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The long-term cycling of anode-free Li-metal cells (i.e., cells where the negative electrode is in situ formed by electrodeposition on an electronically conductive matrix of lithium sourced from the positive electrode) using a liquid electrolyte is affected by the formation of an inhomogeneous solid electrolyte interphase (SEI) on the current collector and irregular Li deposition. To circumvent these issues, we report an atomically defective carbon current collector where multivacancy defects induce homogeneous SEI formation on the current collector and uniform Li nucleation and growth to obtain a dense Li morphology. Via simulations and experimental measurements and analyses, we demonstrate the beneficial effect of electron deficiency on the Li hosting behavior of the carbon current collector. Furthermore, we report the results of testing anode-free coin cells comprising a multivacancy defective carbon current collector, a Li x Ni 0.8 Co 0.1 Mn 0.1 -based cathode and a nonaqueous Li-containing electrolyte solution. These cells retain 90% of their initial capacity for over 50 cycles under lean electrolyte conditions. The development of anode-free batteries requires fundamental investigations at the current collector/electrolyte interface. Here, the authors report an atomically defective carbon current collector to improve the electrochemical behaviour of an anode-free Li-based cell.

Uncontrolled growth of insulating lithium sulfide leads to passivation of sulfur cathodes, which limits high sulfur utilization in lithium-sulfur batteries. Sulfur utilization can be augmented in electrolytes based on solvents with high Gutmann Donor Number; however, violent lithium metal corrosion is a drawback. Here we report that particulate lithium sulfide growth can be achieved using a salt anion with a high donor number, such as bromide or triflate. The use of bromide leads to ~95 % sulfur utilization by suppressing electrode passivation. More importantly, the electrolytes with high-donor-number salt anions are notably compatible with lithium metal electrodes. The approach enables a high sulfur-loaded cell with areal capacity higher than 4 mA h cm −2 and high sulfur utilization ( > 90 %). This work offers a simple but practical strategy to modulate lithium sulfide growth, while conserving stability for high-performance lithium-sulfur batteries. The development of new electrolyte systems is needed to optimize performance in lithium-sulfur batteries. Here the authors employ anions with high donor numbers in electrolytes to prevent passivation of the cathode surface, thereby improving sulfur utilization and energy density in a lithium-sulfur cell.

A deep eutectic solvent (DES) is an ionic liquid‐analog electrolyte, newly emerging due to its low cost, easy preparation, and tunable properties. Herein, a zinc–bromine battery (ZBB) with a Zn‐halide‐based DES electrolyte prepared by mixing ZnBr2, ZnCl2, and a bromine‐capturing agent is reported. The water‐free DES electrolyte allows a closed‐cell configuration for the ZBB owing to the prevention of Br2 evaporation and H2 evolution. It is found that the Cl− anion changes the structure of the zinc‐halide complex anions and demonstrated that it improves the ion mobility and electrode reaction kinetics. The DES electrolyte with the optimized ZnCl2 composition shows much higher rate capability and a cycle life 90 times longer than that of a ZnCl2‐free DES electrolyte. A pouch‐type flexible ZBB battery based on the DES electrolyte exhibits swelling‐free operation for more than 120 cycles and stable operation under a folding test, suggesting its potential in consumer applications such as wearable electronics. Deep eutectic electrolytes are specifically designed for use in zinc–bromine batteries (ZBBs). By virtue of the water‐free property and superb Br2 adsorption ability of these electrolytes, problematic gas‐related issues are effectively suppressed, allowing the operation of ZBBs in consumer‐friendly configurations. The essential role of Cl− with regard to improving the performance capabilities of ZBBs has also been thoroughly studied.

Maximum atom efficiency as well as distinct chemoselectivity is expected for electrocatalysis on atomically dispersed (or single site) metal centres, but its realization remains challenging so far, because carbon, as the most widely used electrocatalyst support, cannot effectively stabilize them. Here we report that a sulfur-doped zeolite-templated carbon, simultaneously exhibiting large sulfur content (17 wt% S), as well as a unique carbon structure (that is, highly curved three-dimensional networks of graphene nanoribbons), can stabilize a relatively high loading of platinum (5 wt%) in the form of highly dispersed species including site isolated atoms. In the oxygen reduction reaction, this catalyst does not follow a conventional four-electron pathway producing H 2 O, but selectively produces H 2 O 2 even over extended times without significant degradation of the activity. Thus, this approach constitutes a potentially promising route for producing important fine chemical H 2 O 2 , and also offers opportunities for tuning the selectivity of other electrochemical reactions on various metal catalysts. Atomically dispersed metal catalysts display high atom efficiency for electrocatalytic processes. Here, the authors report that sulfur-doped zeolite-templated carbon stabilizes highly dispersed platinum species, predominantly as single-atom centres, and probe its oxygen reduction selectivity.

Salt anions with a high donor number (DN) enable high sulfur utilization in lithium‐sulfur (Li‐S) batteries by inducing three‐dimensional (3D) Li2S growth. However, their insufficient compatibility with Li metal electrodes limits their cycling stability. Herein, a new class of salt anion, thiocyanate (SCN−), is presented, which features a Janus character of electron donor and acceptor. Due to a strong Li+ coordination by SCN− and the direct interaction of SCN− with polysulfide anions, the LiSCN electrolyte has a remarkably high lithium polysulfide solubility. This electrolyte induces 3D Li2S formation and ameliorates cathode passivation, even more than Br−, a typical high DN anion. Moreover, SCN− forms a Li3N‐enriched stable SEI layer at the surface of the Li metal electrode, enhancing cycling stability. A Li‐S battery with the LiSCN electrolyte shows high current density operation (2.54 mA cm⁻2) with high discharge capacity (1133 mAh g⁻1) and prolonged cycle life (100 cycles). This work demonstrates that the cathode and anode performance in a Li‐S battery can be simply and concurrently enhanced by the single salt anion. This study investigates the potential of lithium thiocyanate (LiSCN) salt to improve both electrodes by enhancing sulfur utilization and Li metal stability. Based on the high donor number and acceptor number SCN− anion, the intensified 3D growth of lithium sulfide is induced on the sulfur electrode and the robust Li3N solid electrolyte interphase layer is constructed on the Li electrode.

Realizing practical lithium–sulfur batteries with high energy density requires lean electrolyte design. However, under low electrolyte/sulfur ( E/S ) ratios, highly concentrated lithium polysulfides in the electrolyte phase limit cycling and capacity. Here, we report that a small amount of Lewis acidic calcium cation in the electrolyte addresses the problems of lean electrolyte lithium–sulfur batteries. Because of its Lewis acidity, Ca 2+ readily converts lithium polysulfides into CaS and S 8 , preventing electrolyte jamming, polysulfide shuttle and Li corrosion. The in situ-formed CaS catalyzes the reduction reaction of lithium polysulfides. Ca 2+ rejuvenates via electrochemical oxidation of CaS during charging, enabling a sustainable interconversion between Ca 2+ and CaS during cycling. Li-S pouch cells with Ca 2+ additive delivered an energy density of 493 Wh kg −1 ( E/S of 2.4 μL mg −1 ) based on the total mass of the cell excluding external packaging, with 70% capacity retention at 220 cycle under 1 mA cm −2 discharge, and 346 Wh kg −1 (2.9 μL mg −1 ) with 77% capacity retention at 360 cycle under 1.0 C 2 mA cm −2 discharge. The judicious integration of lithium-sulfur and calcium-sulfur chemistries offers a handy but effective approach to overcome the long-lasting trade-off between energy density and cycling stability in the development of lithium–sulfur batteries. High-concentration lithium polysulfides in lean electrolyte lithium–sulfur batteries hinder stable cycling. Here, authors introduce a reversible calcium additive that regulates polysulfides chemistry and catalyzes sulfur redox reactions, improving energy density with stable cycling.

The pulverization of lithium metal electrodes during cycling recently has been suppressed through various techniques, but the issue of irreversible consumption of the electrolyte remains a critical challenge, hindering the progress of energy-dense lithium metal batteries. Here, we design a single-ion-conductor-based composite layer on the lithium metal electrode, which significantly reduces the liquid electrolyte loss via adjusting the solvation environment of moving Li + in the layer. A Li||Ni 0.5 Mn 0.3 Co 0.2 O 2 pouch cell with a thin lithium metal (N/P of 2.15), high loading cathode (21.5 mg cm −2 ), and carbonate electrolyte achieves 400 cycles at the electrolyte to capacity ratio of 2.15 g Ah −1 (2.44 g Ah −1 including mass of composite layer) or 100 cycles at 1.28 g Ah −1 (1.57 g Ah −1 including mass of composite layer) under a stack pressure of 280 kPa (0.2 C charge with a constant voltage charge at 4.3 V to 0.05 C and 1.0 C discharge within a voltage window of 4.3 V to 3.0 V). The rational design of the single-ion-conductor-based composite layer demonstrated in this work provides a way forward for constructing energy-dense rechargeable lithium metal batteries with minimal electrolyte content. The reactivity between lithium and a liquid electrolyte leads to degradation of a lithium metal battery, resulting in the depletion of the liquid electrolyte. Here, authors develop a composite layer that can mitigate the reactivity and consequently enable long-cycling lithium metal batteries.

In this study, we examined the influence of the dispersion solvent in three dipropylene-glycol/water (DPG/water) mixtures, with DPG contents of 0, 50, and 100 wt%, on ionomer morphology and distribution, using dynamic light scattering (DLS) and molecular-dynamics (MD) simulation techniques. The DLS results reveal that Nafion-ionomer aggregation increases with decreasing DPG content of the solvent. Increasing the proportion of water in the solvent also led to a gradual decrease in the radius of gyration (R g ) of the Nafion ionomer due to its strong backbone hydrophobicity. Correspondingly, MD simulations predict Nafion-ionomer solvation energies of −147 ± 9 kcal/mol in water, −216 ± 21 kcal/mol in the DPG/water mixture, and −444 ± 9 kcal/mol in DPG. These results suggest that higher water contents in mixed DPG/water solvents result in increased Nafion-ionomer aggregation and the subsequent deterioration of its uniform dispersion in the solvent. Moreover, radial distribution functions (RDFs) reveal that the (-CF 2 CF 2 -) backbones of the Nafion ionomer are primarily enclosed by DPG molecules, whereas the sulfonate groups (SO 3 − ) of its side chains mostly interact with water molecules.

The vanadium redox flow battery is considered one of the most promising candidates for use in large-scale energy storage systems. However, its commercialization has been hindered due to the high manufacturing cost of the vanadium electrolyte, which is currently prepared using a costly electrolysis method with limited productivity. In this work, we present a simpler method for chemical production of impurity-free V 3.5+ electrolyte by utilizing formic acid as a reducing agent and Pt/C as a catalyst. With the catalytic reduction of V 4+ electrolyte, a high quality V 3.5+ electrolyte was successfully produced and excellent cell performance was achieved. Based on the result, a prototype catalytic reactor employing Pt/C-decorated carbon felt was designed, and high-speed, continuous production of V 3.5+ electrolyte in this manner was demonstrated with the reactor. This invention offers a simple but practical strategy to reduce the production cost of V 3.5+ electrolyte while retaining quality that is adequate for high-performance operations. The vanadium redox flow battery is promising for commercial applications, but is hampered by high-cost electrolytes that are typically prepared via electrolysis. Here the authors demonstrate cost-effective chemical production of a high-quality vanadium electrolyte using platinum nanoparticles as a catalyst.

The inhomogeneous Li electrodeposition of lithium metal electrode has been a major impediment to the realization of rechargeable lithium metal batteries. Although single ion conducting ionomers can induce more homogeneous Li electrodeposition by preventing Li + depletion at Li surface, currently available materials do not allow room-temperature operation due to their low room temperature conductivities. In the paper, we report that a highly conductive ionomer/liquid electrolyte hybrid layer tightly laminated on Li metal electrode can realize stable Li electrodeposition at high current densities up to 10 mA cm −2 and permit room-temperature operation of corresponding Li metal batteries with low polarizations. The hybrid layer is fabricated by laminating few micron-thick Nafion layer on Li metal electrode followed by soaking 1 M LiPF 6 EC/DEC (1/1) electrolyte. The Li/Li symmetric cell with the hybrid layer stably operates at a high current density of 10 mA cm −2 for more than 2000 h, which corresponds to more than five-fold enhancement compared with bare Li metal electrode. Also, the prototype Li/LiCoO 2 battery with the hybrid layer offers cycling stability more than 350 cycles. These results demonstrate that the hybrid strategy successfully combines the advantages of bi-ionic liquid electrolyte (fast Li + transport) and single ionic ionomer (prevention of Li + depletion).