Method for preparing positive electrode material, positive electrode material, positive plate, battery and electric device

Abstract

The invention provides a method for preparing a positive electrode material, the positive electrode material, a positive electrode plate, a battery and an electric device. The method comprises the following steps: mixing a lithium source with a phosphoric acid solution to obtain a first mixture; mixing the first mixture with manganese hydrogen phosphate, an iron source and an optional M element source to obtain a second mixture; and drying and sintering the second mixture to obtain the lithium iron manganese phosphate positive electrode material, wherein the M element comprises one or more of transition metal elements except manganese and iron elements, IIA group metal elements, IIIA group metal elements, IVA group metal elements and VIIA group elements. According to the method, side reaction gas and by-products are reduced, the compaction density of the positive electrode material is improved, the resistivity of the positive electrode material is reduced, and the specific capacity and rate capability of the battery are improved.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a method for preparing a positive electrode material, a positive electrode material, a positive electrode sheet, a battery and an electrical device. Background Art

[0002] In recent years, as the application scope of secondary batteries becomes wider and wider, secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As secondary batteries have made great progress, higher requirements have been put forward for their energy density, rate performance, etc. Summary of the invention

[0003] The present application is made in view of the above-mentioned problems, and its purpose is to provide a method for preparing positive electrode materials, the obtained positive electrode materials, positive electrode plates, batteries and electrical devices. The method of the present application reduces the side reaction gases and by-products in the preparation process, increases the compaction density of the positive electrode materials, reduces the resistivity of the positive electrode materials, and thus improves the specific capacity and rate performance of the battery.

[0004] In order to achieve the above object, the first aspect of the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0005] mixing a lithium source with a phosphoric acid solution to obtain a first mixture;

[0006] The first mixture is mixed with manganese hydrogen phosphate, an iron source, and an optional source of an M element to obtain a second mixture; wherein the M element includes one or more of transition metal elements other than manganese and iron elements, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements;

[0007] The second mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

[0008] Therefore, the present application is beneficial to improving the lithium ion conductivity of the material and reducing the generation of side reaction gases and by-products by first reacting the lithium source with the phosphoric acid solution and then reacting with other raw materials, thereby increasing the compaction density of the positive electrode material, reducing the resistivity of the material, and improving the specific capacity and rate performance of the battery.

[0009] In any embodiment, the positive electrode material includes a compound Li a Mn x Fe y M b PO 4; wherein, x is selected from 0.5-0.9, y is selected from 0.1-0.5, the sum of x and y is 0.96-1, a is selected from 1.01-1.05, b is selected from 0-0.05, and can be selected from 0.01-0.05; M includes one or more of transition metal elements other than manganese and iron, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0010] The second invention of the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0011] mixing a lithium source with a phosphoric acid solution to obtain a third mixture;

[0012] The third mixture is mixed with manganese hydrogen phosphate, an iron source, a carbon source, and an optional source of an M element to obtain a fourth mixture; wherein the M element includes one or more of transition metal elements other than manganese and iron elements, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements;

[0013] The fourth mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

[0014] Therefore, adding a carbon-containing coating layer is beneficial to improving the conductivity of the positive electrode material and further reducing the resistivity of the positive electrode material, thereby improving the specific capacity and rate performance of the battery.

[0015] In any embodiment, the positive electrode material includes a core and a coating layer coating the core, wherein the core includes the compound Li a Mn x Fe y M b PO 4 ; wherein, the x is selected from 0.5-0.9, the y is selected from 0.1-0.5, the sum of x and y is 0.96-1, the a is selected from 1.01-1.05, the b is selected from 0-0.05, and can be selected from 0.01-0.05; the M includes one or more transition metal elements other than manganese and iron, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; the coating layer includes carbon.

[0016] In any embodiment, the M element includes one or more elements selected from titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0017] In any embodiment, the sintering temperature is 620° C.-780° C., optionally 650° C.-750° C.; and / or,

[0018] The sintering time is 6-14 hours, and can be 6-12 hours; and / or,

[0019] The sintering is carried out in an inert atmosphere, and may be carried out in a nitrogen atmosphere; and / or,

[0020] The temperature is raised to the sintering temperature at a rate of 1-15°C / min, and can be optionally raised to the sintering temperature at a rate of 2-10°C / min.

[0021] Therefore, the above-mentioned calcination temperature, time and / or other calcination conditions are beneficial to reducing the resistivity of the positive electrode material and improving the specific capacity and rate performance of the battery.

[0022] In any embodiment, the carbon source includes one or more of an inorganic carbon source and an organic carbon source, and may be selected from glucose, sucrose, polyethylene glycol, polyvinyl alcohol, citric acid, hydroxypropyl β-cyclodextrin, polyvinyl pyrrolidone, polyacrylic acid, polyvinylidene fluoride, polystyrene, polypropylene, ethylene glycol, and may be selected from one or more of hydroxypropyl β-cyclodextrin; and / or,

[0023] The weight of the carbon source is 4%-7% of the sum of the weight of the manganese hydrogen phosphate and the iron source.

[0024] Therefore, the use of the above-mentioned carbon source is conducive to forming nanoparticles of the positive electrode material and increasing the specific surface area of ​​the positive electrode material.

[0025] In any embodiment, the Dv50 particle size of the insoluble matter in the second mixture and the fourth mixture is independently 0.2-1.0 μm, and optionally 0.2-0.6 μm.

[0026] In any embodiment, the molar ratio of phosphorus in the phosphoric acid solution to manganese hydrogen phosphate is 0.02-0.07, and can be 0.02-0.04; and / or,

[0027] The molar ratio of the lithium element in the lithium source to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 1.01-1.05; and / or,

[0028] The molar ratio of the iron element in the iron source to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 0.1-0.5; and / or,

[0029] The molar ratio of the M element in the source of the M element to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 0.01-0.05; and / or,

[0030] The concentration of the phosphoric acid solution is 75 wt%-85 wt%; and / or,

[0031] In the steps of preparing the first mixture and the third mixture, the mixing time is independently 15-20 minutes; and / or,

[0032] In the step of preparing the second mixture and the fourth mixture, mixing is performed sequentially by stirring and ball milling; and / or,

[0033] The drying is performed by a spray dryer; optionally, the air inlet temperature of the spray dryer is 200°C-250°C, and the air outlet temperature is 100°C-120°C.

[0034] In any embodiment, the lithium source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of lithium, and may be selected from one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium citrate, lithium dihydrogen phosphate, and lithium phosphate; and / or,

[0035] The iron source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of iron, and may be selected from one or more of ferrous oxalate, ferrous acetate, ferrous carbonate, ferrous phosphate, and ferric hydrogen phosphate; and / or,

[0036] The source of the M element includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of the M element, and may optionally include one or more of an oxalate, an acetate, a carbonate, a phosphate, an oxide, and a hydroxide of the M element.

[0037] The third aspect of the present application also provides a positive electrode material, including a compound Li a Mn x Fe y M b PO 4 ; wherein, x is selected from 0.5-0.9, y is selected from 0.1-0.5, the sum of x and y is 0.96-1, a is selected from 1.01-1.05, b is selected from 0-0.05, and can be selected from 0.01-0.05; M includes one or more of transition metal elements other than manganese and iron, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0038] Therefore, the positive electrode material of the present application contains less by-products, the compaction density of the positive electrode material is improved, and the resistivity of the positive electrode material is reduced, thereby improving the specific capacity and rate performance of the battery.

[0039] The fourth aspect of the present application also provides a positive electrode material, comprising a core and a coating layer coating the core; the core comprises the compound Li a Mn x Fe y M b PO 4 ; wherein, the x is selected from 0.5-0.9, the y is selected from 0.1-0.5, the sum of the x and y is 0.96-1, the a is selected from 1.01-1.05, the b is selected from 0-0.05, and can be selected from 0.01-0.05; the M includes one or more transition metal elements, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements other than manganese and iron elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; the coating layer includes carbon;

[0040] Optionally, the average thickness of the coating layer is 6-12 nm, more preferably 8-12 nm;

[0041] Optionally, the weight of the carbon is 1.1%-2% of the total weight of the positive electrode material, and more optionally 1.3%-1.5%.

[0042] Therefore, adding a carbon-containing coating layer is beneficial to improving the conductivity of the positive electrode material and further reducing the resistivity of the positive electrode material, thereby improving the specific capacity and rate performance of the battery.

[0043] In any embodiment, the compaction density of the positive electrode material at 294.2 MPa is 2.09-2.48 g / cm 3 , optional: 2.1-2.3g / cm 3 and / or,

[0044] The primary particles of the positive electrode material have a Dv50 particle size of 100-600 nm, and may be 100-300 nm; and / or,

[0045] The BET specific surface area of ​​the positive electrode material at liquid nitrogen temperature is 6-20 m 2 / g, optional: 14-19.87m 2 / g; and / or,

[0046] The powder resistivity of the positive electrode material at 7.85 MPa is 10.8-870.6 Ω·cm, and can be 48.5-205.1 Ω·cm; and / or,

[0047] The positive electrode material is prepared by the method of the first or second aspect of the present application.

[0048] The fifth aspect of the present application provides a positive electrode plate, comprising the positive electrode material of the third or fourth aspect of the present application or the positive electrode material prepared according to the method of the first or second aspect of the present application.

[0049] The sixth aspect of the present application provides a battery, comprising the positive electrode material of the third or fourth aspect of the present application, the positive electrode material prepared according to the method of the first or second aspect of the present application, or the positive electrode plate of the fifth aspect of the present application.

[0050] The seventh aspect of the present application provides an electrical device, comprising the battery of the sixth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of a battery cell according to an embodiment of the present application.

[0052] Figure 2 yes Figure 1 An exploded view of a battery cell according to an embodiment of the present application is shown.

[0053] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0054] Figure 4 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0055] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0056] Figure 6 It is a schematic diagram of an electrical device using a battery cell according to an embodiment of the present application as a power source.

[0057] Figure 7 This is a SEM photograph of the positive electrode material of Example 1 of the present application.

[0058] Description of reference numerals:

[0059] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0060] Hereinafter, the embodiments of the positive electrode material and preparation method thereof, positive electrode sheet, battery cell, battery module, battery pack and electric device of the present application are specifically disclosed with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0061] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0062] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0063] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0064] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0065] Unless otherwise specified, the Dv50 particle size in this application refers to the particle size when the cumulative value of the volume distribution of the particles is 50%.

[0066] [Battery Cell]

[0067] A battery cell, also known as a rechargeable battery or storage battery, refers to a battery that can be recharged to activate the active material after being discharged and continue to be used.

[0068] Normally, a battery cell includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. During the charge and discharge process of the battery, active ions (such as lithium ions) are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, and at the same time allow active ions to pass through. The electrolyte is between the positive electrode sheet and the negative electrode sheet, mainly to conduct active ions.

[0070] [Method for preparing positive electrode material]

[0071] One embodiment of the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0072] mixing a lithium source with a phosphoric acid solution to obtain a first mixture;

[0073] The first mixture is mixed with manganese hydrogen phosphate, an iron source, and an optional source of an M element to obtain a second mixture; wherein the M element includes one or more of transition metal elements other than manganese and iron elements, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements;

[0074] The second mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

[0075] When the lithium source, manganese hydrogen phosphate, iron source, and optional other transition metal sources react with the phosphoric acid solution, side reactions are likely to occur, producing more side reaction gases and by-products, resulting in a decrease in the compaction density of the positive electrode material and an increase in the resistivity, resulting in a decrease in the yield of the preparation method, thereby adversely affecting the energy density and rate performance of the battery.

[0076] Although the mechanism is not yet clear, the applicant unexpectedly discovered that the present application reduces the generation of side reaction gases and by-products by first reacting the lithium source with a phosphoric acid solution and then reacting with other raw materials, and is also beneficial to improving the lithium ion conductivity of the material, thereby increasing the compaction density of the positive electrode material, reducing the resistivity of the material, and improving the specific capacity and rate performance of the battery.

[0077] In some embodiments, the positive electrode material includes a compound Li a Mn x Fe y M b PO 4 ; wherein, the x is selected from 0.5-0.9, and can be selected from 0.58-0.6, such as 0.52, 0.53, 0.55, 0.56, 0.58, 0.59, 0.6, 0.63, 0.65, 0.67, 0.7, 0.72, 0.74, 0.76, 0.8, 0.83, 0.85, 0.87, 0.9 or any range thereof, and the y is selected from 0.1-0.5, and can be selected from 0. 38-0.4, for example, 0.1, 0.12, 0.15, 0.16, 0.18, 0.2, 0.23, 0.25, 0.27, 0.29, 0.3, 0.32, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.43, 0.45, 0.46, 0.5 or any range thereof, wherein the sum of x and y is 0.96- 1, for example, 0.96, 0.98, 0.99, 1 or any range thereof, wherein a is selected from 1.01-1.05, and may be 1.01-1.04, for example, 1.01, 1.02, 1.03, 1.04, 1.05 or any range thereof, and b is selected from 0-0.05, and may be 0.01-0.05, and may be 0.015-0.03, for example, 0.005, 0.01, 0.015 , 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05 or a range consisting of any of the above values; the M includes one or more of transition metal elements other than manganese and iron, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements, and can be selected from one or more elements including titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0078] Another embodiment of the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0079] mixing a lithium source with a phosphoric acid solution to obtain a third mixture;

[0080] The third mixture is mixed with manganese hydrogen phosphate, an iron source, a carbon source, and an optional source of an M element to obtain a fourth mixture; wherein the M element includes one or more of transition metal elements other than manganese and iron elements, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements;

[0081] The fourth mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

[0082] Therefore, adding a carbon-containing coating layer is beneficial to improving the conductivity of the positive electrode material and further reducing the resistivity of the positive electrode material, thereby improving the specific capacity and rate performance of the battery.

[0083] In some embodiments, the positive electrode material includes a core and a coating layer coating the core, wherein the core includes the compound Li a Mn x Fe y M b PO 4wherein x is selected from 0.5-0.9, and may be 0.58-0.6, such as 0.52, 0.53, 0.55, 0.56, 0.58, 0.59, 0.6, 0.63, 0.65, 0.67, 0.7, 0.72, 0.74, 0.76, 0.8, 0.83, 0.85, 0.87, 0.9 or any range thereof, and y is selected from 0.1- 0.5, can be selected from 0.38-0.4, for example 0.1, 0.12, 0.15, 0.16, 0.18, 0.2, 0.23, 0.25, 0.27, 0.29, 0.3, 0.32, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.43, 0.45, 0.46, 0.5 or a range consisting of any of the above values, the sum of x and y is 0.96-1, for example 0.96, 0.98, 0.99, 1 or a range consisting of any of the above values, the a is selected from 1.01-1.05, can be selected from 1.01-1.04, for example 1.01, 1.02, 1.03, 1.04, 1.05 or The range of any of the above numerical values, the b is selected from 0-0.05, optionally 0.01-0.05, more optionally 0.015-0.03, for example 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05 or the range of any of the above numerical values; the M includes one or more of transition metal elements, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements other than manganese and iron elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; the coating layer includes carbon.

[0084] In some embodiments, the M element includes one or more elements selected from the group consisting of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0085] In some embodiments, the sintering temperature is 620°C-780°C, optionally 650°C-750°C, such as 620°C, 630°C, 640°C, 650°C, 670°C, 690°C, 700°C, 720°C, 740°C, 750°C, 770°C, 780°C or any range thereof; and / or,

[0086] The sintering time is 6-14 hours, and can be 6-12 hours, for example, 6, 7, 8, 9, 10, 11, 12, 13, 14 hours or any range thereof; and / or,

[0087] The sintering is carried out in an inert atmosphere, and may be carried out in a nitrogen atmosphere; and / or,

[0088] The temperature is raised to the sintering temperature at a rate of 1-15°C / min, and can be optionally raised to the sintering temperature at a rate of 2-10°C / min, for example, at a rate of 1°C / min, 2°C / min, 4°C / min, 5°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min or in a range of any of the above values.

[0089] Therefore, the above-mentioned calcination temperature, time and / or other calcination conditions are beneficial to reducing the resistivity of the positive electrode material and improving the specific capacity and rate performance of the battery.

[0090] In some embodiments, the carbon source includes one or more of an inorganic carbon source and an organic carbon source, and may be selected from glucose, sucrose, polyethylene glycol, polyvinyl alcohol, citric acid, hydroxypropyl β-cyclodextrin, polyvinyl pyrrolidone, polyacrylic acid, polyvinylidene fluoride, polystyrene, polypropylene, and ethylene glycol, and may be selected from hydroxypropyl β-cyclodextrin; and / or,

[0091] The weight of the carbon source is 4%-7% of the sum of the weight of the manganese hydrogen phosphate and the iron source, for example, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7% or a range consisting of any of the above values.

[0092] Therefore, the use of the above-mentioned carbon source is conducive to forming nanoparticles of the positive electrode material and increasing the specific surface area of ​​the positive electrode material.

[0093] In some embodiments, the Dv50 particle size of the insoluble matter in the second mixture and the fourth mixture is independently 0.2-1.0 μm, optionally 0.2-0.6 μm, such as 0.2 μm, 0.23 μm, 0.25 μm, 0.27 μm, 0.28 μm, 0.3 μm, 0.32 μm, 0.34 μm, 0.36 μm, 0.38 μm, 0.4 μm, 0.42 μm, 0.44 μm, 0.45 μm, 0.47 μm, 0.49 μm, 0.5μm, 0.53μm, 0.55μm, 0.57μm, 0.6μm, 0.62μm, 0.64μm, 0.65μm, 0.67μm, 0.7μm, 0.73μm, 0.75μm, 0 .78μm, 0.8μm, 0.83μm, 0.85μm, 0.87μm, 0.9μm, 0.92μm, 0.95μm, 0.97μm, 0.99μm, 1.0μm or a range consisting of any of the above values.

[0094] In some embodiments, the molar ratio of phosphorus in the phosphoric acid solution to manganese hydrogen phosphate is 0.02-0.07, and can be 0.02-0.04, such as 0.02, 0.03, 0.04, 0.05, 0.06, 0.07 or any range thereof; and / or,

[0095] The molar ratio of the lithium element in the lithium source to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 1.01-1.05, for example, 1.01, 1.02, 1.03, 1.04, 1.05 or any range thereof; and / or,

[0096] The molar ratio of the iron element in the iron source to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 0.1-0.5, for example, 0.13, 0.15, 0.18, 0.2, 0.22, 0.24, 0.25, 0.27, 0.29, 0.3, 0.32, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.42, 0.44, 0.45, 0.47, 0.48, 0.49, 0.5 or any range thereof; and / or,

[0097] The molar ratio of the M element in the source of the M element to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 0.01-0.05, for example, 0.01, 0.02, 0.03, 0.04, 0.05 or any range thereof; and / or,

[0098] The concentration of the phosphoric acid solution is 75 wt %-85 wt %, such as 75 wt %, 78 wt %, 80 wt %, 82 wt %, 84 wt %, 85 wt % or any range thereof; and / or,

[0099] In the step of preparing the first mixture and the third mixture, the mixing time is independently 15-20 minutes, for example, 15, 16, 17, 18, 19, 20 minutes or a range consisting of any of the above values; and / or,

[0100] In the step of preparing the second mixture and the fourth mixture, mixing is performed sequentially by stirring and ball milling; and / or,

[0101] The drying is carried out by a spray dryer; optionally, the inlet air temperature of the spray dryer is 200°C-250°C, for example 200°C, 210°C, 220°C, 230°C, 240°C, 250°C or a range consisting of any of the above values, and the outlet air temperature is 100°C-120°C, for example 100°C, 105°C, 110°C, 115°C, 120°C or a range consisting of any of the above values.

[0102] In the present application, the Dv50 particle size of the insoluble matter in the mixture is tested by conventional methods in the art, for example, taking an appropriate amount of the mixture, adding deionized water, ultrasonically treating the sample to completely disperse it, and measuring it by a laser particle size analyzer.

[0103] In some embodiments, the lithium source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of lithium, and may be selected from one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium citrate, lithium dihydrogen phosphate, and lithium phosphate; and / or,

[0104] The iron source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of iron, and may be selected from one or more of ferrous oxalate, ferrous acetate, ferrous carbonate, ferrous phosphate, and ferric hydrogen phosphate; and / or,

[0105] The source of the M element includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of the M element, and may optionally include one or more of an oxalate, an acetate, a carbonate, a phosphate, an oxide, and a hydroxide of the M element.

[0106] [Cathode material]

[0107] One embodiment of the present application provides a positive electrode material, including a compound Li a Mn x Fe y M b PO 4wherein x is selected from 0.5-0.9, and may be 0.58-0.6, such as 0.52, 0.53, 0.55, 0.56, 0.58, 0.59, 0.6, 0.63, 0.65, 0.67, 0.7, 0.72, 0.74, 0.76, 0.8, 0.83, 0.85, 0.87, 0.9 or any range thereof, and y is selected from 0.1- 0.5, optionally 0.38-0.4, for example 0.1, 0.12, 0.15, 0.16, 0.18, 0.2, 0.23, 0.25, 0.27, 0.29, 0.3, 0.32, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.43, 0.45, 0.46, 0.5 or any range thereof, the sum of x and y is 0.96- 1, for example, 0.96, 0.98, 0.99, 1 or any range thereof, wherein a is selected from 1.01-1.05, and may be 1.01-1.04, for example, 1.01, 1.02, 1.03, 1.04, 1.05 or any range thereof, and b is selected from 0-0.05, and may be 0.01-0.05, and may be 0.015-0.03, for example, 0.005, 0.01, 0.015 , 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05 or a range consisting of any of the above values; the M includes one or more of transition metal elements other than manganese and iron, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements, and can be selected from one or more elements including titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0108] Therefore, the positive electrode material of the present application contains less by-products, the compaction density of the positive electrode material is improved, and the resistivity of the positive electrode material is reduced, thereby improving the specific capacity and rate performance of the battery.

[0109] Another embodiment of the present application provides a positive electrode material, including a core and a coating layer coating the core; the core includes the compound Li a Mn x Fe y M b PO 4; wherein, the x is selected from 0.5-0.9, and can be selected from 0.58-0.6, such as 0.52, 0.53, 0.55, 0.56, 0.58, 0.59, 0.6, 0.63, 0.65, 0.67, 0.7, 0.72, 0.74, 0.76, 0.8, 0.83, 0.85, 0.87, 0.9 or a range consisting of any of the above values, and the y is selected from 0.1, 0.5, optionally 0.38-0.4, for example 0.1, 0.12, 0.15, 0.16, 0.18, 0.2, 0.23, 0.25, 0.27, 0.29, 0.3, 0.32, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.43, 0.45, 0.46, 0.5 or any range thereof, the sum of x and y is 0.96- 1, for example, 0.96, 0.98, 0.99, 1 or any range thereof, the a is selected from 1.01-1.05, and can be selected from 1.01-1.04, for example, 1.01, 1.02, 1.03, 1.04, 1.05 or any range thereof, the b is selected from 0-0.05, and can be selected from 0.01-0.05, and can be selected from 0.015-0.03, for example, 0.005, 0.01, 0.015, 0.0 2, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05 or any range thereof; the M includes one or more of transition metal elements, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements except manganese and iron elements, and may be selected from one or more of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; the coating layer includes carbon;

[0110] Optionally, the average thickness of the coating layer is 6-12 nm, more preferably 8-12 nm, such as 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm or a range consisting of any of the above values;

[0111] Optionally, the weight of the carbon is 1.1%-2% of the total weight of the positive electrode material, and more optionally 1.3%-1.5%, for example 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0% or a range consisting of any of the above values.

[0112] Therefore, adding a carbon-containing coating layer is beneficial to improving the conductivity of the positive electrode material and further reducing the resistivity of the positive electrode material, thereby improving the specific capacity and rate performance of the battery.

[0113] In the present application, the average thickness of the coating layer is tested by conventional methods in the art; for example, a surface scan is performed on the primary particles of the positive electrode material (particle size is Dv50 particle size ± 0.3 μm) by using a SEM-EDS combination instrument to determine the boundary between the inner core and the coating layer, and the distance from the inner core to the boundary line and the distance from the inner core to the outermost edge of the coating layer are measured in the scanning electron microscope image. The measurements are randomly oriented multiple times, and then the above test is repeated on multiple primary particles of the positive electrode material. The average value of the difference between the distance from the inner core to the outermost edge of the coating layer and the distance from the inner core to the boundary line is the average thickness of the coating layer.

[0114] In the present application, the weight percentage of carbon in the positive electrode material is tested by conventional methods in the art; for example, flux metal tungsten particles are added to the positive electrode material, mixed, placed in a high-frequency infrared carbon-sulfur analyzer for sintering, and the weight percentage of carbon in the positive electrode material is tested.

[0115] In some embodiments, the compaction density of the positive electrode material at 294.2 MPa is 2.09-2.48 g / cm 3 , optional: 2.1-2.3g / cm 3 , for example 2.09 g / cm 3 , 2.1g / cm 3 , 2.13g / cm 3 , 2.16g / cm 3 , 2.18g / cm 3 , 2.2g / cm 3 , 2.22g / cm 3 , 2.25g / cm 3 , 2.27g / cm 3 , 2.29g / cm 3 , 2.3g / cm 3 , 2.32g / cm 3 , 2.35g / cm 3 , 2.36g / cm 3 , 2.38g / cm 3 , 2.4g / cm 3 , 2.42g / cm 3 , 2.44g / cm 3 , 2.45g / cm 3 , 2.46g / cm 3 , 2.48g / cm 3 or a range consisting of any of the above values; and / or,

[0116] The Dv50 particle size of the primary particles of the positive electrode material is 100-600nm, and can be optionally 100-300nm, for example, 100nm, 150nm, 200nm, 230nm, 250nm, 280nm, 300nm, 330nm, 350nm, 380nm, 400nm, 450nm, 480nm, 500nm, 530nm, 550nm, 580nm, 600nm or a range consisting of any of the above values; and / or,

[0117] The BET specific surface area of ​​the positive electrode material at liquid nitrogen temperature is 6-20 m 2 / g, optional 14-19.87m 2 / g, for example 6m 2 / g, 8m 2 / g, 9m 2 / g, 10m 2 / g, 11m 2 / g, 12m 2 / g, 13m 2 / g, 15m 2 / g, 15.5m 2 / g, 16m 2 / g, 16.3m 2 / g, 16.7m 2 / g, 17m 2 / g, 17.3m 2 / g, 18m 2 / g, 19m 2 / g, 20m 2 / g or any range consisting of the above values; and / or,

[0118] The powder resistivity of the positive electrode material at 7.85 MPa is 10.8-870.6 Ω·cm, which can be 48.5-205.1 Ω·cm, for example, 10.8 Ω·cm, 15 Ω·cm, 20 Ω·cm, 30 Ω·cm, 35 Ω·cm, 40 Ω·cm, 45 Ω·cm, 48 Ω·cm, 50 Ω·cm, 55 Ω·cm, 56 Ω·cm, 60 Ω·cm, 65 Ω·cm, 68 Ω·cm, 70 Ω·cm, 75 Ω·cm, 80 Ω·cm, 85 Ω·cm, 90 Ω·cm, 95 Ω·cm, 100 Ω·cm, 110 Ω·cm, 120 Ω·cm, 1 50Ω·cm, 160Ω·cm, 180Ω·cm, 190Ω·cm, 200Ω·cm, 205Ω·cm, 210Ω·cm, 250Ω·cm, 270Ω·cm, 300Ω·cm, 350Ω·cm, 400Ω·cm, 450Ω·cm, 500Ω·cm, 5 50Ω·cm, 600Ω·cm, 650Ω·cm, 700Ω·cm, 750Ω·cm, 800Ω·cm, 820Ω·cm, 840Ω·cm, 850Ω·cm, 860Ω·cm, 870Ω·cm, 870.6Ω·cm or a range consisting of any of the above values; and / or,

[0119] The positive electrode material is prepared by the method described above in this application.

[0120] In the present application, the compaction density of the material is tested by conventional methods in the art; for example, the method is: weigh the sample powder and place it in a compaction density mold, put it into a compaction density machine, and test the compaction density after compaction with a certain pressure.

[0121] In the present application, the Dv50 particle size of the primary particles of the material is tested using conventional methods in the art; for example, the method is: testing the positive electrode material by SEM, observing the primary particles based on the SEM photos and randomly taking multiple primary particles to measure the particle size, and statistically calculating the Dv50 particle size of the primary particles of the positive electrode material.

[0122] In the present application, the BET specific surface area of ​​the material at liquid nitrogen temperature is tested using conventional methods in the art; for example, the method is: the sample is placed in a specific surface area test tube, the liquid nitrogen cup is filled with liquid nitrogen, placed in the specific surface area test tube, and tested using a specific surface area analyzer.

[0123] In the present application, the powder resistivity of the material at 7.85 MPa is tested using conventional methods in the art; for example, the method is: the sample is placed in a mold, and then the mold is placed in a four-probe resistivity tester, the pressure is adjusted to 7.85 MPa, and when the mold height and pressure are stable, the forward resistivity and reverse resistivity of the sample are tested respectively, and the average of the two is taken as the powder resistivity of the sample.

[0124] [Positive electrode]

[0125] The positive electrode plate generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the aforementioned positive electrode material or the positive electrode material prepared by the aforementioned method.

[0126] The battery will be accompanied by Li deintercalation and consumption during the charge and discharge process, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after charge and discharge cycles.

[0127] In the list of positive electrode materials in this application, the molar content of O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0128] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0129] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0130] In some embodiments, the positive electrode material may further include positive electrode active materials for batteries known in the art. As an example, the positive electrode material may include at least one of the following materials: lithium transition metal oxides and modified compounds thereof. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 、LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co1 / 3 Mn 1 / 3 O 2 (Also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (Also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (Also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and at least one of its modified compounds.

[0131] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0132] In some embodiments, the positive electrode film layer may further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0133] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0134] [Negative electrode]

[0135] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0136] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0137] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0138] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0139] In some embodiments, the negative electrode film layer may further include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0140] In some embodiments, the negative electrode film layer may further include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0141] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0142] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0143] [Electrolytes]

[0144] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0145] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0146] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0147] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0148] In some embodiments, the electrolyte may further include additives. As examples, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0149] [Isolation film]

[0150] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0151] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0152] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0153] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0154] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0155] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 1 The battery cell 5 is a square structure as an example.

[0156] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0157] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0158] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0159] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0160] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0161] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0162] In addition, the present application also provides an electrical device, which includes at least one of the battery cells, battery modules, or battery packs provided in the present application. The battery cells, battery modules, or battery packs can be used as power sources for electrical devices, or as energy storage units for electrical devices. Electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but are not limited thereto.

[0163] As an electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0164] Figure 6 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of battery cells, a battery pack or a battery module can be used.

[0165] [Example]

[0166] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0167] Example 1

[0168] (1) Preparation of positive electrode materials:

[0169] 45.4 g Li 2 CO 3 (purity ≥ 99.5%) was added to a 75% by weight phosphoric acid solution and mixed for 15 minutes under stirring; then FePO 4 (purity ≥ 99%), MnHPO 4 (purity ≥ 99%), hydroxypropyl β-cyclodextrin, titanium dioxide and 4.8 g PEG4000 were mixed for the second time; Li 2 CO 3 Lithium in phosphoric acid solution and MnHPO 4 The molar ratio of phosphorus to total phosphorus in phosphoric acid solution is 1.02. 4 The molar ratio of FePO is 0.03 4 With phosphoric acid solution and MnHPO 4 The molar ratio of the total phosphorus element in the solution is 0.392, and the molar ratio of titanium dioxide to phosphoric acid solution and MnHPO 4 The molar ratio of total phosphorus is 0.02, and the weight of hydroxypropyl β-cyclodextrin is MnHPO 4 With FePO 4 6% of the total weight; the mixture is transferred into a ball mill and ground with a planetary ball mill until the insoluble matter Dv50 particle size in the final mixture (slurry) reaches 0.38μm. The slurry is spray dried with a 10L centrifugal spray dryer, the inlet air temperature is 200℃, the outlet air temperature is 105℃, and the frequency of the peristaltic feed pump is 20Hz. The dried powder is sintered in a box furnace in a nitrogen atmosphere, the nitrogen flow rate is 6L / min, the heating rate is 2℃ / min, the sintering temperature is 730℃, the sintering time is 12 hours, and the temperature is cooled to obtain the positive electrode material.

[0170] (2) Preparation of positive electrode sheet:

[0171] Weigh 0.3g of polyvinylidene fluoride binder (PVDF) in 10.8g of N-methylpyrrolidone (NMP), stir and completely dissolve; then add 2.4g of the above positive electrode material and 0.3g of carbon black conductive agent (SP), stir evenly to obtain a paste. Use an applicator to evenly apply the paste on aluminum foil, dry it in a vacuum drying oven, remove the solvent NMP, and then roll and punch to obtain a disc with a diameter of 16.0mm as the positive electrode sheet.

[0172] (3) Negative electrode: metal lithium sheet is used.

[0173] (4) Isolation film: PE-PP composite film is used.

[0174] (5) Preparation of electrolyte:

[0175] Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1, and then LiPF 6 is uniformly dissolved in the above solution to obtain an electrolyte. In the electrolyte, LiPF 6 The concentration is 1 mol / L.

[0176] (6) Preparation of button cells:

[0177] The positive electrode sheet, separator, negative electrode sheet and electrolyte are assembled into a CR2032 button battery.

[0178] The secondary battery preparation methods of Examples 2-30 and Comparative Examples 1-2 are similar to those of Example 1, and the different parameters are detailed in Table 1-2.

[0179] Comparative Example 1-2

[0180] Various raw materials were mixed and stirred for 15 minutes according to the proportions in Table 1, and then dried and sintered according to the parameters in Table 1 to obtain a positive electrode material; the rest was the same as in Example 1.

[0181]

[0182]

[0183]

[0184]

[0185]

[0186] Material testing and battery testing

[0187] (1) Test of core chemical formula and carbon content:

[0188] Weigh the positive electrode material into a 100mL beaker, add 10mL of 10% w / w nitric acid solution, heat and digest at 120°C for 0.5 hour, and make up to volume with a 100mL volumetric flask; use a pipette to transfer 1mL to a 100mL volumetric flask and make up to volume to obtain the solution to be tested.

[0189] An inductively coupled plasma optical emission spectrometer (ICP-OES, instrument brand: Agilent 5800) was used to determine the contents of lithium, manganese, iron, phosphorus, oxygen, and doping elements in the test solution, calculate the element ratio in the material, and determine the chemical formula.

[0190] Weigh 0.1g of positive electrode material, add 1.5g of flux metal tungsten particles to mix, put it into a high-frequency infrared carbon-sulfur analyzer for sintering and test the weight percentage of carbon in the positive electrode material.

[0191] (2) Test of average thickness of coating layer of positive electrode material:

[0192] The primary particles of the positive electrode material (particle size is Dv50 particle size ± 0.3 μm) are scanned by SEM-EDS to determine the boundary line between the inner core and the coating layer. The distance from the inner core to the boundary line and the distance from the inner core to the outermost edge of the coating layer are measured in the scanning electron microscope image. The random orientation measurement is performed 50 times. Then, a total of 50 primary particles of the positive electrode material are taken to repeat the above test. The average value of the difference between the distance from the inner core to the outermost edge of the coating layer and the distance from the inner core to the boundary line is the average thickness of the coating layer.

[0193] (3) Test of Dv50 particle size of insoluble matter in the mixture and Dv50 particle size of primary particles of positive electrode material:

[0194] Take an appropriate amount of the mixture, add 20 mL of deionized water, and perform ultrasonic treatment for 5 minutes (53 KHz, 120 W) to completely disperse the sample. Use a laser particle size analyzer (MasterSizer 2000) to measure the Dv50 particle size of the material.

[0195] Dv50 particle size test of primary particles of positive electrode materials:

[0196] The positive electrode material was tested by SEM. The primary particles were observed based on the SEM photos and 100 primary particles were randomly selected to measure the particle size, and the Dv50 particle size of the primary particles of the positive electrode material was calculated.

[0197] (4) Compaction density test:

[0198] Weigh 1 g of sample powder and place it in a compaction density mold, put it into a compaction density machine, and test the compaction density after compaction at a pressure of 294.2 MPa.

[0199] (5) BET specific surface area test:

[0200] Weigh 1g of sample and place it in a specific surface area test tube. Fill the liquid nitrogen cup with liquid nitrogen and put it into the specific surface area test tube. Place the sample in a temperature environment of -200℃ and test it using a specific surface area analyzer (Beijing Jingwei Gaobo, JWBK-112).

[0201] (6) Test of powder resistivity:

[0202] Weigh 1g of sample and place it in a mold. Then put the mold into a four-probe resistivity tester and adjust the pressure to 7.85MPa. When the mold height and pressure are stable, test the forward resistivity and reverse resistivity of the sample respectively, and take the average of the two as the powder resistivity of the sample.

[0203] (7) Microscopic morphology evaluation:

[0204] The microstructure of the positive electrode material of Example 1 was observed using a scanning electron microscope (SEM, instrument brand: ZEISS sigma 300). Figure 7 shown.

[0205] (8) Test method for battery capacity in grams:

[0206] After the button cell is assembled, place it aside for 3 hours, charge it to 4.3V at 0.1C (1C, 2C or 3C), charge it at 4.3V constant voltage until the current is less than or equal to 0.02C, place the cell aside for 5 minutes, discharge it to 2V at 0.1C (1C, 2C or 3C), and record the discharge capacity D1 at this time. Divide the discharge capacity D1 by the mass of the positive electrode material to get the gram capacity of the battery.

[0207] Table 3: Performance test results of Examples 1-30 and Comparative Examples 1-2

[0208]

[0209]

[0210] According to the above results, we can know that:

[0211] Compared with the comparative example 1-2 in which the raw materials are mixed together, the battery of the embodiment 1-27 of the present application has a higher gram capacity and better rate performance;

[0212] Compared with the lower sintering temperature used in Example 22, the battery in Example 19 of the present application has a higher gram capacity and better rate performance;

[0213] Compared with the higher sintering temperature used in Example 28, the battery in Example 8 of the present application has a higher gram capacity and better rate performance;

[0214] Compared with the higher molar ratio of phosphorus element to manganese hydrogen phosphate in the phosphoric acid solution in Example 23, the battery gram capacity of Examples 1, 9, 12, and 20 of the present application is higher and the rate performance is better;

[0215] Compared with the positive electrode materials of Examples 24-25 having a higher primary particle Dv50 particle size and a lower powder resistivity, the batteries of Examples 1, 5, 9-12, 17, and 20 of the present application have a higher gram capacity and better rate performance;

[0216] Compared with the lower powder resistivity of the positive electrode material of Example 26, the battery of Example 8 of the present application has a higher gram capacity and better rate performance;

[0217] Compared with the thin average thickness of the coating layer in Example 27, the battery gram capacity of Examples 1, 8, 9, 12, 19, and 20 of the present application is higher and the rate performance is better;

[0218] Compared with the larger particle size Dv50 of the insoluble matter in the final mixture of Example 29, the battery gram capacity of Examples 1, 5, 9, 10, 11, 12, 17, and 20 of the present application is higher and the rate performance is better;

[0219] Compared with Example 21 using glucose as the carbon source, the 1C, 2C, and 3C gram capacities of the battery in Example 19 of the present application are higher and the rate performance is better;

[0220] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a positive electrode material, comprising the following steps: mixing a lithium source with a phosphoric acid solution to obtain a first mixture; Mixing the first mixture with manganese hydrogen phosphate, an iron source, and an optional source of the M element to obtain a second mixture; in, The M element includes one or more of transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, group IVA metal elements, and group VIIA elements; The second mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

2. The method according to claim 1, in, The positive electrode material includes a compound Li a Mn x Fe y M b PO 4 ; wherein, x is selected from 0.5-0.9, y is selected from 0.1-0.5, the sum of x and y is 0.96-1, a is selected from 1.01-1.05, b is selected from 0-0.05, and can be selected from 0.01-0.05; M includes one or more of transition metal elements other than manganese and iron, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

3. A method for preparing a positive electrode material, comprising the following steps: mixing a lithium source with a phosphoric acid solution to obtain a third mixture; Mixing the third mixture with manganese hydrogen phosphate, an iron source, a carbon source, and an optional source of the M element to obtain a fourth mixture; in, The M element includes one or more of transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, group IVA metal elements, and group VIIA elements; The fourth mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

4. The method according to claim 3, in, The positive electrode material comprises a core and a coating layer covering the core, wherein the core comprises the compound Li a Mn x Fe y M b PO 4 ; wherein, the x is selected from 0.5-0.9, the y is selected from 0.1-0.5, the sum of x and y is 0.96-1, the a is selected from 1.01-1.05, and the b is selected from 0-0.05, and can be selected from 0.01-0.05; the M includes one or more transition metal elements other than manganese and iron elements, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; the coating layer includes carbon.

5. The method according to any one of claims 1 to 4, in, The M element includes one or more elements selected from titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

6. The method according to any one of claims 1 to 5, in, The sintering temperature is 620°C-780°C, and can be 650°C-750°C; and / or, The sintering time is 6-14 hours, and can be 6-12 hours; and / or, The sintering is carried out in an inert atmosphere, and may be carried out in a nitrogen atmosphere; and / or, The temperature is raised to the sintering temperature at a rate of 1-15°C / min, and can be optionally raised to the sintering temperature at a rate of 2-10°C / min.

7. The method according to claim 3 or 4, in, The carbon source includes one or more of an inorganic carbon source and an organic carbon source, and may be selected from one or more of glucose, sucrose, polyethylene glycol, polyvinyl alcohol, citric acid, hydroxypropyl β-cyclodextrin, polyvinyl pyrrolidone, polyacrylic acid, polyvinylidene fluoride, polystyrene, polypropylene, and ethylene glycol, and may be selected from hydroxypropyl β-cyclodextrin; and / or, The weight of the carbon source is 4%-7% of the sum of the weight of the manganese hydrogen phosphate and the iron source.

8. The method according to any one of claims 1 to 7, in, The Dv50 particle sizes of the insoluble matter in the second mixture and the fourth mixture are independently 0.2-1.0 μm, and optionally 0.2-0.6 μm.

9. The method according to any one of claims 1 to 8, in, The molar ratio of phosphorus in the phosphoric acid solution to manganese hydrogen phosphate is 0.02-0.07, and can be 0.02-0.04; and / or, The molar ratio of the lithium element in the lithium source to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 1.01-1.05; and / or, The molar ratio of the iron element in the iron source to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 0.1-0.5; and / or, The molar ratio of the M element in the source of the M element to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 0.01-0.05; and / or, The concentration of the phosphoric acid solution is 75 wt%-85 wt%; and / or, In the steps of preparing the first mixture and the third mixture, the mixing time is independently 15-20 minutes; and / or, In the step of preparing the second mixture and the fourth mixture, mixing is performed sequentially by stirring and ball milling; and / or, The drying is performed by a spray dryer; optionally, the air inlet temperature of the spray dryer is 200°C-250°C, and the air outlet temperature is 100°C-120°C.

10. The method according to any one of claims 1 to 9, in, The lithium source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of lithium, and may be selected from one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium citrate, lithium dihydrogen phosphate, and lithium phosphate; and / or, The iron source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of iron, and may be selected from one or more of ferrous oxalate, ferrous acetate, ferrous carbonate, ferrous phosphate, and ferric hydrogen phosphate; and / or, The source of the M element includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of the M element, and may optionally include one or more of an oxalate, an acetate, a carbonate, a phosphate, an oxide, and a hydroxide of the M element.

11. A positive electrode material comprising a compound Li a Mn x Fe y M b PO 4 ; in, The x is selected from 0.5-0.9, the y is selected from 0.1-0.5, the sum of x and y is 0.96-1, the a is selected from 1.01-1.05, and the b is selected from 0-0.05, and can be selected from 0.01-0.05; the M includes one or more transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, group IVA metal elements, and group VIIA elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

12. A positive electrode material, comprising a core and a coating layer coating the core; the core comprising the compound Li a Mn x Fe y M b PO 4 ; in, The x is selected from 0.5-0.9, the y is selected from 0.1-0.5, the sum of x and y is 0.96-1, the a is selected from 1.01-1.05, the b is selected from 0-0.05, and can be selected from 0.01-0.05; the M includes one or more transition metal elements, ⅡA group metal elements, ⅢA group metal elements, ⅣA group metal elements, and VIIA group elements other than manganese and iron elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; the coating layer includes carbon; Optionally, the average thickness of the coating layer is 6-12 nm, more preferably 8-12 nm; Optionally, the weight of the carbon is 1.1%-2% of the total weight of the positive electrode material, and more optionally 1.3%-1.5%.

13. The positive electrode material according to claim 11 or 12, in, The compaction density of the positive electrode material at 294.2 MPa is 2.09-2.48 g / cm 3 , optional: 2.1-2.3g / cm 3 and / or, The primary particles of the positive electrode material have a Dv50 particle size of 100-600 nm, and may be 100-300 nm; and / or, The BET specific surface area of ​​the positive electrode material at liquid nitrogen temperature is 6-20 m 2 / g, optional: 14-19.87m 2 / g; and / or, The powder resistivity of the positive electrode material at 7.85 MPa is 10.8-870.6 Ω·cm, and can be 48.5-205.1 Ω·cm; and / or, The positive electrode material is prepared by the method according to any one of claims 1 to 9. 14 . A positive electrode sheet, comprising the positive electrode material prepared by the method according to claim 1 or the positive electrode material according to claim 11 . 15 . A battery comprising a positive electrode material prepared by the method of claim 1 , a positive electrode material of claim 11 , or a positive electrode sheet of claim 14 .

16. An electrical device comprising the battery according to claim 15.

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