Latest ArticlesWith the development of science and technology, there is an increasing demand for energy storage batteries. Aqueous zinc-ion batteries (AZIBs) are expected to become the next generation of commercialized energy storage devices due to their advantages. The aqueous zinc ion battery is generally composed of zinc metal as the anode, active material as the cathode, and aqueous electrolyte. However, there are still many problems with the cathode/anode material and voltage window of the battery, which limit its use. This review introduces the recent research progress of zinc-ion batteries, including the advantages and disadvantages, energy storage mechanisms, and common cathode/anode materials, electrolytes, etc. It also gives a summary of the current research status of each material and provides solutions to the problems they face. Finally, it looks at the future direction and methods to optimize the performance of zinc-ion full batteries.
High-capacity Ni-rich layered cathodes LiNixCoyMn1−x−yO2 (NCM) have been widely recognized as highly promising candidates for lithium-ion batteries (LIBs). However, NCM cathodes are suffered from sluggish Li-ion kinetics and fast capacity decay. Herein, the Nb/Ti co-doping strategy has been proposed by formation energy analysis to enhance the mechanical and chemical integrities of NCM cathode. Nb/Ti co-doping facilitates Li-ion transport of NCM cathode for boosting the rate ability. Furthermore, the structure stability is prominently improved for the stronger Nb–O and Ti–O bonds, resulting from the suppressed sharp contraction of c axis, inhibited microcracks formation, and alleviated electrolyte corrosion. Inspired by the synergistic effect of Nb/Ti co-doping, the modified NCM exhibits superior comprehensive electrochemical performances. The Nb/Ti co-doping NCM exhibits an increased discharge capacity of 144.3 mAh/g at 10 C and an outstanding capacity retention remained 92.7% after 300 cycles at 1 C. This work offers a promising approach to developing high-performance cathode materials.
For realizing the goals of “carbon peak” and “carbon neutrality”, lithium-ion batteries (LIB) with LiFePO4 as the cathode material have been widely applied. However, this has also led to a large number of spent lithium-ion batteries, and the safe disposal of spent lithium-ion batteries is an urgent issue. Currently, the main reason for the capacity decay of LiFePO4 materials is the Li deficiency and the formation of the Fe3+ phase. In order to address this issue, we performed high-temperature calcination of the discarded lithium iron phosphate cathode material in a carbon dioxide environment to reduce or partially remove the carbon coating on its surface. Subsequently, mechanical grinding was conducted to ensure thorough mixing of the lithium source with the discarded lithium iron phosphate. The reaction between CO2 and the carbon coating produced a reducing atmosphere, reducing Fe3+ to Fe2+ and thereby reducing the content of Fe3+. The Fe3+ content in the repaired LiFePO4 material is reduced. The crystal structure of spent LiFePO4 cathode materials was repaired more completely compare with the traditional pretreatment method, and the repaired LiFePO4 material shows good electrochemical performance and cycling stability. Under 0.1 C conditions, the initial capacity can reach 149.1 mAh/g. It can be reintroduced for commercial use.
Urea-assisted water electrolysis offers a promising route to reduce energy consumption for hydrogen production and meanwhile treat urea-rich wastewater. Herein, we devised a shear force-involved polyoxometalate-organic supramolecular self-assembly strategy to fabricate 3D hierarchical porous nanoribbon assembly Mn-VN cardoons. A bimetallic polyoxovanadate (POV) with the inherent structural feature of Mn surrounded by [VO6] octahedrons was introduced to trigger precise Mn incorporation in VN lattice, thereby achieving simultaneous morphology engineering and electronic structure modulation. The lattice contraction of VN caused by Mn incorporation drives electron redistribution. The unique hierarchical architecture with modulated electronic structure that provides more exposed active sites, facilitates mass and charge transfer, and optimizes the associated adsorption behavior. Mn-VN exhibits excellent activity with low overpotentials of 86 mV and 1.346 V at 10 mA/cm2 for hydrogen evolution reaction (HER) and urea oxidation reaction (UOR), respectively. Accordingly, in the two-electrode urea-assisted water electrolyzer utilizing Mn-VN as a bifunctional catalyst, hydrogen production can occur at low voltage (1.456 V@10 mA/cm2), which has the advantages of energy saving and competitive durability over traditional water electrolysis. This work provides a simple and mild route to construct nanostructures and modulate electronic structure for designing high-efficiency electrocatalysts.
In the practical operations of the sodium ion (Na+) batteries (SIBs), the fast transport of Na+ is desired for the rate performance, because the other ions in an electrolyte are electrochemically inert. In this study, we use molecular dynamics simulations to investigate the partial conductivity of Na+ (σNa+) in the salt-in-ionic liquid electrolytes (SILEs) composed of 1-ethyl-3-methylimidazolium (EMIM+) and bis(fluorosulfonyl)imide (FSI−) with various molar fraction of NaFSI. The simulations show that while the ionic conductivity of the SILE decreases monotonically with the increase of salt fraction of NaFSI, σNa+ peaks in the SILE with 0.5 molar fraction of NaFSI. Detailed analyses indicate that with the increase of salt fraction, the coordination structure of FSI− around Na+ changed from bidentate manner to monodentate manner which weakens the binding of FSI− to Na+. The effects are two folds. On one hand, the increased monodentate coordinations cause a large aggregate that hinders the transport of Na+ within the aggregate; on the other hand, the large aggregate captures most FSI− to form percolating ion network, and thus leaves a small portion of Na+’s that are not in the large aggregate to be more "free" to transport in the SILE.
Multi-metal porous crystalline materials (MPCM), integrating the functions of both multi-metal centres and porous crystalline materials (e.g., metal-organic frameworks (MOFs) and covalent organic frameworks (COFs)), are an extended class of porous materials that have attracted much attention for a broad range of applications. Owing to the advantages of these materials, they generally display high porosity, multi-metal active sites, well-tuned functions, and pre-designable structures, etc., serving as desired platforms for the study of structure-property relationships. In view of the clean and sustainable target, a series of MPCM have been explored as electrocatalysts for electrocatalytic reactions like hydrogen evolution reaction, oxygen evolution reaction and electrocatalytic CO2 reduction reaction. Concerning the progress achieved for MPCM in electrocatalytic field during past years, this review will provide a brief introduction on the recent breakthrough of MPCM based electrocatalysts including their synthesis methods, structure design, component/morphology tuning, electrocatalytic property and structure-property relationship, etc. Besides, it will also conclude the current challenges and present perspectives for the MPCM based electrocatalysts, which might promote the development of porous crystalline materials in electrocatalysis and hope to provide new insights for scientists in related fields.
Transition metal selenides are considered promising electrochemical energy storage materials due to their excellent rate properties and high capacity based on multi-step conversion reactions. However, its practical applications are hampered by poor conductivity and large volume variation for Na+ storage, which resulting fast capacity decay. Herein, a facile metal-organic framework (MOF) derived method is explored to embed Cu2-xSe@C particles into a carbon nanobelts matrix. Such carbon encapsulated nanobelts' structural moderate integral electronic conductivity and maintained the structure from collapsing during Na+ insertion/extraction. Furthermore, the porous structure of these nanobelts endows enough void space to mitigate volume stress and provide more diffusion channels for Na+/electrons transporting. Due to the unique structure, these Cu2-xSe@C nanobelts achieved ultra-stable cycling performance (170.7 mAh/g at 1.0 A/g after 1000 cycles) and superior rate capability (94.6 mAh/g at 8 A/g) for sodium-ion batteries. The kinetic analysis reveals that these Cu2-xSe@C nanobelts with considerable pesoudecapactive contribution benefit the rapid sodiation/desodiation. This rational design strategy broadens an avenue for the development of metal selenide materials for energy storage devices.
Nickel-rich cathode materials have received widespread attention due to their high energy density. However, the poor rate capability and inferior cycle stability seriously hinder their large-scale application. The traditional co-precipitation method for preparing them has a long process and easily arises agglomeration leading to inhomogeneous element distribution. Here, a novel precursor containing Li element was prepared by ultrafast spray pyrolysis (SP) in 3–5 s. Then the precursor was used to synthesize pristine LiNi0.9Co0.05Mn0.05O2 (NCM90) and 1% Mg modified LiNi0.9Co0.05Mn0.05O2 (NCM90-Mg1). This method gets rid of mixing Li/Mg source and the precursor prepared by common co-precipitation, thus could achieve homogeneous lithiation and Mg2+ doping. The cell parameter c is expanded, and the cation disorder is reduced after Mg2+ doping. Furthermore, the harmful H2-H3 phase transition in NCM90-Mg1 is also well suppressed. As a result, the obtained NCM90-Mg1 shows better electrochemical performance than NCM90. Within 2.8–4.3 V (25 ℃), the specific discharge capacity of NCM90-Mg1 at 5 C is as high as 169.1 mAh/g, and an outstanding capacity retention of 70.0% (10.0% higher than NCM90) can be obtained after 400 cycles at 0.5 C. At 45 ℃, a capacity retention of 81.9% after 100 cycles at 1 C is recorded for NCM90-Mg1. Moreover, the NCM90-Mg1 also exhibits superior cycle stability when cycled at high cut-off voltage (4.5 V, 25 ℃), possessing the capacity retention of 79.2% after 200 cycles at 1 C. Therefore, SP can be proposed as a powerful method for the preparation of multi-element materials for next-generation high energy density LIBs.
Despite significant progress has been achieved regarding the shuttle-effect of lithium polysulfides, the suppressed specific capacity and retarded redox kinetics under high sulfur loading still threat the actual energy density and power density of lithium-sulfur batteries. In this study, a graham condenser-inspired carbon@WS2 host with coil-in-tube structure was designed and synthesized using anodic aluminum oxide (AAO) membrane with vertically aligned nanopores as template. The vertical array of carbon nanotubes with internal carbon coils not only leads to efficient charge transfer across through the thickness of the cathode, but also provides significant confinement to polysulfide diffusion towards both the lateral and longitudinal directions. Few-layer WS2 in the carbon coils perform a synergistic role in suppressing the shuttle-effect as well as boosting the cathodic kinetics. As a result, high specific capacity (1180 mAh/g at 0.1 C) and long-cycling stability at 0.5 C for 500 cycles has been achieved at 3 mgS/cm2. Impressive areal capacity of 7.4 mAh/cm2 has been demonstrated when the sulfur loading reaches 8.4 mg/cm2. The unique coil-in-tube structure developed in this work provides a new solution for high sulfur loading cathode towards practical lithium-sulfur batteries.
The excited state dynamics and critically regulated factors of reverse intersystem crossing (RISC) in through-space charge transfer (TSCT) molecules have received insufficient attention. Here, five molecules of through space/bond charge transfer inducing thermally activated delayed fluorescence (TADF) are prepared, and their excited state charge transfer processes are studied by ultrafast transient absorption and theoretical calculations. DM-Z has a larger ∆EST, leading to a longer lifetime of intersystem crossing (ISC), resulting in the lowest photoluminescence quantum yield (PLQY). Oppositely, ISC and RISC are demonstrated to take place with shorter lifetimes for TSCT molecules. The face-to-face π-π stacking interactions and electron communication enable DM-B and DM-BX to have an efficient RISC, increasing the weight coefficient of RISC from 1.7% (DM-X) to close to 50% (DM-B and DM-BX) in the solvents, which make DM-BX and DM-B to have a high PLQY. However, partial local excitation in the donor center is observed and the charge transfer is decreased for DM-G and DM-X. The triplet excited state (DM-G) or singlet excited state (DM-X) mainly undergoes inactivation through a non-radiative relaxation process, resulting in less RISC and low PLQY. This work provides theoretical hints to enhance the RISC process in the TADF materials.
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