Three–dimensional fiber network reinforced polymer electrolyte for dendrite–free all–solid–state lithium metal batteries

All–solid–state lithium metal batteries (ASSLMBs) are considered the holy grail of next–generation high–energy–density energy storage systems. However, the growth of lithium (Li) dendrites and poor solid–solid interfacial contact limit their development. The design of a solid electrolyte structure is an effective strategy for solving this problem. In this study, a composite solid electrolyte (CSE) was reported that was reinforced by a three–dimensional (3D) fiber network of PAN/LLZTO, uniformly dispersed in the PEO polymer (PPL) matrix to form a continuous path. This continuous framework not only facilitated the rapid migration and uniform deposition of Li ion, but also improved the mechanical strength of the polymer matrix and effectively inhibited dendrite growth. PPL electrolyte had a high ionic conductivity of 1.76×10–4 S cm–1 (30 °C), wide electrochemical stability window of 5.2 V, and high Li ion transfer number of 0.53. These CSEs ran stably for more than 4000 h in Li symmetrical batteries. A reversible capacity of 120.7 mA h g–1 was obtained after 1000 cycles at a current density of 1.0 C in LiFePO4/PPL/Li batteries. In addition, PPL electrolyte exhibited stable cycling performance with a high–voltage cathode. The reversible capacity of the LiNi0.5Mn0.3Co0.2O2 (LiCoO2)/PPL/Li battery was 138.8 mA h g–1 (130.3 mA h g–1) after 100 cycles (0.2 C). And the, LiFePO4/PPL/Li battery cycled stably at room temperature, with the capacity stabilized at 52.0 mA h g–1 after 1700 cycles (1.0 C), which further broadened the potential application of CSEs. This study showed that this 3D fiber network reinforced polymer electrolyte possessed broad application prospects in next–generation ASSLMB systems.