Accelerated Charge Transfer Kinetics and Byproduct Suppression in Surface-Tailored LiNi0.83Mn0.05Co0.12O2 Cathode at –40 °C

In extreme-environment applications such as military, aerospace, and polar research, batteries capable of reliable operation at ultralow temperatures are urgently needed. Current low-temperature battery research has largely focused on electrolyte optimization, while cathode material design remains relatively underexplored. LiNi0.83Mn0.05Co0.12O2 cathodes, however, suffer from sluggish interfacial charge-transfer kinetics and accelerated parasitic reactions at -40 °C. Here, a simple polypyrrole (PPy) surface coating is demonstrated to simultaneously enhance the rate capability and cycling stability of LiNi0.83Mn0.05Co0.12O2 at -40 °C. The π-conjugated PPy coating improves electronic transport while stabilizing the surface/interfacial chemical environment, thereby reducing the kinetic barrier for interfacial charge transfer, suppressing excessive interphase growth, and facilitating Li+ transport. Consequently, the PPy-coated cathode delivers 103.1 mAh g-1 at 1C and retains 78.7% of its capacity over 300 cycles at -40 °C. Furthermore, a practical 1.6 Ah lithium-metal pouch cell delivers 75% of its nominal energy at -40 °C and maintains 92.2% capacity retention after 50 cycles. This work highlights cathode interfacial engineering as an effective complement to electrolyte optimization for developing high-rate and long-life LiNixMnyCo1-x-yO2-based lithium-metal batteries under extreme cold.