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Formation of an Anti-Core–Shell Structure in Layered Oxide Cathodes for Li-Ion Batteries
ACS Energy Letters ( IF 22.0 ) Pub Date : 2017-10-23 00:00:00 , DOI: 10.1021/acsenergylett.7b00921
Hanlei Zhang 1, 2 , Fredrick Omenya 2 , M. Stanley Whittingham 2 , Chongmin Wang 3 , Guangwen Zhou 1, 2
Affiliation  

The layered → rock-salt phase transformation in the layered dioxide cathodes for Li-ion batteries is believed to result in a “core–shell” structure of the primary particles, in which the core region remains as the layered phase while the surface region undergoes a phase transformation to the rock-salt phase. Using transmission electron microscopy, here we demonstrate the formation of an “anti-core–shell” structure in cycled primary particles with a formula of LiNi0.80Co0.15Al0.05O2, in which the surface and subsurface regions remain as the layered structure while the rock-salt phase forms as domains in the bulk with a thin layer of the spinel phase between the rock-salt core and the skin of the layered phase. Formation of this anti-core–shell structure is attributed to oxygen loss at the surface that drives the migration of oxygen from the bulk to the surface, thereby resulting in localized areas of significantly reduced oxygen levels in the bulk of the particle, which subsequently undergoes phase transformation to the rock-salt domains. The formation of the anti-core–shell rock-salt domains is responsible for the reduced capacity, discharge voltage, and ionic conductivity in cycled cathodes.

中文翻译:

锂离子电池分层氧化物阴极中反核-壳结构的形成

据认为,锂离子电池层状二氧化物阴极中的层状→岩盐相变会导致一次粒子的“核-壳”结构,其中核心区域保留为层状相,而表面区域经历从相变到岩盐相。使用透射电子显微镜,在这里我们证明了循环初级粒子中具有“ LiNi 0.80 Co 0.15 Al 0.05 O 2”分子式的“反核-壳”结构的形成。,其中表面和地下区域仍保留为层状结构,而岩盐相则在主体中形成畴,在岩盐核与层状相的表层之间具有尖晶石相的薄层。这种反核-壳结构的形成归因于表面上的氧气流失,该氧气流驱动氧气从主体迁移到表面,从而导致局部区域中的粒子主体中的氧气水平显着降低,随后发生了这种情况。相转变成岩盐域。反核-壳岩盐域的形成是循环阴极中容量,放电电压和离子电导率降低的原因。
更新日期:2017-10-24
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