The electrochemical discharge mechanism is reported for all-solid lithium sulfur batteries. Upon milling with carbon fibers, the solid electrolyte used within the cathode composite becomes electrochemically active. Analysis with Raman spectroscopy and XPS revealed the importance of bridging S-S bond formation and breaking in lithium polysulfidophosphates during electrochemical lithiation of the active solid electrolyte. Remarkably, when sulfur is introduced as an active material in the cathode composite, lithium polysulfides are formed as an intermediate product before full lithiation into lithium sulfide. The synthesis of materials based on bridging S-S bonds is an important avenue to the design of new cathodes for all-solid batteries.

Lithium solid-state composite electrolytes (LiSCEs) provide the opportunity for long life spans, low self-discharge, high reliability, high energy density, and safety. Additionally, this class of electrolytes can be used in electrolytically formed solid-state batteries (EFBs), which may promote reductions in cell manufacturing costs due to their simplicity of design and permit the formation of batteries with diverse architectures. Herein, we provide a discussion of LiSCEs, highlight some of the recent progress in EFB development, and present a forward outlook.

Lithium-ion capacitors (LICs) and Hybrid LICs (H-LICs) were assembled as three-layered pouch cells in an asymmetric configuration employing Faradaic pre-lithiated hard carbon anodes and non-Faradaic ion adsorption-desorption activated carbon (AC) cathodes for LICs and lithium iron phosphate (LiFePO4-LFP)/AC composite cathodes for H-LICs. The room temperature rate performance was evaluated after the initial LIC and H-LIC cell formation as a function of the electrolyte additives. The capacity retention was measured after charging at high temperature conditions, while the design factor explored was electrolyte additive formulation, with a focus on their stability. The high temperature potential holds simulate electrochemical energy materials under extreme environments and act to accelerate the failure mechanisms associated with cell degradation to determine robust electrolyte/additive combinations.

Aqueous rechargeable batteries are attractive owing to their higher operational safety, high ionic conductivity, scalable and easy manufacturing. These aqueous batteries form an economic option for large-scale (grid) power storage. In the aqueous battery sector, Mn-based compounds are highly attractive with their non-toxic nature, low-cost, rich mineral chemistry and robust operational safety. Several Mn-based systems like LiMn2O4 spinel and LiNi1/3Mn1/3Co1/3O2 have seen successful commercialization. Pursuing Mn-based materials, we have shown layer structured Na2Mn3O7 as a versatile cathode material for non-aqueous systems like Li-, Na- and K-ion batteries. In the current work, we have exploited Na2Mn3O7 as a cathode material for aqueous Zn-ion battery for the first time. This Na-Mn-O ternary system was prepared using two-step emulsion-based synthesis. The phase-pure Na2Mn3O7 was formed in a triclinic structure with a space group of P-1. It exhibited versatile electrochemical insertion of different ions like Li-, Na- and K-ions involving phase transition. Na2Mn3O7 exhibited reversible Zn-ion intercalation delivering capacity of 245 mA h g-1 with a nominal voltage of 1.5 V. Upon discharge, it triggered phase transformation to an unknown phase. Layered Na2Mn3O7 oxide was found to act as an efficient cathode for Zn-ion batteries with good cycling stability.

Polymer-mineral composite solid electrolytes have been prepared by hot pressing using lithium ion-exchanged bentonite (LIEB) and mineral derived LATSP (Li1.2Al0.1Ti1.9Si0.1P2.9O12) NASICON materials as solid electrolyte fillers in the polyethylene oxide (PEO) polymer containing LiTFSI salt. The mineral based solid electrolyte fillers not only increase ionic conductivity but also improve thermal stability. The highest ionic conductivities in the PEO-LIEB and PEO-LATSP composites were found to be 9.4×10-5 and 3.1×10-4 S·cm-1 at 40°C, respectively. The flexible, thermal stable and mechanical sturdy polymer-mineral composite solid electrolyte films can be used in the all-solid-state batteries.

Nb-doped TiO2 thin-films were prepared on fluorine-doped tin oxide (FTO) coated glass directly with niobium ethoxide and TiCl4 in water under the acidic conditions with several concentrations of HCl at 70-90 °C for 45 minutes or 1 hour followed by rinsing with water and annealing at 100 °C for 1 hour. Thin films of 0-1% Nb-doped TiO2 with rutile phase on FTO were obtained, which were confirmed through X-ray diffraction analyses and measurements of energy dispersive X-ray spectroscopy (EDS). Scanning electron microscopy observations equipped with EDS revealed that higher growth temperature over 90 °C is required for doping of Nb. While higher concentration of HCl resulted in much amount of Nb-doping. Band gap of rutile TiO2 gradually reduced from 3.3 eV to 3.23 eV through Nb-doping from 0% to 1%, which were estimated from uv-vis absorption spectroscopic analyses. Hall effect measurements by taking van der Pauw method confirmed that 2.26 times increase of the carrier density and 1.78 times enhancement of the conductivity have been achieved in the case of 1% Nb-doping.