Recently, Lynden A. from Cornell University, USA Professor Archer published a research report entitled "Fast ion transport at solid–solid interfaces in hybrid battery anodes" at Nature Energy. A mixed material (Sn-Li, etc.) is prepared by depositing an electrochemically active metal (such as Sn, In or Si) on an alkali metal electrode material by rapid and simple ion displacement, and further discovers that ions can pass through at high speed without hindrance The solid-solid interface of the mixed material and the realization of the Sn plating layer (Sn SEI film) can protect the alkali metal electrode from side reactions and provide a good interface for suppressing volume change and alloying and plating of the electrode material. And inhibit the formation of dendrites, and finally realize the preparation of Sn-Li and Sn-Na high-capacity, dendritic electrode materials.

Figure 1 Preparation process and interface characterization of Sn plating

The above figure shows a rapid ion exchange deposition reaction on the surface of metal Li, that is, mainly by using tin bis(trifluoromethanesulfonyl)imide mixed with an organic solvent (EC/DMC solution dissolving 1M LiPF6) due to Sn and The huge difference in Li electronegativity enables a rapid deposition process to control different Sn salt concentrations during deposition to achieve different thicknesses. The reason for choosing Sn is that Li can rapidly diffuse into each other and both alloy phases and lithium. Small separation between layers <500 mV). It can be seen from the interface morphology and element distribution characterized by low temperature conditions in the 1b-1e diagram that the whole material forms a three-layer structure, including the upper layer of frozen electrolyte, the middle layer of Sn-rich layer and the lower layer of metal Li, which can be seen. The Sn nanoparticles are evenly distributed on the surface of the Li negative electrode material, and the surface of the material after the plating is greatly different from the uncoated surface.

Figure 2 Characterization of physical and electrochemical properties of Sn-Li hybrid materials

It can be seen from the XRD characterization of Fig. 2a that the coating of different thicknesses of the surface of the metal Li can be obtained by using different concentrations of the Sn salt solution. When the concentration is increased from small, the diffraction result shows that the main substance is gradually converted from Li to Sn and Li5Sn2 indicates that the coating has an alloy reaction with Li metal. Through the investigation of the surface morphology of sediment layers with different thicknesses, the performance of the mixed electrode materials prepared with a concentration of 10 nm at 500 mM was determined. In order to investigate the charge transport process between the coating and the electrolyte interface, it can be seen in Figures 2b and 2c that as the temperature decreases, the charge transport resistance of the interface decreases, and the interface of the Sn-Li material is compared with the uncoated raw Li interface. The interface charge transfer resistance is significantly reduced, and a semicircle of the curve also indicates that the Sn-Li material does not introduce additional interface resistance. As the thickness of the Sn layer increases, the internal resistance of the interface decreases significantly. It can be seen that the Sn SEI layer not only does not affect the electron transport, but also promotes the electron transport. Further testing the ionic conductivity of the electrolyte in contact with the Li metal material with the Li metal material as a function of temperature (as shown in Figure 2d), the ionic conductivity decreases with increasing temperature, and the Sn layer with a thickness of 500 nm. Having good ionic conductivity may be due to the fact that the nanoparticles produced by this thickness provide a larger specific surface area. In order to confirm the electrochemical properties of the Sn-Li hybrid material, the researchers assembled a symmetric battery of Li//Sn-Li and tested its CV curve. A typical Li/Li+ polarization curve can be obtained from the figure, and it is also found at 100. The Sn-intercalation reaction of Li occurred under the voltage of mV, and there was no significant change in peak intensity and peak position during multiple cycles, indicating that the Sn layer is electrochemically active and stable in electrochemical properties during the cycle, without SEI film. The generation.

Fig. 3 Characterization of Sn-Li composites as anode materials for lithium metal batteries

In order to further confirm the value of Sn-Li composites in lithium metal batteries, the researchers built a real-time test device in which Sn deposition and electrochemical performance are interconnected, which can observe the surface morphology of metal Li and test it in real time during the deposition process. Related electrochemical performance results. The micrograph in the upper row of Figure 3a characterizes the evolution of the interface during deposition at a current density of 4 mA/cm2. It can be seen from the figure that the surface of the Sn-Li electrode material is smooth and substantially free of dendrite formation, and the growth rate is significantly slowed compared with the original Li surface (Fig. 3b). In the detection of the electrochemical properties of Sn-Li mixed materials, the artificial phase difference is an important part of determining the cycle performance. It can be seen from Fig. 3d and 3e that the protection of the Sn layer is compared with the original Li metal. In other words, the Sn-Li hybrid material has good cycle stability, and it is further assembled with NCA to form a full battery with good cycle stability, confirming the applicability of the material in a lithium metal battery.

Fig. 4 Characterization and electrochemical performance characterization of Sn-Na mixed anode material

On the basis of the successful application of Sn-Li mixed anode material, the method was applied to the metal Na electrode material, and it was found that the interface resistance was greatly reduced (Fig. 4a), and the surface flatness was obviously improved. Figure 4b). Similarly, the voltage values ​​of Na//Sn-Na and Na//Na symmetrical batteries were also determined, which also confirmed the good protection of the Sn layer for the metal Na layer. The original metal Na surface quickly failed and showed significant voltage divergence (eg Figure 4d), even at low current densities, after only 250 hours, the original sodium battery will have a rapid voltage divergence to 1 V (Figure 4f), while the metal Na under the Sn layer can be used for a long time. Stable cycle.

Second, Adv. Funct. Mater. : Capacitance Enhancement Mechanism and Design Principle of High Performance Graphene Oxide All-Solid Supercapacitors

Recently, Professor Xia Zhenhai (Corresponding Author) of Northwestern Polytechnical University published a paper entitled "Capacitive Enhancement Mechanisms and Design Principles of High-Performance Graphene Oxide-ba sed All-Solid-State Supercapacitors" at Advanced Functional Materials. All-solid-state supercapacitors are highly efficient and stable energy storage devices that can be integrated on a chip in a variety of geometries to meet the needs of different smart wearable electronic devices. However, low energy density has always been a bottleneck restricting its application. In this study, through molecular dynamics simulation and theoretical analysis of graphene oxide supercapacitor, the following results were obtained: First, the design principle of high energy density of graphene oxide alkynes was established. Second, based on this design principle, The new graphene oxide-based supercapacitor is designed to have the highest energy density among the current liquid-based and solid-state electrolyte capacitors. Third, two novel high-performance multilayer graphene oxides (GO)/ Design ideas for graphene (rGO) capacitors. The above research results are not only supported by experimental results, but also provide theoretical guidance and technical support for the design of future supercapacitor designs and other energy storage and conversion devices.

[Introduction to the graphic] Figure 1. Schematic diagram of three basic units of graphene oxide (GO) based supercapacitors

a) two rGO layers with a spacing of 8;

b) two GO layers with a spacing of 8;

c) a GO layer and an rGO layer with a pitch of 8;

d) a 3D schematic of the model in (a);

figure 2. Molecular structure and atomic density

a) applying an external field of 3 V 1 in the Z direction, limiting the structure in which water molecules between the two rGO layers are polarized;

b) applying an external field of 4 V 1 in the Z direction, limiting the structure in which water molecules between the two GO layers are polarized;

c) applying an external field of 7 V 1 in the Z direction, limiting the structure in which water molecules between the GO layer and the rGO layer are polarized;

d) the atomic density distribution between the corresponding two rGO layers after applying an external field of 3 V 1 in the Z direction;

e) the atomic density distribution between the corresponding two GO layers after applying an external field of 4 V 1 in the Z direction;

f) the atomic density distribution between the corresponding GO layer and the rGO layer after applying an external field of 7 V 1 in the Z direction;

Third, Science Advances: Using a disordered sodium vacancy to construct a high-rate sodium ion battery cathode material

Recently, Dr. Guo Yuguo, a researcher at the Institute of Chemistry of the Chinese Academy of Sciences, and Gu Lin, a researcher at the Institute of Physics of the Chinese Academy of Sciences (co-author), selected a typical P2-Na2/3Ni1/3Mn2/3O2 (P2-NaNM) material as a model research system. The structure modulation strategy designed a P2-Na2/3Ni1/3Mn1/3Ti1/3O2 (P2-NaNMT) cathode material with completely disordered sodium vacancies. The assembly of sodium ion battery test shows that the sodium vacancy disorder completely eliminates the voltage platform caused by the orderly rearrangement of sodium vacancies. The whole electrochemical process is completely slope-type solid solution reaction, which greatly improves the P2 type positive electrode at high magnification. Battery performance. The first-principles density functional theory calculations show that the introduction of titanium reduces the potential difference between Nae and Naf, and significantly improves the diffusion properties of sodium ions between transition metal layers. This was further verified by constant current intermittent titration combined with first-principles molecular dynamics simulation (sodium ion diffusion coefficient in the order of 10-10 cm2 s-1, diffusion activation energy 170 meV). The work was recently published in the journal Science Advances under the title "Na+/vacancy disordering promises high-rate Na-ion batteries".

[Graphic introduction]

Figure 1 Crystal structure of P2-NaNM and P2-NaNMT

(A) XRD refinement spectra of P2-NaNM and (B) P2-NaNMT.

(C) Schematic diagram of the crystal structure of P2-NaNMT.

(D, E) P2-NaNMT in [010] Axis ABF-STEM and HAADF-STEM images.

(F, G) P2-NaNMT ABF-STEM and HAADF-STEM images of the [001] ribbon.

(H) TEM-EDS pattern of P2-NaNMT.

Figure 2 Electrochemical performance of P2-NaNM and P2-NaNMT

(A) Constant current charge and discharge curves at 0.1 C for P2-NaNM and (B) P2-NaNMT.

(C) Charge-discharge curves corresponding to the number of different cycles of P2-NaNMT.

(D) Comparison of the rate performance of P2-NaNM and P2-NaNMT.

(E) Comparison of long cycle performance of P2-NaNM and P2-NaNMT at 1C.

Fourth, Angew. Chem. Int. Ed. : Solar Drive Electrochemical Co-Transition of CO2 and H2S

Recently, Academician Li Can, Academician Zong Xu (co-communication author) and postdoctoral Dr. Ma Weiguang of the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences proposed and implemented an electrochemical strategy for the synergistic conversion of H2S and CO2 into high value-added chemicals using solar energy. The strategy uses graphene-encapsulated zinc oxide as the CO2 reduction catalyst, graphene as the mediator EDTA-Fe2+ (used to capture H2S) oxidation catalyst, chemical ring reaction to decompose H2S into elemental S and protons, protons are used The CO2 electrochemical reduction produces CO reaction, and the final net result is the coordinated conversion of the quantitative chemical reaction (H2S+CO2 → CO + S+ H2O). The solar-driven electrocatalytic reaction can be carried out under near-neutral conditions using a non-precious metal inexpensive catalyst to continuously, efficiently and selectively convert CO2 and H2S to carbon monoxide and elemental sulfur, respectively. This strategy provides a green way to combine natural gas purification with economic and environmental benefits. This research has been patented and recently in the research paper entitled "Achieving Simultaneous CO2 and H2S Co nversion via a Coupled Solar-Driven Electrochemical Approach on Non-Precious-Metal Catalysts" in Angew. Chem. Int. Ed. Published on.

[Introduction to the graphic] Figure 1 Photoelectrochemical conversion process of CO2 and H2S

Schematic diagram of the reaction process of co-conversion of CO2 and H2S by photocatalysis of an inexpensive metal catalyst.

Figure 2 Structure and morphology of ZnO and ZnO@G (graphene coated ZnO) catalysts

a) XRD spectrum of ZnO and ZnO@G;

b) Raman spectra of ZnO and ZnO@G;

c) TEM image of ZnO@G;

d, e) HRTEM image of ZnO@G.

Figure 3 ZnO@G selective catalytic conversion of CO2 to CO

a) LSV curves of three catalysts in a CO2 saturated EMIM-BF4/H2O solution;

b) FECO (CO Faraday efficiency) of three catalysts at different potentials;

c) three catalysts in the range of 0.508-0.908 V overpotential TOFCO;

d) Stability of the three catalysts for the reduction of CO2 in a 0.813 V and CO2 saturated EMIM-BF4/H2O solution.

Figure 4 Electrochemical coordinated transformation process of CO2 and H2S

a) changes in the penetration of FeCl3 and EDTA-Fe3+ through the Nafion membrane over time in a H-type electrolytic cell;

b) the LSV curve of 0.1M EDTA-Fe2+ in the three-electrode system of the GCS and G/GCS electrodes;

c) the effect of different anode reactions on CO2 reduction in a two-electrode system;

d) Reaction stability of rZnO@G modified electrode in CO2 saturated EMIM-BF4/H2O solution in two-electrode system.

Figure 5 Photoelectrochemical synergistic conversion process of CO2 and H2S

a) The J-V curve of the triple junction silicon solar cell in the dark state and the simulated AM 1.5G 100 mW·cm-2 irradiation and the LSV curve of the electrocatalytic reaction of the two-electrode system. The intersection of the two curves is the reaction working point. .

b) The chronocurrent curve of the solar-driven electrochemical system under simulated solar illumination (AM 1.5 G).

5. Advanced Energy Materials: sodium ion full battery

Recently, the research team of Associate Professor Wu Xinglong from the School of Chemistry of Northeast Normal University has designed and successfully achieved the excellent low temperature performance of sodium ion full battery (3DSG//NVPOF) and showed an extremely long cycle life. In the developed 3DSG//NVPOF sodium ion full battery, the positive electrode is the high voltage, long-life Na3V2(PO4)2O2F (NVPOF, Adv. Mater. 2017, 29 (33), 1701968) material recently reported by the research group. The negative electrode is a newly prepared three-dimensional self-supporting selenium/graphene (3DSG) nanocomposite. Electrochemical test results show that the 3DSG//NVPOF can achieve higher energy storage density (about 313 Wh/kg, calculated from the total mass of the positive/negative active material), as well as excellent low temperature and long cycle life ( The capacity retention rate after 85,000 cycles is 86.3 %) and excellent rate performance. In addition, the authors also studied the Na+ deintercalation process kinetics and the contribution of tantalum capacitance of the 3DSG negative electrode in the 3DSG//NVPOF full cell. The paper was published in the recent internationally renowned journal of Materials, Advanced Energy Materials (Impact Factor: 16.721).

Figure 1 shows the results of sodium storage performance of a half-cell of a 3DSG nanocomposite anode material developed for the assembly of a sodium ion full cell. The three-dimensional self-supporting conductive network constructed by reduced graphene oxide (rGO) can not only realize the efficient and rapid transmission of electrons and sodium ions, but also serve as an effective buffer structure in the continuous sodium/de-sodium process, alleviating the corresponding The volume changes to maintain the structural stability of the electrode as a whole. When used as a negative electrode material for SIBs, it exhibits high specific capacity and ultra high rate performance. For example, at a current density of 0.05 A/g, the sodium storage capacity can reach 499 mA h/g; when the current density increases by 20 A/g, the capacity value of 202 mA h/g can still be maintained. At the same time, the 3DSG anode also exhibits excellent cycle and low temperature performance, laying the foundation for the development of low temperature and long life sodium ion full battery.

Figure 1.3 Electrochemical performance of a half-cell when a DSG nanocomposite is used as a negative electrode for SIBs. (a) cyclic voltammetry; (b) ratio performance comparison; (c) charge and discharge curves at different current densities; (d) capacity retention as a function of current density and temperature; (e) power at different temperatures Relationship between energy density and (f) cycle stability of the electrode at different temperatures (current density 2 A/g). (g) Schematic diagram of the transmission pathways of Na+ and e- in the 3DSG electrode.

Based on the excellent half-cell performance of the above 3DSG negative electrode, it is further matched with NVPOF, and a 3DSG//NVPOF sodium ion full battery is assembled. The schematic diagram of the working principle is shown in Fig. 2a. Figures 2b and 2c show the change of the charge-discharge curve and the specific capacity (the specific capacity value is calculated based on the mass of the positive electrode active material) of the obtained sodium ion full battery at different current densities, respectively. It can be seen that at a low current density of 0.02 A/g, 3DSG//NVPOF can store a specific capacity of 128.1 mAh/g; when the current density is gradually increased to 2 A/g or 4 A/g, The specific capacity is still up to 83.1 or 72.7 mA h/g. The current density is 2 A/g. For example, compared with 0.02 A/g, although the current density is increased by 100 times, the capacity loss rate is only 35.1%. It shows that the assembled 3DSG//NVPOF full battery has excellent rate performance. As shown in Fig. 2d, the calculated energy density and power density of the electrode material are higher than most of the sodium ion full cells reported so far. In addition, the 3DSG//NVPOF full battery also exhibits exceptionally long cycle stability. For example, after 15,000 cycles at room temperature and a current density of 1 A/g, the capacity retention rate is still as high as 86.3%.

Figure 2.3 Energy storage performance of DSG//NVPOF sodium ion battery at room temperature: (a) Schematic diagram of operation; (b) charge and discharge curve and (c) rate performance at different current densities; illustration in Figure c : A single soft pack battery illuminates the display of 47 green LED bulbs; (d) the correlation between power density and energy density, and its comparison with the work reported in the literature; and (e) cycle performance .

Figure 3.3 Low-temperature energy storage performance of DSG//NVPOF sodium ion battery: (a) capacity retention rate as a function of current density and temperature; (b) relationship between power density and energy density at different temperatures and (c) Circulation stability

Six, Adv. Mater. Electrocatalytic hydrogen evolution of graphene carbon-based materials

Recently, a researcher at the Strong Magnetic Field Science Center of the Chinese Academy of Sciences, Professor Chen Ganwang of the National University of Science and Technology of Hefei, China, and the Institute of Chemistry and Materials Science of the University of Science and Technology of China, a metal-organic framework material doped with precious metals, as a precursor, one-step calcination A nitrogen-doped graphene-like layer-coated samarium-cobalt core-shell structure material was prepared, which showed high activity and high stability in the hydrogen evolution reaction of acidic electrolyte. Relevant research results were published in Advanced Materials, and Ph.D. students Jiang Peng, Chen Jitang and Wang Changlai were the co-first authors of the paper.

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