Bipolar solid-state lithium battery and preparation method thereof

Abstract

The invention relates to the technical field of lithium batteries, in particular to a bipolar solid-state lithium battery and a preparation method thereof.The bipolar solid-state lithium battery comprises multiple layers of stacked bipolar unit battery modules, and each bipolar unit battery module is composed of a bipolar plate (BP), a solid-state electrolyte layer (SE), a positive active material layer, a negative active material layer and an insulation structure; the positive electrode active material layer and the negative electrode active material layer are coated on two side surfaces of the bipolar plate; a buffer layer is introduced into the interface of the positive / negative electrode active material and the solid electrolyte or a porous electrode is filled through a solution impregnation method, so that the interface contact and lithium ion transmission efficiency is improved; through collaborative innovation of a bipolar architecture design, solid electrolyte optimization and an interface regulation and control technology, the safety, the energy density and the power density of the battery are remarkably improved, and the manufacturing cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a bipolar solid-state lithium battery and a preparation method thereof. Background Art

[0002] Traditional lithium-ion batteries use liquid electrolytes, which pose safety risks such as flammability and leakage. Furthermore, their unipolar design, which connects the individual cells in series via external wires, results in low energy density and high resistance losses. To address the safety issues of traditional lithium-ion batteries, solid-state lithium batteries have emerged. Solid-state lithium batteries use solid electrolytes instead of liquid electrolytes, fundamentally avoiding the flammability and leakage issues of liquid electrolytes and significantly improving battery safety. However, solid-state lithium batteries have also faced numerous challenges during their development. Among them, poor interfacial contact is a key issue. The high interfacial impedance between the solid electrolyte and the electrodes leads to low ion conduction efficiency, severely impacting the battery's charge and discharge performance. Furthermore, during the cycling of solid-state lithium batteries, lithium dendrites easily grow on the electrode surfaces. Once these dendrites penetrate the solid electrolyte, they can cause internal short circuits in the battery, significantly threatening battery safety. Furthermore, the traditional unipolar design still exists in solid-state lithium batteries, preventing them from effectively improving power density and modular efficiency. Therefore, there is an urgent need for a bipolar solid-state lithium battery architecture that combines high safety, high energy density, and low cost. Summary of the Invention

[0003] The object of the present invention is to provide a bipolar solid-state lithium battery and a preparation method thereof to solve the problems raised in the above background technology.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: a bipolar solid-state lithium battery, comprising a multi-layer stacked bipolar unit battery module, each bipolar unit battery module consisting of a bipolar plate (BP), a solid electrolyte layer (SE), positive and negative electrode active material layers and an insulating structure, the positive electrode active material layer and the negative electrode active material layer being coated on both sides of the bipolar plate; a buffer layer is introduced at the interface between the positive / negative electrode active material and the solid electrolyte or a porous electrode is filled by a solution impregnation method to improve the interface contact and lithium ion transmission efficiency.

[0005] Preferably, the bipolar plates are made of laminated metal composite foil or conductive polymer composite material.

[0006] Preferably, the solid electrolyte layer material is selected from sulfide-based, oxide-based or mixed solid electrolytes.

[0007] Preferably, the edges of the bipolar plates are covered with an insulating layer to prevent short circuits between adjacent bipolar unit cells.

[0008] Preferably, the laminated metal composite foil is an Al / Cu composite foil.

[0009] Preferably, the buffer layer material is LiNbO 3 or Al 2 O 3 .

[0010] Preferably, the sulfide group is Li 10 GeP2S 12 , oxide base is Li7La3Zr2O 12 , the hybrid solid electrolyte is a composite of LLZO and ionic liquid.

[0011] A method for preparing the above-mentioned bipolar solid-state lithium battery comprises the following steps: S1: Bipolar plate treatment, using Al / Cu composite metal foil or conductive polymer composite material as the bipolar plate substrate and covering the edge of the bipolar plate with an insulating layer; S2: coating the positive and negative electrode active materials, coating the positive and negative electrode active materials on both sides of the bipolar plate to form a unit cell direct series structure; S3: Interface optimization treatment, forming a buffer layer on the electrode surface by atomic layer deposition (ALD), magnetron sputtering or solution coating; or filling the porous electrode by solution impregnation to form a three-dimensional ion conductive network; S4: forming a solid electrolyte layer, using a lamination method or a printing method to form a solid electrolyte layer; S5: Unit cell stacking: Alternately stacking the plurality of bipolar unit cells in the manner of "upper bipolar plate negative electrode active material layer (NE-) - solid electrolyte layer (SE) - lower bipolar plate positive electrode active material layer (PE+)" to form an internal series structure; S6: Packaging and testing.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a bipolar solid-state lithium battery and a preparation method thereof. Through the collaborative innovation of bipolar architecture design, solid-state electrolyte optimization and interface control technology, the battery safety, energy density, power density and manufacturing cost are significantly improved.

[0013] By integrating the positive and negative electrodes on bipolar plates, the internal series connection of the unit cells is achieved, eliminating external wire resistance losses and improving energy density and modular efficiency.

[0014] The lithium ion flux at the electrode / solid electrolyte interface is regulated by the interface buffer layer, and a three-dimensional ion conductive network is formed in combination with the porous electrode filling technology to uniformize the local current density on the surface of the lithium metal negative electrode and reduce the growth rate of the lithium dendrite tip.

[0015] By simplifying the manufacturing process, material utilization is improved, making it suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of bipolar plate; Figure 2 Schematic diagram of the laminated stack of bipolar plates, positive and negative electrodes, and solid electrolytes; Figure 3 Schematic diagram of the bipolar solid-state lithium battery structure; In the figure, bipolar plate-1, solid electrolyte layer-2, positive electrode active material layer-3, negative electrode active material layer-4. DETAILED DESCRIPTION

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0018] Please refer to Figure 1-3 The present invention provides a technical solution: a bipolar solid-state lithium battery, including a multi-layer stacked bipolar unit battery module, each bipolar unit battery module consists of a bipolar plate (BP) 1, a solid electrolyte layer (SE) 2, a positive electrode active material layer 3, a negative electrode active material layer 4 and an insulating structure.

[0019] The bipolar plate 1 is made of a laminated metal composite foil, such as an Al / Cu composite foil, or a conductive polymer composite material, which has both high conductivity and mechanical strength.

[0020] The positive electrode active material layer 3 and the negative electrode active material layer 4 are respectively coated on both sides of the bipolar plate 1 and are tightly bonded to the bipolar plate 1 through a binder.

[0021] The solid electrolyte layer 2 material is sulfide-based (such as Li 10 GeP2S 12 ), oxide-based (such as Li7La3Zr2O 12 ) or mixed solid electrolytes (such as LLZO and ionic liquid composites) with high lithium ion conductivity (1×10 -3 S / cm) and a wide electrochemical window (0-5 V vs. Li / Li+).

[0022] A buffer layer (such as LiNbO3, Al2O3) is introduced at the interface between the positive electrode active material layer 3, the negative electrode active material layer 4 and the solid electrolyte, or a porous electrode is filled by solution impregnation to improve the interface contact and lithium ion transmission efficiency.

[0023] The edges of the bipolar plates are covered with an insulating layer to prevent short circuits between adjacent bipolar cells.

[0024] The method for preparing the above-mentioned bipolar solid-state lithium battery comprises the following steps: S1: Bipolar plate processing, using Al / Cu composite metal foil or conductive polymer composite material as the bipolar plate substrate, and covering the edge of the bipolar plate with an insulating layer.

[0025] S2: coating the positive and negative electrode active materials, coating the positive and negative electrode active materials on both sides of the bipolar plate to form a unit cell direct series structure.

[0026] S3: Interface optimization treatment, forming a 5-20nm thick buffer layer (such as LiNbO3, Al2O3) on the electrode surface through atomic layer deposition (ALD), magnetron sputtering or solution coating; or filling the porous electrode through solution impregnation to form a three-dimensional ion conductive network.

[0027] S4: forming a solid electrolyte layer by lamination or printing.

[0028] S5: Unit cell stacking: Alternately stacking the plurality of bipolar unit cells in the manner of "upper bipolar plate negative electrode active material layer (NE-) - solid electrolyte layer (SE) - lower bipolar plate positive electrode active material layer (PE+)" to form an internal series structure.

[0029] S6: Packaging and testing. Example 1

[0030] In this embodiment, a lamination method is used to form the solid electrolyte layer.

[0031] First, an Al / Cu composite foil bipolar plate was prepared, and a polyimide insulating layer was coated on the edge; a LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622) slurry, the negative electrode side is coated with metal lithium foil; Li7La3Zr2O 12 (LLZO) solid electrolyte sheets are cold-pressed onto both sides of the bipolar plate; three unit cells are repeatedly stacked and packaged to obtain a module with an output voltage of 9-12 V. Example 2

[0032] In this embodiment, a printing method is used to form the solid electrolyte layer.

[0033] Li3PS4 sulfide electrolyte slurry was screen-printed on the Al / Cu composite foil bipolar plate and dried at 80°C to form a 10 μm thick electrolyte layer; LiCoO2 slurry was printed on the positive electrode side and Li4Ti5O 12 slurry; after UV curing, two unit cells are stacked and packaged to obtain a module with an output voltage of 6.6 V.

[0034] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations that come within the meaning and range of equivalents of the claims are intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0035] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A bipolar solid-state lithium battery, characterized in that: A multi-layer stacked bipolar unit battery module is provided, wherein each bipolar unit battery module is composed of a bipolar plate (1), a solid electrolyte layer (2), a positive electrode active material layer (2), a negative electrode active material layer (3) and an insulating structure, wherein the positive electrode active material layer (2) and the negative electrode active material layer (3) are coated on both sides of the bipolar plate (1); A buffer layer is introduced at the interface between the positive electrode active material layer (2) and the negative electrode active material layer (3) and the solid electrolyte, or a porous electrode is filled by a solution impregnation method to improve the interface contact and lithium ion transmission efficiency.

2. The bipolar solid-state lithium battery according to claim 1, characterized in that: The bipolar plate (1) is made of laminated metal composite foil or conductive polymer composite material.

3. The bipolar solid-state lithium battery according to claim 1, characterized in that: The material of the solid electrolyte layer (2) is selected from sulfide-based, oxide-based or mixed solid electrolytes.

4. The bipolar solid-state lithium battery according to claim 1, characterized in that: The edges of the bipolar plates (1) are covered with an insulating layer to prevent short circuits between adjacent bipolar unit cells.

5. The bipolar solid-state lithium battery according to claim 2, characterized in that: The laminated metal composite foil is an Al / Cu composite foil.

6. The bipolar solid-state lithium battery according to claim 1, characterized in that: The buffer layer material is LiNbO3 or Al2O3.

7. The bipolar solid-state lithium battery according to claim 3, characterized in that: Sulfide-based Li 10 GeP2S 12 , oxide base is Li7La3Zr2O 12 , the hybrid solid electrolyte is a composite of LLZO and ionic liquid.

8. The bipolar solid-state lithium battery according to any one of claims 1 to 7, wherein the preparation method comprises the following steps: S1: Bipolar plate treatment, using Al / Cu composite metal foil or conductive polymer composite material as the bipolar plate substrate and covering the edge of the bipolar plate with an insulating layer; S2: coating the positive and negative electrode active materials, coating the positive and negative electrode active materials on both sides of the bipolar plate to form a unit cell direct series structure; S3: Interface optimization treatment, forming a buffer layer on the electrode surface by atomic layer deposition (ALD), magnetron sputtering or solution coating; or filling the porous electrode by solution impregnation to form a three-dimensional ion conductive network; S4: forming a solid electrolyte layer, using a lamination method or a printing method to form a solid electrolyte layer; S5: Unit cell stacking: Alternately stacking the plurality of bipolar unit cells in the manner of "upper bipolar plate negative electrode active material layer (NE-) - solid electrolyte layer (SE) - lower bipolar plate positive electrode active material layer (PE+)" to form an internal series structure; S6: Packaging and testing.

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