Solid state electrolyte systems boasting Li + conductivity of >10 mS cm −1 at room temperature have opened the potential for developing a solid state battery with power and energy densities that are competitive with conventional liquid electrolyte systems. The primary focus of this review is twofold. First, differences in Li penetration resistance in solid state systems are discussed, and kinetic limitations of the solid state interface are highlighted. Second, technological challenges associated with processing such systems in relevant form factors are elucidated, and architectures needed for cell level devices in the context of product development are reviewed. Specific research vectors that provide high value to advancing solid state batteries are outlined and discussed. Solid state battery systems are of great interest because of potential benefits in gravimetric and volumetric energy density, operable temperature range, and safety in comparison to traditional liquid electrolyte based systems. However, unresolved fundamental issues remain in the quest to fully understand the behavior of all-solid batteries, especially in the area of electrochemical interfaces.1 There are also a number of significant engineering challenges that require methodical effort to enable a tangible product. Some transitions from academic laboratories to entrepreneurial efforts attempting to overcome these challenges remain unsuccessful in efforts to bring a product to the market.2,3 Vital parameters that require robust understanding from a product development standpoint are material cost, cell lifetime and shelf life, cell energy density on a volumetric and gravimetric basis, operable capabilities for given temperature conditions, and safety. The advantage of energy density remains to be realized in solid state electrolytes (SSEs) since most studies to date utilize thick SSEs or cathodes with low active loading compared to liquid counterparts. 4,5 Furthermore, the desire to use SSEs in conjunction with Li metal anodes requires understanding and managing the morphology of Li metal plating, which can impact volumetric energy density. Operation at both higher and lower temperature compared to conventional technologies is a significant potential advantage of SSE systems. However, reports of solid state cells achieving parity with traditional systems at room temperature or any other temperature do not currently exist. The safety, specifically decreased flammability, of SSE systems is another potential advantage but requires ongoing validation and study.6 Unlike current liquid electrolyte systems, 7 the manufacturability and material component costs of SSEs have not been well characterized, and thus the value of these features will need to be weighed accordingly with any added cost. Operating lifetime of SSEs capturing intrinsic materials parameters such as voltage stability, 8 as well as catastrophic failure modes such as shorting, 9 have been briefly investigated, but in the absence of high energy density electrode formulations and appli...

We generalize the conditions for stable electrodeposition at isotropic solid-solid interfaces using a kinetic model which incorporates the effects of stresses and surface tension at the interface. We develop a stability diagram that shows two regimes of stability: a previously known pressure-driven mechanism and a new density-driven stability mechanism that is governed by the relative density of metal in the two phases. We show that inorganic solids and solid polymers generally do not lead to stable electrodeposition, and provide design guidelines for achieving stable electrodeposition.

First-row transition metal oxides and chalcogenides have been found to rival or exceed the performance of precious metal-based catalysts for the interconversion of water and O2, central reactions that underlie renewable electricity storage and utilization. However, the high lability of the first-row transition metal ions leads to surface dynamics under the conditions of catalysis and results in active site structures distinct from those expected by surface termination of the bulk lattice. While these surface transformations have been well-characterized on many metal oxides, the surface dynamics of heavier chalcogenides under electrocatalytic conditions are largely unknown. We recently reported that the heazlewoodite Ni3S2 bulk phase supports efficient ORR catalysis under benign aqueous conditions and exhibits excellent tolerance to electrolyte anions such as phosphate which poison Pt. Herein, we combine electrochemistry, surface spectroscopy and high resolution microscopy to characterize the surface dynamics of Ni3S2 under ORR catalytic conditions. We show that Ni3S2 undergoes self-limiting oxidative surface restructuring to form an approximately 2 nm amorphous surface film conformally coating the Ni3S2 crystallites. The surface film has a nominal NiS stoichiometry and is highly active for ORR catalysis. Using DFT simulations we show that, to a first approximation, the catalytic activity of nickel sulfides is determined by the Ni-S coordination numbers at surface exposed sites through a simple geometric descriptor. In particular, we find that the surface sites formed dynamically on the surface of amorphous NiS during surface restructuring provide an optimal energetic landscape for ORR catalysis. This work provides a systematic framework for characterizing the rich surface chemistry of metal-chalcogenides and provides principles for the development of structure-energy-activity descriptors leading to a broader understanding of electrocatalysis mediated by amorphous materials.The interconversion of water and oxygen is a central chemistry underlying the storage of renewable electricity in energy-dense chemical bonds (Lewis and Nocera, 2006). The oxidation of H2O to O2 is the efficiency limiting half reaction for the splitting of water to generate H2 fuel, whereas the reduction of O2 to H2O is the efficiency limiting cathode reaction in low temperature fuel cells (Katsounaros et al., 2014). Platinum group metals and their corresponding oxides and chalcogenides are well-known catalysts for these reactions(Matsumoto and Sato, 1986) - (Gasteiger et al., 2005), but recent studies have uncovered a diversity of earth abundant first-row transition metal oxides(Kanan and Nocera, 2008) - (Long et al., 2014) and chalcogenides (Gao et al., 2012) , (Gao et al., 2013) that, depending on the reaction conditions, rival the activity of their precious metal analogs.Unlike their precious metal congeners, first-row transition metal ions are labile, Merbach, 1999, 2005) and as a result, the surfaces of these materials are expected to ...

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Battery degradation strongly depends on temperature, and many plug-in electric vehicle applications employ thermal management strategies to extend battery life. The effectiveness of thermal management depends on the design of the thermal management system as well as the battery chemistry, cell and pack design, vehicle system characteristics, and operating conditions. We model a plug-in hybrid electric vehicle with an air-cooled battery pack composed of cylindrical LiFePO 4 /graphite cells and simulate the effect of thermal management, driving conditions, regional climate, and vehicle system design on battery life. We estimate that in the absence of thermal management, aggressive driving can cut battery life by two thirds; blended-operation (gasoline-electric mix used when the battery is charged) can quadruple battery life relative to all-electric operation (electric only when the battery is charged); larger battery packs can extend life by an order of magnitude relative to small packs used for all-electric operation; and batteries last 73-94% longer in mild-weather San Francisco than in hot Phoenix. Air cooling can increase battery life by a factor of 1.5 to 6, depending on regional climate and driving patterns. End of life criteria has a substantial effect on battery life estimates.

Based on a simple thermodynamic analysis, we show that iodide-mediated electrochemical decomposition of lithium hydroxide (LiOH) likely occurs through a different mechanism than that proposed by Liu et al. (Research Article, 30 October 2015, p. 530 Although no thermodynamic barriers exist for the LiI-mediated formation of LiOH during discharge of water-contaminated Li-O 2 cells, the charging process warrants further analysis. We present a simple thermodynamic analysis of the triiodide-mediated LiOH oxidation mechanism proposed in their work (1). We consider their overall proposed charging reaction.This reaction has an equilibrium potential of 3.34 V under standard conditions (2). The activity of water is not at standard conditions in these experiments, but even at parts per million (ppm) quantities of water, there are negligible changes to the equilibrium potential. For example, in an experiment with~100 to 45,000 ppm, this corresponds to an equilibrium potential shift of~0.02 to 0.009 V.We now consider the iodide/triiodide redox reaction, shown in figure 4 of (1), given byThe redox potential for this reaction depends on the solvent (3). As reported in (1), we use the equilibrium potential-i.e.,~3.0 V-as shown in figure 1 of (1). Liu et al. point out in the caption that the crossing points of the charge/discharge curves indicate the positions of the redox potential of I − /I 3 − in the specific electrode/electrolyte system. The chemical reaction, shown in figure 4 of (1), to complete the charging cycle, is given byThis chemical reaction is uphill in free energy by DG c2 = 4 × (3.347 − 3.00) = 1.39 eV. This corresponds to an equilibrium constant, given by. Even if every cathode site were electrochemically active, the fraction that would transform to the product, O 2 , would be exceptionally small and therefore cannot account for a reversible process regenerating O 2 .The overall free-energy diagram for the charging mechanism proposed by Liu et al. at U = 3 V is shown in Fig. 1. A simpler way to understand the inconsistency is that the minimum potential required to oxidize LiOH is 3.34 V. The iodide/ triiodide redox couple has an oxidation potential of only~3 V and hence it is not feasible to oxidize LiOH(s) with such a scheme.In a rigorously anhydrous Li-O 2 battery that produces Li 2 O 2 as the discharge product (4, 5), the free-energy diagram involving an iodide/ triiodide redox couple is shown in Fig. 2

Polydopamine (PDA) is a complex biomimetic material exhibiting advantageous properties of both melanin polymers and biological adhesives. These concomitant features have prompted an increasing interest in exploiting PDA for bioelectronics, smart coatings, and functional membranes. The ability to apply the rich biochemistry of melanins in structurally durable contexts will help accelerate their practical implementation and the design of next‐generation materials. Here, this paper presents approaches for manipulating the adhesion and cohesive mechanics of PDA nanomembranes. Visual recording of PDA film delamination from SiO2 substrates reveals accelerated delamination (spanning orders of magnitude from 12 h to 1 min) with increasing pH and monovalent salt concentration. Delamination is retarded for films synthesized from higher dopamine concentrations, and it is completely prevented in the presence of Ca2+. Delaminated nanomembranes exhibit orientation‐dependent underwater adhesion to polydimethylsiloxane elastomer. Elastic moduli of PDA nanomembranes are quantified by compressive thin film buckling, and the measured value of 2.0 ± 0.9 GPa supports compositional simulations of PDA. Crosslinking of primary amines within the nanomembranes by genipin is successful in increasing the modulus to 7.9 ± 2.5 GPa. These results demonstrate that the adhesive stability and elastic modulus of PDA films/nanomembranes can be controlled by synthesis and postprocessing techniques.

We investigate the stability of electrodeposition at solid-solid interfaces for materials exhibiting an anisotropic mechanical response. The stability of electrodeposition or resistance to formation of dendrites is studied within a linear stability analysis. The deformation and stress equations are solved using the Stroh formalism and faithfully recover the boundary conditions at the interface. The stability parameter is used to quantify the stability of different solid-solid interfaces incorporating the full anisotropy of the elastic tensor of the two materials. Results show a high degree of variability in the stability parameter depending on the crystallographic orientation of the solids in contact and points to opportunities for exploiting this effect in developing Li metal anodes. arXiv:1707.00064v3 [cond-mat.mtrl-sci]