Identifying lithium difluoro(oxalate)borate as a multifunctional electrolyte additive to enable high-voltage Li4Ti5O12 lithium-ion batteries

Abstract

Li₄Ti₅O₁₂ (LTO) is an excellent anode for lithium-ion batteries (LIBs). However, the large-scale commercialization of LTO-based LIBs is hindered by the shortcomings of LTO, including sluggish kinetics, severe gas generation, and especially low energy density. Although considerable efforts have been made to address the low-energy-density issue of LTO by pairing it with a high-potential LiNi_0.5Mn_1.5O₄ (LNMO) cathode, the operation of the resultant high-voltage LNMO//LTO batteries becomes more difficult since issues concerning not only the LTO anode but also the LNMO cathode and the electrolyte now need to be considered. It is greatly challenging to develop a simple yet versatile strategy for simultaneously addressing all of the issues of the LNMO//LTO system. Herein, we identify lithium difluoro(oxalate)borate (LiDFOB) as a multifunctional electrolyte additive to enable high-performance high-voltage LNMO//LTO batteries. We demonstrate the multifunctionalities of LiDFOB for suppressing the decomposition and hydrolysis of LiPF₆ and capturing Mn²⁺ in the electrolyte as well as preforming superior surface coatings at the LTO anode and LNMO cathode, effectively stabilizing the electrolyte, and enabling well-defined electrochemical behaviors for both electrodes. These endow our LNMO//LTO battery with an excellent overall performance at an operating voltage up to 3.50 V, significantly outperforming its previously reported LNMO//LTO counterparts with various strategies.