Development of Cation-Disordered Rocksalt Cathodes

Abstract

In order to meet the demand for large-scale energy storage applications such as electric vehicles and power grid storage systems, Li-ion batteries (LIBs) with higher energy density and power density, lower cost, better safety, and longer lifespans are needed. In the past several years, cation-disordered Li-excess rocksalts (DRXs) have quickly emerged as a new class of promising high-energy LIB cathode materials. [1] This is largely owing to their high charge storage capacities, a result of combined redox reactions of cationic transition metals and anionic oxygen similar to what was reported on the Li- and Mn-rich NMC cathodes. Compared to the conventional layered oxides, the three-dimensional host structure is considerably more stable as the randomized cation distribution eliminates structural instability associated with changes in the interlayer spacing. However, DRX cathodes currently face challenges in cycling stability as extensive involvement of oxygen redox, which is needed for the capacity boost, often leads to fast capacity fade and, in some cases, voltage hysteresis.In this presentation, we will show our recent effort in understanding charge storage mechanisms, materials degradation mechanisms, and key factors influencing DRX cathode performance. [2-6] Our perspectives on future development will also be discussed. References Lee, J.; Urban, A.; Li, X.; Su, D.; Hautier, G.; Ceder, G. Unlocking the Potential of Cation-Disordered Oxides for Rechargeable Lithium Batteries.Science 2014, 343, 519.Kan, W. H.; Chen, D.; Papp, J. K.; Shukla, A. K.; Huq, A.; Brown, C. M.; McCloskey, B. D.; Chen, G. Unravelling Solid-State Redox Chemistry in Li3Nb0.3Mn0.4O2 Single-Crystal Cathode Material. Chem. Mater. 2018, 30, 1655.Kan, W. H.; Wei, C.; Chen, D.; Bo, T.; Wang, B. T.; Zhang, Y.; Tian, Y.; Lee, J. S.; Liu, Y.; Chen, G. Evolution of Local Structural Ordering and Chemical Distribution upon Delithiation of a Rock Salt–Structured Li3Ta0.3Mn0.4O2 Cathode. Adv. Funct. Mater. 2019, 29, 1808294.Chen, D.; Kan, W. H.; Chen, G. Understanding Performance Degradation in Cation-Disordered Rock-Salt Oxide Cathodes. Energy Mater. 2019, 9, 1901255.Chen, D.; Wu, J.; Papp, J. K.; McCloskey, B. D.; Yang, W.; Chen, G. Role of Redox-Inactive Transition-Metals in the Behavior of Cation-Disordered Rocksalt Cathodes. Small 2020, 16, 2000656.Ahn, J.; Chen, D.; Chen, G.. A Fluorination Method for Improving Cation-Disordered Rocksalt Cathode Performance. Energy Mater. 2020, 10, 2001671.