Insights into the phase evolution during an electrochemical cycle of the Na-ion battery anode Bi2Te3 through solid-state NMR crystallography

• Tetradymite-type (Bi2Te2S) structures and their analogues (P2X3, where P = Sb,Bi and X = S, Se, Te) have recently garnered attention as interesting materials as potential anodes in Li- and Na-ion batteries. As of now, potential mechanisms of the electrochemical cycle are conflicting, as both intercalation of the ion followed by a conversion and an alloying reaction, or a conversion followed by an alloying reaction straight up have been reported. It is, thus, of importance to determine the exact phases that are being produced during each reaction step, in order to optimize the conditions, under which these structures can thrive as anodes. In this study, we succeed this, by employing a combination of ex-situ solid-state nuclear magnetic resonance (ssNMR) and transmission electron microscopy (TEM), during various points during the first discharge and subsequent charge of microcrystalline Bi2Te3. The results are aided by density functional theory calculations (DFT) of the NMR Knight shifts and the electronic structure of all phases present during the cycle. This highlights the ability of solid-state NMR to monitor the phase evolution during cycling of electronically non-trivial systems.

Ämnesord

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

Nyckelord

Solid-state NMR

Knight Shifts

Na-ion batteries

TEM

Physical Chemistry

fysikalisk kemi

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