Research results of lithium battery materials from Professor Wang Yong's research group of the School of Environmental Chemistry

　　As a high-performance energy storage device, lithium-ion batteries have been widely used in various mobile power sources and other renewable clean energy carriers, and a new generation of lithium-ion batteries with high energy density and power density has attracted increasing attention. In order to further improve the performance of lithium-ion batteries, Professor Yong Wang and Associate Professor Sun Weiwei's research group conducted research on the application of environmentally friendly and renewable organic electrode materials to lithium-ion batteries.

　　The latest research results of Professor Wang Yong's research group in the field of organic electrode materials for lithium-ion batteries.

　　Lithium-ion batteries, as a high-performance energy storage device, have been widely used in various mobile power sources and other renewable clean energy carriers. A new generation of lithium-ion batteries with high energy density and power density has attracted increasing attention. In order to further improve the performance of lithium-ion batteries, Professor Yong Wang and Associate Professor Sun Weiwei’s research group carried out research on the application of environmentally friendly and renewable organic electrode materials in lithium-ion batteries, and constructed a two-dimensional co-existence with a few layers through molecular-level design. Conjugated covalent organic frame electrode materials greatly improve the lithium storage performance of organic electrodes, and the reversible lithium storage capacity can be as high as 1500mAh/g, which is not inferior to high-capacity inorganic electrode materials. This research result has realized the full excitation and utilization of the active lithium storage sites between the layers or inside the organic framework material structure, thus obtaining the organic electrode material of lithium ion battery with ultra-high reversible lithium storage capacity and excellent cycle stability. At the same time, through the in-depth study of the staged lithium storage mechanism, it provides a certain theoretical support and guidance for the design, synthesis, derivative modification and further application of organic frame electrode materials.

　　The next generation of lithium batteries for electric vehicles and mobile phones will choose all-solid-state lithium-ion batteries with higher energy density and better safety. In order to accelerate the research and development of new materials and all-solid-state lithium-ion batteries, our country established the “Material Genome Technology” national key research and development plan for the first time during the “Thirteenth Five-Year Plan” period, and hopes to pass the high-throughput calculation, synthesis, detection and database of the material genome ( Big data machine learning and intelligent analysis) new concepts and new technologies to accelerate the research and development of all-solid-state lithium-ion batteries, and set up a national key special project of “All-solid-state battery research and development based on material genome technology”, which is sponsored by Peking University Shenzhen Graduate School As the chief scientist, Professor Pan Feng of the School of New Materials took the lead in organizing the joint responsibility of 11 units.

　　An important part of the research and development of the project includes the research and development of new solid electrolytes and the control of each interface of solid battery materials. Solid electrolytes are mainly divided into inorganic solid electrolytes, solid polymer electrolytes and composite solid electrolytes. Traditional solid polymer electrolytes have low conductivity near normal temperature and a narrow potential window, while inorganic solid electrolytes have poor flexibility and large interface impedance. As a combination of the two, the composite solid electrolyte not only has flexibility, but also has good electrical conductivity at relatively low temperatures, and has broad research prospects.

　　The three components play their own roles. The inorganic solid electrolyte provides a channel for lithium ions, and can also make the composite solid electrolyte have higher mechanical strength; the organic macromolecule PEO can not only conduct lithium ions, but also act as a bonding ceramic The role of particles; the organic small molecule BPEG first reduces the crystallinity of PEO, and secondly changes the hard contact between the solid-solid interface into a soft contact, which can make the deposition and extraction of lithium on the metal lithium more uniform. By having the above characteristics, the electrolyte can well physically and chemically block the generation of lithium dendrites. In addition, the composite solid electrolyte was electrochemically tested at 60 degrees Celsius using the lithium iron phosphate and metal lithium of the solid battery as the positive and negative electrodes. The specific capacity was 158mAhg-1 at a rate of 0.1C and a specific capacity of 158mAhg-1 at a rate of 2C. Specific capacity of 94mAhg-1. This research has important guiding value for the study of solid electrolytes.

　　The research results were published in the recent top international journals of materials and energy. The work was supervised by Professor Pan Feng and completed by postdoctoral fellow Yang Luyi as the first author and the team. This work was supported by the National Material Gene Key Special Project and the Guangdong Provincial Innovation Team.

　　Polaris Energy Storage Network News: Recently, the research group of Professor Xia Yongyao from the Department of Chemistry and New Energy Research Institute of Fudan University proposed a new type of lithium ion (sodium ion) battery system for the first time. /Sodium ion aqueous solution, the negative electrode adopts a solid organic polymer, the electrolyte adopts an aqueous solution of lithium nitrate or lithium sulfate, and the polymer ion exchange membrane is used as a separator to separate the liquid positive electrode from the solid negative electrode.

　　According to the introduction, the working principle of the traditional lithium battery is based on the intercalation/deintercalation of lithium ions in the positive and negative electrodes, also known as "rocking chair batteries." The working principle of the new battery is similar to that of the traditional lithium ion battery: the positive electrode reaction is based on the redox of the I3-/I- pair in the solution, the negative electrode reaction is based on the reversible enolization reaction of the carbonyl group on the polyimide, and the lithium ion/sodium ion polymer The exchange membrane is a battery diaphragm, which is accompanied by the migration of lithium ions Li+ (or sodium ions Na+) between the positive and negative electrodes during charging and discharging. Compared with the limited cycle life and power density of traditional batteries, the positive and negative electrode reactions of the battery in this system do not involve the diffusion of ions in the solid material and the volume of the electrode material during the charge and discharge process caused by it. The high energy density of the battery and the long cycle life of the capacitor are effectively combined with the high power density. Experiments have shown that both the positive and negative materials exhibit faster electrode reaction kinetics, making the battery exhibit high-power performance similar to capacitors. The battery is charged and discharged between the voltage window of 0~1.6V and can be cycled up to 50,000 times, which far exceeds the cycle life of traditional rechargeable batteries (<10,000 times).

　　Compared with the existing secondary batteries and flow batteries using metal oxide electrode materials or organic electrolyte solutions, all components in this new type of lithium ion (sodium ion) battery system (including aqueous electrolyte and electrode material polyamide) Both imine and iodine-based active substances) are environmentally friendly and pollution-free. Moreover, the electrode reaction in the battery system does not involve the oxidation-reduction of metal elements, which also greatly reduces the manufacturing cost of the battery. The battery has excellent performance such as high energy density, high power density, long cycle life, high safety, and low cost. It is expected to be used in wind power, solar power and other energy storage, smart grid peak and valley load regulation in the future.