Improving the Interfacial Stability between Lithium and Solid-State Electrolyte via Dipole-Structured Lithium Layer Deposited on Graphene Oxide.

Utilization of lithium (Li) metal anode in solid-state batteries (SSBs) with sulfide solid-state electrolyte (SSE) is hindered by the instable Li/SSE interface. A general solution to solve this problem is to place an expensive indium (In) foil between the SSE and Li, while it decreases the output voltage and thus the energy density of the battery. In this work, an alternative strategy is demonstrated to boost the cycling performances of SSB by wrapping a graphene oxide (GO) layer on the anode. According to density functional theory results, initial deposition of a thin Li layer on the defective GO sheets leads to the formation of a dipole structure, due to the electron-withdrawing ability of GO acting on Li. By incorporating GO sheets in a nanocomposite of copper-cuprous oxide-GO (Cu-Cu2O-GO, CCG), a composite Li anode enables a high coulombic efficiency above 99.5% over 120 cycles for an SSB using Li10GeP2S12 SSE and LiCoO2 cathode, and the sulfide SSE is not chemically decomposed after cycling. The highest occupied molecule orbital/lowest unoccupied molecular orbital energy gap of this Li/GO dipole structure likely stretches over those of Li and sulfide SSE, enabling stabilized Li/SSE interface that can replace the expensive In layer as Li protective structure in SSBs.

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.

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.

Passivation of the Cathode-Electrolyte Interface for 5 V-Class All-Solid-State Batteries.

An all-solid-state battery is a potentially superior alternative to a state-of-the-art lithium-ion battery owing to its merits in abuse tolerance, packaging, energy density, and operable temperature ranges. In this work, a 5 V-class spinel LiNi0.5Mn1.5O4 (LNMO) cathode is targeted to combine with a high-ionic-conductivity Li6PS5Cl (LPSCl) solid electrolyte for developing high-performance all-solid-state batteries. Aiming to passivate and stabilize the LNMO-LPSCl interface and suppress the unfavorable side reactions such as the continuous chemical/electrochemical decomposition of the solid electrolyte, oxide materials including LiNbO3, Li3PO4, and Li4Ti5O12 are rationally applied to decorate the surface of pristine LNMO particles with various amounts through a wet-chemistry approach. Electrochemical characterization demonstrates that the composite cathode consisting of 8 wt % LiNbO3-coated LNMO and LPSCl in a weight ratio of 70:30 delivers the best electrochemical performance with an initial discharge capacity of 115 mA h g-1 and a reversible discharge capacity of 80 mA h g-1 at the 20th cycle, suggesting that interfacial passivation is an effective strategy to ensure the operation of 5 V-class all-solid-state batteries.

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.

Selenium-Infused Ordered Mesoporous Carbon for Room-Temperature All-Solid-State Lithium-Selenium Batteries with Ultrastable Cyclability.

Selenium with a similar reaction mechanism with sulfur and a much higher electronic conductivity is considered to be a promising cathode for all-solid-state rechargeable batteries. Herein, selenium-infused ordered mesoporous carbon composites (Se/CMK-3) are successfully prepared by a melt-diffusion method from a ball-milled mixture of Se and CMK-3 (Se-CMK-3). Furthermore, their electrochemical performances are evaluated in all-solid-state lithium-selenium batteries at room temperature. Typically, Li/75%Li2S-24%P2S5-1%P2O5/Li10GeP2S12/Se/CMK-3 all-solid-state lithium-selenium batteries exhibit high reversible capacity of 488.7 mAh g-1 at 0.05 C after 100 cycles. Even being cycled at 0.5C, it still maintains a discharge capacity of 268.7 mAh g-1 after 200 cycles. The excellent electrochemical performances could be attributed to the enhanced electronic/ionic conductivities and structural integrity with the addition of the CMK-3 matrix.

Co3S4@Li7P3S11 Hexagonal Platelets as Cathodes with Superior Interfacial Contact for All-Solid-State Lithium Batteries.

Poor solid-solid contact between an electrode and solid electrolyte is a great challenge for all-solid-state lithium batteries (ASSLBs) which results in limited ion transport and eventually leads to rapid capacity fading. Two-dimensional (2D) materials have incomparable advantage in the construction of the desired interface because of their flat surface and large specific surface area. In order to realize intimate interfacial contact and superior ion transport, monodisperse 2D Co3S4 hexagonal platelets as cathodes for all ASSLBs are synthesized through a series of topological reactions followed with in situ coating of tiny Li7P3S11 using a liquid-phase method. The unique 2D hexagonal platelets are favorable for in situ solid electrolyte coating. Moreover, the well-designed interfacial structure can make the electrode materials contact with solid electrolytes more closely, contributing to a remarkable improvement on electrochemical performance. ASSLBs employing the Co3S4@Li7P3S11 composite platelets as a cathode deliver a large reversible capacity of 685.9 mA h g-1 at 0.5 A g-1 for 50 cycles. Even at a high current density of 1 A g-1, the Co3S4@Li7P3S11 composite cathode still exhibits a high capacity of 457.3 mA h g-1 after 100 cycles. This work provides a simple strategy to design the composite electrode with intimate contact and superior ion transport via morphology controlling.

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.

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%.

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.