Researchers at Oxford University and Tokyo University of Science published separate studies on December 17 detailing advances in battery materials. The Tokyo team showed that sodium-ion batteries using hard-carbon electrodes can charge faster than conventional lithium-ion batteries. Oxford researchers developed electrolytes that retain ionic conductivity when shifting from liquid to solid states.
Professor Shinichi Komaba’s team at Tokyo University of Science used a “diluted electrode method” to assess hard-carbon charging limits. This approach mixes hard-carbon particles with electrochemically inactive aluminum oxide, which prevents ion traffic jams in dense electrodes during rapid charging. Cyclic voltammetry and electrochemical analysis revealed that sodium ions travel faster through hard carbon than lithium ions. The apparent diffusion coefficient, indicating ion mobility, proved higher for sodium in most cases.
“Our results quantitatively demonstrate that the charging speed of an SIB using an HC anode can attain faster rates than that of an LIB,” Komaba said. The study found sodium requires lower activation energy to form pseudo-metallic clusters in hard-carbon nanopores. This trait makes sodium insertion less temperature-sensitive. The research appeared in Chemical Science.
At Oxford University, Paul McGonigal and PhD student Juliet Barclay created cyclopropenium-based electrolytes. These materials challenge the idea that ion mobility drops sharply when liquids solidify. The team designed disc-shaped molecules with flexible side chains that self-assemble into columns upon solidification. This arrangement spreads positive charge over a flat core, avoiding negative ion entrapment and preserving a permeable structure for ion flow.
“We’ve demonstrated that it’s possible to engineer organic materials so that ion mobility does not freeze out when the material solidifies,” Barclay said. Tests in the study confirmed steady conductivity across liquid, liquid-crystal, and solid phases for different ion types. Published in Science, the work appeared on December 17.
The Tokyo findings highlight sodium-ion batteries’ potential for quicker charging with hard-carbon anodes. The Oxford electrolytes offer a path for safer batteries by allowing manufacturers to heat materials into liquid for assembly, then cool them into solids that reduce leakage and fire risks while sustaining performance.
