Simultaneously Achieving Lifespan and Output in High-Nickel Cathodes for Next-Generation All-Solid-State Batteries

No compromise on either lifespan or output.

A particle design technology that simultaneously extends the lifespan and enhances the output of high-nickel cathodes for next-generation all-solid-state lithium-ion batteries has been developed, drawing significant attention.

The research team led by Professor Kim Namhyung from the Department of Advanced Materials System Engineering at Pukyong National University, together with Dr. Cha Hyungyeon’s team at the Korea Institute of Energy Research, succeeded in simultaneously improving both the lifespan and output of high-nickel cathodes for all-solid-state batteries through a “multi-scale structural design strategy” that engineers both the nano and micro structures of the particles.

Although research on next-generation all-solid-state batteries has been active recently, aiming to realize high-energy-density batteries essential for electric vehicles and large-scale storage systems, limitations in stability and performance have persisted.

The research team focused on the issue of rapid performance deterioration when applying NCM (lithium nickel cobalt manganese oxide, LiNi0.8Co0.1Mn0.1O) cathode materials to all-solid-state batteries.

According to their findings, the same cathode material operates without issues in conventional liquid electrolyte environments, but when applied to all-solid-state batteries using sulfide-based solid electrolytes, the capacity drops by about 20%, and reactions within the electrode and inside the particles become uneven.

Research images. (Left) Issues with applying conventional gonickel cathode material in all-solid-state batteries, (Right) Advantages of applying multi-scale design cathode in all-solid-state batteries.

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Conventional polycrystalline high-nickel cathode particles fail to undergo sufficient structural changes due to lithium extraction and insertion during charging and discharging in all-solid-state batteries, resulting in inadequate capacity and the occurrence of “uneven reactions,” where only some particles are active. In particular, under the high-pressure conditions required for all-solid-state batteries, particle cracking and uneven contact with the solid electrolyte lead to the formation of large “dead zones” inside the electrode that do not participate in reactions.

To address this, the research team proposed a “multi-scale structural design strategy” that simultaneously engineers both the nano and micro structures. They first synthesized high-nickel NCM with artificially introduced twin-boundary defects inside the cathode particles, creating internal pathways that allow lithium ions to move more quickly.

In addition, instead of the conventional secondary particle structure, where many primary particles cluster together at the micro level, they introduced single-crystal high-nickel NCM where the entire particle is one single crystal. The single-crystal structure, with almost no grain boundaries inside the particle, prevents micro-cracking even under high pressure and enables the long-term preservation of particle shape and electrode structure.

When the research team evaluated high-nickel cathodes for all-solid-state batteries applying this technology under real all-solid-state battery conditions, the single-crystal NCM exhibited an initial discharge capacity of approximately 197 mAh/g and retained more than 90% of its capacity even after 100 charge-discharge cycles. This demonstrates a lifespan characteristic comparable to that of liquid electrolyte batteries.

Professor Kim Namhyung stated, “It is highly significant that we have presented a ‘cathode structural design paradigm’ optimized for all-solid-state battery environments. This kind of multi-scale material design will serve as an important guideline for the development of commercial cathodes for next-generation all-solid-state batteries in the future.”

The results of this research were published in the international journal, which ranks in the top 5% in the field of materials science, under the title “Synergistic nano-micro structuring boosts high-Ni cathode performance for all-solid-state lithium-ion batteries.”

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