Modeling Degradation Mechanisms in Rechargeable Lithium-Ion Batteries

A physics-based, multiscale framework is presented to describe the degradation in rechargeable lithium-ion batteries. The framework goes beyond traditional (empirical) coulomb-counting approaches and enables the identification of different degradation regimes of behavior. Macroscopically, five degradation mechanisms: (i) solid electrolyte interphase (SEI) growth on the anode, (ii) electrolyte oxidation on the cathode, (iii) anode active material loss and (iv) cathode active material loss due to chemomechanical fracture, and (v) dendrite growth were identified and modeled. Great emphasis was placed on describing the physics of lithium dendrite growth in order to demonstrate five distinguishable regimes: thermodynamic suppression regime, incubation regime, tip-controlled growth regime, base-controlled growth regime, and mixed growth regime. Mesoscopically, three local dendrite growth mechanisms are identified: 1) electrochemical shielding, where there is practically no electrodeposition/electrodissolution, 2) stress-induced electrodissolution and electrodeposition on those interfaces directly facing each other, generating a self-sustained overpotential that pushes the dendrites towards the counter electrode, and 3) lateral plastic extrusion in those side branches experiencing non-hydrostatic stresses. Overall, the experimentally validated theoretical framework allows to fundamentally understand battery degradation and sets the stage to design high energy density and fast charging rechargeable batteries.