Exploring enhanced capacity in lithium-ion battery anodes: Synthesis and electrochemical evaluation of Zn₂GeO₄ encapsulated in porous carbon balls via carbonization

Germanium-based materials, such as Zn₂GeO₄, have recently been attracting attention as anode materials that can be used as an alternative to graphite. However, Zn₂GeO₄ suffers from critical disadvantages—such as low electrical conductivity and volume expansion—during lithiation/de-lithiation processes, which lead to reduced cycling stability and low specific capacity. In this study, we proposed the concept of porous carbon ball-encapsulated Zn₂GeO₄. The porous carbon balls were synthesized using heat treatment to be used as a buffer, with the effectively mitigating the volume expansion of Zn₂GeO₄. We investigated the electrochemical properties and mechanisms of Zn₂GeO₄ during cycling using ex-situ XRD analysis. The final product (H-C@ZGO) demonstrated enhanced cycling stability, with capacities ranging from 550 to 660 mAhg⁻¹ at 0.1 Ag⁻¹. We also examined the improved diffusion pathways facilitated by the encapsulated carbon balls as well as the porous structure formed by heat treatment.