A solid electrolyte, a preparation method thereof and an application thereof

Abstract

The present invention belongs to the technical field of electrolyte materials, and particularly relates to a solid electrolyte, a preparation method thereof, and an application thereof. The present invention provides a solid electrolyte, which comprises the following preparation raw materials in parts by mass: 100 parts of a polymer matrix; 14 to 20 parts of a lithium salt; 1 to 20 parts of nano calcium sulfate. The solid electrolyte provided by the present invention has a high ionic conductivity at room temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolyte materials, and particularly relates to a solid electrolyte, a preparation method thereof, and an application thereof. Background Art

[0002] Traditional lithium-ion battery electrolytes use organic solvents, such as organic carbonates. However, due to problems such as low vapor pressure, low flash point, flammability, and easy leakage of organic solvents, there are relatively large potential safety hazards. Therefore, solid electrolytes are currently commonly used to replace liquid electrolytes to improve the safety of lithium-ion batteries.

[0003] Polymer solid electrolyte materials (such as polyethylene oxide) have advantages such as low reactivity with electrode materials, light weight, easy film formation, good viscoelasticity, low cost, and easy continuous industrial production. However, they still have the defect of relatively low ionic conductivity at room temperature, and their ionic conductivity is only 10 -6 ~10 -5 S / cm -1 . Summary of the Invention

[0004] The purpose of the present invention is to provide a solid electrolyte, a preparation method thereof, and an application thereof. The solid electrolyte provided by the present invention has a relatively high ionic conductivity at room temperature.

[0005] To solve the above problems, the present invention provides a solid electrolyte, which comprises the following preparation raw materials in parts by mass:

[0006] Polymer matrix: 100 parts;

[0007] Lithium salt: 14 - 20 parts;

[0008] Nano calcium sulfate: 1 - 20 parts.

[0009] Preferably, the polymer matrix includes one or more of polyethylene oxide, polyacrylonitrile, or polyvinylidene fluoride.

[0010] Preferably, the lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluoromethanesulfonyl)imide, or lithium difluoro(oxalato)borate.

[0011] Preferably, the particle size of the nano calcium sulfate is 80 - 180 nm.

[0012] Preferably, the preparation method of the nano calcium sulfate includes the following steps:

[0013] Mix glycerol, ethanol, and a surfactant for the first time to obtain a first mixed solution;

[0014] Mix phosphogypsum, nitric acid, and sulfuric acid for the second time to obtain a second mixed solution;

[0015] The first mixed solution and the second mixed solution are mixed for the third time, and the obtained raw material solution is subjected to a hydrothermal reaction to obtain the nano calcium sulfate.

[0016] Preferably, the surfactant includes one or more of sodium dodecyl sulfonate, cetyltrimethylammonium bromide, and Triton.

[0017] The present invention also provides a method for preparing the above-mentioned solid electrolyte, including the following steps:

[0018] A polymer matrix, nano calcium sulfate, a lithium salt, and a polar organic solvent are mixed to obtain a composite material;

[0019] The composite material is dried to obtain the solid electrolyte.

[0020] Preferably, the drying temperature is 20-30°C and the time is 8-12 h.

[0021] The present invention also provides an application of the above-mentioned solid electrolyte or the solid electrolyte prepared by the above-mentioned preparation method as a solid electrolyte membrane in a lithium-ion battery.

[0022] Preferably, the thickness of the solid electrolyte membrane is 20-100 μm.

[0023] The present invention provides a solid electrolyte, which includes the following preparation raw materials by mass: 100 parts of a polymer matrix; 14-20 parts of a lithium salt; 1-20 parts of nano calcium sulfate. In the present invention, the nano calcium sulfate has a small size and a large specific surface area, which can effectively shorten the transmission distance of lithium ions. Therefore, when the solid electrolyte provided by the present invention is applied to a lithium battery, it still has a high ionic conductivity at room temperature. Description of the Drawings

[0024] Figure 1 SEM and XRD test diagrams of the nano CaSO4 obtained in Examples 1-4;

[0025] Figure 2 XPS test diagrams of phosphogypsum (PG) and the nano CaSO4 obtained in Example 3;

[0026] Figure 3 Impedance performance test diagram of the solid electrolyte membrane prepared in Example 7. Detailed Description of the Invention

[0027] The present invention provides a solid electrolyte, which includes the following preparation raw materials by mass:

[0028] 100 parts of a polymer matrix;

[0029] 14 - 20 parts of lithium salt;

[0030] 1 - 20 parts of nano - calcium sulfate.

[0031] In the present invention, by mass, the raw materials for preparing the solid electrolyte include 100 parts of a polymer matrix, and the polymer matrix includes one or more of polyethylene oxide, polyacrylonitrile or polyvinylidene fluoride, more preferably polyethylene oxide (PEO). In the present invention, the weight - average molecular weight of the polyethylene oxide is preferably 100 - 5000 kDa, more preferably 600 - 1000 kDa.

[0032] In the present invention, by mass, the raw materials for preparing the solid electrolyte include 14 - 20 parts of lithium salt, preferably 16 - 18 parts. In the present invention, the lithium salt preferably includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluoromethanesulfonyl)imide or lithium difluoro(oxalato)borate, more preferably lithium bis(trifluoromethanesulfonyl)imide.

[0033] In the present invention, by mass, the raw materials for preparing the solid electrolyte include 1 - 20 parts of nano - calcium sulfate, preferably 5 - 10 parts. In the present invention, the particle size of the nano - calcium sulfate is 80 - 180 nm, more preferably 80 - 120 nm. In the present invention, the structure of the nano - calcium sulfate is preferably a cubic structure.

[0034] In the present invention, the preparation method of the nano - calcium sulfate preferably includes the following steps:

[0035] Mix glycerol, ethanol and a surfactant for the first time to obtain a first mixed solution;

[0036] Mix phosphogypsum, nitric acid and sulfuric acid for the second time to obtain a second mixed solution;

[0037] Mix the first mixed solution and the second mixed solution for the third time, and perform a hydrothermal reaction on the obtained raw material solution to obtain the nano - calcium sulfate.

[0038] In the present invention, glycerol, ethanol and a surfactant are mixed for the first time to obtain a first mixed solution.

[0039] In the present invention, the surfactant preferably includes one or more of sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and Triton, more preferably SDS or Triton.

[0040] In the present invention, the volume ratio of glycerol to ethanol is preferably 50 - 70:20 - 40, more preferably 55 - 65:25 - 35. In the present invention, the mass ratio of the surfactant to the volume of glycerol is preferably 0.1 - 1 g:50 - 70 mL, more preferably 0.5 g:50 - 70 mL.

[0041] In the present invention, the first mixing method is preferably magnetic stirring. In the present invention, the time of magnetic stirring is preferably 10 - 30 min, more preferably 15 - 25 min.

[0042] After obtaining the first mixed solution, the present invention second - mixes phosphogypsum, sulfuric acid and nitric acid to obtain a second mixed solution.

[0043] In the present invention, the mass - to - volume ratio of phosphogypsum to sulfuric acid is preferably 2 g: 1 - 3 mL, more preferably 2 g: 2 mL. In the present invention, the volume ratio of sulfuric acid to nitric acid is preferably 1:1.

[0044] In the present invention, the second mixing method is preferably stirring, the rotation speed of the stirring is preferably 80 - 140 rpm, more preferably 100 - 120 rpm, and the time is preferably 5 - 10 min, more preferably 6 - 8 min.

[0045] After obtaining the second mixed solution, the present invention third - mixes the first mixed solution and the second mixed solution, and the obtained raw material solution is subjected to a hydrothermal reaction to obtain nano - calcium sulfate.

[0046] In the present invention, the third mixing method is preferably stirring, the rotation speed of the stirring is preferably 80 - 140 rpm, more preferably 100 - 120 rpm, and the time is preferably 5 - 10 min, more preferably 6 - 8 min.

[0047] In the present invention, the temperature of the hydrothermal reaction is preferably 100 - 150 °C, more preferably 110 - 130 °C, and the heat - preservation time is preferably 12 - 24 h, more preferably 15 - 20 h.

[0048] In the present invention, the main component of phosphogypsum is CaSO4·2H2O. Phosphogypsum is an insoluble electrolyte, but its solubility can be significantly increased in nitric acid. During the hydrothermal reaction, H + ionized from nitric acid combines with SO4 2- dissolved from CaSO4·2H2O to form HSO4 - . When the concentrations of Ca 2+ and SO4 2- in the solution are greater than the supersaturation of CaSO4, CaSO4 crystal nuclei are formed in the solution. The crystallization of CaSO4 promotes the further dissolution of CaSO4·2H2O until the CaSO4·2H2O crystals are completely converted into CaSO4 crystals.

[0049] In the present invention, after the hydrothermal reaction, it is preferably further included to cool, filter, and dry the product obtained from the hydrothermal reaction in sequence. In the present invention, the way of cooling is not specifically limited, and it can be cooled to room temperature by using the operations well-known in the art. In the present invention, the filtration is not specifically limited, and the operations well-known to those skilled in the art can be adopted. In the present invention, the drying temperature is preferably 40 - 80 °C, more preferably 50 - 70 °C, and the drying time in the present invention is not specifically limited, as long as the obtained calcium sulfate can be dried.

[0050] The present invention also provides a preparation method of the above-mentioned solid electrolyte, including the following steps:

[0051] Mix a polymer matrix, nano calcium sulfate, a lithium salt, and a polar organic solvent to obtain a composite material;

[0052] Dry the composite material to obtain the solid electrolyte.

[0053] In the present invention, the mixing is preferably to initially mix the nano calcium sulfate and the polar organic solvent, and then remix the obtained solution with the polymer matrix and the lithium salt to obtain a composite material. In the present invention, the polar organic solvent includes one or more of acetonitrile, acetone, N-methylpyrrolidone, and N,N-dimethylformamide, and more preferably acetonitrile.

[0054] In the present invention, the way of the initial mixing is preferably stirring. In the present invention, the way of the remixing is preferably stirring, the rotation speed of the stirring is preferably 80 - 140 rpm, more preferably 100 - 120 rpm, and the stirring time is preferably 1 - 3 h, more preferably 2 h.

[0055] In the present invention, the drying temperature is preferably 20 - 30 °C, more preferably 23 - 27 °C, and the time is preferably 8 - 12 h, more preferably 9 - 11 h.

[0056] The present invention also provides the application of the above-mentioned solid electrolyte or the solid electrolyte prepared by the above preparation method as a solid electrolyte membrane in a lithium-ion battery.

[0057] In the present invention, the thickness of the solid electrolyte membrane is preferably 20 - 100 μm, more preferably 50 - 60 μm.

[0058] In the present invention, the preparation of the solid electrolyte membrane preferably includes the following steps:

[0059] Perform film scraping and drying on the composite material in sequence to obtain the solid electrolyte membrane.

[0060] In the present invention, the operation of drying is preferably the same as that for the preparation of the solid electrolyte, which will not be elaborated here. In the present invention, the operation of blade coating is not specifically limited, and it is sufficient to coat to a thickness of 20 - 100 μm. In the present invention, the composite material is preferably the composite material described above.

[0061] To further illustrate the present invention, the solutions of the present invention will be described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0062] Example 1

[0063] ① Preparation of nano-calcium sulfate:

[0064] Place 60 mL of glycerol and 30 mL of ethanol in a beaker. After stirring until homogeneous, add 0.1 g of surfactant CTAB and stir for 20 min to obtain a first mixed solution.

[0065] Place 2 g of dried phosphogypsum in a beaker, add 2 mL of HNO3, stir for 10 min, then add 2 mL of H2SO4 and stir for 10 min to obtain a second mixed solution.

[0066] Slowly add the first mixed solution to the second mixed solution, stir for 10 min until the solution is uniformly mixed, transfer it to a reaction kettle, place it in a vacuum drying oven at 140 °C for hydrothermal reaction for 12 h, then filter and dry in sequence. The drying temperature is 60 °C to obtain nano-CaSO4.

[0067] ② Ultrasonically disperse and then stir and disperse 16 parts by mass of lithium bis(trifluoromethanesulfonyl)imide in 20 mL of acetonitrile to obtain a lithium salt dispersion. The power of ultrasonic dispersion is 500 kW, the rotation speed of stirring and dispersion is 80 rpm, and the time is 0.25 h.

[0068] Add 100 parts by mass of PEO and 5 parts by mass of the above-prepared nano-CaSO4 to the lithium salt dispersion. After ultrasonic dispersion and stirring and dispersion in sequence, scrape it into a composite solid electrolyte membrane with a thickness of 50 μm. The power of ultrasonic dispersion is 500 kW, the rotation speed of stirring and dispersion is 80 rpm, and the time is 3 h.

[0069] Example 2

[0070] The difference from Example 1 is only that the mass of surfactant CTAB is 0.3 g.

[0071] Example 3

[0072] The difference from Example 1 is only that the mass of surfactant CTAB is 0.5 g.

[0073] Example 4

[0074] The difference from Example 1 is only that the mass of the surfactant CTAB is 1.0 g.

[0075] Example 5

[0076] The difference from Example 3 is only that the surfactant is Triton.

[0077] Example 6

[0078] The difference from Example 3 is only that the surfactant is SDS.

[0079] Example 7

[0080] The difference from Example 3 is only that: the mass fraction of nano-CaSO4 is 10 parts.

[0081] Example 8

[0082] The difference from Example 3 is only that: the mass fraction of nano-CaSO4 is 15 parts.

[0083] Example 9

[0084] The difference from Example 3 is only that: the mass fraction of nano-CaSO4 is 20 parts.

[0085] Comparative Example 1

[0086] The difference from Example 3 is only that: nano-CaSO4 is not added.

[0087] Test Example

[0088] The present invention conducts SEM and XRD tests on phosphogypsum (PG) and the nano-CaSO4 obtained in Examples 1 to 4. The test results are as Figure 1 shown, where Figure 1 (a) is the SEM image of the nano-CaSO4 prepared in Example 1; Figure 1 (b) is the SEM image of the nano-CaSO4 prepared in Example 2; Figure 1 (c) is the SEM image of the nano-CaSO4 prepared in Example 3; Figure 1 (d) is the SEM image of the nano-CaSO4 prepared in Example 4; Figure 1 (e) is the XRD test pattern of Examples 1 to 4. It can be seen from Figure 1 this that: phosphogypsum (PG) is micron-sized flakes. After the hydrothermal reaction, the bound water in PG disappears, and the sample changes from calcium sulfate dihydrate (CaSO4·2H2O) to nano-CaSO4, and the nano-CaSO4 is cube-shaped.

[0089] The present invention conducts XPS tests on phosphogypsum (PG) and the nano-CaSO4 obtained in Example 3. The test results are asFigure 2 As shown, from Figure 2 it can be seen that: in the O1s spectrum, the O-H bond of PG disappeared after the reaction, indicating that the bound water of PG disappeared during the reaction, and the sample changed from calcium sulfate dihydrate (CaSO4·2H2O) to nano-CaSO4.

[0090] The present invention tested the flame retardancy and ionic conductivity of the solid electrolyte membranes prepared in Example 3, Examples 7 to 9 and Comparative Example 1. The test method for flame retardancy was to use a microscale combustion calorimeter (MCC-3, Governrk, USA) to test according to the ASTM D7309 standard; the ionic conductivity was tested by the alternating current impedance method: the alternating current impedance test was carried out at room temperature with an electrochemical workstation; through the obtained alternating current impedance spectrum, the ionic conductivity σ of the polyethylene oxide-based solid electrolyte was calculated using the formula σ = t / RA. Among them, t is the thickness of the electrolyte membrane, R is the resistance value of the electrolyte membrane, and A is the cross-sectional area of the electrolyte membrane. The test results are shown in Table 1. It can be seen from Table 1 that: compared with Comparative Example 1, the peak value of the heat release rate (PHRR) and the total heat release amount (THR) of the examples decreased, and with the increase of the addition amount of nano-CaSO4, the decreasing trend was more obvious. With the increase of the addition amount of nano-CaSO4, compared with Comparative Example 1, the ionic conductivity of the examples first increased and then decreased, and Example 7 had the maximum ionic conductivity.

[0091] Table 1 Test results of flame retardancy and ionic conductivity of solid electrolyte membranes

[0092]

[0093] The present invention tested the impedance performance of the solid electrolyte membrane prepared in Example 7. The test method was the alternating current impedance method, and the test results are shown in Figure 3 , from Figure 3 it can be seen that: within a certain temperature range (25 - 60 °C), with the increase of temperature, its impedance gradually decreased and the ionic conductivity gradually increased.

[0094] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all embodiments. Other embodiments can also be obtained according to these embodiments without creative work, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A solid electrolyte, characterized in that, Comprising the following preparation raw materials by mass parts: 100 parts of polymer matrix; 14 - 20 parts of lithium salt; 10 - 15 parts of nano calcium sulfate; The structure of the nano calcium sulfate is a cubic structure; The particle size of the nano calcium sulfate is 80 - 180 nm.

2. The solid electrolyte according to claim 1, wherein The polymer matrix includes one or more of polyethylene oxide, polyacrylonitrile or polyvinylidene fluoride.

3. The solid electrolyte according to claim 1, characterized in that The lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide or lithium difluoro(oxalato)borate.

4. The solid electrolyte according to claim 1, characterized in that, The preparation method of the nano calcium sulfate includes the following steps: First mix glycerol, ethanol and surfactant to obtain a first mixed solution; Second mix phosphogypsum, nitric acid and sulfuric acid to obtain a second mixed solution; Third mix the first mixed solution and the second mixed solution, and perform hydrothermal reaction on the obtained raw material solution to obtain the nano calcium sulfate.

5. The solid electrolyte according to claim 4, characterized in that, The surfactant includes one or more of sodium dodecyl sulfate, cetyltrimethylammonium bromide and Triton.

6. The method for preparing the solid electrolyte according to any one of claims 1 to 5, characterized in that, Including the following steps: Mix the polymer matrix, nano calcium sulfate, lithium salt and polar organic solvent to obtain a composite material; Dry the composite material to obtain the solid electrolyte.

7. The preparation method according to claim 6, characterized in that, The drying temperature is 20 - 30 °C and the time is 8 - 12 h.

8. Application of the solid electrolyte according to any one of claims 1 - 5 or the solid electrolyte prepared by the preparation method according to any one of claims 6 - 7 as a solid electrolyte membrane in a lithium ion battery.

9. The application according to claim 8, wherein The thickness of the solid electrolyte membrane is 20 - 100 μm.

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