Method for manufacturing porous electrode sheet and lithium ion battery

Abstract

The application provides a porous electrode tab manufacturing method, comprising the following steps: S1, uniformly dispersing an active material, a conductive agent and a binder into a solvent to obtain a slurry; S2, uniformly coating the slurry on a current collector according to a certain surface density; S3, vertically spraying a film-forming additive into the slurry through a micropore using a high-pressure gas directly above the coated slurry; S4, obtaining a dried electrode tab after drying through an oven; and S5, obtaining a product porous electrode tab after rolling the dried electrode tab. The manufacturing method can form pores perpendicular to the electrode on the electrode, reduce the transmission distance of lithium ions, and increase the rate performance, cycle performance and charging speed of the battery. By adding a positive electrode film-forming additive to the positive electrode and a negative electrode film-forming additive to the negative electrode, the film-forming additive can fully react with the electrode to form an SEI film. Compared with uniformly dispersing the film-forming additive into the battery, the manufacturing method has higher use efficiency, can reduce the use amount of the film-forming additive, and reduces the cost.

Description

TECHNICAL FIELD

[0001] One or more embodiments of the present specification relate to the technical field of lithium ion battery, and in particular to a porous electrode sheet manufacturing method and a lithium ion battery. BACKGROUND

[0002] With the rapid development of society, the existing lithium ion battery mainly develops in the direction of high rate. At present, the industry mainly reduces the lithium ion diffusion path, increases the flow area and improves the battery large current charge and discharge performance through material nanocrystallization, porosity, electrode sheet surface density reduction, end face welding structure and the like.

[0003] Among them, by forming an electrode sheet with high porosity, the lithium ion battery can have higher rate performance and cycle performance.

[0004] For example, a patent with Chinese publication number CN105633350A discloses a method for preparing a porous electrode sheet suitable for the field of lithium ion batteries, which comprises the following steps: mixing a pore-forming agent with a slurry and coating it on an electrode sheet; baking the electrode sheet at 100-150°C to obtain a porous electrode sheet; the porosity of the electrode sheet is 35-45%. The present application also provides a lithium ion battery containing the above-mentioned porous electrode sheet. The porous electrode sheet provided by the present application has a higher porosity, and thus has a higher liquid retention capacity. The lithium ion battery containing the electrode sheet has higher rate performance and cycle performance. The pores formed simultaneously facilitate gas removal, increasing the battery life. The porous electrode sheet provided by the present application and its preparation method, as well as the lithium ion battery containing the porous electrode sheet, have simple preparation method, easy operation and can be produced industrially. However, since the patent uses uniform slurry to add pore-forming agent, the porous electrode is obtained by volatilizing the pore-forming agent during electrode baking. This method increases the cost of pore-forming agent, and the electrode porosity is not perpendicular to the electrode, and the ion transfer channel is tortuous.

[0005] For another example, a patent with Chinese publication number CN111755660A discloses an electrode sheet and a preparation method and application thereof. The electrode sheet comprises active material, conductive agent, binder and current collector, the thickness of the electrode sheet is 0.5-4mm, and the electrode sheet is uniformly distributed with holes with a diameter of 0.1-0.3mm, and the hole spacing is 2-5mm. The thickness of the electrode sheet can reach more than 3mm. Under the same condition without vacuumizing, the electrolyte infiltration speed of the porous electrode sheet is accelerated by more than 2h, improving the time efficiency from adding electrolyte to formation. The application of the electrode sheet shortens the ion transmission path in the electrolyte and electrode material, and the rate discharge performance of the battery using the electrode sheet is improved by about 5% under different current densities. However, the patent uses physical method to punch holes on the electrode by using needles, which can cause the active material to be broken and reduce the battery performance, and the friction of the needles can introduce metal foreign matters.

[0006] For example, Chinese patent CN112151743A discloses a thick electrode pore-forming method, its product and use. The pore-forming method includes coating a slurry with a viscosity of 6000 mPa·s-9000 mPa·s on the surface of a current collector with a surface roughness Ra≥1 um, and drying to obtain the thick electrode. The thick electrode obtained by the above method contains air channels from the surface of the pole piece to the surface of the current collector in the active material layer, effectively solving the problems of poor electrolyte wettability of the thick electrode, long lithium ion migration path, and large concentration polarization, thereby improving the electrochemical performance of the thick electrode lithium ion battery. Moreover, the pore-forming method greatly simplifies the process of thick electrode pore-forming and reduces the cost of thick electrode pore-forming. However, this patent uses airflow to blow pores under the electrode during coating. The current collector must have holes, and the current collector is prone to breakage.

[0007] In summary, there is no relatively perfect method for forming pores on the electrode in the prior art. SUMMARY

[0008] Therefore, the first object of the present specification is to provide a porous pole piece manufacturing method. The manufacturing method of the present application uniformly disperses active material, conductive agent and binder into a solvent to obtain a slurry, coats the slurry on a current collector, uses high-pressure gas to vertically inject film-forming additives into the slurry through micropores above the coated slurry, dries the slurry in an oven to obtain a dried pole piece, and finally rolls the dried pole piece to a certain thickness to obtain the pole piece.

[0009] The second object of the present specification is to provide a lithium ion battery comprising the porous pole piece manufactured by the above manufacturing method.

[0010] Based on the above first item, the specification provides the following technical solutions :

[0011] A porous pole piece manufacturing method comprises the following steps:

[0012] S1, uniformly dispersing active material, conductive agent and binder into a solvent to obtain a slurry;

[0013] S2, uniformly coating the slurry on a current collector according to a certain area density;

[0014] S3, using high-pressure gas to vertically inject film-forming additives into the slurry through micropores above the coated slurry;

[0015] S4, drying the slurry in an oven to obtain a dried pole piece;

[0016] S5, rolling the dried pole piece to obtain a product porous pole piece.

[0017] As an implementation form, in step S1, the mass ratio of the active material, the conductive agent and the binder is 90-96: 1.5-5: 1.5-3.

[0018] As an implementation form, the active material is a positive electrode active material or a negative electrode active material; the positive electrode active material is selected from one or more of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, lithium iron phosphate; the negative electrode active material is selected from one or more of graphite, hard carbon, soft carbon, silicon negative electrode, lithium titanate.

[0019] As an implementation form, the conductive agent is selected from one or more of carbon black, carbon nanotubes, graphene, conductive graphite, carbon fibers.

[0020] As an implementation form, the binder is selected from one or more of styrene butadiene rubber, polyvinylidene fluoride, polyacrylic acid, polytetrafluoroethylene, polyvinyl alcohol.

[0021] As an implementation form, in step S2, the certain area density is 10-50 mg / cm 2 .

[0022] As an implementation form, in step S3, the film-forming additive is a positive electrode film-forming additive or a negative electrode film-forming additive; the positive electrode film-forming additive is selected from one or more of 1,3 propylene sulfite, methane disulfide methylene ester, maleic anhydride, vinyl sulfate, etc.; the negative electrode film-forming additive is selected from one or more of vinylene carbonate, fluorinated vinylene carbonate, vinyl vinylene carbonate, 1,3 propylene sulfite.

[0023] As an implementation form, in step S3, the high-pressure gas is helium.

[0024] As an implementation form, in step S3, the diameter of the micropores is 1-1000 μm, preferably 10-100 μm; the density of the film-forming additive injected into the slurry is 1-200 injection points per mm 2 .

[0025] As an implementation form, in step S4, the temperature of the oven is 70-105℃; the drying time is 0.5-3h.

[0026] As an implementation form, in step S5, the thickness of the rolled electrode sheet is 0.1-0.3mm.

[0027] Based on the above second item, the specification provides the following technical solutions :

[0028] A lithium ion battery comprising the positive electrode sheet and the negative electrode sheet prepared by the above method.

[0029] The lithium ion battery is stacked or wound into a roll core in the order of positive sheet, diaphragm and negative sheet, the roll core is packaged, electrolyte is injected, and then sealed to obtain the product.

[0030] As an embodiment, the electrolyte contains a film-forming additive, and the total weight of the film-forming additive in the electrolyte and the film-forming additive in the sheet accounts for 1-5% of the weight of the electrolyte.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] 1) In the sheet manufacturing method of the present application, the film-forming additive is used instead of the pore-forming agent, and the film-forming additive is vertically injected into the film-forming additive by high-pressure airflow after the current collector is coated, so that the film-forming additive can be melted into the electrolyte after injection, and the pores perpendicular to the electrode are formed on the electrode, thereby reducing the transmission distance of lithium ions and increasing the rate performance, cycle performance and charging speed of the battery.

[0033] 2) By adding the positive film-forming additive to the positive electrode and the negative film-forming additive to the negative electrode, the film-forming additive can fully react with the electrode to form an SEI film. The film-forming additive has higher use efficiency than being uniformly dispersed in the battery, and the use amount of the film-forming additive can be reduced, thereby reducing the cost. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the present disclosure is further described in detail below in combination with specific embodiments.

[0035] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of the present disclosure should be understood as the usual meaning understood by those skilled in the art to which the present disclosure belongs. The terms "first", "second" and the like used in one or more embodiments of the present disclosure do not represent any order, quantity or importance, but are only used to distinguish different components. The terms "include" or "contain" and the like mean that the elements or objects before the terms cover the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects.

[0036] In the prior art, there is no relatively perfect method for forming pores on the electrode.

[0037] Therefore, as an aspect of the present application, a porous sheet manufacturing method is provided, which comprises the following steps:

[0038] S1, uniformly dispersing the active material, conductive agent and binder in a solvent to obtain a slurry;

[0039] S2, uniformly coating the slurry on the current collector according to a certain area density;

[0040] S3, using high-pressure gas directly above the coated slurry to vertically spray the film-forming additive into the slurry through the micropores;

[0041] S4, obtaining a dried electrode sheet after drying through an oven;

[0042] S5, obtaining a product porous electrode sheet after rolling the dried electrode sheet.

[0043] As an embodiment, in step S1, the mass ratio of the active material, the conductive agent, and the binder is 90-96: 1.5-5: 1.5-3.

[0044] As an embodiment, the active material is a positive electrode active material or a negative electrode active material; the positive electrode active material is selected from one or more of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, lithium iron phosphate; the negative electrode active material is selected from one or more of graphite, hard carbon, soft carbon, silicon negative electrode, lithium titanate. It can be understood that when making a positive electrode sheet, the active material uses a positive electrode active material, and when making a negative electrode sheet, the active material uses a negative electrode active material.

[0045] As an embodiment, the conductive agent is selected from one or more of carbon black, carbon nanotubes, graphene, conductive graphite, carbon fibers.

[0046] As an embodiment, the binder is selected from one or more of styrene-butadiene rubber, polyvinylidene fluoride, polyacrylic acid, polytetrafluoroethylene, polyvinyl alcohol.

[0047] As an embodiment, in step S2, the certain area density is 10-50 mg / cm 2 .

[0048] As an embodiment, in step S3, the film-forming additive is a positive electrode film-forming additive or a negative electrode film-forming additive; the positive electrode film-forming additive is selected from one or more of 1,3 propylene sulfite, methane disulfide methylene ester, maleic anhydride, vinyl sulfate, etc.; the negative electrode film-forming additive is selected from one or more of vinylene carbonate, fluorinated vinylene carbonate, vinyl vinylene carbonate, 1,3 propylene sulfite. It can be understood that when making a positive electrode sheet, the film-forming additive uses a positive electrode film-forming additive, and when making a negative electrode sheet, the film-forming additive uses a negative electrode film-forming additive.

[0049] As an embodiment, in step S3, the high-pressure gas is helium, and it can be understood that the pressure of the gas can make the film-forming additive vertically spray into the slurry through the micropores, and the specific value can be adjusted according to actual needs.

[0050] As an embodiment, in step S3, the diameter of the micropore is 1-1000 μm, preferably 10-100 μm; the density of the film-forming additive sprayed into the slurry is 1-200 injection points per mm 2 .

[0051] As an embodiment, in step S4, the temperature of the oven is 70-105℃; the drying time is 0.5-3h.

[0052] As an embodiment, in step S5, the thickness of the rolled electrode sheet is 0.1-0.3mm.

[0053] As another aspect of the present application, the present application is a lithium ion battery comprising the positive electrode sheet and the negative electrode sheet prepared by the above method.

[0054] As an embodiment, the lithium ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the positive electrode sheet, the separator and the negative electrode sheet are stacked or wound into a roll core, the roll core is injected with the electrolyte after packaging, and then sealed to obtain the product.

[0055] As an embodiment, the electrolyte contains a film-forming additive, and the total weight of the film-forming additive in the electrolyte and the film-forming additive in the electrode sheet accounts for 1-5% of the weight of the electrolyte.

[0056] The specific embodiments are as follows:

[0057] Example 1

[0058] A porous negative electrode sheet preparation method, comprising the following steps:

[0059] 1) In a dehumidification and dust removal room with relative humidity < 30% and < 10000 cubic meters of dust, 1.5 kg of sodium carboxymethyl cellulose (CMC) solid powder is put into a stirring container containing 100 kg of deionized water, and stirred at high speed for 4h to obtain a CMC glue solution; 1 kg of conductive carbon black powder is put into the stirring tank and stirred at high speed for 2h to obtain a conductive slurry; 85 kg of graphite is put into the stirring tank and stirred at high speed for 2h; 6.25 kg of 40% solid content butadiene rubber solution is put into the stirring tank and stirred at low speed for 0.5h to obtain a negative electrode slurry;

[0060] 2) The negative electrode slurry is coated on the copper foil using a coating machine, and the surface density is 16 mg / cm 2 ;

[0061] 3) Then use high-pressure helium to vertically spray vinyl ethylene carbonate into the slurry through micropores with a diameter of 10 μm, and spray 50 points per square millimeter of slurry;

[0062] 4) Dry the electrode sheet with an oven;

[0063] 5) The electrode sheet is pressed to a density of 1.58 g / cm 3 to obtain a negative electrode sheet.

[0064] Example 2

[0065] A method for making a porous positive electrode sheet, comprising the following steps

[0066] 1) In a dehumidification and dust removal room with relative humidity < 30% and < 10000 number of micro dust per cubic meter, 1.5 kg of PVDF solid powder is put into a stirring container containing 100 kg of NMP, and stirred at high speed for 4 h and rested for 20 h until the PVDF is completely dissolved to obtain a PVDF glue solution; 3 kg of conductive carbon black powder is put into a stirring tank and stirred at high speed for 2 h to obtain a conductive slurry; 95.5 kg of lithium nickel cobalt manganese oxide is put into a stirring tank, stirred at high speed for 4 h, and then stirred at low speed for 0.5 h to obtain a positive electrode slurry;

[0067] 2) The positive electrode slurry is coated on an aluminum foil using a coating machine, and the surface density is 27 mg / cm 2 ;

[0068] 3) Then 1,3 propylene sulfone is vertically sprayed into the slurry through a 15 μm diameter micropore using high pressure helium gas, 30 points per square millimeter of slurry are sprayed;

[0069] 4) The electrode sheet is dried in an oven;

[0070] 5) The electrode sheet is pressed to a density of 3.4 g / cm 3 to obtain a positive electrode sheet.

[0071] Example 3

[0072] A lithium ion battery comprising the positive electrode sheet prepared in Example 2, the negative electrode sheet prepared in Example 1, a separator and an electrolyte; a roll core stacked or wound in the order of positive electrode sheet, separator and negative electrode sheet, the roll core is injected with electrolyte after packaging, and then sealed by conventional technical means to obtain a lithium ion battery.

[0073] It is detected that the lithium ion battery of the present embodiment forms pores perpendicular to the electrode on the electrode, which can reduce the transmission distance of lithium ions, increase the rate performance, cycle performance and charging speed of the battery. Table 1 below is the rate performance of Example 3:

[0074] Table 1

[0075] Example 3 Conventional technology 0.33C discharge 100.0％ 100.0％ 1C discharge 99.8％ 99.5％ 2C discharge 99.0％ 98.2％ 3C discharge 98.4％ 96.9％

[0076] The above described embodiments of the present description have been described. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims can be performed in a different order and still accomplish desirable results. Additionally, the processes depicted in the specification are not necessarily reliant on the precise ordering of steps as shown and described; in some embodiments, multiple tasks or steps can be performed in parallel or concurrently.

[0077] Those of ordinary skill in the art will appreciate that the above discussion regarding any of the embodiments is merely illustrative and not intended to suggest restrictive embodiments of the present disclosure (including claims) in scope. Those of ordinary skill in the art will further appreciate that the technology of the above-described embodiments, or portions thereof, can be combined with the technology of different embodiments, or portions thereof, in any manner to create further embodiments of the present disclosure. Numerous other changes, modifications, and variations of the embodiments disclosed herein can be made in the light of the above teachings. The particular aspects of the disclosure described in this specification, including the specific embodiments thereof, can not have been set forth in this specification to deliberately limit the disclosure.

[0078] In addition, for simplicity and clarity of illustration, the drawing figures depict the general manner of construction and the description and discussion herein utilize technical or scientific terms that are well within the scope of ordinary skill in the art. The drawings provided are intended to be illustrative, and the description is intended to be illustrative and to provide an enabling teaching from which others will be able to utilize the disclosure.

[0079] While the present disclosure has been described with respect to specific embodiments thereof, many alternatives, modifications and variations will be apparent to those skilled in the art.

[0080] It is therefore intended that the disclosure be considered as including all such alternatives, modifications and variations as falling within the scope of the appended claims. Accordingly, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A method of making a porous electrode sheet, characterized by, The method comprises the following steps: S1, uniformly dispersing the active material, conductive agent and binder into the solvent to obtain a slurry; S2, uniformly coating the slurry on the current collector according to a certain area density; S3, using high-pressure gas to vertically spray the film-forming additive into the slurry through the micropores directly above the coated slurry; S4, obtaining the dried electrode sheet after drying in an oven; S5, obtaining the product porous electrode sheet after rolling the dried electrode sheet; In step S1, the mass ratio of the active material, conductive agent and binder is 90-96:1.5-5:1.5-3; In step S1, the active material is a positive electrode active material or a negative electrode active material; the positive electrode active material is selected from one or more of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, lithium iron phosphate; the negative electrode active material is selected from one or more of graphite, hard carbon, soft carbon, silicon negative electrode, lithium titanate; In step S1, the conductive agent is selected from one or more of carbon black, carbon nanotube, graphene, conductive graphite, carbon fiber; In step S1, the binder is selected from one or more of styrene-butadiene rubber, polyvinylidene fluoride, polyacrylic acid, polytetrafluoroethylene, polyvinyl alcohol; In step S2, the face density is 10-50 mg / cm 2 ; In step S3, the film-forming additive is a positive electrode film-forming additive or a negative electrode film-forming additive; the positive electrode film-forming additive is selected from one or more of 1,3 propylene sulfite, methane disulfonate methylene ester, maleic anhydride, vinyl sulfate, etc.; the negative electrode film-forming additive is selected from one or more of vinylene carbonate, fluoroethylene carbonate, vinyl vinyl carbonate, 1,3 propylene sulfite; In step S3, the high-pressure gas is helium; In step S3, the diameter of the micropores is 1-1000 μm; the density of the film-forming additive sprayed into the slurry is 1-200 shot points per mm 2 ; In step S4, the temperature of the oven is 70-105℃; the drying time is 0.5-3h; In step S5, the thickness of the rolled electrode sheet is 0.1-0.3mm; The film-forming additive can be melted into the electrolyte after injection, forming pores perpendicular to the electrode on the electrode.

2. The method of claim 1, wherein: In step S3, the diameter of the micropores is 10-100μm.

3. A lithium-ion battery, characterized by: The method comprises the following steps: The lithium ion battery is stacked or wound into a roll core in the order of positive electrode sheet, separator and negative electrode sheet, the roll core is packaged, electrolyte is injected, and then sealed to obtain the product; The electrolyte contains a film-forming additive, and the total weight of the film-forming additive in the electrolyte and the film-forming additive in the electrode sheet accounts for 1-5% of the weight of the electrolyte.