Dual-crosslinked network binder of alginate with polyacrylamide for silicon/graphite anodes of lithium ion battery

In lithium ion batteries, high-capacity anodes that undergo very large volume change during charge/discharge cycles are needed to apply a strongly adhesive polymer binder due to the severe mechanical stress developed during the cycles. Although bio-derived alginate is known to be a potential candidate for the binder owing to its strong mechanical property, it can be improved using a number of modifications such as physical crosslinking. Here, we propose a significantly better method of improving the electrochemical performance of the binder by introducing dual-crosslinked alginate with polyacrylamide. The polyacrylamide provides strong adhesion in the electrode with resistance to the penetration of the organic electrolyte. Both ionic and covalent crosslinkings in the binder maintain their intrinsic good binding properties and additionally enhance lithium ion diffusion. More interestingly, an in-situ electrochemical dilatometer study indicates that the dual-crosslinked binder is considerably helpful to prevent volume expansion beyond the inevitable value caused by active materials in electrodes during the cycle. Consequently, the Si/C (1/3) electrode retains nearly 840 mAh g(-1) high capacity even after one hundred cycles with excellent cycleability.