A Bilayer Cathode Design Procedure for Li ion Batteries Using the Multilayer Doyle-Fuller-Newman Model (M-DFN)

TL;DR

This paper presents a physics-based optimization of a bilayer cathode in Li-ion batteries using the M-DFN model, resulting in faster charging and higher capacity compared to single-material electrodes.

Contribution

It introduces a novel bilayer cathode design optimized via the multilayer Doyle-Fuller-Newman model, demonstrating improved charge rates and capacity.

Findings

Optimized bilayer cathode charges at 3C in 18.6 minutes

Achieves 41% higher capacity than LFP-only electrode

Homogeneous current distribution improves charge performance

Abstract

Heterogeneities in lithium ion batteries can be significant factors in electrode under utilisation and degradation while charging. Bilayer electrodes have been proposed as a convenient and scalable way to homogenise the electrode response. In this paper, the design of a bilayer cathode for Li-ion batteries composed of separate layers of lithium nickel manganese cobalt oxide (NMC622) and lithium iron phosphate (LFP) is optimised using the multilayer Doyle-Fuller-Newman (M-DFN) model. Changes to the carbon binder domain, electrolyte volume fraction, and tortuosity provided the greatest control for improving Li-ion charge mobility. The optimised bilayer design was able to charge at 3C between 0-90% SOC in 18.6 minutes, achieving 4.4 mAh/cm2. Comparing the optimal bilayer to the LFP-only electrode, the bilayer achieved 41% higher capacity. Through mechanistic physics-based modelling, it was shown that the 3C charging improvement of the optimised bilayer was achieved by enabling a more homogeneous current density distribution through the thickness of the electrode and electrolyte depletion prevention. The findings were confirmed on a high-fidelity X-ray computed tomography (CT) based microstructural model. The results illustrate how modelling can be used to rapidly search novel electrode designs