Elastic and Stretchable Gel Polymer Electrolyte Coating to Improve Long-Term Cycling Stability of High-Areal-Capacity Sio Electrode for Lithium-Ion Battery

Si-based anode is an advanced anode material to improve the energy density of Li-ion battery. In order to pair with commercial cathode, the areal capacity of Si-based anode should be increased to 3-4 mAh/cm 2 . However, high-areal-capacity Si-based anode still encounters fast capacity fading and poor cycling stability, because large volume change upon cycling will damage electrode structure integrity and arise accumulated growth of SEI (solid electrolyte interface) layer. Here we develop an elastic and stretchable polyurethane-urea (PUU) gel polymer electrolyte (GPE) coating strategy to improve the long-term cycling stability of high-areal-capacity SiO anode. The PUU polymer coating can swell and uptake 48 w% carbonate electrolyte, providing a moderate ionic conductivity of 2.4*10 -4 S/cm at room temperature. The GPE shows good chemical and electrochemical stability with lithium metal. At the electrode level, the GPE coating can improve electrode adhesion strength and alleviate electrode thickness change during charge/discharge process. For long-term cycling, the GPE coating can restrict the pulverized particles in a localized space to prevent loss of conductive network and maintain the electrode structure integrity. In the half-cell test, the SiO electrode with GPE coating shows a reversible capacity of 3.0 mAh/cm 2 (or specific capacity of 1200 mAh/g) for 280 cycles. In the full-cell test, the cell of pre-cycled NCM/pre-cycled SiO electrode with GPE coating has a reversible capacity of 2.1 mAh/cm 2 (or specific capacity of 150 mAh/g) for 200 cycles, with an improved Coulombic efficiency of 99.9%.