Reaction Mechanism Exploration of Binary Oxide Bi2Mo3O12@Ti3C2 Composite As Anode for Li-Ion Capacitor

Abstract

Metal oxides as pseudocapacitive materials are widely explored as anode for lithium ion capacitors, owing to their high volumetric and gravimetric lithium storage capacities. We present studies on reaction mechanism of binary Bi2Mo3O12 oxide as an anode for lithium storage. In-situ synchrotron XRD measurements are performed on this exotic material to elucidate lithium storage behaviors, coupled with voltage resolved CVs and ex-situ XPS analyses. Synergistic effect is believed to be the factor on improving electrochemical performance of the binary metal oxide anode instead of simple combination of two single components. The Bi2Mo3O12 anode undergoes an initial irreversible conversion reaction resulting in metallic Bi and Li2MoO4 on electrochemical discharge down to 0.01 V vs. Li+/Li. During successive cycling, the two components reversibly uptake and release lithium ions through alloying/de-alloying and intercalation/de-intercalation reactions by forming Li3Bi alloy and Li2+xMoO4. Cycling stability of the Bi2Mo3O12 anode is considerably enhanced by in-situ composition of Ti3C2 MXene. The Bi2Mo3O12@Ti3C2 composite anode exhibits 227 mAh/g capacity upon prolonged 1000 cycles at 2.5 A/g high charge/discharge rate in the voltage range of 3.0 - 0.01 V. This performance indicates the Bi2Mo3O12@Ti3C2 composite can be a potential candidate as anode for Li-ion capacitors.