家 » 锂离子嵌入机理

锂离子嵌入机理

1980

M. Stanley Whittingham
John B. Goodenough
Akira Yoshino

(generate image for illustration only)

Lithium-ion batteries function via an intercalation mechanism, a reversible insertion of ions into a layered host material. During discharge, 锂 ions ([latex]Li^+[/latex]) de-intercalate from a negative electrode (anode), typically graphite, and move through a non-aqueous electrolyte to intercalate into a positive electrode (cathode), typically a metal oxide. Electrons travel through the external circuit, creating current.

The concept of intercalation is central to the success of lithium-ion batteries. Unlike older battery chemistries where the electrodes undergo significant chemical phase changes, intercalation involves lithium ions acting as ‘guests’ that slide into and out of the ‘host’ crystalline structure of the electrode materials. For the anode, the host is typically graphite, which has a layered structure allowing [latex]Li^+[/latex] ions to fit between its graphene sheets, forming [latex]LiC_6[/latex]. For the cathode, the host is a metal oxide, such as lithium cobalt oxide ([latex]LiCoO_2[/latex]), where lithium ions occupy layers between cobalt oxide sheets.

This process is highly reversible and does not dramatically alter the host’s structure, which leads to a long cycle life with minimal degradation. The movement of ions is facilitated by a non-aqueous organic electrolyte, as lithium is highly reactive with water. A micro-porous polymer separator keeps the anode and cathode from touching and short-circuiting while allowing ions to pass through.

During charging, an external voltage forces the process to reverse: lithium ions are extracted from the cathode, travel back across the electrolyte, and re-insert into the graphite anode. The high electrochemical potential of lithium, combined with its low atomic weight, allows for batteries with very high energy density and specific energy, which is why they have revolutionized portable electronics and are enabling the transition to electric vehicles.