Twin boundary defect engineering improves lithium-ion diffusion for fast-charging spinel cathode materials

Rui Wang,Shuankui Li,Shunning Li,Mihai Chu,Jinlong Yang,Xin Chen,Feng Pan,Chaoqi Wang,Weiming Zhu,Jie Chen,Fusheng Liu,Yinguo Xiao,Tongchao Liu,Zhongyuan Huang,Lunhua He,Lei Jin,Jiaxin Zheng

doi:10.1038/s41467-021-23375-7

Abstract

Defect engineering on electrode materials is considered an effective approach to improve the electrochemical performance of batteries since the presence of a variety of defects with different dimensions may promote ion diffusion and provide extra storage sites. However, manipulating defects and obtaining an in-depth understanding of their role in electrode materials remain challenging. Here, we deliberately introduce a considerable number of twin boundaries into spinel cathodes by adjusting the synthesis conditions. Through high-resolution scanning transmission electron microscopy and neutron diffraction, the detailed structures of the twin boundary defects are clarified, and the formation of twin boundary defects is attributed to agminated lithium atoms occupying the Mn sites around the twin boundary. In combination with electrochemical experiments and first-principles calculations, we demonstrate that the presence of twin boundaries in the spinel cathode enables fast lithium-ion diffusion, leading to excellent fast charging performance, namely, 75% and 58% capacity retention at 5 C and 10 C, respectively. These findings demonstrate a simple and effective approach for fabricating fast-charging cathodes through the use of defect engineering.

Highlights

Defect engineering on electrode materials is considered an effective approach to improve the electrochemical performance of batteries since the presence of a variety of defects with different dimensions may promote ion diffusion and provide extra storage sites
Point defects represented by vacancies, atomic exchanges or so-called antisite defects (e.g., Li–Fe exchange in LiFePO4 and Li–Ni exchange in LiNiO213,14) and substitutional atoms (e.g., Al3+ and Mg2+ doping in LiCoO215,16) can be relatively easier to control by varying the composition and synthesis process to optimize the electrochemical performance of electrode materials[17,18]
The addition of excess lithium salt is the decisive factor for the formation of a twin boundary defect structure in LMOTB, which regulates lithium diffusion in the spinel crystal structure (Fig. 1a)