Progress toward durable and energy-dense lithium-ion batteries has been hindered by instabilities at electrolyte–electrode interfaces, leading to poor cycling stability, and by safety concerns associated with energy-dense lithium metal anodes. Solid polymeric electrolytes (SPEs) can help mitigate these issues; however, the SPE conductivity is limited by sluggish polymer segmental dynamics. We overcome this limitation via zwitterionic SPEs that self-assemble into superionically conductive domains, permitting decoupling of ion motion and polymer segmental rearrangement. Although crystalline domains are conventionally detrimental to ion conduction in SPEs, we demonstrate that semicrystalline polymer electrolytes with labile ion–ion interactions and tailored ion sizes exhibit excellent lithium conductivity (1.6 mS/cm) and selectivity ( t + ≈ 0.6–0.8). This new design paradigm for SPEs allows for simultaneous optimization of previously orthogonal properties, including conductivity, Li selectivity, mechanics, and processability.

<div>The shear-phase compound TiNb₂O₇ has recently emerged as a safe and high-volumetric density replacement for graphite anodes in lithium ion batteries. An appealing feature of TiNb₂O₇ is that it retains capacity even at high cycling rates. Here we demonstrate that phase pure and crystalline TiNb₂O₇ can be rapidly prepared using a high-temperature microwave synthesis method. Studies of the charging and discharging of this material, including through operando calorimetry, permit key thermodynamic parameters to be revealed. The nature of heat generation is dominated by Joule heating, which sensitively changes as the conductivity of the electrode increases with increasing lithiation. The enthalpy of mixing, obtained from operando calorimetry, is found to be small across the different degrees of lithiation pointing to the high rate of lithium ion diffusion at the origin of rapid rate performance.</div>

The Wadsley-Roth phase (W 0.2 V 0.8) 3 O 7 , crystallizing in a structure obtained through crystallographic shear of 3×3×∞ ReO 3 blocks, is a somewhat rare exemplar for this class of compounds in that it contains a relatively small amount of 4d and/or 5d transition elements. Here we demonstrate that it functions as a high-rate, high-capacity material for lithium ion batteries. Electrochemical insertion and de-insertion in micron sized particles made by conventional solid-state preparation and in sub-100 nm particles made by combining sol-gel precursors with freeze-drying methods, indicate good rate capabilities. The materials display high capacity-close to 300 mAh g −1 at low rates-corresponding to insertion of up to 1.3 Li per transition metal at voltages above 1 V. Li insertion is associated with multielectron redox for both V and W observed from ex-situ X-ray photoelectron spectroscopy. The replacement of 4d and 5d elements with vanadium results in a higher voltage than seen in other, usually niobium-containing shear-structured electrode materials, and points to new opportunities for tuning voltage, electrical conductivity, and capacity in compounds in this structural class.

Hybrid layered double perovskite (HLDP) halides comprise hexa-coordinated 1+ and 3+ metals in the octahedral sites within a perovskite layer and organic amine cations between the layers. Progress on such materials has hitherto been limited to compounds containing main group 3+ ions isoelectronic with Pb II (such as Sb III and Bi III ). Here, we report eight HLDP halides from the A2M I M III X8 family, where A = para-phenylenediammonium (PPDA), 1,4-butanediammonium (1,4-BDA) or 1,3propanediammonium (1,3-PDA); M I = Cu or Ag; M III = Ru or Mo; X = Cl or Br. The optical band gaps, which lie in the range 1.55 eV to 2.05 eV, are tunable according to the layer composition, but are largely independent of the spacer. Magnetic measurements carried out for (PPDA)2Ag I Ru III Cl8 and (PPDA)2Ag I Mo III Cl8 show no obvious evidence of a magnetic ordering transition. While the t2g 3 Mo III compound displays Curie-Weiss behavior for a spin-only d 3 ion, the t2g 5 Ru III compound displays marked deviations from the Kotani theory. ASSOCIATED CONTENT Supporting InformationSynthesis and characterization, scXRD refinement details, key bond lengths and bond angles, hydrogen bond interactions, power x-ray diffraction patterns, x-ray photoelectron spectra (XPS), scanning electron microscope (SEM) images, additional single-crystal x-ray structures, octahedral tilting Accession CodesCCDC (2122532 -2122540) contain the supplement crystallographic data for this paper which can be obtained free of charge via www.ccdc.cam.ac.uk

Electrode materials for Li + -ion batteries require optimization along several disparate axes related to cost, performance, and sustainability. One of the important performance axes is the ability to retain structural integrity though cycles of charge/discharge. Metal-metal bonding is a distinct feature of some refractory metal oxides that has been largely underutilized in electrochemical energy storage, but that could potentially impact structural integrity. Here LiScMo 3 O 8 , a compound containing triangular clusters of metal-metal bonded Mo atoms, is studied as a potential anode material in Li + -ion batteries. Electrons inserted though lithiation are localized across rigid Mo 3 triangles (rather than on individual metal ions), resulting in minimal structural change as suggested by operando diffraction. The unusual chemical bonding allows this compound to be cycled with Mo atoms below a formally +4 valence state, resulting in an acceptable voltage regime that is appropriate for an anode material.Several characterization methods including potentiometric entropy measurements indicate two-phase regions, which are attributed through extensive first-principles modeling to Li + ordering. This study of LiScMo 3 O 8 provides valuable insights for design principles for structural motifs that stably and reversibly permit Li + (de)insertion.