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The significant reduction in capacity and cyclability of lithium-ion batteries (LIBs) at low temperature is still limiting its application in cold climate. Limited literature has addressed the low temperature performance of LIB anodes, mostly restrict to low current performance showing low durability (<100 cycles). This is the first report of excellent durability in Li 4 Ti 5 O 12 -based composite cycling at a high current (10C) over 1000 cycles under sub-zero temperatures. We embed Li 4 Ti 5 O 12 nanoparticles in hierarchical macropore-mesoporous shell carbon network (HCMS carbon) to form Li 4 Ti 5 O 12 /HCMS carbon nanocomposite. The HCMS carbon is an ideal support for Li 4 Ti 5 O 12 to achieve excellent high rate sub-freezing LIB performance by providing short, intertwining Li-ion diffusion pathways between embedded Li 4 Ti 5 O 12 particles and Li-ion reservoirs, and ample routes for continuous, multi-directional electron flow to Li 4 Ti 5 O 12 particles. At −20 °C, the Li 4 Ti 5 O 12 /HCMS carbon composite delivers the highest literature-reported specific energy of 80 Wh/kg at a high specific power of 3000 W/kg. This work demonstrates our Li 4 Ti 5 O 12 /HCMS carbon composite can be a viable LIB anode material with fast and efficient Li-ion and electron transport active in sub-zero temperature operation. Image 1 [ABSTRACT FROM AUTHOR]

Abstract A three-electrolyte cell configuration, in which an additional compartment filled with salt solution is created between the cation-exchange membrane and the anion-exchange membrane to separate the respective opposite charged ionic species, can be used to realize novel electrochemical systems using promising redox couples. Using lead-acid metal hydride hybrid redox couple as a typical three-electrolyte prototype, we monitored the potential change of individual components during operation to obtain better understanding on the factors affecting the electrochemical performance (including types of salt solution, electrolyte concentration, inter-electrode gap). Key issues (i.e., salting-out) and proposed solutions are discussed. This work offers new solutions to develop promising energy storage techniques. Highlights • Effect of salt solution, concentration and inter-electrode gap of the three-electrolyte battery system was studied. • Salt solution with higher ionic conductivity in the buffer chamber, lowers the change voltage across the membranes. • The inter-electrode gap is optimised to reduce the internal resistance of the system. [ABSTRACT FROM AUTHOR]

Abstract: A series of experiments have been performed to investigate the effects of three electrolytes of different compositions (EO, EA and EM) on the electrochemical characteristics of MmNi3.55Co0.72Al0.3Mn0.43 hydrogen storage alloy electrode. Electrolytes EA and EM were obtained by adding appropriate amounts of Al2(SO4)3 and MnSO4 to the original electrolyte EO (6M KOH+1wt% LiOH), respectively. Electrode activation, maximum capacity, cycle life, self-discharge and high-rate discharge characteristics have been studied. It was found that a maximum capacity of about 260mAh/g has been obtained for the alloy electrodes in all these electrolytes after 5–7 cycles of charging/discharging. The alloy electrodes have a good durability in electrolytes EA and EM, especially after 175 cycles. Using the capacity retention as an indication of self-discharge resistance, almost identical degree of capacity retention (82% after 4 days and 45% after 16 days) has been observed at 298K, regardless of the electrolytes used. When tested at higher temperature, however, a higher capacity retention (46% after 3 days) at 333K has been observed for electrodes in electrolyte EA, and about 32% for electrodes in both electrolytes EO and EM. As to high-rate discharge behavior of the results of high-rate discharge tests indicated that about 50% of discharge efficiencies were obtained in the three electrolytes at 333K by continuous-model high-rate discharge method, at a discharge rate of 7C, and 22% in 298K. The alloy electrode in electrolyte EM has the best durability, in which about 50% of discharge efficiency at DC=9C was obtained by step-model high-rate discharge method at 333K, which was even higher than that at 298K. [Copyright &y& Elsevier]

Abstract: A comparison is made of the electrochemical and structural properties of LaNi4.25Al0.75 alloys in thin film and powder forms. X-ray diffraction (XRD) revealed that both the LaNi4.25Al0.75 thin film and powder materials are crystalline. Atomic force microscopy (AFM) and focused ion beam microscopy (FIB) proved that the film appeared to have a hill-like surface morphology, but was rather dense with a thickness of about 4.2 μm. Simulated battery tests indicate that both exhibit similar electrochemical behavior, possibly due to their crystal structure, as it requires a primary activation to reach its fully active state. However it took a longer activation period for the film to be activated; an apparent initial decrease of charging voltage with cycle number was observed, as were abnormal discharge processes during activation. After 30 charge/discharge cycles, small needle-shaped aluminium oxide particles were formed on both the powder and film surfaces. [Copyright &y& Elsevier]

Three-electrolyte configuration with two oppositely charged ion-exchange membranes can be used to yield various promising pH differential power sources. pH change, ion transport and potential profiles across the membranes and electrode/electrolyte interfaces of a three-electrolyte pH differential lead dioxide-metal hydride system are therefore systematically investigated for the first time. We find that i) pH changes of the acid and alkaline chambers are dependent on the combined effect of the electrode reaction and the ion transport. In addition, the pH change of the middle chamber is also affected by the crossover of protons from acid chamber if the anion-exchange membrane has a low permselectivity; ii) the electrical potential gradient mainly controls the ion transport with current flows; iii) the high overall cell voltage is attributed to the large pH acid-alkaline , while the potential across the membranes and electrode/electrolyte interfaces is affected by both pH and the concentration gradient. Key issues and proposed solutions are discussed to improve the electrochemical performance of this three-electrolyte pH differential electrochemical system. This work offers new opportunities to develop promising energy storage technologies. Ionic interfaces of a three-electrolyte pH differential system are studied, and feasible solutions are put forward to further improve the electrochemical performance of such a system. Image 1 • Ionic interfaces of a three-electrolyte pH differential system were studied. • Adding salts into electrolyte solutions was put forward to improve the cell performance. • This work offers new opportunities to develop promising energy technologies. [ABSTRACT FROM AUTHOR]

Abstract: Performance characteristics of a three electrolyte rechargeable acid–alkaline hybrid battery using a PbO2 positive plate and a nickel metal hydride (NiMH x ) negative electrode in separate electrolyte of H2SO4 and KOH were studied. This hybrid battery has three electrolytes in a single cell. A neutral K2SO4 salt solution was placed between the acid and alkaline compartments of the cell, in which a cation exchange membrane and an anion exchange membrane, were employed to separate these three electrolytes. The open circuit voltage of this hybrid cell was found to be 2.64V in an electrolyte configuration of 1M H2SO4|0.2MK2SO4|2M KOH electrolyte configuration, compared to 1.92V in the conventional lead-acid cell in 1M H2SO4 and 1.40V in a NiMH x cell in 2M KOH. This hybrid acid–alkaline PbO2/NiMH x battery was shown to operate with a voltage 20% higher than the conventional lead acid battery and 110% higher than nickel–metal hydride battery at 1/3C discharging rate. The concentrations of the three electrolytes, the dimension of the electrolyte chamber, and other cell/operation parameters with impacts on the hybrid cell performance were investigated. [Copyright &y& Elsevier]

We report one step synthesis of anion exchange polymer threaded in a metal-organic framework (MOF) via in situ polymerization of an ionic liquid (IL) monomer. The ionic liquid 3-methyl-1-vinylimidazolium iodide (3MVIm-I) is water miscible and can be easily impregnated into hydrophilic UiO-66 before triggering in situ polymerization to produce the composite. This simple synthesis does not involve an amination step, which was previously required to incorporate anion-exchange function of a polymer threaded into ZIF-8. This method also avoids difficult impregnation of hydrophobic precursors into hydrophilic MOF for in situ ionic liquid formation and their removal. The synthesized P3MVim-I∼UiO-66 composite is tested for anion exchange and cation rejection in aqueous solvent. P3MVim-I∼UiO-66 demonstrates outstanding ion selectivity over pristine UiO-66 and commercial anion exchange resin (Amberlyst A26). Aside the high OH − exchange capacity (6.05 meq g −1 ), more than 95% of inorganic anions (AuCl 4 − ) and 90% of anionic organic dye (Acid Blue 9) are exchanged by P3MVim-I∼UiO-66 within 30 min. In addition, there is complete rejection of standalone cationic dye (Rhodamine B) by P3MVim-I∼UiO-66 while the pristine UiO-66 exhibits no rejection. Crystallinity of the UiO-66 host is retained after impregnation and ion exchange. [ABSTRACT FROM AUTHOR]