Crystal structural design of exposed planes: express channels, high-rate capability cathodes for lithium-ion...

Developing high-performance lithium ion batteries (LIBs) requires optimization of every battery component. Currently, the main problems lie in the mismatch of electrode capacities, especially the excessively low capacity of cathodes compared with that of anodes. Due to the anisotropy of the crystal structure, different crystal planes play different roles in the transmission of lithium ions. Among these, the {010} facets of layered-structure materials, the (110) planes of spinel cathodes and the (010) planes of olivine cathodes can provide open surface structures, which furnish express channels for the rapid and efficient transmission of lithium ions, leading to enhanced rate performance. However, due to the high-energy surfaces of these crystal planes, they tend to disappear in the synthetic process, forming thermodynamic equilibrium products dominated by low-energy and electrochemically-inactive planes. From the structure design of the material itself, preparing functional materials with specific morphologies and crystal structures is considered to be the most effective way to improve the cyclability and rate performance of LIB cathodes. In this review, we highlight the latest developments in selectively exposing the crystal planes of LIB cathode materials. The synthetic method, the corresponding electrochemical performance, especially the rate capability, and the growth mechanism have been systematically summarized for layered-structure cathodes of LiCoO2, LiNixCoyMn1-x-yO2 and Li2MnO3·LiMO2, spinel cathodes of LiMn2O4 and LiNi0.5Mn1.5O4, and olivine cathodes of LiFePO4. This in-depth discussion and understanding is beneficial for the rational design of well-performing LIB cathodes and can provide direction and perspectives for future work.