Electrolyte Additive Therapy Realizes Simultaneous Ni and Mn Redox for Spinel LiNi_0.5Mn_1.5O₄ Cathode at 2.3–4.95 V

Abstract

The development of cobalt‐free, high‐energy‐density cathode materials is an important prerequisite for the commercialization of the next generation of high‐energy‐density, cost‐effective lithium batteries. Co‐free spinel LiNi0.5Mn1.5O4 (LNMO) with simultaneous Ni and Mn multi‐cation redox reactions possesses a high theoretical specific capacity of 230 mAh g−1 and a theoretical energy density of 865 Wh kg−1. Unfortunately, LNMO cycled at 2.3–4.95 V suffered from severe interfacial dynamic evolution and electrolyte decomposition, leading to uncontrollable transition metal dissolution and a rapid decrease of reversible specific capacity. Here, It is demonstrated that the addition of an appropriate amount of lithium difluorophosphate (LiDFP) to a common carbonate‐based electrolyte can achieve stable cycling of LNMO in the voltage range of 2.3–4.95 V. The LNMO‐Li cell retained 82.8% of its initial capacity (175.2 mAh g−1) after 300 cycles. The improved cycle performance is attributed to the robust interface formed by the decomposition of LiDFP, which inhibits the dissolution of transition metals and the continued decomposition of the electrolyte. This work provides important insights for the development of the next generation of high‐energy‐density cobalt‐free lithium batteries.