Manufacturing large-format practical Na-ion battery with over 200 Ah and 3 000 cycles

Na-ion batteries (NIBs) are compelling technologies for electric trucks and large-scale energy storage, where long-term cycling stability remains a pivotal challenge—especially for prismatic cells with capacities exceeding 200 Ah. As the cell capacity increases, the detrimental effects of gas evolution and impedance growth—driven by persistent electrode–electrolyte side reactions—on cycling performance become more pronounced. To address this, we report a multi-anion synergistic electrolyte designed to reconstruct the Na⁺ solvation sheath into an anion-rich configuration. This modulation triggers selective anion decomposition, yielding thin, mechanically robust, and inorganic-rich electrode–electrolyte interphases (EEIs) on both the hard carbon (HC) anode and the layered NaCu_1/9Ni_2/9Fe_1/3Mn_1/3O₂ (NaCNFM) cathode. Consequently, 210 Ah prismatic cells achieve remarkable stability over 1 670 cycles (92.7% retention at 25 °C; 88.6% at 45 °C), while 270 Ah cells maintain 89.2% capacity after 3 333 cycles at 1 C. In addition, the cells exhibit excellent low-temperature discharge and rate performance: 92.8% capacity retention at −40 °C and 0.33 C, along with 94.3% charge capacity and 99.1% discharge capacity at 3 C and 25 °C. This study offers a scalable strategy for high-capacity NIBs, providing critical insights into electrolyte engineering for next-generation energy storage technology.