Global energy and climate-change concerns have accelerated the electrifi cation of vehicles, aided by advances in battery technology. It is now recognized that low-cost, scalable energy storage will also be key to continued growth of renewable energy technologies (wind and solar) and improved effi ciency of the electric grid. While electrochemical energy storage remains attractive for its high energy density, simplicity, and reliability, existing battery technologies remain limited in their ability to meet many future storage needs. Here we propose and demonstrate a new storage concept, the semi-solid fl ow cell (SSFC), which combines the high energy density of rechargeable batteries with the fl exible and scalable architecture of fuel cells and fl ow batteries. In contrast to previous fl ow batteries, energy is stored in suspensions of solid storage compounds to and from which charge transfer is accomplished via dilute yet percolating networks of nanoscale conductors. These novel electrochemical composites constitute fl owable semi-solid 'fuels' that are here charged and discharged in prototype fl ow cells. Potential advantages of the SSFC approach include projected system-level energy densities that are more than ten times those of aqueous fl ow batteries, and the simplifi ed low-cost manufacturing of large-scale storage systems compared to conventional lithiumion batteries.Demand for batteries of higher energy and power has driven several decades of research in electrochemical storage materials, resulting recently in signifi cant improvements in the stored energy of cathodes and anodes. [ 1 , 2 ] However, most batteries have designs that have not departed substantially from Volta's galvanic cell of 1800, and which accept an inherently poor utilization of the active materials. [ 3 ] Even the highest energy density lithium ion cells currently available, e.g., 2.8-2.9 Ah 18650 cells having > 600 Wh L − 1 , have less than 50 vol% active material. The reduced energy density, along with higher cost, result because the high-energy-storage compounds are diluted by inactive and costly components necessary to extract power (e.g., currentcollector foils, tabs, separator fi lm, liquid electrolyte, electrode binders and conductive additives, and external packaging). Further dilution of energy density, by about a factor of two, occurs between the cell and system level. [ 4 ] Electrode designs that minimize inactive material, bio-and self-assembly, and 3D architectures are new approaches that promise improved design efficiency but have yet to be fully realized. [ 5 -9 ] Decoupling power components from energy-storage components so that stored energy can be scaled independently of power is a strategy for improving system-level energy density. Redox fl ow batteries have such a design, in which active materials are stored within external reservoirs and pumped into an ion-exchange/electron-extraction power stack. [ 10 ] As the system increases in capacity, its energy density may asymptotically approach that of the redox acti...

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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...

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An aqueous Li-ion flow cell using suspension-based flow electrodes based on the LiTi2(PO4)3-LiFePO4 couple is demonstrated. Unlike conventional flow batteries, the semi-solid approach utilizes fluid electrodes that are electronically conductive. A model of simultaneous advection and electrochemical transport is developed and used to separate flow-induced losses from those due to underlying side reactions. The importance of plug flow to achieving high energy efficiency in flow batteries utilizing highly non-Newtonian flow electrodes is emphasized.