The movement of lithium ions into and out of electrodes is central to the operation of lithium-ion batteries. Although this process has been extensively studied at the device level, it remains insufficiently characterized at the nanoscale level of grain clusters, single grains and defects. Here, we probe the spatial variation of lithium-ion diffusion times in the battery-cathode material LiCoO(2) at a resolution of ∼100 nm by using an atomic force microscope to both redistribute lithium ions and measure the resulting cathode deformation. The relationship between diffusion and single grains and grain boundaries is observed, revealing that the diffusion coefficient increases for certain grain orientations and single-grain boundaries. This knowledge provides feedback to improve understanding of the nanoscale mechanisms underpinning lithium-ion battery operation.

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The properties of rechargeable lithium-ion batteries are determined by the electrochemical and kinetic properties of their constituent materials as well as by their underlying microstructure. In this paper a method is developed that uses microscopic information and constitutive material properties to calculate the response of rechargeable batteries. The method is implemented in OOF, a public domain finite element code, so it can be applied to arbitrary two-dimensional microstructures with crystallographic anisotropy. This methodology can be used as a design tool for creating improved electrode microstructures. Several geometrical two-dimensional arrangements of particles of active material are explored to improve electrode utilization, power density, and reliability of the Li y C 6 ͉Li x Mn 2 O 4 battery system. The analysis suggests battery performance could be improved by controlling the transport paths to the back of the positive porous electrode, maximizing the surface area for intercalating lithium ions, and carefully controlling the spatial distribution and particle size of active material. Important advances in materials have paved the way to the introduction of new devices of ever-increasing functionality. 1 In many cases, however, the full potential of these devices remains unreachable due to limitations of the batteries that power them. These limitations find their origin on the constituents of the battery: the different ohmic contributions, the low diffusivity of the involved charged species, the underlying oxidation-reduction processes, etc. Thus, battery technology improvement is critical to the development of many electric-based applications.In this context, modeling the galvanostatic cycling of a rechargeable battery provides valuable insight into optimizing the performance of the device. Furthermore, an analysis that simultaneously resolves the microstructural details and includes the nonlinearities and history from successive charge-discharge cycles will be useful for improving cell design.The discharging and recharging process involves electronic and ionic flow and their spatial relationships to conductivity in multiple phases as well as interfacial contact potential. Stress distributions that arise due to concentration-induced strains and resistive heating affect battery performance and reliability. Fundamentally, these processes depend on the structure, size, and spatial distribution of electrolyte and active material phases. The incorporation of microstructure into battery models can provide design criteria for improved battery performance. In this paper, a two-dimensional microstructural model for battery discharge is presented and accounts for geometry, connectivity, electrochemical properties of the component phases as well as elastic stresses that develop during battery use. The model presented in this paper links previously developed models for the homogeneous behavior of individual battery components and interfaces. The models are coupled together in a way that geometrically and physica...

By starting from fundamental principles, the heterogeneous nucleation and growth of electrodeposited anode materials is analyzed. Thermodynamically, we show that an overpotential-controlled critical radius has to be overcome in order for dendrite formation to become energetically favorable. Kinetically, surface tension and overpotential driving forces define a critical kinetic radius above which an isolated embryo will grow and below which it will shrink. As a result, five regimes of behavior are identified: nucleation suppression regime, long incubation time regime, short incubation time regime, early growth regime, and late growth regime. In the nucleation suppression regime, embryos are thermodynamically unstable and unable to persist. For small overpotentials, below a critical overpotential, 2η○, and between the thermodynamic and kinetic critical radius, a metastable regime exists where the local electrochemically enabled Gibbs-Thomson interactions control the coarsening of the embryos, thus defining the long incubation time regime. In addition, very broad nuclei size distributions are favored. For large overpotentials, above 2η○, a short incubation time regime develops as a result of the small energy barrier and large galvanostatic driving forces. In addition, very narrow size distributions of nuclei are favored. In the early growth regime, thermodynamically and kinetically favored nuclei grow to reach an asymptotic growth velocity. Finally, in the late growth regime, morphological instabilities and localized electric fields dominate the morphology and microstructural evolution of the deposit.

The ability to engineer electrode microstructures to increase power and energy densities is critical to the development of high-energy density lithium-ion batteries. Because high tortuosities in porous electrodes are linked to lower delivered energy and power densities, in this paper, we experimentally and computationally study tortuosity and consider possible approaches to decrease it. We investigate the effect of electrode processing on the tortuosity of in-house fabricated porous electrodes, using three-dimensionally reconstructed microstructures obtained by synchrotron x-ray tomography. Computer-generated electrodes are used to understand the experimental findings and assess the impact of particle size distribution and particle packing on tortuosity and reactive area density. We highlight the limitations and tradeoffs of reducing tortuosity and develop a practical set of guidelines for active material manufacture and electrode preparation.