In-situ Construction of Self-Healing Polyelectrolyte/Polyzwitterion Coacervate Framework for High-Performance Silicon Anodes

Silicon is considered as a promising candidate for anode materials due to its ultrahigh theoretical capacity and natural abundance. However, the commercialization is severely hampered by the large strain and short cycle life. Herein, we have synthesized a reversible polyelectrolyte/polyzwitterion coacervate framework to achieve high-performance silicon anodes with high initial Coulombic efficiency (ICE) and stable cyclability. Such coacervate framework is formed via in-situ free radical polymerization of zwitterionic 2-methacryloyloxy ethyl phosphorylcholine (MPC) with polyacrylic acid (pAA) during heating the slurry. The resulting pAA/pMPC coacervate framework presents excellent adhesion, thermal stability, and negligible swelling in the electrolyte. Comparing with pAA, pAA/pMPC0.1 coacervate framework binder exhibits superior performance during charge/discharge. The ICE is improved from 84.41 %, to 87.61 %. After 250 cycles, the specific capacity of pAA/pMPC0.1 silicon anode is 1678 mAh g-1 with a retention of 78 % while the pAA silicon anode completely failed after less than 200 cycles. Such improvement is ascribed to the structural integrity of the electrode endowed by the self-healing ability of pAA/pMPC coacervate framework. This work not only offers a feasible method to in-situ construct coacervate framework with self-healing capability to achieve high-performance silicon anodes but also a compatible electrode preparation process for other high-capacity materials. We construct an in-situ self-healing polyelectrolyte/polyzwitterion coacervate framework of pAA/pMPC as binder for silicon anode. Two polymers interact with each other to form 3-dimentional network via dipole interaction. As the result, pAA/pMPC framework significantly improves the cycle life and capacity of silicon anodes through ameliorating the kinetics and self-healing the crack of electrode. image