Real-Time Imaging of the Electrochemical Process in Na–O2 Nanobatteries Using Pt@CNT and Pt0.8Ir0.2@CNT Air Cathodes

Compared to lithium–oxygen batteries, sodium–oxygen (Na–O2) batteries exhibit a number of advantages: extremely low cost, low charging overpotential, and stability under nitrogen. However, accumulation of insoluble discharge products and failure of catalysts often result in poor performance of Na–O2 batteries and limit their cycling life. In this work, electrochemical reactions of Na–O2 batteries were directly investigated in situ by assembling a solid-state Na–O2 nanobattery in an aberration-corrected environmental transmission electron microscope. During discharge, NaO2 hollow spheres formed and expanded continuously, accompanying their partial decomposition into Na2O2. These spheres shrank and collapsed into Na2O2 nanoparticles during the charging process. Carbon nanotubes doped with Pt and bimetallic Pt/Ir nanoscale catalyst can promote product formation and reversible evolution. In-depth investigation of the electrochemical reaction mechanism in Na–O2 cells helps to accelerate the development of metal–air devices.与锂氧电池相比，钠氧（Na–O₂）电池具备多项显著优势：成本极低、充电过电位低，且在氮气氛围下具有良好稳定性。然而，不溶性放电产物的累积与催化剂失效常会导致钠氧电池性能劣化，进而限制其循环寿命。本研究通过在球差校正环境透射电子显微镜内组装固态钠氧纳米电池，对钠氧电池的电化学反应进行了原位直接观测。放电过程中，超氧化钠（NaO₂）空心球不断形成并持续扩张，同时部分分解为过氧化钠（Na₂O₂）；充电过程中，此类空心球发生收缩并坍塌为过氧化钠（Na₂O₂）纳米颗粒。掺杂铂（Pt）的碳纳米管与双金属铂/铱（Pt/Ir）纳米催化剂，可有效促进放电产物的生成与可逆演化。对钠氧电池电化学反应机制的深入探究，将有助于加速金属空气电池器件的研发进程。