OLC1300V as conductive carbon additive provides an optimum Sb–C interaction. A remarkable rate performance is attained, electrode cracking from volume expansion is prevented, and the solid electrolyte interphase homogeneity is significantly improved.

Herein, an eco‐friendly and high safety aqueous Mg‐ion electrolyte (AME) with a wide electrochemical stability window (ESW) ≈3.7 V, containing polyethylene glycol (PEG) and low‐concentration salt (0.8 m Mg(TFSI)2), is proposed by solvation structure reorganization of AME. The PEG agent significantly alters the Mg2+ solvation and hydrogen bonds network of AMEs and forms the direct coordination of Mg2+ and TFSI‐, thus enhancing the physicochemical and electrochemical properties of electrolytes. As an exemplary material, V2O5 nanowires are tested in this new AME and exhibit initial high discharge/charge capacity of 359/326 mAh g‐1 and high capacity retention of 80% after 100 cycles. The high crystalline α‐V2O5 shows two 2‐phase transition processes with the formation of ε‐Mg0.6V2O5 and Mg‐rich MgxV2O5 (x ≈1.0) during the first discharge. Mg‐rich MgxV2O5 (x ≈1.0) phase formed through electrochemical Mg‐ion intercalation at room temperature is for the first time observed via XRD. Meanwhile, the cathode electrolyte interphase (CEI) in aqueous Mg‐ion batteries is revealed for the first time. MgF2 originating from the decomposition of TFSI‐ is identified as the dominant component. This work offers a new approach for designing high‐safety, low‐cost, eco‐friendly, and large ESW electrolytes for practical and novel aqueous multivalent batteries.