'Capture the oxygen!' The key to extending next-generation lithium-ion battery life

Lithium-ion batteries are indispensable in applications such as electric vehicles and energy storage systems (ESS). The lithium-rich layered oxide (LLO) material offers up to 20% higher energy density than conventional nickel-based cathodes by reducing the nickel and cobalt content while increasing the lithium and manganese composition. As a more economical and sustainable alternative, LLO has garnered significant attention. However, challenges such as capacity fading and voltage decay during charge-discharge cycles have hindered its commercial viability.

While previous studies have identified structural changes in the cathode during cycling as the cause of these issues, the exact reasons behind the instability have remained largely unclear. Additionally, existing strategies aimed at enhancing the structural stability of LLO have failed to resolve the root cause, hindering commercialization.

The POSTECH team focused on the pivotal role of oxygen release in destabilizing the LLO structure during the charge-discharge process. They hypothesized that improving the chemical stability of the interface between the cathode and the electrolyte could prevent oxygen from being released. Building on this idea, they reinforced the cathode-electrolyte interface by improving the electrolyte composition, which resulted in a significant reduction in oxygen emissions.

The research team's enhanced electrolyte maintained an impressive energy retention rate of 84.3% even after 700 charge-discharge cycles, a significant improvement over conventional electrolytes, which only achieved an average of 37.1% energy retention after 300 cycles.

The research also revealed that structural changes on the surface of the LLO material had a significant impact on the overall stability of the material. By addressing these changes, the team was able to dramatically improve the lifespan and performance of the cathode while also minimizing unwanted reactions like electrolyte decomposition inside the battery.

Professor Jihyun Hong commented, "Using synchrotron radiation, we were able to analyze the chemical and structural differences between the surface and interior of the cathode particles. This revealed that the stability of the cathode surface is crucial for the overall structural integrity of the material and its performance. We believe this research will provide new directions for developing next-generation cathode materials."

This research was supported by the Ministry of Trade, Industry and Energy through the Korea Institute for Advancement of Technology, and the Ministry of Science and ICT through the National Research Foundation of Korea, with funding for 2024.