Solid electrolyte insulating coating, positive pole piece and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a solid electrolyte insulating coating, a positive pole piece and a lithium ion battery. The solid electrolyte insulating coating is prepared from slurry comprising an oxide solid electrolyte, a lithium supplement agent, an oil binder, a dispersant and N-methyl pyrrolidone; and the oil binder is polyvinylidene fluoride. In the invention, the original effect of the insulating coating can be ensured by the electronic insulativity of the oxide solid electrolyte and the lithium supplement agent, and meanwhile, the lithium ion conductivity of the oxide solid electrolyte is utilized to provide a channel for lithium transmission of the lithium supplement agent, so that the lithium ion action effect of the lithium supplement agent is ensured, and the cycle retention rate is improved. Furthermore, all the components in the solid electrolyte insulating coating can be well matched under a specific ratio, the finally obtained coating is relatively excellent in uniformity and relatively excellent in electric breakdown strength, and the finally prepared lithium ion battery is relatively excellent in electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a solid electrolyte insulating coating, a positive electrode sheet and a lithium ion battery. Background Art

[0002] The current collector tabs of the positive electrode of the battery need to be prepared through a die-cutting process. During the cutting process, burrs will be generated on the cutting surface. If the burrs on one side of the tab pierce the diaphragm, a short circuit will occur, and a large current discharge will occur instantly, causing the battery cell to thermally run away, flame out and explode. In order to avoid this problem, the commonly used method is to apply an insulating coating on the surface of the positive tab. At present, insulating coating has become a standard feature of mass production of power battery industry products.

[0003] The main materials of the insulating coating used in the prior art are usually ceramic powder coatings such as alumina and boehmite, which do not have ion conductivity and only play a safety role.

[0004] For example, the coating material used in patent application document CN117832773A is at least one of boehmite and alumina, which does not have ion transmission ability and lithium replenishment ability, and only provides basic insulation effect.

[0005] The coating material used in the patent application document CN118399031A is one or more of the ceramic materials silicate, aluminum oxide, silicon carbide, silicon nitride, boron nitride, zirconium boride, aluminum nitride and the derivatives of the ceramic materials, which have no electron transmission ability. At the same time, the preparation process is to first coat the insulating layer on the current collector, and then coat the positive electrode coating. Because the insulating coating is partially coated on the two sides of the current collector, the insulating coating applied first will cause the lateral thickness of the current collector to be uneven, resulting in problems such as burst veins and wrinkles during the winding process, affecting the smooth appearance quality of the current collector, and then affecting the effect of coating the positive electrode coating on the current collector.

[0006] Patent application document CN118522976A directly adds lithium supplement to the positive electrode, which will affect the stirring and dispersion effect of the positive electrode. At the same time, adding lithium supplement to the positive electrode also affects the effective mass ratio of the active material. The various side effects of the lithium supplement and the active material in the electrochemical stage also affect the effect of the active material. Summary of the invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a solid electrolyte insulating coating, a positive electrode plate and a lithium-ion battery, which have excellent coating uniformity and can further enhance the electrochemical performance of the lithium battery while ensuring the safety effect of the original insulating coating, providing more performance advantages compared to existing insulating coatings.

[0008] The present invention provides a solid electrolyte insulating coating, which is prepared from a slurry comprising a solid electrolyte, a lithium supplement agent, an oil-based binder, a dispersant, and N-methylpyrrolidone;

[0009] The solid electrolyte is an oxide solid electrolyte or a halide solid electrolyte;

[0010] The oil-based binder is polyvinylidene fluoride.

[0011] Preferably, the mass ratio of the solid electrolyte, the lithium supplement agent, the oil-based binder, and the dispersant is 40-50:40-50:5-10:1-3.

[0012] Preferably, the oxide solid electrolyte includes at least one of lithium aluminum titanium phosphate, lithium lanthanum titanate, and lithium lanthanum zirconate; the halide solid electrolyte includes at least one of Li2ZrF6, Li3ZrCl6, Li4ZrF8, and Li2TiF6.

[0013] Preferably, the D50 value of the solid electrolyte particles is 250-350 nm.

[0014] Preferably, the lithium supplement agent includes at least one of lithium-rich lithium ferrate, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium hexafluorophosphate, and lithium oxalate.

[0015] Preferably, the oil-based binder is PVDF K30.

[0016] Preferably, the solid content of the slurry is 35%-45%.

[0017] The present invention further provides a positive electrode sheet, comprising:

[0018] A positive electrode current collector;

[0019] An active material coating formed on one side of the positive electrode current collector;

[0020] A solid electrolyte insulating coating formed on the edge of the active material coating;

[0021] The solid electrolyte insulating coating is the solid electrolyte insulating coating described above.

[0022] Preferably, the active material coating is prepared from a slurry comprising lithium iron phosphate, SP, polyvinylidene fluoride, and N-methylpyrrolidone;

[0023] The mass ratio of the lithium iron phosphate, SP, polyvinylidene fluoride, and N-methylpyrrolidone is 48-50:0.5-1.5:1-3:47-49.

[0024] Preferably, the thickness of the active material coating is 247 μm or more.

[0025] Preferably, the thickness of the solid electrolyte insulating coating is 2-8 μm; the width is 5-20 mm.

[0026] Preferably, the overlapping width of the solid electrolyte insulating coating and the active material coating is 0-1.5 mm.

[0027] The present invention also provides a lithium-ion battery, the positive electrode of which is the positive electrode sheet described above.

[0028] The present invention provides a solid electrolyte insulating coating, which is prepared from a slurry comprising a solid electrolyte, a lithium supplement agent, an oil-based binder, a dispersant, and N-methylpyrrolidone; the solid electrolyte is an oxide solid electrolyte or a halide solid electrolyte; the oil-based binder is polyvinylidene fluoride. In the present invention, the electronic insulation of the oxide solid electrolyte and the lithium supplement agent itself can ensure the original effect of the insulating coating. At the same time, the lithium ion conductivity of the oxide solid electrolyte is used to provide a channel for the lithium transport of the lithium supplement agent, ensuring the lithium ion action effect of the lithium supplement agent, thereby improving the cycle retention rate. Further, each component in the solid electrolyte insulating coating can cooperate well under specific ratios, and the finally obtained coating has better uniformity and better electric breakdown strength resistance, and the electrochemical performance of the finally prepared lithium-ion battery is better. Detailed Embodiments

[0029] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0030] The present invention provides a solid electrolyte insulating coating, which is prepared from a slurry comprising a solid electrolyte, a lithium supplement agent, an oil-based binder, a dispersant, and N-methylpyrrolidone (NMP);

[0031] The solid electrolyte is an oxide solid electrolyte or a halide solid electrolyte;

[0032] The oil-based binder is polyvinylidene fluoride (PVDF).

[0033] In some embodiments of the present invention, the oxide solid electrolyte is selected from at least one of lithium aluminum titanium phosphate LATP, lithium lanthanum titanate LLTO, and lithium lanthanum zirconate LLZO.

[0034] The halide solid electrolyte is a ternary halide, specifically at least one of Li2ZrF6, Li3ZrCl6, Li4ZrF8, and Li2TiF6. The D50 value of the solid electrolyte particles is 250 - 350 nm, so as to ensure sufficient particle packing density at the coating thickness and ensure insulation.

[0035] In some embodiments of the present invention, the lithium supplementing agent is selected from at least one of lithium-rich lithium ferrate, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), and lithium oxalate (Li2C2O4).

[0036] In some embodiments of the present invention, the oil-based binder is PVDF K30.

[0037] In some embodiments of the present invention, the dispersant is selected from at least one of dodecyltrimethoxysilane, dodecyltriethoxysilane, and hexadecyltrimethoxysilane.

[0038] In the present invention, N-methylpyrrolidone (NMP) is used as the solvent.

[0039] In some embodiments of the present invention, the mass ratio of the solid electrolyte, lithium supplementing agent, oil-based binder, and dispersant is 40 - 50:40 - 50:5 - 10:1 - 3; for example, 45:46:8:1, 41:50:8:1, 50:40:7:3.

[0040] In some embodiments of the present invention, the solid content of the slurry is 35% - 45%, for example, 40%.

[0041] In some embodiments of the present invention, the solid electrolyte insulating coating is obtained by coating and drying a slurry comprising a solid electrolyte, a lithium supplementing agent, an oil-based binder, a dispersant, and N-methylpyrrolidone.

[0042] In some embodiments of the present invention, the method for preparing the solid electrolyte insulating coating comprises the following steps:

[0043] After mixing the solid electrolyte, lithium supplementing agent, oil-based binder, dispersant, and N-methylpyrrolidone evenly, a slurry is obtained, and after coating and drying, the solid electrolyte insulating coating is obtained.

[0044] The present invention also provides a positive electrode plate, comprising:

[0045] A positive electrode current collector;

[0046] An active material coating formed on one side of the positive electrode current collector;

[0047] A solid electrolyte insulating coating formed on the edge of the active material coating;

[0048] The solid electrolyte insulating coating is the solid electrolyte insulating coating described above.

[0049] In some embodiments of the present invention, the positive electrode current collector is a carbon-coated aluminum foil, which is commercially available.

[0050] In some embodiments of the present invention, the active material coating is prepared from a slurry comprising lithium iron phosphate, SP (conductive carbon), polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP). The mass ratio of lithium iron phosphate, SP (conductive carbon), polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) is 48-50:0.5-1.5:1-3:47-49; for example, 49:1:2:48.

[0051] In some embodiments of the present invention, the thickness of the active material coating is above 247 μm, for example, 250 μm. If the solid electrolyte insulating coating is too thick, it will affect the thickness fluctuation of the positive electrode. If the solid electrolyte insulating coating is too thin, the insulation performance will be insufficient and it is easily broken down by a large current.

[0052] In some embodiments of the present invention, the thickness of the solid electrolyte insulating coating is 2-8 μm; the width is 5-20 mm, for example, 5 mm.

[0053] In some embodiments of the present invention, the width of the overlap between the solid electrolyte insulating coating and the active material coating is 0-1.5 mm.

[0054] The solid electrolyte insulating coating is coated on both side edges of the active material coating.

[0055] In some embodiments of the present invention, the method for preparing the positive electrode sheet includes the following steps:

[0056] S1) A slurry comprising lithium iron phosphate, SP (conductive carbon), polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) is uniformly coated on the positive electrode current collector. After curing, an active material coating is obtained on the positive electrode current collector;

[0057] S2) A slurry comprising a solid electrolyte, a lithium supplement agent, an oil-based binder, a dispersant, and N-methylpyrrolidone (NMP) is uniformly coated on the edge of the active material coating. After curing, a solid electrolyte insulating coating is obtained on the active material coating, thereby obtaining a positive electrode sheet.

[0058] Regarding step S1):

[0059] Specifically, it includes:

[0060] Mix lithium iron phosphate, SP (conductive carbon), polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) evenly to obtain a positive electrode active paste. Coat the positive electrode active paste evenly on a positive electrode current collector. After curing, an active material coating is obtained on the positive electrode current collector.

[0061] Regarding step S2):

[0062] Specifically, it includes:

[0063] Mix a solid electrolyte, a lithium supplement agent, an oil-based binder, and a dispersant, and then add N-methylpyrrolidone (NMP) and mix evenly to make a paste. Coat the paste evenly on the two side edges of the active material coating. After curing, a solid electrolyte insulating coating is obtained on the active material coating, thereby obtaining a positive electrode plate.

[0064] The present invention also provides a lithium-ion battery, and the positive electrode of the lithium-ion battery is the positive electrode plate described above.

[0065] The lithium-ion battery can be a soft-pack battery.

[0066] Specifically, the lithium-ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The positive electrode is the positive electrode plate described above.

[0067] In some embodiments of the present invention, the negative electrode of the lithium-ion battery is a graphite negative electrode. The electrolyte is a 1mol / L LiPF6 solution, and the solvent is ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) with a mass ratio of 20:40:40. The separator is a PE composite separator; it includes a PE film and alumina coatings formed on both sides of the PE film; wherein, the thickness of the PE film is 9μm, and the thickness of each alumina coating on both sides is 2μm.

[0068] The soft-pack battery can be prepared according to the following method:

[0069] Wind the positive electrode plate, the separator, and the negative electrode plate into an electrode core, and after hot pressing, pole ear welding, and aluminum-plastic film encapsulation, a soft-pack battery is obtained.

[0070] By using an insulating coating containing an oxide solid electrolyte and a lithium supplement agent, the present invention not only ensures the original effect of the insulating coating but also provides an additional lithium supplement function for the battery without occupying the effective mass ratio of the active coating, thereby increasing the proportion of the active material.

[0071] By adding the lithium supplement agent to the insulating coating, the present invention avoids various side reactions between the lithium supplement agent and the positive electrode active material caused by adding the lithium supplement agent to the positive electrode paste, and fully exerts the effect of the lithium supplement agent.

[0072] The solid electrolyte insulating coating of the present invention can simultaneously provide buffering and site margin for the migration and insertion of lithium ions during the charge and discharge of the positive and negative electrodes, avoiding the precipitation of lithium ions caused by overcharging and over-discharging, and improving the cycle life of active lithium ions.

[0073] In the present invention, the dispersant ensures the dispersion and suspension uniformity of the mixed slurry through the amphiphilicity of the silicon-based and carboxyl groups and the steric hindrance effect of the long chain.

[0074] The present invention places no special restrictions on the sources of the raw materials used above, and they can be commercially available.

[0075] To further illustrate the present invention, the following provides a detailed description of the solid electrolyte insulating coating, the positive electrode plate, and the lithium-ion battery provided by the present invention in conjunction with embodiments, but it should not be construed as limiting the protection scope of the present invention.

[0076] Example 1

[0077] 1) Preparation of the solid electrolyte insulating layer slurry (Slurry A):

[0078] Mix the solid electrolyte (LATP, D50 value of the particles is 250 - 350 nm), the lithium supplement agent (lithium-rich iron ferrite), the oil-based binder (PVDF K30), and the dispersant (dodecyltrimethoxysilane) in a mass ratio of 45:46:8:1, and then add the solvent (NMP) and mix well to prepare Slurry A with a solid content of 40%.

[0079] 2) Preparation of the positive electrode plate:

[0080] 2-1) Mix lithium iron phosphate, SP (conductive carbon), PVDF, and NMP in a mass ratio of 49:1:2:48 to obtain the positive electrode active slurry B. Coat the Slurry B evenly on the carbon-coated aluminum foil (commercially available product). After curing, an active material coating is obtained on the carbon-coated aluminum foil; the thickness of the active material coating is 250 μm.

[0081] 2-2) Coat Slurry A evenly on both side edges of the active material coating. After curing, a solid electrolyte insulating coating is obtained on the active material coating, thereby obtaining the positive electrode plate.

[0082] The thickness of the solid electrolyte insulating coating is 3.5 μm. The width of the overlap between the solid electrolyte insulating coating and the active material coating is 5 mm. The width of the overlap between the solid electrolyte insulating coating and the active material coating is 0 - 1.5 mm.

[0083] 3) Use a 1mol / L LiPF6 solution as the electrolyte, where the solvent is ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), with a mass ratio of 20:40:40;

[0084] Wind the positive electrode sheet, separator (the separator is a PE composite separator; including a PE film and alumina coatings formed on both sides of the PE film; where the thickness of the PE film is 9μm and the thickness of each alumina coating is 2μm), and negative electrode sheet (graphite negative electrode) into an electrode core, and obtain a soft-pack battery through hot pressing, tab welding, and aluminum-plastic film encapsulation.

[0085] Example 2

[0086] The difference from Example 1 is:

[0087] In step 1), the mass ratio of the solid electrolyte (LATP, D50 value of the particles is 250 - 350nm), lithium supplement agent (lithium-rich iron ferrite), oil-based binder (PVDF K30), and dispersant (dodecyltrimethoxysilane) is 41:50:8:1.

[0088] The remaining steps are the same as those in Example 1 to obtain a soft-pack battery.

[0089] Example 3

[0090] The difference from Example 1 is:

[0091] In step 1), the mass ratio of the solid electrolyte (LATP, D50 value of the particles is 250 - 350nm), lithium supplement agent (lithium-rich iron ferrite), oil-based binder (PVDF K30), and dispersant (dodecyltrimethoxysilane) is 50:40:7:3.

[0092] The remaining steps are the same as those in Example 1 to obtain a soft-pack battery.

[0093] Example 4

[0094] The difference from Example 1 is:

[0095] In step 1), the solid electrolyte is LLTO, and the D50 value of the particles is 250 - 350nm.

[0096] The remaining steps are the same as those in Example 1 to obtain a soft-pack battery.

[0097] Example 5

[0098] The difference from Example 1 is:

[0099] In step 1), the solid electrolyte is LLZO, and the D50 value of the particles is 250 - 350 nm. The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0100] Example 6

[0101] The difference from Example 1 is as follows:

[0102] In step 1), the solid electrolyte is Li2ZrF6, and the D50 value of the particles is 250 - 350 nm. The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0103] Example 7

[0104] The difference from Example 1 is as follows:

[0105] In step 1), the solid electrolyte is Li2TiF6, and the D50 value of the particles is 250 - 350 nm. The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0106] Example 8

[0107] The difference from Example 1 is as follows:

[0108] In step 1), the lithium supplement is LiTFSI.

[0109] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0110] Example 9

[0111] The difference from Example 1 is as follows:

[0112] In step 1), the lithium supplement is LiClO4.

[0113] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0114] Example 10

[0115] The difference from Example 1 is as follows:

[0116] In step 1), the lithium supplement is LiPF6.

[0117] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0118] Example 11

[0119] The difference from Example 1 is as follows:

[0120] In step 1), the lithium supplement is Li2C2O4.

[0121] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0122] Example 12

[0123] The difference from Example 1 is as follows:

[0124] In step 1), the dispersant is cetyltrimethoxysilane.

[0125] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0126] Comparative Example 1

[0127] The difference from Example 1 is as follows:

[0128] In step 1), the A slurry does not contain a dispersant (dodecyltrimethoxysilane). The mass ratio of the solid electrolyte (LATP, D50 value of the particles is 250 - 350 nm), the lithium supplement agent (lithium-rich iron ferrite), and the oil-based binder (PVDF K30) is 45:46:8.

[0129] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0130] Comparative Example 2

[0131] The difference from Example 1 is as follows:

[0132] The solid electrolyte (LATP, D50 value of the particles is 250 - 350 nm) is replaced with alumina, and the D50 value of the particles is 250 - 350 nm.

[0133] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0134] Comparative Example 3

[0135] The difference from Example 1 is as follows:

[0136] The lithium supplement agent (lithium-rich iron ferrite) is replaced with alumina.

[0137] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0138] Comparative Example 4

[0139] The difference from Example 1 is as follows:

[0140] In step 1), the A slurry does not contain a lithium supplement agent (lithium-rich iron ferrite). The mass ratio of the solid electrolyte (LATP, D50 value of the particles is 250 - 350 nm), the oil-based binder (PVDF K30), and the dispersant (dodecyltrimethoxysilane) is 91:8:1.

[0141] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0142] Comparative Example 5

[0143] The difference from Example 1 is that:

[0144] The D50 value of the solid electrolyte LATP particles is 500 nm.

[0145] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0146] Comparative Example 6

[0147] The difference from Example 1 is that:

[0148] In step 1), the mass ratio of the solid electrolyte (LATP, with the D50 value of the particles being 250 - 350 nm), the lithium supplement agent (lithium-rich iron ferrite), the oil-based binder (PVDF K30), and the dispersant (dodecyltrimethoxysilane) is 60:31:8:1.

[0149] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0150] Comparative Example 7

[0151] The difference from Example 1 is that:

[0152] In step 1), the mass ratio of the solid electrolyte (LATP, with the D50 value of the particles being 250 - 350 nm), the lithium supplement agent (lithium-rich iron ferrite), the oil-based binder (PVDF K30), and the dispersant (dodecyltrimethoxysilane) is 30:61:8:1.

[0153] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0154] Comparative Example 8

[0155] The difference from Example 1 is that:

[0156] In step 1), the mass ratio of the solid electrolyte (LATP, with the D50 value of the particles being 250 - 350 nm), the lithium supplement agent (lithium-rich iron ferrite), the oil-based binder (PVDF K30), and the dispersant (dodecyltrimethoxysilane) is 48:48:3:1.

[0157] The remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0158] Comparative Example 9

[0159] The difference from Example 1 is that:

[0160] In Step 1), the mass ratio of the solid electrolyte (LATP, D50 value of the particles is 250 - 350 nm), the lithium supplement agent (lithium-rich lithium ferrite), the oil-based binder (PVDF K30), and the dispersant (dodecyltrimethoxysilane) is 44:44:8:4.

[0161] All the remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0162] Comparative Example 10

[0163] Replace the lithium supplement agent (lithium-rich lithium ferrite) with lithium bis(trifluoromethanesulfonyl)imide.

[0164] All the remaining steps are the same as those in Example 1, and a soft-pack battery is obtained.

[0165] The performance of the insulating coatings of Examples 1 - 12 and Comparative Examples 1 - 10 was tested, and the results are shown in Table 1.

[0166] Among them, the electric breakdown strength test is the withstand voltage test (Hi-pot). The test equipment is a Hioki 7470 withstand voltage tester. The current uses alternating current, and the implementation time is 1 min to test the insulation of the solid electrolyte insulating coating.

[0167] Detection of coating uniformity: Use EDS energy spectrum to scan the titanium or halogen element (one of the unique elements of the solid electrolyte) on the cross-section of the solid electrolyte insulating coating, denoted as A1; and iron, fluorine or carbon (one of the unique elements of the lithium supplement agent), denoted as A2. The ratio of A1:A2 in any 5 nm × 5 nm area is X1, and the ratio of A1:A2 in another 5 nm × 5 nm area is X2; the uniformity is the absolute value of (X1 - X2) / (X1 + X2).

[0168] The performance of the soft-pack batteries prepared in Examples 1 - 12 and Comparative Examples 1 - 10 was tested, and the results are shown in Table 1.

[0169] At 25 °C, charge the soft-pack batteries prepared in each example and comparative example with a current of 0.5C (C is the nominal capacity of the battery, 0.5C means the charging current is 0.5 times the nominal capacity value). When the battery voltage reaches 3.65V, switch to constant voltage charging until the charging current drops to 0.05C.

[0170] Then, let the battery stand for 30 min to stabilize the electrochemical state inside the battery. After that, discharge with a discharge current of 0.2C until the battery voltage drops to the specified voltage of 2.5V. Record the capacity during the discharge process, and this capacity is the initial capacity C0 of the battery.

[0171] Repeat the above process, and the capacity retention rate = Cn (the Nth test) / C0.

[0172] Table 1 Solid electrolyte insulating layer slurry components and effect data

[0173]

[0174]

[0175] It can be seen from Table 1 that:

[0176] In Comparative Example 1, no dispersant was used, resulting in insufficient uniformity of the two-component dispersion. As a result, the active lithium ions in lithium-rich lithium ferrite could not effectively utilize the ion transport network formed by the solid electrolyte to conduct lithium ions, affecting the optimization of the cycle performance.

[0177] In Comparative Example 2, alumina was used as the oxide solid electrolyte, resulting in poor lithium ion transport paths for lithium-rich lithium ferrite.

[0178] In Comparative Example 3, alumina was used as the lithium supplement agent. Although the insertion and extraction of lithium ions during charge and discharge were buffered by part of the solid electrolyte, improving the preservation amount of active lithium and the cycle performance, and optimizing the cycle compared to Comparative Example 4, the battery capacity retention rate was poor because there was no lithium ion supplement.

[0179] In Comparative Example 4, the conventional alumina scheme was used entirely, without the effect of lithium supplementation and the buffering effect on lithium ions, resulting in excessive lithium precipitation, reduction of active lithium, and reduction of cycle retention rate.

[0180] In Comparative Example 5, the material used had relatively large particles, large voids in the packing density, insufficient packing, and insufficient breakdown voltage of the coating.

[0181] In Comparative Example 6, less lithium supplement agent was used, resulting in insufficient supplementation of the subsequent loss of active lithium and poor cycle performance.

[0182] In Comparative Example 7, more lithium supplement agent was used. During subsequent cycles, the lithium supplement agent released lithium ions, resulting in size changes, leading to changes in the packing density of the coating and insufficient breakdown voltage.

[0183] In Comparative Example 8, the binder was insufficient, resulting in the shedding of the insulating coating during the battery production process.

[0184] In Comparative Example 9, an excessive amount of highly compatible dispersant was added, and the side reactions caused by the relevant functional groups in the dispersant became larger, affecting the effect.

[0185] In Comparative Example 10, lithium bis(trifluoromethanesulfonyl)imide was used as the lithium supplement agent. As an organic lithium supplement agent with a relatively complex structure and elements, its molecular weight was too large, and the proportion of lithium element under the unit addition amount was relatively low compared to the lithium supplement agent in the examples. Although it could play a role in lithium supplementation, the relative amount of lithium supplementation was small. Therefore, after cycling, the capacity retention rate was relatively poor compared to other lithium supplement agents.

[0186] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A solid electrolyte insulating coating is prepared from a slurry comprising a solid electrolyte, a lithium supplement agent, an oil-based binder, a dispersant, and N-methylpyrrolidone; The solid electrolyte is an oxide solid electrolyte or a halide solid electrolyte; The oil-based binder is polyvinylidene fluoride.

2. The solid electrolyte insulating coating according to claim 1, characterized in that The mass ratio of the solid electrolyte, the lithium supplement agent, the oil-based binder, and the dispersant is 40-50: 40-50: 5-10: 1-3.

3. The solid electrolyte insulating coating according to claim 1, wherein The oxide solid electrolyte includes at least one of lithium aluminum titanium phosphate, lithium lanthanum titanate, and lithium lanthanum zirconate; the halide solid electrolyte includes at least one of Li2ZrF6, Li3ZrCl6, Li4ZrF8, and Li2TiF6.

4. The solid electrolyte insulating coating according to claim 1, wherein The D50 value of the solid electrolyte particles is 250-350 nm.

5. The solid electrolyte insulating coating according to claim 1, wherein The lithium supplement agent includes at least one of lithium-rich lithium ferrate, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium hexafluorophosphate, and lithium oxalate.

6. The solid electrolyte insulating coating according to claim 1, wherein The oil-based binder is PVDF K30.

7. The solid electrolyte insulating coating according to claim 1, wherein The solid content of the slurry is 35%-45%.

8. A positive electrode plate, comprising: A positive electrode current collector; An active material coating formed on one side of the positive electrode current collector; A solid electrolyte insulating coating formed on the edge of the active material coating; The solid electrolyte insulating coating is the solid electrolyte insulating coating according to any one of claims 1-7.

9. The positive electrode sheet according to claim 8, characterized in that, The active material coating is prepared from a slurry comprising lithium iron phosphate, SP, polyvinylidene fluoride, and N-methylpyrrolidone; The mass ratio of the lithium iron phosphate, SP, polyvinylidene fluoride, and N-methylpyrrolidone is 48-50: 0.5～1.5：1～3：47～49。 10. The positive electrode sheet according to claim 8, characterized in that, The thickness of the active material coating is 247 μm or more.

11. The positive electrode sheet according to claim 8, characterized in that, The thickness of the solid electrolyte insulating coating is 2-8 μm; the width is 5-20 mm.

12. The positive electrode sheet according to claim 8, characterized in that, The width of the overlap between the solid electrolyte insulating coating and the active material coating is 0-1.5 mm.

13. A lithium-ion battery, wherein the positive electrode of the lithium-ion battery is the positive electrode plate according to any one of claims 8-12.

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