An in situ thermal cross-linking binder for silicon-based lithium ion battery

Silicon has been regarded as one of the most promising anode materials for lithium-ion batteries (LIBs) due to its highest specific capacity and low (de)lithiation potential, however, the development of practical applications for silicon are still hindered by devastating volume expansion and low conductance. Herein, we have proposed an in situ thermally cross-linked water-soluble PA@PAA binder for silicon-based LIBs to construct dynamic cross-linking network. Specifically, ester bonds between -P-OH in phytic acid (PA) and –COOH in PAA, which are generated by thermal coupling, are designed to synergize with hydrogen bonds between the PA@PAA binder and silicon particles to dissipate the high mechanical stresses, which is verified by theoretical calculation. GO is further adopted to protect silicon particles from immediate contact with electrolyte to improve initial coulombic efficiency (ICE). A range of heat treatment temperatures is explored to optimize the previous process conditions and the optimum electrochemical performance is provided by Si@PA@PAA-220 electrodes with high reversible specific capacity of 1322.1 mAh/g at a current density of 0.5A/g after 510 cycles. Characterization has also revealed that PA@PAA is involved in electrochemical process and tunes the ratio of organic (LixPFy/LixPOyFZ)-inorganic (LiF) to consolidate solid electrolyte interface (SEI) during cycles. In brief, this applicable fascial in situ strategy can effectively improve the stability of silicon anodes for high energy density lithium-ion batteries.