CN114566704A - Preparation method of semisolid gel electrolyte - Google Patents

Abstract

The invention relates to a preparation method of a semi-solid gel electrolyte. The preparation method comprises the following steps: dissolving nitrate in an organic solvent, mixing with PVP, PAN or PVA solution, preparing a fiber film through high-voltage electrostatic spinning, and then carrying out high-temperature hot-pressing sintering on the fiber film to obtain a fast ion conductor with a continuous structure; and then pouring a PEO, PVA or PAN solution on the surface of the fast ion conductor, drying and then soaking in an electrolyte to obtain the semi-solid fast ion conductor gel electrolyte. The gel electrolyte prepared by the invention can improve the ionic conductivity in the semi-solid electrolyte.

Description

A kind of preparation method of semi-solid gel electrolyte

technical field

The invention belongs to the field of electrolytes, in particular to a preparation method of a semi-solid gel electrolyte, and in particular to a preparation method of a semi-solid gel electrolyte diaphragm slurry.

Background technique

Solid-state electrolytes exhibit high mechanical properties and high stability, providing the possibility for the development of next-generation safe, high-energy energy storage batteries. Compared with liquid electrolytes, solid electrolytes have the following outstanding advantages: First, solid electrolytes have no leakage problems, are stable in contact with air, and have no danger of explosion. Secondly, the solid electrolyte battery that is easy to form a film and is easy to stack is less difficult to package, and it is easy to realize high-voltage integration and large-scale production. In addition, compared with electrolytes, most electrolytes have higher lithium ion migration numbers, which can effectively solve the problem of concentration polarization of batteries. In many solid electrolytes, the ionic conductivity is generally lower than that of traditional liquid electrolytes.

In the prior art, fast ion conductors are dispersed particles and fail to form a complete ion-conducting network. The existing patent CN113644377A describes a semi-solid titanium lithium aluminum phosphate gel electrolyte diaphragm slurry and its preparation method and application; the fast ion conductor titanium lithium aluminum phosphate used is granular; the ionic conductivity is only 2.9ms/ cm is 10 ms/cm lower than the ionic conductance of traditional liquid electrolytes. The present invention proposes to improve the ionic conductivity by constructing a structurally continuous fast ionic conductor gel semi-solid electrolyte. The existing patent CN201811181826 only relies on the gel electrolyte obtained by dissolving PEO and lithium bis-trifluoromethylsulfonylamide (LITFSI) in acetonitrile in a mass ratio of 10:1 to remove the gel electrolyte obtained by infiltrating the membrane obtained by sintering The membrane EIS impedance is relatively large and the ionic conductivity is relatively poor. The method of the present invention adopting the structure continuous fast ionic conductor and soaking the electrolyte can effectively reduce the interface impedance and strengthen the ion-conducting ability of the gel electrolyte.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of a semi-solid gel electrolyte for the problem of low ionic conductivity in the semi-solid electrolyte.

The fast ion conductor prepared by the invention is a 3D network structure with continuous structure. When pouring, the surface of the fast ion conductor is covered by the polymer solution to form a polymer film that is wrapped and penetrated into the structure of the fast ion conductor. The polymer film can be soaked and washed subsequently to absorb the electrolyte to form a gel and protect the relatively fragile internal structure. 3D network-structured fast ionic conductors. Soaked in the electrolyte, the polymer film and the continuous 3D network structure of the fast ion conductor have abundant pore structures that can absorb liquid and swell into a gel electrolyte.

The object of the present invention can be realized through the following scheme:

The invention provides a preparation method of a semi-solid gel electrolyte, and the preparation method comprises the following steps:

S1, nitrate is dissolved in organic solvent 1 to obtain solution A;

S2, dissolve the polymer powder 1 in the organic solvent 1, and stir to obtain a solution B;

S3, adding solution A to solution B, stirring to obtain solution C;

S4, preparing the solution C obtained in step S3 into a fiber film, and then hot-pressing and sintering the fiber film to obtain a fast ion conductor with a continuous structure;

S5, adding the polymer powder 2 into the organic solvent 2; mixing and stirring to obtain a solution D, pouring it on the surface of the fast ion conductor obtained in step S4, and drying to obtain a dry product;

S6. Immerse the dried product obtained in step S5 in an electrolyte to obtain a semi-solid gel electrolyte.

As an embodiment of the present invention, the organic solvent 1 includes at least one of three organic solvents including DMF, NMP, and acetonitrile. The nitrate includes one or more of zirconium nitrate, lithium nitrate and lanthanum nitrate.

As an embodiment of the present invention, the nitrates include lithium nitrate, lanthanum nitrate and zirconium nitrate. The stoichiometric ratio of lithium:lanthanum:zirconium chemical elements is (70-75):(30-40);(10-20).

As an embodiment of the present invention, the polymer powder 1 in step S2 includes one of PVP, PAN, and PVA.

As an embodiment of the present invention, the stirring in step S2 is magnetic stirring, and the stirring time is 3-4h.

As an embodiment of the present invention, the stirring in step S3 is magnetic stirring, and the stirring time is 12h-24h.

As an embodiment of the present invention, the fiber film in step S4 is prepared by high-voltage electrospinning equipment. The process parameters of the high-voltage electrostatic spinning equipment are: the distance between the spinning needle and the take-up reel is 10-20cm; the positive and negative voltage difference is 20-25kv, the spinning speed is 0.5-2ml/h, and the ambient temperature is 25±3 ℃; humidity is 20 ~ 40%.

As an embodiment of the present invention, the temperature of the high-temperature hot pressing sintering in step S4 is 700° C.±50° C., and the time is 7±2 h. Hot pressing sintering is obtained by hot pressing sintering in a ceramic flat plate. The sintering pressure is 3±0.5kpa. When the sintering temperature is lower than 650°C, the crystallinity of the product is low. If the sintering temperature is higher than 750°C or the pressure of the ceramic plate is greater than 3.5kpa, the continuous structure of the solid electrolyte of the fast ion conductor obtained will be destroyed and the brittleness will increase. When the pressure of the ceramic plate is less than 2.5kpa, the fiber film shrinks greatly at high temperature, and the flatness of the obtained fast-conductor cannot be maintained, which is not conducive to the subsequent casting and the preparation of gel electrolyte. When the sintering time is shorter than 5h, the decomposition and crystallization of the material are insufficient, and the fast example conductor with higher crystallinity cannot be synthesized. Preparation of Gel Electrolytes with Better Casting and Flatness

As an embodiment of the present invention, the polymer powder 2 in step S5 includes one of PEO, PVA, and PAN.

As an embodiment of the present invention, the organic solvent 2 in step S5 includes one of acetone and acetonitrile.

As an embodiment of the present invention, the stirring time in step S5 is 3h.

As an embodiment of the present invention, the drying temperature in step S5 is 30±5° C.; the drying time is 12-24 h.

As an embodiment of the present invention, the soaking time in step S6 is 24-36h.

Through the hot pressing and sintering treatment, the invention can ensure that the fiber film will not shrink violently during the heat treatment process, so as to ensure the smoothness and non-breakage of the structure. If the polymer membrane obtained by spinning has not been hot-pressed and sintered, it is only used as a carrier for subsequent growth without abundant pore structure, and the resulting gel electrolyte membrane has a weak ion-conducting ability. On the other hand, the hot-pressed and sintered fibers of the present invention are long fibers and are fast ion conductors as a whole, and have stronger ion-conducting ability.

Compared with the prior art, the present invention has the following beneficial effects:

1. The ionic conductivity of the semi-solid gel network fast ion conductor electrolyte is as high as 6*10 ^-3 s/cm, while the ionic conductivity of the conventional granular fast ion conductor filled gel electrolyte is only 2*10 ^-3 s/cm.

2. The fast ion conductor structure with continuous structure provides continuous and multi-channel for lithium ion migration and transportation.

3. The gel electrolyte swollen by the immersion electrolyte reduces the interface impedance between the electrolyte and the active material of the pole piece.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a schematic diagram of the structure of the fast ion conductor after pouring in Example 1. FIG.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, and provide detailed implementation manners and specific operation procedures, which will help those skilled in the art to further understand the present invention. It should be pointed out that the protection scope of the present invention is not limited to the following embodiments, and several adjustments and improvements made under the premise of the concept of the present invention all belong to the protection scope of the present invention.

The semi-solid gel electrolyte prepared by the present invention is tested by the following method for the ionic conductivity of the electrolyte:

In step a, the semi-solid electrolyte membrane is made into an electrolyte circular sheet in an anhydrous and oxygen-free environment;

In step b, the semi-solid electrolyte membrane disc in step a is placed in a three-pole battery test device, and the positive and negative electrodes are stainless steel electrodes;

Step c, using an electrochemical workstation to perform an AC impedance test on the solid-state battery to obtain an EIS curve of the semi-solid electrolyte membrane, and read the impedance value of the semi-solid electrolyte membrane from the EIS curve;

Step d, according to the impedance value of the solid electrolyte,

The conductivity of the solid electrolyte is calculated by the formula: σ=L/RS;

where σ is the conductivity (S/cm) of the semi-solid electrolyte membrane;

S is the area of the semi-solid electrolyte membrane (cm ² );

L is the thickness (cm) of the semi-solid electrolyte membrane;

R is the semi-solid electrolyte membrane resistance value (Ω) obtained from the AC impedance diagram.

Example 1

This embodiment provides a preparation method of a semi-solid gel electrolyte, and the preparation method includes the following steps:

Step 1. Dissolve lithium nitrate, lanthanum nitrate and zirconium nitrate in NMP, weigh according to the stoichiometric ratio of lithium:lanthanum:zirconium 7:3:2, dissolve in NMP, and the ratio of nitrate to NMP is 1g : 20ml, a clear solution A was obtained after magnetic stirring for 3h;

Step 2. Dissolving the polymer powder PVP in NMP, the dosage ratio is 4g: 20ml, and after magnetic stirring for 3h, a clear solution B is obtained;

Step 3. Slowly drop solution A into solution B, the volume ratio is 1:20, and a clear solution C is obtained after magnetic stirring for 12 hours;

Step 4. Place solution C in an electrospinning device for high-voltage electrospinning. The working parameters of the device are that the spinning needle is 20cm away from the take-up reel; the positive and negative voltage difference is 23kv, the spinning speed is 1ml/h, and the ambient temperature is is 25°C; humidity is 30%;

Step 5. Place the spinning fiber membrane obtained in step 4 in a ceramic flat plate for hot pressing and sintering to obtain a fast ion conductor with a continuous structure. The obtained product is shown in Figure 1. The pressure of the ceramic plate is 3kpa; the sintering temperature is 700°C; Time 6h.

Step 6. Dissolving the polymer powder PEO in the organic solvent acetone, the dosage ratio is 3g: 10ml, and after stirring for 3h, a transparent clear liquid D is obtained, which is subsequently poured on the surface of the fast ion conductor with continuous structure obtained in step 5, 30 ℃ dry for 12h;

Step 7. Immerse the dried product in step 6 in an electrolyte (volume ratio V(EC):V(EMC):V(DMC)=1:1:1; 1mol/LLiPF6) for 24h to obtain a semi-solid gel fast ion conductor electrolyte.

Step 8; Test the electrical conductivity of the semi-solid gel fast ion conductor electrolyte in Step 7. The ionic conductivity of the prepared semi-solid gel network fast ionic conductor electrolyte is as high as 6.2*10 ^-3 s/cm.

Example 2

This embodiment provides a preparation method of a semi-solid gel electrolyte, and the preparation method includes the following steps:

Step 1. Dissolve lithium nitrate, lanthanum nitrate, and zirconium nitrate in NMP, weigh according to the stoichiometric ratio of lithium:lanthanum:zirconium: 7:3:2, dissolve in NMP, and the ratio of nitrate to NMP is 1g: 20ml, after magnetic stirring for 3h, clear solution A was obtained;

Step 2. Dissolving the polymer powder PVP in NMP, the dosage ratio is 4g: 20ml, and after magnetic stirring for 3h, a clear solution B is obtained;

Step 3. Slowly drop solution A into solution B, the volume ratio is 1:20, and a clear solution C is obtained after magnetic stirring for 12 hours;

Step 4. Place solution C in an electrospinning device for high-voltage electrospinning. The working parameters of the device are that the spinning needle is 20cm away from the take-up reel; the positive and negative voltage difference is 23kv, the spinning speed is 1ml/h, and the ambient temperature is is 25°C; humidity is 30%;

Step 5. The spun fiber membrane obtained in step 4 is placed in a ceramic plate for hot pressing and sintering to obtain a fast ion conductor with a continuous structure. The pressure of the ceramic plate is 2.8kpa; the sintering temperature is 650° C.; and the sintering time is 5h.

Step 6. Dissolving the polymer powder PEO in the organic solvent acetone, the dosage ratio is 3g: 10ml, and after stirring for 3h, a transparent clear liquid D is obtained, which is subsequently poured on the surface of the fast ion conductor with continuous structure obtained in step 5, 30 ℃ dry for 12h;

Step 7. Immerse the dried product in step 6 in an electrolyte (volume ratio V(EC):V(EMC):V(DMC)=1:1:1; 1mol/LLiPF6) for 24h to obtain a semi-solid gel fast ion conductor electrolyte;

Step 8. Test the conductivity of Step 7 semi-solid gel fast ionic conductor electrolyte. The ionic conductivity of the semi-solid gel network fast ionic conductor electrolyte is as high as 5.5*10 ^-3 s/cm.

Example 3

This embodiment provides a preparation method of a semi-solid gel electrolyte, and the preparation method includes the following steps:

Step 1. Dissolve lithium nitrate, lanthanum nitrate and zirconium nitrate in acetonitrile, weigh according to the stoichiometric ratio of lithium:lanthanum:zirconium 70:34:17, dissolve in acetonitrile, and the ratio of nitrate to acetonitrile is 1g : 20ml, a clear solution A was obtained after magnetic stirring for 3h;

Step 2. Dissolving the polymer powder PAN in acetonitrile, the dosage ratio is 4g:20ml, and after magnetic stirring for 3h, a clear solution B is obtained;

Step 3. Slowly drop solution A into solution B, the volume ratio is 1:20, and a clear solution C is obtained after magnetic stirring for 12 hours;

Step 4. Place solution C in an electrospinning device for high-voltage electrospinning. The working parameters of the device are that the spinning needle is 10cm away from the take-up reel; the positive and negative voltage difference is 25kv, the spinning speed is 1.5ml/h, and the environment The temperature is 25℃; the humidity is 30%;

Step 5. The spinning fiber membrane obtained in step 4 is placed in a ceramic flat plate for hot pressing and sintering to obtain a fast ion conductor with a continuous structure. The obtained product is shown in Figure 1. The pressure of the ceramic plate is 3kpa; Time 9h.

Step 6. Dissolving the polymer powder PAN in the organic solvent acetone, the dosage ratio is 3g: 10ml, and after stirring for 3h, a transparent clear liquid D is obtained, which is subsequently poured on the surface of the continuous fast ion conductor obtained in step 5, 30 ℃ dry for 12h;

Step 7. Immerse the dried product in step 6 in an electrolyte (volume ratio V(EC):V(EMC):V(DMC)=1:1:1; 1mol/LLiPF6) for 24h to obtain a semi-solid gel fast ion conductor electrolyte.

Step 8; Test the electrical conductivity of the semi-solid gel fast ion conductor electrolyte in Step 7. The prepared semi-solid gel network fast ion conductor electrolyte has an ionic conductivity of up to 5.0*10 ^-3 s/cm.

Comparative Example 1

This comparative example provides a solid-state fast ion conductor electrolyte, the preparation method of which is basically the same as that of Example 1, the only difference is that no pressure is applied during the hot-pressing sintering process, and only sintering is performed.

The network-like fast ion conductor prepared in this example is not subjected to hot pressing treatment, the flatness of the fast ion conductor is not good, the fibers are broken, and the ionic conductivity of the electrolyte of the semi-solid gel network-like fast ion conductor is 2.8*10 ^-3 s /cm.

Comparative Example 2

This comparative example provides a solid-state fast ion conductor electrolyte, the preparation method of which is basically the same as that of Example 1, and the only difference lies in the difference between the fast ion conductor and the conventional filler.

Step 1. Dissolve the polymer powder PEO in the organic solvent 2 acetone and stir for 3 hours to obtain a transparent clear liquid D, which is subsequently mixed with commercial SiO ₂ , D50 is 1um particles, and uniformly mixed according to the mass ratio of 8:2 , dried in a petri dish for 12h to form a film.

Step 2. Immerse the dried product in step 1 in an electrolyte (volume ratio V(EC):V(EMC):V(DMC)=1:1:1; 1mol/LLiPF6) for 24h to obtain a semi-solid gel fast ion conductor electrolyte;

Step 3; test the electrical conductivity of the semi-solid gel fast ion conductor electrolyte in step 2.

The semi-solid gel network fast ion conductor electrolyte has an ionic conductivity of 1.0*10 ^-3 s/cm.

Comparative Example 3

This comparative example provides a solid-state fast ion conductor electrolyte, the preparation method of which is basically the same as that of Example 1, the only difference is that the temperature of hot pressing and sintering is 500°C.

The semi-solid gel network fast ion conductor electrolyte has an ionic conductivity of 1.3*10 ^-3 s/cm.

Comparative Example 4

This comparative example provides a solid-state fast ion conductor electrolyte, the preparation method of which is basically the same as that of Example 1, the only difference is that the pressure of hot-pressing sintering is 6 kPa.

The semi-solid gel network fast ion conductor electrolyte has an ionic conductivity of 2.5*10 ^-3 s/cm.

Comparative Example 5

This comparative example provides a solid-state fast ion conductor electrolyte, the preparation method of which is basically the same as that of Example 1, the only difference is that the time for hot pressing and sintering is 3 hours.

The semi-solid gel network fast ion conductor electrolyte has an ionic conductivity of 2.0*10 ^-3 s/cm.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and those skilled in the art can make various variations or modifications within the scope of the claims, which do not affect the essential content of the present invention.

Claims (10)

1. a preparation method of semi-solid gel electrolyte, is characterized in that, described method comprises the steps: S1, nitrate is dissolved in organic solvent 1 to obtain solution A; S2, dissolve the polymer powder 1 in the organic solvent 1, and stir to obtain a solution B; S3, adding solution A to solution B, stirring to obtain solution C; S4, preparing the solution C obtained in step S3 into a fiber film, and then hot-pressing and sintering the fiber film to obtain a fast ion conductor with a continuous structure; S5, adding the polymer powder 2 into the organic solvent 2; mixing and stirring to obtain a solution D, pouring on the surface of the fast ion conductor obtained in step S4, and drying to obtain a dry product; S6. Immerse the dried product obtained in step S5 in an electrolyte to obtain a semi-solid gel electrolyte. 2 . The preparation method according to claim 1 , wherein the organic solvent 1 comprises at least one of the three organic solvents of DMF, NMP and acetonitrile. 3 . 3. The preparation method according to claim 1, wherein the nitrate in step S1 comprises one or more of zirconium nitrate, lithium nitrate and lanthanum nitrate. 4 . The preparation method according to claim 1 , wherein the polymer powder 1 in step S2 comprises one of PVP, PAN, and PVA. 5 . 5 . The preparation method according to claim 1 , wherein the fiber film in step S4 is prepared by high-voltage electrospinning equipment. 6 . 6. The preparation method according to claim 5, wherein the process parameters of the high-voltage electrostatic spinning equipment are: the distance between the spinning needle and the receiving reel is 10-20cm; the positive and negative voltage difference is 20-25kv, The spinning speed is 0.5～2ml/h, the ambient temperature is 25±3℃, and the humidity is 20～40%. 7 . The preparation method according to claim 1 , wherein the temperature of the hot-press sintering in step S4 is 700° C.±50° C. and the time is 7±2 h. 8 . 8 . The preparation method according to claim 1 , wherein the pressure of the hot pressing sintering in step S4 is 3±0.5 kpa. 9 . 9 . The preparation method according to claim 1 , wherein the polymer powder 2 in step S5 comprises one of PEO, PVA, and PAN. 10 . 10. The preparation method according to claim 1, wherein the organic solvent 2 in step S5 comprises one of acetone and acetonitrile.

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