Raspberry-like micro-size polymer with high spherical shape-retention capability and adhesion as binder for ceramic separators

Surface coating with binders and ceramic particles is one of the most effective strategies to enhance thermal stability and electrolyte wettability of polyolefin separators, yet is still challenged by the issue of hole blocking and contradiction between adhesion and thermostability of binders. Herein, a raspberry-like micro-size polymer (RMP) binder with a soft core inside and hard spheres outside was prepared through seed swelling polymerization. The micron size helps RMP binder to effectively bond separator and electrode, solving the pore blocking problem encountered with traditional liner binders. The raspberry-like structure combines softness and rigidity, ensuring both high spherical shape-retention capability and good binding strength. The ceramic separator with RMP binder shows low thermal shrinkage and high ionic conductivity, achieving high cycling stability and low impedance of the batteries. This work provides new inspiration to construct novel binders for ceramic-coated separators with long-term stability for high-performance lithium-ion batteries.