• The usage of flammable non-aqueous electrolytes in commercial Li-ion batteries has raised concerns of safety, the development of non-flammable aqueous electrolytes is urgent
• The application of traditional aqueous electrolytes in Li-ion batteries is limited by the narrow stability window of water (1.23 V) and low energy density (<80 Wh/kg), high-voltage aqueous electrolytes are needed
• The existing high-voltage aqueous electrolytes such as “water-in-salt” aqueous electrolytes expand the voltage window of water using high concentration (>21 mol/kg) of organic Li salts, which are expansive and toxic. It calls for the design of low-cost and non-toxic high-voltage aqueous electrolytes
• The developed aqueous electrolyte is a promising candidate to replace commercial Li-ion battery electrolytes. Taking the market of Li-ion battery as a reference, the market size may be 7 billion, and the market value may be USD 2 billion

• Our developed electrolyte is water-based and safer than commercial flammable non-aqueous electrolytes
• We expand the stability window of water from 1.23 V to 3.2 V and achieve higher energy density (110 Wh/kg) than the batteries using traditional aqueous electrolytes (<80 Wh/kg)
• We expand the voltage window of water using low-cost and non-toxic polyethylene glycol at a low concentration (2 mol/kg) of Li salt, the developed high-voltage electrolyte is cheaper and more eco-friendly than the existing high-voltage “water-in-salt” aqueous electrolytes

• Portable electronics like mobile phones, power banks and laptops
• Electric vehicles
• Grid energy storage for renewable electricity sources such as wind power, solar power and tidal power

(a) CUHK aqueous electrolyte achieves full Li-ion cells between 2.5 to 4.0 V
(b) The flammability test of CUHK electrolyte and commercial electrolyte

P-2019-0921

US Application No.: 16/798136

Lu et al, Nat. Mater, 2020

orkts.liaison@cuhk.edu.hk