Fast‐Charging Long‐Life Solid‐State Sodium Metal Batteries Enabled by 2D Boron Nitride Nanosheets Based Quasi‐Solid‐State Electrolytes

Boron nitride nanosheets are employed as 2D functional fillers to accelerate and homogenize Na⁺ ion transport in photopolymerized ethoxylated trimethylpropane triacrylate based quasi-solid-state electrolytes, which exhibit enhanced ionic conductivity, wide electrochemical stability window, and excellent compatibility with Na metal anode without dendrites, toward safe, fast-charging and long-life solid-state sodium metal batteries.

Abstract

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, a safe, fast-charging, and long-life SSMB is reported, utilizing photopolymerized ethoxylated trimethylpropane triacrylate based QSSEs (BN-QSSE) reinforced by 2D 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 h 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 the 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.