China’s lithium-air battery breakthrough achieves 960-hour life, 95.8% efficiency

Overcoming battery limitations

Li-O2 batteries offer a different approach to energy storage compared to lithium-ion batteries. Instead of shuttling lithium ions between two electrodes, Li-O2 batteries use a metallic lithium anode.

Lithium ions disperse from the anode during discharge and go to the porous cathode, where they react with ambient oxygen to generate lithium peroxide (Li2O2). The process is reversed when charged: lithium ions return to the anode as metallic lithium and oxygen is liberated. Although this design has the potential to store a lot more energy, real-world obstacles have limited its use.

Overpotential is a significant problem since it slows down the essential reactions that produce and break down Li2O2. This compound’s low conductivity and sluggish formation and breakdown lead to inefficiencies. Performance is further hampered by the cathode’s pores, which frequently become clogged with reaction products.

Moreover, the high voltages needed to generate oxygen can degrade the electrolyte and trigger unwanted side reactions. These problems result in significant performance loss, limiting the battery’s lifespan to just a few charge/discharge cycles.

Overcoming these challenges is critical to realizing the promise of Li-O2 batteries as a superior energy storage solution, with ongoing research focusing on improving efficiency and durability.

Catalyst boosts lifespan

The research team has introduced a novel imidazole iodide salt, 1,3-dimethyl imidazolium iodide (DMII), as a catalyst and redox mediator to improve the performance and lifespan of lithium-air batteries.

During the discharge and charge operations, the salt’s iodide ions (I−) can readily transition to I3− and back, exchanging electrons. This redox process lowers the cathode’s overpotential, speeds up reactions, improves charge transport, and expands the battery’s discharge capacity.

DMI+ ions, which have a special ring shape of three carbon and two nitrogen atoms that permit freely movable electrons, are also present in the DMII salt. By effectively “capturing” lithium ions during discharge and transferring them to oxygen at the cathode, these ions increase the efficiency of the process.

Furthermore, by avoiding direct contact between the electrolyte and the lithium surface, DMI+ ions form a thin but incredibly stable interface film on the anode, protecting it.

According to researchers, the electrochemical test cells showed remarkable results, including a very low overpotential of 0.52 V, outstanding cycle stability exceeding 960 hours, and the highly reversible formation and breakdown of lithium peroxide (Li2O2) with no undesired side reactions.

The breakthrough, according to the team, represents a significant step toward long-lasting, high-capacity Li-O2 batteries. This stabilizes the anode and extends the battery’s life by reducing electrolyte breakdown and adverse reactions.

The details of the team’s research were published in Wiley Online Journal.