A polyisoindigo derivative as novel n-type conductive binder inside Si@C nanoparticle electrodes for Li-ion battery applications

Herein we report the successful use of a polyisoindigo derivative (P(iso)) as a new conductive binder inside electrode formulations containing silicon nanoparticles covered with a carbon shell (Si@C) for Li-ion batteries. The expected role of the carbon shell is to stabilize the Solid Electrolyte Interphase layer (SEI) to prevent it from cracking under nanoparticle volume variations during lithiation processes. The P(iso) conducting polymer is used to act both as mechanical binder and n-type conductive component in replacement of usual carbonaceous additive materials. Ultimately, the cumulative contributions of both materials inside a two-electrode component formulation (Si@CP(iso)) aim to address the stability drawbacks commonly faced by silicon electrodes. Physico-chemical characterizations revealed that the Si@C nanoparticles are uniformly embedded inside the polymeric matrix. Electrochemical measurements in half-cells clearly show the formation of LiSi alloys during cycling. Moreover specific capacities up to 1400 mAh/g with a remarkable stability until 500 cycles have been achieved, proving this conductive polymer to be a valid alternative to classical polymeric binders mixed with carbonaceous additives. These very promising results highlight the use of this polyisoindigo family as new conductive binders inside Si@C electrode formulations for Li-ion battery applications. •Synthesis of a polyisoindigo derivative (P(iso)) by Yamamoto cross-coupling.•Characterization of the (P(iso)) as a new conductive binder with Si@C nanoparticles.•High stability of the Si@CP(iso) electrode (1400 mAh/g) over 500 cycles.•Higher capacity retention for Si@CP(iso) electrode than Si@C/CMC/CB electrode.