“…At 0.5 M, the formed SEI is Na-deficient (see Table ). Figure a also reveals a relatively low intensity of Na, which is mainly in Na–O bonding form (such as Na 2 O/NaOH). , In the S 2p spectrum (Figure b), peaks corresponding to −SO 4 – (169.8 eV), −SO 2 – (168.1 eV), and SO X (166.1 eV) species, which resulted from FSI – decomposition, were found. , The N 1s spectrum (Figure c) consists of N–C (402.9 eV), N–O (400.2 eV), and N–S (397.9 eV) peaks. , The first component was associated with the reductive decomposition of PMP + , and the latter two components were derived from FSI – . The decomposition (both cations and anions) of the 0.5 M electrolyte was notable (see Table ), leading to excessive SEI formation.…”