Synergistic dual-additive regulated carbonate electrolyte stabilizes bidirectional interface for aggressive Ni-rich Li-metal full batteries

Abstract

The escalating energy demands underscore the importance of Ni-rich Li-metal batteries (LMBs); however, their aggressive bidirectional electrode-electrolyte interfacial issues hinder the practical implementation. Overcoming the limited solubility (∼800 ppm) of lithium nitrate (LiNO3) in commercially available carbonate electrolytes holds promise. Nevertheless, unintended effects caused by solubilizers raise emerging concerns. Herein, an additive solubilized additive strategy is introduced to synergistically stabilize the Ni-rich cathode and Li-metal anode (LMA) in carbonate electrolytes, where tris (2, 2, 2-trifluoroethyl) borate (TTFEB) as a solubilizer utilizes its electron-deficient B atom to snatch electron-rich NO3- anion of insoluble LiNO3 and thus forms a unique TTFEB-LiNO3 solvation structure in carbonate electrolytes. Valuably, the dual-additive electrolyte facilitates the formation of a robust LiF/Li3N-rich solid electrolyte interphase on LMA and a thin, uniform F, B, N-rich cathode electrolyte interphase on Ni-rich cathode, effectively suppressing the breeding of Li dendrites and mitigating the structure degradation of Ni-rich cathode. Consequently, the full cell, featuring a thin Li anode (50 µm) and a high-loading NCM811 cathode (4.04 mAh cm−2) in the dual-additive electrolyte, demonstrates a notable capacity retention of 81.5 % after 140 cycles. This work reveals the intricated LiNO3-carbonate solvation chemistry, inspiring further advancements in electrolyte engineering for practical LMBs.