We unravel the lithiation/delithiation mechanism of Zn2SnO4 as a conversion-type negative electrode material in a lithium-ion battery cell by rigorous phase identification via ex situ 7Li magic-angle spinning (MAS) NMR, static 119Sn WCPMG NMR, and operando X-ray diffraction (XRD) techniques. With ongoing lithiation/delithiation, a cascade of LixZn phases is observed, and the 7Li shift for the formed LixZn phases is reported for the first time. Our results show that Zn undergoes an alloying/dealloying-type reaction during electrochemical lithiation/delithiation according to xLi + Zn ↔ LixZn (0 ≤ x ≤ 1). However, considering the Sn alloying/dealloying reaction, the 119Sn WCPMG NMR results indicate that the formed LixSn species differ from those expected for the lithiation of metallic Sn; hence, the alloying/dealloying processes differ from those known for Sn: xLi + Sn ↔ LixSn (0 ≤ x ≤ 4.4), indicating a more complicated conversion mechanism for Zn2SnO4. Furthermore, the 119Sn WCPMG NMR data of the delithiation reaction reveal the formation of amorphous SnO caused by partial oxidation of reformed Sn.
Frerichs et al. (Tue,) studied this question.