Additive Strategy Enhancing In Situ Polymerization Uniformity for High-Voltage Sodium Metal Batteries

作者：Ma, Jian; Yu, Mengyue; Huang, Minghao; Wu, Yueyue; Fu, Chengyu; Dong, Lei; Zhu, Zhendong; Zhang, Le; Zhang, Zheng; Feng, Xuyong; Xiang, Hongfa^*

来源：Small, 2024, 20(5).

DOI：10.1002/smll.202305649

• gas residue
• H2O and HF scavenge
• high-voltage cathodes
• in situ polymerization
• quasi-solid polymer electrolytes

In situ polymerization to prepare quasi-solid electrolyte has attracted wide attentions for its advantage in achieving intimate electrode-electrolyte contact and the high process compatibility with current liquid batteries; however, gases can be generated during polymerization process and remained in the final electrolyte, severely impairing the electrolyte uniformity and electrochemical performance. In this work, an in situ polymerized poly(vinylene carbonate)-based quasi-solid electrolyte for high-voltage sodium metal batteries (SMBs) is demonstrated, which contains a novel multifunctional additive N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA). MSTFA as high-efficient plasticizer diminishes residual gases in electrolyte after polymerization; the softer and homogeneous electrolyte enables much faster ionic conduction. The HF/H2O scavenge effect of MSTFA mitigates the corrosion of free acid to cathode and interfacial passivating layers, enhancing the cycle stability under high voltage. As a result, the 4.4 V Na||Na3V2(PO4)(2)F-3 cell employing the optimized electrolyte possesses an initial discharge capacity of 112.0 mAh g(-1) and a capacity retention of 91.3% after 100 cycles at 0.5C, obviously better than those of its counterparts without MSTFA addition. This work gives a pioneering study on the gas residue phenomenon in in situ polymerized electrolytes, and introduces a novel multifunctional silane additive that effectively enhances electrochemical performance in high-voltage SMBs, showing practical application significance.