Tab ceramic coating material, tab ceramic coating, pole piece and preparation method of pole piece

Abstract

The invention relates to the technical field of batteries, in particular to a tab ceramic coating material, a tab ceramic coating, a pole piece and a preparation method of the pole piece. The invention relates to a ceramic coating material for a tab, which comprises the following components in percentage by mass: 0.1 to 10 percent of LiTaO3, 10 to 30 percent of BaTiO3 and 60 to 89.9 percent of Li < 0.33 > La < 0.56 > TiO3, and the Li < 0.33 > La < 0.56 > TiO3 is of a nanowire structure. The tab ceramic coating material is compounded with boehmite and / or aluminum oxide and then is coated on a single surface or double surfaces of a tab body to form a tab ceramic coating. According to the invention, LiTaO3, BaTiO3 and Li < 0.33 > La < 0.56 > TiO3 are mixed according to a specific ratio and are compounded with boehmite and / or aluminum oxide for use, so that the total conductivity and lithium ion conductivity of the material are improved, the mechanical strength is also improved, and the continuity and safety of an internal circuit in battery transportation or use can be ensured.

Description

Technical Field

[0001] The invention relates to the technical field of batteries, and in particular to a tab ceramic coating material, a tab ceramic coating, a pole piece and a preparation method thereof. Background Art

[0002] Lithium batteries have the characteristics of high output power and high energy density, and are widely used in many fields such as electric vehicles and energy storage facilities. Tabs, as the connecting part between the positive and negative electrode materials and the current collector, are one of the key components of lithium batteries, playing an important role in conductivity, battery safety and stability, manufacturing process and application fields. The surface of the tab is usually provided with a ceramic coating. The ceramic coating has the following main functions: (1) Improving battery safety. The ceramic coating covers the surface of the root of the positive tab and can effectively prevent short circuits between the positive and negative electrodes. This short circuit protection is particularly important in high energy density batteries. In addition, the ceramic coating has good heat resistance and fire resistance, which can improve the overall heat resistance and fire resistance of the battery and reduce safety issues such as expansion, leakage, and explosion caused by overheating during charging, discharging, and use of the battery. (2) Improving battery performance. The ceramic coating can effectively isolate the positive active material and inhibit the reaction between the positive electrode and the electrolyte and diaphragm during charging and discharging, thereby helping to improve the battery's cycle performance. The ceramic coating also has a positive effect on the battery's charge retention performance. (3) Optimizing the battery structure. By controlling the thickness of the ceramic coating, the elongation of the pole piece during the rolling process can be effectively adjusted, and the arc rate of the pole piece after flattening can be reduced, which helps to solve the cracking problem at the root of the tab and improve the overall structural stability of the battery.

[0003] Chinese invention patent application No. 201610605106.3 proposes a safe soft-package lithium-ion battery tab, including a tab body and a PTC coating coated on the surface of the tab body, wherein the PTC coating is solidified by a PTC slurry, wherein the PTC slurry includes a PTC matrix material, a dispersant, a binder and a solvent; and the PTC matrix material is selected from at least one of BaTiO3 and BaPbO3. The application applies a layer of PTC material on the positive and negative tabs of the soft-package lithium-ion battery. The PTC material has the characteristic of a positive temperature coefficient, and its resistance value increases significantly with the increase of temperature. In the early stage of thermal runaway of the battery, the resistance of the PTC material will increase rapidly, thereby cutting off the current between the tab and the current collector, and between the tab and the active coating, effectively preventing thermal runaway caused by overcurrent; when the temperature drops to a safe temperature, the resistivity of the PTC material becomes smaller again, and the battery can still be used normally. In the design and application of lithium batteries, the PTC coating on the electrode tabs not only needs to have specific electrical properties, such as ideal ionic conductivity and thermal conductivity, to ensure the safety and performance of the battery, but also needs to meet certain mechanical strength requirements. This mechanical strength requirement is to ensure that during the use of the battery, especially under conditions such as charge and discharge cycles, temperature changes, and mechanical vibrations, the PTC coating can maintain its structural and functional integrity, thereby effectively playing its role in battery safety.

[0004] However, the PTC matrix material of the prior art is selected from at least one of BaTiO3 and BaPbO3. BaTiO3 and BaPbO3 are high dielectric materials of the same type, which not only have limited ion conductivity but also poor mechanical strength and are prone to cracking or falling off. They cannot optimize electrical performance and pose safety risks.

[0005] This application is filed for this purpose. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a pole tab ceramic coating material, a pole tab ceramic coating, a pole piece and a preparation method thereof.

[0007] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0008] First, the present invention provides a ceramic coating material for a tab, comprising the following components in mass percentage: LiTaO3 0.1%-10%, BaTiO3 10%-30% and Li 0.33 La 0.56 TiO3 60%-89.9%, Li 0.33 La 0.56 TiO3 has a nanowire structure.

[0009] LiTaO3 is an important multifunctional crystal material with excellent piezoelectric and thermoelectric properties, and is widely used in RF filters, infrared detectors, acousto-optic devices, etc. It also has lithium conductivity and can quickly transfer lithium ions, thus showing strong ionic conductivity.

[0010] BaTiO3 has a high dielectric constant and low dielectric loss. Its main function is to provide a positive temperature coefficient characteristic. When the battery temperature rises to a dangerous temperature, it transforms from a tetragonal phase to a cubic phase. At this time, the resistivity jumps by several orders of magnitude, thereby controlling the current and preventing overcharge and over-discharge, preventing breakdown under high voltage, and improving battery distribution, reducing local electric field concentration, reducing the risk of short circuits, and improving the safety and performance of lithium batteries.

[0011] Li 0.33 La 0.56 TiO3 (LLTO for short) has good lithium ion transport capacity, can significantly improve ion conductivity efficiency, and also has a high dielectric constant. Under the action of an external electric field, it can polarize and dissociate lithium salts to produce more free lithium ions available for transmission.

[0012] LiTaO3 has never been used as a ceramic coating material for tabs. The present invention unexpectedly discovered that when LiTaO3, BaTiO3, Li 0.33 La 0.56 After TiO3 is compounded according to the above ratio, not only the total conductivity and lithium ion conduction performance of the material are significantly improved, but also the mechanical strength is significantly improved. The reason is speculated in the present invention: the dielectric materials LiTaO3, BaTiO3 and LLTO generate polarization and electric field under external pressure, which can promote the dissociation of lithium salts and generate more free lithium ions for transmission. After the lithium salts are dissociated, they are coupled with the nanowire LLTO at the LLTO / electrolyte interface in the orientation direction to form a lithium-rich transmission channel. At the same time, the fast lithium-conducting material LiTaO3 and the nanowire LLTO jointly play the role of a bridge to build a fast lithium ion channel. Under the synergistic effect, a large number of continuous and fast lithium ion transmission channels are formed in the material, which not only greatly improves the lithium ion conduction ability of the material, but also improves the mechanical properties, enhances the mechanical strength, improves the lithium ion conduction ability in the battery cell and improves safety.

[0013] It should be noted that the nanowire structured LLTO can be directly purchased commercially or made in-house. Figure 3 As shown in Figure 2, the nanowire-structured LLTO can not only provide abundant channels for the rapid migration of lithium ions, but also play a structural support role, significantly enhancing the mechanical properties and mechanical strength of the material.

[0014] Furthermore, in the above embodiment, the following mass percentages of the components are preferably included: LiTaO3 3%-8%, BaTiO3 15%-25% and Li 0.33 La 0.56 TiO3 70%-80%, Li 0.33 La 0.56 The aspect ratio of TiO3 is 10-1000.

[0015] The addition amount of LiTaO3 includes but is not limited to 3%, 4%, 5%, 6%, 7%, 8%, the addition amount of BaTiO3 includes but is not limited to 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, Li 0.33 La 0.56 The added amount of TiO3 includes but is not limited to 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, and 80%.

[0016] The ceramic coating material of the electrode ear preferably includes the following components in mass percentage: LiTaO3 5%, BaTiO3 20% and Li 0.33 La 0.56 TiO3 75%, Li 0.33 La 0.56 The aspect ratio of TiO3 is 800.

[0017] Second, the present invention provides a tab ceramic coating, comprising boehmite and / or alumina and a tab ceramic coating material, wherein the mass percentage of the tab ceramic coating material in the boehmite and / or alumina is not less than 5%.

[0018] Boehmite and alumina have high resistivity and are easy to disperse to form a uniform coating, which can effectively prevent short circuits between the positive electrode tab and the battery casing or other components. In addition, both have good stability at high temperatures, stable chemical properties, high mechanical strength, and low cost. Boehmite and / or alumina are used in combination with tab ceramic coating materials. Boehmite and alumina provide insulation, and the tab ceramic coating material supplements the lithium ion conductivity, so that the tab ceramic coating achieves a balance between insulation and ion conduction, meeting the use requirements of high energy density lithium batteries.

[0019] In this embodiment, boehmite and / or alumina are the main materials, and the mass percentage of the tab ceramic coating material added to the main materials is not less than 5%, generally 5%-90%, preferably 8%-20%. Within this addition range, the obtained tab ceramic coating can take into account both cost and performance.

[0020] Third, the present invention proposes a pole piece, which includes a foil material, wherein the foil material includes a pole tab body and an active material coating area, wherein the active material coating area is coated with an active material, and a single side or both sides of the pole tab body are coated with a pole tab ceramic coating.

[0021] It should be noted that:

[0022] (1) The electrode is a positive electrode, and the foil is generally aluminum foil.

[0023] (2) In order to enhance the stability of the active material and the tab ceramic coating, it is preferred that the material of the connection area between the tab body and the active material coating area is connected by a bevel, that is, the edge of the active material adjacent to the tab body is a bevel, and the edge of the tab ceramic coating adjacent to the active material coating area is also a bevel. The two bevels are in contact with each other, with a large contact area and good bonding strength.

[0024] Furthermore, at least one surface of the pole lug body at one end away from the battery cell has a blank area where the pole lug ceramic coating is not provided; the pole lug ceramic coating covers the connection area between the pole lug body and the active material coating area; the active material coating area is coated with the active material to form a main material coating area, and the pole lug ceramic coating with a width of 2.5±0.5mm is also provided on two opposite sides of the main material coating area.

[0025] Specifically, the end of the tab body away from the battery cell needs to be welded to the collector plate or shell. If the surface of the tab body is fully covered with ceramic coating, it will have an adverse effect on welding. Therefore, it is necessary to leave a blank area that does not cover the tab ceramic coating, and the tab ceramic coating adjacent to the blank area is inclined to transition to avoid affecting the bonding strength between the tab ceramic coating and the foil. As for the width of the blank area, it is generally set to 1-5mm, of course, it can also be adjusted according to actual needs.

[0026] Specifically, the tab ceramic coating can be provided not only on the tab body, but also on the active material coating area, especially where the active material is less distributed on the active material coating area. For example, the tab ceramic coating preferably also covers the connection area between the tab body and the active material coating area, so as to effectively solve the problem of uneven thickness of the battery caused by the inconsistent thickness between the tab body area and the active material coating area, and further improve the consistency of the battery; moreover, after the tab ceramic coating is provided in the connection area, it is also helpful to solve the problem of internal short circuit of the battery during the battery manufacturing process and lithium precipitation during use, thereby improving the safety of the battery and extending the service life of the battery. For another example, the tab ceramic coating is preferably also provided on the opposite sides of the main material coating area (such as Figure 4As shown), the width thereof is preferably set to 2.5±0.5 mm to compensate for the adverse effect on the battery caused by the active material coating amount at the edge of the main material coating area being lower than that at the middle of the main material coating area.

[0027] In this embodiment, the tab body is a positive tab body, and the positive tab body is formed by cutting the empty foil area of ​​the positive current collector. As for the material of the positive current collector, it is a conventional positive current collector material in the art, such as aluminum foil.

[0028] Furthermore, chamfers are arranged at the edges of the tab body, and the tab ceramic coating is coated on both sides of the tab body, and the thickness of the tab ceramic coating on each side is 25-40 μm.

[0029] The edge of the tab body is chamfered to effectively reduce stress concentration in the area, reduce the risk of the tab breaking during rotation, and achieve better tab protection. The present invention has been verified through several experiments: the tab ceramic coating is coated on both sides and the thickness of the tab ceramic coating on each side is preferably 25-40 μm. The tab ceramic coating in this thickness range can ensure effective insulation between the tab and the housing or other components to prevent short circuits, and can provide sufficient mechanical strength to prevent the tab from being damaged during assembly or use, and does not affect the heat dissipation performance of the tab, achieving a balance between insulation and heat dissipation. If the thickness of the tab ceramic coating on each side exceeds 40 μm, an overly thick coating layer will result in uneven coating, affecting the assembly of the tab; if the thickness of the tab ceramic coating on each side is less than 25 μm, an overly thin coating layer cannot provide sufficient insulation and protection.

[0030] Fourthly, the present invention provides a method for preparing a pole piece, which specifically comprises the following steps:

[0031] S1. coating active material: coating active material slurry on one side or both sides of the active material coating area;

[0032] S2. Applying a ceramic coating on the tab: while applying the active material, a slurry containing the ceramic coating material on the tab body is applied on one side or both sides thereof, wherein the slurry is prepared by first dissolving a binder in a solvent to prepare a binder glue, and then mixing the binder glue, the ceramic coating material on the tab, boehmite and / or alumina, and an oily solvent and stirring them uniformly;

[0033] S3, vacuum drying, cold pressing, and slitting.

[0034] The preparation method is simple and has a high yield.

[0035] It should be noted that:

[0036] There are many specific coating implementation methods involved in step S1 and step S2, and any coating method that is currently available or may appear in the future can be used. Further, in S2, when preparing the binder glue, NMP is used as the solvent, and the mass percentage of the binder is 6%-8%; the oily solvent is NMP. The binder is first made into a binder glue with the above mass percentage, and then the tab ceramic coating material, boehmite and / or alumina are added, which helps to disperse the various components relatively evenly, and the formed tab ceramic coating has good compatibility with the tab, and can be stably adhered to the tab body for a long time after being coated.

[0037] Furthermore, the binder is selected from at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, polyethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, and carboxymethyl cellulose.

[0038] Compared with the prior art, the present invention combines LiTaO3, BaTiO3, Li 0.33 La 0.56 After TiO3 is compounded in a certain proportion, LiTaO3, BaTiO3, Li 0.33 La 0.56 TiO3 generates polarization and electric field under external pressure, which can promote the dissociation of lithium salt and produce more free lithium ions for transmission; LiTaO3 and Li 0.33 La 0.56 The synergistic effect of TiO3 promotes the construction of lithium ion fast channels, and finally forms a large number of continuous and fast lithium ion transmission channels in the material; the pole ear ceramic coating material is added to boehmite and / or alumina to form a pole ear ceramic coating, which not only significantly improves the total conductivity and lithium ion conductivity of the material, but also significantly improves the mechanical strength, ensuring the continuity and safety of the internal circuit during battery transportation or use. The present invention improves the safety and electrical performance of the battery without significantly increasing the cost, and has certain economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 This is a graph showing the change in the lug resistance of the electrode sheet obtained in Example 2 of the present invention with temperature.

[0041] Figure 2 This is a photograph of the appearance of the electrode prepared in Example 2 after the peel strength test.

[0042] Figure 3 is Li used in the embodiments of the present invention 0.33 La 0.56 Schematic diagram of the structure of TiO3 nanowires.

[0043] Figure 4 Schematic diagram of the distribution of the tab ceramic coating material on the positive electrode sheet in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0045] The substances involved in the examples except Li 0.33 La 0.56 Except for TiO3 nanowires, all other materials were purchased commercially. 0.33 La 0.56 TiO3 nanowires were obtained by self-production. The specific preparation method is as follows:

[0046] Preparation of solution A: DMF (purity 99.8%) and acetic acid were mixed in a mass ratio of 6:1 to obtain solution A;

[0047] Preparation of solution B: dissolving a PVP polymer having a molecular weight of Mw=1300000 into the above solution A to obtain a solution B having a PVP mass fraction of 7%;

[0048] Solution C was prepared according to the stoichiometric ratio of LLTO (Li 0.33 La 0.557 TiO3), adding LiNO3 and La(NO)3·6H2O to the solution B, and stirring for 2 hours to obtain a solution C;

[0049] Solution D was prepared according to the stoichiometric ratio of LLTO (Li 0.33 La 0.557 TiO3), adding Ti(OC4H9)4 (tetrabutyl titanate, purity 99.0%) to the solution C, heating in a water bath at 50°C and stirring for 4h to obtain a solution D;

[0050] Electrospinning: Solution D was added to the electrospinning ejector for spinning. The relevant equipment parameters are shown in Table 1 below:

[0051] Table 1

[0052] Parameter Level Pinhole size diameter (mm) 0.2-0.4 Injection speed (ml / h) 0.3-0.5 Voltage(kV) 20.0 Distance(cm) 17 Collection roller speed (rpm) 1500 Temperature(℃) 25±5 RH humidity ≤10％

[0053] High temperature sintering: The fiber obtained in the previous step was sintered at high temperature in air atmosphere, the heating rate was set to 3℃ / min, the temperature was kept at 800-1000℃ for 5h, and LLTO nanofibers were obtained after cooling. After experiments: the needle hole diameter was controlled to 0.2mm, the injection speed was 0.5ml / h, and the sintering temperature was 800℃, and Li with an aspect ratio of 1000 was obtained. 0.33 La 0.56 TiO3 nanowires; control the pinhole diameter to 0.4mm, injection speed to 0.3ml / h, sintering temperature to 1000℃, and obtain Li with aspect ratio of 10 0.33 La 0.56 TiO3 nanowires; control the pinhole diameter to 0.2mm, injection speed to 0.4ml / h, sintering temperature to 850℃, and obtain Li with aspect ratio of 800 0.33 La 0.56 TiO3 nanowires; control the pinhole diameter to 0.2mm, injection speed to 0.5ml / h, sintering temperature to 950℃, and obtain Li with aspect ratio of 500 0.33 La 0.56 TiO3 nanowires; control the pinhole diameter to 0.4mm, injection speed to 0.3ml / h, sintering temperature to 950℃, and obtain Li with aspect ratio of 100 0.33 La 0.56 TiO3 nanowires.

[0054] Example 1

[0055] A ceramic coating material for a tab comprises the following components in mass percentage: 0.1% LiTaO3, 10% BaTiO3 and 1% Li 0.33 La 0.56 TiO3 89.9%, Li 0.33 La 0.56 TiO3 is a nanowire structure with an aspect ratio of 800.

[0056] A positive electrode sheet, comprising an aluminum foil with a thickness of 10 μm, the aluminum foil comprising a tab body and an active material coating area, the edge of the tab body is chamfered, the tab body is coated with the above-mentioned tab ceramic coating material, and a blank area with a width of 2 mm is left on one surface of the free end of the tab body for welding; the active material coating area is coated with a positive electrode slurry, the positive electrode slurry is prepared by dissolving a positive electrode active material LiCoO2, a conductive agent acetylene black, and a binder PVDF in a solvent NMP in a mass ratio of 94:3:3, and stirring and mixing them uniformly, and the positive electrode slurry is coated on the active material. The coating area has a coating thickness of 60 μm; the PVDF powder is first mixed with NMP to form a binder glue with a mass percentage of 7%, and then the binder glue is mixed with the ear ceramic coating material, boehmite, and NMP. After mixing evenly, a slurry is formed, wherein: the mass ratio of the binder glue, the ear ceramic coating material, boehmite, and NMP is 58:5:25:12; finally, the slurry is double-sidedly coated on the positive electrode ear body, and the coating thickness of each side is 30 μm and the width is 2.5 mm. After drying, cold pressing, and slitting, the positive electrode sheet is obtained.

[0057] A negative electrode sheet comprises a copper foil with a thickness of 10 μm, wherein the copper foil comprises a tab body and an active material coating area, wherein a chamfer is arranged at an edge of the tab body, wherein the active material coating area is coated with a negative electrode slurry, wherein the negative electrode slurry is prepared by dissolving a negative electrode active material hard carbon, a conductive agent carbon black, and an adhesive SBR in a mass ratio of 80:10:10 in a solvent NMP and stirring and mixing the mixture thoroughly, wherein the negative electrode slurry is coated on the active material coating area, and the thickness after double-sided coating is 130 μm, and the negative electrode sheet is obtained by drying, cold pressing, and slitting.

[0058] Using PE porous polymer film as the separator and 1 mol / L LiPF6 / (EC+PC+DEC, volume ratio of 1:1:1) as the electrolyte, the positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator located between the positive electrode sheet and the negative electrode sheet. After winding or stacking, an electrode assembly is obtained, which is placed in an outer package, injected with electrolyte and packaged to obtain the battery to be tested.

[0059] Example 2

[0060] Compared with Example 1, the composition of the tab ceramic coating material is changed, including the following components in mass percentage: LiTaO3 5%, BaTiO3 20% and Li 0.33 La 0.56 TiO3 75%. The rest are the same as in Example 1.

[0061] Example 3

[0062] Compared with Example 1, the composition of the tab ceramic coating material is changed, including the following components in mass percentage: LiTaO3 10%, BaTiO3 30% and Li 0.33 La 0.56 TiO3 60%. The rest are the same as in Example 1.

[0063] Example 4

[0064] Compared with Example 1, the composition of the tab ceramic coating material is changed, including the following components in mass percentage: LiTaO3 3%, BaTiO3 25% and Li 0.33 La 0.56 TiO3 72%. The rest are the same as in Example 1.

[0065] Example 5

[0066] Compared with Example 1, the composition of the tab ceramic coating material is changed, including the following components in mass percentage: LiTaO3 4%, BaTiO3 22% and Li 0.33 La 0.56 TiO3 74%. The rest are the same as in Example 1.

[0067] Example 6

[0068] Compared with Example 1, the composition of the tab ceramic coating material is changed, including the following components in mass percentage: LiTaO3 5%, BaTiO3 15% and Li 0.33 La 0.56 TiO3 80%. The rest are the same as in Example 1.

[0069] Example 7

[0070] Compared with Example 1, the composition of the tab ceramic coating material is changed, including the following components in mass percentage: LiTaO3 8%, BaTiO3 22% and Li 0.33 La 0.56 TiO3 70%. The rest are the same as in Example 1.

[0071] Example 8

[0072] Compared with Example 1, in the preparation of the positive electrode sheet, when the slurry is coated on both sides of the positive electrode tab body, the coating thickness on each side is adjusted to 25 μm. The rest is the same as Example 1.

[0073] Example 9

[0074] Compared with Example 1, in the preparation of the positive electrode sheet, when the slurry is coated on both sides of the positive electrode tab body, the coating thickness on each side is adjusted to 35 μm. The rest is the same as Example 1.

[0075] Example 10

[0076] Compared with Example 1, in the preparation of the positive electrode sheet, when the slurry is coated on both sides of the positive electrode tab body, the coating thickness on each side is adjusted to 40 μm. The rest is the same as Example 1.

[0077] Embodiment 11

[0078] Compared with Example 2, Li 0.33 La 0.56 The aspect ratio of TiO3 is 10. The rest are the same as in Example 2.

[0079] Example 12

[0080] Compared with Example 2, Li 0.33 La 0.56 The aspect ratio of TiO3 is 100. The rest are the same as in Example 2.

[0081] Example 13

[0082] Compared with Example 2, Li 0.33 La 0.56 The aspect ratio of TiO3 is 500. The rest are the same as in Example 2.

[0083] Embodiment 14

[0084] Compared with Example 2, Li 0.33 La 0.56 The aspect ratio of TiO3 is 1000. The rest are the same as in Example 2.

[0085] Embodiment 15

[0086] Compared with Example 2, boehmite is replaced by alumina, and the amount of the tab ceramic coating material added to the alumina is 5%, that is, the mass ratio of the binder glue, the tab ceramic coating material, the alumina, and the NMP is 58:1.4:28.6:12. The rest is the same as Example 2.

[0087] Example 16

[0088] Compared with Example 2, boehmite is replaced by a mixture of boehmite and alumina, and the amount of the tab ceramic coating material added to the mixture of boehmite and alumina is 10%, that is, the mass ratio of the binder glue, the tab ceramic coating material, boehmite, alumina, and NMP is 58:2.8:13.6:13.6:12. The rest is the same as Example 2.

[0089] Comparative Example 1

[0090] Compared with Example 2, no Li 0.33 La 0.56 The specific added mass of TiO3, LiTaO3 and BaTiO3 is consistent with that in Example 2.

[0091] Comparative Example 2

[0092] Compared with Example 2, it does not contain LiTaO3, Li 0.33 La 0.56 The specific added mass of TiO3 and BaTiO3 is consistent with that in Example 2.

[0093] Comparative Example 3

[0094] Compared with Example 2, it does not contain BaTiO3, Li 0.33 La 0.56 The specific added mass of TiO3 and LiTaO3 is consistent with that in Example 2.

[0095] Comparative Example 4

[0096] Compared with Example 2, the nanowire structure of Li 0.33 La 0.56 TiO3 is adjusted to Li nanosphere structure 0.33 La 0.56 TiO3. The rest are the same as in Example 2.

[0097] Comparative Example 5

[0098] Compared with Example 2, the composition of the tab ceramic coating material is changed, including the following components in mass percentage: LiTaO3 3%, BaTiO3 3% and Li 0.33 La 0.56 TiO3 92%. The rest are the same as in Example 2.

[0099] Comparative Example 6

[0100] Compared with Example 2, the composition of the tab ceramic coating material is changed, including the following components in mass percentage: LiTaO3 20%, BaTiO3 25% and Li 0.33 La 0.56 TiO3 55%. The important technical parameters of each embodiment and comparative example are shown in Table 2.

[0101] Table 2

[0102]

[0103]

[0104] Conduct resistance test, electrochemical performance, peel strength and electrode resistance test on each lithium battery to be tested. The specific requirements are as follows:

[0105] (1) Resistance test

[0106] The resistance test of the pole lugs of the pole piece obtained in Example 2 was performed. Figure 1 The curve in the figure shows the change of resistance with temperature: when the temperature is 10-80℃, the resistance of the tab is relatively small; when the temperature exceeds 80℃, the resistance increases rapidly. It can be seen that the tab ceramic coating has excellent thermal insulation performance, which can effectively block heat transfer and delay the spread of thermal runaway; at high temperatures, it can still remain stable, avoid aggravating thermal runaway due to high temperature decomposition, and regulate heat conduction to prevent local overheating and avoid the occurrence of thermal runaway.

[0107] (2) Electrochemical performance test

[0108] The battery is tested for capacity retention of not less than 80% at room temperature and 45°C cycles, capacity retention at 2C / 0.1C, 130°C hot box pass rate, needle puncture pass rate and 50-cycle battery cell expansion rate.

[0109] Normal temperature cycle test: At room temperature, constant current 0.5C charging to 4.53V, CC-CV charging to a current less than 0.05C, 0.5C discharge to 3.0V, record the number of cycles before the battery capacity is less than 80%. High temperature 45℃ cycle test: 45℃, constant current 0.5C charging to 4.53V, CC-CV charging to a current less than 0.05C, 0.5C discharge to 3.0V, record the number of cycles before the battery capacity is less than 80%. Rate performance test: The test environment is 25℃, the voltage range is 3-4.53V, the current density is 1C=200mA / g, and it is cycled 5 times at a current density of 2C / 0.1C. 130℃ hot box pass rate test: At 25℃, charge the battery to 4.53V at 1C, then charge at 4.53V constant voltage to a cut-off current of 0.05C, place the battery in a hot box, heat it to 130℃ at a rate of 5℃ / min, and keep it at 130℃ for 60min. 50-cycle battery expansion rate test: record the initial thickness of the battery T0, and record the thickness after 50 cycles as T. The battery expansion rate is expressed as the thickness change rate, thickness change rate (%) = (T-T0) / T0×100%.

[0110] (3) Peel strength and electrode resistance test

[0111] The electrode ceramic coating material obtained in each embodiment and comparative example was coated on aluminum foil (aluminum foil thickness 9 μm, coating thickness 30 μm) with a 150 μm scraper, and the resistance and peel strength of the electrode were tested after baking at 70° C. for 12 h (such as Figure 2 The figure shows the appearance of the electrode obtained in Example 2 after the peel strength test), and the data is collected.

[0112] The electrochemical performance test and peel strength test results of each embodiment and comparative example are shown in Table 3.

[0113] Table 3

[0114]

[0115] As shown in Table 2 and Table 3:

[0116] (1) From the comparison between Example 2 and Comparative Examples 1, 2 and 3, it can be seen that LiTaO3, BaTiO3, Li 0.33 La 0.56 When any two combinations of TiO3 are added, although the 2C / 0.1C rate performance and 50-cycle battery expansion rate are acceptable, the cycle performance is not ideal. When these three substances are added in combination, both the cycle performance of the battery and the peel strength of the tab ceramic coating material are significantly improved. Moreover, the 130°C hot box pass rate quickly increased to 5 / 5, and the 2C / 0.1C rate performance was also optimized to a certain extent. Obviously, the dielectric materials LiTaO3, BaTiO3 and Li 0.33 La 0.56 TiO3 can produce a positive synergistic effect on the battery cycle performance and the peel strength of the tab ceramic coating material. All three substances are indispensable.

[0117] (2) From the comparison between Examples 1 to 14 and Comparative Examples 5 and 6, it can be seen that when LiTaO3, BaTiO3, Li 0.33 La 0.56 After TiO3 is compounded according to the ratio specified in the present invention, it will produce obvious positive synergistic effects on the battery's cycle performance, the peel strength of the tab ceramic coating material, the 130°C hot box pass rate and the 2C / 0.1C rate performance; when the addition amount of the corresponding substance is too low or too high, the synergistic effect is not obvious and better experimental results cannot be obtained.

[0118] (3) From the comparison between Example 2 and Comparative Example 4, it can be seen that: Li 0.33 La 0.56 Whether TiO3 is a nanowire structure has a significant impact on the experimental results. 0.33 La 0.56After TiO3 was adjusted from a nanowire structure to a nanosphere structure, the battery's cycle performance, rate performance, 130°C hot box pass rate, and the peel strength of the tab ceramic coating material all deteriorated significantly. The reason for this is that the nanosphere structured LLTO cannot couple with the dissociated lithium salt, so it cannot form a lithium-rich transmission channel, and then it cannot build a bridge that helps lithium ions pass quickly, and the lithium conductivity of the material cannot be effectively improved.

[0119] Furthermore, nanowire-structured Li 0.33 La 0.56 TiO3, its specific aspect ratio also has a significant impact on the experimental results. Theoretically, the larger the aspect ratio, the better the coupling effect. However, too large an aspect ratio is not only difficult to obtain, but also has an adverse effect on its dispersibility, which in turn leads to the inability to fully exert the coupling effect. From the comparison of Example 2, Example 11, Example 12, Example 13, and Example 14, it can be seen that when the aspect ratio is 10-1000, it has a good coupling effect, and the aspect ratio of 800 is better. In summary: the present invention combines LiTaO3, BaTiO3, Li 0.33 La 0.56 TiO3 is mixed and added to boehmite and / or alumina in an appropriate proportion, which optimizes the lithium ion transmission performance while ensuring insulation, mechanical strength and thermal stability, and also significantly improves the lithium ion conductivity of the material, and improves the mechanical strength of the pole ear ceramic coating, meeting the dual requirements of safety and performance of high energy density lithium batteries; in addition, the pole ear ceramic coating has a strong adhesion to the positive pole ear, which helps to form a complete, stable, and not easy to break or fall off coating. Even after experiencing multiple charge and discharge cycles, temperature changes and other conditions, it can maintain its complete structure and function, thereby ensuring the continuity and safety of the internal circuit of the battery; the test results of each embodiment show that when the pole piece obtained by the present invention is used in a battery, the battery's cycle performance, rate performance, 130°C hot box pass rate and other properties can be significantly improved.

[0120] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and deform the above embodiments within the scope of the present invention. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples without contradiction.

Claims

1. A tab ceramic coating material, characterized in that: The components include the following mass percentages: LiTaO3 0.1%-10%, BaTiO3 10%-30% and Li 0.33 La 0.56 TiO3 60%-89.9%, Li 0.33 La 0.56 TiO3 has a nanowire structure.

2. The tab ceramic coating material according to claim 1, characterized in that: The components include the following mass percentages: LiTaO3 3%-8%, BaTiO3 15%-25% and Li 0.33 La 0.56 TiO370%-80%, Li 0.33 La 0.56 The aspect ratio of TiO3 is 10-1000.

3. The tab ceramic coating material according to claim 1, characterized in that: The components include the following mass percentages: LiTaO3 5%, BaTiO3 20% and Li 0.33 La 0.56 TiO3 75%, Li 0.33 La 0.56 The aspect ratio of TiO3 is 800.

4. A tab ceramic coating, characterized in that: The present invention comprises boehmite and / or alumina and the tab ceramic coating material as claimed in any one of claims 1 to 3, wherein the mass percentage of the tab ceramic coating material in the boehmite and / or alumina is not less than 5%.

5. A pole piece, comprising a foil, wherein the foil comprises a pole lug body and an active material coating area, wherein the active material coating area is coated with an active material, characterized in that: One side or both sides of the tab body are coated with the tab ceramic coating as claimed in claim 4.

6. The pole piece according to claim 5, characterized in that: At least one surface of the end of the tab body away from the battery core has a blank area where the tab ceramic coating is not provided; The tab ceramic coating covers the connection area between the tab body and the active material coating area; The active material coating area is coated with active material to form a main material coating area, and the tab ceramic coating with a width of 2.5±0.5 mm is also provided on opposite sides of the main material coating area.

7. The pole piece according to claim 5, characterized in that: Chamfers are arranged at the edges of the tab body, and the thickness of the tab ceramic coating on each side is 25-40 μm.

8. A method for preparing a pole piece according to any one of claims 5 to 7, characterized in that: The specific steps include the following: S1. coating active material: coating active material slurry on one side or both sides of the active material coating area; S2. Applying a ceramic coating on the tab: while applying the active material, a slurry containing the ceramic coating material on the tab body is applied on one side or both sides thereof, wherein the slurry is prepared by first dissolving a binder in a solvent to prepare a binder glue, and then mixing the binder glue, the ceramic coating material on the tab, boehmite and / or alumina, and an oily solvent and stirring them uniformly; S3, vacuum drying, cold pressing, and slitting.

9. The method for preparing a pole piece according to claim 8, characterized in that: In S2, when preparing the adhesive glue, NMP is used as the solvent, and the mass percentage of the adhesive is 6%-8%; the oily solvent is NMP.

10. The method for preparing a pole piece according to claim 8, characterized in that: The binder is selected from at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, polyethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, and carboxymethyl cellulose.

Images