CN107346834A - Without lithium salts addition composite solid electrolyte material, dielectric film and preparation method thereof - Google Patents

Abstract

The invention relates to a lithium salt-free composite solid electrolyte material, an electrolyte membrane and a preparation method thereof, comprising a polymer matrix material and a fast ion conductor powder material, and the chemical formula of the fast ion conductor material is Li _7‑x La ₃ Zr _{2‑ x} M _x O ₁₂ , wherein M is at least one of Al, Ta, Nb, W, Ga, Y, Te, 0≤x≤1, and the composite solid electrolyte material does not include lithium salt. Compared with other composite solid state electrolytes, the biggest difference of the present invention is that no lithium salt of any kind is added to the polymer, and under this condition, its room temperature ion conductivity can reach 10 ^‑4 S cm ^‑1 . When the composite solid electrolyte membrane in the present invention is applied to a lithium secondary battery, it has good cycle performance and rate performance at both room temperature (25°C) and 60°C.

Description

Lithium-free salt-added composite solid-state electrolyte material, electrolyte membrane and preparation method thereof

technical field

The invention relates to a high ion conductance composite solid electrolyte material, an electrolyte membrane and a preparation method thereof, which can be applied to an all-solid lithium secondary battery without adding lithium salt, and belongs to the technical field of batteries.

Background technique

As a new generation of green high-energy batteries, lithium secondary batteries have the advantages of small weight, high energy density, long cycle life, high working voltage, no memory effect, and no environmental pollution. They have been widely used in portable batteries such as mobile phones, notebook computers, and cameras. In electronic equipment, it is also the preferred power source for electric vehicles and hybrid electric vehicles in the future, with broad application prospects and huge economic benefits.

The electrolyte material is the carrier of lithium ions in the lithium secondary battery system, and it is a key component for the normal operation of the system. At present, lithium secondary batteries widely used in the market mainly use organic liquid electrolytes, which have problems such as flammability and explosion, low electrochemical window, and small operating temperature range, which not only brings safety hazards to the use of lithium secondary batteries, but also It also cannot meet the future requirements for high specific energy of lithium secondary batteries and stable energy storage in a wide operating temperature range.

The use of composite solid electrolytes with high ion conductivity is an excellent way to solve the above problems. Compared with organic liquid electrolytes, composite solid electrolytes can effectively slow down the growth of lithium dendrites due to the presence of polymer matrix, and have better safety and machinability. At the same time, the addition of inorganic powder materials makes the composite solid electrolyte have a higher electrochemical window and thermal stability, which can be suitable for high-voltage positive electrode materials and work environments with large temperature changes.

The existing composite solid electrolytes are all solid electrolytes with lithium salt added. Although the addition of lithium salt is beneficial to improve the ionic conductivity of the electrolyte, the crosslinking or coupling reaction between the lithium salt and the polymer will make the polymer amorphous, thereby reducing the melting point of the polymer, which in turn affects the operating temperature range of the electrolyte. In addition, the addition of lithium salts will change the polymer matrix from an ionic insulator to an ionic conductor. When the charge-discharge cycle reaches a certain level, lithium ions will be deposited and lithium dendrites will gradually grow. Eventually, the electrolyte will be degraded due to lithium dendrites. Crystal penetration and failure. Therefore, there is an urgent need to develop a composite solid-state electrolyte that does not add lithium salts, has high ionic conductivity, has a wide operating temperature range, and can inhibit the growth of lithium dendrites.

Contents of the invention

In view of the problems existing in the prior art, the object of the present invention is to provide a composite solid electrolyte material, an electrolyte membrane and a preparation method thereof without adding lithium salts, having high ion conductivity, a wide operating temperature range, and inhibiting the growth of lithium dendrites, and A lithium secondary battery including the electrolyte membrane.

In the first aspect, the present invention provides a composite solid electrolyte material, which is characterized in that it includes a polymer matrix material and a fast ion conductor powder material, and the chemical formula of the fast ion conductor material is Li _7-x La ₃ Zr _2-x M _x O ₁₂ , wherein M is at least one of Al, Ta, Nb, W, Ga, Y, Te, 0≤x≤1, and the composite solid electrolyte material does not include lithium salt.

In the composite solid electrolyte material of the present invention, during the charge and discharge process of the battery, Li ⁺ in the fast ion conductor inorganic powder conducts and moves rapidly at the interconnected powder particles and the interface between the particles and the polymer, thereby conducting Li ⁺ . The present invention does not add any form of lithium salt to the polymer, and it is difficult for lithium to deposit and form lithium dendrites in the polymer matrix, so internal short circuits are not easy to occur, and it has higher safety when applied to lithium secondary batteries, and There is no cross-linking or coupling between the fast ion conductor inorganic powder and the polymer, which can avoid polymer amorphization, so the working temperature range is wide. At the same time, the composite solid electrolyte material of the present invention still maintains excellent ionic conductivity, and its ionic conductivity can reach 10 ^-4 S cm ^-1 at room temperature, and has a lithium ion migration number close to 1, and a wide electrochemical window (above 5V) Etc.

Preferably, the composite solid electrolyte material is composed of the polymer matrix material and the fast ion conductor powder material, wherein the mass content of the polymer matrix material is 95-20%, and the mass content of the fast ion conductor powder material is The content is 5-80%.

Preferably, the polymer matrix material can be polyethylene oxide (PEO), polyethylene terephthalate (PET), polyimide (PI), polyvinylidene fluoride (PVdF), polymethyl At least one of methyl acrylate (PMMA), polyacrylonitrile (PAN), polypropylene carbonate (PPC), polyvinyl chloride (PVC) and copolymers thereof.

Preferably, the particle size of the fast ion conductor powder material is 20nm-20μm.

The working temperature of the composite solid electrolyte material of the present invention can be from room temperature to 120°C, preferably 60-100°C. High temperature helps to enhance the activity at the interface between powder particles and polymer, so the ion conductivity is higher when the temperature increases within a certain range.

In a second aspect, the present invention provides a composite solid electrolyte membrane, which is formed from the above composite solid electrolyte material.

In a third aspect, the present invention provides a method for preparing the above-mentioned composite solid electrolyte membrane, comprising the following steps:

1) Uniformly dispersing the fast ion conductor powder material and the polymer matrix material in an organic solvent to obtain a composite solid electrolyte slurry;

2) Coating the composite solid electrolyte slurry on the substrate and drying to obtain a composite solid electrolyte membrane.

The invention has the advantages of simple process, low cost, good repeatability and large-scale application.

Preferably, the fast ion conductor powder material is pre-dehydrated, and the step 1) is performed under a protective atmosphere.

Preferably, the solid content of the composite solid electrolyte slurry is 6%-15%.

In a fourth aspect, the present invention provides an all-solid lithium secondary battery, which includes: a positive electrode, a negative electrode, and the above-mentioned composite solid electrolyte membrane disposed between the positive electrode and the negative electrode.

The present invention has following beneficial effect:

1. Compared with other composite solid electrolytes, the biggest difference of the present invention is that no lithium salt of any kind is added to the polymer, and under this condition, its room temperature ion conductivity can reach 10 ^-4 S cm ^-1 ;

2. When the composite solid electrolyte membrane in the present invention is applied to a lithium secondary battery, it has good cycle performance and rate performance at room temperature (25°C) and 60°C;

3. The composite solid electrolyte membrane in the present invention is a self-supporting electrolyte membrane, which is convenient for processing and transportation;

4. Lithium metal can be directly used as the negative electrode material, which can significantly increase the energy density of the battery.

Description of drawings

Figure 1a is a digital photo of the composite solid electrolyte membrane of the present invention, which shows that the composite solid electrolyte membrane is a self-supporting flexible membrane electrolyte;

Figure 1b is a scanning electron microscope (SEM) figure of the composite solid electrolyte membrane of the present invention;

Fig. 2a is the X-ray diffraction spectrum (XRD) of Li ₇ La ₃ Zr ₂ O ₁₂ (LLZTO):PEO composite solid electrolyte membrane in Example 1 of the present invention;

Figure 2b is the AC impedance spectrum at room temperature of the LLZTO:PEO composite solid electrolyte membrane;

Figure 3a is the first charge and discharge curve of the all-solid-state battery in Example 3 of the present invention at a rate of 0.05C and 25°C;

Figure 3b is the cycle curve of the all-solid-state battery in Example 3 of the present invention at 25°C, 0.05, 0.1, 0.2, 1.0, and 2.0C;

Figure 4a is the first charge and discharge curve of the all-solid-state battery in Example 4 of the present invention at a rate of 0.05C and 60°C;

Figure 4b is the cycle curves of the all-solid-state battery in Example 4 of the present invention at 60°C, 0.05, 0.1, 0.2, 1.0, and 2.0C rates.

detailed description

The present invention will be further described below in conjunction with the drawings and the following embodiments. It should be understood that the drawings and the following embodiments are only used to illustrate the present invention rather than limit the present invention.

The invention provides a composite solid electrolyte without addition of lithium salt, which can be applied to an all-solid lithium secondary battery. The polymer and fast ion conductor powder are composited without adding lithium salt. Preferably, the composite solid electrolyte is composed of a polymer matrix material and a fast ion conductor inorganic powder material.

The selected polymer matrix material can be a commonly used solid electrolyte polymer matrix material, including but not limited to one or two copolymers of PEO, PET, PI, PVdF, PMMA, PAN, PPC, PVC, etc. mix.

The fast ion conductor inorganic powder is Li ₇ La ₃ Zr ₂ O ₁₂ based powder, which is formed by doping Li ₇ La ₃ Zr ₂ O ₁₂ with different ions, such as Al, Ta, Nb, W, Ga, One or more mixtures doped or co-doped with elements such as Y and Te. Its chemical formula can be expressed as Li _7-x La ₃ Zr _2-x M _x O ₁₂ , wherein the doping amount of doping elements can be 0≤x≤1. The particle size of the Li ₇ La ₃ Zr ₂ O ₁₂ -based powder may be 20 nm to 20 μm, preferably 20 nm to 200 nm.

The fast ion conductor inorganic powder can be evenly mixed with the polymer matrix material. Wherein, the mass content of the fast ion conductor inorganic powder can be 5-80%, preferably 10-70%, more preferably 20-60%; the mass content of the polymer matrix material is 95-20%, preferably 90-60%. 30%, more preferably 80-40%.

The composite solid electrolyte of the present invention can be formed into a film-like composite solid electrolyte, that is, the present invention also provides a high ion conductance composite solid electrolyte membrane without lithium salt added, which is a thin film formed of the above composite solid electrolyte.

The working mechanism of the solid electrolyte membrane of the present invention is:

The solid electrolyte membrane does not add any organic solvent and any form of lithium salt. During the charging and discharging process of the battery, Li ⁺ in the fast ion conductor inorganic powder conducts and moves rapidly at the interconnected powder particles and the interface between the particles and the polymer, thereby conducting Li ⁺ . High temperature helps to enhance the activity at the interface between powder particles and polymer, so the ion conductivity is higher when the temperature increases within a certain range. The working temperature range of the solid electrolyte membrane of the present invention can be from room temperature to 120°C, preferably 60-100°C.

The solid electrolyte membrane of the present invention has high ionic conductivity, and the ionic conductivity at room temperature can reach 10 ^-4 S cm ^-1 ; the lithium ion migration number is close to 1; the electrochemical window is wide, and its electrochemical window can reach 5V by cyclic voltammetry test Above (above 5V) and other advantages. The ionic conductivity of the solid electrolyte membrane of the invention is obviously higher than that of the composite solid electrolyte membrane added with other non-ionic conductor inorganic powders. The solid electrolyte membrane of the invention can be used in lithium secondary batteries with high voltage and high specific energy systems, supercapacitors, fuel cells and the like. When the composite solid electrolyte membrane in the present invention is applied to a lithium secondary battery, it has good cycle performance and rate performance at both room temperature (25°C) and 60°C.

Figure 1a shows a digital photo of a composite solid electrolyte membrane of the present invention. It can be seen that the solid electrolyte membrane of the present invention can be a self-supporting flexible membrane with mechanical stability and easy processing and transportation. The solid electrolyte membrane of the present invention may have a thickness of 20 μm to 150 μm. Fig. 1b shows an SEM image of the composite solid electrolyte membrane of an example of the present invention, it can be seen that the fast ion conductor powder is evenly distributed in the polymer matrix.

The composite solid electrolyte membrane of the present invention can be prepared by non-vacuum coating method. In one example, the fast ion conductor powder material and the polymer matrix material can be uniformly dispersed in an organic solvent to obtain a composite solid electrolyte slurry; then the composite solid electrolyte slurry is coated on a substrate and dried to obtain a composite solid electrolyte slurry. electrolyte membrane.

The source of the fast ion conductor powder is not limited, commercially available products can be used, and it can also be prepared by oneself. In one example, its preparation method is as follows: According to the chemical formula Li _7-x La ₃ Zr _2-x M _x O ₁₂ (x=0~1, M=Al, Ta, Nb, W, Ga, Y, Te, etc.) The molar ratio of Li, La, Zr, M in Li, La(OH) ₃ , ZrO ₂ and the corresponding oxides M _x O _y are selected as raw materials, and the excess of LiOH is 15%, after ball milling in alcohol medium for 24 hours drying, and then calcining at 900°C for 12 hours with a heating rate of 3°C/min to obtain Li _7-x La ₃ Zr _2-x M _x O ₁₂ fast ion conductor powder. .

The fast ion conductor powder can be dehydrated in advance, such as vacuum drying at 100°C for 24 hours, so as to remove trace moisture contained in the powder and reduce the influence of moisture on its ionic conductivity.

Preparation of Composite Solid Electrolyte Slurry

Disperse the fast ion conductor powder in the organic solvent. In order to promote its uniform dispersion, ultrasonic treatment can also be performed, for example, in an ultrasonic reactor at 80% power for 1 hour, so that the fast ion conductor powder is fully dispersed in the organic solvent. As the organic solvent, there are included, but not limited to, N-methylpyrrolidone, acetonitrile, N-N-dimethylformamide, dimethyl carbonate, ethylene carbonate, and the like. The concentration of the fast ion conductor powder can be 0.01-0.2 g/mL. Then, add the polymer matrix material to the organic solution in which the fast ion conductor powder is dispersed, for example, slowly by using a feeder, and at the same time assist stirring (for example, 24 hours), thereby obtaining a composite solid electrolyte slurry. The mass content of the fast ion conductor inorganic powder can be 5-80%, and the mass content of the polymer matrix material is 95-20%. The preparation of the composite solid electrolyte slurry is preferably carried out under a protective atmosphere, for example, in a high-purity argon glove box.

It should be understood that the preparation steps of the composite solid electrolyte slurry (the order of adding the fast ion conductor powder and the polymer matrix material) are not limited to the above, for example, the polymer matrix material can also be dissolved in an organic solvent before adding the fast ion conductor powder; or adding the polymer matrix material and the fast ion conductor powder into the organic solvent at the same time. In addition, it should be understood that the composite solid electrolyte slurry may also contain other possible additives such as dispersion aids and the like.

The composite solid electrolyte slurry is coated on the substrate, and after drying, a flexible composite solid electrolyte membrane is obtained. It does not specifically limit as a board|substrate, For example, a polytetrafluoroethylene plate etc. can be used. The coating method can be, for example, spin coating, roll coating, spray coating and the like. The drying method can be heating or allowing the organic solvent to volatilize naturally. The resulting flexible membrane is peeled off from the substrate to obtain a self-supporting composite solid electrolyte membrane.

The composite solid electrolyte and its film of the invention can be applied to all solid lithium secondary batteries. The present invention also provides an all-solid lithium secondary battery, which includes the composite solid electrolyte of the present invention. In one example, an all-solid lithium secondary battery includes a positive electrode, a negative electrode, and the composite solid electrolyte membrane of the present invention, which is disposed between the positive electrode and the negative electrode. In addition, the all-solid lithium secondary battery of the present invention may also include other components, such as conductive additives and the like. The composite solid electrolyte membrane of the invention can inhibit the growth of lithium dendrites in lithium secondary batteries, has high room temperature conductivity and has stable battery cycle.

The composite solid electrolyte of the present invention has excellent adaptability and stability in lithium secondary batteries, and the all-solid lithium secondary battery of the present invention has no special restrictions on positive electrode materials and negative electrode materials.

As the positive electrode material, it can be one or a mixture of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, and ternary nickel-cobalt-manganese composite materials.

As the conductive additive, it can be one or more mixtures of acetylene black, graphite, graphene, graphene oxide, porous carbon, carbon nanotube, carbon fiber, nitrogen-doped carbon, and KB (Ketjen black).

As the negative electrode material, metal lithium sheet or graphite carbonized material can be used. The invention can directly use lithium metal as the negative electrode material, which can significantly improve the energy density of the battery.

The present invention has the following significant advantages:

(1) Provide a self-supporting film-like composite solid electrolyte with mechanical stability and an ionic conductivity of 10 ^-4 S cm ^-1 at room temperature;

(2) Good stability to lithium metal, because no lithium salt is added, lithium is difficult to deposit and form lithium dendrites in the polymer matrix, so internal short circuit is not easy to occur, and it has higher safety when applied to lithium secondary batteries sex;

(3) The electrochemical working window is wide, and its electrochemical window can reach more than 5V through cyclic voltammetry test, so it can be used in lithium secondary batteries with high voltage and high specific energy systems, or supercapacitors, fuel cells and other fields;

(4) Experiments have proved that the composite solid electrolyte in the present invention has good cycle stability at room temperature (25°C) and 60°C when it is applied to lithium secondary batteries;

(5) In the process of the composite solid electrolyte in the present invention forming an all-solid lithium secondary battery with the positive electrode and the negative electrode, the positive electrode material and negative electrode material used are not particularly limited, and the composite solid electrolyte has excellent adaptability and stability .

The present invention will be further described below in conjunction with specific experimental examples and accompanying drawings, but the present invention is only used to illustrate the purpose of the invention, and is not limited to the following examples. The methods described in the following examples are conventional methods unless otherwise specified. The materials can be purchased from open commercial channels unless otherwise specified. Some non-essential improvements and adjustments made by those skilled in the art based on the above contents of the present invention belong to the protection scope of the present invention. The specific process parameters and the like in the following examples are only examples of suitable ranges, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values exemplified below.

Test Methods:

Powder particle size: The particle size distribution of the obtained fast ion conductor powder is determined by a laser diffraction particle size tester, and at the same time, it is assisted by SEM for further observation and determination;

AC impedance spectroscopy: Assemble the prepared composite electrolyte membrane and stainless steel sheet into a <stainless steel sheet/electrolyte membrane/stainless steel sheet> blockage battery, and use an electrochemical workstation to measure the AC impedance of the battery;

Ionic Conductivity: Through the AC Impedance Spectrum obtained in the above method with the formula Calculating the Ionic Conductivity of Electrolyte Membranes . Where 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;

Lithium ion migration number: Assemble the prepared composite electrolyte membrane and metal lithium sheet into a <metal lithium sheet/electrolyte membrane/metal lithium sheet> blocking battery, and perform DC polarization measurement on the battery with an electrochemical workstation. Combined with AC impedance spectrum and DC polarization curve, according to the formula T _Li+ ＝{I _(t＝∞) [ΔV-I _(t＝0) R _(t＝0) ]}/{I _(t＝0) [VΔ- I _(t=∞) R _(t=∞) ]}, the lithium ion migration number T _Li+ of the electrolyte membrane can be calculated. Among them, ΔV is the voltage amplitude, I _(t=0) is the initial current value, R _(t=0) is the electrolyte resistance before polarization, I _(t=∞) is the polarization stable current value, R _{(t= ∞)} is the electrolyte resistance after polarization;

Electrochemical window: Assemble the prepared composite electrolyte membrane, metal lithium sheet and stainless steel sheet into a <metal lithium sheet/electrolyte membrane/stainless steel sheet> battery, and use an electrochemical workstation to measure the cyclic voltammetry and linear voltammetry curves of the battery to determine Determine the electrochemical operating window of the electrolyte membrane. The cyclic voltammetry voltage range is usually -0.5V to 6.0V, and the linear voltammetry test voltage is usually 2.0V to 6.0V.

Example 1

A high ionic conductance composite solid electrolyte membrane that can be used in all-solid lithium secondary batteries without lithium salt addition, its digital photos and SEM pictures are shown in Figures 1a and 1b, and its preparation process is as follows:

Stir 1 gram of PEO in 10 mL of organic solvent N-methylpyrrolidone in an Ar atmosphere glove box to fully dissolve, then add a certain amount of Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO, particle size 10 μm,) and continue Stir to disperse evenly, wherein the mass ratio of PEO to LLZO is 10:x, x=1-8, x=5 in this embodiment. A certain amount of composite solid electrolyte slurry is coated on the substrate, and left standing at room temperature for 24 hours to completely volatilize the solvent to obtain a composite solid electrolyte membrane. Among them, the preparation method of LLZO powder is as follows: according to the molar ratio of Li, La, and Zr in the chemical formula Li ₇ La ₃ Zr ₂ O ₁₂ , LiOH, La(OH) ₃ , and ZrO ₂ are selected as raw materials, and the excess of LiOH is 15%. It was ball-milled in an alcohol medium for 24 hours, dried, and then calcined at 900° C. for 12 hours with a heating rate of 3° C./min to obtain Li ₇ La ₃ Zr ₂ O ₁₂ fast ion conductor powder.

Example 2

A novel composite solid electrolyte membrane, the preparation method of which is the same as in Example 1. The particle size of the selected LLZO is 200nm, and the mass ratio of PEO to LLZO is 10:3. The XRD of the electrolyte membrane is shown in Figure 2a, and it can be seen that the main phase of the electrolyte membrane is a cubic garnet structure. Using a circular Li electrode as the test electrode, the electrical performance of the electrolyte membrane sample was tested at room temperature, and its AC impedance spectrum was obtained as shown in 2b. The room temperature ionic conductivity was calculated to be 2.0×10 ^-4 S·cm ^-1 . After testing, the lithium ion migration number is 0.46, and the electrochemical window is 0V-4.8V.

Example 3

An all-solid-state lithium secondary battery based on a composite solid-state electrolyte membrane, the negative electrode and positive electrode materials used are as follows:

The composite solid electrolyte membrane that adopts is with example 1;

The negative electrode directly uses metal lithium sheet;

Positive electrode LiFePO ₄ :SP:PEO:LiTFSI; each mass ratio is 8:1:7:0.3;

Battery test temperature: 25°C;

Figure 3a is the first charge and discharge curve of the all-solid-state battery in this example at 25°C and 0.05C rate, and Figure 3b is the cycle curve of the all-solid-state battery at 25°C and 0.05, 0.1, 0.2, 1.0, and 2.0C rate. It can be seen that It has good cycle stability at 25°C.

Example 4

An all-solid-state lithium secondary battery based on a composite solid-state electrolyte membrane, the negative electrode and positive electrode materials used are as follows:

The composite solid electrolyte membrane that adopts is with example 1;

The negative pole that adopts is with embodiment 3;

The positive pole that adopts is the same as embodiment 3;

Battery test temperature: 60°C;

Figure 4a is the first charge and discharge curve of the all-solid-state battery at 60°C, 0.05C rate, and Figure 4b is the cycle curve of the all-solid-state battery at 60°C, 0.05, 0.1, 0.2, 1.0, 2.0C rate. It has good cycle stability at 60°C.

Example 5

The fast ion conductor inorganic powder is a doped Li _6.7 La ₃ Zr _1.7 Ta _0.3 O ₁₂ (LLZTO) powder. The preparation method is as follows: Li, La, Zr, Ta in the chemical formula Li _6.7 La ₃ Zr _1.7 Ta _0.3 O ₁₂ The molar ratio of LiOH, La(OH) ₃ , ZrO ₂ and the corresponding oxide TaO are selected as raw materials, and the excess of LiOH is 15%, and it is ball-milled in an alcohol medium for 24 hours, then dried, and then calcined at 900 ° C for 12 hours, The heating rate was 3°C/min, and Li _6.7 La ₃ Zr _1.7 Ta _0.3 O ₁₂ fast ion conductor powder was obtained. Then, in an Ar atmosphere glove box, 1 gram of PEO was stirred in 10 mL of organic solvent N-methylpyrrolidone to fully dissolve it, and then a certain amount of Li _6.7 La ₃ Zr _1.7 Ta _0.3 O ₁₂ (LLZTO, particle size 10 μm, ) and continue stirring to disperse evenly, wherein the mass ratio of PEO to LLZTO is 10:x, x=1-8, and x=5 in this embodiment. A certain amount of composite solid electrolyte slurry is coated on the substrate, and left to stand at room temperature for 24 hours to completely volatilize the solvent to obtain a composite solid electrolyte membrane.

Comparative example 1

A composite solid electrolyte membrane, the preparation method of which is the same as in Example 1. The selected LLZO particle size is 200nm, the mass ratio of PEO to LLZO is 10:3, and the added lithium salt (can be LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ (LiTFSI), LiN(C ₂ F ₅ SO ₂ ) ₂ (LiBETI), LiPF ₃ (CF ₃ CF ₂ ) ₃ (LiFAP), LiBF ₃ CF ₃ CF ₂ (LiFAB), LiC(CF ₃ SO ₂ ) ₃ (LiTFSM), LiB(C ₂ O ₄ ) ₂ (LiBOB), LiBF ₂ (CO ₂ ) ₂ (LiODFB), lithium ions in polylithium borate salt PLTB) and [ The molar ratio of EO] units is 1:12. A circular Li electrode was used as the test electrode, and the electrical properties of the electrolyte membrane samples were tested at room temperature. The room temperature ionic conductivity was calculated to be 4.3×10 ^-4 S·cm ^-1 . After testing, the lithium ion migration number is 0.47, and the electrochemical window is 0V-4.65V. Compared with the composite electrolyte membrane without lithium salt added in the present invention, the membrane ion conductivity and lithium ion mobility of the electrolyte added with lithium salt are slightly improved and the improvement is not significant, but the electrochemical working window is significantly reduced . In addition, the addition of lithium salt increases the preparation cost and complexity of the electrolyte membrane on the one hand, and on the other hand makes the electrolyte membrane easy to absorb moisture and affects the measurement of its ionic conductivity. Risk of lithium dendrite growth.

Claims (10)

1. a kind of composite solid electrolyte material, it is characterised in that including polymeric matrix material and fast-ionic conductor powder body material, the chemical formula of the fast ion conducting material is Li_7-xLa₃Zr_2-xM_xO₁₂, wherein M is at least one of Al, Ta, Nb, W, Ga, Y, Te, and 0≤x≤1, the composite solid electrolyte material does not include lithium salts.

2. composite solid electrolyte material according to claim 1, it is characterized in that, it is made up of the polymeric matrix material and the fast-ionic conductor powder body material, wherein the mass content of polymeric matrix material is 95~20%, and the mass content of fast-ionic conductor powder body material is 5~80%.

3. composite solid electrolyte material according to claim 1 or 2, characterized in that, the polymeric matrix material is at least one of polyoxyethylene, polyethylene terephthalate, polyimides, Kynoar, polymethyl methacrylate, polyacrylonitrile, poly (propylene carbonate), polyvinyl chloride and its copolymer.

4. composite solid electrolyte material according to any one of claim 1 to 3, it is characterised in that the grain diameter of the fast-ionic conductor powder body material is 20 nm~20 μm.

5. composite solid electrolyte material according to any one of claim 1 to 4, it is characterised in that the operating temperature of the composite solid electrolyte material be room temperature to 120 DEG C, preferably 60~100 DEG C.

6. a kind of composite solid electrolyte film, it is characterised in that formed as the composite solid electrolyte material any one of claim 1 to 5.

7. the preparation method of the composite solid electrolyte film described in a kind of claim 6, it is characterised in that comprise the following steps：

1）Fast-ionic conductor powder body material and polymeric matrix material are dispersed in organic solvent, obtain composite solid electrolyte slurry；

2）Composite solid electrolyte slurry is coated on substrate, dries, obtains composite solid electrolyte film.

8. preparation method according to claim 7, it is characterised in that the fast-ionic conductor powder body material carries out anhydrous processing, the step 1 in advance）Carried out under protective atmosphere.

9. the preparation method according to claim 7 or 8, it is characterised in that the solid content of the composite solid electrolyte slurry is 6~15%.

A kind of 10. all solid lithium secondary battery, it is characterised in that including：Positive pole, negative pole and the composite solid electrolyte film as claimed in claim 6 being arranged between the positive pole and the negative pole.