A kind of polymer electrolyte and its preparation method and application

Abstract

The invention discloses a polymer electrolyte and a preparation method and application thereof, wherein the polymer electrolyte comprises a polymer matrix, and the polymer matrix is ​​composed of three blocks of acryl, urethane and phosphate. The polymer formed by the self-polymerization of the polymerized monomer, or the polymer formed by the copolymerization of the polymerized monomer composed of the three building blocks of acryl, urethane and phosphate ester and other monomers. The polymer electrolyte can be used in a battery, and the polymer matrix can undergo a self-crosslinking reaction at a high temperature of 130-190° C. to generate a dense thermosetting polymer that can cut off ion transport and prevent the occurrence of thermal runaway of the battery; and The self-crosslinking reaction is an endothermic reaction, which helps to quickly reduce the battery temperature and prevent the battery from thermal runaway; the polymer electrolyte can also capture free radicals and has intrinsic flame retardancy; the above characteristics of the polymer matrix act synergistically , which can effectively prevent the occurrence of thermal runaway of the battery.

Description

technical field [0001] The invention relates to the technical field of battery electrolytes, in particular to a polymer electrolyte and a preparation method and application thereof. Background technique [0002] Secondary lithium-ion batteries have the advantages of high energy density, long cycle life, and no memory effect, and have been widely used in 3C electronic products, electric vehicles and other fields. However, volatile and flammable organic carbonate liquid electrolytes are commonly used in commercial lithium batteries, which can easily lead to safety hazards such as fire and explosion. In order to improve the safety of the battery, the researchers proposed a series of optimization measures, including changing the electrolyte solvent, designing high-concentration salt electrolytes, and using inorganic solid-state electrolytes or polymer electrolytes. Among them, the use of polymer electrolytes instead of liquid electrolytes is an effective method. Compared with ...

AI Technical Summary

Problems solved by technology

As mentioned above, although these polyphosphate-based electrolytes are flame retardant, they still cannot completely avoid the occurrence of thermal runaway of high-energy-density lithium batteries under abusive conditions (such as short circuit, extrusion, needle sticking, etc.)

For example, CN107863555B and CN107819151B respectively disclose a non-combustible solid electrolyte containing polyphosphate polymer and composite solid electrolyte, but the polymer electrolyte does not have the ability of secondary cross-linking at high temperature, so it is difficult to reduce the high-energy lithium battery (such as NCM811 / Li metal battery) the risk of thermal runaway due to short circuit under acupuncture and extrusion conditions; A non-flammable polymer electrolyte prepared by in-situ curing of the electrolyte precursor solution, but the electrolyte has a low room temperature ionic conductivity (1.3×10-4~4.5×10-4Scm-1) and a narrow potential window (4~5V ), it is difficult to meet the needs of high energy density lithium batteries

Moreover, this method of preparing polymer electrolytes by ring-opening polymerization of terminal epoxy groups in situ suffers from the drawbacks of low molecular weight and low monomer conversion

Furthermore, although this polymer electrolyte improves the flame retardancy of the battery to a certain extent, it does not have the ability of secondary crosslinking at high temperature to cause the battery to self-shut down; CN111499873A discloses a polyphosphoric acid-based polymer and its preparation method and application

Although the polymer-based electrolyte has a certain flame retardancy, it also does not have the ability of high-temperature secondary crosslinking to cause battery self-shutdown at high temperatures, so it cannot meet the safety requirements of high specific energy lithium batteries; CN111620974A discloses a A phosphorus-containing polyester electrolyte for high-voltage lithium-ion batteries, but its polymer matrix does not have the reactivity of high-temperature secondary crosslinking to cause battery self-shutdown, so it cannot ensure the safety of batteries under abuse conditions; CN110247111A and CN111253523A In situ polymerizable polyphosphate-based polymer electrolytes were disclosed

Although these two electrolytes are non-flammable and have excellent electrochemical properties, they also do not have the ability to self-shutdown the battery due to secondary cross-linking at high temperatures, so they cannot meet the safety requirements of the battery under abuse conditions.

Images