Preparation method of composite oxide solid electrolyte, current collector and diaphragm

Abstract

The invention discloses a preparation method of a composite oxide solid electrolyte, a current collector and a diaphragm, the composite oxide solid electrolyte comprises Li1. 3Al0. 3Ti1.7 (PO4) 3 and Li7La3Zr2O12, the preparation method comprises the following steps: adding LATP and LLZO into a planetary ball mill containing zirconium oxide and ethanol according to parts by mass for ball milling; drying and sanding; high-temperature sintering is conducted, and the sintering temperature is 800-1100 DEG C. In the preparation process of the composite solid electrolyte, the sintering temperature is lower than that of other types of solid electrolytes, and the composite solid electrolyte has higher ionic conductivity and lower electronic conductivity. When the microporous foil is used as the composite solid electrolyte, the surface of the microporous foil is coated with the composite solid electrolyte, so that the rate capability of the solid-state lithium ion battery can be remarkably improved. The composite solid-state electrolyte is coated on a current collector and a diaphragm, so that the safety performance of the solid-state lithium ion battery can be obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly relates to a composite oxide solid electrolyte coated on a current collector and a separator, a current collector for a lithium-ion battery current collector, and a separator. Background Art

[0002] In recent years, with the continuous increase in the energy density of lithium-ion batteries, the safety performance of lithium-ion batteries has gradually attracted wide attention. The development trend of high energy density of lithium-ion batteries has forced people to pay particular attention to the safety performance of lithium-ion batteries. The risk of lithium dendrite precipitation during the use of lithium-ion batteries can easily cause internal short circuits in lithium-ion batteries, leading to safety problems such as fires and explosions. To improve the safety of lithium-ion batteries, semi-solid and all-solid lithium-ion batteries have become research hotspots, and the key material in semi-solid and all-solid lithium-ion batteries is the oxide solid electrolyte. Oxide solid electrolytes can be classified into crystalline electrolytes and glassy (amorphous) electrolytes according to their material structures. Crystalline electrolytes include garnet-type solid electrolytes, perovskite-type solid electrolytes, NASICON-type solid electrolytes, etc., and glassy electrolytes include inverse perovskite-type solid electrolytes and LiPON thin film solid electrolytes. Solid electrolytes have high ionic conductivity and good environmental stability, and are an ideal choice for solid battery materials.

[0003] At present, there are many problems in the material development and practical application of oxide solid electrolytes. The preparation of oxide solid electrolyte materials requires high-temperature sintering, and the high-temperature sintering process at several thousand degrees directly leads to high material costs. Moreover, second impurity phases are easily generated during the high-temperature sintering process of oxide solid electrolytes. Therefore, the development of a low-temperature sintering process for oxide solid electrolytes is particularly important for the future development of solid-state batteries. In addition, during the actual storage process of single-type oxide solid electrolytes, the environmental stability is poor, and they are easily affected by the moisture and oxygen content in the environment. Therefore, the future storage and transportation conditions of oxide solid electrolytes are extremely harsh.

[0004] The currently mass-producible oxide solid electrolytes mainly include garnet-type solid electrolyte LLZO and NASICON-type solid electrolyte LATP. Usually, undoped LLZO has advantages such as stable electrochemical performance and wide electrochemical window, but it has poor phase structure stability, low tap density, large grain boundary resistance, and low room temperature ionic conductivity, and there will be a large interfacial resistance in the application of all-solid-state batteries. Moreover, when LLZO is exposed to air with moisture and CO2, due to H + / Li +The effect of the exchange will generate Li2CO3 on the surface, resulting in gradual deterioration of the performance. Therefore, how to enhance the chemical stability of the LLZO-based solid electrolyte in the atmospheric environment is a key issue it faces. The LATP system has a very high ionic conductivity and is chemically stable in humid air or carbon dioxide, but Ti 4+ is easily reduced by Li + , and its stable window for Li / Li + is less than 2.5V.

[0005] It is not difficult to see that the advantages and disadvantages of different types of oxide solid electrolytes are relatively obvious. How to complement the advantages and disadvantages of various oxide solid electrolytes is the key to the future development of oxide solid electrolytes. At present, there is no solid oxide electrolyte hybrid development technology and actual application technology for lithium-ion batteries. Therefore, developing a mixed oxide solid electrolyte with excellent performance is the key to the future development of solid-state batteries. Summary of the Invention

[0006] The purpose of the present invention is to solve the above-mentioned defects in the prior art, and to provide a preparation method of a composite oxide solid electrolyte, a current collector for a lithium-ion battery, and a separator.

[0007] The first object of the present invention is to disclose a preparation method of a composite oxide solid electrolyte, and the composite oxide solid electrolyte includes Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and Li7La3Zr2O 12 , wherein, Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is abbreviated as LATP, and Li7La3Zr2O 12 is abbreviated as LLZO;

[0008] The preparation method of the above-mentioned composite oxide solid electrolyte includes the following steps:

[0009] S1: Add LATP and LLZO by mass parts to a planetary ball mill containing zirconia and ethanol for ball milling;

[0010] S2: Dry and sand;

[0011] S3: High-temperature sintering.

[0012] Further, the mass ratio of LATP to LLZO in step S1 is 1:1;

[0013] Further, the ball milling time in step S1 is 2-6h;

[0014] Further, in the step S2, the high-temperature drying time is 0.5 to 3 h, the drying temperature is 180 to 220 °C, and the drying atmosphere is air;

[0015] Further, in the step S2, a sand mill is used to further grind the powder and press it into microspheres with a diameter of 2 mm;

[0016] Further, in the step S3, the high-temperature sintering temperature is 800 to 1100 °C, and the sintering time is 2 to 5 h.

[0017] In the above technical solution, in order to reduce the porosity of the solid electrolyte and improve the conductivity, and to increase the sintering density of the oxide solid electrolyte, the sintering temperature usually needs to reach above 1200 °C. Therefore, when preparing a single type of oxide solid electrolyte, a high sintering temperature is required. However, during the high-temperature sintering process, a second impurity phase is easily generated, and high-temperature sintering easily leads to the vaporization loss of lithium and more irreversible reactions between the solid electrolyte and the electrode material. When LATP and LLZO are sintered in combination, the combination of the two materials reduces the environmental sensitivity, the physical state is more stable, and it is not easily affected by other external environmental factors. Therefore, low-temperature sintering can be carried out. Moreover, LATP also acts as an active ion conductor and a ceramic additive during the combined sintering process, and can overcome the drawback of loose sintering density during the sintering process of LLZO.

[0018] The second object of the present invention is to disclose a composite oxide solid electrolyte current collector. A composite oxide solid electrolyte is coated on the surface of a lithium-ion battery current collector to form a surface coating layer;

[0019] In the above technical solution, the current collector is aluminum foil or microporous aluminum foil;

[0020] Further, the thickness of the aluminum foil or microporous aluminum foil ≤ 25 μm;

[0021] Further, when microporous aluminum foil is selected, the pore diameter of the microporous aluminum foil is 10 to 80 μm;

[0022] In the above technical solution, microporous aluminum foil is the best choice. On the one hand, the pore structure of the microporous aluminum foil can fill part of the oxide solid electrolyte, can change the single functional role of the traditional aluminum foil in conducting electricity, and through the pore filling effect of the oxide solid electrolyte, the ion conduction function of the aluminum foil current collector can also be realized, and the rate performance of the lithium-ion battery can be improved; on the other hand, the solid electrolyte filled in the micropores on the surface of the aluminum foil only has the function of conducting ions and no function of conducting electrons. Therefore, it can reduce the surface current density of the aluminum foil and improve the safety of the lithium-ion battery, especially the safety risk caused by the short circuit of the positive and negative electrodes due to mechanical abuse.

[0023] In the above technical solution, the slurry composition of the composite oxide solid electrolyte coated on the surface of the current collector includes: 85-90% of the composite oxide solid electrolyte, 3-6% of the conductive agent, 5-13% of the binder, and 0.5-1.8% of the dispersant;

[0024] Further, the viscosity of the bottom coating slurry of the composite oxide solid electrolyte is 500-1500 MPa·s, and the solid content is 20-50%;

[0025] Further, the conductive agent is one or more mixtures of conductive carbon materials and conductive polymers;

[0026] Further, the conductive carbon material is one or more mixtures of single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, reduced graphene oxide, conductive carbon black, carbon microspheres, graphite, and acetylene black;

[0027] Further, the conductive polymer is one or more mixtures of polyacetylene, polythiophene, polypyrrole, polyaniline, polyphenylene, polyphenylene ethylene, and polydiyne;

[0028] Further, the dispersant is any one of inorganic dispersants, organic dispersants, or polymer dispersants;

[0029] Further, the inorganic dispersants include but are not limited to the following: sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate; organic dispersants: there are anionic, cationic, and non-ionic types, such as anionic types like alkyl aryl phosphates, alkyl benzene sulfonates, dialkyl sulfosuccinates, etc., cationic types like trimethyl stearamide chloride, and non-ionic types like polyoxyethylene alkylphenol ethers, sorbitol alkylates, etc.; polymer dispersants: polycarboxylates, poly(meth)acrylic acid derivatives, maleic anhydride copolymers, etc.;

[0030] In the above technical solution, the single-sided thickness of the bottom coating of the composite oxide solid electrolyte is ≤5 μm.

[0031] The third object of the present invention is to disclose a composite oxide solid electrolyte separator, and the composite oxide solid electrolyte separator is obtained by coating the composite oxide solid electrolyte on one or both sides of a separator base film;

[0032] Further, the separator base film is any one or a mixture of two of polyethylene and polypropylene;

[0033] Further, the thickness of the separator base film is ≤15 μm;

[0034] Further, the single-sided thickness of the composite oxide solid electrolyte coating is ≤5 μm;

[0035] Furthermore, the solid electrolyte coating slurry for the diaphragm is composed of: 90% to 96% composite oxide solid electrolyte, 5% to 10% binder, and 0.5% to 2% high-efficiency dispersant;

[0036] In the above technical solution, the slurry composition of the composite oxide solid electrolyte coated on the surface of the diaphragm base film includes: 85-90% composite oxide solid electrolyte, 3-6% conductive agent, 5-13% binder, 0.5-1.8% dispersant;

[0037] Furthermore, the viscosity of the slurry for coating the diaphragm of the composite oxide solid electrolyte is 200-2000 MPa.s, the solid content is 30-45%, and the particle size (scraper fineness) is controlled to be ≦5 μm.

[0038] The fourth object of the present invention is to disclose a solid-state lithium-ion battery, comprising a composite oxide solid electrolyte membrane and positive and negative electrode sheets, wherein the positive and negative electrode sheets are respectively formed by coating positive and negative electrode active materials on the composite oxide solid electrolyte membrane to form active material layers, and the solid-state lithium-ion battery is formed by winding the composite oxide solid electrolyte membrane and the positive and negative electrode sheets in the above technical scheme.

[0039] Compared with the prior art, the present invention has the following advantages and effects:

[0040] 1. In the preparation process of the composite solid electrolyte of the present invention, the sintering temperature is lower than that of other types of solid electrolytes, which can reduce the production cost. The composite solid electrolyte has higher ionic conductivity and lower electronic conductivity, and has more stable environmental stability.

[0041] 2. When the composite solid electrolyte in the present invention uses a microporous foil, coating the composite solid electrolyte on the surface of the microporous foil can significantly improve the rate performance of the solid-state lithium-ion battery. Since the solid electrolyte primer layer only has ion conductivity but no electronic conductivity, the safety performance of the lithium-ion battery is significantly improved.

[0042] 3. Coating the composite solid electrolyte prepared by the present invention on the current collector and the diaphragm can significantly improve the safety performance of the solid-state lithium-ion battery, especially improve the safety hazards of the lithium-ion battery in mechanical abuse, and especially improve the pass rate of the lithium-ion battery needle puncture and heavy object impact test.

[0043] 4. Primer The composite solid electrolyte prepared by the present invention can protect the stability of the current collector in the electrolyte, reduce the dual corrosion of the current collector in the electrolyte and the electrochemical environment, and is very beneficial to improving the cycle stability of lithium-ion batteries. It can ensure the stability of solid-state lithium-ion batteries under high voltage systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings described herein are used to provide a further understanding of the present invention and form a part of this application. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0045] Figure 1 is a flowchart of the preparation method of the composite oxide solid electrolyte disclosed in the present invention;

[0046] Figure 2 is a schematic diagram of the electrode structure in an embodiment of the present invention;

[0047] Figure 3 is a schematic diagram of the battery cell structure in an embodiment of the present invention.

[0048] In the drawings, the reference numerals are explained as follows:

[0049] 1---Metal current collector; 2---Solid electrolyte coating; 3---Active material coating; 4---Positive electrode tab; 5---Positive electrode; 6---Negative electrode; 7---Negative electrode tab; 8&9---Composite oxide solid electrolyte separator. Detailed Embodiments

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0051] Embodiment 1

[0052] As Figure 1 shown, this embodiment discloses a preparation method of a composite oxide solid electrolyte, characterized in that the composite oxide solid electrolyte includes Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and Li7La3Zr2O 12 , where Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is abbreviated as LATP, and Li7La3Zr2O 12 is abbreviated as LLZO; the preparation method of the composite oxide solid electrolyte includes the following steps:

[0053] S1: Add LATP and LLZO by mass parts to a planetary ball mill containing zirconia and ethanol for ball milling;

[0054] S2: Drying and sanding;

[0055] S3: High-temperature sintering, where the high-temperature sintering temperature is 800 - 1100 °C and the sintering time is 2 - 5 h.

[0056] In step S1 of Example 1, the mass ratio of LATP to LLZO is 1:1 and the ball milling time is 6 h.

[0057] In step S2 of Example 1, the high-temperature drying time is 3 h, the drying temperature is 220 °C, and the drying atmosphere is air; the powder is further ground using a sand mill and pressed into microspheres with a diameter of 2 mm.

[0058] In step S3 of Example 1, the high-temperature calcination temperature is 800 °C and the sintering time is 4 h. The ionic conductivity of the prepared composite oxide solid electrolyte is measured using an ionic conductivity meter, and the measured ionic conductivity is 1.35×10 -6 S / cm.

[0059] Example 2

[0060] Referring to the preparation method of a composite oxide solid electrolyte in Example 1, the sintering temperature in step S3 is 900 °C and the time is 4 h, and the other steps are the same as in Example 1. The ionic conductivity of the prepared composite oxide solid electrolyte is 9.8×10 -9 S / cm.

[0061] Example 3

[0062] Referring to the preparation method of a composite oxide solid electrolyte in Example 1, the sintering temperature in step S3 is 1000 °C and the time is 4 h, and the other steps are the same as in Example 1. The ionic conductivity of the prepared composite oxide solid electrolyte is 3.6×10 -8 S / cm.

[0063] Example 4

[0064] Referring to the preparation method of a composite oxide solid electrolyte in Example 1, the sintering temperature in step S3 is 1100 °C and the time is 4 h, and the other steps are the same as in Example 1. The ionic conductivity of the prepared composite oxide solid electrolyte is 5.3×10 -9 S / cm.

[0065] Example 5

[0066] Example 5 discloses a current collector for a composite oxide solid electrolyte. The preparation method of the composite oxide solid electrolyte refers to Example 1, and its sintering temperature is adjusted to 1050 °C. The ionic conductivity of the prepared composite oxide solid electrolyte is 8.3×10 -8S / cm. The prepared composite oxide solid electrolyte is coated on the surface of the current collector of the lithium-ion battery to form a surface coating layer; the current collector is aluminum foil or microporous aluminum foil; the bottom coating thickness of the composite oxide solid electrolyte is ≤5 μm.

[0067] In this Example 5, the thickness of the aluminum foil or microporous aluminum foil is ≤25 μm; when microporous aluminum foil is selected, the pore diameter of the microporous aluminum foil is 10 - 80 μm.

[0068] In this Example 5, the slurry composition of the composite oxide solid electrolyte coated on the surface of the current collector of the lithium-ion battery includes: 85 - 90% composite oxide solid electrolyte, 3 - 6% conductive agent, 5 - 13% binder, 0.5 - 1.8% dispersant;

[0069] Among them, the viscosity of the bottom coating slurry of the composite oxide solid electrolyte is 500 - 1500 MPa·s, and the solid content is 20 - 50%;

[0070] The conductive agent is one or more mixtures of conductive carbon materials and conductive polymers;

[0071] The dispersant is any one of inorganic dispersants, organic dispersants or polymer dispersants.

[0072] In this Example 5, the conductive carbon material is one or more mixtures of single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, reduced graphene oxide, conductive carbon black, carbon microspheres, graphite, acetylene black;

[0073] The conductive polymer is one or more mixtures of polyacetylene, polythiophene, polypyrrole, polyaniline, polyphenylene, polyphenylene vinylene and polydiyne;

[0074] The inorganic dispersant is one or more mixtures of sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate;

[0075] The organic dispersant is one or more mixtures of anionic, cationic and non-ionic types;

[0076] The polymer dispersant is one or more mixtures of polycarboxylates, poly(meth)acrylic acid derivatives, maleic anhydride copolymers.

[0077] Example 6

[0078] As Figure 2 shown, this Example 6 discloses a composite oxide solid electrolyte separator, wherein, the preparation method of the composite oxide solid electrolyte refers to Example 1, and its sintering temperature is adjusted to 930 °C, and the ionic conductivity of the prepared composite oxide solid electrolyte is 3.7×10 -8 The obtained composite oxide solid electrolyte is coated on one or both sides of the separator base film.

[0079] In Example 6, the separator base film is any one or a mixture of two of polyethylene and polypropylene; the thickness of the separator base film is ≤ 15 μm; the single-sided thickness of the composite oxide solid electrolyte coating is ≤ 5 μm.

[0080] In Example 6, the coating slurry composition of the composite oxide solid electrolyte separator comprises 92% composite solid electrolyte, 8% binder PVDF, and 2% high-efficiency dispersant polyoxyethylene alkylphenol ether;

[0081] The viscosity of the slurry is 200 - 2000 MPa·s, and the solid content is 30 - 45%;

[0082] In this example, the slurry is coated on both sides of a 7-μm separator, and the single-layer coating thickness is 2 μm.

[0083] Example 7

[0084] As Figure 3 shown, Example 7 discloses a solid-state lithium-ion battery, which is wound by a separator containing a composite oxide solid electrolyte and positive and negative electrode sheets. The sintering temperature during the preparation of the composite oxide solid electrolyte is 850 °C, and the sintering time is 5 h. The rest of the process is the same as that in Example 1. The ionic conductivity of the prepared composite oxide solid electrolyte is 2.0×10 -7 . The prepared composite oxide solid electrolyte is coated on the separator and the current collector according to the ratio, and an active material layer is coated on the current collector.

[0085] In Example 7, the composite oxide solid electrolyte, the current collector, and the separator in the above Examples 1, 2, 3, 4, 5, and 6 can also be used for the preparation of solid-state lithium-ion batteries.

[0086] Table 1 Ionic conductivity of composite oxide solid electrolyte at different sintering temperatures

[0087]

[0088] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of a composite oxide solid electrolyte, characterized in that, The composite oxide solid electrolyte includes Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and Li7La3Zr2O 12 , wherein, Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is abbreviated as LATP, and Li7La3Zr2O 12 is abbreviated as LLZO; The preparation method of the composite oxide solid electrolyte includes the following steps: S1: Add LATP and LLZO by mass parts into a planetary ball mill containing zirconia and ethanol for ball milling; S2: Dry and sand grind; S3: Sinter at high temperature, where the high-temperature sintering temperature is 800 - 1100 °C and the sintering time is 2 - 5 h.

2. The preparation method of a composite oxide solid electrolyte according to claim 1, characterized in that, In the step S1, the mass ratio of LATP to LLZO is 1:1, and the ball milling time is 2 - 6 h.

3. The preparation method of a composite oxide solid electrolyte according to claim 1, characterized in that, In the step S2, the high-temperature drying time is 0.5 - 3 h, the drying temperature is 180 - 220 °C, and the drying atmosphere is air; further grind the powder with a sand mill and press it into microspheres with a diameter of 2 mm.

4. A composite oxide solid electrolyte current collector, characterized in that, Coat the composite oxide solid electrolyte described in any one of claims 1 to 3 above on the surface of the current collector of a lithium-ion battery to form a surface coating layer; the current collector is aluminum foil or microporous aluminum foil; the single-sided thickness of the bottom coating of the composite oxide solid electrolyte ≤ 5 μm.

5. A current collector for a composite oxide solid electrolyte according to claim 4, characterized in that, The thickness of the aluminum foil or microporous aluminum foil ≤ 25 μm; when microporous aluminum foil is selected, the pore diameter of the microporous aluminum foil is 10 - 80 μm.

6. The current collector of a composite oxide solid electrolyte according to claim 4, characterized in that, The slurry composition of the composite oxide solid electrolyte coated on the surface of the current collector of a lithium-ion battery includes: 85 - 90% composite oxide solid electrolyte, 3 - 6% conductive agent, 5 - 13% binder, 0.5 - 1.8% dispersant; Among them, the viscosity of the bottom coating slurry of the composite oxide solid electrolyte is 500 - 1500 MPa·s, and the solid content is 20 - 50%; The conductive agent is one or a mixture of more than one of conductive carbon materials and conductive polymers; The dispersant is any one of inorganic dispersants, organic dispersants, or polymer dispersants.

7. The current collector of a composite oxide solid electrolyte according to claim 6, characterized in that, The conductive carbon material is one or a mixture of more than one of single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, reduced graphene oxide, conductive carbon black, carbon microspheres, graphite, and acetylene black; The conductive polymer is one or a mixture of more than one of polyacetylene, polythiophene, polypyrrole, polyaniline, polyphenylene, polyphenylene vinylene, and polydiyne; The inorganic dispersant is one or a mixture of more than one of sodium pyrophosphate, sodium tripolyphosphate, and sodium hexametaphosphate; The organic dispersant is one or a mixture of more than one of anionic, cationic, and non-ionic types; The polymer dispersant is one or a mixture of more than one of polycarboxylates, poly(meth)acrylic acid derivatives, and maleic anhydride copolymers.

8. A composite oxide solid electrolyte separator, characterized in that, The composite oxide solid electrolyte separator is to coat the composite oxide solid electrolyte described in any one of claims 1 to 3 above on one or both sides of the separator base film.

9. A composite oxide solid electrolyte separator according to claim 8, characterized in that, The separator base film is any one or a mixture of two of polyethylene and polypropylene; the thickness of the separator base film ≤ 15 μm; the single-sided thickness of the composite oxide solid electrolyte coating ≤ 5 μm.

10. A solid-state lithium-ion battery, characterized in that, The solid-state lithium-ion battery includes the composite oxide solid electrolyte separator described in claim 8 above and positive and negative electrode plates. The positive and negative electrode plates are respectively formed by coating positive and negative active materials on the composite oxide solid electrolyte separator to form active material layers. The solid-state lithium-ion battery is wound by the composite oxide solid electrolyte separator and the positive and negative electrode plates.

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