Preparation method of positive pole piece, positive pole piece and lithium battery

Abstract

The invention discloses a preparation method of a positive pole piece, the positive pole piece and a lithium battery, and the preparation method comprises the following steps: providing a positive current collector, adding a binder into a solvent, and fully dissolving to obtain bonding glue; adding a conductive agent into the adhesive glue, and uniformly stirring to obtain first slurry; adding a ternary positive electrode material into the first slurry, and uniformly stirring to obtain second slurry; adding Mg0. 5Ti2 (PO4) 3 and a dispersing agent into the second slurry, and uniformly stirring to obtain positive electrode slurry; and coating at least one side of a positive current collector along the thickness direction with the positive slurry, and drying to form a composite coating on the surface of the positive current collector, thereby obtaining the positive pole piece. The preparation method of the positive pole piece provided by the invention comprises the following steps: adding Mg0. 5Ti2 (PO4) 3, an adhesive, a conductive agent, a ternary positive pole material and a dispersing agent to prepare positive pole slurry coated on a positive pole current collector; and meanwhile, a high-temperature means is not used, so that the energy consumption is low, the safety coefficient is high, and the structural damage of high-temperature sintering to the ternary positive electrode material is avoided.

Description

TECHNICAL FIELD

[0001] The application relates to the field of new energy sources, in particular to a preparation method of a positive pole piece, the positive pole piece and a battery. BACKGROUND

[0002] The energy density, market price, safety factor and other problems of a lithium ion battery seriously affect the development of a new energy vehicle market. A high-nickel layered nickel-cobalt-manganese (NCM) ternary positive electrode material LiNixCoyMnzO2 is widely researched due to its high specific capacity and low cost. However, problems such as surface lithium compound residues, transition metal mixing, oxygen evolution reaction (OER), phase change in the cycle process, side reaction of the electrode / electrolyte interface, transition metal dissolution, microcracks and secondary particle crushing hinder the commercialization process.

[0003] During the material synthesis stage and the charging and discharging process of the NCM ternary positive electrode material, cation mixing is prone to occur. During the sintering process of the high-nickel ternary material, Ni 2+ is difficult to be completely oxidized into Ni 3+ . The radius of Ni 2+ ion is 0.069 nm, and the radius of Li + ion is 0.076 nm, and the radii of the two ions are similar. Part of the Ni 2+ existing in the material may migrate from the transition metal layer in the layered structure to the Li layer, and at the same time, Li + may also enter the transition metal layer, and both of them occupy each other's sites to cause Li + / Ni 2+ mixing. During the charging and discharging process, Li + is detached from the material interlayer, and a large number of vacancies are generated, and part of the Ni 2+ may spontaneously migrate to the Li layer to occupy the position of Li+. The radius of the Ni 2+ in the Li layer is smaller than the radius of Li + , thereby reducing the interlamellar sheet thickness, and being oxidized into Ni 3+ or Ni 4+ during charging, causing local collapse of the interlamellar sheet space, increasing the difficulty of Li + insertion during discharging, and reducing the reversible capacity of the material. Excessive Ni 2+ occupying the Li layer will exacerbate the transformation of the layered structure to the spinel structure or even the rock salt phase structure, causing serious capacity attenuation. Li +The transition metal layer will expand the main wafer thickness and be difficult to de-embed, which will deteriorate the electrochemical performance of the material. In simple terms, in the layered structure of the ternary material, nickel forms a framework that can embed lithium ions. When the battery is charged, lithium ions are de-embedded from the positive electrode and leave space, so nickel ions take the place of lithium ions. When lithium ions return to the positive electrode during the discharge process, they run to the space originally belonging to nickel because their original space has been occupied, and thus nickel-lithium mixing occurs. In ternary positive electrode materials, maintaining a suitable Li + / Ni 2+ ratio, i.e. low mixing degree and complete layered structure, is the key to improving the electrochemical performance of high-nickel NCM materials. However, if the chain reaction of nickel-lithium mixing occurs, the layered structure will collapse, resulting in chaos at the micro level, and the macro result is that the battery cycle life is shortened, the battery capacity is reduced, and even safety hazards occur. The prior art uses titanium magnesium phosphate to coat high-nickel ternary or lithium-rich manganese-based positive electrode materials, and the specific method is: putting high-nickel ternary positive electrode into titanium magnesium phosphate gel and then drying and sintering at high temperature to obtain coated ternary materials, which improve the specific capacity and other electrical properties. However, the unevenness of the coating and the poor adhesion of the coating affect the instability of the battery electrical performance, and the coated product is prone to fall off during subsequent slurry processing and stirring. SUMMARY

[0004] The technical problem to be solved by the embodiments of the present application is to provide a preparation method of a positive electrode sheet, a positive electrode sheet and a lithium battery, which can provide a preparation method with simple process and low energy consumption, and the prepared positive electrode sheet can improve the safety performance of the lithium battery while achieving good electrical performance.

[0005] To solve the above technical problems, the present application provides a preparation method of a positive electrode sheet, which comprises: providing a positive electrode current collector; adding a binder to a solvent, dissolving sufficiently to obtain a bonding glue; adding a conductive agent to the bonding glue, stirring uniformly to obtain a first slurry; adding a ternary positive electrode material to the first slurry, stirring uniformly to obtain a second slurry; adding Mg 0.5 Ti2(PO4)3 and a dispersing agent to the second slurry, stirring uniformly to obtain a positive electrode slurry; coating the positive electrode slurry on at least one side of the positive electrode current collector in the thickness direction, and forming a composite coating on the surface of the positive electrode current collector after drying to obtain a positive electrode sheet.

[0006] In a feasible implementation manner, the binder is selected from at least one of PVDF HSV900 and PVDF5130;

[0007] The conductive agent is selected from at least one of carbon nanotubes, conductive carbon black, conductive graphite, nanocarbon fibers, and graphene.

[0008] The ternary positive electrode material is selected from at least one of NCM811, NCM622, and NCM523.

[0009] The dispersant is selected from at least one of sodium methylene diphthalate, linear alkyl benzene sulfonate, sodium dodecyl succinate, sodium dodecyl sulfate, alkyl phenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, polyoxyethylene fatty acid ester, titanate, maleic anhydride, methacrylic acid, vinyl pyrrolidone, and propylene oxide.

[0010] In a feasible implementation, the conductive agent accounts for 0.1-10% of the mass of the composite coating; the Mg 0.5 Ti2(PO4)3 accounts for 0.1-5% of the mass of the composite coating; the ternary positive electrode material accounts for 94-98% of the mass of the composite coating; the binder accounts for 0.1-8% of the mass of the composite coating; and the dispersant accounts for 0.1-3% of the mass of the composite coating.

[0011] In a feasible implementation, the positive electrode current collector is an aluminum foil, the thickness of the aluminum foil is 5 μm-30 μm, and the thickness of the composite coating is 100 μm-300 μm.

[0012] In a feasible implementation, the solvent is N-methyl pyrrolidone, and the solid content percentage in the positive electrode slurry is 40%-70%.

[0013] In a feasible implementation, the Mg 0.5 The particle size D50 of Ti2(PO4)3 is 0.1 μm-5 μm.

[0014] In a feasible implementation, the environment for preparing the positive electrode sheet has a dew point lower than -50°C.

[0015] In a feasible implementation, the preparation method further includes adjusting the viscosity of the positive electrode slurry to 3000 cps-6000 cps.

[0016] Correspondingly, the application also provides a positive electrode sheet prepared by the above preparation method.

[0017] Correspondingly, the application also provides a lithium battery including the above positive electrode sheet.

[0018] The application has the following beneficial effects:

[0019] The preparation method of the positive electrode sheet provided by the application adds Mg 0.5Ti2(PO4)3, binder, conductive agent, ternary positive electrode material and dispersant are used to prepare a positive electrode slurry coated on a positive electrode current collector; the electrical performance of the positive electrode sheet is effectively improved, on the other hand, high-temperature means is not used, the energy consumption is low, the safety factor is high, meanwhile, the structure damage of the ternary positive electrode material caused by high-temperature sintering is avoided, which is conducive to wide application. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a flowchart of a preparation method of a positive electrode sheet provided by the embodiment of the present application. DETAILED DESCRIPTION

[0021] In order to make the above objectives, characteristics and advantages of the present application more apparent, specific embodiments of the present application are described in detail below with reference to the accompanying drawings. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many different ways other than the ways described herein, and those skilled in the art can make similar improvements without departing from the scope of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0023] The embodiment of the present application provides a preparation method of a positive electrode sheet. Figure 1 The preparation method of the positive electrode sheet comprises the following steps:

[0024] S110, providing a positive electrode current collector.

[0025] In a feasible implementation, the positive electrode current collector is an aluminum foil.

[0026] In a feasible implementation, the thickness of the positive electrode current collector aluminum foil is 5 μm to 30 μm. Alternatively or preferably, the thickness of the positive electrode current collector aluminum foil is 5 μm to 25 μm.

[0027] S120, adding a binder to a solvent and sufficiently dissolving to obtain a bonding glue.

[0028] In an implementable embodiment, the binder is selected from at least one of PVDF HSV900 and PVDF5130. The binder is selected from PVDF HSV900 and PVDF5130, and the selection of the two binders is conducive to the sufficient dispersion of the binder in the solvent, which is conducive to the adhesion effect of the binder, and the final positive electrode slurry is uniform in texture and stable in structure, which is conducive to the stability, safety and service life of the battery prepared therefrom.

[0029] In an implementable embodiment, the solvent is N-methyl pyrrolidone. N-methyl pyrrolidone is selected as the solvent, on the one hand, N-methyl pyrrolidone can sufficiently dissolve the binder and the subsequent additives, which is conducive to the uniformity of the slurry; on the other hand, N-methyl pyrrolidone has good volatility, which is conducive to removal, can shorten the volatilization time, and reduce the unsafe factors caused by solvent residues.

[0030] In an implementable embodiment, the operation of adding the binder to the solvent can be carried out in a stirring device. For example, the solvent is first added to the stirring device, and then the binder is added to the stirring device while stirring, and the stirring rate is 1500 rpm, which is conducive to uniform mixing and can avoid the generation of air bubbles caused by excessive stirring.

[0031] S130, adding a conductive agent to the bonding glue obtained in S120 and stirring uniformly to obtain a first slurry.

[0032] In an implementable embodiment, the conductive agent is selected from at least one of carbon nanotubes, conductive carbon black, conductive graphite, nano carbon fiber and graphene.

[0033] In an implementable embodiment, the operation of adding the conductive agent to the bonding glue obtained in S130 is that the conductive agent is first mixed uniformly with part of the solvent and then added to the bonding glue.

[0034] S140, adding a ternary positive electrode material to the first slurry obtained in S130 and stirring uniformly to obtain a second slurry.

[0035] In an implementable embodiment, the ternary positive electrode material is selected from at least one of NCM811, NCM622 and NCM523.

[0036] In an implementable embodiment, the particle size D50 of the ternary positive electrode material is 0.1-5 μm. The ternary positive electrode material with such a particle size is conducive to sufficient dispersion and is further surrounded by the subsequent additives, which has a better surrounding effect.

[0037] S150, adding Mg 0.5Ti2(PO4)3and dispersant are added into the second slurry obtained from S140, stirred uniformly to obtain the positive electrode slurry.

[0038] In an embodiment, Mg 0.5 The particle size D50 of Ti2(PO4)3is 0.1 μm-5 μm. Alternatively or preferably, Mg 0.5 The particle size D50 of Ti2(PO4)3is 0.1 μm-4 μm. The Mg 0.5 Ti2(PO4)3is beneficial to be fully dispersed in the positive electrode slurry, so as to fully surround the ternary positive electrode material.

[0039] In an embodiment, the dispersant is selected from at least one of sodium methylene bisbenzene sulfonate, linear alkyl benzene sulfonate, sodium dodecyl succinate, sodium dodecyl sulfate, alkyl phenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, polyoxyethylene fatty acid ester, titanate, maleic anhydride, methacrylic acid, vinyl pyrrolidone and propylene oxide. Alternatively or preferably, the dispersant is selected from at least one of sodium methylene bisbenzene sulfonate, linear alkyl benzene sulfonate, sodium dodecyl succinate, sodium dodecyl sulfate, alkyl phenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, polyoxyethylene fatty acid ester, titanate, maleic anhydride, methacrylic acid, vinyl pyrrolidone and propylene oxide.

[0040] In an embodiment, Mg 0.5 The operation of adding Ti2(PO4)3and dispersant into the second slurry obtained from S140 can be sequentially adding Mg 0.5 Ti2(PO4)3and dispersant are first mixed uniformly and then added into the second slurry. This is beneficial to Mg 0.5 The sufficient dispersion of Ti2(PO4)3in the second slurry is beneficial to the uniformity of the positive electrode slurry.

[0041] In an embodiment, the solid content percentage in the positive electrode slurry is 40%-70%. Alternatively or preferably, the solid content percentage in the positive electrode slurry is 45%-65%.

[0042] In an embodiment, the environment dew point for preparing the positive electrode sheet is lower than -50°C.

[0043] In an embodiment, the preparation method further comprises adjusting the viscosity of the positive electrode slurry to 3000 cps-6000 cps. The positive electrode slurry with such viscosity is beneficial to coating, more uniform coating and wide application. Alternatively or preferably, the viscosity of the positive electrode slurry can be adjusted to 3000 cps-5000 cps. Alternatively or preferably, the viscosity of the positive electrode slurry can be adjusted to 3500 cps-5000 cps.

[0044] S160, coating the positive electrode slurry obtained in S150 on at least one side of the positive electrode current collector obtained in S110 along the thickness direction, and forming a composite coating on the surface of the positive electrode current collector after drying to obtain a positive electrode sheet.

[0045] In an embodiment, the thickness of the composite coating is 100-300 μm. Alternatively or preferably, the thickness of the composite coating is 150-300 μm. When the thickness of the composite coating is in this range, the performance of the positive electrode sheet is optimal.

[0046] In an embodiment, the positive electrode slurry obtained in S150 can be coated on one side of the positive electrode current collector obtained in S110 along the thickness direction, or the positive electrode slurry obtained in S150 can be coated on both sides of the positive electrode current collector obtained in S110 along the thickness direction.

[0047] In an embodiment, the operation of coating the positive electrode slurry obtained in S150 on at least one side of the positive electrode current collector obtained in S110 along the thickness direction can be performed by screen printing, doctor blading, gravure transfer, spraying, etc.

[0048] In an embodiment, the method for preparing the positive electrode sheet can further comprise coating the positive electrode slurry on the positive electrode current collector, and then performing drying, rolling, slitting, cutting, etc. to obtain the positive electrode sheet.

[0049] A composite ternary positive electrode coating positive electrode sheet and a battery are provided. The ternary material is not sintered in a large amount of energy, and the titanium magnesium phosphate is uniformly distributed around the high-nickel ternary material. The transition metal mixing and oxygen evolution of the ternary material are inhibited, and the cycle performance and safety performance of the lithium battery are greatly improved.

[0050] In an embodiment, the conductive agent accounts for 0.1-10% of the mass of the composite coating.

[0051] The Mg 0.5 The Ti2(PO4)3 accounts for 0.1-5% of the mass of the composite coating.

[0052] The ternary positive electrode material accounts for 94-98% of the mass of the composite coating.

[0053] The binder accounts for 0.1-8% of the mass of the composite coating.

[0054] The dispersant accounts for 0.1-3% of the mass of the composite coating.

[0055] Correspondingly, the application also provides a positive electrode sheet prepared by the above method.

[0056] Correspondingly, the application also provides a battery comprising the positive electrode sheet.

[0057] The technical scheme of the application has the following advantages:

[0058] 1. The preparation method of the positive electrode sheet provided by the application adds Mg 0.5 Ti2(PO4)3, an adhesive, a conductive agent, a ternary positive electrode material, and a dispersing agent to prepare a positive electrode slurry coated on a positive electrode current collector; the electrical performance of the positive electrode sheet is effectively improved, high-temperature means is not used, energy consumption is low, the safety factor is high, and the structural damage of the ternary positive electrode material caused by high-temperature sintering is avoided, which is conducive to wide application;

[0059] 2. The preparation method of the positive electrode sheet provided by the application controls the ratio relationship between the components, so that Mg 0.5 Ti2(PO4)3 is uniformly dispersed around the ternary positive electrode material to form a coating-like effect, which avoids the electrical effect of coating and avoids the structural collapse and other safety hazards caused by high-temperature coating means, thereby improving the safety performance of the lithium battery.

[0060] 3. The preparation method of the positive electrode sheet provided by the application provides appropriate condition parameters and raw material sources, so that the adhesion effect between the prepared positive electrode slurry and the positive electrode current collector is good, the bonding force is stable and durable, interface separation and active material layer powdering are less likely to occur during long-term cycling of the lithium ion battery, and the cycle life of the lithium battery is improved.

[0061] 4. The positive electrode sheet provided by the application has good electrical performance and a high safety factor.

[0062] With reference to the above implementation content, in order to make the technical scheme of the application more specific, clear, and easy to understand, the technical scheme of the application will be exemplified, but it should be noted that the content to be protected by the application is not limited to the following examples.

[0063] Example 1

[0064] 3 grams of PVDF5130 were added to 200 grams of N-methyl pyrrolidone, and stirred at 1500 rpm until the polymer solution became transparent and particle-free, to obtain a bonding glue;

[0065] 4 grams of SUPER Li were added to the bonding glue, and stirred at 2000 rpm until uniform, to obtain a first slurry;

[0066] 288 grams of NCM811 were added to the first slurry, and stirred at 3600 rpm until uniformly dispersed into a particle-free fluid, to obtain a second slurry;

[0067] 0.6 grams of vinyl pyrrolidone and 12 grams of 700 nm Mg0.5 Ti2(PO4)3, 4000 rpm stirring until evenly dispersed, to obtain the positive electrode slurry;

[0068] Add 5 grams of N-methyl pyrrolidone to the positive electrode slurry to adjust the viscosity of the positive electrode slurry to 4800CPS,

[0069] The prepared positive electrode slurry is uniformly coated on both sides of the 18 μm aluminum foil.

[0070] Example 2

[0071] Add 2 grams of PVDF5130 to 300 grams of N-methyl pyrrolidone and stir at 1500 rpm until the polymer solution is transparent and particle-free, to obtain the bonding glue;

[0072] Add 3 grams of SUPER Li to the bonding glue and stir evenly at 2000 rpm, to obtain the first slurry;

[0073] Add 301.4 grams of NCM811 to the first slurry and stir at 3600 rpm until evenly dispersed into a particle-free fluid, to obtain the second slurry;

[0074] Add 0.6 grams of vinyl pyrrolidone and 9.2 grams of 700 nm Mg 0.5 Ti2(PO4)3, 3800 rpm stirring until evenly dispersed, to obtain the positive electrode slurry;

[0075] Add 16.2 grams of N-methyl pyrrolidone to the positive electrode slurry to adjust the viscosity of the positive electrode slurry to 4000CPS,

[0076] The prepared positive electrode slurry is uniformly coated on both sides of the 18 μm aluminum foil.

[0077] Example 3

[0078] Add 4 grams of PVDF5130 to 448 grams of N-methyl pyrrolidone and stir at 1500 rpm until the polymer solution is transparent and particle-free, to obtain the bonding glue;

[0079] Add 5 grams of SUPER Li to the bonding glue and stir evenly at 2000 rpm, to obtain the first slurry;

[0080] Add 289.2 grams of NCM811 to the first slurry and stir at 3600 rpm until evenly dispersed into a particle-free fluid, to obtain the second slurry;

[0081] Add 0.6 grams of vinyl pyrrolidone and 0.32 grams of 700 nm Mg 0.5 Ti2(PO4)3, 3800 rpm stirring until evenly dispersed, to obtain the positive electrode slurry;

[0082] Add 16.2 grams of N-methyl pyrrolidone to the positive electrode slurry to adjust the viscosity of the positive electrode slurry to 3200CPS,

[0083] The prepared positive electrode slurry is uniformly coated on both sides of an 18 μm aluminum foil.

[0084] Example 4

[0085] Add 3.5 grams of PVDF HSV900 to 488 grams of N-methyl pyrrolidone and stir at 1500 rpm until the polymer dissolves into a particle-free transparent solution to obtain a bonding glue;

[0086] Add 5 grams of CNTs to the bonding glue and stir uniformly at 2000 rpm to obtain a first slurry;

[0087] Add 298 grams of NCM622 to the first slurry and stir at 3600 rpm until it is uniformly dispersed into a particle-free fluid to obtain a second slurry;

[0088] Add 0.6 grams of vinyl pyrrolidone and 3 grams of 500 nm Mg 0.5 Ti2(PO4)3 to the second slurry and continuously stir at 3800 rpm until it is uniformly dispersed to obtain a positive electrode slurry;

[0089] Add 5 grams of N-methyl pyrrolidone to the positive electrode slurry to adjust the viscosity of the positive electrode slurry to 5000CPS,

[0090] The prepared positive electrode slurry is uniformly coated on both sides of an 18 μm aluminum foil.

[0091] Example 5

[0092] Add 3.5 grams of PVDF HSV900 to 448 grams of N-methyl pyrrolidone and stir at 1500 rpm until the polymer dissolves into a particle-free transparent solution to obtain a bonding glue;

[0093] Add 5 grams of GNs to the bonding glue and stir uniformly at 2000 rpm to obtain a first slurry;

[0094] Add 298 grams of NCM622 to the first slurry and stir at 3600 rpm until it is uniformly dispersed into a particle-free fluid to obtain a second slurry;

[0095] Add 0.6 grams of vinyl pyrrolidone and 8 grams of 500 nm Mg 0.5 Ti2(PO4)3 to the second slurry and continuously stir at 3800 rpm until it is uniformly dispersed to obtain a positive electrode slurry;

[0096] 5 grams of N-methyl pyrrolidone was added to the positive electrode slurry to adjust the viscosity of the positive electrode slurry to 5000CPS,

[0097] The prepared positive electrode slurry was uniformly coated on both sides of an 18 μm aluminum foil.

[0098] Comparative Example 1

[0099] The same as Example 1, except that only 0.6 grams of vinyl pyrrolidone was added to the second slurry, and no Mg 0.5 Ti2(PO4)3.

[0100] Performance test:

[0101] The positive electrode sheets obtained in each example and comparative example were made into 5 Ah soft package batteries, with an N / P design of 1.1, a negative electrode of a graphite system, and an aluminum oxide ceramic separator.

[0102] (1) Charge-discharge cycle test: The prepared soft package batteries were respectively placed in a normal temperature condition, 45°C and 60°C environment, and subjected to 500 cycles of charge-discharge cycle test, and the initial discharge capacity (mAh·g-1), the initial charge-discharge efficiency (%), the capacity retention rate at normal temperature after 500 cycles (%), the capacity retention rate at 45°C after 500 cycles (%), and the high-temperature storage recovery rate at 60°C (%) were recorded or calculated, and the test results are shown in Table 1.

[0103] (2) Thermal abuse test: The prepared soft package batteries were subjected to thermal abuse test, and the thermal abuse pressure drop (mV) and the overcharge temperature difference (°C) were recorded, and the test results are shown in Table 2.

[0104] Table 1: Charge-discharge cycle test results

[0105]

[0106] Table 2: Thermal abuse test results:

[0107]

[0108] From the test results in Tables 1 and 2, it can be seen that the electrical performance test and thermal abuse test results of the soft package batteries prepared from the positive electrode sheets provided by Examples 1-8 are better than those of the soft package batteries prepared from the positive electrode sheets provided by Comparative Examples 1-4, that is, the positive electrode sheets prepared by the preparation method provided in the present application have good electrical performance and high safety performance. Specifically, the positive electrode sheet prepared in Example 1 has the best electrical performance.

[0109] Having now described the basic concept, it will be apparent to those skilled in the art that many modifications, adaptations, and variations of the specific embodiments described can be used, and that equivalents can be substituted, without departing from the true spirit and scope of the disclosure. Accordingly, the disclosure is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and scope of the disclosure. Although specific adaptations, modifications, and variations are described above, other adaptations, modifications, and variations are possible. Specifically, it is contemplated that to practice the embodiments described above, other components, adaptations, modifications, and variations can be used. For example, the above description describes a number of specific embodiments of the present disclosure as implemented in a specific environment. However, one skilled in the art will recognize that the embodiments described above can be practiced with other components, adaptations, modifications, and variations. For example, the above description describes a number of specific embodiments of the present disclosure as implemented in a specific environment. However, one skilled in the art will recognize that the embodiments described above can be practiced with other components, adaptations, modifications, and variations. Accordingly, the disclosure is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and scope of the disclosure.

[0110] Also, the use of "a" or "an" to describe elements, items or components can be taken to mean one or more unless explicitly stated to the contrary. Additionally, the use of "comprise", "comprises", "comprising", "containing", "contains", "contained", "including", "includes", "included", "contain" or variations thereof are used to indicate, in open-closed terms, that an element, item, or component can or does comprise, include, or contain one or more of the recited elements, items, or components, and any combinations thereof. Also, the terms "plurality" and "a plurality" are used to indicate that there is more than one of the elements, items, or components being described.

[0111] In addition, the order of presentation of the treatment elements and sequences, use of the numerals, or use of other designations in the description of the present disclosure is not intended to be limiting of the order of the processes and methods of the present disclosure. Although the above disclosure discusses some presently preferred embodiments of the application, it is to be understood that numerous additions, modifications, and deletions can be made to the above-described embodiments without departing from the spirit and scope of the disclosure. Accordingly, it is intended that all such additions, modifications, and deletions be within the scope of the claims.

[0112] Similarly, it is noted that the use of particular language when describing the embodiments should not be taken to indicate that such language is inappropriate. The use of the articles "a" and "an" are to be taken in their inclusive, not their exclusive, sense to mean that a plurality of the elements to which the articles refer can exist. Additionally, the use of the singular is also taken to include the plural unless specifically stated otherwise. Furthermore, to the extent that the terms "including", "includes", "having", "has", "with", or variants thereof to be taken to mean that there are no additional elements other than the recited elements, it is noted that additional elements can or can not be present other than the claimed elements. Additionally, it is noted that the terms "comprising", "comprises", "including", "includes", "containing", "contains", "having", "has", "with", or variants thereof do not exclude additional elements. Additionally, the terms "coupled", "coupling", "connected", "connecting", or variants thereof are used to describe both an indirect and direct electrical or mechanical connection between two elements and can mean that intervening elements can or can not be present. Furthermore, the term "operatively coupled" is used to describe that a first element can be coupled to a second element either directly or indirectly via one or more intervening elements, and can mean that additional elements can or can not be present. In other words, the direct or indirect connection between the first element and the second element can include one or more intervening elements. Furthermore, the term "operatively connected" is used to describe that a first element can be connected to a second element either directly or indirectly via one or more intervening elements, and can mean that additional elements can or can not be present. In other words, the direct or indirect connection between the first element and the second element can include one or more intervening elements.

[0113] In some embodiments, numbers are used to describe the quantity of components and attributes. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise stated, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the description and claims are approximate values, which may change according to the required characteristics of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of this specification are approximate values, in specific embodiments, the settings of such numerical values ​​are as accurate as possible within the feasible range.

[0114] Each patent, patent application, patent application publication, and other materials, such as articles, books, specifications, publications, and documents, cited in this specification is hereby incorporated by reference in its entirety. This includes application history documents that are inconsistent with or conflict with the content of this specification, as well as documents (currently or subsequently attached to this specification) that limit the broadest scope of the claims of this specification. It should be noted that if the descriptions, definitions, and / or terminology used in the accompanying materials are inconsistent or conflicting with the content of this specification, the descriptions, definitions, and / or terminology used in this specification will control.

[0115] Finally, it should be understood that the embodiments described in this specification are intended only to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, by way of example and not limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly described and illustrated in this specification.

Claims

1. A method for preparing a positive electrode sheet, characterized in that: The preparation method comprises: providing a positive electrode current collector, Adding the adhesive to the solvent and fully dissolving it to obtain adhesive glue; Adding a conductive agent to the adhesive solution and stirring evenly to obtain a first slurry; Adding the ternary cathode material to the first slurry and stirring evenly to obtain a second slurry; Add Mg 0.5 Ti2(PO4)3 and a dispersant are added to the second slurry and stirred to obtain a positive electrode slurry; The positive electrode slurry is coated on at least one side of the positive electrode current collector along the thickness direction, and after drying, a composite coating is formed on the surface of the positive electrode current collector to obtain a positive electrode sheet.

2. The preparation method according to claim 1, characterized in that The binder is selected from at least one of PVDF HSV900 and PVDF5130; The conductive agent is selected from at least one of carbon nanotubes, conductive carbon black, conductive graphite, nanocarbon fibers, and graphene; The ternary positive electrode material is selected from at least one of NCM811, NCM622 and NCM523; The dispersant is selected from at least one of sodium methylene dibenzene sulfonate, linear alkylbenzene sulfonate, sodium dodecyl succinate, sodium dodecyl sulfate, alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, polyoxyethylene fatty acid ester, titanate, maleic anhydride, methacrylic acid, vinyl pyrrolidone and propylene oxide.

3. The preparation method according to claim 1, characterized in that The conductive agent accounts for 0.1-10% of the composite coating mass; The Mg 0.5 Ti2(PO4)3 accounts for 0.1-5% of the composite coating mass; The ternary cathode material accounts for 94-98% of the composite coating mass; The binder accounts for 0.1-8% of the composite coating mass; The dispersant accounts for 0.1-3% of the mass of the composite coating.

4. The preparation method according to claim 1, characterized in that The positive electrode current collector is aluminum foil, the thickness of the aluminum foil is 5 μm to 30 μm, and the thickness of the composite coating is 100 μm to 300 μm.

5. The preparation method according to claim 1, characterized in that The solvent is N-methylpyrrolidone, and the solid content percentage in the positive electrode slurry is 40%-70%.

6. The preparation method according to claim 1, characterized in that The Mg 0.5 The particle size D50 of Ti2(PO4)3 is 0.1μm to 5μm.

7. The preparation method according to claim 1, characterized in that The dew point of the environment used to prepare the positive electrode sheet is lower than -50°C.

8. The preparation method according to claim 1, characterized in that The preparation method further includes adjusting the viscosity of the positive electrode slurry to 3000 cps-6000 cps.

9. A positive electrode plate, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. A lithium battery, characterized in that: Comprising the positive electrode sheet as claimed in claim 9.

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