CN-122025790-A - Modified relaxor ferroelectric polymer, modified semi-solid electrolyte, preparation method and application thereof, and battery

CN122025790ACN 122025790 ACN122025790 ACN 122025790ACN-122025790-A

Abstract

The invention belongs to the field of semi-solid batteries, and in particular relates to a modified relaxor ferroelectric polymer, a modified semi-solid electrolyte, a preparation method, application and a battery thereof, wherein the preparation method of the modified relaxor ferroelectric polymer comprises the steps of pre-dehalogenating the relaxor ferroelectric polymer to be modified to prepare a polymer modified intermediate with double bonds modified on polymer chains, and then polymerizing the polymer modified intermediate and a modifier to prepare the modified relaxor ferroelectric polymer, wherein the modifier comprises the following components in formula 1# ). The invention innovatively carries out dehalogenation treatment on the relaxation polymer, and then innovatively combines with the formula 1 for polymerization, so that the polymerization behavior and the polymerization structure can be regulated and controlled, the application requirements of the semi-solid electrolyte can be accidentally adapted, the fluidity of the electrolyte can be effectively restrained, the electrochemical window of the liquid electrolyte is improved, the growth of lithium dendrites on the negative electrode side is inhibited, and the high-pressure resistance, the high-temperature resistance stability and the long-cycle performance of the semi-solid polymer electrolyte are further improved.

Inventors

WEI WEIFENG
Yan Kunyun
HUANG XIAOWEI
ZHANG CHUNXIAO

Assignees

中南大学
江西赣锋锂电科技股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260325

Claims (10)

1. A preparation method of a modified relaxor ferroelectric polymer is characterized in that the relaxor ferroelectric polymer to be modified is subjected to dehalogenation treatment in advance to prepare a polymer modified intermediate with double bonds modified on polymer chains, and then the polymer modified intermediate and a modifier are polymerized to prepare the modified relaxor ferroelectric polymer; the modifier comprises formula 1; Formula 1.
2. The method of preparing a modified relaxor ferroelectric polymer as claimed in claim 1, wherein the relaxor ferroelectric polymer to be modified comprises at least one of PVDF-TrFE-CTFE, PVDF-TrFE-CFE, PVDF-CFE-DB, PVDF-CTFE-DB; the modifier also comprises at least one of the formulas 2 and 3; The method comprises the steps of (2), Formula 3; preferably, the content of formula 1 in the modifier is above 60 wt.%.
3. The method for preparing a modified relaxor ferroelectric polymer as claimed in claim 1, wherein the dehalogenation treatment comprises the steps of heat-treating the relaxor ferroelectric polymer to be modified in an alkali solution; The alkali liquor is a solution in which alkaline components are dissolved; preferably, the alkaline component comprises at least one of an organic base and an inorganic base; preferably, the solvent in the solution in which the alkaline component is dissolved includes at least one of THF, DMF, acetonitrile, NMP, DMAc; preferably, the weight ratio of the relaxor ferroelectric polymer to be modified to the alkaline component is 1:0.1-1; Preferably, the temperature of the heat treatment is reflux; preferably, the heat treatment time is more than 5 hours, preferably 5-48 hours.
4. The method for preparing a modified relaxor ferroelectric polymer as claimed in claim 1, wherein the weight ratio of the polymer modification intermediate to the modifier is 1:1 to 10, preferably 1:3 to 6, further 1:3.5 to 4.5; Preferably, a free radical initiator is further added into the polymerization system, and the free radical initiator comprises at least one of a photo free radical initiator and a thermal free radical initiator; Preferably, the free radical initiator is 0.1-1% of the total weight of the polymer intermediate and the modifier of formula 1.
5. A modified relaxor ferroelectric polymer produced by the production method as claimed in any one of claims 1 to 4.
6. Use of the modified relaxor ferroelectric polymer produced by the production method as claimed in any one of claims 1 to 4, for producing a semi-solid electrolyte; Preferably, it is used to prepare a semi-solid lithium secondary battery.
7. A modified semi-solid electrolyte comprises a polymer skeleton and electrolyte, and is characterized in that the polymer skeleton is a modified relaxor ferroelectric polymer prepared by the preparation method according to any one of claims 1-4; Preferably, the electrolyte comprises an organic solvent and a conductive metal salt; preferably, the organic solvent comprises at least one of an ester solvent, an ether solvent, a carbonate solvent, and an aromatic hydrocarbon solvent; preferably, the conductive metal salt comprises at least one of a single conductive lithium salt, a conductive sodium salt, a conductive potassium salt; preferably, the concentration of the conductive metal salt in the electrolyte is 0.8-1.5M; Preferably, the percentage of the skeleton polymer in the modified semi-solid electrolyte is 1 wt-30 wt%.
8. A method for preparing a modified semi-solid electrolyte according to claim 7, wherein the modified semi-solid electrolyte is prepared by mixing the solid polymer and the electrolyte, or by mixing the polymer modified intermediate, the modifier of formula 1 and the electrolyte and then polymerizing in situ.
9. A semi-solid polymer secondary battery comprising the modified relaxor ferroelectric polymer produced by the production method according to any one of claims 1 to 4; Preferably, the modified semi-solid electrolyte according to claim 7 or the modified semi-solid electrolyte produced by the production method according to claim 8 is contained.
10. The semi-solid polymer secondary battery according to claim 9, wherein the active material in the positive electrode of the semi-solid polymer lithium secondary battery comprises at least one of lithium-rich manganese-based material, lithium manganate, lithium iron phosphate, lithium nickel manganate, NCM622, NCM811, and the negative electrode is a lithium metal negative electrode.

Description

Modified relaxor ferroelectric polymer, modified semi-solid electrolyte, preparation method and application thereof, and battery Technical Field The invention relates to the field of lithium metal batteries, in particular to the field of semi-solid polymer electrolytes. Background The urgent need for high energy density batteries in modern society continues to drive the intensive research of battery technology. In order to obtain high energy density, lithium-enriched manganese-based cathode materials with high operating voltage and high capacity (> 250 mAh g -1), and lithium metal anodes with ultra-high specific capacity of 3830: 3860 mAh g -1 have received widespread attention. However, lithium-rich manganese-based material (LRMO) anodes suffer from inherent defects such as poor electron conductivity and lattice oxygen release, resulting in low coulombic efficiency and severe structural degradation during cycling, greatly limiting their commercial application. Meanwhile, the lithium metal anode can continuously react with the electrolyte, and the continuous growth of lithium dendrites in the cycling process can cause internal short circuit, so that serious safety risks are brought to the lithium metal battery. The gel electrolyte (semi-solid electrolyte) has a relatively wide electrochemical window and can effectively bind the liquid electrolyte, thereby remarkably improving the safety of the battery. Gel electrolytes have higher ionic conductivity and better interface contact than solid polymer electrolytes. However, its ionic conductivity and interfacial permeability remain inferior to liquid electrolytes, which still limits the achievable energy density. Contact of the gel electrolyte with the lithium metal negative electrode is also a critical issue, and poor interfacial contact may result in low discharge capacity and poor cycle retention. The prior art also discloses some gel electrolyte schemes, for example, patent document with publication number CN118213598a discloses a lithium-rich manganese-based solid-state battery, which comprises a battery cell and a solid or semi-solid electrolyte arranged in the battery cell, wherein the battery cell comprises a positive electrode, a diaphragm and a negative electrode which are sequentially compounded, the diaphragm comprises a base film and a ferroelectric polymer modified layer compounded on the surface of the base film, and the ferroelectric polymer comprises at least one of ferroelectric PVDF, ferroelectric P (VDF-TrFE), ferroelectric P (VDF-TrFE-CTFE) and ferroelectric P (VDF-HPP). Ferroelectric polymers have good modifying ability but also have inherent drawbacks such as being unfavorable for ion dissociation and migration, whereas relaxor ferroelectrics (PVTC) have a high dielectric constant, favoring lithium salt dissociation. The relaxed nano-domains are free to rotate in the electrolyte so that the positive end of the dipole can interact with the alkali metal and the negative end can bind with the higher transition metal in the cathode. This feature can effectively improve interface contact. In addition, the nano domains can promote the transmission of lithium ions across an electric double layer, thereby improving the dynamic performance of the battery. The prior art also discloses few schemes, for example, patent document with publication number of CN120149521A discloses a blended relaxor ferroelectric polymer super-ionic solid electrolyte, and preparation and application thereof, wherein the super-ionic solid electrolyte comprises a polymer matrix, lithium salt and a relaxor ferroelectric polymer, the mass ratio of the relaxor ferroelectric polymer to the polymer matrix is 1:1-20, and the lithium salt accounts for 1-80 wt% of the total weight proportion of the solid electrolyte. In summary, the prior art also discloses some schemes for modifying solid electrolyte by using a relaxor ferroelectric polymer, but mainly relates to modification of all solid electrolyte, and the prior art does not have a technical means for preparing semi-solid electrolyte by using the relaxor ferroelectric polymer as a framework so as to solve the problems of the semi-solid electrolyte. Disclosure of Invention Aiming at the technical blank that the relaxor ferroelectric polymer is taken as a semi-solid electrolyte skeleton, the first aim of the invention is to provide a preparation method of the modified relaxor ferroelectric polymer suitable for semi-solid electrolyte, and the aim is to prepare the polymer with excellent electrolyte limiting capacity, ion migration and excellent wide temperature performance. A second object of the present invention is to provide a modified relaxor ferroelectric polymer produced by the production method. A third object of the present invention is to provide a modified semi-solid electrolyte (also referred to as gel electrolyte), a method for preparing the same, and an application in a lithium secondary battery. A fourth object of the