Si,P vacancy-enriched CoSi3P3 anode with exceptional Li storage performance

Abstract To address the challenges associated with the severe volume changes and unstable cycling performance of conversion- and alloying-type P- and Si-rich anodes in Li-ion batteries, a Si,P-vacancy-rich cobalt phospho-silicide (CoSi3P3) is introduced for the first time as a representative material of ternary MSixPy alloys with an additional vacancy-generating strategy via a simple NaOH treatment. The porous CoSi3P3–carbon nanotube composite possesses modulated defects and electronic properties, and exhibits superior Li storage performance. Specifically, it delivers an eventual discharge capacity of 1508 mAh g−1 after 600 cycles at a current density of 0.5 A g−1, and remains fully stable over 2000 cycles at symmetric/asymmetric cyclic tests at 5 A g−1. This outstanding performance can be attributed to the defective nature of the composite with strong chemical bonds, zero bandgap energy, remarkable electronic conductivity, and excellent ion transport during cycling, which together suppress the formation of detrimental crystalline-Li15Si4 and LiP phases, and guarantee the reversible reconstruction of CoSi3P3 when recharged, with a robust and monotonic solid-electrolyte interphase. These results suggest a simple active-site engineering approach to tune the electrochemical reaction pathways and electronic properties, thereby providing pioneering insights into the design of conversion-type electrodes for practical high-energy batteries.