“Uncommon” Findings Overturn Present Battery Knowledge

Scientists have made a big breakthrough in understanding and overcoming the challenges related to Ni-rich cathode supplies utilized in lithium-ion batteries.

Whereas these supplies can attain excessive voltages and capacities, their real-world utilization has been restricted by structural points and oxygen depletion.

Their examine revealed that ‘oxygen gap’ formation – the place an oxygen ion loses an electron — performs a vital position within the degradation of LiNiO₂ cathodes accelerating the discharge of oxygen which may then additional degrade the cathode materials.

Utilizing a set of state-of-the-art computational strategies on UK regional supercomputers, the researchers examined the conduct of LiNiO₂ cathodes as they’re charged. They discovered that in charging the oxygen within the materials undergoes adjustments whereas the nickel cost stays basically unchanged.

Co-author Prof Andrew J. Morris, from the College of Birmingham, commented: “We discovered that the cost of the nickel ions stays round +2, no matter whether or not it’s in its charged or discharged kind. On the similar time, the cost of the oxygen varies from -1.5 to about -1. That is uncommon, the traditional mannequin assumes that the oxygen stays at -2 all through charging, however these adjustments present that the oxygen shouldn’t be very steady, and we have now discovered a pathway for it to depart the nickel-rich cathode.”

The researchers in contrast their calculations with experimental information and located that their outcomes aligned properly with what was noticed. They proposed a mechanism for a way oxygen is misplaced throughout this course of, involving the mix of oxygen radicals to kind a peroxide ion, which is then transformed into oxygen gasoline, leaving vacancies within the materials. This course of releases vitality and kinds singlet oxygen, a extremely reactive type of oxygen.

 “Doubtlessly, by including dopants that scale back oxygen redox, whereas selling transition-metal redox, significantly on the floor, mitigating the era of singlet oxygen, we will improve the soundness and longevity of most of these lithium-ion batteries, paving the best way for extra environment friendly and dependable vitality storage methods,” first writer Dr Annalena Genreith-Schriever from the College of Cambridge provides.

Lithium-ion batteries are broadly used for numerous purposes due to their excessive vitality density and rechargeability, however challenges related to the soundness of cathode supplies have hindered their total efficiency and lifespan.

Reference: “Oxygen gap formation controls stability in LiNiO2 cathodes” by Annalena R. Genreith-Schriever, Hrishit Banerjee, Ashok S. Menon, Euan N. Bassey, Louis F.J. Piper, Clare P. Gray and Andrew J. Morris, 19 July 2023, Joule.
DOI: 10.1016/j.joule.2023.06.017