Battery cell, battery device and power-consuming device

Abstract

Battery cell, characterized in that it comprises the following: a cathode foil and an anode foil arranged in a cascade; wherein the cathode foil comprises a cathode collector and a cathode film layer arranged on the surface of at least one side of the cathode collector, wherein the cathode film layer comprises a carbon-coated lithium iron phosphate material, wherein the carbon-coated lithium iron phosphate material comprises a lithium iron phosphate substrate and a carbon coating layer arranged on the surface of the substrate; where the carbon-coated lithium iron phosphate material has a carbon coating factor of η = BET 1 BET 2 exhibits, wherein BET1 is the specific surface area of ​​a mesopore and macropore structure of the carbon-coated lithium iron phosphate, and wherein BET2 is the total specific surface area of ​​the carbon-coated lithium iron phosphate material, satisfying η 0.81 ≤ η ≤ 0.95. wherein the cathode foil has a pressing density of the electrode foil of not less than 2.35 g / cm³ 3 exhibits.

Description

TECHNICAL AREA

[0001] The present application relates to the technical field of electrochemistry, in particular a battery cell, a battery device and a power-consuming device. STATE OF THE ART

[0002] With the rapid development of new energy technologies, lithium-ion batteries are being used in various types of large-scale installations, energy storage systems, and consumer products due to their excellent electrochemical performance, lack of memory effect, low environmental impact, and other advantages. They are particularly widespread in pure electric vehicles, hybrid electric vehicles, and other new energy vehicles.

[0003] Among the active cathode materials commonly used in lithium-ion batteries, lithium iron phosphate is one of the most widely used in industrialized lithium-ion batteries. However, since the gram capacity of lithium iron phosphate is lower than that of ternary materials, research and development in recent years has focused primarily on improving its capacity. Focusing solely on improving the capacity performance of lithium iron phosphate, however, inevitably leads to a loss of other battery performance characteristics, such as cycle life and processing power.

[0004] It is therefore expected that a lithium-ion battery with high energy density, high cycle performance and excellent processing power will be developed. CONTENTS OF THE PRESENT USE SAMPLE

[0005] In view of the problems in the prior art, the purpose of the present application is to provide an active lithium iron phosphate cathode material with a carbon coating. The material has a high capacity ratio, high density, and easy dewatering of the electrode foils, so that the lithium-ion battery combines excellent energy density, cycle performance, and excellent processing performance, which significantly improves the battery's production efficiency and reduces battery production costs.

[0006] A first aspect of the present application provides an active lithium iron phosphate cathode material with a carbon coating, wherein the active cathode material comprises a lithium iron phosphate substrate and a carbon coating layer located on the surface of the substrate, wherein the lithium iron phosphate substrate has a general structural formula LiFel-aMaPO4, wherein M is selected from more than one of the elements Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti, where 0 ≤ a ≤ 0.01; wherein the lithium iron phosphate cathode material with a carbon coating has a carbon coating factor η=BET1BET2 exhibits, wherein BET1 is the specific surface area of ​​a mesopore and macropore structure of the carbon-coated lithium iron phosphate, wherein BET2 is the total specific surface area of ​​the carbon-coated lithium iron phosphate, where η 0.81 ≤ η ≤ 0.95 is satisfied.

[0007] In one embodiment, η optionally satisfies 0.85 ≤ η ≤ 0.93 and further optionally 0.88 ≤ η ≤ 0.92.

[0008] In one of the embodiments, BET1 lies within a value range of 5.5 m. 2 / g up to 9.5 m 2 / g, while BET2 in a value range of 6.0 m 2 / g up to 11.5 m 2 / g lies.

[0009] In one embodiment, the ratio H / D between the thickness H of a carbon coating layer and the average particle size D of the carbon-coated lithium iron phosphate is 0.01 to 0.04.

[0010] In one embodiment, the proportion of a carbon component to the total mass of the carbon-coated lithium iron phosphate is 0.7% to 1.3%, optionally 0.9% to 1.3%, and further optionally 0.9% to 1.1%.

[0011] In one embodiment, the volume-average particle size Dv50 of the carbon-coated lithium iron phosphate meets 840 nm≤Dv50≤3570 nm, optionally 1170 nm≤Dv50≤1820 nm.

[0012] In one embodiment, the powder density of the carbon-coated lithium iron phosphate is not less than 2.4 g / cm³. 3 , optional 2.5 g / cm² 3 and optionally 2.6 g / cm² 3 .

[0013] In one embodiment, the degree of graphitization of the carbon-coated lithium iron phosphate is 0.15 to 0.32, optionally 0.19 to 0.26.

[0014] In one embodiment, the powder resistance of the carbon-coated lithium iron phosphate is no more than 60 Ω-m, optionally no more than 30 Ω-m, and further optionally no more than 20 Ω-m.

[0015] A second aspect of the present application provides a manufacturing process for the active cathode material, the process comprising the following steps:

[0016] Providing a lithium iron phosphate substrate;

[0017] Coating the lithium iron phosphate substrate with carbon to obtain an active lithium iron phosphate cathode material with a carbon coating; wherein the active cathode material comprises a lithium iron phosphate substrate and a carbon coating layer located on the surface of the substrate, wherein the lithium iron phosphate substrate has a general formula LiFe1-aMaPO4, where M is selected from more than one of the elements Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti, where 0 ≤ a ≤ 0.01; wherein the lithium iron phosphate cathode material with a carbon coating has a carbon coating factor η=BET1BET2 exhibits, wherein BET1 is the specific surface area of ​​a mesopore and macropore structure of the carbon-coated lithium iron phosphate, wherein BET2 is the total specific surface area of ​​the carbon-coated lithium iron phosphate, where η 0.81 ≤ η ≤ 0.95 is satisfied.

[0018] In one embodiment, the manufacturing process for an active cathode material comprises the following steps:

[0019] (1) Providing a lithium iron phosphate substrate; wherein the raw materials of the Fe source, Li source, M source and / or P source and the reagent as the reducing agent and the carbon source are mixed and the mixture obtained is processed at high temperature under an inert atmosphere to obtain a lithium iron phosphate substrate;

[0020] (2) Coating the lithium iron phosphate substrate with carbon; wherein the lithium iron phosphate substrate is processed at high temperature under an inert atmosphere while the carbon source is sprayed, and the carbon-coated lithium iron phosphate material is obtained by vapor deposition.

[0021] The Fe source can be selected from one or more of FeSO4, FePO4, FeCl2, FeC2O4, Fe2O3.

[0022] The Li source can be selected from one or more of Li2CO3, LiH2PO4, Li3PO4.

[0023] The phosphorus source can be selected from one or more of NH4H2PO4 or H3PO4. The magnesium source comprises one element selected from Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, or Ti.

[0024] The reagent used in step (1) as a reducing agent and carbon source can be one or more selected from C2H2, CH4, glucose, polyethylene glycol, sucrose, starch, H2, and CO. Optionally, the amount added as a reducing agent and carbon source is 4% to 8% of the total mass of the raw material, or optionally 6%.

[0025] The carbon source in step (2) can be a material such as acetone.

[0026] The treatment temperature in step (1) or (2) can be varied over a wide range, e.g. 500 to 800°C.

[0027] A third aspect of the present application provides a cathode foil for lithium-ion batteries, comprising a cathode collector and an active cathode material provided on at least one surface of the cathode collector, wherein the active cathode material is an active cathode material according to the first aspect of the present application or an active cathode material produced by the method according to the second aspect of the present application.

[0028] In one embodiment, the cathode foil has a saturated water content of no more than 500 ppm at a temperature of 25°C and a relative humidity of 45%.

[0029] A fourth aspect of the present application provides a lithium-ion battery comprising a cathode foil and an anode foil, wherein the cathode foil comprises a cathode collector and an active cathode material provided on at least one surface of the cathode collector, wherein the active cathode material is an active cathode material according to the first aspect of the present application or an active cathode material produced by the method according to the second aspect of the present application, wherein the cathode foil has a saturated water content of not more than 500 ppm at a temperature of 25°C and a relative humidity of 45%.

[0030] In one embodiment, the cathode foil has a pressing density of the electrode foil of not less than 2.35 g / cm³. 3 on, while the anode foil has a pressing density of the electrode foil of not less than 1.6 g / cm³ 3exhibits, wherein the active anode material in the anode foil consists of graphite coated with amorphous carbon.

[0031] A fifth aspect of the present application provides a battery module comprising a lithium-ion battery according to the fourth aspect of the present application. The battery module can be manufactured using methods known in the prior art for manufacturing battery modules.

[0032] A sixth aspect of the present application provides a battery pack comprising a lithium-ion battery according to the fourth aspect of the present application or a battery module according to the fifth aspect of the present application. The battery pack can be manufactured using methods known in the prior art for manufacturing battery packs.

[0033] A seventh aspect of the present application provides a power-consuming device comprising a lithium-ion battery according to the fourth aspect of the present application, a battery module according to the fifth aspect of the present application, or a battery pack according to the sixth aspect of the present application, wherein the lithium-ion battery, battery module, or battery pack is used as a power source for the power-consuming device or as an energy storage unit for the power-consuming device. The power-consuming device can be manufactured using methods known in the prior art for manufacturing power-consuming devices. [Beneficial effects]

[0034] In the present application, the active cathode material is obtained by regulating the relative proportion of the specific surface area of ​​carbon structures of various microforms in the surface layer of the carbon-coated lithium iron phosphate material. The active carbon-coated lithium iron phosphate material of the present application has a carbon coating factor η, and when η ≤ 0.81 ≤ 0.95, the carbon-coated lithium iron phosphate exhibits a high-quality carbon coating, which significantly reduces the difficulty of dehydrating the electrode foil, resulting in the lithium-ion battery produced from it exhibiting excellent energy density, good cycle performance, and excellent processing performance.

[0035] The battery module, battery set and power-consuming device of the present application comprise the lithium-ion battery provided in the present application and thus have at least the same advantages as the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWING Fig. Figure 1 is a TEM image of a lithium iron phosphate cathode material with a carbon coating of an embodiment of the present application at various magnifications. Fig. Figure 2 shows a schematic representation of a lithium-ion battery in an embodiment of the present application. Fig. 3 is a decomposition representation of the in the Fig. 2 lithium-ion battery shown in an embodiment of the present application. Fig. Figure 4 shows a schematic representation of a battery module in an embodiment of the present application. Fig. Figure 5 shows a schematic representation of a battery pack in an embodiment of the present application. Fig. 6 is a decomposition representation of the in the Fig. 5 battery packs shown in an embodiment of the present application. Fig. Figure 7 shows a schematic representation of a power-consuming device in an embodiment of the present application. Reference symbol list: 1 battery pack 2 upper box body 3 lower box body 4 battery modules 5 lithium-ion batteries 51 Housing body 52 Electrode assembly 53 Top cover assembly DETAILED DESCRIPTION

[0036] The embodiments of an active lithium iron phosphate cathode material with a carbon coating and its manufacturing process, the cathode foil comprising the cathode material, the lithium-ion battery, the battery module, the battery pack, and the power-consuming device of the present application are described in detail with reference to the accompanying drawings, omitting unnecessary details in some cases. For example, detailed descriptions of things that are already well known and repeated descriptions of the same structure are omitted. This is to avoid making the following description unnecessarily long and to facilitate understanding by the person skilled in the art.Furthermore, the attached drawings and the following description serve to provide a person skilled in the art with a complete understanding of the present application and are not intended to limit the subject matter specified in the claims.

[0037] For the sake of simplicity, a series of numerical ranges are expressly specified in the present application, and different numerical ranges can be combined with one another to form corresponding embodiments. Each lower limit can be combined with any upper limit to form the scope of the present application; and each lower limit can be combined with other lower limits to form the scope of the present application, and likewise each upper limit can be combined with any other upper limit to form the scope of the present application. Furthermore, each individually disclosed point or value can itself be used as a lower or upper limit in combination with any other point or value, or in combination with other lower or upper limits, to form the scope of the present application.

[0038] Unless otherwise stated, the terms used in this application have the known meanings generally understood by those skilled in the art. For the purposes of this application, unless otherwise stated, the terms 'above' and 'below' include the present number. For example, 'more than one of a and b' means at least one of a and b, for example a, b, or a and b. Similarly, 'one or more' means that at least one is included. In the present descriptions, the term 'or' is comprehensive unless otherwise stated. That is to say, the phrase 'A or (or) B' means 'A, B, or both A and B'.

[0039] It should be noted that the term "carbon coating layer" refers to a portion of the lithium iron phosphate substrate that may, but need not, be completely coated on the lithium iron phosphate substrate, and that the use of the term "carbon coating" is solely for the sake of simplicity of description and is not intended to restrict the present application. Similarly, the term "thickness of the carbon coating layer" refers to the maximum thickness of the portion coated on the lithium iron phosphate substrate.

[0040] The inventors of the present application, after investigating the active lithium iron phosphate cathode material, found that the low electronic conductivity and low ionic conductivity of the active lithium iron phosphate cathode material in pure phase (without carbon) worsens the capacity game of the active lithium iron phosphate cathode material, so that the energy density of lithium-ion batteries using lithium iron phosphate as the active cathode material differs significantly from that of ternary lithium-ion batteries.

[0041] To address the problem of the poor electronic and ionic conductivity of the active lithium iron phosphate cathode material, the material can be treated with carbon coating and nano-treatment. However, the inventor of the present application has found that both the carbon coating and the nano-treatment inevitably lead to a deterioration in the performance of other aspects of the battery, in particular the battery cycle performance and the processing performance.

[0042] In particular, the inventors observed during actual operation that, for the lithium iron phosphate material, different carbon coating processes result in pore structures with varying microscopic morphologies in the active cathode material after treatment with the carbon coating. These include, for example, micropore structures (network structures with pores smaller than 2 nm), mesopore structures (network structures with pores between 2 nm and 50 nm), macropore structures (network structures with pores larger than 50 nm), and other structures without apparent pores, such as layered carbon structures.After numerous experiments, the inventor determined that, following the carbon coating of the lithium iron phosphate material, the irrational arrangement of various pore structures in the surface layer not only has no apparent effect on improving the electronic and ionic conductivity of the active lithium iron phosphate cathode material, but also significantly increases the difficulty of dewatering the electrode foil produced from this material. Even after prolonged dewatering treatment, the water in the resulting electrode foil does not reach the dewatering rate required for battery production. In particular, when the coating thickness of the active cathode material layer is increased to raise the battery's energy density, achieving the required dewatering rate of the electrode foil becomes more challenging.

[0043] In particular, the inventors have found in practice that the nanotreatment also exacerbates the difficulties in dehydrating the electrode foil, thus worsening the battery's cycle performance. Furthermore, the nanotreatment also reduces the powder density of the active lithium iron phosphate cathode material, significantly reducing the energy density resulting from the increased electronic and ionic conductivities.

[0044] Excessive water content in the electrode foil leads to problems such as the easy detachment of the cathode film layer in the electrode foil, structural and chemical instability, which ultimately affects the cycle performance of the battery; on the other hand, it also increases the risk of defective products in the manufacture of the battery, which not only increases costs but also seriously impairs the efficiency of battery production.

[0045] In summary, it is expected that an active cathode material with high capacity clearance, high packing density and easy dewatering of the electrode foil will be developed in order to then develop a lithium-ion battery with high energy density, high cycle performance and excellent processing performance.

[0046] After a large number of experiments and studies, the inventors of the present application have found a technical solution that allows the active lithium iron phosphate cathode material to combine a high capacity ratio, high compressive density, and easy dewatering of the electrode foils, so that the lithium-ion battery combines excellent energy density, cycle performance, and excellent processing performance, which significantly improves the production efficiency of the battery and reduces the cost of battery production. [Active lithium iron phosphate cathode material with a carbon coating]

[0047] The present application provides an active lithium iron phosphate cathode material with a carbon coating, wherein the active cathode material comprises a lithium iron phosphate substrate and a carbon coating layer located on the surface of the substrate, wherein the lithium iron phosphate substrate has a general formula LiFe 1-a M a PO4, wherein M is selected from more than one of the elements Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti and wherein: 0≤a≤0.01.

[0048] The lithium iron phosphate cathode material with a carbon coating has a carbon coating factor η=BET1BET2 on, where BET1 is the specific surface area of ​​an intermediate pore and macropore structure of the carbon-coated lithium iron phosphate, where BET2 is the total specific surface area of ​​the carbon-coated lithium iron phosphate, where η 0.81 ≤ η ≤ 0.95 is satisfied.

[0049] The substrate has a general formula LiFe 1-a M a PO4, where M is selected from one or more of the elements Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti, where 0≤a≤0.01. Doping with M elements contributes to improving the structural stability of the lithium iron phosphate substrate and prevents the structural breakdown of the active lithium iron phosphate cathode material after several charge / discharge cycles.

[0050] The carbon coating layer can improve the electronic and ionic conductivity and increase the battery's energy density. However, as a porous structure composed of carbon, the carbon coating layer significantly increases the overall specific surface energy of the active lithium iron phosphate cathode material, which in turn significantly increases the active lithium iron phosphate cathode material's water absorption capacity. The inventor of the present application has determined, after numerous experimental verifications, that when the carbon-coated lithium iron phosphate material η=BET1BET2, By fulfilling the requirements of 0.81 ≤ η ≤ 0.95, the carbon-coated lithium iron phosphate exhibits a suitable specific surface energy while maintaining a high capacity. This significantly reduces the overall specific surface energy of the electrode foil, which is manufactured from the active lithium iron phosphate cathode material with the carbon coating. The dewatering efficiency of the electrode foil is also significantly improved, and the difficulty of dewatering the electrode foil is considerably reduced. Therefore, the battery manufactured from the active lithium iron phosphate cathode material with a carbon coating of 0.81 ≤ η ≤ 0.95 has excellent energy density, cycle life, and processing performance.

[0051] In the present application, the carbon coating factor η characterizes the relative proportion of the specific surface area of ​​the pore structures of different microscopic morphologies in the carbon-coated lithium iron phosphate material and reflects the magnitude of the ratio between the specific surface area of ​​the micropore structure, which contributes much to the surface energy, and the ratio of the specific surface area of ​​all pores; its magnitude reflects the effectiveness of the carbon coating of the lithium iron phosphate.Through a large number of experiments and many years of experience in the production of cathode materials, the inventor found that at a value of 0.81 ≤ η ≤ 0.95, the dense and efficient carbon coating layer can significantly improve the capacity game of the active lithium iron phosphate cathode material and significantly reduce the surface energy of the active lithium iron phosphate cathode material, so that the lithium-ion batteries have excellent energy density, while the cycle performance and processing performance of the battery are also significantly improved.

[0052] After numerous experimental trials, the inventor determined that the lithium iron phosphate exhibits a high-quality carbon coating when the carbon coating factor η is in the range of 0.85 ≤ η ≤ 0.93, with the relative proportion of pores in the surface layer of various microscopic morphologies within a reasonable range. This is conducive to improving the capacity of the active lithium iron phosphate cathode material, significantly reducing the amount of water absorption by the electrode foil, and the resulting lithium-ion battery exhibits excellent energy density, cycle performance, and excellent processing performance.

[0053] In some embodiments, η is optionally in the range of 0.88 ≤ η ≤ 0.92, and the lithium-ion battery exhibits improved electrochemical performance and processing power.

[0054] In summary, the active lithium iron phosphate cathode material with a carbon coating of the present application is obtained by regulating the relative proportion of the specific surface area of ​​carbon structures of different microscopic morphologies in the surface layer of the lithium iron phosphate material with the carbon coating. When the carbon coating factor η of the carbon-coated lithium iron phosphate material of the present application is 0.81 ≤ η ≤ 0.95, the lithium iron phosphate material has a high-quality carbon coating, which contributes to a significant improvement in the dehydration efficiency of the electrode foil, and the lithium-ion batteries produced from it exhibit excellent energy density and cycle performance as well as excellent processing performance. See in particular Table 1.

[0055] Optionally, η can be a value of 0.811, 0.836, 0.862, 0.894, 0.915, 0.922, 0.928, 0.939, or a value in the range of any two of the above-mentioned points. In some embodiments, the BET1 value can be between 5.5 and 9.5 m² / g and the BET2 value between 6.0 and 11.5 m² / g. At this point, the relative proportion of carbon structures of different microscopic morphologies in the surface layer is within a reasonable range, and the electrode is less likely to absorb water, which is more conducive to improving the battery's energy density and cycle performance.

[0056] Optionally, BET1 can have a value of 9.08, 8.86, 7.05, 6.68, 6.93, 6.46, 5.95, 5.82, or a value in the range of any two of the above-mentioned point values. Optionally, BET2 can have a value of 11.2, 10.6, 8.19, 7.48, 7.16, 7.01, 6.40, 6.20, or a value in the range of any two of the above-mentioned point values.

[0057] In some embodiments, the ratio H / D of the active cathode material of the present application optionally ranges from 0.01 to 0.04 between the thickness H of a carbon coating layer and the average particle size D of the carbon-coated lithium iron phosphate.

[0058] When the ratio of carbon coating thickness to the average particle size of the carbon-coated lithium iron phosphate is 0.01 to 0.04, the integrity of the carbon coating on the surface of the lithium iron phosphate material and the electronic conductivity are improved, resulting in high electronic conductivity. Simultaneously, the lithium iron phosphate material has a high powder density, thus improving the energy density and cycle life of lithium-ion batteries, as the carbon coating thickness is within a reasonable range relative to the overall particle size. An appropriate carbon coating thickness also reduces the difficulty of dewatering the electrode foil produced from the lithium iron phosphate material, enabling better processing.

[0059] In some embodiments, the proportion of a carbon component in the total mass of the carbon-coated lithium iron phosphate is optionally 0.7% to 1.3%, optionally 0.9% to 1.3%, and further optionally 0.8% to 1.1%.

[0060] If the carbon content is too low, the integrity of the carbon coating on the surface of the lithium iron phosphate material is poor, and the material dynamics are unfavorable, resulting in a lower battery energy density. Conversely, if the carbon content is too high, it prevents the growth of individual particles during sintering, which in turn causes the lithium iron phosphate material to tend to form secondary particles composed of numerous small particles. Furthermore, the carbon content does not contribute to the battery capacity, again resulting in a lower lithium-ion battery energy density. Based on the total mass of the carbon-coated lithium iron phosphate, the carbon content in the present application is 0.7% ≤ C ≤ 1.3%; optionally 0.9% ≤ C ≤ 1.3%; and further optionally 0.8% ≤ C ≤ 1.1%. See in particular Table 2.

[0061] Optionally, based on the total mass of the carbon-coated lithium iron phosphate, the proportion of the carbon component can be 0.70%, 0.82%, 0.95%, 1.12%, 1.3%, or a value in a range of any two of the above-mentioned point values.

[0062] In some embodiments, the volume-average particle size Dv50 of the carbon-coated lithium iron phosphate of the present application meets 840 nm≤Dv50≤3570 nm, optionally 1170 nm≤Dv50≤1820 nm.

[0063] The inventor of the present application determined that, to solve the problem of the poor electronic and ionic conductivity of the active lithium iron phosphate cathode material, the material could be treated with nano-coating. However, after extensive practical experience, it has been found that nano-treatment also increases the surface energy of the active lithium iron phosphate cathode material, increases the water absorption capacity of the electrode foil, and leads to dewatering difficulties, ultimately degrading the cycle and processing performance of the battery. Furthermore, nano-treatment also reduces the powder density of the active lithium iron phosphate cathode material, thereby significantly reducing the energy density resulting from the increased electronic and ionic conductivities.

[0064] Experiments have shown that within the range of 0.81 ≤ η ≤ 0.95, if the carbon-coated lithium iron phosphate further meets the volume-mean particle size of 840 nm ≤ Dv50 ≤ 3570 nm, optionally 1170 nm ≤ Dv50 ≤ 1820 nm, the powder density of the carbon-coated lithium iron phosphate can reach up to 2.64 g / cm³. 3 can be up to 2.64 g / cm³ and the pressing density of the electrode foil up to 2.64 g / cm³ 3 The energy density of the battery can vary. In the present application, increasing volume-mean particle size Dv50 shows a decreasing trend for both the powder compaction density and the electrode foil compaction density, and the battery energy density gradually decreases. However, increasing Dv50 improves the dewatering efficiency of the electrode foil, leading to an improvement in the basic cycle performance of the lithium-ion battery. See Table 4 in particular.

[0065] Optionally, Dv50 can be a value of 840, 1170, 1430, 1820, 3520 or a value in the range of two of the above point values.

[0066] In some embodiments, the degree of graphitization of the carbon-coated lithium iron phosphate is optionally 0.15 to 0.32. If the carbon-coated lithium iron phosphate material of the present application has a carbon coating factor of 0.81 ≤ η ≤ 0.95 and a degree of graphitization of the carbon-coated lithium iron phosphate of 0.15 to 0.32, it is not only beneficial for the capacity game of the lithium iron phosphate material, but also more beneficial for improving the powder resistance of the lithium iron phosphate material and for improving the energy density of the battery. See in particular Table 5.

[0067] The “degree of graphitization” of the carbon-coated lithium iron phosphate refers to the degree of graphitization of the carbon component, which reflects the degree of integrity of the graphite crystal structure in the carbon-coated lithium iron phosphate of the present application, in particular in the carbon coating layer, i.e., the degree of regularity of the arrangement of the carbon atoms in the graphite structure.

[0068] Optionally, the degree of graphitization can be a value of 0.155, 0.197, 0.255, 0.245, 0.312 or a value in the range of two of the above-mentioned point values.

[0069] In some embodiments, the lithium iron phosphate substrate is doped with carbon elements, optionally with 0.1% to 0.5% carbon elements, based on the mass of the lithium iron phosphate substrate.

[0070] In some embodiments, the powder resistance of the carbon-coated lithium iron phosphate of the present application is optionally no more than 60 Ω-m, optionally no more than 30 Ω-m, and further optionally no more than 20 Ω-m.

[0071] In some embodiments, the active cathode material of the present application may comprise, in addition to the carbon-coated lithium iron phosphate, other active cathode materials commonly used in the art, such as other olivine-structured lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials suitable for use as active cathode materials in batteries may also be employed. It is possible to use only one of these active cathode materials or to use more than two in combination. The layered transition metal oxides include, for example, at least one of the following compounds: lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g.,LiMnO2, LiMn2O4), lithium-nickel-cobalt oxide, lithium-manganese-cobalt oxide, lithium-nickel-manganese oxide, lithium-nickel-cobalt-manganese oxide (e.g. LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be abbreviated as NCM333), LiNi 0,5 Co 0,2 Mn 0,3 O2 (which can also be abbreviated as NCM523), LiNi 0,5 Co 0,25 Mn 0,25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0,8 Co 0,1 Mn 0,1 O2 (also known as NCM811) and lithium nickel cobalt aluminum oxide (e.g. LiNi) 0,85 Co 0,15 Al 0,05 O2) and modified compounds thereof, and the like. Other lithium-containing phosphates with an olivine structure include, for example, lithium manganese phosphate (e.g., LiMnPO4), a compound of lithium manganese phosphate and carbon, a compound of lithium ferromanganese phosphate, and lithium manganese iron phosphate and carbon. [Cathode foil]

[0072] The present application provides a cathode foil comprising a cathode collector and an active cathode material provided on at least one surface of the cathode collector, wherein the active cathode material is a carbon-coated lithium iron phosphate according to the first aspect of the present application.

[0073] The lithium-ion battery of the present application comprises a cathode foil and an anode foil, the cathode foil comprising the above-mentioned active carbon-coated lithium iron phosphate cathode material with a carbon coating of the present application, wherein the cathode foil has a saturated water content of no more than 500 ppm at a temperature of 25°C and a relative humidity of 45%. In the prior art, the proportion of saturated water in the electrode foil produced from the active lithium iron phosphate cathode material by conventional carbon coating can be up to 1000 ppm at a temperature of 25°C and a relative humidity of 45%, which is significantly higher than the amount of water absorption of the electrode foil produced from the active lithium iron phosphate cathode material with the carbon coating of the present application.

[0074] In some embodiments, the cathode foil optionally has a pressing density of the electrode foil of up to 2.65 g / cm³. 3 on, while the anode foil has a pressing density of the electrode foil of not less than 1.6 g / cm³ 3 exhibits, wherein the active anode material in the anode foil consists of graphite coated with amorphous carbon.

[0075] In order to match the active lithium iron phosphate cathode material of the present application with a high capacity range, a graphite anode with a capacity range of not less than 350 mAh / g and an electrode foil density of not less than 1.6 g / cm3 is provided, and at the same time the graphite surface has an amorphous carbon coating which has an embedded lithium ion capacity and a higher charging window that is matched to the cathode of the present application.

[0076] In some embodiments, the proportion of active lithium iron phosphate cathode material with the carbon coating in the cathode film layer of the cathode foil of the present application is 90% to 98% of the mass of the total cathode film layer. The active lithium iron phosphate cathode material with the carbon coating of the present application can bind more active lithium iron phosphate cathode material for the same binder content because it is bonded to a suitable specific surface area determined by carbon structures of various microscopic morphologies. When the cathode film layer is bonded with 2% PVDF, the coating amount is ≥300 mg / mm². 2 , and the coating speed in mass production is up to 60 m / min, which significantly improves processing efficiency in actual operation, and the energy density of the battery is also significantly improved.

[0077] The cathode foil comprises a cathode collector and a cathode material that is provided on at least one surface of the cathode collector. For example, the cathode collector has two surfaces that are opposite each other in its thickness direction, and the cathode material is provided on one or both of the two surfaces opposite the cathode collector.

[0078] In the lithium-ion battery of the present application, the cathode collector can be a metal foil or a composite collector. For example, an aluminum foil can be used as the metal foil. The composite collector can comprise a base layer of polymeric material and a metal layer formed on at least one surface of the polymeric base layer. The composite collector can be formed by depositing metallic material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) onto a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), 1,3-propanesulfonate lactone (PS), polyethylene (PE), etc.), but the present application is not limited to these materials.

[0079] The cathode material optionally comprises a conductive element. The present application does not specifically restrict the type of conductive element; the person skilled in the art may select one according to their actual needs. For example, the conductive element for the cathode material may be selected from one or more of the following: superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dot, carbon nanotubes, graphene, and carbon nanofibers.

[0080] In the present application, the cathode foil can be produced according to methods known in the field. For example, the active cathode material of the present application, the conductive agent and the binder can be dispersed in a solvent (such as N-methylpyrrolidone (NMP)) to form a homogeneous cathode slurry, and the cathode slurry is applied to the cathode collector, and the cathode foil is obtained after drying, cold pressing and other processes. [Anode foil]

[0081] The anode foil comprises an anode collector and an anode film layer, which is provided on at least one surface of the anode collector, the anode film layer comprising an active anode material.

[0082] For example, the anode collector has two surfaces that are opposite each other in its thickness direction, and the anode film layer is provided on one or both of the two surfaces opposite the anode collector.

[0083] In some embodiments, the cathode foil of the present application optionally has a pressing density of the electrode foil of not less than 2.35 g / cm³. 3 on, while the anode foil has a pressing density of the electrode foil of not less than 1.6 g / cm³ 3 exhibits, wherein the active anode material in the anode foil consists of graphite coated with amorphous carbon.

[0084] In order to adapt the active lithium iron phosphate cathode material of the present application with high capacity, a graphite anode with a capacity of not less than 350 mAh / g and an electrode foil density of not less than 1.6 g / cm³ is used.3 provided, and at the same time the graphite surface has an amorphous carbon coating which has an embedded lithium-ion capacity and a higher charging window that is matched to the cathode of the present application.

[0085] In the lithium-ion battery of the present application, the anode collector can be a metal foil or a composite collector. For example, a copper foil can be used as the metal foil. The composite collector can comprise a base layer of polymeric material and a metal layer formed on at least one surface of the polymeric base layer. The composite collector can be formed by depositing metallic material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) onto a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.), but the present application is not limited to these materials.

[0086] In the anode foil of the present application, the anode film layer typically comprises an active anode material as well as an optional binder, an optional conductive agent, and other optional additives, which are usually applied from an anode slurry and dried. The anode slurry is generally prepared by dispersing the active anode material, an optional conductive agent, and an optional binder, etc., in a solvent and mixing thoroughly. The solvent may be N-methylpyrrolidone (NMP) or deionized water.

[0087] For example, the conductive medium can be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dot, carbon nanotubes, graphene and carbon nanofibers.

[0088] In the anode foil of the present application, the anode film layer may contain, in addition to the active anode material, other commonly used active anode materials, such as synthetic graphite, natural graphite, soft charcoal, hard charcoal, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be one or more of monolithic silicon, silicon oxides, silicon-carbon complexes, silicon-nitrogen complexes, and silicon alloys. The tin-based material may be one or more of monolithic tin, tin oxide compounds, and tin alloys. [Electrolyte solution]

[0089] The electrolyte serves as an ion conductor between the cathode foil and the anode foil. The present application does not impose any specific restrictions regarding the type of electrolyte, which can be selected as needed. For example, the electrolyte can be selected from at least one solid and one liquid electrolyte (i.e., an electrolyte solution).

[0090] In some embodiments, an electrolyte solution is used for the electrolyte. This electrolyte solution consists of an electrolyte salt and a solvent.

[0091] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium borate dioxylic acid (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxylic acid phosphate (LiDFOP) and / or lithium tetrafluorooxalate phosphate (LiTFOP).

[0092] In some embodiments, the solvent can be selected from at least one of ethylidene carbonate (EC), propylidene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylenepropylene carbonate (MPC), ethylenepropylene carbonate (EPC), butylidene carbonate (BC), fluorinated ethylene 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), cyclobutane sulfone (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0093] In some embodiments, the electrolyte solution optionally includes an additive. The additive may, for example, include a film-forming additive for the anode and a film-forming additive for the cathode, and may also include an additive that can improve certain battery properties, such as an additive to improve the battery's overcharge performance, an additive to improve its high-temperature performance, an additive to improve its low-temperature performance, etc.

[0094] In some embodiments, the electrolyte solution of the present application optionally comprises an electrolyte solution having a conductivity of not less than 13 mS / cm, which is paired with the cathode foil and the anode foil of the present application. [Separator]

[0095] The lithium-ion battery that uses a solution electrolyte, and some lithium-ion batteries that use a solid electrolyte, also contain a separator. The separator is positioned between the cathode foil and the anode foil and serves as insulation. The present application does not impose any specific restrictions regarding the type of separator, and any known separator with a porous structure and good chemical and mechanical stability may be selected. In some embodiments, the separator material may be one or more of the following: glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. Without any particular restriction, the separator may be a single-layer film or a multi-layer composite film.If the insulating film is a multi-layered composite film, the materials of the layers can be the same or different without any particular restrictions. [Lithium-ion battery]

[0096] In some embodiments, the cathode foil, the anode foil and the insulating film can be assembled into an electrode assembly by a winding process or a stacking process; the cathode foil comprises the carbon-coated lithium iron phosphate of the present application.

[0097] In some embodiments, the lithium-ion battery may include an outer packaging. The outer packaging can be used to encapsulate the electrode component and electrolyte described above.

[0098] In some embodiments, the outer packaging of the lithium-ion battery can be a hard casing, such as a hard plastic casing, an aluminum casing, a steel casing, etc. The outer packaging of the lithium-ion battery can also be a soft casing, such as a bag-like soft casing. The soft casing can be made of plastic, and examples of such plastics include polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0099] The present application does not impose any specific restrictions regarding the shape of the lithium-ion battery, which may be cylindrical, square, or any other shape. For example, in Fig. Figure 2 shows an example of a lithium-ion battery 5 with a rectangular structure.

[0100] In some embodiments, such as in Fig.As shown in Figure 3, the outer packaging can comprise a housing 51 and a cover plate 53. The housing 51 can comprise a base plate and side plates connected to the base plate, the base plate and the side plates forming a receiving cavity. The housing 51 has an opening that communicates with the receiving cavity, and the cover plate 53 can serve to cover the opening to close the receiving cavity. The cathode foil, the anode foil, and the separator can be assembled into an electrode assembly 52 by a winding or stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte solution is exchanged into the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the lithium-ion battery 5 can be one or more, and the person skilled in the art can make the selection as required. [Battery module]

[0101] In some embodiments, the lithium-ion batteries can further be assembled into a battery module, and the number of lithium-ion batteries contained in the battery module can be one or a plurality, the exact number being selectable by the person skilled in this technical field depending on the application and capacity of the battery module.

[0102] Fig. Figure 4 shows a battery module 4 as an example. As in Fig. As shown in Figure 4, the multiple lithium-ion batteries 5 in the battery module 4 can be arranged sequentially along a longitudinal direction of the battery module 4. Of course, they can also be arranged in any other desired manner. Furthermore, the multiple lithium-ion batteries 5 can be secured by fastening elements.

[0103] Optionally, the battery module 4 can also include a housing with a receiving space in which the multitude of lithium-ion batteries 5 are accommodated. [Battery pack]

[0104] In some embodiments, the battery modules described above can also be assembled into a battery pack, wherein the number of battery modules contained in the battery pack can be selected by the person skilled in this art depending on the application and capacity of the battery pack.

[0105] The Fig. 5 and Fig. Figure 6 shows a battery pack 1 as an example. As in Fig. 5 and Fig.As shown in Figure 6, the battery pack 1 can comprise a battery housing and a plurality of battery modules 4 arranged within the battery housing. The battery housing comprises an upper housing 2 and a lower housing 3, the upper housing 2 serving to cover the lower housing 3 and form an enclosed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged within the battery housing in any desired configuration. [Power-consuming device]

[0106] Furthermore, the present application provides a power-consuming device, the power-consuming device comprising one or more lithium-ion batteries of the present application, a battery module, and a battery pack. The lithium-ion battery, battery module, or battery pack can be used as a power source for the device or as an energy storage unit for the device. The power-consuming device can include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0107] Depending on requirements, a lithium-ion battery, a battery module or a battery pack can be selected as the power-consuming device.

[0108] Fig. Figure 7 shows an example of the device. The device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the lithium-ion battery of this device, a battery pack or battery module can be used.

[0109] Another example of such a device is a mobile phone, a tablet, a laptop, etc. The device usually needs to be light and thin and can use a lithium-ion battery as a power source. Example of implementation

[0110] The following describes exemplary embodiments of the present application. The embodiments described below are exemplary, serve to explain the present application, and cannot be construed as limiting the present application. Unless specific techniques or conditions are indicated in the exemplary embodiments, they correspond to the techniques or conditions described in the relevant literature or to the information in the product specification. The reagents or instruments used without manufacturer identification are all commercially available products. The proportions of the components in the exemplary embodiments of the present application refer to mass unless otherwise stated. Example of implementation Example of implementation 1-1

[0111] Production of carbon-coated lithium iron phosphate as an active cathode material

[0112] Preparation of lithium iron phosphate substrate: Iron phosphate, lithium carbonate, and titanium oxide were used as raw materials. These materials were mixed in the stoichiometric ratio of the molar ratio FePO4:Li2CO3:TiO2 = 0.996:0.498:0.004, and glucose and polyethylene glycol, used as carbon source and reducing agent, were added (the mass ratio of glucose and polyethylene glycol was 1:1, and the amount of carbon source was 6% of the total mass of the raw materials). Subsequently, solvent water was added for wet milling to obtain a mixed slurry. The resulting slurry was spray-dried, and the dried product was sintered in a roller furnace at 500 °C with insulated air for 20 hours, naturally cooled to the material temperature <80 °C, and then discharged to obtain the calcined material.The calcined material was crushed, sieved and demagnetized to obtain the lithium iron phosphate substrate LiFe; 0,998 Ti 0,002 to obtain PO4 doped with approximately 0.3% carbon.

[0113] Carbon coating: The above substrate was sintered in a roller furnace under a nitrogen atmosphere. Simultaneously, an acetone solution was sprayed into the sintering furnace as a carbon source, and sintering was carried out at a constant temperature of 770 °C for 10 hours. After the material had cooled naturally to a temperature of <80 °C, it was removed; and further comminution with an air stream crusher yielded the carbon-coated lithium iron phosphate of embodiment 1-1. [Cathode foil]

[0114] The active lithium iron phosphate cathode material with carbon coating, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black were mixed in a mass ratio of 96.5:2.0:1.5, and then the solvent N-methylpyrrolidone (NMP) was added to form a homogeneous cathode slurry; this slurry was applied to a carbon-coated aluminum foil with a thickness of 13 µm and a coating surface density of 26 mg / cm². 2 applied, dried, cold pressed and cut to obtain the cathode foil of embodiment 1-1 of the present application. [Anode foil]

[0115] The active anode material graphite, the thickening agent sodium carboxymethylcellulose, the binder styrene-butadiene rubber, and the conductive agent acetylene black were mixed in a mass ratio of 97:1:1:1, deionized water was added, and the anode slurry was obtained under the action of a vacuum mixer; the anode slurry was applied uniformly to a copper foil with a thickness of 8 µm; after drying, the anode foil was obtained by cold pressing and cutting to obtain the anode foil of embodiment 1-1 of the present application. [Electrolyte solution]

[0116] The solvents ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in a mass ratio of 30:70, and LiPF6 was added after complete dissolution; then vinylidene carbonate (VC) and fluoroethylidene carbonate (FEC) were added and mixed well to obtain an electrolyte solution with a LiPF6 concentration of 1 mol / L and a mass content of vinylidene carbonate (VC) or fluoroethylidene carbonate (FEC) of 3%. [Separator]

[0117] A polypropylene separator with a thickness of 12 µm was chosen. [Manufacturing of the lithium-ion battery]

[0118] The electrode foil was baked in a high-temperature oven at 110 °C for 7 hours to remove the water from the electrode foil, and then the cathode foil, the separator and the anode foil were stacked in sequence so that the separator took on the role of insulation between the cathode foil and the anode foil, and then wound into a square bare electrical core, inserted into the aluminum-plastic foil, injected with the appropriate non-aqueous electrolyte solution and sealed; After the processes of standing, hot and cold pressing, forming, vibrating and capacity sharing, the lithium-ion battery of embodiment 1-1 of the present application is obtained. Example 1-2

[0119] The steps are the same as in embodiment 1-1, except that in the "carbon coating" step the sintering temperature is 780°C at a constant temperature. Example 1-3

[0120] The steps are the same as in embodiment 1-1, except for the step of “carbon coating”.

[0121] The "carbon coating" step in embodiment 1-3 proceeds as follows: The lithium iron phosphate substrate of embodiment 1-3 was sintered in a roller furnace under a nitrogen atmosphere, simultaneously sprayed with acetone solution, and sintered at a constant temperature of 550°C for 10 hours. It was then discharged when the material had naturally cooled to a temperature below 80°C. After comminution and sieving, the material was again placed in a roller furnace, sprayed with acetone solution, sintered at a constant temperature of 770°C for 10 hours, and discharged after naturally cooling to a temperature below 80°C. The product of the second sintering was then comminuted by airflow to obtain the carbon-coated lithium iron phosphate of embodiment 1-3. Exemplary embodiment 1-4

[0122] The steps are the same as in embodiment 1-3, except that in the "carbon coating" step the temperature of the second sintering is 780°C at a constant temperature. Example 1-5

[0123] The steps are the same as in embodiment 1-3, except that the temperature of the second sintering at constant temperature in the "carbon coating" step is 790°C. Example 1-6

[0124] The steps are the same as in embodiment 1-3, except that in the "carbon coating" step the temperature of the first sintering at constant temperature is 600°C and the temperature of the second sintering at constant temperature is 770°C. Exemplary embodiment 1-7

[0125] The steps are the same as in embodiment 1-6, except that the temperature of the second sintering at constant temperature in the "carbon coating" step is 780°C. Example 1-8

[0126] The steps are the same as in embodiment 1-6, except that the temperature of the second sintering at constant temperature in the "carbon coating" step is 790°C. Comparative example 1

[0127] The steps are the same as in embodiment 1-1, except that in the "carbon coating" step the sintering temperature is 750°C at a constant temperature. Comparative example 2

[0128] Conventional sintering: Iron phosphate, lithium carbonate, and titanium oxide were used as raw materials. These materials were mixed in the stoichiometric molar ratio of FePO4:Li2CO3:TiO2 = 0.996:0.498:0.004, and glucose and polyethylene glycol were added as a carbon source (the mass ratio of glucose and polyethylene glycol was 1:1, and the amount of carbon source was 6% of the total mass of the raw materials). Water was then added for wet milling to obtain a mixed slurry. The resulting slurry was spray-dried, and the dried product was sintered in a roller furnace at 750°C with insulated air for 10 hours, cooled naturally to a material temperature of <80°C, and then discharged to obtain the calcined material.The calcined material was crushed, sieved, and demagnetized to obtain the lithium iron phosphate from comparative example 2. Comparative example 3

[0129] The steps are the same as in embodiment 1-6, except that in the "carbon coating" step the temperature of the first sintering at constant temperature is 650°C and the temperature of the second sintering at constant temperature is 830°C. Example 2-1

[0130] The steps are the same as in embodiment 1-1, except that in the "substrate production" step, the amount of carbon source added is reduced to 4% of the total mass of the raw material, and in the "carbon coating" step, the constant sintering temperature is 800°C and the constant sintering time is 13 hours. The substrate is doped with approximately 0.15% carbon elements. Example 2-2

[0131] The steps are the same as in embodiment 1-3, except that in the step “production of the substrate” the amount of carbon source added is reduced to 5% of the total mass of the raw material, and that in the step “carbon coating” the temperature of the first sintering at constant temperature is 600°C and the temperature of the second sintering at constant temperature is 800°C. Example 2-3

[0132] The steps are the same as in embodiment 2-2, except that in the step “production of the substrate” the amount of carbon source added is 6% of the total mass of the raw material, and that in the step “carbon coating” the temperature of the first sintering at constant temperature is 600°C and the temperature of the second sintering at constant temperature is 780°C. Example 2-4

[0133] The steps are the same as in embodiment 2-3, except that in the step “production of the substrate” the amount of carbon source added is increased to 7% of the total mass of the raw material, and that in the step “carbon coating” the temperature of the first sintering at constant temperature is 550°C and the temperature of the second sintering at constant temperature is 800°C. Example 2-5

[0134] The steps are the same as in embodiment 2-4, except that in the step “production of the substrate” the amount of carbon source added is increased to 8% of the total mass of the raw material, and that in the step “carbon coating” the temperature of the first sintering at constant temperature is 550°C and the temperature of the second sintering at constant temperature is 780°C. Comparative example 4

[0135] The steps are the same as in embodiment 2-1, except that in the step “production of the substrate” the amount of carbon source added is reduced to 3% of the total mass of the raw material, and that in the step “carbon coating” the temperature of sintering at constant temperature is 830°C and the sintering time of sintering at constant temperature is 15 hours. Comparative example 5

[0136] The steps are the same as in embodiment 2-5, except that in the step “production of the substrate” the amount of carbon source added is increased to 10% of the total mass of the raw material, and that in the step “carbon coating” the temperature of the first sintering at constant temperature is 550°C and the temperature of the second sintering at constant temperature is 770°C. Comparative example 6

[0137] The steps are the same as in comparison example 5, except that in the step “production of the substrate” the amount of carbon source added is increased to 15% of the total mass of the raw material. Example 3-1

[0138] The steps are the same as in embodiment 2-5, except that in the step “production of the substrate” the amount of carbon source added is 5% of the total mass of the raw material, and that in the step “carbon coating” the temperature of the first sintering at constant temperature is 620°C (sintering time at constant temperature is 12 hours) and the temperature of the second sintering at constant temperature is 820°C (sintering time at constant temperature is 12 hours). Example 3-2

[0139] The steps are the same as in embodiment 3-1, except that in the step “production of the substrate” the amount of carbon source added is 6% of the total mass of the raw material, and that in the step “carbon coating” the temperature of the first sintering at constant temperature is 600°C (sintering time at constant temperature is 10 hours) and the temperature of the second sintering at constant temperature is 780°C (sintering time at constant temperature is 10 hours). Example 3-3

[0140] The steps are the same as in embodiment 3-2, except that in the step “production of the substrate” the amount of carbon source added is 8% of the total mass of the raw material, and that in the step “carbon coating” the temperature of the first sintering at constant temperature is 600°C (sintering time of the sintering at constant temperature is 10 hours) and the temperature of the second sintering at constant temperature is 780°C (sintering time of the sintering at constant temperature is 10 hours). Comparative example 7

[0141] The steps are the same as in embodiment 3-1, except that in the step “production of the substrate” the amount of carbon source added is 3% of the total mass of the raw material, and that in the step “carbon coating” the temperature of the first sintering at constant temperature is 650°C (sintering time of the sintering at constant temperature is 10 hours) and the temperature of the second sintering at constant temperature is 830°C (sintering time of the sintering at constant temperature is 12 hours). Comparative example 8

[0142] The steps are the same as in comparative example 7, except that in the step "production of the substrate" the amount of carbon source added is 12% of the total mass of the raw material, and that in the step "carbon coating" the temperature of the first sintering at constant temperature is 600°C (sintering time of the sintering at constant temperature is 10 hours) and the temperature of the second sintering at constant temperature is 780°C (sintering time of the sintering at constant temperature is 10 hours). Example 4-1

[0143] The steps are the same as in embodiment 2-3, except that in the "carbon coating" step, the temperature of the first constant-temperature sintering is 550°C (sintering time at constant temperature is 10 hours) and the temperature of the second constant-temperature sintering is 790°C (sintering time at constant temperature is 15 hours). The volume-mean particle size Dv50 of the active lithium iron phosphate cathode material with the carbon coating finally obtained in embodiment 4-1 was 530 nm. Exemplary embodiment 4-2 to Exemplary embodiment 4-7

[0144] The volume-mean particle size Dv50 of the finally obtained active lithium iron phosphate cathode material with the carbon coating was 840 nm, 1170 nm, 1430 nm, 1820 nm, 3520 nm and 5070 nm respectively, and by adjusting the sorting frequency of the airflow crusher, i.e., of the active lithium iron phosphate cathode material, a different Dv50 was achieved. Comparative example 9

[0145] For sintering at room temperature, the steps are the same as in embodiment 1-1, except that the temperature of the sintering at a constant temperature is 750°C. Example 5-1

[0146] The steps are the same as in embodiment 1-1, except that in the step “production of the substrate” the amount of carbon source added is 8% of the total mass of the raw material, and that in the step “carbon coating” the temperature of sintering at constant temperature is 750°C (sintering time at constant temperature is 10 hours). Example 5-2

[0147] The steps are the same as in embodiment 2-2, except that in the step “production of the substrate” the amount of carbon source added is 6% of the total mass of the raw material, and that in the step “carbon coating” the temperature of the first sintering at constant temperature is 550°C (sintering time of the sintering at constant temperature is 10 hours) and the temperature of the second sintering at constant temperature is 790°C (sintering time of the sintering at constant temperature is 10 hours). Example 5-3

[0148] The steps are the same as in embodiment 5-3, except that in the step “production of the substrate” the amount of carbon source added is 5% of the total mass of the raw material, and that in the step “carbon coating” the temperature of the first sintering at constant temperature is 600°C (sintering time of the sintering at constant temperature is 10 hours) and the temperature of the second sintering at constant temperature is 830°C (sintering time of the sintering at constant temperature is 14 hours). Comparative example 10

[0149] The steps for "substrate production" are the same as in comparative example 7, but the difference lies in the "carbon coating" step. The specific step for "carbon coating" is as follows:

[0150] The lithium iron phosphate substrate of comparison example 10 was sintered in a roller furnace under a nitrogen atmosphere and simultaneously sprayed with an acetone solution and sintered at a constant temperature of 600°C for 10 hours and then discharged when the material had cooled naturally to a temperature of <80°C.After comminution and sieving, the substrate is further sintered in a roller furnace and then unloaded in a roller furnace; after comminution and sieving, the material is again fed into the roller furnace and sprayed with acetone solution, sintered at a constant temperature of 650 °C for 10 hours, and removed when the material has naturally cooled to a temperature below 80 °C; after comminution and sieving, the material is again fed into the roller furnace and sprayed with acetone solution a third time, sintered at a constant temperature of 830 °C for 10 hours, and removed when the material has naturally cooled to a temperature below 80 °C. The product of the third sintering was crushed in an air stream to obtain the active lithium iron phosphate cathode material of Comparative Example 10.

[0151] The specific surface area, the volume mean particle size Dv50, the carbon content, the dewatering efficiency of the electrode foil, the powder compaction density and the data of the dewatering efficiency of the electrode foil, the energy density of the battery and the cycle capacity maintenance rate of the battery of the active lithium iron phosphate cathode material of the above embodiments and the comparative examples are given in Tables 1 to 5. [Test of the relevant parameters of the active lithium iron phosphate cathode material] 1. Average particle size D

[0152] The X-ray powder diffractometer used in the present application is an X'pert PRO from the USA. The detailed test procedure for the average particle size D is as follows: 1) The measured width Bm of the sample under test was measured. The instrument's sampling rate was set to 2 degrees / minute to obtain the XRD spectrum of the sample. Subtraction of the Cu Kα2 support using JADE software was performed to obtain the Bm of each diffraction peak. 2) Measurement of instrumental broadening, e.g.

[0153] Using the same material as the samples to be tested and with a grain size of 5-20 µm, the XRD spectra of the samples were measured under the same experimental conditions as the samples to be tested, and the Bs was determined from the spectra.

[0154] 3) Calculation of the full width at half maximum (FWHM) B. B = Bm - Bs. (Note: If B is calculated in angular units, it must be converted to radians.)

[0155] 4) Calculation of the average particle size D. Using Scheller's formula D = Kλ / Bcosθ, where K is assumed to be 0.89, θ is the diffraction angle, λ = 0.154056 nm, and substituting B, the grain thickness D' normal to the grain surface is obtained, which is represented by a single diffraction peak. Several diffraction peaks were taken to calculate D' separately, and the average value was used to obtain the average particle size D. 2. Scanning Electron Microscope (SEM)

[0156] The active lithium iron phosphate cathode materials of all embodiments and comparison examples were examined using a ZEISS sigma 300 scanning electron microscope, and the sample morphology was subsequently observed with reference to the standard JY / T010-1996.

[0157] It should be noted that the shape of the lithium iron phosphate substrate in the present application is not necessarily perfectly spherical, but may also be irregular, such as primary particles. It should also be noted that the shape of the active lithium iron phosphate cathode material with the carbon coating produced in the present application is likewise not necessarily spherical and may also be irregular. 3. Transmission electron microscope (TEM)

[0158] The active lithium iron phosphate cathode materials of all embodiments and comparison examples were tested using the JEOL2010 transmission electron microscope. The test standard is: GB / T 34002-2017. 4. Powder compaction density

[0159] One gram of the active lithium iron phosphate cathode material from all embodiments and comparative examples was weighed separately and placed into a cylindrical mold with the cross-sectional area of ​​the mold's circular holes designated as S. The powder was then compressed in the cylindrical mold with the cross-sectional area of ​​the holes. A pressure of 3t was applied to the powder in the mold and held for 30 s. The thickness of the powder was recorded as t. Subsequently, the powder compaction density ρ of the active lithium iron phosphate cathode material from all embodiments and comparative examples can be calculated using the following formula: ρ = m / (S × t). 5. Electrode foil compression density

[0160] The electrode foils of the exemplary embodiments and the comparative examples were cut into a foil 1000 mm long, and the electrode foil was milled with a specific pressure so that the length of the foil was 1006 mm due to the extensibility of the aluminum foil. Then 1540.25 mm 2 Small discs were punched onto the foil, and the weight M and thickness L of the small discs were measured. The pure aluminum foil is cut into small discs of 1540.25 mm. 2 If the aluminum foil is punched and the mass M0 of the empty foil is weighed, then the pressing density of the cathode foil of each of the exemplary embodiments and each of the comparative examples can be calculated using the following formula: PD=(M−M0) / 1.54025 / 2 / L. 6. Testing the carbon content

[0161] The carbon content of the active cathode material in all embodiments and comparative examples is tested by the infrared absorption method after combustion in a high-frequency induction furnace. The specific test procedure is based on the standard GB / T 20123-2006 / ISO 15350:2000 "Determination of the total carbon and sulfur content of the combustion of iron and steel in a high-frequency induction furnace, followed by the infrared absorption method," which is expediently carried out using a carbon and sulfur analyzer such as the Deckert HCS infrared carbon and sulfur analyzer. 7. Specific surface area test

[0162] The specific surface area parameters of exemplary embodiments and comparative examples were tested using a 3Flex specific surface area analyzer from Mack, USA. In the present application, the specific surface area BET2 of pore structures with pore diameters from 0.5 nm to 100 nm was determined by T-plot fitting, reflecting the sum of the surface areas of micropores, mesopores, and macropores in the lithium iron phosphate material; BET1 is the specific surface area of ​​mesopore and macropore structures with pore diameters above 2.0 nm and below 100 nm, determined using the T-plot method. 8. Powder resistance

[0163] The powder resistance of the above active cathode material of all embodiments and comparison examples was tested with a powder resistance measuring device (ST2722) in accordance with standard GB / T 30835-2014. 9. Dewatering efficiency of the electrode foil

[0164] The active lithium iron phosphate cathode material, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black of the exemplary embodiments and comparative examples were mixed according to the mass ratio of 96.5:2.0:1.5, and the corresponding amount of the solvent N-methylpyrrolidone (NMP) was added and stirred and mixed sufficiently to form a homogeneous cathode slurry. This slurry was applied to a carbon-coated aluminum foil of the cathode collector with a thickness of 13 µm and a surface density of 26 mg / cm². 2The material was applied, then dried, cold-pressed, cut, and stored to obtain the cathode foil. The electrode foil tray was placed in a humid environment with 50% water content and allowed to absorb water for 24 hours until nearly saturated. A small disc, 1.4 cm in diameter, was then punched using a flake punch, cut into small pieces approximately 0.5 cm × 0.5 cm, and placed in a moisture meter to test the water content in ppm. The remaining electrode foil was then placed in a vacuum oven, sealed with a plastic bag to prevent moisture absorption. After drying at 110°C for 7 hours, the same small round disc was punched, cut into pieces, and tested for a water content of ppm. The dewatering efficiency of the material was W = (AB) / 420 ppm / min. 10. Volume mean particle size Dv50

[0165] In the particle group, if 50% of the total volume of particles has a diameter larger than a certain D-value, and another 50% of the total volume of particles has a diameter smaller than this D-value, then this D-value is the mean particle size of the particles.

[0166] Instrument model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer, reference standard procedure: GB / T19077-2016 / ISO 13320:2009. Specific test procedure: An appropriate quantity of the active lithium iron phosphate cathode material from the embodiments and comparison examples was taken and made up to 20 ml with deionized water (the sample concentration should be 8 to 12%), while ultrasonic dispersion was performed for 5 minutes (53 kHz / 120 W) to ensure complete sample dispersion. Subsequently, the samples from the embodiments and comparison examples were measured according to standards GB / T19077-2016 / ISO 13320:2009. The particle size volume distribution plot and the particle size number distribution plot were prepared from the test data.This distribution diagram shows that if 50% of the total volume of particles has a diameter larger than a certain D-value and another 50% of the total volume of particles has a diameter smaller than this D-value, then this D-value is the mean particle size. 11. Degree of graphitization

[0167] Graphitization tests were performed using a Raman spectrometer for characterization. The Raman spectrometer used was a high-resolution, next-generation model LabRAM HR Evolution from HORIBA Jobin Yvon, France, and the wavelength of the light source was 532 nm. Spectra in the range of 750–2000 cm⁻¹ were recorded and, after subtracting the back bottom, fitted using the following Gaussian function. Ai, vi, and wi represent the peak intensity, peak position, and peak width, respectively. The two peaks corresponding to the carbon coating layer can be fitted with four peaks, and the corresponding peak strengths are recorded as D2, D1, D3, and G, respectively. The degree of graphitization is G / (D3+G). G(v)=Aiexp[−4 ln(2)(v−viwi)2], [Battery performance test] 1. Energy density test procedure

[0168] The lithium-ion batteries of all embodiments and comparative examples were placed in an oven at 25°C and left for 2 hours, then charged and discharged for testing. The primary charging and discharging process is as follows: charging at a constant current of 1C to 3.65V, continuing to charge at a constant voltage until the charging current is less than 0.05C and then disconnecting; interruption for 5 minutes; discharging at a constant current of 1C to 2.0V; interruption for 5 minutes. This constitutes one charge and discharge cycle of the battery. The mass energy density of the electrical core (Wh / kg) = the energy of the third discharge / the mass of the active lithium iron phosphate material in the battery. 2. Cycle performance test

[0169] The lithium-ion batteries of all embodiments and comparative examples were placed in an oven at 60°C and left for 2 hours, then charged and discharged for testing. The primary charge and discharge procedure is as follows: charging at a constant current of 1C to 3.65V, continuing to charge at a constant voltage until the charging current is less than 0.05C and then disconnecting; interruption for 5 minutes; discharging at a constant current of 1C to 2.5V; interruption for 5 minutes. This is one charge and discharge cycle of the battery, which is repeated until the battery capacity drops to 80% of its initial value, and the number of cycles is recorded. Table 1 Relative parameters of the lithium-ion battery in the exemplary embodiments and the comparative examples number Treatment by carbon coating Active lithium iron phosphate cathode material Performance parameters Total carbon content / % BET1 / m 2 / g BET2 / m 2 / g η Cathode foil drainage efficiency (ppm / min) Capacity maintenance rate for cycles (%) Energy density (Wh / kg) S1-1 One carbon injection, 770°C, 10 hours 1,282 9,08 11,20 0,811 7,8 73,3 ≥160 S1-2 One carbon injection, 780°C, 10 hours 1,216 8,86 10,60 0,836 8,5 76,4 ≥170 S1-3 Two carbon injections, 550+770°C, each for 10 hours 1,197 7,05 8,19 0,861 9,7 82,8 ≥180 S1-4 Two carbon injections, 550+780°C, each for 10 hours 1,056 6,68 7,48 0,893 10,9 84,6 ≥180 S1-5 Two carbon injections, 550+790°C, each for 10 hours 0,966 6,56 7,16 0,916 11,6 85,6 ≥190 S1-6 Two carbon injections, 600+770°C, 10 hours each 0,903 6,46 7,01 0,922 12,1 83,6 ≥190 S1-7 Two carbon injections, 600+780°C, each for 10 hours 0,734 5,95 6,40 0,929 12,9 87,3 ≥180 S1-8 Two carbon injections, 600+790°C, each for 10 hours 0,654 5,82 6,20 0,939 13,5 81,0 ≥170 D1 One carbon injection, 750°C, 10 hours 1,282 9,38 11,80 0,795 7,5 80,1 ≥170 D2 Conventional sintering, without carbon coating 1,271 9,86 12,80 0,770 6,8 82,5 ≥190 D3 Two carbon injections, 650+830°C, each for 10 hours 0,582 4,84 5,01 0,966 15,5 72,1 ≥150 Table 2 Relative parameters of the lithium-ion battery in the exemplary embodiments and the comparative examples number Treatment methods of respective examples Active lithium iron phosphate cathode material Performance parameters Amount of carbon source added during substrate preparation step / % Main process parameters of the carbon coating Total carbon content / % BET1 / m 2 / g BET2 / m 2 / g η Cathode foil drainage efficiency (ppm / min) Capacity maintenance rate for cycles (%) Energy density (Wh / kg) S2-1 4% One carbon injection, 800°C, 13 hours 0,70 5,87 6,24 0,940 12,2 85,5 ≥160 S2-2 5% Two carbon injections, 600+800°C, 10 hours each 0,82 6,11 6,62 0,923 11,7 84,1 ≥170 S2-3 6% Two carbon injections, 600+780°C, each for 10 hours 0,95 7,23 8,02 0,901 10,5 84,8 ≥190 S2-4 7% Two carbon injections, 550+800°C, each for 10 hours 1,12 6,99 7,97 0,877 10,2 86,0 ≥190 S2-5 8% Two carbon injections, 550+780°C, each for 10 hours 1,30 8,81 10,75 0,819 8,3 85,6 ≥180 D4 3% One carbon injection, 830°C, 15 hours 0,55 5,12 5,28 0,970 14,6 71,7 ≥150 D5 10% Two carbon injections, 550+770°C, each for 10 hours 1,60 12,50 16,50 0,758 5,4 75,5 ≥170 D6 15% Two carbon injections, 550+770°C, each for 10 hours 2,00 13,50 19,30 0,700 3,6 70,1 ≥150 Table 3 Relative parameters of the lithium-ion battery in the exemplary embodiments and the comparative examples number Main process parameters of carbon coating Active lithium iron phosphate cathode material Performance parameters Total carbon content / % Carbon coating layer thickness H / nm Average particle size D / nm H / D value BET1 / m 2 / g BET2 / m 2 / g η Dewatering efficiency of the electrode foil (ppm / min) Capacity maintenance rate for cycles (%) Energy density (Wh / kg) D7 Two carbon injections, 650+830°C, 10 hours + 12 hours 0,65 4,1 490 0,008 4,95 5,07 0,976 15,3 69,8 ≥150 S3-1 Two carbon injections, 620+820°C, 12 hours + 12 hours 0,83 5,2 365 0,014 5,88 6,26 0,939 12,4 78,7 ≥170 S3-2 Two carbon injections, 600+780°C, 10 hours ++ 10 hours 0,916 6,2 234 0,026 6,93 7,57 0,915 11,6 85,6 ≥190 S3-3 Two carbon injections, 600+780°C, 10 hours ++ 10 hours 1,56 7,7 211 0,036 8,58 10,43 0,822 8,1 83,2 ≥180 D8 Two carbon injections, 600+780°C, 10 hours ++ 10 hours 2,0 8,9 185 0,056 13,0 16,8 0,774 5,2 73,9 ≥160 Table 4 Relative parameters of the lithium-ion battery in the exemplary embodiments and the comparative examples number Examples of treatment methods Active lithium iron phosphate cathode material Performance parameters Total carbon content / % Volume average particle size Dv50 / nm BET 1 / m 2 / g BET2 / m 2 / g η Dewatering efficiency of the electrode foil (ppm / min) Capacity maintenance rate for cycles (%) Powder density / g / cm³ 3 Electrode foil density / g / cm³ 3 Energy density (Wh / kg) S4-1 The amount of carbon source added during the substrate preparation step is 6%. Two carbon injections, 550+790°C, 10 hours + 15 hours 0,90 530 9,09 11,18 0,813 7,4 82,9 2,64 2,65 ≥190 S4-2 840 8,06 9,95 0,810 8,7 84,3 2,61 2,64 ≥190 S4-3 1170 7,28 8,01 0,909 8,8 85,3 2,57 2,62 ≥190 S4-4 1430 6,66 7,28 0,915 11,6 85,6 2,55 2,60 ≥190 S4-5 1820 6,04 6,55 0,922 12,4 85,9 2,47 2,49 ≥180 S4-6 3520 5,18 5,58 0,928 14,4 87,8 2,40 2,35 ≥170 S4-7 5070 4,56 4,89 0,933 15,1 88,7 2,35 2,32 ≥170 Table 5 Relative parameters of the lithium-ion battery in the exemplary embodiments and the comparative examples number Carbon coating treatment agents Active lithium iron phosphate cathode material Performance parameters Total carbon content / % Degree of graphitization BET1 / m 2 / g BET2 / m 2 / g η Powder resistance / Ω·m Dewatering efficiency of the electrode foil (ppm / min) Capacity maintenance rate for cycles (%) Energy density (Wh / kg) D9 Conventional sintering, without carbon coating 1,46 0,097 11,86 16,7 0,710 33,2 5,3 70,2 ≥160 S5-1 One carbon injection, 750°C, 10 hours 1,40 0,155 9,58 12,6 0,760 11,1 7,1 78,2 ≥170 S5-2 Two carbon injections, 550+790°C, 10 hours ++ 10 hours 0,95 0,255 6,63 7,25 0,914 18,5 10,6 85,6 ≥190 S5-3 Two carbon injections, 600+830°C, + 14 hours ++ 10 hours 0,89 0,300 6,17 6,55 0,942 9,8 11,9 80,1 ≥180 D10 Three carbon injections, 600°C + 650°C + 830°C, 10 hours + 10 hours + 10 hours 0,82 0,437 5,88 6,00 0,979 3,5 13,9 77,3 ≥170

[0170] Table 1 shows that when comparing S1-1 to S1-8 and D1 to D3, when η is in the range of 0.81 to 0.95 (S1-1 to S1-8), the corresponding electrode foil dewatering rate is significantly better than that of D1 to D3 overall, and that the corresponding lithium-ion battery simultaneously exhibits excellent cycle capacity retention and high energy density; when η is in the range of 0.82 to 0.93 (S1-2 to S1-7), the corresponding electrode foil dewatering rate is better, while the corresponding lithium-ion battery also exhibits excellent cycle performance and higher energy density; If η is in the range of 0.88 to 0.92 (S1-4 to S1-6), the corresponding dehydration rate of the electrode foil is better, while the corresponding cycle performance and energy density of the lithium-ion battery are also better, and the lithium-ion battery has excellent overall performance.However, none of the comparison examples D1 to D3 can simultaneously combine a good dewatering rate of the electrode foil, a higher capacity maintenance rate in the cycle and a higher energy density.

[0171] Table 2 shows that when comparing S2-1 to S2-5 and D4 to D6, when the carbon content is in the range of 0.82% to 1.3% and 0.81 ≤ η ≤ 0.95, the lithium-ion battery exhibits a good electrode foil dewatering rate, excellent capacity retention over cycle, and high energy density; when the carbon content is 0.9% to 1.3%, the corresponding electrode foil dewatering rate is better, while the corresponding lithium-ion battery exhibits better cycle performance and energy density; when the carbon content is 0.9% to 1.1%, the corresponding electrode foil dewatering rate is even better, while the corresponding cycle performance and energy density of the lithium-ion battery are also better, and the overall performance of the lithium-ion battery is better.However, none of the D4 to D6 can simultaneously combine a good dewatering rate of the electrode foil, a higher capacity maintenance rate in the cycle and a higher energy density.

[0172] Table 3 shows that, when comparing S3-1 to S3-3 and D7 to D8, the lithium-ion battery exhibits a good electrode foil dewatering rate, excellent capacity retention during the cycle, and high energy density at 0.81 ≤ η ≤ 0.95 and an H / D ratio of 0.01 to 0.04. However, none of the batteries D7 to D8 can simultaneously combine a good electrode foil dewatering rate, a higher capacity retention rate during the cycle, and higher energy density.

[0173] Table 4 shows that when comparing S4-1 to S4-7, when 0.81 ≤ η ≤ 0.95 and 530 nm ≤ Dv50 ≤ 5070 nm, the lithium-ion battery exhibits a good electrode foil dewatering rate, excellent cycle capacity retention, and high energy density; when 1170 nm ≤ Dv50 ≤ 1820 nm, the corresponding electrode foil dewatering rate is better, and the corresponding lithium-ion battery also has better cycle performance and energy density, and the lithium-ion battery has better overall performance.

[0174] Table 5 shows that when comparing S5-1 to S5-3 and D9 to D10, if the graphitization degree of the active cathode material is 0.15 to 0.32, the lithium-ion battery exhibits a good electrode foil dewatering rate, excellent capacity retention over the cycle, and high energy density. If the graphitization degree of the carbon coating layer is in the range of 0.19 to 0.26, the electrode foil dewatering rate is better, and the corresponding lithium-ion battery also has better cycle performance and energy density, resulting in better overall performance. However, none of the comparison examples, D9 to D10, can simultaneously combine a good electrode foil dewatering rate, higher capacity retention over the cycle, and higher energy density.

[0175] It should be noted that the present application is not limited to the embodiments mentioned above. The embodiments mentioned above are only examples, and embodiments within the scope of the technical solution of the present application that have essentially the same composition as the technical idea and have the same effect are included in the technical scope of the present application. Furthermore, within the scope of the present application, other possibilities for constructing the embodiments by combining some of the constituent elements of the embodiments and applying various deformations to the embodiments that a person skilled in the art can imagine without departing from the subject matter of the present application are also included. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] Standard GB / T 20123-2006 / ISO 15350:2000

[0161] Standard GB / T 30835-2014

[0163] GB / T19077-2016 / ISO 13320:2009

[0166]

Claims

[1] Battery cell, characterized by that it includes the following: a cathode foil and an anode foil arranged in a cascade; wherein the cathode foil comprises a cathode collector and a cathode film layer arranged on the surface of at least one side of the cathode collector, wherein the cathode film layer comprises a carbon-coated lithium iron phosphate material, wherein the carbon-coated lithium iron phosphate material comprises a lithium iron phosphate substrate and a carbon coating layer arranged on the surface of the substrate; where the carbon-coated lithium iron phosphate material has a carbon coating factor of η=BET1BET2 exhibits, wherein BET1 is the specific surface area of ​​a mesopore and macropore structure of the carbon-coated lithium iron phosphate, and wherein BET2 is the total specific surface area of ​​the carbon-coated lithium iron phosphate material, satisfying η 0.81 ≤ η ≤ 0.

95. wherein the cathode foil has a pressing density of the electrode foil of not less than 2.35 g / cm³ 3 exhibits. [2] Battery cell according to claim 1, characterized by , that η optionally 0.85 ≤ η ≤ 0.93, and further optionally 0.88 ≤ η ≤ 0.

92. [3] Battery cell according to one of claims 1 to 2, characterized by , that BET1 in a range of 5.5 to 9.5 m 2 / g and BET2 in a range of 6.0 to 11.5 m 2 / g lies. [4] Battery cell according to any one of claims 1 to 3, characterized by, that the proportion of a carbon component in the total mass of the carbon-coated lithium iron phosphate is 0.7% to 1.3%, optionally 0.9% to 1.3%, and further optionally 0.9% to 1.1%. [5] Battery cell according to any one of claims 1 to 4, characterized by , that the ratio H / D between the thickness H of a carbon coating layer and the average particle size D of the carbon-coated lithium iron phosphate is 0.01 to 0.

04. [6] Battery cell according to any one of claims 1 to 5, characterized by , that the volume-mean particle size Dv50 of the carbon-coated lithium iron phosphate meets 840 nm≤Dv50≤3570 nm, optionally 1170 nm≤Dv50≤1820 nm. [7] Battery cell according to any one of claims 1 to 6, characterized by that the powder density of the carbon-coated lithium iron phosphate is not less than 2.4 g / cm³ 3 , optional 2.5 g / cm² 3 and optionally 2.6 g / cm² 3 amounts. [8] Battery cell according to any one of claims 1 to 7, characterized by , that the carbon-coated lithium iron phosphate has a degree of graphitization of 0.15 to 0.32, optionally 0.19 to 0.

26. [9] Battery cell according to any one of claims 1 to 8, characterized by , that the powder resistance of the carbon-coated lithium iron phosphate is no more than 60 Ω-m, optionally no more than 30 Ω-m, and further optionally no more than 20 Ω-m. [10] Battery cell according to any one of claims 1 to 9, characterized by , that the lithium iron phosphate substrate is doped with carbon elements, optionally with 0.1% to 0.5% carbon elements, based on the mass of the lithium iron phosphate substrate. [11] Battery cell according to any one of claims 1 to 10, characterized by that the cathode foil has a saturated water content of no more than 500 ppm at a temperature of 25°C and a relative humidity of 45%. [12] Battery cell according to any one of claims 1 to 11, characterized by that the anode foil has a density of not less than 1.6 g / cm³ 3 exhibits, wherein the active anode material in the anode foil comprises graphite coated with amorphous carbon. [13] Battery cell according to any one of claims 1 to 12, characterized by that the cathode foil has a pressing density of the electrode foil of 2.35 g / cm³ 3 up to 2.65 g / cm³ 3 exhibits. [14] Battery cell according to any one of claims 1 to 13, characterized by , that the cathode film layer comprises a binder, wherein the percentage by mass of the binder is 2%, based on the total mass of the cathode film layer, wherein the cathode film layer has a one-sided coating weight of ≥300 mg / mm 2 exhibits. [15] Battery cell according to any one of claims 1 to 14, characterized bythat the battery cell has a capacity of no less than 350 mAh / g. [16] Battery cell according to any one of claims 1 to 15, characterized by that the electrolyte solution has an electrical conductivity of not less than 13 mS / cm. [17] Battery device, characterized by that it comprises a battery cell according to one of claims 1 to 16. [18] Power-consuming device, characterized by that it comprises a battery cell according to one of claims 1 to 16 or a battery device according to claim 17.

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