Lithium bis((trifluoromethyl)sulfonyl)azanide (LiTFSI) based electrolytes have become the preferred electrolytes for lithium metal batteries (LMBs) due to their exceptional anode stability and ionic conductivity. However, challenges including unstable cathode electrolyte interface (CEI) formation and aluminum current collector (AlCC) corrosion have hindered the application of LiTFSI-based electrolyte in high-voltage LMBs. In this work, a universal passivation strategy is proposed and achieved with additive 8-hydroxyquinoline (8-HQ) in LiTFSI based electrolyte (ED-HQ). The 8-HQ additive preferentially decomposes on the cathode surface to generate Li 3 N, inducing the formation of inorganic-rich CEI with a uniform thickness of only 10 nm. The dense and homogeneous inorganic-rich CEI enables the cycling stability of the cathode. Meanwhile, the 8-HQ additive shows strong adsorption on the AlCC surface, which promotes the formation of a composite passivation layer consisting of an Aluminum-8-hydroxyquinoline (Alq 3 ) chelate layer and an AlF 3 /LiF inorganic layer, increasing the stable operating voltage of AlCC to 4.9 V and reducing the corrosion current density to one tenth. As a result, the joint effects enable Li||LiFePO 4 cells with ED-HQ electrolyte to achieve 89.8% capacity retention after 500 cycles at an elevated cutoff voltage of 4.5 V, demonstrating a viable pathway toward stable high-voltage LMB operation.
Kangshuai Zhu,Jing Yang,Yuxuan Li,Tongle Xu,Qinmin Pan
Solid polymer electrolytes (SPEs) have attracted significant attention in next-generation solid-state batteries (SSBs). However, SPEs-based SSBs suffer from performance fading and safety concerns at high temperatures caused by the thermal instability and degradation of their electrode/electrolyte interfaces. Herein, a poly(vinylene carbonate-co-methyl acrylate)-based solid polymer electrolyte (PVC-MA-SPE) with a highly self-adaptive structure is designed. The resulting PVC-MA-SPE exhibits an ionic conductivity of 4.93 × 10 −4 S cm −1 at 120 °C and high adhesion to electrodes. At zero pressure, solid-state Li|PVC-MA-SPE|LFP batteries maintain 152.6 mAh g −1 discharge capacity and 95.4% capacity retention after 150 cycles at 1C and 120 °C. The mechanism for the improved performance is attributed to the strong intermolecular interaction of the poly(vinylene carbonate-co-methyl acrylate) (PVC-MA) network with volatile molecules. Importantly, the PVC-MA network not only enables the SPE to tightly contact with electrodes, but also contributes to forming thermally stable SEI/CEI enriched in flexible polymeric components and LiF. These properties result in enhanced interfacial stability at high temperature. This work presents a novel approach to enhance the intrinsic safety of solid-state batteries at high temperatures.
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