Using atomic layer deposition to hinder solvent decomposition in lithium ion batteries: first principles modeling and experimental studies

TL;DR

This study combines first principles modeling and experimental work to show that atomic layer deposition coatings on lithium-ion battery electrodes effectively reduce electrolyte decomposition by hindering electron tunneling, thereby enhancing battery stability.

Contribution

It provides new insights into how ALD coatings alter electron transfer regimes at electrode surfaces, combining theoretical calculations with experimental validation.

Findings

ALD coatings change electron transfer from adiabatic to non-adiabatic regimes.

Coatings significantly decrease electrolyte decomposition rates.

Experimental data supports theoretical predictions of reduced electron tunneling.

Abstract

Passivating lithium ion battery electrode surfaces to prevent electrolyte decomposition is critical for battery operations. Recent work on conformal atomic layer deposition (ALD) coating of anodes and cathodes has shown significant technological promise. ALD further provides well-characterized model platforms for understanding electrolyte decomposition initiated by electron tunneling through a passivating layer. First principles calculations reveal two regimes of electron transfer to adsorbed ethylene carbonate molecules (EC, a main component of commercial electrolyte) depending on whether the electrode is alumina-coated. On bare Li metal electrode surfaces, EC accepts electrons and decomposes within picoseconds. In contrast, constrained density functional theory calculations in an ultra-high vacuum setting show that, with the oxide coating, e- tunneling to the adsorbed EC falls within the non-adiabatic regime. Here the molecular reorganization energy, computed in the harmonic approximation, plays a key role in slowing down electron transfer. Ab initio molecular dynamics simulations conducted at liquid EC-electrode interfaces are consistent with the view that reactions and electron transfer occur right at the interface. Microgravimetric measurements demonstrate that the ALD coating decreases electrolyte decomposition and corroborate the theoretical predictions.