A porous electrode sheet, a method of forming the same, and an application thereof

Abstract

The application discloses a porous pole piece and a forming method and application thereof. The porous pole piece comprises a first coating, a metal foil and a second coating from top to bottom. The upper surface of the porous pole piece has a row of indentations, and the indentations are round dots or circles. The cross section of the indentations is in a V shape. The first coating and the second coating have cracks at the bottom of the V shape. The metal foil is broken into holes at the bottom of the V shape. The application uses a stamping die or protrusions and recesses of an engaging mechanism to make the surface-continuous pole piece or pole roll break due to V-shaped deformation caused by shear stress, thereby forming a pore structure. The obtained porous pole piece greatly improves the rate performance of the battery cell, and can obviously improve the cycle performance of the lithium battery. In combination with a battery cell pre-lithiation process, the discharge capacity of the lithium battery and the cycle performance can be further improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a porous electrode sheet, its forming method, and its application. Background Technology

[0002] To improve the energy density and rate performance of lithium-ion batteries, porous metal foils with perforations have been used to replace traditional copper and aluminum foils. However, porous metal foils have significant drawbacks, such as extremely high manufacturing costs, susceptibility to breakage, and difficulties in coating, making their widespread application extremely challenging.

[0003] To address this, existing technologies propose first coating the electrode sheet with a continuous metal foil, and then using a perforation mechanism to punch holes in the electrode sheet. This not only expands the contact area between the electrode sheet and the electrolyte, increasing ionic conductivity and improving the charge-discharge cycle performance and capacity of the battery, but also solves the aforementioned problems caused by using porous metal foil materials. For example, CN108746321A discloses using a perforating needle to mechanically punch holes in the rolled electrode sheet, penetrating the entire electrode sheet. However, this perforation method has the drawback of damaging the electrode sheet, resulting in a loss of electrode sheet strength and cell capacity. Summary of the Invention

[0004] The purpose of this invention is to provide a novel porous electrode sheet, its forming method, and a method for preparing lithium batteries. Without significantly increasing costs, this invention disrupts the integrity of the interlayer metal foil in the electrode sheet by mechanically stamping or meshing a conventional, continuous, non-porous metal foil, thus creating pores. Simultaneously, it causes cracks to appear on the surfaces of the upper and lower coatings of the electrode sheet. This novel structure greatly improves the power performance of the lithium battery. Furthermore, based on the structural characteristics of this porous electrode sheet, pre-lithiation treatment can be performed on the assembled battery cells, which not only shortens the lithium battery manufacturing process but also further improves the energy density and cycle performance of the lithium battery, while simultaneously enabling safe mass production.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a porous electrode sheet for a lithium battery, comprising, from top to bottom, a first coating, a metal foil sheet, and a second coating; wherein:

[0007] The upper surface of the porous electrode sheet has a row of indentations, which are dots or circles;

[0008] The cross-section of the indentation is V-shaped;

[0009] Both the first and second coatings have cracks at the bottom of the "V" shape;

[0010] The metal foil breaks into a hole at the bottom of the "V" shape.

[0011] Furthermore, in the metal foil, the pore diameter is 10-3000 μm, preferably 1500-2000 μm, and the porosity of the pore is 1-15%, preferably 10-12%.

[0012] Furthermore, the first coating and the second coating are positive electrode materials or negative electrode materials.

[0013] The first coating and the second coating have the same thickness; the thickness is 40-300 μm, preferably 50-100 μm.

[0014] The thickness of the metal foil is 3-30 μm, preferably 6-13 μm.

[0015] For example, when the first coating and the second coating are positive electrode materials, the thickness of the first coating and the second coating is 100 μm, and the thickness of the metal foil is 13 μm.

[0016] When the first coating and the second coating are negative electrode materials, the thickness of the first coating and the second coating is 50 μm, and the thickness of the metal foil is 6 μm.

[0017] Secondly, the present invention further provides a method for preparing the porous electrode sheet of the lithium battery, comprising the following steps: slurry mixing, coating, roll forming and slitting, tab forming and electrode sheet pore making, to obtain the porous electrode sheet.

[0018] Furthermore, the slurry used in the mixing process can be either a positive electrode slurry or a negative electrode slurry, which can be any existing positive or negative electrode slurry used in lithium-ion batteries that is known to those skilled in the art.

[0019] For example, the positive electrode slurry is formulated as LFP:SP:PVDF in a mass ratio of LFP:SP:PVDF = 95.5:3:1.5. The negative electrode slurry is formulated as graphite:SP:SBR:CMC in a mass ratio of graphite:SP:SBR:CMC = 96:1:1.2:1.8.

[0020] The metal foil used for coating is a continuous, non-porous metal foil.

[0021] The hole-making mechanism used in the hole-making process consists of several pairs of matching protrusions and recesses; the protrusions are cones or frustums of cones; the height of the protrusions is 0.5-10 mm, preferably 0.5-5 mm.

[0022] The hole-forming mechanism is a stamping die or an engagement mechanism. Depending on the shape of the hole, the hole-forming is performed in the following two ways:

[0023] Method 1: First, weld the tabs to the electrode sheet, and then use the stamping die to stamp holes in the electrode sheet to obtain a porous electrode sheet;

[0024] Method 2: First, use the meshing mechanism to mesh and create holes in the electrode sheet, and then weld the electrode tabs onto the electrode sheet to obtain a porous electrode sheet.

[0025] The stamping die includes a main punch, which is composed of a series of sub-punches; the shape of the sub-punches is one of a cone, a dome, and a truncated cone; the effective projected size of the sub-punches is 10-3000 μm, preferably 1500 μm; the distribution of the sub-punches accounts for 1-15% of the main punch, preferably 10%; the running cycle of the sub-punches = width of the main punch / electrode tape speed.

[0026] The meshing mechanism consists of a set of upper and lower drive rollers, wherein the upper drive roller is composed of a series of protrusions and the lower drive roller is composed of a series of matching recesses. The distribution of the protrusions or recesses accounts for 1-15% of the total rollers, preferably 10%. The running rhythm of the rollers is consistent with the belt speed of the electrode sheet.

[0027] Thirdly, the present invention further provides a lithium battery comprising: an electrode, an electrolyte, and a separator; wherein the electrode is the aforementioned porous electrode.

[0028] Fourthly, the present invention further provides a method for preparing the above-mentioned lithium battery, comprising the following steps:

[0029] S1. Following the above preparation method, a porous electrode sheet is obtained;

[0030] S2. The porous electrode sheets are wound / stacked, welded, and baked to obtain a battery cell;

[0031] S3. The cell is pre-charged with lithium, then packaged, formed, aged, vented, and capacity tested to obtain the lithium battery.

[0032] In step S3, the pre-lithiation process conditions are as follows:

[0033] The electrolyte is prepared as follows: EC, DEC and EMC are mixed in a mass ratio of EC:DEC:EMC = 3:5:2, and then LiPF6 is added to prepare a 1 mol / L electrolyte.

[0034] The pre-lithiation current is 0.0001-0.1C of the design capacity of the lithium battery, preferably 0.001C.

[0035] The pre-lithiation time is 24-120 hours, preferably 48 hours.

[0036] In step S3, the encapsulation, formation, aging, venting, and capacity testing can all be carried out using existing conventional lithium-ion battery manufacturing processes.

[0037] Fifthly, the present invention further provides a lithium battery obtained by the preparation method described above.

[0038] The beneficial effects achieved by this invention are as follows:

[0039] 1. This invention uses a stamping die or meshing mechanism to cause deformation of the electrode sheet due to shear stress, thereby creating cracks in the electrode coating and breaking the interlayer metal foil to form holes, thus obtaining a porous electrode sheet. This improvement achieves the performance of a porous electrode sheet without using porous foil, avoiding the problems of high manufacturing costs, easy breakage, and coating difficulties caused by porous metal foil in existing production processes. Furthermore, by controlling the structural morphology of the protrusions and recesses, porous electrode sheets with different morphologies and pore densities can be obtained.

[0040] 2. The porous electrode preparation method provided by the present invention only requires adding a stamping die or installing a meshing mechanism to the conventional lithium-ion battery manufacturing process, which basically does not increase production and manufacturing costs and is simple and easy to implement; moreover, the coating process does not have the problems of strip breakage or material leakage, and does not require special coating equipment, thus not increasing production and manufacturing costs.

[0041] 3. Based on the structural characteristics of porous electrode sheets and combined with existing electrode pre-lithiation technology, this invention has developed a safe and mass-producible pre-lithiation charging technology for battery cells. This technology enables lithium ions to be transported through cracks and pores on porous electrode sheets, reducing lithium ion concentration polarization and achieving effective pre-lithiation at the battery cell level. This improves the energy density of lithium batteries and enhances cycle life. At the same time, it eliminates the liquid injection and wetting processes in conventional lithium batteries. Attached Figure Description

[0042] Figure 1 The present invention provides a process flow diagram for preparing porous electrode sheets and corresponding lithium batteries using stamping dies.

[0043] Figure 2 This is a schematic diagram of the stamping die used in the porous electrode preparation method provided by the present invention; wherein (a) represents a conical protrusion and (b) represents a truncated cone protrusion.

[0044] Figure 3 The diagram shows a cross-sectional view of the porous electrode provided by the present invention; in the diagram: 1-first coating; 2-metal foil; 3-second coating.

[0045] Figure 4 This is a schematic diagram of the structure of the porous electrode provided by the present invention, viewed from top view.

[0046] Figure 5The process flow diagram for preparing porous electrode sheets using stamping dies and preparing lithium batteries using pre-lithiation processes provided by the present invention is shown.

[0047] Figure 6 A schematic diagram of the pre-lithiation process provided by the present invention; in the figure: 7-external power supply; 8-electrolytic cell; 9-lithium metal foil.

[0048] Figure 7 The diagram shows the structure of a lithium battery provided by this invention; in the diagram: 4-negative electrode; 5-separator; 6-positive electrode.

[0049] Figure 8 The present invention provides a process flow diagram for preparing porous electrodes and corresponding lithium batteries using an interlocking mechanism.

[0050] Figure 9 This is a schematic diagram of the meshing mechanism used in the porous electrode preparation method provided by the present invention; wherein (a) represents a protrusion with a conical shape; and (b) represents a protrusion with a frustum-shaped cone shape.

[0051] Figure 10 A process flow diagram for preparing porous electrode sheets and preparing lithium batteries using the meshing mechanism provided by this invention.

[0052] Figure 11 This is a process flow diagram of existing conventional lithium battery manufacturing methods.

[0053] Figure 12 The cycle performance of the lithium battery provided by this invention. Detailed Implementation

[0054] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0055] Unless otherwise specified, all methods described herein are conventional methods.

[0056] Unless otherwise specified, all raw materials are available from publicly available commercial sources.

[0057] Example 1: Preparation of porous electrode sheets with punched holes and lithium batteries (without pre-lithiation)

[0058] like Figure 1 As shown, the operation steps are as follows:

[0059] S1, Electrode Production

[0060] (1) Slurry mixing: Add each raw material into the slurry mixing tank in proportion, and after thorough stirring, obtain positive electrode slurry or negative electrode slurry;

[0061] The positive electrode slurry is formulated with LFP:SP:PVDF in a mass ratio of 95.5:3:1.5; the negative electrode slurry is formulated with graphite:SP:SBR:CMC in a mass ratio of 96:1:1.2:1.8.

[0062] (2) Coating: The above slurry is coated on both sides of the continuous, non-porous metal foil to form a coating and obtain a wider rolled electrode sheet;

[0063] (3) Roller pressing and slitting: The wider roll of electrode sheets is continuously longitudinally cut to obtain several narrow electrode sheets;

[0064] (4) Electrode forming: By controlling the meshing between the upper and lower dies of the equipment, the two sides of the narrow electrode sheet are cut according to the design size requirements to form the electrode tab;

[0065] (5) Electrode preparation: Cut the long electrode with tabs according to the design requirements to form standard size electrode sheets;

[0066] (6) Electrode stamping and hole making: The electrode is punched and hole made using a stamping die to obtain a porous electrode.

[0067] like Figure 2 As shown, the protrusion in the structure of the above-mentioned stamping die is a truncated cone with a height of 0.5 mm;

[0068] The stamping process conditions are as follows: the main punch consists of a series of sub-punches, the sub-punches are conical in shape, the effective projection size of the sub-punches is 1500μm, the distribution of the sub-punches accounts for 10% of the main punch, and the running cycle of the punch is equal to the width of the main punch / the electrode tape speed.

[0069] If the coating is a positive electrode material, the thickness of the upper surface coating of the obtained porous electrode sheet is 100 μm, the thickness of the lower surface coating is 100 μm, and the thickness of the middle metal foil is 13 μm.

[0070] If the coating is a negative electrode material, the thickness of the upper surface coating of the resulting porous electrode is 50 μm, the thickness of the lower surface coating is 50 μm, and the thickness of the middle metal foil is 6 μm.

[0071] like Figure 3 , Figure 4 As shown, a row of small circular indentations are formed on the surface of the upper coating of the obtained porous electrode. The cross-section of the indentation is "V". The upper and lower coating surfaces of the electrode are continuous but have cracks. The metal foil in the middle breaks at the bottom position of the corresponding "V" shape, forming a hole with a pore diameter of 1500μm and a porosity of 10%.

[0072] S2, Battery Cell Manufacturing

[0073] (7) Stacking: Stacking the fabricated individual electrode sheets into a chip;

[0074] (8) Welding & Packaging;

[0075] (9) Bake to obtain dry battery cells;

[0076] S3, Lithium Battery Manufacturing

[0077] (10) Electrolyte injection: The electrolyte with a formula of 1 mol / L LiPF6 and EC:DEC:EMC = 3:5:2 is used and the electrolyte is injected according to the injection coefficient of 3 g / Ah.

[0078] (11) Soaking: Soak at 45℃ for 48 hours;

[0079] (12) Formation: Formation at 0.02C for 4 hours;

[0080] (13) Aging: Immerse at 45℃ for 24 hours;

[0081] (14) Degas: -85Kpa, vacuuming for 20s;

[0082] (15) Capacity testing: A lithium battery E-1 was obtained by charging and discharging at 0.33C for one week.

[0083] Example 2: Preparation of porous electrode sheets with punched holes and pre-lithiated lithium batteries

[0084] like Figure 5 As shown, the operation steps are as follows:

[0085] S1, Electrode Production

[0086] (1)-(6): The difference from steps (1)-(6) of Example 1 is that the protrusion of the stamping die is conical in shape and has a height of 0.5mm;

[0087] The stamping process conditions are as follows: the main punch consists of a series of sub-punches, the sub-punches are conical in shape, the effective projection size of the sub-punches is 1500μm, the distribution of the sub-punches accounts for 10% of the main punch, and the running cycle of the punch is equal to the width of the main punch / the electrode tape speed.

[0088] In the resulting porous electrode, the surface coating forms a row of circular indentations; the pores formed on the metal foil have a diameter of 1500 μm and a porosity of 10%.

[0089] S2, Battery Cell Manufacturing

[0090] (7) Stacking: Stacking the fabricated porous electrode sheets into a chip;

[0091] (8) Welding;

[0092] (9) Bake to obtain dry battery cells;

[0093] S3, Lithium Battery Manufacturing

[0094] (10) Pre-lithiation: such as Figure 6 As shown, the obtained dry cell was immersed in an electrolyte tank filled with electrolyte for 24 hours. Then, lithium metal foils of similar size to the battery were placed on both sides of the cell. The lithium metal foils and the outer side of the cell (i.e., the outermost negative electrode) were connected through an external circuit. The cell was charged at 0.001C for 48 hours according to the battery capacity. The cell was then removed and excess electrolyte was squeezed out.

[0095] The electrolyte formulation is 1 mol / L LiPF6, EC:DEC:EMC = 3:5:2;

[0096] (11) Encapsulation: Heat seal after squeezing out excess electrolyte;

[0097] (12) Formation: Formation at 0.02C for 4 hours;

[0098] (13) Aging: Immerse at 45℃ for 24 hours;

[0099] (14) Degas: -85Kpa, vacuuming for 20s;

[0100] (15) Capacity testing: After one cycle of charging and discharging at 0.33C, lithium battery A-1 was obtained, with the structure as follows. Figure 7 As shown.

[0101] Example 3: Preparation of porous electrode sheets with punched holes and pre-lithiated lithium batteries

[0102] The difference from Example 2 is as follows:

[0103] The protrusion of the stamping die used is conical in shape and has a height of 1mm;

[0104] The stamping process conditions are as follows: the main punch consists of a series of sub-punches, the sub-punches are conical in shape, the effective projection size of the sub-punches is 1500μm, the distribution of the sub-punches accounts for 10% of the main punch, and the running cycle of the punch is equal to the width of the main punch / the electrode tape speed.

[0105] The obtained porous electrode has a pore size of 2000 μm and a porosity of 12% in the pores formed on the metal foil.

[0106] The resulting lithium battery is A-2.

[0107] Example 4: Preparation of porous electrode sheets with punched holes and pre-lithiated lithium batteries

[0108] The difference from Example 2 is as follows:

[0109] The protrusion of the stamping die is shaped like a truncated cone with a height of 5mm;

[0110] The stamping process conditions are as follows: the main punch consists of a series of sub-punches, the sub-punches are conical in shape, the effective projection size of the sub-punches is 1500μm, the distribution of the sub-punches accounts for 10% of the main punch, and the running cycle of the punch is equal to the width of the main punch / the electrode tape speed.

[0111] The obtained porous electrode has a pore size of 2000 μm and a porosity of 12% in the pores formed on the metal foil.

[0112] The resulting lithium battery is designated B-1.

[0113] Example 5: Preparation of porous electrodes with interlocking pores and lithium batteries (without pre-lithiation)

[0114] like Figure 8 As shown, the operation steps are as follows:

[0115] (1) Mixing: Mix the raw materials in proportion in a mixing tank to obtain positive electrode slurry or negative electrode slurry;

[0116] The positive electrode slurry has a formulation of LFP:SP:PVDF = 95.5:3:1.5; the negative electrode slurry has a formulation of graphite:SP:SBR:CMC = 96:1:1.2:1.8.

[0117] (2)-(4) are the same as steps (2)-(4) in Example 1;

[0118] (5) Meshing and hole making: Meshing and hole making is performed on the slit electrode sheets by using a meshing mechanism;

[0119] The structure of the meshing mechanism is as follows Figure 9 As shown, the protrusion is conical in shape and has a height of 0.5 mm;

[0120] The process conditions for meshing and hole forming are as follows: the mechanism consists of a set of drive rollers, wherein the upper drive roller is composed of a series of protrusions and the lower drive roller is composed of a series of matching recesses. The protrusions or recesses account for 10% of the total rollers, and the running rhythm of the rollers is consistent with the speed of the electrode tape.

[0121] (6) Fabrication: Cut the long electrode sheet after hole making according to the design requirements to obtain a porous electrode sheet of standard size;

[0122] If the coating is a positive electrode material, the thickness of the upper surface coating of the obtained porous electrode sheet is 100 μm, the thickness of the lower surface coating is 100 μm, and the thickness of the middle metal foil is 13 μm.

[0123] If the coating is a negative electrode material, the thickness of the upper surface coating of the resulting porous electrode is 50 μm, the thickness of the lower surface coating is 50 μm, and the thickness of the middle metal foil is 6 μm.

[0124] The resulting porous electrode has a row of small circular indentations on the upper coating surface. The cross-section of the indentations is "V". The upper and lower coating surfaces of the electrode are continuous but have cracks. The metal foil in the middle breaks at the bottom of the corresponding "V" shape, forming a hole. The pore size is 1500μm and the porosity is 10%.

[0125] S2, Battery Cell Manufacturing

[0126] (7)-(9) are the same as steps (7)-(9) in Example 1.

[0127] S3, Lithium Battery Manufacturing

[0128] (8)-(15) are the same as steps (8)-(15) in Example 1.

[0129] Example 6: Fabrication of porous electrodes with interlocking pores and pre-lithiation lithium batteries

[0130] like Figure 10 As shown, the steps are as follows:

[0131] S1, Electrode Production

[0132] (1)-(6): Same as steps (1)-(6) of Example 5;

[0133] S2, Battery Cell Manufacturing

[0134] (7)-(9): Same as punching hole making;

[0135] S3, Lithium Battery Manufacturing

[0136] (8)-(15): Same as punching hole making;

[0137] The resulting lithium battery is C-1.

[0138] Example 7: Fabrication of porous electrodes with interlocking pores and pre-lithiation lithium batteries

[0139] The difference from Example 6 is as follows:

[0140] The protrusion of the meshing mechanism is shaped like a truncated cone with a height of 0.5 mm;

[0141] The meshing process conditions are as follows: the mechanism consists of a set of drive rollers, wherein the upper drive roller is composed of a series of protrusions and the lower drive roller is composed of a series of matching recesses. The protrusions or recesses account for 10% of the total rollers, and the running rhythm of the rollers is consistent with the speed of the electrode tape.

[0142] The resulting porous electrode has a pore size of 1500 μm and a porosity of 10% in the pores formed on the metal foil.

[0143] The resulting lithium battery is D-1.

[0144] Comparative Example 1: Conventional Preparation of Lithium-ion Batteries

[0145] like Figure 11 As shown, the difference from Example 1 is that step (6) of punching holes in the electrode sheet is omitted.

[0146] The resulting battery is F-1.

[0147] The performance of the aforementioned lithium batteries was tested.

[0148] 1. Test method for discharge capacity: Battery 0.33C discharge capacity / mass of positive electrode active material.

[0149] 2. Test method for 1C cycle performance (@500cls): Charge to 3.65V with 1C and cut off with 0.05C; discharge to 2V with 1C, record the discharge capacity per cycle, and calculate the capacity retention rate.

[0150] 3. Test method for high-rate charging: Fully charge to 3.65V using constant current and constant voltage at different rates, then disassemble the interface and observe whether there is obvious lithium plating.

[0151] The results are shown in Table 1 and Figure 12 .

[0152] Table 1 Performance Comparison of Lithium Batteries

[0153] Example 2 Example 3 Example 4 Example 6 Example 7 Example 1 Comparative Example 1 distinguish A-1 A-2 B-1 C-1 D-1 E-1 F-1 Process type Stamping, pre-lithiation Stamping, pre-lithiation Stamping, pre-lithiation meshing, pre-lithiation meshing, pre-lithiation stamping Discharge capacity 151.2 151.2 151.1 151.3 151.0 146.7 146.5 1C Cyclic Performance 102％ 101％ 100％ 101％ 103％ 97％ 93％ High-rate charging 3C 3C 3C 3C 3C 3C 2C

[0154] As shown in the table above, compared to Comparative Example 1, Examples 1-7, through the pore-forming technology, significantly improved the cycle performance of the full cell. Furthermore, compared to Example 1, Examples 2-5 and 6-7, through the pore-forming technology combined with pre-lithiation, significantly improved both the discharge capacity and cycle performance of the full cell. In addition, the presence of electrode pores greatly improved the rate performance of the cell. Simultaneously, due to… Figure 12 It can be seen that the capacity retention rate is still greater than 100% after 500 cycles of 1C.

[0155] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A porous electrode sheet for a lithium battery, comprising, from top to bottom, a first coating, a metal foil, and a second coating; wherein: The upper surface of the porous electrode sheet has a row of indentations, which are dots or circles; The cross-section of the indentation is V-shaped; The lower surfaces of the first coating and the second coating have cracks at the bottom of the "V" shape; The metal foil breaks into a hole at the bottom of the "V" shape.

2. The porous electrode sheet of the lithium battery according to claim 1, characterized in that, In the metal foil, the pore diameter is 10-3000μm, and the porosity of the pore is 1-15%.

3. The porous electrode sheet of the lithium battery according to claim 1 or 2, characterized in that, The first coating and the second coating have the same thickness, which is 40-300 μm; The thickness of the metal foil is 3-30 μm.

4. A method for preparing a porous electrode sheet for a lithium battery according to any one of claims 1-3, comprising the following steps: slurry mixing, coating, roll forming and slitting, tab forming and pore making, to obtain the porous electrode sheet; The metal foil used for coating is a continuous, non-porous metal foil. The hole-making mechanism used in the hole-making process consists of several pairs of protrusions and recesses with matching upper and lower structures. The hole-making mechanism is a stamping die or a meshing mechanism; Depending on the shape of the hole, the hole is created in the following two ways: Method 1: First, weld the tabs to the electrode sheet, and then use the stamping die to stamp holes in the electrode sheet to obtain a porous electrode sheet; Method 2: First, use the meshing mechanism to mesh and create holes in the electrode sheet, and then weld the electrode tabs onto the electrode sheet to obtain a porous electrode sheet.

5. The method for preparing porous electrode sheets for lithium batteries according to claim 4, characterized in that, The slurry used in the mixing process is either a positive electrode slurry or a negative electrode slurry; The protrusion is conical or truncated cone in shape; the height of the protrusion is 0.5-10 mm.

6. The method for preparing porous electrode sheets for lithium batteries according to claim 4 or 5, characterized in that, The stamping die includes a main punch; the main punch is composed of a series of sub-punches; the shape of the sub-punches is one of a cone, a dome, and a truncated cone; the effective projected size of the sub-punches is 10-3000μm; the distribution of the sub-punches accounts for 1-15% of the main punch; the running cycle of the sub-punches = width of the main punch / electrode conveyor speed; The meshing mechanism consists of a set of upper and lower drive rollers; the upper drive roller is composed of a series of protrusions, and the lower drive roller is composed of a series of matching recesses; the distribution of the protrusions or the recesses accounts for 1-15% of the total rollers; the running rhythm of the rollers is consistent with the belt speed of the electrode sheet.

7. A lithium battery comprising: an electrode, an electrolyte, and a separator; wherein the electrode is a porous electrode as described in any one of claims 1-3.

8. A method for preparing a lithium battery, comprising the following steps: S1. A porous electrode sheet is obtained according to any one of claims 4-6; S2. The porous electrode sheets are wound / stacked, welded, and baked to obtain a battery cell; S3. The cell is pre-charged with lithium, then packaged, formed, aged, vented, and capacity tested to obtain the lithium battery.

9. The lithium battery obtained by the preparation method of claim 8.

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