Electrochemical phase evolution of tetradymite-type Bi2Te3 in lithium, sodium and potassium ion half cells

Abstract

Tetradymite-type Bi2Te3 is synthesised via a solid-state method, and its electrochemical phase evolution upon discharge against Li, Na and K counter-electrodes detailed. Rietveld analysis of ex-situ X-ray diffraction data reveal that the Li and K systems undergo a sequence of intercalation, conversion and alloying reactions. Additionally, a preliminary assessment of the performance of Bi2Te3 as an electrode material for rechargeable Li, Na and K-ion batteries is undertaken. Initial capacities are high, with Li, Na and K cells exhibiting first discharge capacities of 480, 498, 456 mAh/g respectively. However, cyclabilities are poor, with second discharge capacities dropping to 404 and 248 mAh/g for Na and K cells respectively. For the case of Li, capacity increases over the first few cycles, however by the fifth cycle, discharge capacity decreases to 325 mAh/g. This poor cyclability was generally due to the large volume changes and irreversibilities associated with the insertion/extraction reactions. The gravimetric capacities for Li, Na and K half-cells decrease by 25%, 43% and 57% respectively by the tenth cycle.