Solid electrolyte, preparation method and application thereof, and lithium battery using solid electrolyte

Abstract

The invention discloses a solid electrolyte and a preparation method thereof. The solid electrolyte is prepared by uniformly mixing 30-97mass% of a polyphenylene high-molecular organic polymer, 3-70mass% of a lithium salt and 0-20mass% of a surfactant. The conductive performance and the mechanical performances of the solid electrolyte are comprehensively improved, so the solid electrolyte has a very high conductivity in a large temperature range. The solid electrolyte provided by the invention can substitute original isolation films and liquid electrolytes in original lithium batteries, or original gel electrolytes.

Description

technical field [0001] The invention relates to the technical field of solid-state electrolytes for lithium-ion batteries, in particular to a solid-state electrolyte, a preparation method for the solid-state electrolyte, an application of the solid-state electrolyte, and a lithium battery using the solid-state electrolyte. Background technique [0002] Lithium-ion batteries have been widely used due to their high energy density, long cycle life, high open circuit voltage, no memory effect, safety and no pollution. [0003] The internal structure of commercially available lithium-ion batteries generally includes: a positive electrode and a negative electrode, a liquid electrolyte containing lithium salts, and an ion-exchange membrane separating the positive and negative electrodes. As we all know, the existence of a large amount of organic liquid electrolyte not only increases the risk of battery leakage, but also accelerates the rate of thermal runaway of the battery under a...

AI Technical Summary

Problems solved by technology

Gel-type electrolyte has high conductivity, but lacks mechanical strength, is almost liquid, and the processing method is relatively complicated

[0007] Solid polymer electrolytes, such as thin films formed by complexation between lithium salts and linear polyethers such as polyethylene oxide and polypropylene oxide, although possessing certain remarkable features such as high electrochemical and chemical stability characteristics and the characteristics of being easy to make thin films, etc., but because the solid polymer electrolyte formed by polymer and lithium salt has a high crystallization phase at room temperature, the formed electrolyte can only be used at high temperature, and, at room temperature The electrical conductivity is very poor, and its material itself does not have safety properties such as flame retardant and flame retardant, which limits its application range

For example, US20130063092A1 and CN103026542A disclose a high-temperature lithium battery with a solid polymer electrolyte. The technical solution is proposed for the reduction of the mechanical properties of the previous solid electrolyte at high temperatures, and there is no substantial improvement in the electrical conductivity.

Specifically, it describes copolymerized polymers whose molecular structure is It is formed by chemical reaction and copolymerization of two or more repeating units (monomers) of a and b, and each molecular chain forms a heterogeneous structure, that is, some units provide mechanical strength, and some units provide ion conductivity; first, its molecular structure Part of the repeating unit (PEO part) in the PEO is a low mechanical strength unit. Although the mechanical strength of the conventional PEO solid electrolyte has been improved, it is still not enough for production; second, its conductive principle is similar to that of many patents or published Similar to substances, they are complexed with polyethylene oxide (PEO) and salts, and guide the movement of ions through the mobility brought by the amorphous state of polyethylene oxide at high temperature, that is, through the molecular chain movement to form ions Conductivity

Third, it can be seen from the graph of the relationship between conductivity and temperature in Figure 6 disclosed by CN103026542A that the conductivity of its solid electrolyte at 90°C to 120°C ranges from 1×10 -3 S / cm gradually increased to 2×10 -3 S / cm, so in fact it must work normally under high temperature conditions; fourth, the polyethylene oxide (PEO) in its copolymer compound is combustible in the air, making it possess greater risk

Its disadvantages are (1) at low temperature, the performance of lithium ion conduction will drop sharply, so that the battery will no longer work; (2) the main chain of lithium conducting siloxane polymer is Si-O interphase, and the branched chain The essence is still ethylene oxide-[CH 2 -CH 2 -O] n -

Due to the relatively high mass ratio of vulcanized glass powder, the mass ratio of the second group of polymers that provide mechanical strength is relatively small, so its mechanical properties are not high; all the examples in the technical scheme use small molecule polymers and salt solutions Solidification after adding powder, the solid itself formed by small molecule polymer has poor mechanical properties

In addition, the high cost of ionic glass will lead to high processing costs

[0010] In the prior art, there is also a method of improving polymer electrolytes by combining solid-liquid two phases, adding plasticizers to polymers to form similar "wet" polymers or gel electrolytes, which can improve electrical conductivity at low temperatures However, it will lead to the loss of mechanical characteristics, and cannot guarantee the processing and reliability of the battery

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