3‐Dimensional Cross‐Linked Polymer Electrolytes Enabled Fast Ion Transport and Interface Stability for Solid‐State Lithium Metal Batteries

The practical application in solid‐state lithium metal batteries (SSLMBs) with polymer electrolytes is still hindered by poor compatibility with lithium metal, lithium dendrite growth, and low ionic conductivity. To challenge these issues, we developed a composite electrolyte consisting of electrospun polyacrylonitrile (PAN) and poly(ethyleneimine) (PEI) fibers scaffold via cross‐linking, poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) as the main polymer matrix, succinonitrile (SN) as plasticizer, and hydrolyzed polymeric anhydride (HPMA) as cross‐linking modifier. Interestingly, the abundant COOH groups in HPMA promote the cross‐linking, substantially reducing the crystallinity of electrolyte. As a result, the PPF‐5HP electrolyte exhibits a high ionic conductivity of 9.92 × 10 −4 S cm −1 at 30°C, along with the improved mechanical strength (tensile strength of 6.45 MPa), the broader electrochemical window (~4.92 V) and enhanced compatibility with lithium metal (2500 h for Li symmetric cell). Also, compared with the HPMA‐free electrolyte, LiFePO 4 |PPF‐5HP|Li full cell delivered a higher discharge specific capacity and better capacity retention, for example, an 82.35% of its initial capacity after 106 cycles at 0.5C. More impressively, LiNi 0.8 Co 0.1 Mn 0.1 O 2 |PPF‐5HP|Li full cell displayed a 96.5% capacity retention after 128 cycles at 0.3C. These results demonstrate the effectiveness of our proposed 3‐dimensional cross‐linking strategy in developing the high‐performance PEs and SSLMBs.