Superconcentrated electrolytes for a high-voltage lithium-ion battery

TLDR

Next‑generation 5 V lithium‑ion batteries require stable electrolytes, but conventional LiPF₆ salts cause transition‑metal dissolution and aluminium oxidation, posing a major challenge. The study proposes an electrolyte formulation to overcome the trade‑off between transition‑metal and aluminium dissolution. The authors create a superconcentrated LiN(SO₂F)₂/DMCC electrolyte that forms a 3‑D anion–solvent network coordinating strongly to Li⁺. The superconcentrated electrolyte suppresses aluminium and transition‑metal dissolution at ~5 V, enabling a LiNi₀.₅Mn₁.₅O₄/graphite cell with excellent cycling, high‑rate performance, and improved safety.

Abstract

Abstract Finding a viable electrolyte for next-generation 5 V-class lithium-ion batteries is of primary importance. A long-standing obstacle has been metal-ion dissolution at high voltages. The LiPF 6 salt in conventional electrolytes is chemically unstable, which accelerates transition metal dissolution of the electrode material, yet beneficially suppresses oxidative dissolution of the aluminium current collector; replacing LiPF 6 with more stable lithium salts may diminish transition metal dissolution but unfortunately encounters severe aluminium oxidation. Here we report an electrolyte design that can solve this dilemma. By mixing a stable lithium salt LiN(SO 2 F) 2 with dimethyl carbonate solvent at extremely high concentrations, we obtain an unusual liquid showing a three-dimensional network of anions and solvent molecules that coordinate strongly to Li + ions. This simple formulation of superconcentrated LiN(SO 2 F) 2 /dimethyl carbonate electrolyte inhibits the dissolution of both aluminium and transition metal at around 5 V, and realizes a high-voltage LiNi 0.5 Mn 1.5 O 4 /graphite battery that exhibits excellent cycling durability, high rate capability and enhanced safety.