Preparation method of an amorphous polymer electrolyte based on epoxy resin and a composite polymer electrolyte

Abstract

The application discloses an amorphous polymer electrolyte based on epoxy resin and a preparation method of a composite polymer electrolyte, and the electrolyte is composed of an amorphous polymer electrolyte based on epoxy resin, a metal organic framework and inorganic solid electrolyte powder. In the preparation process of the composite electrolyte, the metal organic framework material is introduced, the lithium salt anion is anchored through the unsaturated metal coordination site, so that the lithium ion transference number of the composite electrolyte is improved. In addition, the inorganic solid electrolyte powder is introduced, the ionic conductivity of the composite electrolyte is further improved, so that the composite electrolyte can meet the charge and discharge cycle requirements of the lithium iron phosphate battery at room temperature and under a certain rate. The polymer electrolyte preparation method is simple, raw materials are easy to obtain, and has the prospect of industrial production and application, and has an enlightening effect on the development of polymer-based solid-state batteries.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of polymer electrolyte based on epoxy resin and the preparation method of composite polymer electrolyte with the polymer electrolyte as matrix. BACKGROUND

[0002] With the development of new energy automobile industry, higher requirements are put forward for the energy density, safety and rate performance of power battery. According to the electrolyte used by power battery, it can be divided into lithium ion battery using liquid electrolyte and solid-state lithium battery using polymer electrolyte. Compared with solid-state lithium battery using polymer and composite electrolyte, lithium ion battery using liquid electrolyte is prone to electrolyte leakage, explosion and other safety risks, and the energy density has reached the limit. Therefore, in order to improve the safety, energy density and other key performances of power battery, solid-state battery using solid-state electrolyte is a major development direction of current power battery.

[0003] The polymer matrix of the current polymer electrolyte is mostly polyethylene oxide (PEO) or polyvinylidene fluoride (PVDF). PEO has semi-crystalline characteristics, and PVDF has poor compatibility with various lithium salts (such as LiTFSI, LiFSI, LiBF4, LiODFB), which is easy to separate with lithium salt, hindering the improvement of ionic conductivity and comprehensive performance of polymer electrolyte. It is difficult to make a breakthrough in the ionic conductivity of the currently developed polymer electrolyte based on PEO and PVDF, and its forming method mostly uses solution volatilization, which needs to use a large amount of solvent, increasing the processing difficulty.

[0004] Therefore, it is necessary to develop a polymer electrolyte system with high ionic conductivity and convenient processing technology to meet the development needs of solid-state lithium battery. SUMMARY

[0005] In order to solve the above technical problems, the application provides a preparation method of an amorphous polymer electrolyte based on epoxy resin and a composite polymer electrolyte. The application prepares a polymer electrolyte with an amorphous condensed state structure based on the polymerization of a multifunctional epoxy resin and a molecular chain flexible polyether, introduces a metal organic framework material (MOF) and a tantalum-doped lithium lanthanum zirconium oxide (LLZTO) into the polymer electrolyte as a matrix by using a blending process to prepare an organic-inorganic composite solid electrolyte, and then in-situ solidification is carried out to obtain an organic-inorganic composite polymer-based solid electrolyte, so that the problems of semi-crystallinity and poor compatibility with lithium salt of the existing polymer electrolyte using a PEO and PVDF polymer matrix are completely solved. The synthesized polymer electrolyte has an ionic conductivity at room temperature which is 1-2 orders of magnitude higher than that of a PEO electrolyte, and has a low glass transition temperature and good dissociation capacity for various lithium salts. In addition, the introduction of the MOF makes the obtained composite electrolyte system have a high lithium ion transference number, and the introduction of the LLZTO further improves the ionic conductivity of the composite electrolyte system, so that it can work at room temperature. The application has great enlightenment value for the construction of a polymer electrolyte system and a composite electrolyte system and the building of a solid electrolyte system, and has great promoting effect on the development of a new generation of power batteries.

[0006] The object of the application is achieved by the following technical solutions.

[0007] A preparation method of an amorphous polymer electrolyte based on epoxy resin, which completes the preparation of the polymer electrolyte by using a one-pot method, and the reaction process is as follows:

[0008]

[0009] The specific steps are as follows:

[0010] Step one, the epoxy resin, curing agent and lithium salt are stirred and dissolved at room temperature for 10-15 hours until a transparent and uniform prepolymer liquid is formed, wherein:

[0011] The mass ratio of the epoxy resin and the curing agent is 1:1-1:10;

[0012] The lithium salt is not limited to one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluorosulfonyl)imide, lithium difluoro(oxalato)borate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate and lithium perchlorate, and the mass of the lithium salt is 10-50% of the total mass of the polymer electrolyte;

[0013] The epoxy resin has the following molecular structure characteristics:

[0014]

[0015] In the formula, R1 and R2 are not limited to one or more of alkyl, amino, heterocycle, aromatic heterocycle, hydrogen, fluorine; n is an arbitrary number between 1 and 100;

[0016] The curing agent is a long-chain flexible curing agent, having the following molecular structure characteristics:

[0017]

[0018] In the formula, Ra, Rb, Rc are not limited to one or more of hydrogen, alkyl, long-chain alkyl, hydroxymethyl, carboxymethyl; n is an arbitrary number between 1 and 100;

[0019] After the second step of forming a prepolymer solution, curing at a temperature of 50-150°C for 4-48 hours, a polymer electrolyte containing the following breakable cross-linking structure can be obtained:

[0020]

[0021] A composite polymer electrolyte is composed of the above-mentioned amorphous polymer electrolyte based on epoxy resin, metal organic framework, and inorganic solid electrolyte powder, wherein:

[0022] The metal organic framework material is not limited to one or more of copper-based metal organic framework material (copper-based MOF), nickel-based metal organic framework material (nickel-based MOF), cobalt-based metal organic framework material (cobalt-based MOF), iron-based metal organic framework material (iron-based MOF), zinc-based metal organic framework material (zinc-based MOF), titanium-based metal organic framework material (titanium-based MOF), and zirconium-based metal organic framework material (zirconium-based MOF);

[0023] The inorganic solid electrolyte powder is not limited to one or more of Li 0.38 La 0.56 Ti 0.99 Al 0.01 O3, Li-excess Li 0.22 La 0.60 TiO3, Li 2.99 Ba 0.005 ClO, Li 1.2 Al 0.2 Ti 1.8 (PO4)3, Li2SiS3, Li3YCl6, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 5.35 Ca 0.1 PS 4.5 Cl 1.55 , Li 6+x Sb1-x Si x S5I(x=0.7), Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , Li7La3Zr2O 12 , Li 6.55 Ga 0.15 La3Zr2O 12 one or more of them.

[0024] The mass ratio of the amorphous polymer electrolyte, the metal organic framework, and the inorganic solid electrolyte powder is 1:0.5-2:2-5.

[0025] A preparation method of the composite polymer electrolyte, which is prepared by one-pot method, comprises the following steps:

[0026] The epoxy resin, the curing agent, the lithium salt, the metal organic framework, and the inorganic solid electrolyte powder are uniformly mixed, and then are placed in a mold and cured at a temperature of 50-150 DEG C for 4-48 hours to obtain the composite electrolyte film.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] 1. In the present application, the amorphous long flexible chain segment polyether amine is combined into the polymer molecular system through the ring-opening polymerization reaction of the epoxy group and the amino group, and the obtained polymer electrolyte system has the advantages of high flexibility, low crystallinity, and high room temperature ionic conductivity.

[0029] 2. In the preparation process of the composite electrolyte, the metal organic framework material is introduced, the lithium salt anion is anchored through the unsaturated metal coordination site, so as to improve the lithium ion migration number of the composite electrolyte. In addition, the inorganic solid electrolyte powder is introduced, which further improves the ionic conductivity of the composite electrolyte, so that it can meet the charge and discharge cycle requirements of the lithium iron phosphate battery at room temperature and a certain rate.

[0030] 3. The preparation method of the polymer electrolyte of the present application is simple, the raw materials are easy to obtain, and has the prospect of industrial production and application, and has an enlightening effect on the development of polymer-based solid-state batteries. DETAILED DESCRIPTION

[0031] The technical solutions of the present application are further described below in conjunction with the embodiments, but are not limited thereto. Any modification or equivalent replacement to the technical solutions of the present application without departing from the spirit and scope of the present application shall be covered in the protection scope of the present application.

[0032] Example 1: Preparation of polymer electrolyte A

[0033] Take 6 g of curing agent A, 3 g of lithium bis-trifluoromethanesulfonimide at room temperature for 12 hours, until the lithium salt is completely dissolved, then add 1.2 g of epoxy resin A, stir for 5 minutes to mix evenly, form a prepolymer liquid A, and then deaerate with ultrasonic. Then transfer to a circular mold, and cure at 100°C for 10 hours to obtain polymer electrolyte A, whose physical properties and electrochemical properties are shown in Table 1.

[0034] In this embodiment, the molecular structure of the curing agent A is:

[0035]

[0036] In this embodiment, the molecular structure of the epoxy resin A is:

[0037]

[0038] In this embodiment, the molecular structure of the polymer electrolyte A is:

[0039]

[0040] Table 1 Physical properties and electrochemical properties of polymer electrolyte A

[0041] Item Performance Tensile strength (MPa) 2.1±0.5 Tensile modulus (MPa) 650.0±0.5 Tensile strain (%) 200.0±0.5 Tg (°C) -57.0±0.5 Lithium ion conductivity (10 -5 S / cm) 1.51±0.05 Electrochemical window (V) 4.2±0.05 Lithium ion transference number 0.31±0.05

[0042] Example 2: Preparation of polymer electrolyte B

[0043] Take 5 g of curing agent B, 2.5 g of lithium bis-trifluorosulfonimide at room temperature for 12 hours, until the lithium salt is completely dissolved, then add 1.0 g of epoxy resin B, stir for 5 minutes to mix evenly, form a prepolymer liquid B, and then deaerate with ultrasonic. Then transfer to a circular mold, and cure at 120°C for 5 hours to obtain polymer electrolyte B, whose physical properties and electrochemical properties are shown in Table 2.

[0044] In this embodiment, the molecular structure of the curing agent B is:

[0045]

[0046] In this embodiment, the molecular structure of the epoxy resin B is:

[0047]

[0048] In this embodiment, the molecular structure of the polymer electrolyte B is:

[0049]

[0050] Table 2 Physical properties and electrochemical properties of polymer electrolyte B

[0051] Item Performance Tensile strength (MPa) 1.6±0.5 Tensile modulus (MPa) 720.0±0.5 Tensile strain (%) 310.0±0.5 Tg (°C) -55.0±0.5 Lithium ion conductivity (10 -5 S / cm) 2.31±0.05 Electrochemical window (V) 4.1±0.05 Lithium ion transference number 0.30±0.05

[0052] Example 3: Preparation of polymer electrolyte C

[0053] Take 6 g of curing agent C, 2.5 g of lithium bis-trifluorosulfonimide, stir at room temperature for 12 hours until the lithium salt is completely dissolved, then add 1.0 g of epoxy resin C, stir for 5 minutes to mix evenly, form a prepolymer liquid C, and then deaerate with ultrasonic. Then transfer to a round mold, cure at 120°C for 5 hours to obtain polymer electrolyte C.

[0054] In this embodiment, the molecular structure of the curing agent C is:

[0055]

[0056] In this embodiment, the molecular structure of the epoxy resin C is:

[0057]

[0058] In this embodiment, the molecular structure of the polymer electrolyte C is:

[0059]

[0060] Example 4: Preparation of composite polymer electrolyte A by polymer electrolyte A

[0061] At room temperature, 0.3 g of prepolymer liquid A and 0.3 g of copper-based metal organic framework material (CuBTC) are mixed evenly, then 1.0 g of Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , mix evenly and deaerate with a stirrer, transfer to a round polytetrafluoroethylene mold, cure at 100°C for 10 hours, and cool to room temperature to obtain composite polymer electrolyte A. The physical properties and electrochemical properties are shown in Table 3.

[0062] Table 3 Physical properties and electrochemical properties of composite polymer electrolyte A

[0063]

[0064]

[0065] Example 5: Preparation of composite polymer electrolyte B by polymer electrolyte B

[0066] At room temperature, 0.5 g of prepolymer liquid B and 0.3 g of nickel-based metal organic framework material (NiBDC) are mixed evenly, then 1.2 g of Li 6.4La3Zr 1.4 Ta 0.6 O 12 , mixed homogeneously with a stirrer and degassed of bubbles, transferred into a round polytetrafluoroethylene mold, cured at 120°C for 5 hours, and after cooling to room temperature, a composite polymer electrolyte B was obtained, the physical properties and electrochemical properties of which are shown in Table 4.

[0067] Table 4 Physical properties and electrochemical properties of composite polymer electrolyte A

[0068] Item Performance Tensile strength (MPa) 4.2±0.5 Tensile modulus (MPa) 1150.0±0.5 Tensile strain (%) 85.0±0.5 Tg (°C) -40.0±0.5 Lithium ion conductivity (mS / cm) 1.02±0.05 Electrochemical window (V) 4.7±0.05 Lithium ion transference number 0.57±0.05

Claims

1. A composite polymer electrolyte, characterized in that... The electrolyte is composed of an epoxy resin-based amorphous polymer electrolyte, a metal-organic framework, and inorganic solid electrolyte powder, wherein the mass ratio of the epoxy resin-based amorphous polymer electrolyte, the metal-organic framework, and the inorganic solid electrolyte powder is 1:0.5~2:2~5; the preparation method of the epoxy resin-based amorphous polymer electrolyte includes the following steps: Step 1: Stir and dissolve the epoxy resin, curing agent, and lithium salt until a transparent and homogeneous prepolymer solution is formed, wherein: The mass ratio of the epoxy resin to the curing agent is 1:1 to 1:10; The lithium salt accounts for 10-50% of the total mass of the polymer electrolyte; The epoxy resin has the following molecular structural characteristics: In the formula, R1 and R2 are one or more of alkyl, amino, heterocyclic, aromatic heterocyclic, hydrogen, and fluorine; n is any number between 1 and 100; The curing agent has the following molecular structural characteristics: In the formula, Ra, Rb, and Rc are one or more of hydrogen, alkyl, long-chain alkyl, hydroxymethyl, and carboxymethyl; n is any number between 1 and 100; Step 2: After forming the prepolymer solution, cure it at a temperature of 50~150℃ for 4~48 hours to obtain the polymer electrolyte, which contains the following breakable crosslinked structure: 。 2. The composite polymer electrolyte according to claim 1, characterized in that... The lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, and lithium perchlorate.

3. The composite polymer electrolyte according to claim 1, characterized in that... The stirring and dissolving time is 10-15 hours.

4. The composite polymer electrolyte according to claim 1, characterized in that... The metal-organic framework material is one or more of the following: copper-based metal-organic framework materials, nickel-based metal-organic framework materials, cobalt-based metal-organic framework materials, iron-based metal-organic framework materials, zinc-based metal-organic framework materials, titanium-based metal-organic framework materials, and zirconium-based metal-organic framework materials.

5. The composite polymer electrolyte according to claim 1, characterized in that... The inorganic solid electrolyte powder is Li 0.38 La 0.56 Ti 0.99 Al 0.01 O3, Li-excess Li 0.22 La 0.60 TiO3, Li 2.99 Ba 0.005 ClO, Li 1.2 Al 0.2 Ti 1.8 (PO4)3, Li2SiS3, Li3YCl6, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li 5.35 Ca 0.1 PS 4.5 Cl 1.55 Li 6+x Sb 1−x Si x S5I (x=0.7), Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Li7La3Zr2O 12 Li 6.55 Ga 0.15 La3Zr2O 12 One or more of them.

6. A method for preparing the composite polymer electrolyte according to any one of claims 1-5, characterized in that... The method includes the following steps: The epoxy resin, curing agent, and lithium salt are mixed evenly with the metal-organic framework and inorganic solid electrolyte powder, and then placed in a mold and cured at a temperature of 50~150℃ for 4~48 hours to obtain the composite electrolyte film.

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