Layered germanium phosphide-based anodes for high-performance lithium- and sodium-ion batteries

A layered germanium phosphide (GeP3) was synthesized in a straightforward manner using a simple solid-state synthetic method, and its electrochemical behavior for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) was investigated. During Li-insertion and extraction, the GeP3 experienced a sequential three-step (topotactic-transition, conversion, and alloying) and two-step (dealloying and recombination) reaction. During Na-insertion and extraction, GeP3 had a one-step (conversion) and two-step (recombination and topotactic-transition) reaction. Based on the interesting phase change mechanisms during Li- and Na-insertion/extraction, the GeP3–based nanocomposite exhibited superior electrochemical performance, such as large reversible capacity (first reversible capacity: 1526 mAh g-1 for LIB, 984 mAh g-1 for SIB), high initial Coulombic efficiencies (86.3% for LIB, 81.3% for SIB), stable cycle life (capacity retention for LIB: 95% in 0–2 V after 30 cycles, 87% in 0.35–2 V after 100 cycles, and 93% in 0.64–2 V after 100 cycles, capacity retention for SIB: 95% in 0–2 V after 30 cycles), and rapid rate-capabilities (LIB: 860 mAh g-1 in 0.35–2 V at 2C-rate, SIB: 520 mAh g-1 in 0–2 V at 2C-rate). Overall, the layered GeP3–based anode with its interesting Li- and Na-reaction mechanisms will be a promising alternative anode for high-performance LIBs and SIBs.