Stacked battery cell, square lithium battery, and battery pack

Abstract

The present application discloses a stacked battery cell, a square lithium battery, and a battery pack. The size of a positive electrode sheet and the size of a negative electrode sheet are controlled to ensure that the stacked battery cell has acceptable internal resistance; moreover, the actual capacity, energy density, rate capability and cycle stability of the square lithium battery comprising the stacked battery cell are improved, and the safety of the square lithium battery is improved.

Description

Laminated cells, square lithium batteries and battery packs

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 21, 2023, with application number 202311566713.X. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of lithium batteries, and in particular to a laminated battery cell, a square lithium battery and a battery pack. Background Art

[0003] With the continuous development of portable electronic devices, new energy vehicles, and large-scale energy storage markets, the demand for lithium batteries continues to grow. The size of the lithium battery's electrode will affect its performance in actual applications. For example, the internal resistance of a lithium battery cell is related not only to the length of the electrode, but also to its thickness. Under the premise that the length and width of the electrode are constant, the thicker the electrode, the longer the lithium ion diffusion distance and the greater the internal resistance of the cell. Conversely, under the premise that the length and width of the electrode are constant, the thinner the electrode, the smaller the internal resistance of the cell. However, if the electrode is too thin, the energy density of the lithium battery will be reduced. SUMMARY OF THE INVENTION

[0004] How to regulate the size of the electrode to enable lithium batteries to have both lower cell internal resistance and higher energy density is of great significance to the application and development of lithium batteries.

[0005] The present application provides a laminated battery cell, the laminated battery cell comprising a plurality of battery cell units stacked in sequence along a first direction, each of the battery cell units comprising a positive electrode sheet, a separator and a negative electrode sheet stacked in sequence, and a separator is provided between two adjacent battery cell units, the first direction is perpendicular to the first surface of the positive electrode sheet close to the separator, the positive electrode sheet of each battery cell unit is provided with a sub-electrode ear, and the negative electrode sheet of each battery cell unit is provided with a sub-electrode ear; the sub-electrode ears of the positive electrode sheets of the plurality of battery cell units are connected in sequence to form a positive electrode ear, and the sub-electrode ears of the negative electrode sheets of the plurality of battery cell units are connected in sequence to form a negative electrode ear; the ratio of the length to the thickness of the positive electrode sheet and the ratio of the length to the thickness of the negative electrode sheet are independently selected from 6.3×10 2 ~9.4×10 2 The ratio of the width to the thickness of the positive electrode sheet and the ratio of the width to the thickness of the negative electrode sheet are independently selected from 6.3×10 2 ~9.4×10 2 .

[0006] The present application also provides a square lithium battery, the square lithium battery comprising one or more laminated cells, each of the laminated cells comprising a plurality of cell units stacked in sequence along a first direction, each cell unit comprising a positive electrode sheet, a separator and a negative electrode sheet stacked in sequence, and a separator is provided between two adjacent cell units, the first direction is perpendicular to the first surface of the positive electrode sheet close to the separator, the positive electrode sheet of each cell unit is provided with a sub-electrode ear, and the negative electrode sheet of each cell unit is provided with a sub-electrode ear; the sub-electrode ears of the positive electrode sheets of the plurality of cell units are connected in sequence to form a positive electrode ear, and the sub-electrode ears of the negative electrode sheets of the plurality of cell units are connected in sequence to form a negative electrode ear; the ratio of the length of the positive electrode sheet to the thickness and the ratio of the length of the negative electrode sheet to the thickness are independently selected from 6.3×10 2 ~9.4×10 2 The ratio of the width to the thickness of the positive electrode sheet and the ratio of the width to the thickness of the negative electrode sheet are independently selected from 6.3×10 2 ~9.4×10 2 .

[0007] The present application also provides a battery pack, which includes a box and a plurality of square lithium batteries, wherein the box is formed with a storage space, and the plurality of square lithium batteries are arranged in sequence in the storage space; the square lithium battery includes one or more laminated cells, each of the laminated cells includes a plurality of cell units stacked in sequence along a first direction, each cell unit includes a positive electrode sheet, a separator and a negative electrode sheet stacked in sequence, and a separator is provided between two adjacent cell units, the first direction is perpendicular to the first surface of the positive electrode sheet close to the separator, the positive electrode sheet of each cell unit is provided with a sub-electrode ear, and the negative electrode sheet of each cell unit is provided with a sub-electrode ear; the sub-electrode ears of the positive electrode sheets of the plurality of cell units are connected in sequence to form a positive electrode ear, and the sub-electrode ears of the negative electrode sheets of the plurality of cell units are connected in sequence to form a negative electrode ear; the ratio of the length of the positive electrode sheet to the thickness and the ratio of the length of the negative electrode sheet to the thickness are independently selected from 6.3×10 2 ~9.4×10 2 The ratio of the width to the thickness of the positive electrode sheet and the ratio of the width to the thickness of the negative electrode sheet are independently selected from 6.3×10 2 ~9.4×10 2 . Beneficial effects

[0008] The laminated battery cell provided in the present application ensures that the laminated battery cell has an acceptable internal resistance by controlling the sizes of the positive electrode sheet and the negative electrode sheet.

[0009] The square lithium battery provided in the present application includes one or more of the above-mentioned stacked battery cells, which improves the actual capacity, energy density, rate performance and cycle stability of the square lithium battery, and is beneficial to improving the safety of the square lithium battery.

[0010] The battery pack provided in the present application includes a box body and a plurality of the above-mentioned square lithium batteries. The plurality of square lithium batteries are arranged in sequence in the accommodating space of the box body, thereby improving the internal space utilization and battery life of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG1 is a schematic structural diagram of a laminated battery cell provided by some implementations of the present application.

[0012] FIG2 is a schematic structural diagram of a positive electrode sheet provided by some implementations of the present application.

[0013] FIG3 is a schematic structural diagram of a square lithium battery provided by some implementations of the present application.

[0014] FIG4 is a schematic structural diagram of a battery pack provided by some implementations of the present application.

[0015] The reference numerals are as follows:

[0016] 1: Battery pack, 10: Prismatic lithium battery, 20: Box, 30: Cover, 40: Buffer, 101: Laminated cell, 102: Shell, 103: Positive electrode column, 104: Negative electrode column, 105: Connecting piece, 201: Accommodation space, 202: Box wall, 1011: Cell unit, 1012: Positive electrode ear, 1013: Negative electrode ear, 10111: Positive electrode sheet, 10112: Diaphragm, 10113: Negative electrode sheet, 101110: Sub-electrode ear, 101111: First side, 101112: Positive current collector, 101113: Positive active material layer. Modes for Carrying Out the Invention

[0017] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art, and the materials and reagents used in the Examples and Comparative Examples of this application are commercially available. In addition, any methods and materials similar or equivalent to those described herein can be applied to this application. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0019] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. Each embodiment of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is for convenience and brevity and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0020] In the description of this application, the term "including" means "including but not limited to".

[0021] The terms "multiple", "multiple times" or similar expressions refer to two (times) or more than two (times), for example, it can be two (times), three (times), four (times), five (times), six (times), etc.

[0022] The selection scope of the term "and / or" includes any one of two or more related listed items, and also includes any and all combinations of the related listed items. Any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items. For example, "A and / or B" includes three parallel solutions of A, B and A+B. For another example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, technical solutions all connected by "logical OR"), and also includes any and all combinations of A, B, C, and D, that is, combinations of any two or any three of A, B, C, and D, and also includes four combinations of A, B, C, and D (that is, technical solutions all connected by "logical AND").

[0023] The term "solid content" refers to the ratio of the mass of solid matter in the slurry to the total mass of the slurry.

[0024] The embodiment of the present application provides a laminated battery cell, as shown in Figures 1 and 3, the laminated battery cell 101 includes a plurality of battery cell units 1011 stacked in sequence along a first direction X1, each battery cell unit 1011 includes a positive electrode sheet 10111, a diaphragm 10112 and a negative electrode sheet 10113 stacked in sequence, and a diaphragm 10112 is provided between two adjacent battery cell units 1011, and the first direction X1 is perpendicular to the first surface 1011 of the positive electrode sheet 10111 close to the diaphragm 10112. 111. The positive electrode sheet 10111 of each battery cell 1011 is provided with a sub-electrode tab 101110 (positive electrode sheet sub-electrode tab), and the negative electrode sheet 10113 of each battery cell 1011 is provided with a sub-electrode tab 101110 (negative electrode sheet sub-electrode tab). The sub-electrode tabs 101110 of the positive electrode sheets 10111 of multiple battery cells 1011 are sequentially connected to form a positive electrode tab 1012, and the sub-electrode tabs 101110 of the negative electrode sheets 10113 of multiple battery cells 1011 are sequentially connected to form a negative electrode tab 1013. It should be noted that the surface of the outermost electrode sheet of the laminated battery cell 101 is also provided with a separator 10112.

[0025] Among them, the length of the positive electrode sheet 10111 and the length of the negative electrode sheet 10113 are independently selected from 135 mm to 165 mm, for example, they can be 135 mm to 140 mm, 135 mm to 145 mm, 135 mm to 150 mm, 135 mm to 155 mm, 135 mm to 160 mm, 145 mm to 150 mm, 145 mm to 155 mm, 145 mm to 160 mm, 145 mm to 165 mm, 150 mm to 155 mm, 150 mm to 160 mm, 150 mm to 165 mm, 155 mm to 160 mm, 155 mm to 165 mm, or 160 mm to 165 mm, examples are 135 mm, 140 mm, 145 mm, 151 mm, 155 mm, 160 mm, 165 mm or a value between any two of the foregoing values.

[0026] The width of the positive electrode sheet 10111 and the width of the negative electrode sheet 10113 are independently selected from 135 mm to 165 mm, for example, 135 mm to 140 mm, 135 mm to 145 mm, 135 mm to 150 mm, 135 mm to 155 mm, 135 mm to 160 mm, 145 mm to 150 mm, 145 mm to 155 mm, 145 mm to 160 mm, 145 mm to 165 mm, 150 mm to 155 mm, 150 mm to 160 mm, 150 mm to 165 mm, 155 mm to 160 mm, 155 mm to 165 mm, or 160 mm to 165 mm, examples are 135 mm, 140 mm, 145 mm, 148 mm, 155 mm, 160 mm, 165 mm or a value between any two of the foregoing values.

[0027] The length to thickness ratio of the positive electrode sheet 10111 and the length to thickness ratio of the negative electrode sheet 10113 are independently selected from 6.3×10 2 ~9.4×10 2 , for example, it can be 6.3×10 2 ~8.0×10 2 , 6.3×10 2 ~7.5×10 2 , 7.7×10 2 ~8.5×10 2 , or 8.0×10 2 ~8.5×10 2 , for example, 6.3×10 2 , 6.5×10 2 , 7.0×10 2 , 7.4×10 2 , 7.7×10 2 , 8.0×10 2 , 8.5×10 2 , 9.0×10 2 , 9.4×10 2 Or a value between any two of the above values. The ratio of the width to the thickness of the positive electrode sheet 10111 and the ratio of the width to the thickness of the negative electrode sheet 10113 are independently selected from 6.3×10 2 ~9.4×10 2 , for example, it can be 6.3×10 2 , 6.5×10 2 , 7.0×10 2 , 7.4×10 2 , 7.7×10 2 , 8.0×10 2, 8.5×10 2 , 9.0×10 2 , 9.4×10 2 Or a value between any two of the above values.

[0028] It should be noted that, as shown in FIG2 , the positive electrode sheet 10111 includes a positive electrode current collector 101112 and a positive electrode active material layer 101113, and the positive electrode active material layer 101113 is disposed on the surface of the positive electrode current collector 101112. Under the premise that the thickness of the positive electrode current collector 101112 is constant and all other structures and components of the lithium battery except the positive electrode sheet 10111 remain unchanged, if the thickness of the positive electrode active material layer 101113 is thicker, the internal resistance of the battery cell will be greater, which corresponds to a longer ion diffusion distance in the lithium battery and a greater impedance of the lithium battery; if the thickness of the positive electrode active material layer 101113 is thinner, the internal resistance of the battery cell will be smaller, which corresponds to a lower battery capacity of the lithium battery. If the battery capacity is to be increased to a preset value, the number of positive electrode sheets 10111 needs to be increased, resulting in an increase in the amount of foil used for the positive electrode current collector 101112, thereby increasing the weight and manufacturing cost of the lithium battery and reducing the energy density of the lithium battery. Similarly, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is arranged on the surface of the negative electrode current collector; under the premise that the thickness of the negative electrode current collector is a constant value and all other structures and components in the lithium battery except the negative electrode sheet remain unchanged, if the thickness of the negative electrode active material layer is thicker, the internal resistance of the battery cell is greater, and the corresponding impedance of the lithium battery is greater; if the thickness of the negative electrode active material layer is thinner, the internal resistance of the battery cell is smaller, and the battery capacity of the corresponding lithium battery is reduced. If the battery capacity is to be increased to a preset value, the number of negative electrode sheets needs to be increased, thereby increasing the weight and manufacturing cost of the lithium battery, and causing the energy density of the lithium battery to decrease.

[0029] Based on this, in the laminated battery cell 101 of the embodiment of the present application, on the premise that the length of the positive electrode sheet 10111 and the length of the negative electrode sheet 10113 are respectively controlled within the range of 135 mm to 165 mm, and the width of the positive electrode sheet 10111 and the width of the negative electrode sheet 10113 are respectively controlled within the range of 135 mm to 165 mm, within the range of the ratio of the length to the thickness and the range of the ratio of the width to the thickness of the aforementioned electrode sheets, it can be ensured that the laminated battery cell 101 has an acceptable internal resistance and that the lithium battery including the laminated battery cell 101 has a good energy density.

[0030] In order to make the lithium battery have both lower internal resistance and higher energy density, in some embodiments of the present application, the thickness of the positive electrode sheet 10111 and the thickness of the negative electrode sheet 10113 are independently selected from 180 μm to 215 μm, for example, they can be 180 μm to 190 μm, 180 μm to 200 μm, 180 μm to 210 μm, 190 μm to 200 μm, 190 μm to 210 μm, 190 μm to 215 μm, 200 μm to 210 μm or 210 μm to 215 μm, and examples are 180 μm, 185 μm, 190 μm, 193 μm, 197 μm, 200 μm, 205 μm, 210 μm, 215 μm or a value between any two of the foregoing values.

[0031] In order to improve the actual capacity and cycle life of the lithium battery including the laminated battery core 101, in some embodiments of the present application, referring to FIG2 , the material of the positive electrode active material layer 101113 includes a lithium iron manganese phosphate material. The general chemical formula of the lithium iron manganese phosphate material is Li a Mn x Fe y M z (PO4) b , a, x, y, z and b respectively represent the molar amounts of the corresponding elements, the sum of x, y and z is c, and M is selected from one or more of Mg, Ca, Sr, Co, Ti, Zr, Mo, V, Nb, Nd, Y, Ni, Sc, Cr, Cu, Zn, Be, La and Al.

[0032] In the chemical formula Li a Mn x Fe y M z (PO4) b , 0.10≤x≤0.70, where x is, for example, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, or a value between any two of the foregoing values. It should be noted that a higher x corresponds to a higher molar content of Mn in the lithium manganese iron phosphate material and a higher average voltage of the positive electrode sheet 10111. If x is greater than 0.7, lithium ion diffusion may be weakened during actual use, resulting in a decrease in the conductivity of the positive electrode sheet 10111, thereby reducing the power of the lithium battery including the laminated battery cell 101.

[0033] In order to increase the average voltage of the positive electrode sheet 10111 and ensure that the positive electrode sheet 10111 has good conductivity, thereby improving the electrochemical performance of the laminated battery cell 101, in some embodiments of the present application, 0.10≤x≤0.68, 0.26≤x≤0.68, or 0.4≤x≤0.68.

[0034] In the chemical formula Li a Mn x Fe y M z (PO4) b In the above, the ratio of a to c, a / c, 1.01≤a / c≤1.10, a / c can be, for example, 1.01-1.03, 1.01-1.05, 1.01-1.08, 1.015-1.035, 1.035-1.05, 1.035-1.08, 1.035-1.10, 1.05-1.08, or 1.05-1.10, exemplified by 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, or a value between any two of the foregoing values. If a / c is lower than 1.01 (i.e., the Li content is low), the actual gram capacity of the lithium iron manganese phosphate material will decrease. If a / c is greater than 1.10 (i.e., the Li content is high), when the lithium iron manganese phosphate material is wetted by water, the residual alkali content on the surface of the lithium iron manganese phosphate material will increase. If the residual alkali content is too high, the lithium battery will "flatulence", resulting in a decrease in the cycle performance of the square lithium battery.

[0035] Phosphorus stoichiometry is one of the key factors affecting the performance of lithium manganese iron phosphate materials. In order to ensure that lithium batteries containing lithium manganese iron phosphate materials have good rate performance and cycle stability, the stoichiometry of phosphorus in the chemical formula Li a Mn x Fe y M z (PO4) bIn the formula, the ratio of a to b is a / b, 0.95<a / b<1.10, for example, it can be 0.95<a / b≤1.00, 0.95<a / b≤1.03, 0.95<a / b≤1.05, 0.95<a / b≤1.08, 1.00≤a / b≤1.03, 1.00≤a / b≤1.08, 1.00≤a / b<1.10 or 1.03<a / b<1.10, examples of a / b are 0.96, 0.98, 1.00, 1.01, 1.02, 1.03, 1.05, 1.08, 1.10 or any two values ​​between the foregoing. The ratio of c to b is c / b, 0.90<c / b<1.10, for example, it can be 0.90<c / b≤1.00, 0.90<c / b≤1.01, 0.90<c / b<1.02, 0.90<c / b≤1.05, 0.90<c / b≤1.07, 0.90<c / b≤1.09, or 0.95≤c / b≤1.10, and examples of c / b are 0.91, 0.93, 0.95, 0.97, 0.99, 1.00, 1.01, 1.02, 1.05, 1.07, 1.10 or a value between any two of the foregoing values.

[0036] The element type of M is one of the key factors affecting the performance of the lithium iron manganese phosphate material. For example, M is selected from Mg, which can improve the sintering properties of the lithium iron manganese phosphate material and is beneficial to improving the rate performance of lithium batteries containing the lithium iron manganese phosphate material. Under the premise that M is a specific element type, the molar amount of M will also affect the performance of the lithium iron manganese phosphate material. In order to ensure that M has a good modification effect on the lithium iron manganese phosphate material and avoid poor electrochemical performance due to excessive molar amount of M, 0.01≤z≤0.12, for example, it can be 0.01≤z≤0.03, 0.01≤z≤0.05, 0.01≤z≤0.08, 0.01≤z≤0.10, 0.05≤z≤0.08, or 0.05≤z≤0.12, and examples are 0.01, 0.02, 0.03, 0.05, 0.08, 0.10, 0.12 or a value between any two of the foregoing values.

[0037] To improve the electron transfer efficiency and ionic conductivity of the lithium iron manganese phosphate material, in some embodiments of the present application, a coating layer is provided on the surface of the lithium iron manganese phosphate material. The coating layer comprises a carbon material, with the mass of the carbon material accounting for 0.5% to 3% of the combined mass of the carbon material and the lithium iron manganese phosphate material. It should be noted that the coating layer also protects the lithium iron manganese phosphate material, reducing the dissolution of Fe and Mn caused by the infiltration of water (e.g., electrolyte) into the lithium iron manganese phosphate material. The thickness of the coating layer is, for example, 3 nm to 5 nm.

[0038] The present application also provides a method for preparing a lithium iron manganese phosphate material, which can be used to prepare any of the lithium iron manganese phosphate materials mentioned above, comprising the following steps:

[0039] S1. Providing a first slurry including a lithium source, a manganese source, an iron source, a phosphorus source and an M source;

[0040] S2, grinding the first slurry to obtain a second slurry;

[0041] S3, spray drying the second slurry to obtain a pre-burned material;

[0042] S4. Sintering the pre-burned material to obtain lithium manganese iron phosphate material.

[0043] Specifically, in step S1, each raw material can be selected according to conventional methods in the art. The lithium source can be one or more of lithium oxide, lithium hydroxide, and lithium salts. The lithium oxide includes, but is not limited to, Li2O. The anions generated by the ionization of the lithium salt include, but are not limited to, one or more of oxalate ions, carbonate ions, sulfate ions, nitrate ions, acetate ions, halide ions, phosphate ions, and dihydrogen phosphate ions. Examples of lithium salts include one or more of lithium carbonate, lithium sulfate, lithium nitrate, lithium acetate, lithium dihydrogen phosphate, lithium phosphate, and lithium oxalate.

[0044] The manganese source can be one or more of manganese oxide, manganese hydroxide and manganese salt. Manganese oxide includes but is not limited to one or more of manganese monoxide, manganese dioxide and manganese tetraoxide. The anions generated by the ionization of manganese salt include but are not limited to one or more of oxalate ion, carbonate ion, sulfate ion, nitrate ion, acetate ion, halide ion and phosphate ion. Examples of manganese sources are one or more of manganese carbonate, manganese phosphate, manganese oxalate, manganese nitrate, manganese acetate, manganese sulfate and manganese chloride.

[0045] The iron source is one or more of iron oxide, iron hydroxide and iron salt. The iron oxide includes but is not limited to one or more of ferroferric oxide, ferrous oxide and ferrous oxide. The anions generated by the ionization of the iron salt include but are not limited to one or more of oxalate ion, carbonate ion, sulfate ion, nitrate ion, acetate ion, halide ion and phosphate ion. Examples of iron salts are one or more of ferrous sulfate, ferric chloride, ferrous phosphate, ferric phosphate, ferrous pyrophosphate, ferric pyrophosphate, ferric nitrate, ferric acetate, ferric citrate, ferrous oxalate and ferrous chloride.

[0046] The phosphorus source includes but is not limited to one or more of phosphoric acid and phosphorus-containing metal salts, wherein the phosphorus-containing metal salt includes but is not limited to one or more of ammonium phosphate, ammonium dihydrogen phosphate, potassium dihydrogen phosphate, sodium dihydrogen phosphate and iron phosphate.

[0047] The M source is, for example, a compound containing one or more of Mg, Ca, Sr, Co, Ti, Zr, Mo, V, Nb, Nd, Y, Ni, Sc, Cr, Cu, Zn, Be, La and Al. The compound may be an oxide, hydroxide or metal salt compound. Taking the M source as a titanium source as an example, the titanium source may be one or more of titanium oxide, metatitanic acid, tetrabutyl titanate, titanium hydroxide and titanium salts. The titanium oxide includes but is not limited to TiO2. The anions generated by the ionization of the titanium salt include but are not limited to one or more of oxalate ions, carbonate ions, sulfate ions, nitrate ions, acetate ions, halogen ions and phosphate ions. Examples of titanium salts include one or more of titanium sulfate, titanium nitrate and titanium chloride. Taking the M source as a cobalt source as an example, the cobalt source includes but is not limited to one or more of cobalt trioxide, cobalt nitrate, cobaltous oxide, cobalt acetate and cobalt phosphate. Taking the M source as a nickel source as an example, the nickel source includes but is not limited to The invention is limited to one or more of nickelous oxide, nickel oxide, nickel nitrate, nickel acetate and nickel phosphate; taking the M source as a magnesium source as an example, the magnesium source includes but is not limited to one or more of magnesium oxide, magnesium chloride, magnesium sulfate, magnesium nitrate and magnesium acetate; taking the M source as a zinc source as an example, the zinc source includes but is not limited to one or more of zinc oxide, zinc nitrate, zinc sulfate, zinc chloride and zinc acetate; taking the M source as a vanadium source as an example, the vanadium source includes but is not limited to one or more of vanadium oxide, vanadium pentoxide, vanadium trioxide, vanadium nitrate and vanadium acetate; taking the D source as a niobium source as an example, the niobium source includes but is not limited to one or more of niobium pentoxide, niobium hydroxide, niobium oxalate, niobium acetate and niobium nitrate.

[0048] It should be noted that if the surface of the prepared lithium manganese iron phosphate material has a coating layer, the first slurry also includes a carbon source, which can be one or more of an inorganic carbon source and an organic carbon source, wherein the inorganic carbon source includes but is not limited to one or more of graphene, carbon nanotubes and graphite, and the organic carbon source includes but is not limited to one or more of glucose, sucrose, lactose, starch, organic acid, vitamins and phenolic resin. The carbon source can act as a reducing agent to effectively improve the Mn 2+ and Fe 2+ In addition, those skilled in the art know how to determine the amount of raw materials so that the molar amount of each element in the prepared lithium manganese iron phosphate material reaches the expected value.

[0049] In step S1, the solvent for the first slurry can be, for example, water and / or an organic solvent. Water is preferably deionized water. Optional organic solvents include, but are not limited to, alcohols with 1 to 10 carbon atoms, such as one or more of methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-methyl-2-propanol, n-pentanol, 2-methyl-1-butanol, and 2,2-dimethyl-1-propanol. The solvent for the first slurry is preferably water because, compared to organic solvents, water is less expensive and offers advantages such as environmental friendliness, low equipment requirements, and high safety.

[0050] In some embodiments of the present application, the solid content of the first slurry is 10% to 40%, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or a value between any two of the foregoing values, so that the first slurry has a suitable viscosity for subsequent grinding processing.

[0051] In step S2, the purpose of the grinding treatment is to refine the raw materials, improve the uniformity of the subsequent spray drying and sintering treatments, and help control the particle size of crystal growth during the sintering process. The grinding treatment method includes but is not limited to one or more of sand milling, ball milling, mechanical stirring milling and air flow milling. The process conditions of the grinding treatment can refer to the conventional conditions used in the art, for example: grinding treatment is carried out by sand milling, and sand milling is carried out at a speed of 200 r / min to 1000 r / min for 1 h to 6 h.

[0052] In step S3, the process conditions of the spray drying treatment can refer to the conventional conditions used in the art.

[0053] In step S4, the purpose of the sintering treatment is to cause all raw materials to undergo a solid-phase reaction to generate lithium manganese iron phosphate. It should be noted that when the surface of the obtained lithium manganese iron phosphate material has a carbon coating layer, the sintering treatment needs to be carried out in an environment isolated from oxygen, for example, in an inert gas atmosphere, and the inert gas includes but is not limited to one or more of nitrogen, argon, helium, argon, neon, krypton and xenon; when the surface of the obtained lithium manganese iron phosphate material does not have a carbon coating layer, the sintering treatment can be carried out in an atmosphere containing oxygen or in an inert gas atmosphere; the equipment used for the sintering treatment includes but is not limited to a muffle furnace, a tubular furnace, a rotary kiln, a roller kiln or a push plate kiln.

[0054] In order to obtain a lithium iron manganese phosphate material with a specific particle size, in some embodiments of the present application, after the sintering step and before the step of obtaining the lithium iron manganese phosphate material, the preparation method of the lithium iron manganese phosphate material further includes the steps of: crushing the sintered material obtained after the sintering treatment, and then passing the crushed material through a 150-200 mesh sieve for screening, and the material passing through the sieve is the lithium iron manganese phosphate material.

[0055] Regarding the laminated battery cell 101, it should also be noted that the materials of the positive electrode active material layer 101113 also include a positive electrode binder and a positive electrode conductor. The materials, positive electrode binder, and positive electrode conductor of the positive electrode current collector 101112 can be conventional materials in the art. For example, the materials of the positive electrode current collector 101112 include, but are not limited to, aluminum foil or composite aluminum foil; the positive electrode binder includes, but is not limited to, one or more of vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, and polytetrafluoroethylene; and the positive electrode conductor includes, but is not limited to, one or more of carbon black, graphite, and graphene.

[0056] The method for preparing the positive electrode sheet 10111, for example, includes the steps of: mixing a lithium manganese iron phosphate material, a positive electrode conductive agent, a positive electrode binder, and a first solvent to obtain a first mixture; then, coating the first mixture on the positive electrode current collector 101112, followed by a drying process and a roll pressing process to obtain the positive electrode sheet 10111. It is understood that the first mixture can also be cast on a separate carrier to form a film layer, which is then separated from the carrier and laminated onto the surface of the positive electrode current collector 101112. The first solvent includes, but is not limited to, N-methylpyrrolidone, dimethylformamide, or ethylene glycol dimethyl ether.

[0057] The materials of the negative electrode active material layer include a negative electrode active substance, a negative electrode binder, and a negative electrode conductive agent. The materials of the negative electrode current collector, the negative electrode active substance, the negative electrode binder, and the negative electrode conductive agent can be conventional materials in the art. For example, the materials of the negative electrode current collector include, but are not limited to, copper foil, composite copper foil, or copper mesh; the negative electrode active substance includes, but is not limited to, one or more of lithium单质, metals that can be alloyed with lithium, semi-metals, transition metal oxides, non-transition metal oxides, and carbon materials. Metals or semi-metals that can be alloyed with lithium include, but are not limited to, Si, Sn, Al, Ge, Pb, Bi, Sb, Si-Y1 alloy (Y1 is an alkali metal, alkaline earth metal, group 13-16 element, transition metal, rare earth element, or a combination thereof, excluding Si), and Sn-Y2 alloy (Y2 is an alkali metal, alkaline earth metal, group 13-16 element, transition metal, rare earth element, or a combination thereof, excluding Sn). Transition metal oxides include, but are not limited to, one or more of lithium titanium oxide, vanadium oxide, lithium vanadium oxide, and titanium niobium oxide. Non-transition metal oxides include, but are not limited to, SnO2 and SiO x (0 < x < 2), and carbon materials include, but are not limited to, one or more of crystalline carbon (such as graphite) and amorphous carbon. The negative electrode binder is deionized water or can be the same as the positive electrode binder, and the negative electrode conductive agent can be the same as the positive electrode conductive agent. The preparation method of the negative electrode sheet 10113 can be carried out by referring to the preparation method of the positive electrode sheet 10111.

[0058] The materials of the separator 10112 include, but are not limited to, one or more of glass fiber, polyester, Teflon, polyethylene, polypropylene, and polytetrafluoroethylene.

[0059] The embodiment of the present application also provides a square lithium battery. As shown in Figure 3, the square lithium battery 10 includes one or more stacked type battery cells 101 as described in any of the foregoing, and one or more stacked type battery cells 101 constitute the battery cells of the square lithium battery 10.

[0060] In some embodiments of the present application, the ratio of the length to the width of the square lithium battery 10 is 1.00 - 1.13. For example, it can be 1.00 - 1.03, 1.00 - 1.05, 1.00 - 1.08, 1.00 - 1.12, 1.06 - 1.07, or 1.06 - 1.13, and examples are 1.00, 1.03, 1.05, 1.08, 1.10, 1.13, or values between any two of the foregoing values.

[0061] The length of the square lithium battery is selected from 165 mm to 185 mm, for example, it can be 165 mm to 170 mm, 170 mm to 180 mm, 174 mm to 180 mm, 175 mm to 176 mm, or 180 mm to 185 mm, and examples are 165 mm, 170 mm, 175 mm, 180 mm, 185 mm or a value between any two of the foregoing values; and / or, the width of the square lithium battery is selected from 155 mm to 170 mm, for example, it can be 160 mm to 170 mm, 160 mm to 165 mm, 164 mm to 165 mm, or 165 mm to 170 mm, and examples are 155 mm, 160 mm, 165 mm, 170 mm or a value between any two of the foregoing values.

[0062] It should be noted that when the square lithium battery 10 is used as a battery element of a vehicle battery pack, especially a commercial vehicle (including but not limited to trucks, logistics vehicles or engineering vehicles), the length and width size design of the aforementioned square lithium battery 10 is conducive to improving the internal space utilization and endurance of the battery pack, and can take into account the structural strength and heat dissipation effect of the square lithium battery 10.

[0063] In some embodiments of the present application, the ratio of the length to the thickness of the square lithium battery 10 is 3.4×10 3 ~4.5×10 3 , for example, it can be 3.4×10 3 ~3.8×10 3 , 3.4×10 3 ~4.0×10 3 , 3.4×10 3 ~4.3×10 3 , 3.8×10 3 ~4.0×10 3 , 4.0×10 3 ~4.1×10 3 , or 4.0×10 3 ~4.5×10 3 , for example 3.4×10 3 , 3.8×10 3 , 4.0×10 3 , 4.5×10 3 or a value between any two of the above values; the ratio of the width to the thickness of the square lithium battery 10 is 3.3×10 2 ~4.3×10 2 , for example, it can be 3.3×10 3 ~3.5×10 3 , 3.3×10 3 ~4.0×103 , 3.3×10 3 ~4.3×10 3 , 3.7×10 3 ~3.8×10 3 , 3.8×10 3 ~4.0×10 3 , or 4.0×10 3 ~4.3×10 3 , for example, 3.3×10 3 , 3.8×10 3 , 4.0×10 3 , 4.3×10 3 Or a value between any two of the above values.

[0064] The thickness of the square lithium battery 10 is selected from 35 mm to 55 mm, for example, it can be 35 mm to 40 mm, 35 mm to 45 mm, 35 mm to 50 mm, 40 mm to 45 mm, 40 mm to 50 mm, 43 mm to 44 mm or 45 mm to 50 mm, and examples are 35 mm, 40 mm, 43 mm, 44 mm, 45 mm, 50 mm, 55 mm or a value between any two of the foregoing values.

[0065] It should be noted that when the square lithium battery 10 is used as a battery element of a vehicle battery pack, especially a commercial vehicle (including but not limited to a truck, logistics vehicle or engineering vehicle), the length to thickness ratio design and the width to thickness ratio design of the aforementioned square lithium battery 10 can optimize the spatial distribution of energy of the square lithium battery 10 in the battery pack; in addition, the thickness dimension design of the aforementioned square lithium battery 10 can ensure that there is sufficient heat dissipation area between any two adjacent square lithium batteries 10 in the battery pack, thereby ensuring the heat dissipation effect, and reducing the volume share of a single square lithium battery 10, which is conducive to the compact arrangement of multiple square lithium batteries 10 in the battery pack.

[0066] It should be noted that the square lithium battery 10 also includes other conventional structural parts. For example, referring to Figures 1 and 3, the square lithium battery 10 also includes a shell 102, a positive electrode column 103, and a negative electrode column 104. The positive electrode column 103 and the negative electrode column 104 are respectively arranged on the surface of the shell 102, and the laminated battery cell 101 is arranged in the shell 102. The material of the shell 102 is, for example, aluminum. Among them, the positive electrode ear 1012 and the positive electrode column 103 are welded together through the connecting piece 105 by a spot welding process to form the positive electrode of the square lithium battery 10, and the negative electrode ear 1013 and the negative electrode column 104 are welded together through the connecting piece 105 by a spot welding process to form the negative electrode of the square lithium battery 10.

[0067] In addition, the square lithium battery 10 also includes an electrolyte, and the electrolyte soaks the laminated battery core 101. The electrolyte can be a conventional component in the field, for example: the electrolyte includes a lithium salt and an organic solvent, wherein the organic solvent is selected from a combination of two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene sulfite, ethyl acetate, diethyl sulfite, and 1,3-propane sultone; the lithium salt is selected from LiPF6, LiClO4, LiBF4, LiSbF6, LiAsF6, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiODFB, LiTFSI, LiFSI, LiCl, LiI and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2), wherein x and y are integers of 1 to 20, and the ratio of the mass of the lithium salt to the total mass of the electrolyte is 10% to 15%.

[0068] In some embodiments of the present application, the AC internal resistance of the square lithium battery 10 (composed of one or more laminated battery cells 101) at 25°C is 0.2 mΩ to 0.5 mΩ, and / or the energy density of the square lithium battery is 190 Wh / kg to 220 Wh / kg, and / or the capacity of the square lithium battery is 175 Ah to 250 Ah, and / or the voltage of the square lithium battery is 2.5 V to 4.2 V.

[0069] An embodiment of the present application also provides a battery pack, as shown in FIG4 , wherein the battery pack 100 includes a box body 20 and a plurality of square lithium batteries 10 as described above. The box body 20 forms a receiving space 201 , and the plurality of square lithium batteries 10 are arranged in sequence in the receiving space 201 .

[0070] It should be noted that the battery pack 100 also includes other conventional structural components. For example, referring to FIG4 , the battery pack 100 also includes a cover 30 and a buffer 40. The cover 30 is used to cover the interior space of the box 20, and the buffer 40 is disposed within the box 20 and located on the box wall 202 of the box 20. It is understood that the battery pack 100 may also include components such as a battery management system and a cooling device.

[0071] An embodiment of the present application also provides an application of any laminated battery cell as described above, or any square lithium battery as described above, or any battery pack as described above in a vehicle, wherein the battery cell, or square lithium battery, or battery pack serves as a power source for the vehicle.

[0072] In some embodiments of the present application, the vehicle is selected from a truck, a logistics vehicle, or an engineering vehicle.

[0073] The technical solutions and technical effects of the present application are described in detail below through specific embodiments, comparative examples and experimental examples. The following embodiments are part of the present application and do not specifically limit the present application.

[0074] Example 1

[0075] This embodiment provides a square lithium battery. As shown in Figure 3, the square lithium battery 10 includes a laminated battery cell 101, a shell 102, a positive electrode column 103 and a negative electrode column 104, wherein the laminated battery cell 101 is arranged in the shell 102, the material of the shell 102 is, for example, aluminum, and the positive electrode column 103 and the negative electrode column 104 are respectively arranged on the surface of the shell 102. As shown in Figure 1, the laminated battery cell 101 includes 55 battery cell units 1011 stacked in sequence along a first direction X1, and each battery cell unit 1011 includes a positive electrode sheet 10111, a diaphragm 10112 and a negative electrode sheet 10113 stacked in sequence. The first direction X1 is perpendicular to the first surface 101111 of the positive electrode sheet 10111 close to the diaphragm 10112. The sub-pole ears 101110 of the positive electrode sheets 10111 of all battery cell units 1011 are connected in sequence to form the positive electrode ears 1012, and the sub-pole ears 101110 of the negative electrode sheets 10113 of all battery cell units 1011 are connected in sequence to form the negative electrode ears 1013. Continuing with FIG3 , the positive tab 1012 and the negative tab 1013 are respectively located at the openings of the housing 102 . The positive tab 1012 is welded to the positive electrode post 103 to form the positive electrode of the prismatic lithium battery 10 , while the negative tab 1013 is welded to the negative electrode post 104 to form the negative electrode of the prismatic lithium battery 10 . The prismatic lithium battery 10 also includes an electrolyte, which infiltrates the laminated cell 101 .

[0076] As shown in FIG2 , the positive electrode sheet 10111 includes a positive electrode current collector 101112 and a positive electrode active material layer 101113. The positive electrode active material layer 101113 is disposed on the surface of the positive electrode current collector 101112. The material of the positive electrode current collector 101112 is a carbon-coated aluminum foil (thickness of 12 μm). The material of the positive electrode active material layer 101113 includes a carbon-coated Li 0.96 Fe 0.3 Mn 0.6 Mg 0.04 PO4, the average thickness of the coating layer is 3 nm, and the mass of the carbon material accounts for 0.96 Fe 0.3 Mn 0.6 Mg 0.04 1.5% of the total mass of PO4.

[0077] The preparation method of the positive electrode sheet 10111 comprises the following steps: 0.96 Fe 0.3 Mn 0.6 Mg 0.04 The mass ratio of PO4: carbon black conductive (Super PLL): carbon nanotubes: polyvinylidene fluoride is 97:0.4:0.5:2.1. The above four raw materials are weighed and evenly mixed with N-methylpyrrolidone to obtain a positive electrode slurry with a solid content of 65%. Then, the positive electrode slurry is coated on an aluminum foil with a thickness of 12 μm (coated on both sides) by a coating machine, and then placed at 120°C for baking and curing to form a positive electrode active material layer, and then cold pressed to the corresponding thickness by a roller press to obtain a positive electrode sheet.

[0078] Among them, carbon-coated Li 0.96 Fe 0.3 Mn 0.6 V 0.04 The preparation method of PO4 comprises the following steps:

[0079] S1.1. Add 45.76 kg of manganese tetraoxide, 45.25 kg of ferric phosphate, 35.46 kg of lithium carbonate, 1.6 kg of magnesium oxide, 80.68 kg of 85% by mass phosphoric acid aqueous solution, and 2.72 kg of glucose into a mixer to mix the raw materials for 2 h to obtain a mixture. Then, transfer the mixture to a sand mill, and add deionized water to the mixture at a mass ratio of 1:1.5 of the mass of the mixture to the mass of deionized water to obtain a first slurry.

[0080] S1.2. Sand mill the first slurry at a speed of 500 r / min and a time of 1.5 h to obtain a second slurry.

[0081] S1.3. spray drying the second slurry, ensuring that the slurry is stirred during the entire spray drying process to obtain a pre-burned material, wherein the particle size distribution of the pre-burned material is in the range of 2 μm to 5 μm;

[0082] S1.4. Place the pre-burned material in a kiln and introduce protective N2 gas at a flow rate of 80 mL / min. Then, increase the temperature from room temperature to 750°C at a heating rate of 5°C / min, sinter at 750°C for 6 h, and cool to room temperature to obtain the sintered material.

[0083] S1.5, the burned material is subjected to air flow pulverization treatment and 150 mesh sieve screening treatment in sequence, and the material passing through the 150 mesh sieve is subjected to the iron removal treatment process to obtain carbon material coated Li 0.96 Fe0.3 Mn 0.6 V 0.04 PO4.

[0084] The negative electrode sheet 10113 includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is disposed on the surface of the negative electrode current collector. The negative electrode current collector is made of aluminum foil (12 μm thick), and the negative electrode active material layer is made of graphite. The preparation method of the negative electrode sheet 10113 includes the following steps: weighing the graphite: conductive carbon black (Super PLL): carboxymethyl cellulose: styrene-butadiene rubber in a mass ratio of 97:0.7:1.25:1.05; uniformly mixing the above four raw materials with N-methylpyrrolidone to obtain a negative electrode slurry having a solids content of 55%; then, coating the negative electrode slurry on 8 μm thick aluminum foil (coated on both sides) using a coating machine, then baking and curing at 80°C to form a negative electrode active material layer, and then cold-pressing the negative electrode sheet to the desired thickness using a roller press.

[0085] The preparation method of the electrolyte includes the steps of: mixing ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methyl carbonate (EMC) in a volume ratio of 4:3:3 to obtain a solvent, then adding LiPF6 and an additive to the solvent, and mixing them evenly to obtain an electrolyte, wherein the concentration of LiPF6 in the electrolyte is 1.0 mol / L, the mass of the additive accounts for 10% of the total mass of the electrolyte, and the additive is composed of vinylene carbonate, 1,3-propane sultone, fluoroethylene carbonate and cyclohexylbenzene, and the mass ratio of vinylene carbonate: 1,3-propane sultone: fluoroethylene carbonate: cyclohexylbenzene is 3:2:1:1.

[0086] The preparation method of the square lithium battery 10 includes the following steps: stacking a positive electrode sheet 10111, a PP separator 10112 with a thickness of 12 μm, and a negative electrode sheet 10113 to form a battery unit 1011; stacking 55 battery units 1011 to form a stacked battery core 101; assembling two stacked battery cores 101 with an aluminum shell; injecting electrolyte; and finally undergoing aging, formation, shaping, packaging and other processes to obtain the square lithium battery 10.

[0087] In this embodiment, the dimensions of the positive electrode sheet 10111 and the negative electrode sheet 10113 are exactly the same (the dimensions of the positive electrode active material layer and the negative electrode active material layer are exactly the same). The dimensions of the positive electrode sheet 10111, the negative electrode sheet 10113, and the square lithium battery 10 in this embodiment are shown in Table 1 below:

[0088] Table 1

[0089] Item Value Length of positive electrode sheet (negative electrode sheet) (mm) 151 Width of positive electrode sheet (negative electrode sheet) (mm) 148 Thickness of positive electrode sheet (negative electrode sheet) (μm) 197 Length of square lithium battery (mm) 175 Width of square lithium battery (mm) 164 Thickness of square lithium battery (mm) 43

[0090] Example 2

[0091] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the thickness of the positive electrode sheet and the negative electrode sheet are respectively replaced with "190 μm".

[0092] Example 3

[0093] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the thickness of the positive electrode sheet and the negative electrode sheet are respectively replaced with "180 μm".

[0094] Example 4

[0095] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the thickness of the positive electrode sheet and the negative electrode sheet are respectively replaced with "210 μm".

[0096] Example 5

[0097] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the thickness of the positive electrode sheet and the negative electrode sheet are respectively replaced with "215 μm".

[0098] Example 6

[0099] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the width of the positive electrode sheet and the negative electrode sheet are respectively replaced with "145 mm".

[0100] Example 7

[0101] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the width of the positive electrode sheet and the negative electrode sheet are respectively replaced with "155 mm".

[0102] Example 8

[0103] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the width of the positive electrode sheet and the negative electrode sheet are respectively replaced with "135 mm".

[0104] Example 9

[0105] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the width of the positive electrode sheet and the negative electrode sheet are respectively replaced with "165 mm".

[0106] Example 10

[0107] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the lengths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "145 mm".

[0108] Example 11

[0109] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the lengths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "155 mm".

[0110] Example 12

[0111] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the lengths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "135 mm".

[0112] Example 13

[0113] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the lengths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "165 mm".

[0114] Example 14

[0115] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is only that the lengths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "145 mm", and the widths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "140 mm".

[0116] Example 15

[0117] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is only that the lengths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "150 mm", and the widths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "140 mm".

[0118] Example 16

[0119] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is only that the lengths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "155 mm", and the widths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "155 mm".

[0120] Example 17

[0121] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is only that the lengths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "165 mm", and the widths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "135 mm".

[0122] Example 18

[0123] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the thickness of the square lithium battery is replaced by "35 mm".

[0124] Example 19

[0125] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the thickness of the square lithium battery is replaced by "55 mm".

[0126] Example 20

[0127] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the thickness of the square lithium battery is replaced by "40 mm".

[0128] Example 21

[0129] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the thickness of the square lithium battery is replaced by "50 mm".

[0130] Example 22

[0131] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the width of the square lithium battery is replaced by "170 mm".

[0132] Example 23

[0133] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is only that the width of the square lithium battery is replaced by "155 mm".

[0134] Example 24

[0135] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the length of the square lithium battery is replaced by "165 mm".

[0136] Example 25

[0137] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this embodiment is that the length of the square lithium battery is replaced by "185 mm".

[0138] Example 26

[0139] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference between the square lithium battery in this embodiment is that the "Li 0.96 Fe 0.3 Mn 0.6 Mg 0.04 PO4" is replaced by "Li 0.96 Fe 0.3 Mn 0.6 V 0.04 PO4".

[0140] Among them, Li 0.96 Fe 0.3 Mn 0.6 V 0.04 The preparation method of PO4 comprises the steps of replacing "1.6 kg of magnesium oxide" in step S1.1 with "3 kg of vanadium trioxide".

[0141] Example 27

[0142] This embodiment provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference between the square lithium battery in this embodiment is that the "Li 0.96 Fe0.3 Mn 0.6 Mg 0.04 PO4" is replaced by "Li 0.96 Fe 0.3 Mn 0.6 Mg 0.02 V 0.02 PO4".

[0143] Among them, Li 0.96 Fe 0.3 Mn 0.6 Mg 0.02 V 0.02 The preparation method of PO4 comprises the steps of replacing "1.6 kg of magnesium oxide" in step S1.1 with "0.8 kg of magnesium oxide and 1.5 kg of vanadium trioxide".

[0144] Comparative Example 1

[0145] This comparative example provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this comparative example is that the thickness of the positive electrode sheet and the negative electrode sheet are respectively replaced with "250 μm".

[0146] Comparative Example 2

[0147] This comparative example provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this comparative example is that the widths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "110 mm".

[0148] Comparative Example 3

[0149] This comparative example provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this comparative example is that the lengths of the positive electrode sheet and the negative electrode sheet are respectively replaced with "110 mm".

[0150] Comparative Example 4

[0151] This comparative example provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the difference of the square lithium battery in this comparative example is that the width of the square lithium battery is replaced by "140 mm".

[0152] Comparative Example 5

[0153] This comparative example provides a square lithium battery. Compared with the square lithium battery provided in Example 1, the square lithium battery in this comparative example is different only in that the length of the square lithium battery is replaced by "150 mm.

[0154] Experimental Example 1

[0155] The AC internal resistance of the cells of the square lithium batteries in Examples 1 to 17, Example 26, and Comparative Examples 1 to 3 was tested (25° C.), and the test results are shown in Table 2 below:

[0156] Table 2

[0157] No. Battery cell AC internal resistance (mΩ) Example 10.31 Example 2 0.29 Example 3 0.26 Example 4 0.33 Example 5 0.34 Example 6 0.31 Example 7 0.32 Example 8 0.28 Example 9 0.37 Example 10 0.30 Example 11 0.31 Example 12 0.27 Example 13 0.33 Example 14 0.29 Example 15 0.31 Example 16 0.33 Example 17 0.32 Example 26 0.31 Example 27 0.28 Comparative Example 10.62 Comparative Example 20.38 Comparative Example 3 0.37

[0158] As can be seen from Table 2, compared with the AC internal resistance (25° C.) of the square lithium batteries in Comparative Examples 1 to 3, the AC internal resistance (25° C.) of the square lithium batteries in Examples 1 to 26 is smaller.

[0159] Experimental Example 2

[0160] The square lithium batteries in Examples 1 to 26 and Comparative Examples 1 to 5 were subjected to electrical performance tests and thermal runaway tests, respectively. The electrical performance test method comprises the following steps: charging each square lithium battery to 4.2 V at a constant current and constant voltage rate of 0.2C at 25°C, wherein the constant voltage charge cutoff current is 0.02C, and then discharging at a constant current of 0.2C until the voltage reaches 2.5V, obtaining the first discharge capacity and first charge capacity at 25°C and 0.2C rate, and calculating the first charge and discharge efficiency of each square lithium battery at 25°C and 0.2C rate (the ratio of the first discharge capacity to the first charge capacity × 100%). The detection method of the thermal runaway test is carried out with reference to the thermal runaway test method in Appendix A of GB38032-2020.

[0161] The test results are shown in Table 3 below:

[0162] Table 3

[0163] No. First charge capacity (mAh / g) First discharge capacity (mAh / g) First charge and discharge efficiency (%) Thermal runaway test Example 1 139.32 158.5 87.9 Passed Example 2 139.44 157.2 88.7 Passed Example 3 139.35 155.7 89.5 Passed Example 4 138.71 159.8 86.8 Passed Example 5 136.74 160.3 85.3 Passed Example 6 135.12 160.1 84.4 Passed Example 7 136.00 162. 183.9 through Example 8 131.30 162.9 80.6 through Example 9 137.23 158.1 86.8 through Example 10 139.11 157.9 88.1 through Example 11 138.82 159.2 87.2 through Example 12 132.80 153.7 86.4 through Example 13 128.56 160.58 0.1 through Example 14 137.43 157.6 87.2 through Example 15 138.02 157.2 87.8 through Example 16140.34158.488.6 through Example 17137.56159.486.3 through Example 18137.57157.487.4 through Example 19140.84161.787.1 through Example 20137.85157.987.3 through Example 21138.46158.687.3 through Example 22133.74156.685.4 through Example 23131.00154.384.9 through Example 24137.51 158.686.7 Passed Example 25 135.18 155.287.1 Passed Example 26 139.37 158.288.1 Passed Example 27 143.69 159.390.2 Passed Comparative Example 1 124.88 164.176.1 Passed Comparative Example 2 120.58 154.278.2 Passed Comparative Example 3 115.14 152.375.6 Passed Comparative Example 4 114.63 156.673.2 Not passed Comparative Example 5 115.77 157.373.6 Not passed

[0164] It can be seen from Tables 2 and 3 that the comprehensive performance of the square lithium batteries in Examples 1 to 26 is better than that in Comparative Examples 1 to 5. It can be seen that in the square lithium battery, the length of the positive electrode sheet and the length of the negative electrode sheet are respectively controlled within the range of 135 mm to 165 mm, and the width of the positive electrode sheet and the width of the negative electrode sheet are respectively controlled within the range of 135 mm to 165 mm, and the thickness of the positive electrode sheet and the thickness of the negative electrode sheet are respectively controlled within the range of 190 μm to 210 mm, and the length of the square lithium battery is controlled within the range of 165 mm to 185 mm, and the width of the square lithium battery is controlled within the range of 155 mm to 170 mm, and the thickness of the square lithium battery is controlled within the range of 35 mm to 55 mm, which can ensure that the battery cell of the square lithium battery has an acceptable internal resistance, and can improve the actual capacity, energy density, rate performance and cycle stability of the square lithium battery, and the square lithium battery has good safety.

Claims

1. A laminated battery cell, wherein: The laminated battery cell comprises a plurality of battery cell units stacked in sequence along a first direction, each of the battery cell units comprises a positive electrode sheet, a separator and a negative electrode sheet stacked in sequence, and a separator is arranged between two adjacent battery cell units, the first direction is perpendicular to the first surface of the positive electrode sheet close to the separator, the positive electrode sheet of each battery cell unit is provided with a sub-electrode ear, and the negative electrode sheet of each battery cell unit is provided with a sub-electrode ear; the sub-electrode ears of the positive electrode sheets of the plurality of battery cell units are connected in sequence to form a positive electrode ear, and the sub-electrode ears of the negative electrode sheets of the plurality of battery cell units are connected in sequence to form a negative electrode ear; The ratio of the length to the thickness of the positive electrode sheet and the ratio of the length to the thickness of the negative electrode sheet are independently selected from 6.3×10 2 ~9.4×10 2 The ratio of the width to the thickness of the positive electrode sheet and the ratio of the width to the thickness of the negative electrode sheet are independently selected from 6.3×10 2 ~9.4×10 2 .

2. The laminated battery cell according to claim 1, wherein: The length of the positive electrode sheet and the length of the negative electrode sheet are independently selected from 135 mm to 165 mm, and the width of the positive electrode sheet and the width of the negative electrode sheet are independently selected from 135 mm to 165 mm; and / or The thickness of the positive electrode sheet and the thickness of the negative electrode sheet are independently selected from 180 μm to 215 μm; and / or The size of the positive electrode sheet is the same as that of the negative electrode sheet.

3. The laminated battery cell according to claim 1 or 2, wherein: The length of the positive electrode sheet and the length of the negative electrode sheet are respectively 145 mm to 155 mm; and / or The width of the positive electrode sheet and the width of the negative electrode sheet are 145 mm to 155 mm respectively; and / or The ratio of the length to thickness of the positive electrode sheet and the ratio of the length to thickness of the negative electrode sheet are 7.7×10 2 ~8.5×10 2 ; and / or The ratio of the width to thickness of the positive electrode sheet and the ratio of the width to thickness of the negative electrode sheet are 7.7×10 2 ~8.5×10 2 ; and / or The thickness of the positive electrode sheet and the thickness of the negative electrode sheet are independently selected from 190 μm to 210 μm.

4. The laminated battery cell according to any one of claims 1 to 3, wherein: The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector; the material of the positive electrode active material layer includes lithium manganese iron phosphate material, and the chemical formula of the lithium manganese iron phosphate material is Li a Mn x Fe y M z (PO4) b , a, x, y, z and b represent the molar amounts of the corresponding elements respectively, the sum of x, y and z is c, and M is selected from one or more of Mg, Ca, Sr, Co, Ti, Zr, Mo, V, Nb, Nd, Y, Ni, Sc, Cr, Cu, Zn, Be, La and Al; Among them, 0.10≤x≤0.70, 0.01≤z≤0.12; the ratio of a to c is a / c, 1.01≤a / c≤1.10; the ratio of a to b is a / b, 0.95<a / b<1.10; the ratio of c to b is c / b, 0.90<c / b<1.

10.

5. The laminated battery cell according to claim 4, wherein: In the lithium manganese iron phosphate material, 0.26≤x≤0.68, and / or 0.01≤z≤0.05, and / or 1.015≤a / c≤1.035, and / or 0.95<a / b<1.03, and / or 0.90<c / b<1.02; and / or A coating layer is provided on the surface of the lithium manganese iron phosphate material. The material of the coating layer includes a carbon material. The mass of the carbon material accounts for 0.5% to 3% of the sum of the mass of the carbon material and the lithium manganese iron phosphate material.

6. A square lithium battery, wherein: The square lithium battery includes one or more laminated cells, each of which includes a plurality of cell units stacked in sequence along a first direction, each of which includes a positive electrode sheet, a diaphragm and a negative electrode sheet stacked in sequence, and a diaphragm is provided between two adjacent cell units, the first direction is perpendicular to the first surface of the positive electrode sheet close to the diaphragm, the positive electrode sheet of each cell unit is provided with a sub-pole ear, and the negative electrode sheet of each cell unit is provided with a sub-pole ear; the sub-pole ears of the positive electrode sheets of the plurality of cell units are connected in sequence to form a positive electrode ear, and the sub-pole ears of the negative electrode sheets of the plurality of cell units are connected in sequence to form a negative electrode ear; The ratio of the length to the thickness of the positive electrode sheet and the ratio of the length to the thickness of the negative electrode sheet are independently selected from 6.3×10 2 ~9.4×10 2 The ratio of the width to the thickness of the positive electrode sheet and the ratio of the width to the thickness of the negative electrode sheet are independently selected from 6.3×10 2 ~9.4×10 2 .

7. The square lithium battery according to claim 6, wherein: The length of the positive electrode sheet and the length of the negative electrode sheet are independently selected from 135 mm to 165 mm, and the width of the positive electrode sheet and the width of the negative electrode sheet are independently selected from 135 mm to 165 mm; and / or The thickness of the positive electrode sheet and the thickness of the negative electrode sheet are independently selected from 180 μm to 215 μm; and / or The size of the positive electrode sheet is the same as the size of the negative electrode sheet; and / or The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector; the material of the positive electrode active material layer includes lithium manganese iron phosphate material, and the chemical formula of the lithium manganese iron phosphate material is Li a Mn x Fe y M z (PO4) b , a, x, y, z and b respectively represent the molar amounts of the corresponding elements, the sum of x, y and z is c, M is selected from one or more of Mg, Ca, Sr, Co, Ti, Zr, Mo, V, Nb, Nd, Y, Ni, Sc, Cr, Cu, Zn, Be, La and Al, 0.10≤x≤0.70, 0.01≤z≤0.12; the ratio of a to c is a / c, 1.01≤a / c≤1.10; the ratio of a to b is a / b, 0.95<a / b<1.10; the ratio of c to b is c / b, 0.90<c / b<1.

10.

8. The square lithium battery according to claim 6 or 7, wherein: The ratio of the length to the width of the square lithium battery is 1.00 to 1.13, and the ratio of the length to the thickness of the square lithium battery is 3.4×10 3 ~4.5×10 3 The ratio of the width to thickness of the square lithium battery is 3.3×10 2 ~4.3×10 2 ; and / or The square lithium battery further comprises a shell, and the laminated battery core is arranged in the shell; and / or The AC internal resistance of the square lithium battery cell at 25°C is 0.2 mΩ to 0.5 mΩ, and / or the energy density of the square lithium battery is 190 Wh / kg to 220 Wh / kg, and / or the capacity of the square lithium battery is 175 Ah to 250 Ah, and / or the voltage of the square lithium battery is 2.5 V to 4.2 V.

9. The square lithium battery according to any one of claims 6 to 8, wherein: The ratio of the length to the width of the square lithium battery is 1.06 to 1.07; and / or The ratio of the length to the thickness of the square lithium battery is 4.0×10 3 ~4.1×10 3 ; and / or The ratio of the width to thickness of the square lithium battery is 3.7×10 2 ~3.8×10 2 ; and / or The length of the square lithium battery is selected from 165 mm to 185 mm; and / or The width of the square lithium battery is selected from 155 mm to 170 mm; and / or The thickness of the square lithium battery is selected from 35 mm to 55 mm.

10. The square lithium battery according to any one of claims 6 to 9, wherein: The length of the square lithium battery is selected from 170 mm to 180 mm; and / or The width of the square lithium battery is selected from 160 mm to 170 mm; and / or The thickness of the square lithium battery is selected from 40 mm to 50 mm.

11. The square lithium battery according to any one of claims 6 to 10, wherein: The length of the square lithium battery is selected from 174 mm to 180 mm; and / or The width of the square lithium battery is selected from 160 mm to 165 mm; and / or The thickness of the square lithium battery is selected from 40 mm to 45 mm.

12. A battery pack, wherein: The battery pack includes a box body and a plurality of square lithium batteries, wherein the box body is formed with a receiving space, and the plurality of square lithium batteries are sequentially arranged in the receiving space; The square lithium battery includes one or more laminated cells, each of which includes a plurality of cell units stacked in sequence along a first direction, each of which includes a positive electrode sheet, a diaphragm and a negative electrode sheet stacked in sequence, and a diaphragm is provided between two adjacent cell units, the first direction is perpendicular to the first surface of the positive electrode sheet close to the diaphragm, the positive electrode sheet of each cell unit is provided with a sub-pole ear, and the negative electrode sheet of each cell unit is provided with a sub-pole ear; the sub-pole ears of the positive electrode sheets of the plurality of cell units are connected in sequence to form a positive electrode ear, and the sub-pole ears of the negative electrode sheets of the plurality of cell units are connected in sequence to form a negative electrode ear; The ratio of the length to the thickness of the positive electrode sheet and the ratio of the length to the thickness of the negative electrode sheet are independently selected from 6.3×10 2 ~9.4×10 2 The ratio of the width to the thickness of the positive electrode sheet and the ratio of the width to the thickness of the negative electrode sheet are independently selected from 6.3×10 2 ~9.4×10 2 .

13. The battery pack according to claim 12, wherein: The length of the positive electrode sheet and the length of the negative electrode sheet are independently selected from 135 mm to 165 mm, and the width of the positive electrode sheet and the width of the negative electrode sheet are independently selected from 135 mm to 165 mm; and / or The thickness of the positive electrode sheet and the thickness of the negative electrode sheet are independently selected from 180 μm to 215 μm; and / or The size of the positive electrode sheet is the same as the size of the negative electrode sheet; and / or The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector; the material of the positive electrode active material layer includes lithium manganese iron phosphate material, and the chemical formula of the lithium manganese iron phosphate material is Li a Mn x Fe y M z (PO4) b , a, x, y, z and b respectively represent the molar amounts of the corresponding elements, the sum of x, y and z is c, M is selected from one or more of Mg, Ca, Sr, Co, Ti, Zr, Mo, V, Nb, Nd, Y, Ni, Sc, Cr, Cu, Zn, Be, La and Al, 0.10≤x≤0.70, 0.01≤z≤0.12; the ratio of a to c is a / c, 1.01≤a / c≤1.10; the ratio of a to b is a / b, 0.95<a / b<1.10; the ratio of c to b is c / b, 0.90<c / b<1.

10.

14. The battery pack according to claim 12 or 13, wherein: The ratio of the length to the width of the square lithium battery is 1.00 to 1.13, and the ratio of the length to the thickness of the square lithium battery is 3.4×10 3 ~4.5×10 3 The ratio of the width to thickness of the square lithium battery is 3.3×10 2 ~4.3×10 2 ; and / or The square lithium battery further comprises a shell, and the laminated battery core is arranged in the shell; and / or The AC internal resistance of the square lithium battery cell at 25°C is 0.2 mΩ to 0.5 mΩ, and / or the energy density of the square lithium battery is 190 Wh / kg to 220 Wh / kg, and / or the capacity of the square lithium battery is 175 Ah to 250 Ah, and / or the voltage of the square lithium battery is 2.5 V to 4.2 V; and / or The length of the square lithium battery is selected from 165 mm to 185 mm; and / or The width of the square lithium battery is selected from 155 mm to 170 mm; and / or The thickness of the square lithium battery is selected from 35 mm to 55 mm.

15. The battery pack according to any one of claims 12 to 14, wherein: The battery pack serves as a power source for the vehicle.

16. The battery pack according to claim 15, wherein: The vehicle is selected from a truck, a logistics vehicle or an engineering vehicle.

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