SnO₂ Model Electrode Cycled in Li-Ion Battery Reveals the Formation of Li₂SnO₃ and Li₈SnO₆ Phases through Conversion Reactions

Abstract

SnO is an attractive negative electrode for Li-ion battery owing to its high specific charge compared to commercial graphite. However, the various intermediate conversion and alloy reactions taking place during lithiation/delithiation, as well as the electrolyte stability, have not been fully elucidated, and many ambiguities remain. An amorphous SnO thin film was investigated for use as a model electrode by a combination of postmortem X-ray photoelectron spectroscopy supported by density functional theory calculations and scanning electron microscopy to shed light on these different processes. The early stages of lithiation reveal the presence of multiple overlapping reactions leading to the formation of LiSnO and Sn phases between 2 and 0.8 V vs Li/Li. Between 0.45 V and 5 mV vs Li/Li LiSnO, LiO and Li Sn phases are formed. Electrolyte reduction occurs simultaneously in two steps, at 1.4 and 1 V vs Li/Li, corresponding to the decomposition of the LiPF salt and ethylene carbonate/dimethyl carbonate solvents, respectively. Most of the reactions during delithiation are reversible up to 1.5 V vs Li/Li, with the reappearance of Sn accompanied by the decomposition of LiO. Above 1.5 V vs Li/Li, Sn is partially reoxidized to SnO . This process tends to limit the conversion reactions in favor of the alloy reaction, as also confirmed by the long-term cycling samples.

Engineering of Sn and Pre‐Lithiated Sn as Negative Electrode Materials Coupled to Garnet Ta‐LLZO Solid Electrolyte for All‐Solid‐State Li Batteries

“…Indeed, when the particles are large (44 μm), SnO 2 is only present at the outer surface (couple of nm) but the ratio Sn/SnO 2 makes the contribution of SnO 2 negligible whereas when the Sn particles are in the nanometer range, the contribution of SnO 2 is clearly visible as in the present case. Thus, in this potential range, we supposed that SnO 2 is reduced to another phase that could be reduced and attributed to Li 2 SnO 3 as analogy with liquid electrolyte measurement or to Li 2 SnO 2 as we have less oxygen in this system than in liquid organic electrolyte From 0.8 V down to 0.2 V vs. Li + /Li, three defined potential plateaus at 0.63 V, 0.52 V, and 0.39 V vs. Li + /Li are observed and are related to the formation of several Li−Sn alloys, as described in the literature (LiSn, Li 2 Sn 5 , Li 7 Sn 5 , etc., see Operando XRD section below).…”

“…Indeed, when the particles are large (44 μm), SnO 2 is only present at the outer surface (couple of nm) but the ratio Sn/SnO 2 makes the contribution of SnO 2 negligible whereas when the Sn particles are in the nanometer range, the contribution of SnO 2 is clearly visible as in the present case. Thus, in this potential range, we supposed that SnO 2 is reduced to another phase that could be reduced and attributed to Li 2 SnO 3 as analogy with liquid electrolyte measurement or to Li 2 SnO 2 as we have less oxygen in this system than in liquid organic electrolyte …”

Understanding Ostwald Ripening and Surface Charging Effects in Solvothermally‐Prepared Metal Oxide–Carbon Anodes for High Performance Rechargeable Batteries

“…[12a,14] This peak was split into two peaks at around 0.91 and 1.2 V in the following cycles, corresponding to the conversion reaction from SnO 2 to Sn/Li 2 O (i.e., SnO 2 + 4Li + + 4e − → Sn + 2Li 2 O). [16] In addition, the high reversibility of our SnO 2 -C materials was confirmed by the charge capacity contribution, where the conversion and alloying reactions were considered, respectively (Figure 6b,c; Figure S8, Supporting Information). Reversibly, the peak located at 0.54, 1.26, and 1.86 V can be ascribed to the reaction from Li x Sn to the Sn, SnO (i.e., Sn + Li 2 O → SnO + 2Li + + 2e − ) and SnO 2 (i.e., SnO + Li 2 O → SnO 2 + 2Li + + 2e − ), respectively.…”

Reactivating Li2O with Nano‐Sn to Achieve Ultrahigh Initial Coulombic Efficiency SiO Anodes for Li‐Ion Batteries

“…We employed ex‐situ X‐ray photoelectron spectroscopy (XPS) to unveil the phase evolution during the delithiation process as shown in Figure . When the Sn/SiO electrode is discharged to 0.005 V, Li–Sn alloy (482.6 eV) and some SnO (485.0 eV), which may be oxidized during transfer processing, are detected in Sn 3d 5/2 (Figure a). Binding energies of 531.7 and 528.7 eV are assigned as Li 2 CO 3 /SiO x /Li‐silicates and Li 2 O in O 1s (Figure b).…”