Electrolyte composition for lithium secondary batteries and lithium secondary battery comprising the same

Carbonate electrolyte for lithium metal batteries forming a Li-Mg alloy protective layer using magnesium nitrate additives

This technology uses magnesium nitrate (Mg(NO3)2) as an additive in carbonate-based electrolytes for secondary batteries with lithium metal anodes. It creates a high-strength protective layer (SEI) composed of Li-Mg alloy, LiF, and LiNxOy on the anode surface and controls the solvation structure of lithium ions to suppress dendrite growth.

Lithium metal anodes have historically suffered from dendrite growth due to uneven lithium deposition and surface degradation from side reactions with the electrolyte, leading to reduced energy efficiency. In particular, conventional ether-based electrolytes have been limited in high-voltage applications due to instability.

This technology utilizes an electrolyte consisting of magnesium nitrate dissolved in a mixture of chain and cyclic carbonate solvents, such as EMC and FEC. This alters the solvation structure of lithium ions, and during charge/discharge cycles, Mg and nitrate ions react with lithium to promote spherical lithium deposition while forming an inorganic protective layer of Li3Mg7 alloy, LiF, and LiNxOy on the anode surface. It can be applied to electrolyte design for lithium metal batteries paired with 4V-class high-voltage cathodes, high-energy pouch cells, and next-generation electric vehicle cells, allowing for improved charge/discharge efficiency of lithium metal anodes while utilizing existing carbonate electrolyte processes.

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Key Features:

• An electrolyte positioned between a lithium metal anode and a cathode, containing magnesium nitrate, a lithium salt, and a carbonate-based solvent
• A protective layer formed on the surface of the lithium metal anode, comprising Li3Mg7, LiF, and LiNxOy
• A carbonate-based solvent comprising a mixture of the chain carbonate compound EMC and the fluorine-containing cyclic carbonate FEC
• A magnesium nitrate additive included in the electrolyte at a concentration of 0.025M to 0.15M to induce spherical lithium deposition

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This invention was developed with support from the Ministry of Science and ICT for the development of core technologies for high-energy-density lithium metal batteries based on the design of natural organic/inorganic composite membrane formation reactions.

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