Hollow Graphene as an Expansion-Inhibiting Electrical Interconnector for Silicon Electrodes in Lithium-Ion Batteries

Abstract

Huge volume changes of silicon particles upon alloying and dealloying reactions with lithium are a major reason for the poor cycle performance of silicon-based anodes for lithium-ion batteries. To suppress dimensional changes of silicon is a key strategy in attempts to improve the electrochemical performance of silicon-based anodes. Here, we demonstrate that a conductive agent can be exploited to offset the mechanical strain imposed on silicon electrodes caused by volume expansion of silicon associated with lithiation. Hollow graphene particles as a conductive agent inhibit volume expansion by absorbing the swelling of silicon upon lithiation through flattening the free voids surrounded by the graphene shell. As a result, silicon electrodes with hollow graphene showed a height expansion of 20.4% after full lithiation with a capacity retention of 69% after 200 cycles, while the silicon electrode with conventional carbon black showed an expansion of 76.8% under the same conditions with a capacity retention of 38%. Some of the deflated hollow graphene returns to its initial shape on delithiation due to the mechanical flexibility of the graphene shell layer. Such a robust microstructure of a silicon electrode incorporating hollow graphene that serves as both an expansion inhibitor and a conductive agent greatly improves capacity retention compared with silicon electrodes with the conventionally used carbon black.

Integrating SEI into Layered Conductive Polymer Coatings for Ultrastable Silicon Anodes

“…Numerous attempts have been made to stabilize SEI, including the nanostructure engineering, [9][10][11][12][13][14][15][16][17][18][19] surface modification, [20][21][22][23][24] composite design, [25][26][27][28] binder optimization, [19,[29][30][31][32][33][34][35] and electrolyte modulation. [36][37][38][39] Carbon coating is one of the most effective strategies to improve the conductivity, buffer the volume expansion as well as stabilize the SEI.…”

Reduced graphene oxide-encaged submicron-silicon anode interfacially stabilized by Al2O3 nanoparticles for efficient lithium-ion batteries

“… 27 Serving as a conductive agent, hollow graphene particles were found to effectively alleviate the volumetric expansion of silicon, showing a thickness expansion of 20.4% in the fully-lithiation state over 200 cycles. 28 Recently, Lu and coworkers developed a graphene-supported double-layer carbon-wrapped Si anode, which was synthesized from metal–organic frameworks, sucrose and graphene oxide precursors using solvothermal reaction and high-temperature pyrolysis. The resulting anode achieved a high capacity of 1182 mA h g −1 with 89.5% retention over 240 cycles at 0.2 A g −1 .…”

Magnetic Force Dilatometry of Silicon-NMC622 Lithium-Ion Coin Cells: The Effects of Binder, Capacity Ratio, and Electrolyte Selection

“…46 Park et al demonstrated the use of hollow graphene to reversibly buffer electrode volume expansions. 47 Few electrode formulation studies report in-cycle volume changes, 38 although we expect these also to be affected.…”