Microstructural intra-granular cracking in Cu2ZnSnS4@C thin-film anode enhanced the electrochemical performance in lithium-ion battery applications

Abstract

Cu₂ZnSnS₄ (CZTS) has demonstrated excellent performance as an anode material for lithium-ion batteries. However, the repeated lithiation and delithiation create a cracking pattern and lead to island formation in the thin-film electrode, resulting in a capacity fading over cycling in lithium-ion batteries (LIB's). In order to control this crack behaviour, we introduce carbon into CZTS thin-films by a hydrothermal method to form CZTS@C composite. CZTS@C significantly reduced the crack pattern formation on the electrode surface as well as improved the conductivity of the CZTS@C electrode. At the early stages of lithiation and delithiation, the volume expansion and contraction of Li–CZTS@C create intra-granular cracking only at the surface level, and it offers a high capacity of about 785 mA h g⁻¹ after 150 cycles at 1000 mA g⁻¹ charging rate, excellent rate capability (942 mA h g⁻¹, 678 mA h g⁻¹ and 435 mA h g⁻¹ at 500 mA g⁻¹, 2000 mA g⁻¹ and 5000 mA g⁻¹), and superior cyclability (925 mA h g⁻¹ even after 200 cycles at 500 mA g⁻¹). The excellent electrochemical performance at high-current rates can be attributed to intra-granular cracking together with carbon coating that provides a short transportation length for both lithium ions and electrons. Moreover, the controlled cracking pattern formation in CZTS@C facilitates faster reaction kinetics, which open up a new solution for the development of high-power thin-film anodes for next-generation LIBs applications.