Effect of Al2O3 Coating on Stabilizing LiNi0.4Mn0.4Co0.2O2 Cathodes
Effect of Al2O3 Coating on Stabilizing LiNi0.4Mn0.4Co0.2O2 Cathodes
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DOI：
10.1021/acs.chemmater.5b02952
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发表时间：
2015-09-08
影响因子：
8.6
通讯作者：
Toney, Michael F.
中科院分区：
文献类型：
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作者：
Wise, Anna M.;Ban, Chunmei;Toney, Michael F.
利用原子层沉积Al_2O_3涂层，改善了层状镍锰钴伪三元氧化物LiNi0.4Mn0.4Co0.2O2的高压循环稳定性。为了了解Al_2O_3涂层的影响，我们利用电化学阻抗谱、基于操作手同步加速器的X射线衍射和操作手X射线吸收近边精细结构谱来表征LiNi0.4Mn0.4Co0.2O2正极在循环过程中的结构和化学演变。结合使用这些技术，我们发现，在较高的电压(>；4.4V)下，氧化铝涂层成功地缓解了活性物质与电解液的强烈副反应，而不限制锂离子的吸收和释放。Al_2O_3涂层对锂离子脱嵌的影响也在锂的脱嵌初期被揭示出来，由于表面的保护，涂层电极中Co和Mn离子的氧化和配位环境的演化被观察到延迟。这种保护防止了电解液与高活性的镍氧化物中心的竞争副反应，通过氧化镍促进了电荷补偿，并实现了高压循环稳定性。
Using atomic layer deposition of Al2O3 coating, improved high-voltage cycling stability has been demonstrated for the layered nickelmanganesecobalt pseudoternary oxide, LiNi0.4Mn0.4Co0.2O2. To understand the effect of the Al2O3 coating, we have utilized electrochemical impedance spectroscopy, operando synchrotron-based X-ray diffraction, and operando X-ray absorption near edge fine structure spectroscopy to characterize the structure and chemistry evolution of the LiNi0.4Mn0.4Co0.2O2 cathode during cycling. Using this combination of techniques, we show that the Al2O3 coating successfully mitigates the strong side reactions of the active material with the electrolyte at higher voltages (>4.4 V), without restricting the uptake and release of Li ions. The impact of the Al2O3 coating is also revealed at beginning of lithium deintercalation, with an observed delay in the evolution of oxidation and coordination environment for the Co and Mn ions in the coated electrode due to protection of the surface. This protection prevents the competing side reactions of the electrolyte with the highly active Ni oxide sites, promoting charge compensation via the oxidation of Ni and enabling high-voltage cycling stability.