A Better Way to Make Li-Ion Batteries

The first time a lithium-ion battery is charged, a portion of its electrolyte solidifies and coats the negative electrode. Called the solid-electrolyte interphase, this coating prevents further loss of electrolyte during later discharge-recharge cycles. However, it also consumes a portion of the battery’s lithium, reducing the capacity of today’s commercial batteries by around 5–10%. With next-generation electrode materials, the loss is even higher — up to 30%.

“If we want to use these new electrode materials, we need to find a way to compensate the lithium loss,” says Yuan Yang, a professor of materials science and engineering at Columbia Univ. Yang and his colleagues at Columbia and the Institute Recherche d’Hydro-Québec came up with a solution: A new method to fabricate lithiated electrodes at room temperature and ambient humidity.

“Our idea is to add some lithium metal to compensate for the lithium loss, but lithium metal is not stable in air,” Yang says. To protect the lithium, the researchers developed a temporary polymer coating that dissolves after the battery is fabricated.

Lithium-ion batteries generally consist of a lithium-metal cathode (often lithium cobalt oxide), a liquid (aqueous, aprotic, or mixed) electrolyte, and an anode (typically graphite). Lithium metal is oxidized at the anode, forming lithium ions and electrons. The electrons flow through an external circuit to provide electrical power, and the lithium ions...