Lithium-sulfur battery cathode material based on cluster-like molecules

introduction

At present, lithium-ion batteries are widely used in various portable electronic devices and electric vehicles , but with the continuous development of these devices, lithium-ion batteries are gradually unable to meet the needs of social development. In order to further expand the application prospects of lithium-ion batteries, batteries of various systems have attracted the attention of researchers. Among them, lithium-sulfur batteries have received increasing attention. The lithium-sulfur battery is a lithium battery in which a sulfur element is used as a positive electrode material of a battery and lithium metal is used as a negative electrode material. Elemental sulfur is abundant in the earth and has the characteristics of low price and environmental friendliness. Lithium-sulfur batteries using sulfur as a positive electrode material have higher theoretical theoretical specific capacity and battery theoretical energy, reaching 1675m Ah/g and 2600Wh/kg, respectively, which is almost the theoretical ratio of traditional cathode materials such as transition metal oxides and phosphate materials. 10 times the capacity; in addition, sulfur has also inexpensive, environmentally friendly, etc., is a very promising lithium battery.

Summary of results

Recently, Professor Dong Quanfeng from the College of Chemistry and Chemical Engineering of Xiamen University and Prof. Leroy Cronin from the University of Glasgow in the UK have made new progress in the research of lithium-sulfur batteries. The related results are “Strategies to Explore and Develop Reversible Redox Reactions of Li-S in Electrode Architectures using The issue of Silver-Polyoxome talate Clusters was published on JACS (DOI: 10.1021/jacs.8b0041). Prior to this, Professor Dong Quanfeng's research group conducted a systematic study on lithium-sulfur battery sulfur composite cathode materials. In the early stage, the in-situ Raman technique was combined with theoretical calculations to investigate the reaction mechanism of lithium-sulfur batteries. It was confirmed that the nitrogen-doped modification of the sulfur-carrying matrix material can achieve the complete charge-discharge cycle of elemental sulfur as the positive electrode active material (Chem. Mater., 2015, 27, 2048? 2055); for the first time, the synergistic catalytic effect of Co-N was successfully applied to the redox process of S, and the concept of “multi-functional, dual-catalysis” was proposed (EES, 2016, 9, 1998-2004); On the basis of increasing the sulfur content of the composite positive electrode material, the group first prepared non-carbon mesoporous Co4N microspheres to achieve a sulfur loading of up to 95% (ACS Nano, 2017, 11, 6031-6039).

Transition metal polyacid oxides (POMs) are a class of molecular cluster materials with nanometer size and have the characteristics of reversible multi-electron reaction. They are called “electron sponges” because they can reversibly store ions and electrons. It has the feasibility of having an energy storage material with a higher specific capacity. For the first time, this study used polyoxometallate clusters as the cathode matrix material for lithium-sulfur batteries. This material (K3[H3AgIPW11O39]) has both Lewis acid and Lewis base sites, and thus has the function of adsorbing polysulfides at two sites. Efficient regulation of the electrochemical reaction process of sulfur can be achieved. The experimental results and DFT theoretical calculations show that the heterometallic ions of Ag(I) can regulate the adsorption of polysulfides in the whole system and the adsorption of lithium ions by the terminal oxygen atoms in the framework structure of polyanions. A lithium-sulfur battery prepared by using it as a skeleton material exhibits excellent electrochemical performance.

Graphic guide

figure 1. Schematic diagram of Li2S generated by POMs absorbing lithium-sulfur battery system

figure 2. The optimized structure of the calculated Gibbs free energy difference (ΔGads) and Li2Sn (n=8, 6, 4) and PW12O40 and K3[H3AgIPW11O39] clusters

image 3. Raman spectra and optical photographs of A, B, C, D, and E

A: a blank solution of DME/DOXL;

B: DME/DOXL solution of Li2S6;

C: DME/DOXL solution of Li2S6 and superconducting carbon black;

D: DME/DOXL solution of Li2S6 and PW12O40;

E: DME/DOXL solution of Li2S6 and AgIPW11O39.

Figure 4. Electrochemical Characterization of AgPW11/S Electrode

A): AgPW11/S electrode discharge-charge curve at different rates;

B): AgPW11/S, K3PW12O40/S and superconducting carbon black/S electrode lithium-sulfur batteries are tested at a battery cycle rate of 1C;

C): AgPW11/S electrode and superconducting carbon black/S for a long time battery cycle at a rate of 2C.

summary

Compared with other non-carbon lithium-sulfur battery positive carrier materials, POMs molecular clusters have the characteristics of simple preparation, low price, environmental friendliness and various kinds. At the same time, POMs materials are still a new type of energy storage materials.

Corresponding author profile

Dong Quanfeng, professor and doctoral tutor at Xiamen University. After graduating from the Department of Chemistry of Wuhan University, he went to the Israel Institute of Technology to do postdoctoral research. After returning to China in 2001, he worked at Xiamen University, member of the International Electrochemical Society (ISE), and member of the American Electrochemical Society (ECS). He has been working on new types of chemical power sources and energy storage materials for a long time. In recent years, Professor Dong Quanfeng has systematically studied the cathode materials of lithium-sulfur batteries. The related results have been published many times in Chemistry of Materials, Energy & Enviralmental Science, ACS Nano, Journal of In the well-known journals such as the American Chemical Society. He is currently chairing the National Natural Science Foundation, the “973” subproject, and the construction of the Fujian Chemical Power Technology Innovation Platform.