Inward lithium-ion breathing of hierarchically porous silicon anodes

Abstract

Silicon has been identified as a highly promising anode for next-generation lithium-ion batteries (LIBs). The key challenge for Si anodes is large volume change during the lithiation/delithiation cycle that results in chemomechanical degradation and subsequent rapid capacity fading. Here we report a novel fabrication method for hierarchically porous Si nanospheres (hp-SiNSs), which consist of a porous shell and a hollow core. On charge/discharge cycling, the hp-SiNSs accommodate the volume change through reversible inward Li breathing with negligible particle-level outward expansion. Our mechanics analysis revealed that such inward expansion is enabled by the much stiffer lithiated layer than the unlithiated porous layer. LIBs assembled with the hp-SiNSs exhibit high capacity, high power and long cycle life, which is superior to the current commercial Si-based anode materials. The low-cost synthesis approach provides a new avenue for the rational design of hierarchically porous structures with unique materials properties.

Chemomechanical modeling of lithiation-induced failure in high-volume-change electrode materials for lithium ion batteries

“…44,[102][103][104][105][106][107] Porous materials can provide large surface areas for reaction, interconnected and fast interfacial transport, and hence enhanced rate performance. The internal pores can accommodate volume changes and alleviate mechanical stress generation during lithiation/delithiation cycles, thereby improving the structural stability and durability.…”

“…A recent work by Xiao et al 44 showed that hierarchically porous SiNPs (hp-SiNPs) can reverse the deformation mode seen in lithiated solid Si. The hp-SiNP, about 400 nm in diameter, consists of a hollow core and a porous shell.…”

“…63 III Inward Li breathing of hp-SiNPs. 44 e, g Time-lapse TEM images of the first lithiation (e) and delithiation (g) of a hpSiNP (Scale bar: 200 nm). Blue and green dashed lines are the outer and inner surface profiles of the hp-SiNP prior to lithiation, and the red dashed line marks the lithiation and delithiation front.…”

“…In parallel to these experiments, models of different length scales have been established, ranging from first-principles simulations, [25][26][27][28][29][30][31][32][33][34][35][36] molecular dynamics with empirical force fields on the atomic scale, [37][38][39][40][41][42] continuum-level simulations that couple field equations dictating Li transport and mechanical equilibrium. 9,12,[43][44][45][46][47][48][49][50][51][52][53][54][55] Together, this has opened a bottom-up avenue for developing high-performance LIBs, in contrast to the top-down approach adopted by the conventional battery development.…”

Incommensurate Graphene Foam as a High Capacity Lithium Intercalation Anode

“…However, Si anodes exhibit significant volume change during the initial charge/discharge cycles that results in significant chemical and mechanical degradation in anode and consequent rapid capacity fading23. Various scientific and technological solutions have been proposed including to redesign Silicon structures or integrate it with another high conductive protective carbon materials such as graphene45.…”