Insights on microstructural evolution and capacity fade on diatom hbox {SiO}_2 anodes for lithium-ion batteries

Abstract

hbox {SiO}_2 is a promising material for developing high-capacity anodes for lithium-ion batteries (LIBs). However, microstructural changes of hbox {SiO}_2 anodes at the particle and electrode level upon prolonged cycling remains unclear. In this work, the causes leading to capacity fade on hbox {SiO}_2 anodes were investigated and simple strategies to attenuate anode degradation were explored. Nanostructured hbox {SiO}_2 from diatomaceous earth was integrated into anodes containing different quantities of conductive carbon in the form of either a conductive additive or a nanometric coating layer. Galvanostatic cycling was conducted for 200 cycles and distinctive trends on capacity fade were identified. A thorough analysis of the anodes at selected cycle numbers was performed using a toolset of characterization techniques, including electrochemical impedance spectroscopy, FIB-SEM cross-sectional analysis and TEM inspections. Significant fragmentation of hbox {SiO}_2 particles surface and formation of filigree structures upon cycling are reported for the first time. Morphological changes are accompanied by an increase in impedance and a loss of electroactive surface area. Carbon-coating is found to restrict particle fracture and to increase capacity retention to 66%, compared to 47% for uncoated samples after 200 cycles. Results provide valuable insights to improve cycling stability of hbox {SiO}_2 anodes for next-generation LIBs.