A composite structure solid electrolyte, its preparation method and application

Abstract

The present invention relates to the technical field of solid electrolytes, and discloses a composite structure solid electrolyte, a preparation method thereof and an application. The method includes: (1) pressing an oxide electrolyte into a mold to obtain a solid electrolyte sheet; (2) performing a first calcination treatment on the solid electrolyte sheet to obtain a first solid material; (3) performing a second calcination treatment on the first solid material and a carbon source precursor in the presence of a protective atmosphere, so that the carbon source precursor is deposited on the surface of the first solid material. By using the method provided by the present invention, a solid electrolyte sheet with high density can be formed, thereby improving the lithium stability of the solid electrolyte. The solid battery formed by using the solid electrolyte has good cycle stability.

Description

Technical Field

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

[0002] Traditional lithium-ion batteries use organic liquid electrolytes, which contain a large amount of organic solvents. These solvents are volatile at high temperatures, have poor thermal stability, and are prone to combustion and fire, which are important factors for the safety hazards of lithium-ion batteries. Solid-state batteries use solid electrolytes, which have advantages such as high safety, high energy density, and excellent high-temperature performance, and are considered the most promising technical solutions.

[0003] Solid electrolytes are the core of solid-state batteries and directly determine the performance of the batteries. Currently, solid electrolytes are mainly divided into three categories: polymer electrolytes, sulfide electrolytes, and oxide electrolytes.

[0004] Among them, polymer electrolytes have good processing properties, but their own ionic conductivity is low, their strength is low and they cannot inhibit lithium dendrites, and their operating temperature is high and the chemical window is narrow; sulfide electrolytes have the highest ionic conductivity, but their air stability is poor, they are prone to react with water to produce H2S, and the production environment requirements are harsh; oxide electrolytes have relatively high ionic conductivity and high chemical stability, and their comprehensive performance is excellent, which has received extensive attention.

[0005] However, since the contact mode between the solid electrolyte and the electrode is solid-solid contact, the interfacial wettability is poor and the interfacial impedance is high, resulting in large battery polarization and poor rate performance, which are also technical difficulties that need to be overcome urgently.

[0006] CN111403806A discloses a carbon-coated solid electrolyte material, a preparation method thereof, and uses thereof. By using a solid-phase method or a gas-phase method to coat an ultrathin carbon layer on the surface of solid electrolyte particles, the electrochemical performance of the material is improved, and the lithium ionic conductivity and electronic conductivity of the solid electrolyte are well improved, and direct contact with lithium can also be avoided.

[0007] CN113488693A discloses a composite graphene-coated solid electrolyte composite material and a preparation method thereof. Through chemical vapor in-situ growth, a composite graphene-coated solid electrolyte composite material is obtained, which has a high ion migration rate and a low interfacial contact resistance. At the same time, this composite material can directly prevent the growth of lithium dendrites and improve the cycle performance and rate performance.

[0008] However, both of the above two methods aim to improve the stability and wettability with lithium by coating a carbon layer on the surface of the material particles. After coating the carbon layer on the solid electrolyte particles by these two methods, it is very difficult to form a highly dense solid electrolyte sheet, resulting in the problems that the stability of the solid electrolyte with lithium is still insufficient and the interfacial impedance is high. Summary of the Invention

[0009] The object of the present invention is to overcome the defect of poor cycling performance caused by insufficient stability with lithium and high interfacial impedance of the solid electrolyte in the prior art.

[0010] To achieve the above object, the first aspect of the present invention provides a method for preparing a composite structure solid electrolyte, which method includes:

[0011] (1) Pressing an oxide electrolyte into a mold to obtain a solid electrolyte sheet; the oxide electrolyte is a powder with an average particle size of 0.1-20 μm, and the thickness of the solid electrolyte sheet is 0.5-5 mm;

[0012] (2) Performing a first calcination treatment on the solid electrolyte sheet to obtain a first solid material;

[0013] (3) In the presence of a protective atmosphere, performing a second calcination treatment on the first solid material and a carbon source precursor so that the thickness of the carbon layer deposited on the surface of the first solid material is 0.1-10 μm; the conditions of the second calcination treatment at least include: the temperature is 500-1200 °C, and the time is 0.1-10 h;

[0014] Wherein, the oxide electrolyte is selected from at least one of NASICON structure oxide electrolytes, LISICON structure oxide electrolytes, perovskite structure oxide electrolytes, and garnet structure oxide electrolytes;

[0015] The carbon source precursor is a liquid precursor and / or a gaseous precursor;

[0016] In the carbon source precursor, the liquid precursor is selected from at least one of benzene, toluene, o-xylene, m-xylene, and p-xylene; the gaseous precursor is selected from at least one of ethane, propane, and n-butane.

[0017] Preferably, in step (3), the conditions of the second calcination treatment at least include: the temperature is 600-800 °C, and the time is 0.5-2 h.

[0018] Preferably, in step (3), the thickness of the carbon layer is 0.5-50 μm.

[0019] Preferably, in step (3), the carbon source precursor is benzene.

[0020] Preferably, in step (3), the feeding rate of the liquid precursor is 0.1-10 mL / h, and the feeding rate of the gaseous precursor is 5-500 L / h.

[0021] More preferably, in step (3), the feeding rate of the liquid precursor is 0.2-5 mL / h, and the feeding rate of the gaseous precursor is 5-50 L / h.

[0022] Preferably, in step (1), the oxide electrolyte is selected from at least one of lithium aluminum titanium phosphate, lithium aluminum germanium phosphate, and lithium lanthanum titanate.

[0023] Preferably, in step (1), the oxide electrolyte is a compound having a structure shown in formula (I),

[0024] Li 1+x Al x Ti 2-x( PO4)3, formula (I),

[0025] In formula (I), x is 0.3-0.6.

[0026] Preferably, in step (2), the protective atmosphere is selected from at least one of nitrogen, helium, neon and argon.

[0027] Preferably, in step (2), the conditions of the first calcination treatment include at least: a temperature of 500-1200° C. and a time of 1-20 h.

[0028] More preferably, in step (2), the conditions of the first calcination treatment at least include: a temperature of 900-1000° C.; and a time of 5-8 hours.

[0029] The second aspect of the present invention provides a composite structure solid electrolyte prepared by the method described in the first aspect.

[0030] The third aspect of the present invention provides the use of the composite structure solid electrolyte described in the second aspect in an all-solid-state battery.

[0031] The method provided by the present invention can form a high-density solid electrolyte sheet, thereby improving the lithium stability of the solid electrolyte. The solid-state battery formed using the solid electrolyte has good cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a comparison chart of the cycle performance test results of Example 1, Example 2 and Comparative Example 1 provided by the present invention. DETAILED DESCRIPTION

[0033] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the values between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0034] In the present invention, unless otherwise stated, the pressure is gauge pressure, and the room temperature or normal temperature both represent 25 ± 2°C.

[0035] As described above, the first aspect of the present invention provides a method for preparing a composite structure solid electrolyte, the method comprising:

[0036] (1) Compressing and molding an oxide electrolyte to obtain a solid electrolyte sheet; the oxide electrolyte is a powder with an average particle size of 0.1 - 20 μm, and the thickness of the solid electrolyte sheet is 0.5 - 5 mm;

[0037] (2) Performing a first calcination treatment on the solid electrolyte sheet to obtain a first solid material;

[0038] (3) In the presence of a protective atmosphere, performing a second calcination treatment on the first solid material and a carbon source precursor so that the thickness of the carbon layer deposited on the surface of the first solid material is 0.1 - 10 μm; the conditions of the second calcination treatment at least include: the temperature is 500 - 1200°C, and the time is 0.1 - 10 h;

[0039] Among them, the oxide electrolyte is selected from at least one of NASICON structure oxide electrolytes, LISICON structure oxide electrolytes, perovskite structure oxide electrolytes, and garnet structure oxide electrolytes;

[0040] The carbon source precursor is a liquid precursor and / or a gaseous precursor;

[0041] In the carbon source precursor, the liquid precursor is selected from at least one of benzene, toluene, o - xylene, m - xylene, and p - xylene; the gaseous precursor is selected from at least one of ethane, propane, and n - butane.

[0042] Preferably, in step (3), the conditions of the second calcination treatment at least include: the temperature is 600 - 800°C, and the time is 0.5 - 2 h. The inventors found that by adopting the specific implementation in this preferred case, the lithium stability of the composite structure solid electrolyte can be further improved, thereby forming a solid - state battery product with more excellent cycling performance.

[0043] Preferably, in step (3), the thickness of the carbon layer is 0.5 - 50 μm.

[0044] According to a particularly preferred specific embodiment, in step (3), the carbon source precursor is benzene. The inventors have found that by adopting the specific embodiment in this preferred case, a solid-state battery with more excellent cycling performance can be prepared.

[0045] Preferably, in step (3), the feeding rate of the liquid precursor is 0.1 - 10 mL / h, and the feeding rate of the gaseous precursor is 5 - 500 L / h.

[0046] More preferably, in step (3), the feeding rate of the liquid precursor is 0.2 - 5 mL / h, and the feeding rate of the gaseous precursor is 5 - 50 L / h.

[0047] In the present invention, there is no particular requirement for the shape of the solid electrolyte sheet, and it can be designed into a solid electrolyte sheet of any shape according to needs. Exemplarily, the solid electrolyte sheet can be at least one of circular, square, rectangular, and irregular shapes.

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

[0049] Preferably, in step (1), the oxide electrolyte is selected from at least one of lithium aluminum titanium phosphate, lithium germanium aluminum phosphate, and lanthanum lithium titanate.

[0050] According to a particularly preferred specific embodiment, in step (1), the oxide electrolyte is a compound having the structure shown in formula (I),

[0051] Li 1+x Al x Ti 2-x( (PO4)3, formula (I);

[0052] In formula (I), the x is 0.3 - 0.6.

[0053] Preferably, in step (2), the protective atmosphere is selected from at least one of nitrogen, helium, neon, and argon.

[0054] Preferably, the conditions of the first calcination treatment in step (2) at least include: the temperature is 500 - 1,200 °C, and the time is 1 - 20 h.

[0055] More preferably, the conditions of the first calcination treatment in step (2) at least include: the temperature is 900 - 1,000 °C, and the time is 5 - 8 h. The inventors have found during the research process that in the specific embodiment in this preferred case, a composite structure solid electrolyte with higher density can be obtained.

[0056] Preferably, in step (2), the method further includes: cooling the first solid material and then performing post-treatment.

[0057] The present invention has no special requirements for the operating steps of the post-treatment, and only needs to meet the requirements of the present invention. Exemplarily, the post-treatment may include grinding and cutting.

[0058] As described above, the second aspect of the present invention provides a composite structure solid electrolyte prepared by the method described in the first aspect.

[0059] As described above, the third aspect of the present invention provides an application of the composite structure solid electrolyte described in the second aspect in an all-solid-state battery.

[0060] The present invention will be described in detail below by way of examples. In the following examples, various raw materials and instruments used are commercially available products without special instructions.

[0061] Oxide electrolyte 1: Li 1.3 Al 0.3 Ti 1.7( (PO4)3, with an average particle size of 0.6 μm, purchased from Hefei Kejing Materials Technology Co., Ltd.;

[0062] Oxide electrolyte 2: Li 3x La (2 / 3)-x TiO3 (x = 0.11), with an average particle size of 2 μm, purchased from Hefei Kejing Materials Technology Co., Ltd.;

[0063] In the following examples, benzene is an analytical pure chemical reagent; /

[0064] In the following examples, the method for measuring the carbon layer thickness is: measuring the thickness of the first solid material, denoted as L1, and then measuring the thickness of the material after the second calcination treatment, denoted as L2. Among them, L2 - L1 is the carbon layer thickness.

[0065] Example 1

[0066] This example provides a method for preparing a composite structure solid electrolyte, which includes the following steps:

[0067] (1) Under a pressure condition of 200 MPa, 0.35 g of oxide electrolyte 1 is pressed into a circular solid electrolyte sheet with a diameter of 16 mm and a thickness of 1 mm;

[0068] (2) The circular solid electrolyte sheet prepared above is placed in a muffle furnace (with a volume of 90 L) at a temperature of 950 °C for calcination for 6 h. After cooling to room temperature, the calcined material is polished smoothly to obtain the first solid material;

[0069] (3) In the presence of argon, place the first solid material obtained above in a muffle furnace (with a volume of 90 L), heat it to 700 °C, and introduce benzene at a rate of 1 mL / h. Stop introducing benzene after 0.5 h, cool it to room temperature, and then take it out to obtain the composite-structured solid electrolyte S1;

[0070] In the composite-structured solid electrolyte S1, the thickness of the carbon layer is 1 μm.

[0071] Example 2

[0072] This example provides a method for preparing a composite-structured solid electrolyte, which includes the following steps:

[0073] (1) Under a pressure condition of 200 MPa, press 0.35 g of oxide electrolyte 1 into a circular solid electrolyte sheet with a diameter of 16 mm and a thickness of 1 mm;

[0074] (2) Place the circular solid electrolyte sheet prepared above in a muffle furnace (with a volume of 90 L) at a temperature of 950 °C for calcination for 6 h. After cooling to room temperature, polish the material obtained after calcination to obtain the first solid material;

[0075] (3) In the presence of argon, place the first solid material obtained above in a muffle furnace (with a volume of 90 L), heat it to 700 °C, and introduce ethane at a rate of 10 L / h. Stop introducing ethane after 1 h, cool it to room temperature, and then take it out to obtain the composite-structured solid electrolyte S2;

[0076] In the composite-structured solid electrolyte S2, the thickness of the carbon layer is 1 μm.

[0077] Example 3

[0078] Prepare the composite-structured solid electrolyte according to the method of Example 1, except that in step (3), the temperature of the second calcination treatment is 900 °C.

[0079] The remaining steps are the same as those in Example 1 to obtain the composite-structured solid electrolyte S3.

[0080] In the composite-structured solid electrolyte S3, the thickness of the carbon layer is 10 μm.

[0081] Example 4

[0082] Prepare the composite-structured solid electrolyte according to the method of Example 1, except that in step (2), the temperature of the first calcination treatment is 1200 °C.

[0083] The remaining steps are the same as those in Example 1 to obtain the composite-structured solid electrolyte S4.

[0084] In the composite structure solid electrolyte S4, the thickness of the carbon layer is 50 μm.

[0085] Example 5

[0086] The composite structure solid electrolyte was prepared according to the method of Example 1, except that in step (1), the oxide electrolyte 1 was replaced with an equal mass of oxide electrolyte 2.

[0087] The remaining steps were the same as those in Example 1, and the composite structure solid electrolyte S5 was obtained.

[0088] In the composite structure solid electrolyte S5, the thickness of the carbon layer is 1 μm.

[0089] Example 6

[0090] The composite structure solid electrolyte was prepared according to the method of Example 1, except that in step (3), an equal volume of toluene was used to replace benzene.

[0091] The remaining steps were the same as those in Example 1, and the composite structure solid electrolyte S6 was obtained.

[0092] In the composite structure solid electrolyte S6, the thickness of the carbon layer is 2 μm.

[0093] Comparative Example 1

[0094] The solid electrolyte was prepared according to the method of Example 1, except that the second calcination treatment was not carried out;

[0095] Specifically, it includes the following steps:

[0096] (1) Under a pressure condition of 200 MPa, the oxide electrolyte powder was pressed into a circular solid electrolyte sheet with a diameter of 16 mm and a thickness of 1 mm;

[0097] (2) The prepared circular solid electrolyte sheet was placed in a muffle furnace (with a volume of 90 L) at a temperature of 950 °C for calcination for 6 h. After cooling to room temperature, the calcined material was polished smoothly to obtain the solid electrolyte DS1.

[0098] Comparative Example 2

[0099] The composite structure solid electrolyte was prepared according to the method of Example 1, except that the second calcination treatment was not carried out, and the solid electrolyte sheet was directly calcined with the carbon source precursor;

[0100] Specifically, it includes the following steps:

[0101] (1) Under a pressure condition of 200 MPa, the oxide electrolyte powder was pressed into a circular solid electrolyte sheet with a diameter of 16 mm and a thickness of 1 mm;

[0102] (2) In the presence of argon, place the circular solid electrolyte sheet prepared as described above in a muffle furnace (with a volume of 90 L), heat it to 700 °C, and introduce benzene at a rate of 1 mL / h. Stop introducing benzene after 0.5 h, cool it to room temperature, and then take it out to obtain the composite structure solid electrolyte DS2.

[0103] In the composite structure solid electrolyte DS2, the thickness of the carbon layer is 2 μm.

[0104] Comparative Example 3

[0105] Prepare the composite structure solid electrolyte according to the method of Example 2, except that in step (3), ethane is replaced with an equal volume of acetylene.

[0106] The remaining steps are the same as those in Example 2 to obtain the composite structure solid electrolyte DS3.

[0107] In the composite structure solid electrolyte DS3, the thickness of the carbon layer is 5 μm.

[0108] Comparative Example 4

[0109] Prepare the composite structure solid electrolyte according to the method of Example 1, except that in step (3), the carbon source precursor used is citric acid, and the mass ratio of the first solid material to citric acid is 10:1.

[0110] The remaining steps are the same as those in Example 1 to obtain the composite structure solid electrolyte DS4.

[0111] In the composite structure solid electrolyte DS4, the thickness of the carbon layer is 3 μm.

[0112] Comparative Example 5

[0113] Prepare the composite structure solid electrolyte according to the method of Example 1, except that in step (3), the temperature of the second calcination treatment is 480 °C.

[0114] The remaining steps are the same as those in Example 1 to obtain the composite structure solid electrolyte DS5.

[0115] In the composite structure solid electrolyte DS5, the thickness of the carbon layer is 0 μm, that is, no carbon layer is formed.

[0116] Test Example

[0117] Fabricate solid-state batteries with the composite structure solid electrolytes prepared in the examples and comparative examples, and conduct battery cycle performance tests on all-solid-state secondary batteries. The specific test results are shown in Table 1.

[0118] Among them, the preparation method of the all-solid-state secondary battery is as follows: Lithium cobaltate, conductive agent Super P, binder PVDF, and solvent NMP are mixed according to a mass ratio of 9:0.5:0.5:0.4, stirred and formulated into a positive electrode paste, which is coated on aluminum foil, dried at 100 °C, and then cut into 10-mm circular pieces as the positive electrode. Then, the solid electrolyte prepared above is assembled into a CR2032-type button battery in the order of positive electrode sheet - solid electrolyte - lithium foil;

[0119] The specific test method is as follows: The working voltage range of the all-solid-state lithium secondary battery prepared above is set to 3 V - 4.2 V, and it is charged at a constant current of 0.2 C (current density is 0.15 mA / cm 2 ) to 4.2 V, then at a constant voltage until it is cut off at 0.05 C, and cycled 100 times. The specific discharge capacity for the first time and the specific discharge capacity after 100 cycles are recorded respectively, and the capacity retention rate is calculated.

[0120] The calculation formula for the capacity retention rate is: (specific discharge capacity after 100 cycles / specific discharge capacity for the first time) × 100%.

[0121] Table 1

[0122]

[0123] It can be seen from the results in Table 1 that by using the method provided by the present invention, a solid electrolyte sheet with high density can be prepared, the purpose of improving the lithium stability of the solid electrolyte can be achieved, and the solid battery formed by using this solid electrolyte has good cycle stability and rate performance.

[0124] The present invention exemplarily provides a comparison chart of the cycle performance test results of the all-solid-state secondary batteries prepared in Example 1, Example 2, and Comparative Example 1 of the present invention, as shown in Figure 1 .

[0125] From Figure 1 it can be seen that the solid battery made of the solid electrolyte prepared by the method of the present invention has more excellent cycle performance.

[0126] 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 technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite solid electrolyte, characterized in that, The method includes: (1) Pressing and shaping an oxide electrolyte to obtain a solid electrolyte sheet; the oxide electrolyte is a powder with an average particle size of 0.1 - 20 μm, and the thickness of the solid electrolyte sheet is 0.5 - 5 mm; (2) Performing a first calcination treatment on the solid electrolyte sheet to obtain a first solid material; the conditions of the first calcination treatment at least include: a temperature of 900 - 1000 °C and a time of 5 - 8 h; (3) In the presence of a protective atmosphere, performing a second calcination treatment on the first solid material and a carbon source precursor so that the thickness of the carbon layer deposited on the surface of the first solid material is 0.5 - 10 μm; the conditions of the second calcination treatment at least include: a temperature of 600 - 800 °C and a time of 0.5 - 2 h; Wherein, the oxide electrolyte is selected from at least one of NASICON - structured oxide electrolytes, LISICON - structured oxide electrolytes, perovskite - structured oxide electrolytes, and garnet - structured oxide electrolytes; The carbon source precursor is a liquid precursor and / or a gaseous precursor; In the carbon source precursor, the liquid precursor is selected from at least one of benzene, toluene, o - xylene, m - xylene, and p - xylene; the gaseous precursor is selected from at least one of ethane, propane, and n - butane.

2. The method according to claim 1, wherein In step (3), the carbon source precursor is benzene.

3. The method according to claim 1, wherein In step (3), the feeding rate of the liquid precursor is 0.1 - 10 mL / h, and the feeding rate of the gaseous precursor is 5 - 500 L / h.

4. The method according to claim 3, wherein In step (3), the feeding rate of the liquid precursor is 0.2 - 5 mL / h, and the feeding rate of the gaseous precursor is 5 - 50 L / h.

5. The method according to any one of claims 1-4, characterized in that, In step (1), the oxide electrolyte is selected from at least one of lithium aluminum titanium phosphate, lithium germanium aluminum phosphate, and lanthanum lithium titanate.

6. The method according to any one of claims 1-4, characterized in that, In step (1), the oxide electrolyte is a compound having the structure shown in formula (I), Li 1+x Al x Ti 2-x( (PO4)3, formula (I) In formula (I), x is 0.3 - 0.

6.

7. The method according to any one of claims 1 to 4, characterized in that, In step (2), the protective atmosphere is selected from at least one of nitrogen, helium, neon, and argon.

8. A composite - structure solid electrolyte prepared by the method according to any one of claims 1 - 7.

9. Application of the composite - structure solid electrolyte according to claim 8 in an all - solid - state battery.

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