Sodium compensation and interface protection effects of Na3PS3O for sodium-ion batteries with P2-type oxide cathodes

Abstract

Irreversible interfacial reactions occurring on non-sodium-containing anodes and P2-type oxide cathodes can significantly reduce the availability of active sodium ions in full-cells, which is unfavorable for realizing high energy density. In this work, we propose the use of oxygen-doped sodium thiophosphate, Na3PS3O (NPSO), as a self-sacrificing cathode additive for sodium compensation in liquid batteries. The uniform dispersion of NPSO into the Na0.66Ni0.26Zn0.07Mn0.67O2 (NNZM) cathode can be realized by a solution-casting method. The continuous irreversible decomposition of NPSO provides a total sodiation capacity of over 300 mAh g−1 with approximately 60% capacity delivered below 4.0 V. Besides compensating for sodium consumption, NPSO and its non-gaseous decomposition products effectively suppress the growth of cathode electrolyte interphase films caused by electrolyte decomposition and the formation of oxygen vacancies in the crystal structure of NNZM. Coating of NPSO on conventional NNZM cathodes leads to an increase in the capacity retention of half-cells from 62.1% to 83.3% and the energy density of full-cells by 29.7%. This work opens up a new application field for sodium thiophosphates.