Dynamically Cross-Linked Polymeric Binder-Made Durable Silicon Anode of a Wide Operating Temperature Li-Ion Battery

The colossal volumetric expansion (up to 300%) of the silicon (Si) anode during repeated charge-discharge cycles destabilizes the electrode structure and causes a drastic drop in capacity. Here in this work, commercial poly(acrylic acid) (PAA) is cross-linked by hydroxypropyl polyrotaxane (HPR) via reversible boronic ester bonds to achieve a water-soluble polymeric binder (PAA-B-HPR) for making the Si anode of the Li-ion battery. Slidable alpha-cyclodextrins of modified polyrotaxane are allowed to move around when the unwanted volume variation occurs in the course of lithiation and delithiation so that the accumulated internal stress can be equalized throughout the system, while the reversible boronic ester bonds are capable of healing the damages created during manufacturing and service to maintain the electrode integrity. As a result, the Li-ion battery assembled with the Si anode comprised of the PAA-B-HPR binder possesses outstanding specific capacity and cycle stability within a wide temperature range from 25 to 55 degrees C. Especially, the Si@PAA-B-HPR anode exhibits a discharge specific capacity of 1056 mA h/g at 1.4 A/g after 500 cycles under a higher temperature of 55 degrees C, and the corresponding capacity fading rate per cycle is only 0.10%. The present work opens an avenue toward the practical application of the Si anode for Li-ion batteries.

Automated summary

In this study, a water-soluble polymeric binder PAA-B-HPR is developed by crosslinking commercial poly(acrylic acid) and hydroxypropyl polyrotaxane, which is applied to the fabrication of the Si anode for Li-ion batteries. The battery exhibits outstanding specific capacity and cycle stability, with a discharge specific capacity of 1056 mA h/g at 55 degrees C after 500 cycles and a capacity fading rate of only 0.10% per cycle. This work paves the way for the practical application of Si anodes in Li-ion batteries.