J.Y. Shen, X.Y. Shi, F.F. Xing, E.D. Yang, Z.H. Ren, S.H. Liao, S.H. Chen, Y.F. Dong * and Z.-S. Wu *

Advanced Energy Materials, 2025, accepted.

Solid-state sodium metal batteries (SSMBs) are considered as one highly competitive, high-energy-density yet safe energy storage device, however, the conventional quasi-solid-state electrolytes (QSSEs) still suffer from low ion conductivity and limited mechanical properties. Herein, we report a safe, fast-charging and long-life SSMB using photopolymerized ethoxylated trimethylpropane triacrylate based QSSEs (BN-QSSE) reinforced by two-dimensional functional fillers of boron nitride nanosheets (BNNSs). The BNNSs with high Young’s modulus in BN-QSSE can simultaneously accelerate and homogenize ion transport for uniform Na deposition and form a robust electrolyte-Na interface. Only a low proportion of 1% BNNSs in BN-QSSE can effectively realize high ionic conductivity of 1×10−2 mS cm−1, achieve a wide electrochemical stability window of 4.85 V (vs. Na/Na+), and substantively suppress Na dendrites. The resulting Na||BN-QSSE||Na symmetric batteries exhibit a long life of 600 times at 0.1 mA cm−2 and 0.1 mAh cm−2. The as-assembled Na3V2(PO4)3||BN-QSSE||Na full batteries display high capacities of 102 mAh g−1 at 1 C and 75 mAh g−1 at a high rate of 15 C, and maintain 93% of initial discharge capacity after 1000 cycles at 10 C, outperforming most reported SSMBs. The developed 2D filler-reinforced QSSE provides new opportunities for high-performance SSMBs.