Highly Elastic hyperbranched polymer binder for silicon anodes in lithium-ion batteries

With extremely high theoretical capacity, silicon (Si) has been considered as one of the most promising anode materials for next-generation lithium ion batteries (LIBs). However, Si electrodes undergo huge volume changes and pulverization during the actual charge-discharge processes. In response, polymer binders can bind Si particles together, preventing the electrodes from decomposition during operation. On this basis, a novel Si-anodic elastic polymer binder system based on cross-linked hyperbranched polyethyleneimine (HPEI) with optimized cross-linker length was developed, which could achieve a good balance between the mechanical elasticity and bonding reversibility of the network. The as-prepared Si anode exhibits a high discharge capacity of 2630 mAh g −1 at a current density of 500 mA g −1 , and maintains excellent cycling stability with a high capacity retention of 78.7% after 200 cycles at a high current rate of 2000 mA g −1 .