Layered Ge, method for manufacturing the same, Ge nanosheets exfoliated therefrom, and electrode for lithium-ion batteries comprising the same

Two-Dimensional Layered Ge Nanosheets for Lithium-Ion Battery Anodes via Selective Ca Removal from CaGe2 Precursors

This technology utilizes the layered structure of CaGe2 precursors to selectively remove calcium (Ca) ions, enabling the production of two-dimensional layered Ge and Ge nanosheets with excellent exfoliation properties and a high surface area.

Conventional 3D bulk Ge suffers from rapid volume expansion of 300–400% during lithium insertion and extraction. This leads to reduced structural stability of the electrode and a rapid decline in ion storage capacity.

This technology uses CaGe2 with an Rm-3m space group as a precursor, treating it with a mixture of salts like SnCl2 and a solvent to selectively extract Ca ions, forming 2D layered Ge or Ge nanosheets. Applicable to high-capacity Li-ion battery anodes, fast-charging small batteries, and 2D semiconductor research, it mitigates electrode collapse caused by volume expansion while leveraging Ge's high theoretical capacity.

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Key Features:

• Heat-treating a mixture of Ca and Ge powders followed by cooling at a specific rate to produce an Rm-3m rhombohedral CaGe2 layered compound
• Treating the layered compound with a mixture containing an MXa salt and a solvent to selectively remove Ca ions and produce layered Ge
• A lamellar layered compound with alternating layers of CaGe2 (first layer) and Fd-3m crystal structure Ge (second layer), produced by heat treatment followed by quenching
• Ge nanosheets containing both amorphous or Rm-3m rhombohedral Ge nanosheets and Fd-3m crystal structure Ge nanosheets

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This invention was developed with support from the Ministry of Science and ICT for the development of technology to convert bulk materials into 2D materials through crystal structure dimension hierarchy design.

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