WO2024087387A1

WO2024087387A1 - Secondary battery and electrical device

Info

Publication number: WO2024087387A1
Application number: PCT/CN2022/144277
Authority: WO
Inventors: 陈福洲; 贺理珀; 陈巍; 褚春波
Original assignee: 欣旺达动力科技股份有限公司
Priority date: 2022-10-28
Filing date: 2022-12-30
Publication date: 2024-05-02
Also published as: CN115472775A

Abstract

Disclosed are a secondary battery and an electrical device. The secondary battery comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode mixture layer provided on the positive electrode current collector, the positive electrode mixture layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium-containing compound of a layered structure; and the positive electrode sheet satisfies: 4000≤u≤14560, and U=C003/{[2Thea(110)-2Theta(018)]×FWHM[(110)+(018)]}. In the present application, by reasonably controlling the U value of the positive electrode sheet, the layered order degree of the layered compound in the positive electrode sheet can be improved and the orientation degree of the 003 crystal face in the layered compound can be reduced, thereby creating a good crystal structure basis for rapid deintercalation of lithium ions, and ensuring that the lithium ions have high transmission performance between positive electrode material particles, so that the secondary battery has good dynamic performance.

Description

Secondary batteries and electrical equipment

This application claims the priority of the Chinese patent application filed with the China Patent Office on October 28, 2022, with application number 202211336921.6 and invention name “Secondary Batteries and Electrical Equipment”, all contents of which are incorporated by reference in this application.

Technical Field

The present application belongs to the technical field of secondary batteries, and specifically relates to a secondary battery and an electrical device.

Background technique

The performance of secondary batteries depends largely on the positive active materials on the positive electrode sheets. Among them, when nickel-cobalt-manganese ternary materials are used as positive active materials, due to their poor structural stability during long-term cycles, the disordered arrangement of cations will hinder the transmission of lithium ions, resulting in a continuous decline in the power performance of the battery; at the same time, the layered structure of the nickel-cobalt-manganese ternary positive electrode material is greatly damaged under high current, and the structural decay also leads to a rapid decline in the battery cycle life. Improving the rapid charge and discharge capabilities of lithium-ion batteries by reducing the active material load of the electrode sheet or increasing the proportion of the conductive agent usually leads to a decrease in the battery energy density; designing small-sized primary particles is also a common strategy to improve fast charging performance, but when the particle size is too small, the side reactions on the surface increase, resulting in a rapid decline in cycle performance, and small particles are prone to agglomeration, which affects the processing performance of the electrode sheet, resulting in a decrease in the compaction density of the electrode sheet and particle crushing problems caused by high compaction density.

technical problem

The present application provides a secondary battery and an electrical device, which improve the layered order of layered compounds in a positive electrode plate and reduce the orientation degree of the layered compound crystal plane through reasonable control.

Technical Solutions

In a first aspect, an embodiment of the present application provides a secondary battery, comprising a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, wherein the positive electrode mixture layer comprises a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing compound having a layered structure;

The positive electrode sheet meets the following requirements: 4000≤U≤14560,

and

Wherein, _C003 is the peak area of the 003 characteristic diffraction peak in the X-ray diffraction pattern of the positive electrode pole piece, and the unit is AU·min; [2Theta(110)-2Theta(018)] is the relative distance between the 110 characteristic diffraction peak and the 018 characteristic diffraction peak in the X-ray diffraction pattern of the positive electrode pole piece, and the unit is min; FWHM[(110)+(018)] is the sum of the half-peak widths of the 110 characteristic diffraction peak and the 018 characteristic diffraction peak in the X-ray diffraction pattern of the positive electrode pole piece, and the unit is min.

In some embodiments, the positive electrode plate satisfies: 5500≤U≤12500, preferably 6500≤U≤10500.

In some embodiments, the range of U value is related to the peak area of the 003 characteristic diffraction peak obtained by X-ray diffraction test, the relative distance between the 110 characteristic diffraction peak and the 018 characteristic diffraction peak, and the sum of the half-peak widths of the 110 characteristic diffraction peak and the 018 characteristic diffraction peak; wherein, the sum of the peak area and the half-peak width can be directly obtained by spectrum analysis, and the relative distance can be obtained by obtaining the 2θ angle positions of the 110 and 018 diffraction peaks from the XRD diffraction spectrum, and subtracting the two to calculate the relative distance between the 110 and 018 diffraction peaks.

In some embodiments, the peak area of the 003 characteristic diffraction peak satisfies: 2200≤C ₀₀₃ ≤3500;

The relative distance between the 110 characteristic diffraction peak and the 018 characteristic diffraction peak satisfies: 0.40≤[2Theta(110)-2Theta(018)]≤0.70;

The sum of the half-widths of the 110 characteristic diffraction peak and the 018 characteristic diffraction peak satisfies: 0.55≤FWHM[(110)+(018)]≤0.80.

In some embodiments, the positive electrode sheet satisfies: 1050≤U/P≤4500, wherein P g/cm ³ is the compaction density of the positive electrode sheet, and 3.0≤P≤3.8.

In some embodiments, the lithium-containing compound is lithium nickel cobalt oxide, the lithium nickel cobalt oxide further comprises an M element, the lithium nickel cobalt oxide further comprises an A element, and the A element is at least one of Mn, Al, Ti, Mg, and Zr.

In some embodiments, the lithium nickel cobalt oxide further comprises an M element, and the M element comprises one or more of Al, B, Ca, W, Nb, Mg, Zr, Sr, Si, Y, Ti, and Sn.

In some embodiments, the lithium-containing compound comprises Li _x Ni _a Co _b _Ac O ₂ , wherein 0.95≤x≤1.05, 0.5≤a≤0.9, 0≤b≤0.5, 0≤c≤0.5, and a+b+c=1.

In some embodiments, M is a doping element and/or a coating element;

Wherein, the doping element includes one or more of Al, B, Ca, W, Nb, Mg, Zr, and Sr; the coating element includes one or more of Al, B, Zr, Sr, Si, Y, Ti, and Sn;

When M is a combination of the doping element and the cladding element, the doping element and the cladding element are different elements.

In some embodiments, the positive electrode active material has a median particle size D _v 50 of 2 μm to 20 μm.

In some embodiments, the present application also provides an electrical device, comprising the secondary battery, and the secondary battery serves as a power supply for the electrical device.

Beneficial Effects

Compared with the prior art, the present application can improve the layered order of the layered compound in the positive electrode sheet and reduce the orientation degree of the 003 crystal plane in the layered compound by reasonably controlling the U value of the positive electrode mixture layer in the positive electrode sheet, creating a good crystal structure foundation for the rapid deintercalation of lithium ions, ensuring that lithium ions have high transmission performance between the positive electrode material particles, and making the positive electrode sheet have good dynamic performance. The present application also controls the relationship between the U value and the compaction density of the positive electrode sheet to ensure that the structural stability of the positive electrode material is high, the degree of structural damage of the layered structure compound in the cycle is small, and the adverse effect of the structural damage of the positive electrode material on the cycle performance is avoided. Therefore, the lithium-ion battery can have the advantages of high energy density, excellent dynamic performance and long cycle life.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a comparison diagram of rate performance curves of Example 1 and Comparative Example 1 provided in the examples of the present application.

Embodiments of the present invention

The present application provides a secondary battery and an electrical device. To make the purpose, technical solution and effect of the present application clearer and more specific, the present application is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific examples described here are only used to explain the present application and are not used to limit the present application.

Thanks to the advantages of high energy density, low self-discharge, long cycle life and low price, lithium-ion batteries have been widely used in the electric vehicle market in recent years. With the vigorous development of the electric vehicle market, higher and higher requirements are put forward for the cycle life and power density of lithium-ion batteries. Lithium-ion batteries with fast charging and discharging and long cycle life can greatly shorten the charging time of electric vehicles and increase the driving range, which plays a key role in accelerating the global market demand for electric vehicles. The performance of lithium-ion batteries depends to a large extent on the positive electrode material. The selection of high-quality positive electrode material system plays a decisive role in achieving the fast charging and discharging performance and long cycle life of lithium-ion batteries. Therefore, it is particularly important to develop a high-energy density lithium-ion battery positive electrode material system with good fast charging capability and excellent cycle life. Among them, nickel-cobalt-manganese ternary materials have a more prominent energy density advantage than the existing commercial lithium iron phosphate positive electrode materials. It is a type of positive electrode material that has been widely studied in recent years, but there are still relatively significant challenges in the structural stability and cycle life of the materials. When nickel-cobalt-manganese ternary layered materials are used as positive electrode materials, their structural stability during long-term cycles is poor. The disordered arrangement of cations will hinder the transmission of lithium ions, resulting in a continuous decline in power performance. The layered structure of the positive electrode material is greatly damaged under high current, and the decay of the structure leads to a rapid decline in cycle life. Improving the structural stability of layered ternary materials and ensuring fast charging capabilities and cycle performance under high currents have always been the focus of research and improvement. The existing technology often achieves the improvement of the rapid charging and discharging capabilities of lithium-ion batteries by reducing the active material loading of the pole piece or increasing the proportion of the conductive agent, but these methods usually lead to a decrease in the energy density of lithium-ion batteries, which is inconsistent with the high energy density requirements put forward by the power battery market, and practical applications are limited. Designing small-sized primary particles can shorten the diffusion distance of Li ⁺ , which is also a common strategy to improve fast charging performance. However, when the particle size is too small, the side reactions on the surface increase, resulting in a rapid decline in cycle performance. In addition, small particles are prone to agglomeration, which affects the processing performance of the pole piece, resulting in a decrease in the compaction density of the pole piece and the problem of particle breakage under high compaction density, which in turn affects the cycle, gas production and other performances of lithium-ion batteries.

Based on this, the present application proposes a secondary battery and electrical equipment, so that the layered lithium-containing compound of the positive electrode plate has a highly ordered layered structure and a low degree of preferred orientation of the crystal plane, which can greatly improve the speed of lithium ion extraction and embedding and has excellent kinetic performance.

In some embodiments, the present application provides a secondary battery, which includes the following positive electrode plate, negative electrode plate, electrolyte and isolation membrane.

Positive electrode

The positive electrode sheet comprises a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, the positive electrode mixture layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium-containing compound with a layered structure; the positive electrode sheet satisfies: 4000≤U≤14560,

and

Wherein, _C003 is the peak area of the 003 characteristic diffraction peak in the X-ray diffraction pattern of the positive electrode pole piece, and the unit is AU min; [2Theta(110)-2Theta(018)] is the relative distance between the 110 characteristic diffraction peak and the 018 characteristic diffraction peak in the X-ray diffraction pattern of the positive electrode pole piece, and the unit is min; FWHM[(110)+(018)] is the sum of the half-peak widths of the 110 characteristic diffraction peak and the 018 characteristic diffraction peak in the X-ray diffraction pattern of the positive electrode pole piece, and the unit is min.

In some embodiments, the U value of the positive electrode piece can be obtained by testing the positive electrode piece according to the following method: an XRD test is performed on the positive electrode piece according to the X-ray diffraction method to obtain an XRD spectrum, and the 2θ position and half-peak width of the diffraction peaks corresponding to the 018 and 110 crystal planes, and the peak area of the diffraction peak corresponding to the 003 crystal plane are analyzed by the XRD spectrum, and the result is obtained after calculation. The specific test conditions of the XRD spectrum are conventional conditions, for example, the power is 1.6kW, the test scan speed is 5°/min, and kα2 is deducted from the test spectrum. After research, it was found that the U value of the positive electrode piece is closely related to the orderliness of the layered structure and the orientation degree of the 003 crystal plane.

In some embodiments, the peak area is directly obtained by analyzing the X-ray diffraction pattern. The peak area refers to the integral value of the peak height and the retention time, which represents the relative content. The peak area is not determined by a single value, but is related to the corresponding number of crystal planes, unit cell volume, grain volume, etc. related to the sample itself; the relative distance specifically represents the difference in 2θ angles corresponding to the diffraction peaks. The XRD diffraction pattern of the positive electrode can be obtained by X-ray diffraction analysis. The 2θ angles of the 110 characteristic diffraction peak and the 018 characteristic diffraction peak are subtracted to calculate the relative distance between the 110 and 018 diffraction peaks; the half-width (FWHM) is a conventional means to characterize the peak width. The peak width is affected by many factors: such as the wavelength distribution of the X-rays, the grain size, etc., which can be calculated by the Scherrer Equation.

In some embodiments, the peak area of the 003 characteristic diffraction peak satisfies: 2200≤C ₀₀₃ ≤3500, for example, the peak area can be any one of 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3100, 3200, 3300, 3400 or 3500, or any two of them, and the unit of the peak area is AU min; the relative distance between the 110 characteristic diffraction peak and the 018 characteristic diffraction peak satisfies: 0.40≤[2Theta(110)-2Theta(0 18)]≤0.70, for example, the relative distance can be any one of 0.40, 0.50, 0.60 or 0.70 or the range of any two; the sum of the half-widths of the 110 characteristic diffraction peak and the 018 characteristic diffraction peak satisfies: 0.55≤FWHM[(110)+(018)]≤0.80, for example, the sum of the half-widths can be any one of 0.55, 0.60, 0.65, 0.70, 0.75 or 0.80 or the range of any two.

In some embodiments, the layered structure ternary positive electrode material is prone to layered disorder caused by cation mixing. The disordered arrangement of cations in the layered structure will hinder the transmission of lithium ions, resulting in a continuous decrease in power performance. The layered structure of the positive electrode material is greatly damaged under high current, and the decay of the structure leads to a rapid decrease in cycle life. In the layered structure ternary positive electrode material, there is a double peak splitting phenomenon in the XRD characteristic diffraction peaks corresponding to the 018 and 110 crystal planes. The degree of double peak splitting can reflect the layered characteristics of the ternary positive electrode material. The greater the degree of double peak splitting, the stronger the layered structure characteristics and the higher the layered order. Further, the Li/Ni mixing degree can be obtained by refining the XRD spectrum, which can also reflect the order of the ternary layered structure. The splitting degree of the XRD characteristic diffraction peak can be reflected by their relative position and half-peak width, so {[2Thea(110)-2Theta(018)]×FWHM[(110)+(018)]} can be used to reflect the layered order characteristics in the ternary positive electrode material.

In some embodiments, the 003 crystal plane of the layered ternary positive electrode material generally has a preferred orientation, which is reflected in the XRD diffraction spectrum as a larger integral area corresponding to the diffraction peak. The preferred orientation of the 003 crystal plane will have an important impact on the deintercalation rate of lithium ions. The larger the area of the diffraction peak corresponding to the 003 crystal plane, the greater the probability that the layered plane of the lithium-containing compound is parallel to the positive electrode current collector, and the slower the rate of lithium ion deintercalation from the positive electrode pole piece. Conversely, the smaller the area of the diffraction peak corresponding to the 003 crystal plane, the greater the probability that the layered plane of the lithium-containing compound is perpendicular to the positive electrode current collector, the faster the rate of lithium ion deintercalation from the positive electrode pole piece, and the better the kinetic performance of the positive electrode pole piece. Therefore, the degree of orientation is characterized by analyzing the peak area of the 003 characteristic diffraction peak to further characterize the deintercalation rate of lithium ions.

In some embodiments, the U value of the positive electrode sheet is controlled within a certain range, and the positive active material in such a positive electrode sheet has a high degree of order, which creates a good crystal structure foundation for the rapid transmission of lithium ions. The structural stability of the positive electrode material during the cycle is high, which can effectively inhibit the collapse of the structure, and the degree of 003 crystal plane orientation is small, so that lithium ions can be quickly extracted and embedded from the positive electrode sheet, thereby ensuring that the lithium-ion battery has both excellent kinetic performance and long cycle life. When the U value of the positive electrode sheet is greater than 14560 or less than 4000, the layered order of the lithium-containing compound in the positive electrode sheet is low, the degree of structural damage of the positive electrode material during the cycle is large, and the degree of 003 crystal plane orientation is large, the speed of lithium ions being extracted and embedded from the positive electrode sheet slows down, and the rate and cycle performance of the battery are further reduced.

In some embodiments, a typical but non-limiting value of U is 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, 9500, 10000, 10500, 11000, 11500, 12000, 12500, 13000, 13500, 14000, 14500, or any two of the values listed in Table 1. It is worth noting that the specific values of U are given for illustrative purposes only, and any value within the range of 4000 to 14560 is within the protection scope of the present application.

In some embodiments, the U value is 5500≤U≤12500.

In some embodiments, the U value is 6500≤U≤10500.

In some embodiments, the compaction density of the positive electrode sheet will also have a certain impact on the performance of the lithium-ion battery. The positive electrode sheet further satisfies: 1050≤U/P≤4500, where P g/ ^cm3 is the compaction density of the positive electrode sheet. When the positive electrode sheet satisfies the above relationship, the battery's kinetic performance and cycle life can be further improved.

In some embodiments, compaction density = surface density / thickness of active material layer. During the manufacturing process of lithium-ion power batteries, compaction density has a great influence on battery performance. Experiments have shown that compaction density is closely related to sheet specific capacity, efficiency, internal resistance and battery cycle performance.

It is understandable that if the lower limit of U/P is less than 1050, the lithium-containing compound in the positive electrode has a higher layered order and a small degree of 003 crystal plane orientation, which can be beneficial to the deintercalation of lithium ions. However, it may also be because the active material particles in the positive electrode are easily broken during the processing of the electrode, which will aggravate the occurrence of side reactions during the cycle, and the interface impedance between the positive electrode active material and the electrolyte is large, which is not conducive to the improvement of the fast charging and cycle performance of lithium-ion batteries. If the upper limit of U/P is greater than 4500, the layered order of the lithium-containing compound in the positive electrode is relatively low, and the disorder of the structure will hinder the transmission of lithium ions, and at the same time will cause a large degree of structural damage during the cycle, resulting in a rapid decrease in cycle performance. In addition, the degree of 003 crystal plane orientation is large, which will further hinder the speed of lithium ion deintercalation and affect the improvement of the fast charging performance of lithium-ion batteries.

In some embodiments, 1150≤U/P≤4500. By further controlling the relationship between the U value of the positive electrode sheet and the compaction density value of the positive electrode sheet, the product of the two is kept within a reasonable range, that is, 1150≤U/P≤4500, the charging capacity and cycle life of the lithium-ion battery can be better improved.

In some embodiments, the compaction density is tested by a compaction density meter, and the test process can refer to the national standard GB/T24533-2019. The compaction density is 3.0g/cm ³ to 3.8g/cm ³ , preferably 3.2g/cm ³ to 3.6g/cm ³ ; for example, the compaction density can be any one of 3.0g/cm ³ , 3.1g/cm ³ , 3.2g/cm ³ , 3.3g/cm ³ , 3.4g/cm ³ , 3.5g/cm ³ , 3.6g/cm ³ , 3.7g/cm ³ , and 3.8g/cm ³ , or any two of them. It is worth noting that the specific values of the compaction density are only given by way of example, and any value within the range of 3.0g/cm ³ to 3.8g/cm ³ is within the protection scope of this application. When the compaction density meets the above range, it can be ensured that the battery cell has both high energy density and long cycle life. Generally speaking, the greater the compaction density, the higher the battery capacity, so the compaction density is also used as one of the reference indicators of material energy density. However, if the compaction density is too large, the porosity of the electrode will decrease, the wettability of the electrode to the electrolyte will be weakened, the migration rate of lithium ions in the electrode will be reduced, the internal resistance of the battery will increase, polarization will occur, and the cycle stability and rate performance of the battery will be reduced.

In some embodiments, the smaller the compaction density of the positive electrode sheet, the faster the rate of lithium ion deintercalation from the positive electrode sheet, the better the kinetic performance of the positive electrode sheet, and the more conducive to improving the fast charging performance of the battery, but the reduction in the compaction density of the positive electrode sheet will lead to a decrease in the energy density of the battery. When the compaction density of the positive electrode sheet is too large, although the overall energy density of the battery can be improved, it will cause the interfacial charge impedance between the positive electrode active material and the electrolyte to increase, further reducing the rate of lithium ion deintercalation from the positive electrode sheet. Therefore, by further reasonably controlling the compaction density of the positive electrode sheet within a reasonable range, the lithium-ion battery can have both high energy density and long cycle life.

In some embodiments, 1250≤U/P≤3500. Typical but non-limiting values of U/P are 1250, 1300, 1350, 1400, 1450, 1500, 1550, 1600, 1650, 1700, 1750, 1800, 1850, 1900, 1950, 2000, 2050, 2100, 2150, 2200, 2250, 2300, 2350, 2400, 2450, 2500, 2550, 2600, 2650 The range of any one of 0, 2700, 2750, 2800, 2850, 2900, 2950, 3000, 3050, 3100, 3150, 3200, 3250, 3300, 3350, 3400, 3450, and 3500, or any two of them; it is worth noting that the specific numerical value of U/P is only given as an example, and any value within the range of 1250 to 3500 is within the protection scope of this application.

In some embodiments, the positive electrode plate satisfies the relationship 1250≤U/P≤3300.

In some embodiments, the positive electrode plate satisfies the relationship 1800≤U/P≤2500.

In some embodiments, the positive electrode plate also meets the following requirements: the diaphragm resistance of the positive electrode plate is 0.2 to 0.5Ω; the diaphragm resistance of the positive electrode plate meets this range, which can significantly improve the transmission capacity of lithium ions in the solid phase, reduce the initial DCR value and DCR growth rate of the battery, and effectively improve the power performance of the battery.

In some embodiments, the porosity of the positive electrode plate is 20% to 35%. The porosity within this range can control the number of pores in the positive electrode plate to be moderate, ensuring that the electrolyte can infiltrate into the active particles of the plate, thereby conducting the ion path and ensuring that the positive electrode active material has good ion conductivity. At the same time, it can ensure that the positive electrode active material has a certain compressive strength, and ensure that lithium ions are evenly deintercalated during the charge and discharge process, reduce stress concentration, alleviate phase change, and improve the cracking problem of particles during the cycle process, thereby ensuring that the lithium ion battery using the positive electrode plate of the present invention has good cycle performance and dynamic performance.

In some embodiments, the peeling force of the positive electrode sheet is 15 to 50 N/m. The peeling force within this range can improve the bonding strength between the positive electrode active material and the aluminum foil, ensure the stability of the current collector, and prevent the active material from peeling off and falling off from the foil surface during long-term cycling, thereby improving the cycle life of the lithium-ion battery.

In some embodiments, the positive electrode active material includes a layered lithium-containing compound, the lithium-containing compound is lithium nickel cobalt oxide, and the lithium nickel cobalt oxide further includes an A element, and the element includes at least one of Mn, Al, Ti, Mg, and Zr; wherein, the content of the nickel element is greater than or equal to 0.5, based on the sum of the molar amounts of the nickel element, the cobalt element, and the manganese element as 1; or the content of the nickel element is greater than or equal to 0.5, based on the sum of the molar amounts of the nickel element, the cobalt element, and the aluminum element as 1. When the U value meets the above range, when the nickel element is within this range, the side reactions of the secondary battery are reduced, and the overall performance is better.

In some embodiments, the lithium nickel cobalt oxide further comprises an M element, and the M element comprises one or more of Al, B, Ca, W, Nb, Mg, Zr, Sr, Si, Y, Ti, and Sn. The above elements can improve the stability and specific capacity of the lithium nickel cobalt oxide.

In some embodiments, the M element may be a doping element and/or a coating element, that is, the lithium nickel cobalt oxide may contain only the doping element, only the coating element, or both the doping element and the coating element.

In some embodiments, when the M element is a doping element, the M element is embedded in the lithium nickel cobalt oxide, and the doping element is selected from one or more of Al, B, Ca, W, Nb, Mg, Zr, and Sr; when the M element is a coating element, the M element is coated on at least a portion of the surface of the lithium nickel cobalt oxide, and the coating element is selected from one or more of Al, B, Zr, Sr, Si, Y, Ti, and Sn; when the positive electrode active material contains both the doping element and the coating element, the doping element and the coating element may be different elements or the same element.

The composition of the coating element can be characterized by TEM (Transmission Electron Microscope) to distinguish the specific composition; the presence of doping elements can be determined by X-ray photoelectron spectroscopy (XPS) valence state analysis or EDS (Energy Dispersive Spectroscopy) scanning.

The introduction of doping elements can make the layered structure more ordered, the probability of disordered arrangement of cations is lower, the structural stability during the cycle is higher, and it is more beneficial to improve the cycle performance of lithium-ion batteries. The introduction of coating elements can isolate the electrolyte, which can greatly reduce the interface side reactions between the electrolyte and the layered structure compound, and can inhibit the irreversible phase change of the material and the dissolution of transition metal ions during the charge and discharge process of the material, and improve the structural stability of the layered structure compound. In this embodiment, the substance used for doping or coating is the oxide or hydroxide of the above-mentioned doping element or coating element. The introduction of these substances during the sintering process to achieve doping or coating can effectively improve the structural orderliness and stability of the layered material, thereby improving the long-term cycle performance of the battery cell.

In some embodiments, the median particle size D _v 50 of the positive electrode active material is 2 μm to 20 μm, and the preferred median particle size D _v 50 is 6 μm to 15 μm. For example, the median particle size D _v 50 is 2 μm, 3 μm, 4 μm, 56 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm and 20 μm, or any two of them. _{D v} 50 is a well-known meaning in the art, also known as the median particle size, which indicates the particle size corresponding to 50% of the volume distribution of the positive electrode active material particles. The average particle size D _v 50 of the positive electrode active material can be measured using a laser particle size analyzer.

In some embodiments, the average pore size of the positive electrode active material is 30nm to 200nm; preferably, the average pore size of the positive electrode active material is 50nm to 150nm, and more preferably 60nm to 100nm. For example, the average pore size of the positive electrode active material is 80nm. The average pore size of the positive electrode active material reflects the state of primary particle accumulation. The appropriate pore size can provide a transmission channel for the coating material and ensure the density of the secondary particles, so that the mechanical strength of the material can meet the requirements of cycle stability.

In some embodiments, the specific surface area of the positive electrode active material is 0.3m ^{2 /} g to 0.9m ² /g; preferably, the specific surface area of the positive electrode active material is 0.4m ² /g to 0.8m ² /g, and more preferably 0.5m ² /g to 0.7m ² /g. For example, the specific surface area of the positive electrode active material is 0.6m ² /g. When the specific surface area of the positive electrode active material is within an appropriate range, the contact area between the positive electrode active material and the electrolyte is within a relatively good range, so that the positive electrode sheet has a relatively good wetting effect, the ohmic impedance is relatively small, and the battery has relatively good comprehensive performance. The specific surface area of the positive electrode active material is a well-known meaning in the art, and can be measured by instruments and methods well-known in the art, for example, it can be tested by a nitrogen adsorption specific surface area analysis test method, and calculated by a BET (Brunauer Emmett Teller) method.

In some embodiments, the preparation of the positive electrode active material includes: dispersing a nickel source, a cobalt source, and a manganese source in deionized water by a coprecipitation method to obtain a mixed solution; pumping the mixed solution, a strong alkali solution, and a complexing agent solution into a stirred reactor at the same time by a continuous parallel reaction method, controlling the pH value of the reaction solution to be 10-13, the temperature in the reactor to be 25°C-90°C, and passing an inert gas protection during the reaction; after the reaction is completed, washing, filtering, vacuum drying, screening, and iron removal are performed to obtain a transition metal hydroxide precursor; then the loose and porous nickel-cobalt-manganese hydroxide precursor prepared by the coprecipitation method is mixed with a lithium source and a compound containing a doping element in a high-speed mixer, and then the mixed material is placed in an atmosphere tube furnace, a certain amount of oxygen is introduced to calcine, and a gas flow crushing treatment is performed at the same time, so as to prepare a layered oxide positive electrode material; finally, the prepared layered oxide positive electrode material and the compound containing the coating element are placed in a high-speed mixer for mixing, and then transferred to an atmosphere tube furnace, a certain amount of oxygen is introduced to calcine, and a positive electrode active material is obtained.

In some embodiments, the nickel source, cobalt source, and manganese source are one or more oxides, hydroxides, or carbonates containing Ni, Co, and Mn selected in a stoichiometric ratio. In some embodiments, the structure of the precursor can be regulated by adjusting the selection of reaction raw materials, the pH value of the reaction solution, the concentration of the mixed solution, the concentration of the complexing agent, the reaction temperature, and the reaction time in the preparation of the nickel-cobalt-manganese hydroxide precursor. In some embodiments, the nickel source may include one or more of nickel acetate, nickel nitrate, nickel sulfate, nickel hydroxide, nickel chloride, or nickel carbonate. In some embodiments, the cobalt source may include one or more of cobalt sulfate, cobalt hydroxide, cobalt nitrate, cobalt fluoride, cobalt chloride, or cobalt carbonate. In some embodiments, the manganese source may include one or more of manganese sulfate, manganese chloride, manganese nitrate, or manganese hydroxide.

In some embodiments, the strong alkali solution may include one or more of LiOH, NaOH and KOH; the complexing agent may be one or more of ammonia water, ammonium sulfate, ammonium nitrate and ammonium chloride. In some embodiments, there are no particular restrictions on the solvents of the mixed solution, the strong alkali solution and the complexing agent solution. For example, the solvents of the mixed solution, the strong alkali solution and the complexing agent solution are independently one or more of deionized water, methanol, ethanol, acetone, isopropanol and n-hexanol.

In some embodiments, the inert gas is one or more of nitrogen, argon, and helium.

In some embodiments, the lithium source may include one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, or lithium chloride.

In some embodiments, the compound containing the doping element and the compound containing the coating element can be one or more of the oxides, chlorides, sulfates, nitrates, hydroxides, fluorides, carbonates, bicarbonates, acetates, phosphates, dihydrogen phosphates and organic compounds of the respective elements.

In some embodiments, the intermediate product can also be crushed and sieved to obtain a positive electrode active material with an optimized particle size distribution and specific surface area. There is no particular restriction on the crushing method, which can be selected according to actual needs, such as using a particle crusher. The preparation method of the positive electrode active material of the present application is not limited to the above preparation method, as long as the formed positive electrode active material has the characteristics shown in the present application.

In some embodiments, the preparation process of the positive electrode sheet may include the steps of stirring, coating, drying, cold pressing, striping and cutting. In the preparation process of the positive electrode sheet, there are many feasible ways to regulate the structural characteristics of the lithium-containing compound in the positive electrode sheet, thereby affecting the U value of the positive electrode sheet. For example, the synthesis process parameters of the selected positive active material, such as calcination temperature and calcination time, the doping and coating type of the positive active material, and the median particle size D _v 50 physical properties will affect the U value of the positive electrode sheet. The U value required for the positive electrode sheet can be controlled by controlling the synthesis process parameters of the synthesized positive active material, selecting different doping and coating types or positive materials with different physical properties. In addition, in the cold pressing process of the positive electrode sheet manufacturing process, the compaction density of the positive electrode sheet can be adjusted by changing the parameters such as the cold pressing pressure, and the arrangement of the positive active material in the positive electrode sheet can also be changed, thereby changing the U value of the positive electrode sheet.

In some embodiments, the positive electrode plate further includes a conductive agent and a binder, and the types and contents of the conductive agent and the binder are not specifically limited and can be selected according to actual needs. In some embodiments, the conductive agent may include conductive carbon black, carbon nanotubes, graphene, etc., and the binder may include polyvinylidene fluoride.

In some embodiments, the preparation of the positive electrode sheet includes: dispersing the above-mentioned positive electrode active material, conductive agent, and binder in N-methylpyrrolidone (NMP) in a certain proportion, coating the obtained slurry on aluminum foil, drying, and then cold pressing and slitting to obtain the positive electrode sheet.

Negative electrode

In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode active material, a binder and a conductive agent covered on the negative electrode current collector. The types and contents of the negative electrode active material, the binder and the conductive agent are not particularly limited and can be selected according to actual needs. In some embodiments, the negative electrode active material includes one or more of artificial graphite, natural graphite, mesophase carbon microspheres, amorphous carbon, lithium titanate or silicon-carbon alloy. The negative electrode active material also needs to have the characteristics of high compaction density, high mass specific capacity and high volume specific capacity.

Electrolyte

In some embodiments, the main components of the electrolyte include lithium salts and organic solvents, and may also include additive components. The types and compositions of the lithium salts and organic solvents are not particularly limited and may be selected according to actual needs. The lithium salts may include lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, the solvents may include ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and propyl propionate, and the additives may include lithium difluorophosphate, lithium bis(oxalatoborate), and succinonitrile.

Isolation film

In some embodiments, the type of the isolation film is not particularly limited and can be selected according to actual needs. The isolation film can be a polypropylene film, a polyethylene film, a polyvinylidene fluoride, a spandex film, an aramid film, or a multi-layer composite film modified by a coating.

In some embodiments, the preparation of a secondary battery includes: stacking the positive electrode sheet, the isolation membrane, and the negative electrode sheet in order, so that the isolation membrane is between the positive and negative electrode sheets to play an isolating role, and then winding them into a square bare cell, loading them into a battery shell, and then baking them at 65 to 95°C to remove water, injecting electrolyte, sealing, and obtaining a secondary battery after standing, hot and cold pressing, formation, clamping, capacity division and other processes.

In some embodiments, the secondary battery includes a lithium-ion battery. The above only takes a soft-pack lithium-ion battery as an example. This application is not limited to the application of soft-pack batteries, but also includes the application of common lithium-ion battery forms such as aluminum shell batteries and cylindrical batteries.

Electrical equipment

In some embodiments, the present application provides an electrical device, which includes the above-mentioned secondary battery. The electrical device can be used for but not limited to backup power supplies, motors, electric vehicles, electric motorcycles, power-assisted bicycles, bicycles, power tools, large household batteries, etc.

Example 1

Step 1: Prepare the cathode material precursor by coprecipitation method, mix nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of 83:12:5 to prepare a mixed transition metal salt solution with a concentration of 1 mol/L, use sodium hydroxide and ammonia solution as strong alkaline solution and chelating agent respectively, stir the reaction for 6 hours at a water bath temperature of 55°C and a titration end point pH of 11, and after 12 hours of static aging, filter and wash to obtain a transition metal hydroxide precursor.

Step 2: Place the transition metal hydroxide precursor prepared in step 1, lithium hydroxide and doped raw material zirconium oxide in a high-speed mixer at a molar ratio of 0.995:1.05:0.0025 and mix them evenly. Then place the evenly mixed materials in an atmosphere tube furnace, introduce a certain amount of oxygen, calcine at 730°C for 10 hours, and perform air flow crushing treatment at the same time to prepare a layered oxide positive electrode material.

Step 3: The layered oxide positive electrode material prepared in step 2 is mixed with 0.3wt% of the coating raw material alumina in a high-speed mixer, and then transferred to an atmosphere tube furnace _, a certain amount _of oxygen is introduced, and calcined at 450°C for 6h to form an oxide coating layer on _the surface of the positive electrode material to obtain the positive electrode active material _{Li1.02Ni0.83Co0.12Mn0.05O2} _.

Step 4: Mix the positive electrode active material Li _1.02 Ni _0.83 Co _0.12 Mn _0.05 O ₂ , the conductive agent conductive carbon black, and the binder PVDF to prepare the positive electrode slurry, in which the positive electrode active material accounts for 97%, the conductive carbon black accounts for 2%, and the binder PVDF accounts for 1%. Add NMP as a solvent to mix, and stir for a certain period of time to obtain a uniform positive electrode slurry with a certain fluidity; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and then transferred to a 110°C oven for drying, and then rolled, slit, and cut to obtain the positive electrode sheet. In the preparation process of the positive electrode sheet, different positive electrode sheet U values can be obtained by selecting different types of positive electrode active materials and adjusting the rolling process parameters.

Preparation of negative electrode sheet: The negative electrode active material graphite, conductive agent Super P, thickener CMC, and binder SBR are mixed to form a negative electrode slurry, in which graphite accounts for 96.1%, conductive agent Super P accounts for 1%, thickener CMC accounts for 1%, and binder SBR accounts for 1.9%. Deionized water is added as a solvent for mixing, and after stirring for a certain period of time, a uniform negative electrode slurry with a certain fluidity is obtained; the negative electrode slurry is evenly coated on the negative electrode collector copper foil, and then transferred to a 120°C oven for drying, and then rolled, slit, and cut to obtain a negative electrode sheet.

Preparation of electrolyte: Mix organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a volume ratio of 2:2:6. In an argon atmosphere glove box with a water content of <10ppm, dissolve the dried _LiPF6 lithium salt in the above organic solvents and mix them evenly to obtain an electrolyte. The concentration of _LiPF6 in the electrolyte is 1 mol/L.

A 16 μm polypropylene film was selected as the isolation film.

The positive electrode sheet, isolation film and negative electrode sheet are stacked in order, then wound into a square bare cell and placed in an aluminum-plastic film, and then baked at 85°C to remove moisture, and a certain amount of organic electrolyte is injected and sealed. After standing, hot and cold pressing, formation, secondary packaging, capacity division and other processes, a finished secondary battery is obtained.

Example 2

The specific preparation process is the same as that in Example 1, the difference from Example 1 is that in step 1, the titration endpoint pH is 11.5, the stirring reaction time is 8 hours, the doping raw material added in step 2 is niobium pentoxide, the calcination parameters are calcination at 750°C for 10 hours, and the coating raw material added in step 3 is 0.3wt% of boron oxide.

The prepared positive electrode active material is Li _1.02 Ni _0.83 Co _0.12 Mn _0.05 O ₂ .

Example 3

The specific preparation process is the same as that of Example 1, except that the titration endpoint pH in step 1 is 12, the calcination parameter in step 2 is calcination at 750°C for 10 hours, and the coating raw material added in step 3 is 0.3wt% titanium oxide.

Example 4

The specific preparation process is the same as that in Example 1, the difference from Example 1 is that in step 1, the molar ratio of nickel sulfate, cobalt sulfate and manganese sulfate is 60:20:20, and the titration endpoint pH=12.

The prepared positive electrode active material is Li _1.02 Ni _0.6 Co _0.2 Mn _0.2 O ₂ .

Example 5

The specific preparation process is the same as that in Example 1, except that in step 1, the molar ratio of nickel sulfate, cobalt sulfate and manganese sulfate is 50:20:30, the titration endpoint pH is 12, and the stirring reaction time is 8 hours.

The prepared positive electrode active material is Li _1.02 Ni _0.5 Co _0.2 Mn _0.3 O ₂ .

Example 6

The specific preparation process is the same as that of Example 1, except that no doping raw material is added in step 2, and the transition metal oxide precursor prepared in step 1 is directly mixed with lithium hydroxide and then calcined. The calcination parameters are calcined at 750° C. for 12 hours.

Example 7

The specific preparation process is the same as that of Example 1, except that no coating raw material is added in step 3, and the positive electrode active material prepared in step 2 is transferred to a tubular furnace into which oxygen is introduced, and calcined at 500° C. for 8 h.

Example 8

The specific preparation process is the same as that in Example 1, and the difference from Example 1 is that in step 1, nickel sulfate, cobalt sulfate and aluminum sulfate are uniformly mixed in a molar ratio of 83:12:5.

The prepared positive electrode active material is Li _1.02 Ni _0.83 Co _0.12 Al _0.05 O ₂ .

Example 9

The specific preparation process is the same as that of Example 4, except that nickel sulfate, cobalt sulfate and aluminum sulfate are used in a molar ratio of 60:20:20.

The prepared positive electrode active material is Li _1.02 Ni _0.6 Co _0.2 Al _0.2 O ₂ .

Example 10

The specific preparation process is the same as that in Example 1, except that in step 1, nickel sulfate, cobalt sulfate and aluminum sulfate are uniformly mixed in a molar ratio of 50:30:20.

The prepared positive electrode active material is Li _1.02 Ni _0.50 Co _0.3 Al _0.2 O ₂ .

Embodiment 11

The specific preparation process is the same as that in Example 1, except that in step 1, nickel sulfate, cobalt sulfate and aluminum sulfate are uniformly mixed in a molar ratio of 80:10:10.

The prepared positive electrode active material is Li _1.02 Ni _0.8 Co _0.1 Al _0.1 O ₂ .

Example 12

The specific preparation process is the same as that of Example 1, except that the doping raw material in step 2 is magnesium oxide; and the coating raw material in step 3 is strontium oxide.

Example 13

The specific preparation process is the same as that of Example 1, except that the doping raw material in step 2 is strontium oxide; and the coating raw material in step 3 is zirconium oxide.

Embodiment 14

The specific preparation process is the same as that of Example 1, except that the doping raw material in step 2 is calcium oxide; and the coating raw material in step 3 is zirconium oxide.

Comparative Example 1

The specific preparation process is the same as that in Example 1, the difference from Example 1 is that in step 1, the titration endpoint pH is 11.5, and the stirring reaction time is 8 hours; in step 2, no doping raw material is added, and the transition metal oxide precursor prepared in step 1 is directly mixed with lithium hydroxide and then calcined, and the calcination parameters are calcined at 770°C for 12 hours; in step 3, no coating raw material is added, and the positive electrode active material prepared in step 2 is transferred to a tubular furnace into which oxygen is introduced, and calcined at 550°C for 8 hours.

The positive electrode active material finally prepared is Li _1.02 Ni _0.83 Co _0.12 Mn _0.05 O ₂ .

Comparative Example 2

The specific preparation process is the same as that in Example 1, except that in step 1, the molar ratio of nickel sulfate, cobalt sulfate and manganese sulfate is 60:20:20, the titration endpoint pH is 12, and the stirring reaction time is 8 hours; in step 2, no doping raw material is added, and the transition metal oxide precursor prepared in step 1 is directly mixed with lithium hydroxide and then calcined, and the calcination parameters are calcined at 770°C for 12 hours; in step 3, no coating raw material is added, and the positive electrode active material prepared in step 2 is transferred to a tubular furnace into which oxygen is introduced, and calcined at 550°C for 8 hours.

The positive electrode active material finally prepared is Li _1.02 Ni _0.6 Co _0.2 Mn _0.2 O ₂ .

Comparative Example 3

The specific preparation process is the same as that in Example 1, except that in step 1, the molar ratio of nickel sulfate, cobalt sulfate and manganese sulfate is 50:20:30, the titration endpoint pH is 12, and the stirring reaction time is 8 hours; in step 2, no doping raw material is added, and the transition metal oxide precursor prepared in step 1 is directly mixed with lithium hydroxide and then calcined, and the calcination parameters are calcined at 770°C for 12 hours; in step 3, no coating raw material is added, and the positive electrode active material prepared in step 2 is transferred to a tubular furnace into which oxygen is introduced, and calcined at 550°C for 8 hours.

The positive electrode active material finally prepared is Li _1.02 Ni _0.5 Co _0.2 Mn _0.3 O ₂ .

Test Methods

(1) U value test method

The XRD spectrum of the sample under test was scanned slowly at a scanning speed of 5°/min in the range of 10-80°, and kα2 was deducted from the test spectrum. The positions and half-peak widths of the diffraction peaks corresponding to the 018 and 110 crystal planes and the area of the diffraction peaks corresponding to the 003 crystal plane were obtained by analysis and calculation, and the U value of the sample was further calculated by substituting the formula U=C ₀₀₃ /{[2Thea(110)-2Theta(018)]×FWHM[(110)+(018)]}.

(2) Battery cycle performance test

At room temperature, the batteries prepared in Examples 1-7 and Comparative Examples 1-3 were charged at a 1C rate and discharged at a 1C rate for full charge and discharge cycle tests until the capacity of the battery decayed to 80% of the initial capacity, and the number of cycles was recorded.

(3) Battery rate performance test

At room temperature, the batteries prepared in Examples 1-7 and Comparative Examples 1-3 were discharged at a rate of 1C to the lower voltage limit, and then charged at rates of 1/3C, 0.5C, 1C, 1.5C, and 2C to the upper voltage limit (without CV charging), and the capacity and capacity retention rate were recorded to obtain the rate performance curve of the battery.

Table 1 shows the parameter test results of the positive electrode active materials and positive electrode sheets corresponding to Examples 1-7 and Comparative Examples 1-3; Table 2 shows the parameter test results of the batteries prepared corresponding to Examples 1-7 and Comparative Examples 1-3.

Table 1

Table 2

From the analysis of the test results in Table 1 and Table 2, it can be seen that in Examples 1-7 of the present application, the U values of the prepared positive electrode sheets are all within the specified range, and the positive electrode active materials in the positive electrode sheets are highly ordered, which creates a good crystal structure foundation for the rapid transmission of lithium ions. The positive electrode material has high structural stability during the cycle, which can effectively inhibit the collapse of the structure, and the degree of 003 crystal plane orientation is small, so that lithium ions can be quickly extracted and embedded from the positive electrode sheet, thereby ensuring that the lithium-ion battery has both excellent kinetic performance and long cycle life, which can effectively shorten the charging time of electric vehicles and increase the cruising range of electric vehicles, greatly improving the user experience of new energy vehicles.

In Comparative Example 1, the U value of the prepared positive electrode plate is too large, the layered order of the lithium-containing compound in the positive electrode plate is low, and the disorder of the structure will hinder the transmission of lithium ions. At the same time, it will cause a large degree of structural damage during the cycle, resulting in a rapid decrease in cycle performance. In addition, the degree of orientation of the 003 crystal plane is large, which will further hinder the speed of lithium ion deintercalation, which is not conducive to the improvement of the fast charging performance of lithium-ion batteries. It cannot meet the design requirements of fast charging of batteries, nor can it meet the use requirements of long cycle life of batteries. It can also be found from the rate performance and cycle performance test results in Table 2 that the rate performance and cycle performance of Comparative Example 1 are significantly inferior to those of Example 1.

When the compaction density of the positive electrode sheet is further reasonably controlled so that U/P is still between 1150 and 4500, the dynamic performance and cycle life of the battery can be further improved. In Example 6, the U value of the positive electrode sheet is larger than that of Examples 1-3, the compaction density P is smaller, and the upper limit of U/P is greater than 4500. At this time, the layered order of the lithium-containing compound in the positive electrode sheet is lower than that of the other embodiments, the disorder of the structure is increased, and the orientation degree of the 003 crystal plane is greater, which will further hinder the speed of lithium ion deintercalation, which is not conducive to the improvement of the fast charging and cycle performance of lithium-ion batteries. The smaller compaction density P also leads to a decrease in the overall energy density of the battery. In Example 7, the U value of the positive electrode plate is small. Although the lithium-containing compound in the positive electrode plate has a higher layered order and a lower 003 crystal plane orientation, the compaction density of the plate is too high, resulting in the electrolyte being unable to fully infiltrate the positive electrode active material. The interface impedance between the positive electrode active material and the electrolyte is higher, and the particles are prone to breakage during the processing of the plate, resulting in the aggravation of harmful side reactions, which is not conducive to the improvement of battery fast charging and cycle performance. Therefore, it is preferred that the positive electrode plate also satisfies 1150≤U/P≤4500, so that the lithium-ion battery has a higher energy density, fast charging capability, and the advantages of long cycle life.

The positive electrode active materials and electrochemical devices provided in the embodiments of the present application are introduced in detail above. Specific examples are used in the present application to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present application. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

A secondary battery, characterized in that it comprises a positive electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, the positive electrode mixture layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium-containing compound with a layered structure;

The positive electrode sheet meets the following requirements: 4000≤U≤14560,

and

Wherein, C003 is the peak area of the 003 characteristic diffraction peak in the X-ray diffraction pattern of the positive electrode pole piece, and the unit is AU·min; [2Theta(110)-2Theta(018)] is the relative distance between the 110 characteristic diffraction peak and the 018 characteristic diffraction peak in the X-ray diffraction pattern of the positive electrode pole piece, and the unit is min; FWHM[(110)+(018)] is the sum of the half-peak widths of the 110 characteristic diffraction peak and the 018 characteristic diffraction peak in the X-ray diffraction pattern of the positive electrode pole piece, and the unit is min.
The secondary battery according to claim 1 is characterized in that the positive electrode sheet satisfies: 1050≤U/P≤4500, wherein P g/cm 3 is the compaction density of the positive electrode sheet, and 3.0≤P≤3.8.
The secondary battery according to any one of claims 1-2 is characterized in that the positive electrode plate satisfies: 5500≤U≤12500.
The secondary battery according to any one of claims 1 to 3, characterized in that the positive electrode plate satisfies: 6500≤U≤10500.
The secondary battery according to any one of claims 1 to 4, characterized in that the peak area of the 003 characteristic diffraction peak satisfies: 2200≤C 003 ≤3500;
The secondary battery according to any one of claims 1 to 5, characterized in that the relative distance between the 110 characteristic diffraction peak and the 018 characteristic diffraction peak satisfies: 0.40≤[2Theta(110)-2Theta(018)]≤0.70.
The secondary battery according to any one of claims 1 to 6, characterized in that the sum of the half-widths of the 110 characteristic diffraction peak and the 018 characteristic diffraction peak satisfies: 0.55≤FWHM[(110)+(018)]≤0.80.
A secondary battery according to any one of claims 1 to 7, characterized in that the lithium-containing compound is lithium nickel cobalt oxide, and the lithium nickel cobalt oxide further contains element A, and the element A includes at least one of Mn, Al, Ti, Mg, and Zr.
A secondary battery according to claim 8, characterized in that the lithium nickel cobalt oxide further contains an M element, and the M element contains at least one of Al, B, Ca, W, Nb, Mg, Zr, Sr, Si, Y, Ti, and Sn.
A secondary battery according to claim 9, characterized in that M is a doping element; wherein the doping element includes at least one of Al, B, Ca, W, Nb, Mg, Zr, and Sr.
A secondary battery according to any one of claims 9 to 10, characterized in that M is a coating element; the coating element includes at least one of Al, B, Zr, Sr, Si, Y, Ti, and Sn;
The secondary battery according to claim 11, characterized in that, when M is a combination of the doping element and the coating element, the doping element and the coating element are different elements.
A secondary battery according to any one of claims 1 to 12, characterized in that the chemical formula of the lithium-containing compound comprises Li x Ni a Co b Ac O 2 , wherein 0.95≤x≤1.05, 0.5≤a≤0.9, 0≤b≤0.5, 0≤c≤0.5, and a+b+c=1.
A secondary battery according to any one of claims 1 to 13, characterized in that the median particle size D v 50 of the positive electrode active material is 2 μm to 20 μm.
An electrical device, characterized in that it comprises the secondary battery according to any one of claims 1 to 14.