A copper-doped solid-state electrolyte, a preparation method and application thereof, and a full-solid-state battery

Abstract

The application relates to the technical field of solid electrolytes, and discloses a copper-doped solid electrolyte, a preparation method and application thereof, and a full-solid-state battery. The method comprises the following steps: (1) pressing and forming an oxide electrolyte to obtain a solid electrolyte sheet; (2) stacking the solid electrolyte sheet and a copper foil to form a solid electrolyte precursor in the presence of an oxygen-containing atmosphere, and performing calcination treatment on the solid electrolyte precursor; the calcination treatment is performed under the conditions that the temperature rising speed is 1-5 DEG C / min, the temperature is 600-1300 DEG C, and the time is 1-24 h. The method can obtain an oxide solid electrolyte with high ionic conductivity, so that a full-solid-state battery with low impedance and good rate performance is prepared.

Description

Technical Field

[0001] This invention relates to the field of solid-state electrolyte technology, specifically to a copper-doped solid-state electrolyte, its preparation method and application, and an all-solid-state battery. Background Technology

[0002] Since their commercialization in 1991, lithium-ion batteries have rapidly gained global popularity and are now widely used in power plants, satellites, electric vehicles, mobile phones, computers, and other electronic devices. Especially in recent years, stimulated by policies in various countries, the continued rapid growth in electric vehicle sales has fueled a sustained increase in demand for lithium-ion batteries, while also placing higher demands on their energy density, safety, and stability. Structurally, lithium-ion batteries can be simply divided into four parts: positive electrode material, negative electrode material, separator, and electrolyte. Because the liquid electrolyte used contains volatile and flammable organic solvents such as ethylene carbonate and dimethyl carbonate, which have poor thermal stability and are prone to combustion and fire, this is a significant factor contributing to the safety hazards of lithium-ion batteries.

[0003] In addition, liquid electrolytes have disadvantages such as a narrow operating temperature range, inapplicability in many situations, low lithium-ion transference number, easy reaction between the electrolyte and the negative electrode material, and inability to match high-energy-density lithium metal negative electrodes, which affect the further improvement of battery performance such as rate and energy density.

[0004] Solid-state batteries use solid electrolytes, offering advantages such as high stability, high safety, and high energy density, making them a current research hotspot and hailed as the next generation of lithium-ion batteries. Solid electrolytes are non-flammable, non-corrosive, non-volatile, and do not leak, thus all-solid-state batteries offer better safety and a longer lifespan.

[0005] Among them, inorganic solid electrolytes have high mechanical strength, which can prevent the growth of lithium dendrites, and a wider electrochemical window, which can withstand a larger operating voltage. Therefore, they are expected to be used in lithium metal batteries and high-voltage cathodes, with great potential for improving energy density.

[0006] Solid-state electrolytes are the core components of solid-state batteries, and are mainly classified into polymer electrolytes, sulfide electrolytes, and oxide electrolytes. Polymer electrolytes offer advantages such as good electrode interface, ease of processing, and good elasticity, but suffer from low ionic conductivity, high operating temperature, and a narrow chemical window. Sulfide electrolytes, while exhibiting high ionic conductivity, suffer from poor chemical stability, are sensitive to air, are prone to oxidation, and readily react with water to produce H₂S, requiring stringent production environments. Oxide electrolytes, with their high ionic conductivity, high chemical stability, and excellent overall performance, have attracted widespread attention.

[0007] However, the lithium-ion conductivity of existing oxide solid electrolytes is still relatively low, resulting in solid batteries with high impedance and poor rate performance.

[0008] Therefore, in order to obtain solid-state batteries with low impedance and excellent rate performance, it is urgent to develop a solid-state electrolyte with high ionic conductivity. Summary of the Invention

[0009] The purpose of this invention is to solve the problem of low ionic conductivity in solid electrolytes in the prior art.

[0010] During their research, the inventors discovered that doping traditional NaSICON-structured oxide electrolytes with copper ions, and controlling the copper ion doping amount to 0.1-5 wt%, can create additional ion migration channels, increasing the migration speed of lithium ions within the crystal lattice framework. This, in turn, improves the ionic conductivity of the solid-state electrolyte, resulting in an all-solid-state battery with low impedance and excellent rate performance. Based on this, the inventors completed this solution.

[0011] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a copper-doped solid electrolyte, the method comprising:

[0012] (1) The oxide electrolyte is pressed into a solid electrolyte sheet; the oxide electrolyte is a powder with an average particle size of 0.2-20 μm; the oxide electrolyte is a NASICON structure oxide electrolyte;

[0013] (2) In the presence of an oxygen-containing atmosphere, the solid electrolyte sheet and copper foil are stacked to form a solid electrolyte precursor, and the solid electrolyte precursor is calcined; the calcination conditions include at least the following: heating rate of 1-5℃ / min, temperature of 600-1300℃, and time of 1-24h.

[0014] Wherein, the oxygen content in the oxygen-containing atmosphere is ≥20wt%;

[0015] The conditions of the calcination treatment and / or the thickness of the copper foil are controlled so that the doping amount of copper ions in the copper-doped solid electrolyte is 0.1-3 wt%.

[0016] Preferably, in step (2), the conditions of the calcination treatment and / or the thickness of the copper foil are controlled so that the amount of copper ions in the copper-doped solid electrolyte is 0.3-1.5 wt%.

[0017] Preferably, in step (2), the thickness of the copper foil is 6-25 μm.

[0018] Preferably, in step (2), the calcination treatment conditions include at least the following: heating rate of 3-5℃ / min, temperature of 800-1100℃, and time of 4-12h.

[0019] Preferably, in step (1), the oxide electrolyte is a compound having the structure shown in formula (I).

[0020] Li 1+x Al x Ti 2-x (PO4)3, formula (I);

[0021] In equation (I), x is 0.3-0.6.

[0022] Preferably, in step (1), the conditions for compression molding include at least: a pressure of 100-300 MPa.

[0023] Preferably, in step (1), the solid electrolyte sheet is circular, and the diameter of the solid electrolyte sheet is 10-50 mm and the thickness is 0.5-5 mm.

[0024] A second aspect of the present invention provides a copper-doped solid electrolyte prepared by the method described in the first aspect.

[0025] The third aspect of this invention provides the application of the copper-doped solid electrolyte described in the second aspect in solid-state batteries.

[0026] A fourth aspect of the present invention provides an all-solid-state battery, comprising a positive electrode, a negative electrode, a separator, and a copper-doped solid electrolyte as described in the second aspect.

[0027] This invention involves doping a specific amount of copper ions into an oxide solid electrolyte, which can significantly improve the ionic conductivity of the oxide solid electrolyte. When this copper-doped solid electrolyte is applied to an all-solid-state battery, an all-solid-state battery with low impedance and good rate performance can be obtained. Detailed Implementation

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] In this invention, unless otherwise stated, all pressures are gauge pressures.

[0030] As previously described, a first aspect of the present invention provides a method for preparing a copper-doped solid electrolyte, the method comprising:

[0031] (1) The oxide electrolyte is pressed into a solid electrolyte sheet; the oxide electrolyte is a powder with an average particle size of 0.2-20 μm; the oxide electrolyte is a NASICON structure oxide electrolyte;

[0032] (2) In the presence of an oxygen-containing atmosphere, the solid electrolyte sheet and copper foil are stacked to form a solid electrolyte precursor, and the solid electrolyte precursor is calcined; the calcination conditions include at least the following: heating rate of 1-5℃ / min, temperature of 600-1300℃, and time of 1-24h.

[0033] Wherein, the oxygen content in the oxygen-containing atmosphere is ≥20wt%;

[0034] The conditions of the calcination treatment and / or the thickness of the copper foil are controlled so that the doping amount of copper ions in the copper-doped solid electrolyte is 0.1-3 wt%.

[0035] In this invention, "stack the solid electrolyte sheet and copper foil to form a solid electrolyte precursor" means placing the solid electrolyte sheet on the copper foil or placing the solid electrolyte under the copper foil, wherein the solid electrolyte sheet and the copper foil in the solid electrolyte precursor are both one sheet.

[0036] The present invention does not have any special requirements on the size and shape of the copper foil, as long as the size of the copper foil can cover the solid electrolyte sheet. For example, the copper foil has the same shape as the solid electrolyte sheet, the diameter of the copper foil is 20-100mm, and the surface area of ​​the copper foil is larger than the surface area of ​​the solid electrolyte sheet.

[0037] Preferably, in step (2), the conditions of the calcination treatment and / or the thickness of the copper foil are controlled so that the amount of copper ions in the copper-doped solid electrolyte is 0.3-1.5 wt%. The inventors have found that by adopting this preferred embodiment, a copper-doped solid electrolyte with higher ionic conductivity can be obtained.

[0038] Preferably, in step (2), the thickness of the copper foil is 4-100 μm, more preferably 6-25 μm. During their research, the inventors discovered that this preferred embodiment provides sufficient copper ions, thereby obtaining a copper-doped solid electrolyte with higher ionic conductivity.

[0039] Preferably, in step (2), the calcination treatment conditions include at least: a heating rate of 3-5°C / min, a temperature of 800-1100°C, and a time of 4-12 hours. The inventors have found that, in this preferred embodiment, the solid electrolyte has a higher density, thereby effectively improving its ionic conductivity.

[0040] Preferably, in step (2), the oxygen content in the oxygen-containing atmosphere is 20-30 wt%.

[0041] In this invention, there are no special requirements for the type of oxygen-containing atmosphere, as long as the oxygen content meets the requirements of this invention. For example, the oxygen-containing atmosphere can be air or a mixture of oxygen and inert gas.

[0042] Preferably, in step (1), the oxide electrolyte is a compound having the structure shown in formula (I).

[0043] Li 1+x Al x Ti 2-x (PO4)3, formula (I);

[0044] In equation (I), x is 0.3-0.6.

[0045] The inventors discovered that, using the oxide electrolyte under this preferred condition, copper ions can be better doped into the oxide lattice framework at high temperatures, thereby obtaining a solid electrolyte with higher ionic conductivity.

[0046] Preferably, in step (1), the conditions for compression molding include at least: a pressure of 100-300 MPa.

[0047] In this invention, there are no special requirements for the shape of the solid electrolyte sheet. It can be designed into any shape as needed. For example, the solid electrolyte sheet can be at least one of the following: circular, square, rectangular, and irregular shapes.

[0048] According to a particularly preferred embodiment, in step (1), the solid electrolyte sheet is circular, and the diameter of the solid electrolyte sheet is 10-50 mm and the thickness is 0.5-5 mm.

[0049] Preferably, in step (1), the solid electrolyte sheet has a diameter of 10-30 mm and a thickness of 1-3 mm.

[0050] As previously stated, a second aspect of the present invention provides a copper-doped solid electrolyte prepared by the method described in the first aspect.

[0051] As previously stated, the third aspect of the present invention provides the application of the copper-doped solid electrolyte described in the second aspect in solid-state batteries.

[0052] As previously described, a fourth aspect of the present invention provides an all-solid-state battery comprising a positive electrode, a negative electrode, a separator, and a copper-doped solid electrolyte as described in the second aspect.

[0053] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, all raw materials and instruments used are commercially available products.

[0054] Oxide electrolyte 1: Li 1.3 Al 0.3 Ti 1.7( PO4)3, with an average particle size of 0.6 μm, was purchased from Hefei Kejing Materials Technology Co., Ltd.

[0055] Oxide electrolyte 2: Li 1.3 Al 0.3 Ga 1.7( PO4)3, with an average particle size of 0.6 μm, was purchased from Hefei Kejing Materials Technology Co., Ltd.

[0056] Oxide electrolyte 3: Li30.11La 2 / 3 0.11 TiO3 with an average particle size of 2 μm was purchased from Hefei Kejing Materials Technology Co., Ltd.

[0057] Copper foil: 12µm thick, purchased from Hefei Kejing Materials Technology Co., Ltd.

[0058] Iron foil: 18mm in diameter;

[0059] In the following examples, the diameter of both the copper foil and the iron foil used is 18 mm.

[0060] Example 1

[0061] This embodiment provides a method for preparing copper-doped solid electrolytes, which includes:

[0062] (1) Under a pressure of 200 MPa, 0.35 g of oxide electrolyte 1 was pressed into a circular solid electrolyte sheet with a diameter of 16 mm and a thickness of 1 mm.

[0063] (2) In the presence of an air atmosphere with an oxygen content of 25 wt%, the solid electrolyte sheet prepared above was placed on a copper foil with a thickness of 15 μm, and then placed together in a muffle furnace. The temperature was raised to 950 °C at a rate of 5 °C / min, held for 6 h, and then cooled to room temperature before being taken out to obtain copper-doped solid electrolyte S1.

[0064] In the copper-doped solid electrolyte S1, the doping amount of copper ions is 0.6 wt%.

[0065] Example 2

[0066] This embodiment provides a method for preparing copper-doped solid electrolytes, which includes:

[0067] (1) Under a pressure of 240 MPa, 0.75 g of oxide electrolyte 1 was pressed into a circular solid electrolyte sheet with a diameter of 18 mm and a thickness of 2 mm.

[0068] (2) In the presence of an air atmosphere with an oxygen content of 20wt%, the solid electrolyte sheet prepared above was placed on a copper foil with a thickness of 25μm, and then placed together in a muffle furnace. The temperature was increased to 1000℃ at a rate of 3℃ / min, held for 4h, cooled to room temperature, and then taken out to obtain copper-doped solid electrolyte S2.

[0069] In the copper-doped solid electrolyte S2, the doping amount of copper ions is 1.5 wt%.

[0070] Example 3

[0071] This embodiment provides a method for preparing copper-doped solid electrolytes, which includes:

[0072] (1) Under a pressure of 150 MPa, 0.32 g of oxide electrolyte 1 was pressed into a circular solid electrolyte sheet with a diameter of 16 mm and a thickness of 1 mm.

[0073] (2) In the presence of an air atmosphere with an oxygen content of 30wt%, the solid electrolyte sheet prepared above was placed on a copper foil with a thickness of 10μm, and then placed together in a muffle furnace. The temperature was raised to 900℃ at a rate of 3℃ / min, held for 5h, cooled to room temperature, and then taken out to obtain copper-doped solid electrolyte S3.

[0074] In the copper-doped solid electrolyte S3, the copper ion doping amount is 0.8 wt%.

[0075] Example 4

[0076] The copper-doped solid electrolyte was prepared according to the method of Example 1, except that the calcination temperature in step (2) was 1200°C.

[0077] The remaining steps are the same as in Example 1, and copper-doped solid electrolyte S4 is obtained.

[0078] In the copper-doped solid electrolyte S4, the copper ion doping amount is 0.8 wt%.

[0079] Example 5

[0080] A copper-doped solid electrolyte was prepared according to the method of Example 1, except that in step (1), an oxide electrolyte 1 was replaced with an oxide electrolyte 2 of equal mass.

[0081] The remaining steps are the same as in Example 1, and copper-doped solid electrolyte S5 is obtained.

[0082] In the copper-doped solid electrolyte S5, the copper ion doping amount is 0.6 wt%.

[0083] Comparative Example 1

[0084] A solid electrolyte was prepared according to the method of Example 1, except that it was not doped with copper ions;

[0085] Specifically, the following steps are included:

[0086] (1) Under a pressure of 200 MPa, 0.35 g of oxide electrolyte 1 was pressed into a circular solid electrolyte sheet with a diameter of 16 mm and a thickness of 1 mm.

[0087] (2) In the presence of an air atmosphere with an oxygen content of 25 wt%, the solid electrolyte sheet prepared above was placed in a muffle furnace, heated to 950°C at a rate of 5°C / min, held for 6 h, cooled to room temperature and then taken out to obtain solid electrolyte DS1.

[0088] The remaining steps are the same as in Example 1, and solid electrolyte DS1 is obtained.

[0089] Comparative Example 2

[0090] Solid electrolytes were prepared according to the method of Example 1, except that copper foil was replaced with iron foil of the same thickness.

[0091] The remaining steps are the same as in Example 1, and iron-doped solid electrolyte DS2 is obtained.

[0092] In the iron-doped solid electrolyte DS2, the iron ion doping amount is 1 wt%.

[0093] Comparative Example 3

[0094] Solid electrolytes were prepared according to the method of Example 1, except that in step (1), oxide electrolyte 1 was replaced with an equal mass of oxide electrolyte 3.

[0095] The remaining steps are the same as in Example 1, and copper-doped solid electrolyte DS3 is obtained.

[0096] In the copper-doped solid electrolyte DS3, the copper ion doping amount is 1.2 wt%.

[0097] Comparative Example 4

[0098] The copper-doped solid electrolyte was prepared according to the method of Example 1, except that the thickness of the copper foil used in step (2) was 30 μm.

[0099] The remaining steps are the same as in Example 1, and copper-doped solid electrolyte DS4 is obtained.

[0100] In the copper-doped solid electrolyte DS4, the copper ion doping amount is 4 wt%.

[0101] Comparative Example 5

[0102] The solid electrolyte was prepared according to the method of Example 1, except that the calcination temperature in step (2) was 480°C.

[0103] The remaining steps are the same as in Example 1, and copper-doped solid electrolyte DS5 is obtained.

[0104] In the copper-doped solid electrolyte DS5, the copper ion doping amount is 0 wt%.

[0105] Comparative Example 6

[0106] The solid electrolyte was prepared according to the method of Example 1, except that in step (2), the oxygen content in the air atmosphere was 10 wt%.

[0107] The remaining steps are the same as in Example 1, and copper-doped solid electrolyte DS6 is obtained.

[0108] In the copper-doped solid electrolyte DS6, the copper ion doping amount is 0.2 wt%.

[0109] Test Example 1

[0110] The blocking electrodes were assembled and subjected to EIS testing to obtain the ionic conductivity of the solid electrolytes prepared in the aforementioned examples and comparative examples.

[0111] The specific method is as follows: using the solid electrolyte sheet prepared above, a symmetrical cell is constructed using a stainless steel sheet as the blocking electrode. The electrochemical workstation used is a DH7001 with a frequency range of 0.01-10 Hz. 6 Hz, testing the EIS of the solid electrolyte sheet at 25°C.

[0112] The formula for calculating ionic conductivity is δ=L / (R·S);

[0113] Where δ is the ionic conductivity, S / cm;

[0114] L is the thickness of the solid electrolyte sheet, in cm;

[0115] R is the intrinsic resistance of the solid electrolyte, in Ω;

[0116] S is the effective cross-sectional area of ​​the solid electrolyte sheet, in cm². 2 .

[0117] Table 1

[0118]

[0119]

[0120] As can be seen from the results in Table 1, the copper-doped solid electrolyte prepared by the method provided in this invention has the characteristic of high ionic conductivity.

[0121] Test Example 2

[0122] Using lithium cobalt oxide as the positive electrode and lithium metal as the negative electrode, solid-state batteries were assembled using copper-doped solid electrolytes prepared in the examples and comparative examples, respectively. The rate performance of the solid-state batteries was then tested, and the specific test results are shown in Table 2.

[0123] The assembly method is as follows: Lithium cobalt oxide, conductive agent, binder and N-methylpyrrolidone are mixed in a mass ratio of 9:0.5:0.5:0.4, stirred to prepare a positive electrode slurry, coated on aluminum foil, dried at 100°C and cut into 10mm round pieces as positive electrodes, and then assembled into CR2032 coin cells in the order of positive electrode sheet-solid electrolyte sheet-lithium foil.

[0124] The specific testing method is as follows: The operating voltage range of the CR2032 button cell is set to 3V~4.2V, with a current density of 0.1C (0.15mA / cm²). 2 The material was charged to 4.2V under constant current and then charged to 0.01C under constant voltage. Then it was discharged to 3V at currents of 0.1C, 0.2C, 0.5C and 1C respectively. The specific capacity of the material under discharge rates of 0.1C, 0.2C, 0.5C and 1C was obtained, and the ratios of 0.2C / 0.1C, 0.5C / 0.1C and 1C / 0.1C were calculated.

[0125] Table 2

[0126]

[0127]

[0128] Table 2 (continued)

[0129] 0.2C / 0.1C, % 0.5C / 0.1C, % 1C / 0.1C, % Example 1 94.4 90.0 83.8 Example 2 93.9 85.5 75.3 Example 3 93.9 86.6 78.1 Example 4 86.7 85.8 79.5 Example 5 92.2 85.9 71.3 Comparative Example 1 83.7 75.5 65.8 Comparative Example 2 77.9 68.4 51.7 Comparative Example 3 82.9 80 62.4 Comparative Example 4 70.5 48.9 19.1 Comparative Example 5 65.4 34.0 15.7 Comparative Example 6 84.4 76.4 68.0

[0130] As can be seen from Table 2, applying the copper-doped solid electrolyte provided by this invention to all-solid-state lithium batteries can result in all-solid-state lithium batteries with excellent rate performance.

[0131] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method of preparing a copper-doped solid state electrolyte, characterized by, The method comprises: (1) compression molding of an oxide electrolyte to obtain a solid electrolyte sheet; the oxide electrolyte is a powder with an average particle size of 0.2-20 μm; the oxide electrolyte is a NASICON structure oxide electrolyte; the oxide electrolyte is a compound having a structure shown in formula (I), Li 1+x Al x Ti 2-x (PO4)3, formula (I); wherein x is 0.3-0.6; (2) stacking the solid electrolyte sheet and a copper foil to form a solid electrolyte precursor in the presence of an oxygen-containing atmosphere, and performing calcination treatment on the solid electrolyte precursor; the calcination treatment conditions at least include: a temperature rising speed of 1-5 ℃ / min, a temperature of 600-1300 ℃, and a time of 1-24 h; wherein the oxygen content in the oxygen-containing atmosphere is ≮20 wt%; The conditions of the calcination treatment and / or the thickness of the copper foil are controlled so that the doping amount of copper ions in the copper-doped solid electrolyte is 0.1-3 wt%.

2. The method of claim 1, wherein, In step (2), the conditions of the calcination treatment and / or the thickness of the copper foil are controlled so that the doping amount of copper ions in the copper-doped solid electrolyte is 0.3-1.5 wt%.

3. The method according to claim 1 or 2, characterized in that, In step (2), the thickness of the copper foil is 4-100 μm.

4. The method of claim 3, wherein, In step (2), the thickness of the copper foil is 6-25 μm.

5. The method according to claim 1 or 2, characterized in that, In step (2), the conditions of the calcination treatment at least include: a temperature rising speed of 3-5 ℃ / min, a temperature of 800-1100 ℃, and a time of 4-12 h.

6. The method of claim 1 or 2, wherein, In step (1), the conditions of the compression molding at least include: a pressure of 100-300 MPa.

7. The method of claim 1 or 2, wherein, In step (1), the solid electrolyte sheet is circular, and the diameter of the solid electrolyte sheet is 10-50 mm and the thickness is 0.5-5 mm.

8. A copper-doped solid electrolyte prepared by the method of any one of claims 1-7.

9. Use of the copper-doped solid electrolyte of claim 8 in a full solid-state battery.

10. An all-solid battery, characterized by, A full solid-state battery comprising a positive electrode, a negative electrode, a separator, and the copper-doped solid electrolyte of claim 8.

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