High-Entropy-Type Cation-Disordered Rocksalt Cathodes for Li-Ion Batteries with Enhanced Capacity and Rate Capability

摘要

The recent success of Li-excess cation-disordered rocksalt (DRX) cathodes is providing an avenue to develop high energy density cathodes with abundant and low-cost metals, such as Mn, Fe and Ti. As they have high energy density, these cathode materials are currently the most viable strategy to address the resource issues of Co/Ni that will arise as conventional layered-type Li-ion cathodes are scaled towards multiple TWh of annual production. In DRX cathodes, facile Li transport relies mostly on the so-called "0-TM" 3D percolation channel, in which the intermediate tetrahedral sites are coordinated only by Li (no transition metals, TMs). The Li migration barrier along this "0-TM" channel is significantly lower compared to that of "1-TM" channel, where the intermediate tetrahedral sites are coordinated by 3 Li and 1 TM. The complexity of DRX cathodes lies in the fact that in most cases, they present various types of cation short-range order (SRO), which influences the frequency and connectivity of "0-TM" channels, thus controls the capacity and rate capability of DRX cathodes. Monte Carlo simulations have suggested that the presence of SRO in DRX cathodes generally leads to reduced Li percolation, when compared to that of a random arrangement of TM species.