A Universal Cross-Synthetic Strategy for Sub-10 nm Metal-Based Composites with Excellent Ion Storage Kinetics

Alkaline capacity decay induced vacancy-rich LDH for high-performance magnesium ions hybrid supercapacitor

Transition metal double hydroxides (LDHs) are among the most promising electrode materials in electrochemical energy storage. In this study, we synthesized electrodeposited nickel-cobalt layered double hydroxide (NiCo-LDH) to investigate the significant capacity gap in LDHs at different scan rates in an alkaline electrolyte. Experimental results demonstrate that the degradation of capacity at high scan rates is primarily attributed to the slow ion diffusion and the decreased reversibility of active metal ions. Furthermore, by exploiting the low reversibility of the deprotonation reaction at high scan rates, a NiCo-LDH with enriched hydrogen vacancies (Hv-rich LDH) was obtained. Consequently, the Hv-rich LDH, when used as the cathode in a magnesium ions hybrid supercapacitor (Mg-HSC), exhibits a high specific capacity of 94.97mAh g-1 at a current density of 1 A g-1 and maintains a significant capacity of 41.90 mAh g-1 even at 20 A g-1. Moreover, a Mg-HSC device assembled with an Hv-rich LDH cathode and a VS2 anode delivers a high energy density of 48.44 Wh kg-1 and a power density of 937.49 W kg-1, demonstrating its practical application value. This work not only provides a theoretical basis for the defect design of LDHs but also expands their applicability.

In Situ Grown Li2Te Enhanced Lithium Metal Anode Interfacial Kinetics

Lithium metal anode (LMA) is expected to be the ideal anode material for future high-energy-density batteries, but regulating the complex electrolyte-anode interface remains a challenge. In this work, a stable Li2Te coating is formed on the surface of commercial copper mesh (LTCM) using a simple and quick method to improve lithium metal anode interfacial kinetics. Li2Te possesses a strong affinity for both Li+ and TFSI- anions, which reduces the lithium nucleation barrier and guides the formation of inorganic-rich SEI, accelerates the diffusion of Li+, and promotes the growth of lithium metal along the plane. The highly conductive Li2Te and Cu generated by in situ lithiation reaction together constitute an effective electron-conducting network, which synergistically enhances the interfacial kinetics and the cycling stability of LMA. As a result, the LTCM maintains high Coulombic efficiency (98%) even after 2200 cycles at 1 mA cm-2, whereas the symmetric cell has a long cycle life of over 5400 h at 1 mA cm-2. In addition, the full cells with LFP display a high capacity retention ratio (80%) after 480 cycles at 1 C and the corresponding pouch cell can cycle steadily more than 464 cycles at 1 C, which has good application prospects.

Routes to Bidirectional Cathodes for Reversible Aprotic Alkali Metal-CO2 Batteries

Aprotic alkali metal-CO2 batteries (AAMCBs) have garnered significant interest owing to fixing CO2 and providing large energy storage capacity. The practical implementation of AAMCBs is constrained by the sluggish kinetics of the CO2 reduction reaction (CO2RR) and the CO2 evolution reaction (CO2ER). Because the CO2ER and CO2RR take place on the cathode, which connects the internal catalyst with the external environment. Building a bidirectional cathode with excellent CO2ER and CO2RR kinetics by optimizing the cathode's internal catalyst and environment has attracted most of the attention to improving the electrochemical performance of AAMCBs. However, there remains a lack of comprehensive understanding. This review aims to give a route to bidirectional cathodes for reversible AAMCBs, by systematically discussing engineering strategies of both the internal catalyst (atomic, nanoscopic, and macroscopic levels) and the external environment (photo, photo-thermal, and force field). The CO2ER and CO2RR mechanisms and the "engineering strategies from internal catalyst to the external environment-cathode properties-CO2RR and CO2ER kinetics and mechanisms-batteries performance" relationship are elucidated by combining computational and experimental approaches. This review establishes a fundamental understanding for designing bidirectional cathodes and gives a route for developing reversible AAMCBs and similar metal-gas battery systems.

Highly Reversible Sodium-ion Storage in A Bifunctional Nanoreactor Based on Single-atom Mn Supported on N-doped Carbon over MoS2 Nanosheets

Conversion-type electrode materials have gained massive research attention in sodium-ion batteries (SIBs), but their limited reversibility hampers practical use. Herein, we report a bifunctional nanoreactor to boost highly reversible sodium-ion storage, wherein a record-high reversible degree of 85.65 % is achieved for MoS2 anodes. Composed of nitrogen-doped carbon-supported single atom Mn (NC-SAMn), this bifunctional nanoreactor concurrently confines active materials spatially and catalyzes reaction kinetics. In situ/ex situ characterizations including spectroscopy, microscopy, and electrochemistry, combined with theoretical simulations containing density functional theory and molecular dynamics, confirm that the NC-SAMn nanoreactors facilitate the electron/ion transfer, promote the distribution and interconnection of discharging products (Na2S/Mo), and reduce the Na2S decomposition barrier. As a result, the nanoreactor-promoted MoS2 anodes exhibit ultra-stable cycling with a capacity retention of 99.86 % after 200 cycles in the full cell. This work demonstrates the superiority of bifunctional nanoreactors with two-dimensional confined and catalytic effects, providing a feasible approach to improve the reversibility for a wide range of conversion-type electrode materials, thereby enhancing the application potential for long-cycled SIBs.

Effects of external pressure on cycling performance of silicon-based lithium-ion battery: modelling and experimental validation

Controlling the stress state of electrodes during electrochemical cycling can have a positive effect on the cycling performance of lithium-ion battery. In this work, we study the cycling performance of silicon-based lithium-ion half cells under the action of pressure in a range of 0.1 to 0.4 MPa. The cycling performance of the silicon-based lithium-ion half cells increases first with increasing the pressure to 0.2 MPa and then decreases with further increasing the pressure. The analysis of the surface morphologies of cycled electrodes reveals that applying a pressure of 0.2 MPa leads to the formation of fine electrode surface with the least surface cracks after the silicon-based lithium-ion half cells are cycled for 50 times, which supports the dependence of the cycling performance of the lithium-ion half cells on the pressure. The numerical results from the single particle model reveal that applying pressure can tune the stress state in a single electrode particle and reduce the tensile stress. However, the numerical results from the two-particle model point to that applying pressure can introduce tensile stress in the electrode particles due to contact deformation. Suitable pressure applied onto a lithium-ion battery is needed in order to improve the cycling performance of the lithium-ion battery without causing detrimental effects.

Research progress of functional MXene in inhibiting lithium/zinc metal battery dendrites

The layered two-dimensional (2D) MXene has great promise for applications in supercapacitors, batteries, and electrocatalysis due to its large layer spacing, excellent electrical conductivity, good chemical stability, good hydrophilicity, and adjustable layer spacing. Since its discovery in 2011, MXene has been widely used to inhibit the growth of anode dendrites of lithium metal. In the past two years, researchers have used MXene and MXene based materials in the anodes of zinc metal batteries and zinc ion hybrid capacitors, respectively, and made a series of important progressive steps in the inhibition of zinc dendrite growth. In this review, we summarize the research progress of functional MXenes in inhibiting the growth of lithium and zinc metal anode dendrites, and provide a brief overview and outlook on the current challenges of MXene materials, which will help researchers to further understand the methods and their mechanisms, thus to develop novel electrochemical energy storage systems to meet the needs of rapidly developing electric vehicles and wearable/portable electronics.

Heterostructure Engineering of NiCo-LDHs for Enhanced Energy Storage Performance in Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are considered a promising device for next-generation energy storage due to their high safety and low cost. However, developing high-performance cathodes that can be matched with zinc metal anodes remains a challenge in unlocking the full potential of AZIBs. In this study, a typical transition metal layered double hydroxides (NiCo-LDHs) can be in situ reconstructed to NiCo-LDHs/Ni(Co)OOH heterostructure using an electrochemical cycling activation (ECA) method, serving as a novel cathode material for AZIBs. The optimized ECA-NiCo-LDHs cathode demonstrates a high capacity of 181.5 mAh g-1 at 1 A g-1 and retains 75% of initial capacity after 700 cycles at 5 A g-1. The abundant heterointerfaces of the NiCo-LDHs/Ni(Co)OOH material can activate additional active sites for zinc-ion storage and accelerate ion diffusion. Theoretical calculations also suggest the heterostructure can boost charge transfer and regulate ion-adsorption capability, thereby improving the electrochemical performance. Additionally, the flexible AZIBs device exhibits good service performance. This study on interface engineering introduces a new possibility for utilizing LDHs in AZIBs and offers a novel strategy for designing electrode materials.

High-Pressure-Field Induced Synthesis of Ultrafine-Sized High-Entropy Compounds with Excellent Sodium-Ion Storage

Emerging high entropy compounds (HECs) have attracted huge attention in electrochemical energy-related applications. The features of ultrafine size and carbon incorporation show great potential to boost the ion-storage kinetics of HECs. However, they are rarely reported because high-temperature calcination tends to result in larger crystallites, phase separation, and carbon reduction. Herein, using the NaCl self-assembly template method, by introducing a high-pressure field in the calcination process, the atom diffusion and phase separation are inhibited for the general formation of HECs, and the HEC aggregation is inhibited for obtaining ultrafine size. The general preparation of ultrafine-sized (<10 nm) HECs (nitrides, oxides, sulfides, and phosphates) anchored on porous carbon composites is realized. They are demonstrated by combining advanced characterization technologies with theoretical computations. Ultrafine-sized high entropy sulfides-MnFeCoCuSnMo/porous carbon (HES-MnFeCoCuSnMo/PC) as representative anodes exhibit excellent sodium-ion storage kinetics and capacities (a high rating capacity of 278 mAh g-1 at 10 A g-1 for full cell and a high cycling capacity of 281 mAh g-1 at 20 A g-1 after 6000 cycles for half cell) due to the combining advantages of high entropy effect, ultrafine size, and PC incorporation. Our work provides a new opportunity for designing and fabricating ultrafine-sized HECs.

Room-Temperature Salt Template Synthesis of Nitrogen-Doped 3D Porous Carbon for Fast Metal-Ion Storage

The water-soluble salt-template technique holds great promise for fabricating 3D porous materials. However, an equipment-free and pore-size controllable synthetic approach employing salt-template precursors at room temperature has remained unexplored. Herein, we introduce a green room-temperature antisolvent precipitation strategy for creating salt-template self-assembly precursors to universally produce 3D porous materials with controllable pore size. Through a combination of theoretical simulations and advanced characterization techniques, we unveil the antisolvent precipitation mechanism and provide guidelines for selecting raw materials and controlling the size of precipitated salt. Following the calcination and washing steps, we achieve large-scale and universal production of 3D porous materials and the recycling of the salt templates and antisolvents. The optimized nitrogen-doped 3D porous carbon (N-3DPC) materials demonstrate distinctive structural benefits, facilitating a high capacity for potassium-ion storage along with exceptional reversibility. This is further supported by in situ electrochemical impedance spectra, in situ Raman spectroscopy, and theoretical calculations. The anode shows a high rate capacity of 181 mAh g-1 at 4 A g-1 in the full cell. This study addresses the knowledge gap concerning the room-temperature synthesis of salt-template self-assembly precursors for the large-scale production of porous materials, thereby expanding their potential applications for electrochemical energy conversion and storage.