Solvent-mediated oxide hydrogenation in layered cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Self-discharge and mechanical degradation limit the lifespan of energy storage devices.
• In lithium-ion batteries, cathode self-discharge leads to capacity and voltage loss.
• Current models primarily attribute self-discharge to lithium-ion diffusion into the cathode.

Purpose of the Study:

• To investigate an alternative mechanism for self-discharge in layered transition metal oxide cathodes.
• To understand the role of hydrogenation in battery degradation.
• To explore the impact of hydrogenation on cathode chemo-mechanical coupling and calendar life.

Main Methods:

• Analysis of self-discharged cathodes.
• Investigation of hydrogen transfer from carbonate solvents to delithiated oxides.
• Observation of proton and lithium ion concentration gradients.

Main Results:

• Demonstrated hydrogenation as an alternative pathway for cathode self-discharge.
• Identified hydrogen transfer from carbonate solvents to delithiated oxides.
• Observed opposing proton and lithium ion gradients in self-discharged cathodes, leading to heterogeneity and accelerated degradation.

Conclusions:

• Hydrogenation of delithiated cathodes is a significant self-discharge pathway.
• This process contributes to chemical and structural heterogeneities, impacting battery performance.
• Hydrogenation affects chemo-mechanical coupling and calendar life in lithium-ion batteries.