Na2Ge4O9 nanoparticles encapsulated in 3D carbon networks with long-term stability and superior rate capability in lithium ion batteries

Abstract

Tremendous volume expansion of germanium during cycling limits its wide applications in lithium ion batteries. Na₂Ge₄O₉ nanoparticles encapsulated in 3D carbon networks have been designed and fabricated via a salt-templating method. The unique 3D interconnected carbon networks and sodium in Na₂Ge₄O₉ effectively buffer volume expansion and prevent the aggregation of active materials. Furthermore, the thin carbon networks (3–4 nm in thickness) can improve the conductivity of anodes and enhance the diffusion of Li⁺. Thus, the obtained material shows a high specific capacity of ∼800 mA h g⁻¹ in the range of 0.2–1 A g⁻¹ and a retention of 81.2% after 1000 cycles. And it can still maintain a specific capacity of ∼500 mA h g⁻¹ even at 20 A g⁻¹.