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Origins of capacity and voltage fading of LiCoO2 upon high voltage cycling†
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2019-08-23 00:00:00 , DOI: 10.1039/c9ta06579b Yuyuan Jiang 1, 2, 3, 4, 5 , Changdong Qin 1, 2, 3, 4, 5 , Pengfei Yan 1, 2, 3, 4, 5 , Manling Sui 1, 2, 3, 4, 5
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2019-08-23 00:00:00 , DOI: 10.1039/c9ta06579b Yuyuan Jiang 1, 2, 3, 4, 5 , Changdong Qin 1, 2, 3, 4, 5 , Pengfei Yan 1, 2, 3, 4, 5 , Manling Sui 1, 2, 3, 4, 5
Affiliation
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Enhancing the high voltage cycling stability is critical for reviving LiCoO2-based layered cathodes, and this requires in-depth understanding of various degradation mechanisms and their contributions to performance decay. Herein, we conduct systematic investigations into the failure mechanisms of LiCoO2 upon high voltage cycling and reveal that the capacity loss is mainly due to bulk structure degradation and the voltage fading is mainly due to the blocking effect of the cathode/electrolyte interphase (CEI) layer. Furthermore, as the novel points of our characterization, we find that (i) the LiCoO2 grains are in a highly delithiated state after high voltage cycling, causing poor thermal stability; (ii) the stripe-shaped O1 phase is verified in the grain bulk, demonstrating irreversible structural changes upon high voltage cycling; and (iii) the surface phase transition layer, though it can be as thick as tens of nanometers, plays a minor role in the deterioration of LiCoO2 performance. Our findings stress that bulk structure stability and the blocking effect of the CEI layer are the two major challenges for high voltage usage of LiCoO2-based layered oxides.
中文翻译：
高压循环时 LiCoO 2的容量和电压衰减的起因†
增强高压循环稳定性对于恢复基于LiCoO 2的分层阴极至关重要，这需要深入了解各种降解机理及其对性能衰减的贡献。本文中，我们对LiCoO 2在高压循环下的失效机理进行了系统的研究，发现容量损失主要归因于整体结构的退化，电压衰减主要归因于阴极/电解质间相（CEI）的阻断作用层。此外，作为表征的新颖点，我们发现（i）LiCoO 2高压循环后，晶粒处于高度脱锂状态，导致热稳定性差；（ii）在粒状体中验证了条纹状的O1相，表明在高压循环时不可逆的结构变化；（iii）尽管表面相变层的厚度可以达到数十纳米，但是在LiCoO 2性能的降低中起很小的作用。我们的发现强调，本体结构的稳定性和CEI层的阻挡作用是高电压使用基于LiCoO 2的层状氧化物的两个主要挑战。
更新日期：2019-08-23
中文翻译：
高压循环时 LiCoO 2的容量和电压衰减的起因†
增强高压循环稳定性对于恢复基于LiCoO 2的分层阴极至关重要，这需要深入了解各种降解机理及其对性能衰减的贡献。本文中，我们对LiCoO 2在高压循环下的失效机理进行了系统的研究，发现容量损失主要归因于整体结构的退化，电压衰减主要归因于阴极/电解质间相（CEI）的阻断作用层。此外，作为表征的新颖点，我们发现（i）LiCoO 2高压循环后，晶粒处于高度脱锂状态，导致热稳定性差；（ii）在粒状体中验证了条纹状的O1相，表明在高压循环时不可逆的结构变化；（iii）尽管表面相变层的厚度可以达到数十纳米，但是在LiCoO 2性能的降低中起很小的作用。我们的发现强调，本体结构的稳定性和CEI层的阻挡作用是高电压使用基于LiCoO 2的层状氧化物的两个主要挑战。
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