"Knees" in lithium-ion battery aging trajectories

Lithium-ion batteries can last many years but sometimes exhibit rapid, nonlinear degradation that severely limits battery lifetime. In this work, we review prior work on "knees" in lithium-ion battery aging trajectories. We first review definitions for knees and three classes of "internal state trajectories" (termed snowball, hidden, and threshold trajectories) that can cause a knee. We then discuss six knee "pathways", including lithium plating, electrode saturation, resistance growth, electrolyte and additive depletion, percolation-limited connectivity, and mechanical deformation -- some of which have internal state trajectories with signals that are electrochemically undetectable. We also identify key design and usage sensitivities for knees. Finally, we discuss challenges and opportunities for knee modeling and prediction. Our findings illustrate the complexity and subtlety of lithium-ion battery degradation and can aid both academic and industrial efforts to improve battery lifetime.Comment: Submitted to the Journal of the Electrochemical Societ

Chemomechanics: friend or foe of the "AND problem" of solid-state batteries?

Solid electrolytes are widely considered as the enabler of lithium metal anodes for safe, durable, and high energy density rechargeable lithium-ion batteries. Despite the promise, failure mechanisms associated with solid-state batteries are not well-established, largely due to limited understanding of the chemomechanical factors governing them. We focus on the recent developments in understanding solid-state aspects including the effects of mechanical stresses, constitutive relations, fracture, and void formation, and outline the gaps in the literature. We also provide an overview of the manufacturing and processing of solid-state batteries in relation to chemomechanics. The gaps identified provide concrete directions towards the rational design and development of failure-resistant solid-state batteries.Comment: 49 pages, 10 figure

Implications of the electric vehicle manufacturers’ decision to mass adopt lithium-iron phosphate batteries

Lithium-ion batteries are the ubiquitous energy storage device of choice in portable electronics and more recently, in electric vehicles. However, there are numerous lithium-ion battery chemistries and in particular, several cathode materials that have been commercialized over the last two decades, each with their own unique features and characteristics. In 2021, Tesla Inc. announced that it would change the cell chemistry used in its mass-market electric vehicles (EVs) from Lithium-Nickel-Cobalt-Aluminum-Oxide (NCA) to cells with Lithium-Iron-Phosphate (LFP) cathodes. Several other automakers have followed this trend by announcing their own plans to move their EV production to LFP. One of the reasons stated for this transition was to address issues with the nickel and cobalt supply chains. In this paper, we examine the trend of adopting LFP for mass-market electric vehicles, explore alternative reasons behind this transition, and analyze the effects this change will have on consumers

Tradeoffs between automation and light vehicle electrification

All underlying figure data and MATLAB code for Nature Energy manuscript. The results of the Monte Carlo analysis presented in the paper can be reproduced by running the Monte Carlo code provided in MATLAB/Octave. </p