Composite solid electrolytes (CSEs) have emerged as promising contenders for tackling the safety concerns associated with lithium metal batteries and attaining elevated energy densities. Nonetheless, augmenting ion conductivity and curtailing the growth of lithium dendrites within the electrolyte remain pressing challenges. We have developed CSEs featuring a unique structure, in which Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) is distributed in a gradient decline from the center to both sides (GCSE). This distinctive arrangement encompasses heightened polymer content at the edges, thereby enhancing the compatibility between CSEs and electrode materials. Concurrently, the escalated LLZTO content at the center functions to impede the proliferation of lithium dendrites. The uniform gradient distribution state facilitates the consistent and rapid transport of lithium ions. At room temperature, GCSE exhibits an ionic conductivity of 1.5 × 10 −4 S cm −1 , with stable constant current cycling of lithium for over 1200 h. Furthermore, CR2032 coin batteries with a LiFePO 4 (LFP)|GCSE|Li configuration demonstrate excellent rate performance and cycling stability, yielding a discharge capacity of 120 mA h g −1 at 0.5C and retaining 90 % capacity after 200 cycles at 60 °C. Flexible solid electrolytes with gradient structures offer substantial advantages in dealing with ion conductivity and inhibition of lithium dendrites, thereby expected to propel the practical application of lithium metal batteries.
Yuchen Wang,Kun Liu,Henghui Xiao,Zhaorun Zhu,Chenqun Hong,Hongzhen Lin,Jian Wang,Decai Guo,Meinan Liu
Hybrid solid electrolytes have emerged as promising candidates for next-generation high-energy-density solid-state lithium metal batteries owing to the enhanced safety and processability. Nevertheless, the practical implementation remains hindered by severe interfacial Li + transport barriers at ceramic-polymer junctions, particularly under ambient low-temperature or high-power-density surroundings. Herein, the lithium-ion bridge concept has been proposed to accelerate Li + transport kinetics across the ceramic-polymer interphase through the delicate design of a chemical bonding strategy. As demonstrated, the poly(vinylidene fluoride-co-hexafluoropropylene) (PH) chain with Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) particles can be connected by lithium benzene sulfonate as Li + conductive bridges. With these Li + bridges, this unique hybrid PH-LLZTO solid-state electrolyte exhibits an exceptional ionic conductivity of 0.71 mS cm −1 at 25°C with a superior Li + transference number of 0.67. Impressively, this advanced solid-state electrolyte empowers high-voltage LiNi 0.8 Co 0.1 Mn 0.1 O 2 /Li cells under fast charge/discharge capability as high as 4C and a wide temperature range from −20°C to 60°C. Consequently, the optimal solid-state Li metal battery could stabilize at −20°C with a high discharge specific capacity of 130 mAh g −1 . Moreover, a bipolar pouch cell by stacking 4 units can be successfully assembled using this advanced solid-state electrolyte with fast Li + transport kinetics and delivers an ultra-high voltage of 15.12 V, showcasing the great potential of integrated module application in the future.
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