Li0.5PAA domains filled in porous sodium alginate skeleton: A 3D bicontinuous composite network binder to stabilize micro-silicon anode for high-performance lithium ion battery

An important strategy to improve energy density of Li-ion batteries is to substitute the traditional graphite anode by Si-based anode which is endowed with ultra-high theoretical specific capacity. However, the commercialization of Si anodes is hindered by its huge volume variation that results in electrode pulverization. In the current study, we fill up the pores of sodium alginate (SA) network with lithiated polyacrylic acid (LixPAA) to form a cross-linked bicontinuous composite network binder (b-Li0.5[email protected]), in which the pores of the SA skeleton are dominated with the Li0.5PAA domains; within such composite the SA and Li0.5PAA interlock tightly each other via extensive interfacial ester bonding. The resulting b-Li0.5[email protected] network binder can effectively buffer the volume variation of Si microparticles (m-Si) during repeating cycling and prevent pulverization of the electrode, which is evidenced by a cycling capacity of 2762 mAh g−1 in the 1st cycle and a retention of 1584 mAh g−1 after 150 cycles. As a comparison, the m-Si electrode with only SA binder suffers from fatal capacity degradation after merely 20 cycles under the same conditions. Moreover, since the Li0.5PAA domains are ionic conductive and significantly reduce the porosity of the SA network, the b-Li0.5[email protected] network binder could also enable a stable solid electrolyte interphase (SEI) film and fast electron/ion transfer, leading to an enhanced rate capability of the m-Si anodes.