Applications of lithium ion battery have been hampered by a lack of ideal anode materials in terms of capacity and stability. The emergence of metal chalcogenide as a candidate material has reinvigorated the search of a low cost and high capacity material system. However, debate about the underlying mechanisms and overall appraisal of its usage in lithium ion battery system remains. Here, a comprehensive study on the energy storage mechanism of copper zinc tin sulfide (CZTS) nanowalls possessing ultrahigh rate capability (500mAhg−1 charged within 60s) is reported. Structural evolutions along with the accompanying changes in the oxidation state upon charge/discharge were monitored by ex-situ X-ray diffraction and X-ray photoelectron spectroscopy. During lithiation, lithium ion reacted with CZTS to form lithium sulfides. At the same time, a sequential conversion reactions of copper, zinc and tin sulfides enabled the CZTS nanowalls to achieve excellent electrochemical performance (1400mAhg−1 at a current density of 1000mAg−1 over 400 cycles). Multi-element metal chalcogenides in conjunction with an adhesion-enhancing seed layer and a rational nanostructure design hold the key to such ultrahigh capacity and stable anode materials for next generation energy storage devices.