In Situ Partial Pyrolysis of Sodium Carboxymethyl Cellulose Constructing Hierarchical Pores in the Silicon Anode for Lithium-Ion Batteries

Abstract

Silicon is an attractive anode material for the high-energy-density lithium-ion battery due to its high theoretical capacity (4200 mA h g–1). However, larger volume expansion (∼300%) and pulverization during cycling hinder the commercialization of silicon anodes. The modification of silicon materials is a widely recognized approach to enhance the anode performance, but the volume expansion cannot be solved completely when only focusing on the active material but ignoring the overall structural optimization of the anode. In the study, additional hierarchical pores were constructed in the electrodes by in situ partial pyrolysis of the binder sodium carboxymethyl cellulose (CMC) at low temperature. Benefiting from the extra buffer space, the electrodes can accommodate more expansion and enhance the conduction of electrons and ions. In addition, the partially degraded CMC reduced the adsorption energy between the binder and the active material, reducing the stress during the swelling process, which is demonstrated by density functional theory. The as-obtained electrode delivered a high reversible capacity of 1035 mA h g–1 at 1000 mA g–1, while the capacity retention was 78.7%, and the Coulombic efficiency was stable at 99.3% after 200 cycles. The modification of the electrode structure provides guidance for the construction of high-efficiency anodes