High-voltage performance of LiNi0.5Mn1.5O4-based lithium-ion batteries with 4-methyl-1,3,2-dioxathiolane-2,2-dioxide (MDTD) as an electrolyte additive

Abstract

Spinel-type LiNi_0.5Mn_1.5O₄ (LNMO) materials have attracted broad attention as components of rechargeable lithium-ion batteries (LIBs) due to their high energy density. However, continuous decomposition of electrolyte at high working voltage hinders their practical application in carbonate-solvent-based electrolytes. In this work, 4-methyl-1,3,2-dioxathiolane-2,2-dioxide (MDTD) was added as a functional electrolyte additive to the standard electrolyte (i.e., 1 M LiPF₆–ethylene carbonate/ethyl methyl carbonate/dimethyl carbonate) to enhance the electrochemical performances of LNMO-based LIBs. Specifically, the addition of a 0.5% additive to the standard electrolyte significantly improved the capacity retention of LNMO/Li half-cells from 78.5 to 95.8% after 500 cycles at 5C, increased the capacity retention of LNMO/graphite full-cells from 70.8 to 80.9% after 100 cycles at 0.5C, and enhanced the capacity retention of LNMO/LTO full cells from 37.2 to 81.8% after 200 cycles at 5C. In addition, the standard electrolyte containing 0.5% MDTD also improved the cycling performance of LNMO/Li half-cells at 45 °C, expanding the applicable temperature range. Comprehensive characterization combined with theoretical calculations allowed us to reveal the action mechanism of the additive. In this mechanism, MDTD is decomposed and subsequently involved in the decoration of the electrode–electrolyte interfacial films (for the LNMO, Li, and graphite electrodes), endowing it with improved conductivity, protection, and resistance to electrolyte oxidation/reduction decomposition features. These findings suggest that the use of the MDTD additive is a promising strategy to optimize high-voltage electrolytes for the industrialization of LNMO-based LIBs.