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The use of solid electrolytes is a promising direction to improve the energy density of lithium‐ion batteries. However, the low ionic conductivity of many solid electrolytes currently hinders the performance of solid‐state batteries. Sulfide solid electrolytes can be processed in a number of forms (glass, glass‐ceramic, and crystalline) and have a wide range of available chemistries. Crystalline sulfide materials demonstrate ionic conductivity on par with those of liquid electrolytes through the utilization of near ideal conduction pathways. Low‐temperature processing is also possible for these materials due to their favorable mechanical properties. The main drawback of sulfide solid electrolytes remains their electrochemical stability, but this can be addressed through compositional tuning or the use of artificial solid electrolyte interphase (SEI). Implementation of sulfide solid electrolytes, with proper treatment for stability, can lead to substantial improvements in solid‐state battery performance leading to significant advancement in electric vehicle technology.

Digital computing is nearing its physical limits as computing needs and energy consumption rapidly increase. Analogue‐memory‐based neuromorphic computing can be orders of magnitude more energy efficient at data‐intensive tasks like deep neural networks, but has been limited by the inaccurate and unpredictable switching of analogue resistive memory. Filamentary resistive random access memory (RRAM) suffers from stochastic switching due to the random kinetic motion of discrete defects in the nanometer‐sized filament. In this work, this stochasticity is overcome by incorporating a solid electrolyte interlayer, in this case, yttria‐stabilized zirconia (YSZ), toward eliminating filaments. Filament‐free, bulk‐RRAM cells instead store analogue states using the bulk point defect concentration, yielding predictable switching because the statistical ensemble behavior of oxygen vacancy defects is deterministic even when individual defects are stochastic. Both experiments and modeling show bulk‐RRAM devices using TiO2‐X switching layers and YSZ electrolytes yield deterministic and linear analogue switching for efficient inference and training. Bulk‐RRAM solves many outstanding issues with memristor unpredictability that have inhibited commercialization, and can, therefore, enable unprecedented new applications for energy‐efficient neuromorphic computing. Beyond RRAM, this work shows how harnessing bulk point defects in ionic materials can be used to engineer deterministic nanoelectronic materials and devices.

Solid electrolytes have the potential to be safer alternatives to liquid electrolytes for lithium-ion batteries while being effectively configurable for powering small electronics. However, solid electrolytes typically exhibit poor interfaces and low ionic conductivity. Ionogel electrolytes, consisting of ionic liquid trapped inside a mesoporous solid, mitigate these limitations by maintaining a nanoscale fluidic state while behaving macroscopically solid. Adapting the synthesis process to achieve photo-patterning enables ionogels to be utilized in a variety of device architectures.

Understanding the structural transformations that materials undergo during (de)­insertion of Li ions is crucial for designing high-performance intercalation hosts as these deformations can lead to significant capacity fade. Herein, we present a study of the metallic defect perovskite ReO3 to determine whether these distortions are driven by polaronic charge transport (i.e., the electrons and ions moving through the lattice in a coupled way) due to the semiconducting nature of most oxide hosts. Employing numerous techniques, including electrochemical probes, operando X-ray diffraction, X-ray photoelectron spectroscopy, and density functional theory calculations, we find that the cubic structure of ReO3 experiences multiple phase changes involving the correlated twisting of rigid octahedral subunits upon lithiation. This results in exceptionally poor long-term cyclability due to large strains upon lithiation, even though metallic character is maintained throughout. This suggests that phase transformations during alkali ion intercalation are the result of local strains in the lattice and not exclusively due to polaron migration.

We have investigated the charge transport dynamics of a novel solid-like electrolyte material based on mixtures of the ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM] TFSI) and various concentrations of lithium salt bis(trifluoromethylsulfonyl)imide (LiTFSI) confined within a SiO 2 matrix, prepared via a sol−gel method. The translational diffusion coefficients of BMIM + , TFSI − , and Li + in ILs and confined ILs (ionogels, IGs) with different concentrations of lithium salt have been measured at variable temperatures, covering the 20−100 °C range, using nuclear magnetic resonance (NMR) pulsed field gradient diffusion spectroscopy. The mobility of BMIM + , TFSI − , and Li + was found to increase with the [BMIM] TFSI/LiTFSI ratio, exhibiting an almost liquid-like mobility in IGs. Additionally, the effect of confinement on IL rotational dynamics has been analyzed by measuring 1 H, 19 F, and 7 Li spin−lattice relaxation rate dispersions of IGs at different temperatures, using fast field-cycling NMR relaxometry. The analysis of the experimental data was performed assuming the existence of two fractions of the liquid: a bulk fraction (at least several ionic radii from the silica particles) and a surface fraction (close to the silica particles) and using two different models based on translational and rotational diffusion and reorientation mediated by translational displacements. The existence and weighting of these two fractions of ions were obtained from the direct diffusion measurements. The results show that the ion dynamics slowed only modestly under confinement, which evidences that IGs preserve IL transport properties, and this behavior is an encouraging indication for using IGs as a solid electrolyte for Li + batteries.

Poly­(3-hexylthiophene-2,5-diyl) (P3HT), a conducting polymer studied extensively for its optoelectronic devices, offers a number of advantageous properties when used as a conductive binder for lithium-ion battery cathode materials. By mixing with carbon nanotubes (CNT), P3HT-CNT serves as a surface coating for the cathode material LiNi0.8Co0.15Al0.05O2 (NCA). Oxidation of the P3HT enables high electronic and ionic conductivity to be achieved over the potential range where the NCA is electrochemically active. In addition to the conductivity benefits from electrochemical doping, the P3HT-CNT coating suppresses electrolyte breakdown, thus inhibiting growth of the solid electrolyte interphase layer and preventing intergranular cracking in the NCA particles. The use of the P3HT-CNT binder system leads to improved cycling for NCA at high power density with capacities of 80 mAh g–1 obtained after 1000 cycles at 16 C, a value that is 4 times greater than that achieved in the control electrode.

Composite structures for electrochemical energy storage are prepared on the basis of using the high-rate lithium ion insertion properties of NbO. The NbO is anchored on reduced graphene oxide (rGO) by hydrothermal synthesis to improve the charge-transfer properties, and by controlling the surface charge, the resulting NbO-rGO particles are attached to a high-surface-area carbide-derived carbon scaffold without blocking its exfoliated layers. The electrochemical results are analyzed using a recently published multiscale physics model that provides significant insights regarding charge storage kinetics. In particular, the composite electrode exhibits surface-confined charge storage at potentials of <1.7 V (vs Li/Li), where faradaic processes dominate, and electrical double layer charge storage at potentials of >2.2 V. A hybrid device composed of the composite electrode with activated carbon as the positive electrode demonstrates increased energy density at power densities comparable to an activated carbon device, provided the hybrid device operates in the faradaic potential range.