Solid-state electrolyte precursor, preparation method of solid-state electrolyte, solid-state electrolyte and solid-state battery

Abstract

The application discloses a solid-state electrolyte precursor, a preparation method of a solid-state electrolyte, the solid-state electrolyte and a solid-state battery, and relates to the technical field of new energy sources.The solid-state electrolyte precursor comprises mixed oxide electrolyte particles and lithiumated boron cluster molecule particles.By adding the lithiumated boron cluster molecules into the oxide electrolyte particles, the lithiumated boron cluster molecules can inhibit abnormal growth of the oxide electrolyte particles in a high-temperature sintering process, and are beneficial to improving the uniformity of the solid-state electrolyte particles, so that the ionic conductivity of the solid-state electrolyte is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy, in particular to a solid-state electrolyte precursor, a preparation method of a solid-state electrolyte, the solid-state electrolyte and a solid-state battery. BACKGROUND

[0002] Due to the demand for energy saving and emission reduction, batteries are increasingly widely used. Batteries are not only used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, but also widely used in electric bicycles, electric motorcycles, electric vehicles and other electric vehicles. In recent years, with the rapid development of electric vehicles, higher requirements have been put forward for the energy density and safety performance of batteries. The solid-state battery is a battery using a solid-state electrolyte. Due to the use of a solid-state electrolyte, the safety and energy density of the battery are significantly improved.

[0003] How to further improve the performance of the solid-state electrolyte is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0004] Therefore, the present application provides a solid-state electrolyte precursor, a preparation method of a solid-state electrolyte, the solid-state electrolyte and a solid-state battery, aiming to improve the problem of unsatisfactory ionic conductivity of the existing solid-state electrolyte.

[0005] In a first aspect, the present application provides a solid-state electrolyte precursor, comprising mixed oxide electrolyte particles and lithiumated boron cluster molecule particles.

[0006] Optionally, the lithiumated boron cluster molecule particles are attached to the surface of the oxide electrolyte particles.

[0007] Optionally, the lithiumated boron cluster molecule particles coat the surface of the oxide electrolyte particles.

[0008] Optionally, the thickness of the lithiumated boron cluster molecule particles coated on the surface of the oxide electrolyte particles is 5-30 nm.

[0009] Optionally, the chemical formula of the lithiumated boron cluster molecule is LiBn; wherein n is an integer of 2-12.

[0010] Optionally, the average particle size of the lithiumated boron cluster molecule particles is 1-3 nm.

[0011] Optionally, the mass ratio of the oxide electrolyte to the lithiumated boron cluster molecule is 100: (0.1-10) by mass.

[0012] Optionally, the oxide electrolyte comprises at least one of LLZO, LLZTO and LLZAO; and / or

[0013] The average particle size of the oxide electrolyte particles is 100 nm to 500 nm. The second aspect of the present application provides a preparation method of a solid-state electrolyte, comprising the following steps:

[0014] providing a solid-state electrolyte precursor; the solid-state electrolyte precursor comprises oxide electrolyte particles and lithium boron cluster molecules coated on the surface of the oxide electrolyte particles;

[0015] sintering the solid-state electrolyte precursor to obtain a solid-state electrolyte.

[0016] Optionally, in the step of sintering the solid-state electrolyte precursor to obtain a solid-state electrolyte, the sintering temperature is 1000°C to 1400°C, and the sintering time is 0.1 h to 10 h.

[0017] Optionally, the step of providing a solid-state electrolyte precursor comprises:

[0018] preparing oxide electrolyte particles;

[0019] ball-milling a mixture of the oxide electrolyte particles and the lithium boron cluster molecules to coat the surface of the oxide electrolyte particles with the lithium boron cluster molecules;

[0020] compacting the oxide electrolyte particles coated with the lithium boron cluster molecules to obtain the solid-state electrolyte precursor.

[0021] Optionally, the chemical formula of the lithium boron cluster molecules is LiBn; wherein n is an integer of 2-12; and / or

[0022] The mass ratio of the oxide electrolyte to the lithium boron cluster molecules is 100: (0.1-10) by mass; and / or

[0023] The oxide electrolyte comprises at least one of LLZO, LLZTO, and LLZAO; and / or

[0024] The average particle size of the oxide electrolyte particles is 100 nm to 500 nm.

[0025] The third aspect of the present application provides a solid-state electrolyte prepared by the preparation method of the solid-state electrolyte.

[0026] The fourth aspect of the present application provides a solid-state battery comprising the solid-state electrolyte. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0028] Figure 1 is a scanning electron microscope image of the solid-state electrolyte prepared in Example 1, magnified 10,000 times;

[0029] Figure 2 is a scanning electron microscope image of the solid-state electrolyte prepared in Example 1, magnified 500 times;

[0030] Figure 3 is a scanning electron microscope image of the solid-state electrolyte prepared in Comparative Example 1, magnified 10,000 times;

[0031] Figure 4 is a scanning electron microscope image of the solid-state electrolyte prepared in Comparative Example 1, magnified 500 times. DETAILED DESCRIPTION

[0032] The embodiments described herein are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort fall within the scope of the present application. In addition, it should be understood that the specific embodiments described herein are only for the purpose of illustration and explanation of the present application, and are not intended to limit the present application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0034] In the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are only used as labels and do not impose numerical requirements or establish an order.

[0035] In the present application, "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can represent the following cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural.

[0036] In the present application, "at least one" means one or more, and "multiple" means two or more. "One or more", "at least one of the following (one)", or the like, means any combination of these items, including a single item or any combination of multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0037] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the sake of convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the described range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fraction or integer) within the indicated range.

[0038] Due to the demand for energy saving and emission reduction, batteries are increasingly widely used. Batteries are not only used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, but also widely used in electric bicycles, electric motorcycles, electric vehicles and other electric vehicles. In recent years, with the rapid development of electric vehicles, higher requirements have been put forward for the energy density and safety performance of batteries. Solid-state batteries are a kind of batteries using solid electrolyte. Due to the use of solid electrolyte, the safety and energy density of the battery are significantly improved.

[0039] How to further improve the performance of solid-state electrolyte is a technical problem that those skilled in the art need to solve.

[0040] In view of this, the embodiments of the present application provide a solid-state electrolyte precursor, which comprises mixed oxide electrolyte particles and lithiated boron cluster molecule particles. By adding lithiated boron cluster molecule particles to the oxide electrolyte particles in the embodiments of the present application. During the mixing of the lithiated boron cluster molecule particles and the oxide electrolyte particles, at least part of the lithiated boron cluster molecule particles will adhere to the surface of the oxide electrolyte particles, which is beneficial to improve the conduction capacity of lithium ions. At the same time, the lithiated boron cluster molecules can also inhibit the abnormal growth of the oxide electrolyte particles during high-temperature sintering, which is beneficial to improve the uniformity of the solid-state electrolyte and further improve the ionic conductivity of the solid-state electrolyte.

[0041] In some embodiments of the present application, the lithium boride cluster molecules coat the surface of the oxide electrolyte particles, i.e. most of the lithium boride cluster molecules in the solid-state electrolyte precursor are attached to the surface of the oxide electrolyte particles, thereby forming a coating layer of lithium boride cluster molecules on the surface of the oxide electrolyte particles. At this time, the solid-state electrolyte precursor comprises oxide electrolyte particles and lithium boride cluster molecules coated on the surface of the oxide electrolyte particles. This embodiment improves the lithium ion conduction capacity by coating the surface of the oxide electrolyte particles with lithium boride cluster molecules. At the same time, the coating layer of lithium boride cluster molecules can also inhibit the abnormal growth of oxide electrolyte particles during high-temperature sintering, which is conducive to improving the uniformity of the solid-state electrolyte.

[0042] In some embodiments of the present application, the chemical formula of the lithium boride cluster molecules is LiBn; wherein n is an integer of 2-12. Specifically, n can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12. Further, n is an integer of 5-12. In this way, the ionic conductivity of the solid-state electrolyte can be further improved.

[0043] In some embodiments of the present application, the mass ratio of the oxide solid-state electrolyte (i.e. oxide electrolyte) to the lithium boride cluster molecules is 100:(0.1-10), i.e. the mass ratio of the oxide solid-state electrolyte to the lithium boride cluster molecules is 100:(0.1-10). For example, the mass ratio of the oxide solid-state electrolyte to the lithium boride cluster molecules is 100:0.1, 100:0.5, 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, or a range value between any two of the above values.

[0044] In some embodiments of the present application, the thickness of the lithium boride cluster molecule particles coated on the surface of the oxide electrolyte particles is 5-30 nm. Within this range, the ionic conductivity of the solid-state electrolyte prepared can be improved.

[0045] For example, the thickness of the lithium boride cluster molecule particles coated on the surface of the oxide electrolyte particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, or a range value between any two of the above values.

[0046] In some embodiments of the present application, the average particle size of the lithium boride cluster molecule particles is 1-3 nm. Within this range, the uniformity of the coating of the lithium boride cluster molecule particles on the surface of the oxide electrolyte particles can be improved.

[0047] Exemplarily, the average particle size of the lithiumated boron cluster molecule particle is 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, and a range value between any two of the above values.

[0048] Further, in some embodiments of the present application, the mass ratio of the oxide solid electrolyte to the lithiumated boron cluster molecule is 100: (1-9) by mass. Still further, the mass ratio of the oxide solid electrolyte to the lithiumated boron cluster molecule is 100: (3-7) by mass. Still further, the mass ratio of the oxide solid electrolyte to the lithiumated boron cluster molecule is 100: (4-6) by mass. In this way, the ionic conductivity of the solid electrolyte is further improved.

[0049] In some embodiments of the present application, the oxide solid electrolyte particle includes at least one of LLZO (lithium lanthanum zirconium oxide electrolyte), LLZTO (tantalum-doped lithium lanthanum zirconium oxide electrolyte), and LLZAO (aluminum-doped lithium lanthanum zirconium oxide electrolyte). Exemplarily, the oxide solid electrolyte particle is LLZTO.

[0050] In some embodiments of the present application, the average particle size of the oxide solid electrolyte particle is 100 nm to 500 nm. Exemplarily, the average particle size of the oxide solid electrolyte particle is 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, and a range value between any two of the above values.

[0051] Embodiments of the present application also provide a preparation method of a solid electrolyte, including the following steps:

[0052] S10 provides a solid electrolyte precursor; the solid electrolyte precursor includes oxide electrolyte particles and lithiumated boron cluster molecules coated on the surface of the oxide electrolyte particles.

[0053] It should be noted that the oxide electrolyte particles and the lithiumated boron cluster molecules have been described in detail above, and will not be described here.

[0054] S20 sintering the solid electrolyte precursor to obtain a solid electrolyte.

[0055] In some embodiments of the present application, the sintering temperature in step S20 is 1000℃ to 1400℃. Exemplarily, the sintering temperature of the solid electrolyte precursor is 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, and a range value between any two of the above temperatures.

[0056] In some embodiments of the present application, the sintering time in step S20 is 0.1 h to 10 h. Illustratively, the sintering time of the solid electrolyte precursor is 0.1 h, 0.5 h, 0.8 h, 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, 2.5 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, and a range value between any two of the above time values.

[0057] Specifically, the sintering temperature in step S20 is 1300 ℃, the sintering time is 0.1 h to 0.2 h (i.e. the solid electrolyte precursor is kept at 1300 ℃ for 0.1 h to 0.2 h), and the heating rate is 10 ℃ / min. Then the sample is placed in a muffle furnace for natural cooling to obtain the solid electrolyte.

[0058] In some embodiments of the present application, the step of providing the solid electrolyte precursor in step S10 comprises:

[0059] S11. Preparing oxide solid electrolyte particles.

[0060] Further, the oxide solid electrolyte particles can be at least one of LLZO, LLZTO, and LLZAO. It should be noted that LLZO, LLZTO, and LLZAO can be existing materials, which are not limited herein.

[0061] Taking LLZTO as an example, lithium source, lanthanum source, zirconium source, and tantalum source can be mixed according to stoichiometric ratio to obtain a mixed sample. Then the mixed sample raw material is subjected to high-temperature sintering, and after crushing, LLZTO particles are obtained.

[0062] Specifically, the raw materials LiOH, La2O3, ZrO2, and Ta2O5 are weighed according to stoichiometric ratio. The weighed raw materials are placed in a ball mill tank, and an appropriate amount of isopropyl alcohol is added for ball milling and mixing. After ball milling, drying is performed, and then the dried mixed sample raw material is placed in a tube furnace for high-temperature sintering. The sintering temperature is 900 ℃, the sintering time is 10 hours, and the tube furnace heating rate is 5 ℃ / min. After high-temperature sintering, the sintered sample is placed in the tube furnace for natural cooling to room temperature, and then the sintered product is taken out for powder refinement to obtain oxide solid electrolyte particles.

[0063] Further, due to the high-temperature loss of LiOH, the content of LiOH when taking the material can be higher than the theoretical content calculated according to the stoichiometric ratio. Illustratively, the content of LiOH when taking the material is about 10% more than the theoretical content.

[0064] Of course, in some other embodiments of the present application, the oxide solid electrolyte particles can also be sourced from the market, which are not limited herein.

[0065] Further, the average particle size of the oxide solid electrolyte particles is 200 nm to 400 nm. Illustratively, the average particle size of the oxide solid electrolyte particles is 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, and a range value between any two of the above.

[0066] S12 ball-milling the mixed material of the lithiated boron cluster molecules and the oxide solid electrolyte particles obtained in step S11, so that the lithiated boron cluster molecules coat the surface of the oxide electrolyte particles.

[0067] Illustratively, the lithiated boron cluster molecules, the oxide electrolyte particles, and a solvent (e.g., isopropyl alcohol) are weighed according to a preset ratio and added into a ball mill tank, and then ball-milling is performed at a speed of 350 rpm for 12 hours, followed by drying to obtain the oxide electrolyte particles coated with the lithiated boron cluster molecules.

[0068] S13 tabletting the oxide electrolyte particles coated with the lithiated boron cluster molecules to obtain a solid electrolyte precursor.

[0069] Illustratively, the oxide electrolyte particles coated with the lithiated boron cluster molecules are uniaxially tabletted at a pressure of 40 MPa and a pressure holding time of 3 minutes to obtain the solid electrolyte precursor.

[0070] The embodiments of the present application also provide a solid electrolyte, which is prepared by sintering the solid electrolyte precursor described above or by the preparation method of the solid electrolyte described above.

[0071] The embodiments of the present application also provide a solid-state battery, which comprises a positive electrode, a negative electrode, and the solid electrolyte described above, and the solid electrolyte is arranged between the positive electrode and the negative electrode.

[0072] In some embodiments of the present application, the negative electrode is a lithium metal negative electrode. Further, the positive electrode is a positive electrode prepared from a ternary material, and illustratively, the positive electrode is NCM811.

[0073] The solid electrolyte and the solid-state battery in the present application are further described below in combination with experimental examples.

[0074] Example 1

[0075] Preparation of solid electrolyte: raw materials LiOH, La2O3, ZrO2 and Ta2O5 are weighed according to stoichiometric ratio. The weighed raw materials are placed in a ball mill tank, and an appropriate amount of isopropyl alcohol is added for ball milling. After ball milling, the mixture is dried, and then the dried mixture is placed in a tube furnace for high-temperature sintering. The sintering temperature is 900 ℃, the sintering time is 10 hours, and the tube furnace heating rate is 5 ℃ / min. After high-temperature sintering, the sintered sample is naturally cooled to room temperature in the tube furnace, and then the sintered product is taken out for powder refinement to obtain oxide solid electrolyte particles with an average particle size of about 300 nm (chemical formula Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ). Then, the oxide solid electrolyte particles and the lithiumated boron cluster molecules (LiB8, average particle size 2 nm) are mixed in a mass ratio of 100:5. The mixed oxide solid electrolyte particles and lithiumated boron cluster molecules (LiB8) are subjected to ball milling at a rotation speed of 350 rpm for 12 hours, and then dried to obtain oxide electrolyte particles coated with lithiumated boron cluster molecules. The oxide electrolyte particles coated with lithiumated boron cluster molecules are then uniaxially pressed to obtain a solid electrolyte precursor. The prepared solid electrolyte precursor is placed in a muffle furnace, heated at a rate of 10 ℃ / min, and then heated to 1200 ℃ for 10 min. The sample is then naturally cooled in the muffle furnace to obtain a solid electrolyte. The scanning electron microscope image is shown in Figure 1 and Figure 2 .

[0076] Preparation of solid-state battery: the cooled solid-state electrolyte is polished to make the surface flat. Silver (thickness 300 nm) is evaporated on the LLZTO negative electrode side under the conditions of 50 A and 50 s. The evaporated LLZTO and lithium foil are placed in an atmosphere furnace for hot pressing at a temperature of 350 ℃ and a pressure of 10 MPa for 10 minutes to ensure that the lithium foil and the LLZTO are tightly attached. The NCM811 positive electrode is added to assemble the solid-state battery.

[0077] Example 2

[0078] The difference from Example 1 is that the lithiumated boron cluster molecules are LiB2.

[0079] Example 3

[0080] The difference from Example 1 is that the lithiumated boron cluster molecules are LiB3.

[0081] Example 4

[0082] The difference from Example 1 is that the lithiumated boron cluster molecules are LiB4.

[0083] Example 5

[0084] which differs from Example 1 in that the lithiated boron cluster molecule is LiB5.

[0085] Example 6

[0086] which differs from Example 1 in that the lithiated boron cluster molecule is LiB6.

[0087] Example 7

[0088] which differs from Example 1 in that the lithiated boron cluster molecule is LiB7.

[0089] Example 8

[0090] which differs from Example 1 in that the lithiated boron cluster molecule is LiB9.

[0091] Example 9

[0092] which differs from Example 1 in that the lithiated boron cluster molecule is LiB10.

[0093] Example 10

[0094] which differs from Example 1 in that the lithiated boron cluster molecule is LiB11.

[0095] Example 11

[0096] which differs from Example 1 in that the lithiated boron cluster molecule is LiB12.

[0097] Example 12

[0098] which differs from Example 1 in that the mass ratio of the oxide solid-state electrolyte particles to the lithiated boron cluster molecule is 100:1.

[0099] Example 13

[0100] which differs from Example 1 in that the mass ratio of the oxide solid-state electrolyte particles to the lithiated boron cluster molecule is 100:3.

[0101] Example 14

[0102] which differs from Example 1 in that the mass ratio of the oxide solid-state electrolyte particles to the lithiated boron cluster molecule is 100:7.

[0103] Example 15

[0104] which differs from Example 1 in that the mass ratio of the oxide solid-state electrolyte particles to the lithiated boron cluster molecule is 100:9.

[0105] Example 16

[0106] The difference from Example 1 is that the average particle size of the lithiumated boron cluster molecular particles is 1 nm.

[0107] Example 17

[0108] The difference from Example 1 is that the average particle size of the lithiumated boron cluster molecular particles is

[0109] 3 nm.

[0110] Example 18

[0111] The difference from Example 1 is that the sintering temperature of the solid electrolyte precursor is 1000°C.

[0112] Example 19

[0113] The difference from Example 1 is that the sintering temperature of the solid electrolyte precursor is 1400°C.

[0114] Comparative Example 1

[0115] The difference from Example 1 is that no lithiumated boron cluster molecules (LiB8) are added. The scanning electron microscope image of the solid electrolyte is shown in Figure 3 and Figure 4 .

[0116] Experimental Test

[0117] Ion conductivity test:

[0118] After polishing and cleaning the sintered solid electrolyte ceramic sheet, immersing it in glacial acetic acid for 30 s to remove surface impurities such as Li2CO3 and LiOH, and then placing it in a glove box for standby. A layer of Ag is evaporated on both sides of the solid electrolyte sheet using a thermal evaporation coating instrument to form an Ag / LLZTO / Ag blocking system, a lithium sheet is used as an electrode, and a button cell is used for packaging.

[0119] An electrochemical workstation is used to apply a small amplitude sinusoidal wave to the button cell, with an alternating amplitude of 0.01 V and a test temperature of room temperature. The frequency of the applied small amplitude sinusoidal wave is changed in the test frequency range of 1 Hz ~ 1 MHz, a series of impedances at different frequencies are obtained, and the Nyquist plot is obtained with the real part of the impedance as the horizontal axis and the imaginary part as the vertical axis, with each point representing a different frequency. The left side of the graph has a high frequency, called the high frequency region, which is semicircular in shape. The right side has a low frequency, called the low frequency region, which is linear in shape. According to the equivalent circuit analysis, the intersection of the semicircle with the real axis at low frequency corresponds to the ion resistance R of the solid electrolyte ceramic sheet. The conductivity is calculated according to the following formula.

[0120] σ = 1 / p = L / (A x R)

[0121] wherein σ represents the electrical conductivity, with the unit of S / m; L represents the length of the solid-state electrolyte ceramic sheet, with the unit of m; A represents the cross-sectional area of the solid-state electrolyte ceramic sheet, with the unit of m 2 ; and R represents the ionic resistance of the solid-state electrolyte ceramic sheet.

[0122] Cycle life test:

[0123] The prepared solid-state electrolyte was polished to make the surface flat, and the surface was treated with glacial acetic acid to remove Li2CO3 and other impurities. The LLZTO negative electrode side was evaporated with nano-silver (thickness 300 nm), and the evaporation conditions were 50 A and 50 s. The LLZTO and lithium foil (20 um) after evaporation were placed in an atmosphere furnace (Ar) for hot pressing, with a temperature of 200°C, a pressure of 10 MPa, and a pressure holding time of 10 minutes, to ensure that the lithium foil and the LLZTO were tightly attached. The positive electrode was selected from common commercial positive electrodes (ternary or lithium iron phosphate positive electrode), and a button cell was assembled for charge-discharge cycle test. The charge was 0.2C, the discharge was 0.5C, and the voltage range was 3V to 4.2V.

[0124] Critical current density test:

[0125] The prepared solid-state electrolyte was polished to make the surface flat, and the surface was treated with glacial acetic acid to remove Li2CO3 and other impurities. The LLZTO positive and negative electrode sides were evaporated with nano-silver (thickness 300 nm), and the evaporation conditions were 50 A and 50 s. The LLZTO and lithium foil (20 um) after evaporation were placed in an atmosphere furnace (Ar) for hot pressing, with a temperature of 200°C, a pressure of 10 MPa, and a pressure holding time of 10 minutes, to ensure that the lithium foil and the LLZTO were tightly attached. A lithium symmetric cell was prepared, with the structure of lithium / electrolyte / lithium. The lithium symmetric cell was subjected to constant current charging and discharging, with a charging and discharging time of 1h each, and the current size was increased by 0.05 mA / cm 2 from 0.1 mA / cm 2 , and the battery was short-circuited until the maximum current density that the battery could withstand was reached. The maximum current density was the critical current density.

[0126] The test samples obtained from the experimental examples were subjected to ion conductivity test, cycle life test and critical current density test, and the test results are shown in Table 1.

[0127] Table 1

[0128]

[0129] From Figure 1 the scanning electron microscope image of the solid-state electrolyte prepared in Example 1, Figure 2The scanning electron microscope image of the solid-state electrolyte prepared in Example 1 is enlarged 500 times, and Figure 3 The scanning electron microscope image of the solid-state electrolyte prepared in Comparative Example 1 is enlarged 10000 times, Figure 4 The scanning electron microscope image of the solid-state electrolyte prepared in Example 1 is enlarged 500 times, and Figures 1 to 4 It can be seen that after the surface of the oxide electrolyte particles is coated with lithium boron cluster molecules, the sintered solid-state electrolyte particles have smaller crystal phase, more uniform distribution, and higher density.

[0130] From the test results of Example 1 to Example 15 and Comparative Example 1, it can be seen that after the surface of the oxide electrolyte particles is coated with lithium boron cluster molecules, the sintered solid-state electrolyte has higher ionic conductivity, and the prepared battery has higher cycle life and critical current density. The possible reason is that lithium boron has a certain lithium ion conductivity, and coating on the surface of LLZTO can effectively inhibit the abnormal growth of LLTZO, so that the sintered solid-state electrolyte particles have smaller crystal phase, more uniform distribution, and higher density, thereby improving the ionic conductivity of LLTZO.

[0131] Examples 1 to 11 differ in lithium boron cluster molecules. From the test results in Table 1, it can be seen that as the value of n increases, the ionic conductivity of the lithium boron cluster molecule first increases and then decreases. The possible reason is that when n is small, the lithium boron cluster molecule is small, the ability to separate LLZTO particles is poor, and the ability to inhibit the abnormal growth of LLTZO is weak. When the value of n is large, the lithium boron cluster molecule will be larger, resulting in larger gaps between LLTZO particles, which will affect the transmission of lithium ions between LLZTO particles. When the value of n is an integer from 5 to 12, the ionic conductivity of the sintered solid-state electrolyte is above 1.2 mS / cm, and the critical current density is above 1.2 mA / cm 2 The cycle life of the prepared solid-state battery is above 200 cycles. When the value of n is 8, the ionic conductivity approaches the peak value, and the ionic conductivity is about 1.58 mS / cm.

[0132] Examples 1, 12 to 15 differ in the mass ratio of lithium boron cluster molecules to oxide solid-state electrolyte particles. From the test results in Table 1, it can be seen that as the ratio of lithium boron cluster molecules increases, the ionic conductivity first increases and then decreases. When the mass ratio of lithium boron cluster molecules to oxide solid-state electrolyte particles is (3 to 7):100, the ionic conductivity of the obtained solid-state electrolyte is higher.

[0133] The technical solutions provided by the embodiments of the present application are described in detail above, and the principles and implementation manners of the present application are described by applying specific examples. The above description of the embodiments is only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In conclusion, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A solid electrolyte, characterized in that, The solid electrolyte is obtained by sintering a solid electrolyte precursor at 1000°C to 1400°C; The solid electrolyte precursor comprises mixed oxide electrolyte particles and boron lithium cluster molecular particles; the chemical formula of the boron lithium cluster molecular particles is LiBn; where n is an integer from 2 to 12; the boron lithium cluster molecular particles are attached to or coated on the surface of the oxide electrolyte particles.

2. The solid electrolyte as described in claim 1, characterized in that, The thickness of the boron lithium cluster molecular particles coating the surface of the oxide electrolyte particles is 5 nm-30 nm.

3. The solid electrolyte as described in claim 1, characterized in that, The average particle size of the boron lithium cluster molecules is 1 nm to 3 nm.

4. The solid electrolyte as described in claim 1, characterized in that, The mass ratio of the oxide electrolyte particles to the lithium boron cluster molecules is 100:(0.1-10).

5. The solid electrolyte as described in claim 1, characterized in that, The oxide electrolyte particles include at least one of LLZO, LLZTO, and LLZAO; And / or, the average particle size of the oxide electrolyte particles is 100 nm to 500 nm.

6. A method for preparing a solid electrolyte, characterized in that, Includes the following steps: A solid electrolyte precursor is provided, the solid electrolyte precursor comprising mixed oxide electrolyte particles and boron lithium cluster molecular particles; the chemical formula of the boron lithium cluster molecular particles is LiBn; wherein n is an integer from 2 to 12; the boron lithium cluster molecular particles are attached to or coated on the surface of the oxide electrolyte particles. The solid electrolyte precursor is sintered at 1000°C to 1400°C to obtain a solid electrolyte.

7. The preparation method according to claim 6, characterized in that, In the step of sintering the solid electrolyte precursor to obtain the solid electrolyte, the sintering time is from 0.1 h to 10 h.

8. The preparation method according to claim 6, characterized in that, The step of providing the solid electrolyte precursor includes: Preparation of oxide electrolyte particles; A mixture of oxide electrolyte particles and boron lithium cluster molecules is ball-milled to coat the surface of the oxide electrolyte particles with boron lithium cluster molecules. The solid electrolyte precursor is obtained by compacting boron lithium cluster molecules to coat the oxide electrolyte particles.

9. A solid-state battery, characterized in that, The solid-state battery includes the solid electrolyte as described in any one of claims 1 to 5.

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