Avtar Singh

The optimal design and durable utilization of lithium-ion batteries necessitates an objective modeling approach to understand fracture and failure mechanisms. This paper presents a comprehensive chemo-mechanical modeling study focused on elucidating fracture-induced damage and degradation phenomena in the polycrystalline Li x Ni 0.5 Mn 0.3 Co 0.2 O 2 (NMC532) cathode. An innovative approach that utilizes image-based reconstructed 3D geometry as finite element (FE) mesh input is employed to enhance the precision in capturing the convoluted architecture and morphological features. For accurately representing the intricate crack configurations within the polycrystalline system, we adopted the cohesive phase-field fracture (CPF) model. Through the integration of advanced image-based geometry reconstruction technique and the promising CPF modeling approach, lithium (de) intercalation induced …

Models exploring electrochemistry-mechanics coupling in liquid electrolyte lithium-ion battery anodes have traditionally incorporated stress impact on thermodynamics, bulk diffusive transport, and fracture, while stress-kinetics coupling is more explored in the context of all solid-state batteries. Here, we showcase the existence of strong link between active particle surface pressure and reaction kinetics affecting performance even in liquid electrolyte systems. Traction-free and immobile particle surface mechanical boundary conditions are used to delineate the varying pressure magnitudes in graphite host during cycling. Both tensile and compressive stresses are generated in traction-free case, while a fixed surface subjects the entire particle to a compression state. Pressure magnitudes are nearly two to three orders of magnitude higher for the latter resulting in significant depression of open circuit potential and …

In Li-ion battery research, it is common to simulate chemo-mechanical phenomena in reduced dimensions (e.g., 2-D) as opposed to fully resolve these complex physics in 3-D. It is common to assume either (1) the out-of-plane strain is negligible (commonly referred to as plane-strain), or (2) the out-of-plane stress is negligible (commonly referred to as plane-stress). However, there is typically little consideration as to the quantitative consequences of these approximations. Furthermore, the influence of these out-of-plane assumptions can be compounded and convoluted when chemo-mechanics models implement so-called “fully coupled” formulations, where the local species concentrations influence the stress-state and the stress-state influences the local species fluxes. The present manuscript explores the implications of using plane-stress and plane-strain assumptions in 2-D as compared to simulating a full 3-D …

Lithium-nickel-manganese-cobalt-oxides (NMC) embedded in solid-electrolytes are being extensively applied as composite cathodes to match the high energy density of metallic anodes. During charge/discharge, the cathode composite often degrades through the evolution of micro-cracks within the grains, along the grain boundaries, and delamination at the particle-electrolyte interface. Experimental evidence has shown that regulating the morphology of grains and their crystallographic orientations is an effective way to relieve the volume-expansion-induced stresses and cracks, consequently stabilizing the electrochemical performance of the electrode. However, the interplay among the crystal orientation, grain morphology, and chemo-mechanical behavior has not been holistically studied. In that context, a thermodynamically consistent computational framework is developed to understand the role of …

In the present work, phase field model has been implemented for simulating hydraulic fracturing in porous reservoir which consists of several poorly connected natural fractures. We have used the finite element method (FEM) for solving the poro-elastic deformation and phase field equation, while the finite volume method (FVM) has been considered for solving the flow field. The validations of the numerical model with existing analytical and numerical solutions of fracture propagation are presented for an elastic medium subjected to incremental external loads and a poro-elastic medium undergoes hydraulic fracturing due to the increase of fluid injection pressure. The simulation results in this study show the ability of the phase field method based hydraulic fracturing (HF) model to obtain complex fracture propagation patterns including crack branching, merging, curving, and interacting with pre-existing natural …

The utilization of silicon anodes in all‐solid‐state lithium batteries provides good prospects for facilitating high energy density. However, the compatibility of sulfide solid‐state electrolytes (SEs) with Si and carbon is often questioned due to potential decomposition. Herein, operando X‐ray absorption near‐edge structure (XANES) spectroscopy, ex situ scanning electron microscopy (SEM), and ex situ X‐ray nanotomography (XnT) are utilized to investigate the chemistry and structure evolution of nano‐Si composite anodes. Results from XANES demonstrate a partial decomposition of SEs during the first lithiation stage, which is intensified by the presence of carbon. Nevertheless, the performances of first three cycles in Si–SE–C are stable, which proves that the generated media is ionically conductive. XnT and SEM results show that the addition of SEs and carbon improves the structural stability of the anode, with …

View Video Presentation: https://doi.org/10.2514/6.2023-0319.vidThe future of all-electric aircraft depends on the innovation of battery technology today. Since the energy density of conventional Li-ion battery cells with graphite and metal oxides electrodes is limited to about 300 Wh/kg at the cell level, “next-generation batteries” such as the Li-metal all-solid-state batteries (ASSBs) are demanded to achieve the minimum energy density (~600 Wh/kg) necessary to make electric flight viable. The major obstacles preventing the widespread adoption of Li-metal ASSBs are rapid degradation and poor rate capacities, which are directly linked to various interfacial issues involving multiple electro-chemo-mechanical processes. Overcoming these interfacial issues calls for a high-fidelity computational model that could be used for exploring the physical mechanisms involved in degradation and for identifying promising …

Strong binders can be counterproductive for silicon anodes. Here, we show that stresses from cycling Si-based electrodes can cause permanent stretching and wrinkling of the current collector. This deformation damages the electrode coating and accelerates cell aging due to the inactivation of Si domains and facilitation of Li plating. Interestingly, we demonstrate that the formation of wrinkles is size-dependent, being present in pouch cells but absent from coin cells. This size-dependent performance decay indicates that, in extreme cases, testing outcomes are highly dependent on scale and that the validation of battery materials may require testing at larger cell formats.

All-solid-state batteries (ASSBs) provide higher energy densities and safer alternatives to Li-ion batteries by incorporating Li-metal anode and inflammable solid electrolytes. To match the increased capacity of metallic anodes, ASSBs require high-energy-density cathode materials such as LiNixCoyMn1-x-yO2 (also known as NMC cathode) blended with a solid-state electrolyte (SSE). However, a key challenge is resolving the interfacial incompatibility between the active particulate material and the solid-state electrolyte within these composite cathodes. To obtain intimate contact between SSE and the active material, an external load (or stack pressure) needs to be applied during the processing and service life of cell. Nevertheless, such densification of cathode composites can lead to grain boundary fracture and/or complete particle disintegration. Therefore, the present work utilizes a microstructural modulation …

There are abundant electrochemical-mechanical coupled behaviors in lithium-ion battery (LIB) cells on the mesoscale or macroscale level, such as electrode delamination, pore closure, and gas formation. These behaviors are part of the reasons that the excellent performance of LIBs in the lab/material scale fail to transfer to the industrial scale. This paper aims to systematically review these behaviors by utilizing the ‘mechanical origins – structural changes – electrochemical changes – performance’ logic. We first introduce the mechanical origins i.e., the external pressure and internal deformation, based on the different stages of battery life cycle, i.e., manufacture and operation. The response of the batteries due to the two mechanical origins are determined by the mechanical constitutive relation of battery components. The resulting structural changes are ascribed to size and distribution of pores and particles of the …

Evolution of complex fracture patterns during electrochemical cycling for the polycrystalline particulate cathode of lithium-ion batteries is found to be a primary reason towards capacity fading. Such fracture of a particles involves inter- and intra-granular crack propagation and often with its debonding from the binder. Till date, a comprehensive understanding of these fracture mechanisms under chemo-mechanical environment towards overall electrochemical response is lacking. In that context, a thermodynamically consistent multi-physics modeling framework is developed to account for strongly coupled chemo-mechanical environments and the evolution of arbitrary fracture within polycrystalline cathode particles embedded in the matrix. Specifically, a regular phase-field fracture variable is introduced for initiation and propagation of the inter- and intra-granular crack within the particle and debonding of the particle …

Composite possesses wide spectrum of mechanical responses along with remarkable fracture strength and toughness. Such properties evolve due to combination of different failure mechanisms across multiple phases. Understanding the contribution of these mechanisms on overall behavior is necessary to fabricate the composite with desired fracture properties. Although numerous studies have been performed to correlate the fracture response with crack propagation characteristics, they fail to account several underlying micro-mechanical events. Therefore, in the present study, a multi-phase field fracture model is proposed. We consider that constituents are homogeneously distributed within the matrix, while macro-scale phase field descriptors are utilized to represent the failure of its constituents. Further, the reinforced elements are assumed to be anisotropic in nature with preferential fracture direction. Therefore …

Next generation lithium-ion batteries (LIBs) cathodes are composed of polycrystalline microstructures where spatial heterogeneity such as grain size is often comparable to the geometric dimension of the cathodes. Incorporating the influence of the aforementioned heterogeneity in a chemo-mechanical continuum description is necessary to address the diffusion induced stress field during electrochemical cycling. Therefore, in the present study, the micro-structural size-dependent characteristic length of the cathode is embedded through a non-classical continuum mechanics approach known as the strain gradient elasticity (SGE) theory. Accordingly, a thermodynamically consistent multi-physics framework is developed where nonlinear diffusion kinetics is included along with the energetic interaction between the lithium-ions and host lattice of the electrode. The coupled governing equations are derived for the …

A thermodynamically consistent multi-physics framework has been developed to understand the chemo-mechanical interplay towards fracture behavior of polycrystalline microstructure along with the current collector. Adopting non-equilibrium thermodynamics, and considering bulk and interfaces as separate systems, the coupled governing equations are derived. The proposed framework accounts the plastic deformation of the host lattice and the substrate. A chemo-mechanical cohesive zone model (CZM) has been formulated to simultaneously capture the decohesion and transport across grain boundaries, while classical CZM is used between the cathode/substrate interface. Using numerical framework, grain-boundary width is initially calibrated to ensure transport of Li-ions through intact grain boundaries. The proposed numerical scheme has been verified with semi-analytical model for cylindrical cathode …