A biomimetic green binder: Forming a biomorphic polymer network in SiOx anode to buffer expansion and enhance performance

Although SiOx can exhibit a higher specific energy than graphite material in lithium-ion batteries (LIBs), its mass commercial application still suffers from the performance degradation of SiOx anode caused by volume expansion. In this work, based on a biomimetic strategy and the unique double helix structure of xanthan gum (XG), sodium alginate (SA), XG and polyacrylic acid (PAA) are used to design and prepare a new water-based binder (N-SXP) to form a biomorphic polymer binder network in the SiOx anodes and effectively improve the cycling performance. It is indicated that the hydrogen and chemical bonding forces of N-SXP binder can form a solid multiple chain structure, and in particular, the supramolecular ion–dipole effect of each side chain is similar to that of a millipede's leg and can firmly adsorb the SiOx surface, and together with large hydroxyl groups form bonds between N-SXP and SiOx. After 600 cycles at 0.5C, the reversible capacity is 1105 mAh/g. Even after 300 cycles at 1C and 2C, a stable performance can still be obtained. In addition, 250 cycles at 40 °C 0.5C still provide 1101 mAh g-1 de-lithium specific capacity. The full battery capacity remains stable after 150 cycles at 200 mA g−1, and a rate capacity of 115 mAh g-1can be kept at 3C. The quantitative calculations by molecular simulations yield the role of N-SXP in forming the hydrogen bonds on SiOx surfaces, and combining with the spectroscopic characterization results further elucidate the functional mechanism of N-SXP binder in the SiOx anode. This biomimetic binder network pathway derived from N-SXP not only enhances the performance of SiOx anode but also provides an idea for the development of new bonding candidates of silicon-based materials.