A fully soluble solid-state battery positive electrode composite sheet, its preparation method and application

Abstract

This invention discloses a fully soluble solid-state battery positive electrode composite sheet, which consists of an aluminum-based composite current collector and a positive electrode material active layer coated on the aluminum-based composite current collector. The aluminum-based composite current collector is a soluble aluminum-based composite material prepared by aluminum powder, a water-soluble binder, and a conductive agent. The positive electrode material active layer contains 75-85 parts of lithium iron phosphate, 5-10 parts of polyvinyl alcohol, 5-10 parts of composite solid electrolyte Li7O2Br3, and 2-5 parts of graphene. The preparation method and its application in batteries are also disclosed. The composite electrode sheet of this invention can realize the normal function of a positive electrode sheet, and can be assembled with a solid electrolyte and a corresponding negative electrode sheet to form a fully soluble solid-state battery. Furthermore, due to the fully soluble design, the battery is easy to recycle and facilitates the recovery of active materials.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage, specifically relating to a fully soluble solid-state battery positive electrode composite sheet, its preparation method, and its application in lithium batteries. Background Technology

[0002] Against the backdrop of the global energy revolution, lithium batteries have become an indispensable energy storage device in electronic products such as electric vehicles, smartphones, and drones due to their significant advantages such as high energy density, long cycle life, and low self-discharge rate.

[0003] However, with the in-depth research and widespread application of lithium battery technology, the limitations of its positive electrode current collector aluminum foil have gradually become apparent. In particular, in specific applications, issues such as the solubility of aluminum foil, battery self-destruction, and the complexity of active material recycling urgently need to be addressed.

[0004] Aluminum foil, used as a current collector in the positive electrode, cannot achieve complete battery self-destruction in certain applications. In some special applications, such as the military and aerospace fields, it is required that the battery can completely self-destruct when damaged or under specific conditions to prevent information leakage or safety accidents.

[0005] However, due to the poor solubility and high stability of aluminum foil, it is difficult to achieve complete self-destruction of the battery. This may result in the battery still posing potential safety risks after being damaged, thus failing to meet the battery safety requirements of certain fields.

[0006] Using aluminum foil as a positive electrode current collector increases the complexity of lithium battery active material recycling. The recycling process requires separating and recovering various components, including the positive electrode, negative electrode, and electrolyte. Due to the tight bond between the aluminum foil and the positive electrode material and electrolyte, the separation process is complex, increasing the difficulty and cost of recycling. Summary of the Invention

[0007] To address the shortcomings of existing technologies, one objective of this invention is to provide a fully soluble solid-state battery positive electrode composite sheet. This sheet is prepared by using a soluble aluminum-based composite material as the current collector and then coating it with a positive electrode active layer. This invention verifies for the first time that the composite sheet can achieve normal positive electrode function and can be assembled with a solid electrolyte and a corresponding negative electrode sheet to form a fully soluble solid-state battery. Furthermore, due to the fully soluble design, the battery is easy to recycle and facilitates the recovery of active materials.

[0008] The technical solution adopted by this invention to solve its technical problem is: a fully soluble solid-state battery positive electrode composite sheet, which is composed of an aluminum-based composite current collector and a positive electrode material active layer coated on the aluminum-based composite current collector; the aluminum-based composite current collector is a soluble aluminum-based composite material prepared by aluminum powder, water-soluble binder polyvinyl alcohol (PVA), and conductive agent, and the aluminum-based composite current collector contains 50-70 parts of aluminum powder, 25-40 parts of PVA, and 5-10 parts of conductive agent; according to the weight parts, the positive electrode material active layer contains 75-85 parts of lithium iron phosphate, 5-10 parts of PVA, 5-10 parts of composite solid electrolyte Li7O2Br3, and 2-5 parts of graphene. Because the positive electrode current collector is made of soluble aluminum-based composite material and polyvinyl alcohol is used as a binder for molding, the current collector and the positive electrode material use the same water-soluble binder. The current collector and the positive electrode material have good interfacial compatibility. Furthermore, both the positive electrode current collector and the positive electrode active layer can be well dissolved in water, making it suitable for use in special fields and facilitating the recycling and regeneration of active materials.

[0009] Furthermore, the aluminum powder has a particle size of 0.1–10 μm, preferably 2–8 μm, and the conductive agent powder has a particle size of 0.1–1.2 μm. By using the aluminum powder and conductive agent powder in an effective combination of particle sizes, the conductivity of the aluminum-based composite material can reach the same level as that of an aluminum foil current collector, and it also has good water solubility.

[0010] Furthermore, the composite solid electrolyte Li7O2Br3 is obtained by ball milling and pressure sintering of Li2O and LiBr as raw materials, with the pressure sintering pressure being 4... -10 The sintering temperature is 550–900℃. The composite solid electrolyte Li7O2Br3 is not a pure compound. The preparation method for the composite solid electrolyte is based on existing techniques; for details, refer to the synthesis method used by Li et al. in CN116190771A. Sintering under pressure using the above method yields an anti-perovskite solid electrolyte with a Li7O2Br3 purity of 61–72%, which improves the ionic conductivity of the anti-perovskite solid electrolyte.

[0011] Furthermore, the conductive agent is one or more of carbon black, carbon nanotubes, graphite, SuperP, SuperS, Ketjen black, and acetylene black.

[0012] Furthermore, the positive electrode material active layer comprises 83 parts lithium iron phosphate, 8 parts polyvinyl alcohol, 7 parts composite solid electrolyte Li7O2Br3, and 2.5 parts graphene.

[0013] A second objective of this invention is to provide a method for preparing the above-mentioned fully soluble solid-state battery positive electrode composite sheet, comprising the following steps:

[0014] Step 1: Weigh 27.5 parts of polyvinyl alcohol and dissolve it in 1 to 1.5 times its weight of ethanol, stirring to form an organic binder solution; weigh 63.5 parts of aluminum powder and add it to the organic binder solution in three batches, continuously sonicating and stirring to ensure that the aluminum powder and binder are fully and evenly mixed; then add 9 parts of conductive agent, continue stirring and sonicating to obtain a uniform mixture; evaporate the organic solvent to obtain the pretreated mixture.

[0015] Step 2: Place the pretreated mixture into a hot press and hot press at a temperature of 35-60℃ and a pressure of 500kg-1000kg for 1-2 hours, then allow it to cool naturally to obtain a soluble aluminum-based composite material.

[0016] Step 3: Weigh 83 parts of lithium iron phosphate, 7 parts of Li7O2Br3 and 2.5 graphene, mix them, and dry mix them to ensure uniformity. Add a small amount of N-methylpyrrolidone and ball mill to obtain the original slurry. Weigh 8 parts of polyvinyl alcohol and add them to the original slurry. Continue to ball mill the mixture at a rotation speed of 350-4000 r / min and a revolution speed of 2-5 r / min for 8-12 hours. Use a high-shear emulsifier for high-speed stirring to obtain the positive electrode active slurry.

[0017] Step 4: Coat the positive electrode active slurry onto the soluble aluminum-based composite material obtained in Step 2 and dry it at 40-80°C. The above drying temperature can promote the complete fusion of the positive electrode active layer and the aluminum-based composite current collector interface and reduce voids. Use a roller press to roll the dried electrode sheet and control the thickness of the entire electrode sheet to 50μm to obtain a fully soluble solid-state battery positive electrode composite electrode sheet.

[0018] The beneficial effects of this invention are: This invention uses a soluble aluminum-based composite material as a current collector, and then coats it with a positive electrode active layer to prepare a fully soluble solid-state battery positive electrode composite sheet. For the first time, it has been verified that the composite sheet can achieve normal positive electrode function, and can be assembled with a solid electrolyte and a corresponding negative electrode sheet to form a fully soluble solid-state battery. Furthermore, due to the fully soluble design, the battery is easy to recycle and facilitates the recovery of active materials.

[0019] The fully soluble solid-state battery positive electrode composite sheet provided by this invention further expands the special applications of lithium-ion batteries. Furthermore, since the positive electrode current collector is made of soluble aluminum-based composite material and polyvinyl alcohol is used as a binder for molding, the current collector and the binder used in this positive electrode sheet are the same, resulting in good interfacial compatibility between the current collector and the positive electrode material and reducing interfacial impedance. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the positive electrode composite electrode structure of the present invention.

[0021] The figures are labeled as follows: 1—positive electrode material active layer, 2—aluminum-based composite current collector. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. It should be understood that the following description is merely illustrative and is not intended to limit the invention.

[0024] Unless otherwise specified, the raw materials and equipment used in this invention can be purchased from the market or are commonly used in the field. Unless otherwise specified, the methods in the embodiments are conventional methods in the field. Example 1

[0025] The preparation method of the fully soluble solid-state battery positive electrode composite sheet provided in this embodiment includes the following steps.

[0026] Weigh 27.5 parts of polyvinyl alcohol binder powder and dissolve it in 30 parts of ethanol solvent, stirring to form an organic binder solution; weigh 63.5 parts of aluminum powder with a particle size of 0.1-10 μm and add it to the organic binder solution in three batches, continuously sonicating and stirring to ensure that the aluminum powder and polyvinyl alcohol are fully and uniformly mixed; then add 9 parts of one or more of carbon black, carbon nanotubes, graphite, SuperP, SuperS, Ketjen black, and acetylene black with a particle size of 0.1-1.2 μm, continue stirring and sonicating to obtain a uniform mixture, and evaporate the organic solvent to obtain the pretreated mixture.

[0027] The pretreated mixture is placed in a hot press at a temperature of 35–60°C and a pressure of 500–1000 kg for 1–2 hours, and then allowed to cool naturally to obtain a soluble aluminum-based composite material for lithium batteries with a thickness controlled at 25 μm.

[0028] Weigh out 83 parts of lithium iron phosphate, 7 parts of composite solid electrolyte Li7O2Br3 and 2.5 parts of graphene, mix them and dry mix them. Add a small amount of N-methylpyrrolidone and ball mill to obtain the original slurry. Then weigh out 8 parts of polyvinyl alcohol and add them to the original slurry. Continue to ball mill the mixture at a rotation speed of 350-4000 r / min and a revolution speed of 2-5 r / min for 8-12 h. Use a high-shear emulsifier to stir at high speed to obtain the positive electrode active slurry.

[0029] The prepared slurry is coated onto the prepared soluble aluminum-based composite material and dried at 40–80°C. A roller press is used to roll the dried electrode sheet, controlling the overall thickness of the electrode sheet to 50 μm. A punching machine is then used to punch the electrode sheet into small round sheets of the required size and shape, which is the fully soluble solid-state battery positive electrode composite sheet. See the appendix for the specific structure. Figure 1 .

[0030] The obtained positive electrode sheet was cut and then assembled with the negative lithium sheet and electrolyte into a coin cell. The full-charge EIS impedance diagram, discharge capacity, first efficiency and 100-cycle retention rate at 1C were tested at 3-4.35V. The ionic conductivity of the positive electrode material was also tested. The test results are shown in Table 1.

[0031] The prepared positive electrode sheet was used as the test sample. The prepared positive electrode sheet was placed in a certain volume of aqueous solution. The aqueous solution was kept magnetically stirred. After 10 minutes, the positive electrode sheet was observed to see if it was completely dissolved, partially dissolved, or not dissolved. Complete dissolution means that there are no lumps or flakes of material and the material dissolved in the aqueous solution is uniformly dispersed. Partial dissolution means that there are fragments or lumps of material in the solution. Not dissolved means that the positive electrode sheet is not dissolved. For easy recording, complete dissolution is marked as 3, partial dissolution as 2, and not dissolved as 1. The data of the specific embodiment are shown in the table below.

[0032] Furthermore, all the following embodiments and comparative patents were characterized using the same test methods, and the specific corresponding parameters are shown in the table below.

[0033] Comparative Example 1: By weight, 83 parts of lithium iron phosphate, 7 parts of composite solid electrolyte Li7O2Br3 and 2 parts of graphene were weighed and mixed, and then dry-mixed. A small amount of N-methylpyrrolidone was added and the mixture was ball-milled to obtain the original slurry. Then, 8 parts of polyvinyl alcohol were weighed and added to the original slurry, and the mixture was ball-milled and mixed. The mixture was stirred at high speed using a high-shear emulsifier to obtain the slurry. The prepared slurry was coated onto the prepared aluminum foil using an AFA-automatic coating machine and dried at 50°C. The dried electrode was rolled using a roller press, and the electrode was punched into small round pieces of the required size and shape using a punching machine, which is the solid-state battery cathode material.

[0034] The physical performance parameters of the embodiments and comparative examples are shown in the table below.

[0035] .

[0036] As can be seen from the data in the table above, Example 1 and Comparative Example 1 compare the effects of different current collectors on the ionic conductivity and discharge capacity of the positive electrode sheet, as well as the overall dissolution performance of the electrode sheet. Although the discharge capacity and ionic conductivity of the prepared fully soluble solid-state battery positive electrode composite sheet are somewhat reduced, the entire positive electrode sheet can be completely dissolved, and the active material becomes powder and is uniformly dispersed in the solution without large pieces of metal.

[0037] This invention is the first to propose the use of a combination of soluble aluminum-based composite materials and positive electrode active materials, achieving a fully soluble positive electrode sheet for the first time, providing more possibilities for the development of solid-state batteries.

[0038] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fully soluble solid-state battery positive electrode composite sheet, characterized in that: It is composed of an aluminum-based composite current collector (2) and a positive electrode material active layer (1) coated on the aluminum-based composite current collector (2); the aluminum-based composite current collector (2) is a soluble aluminum-based composite material prepared by using 50-70 parts of aluminum powder, 25-40 parts of polyvinyl alcohol and 5-10 parts of conductive agent; the positive electrode material active layer (1) contains 75-85 parts of lithium iron phosphate, 5-10 parts of polyvinyl alcohol, 5-10 parts of Li7O2Br3 and 2-5 parts of graphene.

2. The fully soluble solid-state battery positive electrode composite sheet according to claim 1, characterized in that, The aluminum powder has a particle size of 0.1–10 μm; the conductive agent powder has a particle size of 0.1–1.2 μm.

3. The fully soluble solid-state battery positive electrode composite sheet according to claim 1, characterized in that, The Li7O2Br3 mentioned above is obtained by ball milling and pressure sintering of Li2O and LiBr as raw materials. The pressure sintering pressure is 4. -10 Gpa, sintering temperature is 550~900℃.

4. A fully soluble solid-state battery positive electrode composite sheet according to claim 1, 2, or 3, characterized in that, The conductive agent is one or more of carbon black, carbon nanotubes, graphite, SuperP, SuperS, Ketjen black, and acetylene black.

5. The fully soluble solid-state battery positive electrode composite sheet according to claim 4, characterized in that, The positive electrode material active layer (1) contains 83 parts of lithium iron phosphate, 8 parts of polyvinyl alcohol, 7 parts of Li7O2Br3 and 2.5 parts of graphene.

6. A method for preparing a fully soluble solid-state battery positive electrode composite sheet as described in claim 1, characterized in that, Includes the following steps: Step 1: Weigh polyvinyl alcohol, dissolve it in ethanol, and stir to form a binder organic solution; weigh aluminum powder, add it to the binder organic solution in three batches, and continuously sonicate and stir; then add a conductive agent, continue stirring and sonicating to obtain a uniform mixture; evaporate the organic solvent to obtain the pretreated mixture. Step 2: Place the pretreated mixture into a hot press and hot press at a temperature of 35-60℃ and a pressure of 500kg-1000kg for 1-2 hours, then allow it to cool naturally to obtain a soluble aluminum-based composite material. Step 3: Weigh lithium iron phosphate, Li7O2Br3 and graphene, mix them thoroughly, add N-methylpyrrolidone and ball mill to obtain the original slurry; weigh polyvinyl alcohol and add it to the original slurry, continue to ball mill at a rotation speed of 350-4000 r / min and a revolution speed of 2-5 r / min for 8-12 h to mix, and use a high shear emulsifier for high-speed stirring to obtain the positive electrode active slurry; Step 4: Coat the positive electrode active slurry onto the soluble aluminum-based composite material and dry it at 40-80°C. Use a roller press to roll the dried electrode sheet to obtain the positive electrode composite electrode sheet.

7. The fully soluble solid-state battery positive electrode composite sheet as described in claim 1 is used in lithium batteries.

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