Unlock flow-type reversible aqueous Zn-CO2 batteries.

Metal-CO2 batteries, which use CO2 as the active species at cathodes, are particularly promising, but device design for mass-producible CO2 reduction and energetic power supply lag behind, limiting their potential benefits. In this study, an aqueous reversible flow-type Zn-CO2 battery using a Pd/SnO2@C cathode catalyst has been assembled and demonstrates an ultra-high discharge voltage of 1.38 V, a peak power density of 4.29 mW cm-2, high-energy efficiency of 95.64% and remarkable theoretical energy density (827.3 W h kg-1). In the meantime, this optimized system achieves a high formate faradaic efficiency of 95.86% during the discharge process at a high rate of 4.0 mA cm-2. This energy- and chemical-conversion technology could store and provide electricity, eliminate CO2 and produce valuable chemicals, addressing current energy and environment issues simultaneously.

Dual-Anion Regulation for Reversible and Energetic Aqueous Zn-CO2 Batteries.

Aqueous Zn-CO2 batteries can not only convert CO2 into high-value chemicals but also store/output electric energy for external use. However, their performance is limited by sluggish and complicated CO2 electroreduction at the cathode. Herein, a dual-anion regulated Bi electrocatalyst is developed to selectively reduce CO2 to formate with a Faradaic efficiency of up to 97% at a large current density of 250 mA cm-2 . With O and/or F, the rate-determine step of CO2 electroreduction has been manipulated (from the first hydrogenation to *HCOOH desorption step) with a reduced energy barrier. Significantly, the fabricated Zn-CO2 battery exhibits a high discharge voltage of 1.2 V, optimal power density of 4.51 mW cm-2 , remarkable energy density of 802 Wh kg-1 , and energy-conversion efficiency of 70.74%, stability up to 200 cycles and 68 h. This study provides possible strategies to fabricate reversible and energetic aqueous Zn-CO2 batteries by addressing cathodic problems.

N doped FeP nanospheres decorated carbon matrix as an efficient electrocatalyst for durable lithium-sulfur batteries.

Rational design and synthesis of multifunctional electrocatalysts with high electrochemical activity and low cost are significantly important for new-generation lithium-sulfur (Li-S) batteries. Herein, N-doped FeP nanospheres decorated N doped carbon matrix is successfully synthesized by facile one-pot pyrolysis and in-situ phosphorization technique to mitigate the conversion kinetics and suppress the shuttle effect. The large specific surface area with mesopores can incorporate up to 81.5% sulfur, with the conductive carbon and nitrogen co-matrix providing Li+/e- passage and fastening the redox kinetics. The remarkable adsorption properties and the electrocatalytic activity through physical confinement and chemical immobilization is thoroughly verified. Consequently, the FeP/CN@S deliver a high reversible capacity of 1183 mAh g-1 at 0.1C compared to Co/P/CN@S (961 mAh g-1); whereas, at 1C, a negligible decay rate of 0.04% is observed for 1000 cycles, possessing outstanding cycling stability and rate capability. Hence, the cost-effective in-situ phosphorization strategy to synthesize FeP/CN@S as an efficient nanoreactor is constructive to be applied in Li-S batteries.

Towards high performance room temperature sodium-sulfur batteries: Strategies to avoid shuttle effect.

Room temperature sodium-sulfur battery has high theoretical specific energy and low cost, so it has good application prospect. However, due to the disadvantageous reaction between soluble intermediate polysulfides and sodium anode, the capacity drops sharply, which greatly limits its practical application. In recent years, various strategies have been formulated to address the problem of polysulfides dissolution. This perspective article provides an overview of the research progress on research progress of novel cathode materials, multifunctional host, new electrolyte systems and modified separator/interlayer/anode. The challenge and prospect of the advanced strategies to suppress the polysulfides shuttle for long-life and high-efficiency room temperature sodium-sulfur batteries are proposed.

Low-operating temperature quasi-solid-state potassium-ion battery based on commercial materials.

Quasi-solid-state potassium-ion batteries (QSPIBs) are regarded as one of the most promising safety-enhanced energy storage devices. Herein, a facile method for preparing a potassium-ion composite electrolyte membrane on a large scale is presented for the first time. The as-synthesized membrane displays excellent electrochemical stability, good mechanical flexibility, and high ionic conductivity (9.31 × 10-5 S cm-1 at 25 °C). Furthermore, QSPIBs prepared with this membrane and commercial raw material-based electrodes show superior electrochemical performance even at low temperatures (99.7 mAh g-1 at -20 °C for half QSPIBs and 90.7 mAh g-1 at -15 °C for full QSPIBs), and a promising rate performance (115.6 mAh g-1 for half QSPIBs and 90.9 mAh g-1 for full QSPIBs at 800 mA g-1). The reaction mechanism and structure evolution of a 3,4,9,10-perylene-tetracarboxylicacid-dianhydride (PTCDA) cathode is also systematically studied. The promising characteristics of the prepared low-cost quasi-solid-state potassium-ion batteries in this work open up new possibilities for safer and more durable batteries and a wide range of practical applications in the electronics industry.

Metal chalcogenide hollow polar bipyramid prisms as efficient sulfur hosts for Na-S batteries.

Sodium sulfur batteries require efficient sulfur hosts that can capture soluble polysulfides and enable fast reduction kinetics. Herein, we design hollow, polar and catalytic bipyramid prisms of cobalt sulfide as efficient sulfur host for sodium sulfur batteries. Cobalt sulfide has interwoven surfaces with wide internal spaces that can accommodate sodium polysulfides and withstand volumetric expansion. Furthermore, results from in/ex-situ characterization techniques and density functional theory calculations support the significance of the polar and catalytic properties of cobalt sulfide as hosts for soluble sodium polysulfides that reduce the shuttle effect and display excellent electrochemical performance. The polar catalytic bipyramid prisms sulfur@cobalt sulfide composite exhibits a high capacity of 755 mAh g-1 in the second discharge and 675 mAh g-1 after 800 charge/discharge cycles, with an ultralow capacity decay rate of 0.0126 % at a high current density of 0.5 C. Additionally, at a high mass loading of 9.1 mg cm-2, sulfur@cobalt sulfide shows high capacity of 545 mAh g-1 at a current density of 0.5 C. This study demonstrates a hollow, polar, and catalytic sulfur host with a unique structure that can capture sodium polysulfides and speed up the reduction reaction of long chain sodium polysulfides to solid small chain polysulfides, which results in excellent electrochemical performance for sodium-sulfur batteries.

A Mini-Review: MXene composites for sodium/potassium-ion batteries.

MXenes, as a new type of two-dimensional layered structure material, have attracted much attention. MXenes have high electronic conductivity, a large specific area, excellent mechanical properties and a unique layered structure and have been extensively used in energy storage, adsorption, catalysis and other fields. In recent years, Mxenes and their composite materials have been widely used in the field of secondary batteries. Although oxides, sulfides and other materials have high capacity, there are problems such as low conductivity, volume expansion in the reaction process, poor cycling stability, etc. Therefore, building composite materials with MXenes can not only improve the capacity but also enhance the electronic conductivity of the materials, effectively alleviate volume expansion in the reaction process, and achieve better electrochemical performance. This article reviews the latest research status of MXenes, the synthesis methods, properties and application of MXenes and their composite materials in sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs), briefly introduces the research background of SIBs, PIBs and MXenes, and focuses on the application research of MXene composite materials in SIBs and PIBs, including classification according to sulfide, oxide and carbon materials. Finally, the development and application prospects of MXenes and their composite materials are summarized.

Hierarchical NiMoO4@Co3V2O8 hybrid nanorod/nanosphere clusters as advanced electrodes for high-performance electrochemical energy storage.

Herein, a synergistic strategy to construct hierarchical NiMoO4@Co3V2O8 (denoted as NMO@CVO) hybrid nanorod/nanosphere clusters is proposed for the first time, where Co3V2O8 nanospheres (denoted as CVO) have been uniformly immobilized on the surface of the NiMoO4 nanorods (denoted as NMO) via a facile two-step hydrothermal method. Due to the surface recombination effect between NMO and CVO, the as-prepared NMO@CVO effectively avoids the aggregation of CVO nanosphere clusters. The unique hybrid architecture can make the most of the large interfacial area and abundant active sites for storing charge, which is greatly beneficial for the rapid diffusion of electrolyte ions and fast electron transport. The optimized NMO@CVO-8 composite nanostructure displays battery-like behavior with a maximum specific capacity of 357 C g-1, excellent rate capability (77.8% retention with the current density increasing by 10 times) and remarkable cycling stability. In addition, an aqueous asymmetric energy storage device is assembled based on the NMO@CVO-8 hybrid nanorod/nanosphere clusters and activated carbon. The device shows an ultrahigh energy density of 48.5 W h kg-1 at a power density of 839.1 W kg-1, good rate capability (20.9 W h kg-1 even at 7833.7 W kg-1) and excellent cycling stability (83.5% capacitance retention after 5000 cycles). More notably, two charged devices in series can light up a red light-emitting diode (LED) for 20 min, demonstrating its potential in future energy storage applications. This work indicates that the hierarchical NiMoO4@Co3V2O8-8 hybrid nanorod/nanosphere clusters are promising energy storage materials for future practical applications and also provides a rational strategy for fabricating novel nanostructured materials for high-performance energy storage.

Design and Construction of Sodium Polysulfides Defense System for Room-Temperature Na-S Battery.

Room-temperature Na-S batteries are facing one of the most serious challenges of charge/discharge with long cycling stability due to the severe shuttle effect and volume expansion. Herein, a sodium polysulfides defense system is presented by designing and constructing the cathode-separator double barriers. In this strategy, the hollow carbon spheres are decorated with MoS2 (HCS/MoS2) as the S carrier (S@HCS/MoS2). Meanwhile, the HCS/MoS2 composite is uniformly coated on the surface of the glass fiber as the separator. During the discharge process, the MoS2 can adsorb soluble polysulfides (NaPSs) intermediates and the hollow carbon spheres can improve the conductivity of S as well as act as the reservoir for electrolyte and NaPSs, inhibiting them from entering the anode to make Na deteriorate. As a result, the cathode-separator group applied to room-temperature Na-S battery can enable a capacity of ≈1309 mAh g-1 at 0.1 C and long cycling life up to 1000 cycles at 1 C. This study provides a novel and effective way to develop durable room-temperature Na-S batteries.

A labyrinth-like network electrode design for lithium-sulfur batteries.

The volume expansion of sulfur and the dissolution of polysulfides into the electrolyte are the key issues to be solved in the development of lithium-sulfur batteries. In this work, a labyrinth electrode material design is presented to overcome these difficulties in lithium-sulfur batteries. The shell of NiO-Co3O4 hollow spheres as the "wall" to prevent the polysulfide dissolution cross-links into a labyrinth network as a sulfur host. The 3D labyrinth network not only provides enough inner space to load sulfur but also adapts to its large volume expansion during lithiation and delithiation. In addition, the polar NiO-Co3O4 shells can promote the chemical adsorption of polysulfides, while NiO-Co3O4 shells can promote the conversion of polysulfides into Li2S. With this unique design, the 3D labyrinth-like NiO-Co3O4@S electrode presents a good electrochemical performance, delivering high capacity with a stable cycling life of up to 200 cycles at 1C and the attenuation rate of each cycle is only 0.1%.