# Quaternary Cu2TSiS4 (T = Fe, Mn) Anodes for Li-Ion Batteries

## TL;DR

This paper explores new anode materials for lithium-ion batteries, showing that Cu2FeSiS4 offers high capacity and stability, making it promising for future battery technology.

## Contribution

The study introduces Cu2FeSiS4 as a novel anode material with high cyclic stability and fast-charging capability.

## Key findings

- Cu2FeSiS4 retains 670 mAh g–1 capacity after 400 cycles at 200 mA g–1.
- Cu2FeSiS4 maintains 379 mAh g–1 capacity after 700 cycles at 2 A g–1.
- Cu2FeSiS4 undergoes reversible phase transitions with Li2S as a major product.

## Abstract

Developing high-capacity
and fast-charging anode materials
is critical
for achieving high-performance Li-ion batteries (LIBs). Herein, polycrystalline
quaternary transition metal silicon sulfides, Cu2TSiS4 (T = Fe, Mn), were synthesized using a solid-state method
and investigated as anode materials in LIBs. Cu2FeSiS4 retains a reversible capacity of 670 mAh g–1 at 200 mA g–1 for 400 cycles, while Cu2MnSiS4 suffers from a fast capacity loss in the initial
50 cycles. More importantly, Cu2FeSiS4 can maintain
a reversible capacity of 379 mAh g–1 after 700 cycles
at a high current density of 2 A g–1, demonstrating
high cyclic stability and fast-charging capacity. To further understand
the structure degradation and phase transformation, we investigated
the postcycling electrodes using multiple techniques, including the
scanning electron microscope with energy-dispersive X-ray spectroscopy,
X-ray diffraction, and X-ray photoelectron spectroscopy techniques.
The results indicated that Cu2FeSiS4 undergoes
reversible phase transitions with Li2S as a major product
component. To further assess the performance for practical applications,
Cu2FeSiS4 was coupled with LiFePO4 to make LiFePO4||Cu2FeSiS4 full
cells, which delivered superior electrochemical performance. These
results demonstrate great promise for using quaternary transition
metal silicon sulfides as anodes to achieve low-cost and sustainable
LIBs.