A stress-adaptive interlinked 3D network binder for silicon anodes via tailored chemical bonds and conformation of functionalized poly(vinylidene fluoride) (PVDF) terpolymers

Abstract

Lithium-ion batteries (LIBs) incorporating silicon (Si) anodes offer high energy density; however, they confront challenges arising from large volumetric fluctuations during charge/discharge processes. This leads to the pulverization of the Si particles and loss of electric contact in the Si anodes, resulting in reduced cycle stability and degraded capacity retention. Herein, we propose a conceptually designed binder strategy for chemically modified poly(vinylidene fluoride) (PVDF) by introducing double bonds into the PVDF terpolymer (denoted as PVTD), which can produce crosslinked 3D-network structures (denoted as PVTDX) through a simple heat treatment during the anode fabrication process. Notably, the presence of randomly distributed double bonds in PVTD induces irregular conformations, reducing the crystallinity of PVTD by impairing intra- and inter-chain interactions, which in turn improved the solubility of PVTD in organic solvents such as N-methyl-2-pyrrolidone (NMP) and enabled uniform dispersion of PVTD in the Si anode composition. Additionally, PVTD exhibits a strong affinity for electrolytes and considerable chemical and thermal stability owing to the presence of fluorine atoms. Notably, PVTDX effectively mitigates volumetric changes in Si particles because of its enhanced adhesive force and robust network structure. By leveraging these advantageous characteristics of the PVTDX binder, the structural integrity of the Si anode is in good preservation during cycling, resulting in enhanced specific capacity and reliable long-term cycling performance. This innovative and pragmatic design holds significant promise for advancing the development of high-performance Si-anode-based LIBs.