阅读说明：本技术 一种电解质聚合物基材、固态电解质及其制备方法、锂离子电池 (Electrolyte polymer base material, solid electrolyte, preparation method of solid electrolyte and lithium ion battery ) 是由 李婷婷 刘荣华 吴金祥 单军 于 2019-08-30 设计创作，主要内容包括：本发明提供了一种电解质聚合物基材,所述电解质聚合物基材为聚合物前体经过蒽基官能团之间[4+4]环加成制备得到,所述聚合物前体为包括以下链段A、链段B和链段C的无规聚合物或嵌段聚合物：链段A选自：链段B选自：链段C选自中的一种或多种；其中,链段A中,R选自H或甲基,p选自1～220电解质聚合物基材。本发明还提供了上述电解质聚合物基材的制备方法、固态电解质及其制备方法和锂离子电池。本发明提供的电解质聚合物基材机械强度可调,具有较好的适应性。(The invention provides an electrolyte polymer base material, which is formed by a polymer precursor through [4+4] between anthracene-based functional groups]The polymer precursor is a random polymer or a block polymer comprising the following chain segment A, chain segment B and chain segment C: the segment A is selected from: segment B is selected from: the chain segment C is selected from One or more of; wherein in the chain segment A, R is selected from H or methyl, and p is selected from 1-220 electrolyte polymer base materials. The invention also provides a preparation method of the electrolyte polymer base material, a solid electrolyte, a preparation method of the solid electrolyte and a lithium ion battery. The electrolyte polymer base material provided by the invention has adjustable mechanical strength and better adaptability.)

1. An electrolyte polymer base material, wherein the electrolyte polymer base material is prepared by performing [4+4] cycloaddition between anthracene-based functional groups on a polymer precursor, and the polymer precursor is a random polymer or a block polymer comprising the following segment A, segment B and segment C:

the segment A is selected from:

segment B is selected from:

the chain segment C is selected fromOne or more of;

in the chain segment A, R is selected from H or alkyl, and p is selected from 2-40.

2. The electrolyte polymer base according to claim 1, wherein the mass ratio of the segment A, the segment B and the segment C is 50 to 90:5 to 30:5 to 25.

3. The electrolyte polymer substrate according to claim 1, wherein the reaction ratio of the anthracene-based dimer formed by the anthracene-based functional group is 60% to 80%.

4. The electrolyte polymer substrate according to claim 1, wherein the anthracene-based functional group of segment B is subjected to [4+2] cycloaddition crosslinking with a double bond on a carbocyclic ring of segment C, and the anthracene-based functional group of segment B reacts with a double bond in segment C at a ratio of 70% to 95%.

5. The electrolyte polymer substrate according to claim 1, wherein the number average molecular weight of the electrolyte polymer substrate is 1 to 30 ten thousand.

6. The method of claim 1, wherein the segment A is derived from a monomer a comprising one or more of a methoxypolyethylene glycol methacrylate monomer and a methoxypolyethylene glycol acrylate monomer.

7. The method for producing an electrolyte polymer base according to claim 1, wherein the segment B is derived from a monomer B including anthracene acrylate.

8. The method of claim 1, wherein the segment C is derived from a monomer C comprising one or more of cyclopentadiene, cyclohexadiene, and norbornadiene.

9. The method for producing the electrolyte polymer substrate according to any one of claims 1 to 8, comprising the following steps:

adding a monomer a, a monomer B, a monomer C and a catalyst into a reaction container to carry out polymerization reaction to obtain a polymer precursor with a random structure or a block structure comprising a chain segment A, a chain segment B and a chain segment C;

the segment A is selected from:

segment B is selected from:

the chain segment C is selected fromOne or more of;

in the chain segment A, R is selected from H or methyl, and p is selected from 2-40;

and (3) subjecting the polymer precursor to ultraviolet irradiation, and performing [4+4] cycloaddition on the anthracene-based functional group of the chain segment B to generate anthracene-based dimer, thereby obtaining the electrolyte polymer base material.

10. The method for producing an electrolyte polymer base material according to claim 9, wherein the anthracene-based functional group of the segment B is subjected to [4+2] cycloaddition crosslinking with a double bond on a carbon ring of the segment C by heating the electrolyte polymer base material at 80 to 100 ℃.

11. The method for producing an electrolyte polymer base material according to claim 10, wherein the [4+2] cycloaddition-crosslinked electrolyte polymer base material is heated at 120 to 150 ℃ to partially crosslink the anthryl dimer.

12. A solid electrolyte comprising a lithium salt and the electrolyte polymer substrate according to any one of claims 1 to 8.

13. The solid-state electrolyte of claim 12, wherein the lithium salt is present in an amount of 2% to 30% by weight of the electrolyte polymer substrate, and the lithium salt comprises one or more of lithium bis (trifluoromethanesulfonyl) imide, lithium bis (perfluoroethanesulfonyl) imide, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluorophosphate.

14. The solid electrolyte of claim 12, further comprising a plasticizer in an amount of 1 to 20% by mass of the electrolyte polymer substrate, wherein the plasticizer comprises one or more of ethylene carbonate, propylene carbonate, and vinylene carbonate.

15. A method for preparing a solid-state electrolyte according to any of claims 12 to 14, comprising the following steps:

adding a monomer a, a monomer B, a monomer C and a catalyst into a reaction container to carry out polymerization reaction to obtain a polymer precursor with a random structure or a block structure of a chain segment A, a chain segment B and a chain segment C;

the segment A is selected from:

segment B is selected from:

the chain segment C is selected fromOne or more of;

in the chain segment A, R is selected from H or methyl, and p is selected from 2-40;

preparing a polymer solution from a polymer precursor, lithium salt and a solvent, preparing the polymer solution into a coating, performing ultraviolet irradiation to generate [4+4] cycloaddition between anthracene-based functional groups of a chain segment B to generate anthracene-based dimer, and drying to remove the solvent to obtain the solid electrolyte.

16. A lithium ion battery comprising a positive electrode, a negative electrode, and the solid electrolyte of any one of claims 12 to 14, wherein the solid electrolyte is located between the positive electrode and the negative electrode.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to an electrolyte polymer base material, a solid electrolyte, a preparation method of the solid electrolyte and a lithium ion battery.

Background

The traditional lithium ion secondary battery adopts liquid electrolyte, so that the safety defects of easy volatilization, flammability, explosiveness and the like exist. With the increase of the demand of energy, the development of high-safety lithium ion secondary batteries is urgent. The all-solid-state polymer battery has the advantages of high stability, high safety, light weight, flexibility, customizable shape, low cost and the like, and is a solid electrolyte material with great potential. The study of ionic conductivity of polyethylene oxide (PEO) -alkali metal salt complex was first reported by Wright et al in 1973, and PEO was widely used in the study of solid electrolytes. PEO has gained wide attention because of its abundant raw materials, chemical stability, good flexibility, etc., and polyethylene glycol (PEO) -based polymer solid electrolytes have shown excellent performance, and thus have been widely studied and applied in polymer solid electrolyte systems. However, due to high crystallinity and poor mechanical properties, the solid electrolyte of the PEO matrix has the problems of low room temperature ionic conductivity, poor mechanical strength and the like in use. The poor mechanical strength makes PEO not enough to resist lithium dendrite generated in the using process of the battery, and the PEO is a significant problem influencing the performance of the battery. However, PEO has a melting point of about 70 ℃ and when used at a high temperature of 80-100 ℃, the polymer softens and the mechanical strength of the material decreases. There are various technical documents for increasing the mechanical strength of polymer solid electrolytes by chemical crosslinking and/or physical crosslinking.

In chinese patent document CN201180065551.0 (CN103329332A), a PEO-based solid polymer electrolyte is disclosed, and a composite material comprising an ionic salt doped plastic crystal (succinonitrile) matrix electrolyte and a crosslinked polymer is prepared by using a uv crosslinking method. The method adopts in-situ synthesis, does not need solvent, thus avoiding drying process and having higher ionic conductivity and high mechanical strength.

Chinese patent application No. CN201811196300.6 (CN109546220A) discloses a self-healing polymer electrolyte with dual networks, and its preparation and application, wherein the polymer electrolyte comprises a dual network structure formed by a physical cross-linked network and a chemical cross-linked network. The physical crosslinking network is easy to form dimers when the electrolyte matrix is cracked or damaged by external force, so that the electrolyte is endowed with excellent self-healing performance, and the chemical crosslinking can effectively improve the mechanical performance of the matrix and further prolong the service life of the lithium battery.

The above-mentioned crosslinking method introduces UV initiator, free radical initiator and extra monomer, and these residual substances can produce (electrochemical) reaction in the course of using cell, and can seriously affect cell performance, such as cell capacity, cycle performance, rate capability and coulombic efficiency.

In addition, crosslinking systems can significantly improve the mechanical strength of PEO-based polymers at room temperature, but the problem of material softening at high temperatures is still unavoidable. In the existing research, the crosslinking of PEO-based polymer only occurs when a polymer substrate is prepared, and the crosslinking degree is fixed in the using process, so that the crosslinking degree of the polymer cannot be effectively regulated and controlled. Under the condition of only once crosslinking, if the crosslinking degree of the polymer base material is high, the system can show certain mechanical strength at high temperature, but the combination of polymer chains is tight at room temperature, the freedom degree of the movement of the polymer chains is low, the creeping of the molecular chains is not facilitated, and the high-efficiency transmission of lithium ions is influenced; if the cross-linking degree of the polymer base material is low, the freedom degree of the movement of a polymer chain of the material at room temperature can be ensured, but the improvement of the mechanical strength at high temperature is not obvious, and the polymer base material cannot be better considered.

Disclosure of Invention

The invention provides an electrolyte polymer substrate, a solid electrolyte, a preparation method of the solid electrolyte and a lithium ion battery, and aims to solve the problems that the existing solid electrolyte has crosslinking assistant residues and the polymer crosslinking degree and the ionic conductivity cannot be considered at the same time.

The technical scheme adopted by the invention for solving the technical problems is as follows:

in one aspect, the present invention provides an electrolyte polymer substrate prepared by performing [4+4] cycloaddition between anthracene-based functional groups on a polymer precursor, wherein the polymer precursor is a random polymer or a block polymer comprising the following segment a, segment B, and segment C:

the segment A is selected from:

segment B is selected from:

the chain segment C is selected fromOne or more of;

wherein in the chain segment A, R is selected from H or methyl, and p is selected from 2-40 electrolyte polymer base materials.

Optionally, the mass ratio of the chain segment A to the chain segment B to the chain segment C is 50-90: 5-30: 5-25.

Optionally, the reaction ratio of the anthracene-based dimer formed by the anthracene-based functional group is 60% to 80%.

Optionally, the anthracene-based functional group of the chain segment B and the double bond on the carbon ring of the chain segment C are subjected to [4+2] cycloaddition crosslinking, and the reaction ratio of the anthracene-based functional group of the chain segment B and the double bond in the chain segment C is 70-95%.

Optionally, the number average molecular weight of the electrolyte polymer base material is 1 to 30 ten thousand.

Optionally, the segment a is derived from a monomer a, and the monomer a includes one or more of a polyethylene glycol methyl ether methacrylate monomer and a polyethylene glycol methyl ether acrylate monomer.

Optionally, the segment B is derived from a monomer B, and the monomer B comprises anthracene acrylate.

Optionally, the segment C is derived from a monomer C, and the monomer C comprises one or more of cyclopentadiene, cyclohexadiene and norbornadiene.

In another aspect, the present invention provides a method for preparing an electrolyte polymer substrate as described above, comprising the following operating steps:

adding a monomer a, a monomer B, a monomer C and a catalyst into a reaction container to carry out polymerization reaction to obtain a polymer precursor with a random structure or a block structure of a chain segment A, a chain segment B and a chain segment C;

the segment A is selected from:

segment B is selected from:

the chain segment C is selected fromOne or more of;

in the chain segment A, R is selected from H or methyl, and p is selected from 2-40;

the mass ratio of the chain segment A to the chain segment B to the chain segment C is 50-90: 5-30: 5-25;

and (3) subjecting the polymer precursor to ultraviolet irradiation to generate [4+4] cycloaddition between anthracene-based functional groups of the chain segment B to generate anthracene-based dimer, thereby obtaining the electrolyte polymer base material.

Optionally, the electrolyte polymer substrate is heated at 80-100 ℃, and the anthracene group functional group of the chain segment B and the double bond on the carbon ring of the chain segment C undergo [4+2] cycloaddition crosslinking.

Optionally, heating the electrolyte polymer substrate subjected to [4+2] cycloaddition crosslinking at 120-150 ℃ to partially crosslink the anthryl dimer.

In another aspect, the present invention provides a solid electrolyte comprising a lithium salt and an electrolyte polymer substrate as described above.

Optionally, the mass content of the lithium salt is 2% to 30% of the mass of the electrolyte polymer substrate, and the lithium salt includes one or more of lithium bis (trifluoromethanesulfonyl) imide, lithium bis (perfluoroethanesulfonyl) imide, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluorophosphate.

Optionally, the electrolyte polymer also comprises a plasticizer, the mass content of the plasticizer is 1-20% of the mass of the electrolyte polymer base material, and the plasticizer comprises one or more of ethylene carbonate, propylene carbonate and vinylene carbonate.

In another aspect, the present invention provides a method for preparing a solid electrolyte as described above, comprising the following operating steps:

adding a monomer a, a monomer B, a monomer C and a catalyst into a reaction container to carry out polymerization reaction to obtain a polymer precursor with a random structure or a block structure of a chain segment A, a chain segment B and a chain segment C;

the segment A is selected from:

segment B is selected from:

the chain segment C is selected fromOne or more of;

in the chain segment A, R is selected from H or methyl, and p is selected from 2-40;

preparing a polymer solution from a polymer precursor, lithium salt and a solvent, preparing the polymer solution into a coating, performing ultraviolet irradiation to generate [4+4] cycloaddition between anthracene-based functional groups of a chain segment B to generate anthracene-based dimer, and drying to remove the solvent to obtain the solid electrolyte.

In another aspect, the present invention provides a lithium ion battery comprising a positive electrode, a negative electrode, and a solid state electrolyte as described above, the solid state electrolyte being located between the positive electrode and the negative electrode.

According to the electrolyte polymer base material provided by the invention, a random polymer or a block polymer composed of a chain segment A, a chain segment B and a chain segment C is adopted as a polymer precursor, and the lithium ion conductivity is better, wherein anthracene-based functional groups introduced through the chain segment B undergo [4+4] cycloaddition through ultraviolet irradiation to generate anthracene-based dimer, so that the polymer precursor is crosslinked to form a solid form, the mechanical strength requirement of a solid electrolyte is met, no additional crosslinking agent, catalyst or initiator is required to be added in the crosslinking process, the monomer residue problem does not exist, the unicity of the electrolyte polymer base material is ensured, and the influence of the residual crosslinking assistant on the battery performance is avoided; when the battery is in a high-temperature environment or under the condition of short circuit, the anthracene functional group introduced by the chain segment B and the double bond on the carbon ring of the chain segment C can generate [4+2] cycloaddition crosslinking, so that the crosslinking degree and the mechanical strength of an electrolyte polymer base material are improved, the stability of the battery is ensured under the high-temperature condition, and the safety performance of the battery is improved; on the other hand, the anthracene-based dimer is a reversible structure, the crosslinking degree is adjustable, the crosslinking degree of the electrolyte polymer base material can be reduced through heating and de-crosslinking in subsequent use, the mechanical strength of the electrolyte polymer base material is recovered, and the influence of overhigh crosslinking degree on the ionic conductivity is avoided.

Drawings

Fig. 1 is a flow chart illustrating the preparation of an electrolyte polymer substrate according to an embodiment of the present invention;

FIG. 2 is a schematic view of the [4+4] cycloaddition crosslinking configuration of an electrolyte polymer substrate according to an embodiment of the present invention;

FIG. 3 is a schematic view of the form of the electrolyte polymer substrate [4+2] cycloaddition crosslinking according to an embodiment of the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

One embodiment of the present invention provides an electrolyte polymer substrate, which is prepared by performing [4+4] cycloaddition between anthracene-based functional groups on a polymer precursor, wherein the polymer precursor is a random polymer or a block polymer including the following segment a, segment B, and segment C:

the segment A is selected from:

segment B is selected from:

the chain segment C is selected fromOne or more of;

wherein in the chain segment A, R is selected from H or methyl, and p is selected from 2-40 electrolyte polymer base materials.

The random polymer or the block polymer composed of the chain segment A, the chain segment B and the chain segment C is adopted as a polymer precursor, and the lithium ion conductivity is better.

As shown in figure 2, anthracene-based dimer is generated by [4+4] cycloaddition between anthracene-based functional groups introduced by chain segment B through ultraviolet irradiation, and [4+4] cycloaddition between chain segments B can be generated on a polymer precursor with the same long chain or polymer precursors with different long chains, so that the polymer precursor is crosslinked to form a solid form, the mechanical strength requirement of a solid electrolyte is met, no additional crosslinking agent, catalyst or initiator is required to be added in the crosslinking process, the problem of monomer residue is avoided, the unicity of the polymer base material of the electrolyte is ensured, and the influence of the residual crosslinking assistant on the battery performance is avoided.

As shown in fig. 3, under the condition that the battery is in a high-temperature environment or in a short circuit, the anthracene-based functional group introduced into the chain segment B can undergo [4+2] cycloaddition crosslinking with a double bond on a carbon ring of the chain segment C, so that the crosslinking degree and the mechanical strength of the electrolyte polymer base material are improved, the stability of the battery is ensured at a high temperature, the safety performance of the battery is improved, and the [4+2] cycloaddition crosslinking occurs only at a high temperature, so that the influence of the high crosslinking degree on the ionic conductivity of the battery at normal temperature can be effectively avoided.

On the other hand, the anthracene-based dimer is a reversible structure, the anthracene-based dimer can be recovered to be an independent anthracene-based functional group under the condition that the temperature reaches 120 ℃, the crosslinking degree can be adjusted, the crosslinking degree of the electrolyte polymer base material can be reduced through thermal de-crosslinking in subsequent use, the mechanical strength of the electrolyte polymer base material can be recovered, and the influence of overhigh crosslinking degree on the ionic conductivity can be avoided.

In some embodiments, the mass ratio of the chain segment A, the chain segment B and the chain segment C is 50-90: 5-30: 5-25.

In a more preferable embodiment, the mass ratio of the chain segment A, the chain segment B and the chain segment C is 65-80: 10-20: 10-15.

In one embodiment, the polymer precursor has the formula:

specifically, in the above structural formulaCan also be replaced by

Wherein in the chain segment A, R is selected from H or methyl, m is selected from 1 to 600, and p is selected from 2 to 40;

in the chain segment B, n is selected from 1 to 220;

in the chain segment C, x is selected from 1-200;

q is selected from 1 to 1000.

In some embodiments, the anthracene-based functional group forms an anthracene-based dimer having a reaction ratio of 60% to 80%.

It should be noted that, the anthracene-based dimer is a reversible structure, so the crosslinking degree in the electrolyte polymer base material is also adjustable, and meanwhile, the anthracene-based functional group of the chain segment B and the double bond on the carbon ring of the chain segment C have potential crosslinking possibility, and when the electrolyte polymer base material is in different states, the crosslinking degree can be correspondingly adjusted and controlled.

For example, in some embodiments, such as when the cell is used in a high temperature environment, the anthracene-based functional group of segment B undergoes [4+2] cycloaddition crosslinking with the double bond on the carbon ring of segment C, and the anthracene-based functional group of segment B reacts with the double bond in segment C at a ratio of 70% to 95%.

The crosslinking degree of the electrolyte polymer base material can be effectively improved through the [4+2] cycloaddition crosslinking, so that the mechanical strength and the puncture resistance of the solid electrolyte are improved, the battery is effectively protected in a high-temperature environment, and the safety of the battery is improved.

In some embodiments, the electrolyte polymer base material has a number average molecular weight of 1 to 30 ten thousand.

In some embodiments, the segment a is derived from a monomer a comprising one or more of a methoxypolyethylene glycol methacrylate monomer and a methoxypolyethylene glycol acrylate monomer.

In some embodiments, the segment B is derived from a monomer B comprising an anthracene acrylate.

In some embodiments, the segment C is derived from a monomer C comprising one or more of cyclopentadiene, cyclohexadiene, and norbornadiene.

Another embodiment of the present invention provides a method for preparing the electrolyte polymer substrate as described above, comprising the following operating steps:

adding a monomer a, a monomer B, a monomer C and a catalyst into a reaction container to carry out polymerization reaction to obtain a polymer precursor with a random structure or a block structure of a chain segment A, a chain segment B and a chain segment C;

the segment A is selected from:

segment B is selected from:

the chain segment C is selected fromOne or more of;

wherein in the chain segment A, R is selected from H or methyl, and p is selected from 2 to 40;

and (3) subjecting the polymer precursor to ultraviolet irradiation (365nm-550nm), and performing [4+4] cycloaddition between the anthracene-based functional groups of the chain segment B to generate anthracene-based dimer, thereby obtaining the electrolyte polymer base material.

The catalyst is selected from the group consisting of azobisisobutyronitrile and S- (thiobenzoyl) thioacetic acid.

The polymerization among the monomer a, the monomer b and the monomer c can adopt free radical polymerization (ATRP) or active free radical polymerization (RAFT), wherein the ATRP adopts a CuBr/pyridine/butyl bromoacrylate system to initiate the polymerization. RAFT polymerisation was initiated using an AIBN/RAFT reagent (trithiocarbonate) system.

In some embodiments, heating the electrolyte polymer substrate at 80 ℃ to 100 ℃ causes [4+2] cycloaddition crosslinking of the anthracenyl functionality of segment B with the double bond on the carbocyclic ring of segment C.

It should be noted that the above [4+2] cycloaddition crosslinking may occur under operating conditions where the battery is subjected to a high temperature environment. In other embodiments, the [4+2] cycloaddition crosslinking may also be performed actively in order to increase the degree of crosslinking of the electrolyte polymer substrate.

Because the electrolyte polymer base material generates [4+2] cycloaddition crosslinking at high temperature, the crosslinking degree is larger, although the battery is protected to a certain extent, the reduction of the ionic conductivity can be influenced because the crosslinking degree is too large after the normal temperature is recovered, at the moment, the anthracene-based dimer formed by the [4+4] cycloaddition crosslinking can be subjected to decrosslinking through further heating, so that the crosslinking degree is properly reduced, and the performance of the electrolyte polymer base material used at the normal temperature is recovered.

Specifically, the electrolyte polymer base material after the [4+2] cycloaddition crosslinking is heated at 120-150 ℃ to partially crosslink the anthryl dimer, and the degree of crosslinking of the anthryl dimer can be correspondingly controlled by controlling the heating time.

As shown in FIG. 1, an embodiment of the method for preparing the electrolyte polymer base material of the present invention is shown, wherein in the segment A, R is selected from H or methyl, m is selected from 1 to 600, and p is selected from 2 to 40;

in the chain segment B, n is selected from 1 to 220;

in the chain segment C, x is selected from 1-200;

q is selected from 1 to 1000.

Another embodiment of the present invention provides a solid electrolyte comprising a lithium salt and an electrolyte polymer substrate as described above.

The lithium salt is used for providing lithium ions which flow between the anode and the cathode.

In some embodiments, the lithium salt is present in an amount of 2% to 30% by mass of the electrolyte polymer substrate, and the lithium salt includes one or more of lithium bis (trifluoromethanesulfonyl) imide, lithium bis (perfluoroethanesulfonyl) imide, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluorophosphate.

In some embodiments, the electrolyte polymer further comprises a plasticizer, wherein the mass content of the plasticizer is 1-20% of the mass of the electrolyte polymer base material, and the plasticizer comprises one or more of ethylene carbonate, propylene carbonate and vinylene carbonate.

The plasticizer is used for increasing the free volume among the molecular chains of the electrolyte polymer base material, enhancing the motion capability of the chain segments of the electrolyte polymer base material and reducing the glass transition temperature and the ion transfer activation energy of a system, thereby greatly enhancing the ion transfer and motion capability.

Another embodiment of the present invention provides a method for preparing the solid electrolyte as described above, comprising the following operating steps:

adding a monomer a, a monomer B, a monomer C and a catalyst into a reaction container to carry out polymerization reaction to obtain a polymer precursor with a random structure or a block structure of a chain segment A, a chain segment B and a chain segment C;

the segment A is selected from:

segment B is selected from:

the chain segment C is selected fromOne or more of;

wherein in the chain segment A, R is selected from H or methyl, and p is selected from 2 to 40;

preparing a polymer solution from a polymer precursor, lithium salt and a solvent, preparing the polymer solution into a coating with the thickness of 20-200 mu m, performing ultraviolet irradiation to generate [4+4] cycloaddition between anthracene-based functional groups of a chain segment B to generate anthracene-based dimer, and then drying to remove the solvent, wherein the drying mode is heating baking and vacuum drying to obtain the solid electrolyte.

The lithium salt is pre-dispersed in the polymer precursor, and then the polymer precursor forms the electrolyte polymer base material with a gel structure through an ultraviolet crosslinking curing mode, so that the lithium salt can be fully dispersed in the electrolyte polymer base material.

The preparation method comprises the steps of firstly adopting [4+4] cycloaddition crosslinking to increase the mechanical strength of the solid electrolyte, and when the solid electrolyte is used at high temperature, the [4+2] cycloaddition crosslinking occurs spontaneously on functional groups on the solid electrolyte, so that the crosslinking degree of a crosslinking system is increased, and the high-temperature mechanical strength of the solid electrolyte is improved.

In some embodiments, the solid electrolyte is placed in a plasticizer, such that the solid electrolyte adsorbs the plasticizer, facilitating an increase in ionic conductivity.

In some embodiments, the solvent comprises one or more of N, N-dimethylformamide, water, tetrahydrofuran, acetonitrile, N-methylpyrrolidone, and toluene.

Another embodiment of the present invention provides a lithium ion battery comprising a positive electrode, a negative electrode, and a solid state electrolyte as described above, the solid state electrolyte being located between the positive electrode and the negative electrode.

Due to the adoption of the solid electrolyte, if the battery runaway temperature rises, the [4+4] cycloaddition crosslinking and the [4+2] cycloaddition crosslinking can also provide higher safety guarantee for the battery.

The present invention will be further illustrated by the following examples.

Example 1

This example illustrates an electrolyte polymer substrate, a solid electrolyte, a lithium ion battery and a method for making the same, comprising the following steps:

(1) preparation of Polymer precursors

7g of methoxypolyethylene glycol methacrylic acid (monomer a, p ═ 19), 2.0g of anthracenyl methacrylate (monomer b) and 1.0g of cyclohexadiene (monomer c) were placed in a reaction apparatus, and N, N-dimethylformamide was added and mixed uniformly. 0.0052g of azobisisobutyronitrile is added, the reaction apparatus is closed, the reaction apparatus is cooled and degassed, and argon is introduced for protection. The polymerization reaction is carried out at 60 ℃, after 6 hours, the reaction is quenched by liquid nitrogen, and air is introduced to stop the reaction. Precipitation with hexane, repeated washing, and vacuum drying at 40 ℃ for 24h gave an uncrosslinked polymer precursor. The polymer precursor is of a random structure, the number average molecular weight is 25 ten thousand, the mass fraction of the chain segment A is 70%, the mass fraction of the chain segment B is 20%, and the mass fraction of the chain segment C is 10%.

(2) Preparation of solid electrolyte of "[ 4+4] cycloaddition crosslinking

5g of the polymer precursor prepared above and 0.75g of LiTFSI were dissolved in N, N-dimethylformamide and mixed well. The solution was then cast in a mold and irradiated with 365nm UV light for 1 h. Then heating and baking at 50 ℃ and vacuum drying at 40 ℃ are adopted to remove the solvent. The film thickness was 76 μm. The electrolyte polymer base material of "[ 4+4] cycloaddition crosslinking" was obtained.

Cutting the electrolyte polymer substrate film into a wafer, adding a plasticizer propylene carbonate to obtain the plasticized and modified solid electrolyte with the addition of a 4+4 ring.

In an argon-protected glove box, lithium iron phosphate is used as a positive electrode and a lithium sheet is used as a negative electrode respectively, and the prepared multilayer solid electrolyte is sandwiched between the positive electrode and the negative electrode to assemble a button cell which is marked as S11.

(3) Preparation of solid electrolyte of "[ 4+2] cycloaddition crosslinking

Heating the button cell at 80 ℃ for 2h, and realizing [4+2] cycloaddition through an anthracene group functional group in the polymer chain segment B and a double bond in the polymer chain segment C to prepare the [4+2] cycloaddition crosslinking solid electrolyte. The button cell was opened and the solvent removed by heat baking at 50 c and vacuum drying at 40 c to yield a dried "[ 4+2] cycloaddition cross-linked" solid electrolyte, which was added to the same mass of plasticizer and reassembled into the same button cell, labeled S12.

(4) Decrosslinking

And heating the button cell S12 at 120 ℃ for 2h, and depolymerizing the [4+4] cycloaddition crosslinking site anthryl dimer to realize a solid electrolyte of partial decrosslinking, thereby obtaining a button cell S13. The button cell S13 was again opened and the plasticizer was removed by heat baking at 50 c and vacuum drying at 40 c to give a dry "partially uncrosslinked" solid electrolyte.

Example 2

This example is intended to illustrate an electrolyte polymer substrate, a solid electrolyte, a lithium ion battery and a method for making the same, as disclosed in the present invention, including most of the operating steps in example 1, except that:

the following operations were employed in the preparation of the polymer precursor in step (1):

8g of polyethylene glycol methyl ether acrylate (monomer a, p is 9), 2.0g of anthracene acrylate (monomer b) and 1.5g of cyclopentadiene (monomer c) were placed in a reaction apparatus, and N, N-dimethylformamide was added and mixed uniformly. 0.0078g of azobisisobutyronitrile is added, the reaction device is sealed, the mixture is frozen and degassed, and argon is filled for protection. The polymerization reaction is carried out at 60 ℃, after 6 hours, the reaction is quenched by liquid nitrogen, and air is introduced to stop the reaction. Precipitation with hexane, repeated washing, and vacuum drying at 40 ℃ for 24h gave an uncrosslinked polymer precursor. The polymer precursor is of a random structure, the number average molecular weight is 16 ten thousand, the mass fraction of the chain segment A is 70%, the mass fraction of the chain segment B is 17%, and the mass fraction of the chain segment C is 13%.

Correspondingly, the button cell of the solid-state electrolyte assembly in which the "[ 4+4] cycloaddition cross-links" is labeled S21; a button cell assembled with a "[ 4+2] cycloaddition cross-linking" solid electrolyte is labeled S22; the assembled button cell after the solid electrolyte was uncrosslinked is labeled S23.

Example 3

This example is intended to illustrate an electrolyte polymer substrate, a solid electrolyte, a lithium ion battery and a method for making the same, as disclosed in the present invention, including most of the operating steps in example 1, except that:

the following operations were employed in the preparation of the polymer precursor in step (1):

9g of polyethylene glycol methyl ether acrylate (monomer a, p is 4), 3.0g of anthracene acrylate (monomer b) and 2g of norbornadiene (monomer c) are placed in a reaction device, and N, N-dimethylformamide is added and uniformly mixed. Adding 0.0131g of azobisisobutyronitrile, sealing the reaction device, freezing and degassing, and introducing argon for protection. The polymerization reaction is carried out at 60 ℃, after 6 hours, the reaction is quenched by liquid nitrogen, and air is introduced to stop the reaction. Precipitation with hexane, repeated washing, and vacuum drying at 40 ℃ for 24h gave an uncrosslinked polymer precursor. The polymer precursor is of a random structure, the number average molecular weight is 8 ten thousand, the mass fraction of the chain segment A is 64%, the mass fraction of the chain segment B is 22%, and the mass fraction of the chain segment C is 14%.

Correspondingly, the button cell of the solid-state electrolyte assembly in which the "[ 4+4] cycloaddition cross-links" is labeled S31; a button cell assembled with a "[ 4+2] cycloaddition cross-linking" solid electrolyte is labeled S32; the assembled button cell after the solid electrolyte was uncrosslinked is labeled S33.

Example 4

This example is intended to illustrate an electrolyte polymer substrate, a solid electrolyte, a lithium ion battery and a method for making the same, as disclosed in the present invention, including most of the operating steps in example 1, except that:

in the step (2) "preparation of [4+4] cycloaddition cross-linked" solid electrolyte, the following operations were employed:

5g of the polymer precursor prepared above and 0.75g of LiTFSI were dissolved in N, N-dimethylformamide and mixed well. The solution was then cast in a mold and irradiated with 365nm UV light for 0.5 h. Then heating and baking at 50 ℃ and vacuum drying at 40 ℃ are adopted to remove the solvent. The film thickness was 78 μm. The electrolyte polymer base material of "[ 4+4] cycloaddition crosslinking" was obtained.

Cutting the electrolyte polymer substrate film into a wafer, adding a plasticizer propylene carbonate to obtain the plasticized and modified solid electrolyte with the addition of a 4+4 ring.

In an argon-protected glove box, lithium iron phosphate is used as a positive electrode and a lithium sheet is used as a negative electrode respectively, and the prepared multilayer solid electrolyte is clamped between the positive electrode and the negative electrode to form the button cell.

Correspondingly, the button cell of the solid-state electrolyte assembly in which the "[ 4+4] cycloaddition cross-links" is labeled S41; a button cell assembled with a "[ 4+2] cycloaddition cross-linking" solid electrolyte is labeled S42; the assembled button cell after the solid electrolyte was uncrosslinked is labeled S43.

Example 5

This example is intended to illustrate an electrolyte polymer substrate, a solid electrolyte, a lithium ion battery and a method for making the same, as disclosed in the present invention, including most of the operating steps in example 1, except that:

in the step (3) "4 +2] cycloaddition crosslinking" preparation of the solid electrolyte, the following operations were employed:

heating the button cell at 90 ℃ for 1h, and realizing [4+2] cycloaddition through an anthracene group functional group in the polymer chain segment B and a double bond in the polymer chain segment C to prepare the [4+2] cycloaddition crosslinking solid electrolyte. And opening the button cell, heating and baking at 50 ℃ and vacuum drying at 40 ℃ to remove the solvent and remove the plasticizer to obtain a dried solid electrolyte of the [4+2] cycloaddition crosslinking, adding the same mass of plasticizer into the dried solid electrolyte of the [4+2] cycloaddition crosslinking, and reassembling the same button cell.

Correspondingly, the button cell of the solid-state electrolyte assembly in which the "[ 4+4] cycloaddition cross-links" is labeled S51; a button cell assembled with a "[ 4+2] cycloaddition cross-linking" solid electrolyte is labeled S52; the assembled button cell after the solid electrolyte was uncrosslinked is labeled S53.

Example 6

This example is intended to illustrate an electrolyte polymer substrate, a solid electrolyte, a lithium ion battery and a method for making the same, as disclosed in the present invention, including most of the operating steps in example 1, except that:

the following operations are adopted in the step (4) of decrosslinking:

and heating the button cell at 120 ℃ for 1h, and depolymerizing the [4+4] cycloaddition crosslinking site anthryl dimer to realize a solid electrolyte of partial decrosslinking, so as to obtain a button cell S13. The button cell S13 was again opened and the plasticizer was removed by heat baking at 50 c and vacuum drying at 40 c to give a dry "partially uncrosslinked" solid electrolyte.

Correspondingly, the button cell of the solid-state electrolyte assembly in which the "[ 4+4] cycloaddition cross-links" is labeled S61; a button cell assembled with a "[ 4+2] cycloaddition cross-linking" solid electrolyte is labeled S62; the assembled button cell after the solid electrolyte was uncrosslinked is labeled S63.

Comparative example 1

This example is intended to illustrate by way of comparison the electrolyte polymer substrate, solid electrolyte, lithium ion battery and method of making the same disclosed herein, comprising the following steps:

(1) preparation of Polymer precursors

7g of polyethylene glycol methyl ether methacrylic acid (monomer a), 2.0g of anthracene methacrylate (monomer b) and 1.0g of cyclohexadiene (monomer c) are placed in a reaction device, N-dimethylformamide is added, and the mixture is uniformly mixed. 0.0052g of azobisisobutyronitrile is added, the reaction apparatus is closed, the reaction apparatus is cooled and degassed, and argon is introduced for protection. The polymerization reaction is carried out at 60 ℃, after 6 hours, the reaction is quenched by liquid nitrogen, and air is introduced to stop the reaction. Precipitation with hexane, repeated washing, and vacuum drying at 40 ℃ for 24h gave an uncrosslinked polymer precursor. The polymer precursor is of a random structure, the number average molecular weight is 25 ten thousand, the mass fraction of the chain segment A is 70%, the mass fraction of the chain segment B is 20%, and the mass fraction of the chain segment C is 10%.

(2) Preparation of solid electrolyte

5g of the polymer precursor prepared above and 0.75g of LiTFSI were dissolved in N, N-dimethylformamide and mixed well. The solution was then cast in a mold and then heated to 50 ℃ for baking and dried under vacuum at 40 ℃ to remove the solvent. The film thickness was 85 μm. An electrolyte polymer substrate is obtained.

And cutting the electrolyte polymer base material film into a wafer, and adding a plasticizer propylene carbonate to obtain the plasticized and modified solid electrolyte.

In an argon-protected glove box, lithium iron phosphate is used as a positive electrode and a lithium sheet is used as a negative electrode respectively, and the prepared multilayer solid electrolyte is sandwiched between the positive electrode and the negative electrode to assemble a button cell, which is marked as P1.

Performance testing

The button cell prepared in examples 1 to 6 and comparative example 1 were subjected to an ion conductivity test, and the electrolyte polymer base materials prepared in examples 1 to 6 and comparative example 1 were subjected to a tensile strength test, and the test results are shown in table 1:

ionic conductivity: the ionic conductivity is obtained by deducing an alternating current impedance formula of a test membrane, and the specific mode is as follows: after drying the polymer solid electrolyte, cutting the dried polymer solid electrolyte into a circular piece with the diameter of 19mm by using a die, and placing the circular piece in a glove box for 8 hours. Use of a "stainless steel/electrolyte layer (effective area 2 cm)²) Stainless steel structure in glove box (O)₂<1ppm,H₂O<1ppm) was prepared. The prepared button cell is placed in a thermostat for testing, the testing temperature range is 20-90 ℃, and the alternating current impedance testing frequency range is 10^-5-1Hz, amplitude 100mV, sample thermostatted at a preset temperature for 1h before impedance test. Then, the conductivity of the electrolyte membrane is measured by using an alternating current impedance technology and a CHI660B type electrochemical workstation of Shanghai Chenghua instruments, wherein the test frequency range is 1-100kHz, and the disturbance signal is 5 mV. The intersection point of the measured Nyquist curve (Nyquist plot) and the real axis is the bulk resistance (Rb) of the polymer electrolyte membrane, and then the conductivity σ of the polymer electrolyte membrane is calculated according to the following formula: σ ═ l/(A. Rb), lIs the thickness of the polymer electrolyte membrane; and A is the contact area of the polymer electrolyte membrane and the electrode.

Tensile strength: the test process comprises the following steps: cutting the film into 1 × 5cm strips in advance, keeping the sample dry before testing, measuring the thickness of the sample, clamping two ends of the sample, slowly stretching the sample until the sample is broken at a certain speed (15mm/min) by using a universal testing machine, and recording the mechanical data of the sample by software.

TABLE 1

As can be seen from table 1 above, the solid electrolyte obtained in the present invention has high ionic conductivity and high mechanical strength, and can provide high safety for a solid lithium ion battery, and on the other hand, the solid electrolyte provided in the present invention has controllable mechanical strength, and the mechanical strength of the solid electrolyte can be controlled in different ranges through operations of "[ 4+4] cycloaddition crosslinking", "[ 4+2] cycloaddition crosslinking", and "decrosslinking", so as to adapt to the use environments of lithium ion batteries under different conditions, and take into account both electrical properties and safety properties of the lithium ion batteries.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.