An electrode sheet and its preparation method, a lithium-ion battery, and an electrical device thereof.

Abstract

The application discloses an electrode sheet and a preparation method thereof, a lithium ion battery and an electric device, and relates to the technical field of lithium ion batteries. The electrode sheet comprises: a current collector; a first active material coating layer coated on at least one surface of the current collector; and a second active material coating layer coated on the surface of the first active material layer; wherein the positive projection area of the first active material coating layer is S1, the positive projection area of the second active material coating layer is S2, S1 and S2 satisfy the relationship: |S1-S2|>0; the width of the first active material coating layer is A1, and the width of the second active material coating layer is A2; wherein A1 and A2 satisfy the relationship: |A1-A2|>0 mm. The electrode sheet provided by the application comprises two active material coating layers with different widths and positive projection areas; the width difference part is monitored by using X-ray or β-ray radiation, and the difference value is calculated by comparing with the normal coating area, so that the surface density values of the two active material coating layers can be monitored in real time.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, specifically to an electrode sheet and its preparation method, a lithium-ion battery, and an electrical device. Background Technology

[0002] Lithium-ion batteries have been widely used in various fields, including electronic devices and automobiles, due to their lightweight, high energy density, high voltage platform, low self-discharge rate, long cycle life, low environmental pollution, absence of memory effect, and good safety. Especially in 3C electronic products, battery capacity and charge / discharge performance are critical parameters that directly determine battery lifespan and charging efficiency.

[0003] To balance high energy density and super-fast charging, dual-layer coating technology has emerged. However, the graphite content in the upper and lower slurry formulations of dual-layer coating is often difficult to monitor effectively during manufacturing, resulting in significant differences in the content of the upper and lower slurry compared to the design amount. These differences can directly affect the surface tension of the upper and lower slurries, the appearance and uniformity of the coating, the loss of battery capacity, and the deterioration of charge and discharge performance, among other serious problems.

[0004] Given the limitations of existing technologies, there is an urgent need to develop an electrode sheet and its preparation method that can effectively achieve real-time monitoring of the density of upper and lower layers. Summary of the Invention

[0005] The purpose of this invention is to provide an electrode sheet that can monitor the areal density of a double coating layer in real time, addressing the shortcomings of existing technologies.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An electrode sheet, comprising:

[0008] current collector;

[0009] A first active material coating is applied to at least one surface of the current collector;

[0010] A second active material coating is applied to the surface of the first active material layer;

[0011] Wherein, the projected area of ​​the first active material coating is S1, and the projected area of ​​the second active material coating is S2, wherein S1 and S2 satisfy the relationship: |S1-S2|>0;

[0012] Preferably, |S1-S2|>10.

[0013] The width of the first active material coating is A1, and the width of the second active material coating is A2; where A1 and A2 satisfy the relationship: |A1-A2|>0mm. If A1=A2, the width difference between the upper and lower coating layers cannot be achieved, and when the upper and lower coatings overlap, X-rays or β-rays cannot detect the surface density of the upper or lower layer individually. When X-rays or β-rays penetrate the battery electrode, some rays are absorbed by the electrode. This results in a certain attenuation of the ray intensity after penetrating the electrode relative to the incident ray intensity. The attenuation ratio has a negative exponential relationship with the surface density of the penetrated electrode. By detecting the ray intensity before and after the ray penetrates the electrode in an ionization chamber filled with a special gas, the surface density of the electrode can be calculated. By setting the coating width of the first active material coating and the second active material coating to be different from the forward projected area, the area with the width difference and the forward projected area difference is monitored by X-rays or β-rays and compared with the normal coating area. The difference is calculated to obtain the real-time monitoring surface density values ​​of the first and second active material coatings.

[0014] Preferably, the second active material coating is applied to the middle position of the first active material coating, and a first exposed area and a second exposed area are formed on both sides of the first active material coating, respectively. The area of ​​the first exposed area is B1, and the area of ​​the second exposed area is B2; wherein, B1 = B2; (S1-S2) / 2 = B1.

[0015] Preferably, the porosity of the first active material coating is 10%-20%; the porosity of the second active material coating is 30%-40%. If the porosity is designed to be too high: 1. Reduced battery capacity: When the electrode porosity is too high, the effective active material inside the battery may decrease, leading to a reduction in battery capacity. This is because excessive porosity may mean a reduction in the effective usable area of ​​the electrode material, thus affecting the battery's energy storage capacity. 2. Shortened battery cycle life: Excessive porosity may also lead to a decrease in battery performance during charge-discharge cycles. During cycling, the electrodes expand and contract with the reaction. If the porosity is too high, the deformation of the electrodes may become irreversible, leading to electrode loosening and further affecting battery life. 3. Reduced battery safety: Excessive porosity may also affect battery safety. During battery use, changes in electrode porosity affect the degree of electrode deformation. If the bonding is too loose, it may damage the battery structure, leading to safety hazards such as short circuits and internal short circuits.

[0016] If the porosity is designed too low: 1. Reduced electrolyte wettability and ion transport efficiency: Insufficient porosity limits the electrolyte's wettability range and reduces ion transport efficiency, thus affecting the battery's electrochemical performance. 2. Impact on battery charge / discharge rate and cycle life: Too low porosity may prevent the electrolyte from penetrating the electrode interior, affecting the battery's charge / discharge rate and cycle life. 3. Reduced battery conductivity and diffusion performance: Appropriate porosity promotes electrolyte diffusion within the electrode, improving discharge performance and cycle stability. However, excessively low porosity will reduce these properties.

[0017] Preferably, the compaction density of the first active material coating is 1.80-1.83 g / cm³. 3 The compaction density of the second active material coating is 1.75-1.78 g / cm³. 3 If the electrode compaction density is designed too low: 1. Electrode capacity decreases: Low compaction density increases the voids between electrodes, reducing the electrochemical reaction area and thus decreasing battery capacity. This is because increased voids reduce the effective utilization area of ​​the electrode material, thereby reducing the active sites for electrochemical reactions. 2. Battery lifespan is shortened: Due to low compaction density, the diffusion rate of lithium ions in the battery decreases, leading to a shorter battery life. This is because lithium ions require more time and energy to overcome the resistance of the voids during transport. If the electrode compaction density is designed too high: 1. Battery internal resistance increases: High compaction density reduces the porosity inside the electrode, hindering the movement of electrolyte and ions and increasing the battery's internal resistance. This may lead to increased energy loss during charging and discharging. 2. Discharge performance deteriorates: High compaction density results in insufficient aeration of the electrode, making it difficult for the solution inside the battery to flow and diffuse quickly, thus affecting the battery's discharge performance. Specifically, the diffusion rate of lithium ions in the electrode may slow down, leading to a decrease in discharge capacity.

[0018] Preferably, the areal density of the first active material coating is 44-76 mg / 1540.25 mm. 2 The areal density of the second active material coating is 17-48 mg / 1540.25 mm. 2 This areal density design is suitable for 5C high-power charging products manufactured using a double-layer coating process. If the areal density is too high, the AC internal resistance of the fast-charging lithium-ion battery will increase significantly, thus affecting the battery's capacity retention. If the areal density is too low, the effective utilization area of ​​the electrode material will decrease, thereby reducing the battery's energy density and capacity. Furthermore, this invention also provides a method for preparing an electrode sheet, including the following steps:

[0019] Step S1: Assemble the first gasket and the second gasket at the outlet position of the cavity in the coating device; wherein, the width C1 of the first gasket and the width C2 of the second gasket satisfy the relationship: |C1-C2|>0mm; if C1=C2, the upper and lower coatings overlap, and X-ray or β-ray cannot detect the areal density of the upper or lower layer individually.

[0020] Step S2: Put the first active material coating slurry and the second active material coating slurry into the buffer tank respectively, assemble the buffer tank with the double-layer mold head and perform circulation and degassing;

[0021] Step S3: Apply the first active material coating slurry and the second active material coating slurry to the current collector through a double-layer die, monitor the areal density of the first and second active material coatings in real time, and dry them to obtain the electrode sheet.

[0022] Preferably, in step S3, the method for real-time monitoring of the areal density of the first active material coating and the second active material coating is as follows: an X-ray source or a β-ray source is placed on one side of the prepared electrode sheet, and the intensity of the rays passing through the electrode sheet is measured using a detector. The intensity of the rays after entering and leaving the electrode sheet is obtained, and the attenuation of the X-ray or β-ray passing through the electrode sheet is calculated, thereby obtaining the real-time areal density of the first active material coating and the second active material coating.

[0023] Preferably, in step S3, the formula for calculating the areal density of the first active material coating and the second active material coating is I = I0exp(-λm), where m = 1 / λlog(I0 / I). Where I0 is the weight per unit area of ​​the membrane; I is the intensity of the radiation penetrating the membrane; m is the intensity of the radiation without membrane obstruction; and λ is the absorption coefficient per unit area of ​​the membrane.

[0024] Preferably, when the areal density data measured in step S3 does not match the design value, the flow rate of the slurry in the cavity is controlled by adjusting the micrometer scale so that the areal density of the first active material coating and the second active material coating meets the design value.

[0025] In addition, the present invention also provides a lithium-ion battery comprising the electrode sheet described above.

[0026] In addition, the present invention also provides an electrical device including the lithium-ion battery described above.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] (1) The electrode sheet provided by the present invention sets the coating width of the first active material coating and the second active material coating to be different from the forward projection area. The area with the difference in width and the difference in forward projection area is monitored by X-ray or β-ray and compared with the normal coating area. The difference is calculated to obtain the surface density value of the first active material coating and the second active material coating in real time.

[0029] (2) Compared with traditional coating, which only performs electrode sampling tests before, during and after manufacturing or monitors the overall slurry flow rate of the upper and lower layers during the process, the sampling test cannot achieve full process monitoring with a high risk of leakage, and the flow monitoring cannot be converted into real-time areal density data and monitoring of the distribution state of the first active material coating and the second active material coating slurry, the electrode manufacturing method of this application can utilize the size difference between the first and second pads to design and realize the width difference between the first and second active material coatings. The width difference area is used to reflect the real-time areal density of the first and second active material coatings through X-ray or β-ray monitoring instruments and then corrected. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of an electrode sheet according to an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of the structure of the first gasket according to an embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of the structure of the second gasket according to an embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram of the coating of a first active material coating slurry and a second active material coating slurry during the preparation of an electrode sheet according to an embodiment of the present invention.

[0034] Wherein, 1-current collector; 2-first active material coating; 3-second active material coating; C1-width of the first gasket; C2-width of the second gasket; 1'-first active material coating slurry; 2'-second active material coating slurry. Detailed Implementation

[0035] To make the technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0037] According to a first aspect of this application, this application provides an electrode sheet, comprising:

[0038] current collector 1;

[0039] The first active material coating 2 is coated on at least one surface of the current collector;

[0040] The second active material coating 3 is applied to the surface of the first active material layer;

[0041] The projected area of ​​the first active material coating 2 is S1, and the projected area of ​​the second active material coating 3 is S2, wherein S1 and S2 satisfy the relationship: |S1-S2|>0.

[0042] The width of the first active material coating 2 is A1, and the width of the second active material coating 3 is A2; where A1 and A2 satisfy the relationship: |A1-A2|>0mm.

[0043] In some embodiments, the second active material coating 3 is coated at the middle position of the first active material coating 2, and a first exposed area and a second exposed area are formed on both sides of the first active material coating 2, respectively. The area of ​​the first exposed area is B1, and the area of ​​the second exposed area is B2; wherein, B1 = B2; (S1-S2) / 2 = B1.

[0044] In some embodiments, the porosity of the first active material coating 2 is 10%-20%, for example, it can be 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%; the porosity of the second active material coating 3 is 30%-40%, for example, it can be 30%, 32%, 34%, 36%, 38%, or 40%.

[0045] In some embodiments, the compaction density of the first active material coating 2 is 1.80-1.83 g / cm³. 3 For example, it could be 1.80 g / cm³. 3 1.81 g / cm 3 1.82g / cm 3 The compaction density of the second active material coating 3 is 1.75-1.78 g / cm³. 3 For example, it could be 1.75 g / cm³ 3 1.76 g / cm 3 1.78g / cm 3 .

[0046] In some embodiments, the areal density of the first active material coating 2 is 44-76 mg / 1540.25 mm. 2 The areal density of the second active material coating 3 is 17-48 mg / 1540.25 mm. 2 .

[0047] In some embodiments, the electrode sheet may be a positive electrode sheet and / or a negative electrode sheet.

[0048] According to a second aspect of this application, this application provides a method for preparing an electrode sheet, comprising the following steps:

[0049] Step S1: Assemble the first gasket and the second gasket at the outlet position of the cavity in the coating device; wherein, the width C1 of the first gasket and the width C2 of the second gasket satisfy the relationship: |C1-C2|>0mm;

[0050] Step S2: Put the first active material coating slurry 1' and the second active material coating slurry 2' into the buffer tank respectively, assemble the buffer tank with the double-layer mold head and perform circulation and degassing;

[0051] Step S3: Apply the first active material coating slurry 1' and the second active material coating slurry 2' to the current collector through a double-layer die, monitor the areal density of the first and second active material coatings in real time, and dry them to obtain the electrode sheet.

[0052] In some embodiments, the method for real-time monitoring of the areal density of the first active material coating and the second active material coating in step S3 is as follows: an X-ray source or a β-ray source is placed on one side of the prepared electrode sheet, and the intensity of the rays passing through the electrode sheet is measured using a detector. The intensity of the rays after entering and leaving the electrode sheet is obtained by measuring the intensity of the rays, and the attenuation of the X-ray or β-ray passing through the electrode sheet is calculated, thereby obtaining the real-time areal density of the first active material coating and the second active material coating.

[0053] In some embodiments, when the areal density data measured in step S3 does not match the design value, the flow rate of the slurry in the cavity is controlled by adjusting the micrometer scale so that the areal density of the first active material coating and the second active material coating meets the design value.

[0054] According to a third aspect of this application, this application provides a lithium-ion battery, including a cell wound with a negative electrode, a positive electrode and a separator, an electrolyte, and a casing for encapsulating the cell and the electrolyte, wherein the positive electrode and / or the negative electrode are the aforementioned electrode sheets.

[0055] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. The positive active material layer includes a positive active material, which may be, but is not limited to, a chemical formula such as Li. a Ni x Co y M z O 2-b N b (Where 0.95≤a≤1.2, x>0, y≥0, z≥0, and x+y+z=1, 0≤b≤1, M is selected from one or more combinations of Mn and Al, and N is selected from one or more combinations of F, P, and S) The positive electrode active material may also be, but is not limited to, LiCoO2, LiNiO2, LiVO2, LiCrO2, LiMn2O4, LiCoMnO4, Li2NiMn3O8, LiNi 0.5 Mn 1.5 The positive electrode active material can be one or more combinations thereof, including O4, LiCoPO4, LiMnPO4, LiFePO4, LiNiPO4, LiCoFSO4, CuS2, FeS2, MoS2, NiS, and TiS2. The positive electrode active material can also be modified. Methods for modifying the positive electrode active material are known to those skilled in the art. For example, coating, doping, and other methods can be used to modify the positive electrode active material. The materials used for modification can be one or more combinations thereof, including but not limited to Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, and W. The positive electrode current collector is typically a structure or component that collects current. The positive electrode current collector can be any material suitable for use as a positive electrode current collector in lithium-ion batteries. For example, the positive electrode current collector can be, but is not limited to, metal foil, and more specifically, aluminum foil.

[0056] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, which can be one or more of the following, including but not limited to graphite, soft carbon, hard carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate, or other metals that can form alloys with lithium. Specifically, the graphite can be selected from one or more of artificial graphite, natural graphite, and modified graphite; the silicon-based material can be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys; and the tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. The negative electrode current collector is typically a structure or component that collects current. The negative electrode current collector can be any material suitable for use as a negative electrode current collector in lithium-ion batteries, for example, it can be, but is not limited to, metal foil, and more specifically, copper foil.

[0057] The lithium-ion battery also includes an electrolyte, which comprises an organic solvent, an electrolyte lithium salt, and additives. The electrolyte lithium salt can be LiPF6 and / or LiBOB used in high-temperature electrolytes; it can also be at least one of LiBF4, LiBOB, and LiPF6 used in low-temperature electrolytes; it can also be at least one of LiBF4, LiBOB, LiPF6, and LiTFSI used in overcharge-resistant electrolytes; or it can be at least one of LiClO4, LiAsF6, LiCF3SO3, and LiN(CF3SO2)2. The organic solvent can be a cyclic carbonate, including PC and EC; it can also be a chain carbonate, including DFC, DMC, or EMC; or it can be a carboxylic acid ester, including MF, MA, EA, MP, etc. The additives include, but are not limited to, at least one of film-forming additives, conductive additives, flame-retardant additives, overcharge-resistant additives, additives for controlling the H2O and HF content in the electrolyte, additives for improving low-temperature performance, and multifunctional additives.

[0058] According to a fourth aspect of this application, this application provides an electrical device including the aforementioned lithium-ion battery.

[0059] The present invention will be further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0060] Example 1

[0061] Preparation of negative electrode

[0062] Step S1: Assemble the first gasket and the second gasket at the outlet position of the cavity in the coating device; wherein, the width C1 of the first gasket and the width C2 of the second gasket satisfy the relationship: |C1-C2|>0mm;

[0063] Step S2: Put the first active material coating slurry and the second active material coating slurry into the buffer tank respectively, assemble the buffer tank with the double-layer mold head and perform circulation and degassing;

[0064] Step S3: Apply the first and second active material coating slurries to the current collector using a double-layer die. The width of the first active material coating is A1, and the width of the second active material coating is A2. A first exposed area and a second exposed area are formed on both sides of the first active material coating, with the area of ​​the first exposed area being B1 and the area of ​​the second exposed area being B2. Place an X-ray or β-ray source on one side of the fabricated electrode sheet. After measuring the intensity of the radiation passing through the electrode sheet using a detector, the intensity of the radiation entering and leaving the electrode sheet is obtained. The attenuation of the X-ray or β-ray passing through the electrode sheet is calculated, thereby obtaining the real-time areal density of the first and second active material coatings. When the areal density data measured in step S3 does not match the design value, the flow rate of the slurry in the cavity is controlled by adjusting the micrometer scale to make the areal density of the first and second active material coatings meet the design value. After drying, the electrode sheet is obtained.

[0065] In this design, both the first and second active materials are graphite; |A1-A2|>0 represents the width difference between the upper and lower coatings; |C1-C2|>0 represents the width difference between the upper and lower spacers; the porosity of the first active material coating is 10%-20%, and the porosity of the second active material coating is 30%-40%; the compaction density of the first active material coating is 1.80 g / cm³. 3 The compaction density of the second active material coating is 1.75 g / cm³. 3 The areal density of the first active material coating is 76 mg / 1540.25 mm². 2 The areal density of the second active material coating is 48 mg / 1540.25 mm². 2 . .

[0066] Preparation of positive electrode

[0067] The positive electrode material lithium cobalt oxide, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 97.6:1.4:1.0. The mixture was then coated onto an Al foil, dried, rolled, and slit to obtain the positive electrode sheet.

[0068] Preparation of diaphragm

[0069] Polyethylene (PE) porous polymer film is used as the separator.

[0070] Preparation of electrolyte

[0071] A solution prepared by mixing lithium salt LiPF6 with a non-aqueous organic solvent (ethylene carbonate (EC): fluoroethylene carbonate (FEC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): ethylene carbonate (VC)) at a mass ratio of 25:8:20:15:28:4, with a mass ratio of 8:92) was used as the electrolyte for lithium batteries. The mass ratio a / b of ethylene carbonate to fluoroethylene carbonate in the electrolyte was 3.1.

[0072] Battery manufacturing

[0073] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for safety isolation. The electrodes are then wound to form the electrode assembly. The electrode assembly is placed in a packaging shell, electrolyte is injected, and the assembly is sealed to obtain a lithium battery.

[0074] Comparative Example 1

[0075] Unlike Example 1, the coating method used in this comparative example is conventional double-layer coating, that is, there is no width difference between the width of the first active material coating and the width of the second active material coating.

[0076] The rest is the same as in Example 1, and will not be repeated here.

[0077] The specific parameters of Examples 1-8 and Comparative Examples 1-8 are shown in Table 1 below. Except for Comparative Example 1, the steps of the other examples and comparative examples are the same as those of Example 1, and will not be repeated here.

[0078] Table 1

[0079]

[0080]

[0081]

[0082] The lithium-ion batteries prepared in the examples and comparative examples were subjected to the following performance tests:

[0083] The standard charging methods are: 5C CC to 4.15V; CV to 4.6C, 4.6C CC to 4.2V; CV to 3.5C, 3.5C CC to 4.3V; CV to 3C, 3C CC to 4.4V; CV to 2C, 2C CC to 4.5V; CV to 0.05C.

[0084] 1. Lithium plating test: Perform step charging at 5.2C, 5.4C, 5.6C and 5.8C respectively. After each step, let it rest for 5 minutes. Cycle 20 times according to the following steps 1 to 5: 1) 5.2C CC to 4.15V; CV to 4.6C; 2) 4.6C CC to 4.2V; CV to 3.5C; 3) 5C CC to 4.3V; CV to 3C; 4) 3C CC to 4.4V; CV to 2C; 5) 2C CC to 4.5V; CV to 0.05C.

[0085] The steps for 5.4C, 5.6C, and 5.8C are the same as those for 5.2C, with the only difference being the initial charging rate in step 1).

[0086] 2. Hot box test: 1) Charge using standard charging method and let stand for 10 minutes; 2) Place in a temperature control box and heat the box at (5±2)℃ / min. When the temperature reaches 132℃, 134℃, 136℃ and 138℃, keep it constant for 60 minutes.

[0087] 3. Room temperature cycling test: The test temperature is 23±2℃. Half-cell voltage, internal resistance, and 2000ppg thickness are measured. Cell photos are recorded before and after cycling. Test stop condition: 0.2C capacity retention ≤60%.

[0088] 1) Let stand for 10 minutes at 23℃; 2) Charge according to standard charging method, let stand for 5 minutes, test initial full-charge voltage, internal resistance, and 2000ppg thickness, put back in the cabinet and let stand for 2 hours, then discharge at 1C full charge and let stand for 5 minutes; 3) Charge according to standard charging method, let stand for 5 minutes, discharge at 0.2C and let stand for 5 minutes; 4) Charge according to standard charging method, let stand for 5 minutes, test DCR (0.1C discharge for 10 seconds, 1C discharge for 1 second), and let stand for 5 minutes; 5) Discharge at 1C to... 3V, rest for 5 minutes; 6) Charge according to standard charging method, rest for 5 minutes; 7) Cycle 100 times for steps 5-6; 8) Pause, test full charge voltage, internal resistance, and 2000ppg thickness; 9) Discharge to 3V at 0.2C, rest for 5 minutes; 10) Charge according to standard charging method, rest for 5 minutes, test DCR (0.1C discharge for 10 seconds, 1C discharge for 1 second); 11) Cycle 12 times for steps 5-10; 12) End, test full charge voltage, internal resistance, and 2000ppg thickness.

[0089] 4. High-Temperature Cycling Test: Test temperature: 45±2℃. Test half-cell voltage, internal resistance, and 2000ppg thickness. Record cell photos before and after cycling. Test stop condition: 0.2C capacity retention ≤60%.

[0090] 1) Let stand for 10 minutes at 45℃; 2) Charge according to standard charging method, let stand for 5 minutes, test initial full-charge voltage, internal resistance, and 2000ppg thickness, put back in the cabinet and let stand for 2 hours, then discharge at 1C and let stand for 5 minutes; 3) Charge according to standard charging method, let stand for 5 minutes, discharge at 0.2C and let stand for 5 minutes; 4) Charge according to standard charging method, let stand for 5 minutes, test DCR (0.1C discharge for 10 seconds, 1C discharge for 1 second), and let stand for 5 minutes; 5) Discharge at 1C to 3V and let stand. 5 min; 6) Charge according to standard charging method, rest for 5 min; 7) Cycle 100 times for steps 5-6; 8) Pause, test full charge voltage, internal resistance, and 2000ppg thickness, put back in the cabinet and rest for 2 hours; 9) Discharge to 3V at 0.2C, rest for 5 min; 10) Charge according to standard charging method, rest for 5 min, test DCR (0.1C discharge for 10s, 1C discharge for 1s); 11) Cycle 12 times for steps 5-10; 12) End, test full charge voltage, internal resistance, and 2000ppg thickness.

[0091] The test results are shown in Table 2.

[0092] Table 2

[0093]

[0094]

[0095] As can be seen from Examples 1-8 and Comparative Examples 1-8 in Table 2, compared with traditional coating, the electrode sheet provided by the present invention, by setting the coating width and forward projection area of ​​the first active material coating and the second active material coating to be different, forms a region with a difference in width and a difference in forward projection area. This region is monitored by X-ray or β-ray and compared with the normal coating area. The difference is calculated to obtain the real-time monitoring of the areal density values ​​of the first active material coating and the second active material coating.

[0096] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method of producing an electrode sheet, characterized by, The method comprises the following steps: Step S1, assembling the first gasket and the second gasket at the outlet position of the cavity of the coating device respectively; wherein the width C1 of the first gasket and the width C2 of the second gasket satisfy the relationship: |C1-C2|≥5mm; Step S2, respectively feeding the first active material coating slurry and the second active material coating slurry into the buffer tank, assembling the buffer tank with the double-layer die, and performing circulating degassing; Step S3, coating the first active material coating slurry and the second active material coating slurry on the current collector through the double-layer die, monitoring the area density of the first active material coating and the second active material coating in real time, and drying to obtain the electrode sheet; The first active material coating is coated on at least one surface of the current collector; The second active material coating is coated on the surface of the first active material coating; In step S3 of the preparation method of the electrode sheet, the method for monitoring the area density of the first active material coating and the second active material coating in real time is as follows: placing an X-ray or β-ray source on one side of the prepared electrode sheet, using a detector to measure the intensity of the rays passing through the electrode sheet, obtaining the intensity of the measured rays entering and leaving the electrode sheet, calculating the attenuation amount of the X-ray or β-ray passing through the electrode sheet, setting the coating width of the first active material coating and the second active material coating to be different from the forward projection area, forming a partial area with a width difference and a forward projection area difference, and comparing the X-ray or β-ray monitoring of the partial area with the normal coating area to calculate the difference and obtain the area density value of the first active material coating and the second active material coating monitored in real time; Wherein, the forward projection area of the first active material coating is S1, and the forward projection area of the second active material coating is S2, wherein S1 and S2 satisfy the relationship: |S1-S2|>0; The width of the first active material coating is A1, and the width of the second active material coating is A2; wherein A1 and A2 satisfy the relationship: |A1-A2|≥8mm.

2. The method of producing an electrode sheet according to claim 1, characterized by, When the measured area density data in step S3 does not match the design value, adjust the micrometer scale to control the slurry flow in the cavity, so that the area density of the first active material coating and the second active material coating meets the design value.

3. An electrode sheet prepared by the preparation method of the electrode sheet according to any one of claims 1-2.

4. The electrode pad of claim 3, wherein The second active material coating is coated at the middle position of the first active material coating, and the two sides of the first active material coating form a first exposed area and a second exposed area respectively, the area of the first exposed area is B1, and the area of the second exposed area is B2; wherein B1=B2; (S1-S2) / 2=B1.

5. The electrode pad of claim 3, wherein The porosity of the first active material coating is 10%-20%, and the porosity of the second active material coating is 30%-40%.

6. The electrode pad of claim 3, wherein The first active material coating has a compacted density of 1.80 to 1.83 g / cm 3 The second active material coating has a compacted density of 1.75 to 1.78 g / cm 3 .

7. The electrode pad of claim 3, wherein The areal density of the first active material coating is 44-76 mg / 1540.25 mm 2 The areal density of the second active material coating is 17-48 mg / 1540.25 mm 2 .

8. A lithium-ion battery, characterized by The electrode sheet according to any one of claims 3-7.

9. An electrical device, characterized by The lithium ion battery according to claim 8.

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