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2h ago

MIT Study Rewrites Lithium-Ion Battery Chemistry With Coupled Ion-Electron Model

Using short voltage bursts across more than 50 electrode–electrolyte pairs, researchers found intercalation is limited by simultaneous electron transfer, pointing to electrolyte tuning as a route to faster charging.

electric car lithium battery pack
Lithium intercalation is the process by which lithium ions insert themselves into the solid electrode of a lithium-ion battery. MIT researchers have shown that as lithium ions (green) move from an electrolyte solution (right) to a cobalt oxide electrode (left), electrons also move into the electrode and reduce the cobalt (gray atoms with gold halo).

Overview

  • The work, published in Science, introduces the Coupled Ion-Electron Transfer (CIET) framework to explain the core intercalation reaction in lithium-ion cells.
  • Precise measurements using repeated short voltage pulses produced consistent rate data across diverse materials, including NMC for EVs and LCO for consumer electronics.
  • Observed intercalation rates were far lower than commonly reported and diverged from predictions based on diffusion-limited, Butler–Volmer models.
  • CIET indicates lithium enters the electrode only when an electron transfers at the same moment, a pairing that sets the true reaction rate by lowering the energy barrier.
  • The findings highlight practical levers such as adjusting electrolyte composition to speed charging and curb degradation, with engineering validation in commercial cells still to come.