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

Abstract

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

Description

Technical Field

[0001] The invention relates to a polymer electrolyte based on epoxy resin and a preparation method of a composite polymer electrolyte using the polymer electrolyte as a matrix. Background Art

[0002] With the development of the new energy vehicle industry, higher requirements are placed on the energy density, safety, and rate performance of power batteries. According to the electrolyte used in power batteries, they can be mainly divided into lithium-ion batteries using liquid electrolytes and solid-state lithium batteries using polymer electrolytes. Compared with solid-state lithium batteries using polymers and their composite electrolytes, lithium-ion batteries using liquid electrolytes are prone to safety risks such as electrolyte leakage and deflagration, and their energy density has reached its limit. Therefore, in order to improve the safety, energy density and other key performance of power batteries, solid-state batteries using solid electrolytes are currently a major development direction for power batteries.

[0003] The polymer matrix of current polymer electrolytes 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), and is easily phase separated from lithium salts, which hinders the improvement of the ionic conductivity and comprehensive performance of polymer electrolytes. As a result, it is difficult to achieve a major breakthrough in the ionic conductivity of the polymer electrolytes based on PEO and PVDF currently developed, and their molding methods mostly use solution volatilization, which requires the use of a large amount of solvent, increasing the difficulty of processing.

[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 batteries. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing an amorphous polymer electrolyte and a composite polymer electrolyte based on epoxy resin. The present invention prepares a polymer electrolyte with an amorphous condensed structure based on the polymerization of a multifunctional epoxy resin and a polyether with a flexible molecular chain. The polymer electrolyte is used as a matrix, and a metal organic framework material (MOF) and tantalum-doped lithium lanthanum zirconium oxide (LLZTO) are introduced into the polymer electrolyte by a blending process to prepare an organic-inorganic composite solid electrolyte, and then in-situ solidification is performed to obtain an organic-inorganic composite polymer-based solid electrolyte, which completely solves the problems of semi-crystallinity and poor compatibility with lithium salts in existing polymer electrolytes using polymer matrices such as PEO and PVDF. The synthesized polymer electrolyte has a room temperature ionic conductivity that is 1 to 2 orders of magnitude higher than that of PEO electrolytes, and at the same time, it has a low glass transition temperature and has good dissociation ability for a variety of lithium salts. In addition, the introduction of MOF enables the obtained composite electrolyte system to have a high lithium ion migration number, and the introduction of LLZTO further improves the ionic conductivity of the composite electrolyte system, allowing it to work at room temperature. The present invention has great inspirational value for the construction of polymer electrolyte systems and composite electrolyte systems and the establishment of solid electrolyte systems, and has a huge driving effect on the development of a new generation of power batteries.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A method for preparing an epoxy resin-based amorphous polymer electrolyte, wherein the polymer electrolyte is prepared by a one-pot method, and the reaction process is as follows:

[0008]

[0009] The specific steps are as follows:

[0010] Step 1: Stir and dissolve the epoxy resin, curing agent and lithium salt at room temperature for 10 to 15 hours until a transparent and uniform prepolymer solution is formed, wherein:

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

[0012] The lithium salt is not limited to one or more of lithium bis(trifluoromethanesulfonyl imide), lithium bis(trifluorosulfonyl imide), lithium difluorooxalate borate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, and lithium perchlorate, and the mass of the lithium salt is 10 to 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, heterocyclic, aromatic heterocyclic, hydrogen, and fluorine; n is any number between 1 and 100;

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

[0017]

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

[0019] Step 2: After forming the prepolymer solution, solidify it at a temperature of 50 to 150° C. for 4 to 48 hours to obtain a polymer electrolyte having the following breakable cross-linking structure:

[0020]

[0021] A composite polymer electrolyte, comprising the above-mentioned epoxy resin-based amorphous polymer electrolyte, a metal organic framework, and an inorganic solid electrolyte powder, wherein:

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

[0023] The inorganic solid electrolyte powder is not limited to 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 Ln3Z 1.4 Ta 0.6 O 12 、Li7La3Zr2O 12 , Li 6.55 Ga 0.15 La3Zr2O 12 One or more of the following;

[0024] 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.

[0025] A method for preparing the composite polymer electrolyte is to prepare the composite polymer electrolyte using a one-pot method, and the specific steps are as follows:

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

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

[0028] 1. The present invention combines amorphous long flexible chain segment polyetheramine into the polymer molecular system through the ring-opening polymerization reaction of epoxy groups and amino groups. 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 present invention introduces a metal organic framework material, anchoring the lithium salt anion through the unsaturated metal coordination site, thereby increasing the lithium ion migration number of the composite electrolyte. In addition, the introduced inorganic solid electrolyte powder further improves the ionic conductivity of the composite electrolyte, so that it can meet the charge and discharge cycle requirements of lithium iron phosphate batteries at room temperature and a certain rate.

[0030] 3. The polymer electrolyte preparation method of the present invention is simple, the raw materials are easily available, and it has prospects for industrial production and application, which is inspiring for the development of polymer-based solid-state batteries. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below in conjunction with the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0032] Example 1: Preparation of polymer electrolyte A

[0033] Take 6g of curing agent A and 3g of lithium bis(trifluoromethanesulfonyl)imide and stir at room temperature for 12 hours until the lithium salt is completely dissolved, then add 1.2g of epoxy resin A and stir for 5 minutes until the mixture is evenly mixed to form prepolymer liquid A, which is then defoamed by ultrasound. Then transfer to a round mold and cure at 100°C for 10 hours to obtain polymer electrolyte A, whose physical and electrochemical properties are shown in Table 1.

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

[0035]

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

[0037]

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

[0039]

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

[0041] project performance Tensile strength(MPa) 2.1±0.5 Tensile modulus (MPa) 650.0±0.5 Tensile strain (%) 200.0±0.5 Tg(℃) -57.0±0.5 <![CDATA[Lithium ion conductivity (10 -5 S / cm)]]> 1.51±0.05 Electrochemical Window (V) 4.2±0.05 Lithium ion migration number 0.31±0.05

[0042] Example 2: Preparation of polymer electrolyte B

[0043] Take 5g of curing agent B and 2.5g of lithium bis(trifluorosulfonyl)imide and stir at room temperature for 12 hours until the lithium salt is completely dissolved, then add 1.0g of epoxy resin B and stir for 5 minutes until the mixture is evenly mixed to form prepolymer B, which is then defoamed by ultrasound. Then transfer to a round mold and cure at 120°C for 5 hours to obtain polymer electrolyte B, whose physical and electrochemical properties are shown in Table 2.

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

[0045]

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

[0047]

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

[0049]

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

[0051] project performance Tensile strength(MPa) 1.6±0.5 Tensile modulus (MPa) 720.0±0.5 Tensile strain (%) 310.0±0.5 Tg(℃) -55.0±0.5 <![CDATA[Lithium ion conductivity (10 -5 S / cm)]]> 2.31±0.05 Electrochemical Window (V) 4.1±0.05 Lithium ion migration number 0.30±0.05

[0052] Example 3: Preparation of polymer electrolyte C

[0053] Take 6g of curing agent C and 2.5g of lithium bis(trifluorosulfonyl)imide and stir at room temperature for 12 hours until the lithium salt is completely dissolved, then add 1.0g of epoxy resin C and stir for 5 minutes until the mixture is evenly mixed to form prepolymer liquid C, which is then defoamed by ultrasound. Then transfer to a round mold and cure at 120°C for 5 hours to obtain polymer electrolyte C.

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

[0055]

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

[0057]

[0058] In this embodiment, the molecular structure of 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 prepolymer solution A and 0.3 g copper-based metal organic framework material (CuBTC) were mixed evenly, and then 1.0 g Li 6.4 Ln3Z 1.4 Ta 0.6 O 12 , mixed evenly with a stirrer and debubbled, transferred to a round polytetrafluoroethylene mold, cured at 100 °C for 10 hours, and cooled to room temperature to obtain a composite polymer electrolyte A, whose physical and electrochemical properties are shown in Table 3.

[0062] Table 3 Physical 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 prepolymer solution B and 0.3 g nickel-based metal organic framework material (NiBDC) were mixed evenly, and then 1.2 g Li 6.4Ln3Z 1.4 Ta 0.6 O 12 , mixed evenly with a stirrer and debubbled, transferred to a round polytetrafluoroethylene mold, cured at 120 °C for 5 hours, and cooled to room temperature to obtain a composite polymer electrolyte B, whose physical and electrochemical properties are shown in Table 4.

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

[0068] project performance Tensile strength(MPa) 4.2±0.5 Tensile modulus (MPa) 1150.0±0.5 Tensile strain (%) 85.0±0.5 Tg(℃) -40.0±0.5 Lithium ion conductivity (mS / cm) 1.02±0.05 Electrochemical Window (V) 4.7±0.05 Lithium ion migration number 0.57±0.05

Claims

1. A method for preparing an epoxy resin-based amorphous polymer electrolyte, characterized in that The method comprises the following steps: Step 1: Stir and dissolve the epoxy resin, curing agent and lithium salt until a transparent and uniform prepolymer solution is formed, wherein: The mass ratio of the epoxy resin to the curing agent is 1:1 to 1:10; The mass of the lithium salt is 10 to 50% of the total mass of the polymer electrolyte; The epoxy resin has the following molecular structure characteristics: In the formula, R1 and R2 are one or more of alkyl, amino, heterocycle, aromatic heterocycle, hydrogen, and fluorine; n is any number between 1 and 100; The curing agent has the following molecular structure 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, solidify it at a temperature of 50 to 150° C. for 4 to 48 hours to obtain a polymer electrolyte.

2. The method for preparing an epoxy resin-based amorphous polymer electrolyte according to claim 1, characterized in that The lithium salt is one or more of lithium bis(trifluoromethanesulfonyl imide), lithium bis(trifluorosulfonyl imide), lithium difluorooxalatoborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, and lithium perchlorate.

3. The method for preparing an epoxy resin-based amorphous polymer electrolyte according to claim 1, characterized in that The stirring and dissolving time is 10 to 15 hours.

4. The method for preparing an epoxy resin-based amorphous polymer electrolyte according to claim 1, characterized in that The polymer electrolyte contains the following breakable cross-linked structure:

5. A composite polymer electrolyte, characterized in that The electrolyte is composed of an epoxy resin-based amorphous polymer electrolyte, a metal organic framework, and an inorganic solid electrolyte powder prepared by the method described in any one of claims 1 to 3, 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 to 2:2 to 5.

6. The composite polymer electrolyte according to claim 5, characterized in that The metal organic framework material is one or more of a copper-based metal organic framework material, a nickel-based metal organic framework material, a cobalt-based metal organic framework material, an iron-based metal organic framework material, a zinc-based metal organic framework material, a titanium-based metal organic framework material, and a zirconium-based metal organic framework material.

7. The composite polymer electrolyte according to claim 5, 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 Ln3Z 1.4 Ta 0.6 O 12 、Li7La3Zr2O 12 , Li 6.55 Ga 0.15 La3Zr2O 12 One or more of the .

8. A method for preparing the composite polymer electrolyte according to any one of claims 5 to 7, characterized in that The method comprises 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 to 150° C. for 4 to 48 hours to obtain a composite electrolyte film.

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