Ge–Si/C Nanofiber Composite with Enhanced Cyclic Stability and Rate Capability for Lithium-Ion Batteries

Abstract

To deal with the low conductivity and structural instability of the silicon (Si)-based anode, a Ge–Si/C nanofiber (Ge–Si/CNF) composite is fabricated based on different starting reaction potentials for Si and Ge with lithium and excellent conductivity of Ge. Sucrose is innovatively introduced as a spinning aid to maintain the carbon fiber structure derived from poly(vinyl alcohol) as the spinning polymer. When Ge–Si/CNFs are investigated as the anode material for lithium-ion batteries, it demonstrates excellent cyclic stability and rate capability. Specifically, the Ge–Si/CNFs anode can still retain 764.1 mA h g^–1 at 0.5 A g^–1 after 1000 cycles, and its capacity retention rate reaches 72.1%. Significantly, the specific capacity is 1168.7 mA h g^–1 at 2.0 A g^–1, which is restored to 1731.4 mA h g^–1 when it is adjusted back to 0.1 A g^–1. The excellent lithium storage of Ge–Si/CNF anode is attributed to the effective release of stress during the lithiation/delithiation process because of the different starting potentials of Si and Ge. When one component is lithiated, the other one can act as a buffer matrix for improving the structural stability. Additionally, the addition of Ge and carbon fibers can speed up the transfer rate of Li⁺ and electrons.