Ryu et al. (Nature Energy, 2023).
Over the past few decades, engineers and materials scientists have been working hard to develop battery technologies that are getting better and better. Their efforts are designed to support the needs of the electronics industry, extending the battery life of countless rechargeable devices, electric vehicles, and robotic systems.
Nickel (Ni)-rich layered materials are often used as cathodes in batteries because of their favorable properties that can increase the energy density of batteries. Nonetheless, the capacity of the nickel-rich cathode deteriorates rapidly because the reactivity of the material can lead to undesirable side chemical reactions.
Researchers at Hanyang University in Seoul recently unveiled a new strategy that could help improve the performance of these cathodes, allowing them to maintain their capacity for a longer period of time. This strategy, described in an article published in the journal Nature Energy, involves a simple scrubbing process that helps remove residual lithium compounds from the cathode while also coating them to reduce unwanted reactions.
The instability of nickel-rich layered cathode materials in lithium-ion batteries is attributed to their unstable surface reactivity," Hoon-Hee Ryu, Hyung-Woo Lim and colleagues wrote in their **. "This reactivity leads to the formation of residual lithium impurities on the surface of the cathode and serious side reactions with the electrolyte. We propose a scrubbing process using co-dissolved water to simultaneously remove residual lithium and form a protective coating on a nickel-rich layered cathode.
The main goal of the team's recent work is to identify an effective way to overcome the limitations of nickel-rich cathodes, which in turn contribute to a timely increase in the duration of the battery. Their proposed strategy requires cleaning the cathode with an aqueous solution dissolved in cobalt (CO).
This washing process causes a reaction with residual lithium on the outer surface of the cathode, resulting in a thin, homogeneous and cobalt-rich protective layer. The layer formed eliminates direct contact between the cathode and electrolyte inside the battery, thus preventing further side reactions and consequent rapid degradation of the cathode over time.
The washing induces the reconstitution of the near-surface structure by reacting with the residual lithium compound, thus preventing direct contact between the electrolyte and the nickel-rich surface," Ryu, Lim and their colleagues explained. "The addition of a fluorine coating to the scrubbing cathode hinders the decomposition of the salts and prevents by-products from initiating autocatalytic side reactions at the electrolyte-cathode interface, thereby inhibiting gas production during cycling. ”
The washing and coating strategies introduced by RYU, Lim and their collaborators were tested in a series of preliminary experiments. The results show that it successfully extends the life cycle of the nickel-rich cathode without compromising its energy density and safety.
In the future, this recent work could be used to develop safer and more durable batteries for electric vehicles and other large electronics. In addition, other research teams can draw inspiration from their findings to design other promising methods to prevent rapid capacity deterioration common in nickel-rich cathodes.
More information: Hoon-Hee Ryu et al., Near-surface reconstruction of nickel-rich layered cathodes for high-performance lithium-ion batteries, Nature Energy (2023). doi： 10.1038/s41560-023-01403-8.