Heterogeneous isomorphism hollow SiGe nanospheres with porous carbon reinforcing for superior electrochemical lithium storage

Silicon is emerging as a promising next-generation lithium-ion battery anode because of its high theoretical capacity and low cost. However, the poor cyclability and inferior rate performance hinder its largescale applications. Here, hollow silicon/germanium (H-SiGe) nanospheres with a binary-active component and heterogeneous structure combined with porous carbon (pC) reinforcing are synthesized as lithium-ion battery anodes. Experimental studies demonstrate that the H-SiGe/pC anodes possess tiny volume expansion, high ion/electron conductivity, and stable electrode interface. Theoretical calculations confirm that through the replacement of Si using Ge with rational component control, the diffusion energy barrier of lithium will be reduced and lithium storage ability can be improved because of the slight charge polarization. Benefiting from these unique merits, the H-SiGe/pC anodes display a high initial specific capacity of 2922.2 mA h g-1 at 0.1 A g-1, superior rate capability (59.4% capacity retention from 0.5 to 8 A g-1), and excellent cycling stability (81% retention after 700 cycles at 5 A g-1 at 1.0- 1.2 mg cm-2). An outstanding stability is preserved even at a high loading of 3.2 mg cm-2 with an improved reversible capacity of 429.1 mA h g-1 after 500 cycles at 4 A g-1. Furthermore, the full-cell with the prelithiated H-SiGe/pC anode and LiFePO4 cathode exhibits an impressive capacity performance. (c) 2022 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences.Published by ELSEVIER B.V. and Science Press.

Automated summary

Silicon is a promising material for next-generation lithium-ion battery anodes due to its high theoretical capacity and low cost. However, its poor cyclability and rate performance limit its large-scale applications. In this study, hollow silicon/germanium nanospheres combined with porous carbon are synthesized and used as lithium-ion battery anodes. The experimental results show that these anodes have small volume expansion, high ion/electron conductivity, and stable electrode interface, while theoretical calculations suggest that using germanium instead of silicon can improve lithium storage ability. These unique characteristics enable the anodes to exhibit high initial specific capacity, superior rate capability, excellent cycling stability, and outstanding stability even at high loading. Moreover, when paired with LiFePO4 cathode, the full-cell shows impressive capacity performance.