Sulfur hosts with rationally designed chemistry to confine and convert lithium polysulfides are of prime importance for high-performance lithium-sulfur batteries. A molten salt electrochemical modulation of iron-carbon-nitrogen is herein demonstrated as formation of hollow nitrogen-doped carbon with grafted Fe 3 C nanoparticles (Fe 3 C@C@Fe 3 C), which is rationalized as an excellent sulfur host for lithiumsulfur batteries. Fe 3 C over nitrogen-doped carbon contributes to enhanced adsorption and catalytic conversion of lithium polysulfides. The sulfur-loaded Fe 3 C@C@Fe 3 C electrodes hence show a high capacity, good cyclic stability, and enhanced rate performance. This work highlights the unique chemistry of metal carbides on facilitating adsorption-conversion process of lithium polysulfides, and also extends the scope of molten salt electrolysis to elaboration of energy materials. Electrochemicalenergystorageisakey-enablingprotocoltoachieve a carbon-neutral world. Lithium-sulfur (Li-S) batteries hold great promise to upgrade lithium-ion batteries (LIBs) because of high energy density, low cost and environmental benignity. [1,2] Setbacks in large-scale application of Li-S batteries include intrinsically low conductivity of sulfur and lithium sulfide (Li 2 S), shuttling effects caused by dissolution of lithium polysulfides (LiPSs), and tardy conversion kinetics of LiPSs. [3][4][5][6] The aforenamed challenges can effectively be ameliorated by constructing sulfur hosts with hollow structures and specific compositions. [7,8] Hollow structure could physically lock LiPSs within confined spaces and hence restrain shuttling between electrodes. [9] Sulfur/nanostructured carbon composites could greatly improve conductivity and cycling ability. [8] Other sulfur hosts were introduced to improve the adsorption of LiPSs, including metals, [10] metal carbides, [10,11] oxides, [12] nitrides, [13,14] sulfides and metal-free mediators. [15] Metal carbides are intriguing due to strong adsorption of LiPSs over the high-polarity surface and catalytic conversion of LiPSs. The synergy between adsorption and catalytic conversion of metal carbides thus suppresses the inconvenient
Rechargeable aluminum‐ion batteries (AIBs) are promising for large‐scale energy storage due to the abundant reserves, low cost, and high capacity of the Al anode. However, the development of AIBs is currently hindered by the usage of AlCl3/1‐ethyl‐3‐methylimidazolium chloride electrolyte, which is expensive, highly corrosive, and extremely air‐sensitive. Herein, a new hydrated eutectic electrolyte (HEE) composed of hydrated aluminum perchlorate and succinonitrile for low‐cost, noncorrosive, and air‐stable AIBs is reported. Crystal water in the hydrated aluminum perchlorate plays a vital role in forming the HEE, in which one H2O and five succinonitrile molecules coordinate with one Al3+ ion. The optimized ratio of Al(ClO4)3·9H2O to succinonitrile is 1:12. When combining with the self‐doped polyaniline cathode, the associated AIB delivers a high discharge capacity of 185 mAh g−1 over 300 cycles; and the charge/discharge mechanism in the HEE is studied experimentally and theoretically. The HEE is nonflammable, air‐stable, and noncorrosive, thus enabling good air tolerance and facile fabrication of AIBs.
to epoxides is realized in ionic liquids by Sun and co-workers. [14,15] Fixation and utilization of CO 2 is also elaborately explored via designing the metal-CO 2 batteries by Ding and co-workers. [16] Fixation of CO 2 into functional carbonaceous materials by capture and electrochemical reduction of CO 2 in molten salts has many advantages. [6,17-19] CO 2 shows a high solubility in molten salts, guaranteeing a highflux uptake rate for a direct and deep removal of CO 2 from atmosphere and industrial flue gas. [6] The wide electrochemical window of molten salt electrolytes promises a high current efficiency of the electrochemical reduction of CO 2 in molten salts. [6,20-24] The high-temperature environment of inorganic molten salts brings about enhanced mass transfer and facilitated reaction kinetics, enabling an appealing conversion rate of CO 2 free of any precious catalysts. [6,14,15] Molten salts possess a high heat capacity, which means the heat required by the molten salt fixation of CO 2 can be supplied by solar-thermal systems. [17] The decomposition voltage of CO 2-capture-generated CO 3 2− in molten salts is lower than 2.0 V (1.3 V for Li 2 CO 3 , 1.6 V for Na 2 CO 3 , and 1.8 V for K 2 CO 3 at 500 °C), therefore the electricity for the conversion of CO 2 in molten salts can be supplied by solar photovoltaic systems. [17] Finally, oxygen in CO 2 can simultaneously be released as anodic O 2 , which is of prime implications on future colony on Mars. [6] One of the major challenges for the electrochemical fixation of CO 2 in molten salts is the insufficient functionality of the deposited carbon on cathode. [6] Amorphous and disordered carbon is commonly obtained by electrochemical conversion of CO 2 in molten salts, which contradicts with the demands of application devices for carbonaceous materials with high graphitization degree. [6] For example, aluminum-ion (Al-ion) battery (AIB) possesses the merits of low cost, high volumetric capacity, and high safety. Many cathode materials are reported for Al-ion batteries, including carbon-based materials, metal sulfides, and V 2 O 5. [25-27] For carbon-based materials, the carbon with higher graphitization degree commonly possesses better performance for reversible Al storage. [26,27] In this regard, pioneering works were conducted by Lu and coworkers. [7,28-33] In their strategy, a highly porous 3D graphene foam is used as the cathode for rechargeable Al-ion batteries,
Amphoteric membranes were obtained from imidazoliumfunctionalized polyphenylene oxide (ImPPO) and sulfonated poly(ether ether ketone) (SPEEK) for an all-vanadium redox flow battery (VRFB) application. The SPEEK/ImPPO amphoteric membranes showed a considerably lower swelling degree and water uptake compared to those of pure SPEEK membranes, owing to the formation of ionic bonds between the cationic imidazolium groups of ImPPO and the anionic sulfonate groups of SPEEK. The cationic imidazolium groups of the ImPPO exhibited a Donnan exclusion effect on vanadium ions; therefore, the amphoteric membranes showed a much lower vanadium permeability than the pure SPEEK membrane. In addition, the vanadium permeability of the amphoteric membranes deceased with an increase in the ImPPO content. SPEEK-ImPPO20 with 20 wt% ImPPO showed a vanadium permeability of 0.43 × 10 À 9 cm 2 s À 1 at room temperature, which is 17 times lower than that of Nafion 212 (8 × 10 À 9 cm 2 s À 1 ). The VRFB assembled with SPEEK-ImPPO20 showed a coulombic efficiency of 97.2 % and a voltage efficiency of 85.8 % at a current density of 60 mA cm À 2 , whereas the values for Nafion 212 were 92.4 % and 86.7 % under the same conditions. In addition, the VRFB assembled with SPEEK-ImPPO20 exhibited much better capacity retention than that assembled with Nafion 212. These results indicate that the SPEEK-ImPPO amphoteric membrane is a promising material for VRFB applications.[a] Dr.
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