LMO crystal structure so as to obtain high specific capacity. Lithium ion battery cathode material with long cycle life. The results show that the composite composed of high potential LMO and low potential LFP LCONCM has higher specific capacity and better cycle life than LMO. Li intercalated into high potential LMOs during discharge and then migrated to low potential materials. Li embedded in low potential materials reduced Li enrichment on LMO particles, stabilized material structure and inhibited abnormal strain. During charging, Li is deintercalated from low potential material, Li with high potential LMO is transferred to low potential material, which forms a "phase delithium" process, which achieves the purpose of charging and buffering, thus improving the charge and discharge cycle performance of the material. The optimized LMO-NCM composites show high specific capacity, good rate performance and excellent comprehensive properties of long cycle life. After amplifying, the battery module is produced, and its safety and electrochemical performance are up to the national standard. Market application shows that the LMO-NCM battery module fully meets the expected performance targets.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O646;TM912

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