Cathode material composition, cathode electrode sheet and preparation method thereof, battery and electric device

Abstract

The application provides a positive electrode material composition, a positive electrode plate, a preparation method of the positive electrode plate, a battery and an electric device. The positive electrode material composition comprises a positive electrode active material and an optional positive electrode conductive agent. The positive electrode active material comprises a core part and a shell part on at least part of the surface of the core part. The core part comprises a lithium-containing phosphate, and the shell part comprises a carbon material. The graphitization degree of the positive electrode active material is g1, the mass percentage of the positive electrode conductive agent in the positive electrode material composition is w1, and 10%≤g1≤50% and 0%≤w1≤1%. The battery of the application can balance high energy density and good rate performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and particularly relates to a positive electrode material composition, a positive electrode sheet, a preparation method thereof, a battery, and an electric device. BACKGROUND

[0002] In recent years, batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the application and promotion of batteries, their safety performance has attracted more and more attention. Lithium-containing phosphates represented by lithium iron phosphate have become one of the most concerned positive electrode active materials due to their advantages such as good safety performance, low price and abundant raw material sources. However, the energy density of batteries using lithium-containing phosphates is low and the rate performance is poor. SUMMARY

[0003] The purpose of the present application is to provide a positive electrode material composition, a positive electrode sheet, a preparation method thereof, a battery, and an electric device, which can make the battery have high energy density and good rate performance.

[0004] The first aspect of the embodiments of the present application provides a positive electrode material composition, comprising a positive electrode active material and optionally a positive electrode conductive agent, wherein the positive electrode active material comprises a core part and a shell part located on at least a part of the surface of the core part, the core part comprises a lithium-containing phosphate, and the shell part comprises a carbon material, the graphitization degree of the positive electrode active material is denoted as g1, the mass percentage content of the positive electrode conductive agent in the positive electrode material composition is denoted as w1, and 10%≤g1≤50% and 0%≤w1≤1%.

[0005] The inventors have found that when the graphitization degree of the positive electrode active material is 10%-50% and the mass percentage content of the positive electrode conductive agent in the positive electrode material composition is 0%-1%, the battery can have high energy density and good rate performance. Although the mechanism is not clear, the inventors believe that at this time the migration speed of lithium ions and electrons can be well matched, thereby reducing the battery polarization and the battery internal resistance, so that the battery has good rate performance. At the same time, at this time the reaction rate of the positive electrode is easy to match the reaction rate of the negative electrode, thereby avoiding the problems such as the excessive accumulation of lithium ions on the negative electrode side during charging, the increase of the viscosity of the electrolyte on the negative electrode side, the slow lithium ion transport, and the increase of the battery polarization. In addition, after the amount of the positive electrode conductive agent is reduced, the amount of the lithium-containing phosphate can be higher, thereby also making the battery have high energy density.

[0006] In any embodiment of the present application, 15%≤g1≤48% and 0%≤w1≤0.8%.

[0007] In any embodiment of the present application, 15%≤g1≤48% and 0%≤w1≤0.6%.

[0008] In any embodiment of the present application, 15%≤g1≤48% and 0%≤w1≤0.4%.

[0009] In any embodiment of the present application, 20%≤g1≤45% and 0%≤w1≤0.6%.

[0010] In any embodiment of the present application, 20%≤g1≤45% and 0%≤w1≤0.4%.

[0011] In any embodiment of the present application, 20%≤g1≤45% and 0%≤w1≤0.2%.

[0012] In any embodiment of the present application, 25%≤g1≤50% and 0%≤w1≤0.2%.

[0013] In any embodiment of the present application, 25%≤g1≤50% and w1 is 0%.

[0014] In any embodiment of the present application, 25%≤g1≤40% and w1 is 0%.

[0015] In any embodiment of the present application, 25%≤g1≤35% and w1 is 0%.

[0016] By further adjusting the graphitization degree g1 of the positive electrode active material and the mass percentage content w1 of the positive electrode conductive agent, the amount of the positive electrode conductive agent can be further reduced without affecting the rate performance of the battery, so that the energy density of the battery can be further improved.

[0017] In any embodiment of the present application, the graphitization degree g1 of the positive electrode active material is obtained by X-ray diffraction method.

[0018] In any embodiment of the present application, the powder resistivity of the positive electrode active material is greater than 0 and less than or equal to 30 Ω·cm, which can be 0.5 Ω·cm-10 Ω·cm.

[0019] In any embodiment of the present application, the mass percentage content of carbon element in the positive electrode active material is 0.5%-5%, which can be 1%-3.5%.

[0020] When the mass percentage content of carbon element is within the above range, on the one hand, the conductivity of the positive electrode active material can be improved, on the other hand, the shell part can be prevented from being too thick to reduce the gram capacity of the positive electrode active material, and the specific surface area of the positive electrode active material can be prevented from being too large to affect the processing performance of the positive electrode plate.

[0021] In any embodiment of the present application, the average particle size Dv50 of the positive electrode active material is 0.5-10 μm, which can be 1-4 μm.

[0022] When the average particle size Dv50 of the positive electrode active material is within the above range, the transport performance of lithium ions and electrons can be improved, thereby further improving the cycle performance and rate performance of the battery; and the positive electrode sheet has a high tap density, thereby further improving the energy density of the battery.

[0023] In any embodiment of the present application, the tap density of the positive electrode active material under a 3-ton force is ≥2.5 g / cm 3 . Thus, the energy density of the battery can be improved.

[0024] In any embodiment of the present application, the lithium-containing phosphate includes one or more selected from lithium iron phosphate, lithium manganese iron phosphate, and a composite material obtained by coating and / or doping modification of the above-mentioned materials.

[0025] In any embodiment of the present application, the lithium-containing phosphate has a molecular formula of LiFe 1-x-y Mn x M y PO4, 0≤x≤1, 0≤y<1, M includes one or more selected from transition metal elements other than Fe and Mn and non-transition metal elements, which can be one or more selected from V, Nb, Ti, Co, Ni, Sc, Ge, Mg, Al, Zr, Mn, Hf, Ta, Mo, W, Ru, Ag, Sn and Pb.

[0026] In any embodiment of the present application, the positive electrode conductive agent includes one or more selected from super-conductive carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0027] In any embodiment of the present application, the mass percentage content w2 of the positive electrode active material in the positive electrode material composition is ≥97.0%, which can be 97.0%-98.2%. Thus, a battery with high energy density can be obtained.

[0028] In any embodiment of the present application, the positive electrode material composition further includes a positive electrode binder and / or a positive electrode dispersant. The positive electrode binder is used to improve the adhesion between positive electrode active material particles and between the positive electrode active material and the positive electrode current collector, so that the positive electrode sheet forms a good electronic network. The positive electrode dispersant is used to improve the stability of the positive electrode slurry, reduce the risk of positive electrode film cracking, and also improve the dispersibility of the positive electrode conductive agent.

[0029] In any embodiment of the present application, the mass percentage content w3 of the positive electrode binder in the positive electrode material composition is 1% to 3%.

[0030] In any embodiment of the present application, the mass percentage content w4 of the positive electrode dispersant in the positive electrode material composition is 0% to 0.5%.

[0031] The second aspect of the present application provides a positive electrode tab, comprising a positive electrode current collector and a positive electrode film layer arranged on the positive electrode current collector, wherein the positive electrode film layer comprises the positive electrode material composition of the first aspect of the present application.

[0032] In any embodiment of the present application, the areal density of the positive electrode tab is ≥300 mg / 1540.25 mm 2 , optionally ≥410 mg / 1540.25 mm 2 , ≥450 mg / 1540.25 mm 2 , ≥500 mg / 1540.25 mm 2 .

[0033] At present, the prior art considers that as the coating weight of the positive electrode tab increases, in order to not deteriorate the battery internal resistance, the amount of the positive electrode conductive agent needs to be increased. However, the inventors found in the research process that when the positive electrode film layer comprises the positive electrode material composition of the first aspect of the present application, the battery can have both high energy density and good rate performance; and as the coating weight of the positive electrode tab increases, not only is there no need to increase the amount of the positive electrode conductive agent, but also the amount of the positive electrode conductive agent can be reduced, and even the positive electrode conductive agent can be cancelled, and at this time not only the energy density of the battery can be improved, but also the battery internal resistance and the rate performance are not affected. The positive electrode material composition of the first aspect of the present application helps to improve the performance of the thick coating and / or high compaction density battery system, and enables the battery to have both high energy density and good rate performance.

[0034] In any embodiment of the present application, the areal density of the positive electrode tab is denoted as CW, with the unit of mg / 1540.25 mm 2 , and the positive electrode tab satisfies 0≤100000×(w1 / CW)≤3.4, and optionally 0≤100000×(w1 / CW)≤1.8.

[0035] In any embodiment of the present application, the thickness H of the positive electrode film layer is 70 μm to 145 μm, and optionally 90 μm to 138 μm.

[0036] In any embodiment of the present application, the thickness of the positive electrode film layer is denoted as H, with the unit of μm, and the positive electrode tab satisfies 0≤100000×(w1 / H)≤14, and optionally 0≤100000×(w1 / H)≤11.

[0037] In any embodiment of the present application, the positive electrode tab has a compacted density PD≥2.55 g / cm3. 3 , optionally≥2.58 g / cm3 3 , more optionally≥2.60 g / cm3 3 . Thus, it is beneficial to improve the energy density of the battery.

[0038] In any embodiment of the present application, the positive electrode tab further comprises a conductive coating between the positive electrode current collector and the positive electrode film layer to increase the adhesion between the positive electrode film layer and the positive electrode current collector. Optionally, the conductive coating comprises conductive carbon black and a binder. Optionally, the thickness of the conductive coating is greater than 0 and less than or equal to 2 μm.

[0039] In any embodiment of the present application, the positive electrode tab has an electrical resistance of 0.1 Ω-1 Ω, optionally 0.1 Ω-0.6 Ω. Thus, it is beneficial to improve the cycle performance and rate performance of the battery.

[0040] In any embodiment of the present application, the positive electrode current collector has a thickness of 10 μm-18 μm.

[0041] The third aspect of the present application provides a method for preparing a positive electrode tab, comprising the steps of: providing a positive electrode slurry, coating the positive electrode slurry on at least one surface of a positive electrode current collector, and obtaining a positive electrode tab through drying and compacting processes, wherein the positive electrode slurry comprises the positive electrode material composition of the first aspect of the present application and a solvent.

[0042] The fourth aspect of the present application provides a battery comprising the positive electrode material composition of the first aspect of the present application or the positive electrode tab of the second aspect of the present application or the positive electrode tab prepared by the method of the third aspect of the present application.

[0043] The fifth aspect of the present application provides an electric device comprising the battery of the fourth aspect of the present application.

[0044] The battery of the present application can balance high energy density and good rate performance, and the electric device of the present application comprises the battery provided by the present application, thus at least having the same advantages as the battery. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0046] Figure 1This is a schematic diagram of one embodiment of the battery cell of this application.

[0047] Figure 2 This is an exploded view of one embodiment of the battery cell of this application.

[0048] Figure 3 This is a schematic diagram of one embodiment of the battery module of this application.

[0049] Figure 4 This is a schematic diagram of one embodiment of the battery pack of this application.

[0050] Figure 5 yes Figure 4 An exploded view of an embodiment of the battery pack shown.

[0051] Figure 6 This is a schematic diagram of one embodiment of an electrical device that uses the battery of this application as a power source.

[0052] The accompanying drawings are not necessarily drawn to scale. The reference numerals are explained as follows: 1 Battery pack, 2 Upper casing, 3 Lower casing, 4 Battery module, 5 Individual battery cell, 51 Housing, 52 Electrode assembly, 53 Cover plate. Detailed Implementation

[0053] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode material composition, positive electrode sheet, preparation method thereof, battery, and power device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0054] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges can be "closed" ranges, i.e., the upper and lower limits of the range are included. The ranges can be any combination of open and closed ranges. For example, if a range of 60-120 and a range of 80-110 are listed, it is understood that a range of 60-110 and a range of 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and if a maximum range value of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise indicated, a numerical range "a-b" means a range of any combination of the numbers a and b, in which a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand for listing all of those numbers. Also, when a parameter is stated to be an integer > 2, it is equivalent to state that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0055] Unless otherwise indicated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0056] Unless otherwise indicated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0057] Unless otherwise indicated, all steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0058] Unless otherwise indicated, the "includes" and "contains" mentioned in the present application mean open-ended and can also be closed-ended. For example, the "includes" and "contains" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0059] The term "or" is inclusive in this application, unless otherwise indicated. So for example, a phrase "A or B" means "A, B, or both A and B". More specifically, any of the following satisfy the condition "A or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).

[0060] In this application, the terms "plurality" and "plural" mean two or more.

[0061] Unless otherwise defined, all terms used in this application have the meanings commonly understood by those skilled in the art.

[0062] Unless otherwise indicated, the values of the parameters mentioned in this application can be measured by various test methods commonly used in the art, for example, according to the test methods given in this application.

[0063] The positive active material is an important component of the battery, and its influence on the performance of the battery is crucial. Lithium-containing phosphates represented by lithium iron phosphate are one of the most concerned positive active materials at present, but compared with ternary positive active materials, the energy density of the battery using lithium-containing phosphates is lower. In order to improve the energy density of the battery using lithium-containing phosphates, the commonly used strategy is to increase the coating weight and / or coating thickness of the lithium-containing phosphates. However, existing research shows that the electronic conductivity and ionic conductivity of lithium-containing phosphates are both low, which leads to poor rate performance of the battery, and with the increase of the coating weight and / or coating thickness of the lithium-containing phosphates, the rate performance of the battery will continue to deteriorate, and if the amount of conductive agent is reduced on this basis, the performance of the battery, especially the rate performance, will be accelerated. In order to ensure that the battery has good rate performance, the amount of conductive agent needs to be increased, but after the amount of conductive agent is increased, the amount of lithium-containing phosphates will decrease, which will further lead to the decrease of the energy density of the battery.

[0064] Therefore, the battery using lithium-containing phosphates cannot effectively balance high energy density and good rate performance at present.

[0065] The inventors of the present application found in the research process that by reasonably adjusting the graphitization degree of lithium-containing phosphates and the amount of conductive agent, the battery using lithium-containing phosphates can balance high energy density and good rate performance.

[0066] Positive electrode material composition

[0067] Specifically, the first aspect of the embodiments of the present application provides a positive material composition.

[0068] The positive electrode material composition includes a positive electrode active material and an optional positive electrode conductive agent, the positive electrode active material includes a core part and a shell part located on at least part of the surface of the core part, the core part includes a lithium-containing phosphate, the shell part includes a carbon material, the graphitization degree of the positive electrode active material is denoted as g1, the mass percentage content of the positive electrode conductive agent in the positive electrode material composition is denoted as w1, and 10%≤g1≤50%, 0%≤w1≤1%.

[0069] The inventors of the present application found in the process of in-depth study of battery energy density and rate performance that a key factor affecting the improvement of battery rate performance lies in the matching of lithium ion and electron migration speed. When the battery is charged, lithium ions migrate from the lithium-containing phosphate bulk phase (or lattice) to the surface, enter the electrolyte under the action of an external electric field, and then migrate to the surface of the negative electrode active material (such as graphite, etc.) through the electrolyte, and then enter the inside of the negative electrode active material (such as intercalating between graphite layers). At the same time, electrons flow from the positive electrode to the negative electrode through the external circuit. When the battery is discharged, lithium ions are released from the negative electrode active material, enter the electrolyte under the action of an external electric field, and then migrate to the surface of the positive electrode active material through the electrolyte, and then enter the bulk phase (or lattice) of the positive electrode active material. At the same time, electrons flow from the negative electrode to the positive electrode through the external circuit. Therefore, the charging and discharging process of the battery requires the participation of lithium ions and electrons.

[0070] The electronic conductivity of lithium-containing phosphate is low, and in order to improve its conductivity, the current strategy is mainly to coat amorphous carbon on the surface of lithium-containing phosphate. Using amorphous carbon coating can not only improve the conductivity of lithium-containing phosphate, but also increase the wettability of lithium-containing phosphate to electrolyte, reduce battery polarization and improve the migration speed of lithium ions. However, the conductivity of amorphous carbon is poor, and the effect of improving the conductivity of lithium-containing phosphate is limited, so a large amount of conductive agent still needs to be used in actual application; and after the amount of conductive agent is increased, the amount of lithium-containing phosphate will decrease, which will further lead to the decrease of battery energy density, and the battery cannot have high energy density and good rate performance.

[0071] The inventors found in the research process that selecting the positive electrode active material with the graphitization degree of greater than or equal to 10% helps to improve the conductivity of the lithium-containing phosphate and the rate performance of the battery. However, the inventors further found in the research process that the graphitization degree of the positive electrode active material is not the higher the better. When the graphitization degree of the positive electrode active material exceeds 50%, although the conductivity of the positive electrode active material is excellent, the rate performance of the battery using the same does not continue to improve, and the rate performance of the battery decreases to different degrees with the increase of the charging current. Meanwhile, when the graphitization degree of the positive electrode active material exceeds 50%, the compaction density of the positive electrode plate also decreases, thereby reducing the energy density of the battery. In addition, when the graphitization degree of the positive electrode active material exceeds 50%, the cycle performance of the battery may also deteriorate.

[0072] The possible reason is that when the graphitization degree of the positive electrode active material exceeds 50%, the conductivity thereof is excellent, so that the reaction rate of the positive electrode may be significantly greater than the reaction rate of the negative electrode. Lithium ions will excessively accumulate on the negative electrode side during charging, causing the viscosity of the electrolyte on the negative electrode side to increase, which is not conducive to the transmission of lithium ions and also increases the polarization of the battery. When the graphitization degree of the positive electrode active material exceeds 50%, the performance of the carbon material in the shell may change in quality. At this time, the amorphous carbon tends to be converted into graphitized carbon (or crystalline carbon). Since the interlayer spacing of the graphitized carbon (or crystalline carbon) is small, when it is coated on the surface of the lithium-containing phosphate, it will hinder the rapid intercalation and extraction of lithium ions, aggravate the polarization of the battery, and thus lead to the deterioration of the rate performance of the battery, especially the deterioration of the large-rate charging performance. Meanwhile, when the graphitization degree of the positive electrode active material exceeds 50%, the nano-pore structure in the carbon material becomes less, thereby reducing the wettability of the electrolyte by the lithium-containing phosphate and the migration speed of lithium ions, which will further aggravate the polarization of the battery and affect the rate performance. In addition, when the graphitization degree of the positive electrode active material exceeds 50%, the deformation of the shell is large during the extraction and intercalation of lithium ions, which will also lead to the deterioration of the structural stability of the shell and the easy peeling off of the shell from the surface of the lithium-containing phosphate, thereby not only reducing the conductivity of the lithium-containing phosphate, but also increasing the irreversible consumption of lithium ions and affecting the cycle performance of the battery.

[0073] In addition, the inventors of the present application have also noticed in research that when the graphitization degree of the positive electrode active material is 10%-50%, if a high content of positive electrode conductive agent is also used, on the one hand, the energy density of the battery will be reduced, and on the other hand, the improvement of the rate performance of the battery is also not conducive. The possible reason is that at this time, the reaction rate of the positive electrode can be significantly greater than the reaction rate of the negative electrode, and lithium ions will excessively accumulate on the negative electrode side during charging, causing the viscosity of the electrolyte on the negative electrode side to increase, which is not conducive to the transmission of lithium ions, and also increases the polarization of the battery; in addition, it can also be caused by the mismatch of the migration speed of lithium ions and electrons. During battery operation, the migration speed of electrons in the external circuit is too fast, while the migration speed of lithium ions inside the battery is relatively slow, which leads to excessive polarization of the battery, and the greater the charging current of the battery, the more obvious the polarization of the battery, and the worse the rate performance of the battery, especially the large-rate charging performance.

[0074] The inventors have found in further research that when the graphitization degree of the positive electrode active material is 10%-50% and the mass percentage content of the positive electrode conductive agent in the positive electrode material composition is 0%-1%, the battery can have both high energy density and good rate performance. Although the mechanism is not clear, the inventors believe that at this time, the migration speed of lithium ions and electrons can be well matched, thereby reducing the polarization of the battery, reducing the internal resistance of the battery, and enabling the battery to have good rate performance; at the same time, at this time, the reaction rate of the positive electrode is easy to match the reaction rate of the negative electrode, thereby avoiding as much as possible the problems of excessive accumulation of lithium ions on the negative electrode side during charging, causing the viscosity of the electrolyte on the negative electrode side to increase, the slow transmission of lithium ions, and the increase of the polarization of the battery; in addition, after reducing the amount of positive electrode conductive agent, the amount of lithium-containing phosphate can be higher, thereby also enabling the battery to have high energy density.

[0075] In the present application, the graphitization degree of the positive electrode active material refers to the graphitization degree of the carbon material in the shell part of the positive electrode active material, which has the meaning known in the art and can be measured by instruments and methods known in the art. For example, the d 002 spacing of the C(002) crystal plane in the crystal structure of the positive electrode active material can be measured by an X-ray diffractometer according to JIS K 0131-1996 and JB / T 4220-2011. 002 002 In the above formula, d

[0076] In the present application, when the mass percentage content w1 of the positive electrode conductive agent in the positive electrode material composition is 0%, it means that the positive electrode material composition does not include the positive electrode conductive agent.​

[0077] The inventors have further found that by further adjusting the graphitization degree g1 of the positive electrode active material and the mass percentage content w1 of the positive electrode conductive agent, the amount of the positive electrode conductive agent can be further reduced without affecting the rate capability of the battery, thereby further improving the energy density of the battery.

[0078] In some embodiments, 15%≤g1≤48% and 0%≤w1≤0.8%. Alternatively, 15%≤g1≤48% and 0%≤w1≤0.6%. More alternatively, 15%≤g1≤48% and 0%≤w1≤0.4%.

[0079] In some embodiments, 20%≤g1≤45% and 0%≤w1≤0.6%. Alternatively, 20%≤g1≤45% and 0%≤w1≤0.4%. More alternatively, 20%≤g1≤45% and 0%≤w1≤0.2%.

[0080] In some embodiments, 25%≤g1≤50% and 0%≤w1≤0.2%.

[0081] In some embodiments, 25%≤g1≤50% and w1 is 0%. The inventors have further found that by further adjusting the graphitization degree g1 of the positive electrode active material and the mass percentage content w1 of the positive electrode conductive agent, the positive electrode conductive agent can be cancelled under the premise of ensuring that the battery has good rate capability, thereby further improving the energy density of the battery.

[0082] In some embodiments, 25%≤g1≤40% and w1 is 0%. Alternatively, 25%≤g1≤35% and w1 is 0%. By further adjusting the range of the graphitization degree g1 of the positive electrode active material, the battery can have good cycle performance on the basis of having high energy density and good rate capability. The possible reason is that the interlayer spacing of the shell part is larger at this time, the structural stability is better, and it is also beneficial to improve the electrolyte wettability of the positive electrode sheet and improve the migration speed of lithium ions, and thus the battery can also have good cycle performance.

[0083] In some embodiments, the powder resistivity of the positive electrode active material is greater than 0 and less than or equal to 30 Ω·cm, which can be 0.1 Ω·cm-20 Ω·cm, 0.2 Ω·cm-15 Ω·cm, 0.5 Ω·cm-10 Ω·cm, 0.5 Ω·cm-8 Ω·cm, or 0.5 Ω·cm-5 Ω·cm.

[0084] In the present application, the powder resistivity of the positive electrode active material has the meaning known in the art and can be tested by methods known in the art. An exemplary testing method is as follows: 1-5 g of the sample to be tested is weighed, the depth of the powder resistivity instrument is adjusted, the sample to be tested is added to the powder resistivity instrument, pressure is applied, and the powder resistivity of the positive electrode active material at different pressures is recorded until the test is stopped when the powder resistivity value no longer changes as the pressure continues to increase, and the powder resistivity value at this time is recorded as the powder resistivity of the positive electrode active material. The testing instrument can be a PRCD 2100 powder resistivity instrument from Yuaneng Technology Co., Ltd.

[0085] In some embodiments, the mass percentage of carbon elements in the positive electrode active material is 0.5%-5%, for example, the mass percentage of carbon elements in the positive electrode active material can be 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range formed by any of the above values, optionally, the mass percentage of carbon elements in the positive electrode active material is 1%-4%, 1%-3.5%, 1%-3.2%, 1%-3%.

[0086] When the mass percentage of carbon elements is within the above range, on the one hand, the conductivity of the positive electrode active material can be improved, on the other hand, the shell can be prevented from being too thick to reduce the specific capacity of the positive electrode active material, and the specific surface area of the positive electrode active material can be prevented from being too large to affect the processing performance of the positive electrode plate.

[0087] In some embodiments, the average particle size Dv50 of the positive electrode active material is 0.5 μm-10 μm, for example, the average particle size Dv50 of the positive electrode active material can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or a range formed by any of the above values. Optionally, the average particle size Dv50 of the positive electrode active material is 0.5 μm-8 μm, 0.5 μm-6 μm, 0.5 μm-4 μm, 0.8 μm-4 μm, 1 μm-4 μm.

[0088] When the average particle size Dv50 of the positive electrode active material is within the above range, the transport performance of lithium ions and electrons can be improved, thereby further improving the cycle performance and rate performance of the battery; and the positive electrode plate has a high tap density, thereby further improving the energy density of the battery.

[0089] In the present application, the average particle size Dv50 of the positive electrode active material is the meaning known in the art, which represents the particle size corresponding to the cumulative volume distribution percentage of 50%, and can be measured by using the instruments and methods known in the art. For example, it can be measured by using a laser particle size analyzer according to GB / T 19077-2016. The testing instrument can be a Mastersizer 2000E laser particle size analyzer.

[0090] In some embodiments, the powder compaction density of the positive electrode active material under a 3-ton force is ≥ 2.5 g / cm3. 3 Thus, it is beneficial to improve the energy density of the battery.

[0091] In the present application, the powder compaction density of the positive electrode active material is the meaning known in the art, and can be measured by using the instruments and methods known in the art. For example, it can be measured by using an electronic pressure testing machine according to GB / T 24533-2009. The testing instrument can be a UTM7305 electronic pressure testing machine. The exemplary testing method is as follows: 1 g of the sample to be measured is weighed and added into a mold with a bottom area of 1.327 cm2, and then pressed to 3 tons, kept for 30 s, then unloaded, kept for 10 s, and then the powder compaction density of the positive electrode active material under a 3-ton force is recorded and calculated. 2

[0092] In some embodiments, the specific capacity of the positive electrode active material is ≥ 157 mAh / g. Thus, it is beneficial to improve the energy density of the battery.

[0093] In some embodiments, the lithium-containing phosphate salt can include one or more of lithium iron phosphate, lithium manganese iron phosphate, and a composite material obtained by coating and / or doping modification of the above-mentioned materials.

[0094] In some embodiments, the molecular formula of the lithium-containing phosphate salt can be LiFe 1-x-y Mn x M y PO4, 0≤x≤1, 0≤y<1, optionally, 0≤y≤0.1, M includes one or more selected from transition metal elements other than Fe and Mn, and non-transition metal elements, and optionally includes one or more selected from V, Nb, Ti, Co, Ni, Sc, Ge, Mg, Al, Zr, Mn, Hf, Ta, Mo, W, Ru, Ag, Sn and Pb. As an example, the lithium-containing phosphate salt includes one or more selected from LiFePO4, LiMnPO4, LiFe 1-x1 Mn x1 PO4(0

[0095] ​In some embodiments, the mass percentage content w2 of the cathode active material in the cathode material composition is ≥ 97.0%, optionally 97.0%-98.2%. This can achieve a high energy density battery.

[0096] The application does not have a particular limitation on the type of cathode conductive agent, and materials known in the art can be used. In some embodiments, the cathode conductive agent can include one or more selected from super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0097] In some embodiments, the cathode material composition can further include a cathode binder. The cathode binder is used to improve the adhesion between cathode active material particles and between the cathode active material and the cathode current collector, so that the cathode electrode sheet forms a good electronic network. The application does not have a particular limitation on the type of cathode binder. As an example, the cathode binder can include one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic resin.

[0098] Due to the low content of the cathode conductive agent in the cathode material composition of the application, the content of the cathode binder can also be reduced, thereby further improving the energy density of the battery. In some embodiments, the mass percentage content w3 of the cathode binder in the cathode material composition can be 0.5%-3%, 1%-3%, 1%-2.5%, 1%-2%.

[0099] In some embodiments, the positive electrode material composition can further include a positive electrode dispersant. The positive electrode dispersant is used to improve the stability of the positive electrode slurry, reduce the risk of positive electrode film layer cracking, and also improve the dispersibility of the positive electrode conductive agent. The present application does not have a particular limitation on the type of positive electrode dispersant, which can be selectively used according to actual needs. As an example, the positive electrode dispersant can include one or more selected from cellulose-based compounds, polyalkylene oxides, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetal, polyvinyl ether, polyvinyl sulfonic acid, polyvinyl chloride, chitosan, starch, polyacrylamide, poly(N-isopropyl acrylamide), poly(N,N-dimethyl acrylamide), polyethyleneimine, polyoxyethylene, poly(2-methoxyethoxyethylene), poly(acrylamide-co-diallyldimethylammonium chloride), acrylonitrile / butadiene / styrene polymer, acrylonitrile / styrene / acrylate polymer, nitrile rubber, and fluororubber. In some embodiments, the mass percentage content w4 of the positive electrode dispersant in the positive electrode material composition can be 0%-0.5%, which can be optionally greater than 0 and less than or equal to 0.5%. When w4 is 0%, it means that no positive electrode dispersant is included in the positive electrode material composition.

[0100] In some embodiments, the positive electrode material composition can simultaneously include a positive electrode binder and a positive electrode dispersant.

[0101] [Method for preparing positive electrode active material]

[0102] In some embodiments, after mixing the positive electrode active material or its precursor, the organic carbon source, and other optional components, the mixture is placed in a protective atmosphere, and by controlling the sintering temperature and / or sintering time, or by adding a graphite catalyst or other auxiliary agent during the sintering process, a positive electrode active material with a desired degree of graphitization can be obtained.

[0103] In some embodiments, the sintering temperature can be 500°C-1200°C, for example, it can be 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, or a range consisting of any of the above values.

[0104] In some embodiments, the sintering time can be 1h-20h, for example, it can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, or a range consisting of any of the above values.

[0105] In some embodiments, the protective gas can include nitrogen, argon, helium, or a combination thereof.

[0106] The kind of the organic carbon source is not particularly limited in the present application. In some embodiments, the organic carbon source includes carbonizable organic matter and derivatives thereof, which can include one or more of starch, sucrose, glucose, fructose, maltose, chitosan, citric acid, alkane, alkene, alcohol, ester, and polymer (e.g., polyvinyl alcohol, polyethylene, polypropylene, and polypyrrole, etc.).

[0107] In some embodiments, the graphite catalyst can include a metal or a metal salt, such as nickel, nickel nitrate, etc.

[0108] In some embodiments, the graphite catalyst can include carbonizable organic matter and derivatives thereof having a cyclic structure. Alternatively, the graphite catalyst can include one or more of naphthalene, phenanthrene, anthracene, pyrene, perylene, ferrocene, diphenylphosphine, and triphenylmethane.

[0109] In some embodiments, the graphite catalyst is added in an amount of 5% or less, optionally 3% or less, 2% or less, 1% or less, of the mass of the positive electrode active material.

[0110] In some embodiments, other components can also be added as needed during the preparation of the positive electrode active material, such as additives, so that the shell part also includes other components in addition to the carbon material. In some embodiments, the additives can be components for improving certain properties of the battery, such as additives for improving lithium ion transport properties, additives for improving the interface properties of the positive electrode active material, etc., as long as these additive components do not detract from the main purpose of the present application.

[0111] Positive electrode sheet

[0112] The second aspect of the embodiments of the present application provides a positive electrode tab including the positive electrode material composition of the first aspect of the embodiments of the present application.

[0113] In some embodiments, the positive electrode tab includes a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector, and the positive electrode film layer includes the positive electrode material composition of the first aspect of the embodiments of the present application. For example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0114] In some embodiments, the positive electrode film layer can also include other positive electrode active materials commonly known in the art for batteries, as an example, the other positive electrode active materials can include one or more selected from lithium transition metal oxides and modified compounds thereof. Examples of lithium transition metal oxides can include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds of each thereof.

[0115] In some embodiments, the areal density of the positive electrode tab is ≥ 300 mg / 1540.25 mm 2 , optionally ≥ 410 mg / 1540.25 mm 2 , ≥ 450 mg / 1540.25 mm 2 , ≥ 500 mg / 1540.25 mm 2 . Thus, it is beneficial to improve the energy density of the battery.

[0116] Currently, the prior art considers that as the coating weight of the positive electrode tab increases, in order to not deteriorate the internal resistance of the battery, the amount of the positive electrode conductive agent needs to be increased. However, the inventors found in the research process that when the positive electrode film layer comprises the positive electrode material composition of the first aspect of the embodiments of the present application, the battery can have both high energy density and good rate performance; and as the coating weight of the positive electrode tab increases, not only is there no need to increase the amount of the positive electrode conductive agent, but also the amount of the positive electrode conductive agent can be reduced, and even the positive electrode conductive agent can be cancelled, and at this time, not only the energy density of the battery can be improved, but also the internal resistance and the rate performance of the battery are not affected.

[0117] The positive electrode material composition of the first aspect of the embodiments of the present application is helpful to improve the performance of the thick coating and / or high compaction density battery system, and can make the battery have both high energy density and good rate performance.

[0118] In some embodiments, the areal density of the positive electrode tab is denoted as CW, and the unit is mg / 1540.25 mm 2 , the positive electrode tab satisfies 0≤100000×(w1 / CW)≤3.4, optionally, 0≤100000×(w1 / CW)≤2.4, 0≤100000×(w1 / CW)≤1.8, 0≤100000×(w1 / CW)≤1.5, 0≤100000×(w1 / CW)≤1.

[0119] In some embodiments, the thickness H of the positive electrode film layer is 70 μm-145 μm, optionally 90 μm-138 μm.

[0120] In some embodiments, the thickness of the positive electrode film layer is denoted as H, and the unit is μm, and the positive electrode tab satisfies 0≤100000×(w1 / H)≤14, optionally, 0≤100000×(w1 / H)≤11, 0≤100000×(w1 / H)≤8, 0≤100000×(w1 / H)≤6.

[0121] In some embodiments, the compaction density PD of the positive electrode tab is ≥ 2.55 g / cm 3 , optionally ≥ 2.58 g / cm 3≥ 2.60 g / cm 3 ≥ 2.62 g / cm 3 ≥ 2.65 g / cm 3 Thus, it is beneficial to improve the energy density of the battery.

[0122] In the present application, the area density of the positive electrode tab is the meaning known in the art, which can be tested by the method known in the art. For example, a single-side coated and cold-pressed positive electrode tab (if it is a double-side coated positive electrode tab, the positive electrode film layer on one side can be wiped off first) can be punched into a small disc with an area of S1, weighed, and recorded as M1. Then the positive electrode film layer of the above weighed positive electrode tab is wiped off, and the weight of the positive electrode current collector is weighed and recorded as M0. The area density of the positive electrode tab = (M1-M0) / S1.

[0123] In the present application, the compaction density of the positive electrode tab is the meaning known in the art, which can be tested by the method known in the art. The compaction density of the positive electrode tab = the area density of the positive electrode tab / the thickness of the positive electrode film layer.

[0124] In the present application, the thickness of the positive electrode film layer is the meaning known in the art, which can be tested by the method known in the art. For example, it can be tested by a screw micrometer.

[0125] In some embodiments, the positive electrode tab can further include a conductive coating layer between the positive electrode current collector and the positive electrode film layer to increase the adhesion between the positive electrode film layer and the positive electrode current collector. Of course, in some embodiments, the conductive coating layer can also not be provided.

[0126] In some embodiments, the conductive coating layer includes conductive carbon black and a binder. The present application does not have a particular limitation on the type of binder, and an oily binder known in the art can be used. As an example, the binder can include one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0127] In some embodiments, the thickness of the conductive coating layer is greater than 0 and less than or equal to 2 μm.

[0128] In some embodiments, the resistance of the positive electrode tab is 0.1 Ω-1 Ω, which can be selected as 0.1 Ω-0.8 Ω, 0.1 Ω-0.7 Ω, 0.1 Ω-0.6 Ω. Thus, it is beneficial to improve the cycle performance and rate performance of the battery.

[0129] In the present application, the resistance of the positive electrode tab is the meaning known in the art, which can be tested by instruments and methods known in the art. For example, a two-probe resistance tester is used for testing. As an example, the following test method can be used: take a 4cm*25cm sample along the longitudinal direction of the positive electrode tab, turn on the two-probe resistance tester, select the single-point mode, input the test area of the terminal 1540.25mm 2 , the number of parallel samples is 20, the pressure is 0.4t, the time interval is 15s, place the test sample between the two probes, click the run button on the software first and then turn the reversing valve down, automatically collect a data after 15s, change the test method as above when changing the point, and continue the test by replacing the test sample when 20 points are tested. Take the average of the above test results as the resistance of the positive electrode tab.

[0130] In some embodiments, the thickness of the positive current collector can be 10-18μm, but the present application is not limited thereto.

[0131] In some embodiments, the positive current collector can use a metal foil or a composite current collector. As an example of the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0132] It should be noted that the parameters of each positive electrode tab given in the present application (such as the area density, the compacted density, the thickness, etc.) refer to the parameters of the positive electrode film layer on one side of the positive current collector. When the positive electrode film layer is arranged on both sides of the positive current collector, as long as the parameters of the positive electrode film layer on any one side meet the present application, it is considered to fall within the protection scope of the present application.

[0133] When testing the parameters of the above positive electrode tab, such as the area density, the compacted density, the thickness, and the resistance, the freshly prepared cold-pressed positive electrode tab can be directly taken, or the positive electrode tab can be obtained from the battery. An example of the method of obtaining the positive electrode tab from the battery is as follows: after the battery is fully discharged, the positive electrode tab is disassembled, the positive electrode tab is soaked in an organic solvent (for example, dimethyl carbonate) for a period of time (for example, more than 72h), and then the positive electrode tab is taken out and dried at a certain temperature and time (for example, vacuum oven 80℃, drying for more than 6h).

[0134] Method for preparing a positive electrode sheet

[0135] The third aspect of the embodiments of the present application provides a preparation method of the positive electrode tab.

[0136] The preparation method comprises the steps of providing a positive electrode slurry, coating the positive electrode slurry on at least one surface of a positive electrode current collector, and obtaining a positive electrode tab through a drying and compacting process, wherein the positive electrode slurry comprises the positive electrode material composition of the first aspect of the embodiments of the present application and a solvent.

[0137] In some embodiments, the solvent can include N-methyl pyrrolidone (NMP), but is not limited thereto.

[0138] Battery

[0139] The fourth aspect of the embodiments of the present application provides a battery.

[0140] The battery mentioned in the embodiments or the embodiments of the present application refers to a single physical module comprising one or more battery monomers to provide higher voltage and capacity. For example, the battery mentioned in the present application can include a battery monomer, a battery module or a battery pack, etc. The battery monomer is the smallest unit that constitutes the battery, which can realize the function of charging and discharging by itself. The shape of the battery monomer is not particularly limited in the present application, which can be cylindrical, square or any other shape. For example, Figure 1 is a battery monomer 5 in a square structure as an example.

[0141] In some embodiments, the battery monomer comprises an electrode assembly, and the monomer battery can further comprise an outer package and an electrolyte. The electrode assembly usually comprises a positive electrode tab and a negative electrode tab, etc., and the outer package can be used to package the above-mentioned electrode assembly and electrolyte. The outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package can also be a soft package, such as a bag type soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS). The electrode assembly can be made by a winding process and / or a stacking process.

[0142] In some embodiments, as shown in Figure 2 The outer package can comprise a shell 51 and a cover plate 53. The shell 51 can comprise a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The electrode assembly 52 is packaged in the receiving cavity. The number of electrode assemblies 52 contained in the battery monomer 5 can be one or more, which can be adjusted according to the needs.

[0143] In some embodiments of the present application, the battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 3 is a schematic view of a battery module 4 as an example. As shown in Figure 3 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be made. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0144] Optionally, the battery module 4 can also include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0145] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack. Figure 4 and Figure 5 is a schematic view of a battery pack 1 as an example. As shown in Figure 4 and Figure 5 , the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, the upper box body 2 is used to cover the lower box body 3, and forms a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0146] [Positive electrode sheet]

[0147] The positive electrode sheet used in the battery of the present application is the positive electrode sheet of any one of the embodiments of the second aspect of the present application. Thus, the battery of the present application can balance high energy density and good rate performance.

[0148] [Negative electrode sheet]

[0149] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite in the thickness direction of itself, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0150] The negative active material can employ a negative active material for a battery known in the art. As an example, the negative active material includes, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate. The silicon-based material can include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material can include one or more of elemental tin, tin oxide, and tin alloy material. The present application is not limited to these materials, and other conventionally known materials that can be used as a negative active material for a battery can also be used.

[0151] In some embodiments, the negative electrode film layer can further optionally include a negative electrode conductive agent. The present application does not have a particular limitation on the kind of the negative electrode conductive agent, and as an example, the negative electrode conductive agent can include one or more of super P, conductive graphite, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0152] In some embodiments, the negative electrode film layer can further optionally include a negative electrode binder. The present application does not have a particular limitation on the kind of the negative electrode binder, and as an example, the negative electrode binder can include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0153] In some embodiments, the negative electrode film layer can further optionally include other auxiliary agents. As an example, the other auxiliary agents can include a thickening agent, such as sodium carboxymethyl cellulose (CMC), PTC thermistor material, etc.

[0154] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. As an example of the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0155] The negative electrode film layer is generally formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold-pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0156] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode tab described in the present application can further include a conductive coating layer (e.g., generally composed of a conductive agent and a binder) disposed on the surface of the negative electrode current collector, sandwiched between the negative electrode current collector and the negative electrode film layer; in some embodiments, the negative electrode tab described in the present application can further include a protective layer covering the surface of the negative electrode film layer.

[0157] [Electrolyte]

[0158] The electrolyte functions to conduct lithium ions between the positive electrode tab and the negative electrode tab. The type of the electrolyte is not specifically limited in the present application and can be selected as needed. For example, the electrolyte can include one or more selected from a solid-state electrolyte and a liquid electrolyte (i.e., electrolyte solution).

[0159] In some embodiments, the electrolyte employs an electrolyte solution including an electrolyte salt and a solvent.

[0160] The electrolyte salt can include one or more selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (LiDFOB), lithium bisoxalato borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalato phosphate (LiDFOP), and lithium tetrafluorooxalato phosphate (LiTFOP).

[0161] The kind of the solvent is not particularly limited and can be selected according to actual needs. In some embodiments, the solvent can include one or more selected from ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0162] In some embodiments, the electrolyte can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, and the like.

[0163] [Separator]

[0164] In batteries using electrolytes, and in some batteries using solid electrolytes, a separator is also included. The separator is disposed between the positive electrode sheet and the negative electrode sheet and mainly functions to prevent short circuiting of the positive electrode and the negative electrode while allowing lithium ions to pass through. The kind of the separator is not particularly limited in the present application and any known porous structure separator having good chemical stability and mechanical stability can be used. The separator can be a single layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of the layers can be the same or different.

[0165] In some embodiments, the separator can include a base film and an optional protective coating. The base film can include a non-woven fabric, a film, or a composite film having a porous structure, and the material of the base film can include one or more of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, and polyimide.

[0166] A protective coating can or can not be provided on the surface of the base film. In some embodiments, at least one surface of the base film is provided with a protective coating, which can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic material.

[0167] The inorganic layer includes inorganic particles and a binder. The inorganic particles include, but are not limited to, one or more of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.

[0168] The polymer layer includes a polymer. The polymer includes, but is not limited to, one or more of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, and polyvinylidene fluoride.

[0169] [Manufacturing method]

[0170] The manufacturing method of the battery of the present application is known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a battery. As an example, a positive electrode sheet, a separator, and a negative electrode sheet can be wound and / or stacked to form an electrode assembly, the electrode assembly can be placed in an outer package, and an electrolyte can be injected after drying. The battery can be obtained by going through processes such as formation and capacity. A plurality of battery cells can further be connected in series or in parallel or in a hybrid manner to form a battery module. A plurality of battery modules can further be connected in series or in parallel or in a hybrid manner to form a battery pack. In some embodiments, a plurality of battery cells can directly form a battery pack.

[0171] Electric device

[0172] The embodiments of the present application also provide an electric device including the battery of the present application. The battery can be used as a power source of the electric device or as an energy storage unit of the electric device. The electric device can be, but is not limited to, a mobile device (e.g., a mobile phone, a tablet computer, a notebook computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0173] The electric device can select a specific type of battery according to its use requirements, such as a battery cell, a battery module, or a battery pack.

[0174] Figure 6 is a schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high power and high energy density of the electric device, a battery pack or a battery module can be used as a power source.

[0175] As another example, the power consuming device can be a mobile phone, a tablet computer, a notebook computer, etc. The power consuming device generally requires thinning, and a battery monomer can be used as a power source.

[0176] Examples

[0177] The present disclosure is more specifically described by the following examples, which are merely illustrative and not limiting, as various modifications and equivalents can be apparent to one skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported herein are based on mass, and all reagents used in the examples are commercially available or synthesized according to standard procedures and used without further purification, and the instruments used in the examples are commercially available.

[0178] Preparation of positive electrode active material

[0179] The washed and dried lithium iron phosphate powder and the organic carbon source glucose are uniformly mixed by grinding for 1 h with the aid of a dispersant alcohol, and the proportion of the lithium iron phosphate powder and the glucose is adjusted to 80 wt%:20 wt% to 95 wt%:5 wt% to control the carbon content in the final material to be between 0.7%-3.5%. The ground powder is then divided into two parts, one part is directly ground into a dry powder state, and the other part is added with a certain amount of stone powder glue and then ground into a dry powder state. Then the two samples are mixed and ground for 2 h, and the uniformly mixed powder is placed in a tube furnace protected by nitrogen atmosphere, the nitrogen flow rate is controlled to be 0.02 L / min, then the temperature is raised to 280°C at a rate of 2°C / min and kept for 2 h, so that the glucose is cracked and fully carbonized, which is beneficial to the full coating of the carbon material; then the temperature is continuously raised to the sintering temperature T at a rate of 5°C / min and kept at this temperature for a time t, the graphitization degree of the carbon material is adjusted by adjusting the sintering temperature T and the holding time t, and after the end of the process, the temperature is cooled to room temperature, thereby obtaining carbon-coated lithium iron phosphate with different graphitization degrees.

[0180] The sintering temperature T and the holding time t corresponding to the carbon-coated lithium iron phosphate with different graphitization degrees used in the following examples and comparative examples are shown in Table 1.

[0181] Table 1

[0182] Degree of graphitization g1 Sintering temperature T (°C) Soaking time t (h) 0 500 6 5％ 700 8 15％ 750 8 20％ 800 8 25％ 800 10 30％ 850 10

[0183] 35％ 900 10 40％ 900 12 50％ 1000 12 55％ 1100 12

[0184] Example 1

[0185] Preparation of positive electrode sheet

[0186] Carbon-coated lithium iron phosphate (the content of carbon element is 1.5%, the graphitization degree is 15%, the powder resistivity is 30 Ω·cm, and the powder compaction density is 2.5 g / cm 3 ), conductive agent carbon black (Super P), binder polyvinylidene fluoride (PVDF), and dispersant polyvinyl alcohol are mixed in a mass ratio of 97.4:0.4:2.0:0.2 in a proper amount of solvent NMP, and are fully stirred to form a uniform positive electrode slurry; the positive electrode slurry is uniformly coated on the surface of a positive electrode current collector aluminum foil (thickness is 15 μm), and after drying and cold pressing, a positive electrode sheet is obtained. The area density of the positive electrode sheet is 410 mg / 1540.25 mm 2 , and the compaction density is 2.6 g / cm 3 .

[0187] The graphitization degree of the positive electrode active material refers to the graphitization degree of the carbon material in the shell part of the positive electrode active material, which can be tested by using an X-ray diffractometer according to JIS K 0131-1996 and JB / T 4220-2011 to obtain d 002 , and then the graphitization degree of the positive electrode active material is calculated according to the formula g = (0.344-d 002 ) / (0.344-0.3354) x 100%. In the above formula, d 002 is the interlayer spacing of the C(002) crystal plane in the crystal structure of the positive electrode active material, which is expressed in nanometers (nm). The testing instrument can be a Bruker D8 Discover X-ray diffractometer.

[0188] The powder resistivity of the positive electrode active material can be tested according to the following steps: 1-5 g of the sample to be tested is weighed, the depth of the powder resistivity instrument is adjusted, the sample to be tested is added to the charging cavity, pressure is applied, and the powder resistivity of the positive electrode active material under different pressures is recorded until the pressure continues to increase and the powder resistivity value no longer changes, at which time the powder resistivity value is recorded as the powder resistivity of the positive electrode active material. The testing instrument can be a PRCD 2100 powder resistivity instrument of Yuan Neng Technology Co., Ltd.

[0189] The powder compaction density of the positive electrode active material can be determined by an electronic pressure testing machine according to GB / T 24533-2009. 1 g of the sample to be tested is weighed and added to a mold with a bottom area of 1.327 cm 2 , and is pressed to 3 tons, kept for 30 s, then unloaded, kept for 10 s, and then the powder compaction density of the positive electrode active material under the action of 3 tons is recorded and calculated. The testing instrument can be a UTM7305 electronic pressure testing machine.

[0190] Preparation of negative electrode sheet

[0191] The negative active material graphite, the binder styrene-butadiene rubber (SBR), the thickening agent sodium carboxymethyl cellulose (CMC), and the conductive agent carbon black (Super P) are mixed in a mass ratio of 96.7:1.7:0.7:0.9 in a proper amount of solvent deionized water to form a uniform negative electrode slurry. The negative electrode slurry is uniformly coated on the surface of a negative current collector copper foil (thickness of 6 μm), and after drying and cold pressing, a negative electrode sheet is obtained. The area density of the negative electrode sheet is 180 mg / 1540.25 mm 2 , and the compacted density is 1.65 g / cm 3 .

[0192] Preparation of electrolyte

[0193] The ethylene carbonate (EC), the methyl ethyl carbonate (EMC), and the diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then the fully dried LiPF6 is dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0194] Preparation of battery

[0195] The prepared positive electrode sheet and negative electrode sheet are die-cut and slitting, and then wound with a separator film to form an electrode assembly, and then subjected to heat pressing, film coating, tab welding, adapter fixing, and shell top cover welding. After baking to remove moisture, the electrolyte prepared above is injected, and processes such as formation and capacity are performed. Finally, the battery (i.e., the battery monomer) is prepared by wrapping it with a blue film. The separator film is located between the positive electrode sheet and the negative electrode sheet, and includes a 5 μm polyethylene film and a 15 μm Al2O3 coating.

[0196] Examples 2-17 and Comparative Examples 2-6

[0197] The battery is prepared in a manner similar to that of Example 1, except that the parameters of the positive active material, the mass percentage content w2 of the positive active material, and the mass percentage content w1 of the conductive agent are different. The specific parameters are shown in Tables 1 and 2.

[0198] Example 18

[0199] The battery is prepared in a manner similar to that of Example 4, except that the area density of the positive electrode sheet is 300 mg / 1540.25 mm 2 , and the compacted density is 2.6 g / cm 3 ; the area density of the negative electrode sheet is 135 mg / 1540.25 mm 2 , and the compacted density is 1.65 g / cm 3 .

[0200] Example 19

[0201] The battery was prepared in a similar manner to Example 4, except that the areal density of the positive electrode tab was 500 mg / 1540.25 mm 2 , and the tap density was 2.6 g / cm 3 ; the areal density of the negative electrode tab was 225 mg / 1540.25 mm 2 , and the tap density was 1.65 g / cm 3 .

[0202] Comparative Example 1

[0203] The battery was prepared in a similar manner to Example 1, except that amorphous carbon-coated lithium iron phosphate was used as the positive electrode active material, and the mass percentage content of the positive electrode active material was 95.8%, and the mass percentage content of the conductive agent was 2.0%.

[0204] Test section

[0205] The performance of the battery cell prepared above was tested. It should be noted that the batteries mentioned in the following performance tests refer to the battery cell.

[0206] (1) Battery volume energy density test

[0207] The volume energy density (Wh / L) of the battery = (discharge capacity of the battery x discharge platform voltage of the battery) / volume of the battery.

[0208] The discharge capacity of the battery was tested by the following method: at 25°C, the freshly prepared battery was charged at 1 / 3C constant current to 3.65V, and then discharged at 1 / 3C constant current to 2.0V, i.e. the discharge capacity of the battery was obtained.

[0209] The discharge platform voltage of the battery is the potential when the electrochemical reaction reaches equilibrium, which can be obtained from the battery tester.

[0210] The volume of the battery was tested by the drainage method, and the volume of the battery was obtained by placing the battery in pure water during the test.

[0211] (2) Battery rate performance test

[0212] At 25°C, the freshly prepared battery was charged at 1 / 3C, 1C, 3C and 5C charge rate constant current to the upper limit cut-off voltage of the battery (corresponding to 100% SOC), and then charged at constant voltage until the current was 0.05C, and then discharged at 1 / 3C constant current to the lower limit cut-off voltage of the battery (corresponding to 0% SOC), and the discharge energy of the battery at this time was recorded.

[0213] The discharge energy of the battery obtained at 1 / 3C charge rate was taken as 100%, and the discharge energy retention rate of the battery at 1C, 3C and 5C charge rate was calculated.

[0214] (3) DC internal resistance test of the battery

[0215] The freshly prepared battery was charged at 1C constant current to the upper cut-off voltage of the battery (corresponding to 100% SOC) at 25°C, then charged at constant voltage until the current was 0.05C, and then discharged at 1C constant current to the lower cut-off voltage of the battery (corresponding to 0% SOC). The discharge capacity at this time was recorded as the initial discharge capacity of the battery. The battery was subjected to the above cycle charge-discharge test until the discharge capacity of the battery was attenuated to 80% of the initial discharge capacity of the battery, and the test was stopped.

[0216] The freshly prepared battery and the battery whose cycle capacity was attenuated to 80% of the initial discharge capacity were subjected to a DC internal resistance test at 25°C, respectively, to obtain the initial DC internal resistance of the battery and the DC internal resistance of the battery cycled to 80% SOH, respectively.

[0217] The DC internal resistance of the battery was tested by adjusting the capacity of the battery to 50% SOC, then pulse charging at 4C rate for 30s, and recording the voltage before and after pulse charging. The DC internal resistance of the battery (mΩ) = (voltage at the end of pulse charging - voltage before pulse charging) / charging current.

[0218] (4) Resistance test of the positive electrode tab

[0219] The resistance of the positive electrode tab can be tested by instruments and methods known in the art. As an example, the following test method can be used: a 4cm x 25cm sample was taken along the longitudinal direction of the positive electrode tab, a two-probe resistance tester was opened, the single-point mode was selected, the test area of the input terminal was 1540.25mm 2 , the number of parallel samples was 20, the pressure was 0.4t, the time interval was 15s, the test sample was placed between the two probes, the run button on the software was clicked first, then the reversing valve was turned down, a data was automatically collected after 15s, the test method was as above when changing the point, and the test continued until 20 points were tested, and then a new test sample was replaced. The average value of the above test results was taken as the resistance of the positive electrode tab.

[0220] During the test, the freshly prepared positive electrode tab and the positive electrode tab taken from the battery whose cycle capacity was attenuated to 80% of the initial discharge capacity were subjected to a resistance test, respectively, to obtain the initial resistance of the positive electrode tab and the resistance of the positive electrode tab when the battery was cycled to 80% SOH, respectively.

[0221] An exemplary method for obtaining the positive electrode tab from the battery is as follows: after the battery is fully discharged, the positive electrode tab is disassembled, soaked and cleaned with dimethyl carbonate (DMC) for more than 72 hours, and after the electrolyte solvent, lithium salt, additives, etc. in the positive electrode tab are completely leached out, the positive electrode tab is placed in a vacuum oven for drying. The dried positive electrode tab is subjected to resistance testing according to the above method.

[0222] Table 2

[0223]

[0224]

[0225] Table 3

[0226]

[0227]

[0228] From the test results in Table 3, it can be seen that when the graphitization degree of the positive electrode active material is 10%-50% and the mass percentage content of the positive electrode conductive agent is 0%-1%, the battery can have both high energy density and good rate performance, and in particular, the battery also has good large-rate charging performance.

[0229] Comparative Examples 1-6 do not satisfy the graphitization degree of the positive electrode active material being 10%-50% and / or the mass percentage content of the positive electrode conductive agent being 0%-1%, and thus cannot make the battery have both high energy density and good rate performance.

[0230] In Comparative Example 1, amorphous carbon-coated lithium-containing phosphate is used as the positive electrode active material, and when the areal density of the positive electrode tab is high, the lithium-containing phosphate itself has poor conductivity, and thus even though up to 2% of the positive electrode conductive agent is used, the positive electrode cannot form a good conductive network, and thus the battery also cannot have good rate performance; in addition, because the amount of the positive electrode conductive agent is high, the volumetric energy density of the battery is also reduced.

[0231] In Comparative Example 2, carbon-coated lithium-containing phosphate with a graphitization degree of less than 10% is used as the positive electrode active material, and thus the battery can have high energy density, but the rate performance of the battery is poor. In Comparative Example 3, in order to make the battery have good rate performance, up to 1.5% of the positive electrode conductive agent is added based on Comparative Example 2, and thus the volumetric energy density of the battery is significantly reduced, and the improvement in the discharge energy retention rate of the battery at 3C and 5C charging rates is also limited.

[0232] The comparative example 4 uses a carbon-coated lithium-containing phosphate with a graphitization degree of more than 50% as the positive electrode active material, which cannot make the battery have both high energy density and good rate performance. The possible reason is that when the graphitization degree exceeds 50%, the compaction density of the positive electrode plate is reduced, which further leads to the reduction of the energy density of the battery; in addition, the reaction rate of the positive electrode at this time may be significantly greater than that of the negative electrode, and lithium ions will accumulate on the negative electrode side during charging, which increases the viscosity of the electrolyte on the negative electrode side, which is not conducive to the transmission of lithium ions, and the greater the charging current of the battery, the more obvious the decrease in rate performance. According to the test results of examples 1-7 and comparative example 4, the discharge energy retention rate of comparative example 4 at 1C charging rate is close to that of examples 1-7, but the discharge energy retention rate of comparative example 4 at 3C and 5C charging rates is significantly lower than that of examples 1-7.

[0233] According to the test results of examples 3-12 and comparative example 5, when the graphitization degree of the carbon-coated lithium-containing phosphate is between 25% and 50%, the positive electrode conductive agent can be cancelled although the area density of the positive electrode plate is large, which not only can further improve the energy density of the battery, but also can make the battery have good rate performance, especially good large-rate charging performance. According to the test results of examples 4, 8-12 and comparative example 5, it can also be known that at this time, increasing the amount of the positive electrode conductive agent will not further significantly improve the rate performance of the battery, and when the amount of the positive electrode conductive agent exceeds 1%, the discharge energy retention rate of the battery at 3C and 5C charging rates will be significantly reduced.

[0234] According to the test results of examples 1-2, examples 13-17 and comparative example 6, when the graphitization degree of the positive electrode active material is low, the positive electrode conductive agent can also be cancelled, and the battery can have high energy density and good rate performance, but when the positive electrode plate also uses a low content of the positive electrode conductive agent, for example, the content of the positive electrode conductive agent is greater than 0 and less than or equal to 1%, and optionally greater than 0 and less than or equal to 0.4%, which helps to further improve the rate performance of the battery, especially the large-rate charging performance. However, when the amount of the positive electrode conductive agent exceeds 1%, the discharge energy retention rate of the battery at 3C and 5C charging rates will be significantly reduced.

[0235] The test results of Example 1, Example 9 and Example 14 also show that, when the amount of the positive electrode conductive agent is the same, increasing the graphitization degree of the carbon-coated lithium-containing phosphate within a certain range helps to improve the rate performance of the battery, but when the graphitization degree of the carbon-coated lithium-containing phosphate is further increased, the rate performance of the battery, especially the discharge energy retention rate of the battery at 3C and 5C charging rates, may decrease. Therefore, by reasonably adjusting the graphitization degree of the positive electrode active material and the amount of the positive electrode conductive agent, the battery can better balance high energy density and good rate performance, and in particular, the battery can balance good large-rate charging performance.

[0236] The test results of Example 4 and Examples 18-19 show that when the positive electrode sheet includes the positive electrode material combination of the present application, even if the areal density of the positive electrode sheet is increased, the battery can still balance high energy density and good rate performance. And unlike the prior art research, at this time, the amount of the positive electrode conductive agent does not need to be increased, and the positive electrode conductive agent can even be cancelled.

[0237] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having substantially the same configuration and playing the same role and effect as the technical idea within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art are applied to the embodiments, and other ways constructed by combining part of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode material composition comprising a positive electrode active material and a positive electrode conductive agent, wherein, The positive electrode active material comprises a core part and a shell part on at least part of the surface of the core part, the core part comprises a lithium-containing phosphate, the shell part comprises a carbon material, the graphitization degree of the positive electrode active material is denoted as g1, the mass percentage content of the positive electrode conductive agent in the positive electrode material composition is denoted as w1, and 15% ≤ g1 ≤ 50%, 0% < w1 ≤ 1%.

2. The cathode material composition of claim 1, wherein, 15% ≤ g1 ≤ 48% and 0% < w1 ≤ 0.8%.

3. The cathode material composition of claim 2, wherein, 15% ≤ g1 ≤ 48% and 0% < w1 ≤ 0.6%.

4. The cathode material composition of claim 3, wherein, 15% ≤ g1 ≤ 48% and 0% < w1 ≤ 0.4%.

5. The cathode material composition of any one of claims 1 to 4, wherein, 20% ≤ g1 ≤ 45% and 0% < w1 ≤ 0.6%.

6. The cathode material composition of claim 5, wherein, 20% ≤ g1 ≤ 45% and 0% < w1 ≤ 0.4%.

7. The cathode material composition of claim 6, wherein, 20% ≤ g1 ≤ 45% and 0% < w1 ≤ 0.2%.

8. The cathode material composition according to any one of claims 1 to 7, wherein, 25% ≤ g1 ≤ 50% and 0% < w1 ≤ 0.2%.

9. The cathode material composition according to any one of claims 1 to 8, wherein, The graphitization degree g1 of the positive electrode active material is obtained by X-ray diffraction method.

10. The cathode material composition according to any one of claims 1 to 9, wherein, The powder resistivity of the positive electrode active material is greater than 0 and less than or equal to 30 Ω·cm; and / or, the mass percentage content of carbon element in the positive electrode active material is 0.5%-5%.

11. The cathode material composition of claim 10, wherein, The powder resistivity of the positive electrode active material is 0.5 Ω·cm-10 Ω·cm.

12. The cathode material composition of claim 10, wherein, The mass percentage content of carbon element in the positive electrode active material is 1%-3.5%.

13. The cathode material composition of any of claims 1-12, wherein, The average particle size Dv50 of the positive electrode active material is 0.5 μm to 10 μm; and / or, the powder compaction density of the positive electrode active material under a 3-ton force is ≥ 2.5 g / cm3 3 ; and / or, The lithium-containing phosphate comprises one or more selected from lithium iron phosphate, lithium manganese iron phosphate, and composite materials obtained by coating and / or doping modification of the above-mentioned materials; and / or, The positive electrode conductive agent comprises one or more selected from super-conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

14. The cathode material composition of claim 13, wherein, The average particle size Dv50 of the positive electrode active material is 1 μm-4 μm.

15. The cathode material composition of claim 13, wherein, The lithium-containing phosphate has a molecular formula of LiFe 1-x-y Mn x M y PO4, 0 ≤ x ≤ 1, 0 ≤ y < 1, M includes one or more selected from transition metal elements other than Fe, Mn, and non-transition metal elements.

16. The cathode material composition of claim 15, wherein, M comprises one or more selected from V, Nb, Ti, Co, Ni, Sc, Ge, Mg, Al, Zr, Mn, Hf, Ta, Mo, W, Ru, Ag, Sn and Pb.

17. The cathode material composition of any of claims 1-16, wherein, The mass percentage content w2 of the positive electrode active material in the positive electrode material composition is ≥ 97.0%.

18. The cathode material composition of claim 17, wherein, The mass percentage content w2 of the positive electrode active material in the positive electrode material composition is 97.0%-98.2%.

19. The cathode material composition of any of claims 1-18, wherein, The positive electrode material composition further comprises a positive electrode binder and / or a positive electrode dispersant.

20. The cathode material composition of claim 19, wherein, The mass percentage content w3 of the positive electrode binder in the positive electrode material composition is 1%-3%.

21. The cathode material composition of claim 19, wherein, The mass percentage content w4 of the positive electrode dispersant in the positive electrode material composition is 0%-0.5%.

22. A positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector, wherein, The positive electrode film layer comprises the positive electrode material composition according to any one of claims 1-21.

23. The cathode sheet of Claim 22, wherein, The areal density of the positive electrode sheet is ≥ 300 mg / 1540.25 mm 2 .

24. The cathode sheet of Claim 23, wherein, The areal density of the positive electrode sheet is ≥ 410 mg / 1540.25 mm 2 .

25. The cathode sheet of Claim 24, wherein, The areal density of the positive electrode sheet is ≥ 450 mg / 1540.25 mm 2 .

26. The cathode sheet of Claim 25, wherein, The areal density of the positive electrode sheet is ≥ 500 mg / 1540.25 mm 2 .

27. The cathode sheet of any one of claims 22-26, wherein, The areal density of the positive electrode tab is denoted as CW, with units of mg / 1540.25 mm 2 The positive electrode tab satisfies 0 ≤ 100000 × (w1 / CW) ≤ 3.

4.

28. The cathode sheet of Claim 27, wherein, The areal density of the positive electrode tab is denoted as CW, with units of mg / 1540.25 mm 2 The positive electrode tab satisfies 0 ≤ 100000 × (w1 / CW) ≤ 1.

8.

29. The cathode sheet of any of claims 22-28, wherein, The thickness H of the positive electrode film layer is 70 μm-145 μm.

30. The cathode sheet of Claim 29, wherein, The thickness H of the positive electrode film layer is 90 μm-138 μm.

31. The cathode sheet of any one of claims 22-30, wherein, The thickness of the positive electrode film layer is denoted as H, in units of μm, and the positive electrode sheet satisfies 0 ≤ 100000×(w1 / H) ≤ 14.

32. The cathode sheet of Claim 31, wherein, The positive electrode tab satisfies 0 ≤ 100000 × (w1 / H) ≤ 11.

33. The cathode sheet of any of claims 22-32, wherein, The compacted density PD of the positive electrode sheet is ≥ 2.55 g / cm 3 .

34. The cathode sheet of Claim 33, wherein, The compacted density PD of the positive electrode sheet is ≥ 2.58 g / cm 3 .

35. The cathode sheet of Claim 34, wherein, The compacted density PD of the positive electrode sheet is ≥ 2.60 g / cm 3 .

36. The cathode sheet of any one of claims 22-35, wherein, The positive electrode tab further comprises a conductive coating layer between the positive current collector and the positive film layer.

37. The cathode sheet of Claim 36, wherein, The conductive coating layer comprises conductive carbon black and a binder.

38. The cathode sheet of Claim 36, wherein, The thickness of the conductive coating layer is greater than 0 and less than or equal to 2 μm.

39. The cathode sheet of any one of claims 22-38, wherein, The positive electrode tab has an electrical resistance of 0.1 Ω-1 Ω; and / or, the thickness of the positive current collector is 10 μm-18 μm.

40. The cathode sheet of Claim 39, wherein, The positive electrode tab has an electrical resistance of 0.1 Ω-0.6 Ω.

41. A method of making a positive electrode sheet, comprising the steps of: providing a positive electrode slurry, coating the positive electrode slurry on at least one surface of a positive electrode current collector, and obtaining a positive electrode sheet through a drying and compacting process, wherein, The positive electrode slurry comprises the positive electrode material composition of any one of claims 1-21 and a solvent.

42. A battery comprising the positive electrode material composition of any one of claims 1-21 or the positive electrode tab of any one of claims 22-40 or the positive electrode tab prepared by the preparation method of claim 41.

43. An electric device comprising the battery of claim 42.

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