Anode active material for secondary batteries, method for manufacturing the same, and secondary battery comprising the same

Sodium/Potassium Battery Anode Material with Enhanced Reversibility Using Orthorhombic BiPS4-CNT Composites and KFSI Electrolyte

This technology utilizes a BiPS4 compound with an orthorhombic crystal structure, composed of bismuth (Bi), phosphorus (P), and sulfur (S), as an anode active material. It is composited with carbon nanotubes (CNT) to improve electrochemical reversibility and ion transport performance.

Applying conventional lithium-ion battery anode materials to sodium (Na) or potassium (K) secondary batteries has historically resulted in poor energy density and charge-discharge instability. Furthermore, conventional electrolyte systems like KPF6 have faced limitations where the active material is irreversibly consumed, leading to degraded cycle life.

This technology synthesizes tunnel-structured BiPS4 compounds via ball milling and composites them with CNTs to form electrodes. By using a potassium bis(fluorosulfonyl)imide (KFSI) electrolyte, the structural reversibility of BiPS4 is maintained during charge and discharge. Applicable to low-cost, large-capacity storage systems based on potassium-ion and sodium-ion batteries, this next-generation anode material overcomes lithium resource constraints while securing both initial coulombic efficiency and cycle life.

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Key Features:

• Anode active material for secondary batteries comprising an orthorhombic BiPS4 compound and carbon nanotubes
• BiPS4-CNT composite in which the BiPS4 compound and carbon nanotubes are mixed in a weight ratio of 6 to 8:3
• Step of mixing bismuth, phosphorus, and sulfur in a molar ratio of 1:0.8–1.2:3.8–4.2
• Step of ball-milling the mixture to obtain a BiPS4 compound with an orthorhombic crystal structure

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This invention was developed with support from the Ministry of Science and ICT for the development of high-capacity, long-life metal thiophosphate anode materials for sodium and potassium-ion batteries through the stabilization of layered and tunnel structures.

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