CR1216 battery.Energy Institute has made progress in the research and development of polymer electrolyte materials for power lithium batteries

As global energy shortages and environmental pollution continue to intensify, vigorously developing new near-zero-emission vehicles represented by pure electric vehicles is one of the country's development strategies. Efficient, safe and reliable power batteries are the constraints of the new near-zero-emission automobile industry... Keywords: environmental pollution, pure electric vehicles, zero-emission vehicles, Chinese Academy of Sciences, Qingdao Institute of Bioenergy and Processes.

As global energy shortages and environmental pollution continue to intensify, vigorously developing new near-zero-emission vehicles represented by pure electric vehicles is one of the country's development strategies. Efficient, safe and reliable power batteries are the bottleneck restricting the new near-zero emission automobile industry and one of the shortcomings of new energy vehicles. The biggest potential safety hazard of current power batteries is battery thermal runaway. Qingdao Institute of Bioenergy and Processes, Chinese Academy of Sciences, and Qingdao Energy Storage Industry Technology Research Institute have made progress in developing high-security power battery polymer electrolyte material systems to solve this safety problem. progress and is rapidly advancing its industrialization process.

The existing lithium-ion battery liquid electrolyte system cannot meet the various requirements of power batteries for high energy, high power and safety. The R&D team of Qingdao Energy Storage Industry Technology Research Institute proposed a research and development idea that combines rigidity and softness, and developed a series of new polymer electrolyte systems, which effectively solved the above bottleneck problem and greatly improved the safety performance. Combining rigidity and softness means using rigid skeleton materials, such as polyimide, aramid, polyarylsulfone amide, glass fiber and cellulose (NanoEnergy, 2014, 10, 277-287 Solid State Ionics, 2013, 245-246, 49-55; 232 ,44-48Journal of the Electrochemical Society,2013,161,A1032-A1038Progress in PolymerScience,2015,43,136-164) non-woven materials to improve the mechanical properties and dimensional thermal stability of the battery; use flexible ion transport materials, such as polyethylene oxide (PEO) , polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polymethyl methacrylate (PMMA), cyanoacrylate and polypropylene carbonate (PPC), etc., which provide excellent ionic conductivity and interface stability. Combination refers to the combination of two or more materials to achieve a win-win effect and achieve a substantial improvement in overall performance, thus meeting the requirements of power batteries.

Respecting nature and cherishing things, and adopting natural methods, this research explores a composite polymer electrolyte system that combines rigidity and softness to achieve the unity of rigidity and softness to achieve comprehensive properties such as mechanical strength, heat resistance, potential window, interface stability, and ionic conductivity. improvement. Figure 1 is the design concept of a gel polymer electrolyte that is both rigid and flexible.

Although the traditional vinylidene fluoride system has the advantages of high stability and high potential window, its ionic conductivity is low, and its mechanical strength and thermal stability in the wet state are very poor. In order to improve the traditional vinylidene fluoride system, Based on the properties of the gel polymer electrolyte, the research team used it to combine it with non-woven materials such as polyimide and polysulfone amide at the nanoscale to combine rigidity and softness into one integrated body to improve the dimensional thermal stability and mechanical strength to achieve its Improvement of comprehensive performance (Journal of the Electrochemical Society, 2013, 160, A769-A774 Macromolecular Materials and Engineering, 2013, 298, 806-813; ACS Appl. Mater. Interfaces, 2013, 5, 128-134); Aiming at the problem of low lithium ion migration coefficient, a new type of single ion was developed Polymer lithium borate is used as a surface reinforcement material (CoordinationChemistryReviews, 2015, 292, 56-73; Journal of Materials ChemistryA, 2015, 3, 7773-7779) to improve its ion migration number and compatibility, and combine rigidity and softness to enhance the comprehensive battery system performance.

The traditional polyacrylonitrile polymer electrolyte has the advantage of high ionic conductivity, but its physical properties are brittle and its processing performance is not good. The R&D team used a new polymer electrolyte matrix (ACSAppl.Mater.Interfaces, 2015, 7, 4720- 4727; Electrochim.Acta2015,157,191-198; Electrochem.Comm.DOI:10.1016/j.elecom.2015.10.009), combined with the design concept of rigidity and softness, has achieved an improvement in the overall performance of nitrile-based polymer electrolytes such as processing performance .

Gel-based polymer batteries have played an important role in improving the safety of power batteries, but they still use a small amount of carbonate solvents that are easily volatile and flammable, and there are still certain safety hazards when used under high temperatures or extreme conditions, making it difficult to It fully meets the stringent requirements of electric vehicles for power lithium batteries in terms of high energy and safety performance. Therefore, the development of new high-safety all-solid-state electrolyte systems is of great significance to improving the comprehensive performance of high-energy-density power lithium batteries.

In view of the lower potential window and poor dimensional thermal stability and mechanical strength of the traditional PEO system, the researchers used high-potential cyanoacrylate as the material to increase the potential window; at the same time, they used thermosetting cellulose non-woven membrane as Rigid skeleton, providing dimensional thermal stability and partially improving mechanical strength, a highly safe all-solid polymer electrolyte with high mechanical strength, wide electrochemical window and good dimensional thermal stability was developed. Relevant research results were published in international journals ( Scientific Reports, 2014, 4, 6272). In response to the bottleneck problem of PEO's low room temperature ion conductivity, researchers based on the scientific problem itself, starting from the molecular structure that affects ion conductivity, combined with the multi-scale mechanism of ion transport mechanism and dynamic transport, designed an amorphous Polycarbonate-based room temperature all-solid polymer electrolyte. After characterization, it was found that the room temperature conductivity of this all-solid polymer electrolyte can reach the order of 10-4S/cm, the electrochemical window is 4.6V, the rate performance is good, and the room temperature long cycle is 1000 The circle capacity retention rate is 90%. Relevant research results were published in international journals (Advanced Energy Materials, DOI: 10.1002/aenm.201501082).