Fast-charging heterogeneous ether-ester lithium metal batteries enabled by 12 μm-thick trilayer separator

Lithium metal batteries (LMBs) equipped with high-voltage/capacity cathodes, notably LiNi0.8Co0.1Mn0.1O2 (NCM811), have surpassed specific energy levels of 350 Wh kg- 1, positioning them as potential benchmarks for future electric vehicles. However, fast charging of high-energy-density LMBs remains a significant challenge. In contrast to the commonly adopted approach of utilizing a homogeneous electrolyte for ions conduction within a cell, here we demonstrate the feasibility of a heterogeneous ether-ester LMB configuration, facilitated by a 12 mu m-thick trilayer separator with a porous/dense/porous structure, in conjunction with crosslinked ether and liquid carbonate ester electrolytes. As a demonstration, this porous-dense-porous trilayer separator confines dimethoxyethane (DME) electrolyte to the porous poly(vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) layer, LiTFSI-LiBOB carbonate electrolyte to the porous polyethylene (PE) layer, and effectively impedes the shuttling of ether-ester electrolytes by the Li6.5La3Zr1.5Ta0.5O12 (LLZO)-rich dense interlayer. This configuration induces synergetic reductive and oxidative interfacial stability in the heterogeneous ether-ester LMB. Consequently, when using an NCM811 cathode with a practical loading of 18 mg cm- 2 in the heterogeneous etherester LMB, a capacity retention of 84 % after 100 cycles is achieved, along with a lean electrolyte of 9 mu l mAh-1, under an extremely high charge/discharge current densities of 3.6 mA cm- 2. The fast charging capability and prominent reversibility of the LMBs are attributed to the unique heterogeneous ether-ester LMB configuration, which holds great potential for advancing next-generation battery technology.