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

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.