Recent high-energy lithium-ion batteries contain highly densied electrodes, but they are expected to endure fast charging without safety compromises or accelerated aging. To investigate fast charging strategies, we use a multidimensional model consisting of several newman-type electrochemical models (p2D) coupled to an electrical-thermal cell domain model. Open-circuit potential, infrared thermography and calorimetry experiments of a high-energy 18650 NMC-811/SiC lithium-ion cell are used for model parameterization and validation. First, a single p2D model is used to compare the charging rate capabilities of NMC-811/SiC and NMC-111/graphite cells. We assess the modeling error of the single p2D model relative to the multi-dimensional model as a function of tab design. The multi-dimensional model is then used to study dierent tab and electrode designs regarding their susceptibility to lithium plating, which is evaluated based on local anode overpotential and

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Measurement data gained from quasi-isothermal external short circuit tests on single-layered pouch-type Li-ion cells presented in the first part of this combined work was used to validate a well-known homogenized physical-chemical model for different electrode loadings, cell temperatures, initial cell voltages, and external short circuit resistances. Accounting for diffusion-limited reaction kinetics, effective solid phase diffusion coefficients, and one representative active material particle size within each electrode, the model is capable of describing the experimentally observed characteristic change in magnitudes of current and heat generation rate throughout the short circuit. Underlying mechanisms for the observed characteristics are studied by evaluating the predicted concentration distribution across the electrodes and separator and by calculating the cell polarization due to ohmic losses, diffusion processes, and reaction kinetics. The importance of mass transport in the solid and liquid phase limiting reaction kinetics is discussed and evaluated in the context of a sensitivity analysis. Concentration dependent transport properties, electrode tortuosity, particle size, and electrode energy density are affecting different stages of a short circuit. Simulation results suggest a strong impact of electrode design on the short circuit dynamics allowing for an optimization regarding a cell's energy and power characteristics whilst guaranteeing a high short circuit tolerance.

Whilst extensive research has been conducted on the effects of temperature in lithium-ion batteries, mechanical effects have not received as much attention despite their importance. In this work, the stress response in electrode particles is investigated through a pseudo-2D model with mechanically coupled diffusion physics. This model can predict the voltage, temperature and thickness change for a lithium cobalt oxide-graphite pouch cell agreeing well with experimental results. Simulations show that the stress level is overestimated by up to 50% using the standard pseudo-2D model (without stress enhanced diffusion), and stresses can accelerate the diffusion in solid phases and increase the discharge cell capacity by 5.4%. The evolution of stresses inside electrode particles and the stress inhomogeneity through the battery electrode have been illustrated. The stress level is determined by the gradients of lithium concentration, and large stresses are generated at the electrode-separator interface when high Crates are applied, e.g. fast charging. The results can explain the experimental results of particle fragmentation close to the separator and provide novel insights to understand the local aging behaviors of battery cells and to inform improved battery control algorithms for longer lifetimes.

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