CN114976263A - Solid-state battery integrating positive electrode and electrolyte and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of solid-state batteries, and specifically discloses a solid-state battery with an integrated positive electrode and an electrolyte and a preparation method thereof. By preparing a composite solid electrolyte and a composite positive electrode, spraying a small amount of organic solvent and bonding the two, using the properties of the organic polymer in the positive electrode and the solid electrolyte to dissolve in the organic solvent, the surfaces of the two exhibit liquid characteristics, and they are in contact with each other. At the same time, it can achieve the effect of liquid-liquid immersion contact, promote the effective contact between the two, increase the ion diffusion path, reduce the interface impedance, and improve the battery performance.

Description

Solid-state battery integrating positive electrode and electrolyte and preparation method thereof

technical field

The invention belongs to the technical field of solid-state batteries, and particularly relates to an integrated solid-state battery.

Background technique

Among many renewable energy sources, lithium-ion batteries stand out due to their high energy density, long cycle life and stable discharge range. However, lithium-ion batteries used in power batteries have extremely high safety requirements, which limits the rapid development of electric vehicles to a certain extent.

Solid-state batteries have good mechanical properties, thermal stability and chemical stability due to the solid electrolyte inside, and their safety performance is relatively higher than that of conventional batteries. In addition, solid-state batteries have higher energy density and wider application range. However, the current development of solid-state batteries is relatively slow, and the main bottleneck restricting their rapid development lies in the poor ionic conductivity of solid-state electrolytes and their poor interfacial compatibility with positive and negative electrodes. The problem of poor ionic conductivity of solid-state electrolytes has been alleviated by designing a series of new solid-state electrolytes, but the poor interfacial compatibility between solid-state electrolytes and positive and negative electrodes remains to be resolved, and has become a major obstacle to the commercialization of solid-state batteries. . Interface compatibility includes two aspects: interface contact and interface reaction stability. Poor contact at the solid-solid interface will increase the interface impedance of the battery, which is not conducive to the rapid diffusion of ions, resulting in great polarization during the battery cycle, resulting in poor rate performance and rapid capacity decay.

For the poor interface contact of solid-state batteries, researchers usually use electrolyte structure design, in-situ polymerization, and integrated design to promote the contact between the electrolyte and the electrode interface.

The patent document with the publication number CN112599847B discloses a solid-state battery assembled by a double-layer solid-state electrolyte. The electrolyte is composed of a composite solid-state electrolyte layer and a flexible polymer solid-state electrolyte layer, and has good electrochemical performance and electrode-electrolyte interface compatibility. .

The patent document whose publication number is CN111933894A discloses a solid-state battery of in-situ polymerization. After the pole piece and the solid-state electrolyte membrane containing the polymer and the polymerization initiator are prepared respectively, the polymer in the two undergoes ionization under a certain temperature condition. Secondary polymerization, in-situ modification of the interface between the two, resulting in a solid-state battery with low interface resistance, high conductivity, and high voltage resistance.

The patent document with the publication number CN111342124A discloses an integrated solid-state battery. After the positive electrode, the electrolyte membrane and the negative electrode are prepared, they are stacked and hot-pressed, so that the contents of the solid-state battery can be integrated and bonded, and the electrode is improved. effective contact with the electrolyte.

However, the solid-state batteries disclosed in the above-mentioned patent documents still have the problems of poor cycle performance and insufficient rate performance.

SUMMARY OF THE INVENTION

In view of the defects in the prior art, the purpose of the present invention is to provide a solid-state battery with an integrated positive electrode and an electrolyte and a preparation method thereof, so as to improve the cycle performance and rate performance of the solid-state battery.

To achieve the above objects, the present invention provides the following specific technical solutions.

The present invention provides a method for preparing a solid-state battery with an integrated positive electrode and an electrolyte, comprising the following steps:

Mixing organic polymer, inorganic ceramic filler, lithium salt and organic solvent I uniformly to obtain electrolyte slurry; vacuum drying electrolyte slurry to prepare composite solid electrolyte membrane;

Mixing the positive electrode active material, the conductive agent and the electrolyte slurry uniformly, coating and drying on the aluminum foil to obtain the positive electrode plate;

The organic solvent II is uniformly sprayed on the surface of the composite solid electrolyte membrane and/or the surface of the positive electrode plate, and then the composite solid electrolyte membrane is attached to the positive electrode plate, dried in vacuum, and then assembled with the negative electrode to obtain a solid-state battery integrating the positive electrode and the electrolyte. .

Further, in some preferred embodiments of the present invention, the organic polymer is polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyacrylonitrile (PAN), One or more of polyethylene oxide (PEO).

Further, in some preferred embodiments of the present invention, the inorganic ceramic fillers are lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum tantalum oxide (LLTO), lithium lanthanum zirconium aluminum oxide (LLZAO) ), one or more of lithium lanthanum zirconium tantalum oxide (LLZTO).

Further, in some preferred embodiments of the present invention, the lithium salt is lithium bis-trifluoromethanesulfonimide (LiTFSI), lithium bisfluorosulfonimide (LiFSI), lithium perchlorate (LiClO ₄ ) in one.

Further, in some preferred embodiments of the present invention, the organic solvent I is one or more of N,N-dimethylformamide (DMF), acetone, tetrahydrofuran, and acetonitrile, and the organic solvent II It is N-methylpyrrolidone (NMP).

Further, in some preferred embodiments of the present invention, in the electrolyte slurry, the mass ratio of the organic polymer to the inorganic ceramic filler is 1:0.05~1, and the mass ratio of the organic polymer to the lithium salt is 1:0.2~2 .

Further, in some preferred embodiments of the present invention, the composite solid electrolyte membrane is prepared by the following methods: pouring the electrolyte slurry into a mold, or scraping on the substrate, and then vacuum drying, a composite solid electrolyte membrane of a certain thickness can be obtained. solid electrolyte membrane.

The mold is a polytetrafluoroethylene mold or a petri dish, and the substrate is at least one of glass, aluminum foil, polytetrafluoroethylene, and polyimide.

The temperature of the vacuum drying is 60~90°C, and the drying time is 24~48h.

Further, in some preferred embodiments of the present invention, the thickness of the composite solid-state electrolyte membrane is 50-200 μm.

Further, in some preferred embodiments of the present invention, the positive electrode active material is lithium iron phosphate (LiFePO ₄ ), lithium cobalt oxide (LiCoO ₂ ), lithium manganate (LiMnO ₂ ), lithium nickelate (LiNiO ₂ ) , one of nickel-cobalt-manganese ternary materials or nickel-cobalt-aluminum ternary materials.

Further, in some preferred embodiments of the present invention, the conductive agent is acetylene black.

Further, in some preferred embodiments of the present invention, the method of laminating the composite solid electrolyte membrane and the positive electrode plate is pressure lamination; the pressure during lamination is 0.1-2 Mpa.

Further, the temperature of the vacuum drying is 80-120° C., and the time is 0.5-2 hours.

Further, in some preferred embodiments of the present invention, an organic electrolyte solution containing LiPF ₆ is dropwise added to the interface between the composite electrolyte membrane and the negative electrode plate when the solid-state battery is assembled.

In addition, the present invention provides a solid-state battery with an integrated positive electrode and an electrolyte, which is prepared by the above-mentioned preparation method.

The key components of solid-state batteries include positive electrodes, solid electrolytes, and negative electrodes. Most of the positive electrode material is composed of micron-scale active materials, which causes the surface of the positive electrode sheet to be easily uneven. At the same time, solid-state electrolytes are also difficult to flatten due to their solid-state properties. When assembling the battery, point contact or local contact occurs between the positive electrode and the solid electrolyte, resulting in fewer ion diffusion channels on the interface, high battery interface impedance value, easy to generate large polarization during cycling, low battery coulombic efficiency, rate performance and cycle stability. Poor sex. The present invention prepares a composite solid electrolyte and a composite positive electrode, sprays a small amount of organic solvent and attaches the two, and utilizes the properties of the organic polymer in the positive electrode and the solid electrolyte to dissolve in the organic solvent, so that the surfaces of the two exhibit liquid characteristics, and the surface of the two is liquid. When combined and contacted, the effect of liquid-liquid infiltration contact is achieved, which promotes the effective contact between the two, increases the ion diffusion path, reduces the interface impedance, and improves the battery performance.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The solid-state battery with the integrated cathode and electrolyte of the present invention has an integrated structure that effectively reduces the interface impedance of the battery and suppresses the concentration polarization, and can have a higher discharge specific capacity;

(2) The integrated cathode and electrolyte promote the homogenization of the current density inside the battery, thereby improving the cycle stability of the battery;

(3) The electrolyte slurry added to the positive electrode is conducive to the rapid diffusion of lithium ions on the positive electrode side, so that the assembled battery has good rate performance;

(4) The process of the method of the present invention is simple, the required equipment is basically the same as that of the existing industrialized solid-state battery process, and it can be directly used in the production of the existing production line.

Description of drawings

FIG. 1 is the charge-discharge curve of the solid-state battery with integrated cathode and electrolyte assembled in Example 1 of the present invention at 0.1C.

FIG. 2 is the charge-discharge curve of the solid-state battery with integrated cathode and electrolyte assembled in Example 1 of the present invention at 0.5C.

FIG. 3 is the charge-discharge curve of the solid-state battery with integrated cathode and electrolyte assembled in Example 1 of the present invention at 1C.

FIG. 4 is the charge-discharge curve of the solid-state battery with integrated cathode and electrolyte assembled in Example 1 of the present invention at 2C.

FIG. 5 is a cycle performance diagram of the solid-state battery with integrated cathode and electrolyte assembled in Example 1 of the present invention at 0.5C.

6 is a rate performance diagram of a solid-state battery with an integrated positive electrode electrolyte assembled in Example 1 of the present invention.

7 is an electrochemical impedance diagram of a solid-state battery with an integrated positive electrode and electrolyte assembled in Example 1 of the present invention.

Detailed ways

The present invention is described in detail below. The description in this section is only exemplary and explanatory, and should not have any limiting effect on the protection scope of the present invention. In addition, according to the description in this document, those skilled in the art can make corresponding combinations of features in the embodiments of this document and in different embodiments.

Unless otherwise defined, all technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention.

Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or can be prepared by existing methods.

Example 1

(1) Preparation of composite solid electrolyte membrane: Weigh 0.4 g of LiTFSI, 0.5 g of PVDF, and 0.1 g of LATP, mix them uniformly in 5 mL of DMF, stir magnetically for 6 h and ultrasonically treat them for 1 h. The composite solid electrolyte membrane was prepared by drying the glass plate at 80 °C under vacuum for 24 h to remove most of the DMF solvent;

(2) Preparation of positive pole piece: Weigh 0.04 g LiTFSI, 0.05 g PVDF, 0.001 g LATP, mix them uniformly in 5 mL NMP, stir magnetically for 6 h and ultrasonically treat for 1 h to prepare solid electrolyte slurry; weigh 0.08 g g LiFePO ₄ , 0.01 g acetylene black were dry-milled and mixed in a mortar, and 0.5 mL of electrolyte slurry was added as a binder and dispersant for wet milling, coated on aluminum foil, and dried at 120°C under vacuum conditions. 6 h, the positive pole piece was prepared;

(3) Integrate the positive electrode and the electrolyte and assemble the battery: spray a small amount of NMP on the surface of the composite solid electrolyte membrane and the positive electrode plate to partially dissolve the PVDF, then press the two together at 1Mpa, and then place them in an oven at 80 °C Vacuum dried for 2 hours to obtain an integrated positive electrode and electrolyte; in an inert protective atmosphere, a battery was assembled with metal lithium as the negative electrode.

The assembled battery was tested for electrochemical performance in the voltage range of 2.7-4.3 V (1 C=170 mA/g). The results are shown in Figures 1-7: the specific discharge capacity reaches 158.4 mAh at a rate of 0.1 C. /g, the discharge specific capacity at 0.2C rate is 158.0mAh/g, the discharge specific capacity at 0.3C rate is 158.1mAh/g, the discharge specific capacity at 0.5C rate is 155.8mAh/g, the discharge specific capacity at 1C rate The specific capacity is 146.8mAh/g, the discharge specific capacity at 2C rate is 126.7mAh/g, and the assembled battery has good rate performance; after 50 cycles at 0.5C, the capacity retention rate is 96.3%, and the assembled battery has stable cycling. The electrolyte bulk impedance is 13 Ω, the charge transfer impedance is 202 Ω, and the lithium ion diffusion coefficient is 6.8×10 ^-13 cm ² s ^-1 . The assembled battery has low impedance and fast lithium ion diffusion.

Example 2

(1) Preparation of composite solid electrolyte membrane: Weigh 0.3 g LiTFSI, 0.6 g PVDF-HFP, and 0.1 g LLZAO, mix them uniformly in 10 mL DMF, stir magnetically for 6 h and ultrasonicate for 1 h, pour them into a petri dish at 90 The composite solid electrolyte membrane was prepared by drying under vacuum conditions at ℃ for 24 h to remove most of the DMF solvent;

(2) Preparation of positive pole piece: Weigh 0.03 g LiTFSI, 0.06 g PVDF-HFP, and 0.01 g LLZAO, mix them uniformly in 3 mL NMP, stir magnetically for 6 h and ultrasonically treat for 1 h to prepare a solid electrolyte slurry; 0.08g LiNi _0.83 Co _0.11 Mn _0.06 O ₂ , 0.01g acetylene black were dry-milled in a mortar and mixed uniformly, 0.3 mL of electrolyte slurry was added as a binder and a dispersant for wet-milling, and coated on aluminum foil at 120°C and drying under vacuum conditions for 6 h to obtain a positive electrode plate;

(3) Integrate the positive electrode and the electrolyte and assemble the battery: spray a small amount of NMP on the surface of the composite solid electrolyte membrane and the positive electrode plate to partially dissolve the PVDF-HFP, then press the two at 0.5Mpa, and then place the Vacuum-drying in a 120°C oven for 0.5 hours to obtain an integrated positive electrode and electrolyte; in a glove box with an inert protective atmosphere, a battery was assembled with metal lithium as the negative electrode.

Example 3

(1) Preparation of composite solid electrolyte membrane: Weigh 0.3 g LiFSI and 0.5 g PEO, mix them uniformly in 10 mL acetonitrile, add 0.2 g LLZTO after magnetic stirring for 4 h, continue magnetic stirring for 4 hours and ultrasonically treat for 1 h, pour into The petri dish was dried at 60 °C under vacuum for 48 h to remove most of the acetonitrile to obtain a composite solid electrolyte membrane;

(2) Preparation of positive pole piece: Weigh 0.03 g LiFSI, 0.05 g PEO, 0.02 g LLZTO, mix them uniformly in 5 mL NMP, stir magnetically for 6 h and ultrasonically treat for 1 h to prepare a solid electrolyte slurry; weigh 0.08 g g LiFePO ₄ , 0.01 g acetylene black, dry and mix in a mortar, add 0.5 mL of electrolyte slurry as a binder and dispersant for wet grinding, coat on aluminum foil, and dry at 120°C under vacuum conditions 6 h, the composite positive electrode was prepared;

(3) Integrate the positive electrode and the electrolyte and assemble the battery: spray a small amount of NMP on the surface of the composite solid electrolyte membrane and the positive electrode piece to dissolve the PEO in it, then press the two together at 0.8Mpa, and then place them in a 100°C oven Vacuum dried for 1 hour to obtain an integrated positive electrode and electrolyte; in a glove box in an inert protective atmosphere, a battery was assembled with metal lithium as the negative electrode.

The above-mentioned embodiments are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The equivalent replacement or change of the solution and its concept shall be included within the protection scope of the present invention.

Claims (8)

1. the preparation method of the solid-state battery that a positive electrode and electrolyte are integrated, it is characterised in that, comprise the following steps: Mixing organic polymer, inorganic ceramic filler, lithium salt and organic solvent I uniformly to obtain electrolyte slurry; vacuum drying electrolyte slurry to prepare composite solid electrolyte membrane; Mixing the positive electrode active material, the conductive agent and the electrolyte slurry uniformly, coating and drying on the aluminum foil to obtain the positive electrode plate; The organic solvent II is uniformly sprayed on the surface of the composite solid electrolyte membrane and/or the surface of the positive electrode plate, and then the composite solid electrolyte membrane is attached to the positive electrode plate, dried in vacuum, and then assembled with the negative electrode to obtain a solid-state battery integrating the positive electrode and the electrolyte. . 2. preparation method as claimed in claim 1 is characterized in that, described organic polymer is one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene oxide one or more; the inorganic ceramic filler is one or more of titanium aluminum lithium phosphate, lithium lanthanum zirconium oxide, lithium lanthanum tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium tantalum oxide; the lithium salt is One of lithium bis-trifluoromethanesulfonimide, lithium bis-fluorosulfonimide, and lithium perchlorate; the organic solvent I is N,N-dimethylformamide, acetone, tetrahydrofuran, acetonitrile One or more of, the organic solvent II is N-methylpyrrolidone; the positive active material is lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickelate, nickel-cobalt-manganese ternary material or nickel One of cobalt-aluminum ternary materials; the conductive agent is acetylene black. 3. preparation method as claimed in claim 1 is characterized in that, in electrolyte slurry, the mass ratio of organic polymer and inorganic ceramic filler is 1:0.05～1, and the mass ratio of organic polymer and lithium salt is 1:1: 0.2~2. 4. The preparation method according to claim 1, wherein the composite solid electrolyte membrane is prepared by the following methods: pouring the electrolyte slurry into a mold or scraping on the substrate, and then vacuum drying to obtain a certain solid state electrolyte membrane. Thickness of composite solid electrolyte membrane. 5. The preparation method of claim 4, wherein the mold is a polytetrafluoroethylene mold or a petri dish, and the substrate is at least one of glass, aluminum foil, polytetrafluoroethylene, and polyimide kind. 6 . The preparation method according to claim 1 , wherein the method of laminating the composite solid electrolyte membrane and the positive pole piece is pressure lamination; the pressure during lamination is 0.1-2Mpa. 7 . 7 . The preparation method of claim 1 , wherein an organic electrolyte solution containing LiPF ₆ is dropped on the interface between the composite electrolyte membrane and the negative electrode plate when assembling the solid-state battery. 8 . 8 . A solid-state battery with an integrated positive electrode and an electrolyte, characterized in that, it is prepared by the preparation method according to any one of claims 1 to 7 .

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