Mechanisms for Stable Solid Electrolyte Interphase Formation and Improved Cycling Stability of Tin‐Based Battery Anode in Fluoroethylene Carbonate‐Containing Electrolyte

Abstract

that enable to form a stable solid electrolyte interphase (SEI) layer at the surface of the alternative anode for reliable battery performance. Tin (Sn)-based anode material based on alloy formation with Li has been one of the promising candidates because of the large theoretical capacity (≈992 mAhg −1 ) of Sn compared to that of graphite (372 mAhg −1 ). Sn also holds its merits of appropriate operating voltage above Li, which prevents dendrite formation, and high electronic conductivity as metallic, and improved Li + -transport kinetics. [1][2][3][4] The Sn, however, suffers from a rapid performance fade due to large volume change (≈300%) upon repeated charge (lithiation)-discharge (delithiation) cycling, which results in mechanical and electrical disintegration (i.e., particle cracking) between Sn particles and between the particles and current collector. [1][2][3][4] Several strategies were explored to reduce or accommodate the volume change by mostly adding various carbon (e.g., graphite) and inactive matrix, [2,5,6] and by using nanostructured Sn-carbon composites [7][8][9][10] or functional binder. [11] Since the particle cracking causes the enlarged interfacial area of Sn particles to electrolyte and continuous electrolyte decomposition at the new surface, the volume change event is closely linked to anode-electrolyte interfacial reactivity and stability. Our earlier reported results showed that interfacial irreversible reaction on Sn and destabilization of SEI layer with cycling are additional origins of a rapid performance fade in the ethylene carbonate (EC)-based conventional electrolyte. [12][13][14] Electrophilic attack of LiPF 6 salt-derived acids of PF 5 and PF 3 O (LiPF 6 → PF 5 + LiF, PF 5 + H 2 O PF 3 O + 2HF) [15,16] to the anode surface were determined to be the cause for interfacial reactivity. Surface degradation can also occur by the dissolution of surface oxide by HF. The most explored approaches to improve the interfacial (SEI) stability have been the use of electrolyte additives, such as phosphite [12,13] and fluoroethylene carbonate (FEC) [17][18][19] but just few studies have focused on investigating the SEI formation on Sn-based anode. [12,13,[19][20][21][22] Despite some improvement, challenges in the improvement of performance and SEI stability still remain. Thus, a fundamental understanding of electrode-electrolyte interfacial phenomena Tin-based anode materials are promising candidates for high-energy density Li-ion batteries. Unstable anode-electrolyte interface is a critical problem that needs to be resolved for these materials. The improvement of solid electrolyte interphase (SEI) stability and cycling stability of fluorine-doped Sn-Ni film electrode is observed by the use of fluoroethylene carbonate (FEC)based electrolyte with respect to ethylene carbonate (EC)-based conventional electrolyte. Mechanisms of FEC-derived SEI formation and stabilization are investigated using state of charge-dependent ex situ attenuated total reflection FTIR combined with X-ray photoelectron spectr...

Unveiling the Roles of Formation Process in Improving Cycling Performance of Magnesium Stannide Composite Anode for Magnesium‐Ion Batteries

“…The pattern obtained after 60 cycles ( C 60), which was ended as charged, is the same to those of charged anodes ( C 1, C 2, C 3). Slightly weakened peak intensity of recovered Mg 2 Sn phase upon charge, compared to pristine, might originate from a decrease in crystallinity or structural ordering by the possible occurrence of particle cracking event of this microsized Mg 2 Sn particles due to volume change, as often observed in the Sn‐based anodes in Li‐ion batteries . The peak of graphite is present at all states, confirming the role of graphite of being an electrochemically inactive but conductive agent.…”

“…Curve fitting was conducted on the broad Sn 3d 5/2 peaks ( Figure a) at 490–480 eV and Mg 2p peaks at 54–47 eV to determine the relative concentrations of various surface Sn and Mg species, whose fitting results are summarized in Figure a′ and Figure b′, respectively. First, the Sn 3d 5/2 spectrum of pristine anode (Figure a) exhibits that its surface consists of 38.2% Mg 2 Sn, as confirmed by the Mg 2p spectrum (Figure b), 16% Sn, 10.7% SnO, and 35.1% SnO 2 , as supported by O 1s spectrum ( Figure a) . The presence of surface Sn metal at pristine anode is likely associated with the trace of unreacted Sn during Mg 2 Sn synthesis, probably as remained at the surface, since it was not detectable in the powder XRD pattern (Figure ) that is a bulk analysis tool with the detection depth of ≈5 µm from the surface.…”

Solid electrolyte interphase layer formation on mesophase graphite electrodes with different electrolytes studied by small‐angle neutron scattering

“…FEC, an electrolyte additive, is identified to boost up the performance of the anode materials, by stabilizing the SEI layer 58–60 . The presence of fluorinated carbonates (FEC) in the EC/DMC electrolyte solutions, escalate the first Coulombic efficiencies on FMGP due to the fast formation of SEI film.…”

“…The presence of fluorinated carbonates (FEC) in the EC/DMC electrolyte solutions, escalate the first Coulombic efficiencies on FMGP due to the fast formation of SEI film. A small addition of FEC additive is sufficient for the effective film formation on the graphite surface, it has also been investigated to improve SEI uniformity and eliminate Li dendrite formation on electrodes 60–65 . It was reported recently that addition of FEC additive in EC/DMC solvent produce SEI with completely different composition, compared to pure EC/DMC and found that the formed SEI layer is less current consuming and thus lower the loss of initial active lithium 62–67 …”

Challenges and Development of Tin-Based Anode with High Volumetric Capacity for Li-Ion Batteries

“…In Sony's patent, they tried different combinations of the electrolytes, showing that if the solvent contained FEC, the cycle characteristics were improved and the FEC content could be in a large range from 1 to 80 wt% [59]. A stable FEC-derived SEI layer may be the reason for improved cycling stability, while continuous electrolyte decomposition and variation in the composition and concentration of the SEI species are observed in EC-based electrolytes in Sn-based electrodes [60].…”