Electrochemical stiffness in lithium-ion batteries

• Published in: Nature materials 2016-11, Vol.15 (11), p.1182-1187
• Main Authors: Tavassol, Hadi, Jones, Elizabeth M. C., Sottos, Nancy R., Gewirth, Andrew A.
• Format: Article
• Language: English
• Subjects: 639/166/988; 639/301/299/891; 639/638/161/891; Biomaterials; Condensed Matter Physics; Electric vehicles; Electrochemistry; Electrodes; energy storage (including batteries and capacitors), charge transport, materials and chemistry by design, synthesis (novel materials); Intercalation compounds; Lithium; Lithium-ion batteries; Materials Science; Nanotechnology; Optical and Electronic Materials; Performance degradation; Rechargeable batteries; Stiffness; Strain; Stresses
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat4708

Although lithium-ion batteries are ubiquitous in portable electronics, increased charge rate and discharge power are required for more demanding applications such as electric vehicles. The high-rate exchange of lithium ions required for more power and faster charging generates significant stresses and strains in the electrodes that ultimately lead to performance degradation. To date, electrochemically induced stresses and strains in battery electrodes have been studied only individually. Here, a new technique is developed to probe the chemomechanical response of electrodes by calculating the electrochemical stiffness via coordinated in situ stress and strain measurements. We show that dramatic changes in electrochemical stiffness occur due to the formation of different graphite–lithium intercalation compounds during cycling. Our analysis reveals that stress scales proportionally with the lithiation/delithiation rate and strain scales proportionally with capacity (and inversely with rate). Electrochemical stiffness measurements provide new insights into the origin of rate-dependent chemomechanical degradation and the evaluation of advanced battery electrodes. Electrochemically induced stresses in battery electrodes leading to performance degradation are still poorly understood. In situ measurements show that stress scales proportionally with lithium intercalation rate and strain with capacity.