Endpoint slippage analysis in the presence of impedance rise and loss of active material

TL;DR

This paper investigates how impedance rise and loss of active material affect endpoint slippage analysis in batteries, providing equations to correct for these effects and improve diagnostics of parasitic reactions.

Contribution

It introduces mathematical models linking endpoint slippage to impedance rise and LAM, enabling more accurate quantification of side-reactions in battery aging.

Findings

Equations describing slippage due to impedance rise and LAM.

Mathematical connections between measurable quantities and aging modes.

Discussion on how endpoint tracking can improve battery diagnostics.

Abstract

The endpoint slippage analysis can be used to quantify the reduction and oxidation side-reactions occurring in rechargeable batteries. Application of this technique often disregards the interference of additional aging modes, such as impedance rise and loss of active material (LAM). Here, we show that these modes can themselves induce slippage of endpoints, making the direct determination of parasitic reactions more difficult. We provide equations that describe the slippages caused by LAM and impedance rise. We show that these equations can, in principle, account for the contribution of these additional modes to endpoint slippage, enabling correction of testing data to quantify the side-reactions of interest. However, the challenge with this approach is that it requires information about the average Li content of disconnected active material domains, which is, in many cases, unknowable. The present work explores mathematical connections between measurable quantities (such as capacity fade and endpoint slippages) and the extent of LAM or impedance rise endured by the cell, and discuss how the tracking of endpoints can better serve battery diagnostics.