Tailoring Anion‐Enriched Solvation Structures in Phosphate‐Based Electrolytes for Safety‐Enhanced Lithium Metal Batteries

Abstract Both phosphate‐based high‐concentration electrolytes and localized high‐concentration electrolytes effectively address safety concerns and interfacial compatibility issues in Ni‐rich lithium metal batteries (LMBs). However, their high cost and viscosity have hindered further practical applications. Here, an intrinsically nonflammable phosphate‐based low‐concentration electrolyte is delicately presented, employing 0.7 M lithium difluoro(oxalato)borate and the flame‐retardant trimethyl phosphate solvent, to overcome the aforementioned challenges. The weak interactions between trimethyl phosphate and difluoro(oxalato)borate anions facilitate the formation of anions‐induced solvation structures and the protective layers that are rich in boron oxides and LiF. The as‐designed electrolyte has been employed to build LiNi 0.9 Co 0.05 Mn 0.05 O 2 /Li cell which demonstrates stable cycling for over 180 cycles. Additionally, the battery is also able to operate successfully over a wide temperature range, from ‐20 to 60 °C, and displays elevated thermal runaway temperatures, enhanced high‐temperature charge retention capability, and reduced gas evolution. Moreover, a 20.0 Ah pouch cell achieves a high energy density of 533.8 Wh kg −1 , showcasing great potential for commercial applications. Furthermore, this electrolyte is compatible with both layered and spinel cathodes. The delicate molecular design strategy in this work provides a promising avenue for the development of high‐safety electrolytes for high‐energy‐density Ni‐rich LMBs.