Outperform conventional batteries: lithium-air batteries have become more efficient and longer lasting

Lithium-air batteries can store significantly more energy than lithium-ion batteries, but they have some drawbacks.

A group of scientists led by Zhong-Shuai Wu from the Dalian Institute of Chemical Physics CAS, in collaboration with Xiangkun Ma from Dalian Maritime University, has found a way to improve the performance and service life of lithium-air batteries (Li-O 2). This is reported by the Tech Xplore portal.

As noted in the publication, lithium-air batteries have the potential to surpass conventional lithium-ion batteries, storing significantly more energy at the same weight, but today the potential of these batteries has not been fully revealed. Their theoretically high performance has not yet become a reality. In addition, the service life of such batteries is too short.

Unlike lithium-ion batteries, in which lithium ions are “pushed” back and forth between two electrodes, lithium-air batteries use an anode made of lithium metal. As the battery is used, the positively charged lithium ions dissolve and move to a porous cathode through which air passes.

The oxygen is oxidized and bound to lithium peroxide (Li 2 O 2). During charging, the oxygen is released and the lithium ions are reduced back to lithium metal, which is deposited on the anode. However, in practice, an effect known as overvoltage slows down electrochemical reactions: the formation and decomposition of insoluble Li 2 O 2 occur slowly, and its conductivity is also very low.

In addition, the pores of the cathode tend to become clogged, and the high potential required for oxygen formation decomposes the electrolyte and promotes undesirable side reactions. This leads to the fact that the batteries lose most of their characteristics after just a few charge-discharge cycles.

To solve these problems, scientists have proposed adding a new imidazole iodide salt as a catalyst and redox mediator. This catalyst facilitates charge transfer and counteracts electrode passivation. In addition, the DMI+ ions from the salt form a film on the anode that prevents direct contact of the electrolyte with the lithium surface, minimizing electrolyte decomposition and preventing side reactions. This stabilizes the anode and increases battery life.

According to the scientists, their electrochemical test cells demonstrated a very low overvoltage (0.52 V), high cycling stability for 960 hours, and reversible Li2O2 formation/decomposition without side reactions.