Is it universal that the layered-spinel structure can improve electrochemical performance?

• 作 者: Daqiang Wang Zhenguo Wu Wei Xiang Yuxia Liu Gongke Wang Kanghui Hu Qi Xu Yang Song Xiaodong Guo
• 机 构: College of Chemical Engineering,Sichuan University,Chengdu 610065,Sichuan,China;College of Materials
• 出 处: 能源化学
• 发表日期: 2022年1期
• 关键词: Li-ion battery Li-and Mn-rich layered oxides Spinel phase Mn/Ni ratio

The introduction of spinel phase to form the layered-spinel structure (LSS) is an effective way to improve the electrochemical performance of Li-and Mn-rich layered oxides (LMR).But is this structure universal for all LMR systems?In this work,different Mn/Ni ratio systems with the LSS are discussed in detail.It is found that,high discharge capacity (200.8 mA h g-1 at 1C rate;1C =250 mA h g-1) as well as high capacity-retention (94％ at 1C rate after 100 cycles) can be achieved by forming the LSS for low-Ni system(Mn/Ni =5.0).However,the capacity retention decreases severely in the high-Ni system (Mn/Ni =3.5,2.6).For example,when the ratio of Mn/Ni is 3.5,the capacity-retention of the layered-spinel sample was only 65.8％,compared to the 83％ of the original LMR sample.The Ex-situ XRD,XPS,and HRTEM results demonstrate that the introduction of spinel phase in high-Ni system accelerates the transition and collapse of the crystal structure.This work provides guidance for optimizing the proportions of ele-ments and the design of structures for the LMR.