Free-Standing Stable Silicon-Based Anode with Exceptional Flexibility Realized by a Multifunctional Structure Design in Multiple Dimensions.

Cyclized polyacrylonitrile (cPAN) with decently flexible, elastic, and conductive properties is a promising substrate or binder material for flexible devices. However, it is infeasible to accommodate the large volume expansion and contribute the exceptional rate capability of silicon anodes in lithium-ion batteries only counting on the limited elasticity and conductivity of cPAN. Herein, we report a robust silicon/carbon-cPAN-graphene (SC-CP-G) composite membrane with excellent flexibility based on a multifunctional structure design in multiple dimensions, which can be used as a free-standing integrated anode for lithium ion batteries. In this integrated electrode, silicon nanoparticles are encapsulated in porous carbon with in situ formed confined space, and the silicon/carbon particles are further embedded in cPAN nanofibers, which are inextricably interwoven with a reduced graphene oxide film, forming an interpenetrating network architecture. The unique hierarchical and functional structure design greatly improves the mechanical performance, cycling stability, and capacity accessibility of silicon electrodes, delivering a specific capacity of 1847 mA h g-1 at 2 A g-1 and a capacity retention of 87% after 150 cycles.

Gradient Structure Design of a Floatable Host for Preferential Lithium Deposition.

Herein, a novel sandwichlike host with expandable accommodation and gradient characteristics of lithiophilicity and conductivity is prepared by constructing a reduced graphene oxide (rGO)/SiO2/rGO intercalated structure on the basis of electrospraying and coating an additional PVDF-HFP layer on the top surface. This gradient host electrode enables preferential, ordered, and uniform Li deposition in the SiO2-embedded interlayer space. The dendrite growth and isolated Li are suppressed by the combined rGO/PVDF-HFP layer with robust, flexible, and floatable features, which could function as an artificial solid-electrolyte interphase to impede reckless electrolyte infiltration, homogenize the Li ion flux distribution, and build a stable electrochemical interface. The designed electrodes could be stably cycled with a high capacity of 5 mAh cm-2 and give rise to a high average Coulombic efficiency (CE) of 99.14%. Furthermore, the derived full cells can deliver an average CE of 99.87% in 300 cycles with a capacity retention of 90.22% and successfully operate under lean electrolyte conditions.