Discovering new chemistry and materials to enable rechargeable batteries with higher capacity and energy density is of paramount importance. While Li metal is the ultimate choice of a battery anode, its low efficiency is still yet to be overcome. Many strategies have been developed to improve the reversibility and cycle life of Li metal electrodes. However, almost all of the results are limited to shallow cycling conditions (e.g., 1 mAh cm) and thus inefficient utilization (<1%). Here we achieve Li metal electrodes that can be deeply cycled at high capacities of 10 and 20 mAh cm with average Coulombic efficiency >98% in a commercial LiPF/carbonate electrolyte. The high performance is enabled by slow release of LiNO into the electrolyte and its subsequent decomposition to form a LiN and lithium oxynitrides (LiN O)-containing protective layer which renders reversible, dendrite-free, and highly dense Li metal deposition. Using the developed Li metal electrodes, we construct a Li-MoS full cell with the anode and cathode materials in a close-to-stoichiometric amount ratio. In terms of both capacity and energy, normalized to either the electrode area or the total mass of the electrode materials, our cell significantly outperforms other laboratory-scale battery cells as well as the state-of-the-art Li ion batteries on the market.

The presence of electrocatalysis in lithium-sulfur batteries has been proposed but not yet sufficiently verified. In this study,m olybdenum phosphide (MoP) nanoparticles are shown to play ad efinitive electrocatalytic role for the sulfur cathode working under lean electrolyte conditions featuring alow electrolyte/active material ratio:the overpotentials for the charging and discharging reactions are greatly decreased. As aresult, sulfur electrodes containing MoP nanoparticles show faster kinetics and more reversible conversion of sulfur species, leading to improvements in charging/discharging voltage profiles,c apacity,r ate performance,a nd cycling stability. Taking advantage of the electrocatalytic properties of MoP, high-performance sulfur electrodes were successfully realized that are steadily cyclable at ah igh areal capacity of 5.0 mAh cm À2 with ac hallenging electrolyte/sulfur (E/S) ratio of 4 mL E mg À1 S .Lithium sulfur batteries (LSBs) have as uperior theoretical specific energy of 2600 Wh kg À1 ,b ut an unsatisfactory cycle life. [1] Thecathode material of LSBs,namely sulfur,islimited in cycling stability,d espite its high theoretical specific capacity of 1675 mAh g À1 . [2] Thec apacity decay is tightly associated with the dissolution and diffusion of lithium polysulfide (LPS) intermediates in the electrolyte,w hich on the one hand facilitates the kinetics of electrochemical conversion [3] but on the other hand causes loss of active material and side reactions. [4] Using polar material surfaces, for example,f unctionalized carbons, [5] metal oxides, [6] sulfides, [7] phosphides, [8] nitrides, [9] and metal-organic frameworks, [10] to confine LPS via chemical interactions has been found to be one of the most effective ways for improving the cycling stability of sulfur electrodes.B esides immobilizing LPS on the cathode,i ti sa lso crucial to ensure their rapid electrochemical conversion and thus capacity contribution. Fori nstance,w eh ave recently reported on molybdenum phosphide (MoP) nanoparticles serving an electrocatalystlike function for stabilizing the sulfur cathode. [8b] While the extension of cycle life was significant, electrocatalysis was only preliminarily implied by the larger cyclic voltammetry current on the MoP-modified electrode in aL PS electrolyte. Herein, we report anew observation of akey evidence for the electrocatalytic role played by MoP nanoparticles in LSBs:reduction of overpotential for the charging/discharging reactions of the sulfur cathode,w hich is only obvious under lean electrolyte conditions (that is,w ith al ow electrolyte/ active material ratio). Fora no rdinary sulfur electrode,t he average charging/discharging voltage hysteresis at ac urrent density of 0.8 mA cm À2 increases greatly to 0.43 Vw hen the electrolyte/sulfur (E/S; mL E mg À1 S )ratio is lowered to 6. With MoP nanoparticles incorporated in the electrode structure, the voltage hysteresis is reduced to 0.18 V. MoP effectively catalyzes the electrochemical conversion reactions of sulfur, which helps the...

Developing Na metal anodes that can be deeply cycled with high efficiency for a long time is a prerequisite for rechargeable Na metal batteries to be practically useful despite their notable advantages in theoretical energy density and potential low cost. Their high chemical reactivity with the electrolyte and tendency for dendrite formation are two major issues limiting the reversibility of Na metal electrodes. In this work, we introduce for the first time potassium bis(trifluoromethylsulfonyl)imide (KTFSI) as a bifunctional electrolyte additive to stabilize Na metal electrodes, in which the TFSI anions decompose into lithium nitride and oxynitrides to render a desirable solid electrolyte interphase layer while the K cations preferentially adsorb onto Na protrusions and provide electrostatic shielding to suppress dendritic deposition. Through the cooperation of the cations and anions, we have realized Na metal electrodes that can be deeply cycled at a capacity of 10 mAh cm for hundreds of hours.

The research and applications of fiber materials are directly related to the daily life of social populace and the development of relevant revolutionary manufacturing industry. However, the conventional fibers and fiber products can no longer meet the requirements of automation and intellectualization in modern society, as well as people's consumption needs in pursuit of smart, avant-grade, fashion and distinctiveness. The advanced fiber-shaped electronics with most desired designability and integration features have been explored and developed intensively during the last few years. The advanced fiber-based products such as wearable electronics and smart clothing can be employed as the second skin to enhance information exchange between humans and the external environment. In this review, the significant progress on flexible fiber-shaped multifunctional devices, including fiber-based energy harvesting devices, energy storage devices, chromatic devices, and actuators are discussed. Particularly, the fabrication procedures and application characteristics of multifunctional fiber devices such as fiber-shaped solar cells, lithium-ion batteries, actuators and electrochromic fibers are introduced in detail. Finally, we provide our perspectives on the challenges and future development of functional fiber-shaped devices.

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Solid‐state electrolytes are widely anticipated to enable the revival of high energy density and safe metallic Li batteries, however, their lower ionic conductivity at room temperature, stiff interfacial contact, and severe polarization during cycling continue to pose challenges in practical applications. Herein, a dual‐composite concept is applied to the design of a bilayer heterostructure solid electrolyte composed of Li+ conductive garnet nanowires (Li6.75La3Zr1.75Nb0.25O12)/polyvinylidene fluoride‐co‐hexafluoropropylene (PVDF‐HFP) as a tough matrix and modified metal organic framework particles/polyethylene oxide/PVDF‐HFP as an interfacial gel. The integral ionic conductivity of the solid electrolyte reaches 2.0 × 10−4 S cm−1 at room temperature. In addition, a chemically/electrochemically stable interface is rapidly formed, and Li dendrites are well restrained by a robust inorganic shield and matrix. As a result, steady Li plating/stripping for more than 1700 h at 0.25 mA cm−2 is achieved. Solid‐state batteries using this bilayer heterostructure solid electrolyte deliver promising battery performance (efficient capacity output and cycling stability) at ambient temperature (25 °C). Moreover, the pouch cells exhibit considerable flexibility in service and unexpected endurance under a series of extreme abuse tests including hitting with a nail, burning, immersion under water, and freezing in liquid nitrogen.

Na metal anode receives increasing attention as a low-cost alternative to Li metal anode for the application in high energy batteries. Despite extensive research efforts to improve the reversibility and cycle life of Na metal electrodes, their rate performance, i.e. electrochemical plating and stripping of Na metal at high current, is underexplored. Herein, we report that Na metal electrodes, unlike the more widely studied Li metal electrodes which survive high current density up to 20 mA/cm2, cannot be fast charged or discharged in common ether electrolyte. The fast charging, namely metal plating, is comprised by severe side reactions that decompose electrolyte into electrochemically inactive Na­(I) solid species. The fast discharging, namely metal stripping, is disabled by local Na removal that deteriorates the electrical contact with the current collector. While the fast charging failure is permanent, the capacity loss from fast discharging can be recovered through a restructuring process at a low discharging current which rebuilds the electrical connection. We further reveal that the unsatisfactory rate performance of Na metal electrodes is associated with intrinsic physicochemical properties of Na. This study delineates the mechanistic origins of Na’s limitation in fast plating and stripping, and demonstrates the necessity of improving the charging and discharging rate performance of Na metal electrodes.

Solid‐state electrolytes have drawn enormous attention to reviving lithium batteries but have also been barricaded in lower ionic conductivity at room temperature, awkward interfacial contact, and severe polarization. Herein, a sort of hierarchical composite solid electrolyte combined with a “polymer‐in‐separator” matrix and “garnet‐at‐interface” layer is prepared via a facile process. The commercial polyvinylidene fluoride‐based separator is applied as a host for the polymer‐based ionic conductor, which concurrently inhibits over‐polarization of polymer matrix and elevates high‐voltage compatibility versus cathode. Attached on the side, the compact garnet (Li6.4La3Zr1.4Ta0.6O12) layer is glued to physically inhibit the overgrowth of lithium dendrite and regulate the interfacial electrochemistry. At 25 °C, the electrolyte exhibits a high ionic conductivity of 2.73 × 10−4 S cm−1 and a decent electrochemical window of 4.77 V. Benefiting from this elaborate electrolyte, the symmetrical Li||Li battery achieves steady lithium plating/stripping more than 4800 h at 0.5 mA cm−2 without dendrites and short‐circuit. The solid‐state batteries deliver preferable capacity output with outstanding cycling stability (95.2% capacity retained after 500 cycles, 79.0% after 1000 cycles at 1 C) at ambient temperature. This hierarchical structure design of electrolyte may reveal great potentials for future development in fields of solid‐state metal batteries.