Metal

Battery (electricity)

Quantum mechanics

Engineering

Lithium (medication)

Lithium vanadium phosphate battery

Biology

Lithium-ion battery

Metallurgy

Materials science

Nanoarchitectures for lithium-ion batteries

Endocrinology

Interphase

Power (physics)

Lithium carbonate

Ethylene carbonate

Inorganic chemistry

Chemical engineering

Lithium metal

Physical chemistry

Genetics

Thermodynamics

Physics

Organic chemistry

Elastic modulus

Composite material

Ionic bonding

Fracture (geology)

Medicine

Chemistry

Electrode

Anode

Electrolyte

Energy storage materials

Mechanical integrity of the solid electrolyte interphase (SEI) plays an essential role in determining the life and performance of lithium-ion batteries. Fracture and continued formation of the SEI contribute to consumption of lithium, drying of electrolyte, increase in impedance, and growth of dendrites resulting in capacity fade and premature failure. Electrolyte additives such as fluoroethylene carbonate (FEC) have been known to improve performance, but the underlying reasons have been elusive. Despite its importance, reliable methods for mechanical characterization of SEI have been lacking. Here, we present a new experimental technique that combines atomic force microscopy and membrane-bulge configuration to accurately measure the stress-strain behavior of SEI, including the onset of inelastic response and evolution of fracture. We characterize the SEI formed with two ethylene carbonate-based electrolytes, without and with fluoroethylene carbonate (FEC) additive. The measurements show a striking contrast; SEI with FEC additive has 80% higher elastic modulus and a vastly higher resistance to fracture. These findings offer a mechanical-behavior based rationale to understand how SEI controls battery performance. Moreover, the experimental technique offers a robust diagnostic tool to design electrolytes that can form SEI with the desired mechanical properties for optimal battery performance.

Measurement of mechanical and fracture properties of solid electrolyte interphase on lithium metal anodes in lithium ion batteries