Self-Formed Electronic/Ionic Conductive Fe3 S4  @ S @ 0.9Na3 SbS4 ⋠0.1NaI Composite for High-Performance Room-Temperature All-Solid-State Sodium-Sulfur Battery.

Fe3 S4  @ S @ 0.9Na3 SbS4 ⋅0.1NaI composite cathode is prepared through one-step wet-mechanochemical milling procedure. During milling process, ionic conduction pathway is self-formed in the composite due to the formation of 0.9Na3 SbS4 ⋅0.1NaI electrolyte without further annealing treatment. Meanwhile, the introduction of Fe3 S4 can increase the electronic conductivity of the composite cathode by one order of magnitude and nearly double enhance the ionic conductivities. Besides, the aggregation of sulfur is effectively suppressed in the obtained Fe3 S4  @ S @ 0.9Na3 SbS4 ⋅0.1NaI composite, which will enhance the contact between sulfur and 0.9Na3 SbS4 ⋅0.1NaI electrolyte, leading to a decreased interfacial resistance and improving the electrochemical kinetics of sulfur. Therefore, the resultant all-solid-state sodium-sulfur battery employing Fe3 S4  @ S @ 0.9Na3 SbS4 ⋅0.1NaI composite cathode shows discharge capacity of 808.7 mAh g-1 based on Fe3 S4 @S and a normalized discharge capacity of 1040.5 mAh g-1 for element S at 100 mA g-1 for 30 cycles at room temperature. Moreover, the battery also exhibits excellent cycling stability with a reversible capacity of 410 mAh g-1 at 500 mA g-1 for 50 cycles, and superior rate capability with capacities of 952.4, 796.7, 513.7, and 445.6 mAh g-1 at 50, 100, 200, and 500 mA g-1 , respectively. This facile strategy for sulfur-based composite cathode is attractive for achieving room-temperature sodium-sulfur batteries with superior electrochemical performance.

Construction of 3D Electronic/Ionic Conduction Networks for All-Solid-State Lithium Batteries.

High and balanced electronic and ionic transportation networks with nanoscale distribution in solid-state cathodes are crucial to realize high-performance all-solid-state lithium batteries. Using Cu2 SnS3 as a model active material, such a kind of solid-state Cu2 SnS3 @graphene-Li7 P3 S11 nanocomposite cathodes are synthesized, where 5-10 nm Cu2 SnS3 nanoparticles homogenously anchor on the graphene nanosheets, while the Li7 P3 S11 electrolytes uniformly coat on the surface of Cu2 SnS3 @graphene composite forming nanoscaled electron/ion transportation networks. The large amount of nanoscaled triple-phase boundary in cathode ensures high power density due to high ionic/electronic conductions and long cycle life due to uniform and reduced volume change of nano-Cu2 SnS3. The Cu2 SnS3 @graphene-Li7 P3 S11 cathode layer with 2.0 mg cm-2 loading in all-solid-state lithium batteries demonstrates a high reversible discharge specific capacity of 813.2 mAh g-1 at 100 mA g-1 and retains 732.0 mAh g-1 after 60 cycles, corresponding to a high energy density of 410.4 Wh kg-1 based on the total mass of Cu2 SnS3 @graphene-Li7 P3 S11 composite based cathode. Moreover, it exhibits excellent rate capability and high-rate cycling stability, showing reversible capacity of 363.5 mAh g-1 at 500 mA g-1 after 200 cycles. The study provides a new insight into constructing both electronic and ionic conduction networks for all-solid-state lithium batteries.

Manganese and Cobalt-Free Ultrahigh-Ni-Rich Single-Crystal Cathode for High-Performance Lithium Batteries.

Current commercial nickel (Ni)-rich Mn, Co, and Al-containing cathodes are employed in high-energy-density lithium (Li) batteries all around the globe. The presence of Mn/Co in them brings out several problems, such as high toxicity, high cost, severe transition-metal dissolution, and quick surface degradation. Herein, a Mn/Co-free ultrahigh-Ni-rich single-crystal LiNi0.94Fe0.05Cu0.01O2 (SCNFCu) cathode with acceptable electrochemical performance is benchmarked against a Mn/Co-containing cathode. Despite having a slightly lower discharge capacity, the SCNFCu cathode retaining 77% of its capacity across 600 deep cycles in full-cell outperforms comparable to a high-Ni single-crystal LiNi0.9Mn0.05Co0.05O2 (SCNMC; 66%) cathode. It is shown that the stabilizing ions Fe/Cu in the SCNFCu cathode reduce structural disintegration, undesirable side reactions with the electrolyte, transition-metal dissolution, and active Li loss. This discovery provides a new extent for cathode material development for next-generation high-energy, Mn/Co-free Li batteries due to the compositional tuning flexibility and quick scalability of SCNFCu, which is comparable to the SCNMC cathode.

Improvement of Laccase Activity Via Covalent Immobilization over Mesoporous Silica Coated Magnetic Multiwalled Carbon Nanotubes for the Discoloration of Synthetic Dyes.

Due to its environmental friendliness and biodegradable ability, the enzymatic decolorization of azo dyes is the best option. However, the free enzyme suffers from various limitations, including poor stability, no repeatable use, and a high expense, which is the key drawback for its practical use. In this analysis, the laccase enzyme was immobilized in mesoporous silica coated magnetic multiwalled carbon nanotubes (Fe3O4-MWCNTs@SiO2) by a glutaraldehyde cross-linker to create an easily separable and stable enzyme. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the as-synthesized Fe3O4-MWCNTs@SiO2. Laccase immobilized in Fe3O4-MWCNTs@SiO2 showed a good improvement in temperature, pH, and storage stability. Moreover, the operational stability of the biocatalyst was improved, retaining 87% of its original activity even after 10 cycles of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) oxidation. The biocatalysts were applied for the decolorization of selected azo dyes without a mediator, and up to 99% of Eriochrome Black T (EBT), 98% of Acid Red 88 (AR 88), and 66% of Reactive Black 5 (RB5) were decolorized. Based on these properties, the biocatalysts can be potentially utilized in various environmental and industrial applications.

In Situ Coating of Li7P3S11 Electrolyte on CuCo2S4/Graphene Nanocomposite as a High-Performance Cathode for All-Solid-State Lithium Batteries.

A cathode material, CuCo2S4/graphene@10%Li7P3S11, is reported for all-solid-state lithium batteries with high performance. The electrical conductivity of CuCo2S4 is improved by compounding with graphene. Meanwhile, Li7P3S11 electrolyte is coated on the surface of CuCo2S4/graphene nanosheets to build an intimate contact interface between the solid electrolyte and the electrode effectively, facilitating lithium-ion conduction. Benefitting from the balanced and efficient electronic and ionic conductions, all-solid-state lithium batteries using CuCo2S4/graphene@10%Li7P3S11 composite as cathode materials demonstrate superior cycling stability and rate capabilities, exhibiting an initial discharge specific capacity of 1102.25 mAh g-1 at 50 mA g-1 and reversible capacity of 556.41 mAh g-1 at a high current density of 500 mA g-1 after 100 cycles. These results demonstrate that the CuCo2S4/graphene@10%Li7P3S11 nanocomposite is a promising active material for all-solid-state lithium batteries with superior performances.

Sulfur-Embedded FeS2 as a High-Performance Cathode for Room Temperature All-Solid-State Lithium-Sulfur Batteries.

All-solid-state lithium-sulfur batteries employing sulfur electrodes and a solid electrolyte at room temperature are still a great challenge owing to the low conductivities of sulfur cathodes. In this work, we report room temperature all-solid-state lithium-sulfur batteries using thin sulfur layer-embedded FeS2 (FeS2@S) microsphere composites as active materials in the FeS2@S-Li10GeP2S12-Super P cathode electrode. Setting the cut-off voltage between 1.5 and 2.8 V, only lithiation-delithiation reactions between L2FeS2 and FeSy and direct reaction between Li2S and S will occur, which avoids large volume change of FeS2 caused by the conversion reaction, leading to the structure integrity of FeS2@S. The resultant batteries exhibit excellent rate and cyclic performances, delivering specific capacities of 1120.9, 937.2, 639.7, 517.2, 361.5, and 307.0 mA h g-1 for the FeS2@S composite cathode, corresponding to the normalized capacities of 1645.5, 1252.9, 782.5, 700.2, 478.4, and 363.6 mA h g-1 for sulfur at 30, 50, 100, 500, 1000, and 5000 mA g-1, respectively. Besides, they can retain the normalized capacity of 430.7 mA h g-1 for sulfur at 1000 mA g-1 after 200 cycles at room temperature.

Transitional Metal Catalytic Pyrite Cathode Enables Ultrastable Four-Electron-Based All-Solid-State Lithium Batteries.

All-solid-state batteries can enable reversible four lithium ion storage for pyrite (FeS2) at a cutoff voltage of 1.0-3.0 V. However, strain/stress concentration generating electrode pulverization and sluggish electrochemical reaction of lithium sulfide and sulfur will affect the long cycling stability of the battery. Through experiments and density functional theory (DFT) calculations, it is proved that nanostructure engineering and electronic conduction improvement with introduction of catalytic cobalt can effectively improve the electrochemical activity of FeS2. The optimized loose structured Co0.1Fe0.9S2 based all-solid-state lithium batteries show reversible capacities of 860.5, 797.7, 685.8, and 561.8 mAh g-1 after five cycles at 100, 200, 500, and 1000 mA g-1, respectively, and a stable capacity of 543.5 mAh g-1 can be maintained after cycling at a current density of 500 mA g-1 for 100 cycles. Ex situ TEM and Raman results reveal that, after the first cycle, the reversible reaction 2Li2S + Fe ↔ FeSy + (2 - y)S + 4Li+ + 4e- proceeds from the following cycles onward, while nanocrystalline mackinawite FeS, Fe(III)-containing mackinawite FeS, and Fe3S4 are generated after the first discharge-charge process. This work provides a facile method for improving the electrochemical performance for multi-electron reaction mechanism based all-solid-state lithium batteries.

Highly Crystalline Layered VS2 Nanosheets for All-Solid-State Lithium Batteries with Enhanced Electrochemical Performances.

All-solid-state lithium batteries employing inorganic solid electrolytes have been regarded as an ultimate solution to safety issues because of their features of no leakage as well as incombustibility and they are expected to achieve higher energy densities owing to their simplified structure. Two-dimensional transition-metal dichalcogenides exhibit a great potential in energy storage devices because of their unique physical and chemical characteristics. In this work, 50 nm thick highly crystalline layered VS2 (hc-VS2) nanosheets are prepared by a solvothermal method, and their electrochemical performances are evaluated in Li/75% Li2S-24% P2S5-1% P2O5/Li10GeP2S12/hc-VS2 all-solid-state lithium batteries. At 50 mA g-1, hc-VS2 nanosheets show a high reversible capacity of 532.2 mAh g-1 after 30 cycles. Moreover, stable discharge capacities are maintained at 436.8 and 270.4 mAh g-1 at 100 and 500 mA g-1 after 100 cycles, respectively. The superior rate capability and cycling stability are ascribed to the better electronic conductivity and well-developed layered structure. In addition, the electrochemical reaction kinetics and capacity contributions were analyzed via cyclic voltammetry measurements at different scan rates.

Core-Shell Fe1- xS@Na2.9PS3.95Se0.05 Nanorods for Room Temperature All-Solid-State Sodium Batteries with High Energy Density.

High ionic conductivity electrolyte and intimate interfacial contact are crucial factors to realize high-performance all-solid-state sodium batteries. Na2.9PS3.95Se0.05 electrolyte with reduced particle size of 500 nm is first synthesized by a simple liquid-phase method and exhibits a high ionic conductivity of 1.21 × 10-4 S cm-1, which is comparable with that synthesized with a solid-state reaction. Meanwhile, a general interfacial architecture, that is, Na2.9PS3.95Se0.05 electrolyte uniformly anchored on Fe1- xS nanorods, is designed and successfully prepared by an in situ liquid-phase coating approach, forming core-shell structured Fe1- xS@Na2.9PS3.95Se0.05 nanorods and thus realizing an intimate contact interface. The Fe1- xS@Na2.9PS3.95Se0.05/Na2.9PS3.95Se0.05/Na all-solid-state sodium battery demonstrates high specific capacity and excellent rate capability at room temperature, showing reversible discharge capacities of 899.2, 795.5, 655.1, 437.9, and 300.4 mAh g-1 at current densities of 20, 50, 100, 150, and 200 mA g-1, respectively. The obtained all-solid-state sodium batteries show very high energy and power densities up to 910.6 Wh kg-1 and 201.6 W kg-1 based on the mass of Fe1- xS at current densities of 20 and 200 mA g-1, respectively. Moreover, the reaction mechanism of Fe1- xS is confirmed by means of ex situ X-ray diffraction techniques, showing that partially reversible reaction occurs in the Fe1- xS electrode after the second cycle, which gives the obtained all-solid-state sodium battery an exceptional cycling stability, exhibiting a high capacity of 494.3 mAh g-1 after cycling at 100 mA g-1 for 100 cycles. This contribution provides a strategy for designing high-performance room temperature all-solid-state sodium battery.

Nanoscaled Na3PS4 Solid Electrolyte for All-Solid-State FeS2/Na Batteries with Ultrahigh Initial Coulombic Efficiency of 95% and Excellent Cyclic Performances.

Nanosized Na3PS4 solid electrolyte with an ionic conductivity of 8.44 × 10-5 S cm-1 at room temperature is synthesized by a liquid-phase reaction. The resultant all-solid-state FeS2/Na3PS4/Na batteries show an extraordinary high initial Coulombic efficiency of 95% and demonstrate high energy density of 611 Wh kg-1 at current density of 20 mA g-1 at room temperature. The outstanding performances of the battery can be ascribed to good interface compatibility and intimate solid-solid contact at FeS2 electrode/nanosized Na3PS4 solid electrolytes interface. Meanwhile, excellent cycling stability is achieved for the battery after cycling at 60 mA g-1 for 100 cycles, showing a high capacity of 287 mAh g-1 with the capacity retention of 80%.