An Organic-Aqueous Miscible Electrolyte Enables High-Voltage Magnesium Batteries With Outstanding Cycling Stability

Magnesium batteries offer a safe, high-energy density, and cost-effective alternative to lithium-ion systems, recognized by Europe and the US, but are hindered in aqueous media by the narrow electrochemical window and interfacial instability. Here, we develop an organic-aqueous miscible electrolyte, SEU-01, containing water, ethylene glycol (EG), and lactobionic acid (LBA). EG participates in the solvation structure and expands the electrochemical window, while LBA further regulates the solvation shell and enhances Mg²⁺ desolvation kinetics. Their synergy forms a stable solid-electrolyte interphase (SEI) and induces uniform Mg deposition, thus enabling efficient and stable Mg cycling. So, Mg//Mg symmetric batteries cycle for more than 400 h (0.1 mA cm^-2, 0.1 mAh cm^-2), and the full battery with CuHCF shows a well-maintained discharge platform at 1.9 V and long life (1000 cycles at 1 A g^-1). These findings offer a viable pathway for the development of next-generation magnesium batteries and related electrochemical devices.