Solution-Printable PEDOT Solid-Contact for Nitrate-Selective Electrodes: Enhanced Selectivity from Anion Dopant Exchange.

Poly(3,4-ethylenedioxythiophene)-polyethylene glycol (PEDOT:PEG) is a conductive material adopted in bioelectronics due to its biocompatibility and stability. While PEDOT has established its utility in cationic solid-contact ion-selective electrodes (sc-ISEs), its anionic counterpart remains less explored. Herein, we report the first example of PEDOT:PEG as a solution-printable solid-contact for all-solid-state nitrate-selective electrodes and a simple ion exchange treatment which can significantly enhance nitrate selectivity. Electrochemical impedance spectroscopy revealed that the sc-ISEs with perchlorate (ClO4-)-doped PEDOT:PEG suffered a large overall resistance. Removal of the ClO4- dopant via ion exchange reduced the resistance, resulting in significant improvement in sc-ISE performance. The optimal sc-ISE exhibited near-Nernstian response (-55.8 mV/decade) across a wide dynamic range (0.1 M to 1.12 µM) and excellent Hofmeister selectivity, which was maintained after prolonged continuous usage. This simple drop-cast and ion-exchange protocol is amenable to the scalable preparation of flexible anion sc-ISEs.

Effect of Reducing Agent on Solution Synthesis of Li3V2(PO4)3 Cathode Material for Lithium Ion Batteries.

In this study, Li3V2(PO4)3 (LVP) powders are prepared by a solution synthesis method. The effects of two reducing agents on crystal structure and morphology and electrochemical properties are investigated. Preliminary studies on reducing agents such as oxalic acid and citric acid, are used to reduce the vanadium (V) precursor. The oxalic acid-assisted synthesis induces smaller particles (30 nm) compared with the citric acid-assisted synthesis (70 nm). The LVP powders obtained by the oxalic acid exhibit a higher specific capacity (124 mAh g-1 at 1C) and better cycling performance (122 mAh g-1 following 50 cycles at 1C rate) than those for the citric acid. This is due to their higher electronic conductivity caused by carbon coating and downsizing the particles. The charge-discharge plateaus obtained from cyclic voltammetry are in good agreement with galvanostatic cycling profiles.

Concepts and Emerging Trends for Structural Battery Electrolytes.

The structural battery is a multifunctional energy storage device that aims to address the weight and volume efficiency issues that conventional batteries face, especially in electric transportation. By combining the functions of mechanical load bearing and energy storage, structural batteries can reduce the reliance on, or even eventually replace the main power source in an electric vehicle or a drone. However, one of the key challenges to be addressed before achieving multifunctionality in structural batteries would be the design of a suitable multifunctional structural battery electrolyte. The structural battery electrolyte is the constituent that provides mechanical integrity under flexural loads or impact and hence determines the electrochemical and much of the mechanical performance of a structural battery device. This concept paper aims to cover the key considerations and challenges facing the design of structural battery electrolytes. In addition, the main approaches to surmount these challenges are highlighted, keeping design aspects like sustainability and recyclability in view.

Enhanced Li1+x Al x Ge2-x (PO4)3 Anode-Protecting Membranes for Hybrid Lithium-Air Batteries by Spark Plasma Sintering.

NASICON-type Li1+x Al x Ge2-x (PO4)3 (LAGP) is a promising electrolyte with high ionic conductivity (>10-4 S cm-1), excellent oxidation stability, and moderate sintering temperature. However, preparing dense LAGP pellets with high ionic conductivity is still challenging because of the hazards of dopant loss and partial decomposition on conventional sintering. Here, spark plasma sintering (SPS) of LAGP membranes is explored as a promising ultrarapid manufacturing technique, yielding dense electrolyte membranes. Optimizing the SPS temperature is important to achieve desirable density and hence ionic conductance. Our results show that LAGP samples spark plasma-sintered at 750 °C exhibit the highest total ionic conductivity of 3.9 × 10-4 S cm-1 with a compactness of 97% and nearly single-crystalline particles. Our solid-state NMR results, X-ray diffraction studies, and scanning electron microscopy micrographs confirm that the achievable ionic conductivity is controlled by the retention of the Al dopant within the LAGP phase, necking between particles, and the minimization of grain boundaries between crystallites within a particle. To benchmark the performance of our spark plasma-sintered solid electrolyte membranes over conventionally prepared LAGP, we demonstrate their favorable performance in hybrid Li-air batteries. The highest energy efficiency is achieved for the fastest ion-conducting membrane sintered at 750 °C.

Thermal Conductive 2D Boron Nitride for High-Performance All-Solid-State Lithium-Sulfur Batteries.

Polymer-based solid-state electrolytes are shown to be highly promising for realizing low-cost, high-capacity, and safe Li batteries. One major challenge for polymer solid-state batteries is the relatively high operating temperature (60-80 °C), which means operating such batteries will require significant ramp up time due to heating. On the other hand, as polymer electrolytes are poor thermal conductors, thermal variation across the polymer electrolyte can lead to nonuniformity in ionic conductivity. This can be highly detrimental to lithium deposition and may result in dendrite formation. Here, a polyethylene oxide-based electrolyte with improved thermal responses is developed by incorporating 2D boron nitride (BN) nanoflakes. The results show that the BN additive also enhances ionic and mechanical properties of the electrolyte. More uniform Li stripping/deposition and reversible cathode reactions are achieved, which in turn enable all-solid-state lithium-sulfur cells with superior performances.