US researchers make nickel cathode advances

Research led by the US Department of Energy’s Pacific Northwest National Laboratory (PNNL) has developed a way to synthesise nickel-rich cathodes that could improve the ability of BEVs to store energy and withstand more charging cycles.

Introducing more nickel into the cocktail of metal oxides used in a cathode greatly improves a battery’s ability to store energy. But nickel-rich cathodes can be prone to cracking and decay faster than cathodes with less nickel in them.

However a single-crystal form of nickel developed by the researchers has proved much more resilient, showing no decay even after 1000 charge and discharge cycles.

“This is an important breakthrough that will allow the highest energy density lithium batteries to be used without degradation,” says Stan Whittingham, professor of chemistry at Binghamton University, who was involved in the research.

“In addition, this breakthrough on long-lived batteries will be critical to their use in vehicles that can be tethered to the grid to make it more resilient and to support clean renewable energy sources.”

The researchers say the synthesis method will be easy to scale up as it uses a drop-in approach that allows cathode manufacturers to use existing production facilities to produce cathodes with more than 80pc nickel.

"We are addressing the scientific challenges in synthesis and scaleup of single crystals and reducing the manufacturing cost starting from raw materials,” says Jie Xiao, the principal researcher on the project.

The method involves a pre-heating step that changes the structure and chemical properties of the transition metal hydroxide. When the pre-heated transition metal hydroxide reacts with lithium salt to form the cathode, it creates a uniform single-crystal nickel structure.

In the next research phase — set to begin in early 2024 — the PNNL team will work with chemicals manufacturer Albemarle, which supplies US OEMs Ford and Tesla, to reach commercial scale synthesis, with a view to eventually reaching commercial production.

Chemicals firm LG Chem began producing single-crystal high-nickel cathodes at a plant in South Korea earlier this year.

LG Chem will initially mix single-crystal cathode materials with conventional cathode materials in a 25pc ratio, gradually phasing up to 100pc. The firm aims to reach 50,000t of production from 2027.