Diphenyl Azidophosphate as a Functional Electrolyte Additive for High-Conductivity Film Construction over Lithium Metal Battery

Abstract

Lithium metal batteries (LMBs) with high loading and high current density can be achieved by tailoring electrolyte components. As an effective film-forming electrolyte additive, diphenyl azidophosphate (DPPA) has been proposed here to construct high conductive solid electrolyte interphase (SEI) layers on the Li metal anode surface enriched with Li3N and P–O compounds. Compared with cells without DPPA additive, the Li∣∣Cu cells with 1% DPPA demonstrate evaluated accurate Coulombic efficiency (CE) from 77.9% to 93.8%, and Li∣∣Li symmetric cells are able to cycle for more than 250 h at the current density of 2 mA cm−2. The high conductive SEI layer increases the exchange current density of Li metal anode from 0.247 mA cm−2 to 0.760 mA cm−2. The Li∣∣LiNi0.8Co0.1Mn0.1O2 (NCM811) cell maintain 80.8% capacity retention after 250 cycles in the DPPA-containing electrolyte. Discharge capacity of the Li∣∣NCM811 cell can reach 142 mA h g−1 at a high discharge current of 13.2 mA cm−2. Further theoretical calculations indicate that the DPPA additive can be preferentially reduced to form a stable SEI layer with high conductivity.