Three-dimensional interconnected network GeOx/multi-walled CNT composite spheres as high-performance anodes for lithium ion batteries

Abstract

Germanium (Ge) anode materials are one of the most potential anodes for next generation lithium-ion batteries (LIBs) due to their high theoretical capacity, fast Li-ion diffusivity and high intrinsic electronic conductivity. However, Ge anode materials face significant challenges due to the 260% volume change during the lithiation/delithiation process, which results in pulverization and destabilization of the solid electrolyte interphase (SEI) film and leads to the loss of electrical contact and poor cycle life. Here, we report an industrially established spray-drying process for the synthesis of micro-sized durable three-dimensional (3D) network structure GeO_x/multi-walled carbon nanotube (MWCNT) composite spheres consisting of 5–15 nm nanoparticles for LIB anodes. The 3D GeO_x/MWCNT composite sphere structure not only provides high ability for Li-ion intercalation, but also enhances the electronic conductivity of the composite spheres for LIBs, increasing the rate capabilities. Meanwhile, the 3D network structure provides adequate space for GeO_x expansion resulting in good long-term cycling stability. The interconnected 3D network structure GeO_x/MWCNT spheres exhibited a capacity of over 1000 mA h g⁻¹ at 500 mA g⁻¹ after 300 deep charge–discharge cycles and provided a capacity of 550 mA h g⁻¹ at 5 A g⁻¹. Even at a high current density of 10 A g⁻¹, it can deliver a reversible capacity of 365 mA h g⁻¹. The results showed that when the active material loading reached >1.2 mg cm⁻², the discharge capacity could also retain 723 mA h g⁻¹ after 150 cycles. This scalable and industrial method provides attractive future prospects for high-performance Ge-based anodes with excellent electrochemical performance with a high active material loading in the next generation LIBs.