Local Lattice Distortion Activate Metastable Metal Sulfide as Catalyst with Stable Full Discharge-Charge Capability for Li-O2 Batteries.

The direct lattice strain, either distortion, compressive, or tensile, can efficiently alter the intrinsic electrocatalytic property of the catalysts. In this work, we report a novel and effective strategy to distort the lattice structure by constructing a metastable MoSSe solid solution and thus, tune its catalytic activity for the Li-O2 batteries. The lattice distortion structure with inequivalent interplanar spacing between the same crystals plane were directly observed in individual MoSSe nanosheets with transmission electron microscopy and aberration-corrected transmission electron microscopy. In addition, in situ transmission electron microscopy analysis revealed the fast Li+ diffusion across the whole metastable structure. As expected, when evaluated as oxygen electrode for deep-cycle Li-O2 batteries, the metastable MoSSe solid solution deliver a high specific capacity of ∼730 mA h g-1 with stable discharge-charge overpotentials (0.17/0.49 V) over 30 cycles.

Suppressing the dissolution of polysulfides with cosolvent fluorinated diether towards high-performance lithium sulfur batteries.

The dissolution and shuttle of polysulfides in electrolytes cause severe anode corrosion, low coulombic efficiency, and a rapid fading of the capacity of lithium-sulfur batteries. Fluorinated diether (FDE) was selected as a cosolvent in traditional ether electrolytes to suppress the dissolution of polysulfides. The modified electrolytes lead to a negligible solubility of polysulfides, as well as decreased corrosion of the lithium anode. In an optimal system, the cells show improved cycling performance with an average coulombic efficiency of above 99% and a highly stable reversible discharge capacity of 701 mA h g-1 after 200 cycles at a 0.5C rate. A combination of electrochemical studies and X-ray photoelectron spectroscopy demonstrates the sulfur reduction mechanism with three voltage plateaus.

Atomic-Thick TiO2(B) Nanosheets Decorated with Ultrafine Co3O4 Nanocrystals As a Highly Efficient Catalyst for Lithium-Oxygen Battery.

Development of highly efficient catalysts based on transition metal oxides (TMOs) is desirable and remains a big challenge for lithium-oxygen (Li-O2) batteries. In the present work, atomic-thick TiO2(B) nanosheets decorated with ultrafine Co3O4 nanocrystals (Co3O4-TiO2(B)) were synthesized and utilized as cathode catalyst in Li-O2 batteries by designing a hybrid and inducing oxygen vacancies. The XPS characterization results suggested that the introduction of Co3O4 nanocrystals could induce numerous oxygen vacancies in the TiO2(B) nanosheets through Co doping in the hybrid catalyst. The subsequent electrochemical experiments indicated that the Li-O2 batteries with the prepared hybrid catalysts showed high specific capacity (11000 mAhg-1), and good cycling stability (200 cycles at a limited capacity of 1000 mAhg-1) with low polarization (above 2.7 V for discharge medium voltage and below 4.0 V for charge medium voltage within 80 cycles). Furthermore, a possible working mechanism was proposed for a better understanding of the high performance of Co3O4-TiO2(B) catalysts for the Li-O2 batteries. This work also provided new insights into designing efficient catalysts through interface engineering between 2D (two-dimensional) TMOs and 0D (zero-dimensional) TMOs for Li-O2 batteries or other catalysis-related fields.

Lattice Incorporation of Cu2+ into the BaCe0.7Zr0.1Y0.1Yb0.1O3-δ Electrolyte on Boosting Its Sintering and Proton-Conducting Abilities for Reversible Solid Oxide Cells.

Lattice modification by incorporating heteroatoms could effectively and precisely tune their intrinsic properties to get improved sinterability and electrochemical performance. Here, by introducing Cu2+ into the interstitial position of a ABO3-type perovskite, a 2 times higher protonic conductivity (1.9 × 10-2 S cm-1 at 700 °C) and low-temperature (1200 °C) sinterability were achieved for the BaCe0.68Zr0.1Y0.1Yb0.1Cu0.02O3-δ (BCZYYC2) electrolyte, compared to the precursor electrolyte. Meanwhile, the modified BCZYYC2 also exhibits excellent chemical stability in high-temperature and high-humidity conditions, as well as good compatibility with the components of cell. When used as the electrolyte in reversible fuel cell (FC)/electrolysis cell (EC) operational modes, the reversible solid oxide cell with the BCZYYC2 electrolyte illustrates prominent FC (0.85 W cm-2 at 700 °C) and EC (-1.96 A cm-2 at 700 °C and 1.3 V) performances with high film-electrolyte conductivity (8.7 × 10-3 S cm-1 at 700 °C). Additionally, an obvious increase in current density is observed during the short-term stability test, which has shown great promise for their practical application.

Robust and Conductive Red MoSe2 for Stable and Fast Lithium Storage.

Two-dimensional (2D) layered transition-metal dichalcogenides (LTMDs) display various crystal phases with distinct symmetries, structures, and physical properties. Exploring and designing different structural phases in two dimensions could provide an avenue for switching material properties, aiming at practical applications for potential fields. Here we demonstrate a conceptually designed approach to narrow the band gap of MoSe2 and obtain a conductive red MoSe2 nanosheet. By introducing the high valence state of Mo species and constructing the Mo-O bonding on the surface of the MoSe2 nanosheets, the electronic properties can be modified and the conductivity is accordingly improved, an effect that significantly improves their lithium storage capacity and high-rate capability. We anticipate that the exploration of the conductive red MoSe2 with tunable band gap could help us unlock more potential crystal structures of LTMD-based and even other 2D materials for further applications.

Nanoporous Adsorption Effect on Alteration of the Li+ Diffusion Pathway by a Highly Ordered Porous Electrolyte Additive for High-Rate All-Solid-State Lithium Metal Batteries.

Solid polymer electrolytes (SPEs) have shown extraordinary promise for all-solid-state lithium metal batteries with high energy density and flexibility but are mainly limited by low ionic conductivity and their poor stability with lithium metal anodes. In this work, we propose a highly ordered porous electrolyte additive derived from SSZ-13 for high-rate all-solid-state lithium metal batteries. The nanoporous adsorption effect provided by the highly ordered porous nanoparticles in the poly(ethylene oxide) (PEO) electrolyte is found to significantly improve the Li+ conductivity (1.91 × 10-3 S cm-1 at 60 °C, 4.43 × 10-5 S cm-1 at 20 °C) and widen the electrochemical stability window to 4.7 V vs Li+/Li. Meanwhile, the designed PEO-based electrolyte demonstrates enhanced stability with the lithium metal anode. Through systematically increasing Li+ diffusion, widening the electrochemical stability window, and enhancing the interfacial stability of the SSZ-composite electrolyte (CPE) electrolyte, the LiFePO4/SSZ-CPE/Li cell is optimized to deliver high rate capability and stable cycling performance, which demonstrates great potential for all-solid-state energy storage application.

Sulfonic Groups Originated Dual-Functional Interlayer for High Performance Lithium-Sulfur Battery.

The lithium-sulfur battery is one of the most prospective chemistries in secondary energy storage field due to its high energy density and high theoretical capacity. However, the dissolution of polysulfides in liquid electrolytes causes the shuttle effect, and the rapid decay of lithium sulfur battery has greatly hindered its practical application. Herein, combination of sulfonated reduced graphene oxide (SRGO) interlayer on the separator is adopted to suppress the shuttle effect. We speculate that this SRGO layer plays two roles: physically blocking the migration of polysulfide as ion selective layer and anchoring lithium polysulfide by the electronegative sulfonic group. Lewis acid-base theory and density functional theory (DFT) calculations indicate that sulfonic groups have a strong tendency to interact with lithium ions in the lithium polysulfide. Hence, the synergic effect involved by the sulfonic group contributes to the enhancement of the battery performance. Furthermore, the uniformly distributed sulfonic groups working as active sites which could induce the uniform distribution of sulfur, alleviating the excessive growth of sulfur and enhancing the utilization of active sulfur. With this interlayer, the prototype battery exhibits a high reversible discharge capacity of more than 1300 mAh g-1 and good capacity retention of 802 mAh g-1 after 250 cycles at 0.5 C rate. After 60 cycles at different rates from 0.2 to 4 C, the cell with this functional separator still recovered a high specific capacity of 1100 mAh g-1 at 0.2 C. The results demonstrate a promising interlayer design toward high performance lithium-sulfur battery with longer cycling life, high specific capacity, and rate capability.

Assembly of Multifunctional Ni2P/NiS0.66 Heterostructures and Their Superstructure for High Lithium and Sodium Anodic Performance.

The combination of structure designs at the microscopic and macroscopic level can efficiently enable electrode materials with greatly enhanced lithium and sodium storage. In this paper, the construction of Ni2P/NiS0.66 heterostructures and their assembly into a superstructure at the nanoscale were successfully achieved by a facile and effective strategy. In the obtained superstructure, the Ni2P/NiS0.66 heterostructures are homogeneously coated with ultrathin carbon layers (HT-NPS@C) and, at the same time, assembled into a yolk-shell nanosphere. Upon evaluation as the anode materials for Li-ion batteries, the HT-NPS@C delivers a high reversible capacity of 430 mA h g-1 after 200 cycles at 200 mA g-1 and ultrastable cyclability with negligible capacity loss over 500 cycles. Furthermore, the coin-type full cell with the LiNi1/3Co1/3Mn1/3O2 (LNCMO) cathode and HT-NPS@C anode deliver a high specific capacity of 323.5 mA h g-1 after 50 cycles at 0.3 A g-1. Apart from an excellent performance as promising anode materials for LIBs (Li-ion batteries), the Na-ion batteries with HT-NPS@C sphere electrodes also manifest a remarkable electrochemical performance.

Constructing Highly Oriented Configuration by Few-Layer MoS2: Toward High-Performance Lithium-Ion Batteries and Hydrogen Evolution Reactions.

Constructing three-dimensional (3D) architecture with oriented configurations by two-dimensional nanobuilding blocks is highly challenging but desirable for practical applications. The well-oriented open structure can facilitate storage and efficient transport of ion, electron, and mass for high-performance energy technologies. Using MoS2 as an example, we present a facile and effective hydrothermal method to synthesize 3D radially oriented MoS2 nanospheres. The nanosheets in the MoS2 nanospheres are found to have less than five layers with an expanded (002) plane, which facilitates storage and efficient transport of ion, electron, and mass. When evaluated as anode materials for rechargeable Li-ion batteries, the MoS2 nanospheres show an outstanding performance; namely, a specific capacity as large as 1009.2 mA h g(-1) is delivered at 500 mA g(-1) even after 500 deep charge/discharge cycles. Apart from promising the lithium-ion battery anode, this 3D radially oriented MoS2 nanospheres also show high activity and stability for the hydrogen evolution reaction.