Low-cost positive electrode prefabricated lithium and high specific energy electrode, manufacturing method and quasi-solid-state battery

Abstract

The present invention provides a low-cost positive electrode prefabricated lithium and high specific energy electrode, a manufacturing method and a quasi-solid-state battery. The positive electrode material of the lithium battery is first calcined and then calcined with LiOH for a second time; the positive electrode material, toughening conductive agent, liquid retaining agent and polytetrafluoroethylene powder are mixed and then drawn with dry supersonic jet gas to stretch the molecular chain of polytetrafluoroethylene and form a physical adhesion with the powder; then the powder is sprayed with an alcohol solution, mixed, granulated, hot pressed and cold pressed to obtain a positive electrode film with a required thickness, and after drying, the positive electrode film is hot pressed and laminated on both sides of an aluminum foil to form an electrode. The electrode made by this method has good strength, reasonable pore structure, excellent three-dimensional conductive network and many active sites. The electrode has the advantages of high compaction density and stable PTFE entanglement network structure, and the prefabricated lithium makes up for the lithium source consumed by SEI, reduces the consumption of electrolyte, improves the first effect of the battery, the energy density during battery use and the cycle life of the lithium battery.

Description

Technical Field

[0001] The present invention relates to a low-cost positive electrode prefabricated lithium and a high-energy-density electrode, a manufacturing method and a quasi-solid-state battery, and belongs to the field of new energy materials. Background Art

[0002] Amidst the energy crisis and severe environmental pollution, China has vigorously developed new energy industries. Since the advent of lithium batteries, industries such as electric vehicles, mobile communications, and the Internet of Things have developed rapidly. However, the current lithium battery system can no longer meet people's demand for energy density and production costs. High-nickel or lithium-rich cathode materials have high specific capacity, but the powders of these materials are alkaline. Using traditional wet slurrying methods, the slurry will become jelly-like and cannot be coated. Homogenization requires high-energy drying rooms. Even if coating is possible, the electrodes are prone to cracking and poor flexibility. During the drying process, the conductive agent and binder will agglomerate, causing the active material to precipitate to the bottom of the electrode, resulting in stratification and making it impossible to thicken the electrode. Large amounts of N-methyl-2-pyrrolidone as a solvent are not only expensive and toxic, but also consume a lot of electricity during the coating and drying processes. Therefore, finding a new electrode production method is a hot research topic in the industry. The electrode structure produced by dry electrode technology is stable, and the structure will not be destroyed during charging, and a good framework will be rebuilt after discharge; the dry electrode can be made very thick, and the high compaction density significantly improves its energy density; the electrode has a reasonable pore system, which is convenient for the infiltration of electrolyte; the electrode has good strength; the excellent three-dimensional conductive network and many active sites can effectively improve the life and capacity of lithium batteries and the stability of the system, thereby achieving ultra-high energy density. In addition, it is easy to prefabricate lithium in the process of material and electrode production, which makes up for the lithium source consumed by SEI, reduces the consumption of electrolyte, and improves the initial efficiency of the battery, the energy density during battery use, and the cycle life of the lithium battery. Summary of the Invention

[0003] To overcome the above-mentioned defects, the present invention provides low-cost positive electrode prefabricated lithium and high-energy-density electrode, manufacturing method and quasi-solid-state battery. The prepared pre-lithiation high-energy-density electrode has high porosity, stable electrode structure, three-dimensional conductive network and many active sites, which makes up for the lithium source consumed by SEI, reduces the consumption of electrolyte, improves the first efficiency of the battery, the energy density during battery use and the cycle life of the lithium battery.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A method for manufacturing a low-cost positive electrode prefabricated lithium and a high specific energy electrode, characterized by comprising the following steps:

[0006] The positive electrode material of the lithium battery is calcined in a high temperature calcining furnace at a high temperature to powder A;

[0007] LiOH and powder A are mixed evenly in a powder mixer, and then calcined twice in a high-temperature calcining furnace to obtain powder B;

[0008] The powder B, conductive agent, toughening conductive agent, and liquid retaining agent are uniformly mixed in a powder mixer to form powder C; the conductive agent is one or a mixture of super-P, ECP, and acetylene black; the toughening conductive agent is one or a mixture of artificial graphite and high-purity graphite; the liquid retaining agent is an inorganic powder with electronegativity and volume expansion when exposed to water and / or alcohol;

[0009] The polytetrafluoroethylene powder and powder C are mixed uniformly in a mixer to form powder D; the mixing process is carried out under the temperature condition where the polytetrafluoroethylene is in a glassy state;

[0010] The powder D is subjected to a dry supersonic jet gas to spray-draw polytetrafluoroethylene, so that the molecular chains of the polytetrafluoroethylene in the powder D are extended and opened, forming a physical adhesion with the powder in the powder C without chemical reaction, thereby obtaining powder E;

[0011] Spraying an alcohol solvent on the powder E and stirring continuously, and then forming a uniform micelle after banburying, and then forming the micelle into millimeter-sized particles F with uniform size after shearing and granulation;

[0012] The particles F are hot-pressed once on a horizontal hot roller press to form a positive electrode film G;

[0013] The cathode film G is thinned to the target loading amount by multiple cold roller pressing on a cold roller press to obtain cathode film H;

[0014] After the positive electrode film H is dried, it is compounded with the glue-coated current collector, and then hot-rolled and hot-laminated together to obtain the positive electrode sheet I; the positive electrode sheet is compacted to the target compaction density by a roller press.

[0015] Furthermore, the amount of LiOH added is 1-8 mol% of the amount of Li substance in the primary calcined powder A, the temperature of the primary calcination is 700-900°C, and the temperature of the secondary calcination is 300-800°C.

[0016] Furthermore, the inorganic powder is one or more of bentonite, montmorillonite powder, illite powder, kaolin powder, and halloysite powder.

[0017] Furthermore, the weight percentages of the lithium battery positive electrode material, the conductive agent, the toughening conductive agent, the liquid retaining agent, and the polytetrafluoroethylene powder are: 70-95wt%: 1-10wt%: 1-10wt%: 1-10wt%: 3%-15wt%.

[0018] Furthermore, the alcohol solvent is one of isopropyl alcohol, propylene glycol, ethanol, ethylene glycol, glycerol, or a mixed solvent of any two alcohols, and the volume percentages of the two alcohols are: 40%-80vol%: 20%-60vol%; the solid content of the uniform micelle is 60%-80wt%.

[0019] Furthermore, the particles F are rolled once on a horizontal hot roller press to achieve a thickness of the positive electrode film G of 150-200 μm, and the hot roller pressing temperature is 40-90° C.

[0020] Furthermore, the positive electrode film G is rolled multiple times with a cold roller until the thickness of the positive electrode film H reaches 90-120 μm, and the cold roller pressing temperature is 5-40° C.

[0021] Furthermore, the glue-coated current collector is prepared by printing a highly conductive paste on both sides of the current collector conductive foil using a gravure printing machine. The current collector surface needs to be chemically cleaned before glue coating to remove surface rolling oil. The highly conductive paste is composed of high-purity graphite, a non-hydrophilic adhesive and a non-aqueous solvent.

[0022] The low-cost positive electrode prefabricated lithium and high-specific energy electrode are prepared by the method for manufacturing the low-cost positive electrode prefabricated lithium and high-specific energy electrode.

[0023] Compared with the prior art, the low-cost positive electrode prefabricated lithium and high specific energy electrode prepared by the method described in the present invention have the following characteristics: (1) high compaction density; (2) large thickness; (1) reasonable porosity; (2) large capacity; (3) excellent three-dimensional conductive network with many active sites; (4) stable PTFE entanglement network structure; (5) high strength; (6) high first efficiency; and (7) long battery life.

[0024] This invention organically integrates cathode powder production and lithium replenishment with the semi-dry electrode manufacturing process, eliminating the slurrying and coating drying processes in a dry room, thereby significantly reducing energy consumption and costs. This invention effectively overcomes the problem of excessive LiOH replenishment leading to high alkalinity in the powder, which precludes the use of traditional slurry wet coating processes for electrode production. This improves the cathode specific capacity and cycle performance while reducing electrode manufacturing costs.

[0025] The present invention introduces inorganic powders such as bentonite, montmorillonite powder, illite powder, kaolin powder, and halloysite powder into the semi-dry electrode. When exposed to water and alcohol, the volume expands several to dozens of times, effectively fixing the alcohol, reducing the solid content of the micelles, and preventing the micelles from sticking to the roller during the subsequent film pressing process due to excessive solvent. After film formation, the volume of the inorganic powders shrinks during the drying process, and the pores are introduced, thereby optimizing the pore structure of the semi-dry electrode. In addition, inorganic powders such as bentonite, montmorillonite powder, illite powder, kaolin powder, and halloysite powder have strong electronegativity and can effectively absorb excess cations in the electrolyte through the layered crystal structure, playing a role in slow release of cations, slowing down the large fluctuations of cations in the electrolyte, stabilizing the pH value of the electrolyte, and providing high compatibility of the system. This type of inorganic powder can be used as a low-cost, high-lithium ion conductivity solid electrolyte to effectively improve the rate performance of the electrode.

[0026] The semi-dry electrode of the present invention adopts gradient drying technology to remove ethanol and propylene glycol in the electrode respectively, so as to prevent cracks in the self-supporting electrode caused by direct drying at high temperature, thereby affecting the strength.

[0027] The current collector of the present invention adopts a glue-coated current collector. The rolling oil is removed from the surface of the current collector foil after chemical cleaning, and the rough surface has stronger adhesion with the conductive layer and the positive electrode film. The conductive glue layer is a mixture of high-purity graphite and a non-hydrophilic adhesive, which can effectively prevent the corrosion of the electrolyte on the current collector and prevent the electrode film and the current collector foil from falling off. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the integrated manufacturing process of low-cost pre-lithiation and semi-dry cathode electrodes.

[0029] Figure 2 Surface SEM image of the cathode film.

[0030] Figure 3 SEM image of the cross-section of the cathode membrane showing a spatially entangled network structure composed of PTFE.

[0031] Figure 4 This is the charge and discharge curve of the lithium-supplemented NCMA full battery assembled in Example 1 at room temperature 25°C and a current density of 0.1C;

[0032] Figure 5 The NCMA full battery assembled in Example 1 after lithium supplementation was cycled at room temperature 25°C and a current density of 0.1C;

[0033] Figure 6 This is the charge and discharge curve of the lithium-rich manganese-based full battery assembled in Example 2 at room temperature of 25°C and a current density of 0.1C.

[0034] Figure 7This is the cycle of the lithium-rich manganese-based full battery assembled in Example 2 at room temperature 25°C and a current density of 0.1C. DETAILED DESCRIPTION

[0035] In order to make the purpose, 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. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The elements and features described in one embodiment of the present invention may be combined with the elements and features shown in one or more other embodiments. It should be noted that for the purpose of clarity, the representation and description of components and processes that are not related to the present invention and are known to those of ordinary skill in the art are omitted in the description. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0036] like Figure 1 As shown, the method for manufacturing the low-cost prefabricated lithium positive electrode and the high specific energy electrode of the present invention specifically comprises the following steps:

[0037] First, the lithium battery positive electrode material is calcined at high temperature in a high temperature calcining furnace to powder A; LiOH and powder A are mixed evenly in a powder mixer and calcined twice in a high temperature calcining furnace to obtain powder B; powder B, conductive agent, toughening conductive agent and liquid retaining agent are mixed evenly in a mixer to obtain powder C; polytetrafluoroethylene powder and powder C are mixed evenly in a mixer to obtain powder D, and the mixing process is carried out under the temperature condition that polytetrafluoroethylene is in a glassy state; powder D is subjected to dry supersonic jet gas spray drawing in a grinding equipment to make the molecular chain of polytetrafluoroethylene in powder D The membrane is stretched and opened, forming a physical bond with the powder in powder C without chemically reacting, to obtain powder E. A mixed solvent of two alcohols is sprayed on powder E and continuously stirred, followed by banburying to form a uniform micelle. This micelle is sheared and granulated to produce uniformly sized millimeter-sized particles F with a solids content of 60%-80%. Particles F are hot-pressed once on a horizontal hot roller press to form a positive electrode film G. Positive electrode film G is thinned to the target loading by multiple cold roller presses on a cold roller press to obtain positive electrode film H. After drying, membrane H is composited with a glue-coated current collector, hot-rolled at high temperature, and hot-laminated together to obtain positive electrode sheet I. The positive electrode sheet is compacted to the target density by a roller press.

[0038] Example 1:

[0039] The nickel-cobalt-manganese-aluminum quaternary battery positive electrode material (NCMA) was calcined once in a calcining furnace at 750°C to obtain powder A; LiOH and powder A were mixed evenly in a powder mixer, and the amount of LiOH was 2 mol% of the amount of Li in powder A, and secondary calcination was carried out in a high-temperature calcining furnace to obtain powder B, and the secondary calcination temperature was 750°C; powder B, ECP, high-purity graphite, and montmorillonite powder were mixed evenly in a mixer according to 91wt%:1wt%:1wt%:1wt% to obtain powder C; 6wt% polytetrafluoroethylene powder and 94wt% powder C were mixed evenly in a mixer at 0°C to obtain powder D; powder D was ground using a dry ultra-high-pressure grinding machine. The sonic jet gas is used for wire drawing, so that the molecular chains of polytetrafluoroethylene in powder D are stretched and opened, forming physical adhesion with the powder in powder C without chemical reaction, and powder E is obtained; a mixed solvent of propylene glycol and isopropyl alcohol (30vol%:70vol%) is sprayed on powder E, and stirred continuously, and then formed into a uniform colloid after kneading, and the colloid is sheared and granulated to form millimeter-sized particles F with uniform size and solid content of 75%; particles F are hot-pressed once by a horizontal hot roller press to obtain a 150μm positive electrode film G, and the hot roller pressing temperature is 60°C; the positive electrode film G is cold-rolled multiple times by a cold roller press to reach a 90μm positive electrode film H, and the winding is completed, and the cold roller pressing temperature is 25°C. After winding, the entire roll is dried to remove the solvent. The drying process is gradient drying, which is divided into three temperature gradients of 80°C, 150°C, and 230°C. The surface and cross-sectional structures of the positive electrode film H are shown as follows. Figure 2 and Figure 3 As shown, the introduction of pores optimizes the pore structure of the semi-dry electrode. The entangled network structure formed by PTFE can make the electrode structure more stable. After high-temperature hot roller pressing and hot lamination, the positive electrode sheet I is obtained. The positive electrode sheet is compacted to the target compaction density of 3.6g cm by the roller press. -3 .

[0040] Quasi-solid-state NCMA full battery assembly:

[0041] Assembly: A PPS non-porous membrane / PE porous membrane composite solid separator, semi-dry NCMA positive electrode sheet and graphite laminate were assembled, the tabs were welded, and the battery was packaged into a shell to form a non-liquid-injected battery. An organic electrolyte solution with a concentration of 0.6 mol / L LiDFOB + 0.6 mol / L LiBF4 was injected, and the battery was vacuum-sealed to prepare a quasi-solid-state NCMA full battery. The full battery has a capacity exceeding commercial levels, reaching 5 mAh cm -2 above.

[0042] Example 2:

[0043] The lithium-rich manganese base is calcined once in a high-temperature calcining furnace at 800°C to obtain powder A; LiOH and powder A are mixed evenly in a powder mixer, and the amount of LiOH is 4 mol% of the amount of Li substance in powder A, and a second calcination is carried out in a high-temperature calcining furnace to obtain powder B, and the second calcination temperature is 800°C; powder B, ECP, high-purity graphite, and illite powder are mixed evenly in a mixer according to 91wt%:1wt%:1wt%:1wt% to obtain powder C; 6wt% polytetrafluoroethylene powder and 94wt% powder C are mixed evenly in a mixer at 0°C to obtain powder D; powder D is used in a grinding device. A dry supersonic jet of gas is used to draw the polytetrafluoroethylene (PTFE) molecular chains in powder D, stretching and opening them. This allows them to physically bond with the powder in powder C without chemically reacting, resulting in powder E. Ethanol is sprayed onto powder E as a solvent, and the mixture is continuously stirred. After internal kneading, a uniform micelle is formed. This micelle is sheared and granulated into uniform, millimeter-sized particles F with a solids content of 75%. Particles F are hot-pressed once through a horizontal hot roller press at 60°C to produce a 150μm positive electrode film G. This film G is then cold-rolled multiple times through a cold roller press at 25°C to produce a 90μm positive electrode film H, which is then rolled. After winding, the entire roll is dried to remove the solvent. The drying process is a gradient drying process with three temperatures: 80°C, 150°C, and 230°C. After high-temperature hot roller pressing, the film is hot-laminated together to produce the positive electrode sheet I. The positive electrode sheet is compacted to the target density of 2.6 g cm by a roller press. -3 .

[0044] Quasi-solid-state lithium-rich manganese-based full battery assembly:

[0045] Assembly: A PPS non-porous membrane / PE porous membrane composite solid separator, a semi-dry lithium-rich manganese-based positive electrode sheet, and a graphite negative electrode stack are assembled, the tabs are welded, and the battery is packaged into a case to form a non-liquid-filled battery. A high-voltage organic electrolyte is injected, and the battery is vacuum-sealed to prepare a quasi-solid-state lithium-rich manganese-based full battery. The full battery has a surface capacity exceeding commercial levels, reaching 5 mAh cm -2 Above. And the cycle is stable.

[0046] Although the present invention and its advantages have been described in detail above, it should be understood that various changes, substitutions and modifications may be made without departing from the spirit and scope of the present invention as defined by the appended claims. Moreover, the scope of the present invention is not limited to the specific embodiments of the processes, devices, means, methods and steps described in the specification. It will be readily understood by those skilled in the art from the disclosure of the present invention that existing and future developed processes, devices, means, methods or steps that perform substantially the same functions as the corresponding embodiments described herein or obtain substantially the same results may be used according to the present invention. Therefore, the appended claims are intended to include within their scope such processes, devices, means, methods or steps.

Claims

1. A method for manufacturing a low-cost positive prefabricated lithium and high specific energy electrode, characterized in that: The following steps are involved: The positive electrode material of the lithium battery is calcined in a high temperature calcining furnace at a high temperature to powder A; LiOH and powder A are mixed evenly in a powder mixer, and then calcined twice in a high-temperature calcining furnace to obtain powder B; The powder B, conductive agent, toughening conductive agent, and liquid retaining agent are uniformly mixed in a powder mixer to form powder C; the conductive agent is one or a mixture of super-P, ECP, and acetylene black; the toughening conductive agent is one or a mixture of artificial graphite and high-purity graphite; the liquid retaining agent is an inorganic powder with electronegativity and volume expansion when exposed to water and / or alcohol; The polytetrafluoroethylene powder and powder C are mixed uniformly in a mixer to form powder D; the mixing process is carried out under the temperature condition where the polytetrafluoroethylene is in a glassy state; The powder D is subjected to a dry supersonic jet gas to spray-draw polytetrafluoroethylene, so that the molecular chains of the polytetrafluoroethylene in the powder D are extended and opened, forming a physical adhesion with the powder in the powder C without chemical reaction, thereby obtaining powder E; Spraying an alcohol solvent on the powder E and stirring continuously, and then forming a uniform micelle after banburying, and then forming the micelle into millimeter-sized particles F with uniform size after shearing and granulation; The particles F are hot-pressed once on a horizontal hot roller press to form a positive electrode film G; The cathode film G is thinned to the target loading amount by multiple cold roller pressing on a cold roller press to obtain the cathode film H; After the positive electrode film H is dried, it is compounded with the glue-coated current collector, and then hot-rolled and hot-laminated together to obtain the positive electrode sheet I; the positive electrode sheet is compacted to the target compaction density by a roller press.

2. The method for manufacturing a low-cost prefabricated lithium cathode and a high specific energy electrode according to claim 1, characterized in that: The amount of LiOH added is 1-8 mol% of the amount of Li substance in the primary calcined powder A. The temperature of the primary calcination is 700-900°C, and the temperature of the secondary calcination is 300-800°C.

3. The method for manufacturing a low-cost prefabricated lithium cathode and a high specific energy electrode according to claim 1, characterized in that: The inorganic powder is one or more of bentonite, montmorillonite powder, illite powder, kaolin powder and halloysite powder.

4. The method for manufacturing a low-cost prefabricated lithium cathode and a high specific energy electrode according to claim 1, characterized in that: The weight percentages of lithium battery positive electrode material, conductive agent, toughening conductive agent, liquid retaining agent, and polytetrafluoroethylene powder are: 70-95wt%: 1-10wt%: 1-10wt%: 1-10wt%: 3%-15wt%.

5. The method for manufacturing a low-cost prefabricated lithium cathode and a high specific energy electrode according to claim 1, characterized in that: The alcohol solvent is one of isopropyl alcohol, propylene glycol, ethanol, ethylene glycol, glycerol, or a mixed solvent of any two alcohols, and the volume percentages of the two alcohols are: 40%-80vol%: 20%-60vol%; the solid content of the uniform micelle is 60%-80wt%.

6. The method for manufacturing a low-cost prefabricated lithium cathode and a high specific energy electrode according to claim 1, characterized in that: The particles F are rolled once on a horizontal hot roller press to achieve a positive electrode film G with a thickness of 150-200 μm, and the hot roller pressing temperature is 40-90°C; the positive electrode film G is rolled multiple times on a cold roller to achieve a positive electrode film H with a thickness of 50-120 μm, and the cold roller pressing temperature is 5-40°C.

7. The method for manufacturing a low-cost prefabricated lithium cathode and a high specific energy electrode according to claim 1, characterized in that: The drying process of the membrane H is a step drying process, which is a forced air drying process. The drying process is divided into three temperature gradients, namely 80°C, 150°C and 230°C, and then the temperature is lowered.

8. The method for manufacturing a low-cost prefabricated lithium cathode and a high specific energy electrode according to claim 1, wherein: The glue-coated current collector is prepared by printing a highly conductive paste on both sides of the current collector conductive foil using a gravure printing machine. The current collector surface needs to be chemically cleaned before glue coating to remove surface rolling oil. The highly conductive paste is composed of high-purity graphite, a non-hydrophilic adhesive and a non-aqueous solvent.

9. A low-cost prefabricated lithium cathode and a high-specific-energy electrode prepared by the method for preparing a low-cost prefabricated lithium cathode and a high-specific-energy electrode according to any one of claims 1 to 8.

10. A quasi-solid-state battery made of the low-cost prefabricated lithium cathode and the high specific energy electrode according to claim 9.

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