Garnet-Based Solid Li-Metal Batteries Operable under High External Pressure with HCOOH-Induced Electron-Blocking and Lithiophilic Interlayer
Haoyu Zhao, Mingjie Du, Haoran Mo, Cuie Wang, Wei Zhou, Kaiming Liao, Zongping Shao
Abstract
Despite good compatibility with Li metal, garnet solid electrolytes suffer from severe electron-attack-induced Li-metal penetration and large interfacial resistance. Here, a formic acid (HCOOH)-induced electron-blocking and lithiophilic interlayer is created via a spontaneous reaction with surface Li 2 CO 3 contamination on the garnet electrolyte (LLZTO) pellet. Unlike previous methods that involved immersing LLZTO in acidic solutions, this study employs a volatile small-molecule organic acid that is easily removable, condensed, and recyclable, thus circumventing the environmental drawbacks associated with acid waste. The Li symmetric cell assembled with HCOOH-treated LLZTO exhibits a low interfacial impedance (3 Ω cm 2 ) and a high critical current density (1.7 mA cm –2 ) at room temperature, enabling the cell to cycle continuously for over 1000 h at 0.2 mA cm –2 . Furthermore, under a stacking pressure of 2 MPa, stable lithium plating/stripping was achieved at a current density of 0.3 mA cm –2 with the assistance of HCOOH treatment. Additionally, the battery paired with a LiFePO 4 cathode delivers a high capacity of 151.7 mAh g –1 at 1 C and maintains 88.5% of the initial capacity after 500 cycles, suggesting the feasibility of this interfacial engineering strategy for garnet-based solid Li-metal batteries.