Secondary battery

Abstract

Secondary battery, characterized in that the secondary battery comprises a cathode foil and an anode foil, wherein the cathode foil comprises an active cathode material, the active cathode material comprising an olive-like phosphate and a lithium-containing oxide; wherein the secondary battery satisfies the following: (a×b) / c = 0.6 to 5; where a denotes a slope of a curve segment between a first oxidation plateau and a second oxidation plateau on a charging curve with a unit of V, obtained at 25°C within an operating voltage range of 2.5 V to 4.25 V; wherein a voltage range of the first oxidation plateau is 3.3 to 3.5 V, while a voltage range of the second oxidation plateau is 4.0 to 4.1 V; where b ↑a volume-phase lithium-ion transport impedance of the cathode foil in an EIS test at a SOC value corresponding to a minimum value between a first curve peak and a second curve peak of a dQdV-V curve at 25°C within the operating voltage range of 2.5 V to 4.25 V; where c denotes a decay rate of an anode potential during a charging process of the secondary battery at 25°C within the operating voltage range of 3.7 V to 4.25 V with a unit of V-1.

Description

Technical field The present application relates to the technical field of batteries, in particular a secondary battery. Technical background Olive-like phosphate cathode material systems for secondary batteries exhibit an ideal long cycle life, while their production costs are significantly lower than those of layered ternary cathode material systems. However, the slow ion transport rate of olive-like phosphate cathode materials and their strong tendency to oxidize at high temperatures lead to a significant degradation of cycle performance in secondary batteries under high-temperature operating conditions. Furthermore, secondary batteries are expected to offer optimal fast-charging capability in addition to high-temperature and ambient-temperature cycle performance when used in device and equipment applications. However, this performance depends on the energy density of the cathode material, its performance characteristics, and the corresponding lithium embedding polarization of the anode, making it difficult to achieve a significant improvement by adjusting only a single factor. Content of the invention The purpose of the present application is to provide a secondary battery to overcome disadvantages in the prior art. The secondary battery of the present application uses a composite material consisting of an olivine-containing phosphate material and a lithium-containing oxide material as an active cathode material. By simultaneously regulating the charging behavior of both the cathode and anode materials, as well as a synergistic relationship created by the impedance of the cathode foil, high cycle performance at high temperatures and rapid charging performance are ensured. To achieve the above purpose, according to a first aspect of the present application, the present application provides a secondary battery comprising a cathode foil and an anode foil, the cathode foil comprising an active cathode material, the active cathode material comprising an olive-like phosphate and a lithium-containing oxide; wherein the secondary battery satisfies the following: (a×b) / c = 0.6 to 5; where a denotes a slope of a curve segment between a first oxidation plateau and a second oxidation plateau on a charging curve obtained at 25°C within an operating voltage range of 2.5 V to 4.25 V; wherein a voltage range of the first oxidation plateau is 3.3 to 3.5 V, while a voltage range of the second oxidation plateau is 4.0 to 4.1 V;where b Ω denotes a volume-phase lithium-ion transport impedance of the cathode foil in an EIS test at a SOC value corresponding to a minimum value between a first curve peak and a second curve peak of a dQdV-V curve at 25°C within the operating voltage range of 2.5 V to 4.25 V; where c is a decay rate of an anode potential during a charging process of the secondary battery at 25°C within the operating voltage range of 3.7 V to 4.25 V. According to a second aspect of the present application, the present application provides a power-consuming device comprising the secondary battery, wherein the secondary battery is used as a power supply in the power-consuming device. The present application has the following advantageous effects: The present application provides a secondary battery. The secondary battery of the present application uses a composite material of an olivine-containing phosphate material and a lithium-containing oxide material as an active cathode material. By simultaneously regulating the charging behavior of both the cathode and anode materials, as well as a synergistic relationship created by the impedance of the cathode foil, high cycle performance at high temperatures and fast charging performance are ensured. Brief description of the drawings Fig. 1 shows a dQ / dV-V curve obtained when the secondary battery described in embodiment 23 of the present invention is subjected to an a-test; Fig. 2 shows a dQ / dV-V curve obtained when the secondary battery described in embodiment 23 of the present invention is subjected to a c-test; Fig. 3 shows a negative reference curve obtained when the secondary battery described in embodiment 23 of the present invention is subjected to the c-test. Description of embodiments The technical solution in the embodiments of the present application is explained clearly and completely below, so that the purpose, the technical solutions, and the advantages of the embodiments of the present application become clearer. Obviously, the described embodiments do not represent all embodiments, but only a subset of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments that could be obtained by a person skilled in the art without inventive step fall within the scope of protection of the present application. The present application includes, among the technical features described in an open manner, a closed technical solution with the listed features, and also an open technical solution with the listed features. In the context of this application, a numerical interval is considered continuous within the stated numerical interval unless otherwise specified, and includes a minimum and a maximum value of the range, as well as each value between these minimum and maximum values. If the range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. If several ranges are specified to describe a feature or characteristic, the ranges may also be combined. In other words, unless otherwise specified, all ranges disclosed herein are to be understood as encompassing all subranges contained therein. The present application is explained in more detail below with reference to specific embodiments: A secondary battery comprising a cathode foil and an anode foil, wherein the cathode foil comprises an active cathode material, the active cathode material comprising an olive-like phosphate and a lithium-containing oxide; wherein the secondary battery satisfies the following: (a×b) / c = 0.6 to 5; where a denotes a slope of a curve segment between a first oxidation plateau and a second oxidation plateau on a charging curve obtained at 25°C within an operating voltage range of 2.5 V to 4.25 V; wherein a voltage range of the first oxidation plateau is 3.3 to 3.5 V, while a voltage range of the second oxidation plateau is 4.0 to 4.1 V;where b Ω denotes a volume-phase lithium-ion transport impedance of the cathode foil in an EIS test at a SOC value corresponding to a minimum value between a first curve peak and a second curve peak of a dQdV-V curve at 25°C within the operating voltage range of 2.5 V to 4.25 V; where c is a decay rate of an anode potential during a charging process of the secondary battery at 25°C within the operating voltage range of 3.7 V to 4.25 V. In the technical solution of the present application, an olive-like phosphate and a lithium-containing oxide are combined as the active cathode material to balance the fast-charging performance and cycle performance at high temperatures of secondary batteries. Simultaneously, the charging behavior of the cathode and anode materials of the secondary battery, as well as the ionic impedance of the cathode foil, are regulated. Here, 'a' denotes the slope of the curve in the voltage transition region between two oxidation plateaus within the charging curve during the charging process of the secondary battery. This parameter is related to the equilibrium of the electron / ion transport rates within the secondary battery and the reactivity of interfacial side reactions during lithium disembedding in the active cathode material.This parameter is also related to c, which represents the rate at which the anode potential decreases in the active anode material of the secondary battery during charging due to lithium embedding and polarization. The anode charging curve during the secondary battery's charging process exhibits a region of potential increase, where a is related to this potential increase region of the anode. If a is too small, the degree of polarization increases in the transition region. The potential increase effect of the anode caused by lithium embedding and polarization becomes less pronounced, resulting in a higher rate at which the anode potential decreases during the fast-charging phase. This leads to reduced high-rate charging and discharging capacity and decreased fast-charging capability. Conversely, an excessively high value of a reduces the cycle performance of the secondary battery at high temperatures.This occurs because the low efficiency of ion transport increases the oxidation activity of the olivine-containing phosphate material within the active cathode material. Therefore, by establishing a relationship between b and c in conjunction with a and by achieving synchronous control, it can be effectively ensured that the secondary battery, which uses two composite active cathode materials, achieves both excellent fast-charging performance and high cycle stability at high temperatures. In particular, the test procedure for a is as follows: Disassemble the secondary battery in the discharged state, remove the cathode foil and the anode foil and immerse it in a solution of dimethyl carbonate (DMC) for 1 hour, then remove and dry. Assemble the cathode foil and the anode foil to form a single-cell battery (electrolyte solution formulation: mixing ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate in a 1:1:1 volume ratio as solvent, the electrolyte solution containing 1 mol / L LiPF6 as the lithium salt). Charge using a LAND system at 25°C at a rate of 0.02 C to 4.1 V, followed by constant current charging at a rate of 0.33 C to 4.25 V. Then charge at a constant voltage until the current reached less than or equal to 0.05 C. Allow to stand for 10 minutes, then discharge at a constant current rate of 0.33 C to 2.5 V. Repeat this cycle to determine the capacity for two cycles, with the instrument's signal acquisition frequency being 100 ms.The two charging plateaus (oxidation plateaus) visible in the resulting charging curves of cycle 2 were identified, with the first oxidation plateau at a low potential (3.3 V to 3.5 V) corresponding to the oxidation reaction of Fe²⁺ and the second oxidation plateau at a high potential (4.0 V to 4.1 V) corresponding to the oxidation reaction of Mn²⁺. The slope region between the two oxidation plateaus is the voltage transition region. These data were derived to construct a dQ / dV-V curve and to determine the voltage corresponding to the lowest value between the peak values ​​of Fe²⁺ / Mn²⁺ oxidation (i.e., the position of the lowest point corresponding to the vertical coordinate, the lowest point of the y-value in the curve).The ratio of the difference between the SOC and the voltage 100 ms before and after that voltage is the slope of the voltage transition region a=(U2-U1) / (SOC2-SOC1), where the SOC and the voltage corresponding to the first 100 ms are SOC1 and U1 respectively; and the SOC and the voltage corresponding to the last 100 ms are SOC2 and U2 respectively. In particular, the test procedure for b is as follows: After charging and regulating the charge of the secondary battery at 0.33C to the SOC value corresponding to the lowest value (i.e., the lowest point of the potential between the two oxidation plateaus in the charging curve), disassemble the cathode foil and immerse it in dimethyl carbonate (DMC) solution for 1 hour, remove it, and dry it; then assemble a half-battery with a lithium metal sheet as the counter electrode (the electrolyte solution formulation used is a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate in a volume ratio of 1:1:1 as the solvent, with the electrolyte solution containing 1 mol / L LiPF6 as the lithium salt); subsequently, at 25°C, when the battery has reached equilibrium (i.e.,After the charge regulation of the battery is completed (the battery is left to stand for more than 2 hours at 25°C), an AC impedance test (5 mV) is carried out using an electrochemical workstation, and the data obtained are analyzed by drt to obtain the volume phase ion impedance at a frequency of 105Hz to 0.01Hz, which is b. In particular, the test procedure for c is as follows: Disassembling the secondary battery in its discharged state, removing the cathode foil and the anode foil, soaking the cathode foil and the anode foil in a DMC solution for 1 hour each, removing and drying them; after the cathode foil and the anode foil have been reassembled into a single-cell battery (the electrolyte solution formulation used being a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate in a volume ratio of 1:1:1 as the solvent); charging at a rate of 0.02C to 4.1V, then charging at a constant current rate of 0.33C to 4.25V, and finally charging at a constant voltage to less than or equal to 0.05C.After a 10-minute stand, charge at a constant current rate of 0.33C, then charge at 4C after regulating the charge at a rate of 0.33C to 10% SOC with the LAND system at 25°C, up to an upper limit voltage of 4.25 V or a negative reference potential of 0 mV; then gradually charge with a gradient of 0.2 C until reaching 0.4 C, 0.2 C, 0.1 C and 0.05 C, until the determined capacity reaches the charge capacity of the second cycle or 4.25 V.A dQ / dV-V curve is created for the data, and the negative reference curve corresponding to the charging section, in which the lowest value (the lowest point of the y-value of the curve) is located between the two oxidation plateaus of Fe2+ / Mn2+ (3.7 V to 4.25 V), is selected; the coordinate point corresponding to the highest value of its voltage (SOC3, U3) and the point at the end of the charging curve (SOC4, 0) are selected, and the ratio of the difference between the two points (SOC4-SOC3) / U3 is c. In some embodiments, the secondary battery satisfies the following: (a×b) / c = 0.6, 0.8, 1, 1.1, 1.4, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.5, 3.6, 4, 4.5, 5 or any value in a range between any two of these values. In some embodiments, the secondary battery fulfills the following: (a×b) / c = 1.5 to 3.6. As mentioned above, the charging behavior of the cathode and anode, and the interaction of the secondary battery's ion impedance, effectively ensure that both fast-charging performance and high-temperature cycle performance are maintained at a high level. If the slope of the voltage transition curve segment of the secondary battery is too steep during charging, the balance between electron and ion transport shifts, and the oxidation activity of the active cathode material can increase. Therefore, it is necessary to further regulate b and c to prevent a drop in the secondary battery's high-temperature cycle performance. If a is too small, the overall efficiency of the secondary battery's lithium embedding decreases, and fast-charging capability is not guaranteed. Consequently, the ion impedance of the corresponding cathode foil and the charging behavior of the active anode material must also be regulated.On the other hand, changes in b and c also affect the structural stability, interfacial stability, and lithium debedding efficiency of the active cathode and anode materials. Simultaneously adjusting the range of a ensures that the secondary battery not only forms a stable interfacial film at the anode foil interface during charging and discharging to improve the anode's lithium debedding activity, but also exhibits strong structural stability of the active cathode material, a low metal ion dissolution rate, and a high ion transport rate. Furthermore, if the relationship formula (a×b) / c, constructed by the three key parameters, is regulated within the range described above, the fast-charging performance and high-temperature cycle performance of the secondary battery can be further improved. In some embodiments, a = 8 to 30. In some embodiments, a = 8, 10, 12, 13, 14, 15, 18, 20, 22, 24, 26, 27, 28, 29, 30 or any value in a range between any two of these values. In some embodiments, a = 13 to 27. Since a, as the slope of the charging curve segment in the voltage transition region between the oxidation plateaus, is directly related to the cyclic interfacial stability of the active cathode material of the secondary battery in a high-temperature environment and to the ion transport efficiency, the entire secondary battery can be further optimized by regulating a in the aforementioned region to achieve a balance between charging behavior and cyclic stability and to improve the overall electrochemical performance level. In some embodiments, b = 0.35 Ω to 0.66 Ω. In some embodiments, b = 0.35 Ω, 0.4 Ω, 0.42 Ω, 0.45 Ω, 0.48 Ω, 0.5 Ω, 0.52 Ω, 0.54 Ω, 0.55 Ω, 0.58 Ω, 0.6 Ω, 0.62 Ω, 0.64 Ω, 0.66 Ω or any value in a range between any two of these values. In some embodiments, b = 0.4 Ω to 0.56 Ω. The ion impedance of the cathode foil is related to the ion transport rate during the charging process and the stability of the active cathode material on the cathode foil, and if a cathode foil with the ion impedance described above is selected for the construction of a secondary battery, the product will have a longer cycle life at high temperature. In some embodiments, c = 2.8 to 7.3. In some embodiments, c = 2.8, 3, 3.4, 3.5, 3.8, 4, 4.1, 4.3, 4.6, 5, 5.5, 6, 6.5, 6.8, 7, 7.3 or any value in a range between any two of these values. In some embodiments, c = 3.5 to 6. The magnitude of the anode potential decay rate due to lithium embedding and polarization during charging leads to a change in (a×b) / c, which in turn affects the fast charging performance and the cycle performance of the secondary battery, and the product has better electrochemical performance when the regulated decay rate is within the range mentioned above. In some embodiments, the olive-like phosphate comprises at least one of lithium manganese iron phosphate and doped lithium manganese iron phosphate. In some embodiments, the olive-like phosphate has, for example, the structural formula LiFexMnyPO4, where x=0.15 to 0.4 and y=0.6 to 0.85. In some embodiments, the olive-like phosphate is modified with a coating. In some embodiments, the olive-like phosphate is, for example, a carbon-coated lithium manganese iron phosphate. In some embodiments, the olive-like phosphate can also be doped with a metallic element, wherein the metallic element comprises at least one of the elements vanadium, tungsten, titanium or magnesium. The expert knows that the use of a carbon coating not only improves the dispersion of the olive-like phosphate and prevents agglomeration of the particles, but also increases the electrical conductivity of the material, leading to an increase in the efficiency of ion / electron transport. In some embodiments, the molar content of the manganese element in the olive-like phosphate is 60% to 85% in relation to the total transition metal elements. In some embodiments, the lithium-containing oxide comprises at least one of lithium nickel cobalt manganese oxide, doped lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel manganese oxide, or manganese-rich lithium manganese oxide. In some embodiments, the lithium-containing oxide has, for example, the structural formula LixNidMneCofNgO2, where x=1 to 1.1, d=0.6 to 0.92, e=0.03 to 0.3, f=0.02 to 0.35, 0≤g<0.1 and N is at least one of Al, Na, Ti, Nb, Zr, W, Fe and Cr. In some embodiments, the molar content of a nickel element in the total transition metal elements in the lithium-containing oxide is 60% to 92%, wherein the molar content of a cobalt element in the total transition metal elements is 2% to 35%. With ordinary lithium manganese iron phosphate and lithium nickel manganese cobaltate as the collated active cathode material, it is possible, when applied to the secondary battery described in the present application, to overcome the problems of the transport rate of lithium manganese iron phosphate and manganese dissolution by regulating (axb) / c, while simultaneously increasing the energy density of the entire secondary battery, and significantly increasing the lithium disbedding rate of the active cathode material. Simultaneously, the size of the area a, b, and c in the secondary battery can be comprehensively adjusted by the process parameters of the cathode material during manufacturing, including, but not limited to, the type of cathode and anode materials, the electrode foil formula, the manufacturing process, and the electrolyte solution formula; in particular, for example, by adjusting the manganese content and primary particle size in the olive-like phosphate; the nickel content and primary particle size in the lithium oxide; the mass ratio of the two cathode materials; the porosity of the active cathode material layer; the type of conductive agent; the type of anode material; the composition and ratio of the electrolyte solution components; and the like. Furthermore, physical and chemical parameters, such as...The primary particle size of the material can be adjusted by the technicians on-site through the manufacturing parameters during the synthesis process. For example, if olive-like phosphate is produced by the liquid-phase method, the primary particle size of the olive-like cathode material can be effectively controlled by regulating the ion concentration in the reaction solution and the final sintering temperature. Similarly, the particle size of the primary particles of the lithium-containing oxide can be controlled by adjusting the particle size of the precursor, regulating the molar ratio of the transition metal, and the final sintering temperature. Furthermore, the person skilled in the art can also regulate the three parameters a, b and c by selecting the anode material, the specific composition of the electrolyte solution and even by the chemical manufacturing process of the secondary battery and is not limited to the specific embodiments described and listed in the present application. In some embodiments, the olive-like phosphate may be lithium manganese iron phosphate, and the manufacturing process may be carried out as follows: The manganese source, the iron source, and the phosphorus source are mixed and dispersed in a solvent. Then the lithium source is added and mixed in, and the reaction is carried out at 140°C to 160°C for 8 to 12 hours. The resulting product is mixed with the carbon source and dispersed in the solvent. The resulting mixture is spray-dried and then calcined under a protective atmosphere, yielding lithium manganese iron phosphate. In particular, the molar ratio of the manganese source, the iron source and the phosphorus source is (0.6 to 0.85):(0.15 to 0.4):(1.02 to 1.05); In particular, the solvent is water; In particular, the calcination treatment is carried out at a temperature of 550°C to 680°C for a period of 5 to 8 hours. In some embodiments, the lithium-containing oxygen compound is lithium nickel cobalt manganese oxide, and the manufacturing process can be carried out as follows: mixing a nickel source, a cobalt source, a manganese source and an alkali, followed by a reaction at 80°C to 100°C for 16 to 24 hours, and the resulting precursor is mixed with a lithium source and then calcined and processed, i.e., the lithium nickel cobalt manganate is obtained. In particular, the molar ratio of the nickel source, the cobalt source, the manganese source and the base is (0.6 to 0.92):(0.02 to 0.35):(0.03 to 0.3):(2.1 to 2.5); In particular, the calcination treatment is carried out at a temperature of 730°C to 850°C for a period of 6 to 9 hours. In the present invention there is no restriction regarding the manufacturing process of the lithium manganese iron phosphate and the lithium nickel cobalt manganese oxide, and technicians in the field can produce the lithium manganese iron phosphate or the lithium nickel cobalt manganese oxide according to conventional technical means by applying the above-mentioned process or other processes to obtain the lithium manganese iron phosphate or the lithium nickel cobalt manganese oxide. The manganese source used includes, but is not limited to, at least one of manganese tetraoxide, manganese nitrate, manganese carbonate, manganese oxalate, manganese sulfate, manganese chloride, or manganese acetate; The iron sources used include, but are not limited to, at least one of: iron(III) phosphate, iron(II) phosphate, iron(III) hydroxide, iron(II) hydroxide, iron(III) carbonate, iron(II) carbonate, iron(III) acetate, iron(II) acetate, iron(III) trioxide, iron(III) tetroxide, iron(II) oxalate, iron(III) oxalate; The cobalt source used includes, but is not limited to, at least one of cobalt sulfate, cobalt nitrate, cobalt oxalate, cobalt acetate, or cobalt chloride; The phosphorus source used includes, but is not limited to, at least one of lithium dihydrogen phosphate, lithium phosphate, diammonium hydrogen phosphate, or ammonium phosphate; The lithium source used includes, but is not limited to, at least one of lithium dihydrogen phosphate, lithium phosphate, lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, lithium citrate, or lithium acetate; The carbon source used includes, but is not limited to, at least one of glucose (GLC), sucrose, polyethylene glycol (PEG), or polyvinyl alcohol. Furthermore, in the production of lithium manganese ferromanganese phosphate, a certain amount of dopant sources (if available) can be mixed with the manganese source, the iron source, the phosphorus source, and the lithium source, and dopant sources such as a vanadium source (e.g., vanadium pentoxide), a tungsten source (e.g., ammonium metatungstate), a titanium source (e.g., titanium oxide), and a magnesium source (e.g., magnesium carbonate) can also be mixed as needed to obtain the doped lithium manganese ferromanganese phosphate containing a specific amount of dopant(s). In some embodiments, the mass ratio of the olive-like phosphate and the lithium-containing oxide is (97:3) to (70:30). In some embodiments, the mass ratio of the olive-like phosphate to the lithium-containing oxide is, for example, one of 97:3, 95:5, 93:7, 90:10, 87:13, 85:15, 80:20, 75:15, 70:30 or any value in a range between two of these values. It is noted that the mass ratio between the olive-like phosphate and the lithium-containing oxide can be confirmed by the following procedure: Disassembling the cathode foil from an empty secondary battery and subsequently immersing it in dimethyl carbonate (DMC) and drying it. Scraping the active cathode material layer from the cathode foil to perform an energy dispersive spectrometer (EDS) test and observing the morphology and size of the materials in the electrode foil at 15k magnification. The EDS signal acquisition is used to test the elemental species and their concentrations (normalized percentages of atoms) for particles of different sizes in the field of view, selecting at least three locations of similar particles for the test to obtain accurate results for parallel samples.Based on this data, the material type is identified and the average molar ratio of each type of transition metal element to the total transition metal element is determined, i.e., the chemical composition of each component of the main cathode material in the electrode foil. The sample is then subjected to an ICP test (0.5 g of the scraped active cathode material powder is accurately weighed and dispersed in 20 mL of water, then 10 mL of nitric acid (66% HNO3) is added, dispersed, and heated until the active cathode material powder is completely dissolved, and then the water volume for the solution to be tested is adjusted to 100 mL; the solution to be tested is subjected to an ICP test, and the operating conditions of the ICP instrument are set as follows: gas flow rate of 0.5 L / min, power of 1150 W, ICP test) to determine the concentration of the corresponding chemical components of the active cathode material (i.e.,to confirm the specific molar ratio of the chemical elements); The molar ratio of each type of transition metal to the total metal in the electrode foil is confirmed, and the actual metal molar ratios of each type of material, confirmed above by EDS, are combined to calculate the mass ratio of the cathode materials containing a specific metal element to the total materials θ = ICP molar ratio / EDS molar ratio, and the mass ratio of the remaining other types of materials is 1 - θ. The mass ratios of the two active cathode materials were determined from the chemical compositions, and the mass content of each element in the olive-like phosphates and the lithium-containing oxides alone was also confirmed by the methods described above. In some embodiments, the olive-like phosphate has an average primary particle size of 80 nm to 200 nm. In some embodiments, the average primary particle size of the lithium-containing oxide is 1.5 µm to 2.2 µm. It is noted that the average primary particle size of the olive-like phosphate and the lithium-containing oxide in the active cathode material described in the present application can be confirmed by the following procedure: Disassembling the cathode foil from the secondary battery and subsequently immersing it in dimethyl carbonate (DMC), drying, and scraping the active cathode material layer on the cathode foil for testing by EDS energy spectroscopy. Olive-like phosphate and layered lithium-containing oxide particles were identified by spot scanning at magnification. Subsequently, three regions of the layered lithium-containing oxide were selected to obtain the particle morphology under a scanning electron microscope (SEM) at 10k magnification, and the primary particles of the layered lithium-containing oxide were measured using the cross-hatching method of the nanomeasurer software.The average primary particle size of the lithium-containing oxide was determined from 200 samples. Three regions of olive-like phosphate were selected for particle morphology analysis using a scanning electron microscope at 30k magnification, and the diagonal length of the primary particles of the olive-like phosphate was measured using nanomeasurer software. Eighty samples were tested, and the results from the three regions were combined to determine the average primary particle size of the olive-like phosphate. In some embodiments, the secondary battery further comprises an electrolyte solution, wherein the electrolyte solution comprises a solvent and a lithium salt. In some embodiments, the solvent comprises at least one, for example, carbonate ester solvent, carboxylic acid ester solvent, ether solvent, sulfone solvent, nitrile solvent and phosphate solvent. In some embodiments, the lithium salt comprises at least one of the following substances: lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium diboronate, lithium difluoroborate, lithium trifluoromethanesulfonate, lithium bis(fluoromethane)sulfonimide, lithium bis(trifluoromethane)sulfonimide, lithium difluorodi(fluoro)oxalic acid phosphate, lithium tetrafluorooxalic acid phosphate. In some embodiments, the concentration of the lithium salt in the electrolyte solution is 0.9 mol / L to 2 mol / L. In some embodiments, the concentration of the lithium salt in the electrolyte solution is 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L or any value in a range between two of these values. If the concentration of the lithium salt is preferably within the above range, the lithium-ion transport capability can be further optimized, the impedance of the entire secondary battery system can be reduced, the phenomenon of increasing the anode potential can be improved, and the probability that the rate of decrease of the anode potential is too high can be further reduced, thus improving the fast charging performance of the secondary battery. Furthermore, the electrolyte solution may optionally include an additive. For example, the additive may include a film-forming additive for the anode and a film-forming additive for the cathode, and may also include an additive that improves certain battery properties, such as an additive to improve the battery's overcharge performance, an additive to improve its high-temperature performance, an additive to improve its low-temperature performance, etc. The battery may further include a separator. The separator is arranged between the cathode foil and the anode foil to keep the cathode foil and the anode foil apart and to prevent them from short-circuiting. The separator may be made of various materials suitable for use as insulating films for batteries according to the prior art. For example, the separator may include at least one of the following materials: polypropylene, polyethylene, In some embodiments, the cathode foil comprises a collector and an active cathode material layer, wherein the active cathode material layer comprises an active cathode material. Furthermore, the active cathode material layer preferably comprises a binder and a conductive agent. Furthermore, preferably the mass ratio of the active cathode material, the conductive medium and the binder in the active cathode material layer is (94 to 97.5):(0.8 to 2):(1.5 to 4). In some embodiments, the anode foil comprises a collector and an active anode material layer, wherein the active anode material layer comprises an active anode material. Furthermore, the active anode material layer preferably comprises an active anode material, a binder and a conductive agent. Furthermore, preferably the mass ratio of the active anode material, the conductive medium and the binder in the active anode material layer is (96 to 98):(1 to 2):(1 to 3). It should be noted that the conductive material used in the active cathode material layer and the active anode material layer is intended to ensure electrical conductivity. Any conductive material may be used without particular restriction, provided it exhibits suitable electronic conductivity and does not cause any obviously adverse chemical changes in the battery. For example, the conductive material in the active cathode material layer comprises at least one of the following: carbon nanotubes, carbon black, graphite, carbon fibers, activated carbon, mesoporous carbon, fullerenes, where the carbon fibers are, for example, carbon nanofibers and the like; and the carbon black is, for example, SP (Super P, hereinafter referred to as "SP"), acetylene black, cotinine black, and the like. The binder in the active cathode material layer and the active anode material layer is used to improve the bonding between the particles of the active cathode material and the bonding between the active cathode material and the cathode collector. Any binder may be used without particular restriction, provided it has suitable binder properties and does not cause obviously adverse chemical changes in the battery. For example, the binder in the active cathode material layer includes a fluoropolyolefin-based binder, and the fluoropolyolefin-based binder includes, but is not limited to, polyvinylidene fluoride (PVDF), copolymers of vinylidene fluoride, or modified derivatives thereof (e.g., carboxylic acid, acrylic acid, acrylonitrile, and other modifications thereof). In some embodiments, the active anode material is at least one of natural graphite, synthetic graphite, intermediate phase micro-carbon spheres (MCMB), hard carbon, soft carbon, silicon, SiOf(0 <f<2, z.B. f=1), Siliziumkohlenstoff, Lithiumtitanat. In some embodiments, the porosity of the active cathode material layer is 10% to 20%; In some embodiments, the test procedure for the porosity of the active cathode material layer is as follows: Disassembly of the secondary battery to obtain the cathode foil, soaking of the cathode foil in DMC at room temperature for 60 minutes, removal and drying at room temperature and a relative humidity of ≤15%, cutting of the electrode foil into a disc with a diameter of 12 mm using an electrode punching machine and simultaneous measurement of the thicknesses of the electrode foil and the collector with a thickness gauge as h1 and h2 respectively; The mass was weighed with a scale with an accuracy of 0.00001 g and recorded as m1; The volume of the cut-out electrode foil is calculated according to the formula v = πr2(h1-h2); The cut-out electrode foils are then immersed for 1 hour in a closed container with a specific volume of hexadecane (the volume of hexadecane in the closed solution is not required, but the required amount must ensure that the cut-out electrode foils are completely immersed); the cut-out electrode foils are removed with tweezers and placed on filter paper to absorb until the mass of the cut-out electrode foils reaches a constant weight (generally, the time from absorption to constant weight is 1 hour), and then weighed on a balance to obtain the mass of the cut-out electrode foils, which is recorded as m². Finally, the porosity is calculated according to the formula ε%=(m2-m1) / ρ, where ρ is 0.7734 g / cm3, which corresponds to the density of hexadecane. In some embodiments, the conductive medium in the active cathode material layer comprises carbon nanotubes, wherein the average diameter of the carbon nanotubes is 8 nm to 15 nm, and wherein the specific surface area is 220 m2 / g to 300 m2 / g. Carbon nanotubes are preferably used as a conductive medium when connected to particles of the active material to form a dot-line stacking that optimizes the contact between the particles, which helps to improve the conductivity of the surface of the olive-like phosphate in the active material, thereby improving the battery's lifetime at high temperature to reduce the growth of battery impedance and further improving the battery's high-temperature cycle performance and fast-charging performance; And by regulating the porosity of the cathode foil to a preferred range of 10% to 20%, the inactive, ineffective area between the particles can be further reduced, the conductivity between the particles can be improved, and the high-temperature performance of the secondary battery can be further optimized and improved. In some embodiments, the graphitization level of the active anode material is 91% to 95%; In some embodiments, the active anode material layer comprises graphite, wherein the average particle diameter of the graphite is 8 µm to 13 µm. In some embodiments, the test procedure for the degree of graphitization of the graphite is as follows: Disassembly of a secondary battery in a discharged state. Scraping and pulverizing of the resulting anode foil and then testing with reference to the test procedures for the layer spacing d002 and the degree of graphitization in the national standard GB / T24533-2019. The degree of graphitization of the active anode material and the particle size of the graphite particles contained in the electrode foil influence the volume phase transport performance of the active anode material of the secondary battery. If the degree of graphitization of the preferred material and / or the average particle diameter of the graphite particles in the electrode foil material are within the aforementioned range, the active material layer of the electrode foil exhibits more isotropic structures within the material and a moderate amount of defects in the vacancy structure, which is more conducive to improving the volume phase transport performance of the active anode material and thus the fast-charging performance of the secondary battery. In some embodiments, the solvent in the electrolyte solution comprises a linear carbonate, wherein the mass fraction of the linear carbonate in the total mass of the electrolyte solution is 50% to 90%; In particular, the linear carbonate comprises at least one of dimethyl carbonate, diethyl carbonate and methylethyl carbonate. In some embodiments, the solvent in the electrolyte solution further comprises a carboxylic acid ester solvent. In particular, the carboxylic acid ester solvent comprises at least one of ethyl acetate, methyl formate and 1,4-butyrolactone; In some embodiments, the solvent in the electrolyte solution further comprises an ether solvent; In some embodiments, the solvent in the electrolyte solution further comprises a cyclic carbonate. In particular, the cyclic carbonate comprises at least one of ethylene carbonate, propylene carbonate; the ether solvent comprises at least one of ethylene glycol dimethyl ether, tetrahydrofuran. Furthermore, preferably, if other types of solvents are present in the electrolyte solution in addition to linear carbonate, the ratio of the total volume of the linear carbonate to the other types of solvents is (50 to 90) : (10 to 50). In some embodiments, the additive in the electrolyte solution comprises at least one of vinylidene carbonate (VC) and vinylidene sulfate (DTD), wherein the mass fraction of the vinylidene carbonate and the vinylidene sulfate in the total mass of the electrolyte solution is 0.2% to 1%. In particular, if the additive in the electrolyte solution contains both VC and DTD, the mass ratio of the two is not additionally limited and can be adjusted by a person skilled in the art according to the actual needs. If linear carbonate is preferably used as a component of the solvent and vinylene carbonate and vinylene sulfate as components of the additive, and the component content is optimized within the above range, a thin and dense SEI film layer forms on the anode foil when the secondary battery undergoes the charging and discharging process. This inhibits the tendency to increase the internal impedance caused by the decomposition of the solvent in the electrolyte solution, optimizes the rate of decrease of the anode potential, and thus optimizes the overall performance of the secondary battery. In some embodiments, the type and mass ratio of the solvent and the type and mass ratio of the additive in the electrolyte solution are confirmed by the following procedure: (1) The secondary battery is discharged using charging and discharging devices under the following specific conditions: current 0.33 C, cut-off voltage 2.5 V. Afterwards, the battery is disassembled and the electrolyte solution is collected in a glove box (H₂O ≤ 0.1 ppm, O₂ ≤ 0.1 ppm). There are three ways to collect the electrolyte solution: after disassembling the battery cover, ① if free electrolyte solution is present, collect the electrolyte solution with a pipette into a 5 mL sample tube and seal it with sealant to prevent leakage. ② If no free electrolyte solution is present, a hydraulic press (Beijing HengAoDe Technology Co., Ltd.) can be used.(FY-30 hydraulic press) to maintain pressure until free electrolyte solution appears, collect the electrolyte solution into the sample tube, and seal it. ③ A suitable amount of methylene chloride extractant can be added to the battery, and the methylene chloride content recorded. After the addition of methylene chloride, the battery is placed in an aluminum-plastic bag, sealed with a heat sealer, and shaken in an ultrasonic shaker for 12 hours to ensure sufficient mixing of the electrolyte solution in the electrode foil with the methylene chloride. The methylene chloride and electrolyte solution mixture is then pipetted into a 5 mL sample tube, and the sample tube is sealed with sealant. The collected samples of the electrolyte solution are injected into an Agilent Intuvo 9000 gas chromatograph with a microsampler to test the electrolyte solution composition and obtain the GC-MS spectrum. The additive and solvent are mixed to form EMC solutions of varying concentrations, and each sample is injected into an Agilent Intuvo 9000 gas chromatograph to obtain the GC-MS spectrum of the standard substances. Qualitative analysis is performed by comparing the GC-MS spectrum of the electrolyte solution under test with the GC-MS spectrum of the standard. This determines whether the electrolyte solution under test contains the aforementioned additives or solvents (for example, if a characteristic peak area at the position of VC in the standard spectrum appears within the spectrum of the electrolyte solution under test, it is determined that the electrolyte solution under test contains VC).Other components are evaluated in a similar manner. The concentration of each component is then quantified based on the peak area of ​​that component in the electrolyte solution being tested. The present invention will be explained in more detail below with reference to specific embodiments, which are not to be understood as limiting the scope of protection of the present invention: Example 1 A manufacturing process for the secondary battery comprises the following steps: (1.1) Preparation of olive-type phosphate lithium manganese iron phosphate: Mixing MnSO4, FeSO4, and H3PO4 in a molar ratio of 7:3:10. After mixing with water, a mixed solution with a transition metal concentration of AM is prepared. Subsequently, ascorbic acid and LiOH are added, the ascorbic acid dosage being 0.2% of the total molar number of MnSO4, FeSO4, and H3PO4, and the LiOH dosage being three times the molar number of H3PO4. The resulting mixture is stirred at 70°C for 6 hours, then pressurized and heated to 150°C to carry out a 10-hour reaction. The solid is separated, dried, and then dispersed in water. Glucose, representing 21% by weight of the powder mass, is added, followed by spray drying.Finally, the material is calcined for 6 hours at 1000 °C under a nitrogen atmosphere to obtain carbon-coated lithium manganese iron phosphate. (1.2) Preparation of lithium-containing nickel cobalt manganese oxide: Nickel acetate, cobalt acetate, manganese acetate, and sodium hydroxide are mixed with water in a molar ratio of 6.5:2.5:1:10, dissolved uniformly, reacted for 24 hours at 80 °C, and the solid is separated. The precursor, with an average particle size of C µm, is mixed uniformly with lithium hydroxide in a stoichiometric ratio and then calcined for 8 hours at D °C under an air atmosphere to obtain lithium nickel cobalt manganese oxide. The production and product parameters of lithium manganese iron phosphate and lithium nickel cobalt manganese oxide are listed in Tables 1 and 2. (1,3) Preparation of the cathode foil: The carbon-coated lithium iron manganese phosphate and lithium nickel cobalt manganese oxide obtained above are mixed in a mass ratio of 9:1 to obtain the active cathode material. The active cathode material, the conductive agent of carbon nanotubes, and the binder of polyvinylidene fluoride are dispersed in a mass ratio of 96:2:2 in N-methylpyrrolidone, stirred under vacuum to form a slurry, which is then coated onto both sides of the aluminum foil of a collector, and dried, cold-pressed, and cut to obtain the cathode foil; (2) Production of the anode foil: Dispersing the active anode material of synthetic graphite, the conductive agent of acetylene black and the binder of sodium carboxymethylcellulose in water according to a mass ratio of 96.4:1:2.6, stirring under vacuum to form a slurry, which is then coated onto both surfaces of the copper foil of a collector, and drying, cold pressing and cutting to obtain the anode foil; (3) Preparation of the electrolyte solution: The linear carbonate of dimethyl carbonate and the cyclic carbonate of ethylene carbonate are mixed with the solvent. Lithium hexafluorophosphate is then added to form a mixture with a concentration of 1 mol / l, with the additives VC and DTD being added, thus forming the electrolyte solution, wherein the total mass fraction of VC and DTD in the electrolyte solution is 0.23%, with a mass ratio of VC to DTD of 3:1; wherein the mass fraction of linear carbonate in the total mass of the electrolyte solution is as specified in Table 3; (4) The cathode foil, the separator (commercially available PE separator), the anode foil are stacked in a row and inserted into the electrical core, the electrical core is placed in the outer packaging housing, the electrolyte solution is injected after drying, after vacuum encapsulation, standing, forming and setting the capacity to obtain the secondary battery. The parameters of the secondary batteries are listed in Table 4. Exemplary embodiments 2 to 23 A secondary battery which differs from embodiment 1 only in that the parameter conditions during the manufacture of the secondary battery have been changed, as shown in Tables 1 to 4. In embodiment 2, dimethyl carbonate was replaced by methyl ethyl carbonate and ethylene carbonate by propylene carbonate in the preparation of the electrolyte solution. Additionally, the solvent was supplemented with the ether solvent diethyl ether. The mass fraction of the linear carbonates in the total mass of the electrolyte solution is given in Table 3. In embodiment 3, the solvent additionally contained the ether solvent tetrahydrofuran, the mass fraction of linear carbonates in the electrolyte solution being as specified in Table 3. In embodiment 4, the mass ratio between VC and DTD is 2:3. Here, the molar ratio of manganese within the total transition metal content in lithium manganese iron phosphate is adjusted by modifying the molar ratio of MnSO4 to FeSO4 during material addition (while keeping the total molar number of Mn and Fe constant). The molar content of nickel and cobalt elements relative to the total transition metal content in lithium nickel cobalt manganese oxide is adjusted by changing the molar ratio of nickel acetate to cobalt acetate in the added materials (while keeping the total molar number of Ni, Co, and Mn constant). Parameters a, b, and c are regulated and modified according to the conditions specified in Tables 1 to 3. Example 24 A secondary battery that differs from embodiment 1 only in that the parameter conditions during manufacturing are changed. In addition to synthetic graphite, the active anode material comprises a silicon-carbon material, wherein the mass fraction of the silicon-carbon material within the anode foil (excluding the collector) is 2%. Comparison examples 1 to 4 A secondary battery which differs from embodiment 1 only in that the parameter conditions during the manufacture of the secondary battery have been changed, as shown in Tables 1 to 3. Comparative example 5 to 6 A secondary battery that differs from embodiment 1 only in that the parameter conditions during manufacturing are changed. In addition to synthetic graphite, the active anode material comprises a silicon-carbon material, wherein the mass fraction of the silicon-carbon material within the anode foil (excluding the collector) is 2%, as shown in Tables 1 to 3. The verification procedure for a, b, and c in Table 4 is as described above. Using the example of embodiment 23, during test a, the composite single-cell battery is subjected to a constant-capacity cycle test. The resulting charging curve, as shown in Fig. 1, is differentiated to obtain the dQ / dV-V curve. The voltage corresponding to the lowest point between the Fe2+ / Mn2+ oxidation peaks is determined. The ratio of the SOC and voltage difference values ​​within 100 ms before and after this voltage corresponds to the slope of the voltage transition region: a = (U2-U1) / (SOC2-SOC1). During test b, an impedance test was performed on the composite half-battery. The resulting data were subjected to DRT analysis to obtain parameter b. For test c, the secondary battery was charged, and the obtained data were processed as shown in Fig. 2 to derive the dQ / dV-V curve.A negative reference curve is then recorded as shown in Fig. 3. The coordinate point corresponding to the maximum voltage (SOC3, U3) and the endpoint of the charging curve (SOC4, 0) are selected. The ratio of the difference between these two points (SOC4 - SOC3) to U3 is c. Table 1. Example 10.857070177 Example 20.761068108 Example 30.7566065191 Example 40.960060151 Exemplary embodiment 51.1557080146 Example 6163067131 Example 70.862060102 Exemplary embodiment 81.15907584 Example 90.8554560136 Example 100.9568575125 Example 111,25806388 Example 12161580163 Example 131,0556082188 Example 140.864065200 Example 151,266577118 Example 160.764568141 Example 170.7558565153 Example 181,1568070187 Example 191,055756080 Example 200.7361075160 Example 210.955406094 Example 220.95456083 Exemplary embodiment 230.7361074155 Example 24165070117 Comparative example 10.8555075180 Comparative example 21.16807080 Comparative example 31.2556075122 Comparative example 40.6563065195 Comparative example 50.8562080101 Comparison example 6155060174 Table 2 Table 2 Parameter C µm D°C Molar content of nickel in lithium nickel cobalt manganese oxide relative to the total transition metal elements % Molar content of cobalt in lithium nickel cobalt manganese oxide relative to the total transition metal elements % Primary particle size of lithium nickel cobalt manganese oxide nm Execution at 118065251.7 game 10 Example 2683065202 Exemplary embodiment 31276073251.6 Exemplary embodiment 468108851,9 Exemplary embodiment 51277070151.8 Exemplary embodiment 611.675566221.76 Exemplary design 7778563181.67 Exemplary embodiment 81281068131.5 Exemplary embodiment 96.58358371.94 Exemplary embodiment 1097459082,17 Exemplary embodiment 114.680088101.6 Exemplary embodiment 1212.585077201.87 Exemplary embodiment 139.47307552 Exemplary embodiment 1413,484065132,1 Exemplary embodiment 15482060101.73 Exemplary embodiment 1610.782563181.69 Exemplary embodiment 1712.97909252.05 Exemplary embodiment 183.775085131.5 Exemplary embodiment 195.879060301.53 Exemplary embodiment 208,880065251,83 Exemplary embodiment 215,370077222,1 Exemplary embodiment 2213,17406042,2 Exemplary embodiment 238,88008981,83 Exemplary embodiment 24875088101.7 Comparative example 112.573060151.6 Comparative example 248509062,1 Comparative example 312.774065131.9 Comparative example 48.57709352 Comparative example 5878583151.88 Comparative example 65.681577101.94 Table 3 Table 3 Exemplary embodiment 19,329511,592,4660,23 Exemplary embodiment 212,728712,193,1730,67 Exemplary embodiment 314,327711,893,5780,44 Exemplary embodiment 410,82909,291,7710,31 Exemplary embodiment 59,923410,792,6650,29 Exemplary embodiment 613,12598,993,1560,37 Exemplary embodiment 710,42759,493,9720,49 Version 9.722012.892.5630.66 Example 8 Exemplary embodiment 98,023212,592,8590,35 Exemplary embodiment 108,523911,691,7550,69 Exemplary embodiment 1114,228410,493,7680,90 Exemplary embodiment 1212,929012,293,8780,94 Exemplary embodiment 1313,42378,592,4570,45 Exemplary embodiment 148,928311,491,9630,34 Exemplary embodiment 1511,62899,792,0790,22 Exemplary embodiment 169,530010,991,6630,86 Exemplary embodiment 1710,72759,692,8680,92 Exemplary embodiment 1812,424912,792,9760,28 Exemplary embodiment 1914,525312,493,3730,63 Exemplary embodiment 2014,923811,393,2740,74 Example 2113,52258,494,2620,98 Exemplary embodiment 2210,726410,894,0690,55 Exemplary embodiment 2314,923811,393,2740,74 Exemplary embodiment 2412,62419,692,2740,29 Comparative example 19,229711,792,1710,72 Comparative example 211,32849,293,4750,83 Comparative example 311,828612,494,3790,85 Comparative example 414,327910,591,5690,39 Comparative example 59,825211,792,2790,41 Comparative example 69.42741392.2690.69 Table 4 Table 4 Exemplary embodiment 110220,54,32,6 Exemplary embodiment 27270,554,23,5 Exemplary embodiment 330130,564,81,5 Exemplary embodiment 41526,50,493,63,6 Exemplary embodiment 51013,40,431,8 Exemplary embodiment 63017,80,5652,0 Exemplary embodiment 725250,4542,8 Exemplary embodiment 815190,554,52,3 Exemplary embodiment 93280,423,33,6 Exemplary embodiment 1025100,6641,7 Example 115250,656,52,5 Exemplary embodiment 12727,40,66,12,7 Exemplary embodiment 1325110,623,51,9 Exemplary embodiment 143120,612,82,6 Exemplary embodiment 1512130,425,80,9 Exemplary embodiment 1620160,4251,3 Exemplary embodiment 175240,6243,7 Exemplary embodiment 182014,30,56,51,1 Exemplary embodiment 191226,10,357,11,3 Exemplary embodiment 203080,4560,6 Exemplary embodiment 2125290,583,44,9 Exemplary embodiment 2210300,352,54,2 Exemplary embodiment 23308,50,66,90,7 Exemplary embodiment 241522,60,55,22,2 Comparative example 12090,357,30,4 Comparative example 230280,62,86,0 Comparative example 320100,3570,5 Comparative example 45250,662,85,9 Comparative example 530120,370,51 Comparative example 625250,72,76,48 Example of impact The secondary batteries obtained from each embodiment and each comparison example were tested as follows: (1) Rapid charging performance test: With the secondary battery assembled, a copper wire is attached to the side of the anode foil. The secondary battery is left to stand for 24 hours after assembly and is then charged at 0.02C to 4.1V, then at 0.33C at constant current to 4.25V, and then at constant voltage to 0.05C. After a 10-minute stand, the formation was completed by discharging to 2.5V at 0.33C constant current, followed by charging to 4.25V at 0.33C constant current, then charging to 0.05C at constant voltage, and a 10-minute stand.Discharge at constant current at a rate of 0.33C to 2.5V, as 1 capacity determination cycle; after 2 capacity determination cycles, first lithium plating of the copper wire at a rate of 0.02C for 4 hours, then charging to 10% of the capacity of the second capacity determination cycle at a rate of 0.33C; immediately afterwards, charging at constant current at a rate of 4C to a negative reference potential of 0 or a terminal voltage of 4.25V and then step-down charging with a gradient of 0.2C, with the cut-off condition remaining unchanged, until the charging rate is reduced to 0.4C / 0.2C / 0.1C / 0.05C and the battery reaches 100% of the capacity of the second cycle; The test temperature is 25°C, the signal acquisition frequency of the device is 100ms, and the charging time t required to charge the secondary battery from 10% to 80% SOC is calculated after completion of the test;(2) High-temperature cycle performance test: The secondary battery was left to stand for 24 hours, then charged at 0.02C to 4.1V, then at a constant current of 0.33C to 4.25V, and then at a constant voltage to 0.05C. After standing for 10 minutes, the battery was discharged to 2.5V at a constant current of 0.33C to complete the formation process, then charged to 4.25V at a constant current of 0.33C, then to 0.05C at a constant voltage, then left to stand for 10 minutes, and then discharged to 2.5V at a constant current of 0.33C.Take this as 1 cycle of capacity determination, and after 2 cycles of capacity determination, the secondary battery is subjected to the following cycle at 45°C according to the determined capacity: charging at constant current at a rate of 1C to 4.25V, then charging at constant voltage until cutoff at 0.05C, after a 10-minute stand, discharging at constant current at a rate of 1C to 2.5V, and recording the discharge capacity for this cycle as Q1; After 200 cycles in this manner, the discharge capacity on the 200th cycle is recorded as Q200, and the capacity retention rate of the secondary battery at high temperature is calculated as H%=100%*Q200 / Q1. The test results are listed in Table 5. Table 5 Table 5 Exemplary embodiment 121,597 Exemplary embodiment 21896.7 Exemplary embodiment 322,796,5 Exemplary embodiment 418,896 Exemplary embodiment 52396.1 Exemplary embodiment 62096.3 Exemplary embodiment 72296.7 Exemplary embodiment 81996.3 Exemplary embodiment 923,295,2 Exemplary embodiment 1024,595,6 Exemplary embodiment 1124,295,4 Exemplary embodiment 1223,494,7 Exemplary embodiment 1325,395,2 Exemplary embodiment 142494.8 Exemplary embodiment 1525,594,6 Exemplary embodiment 1626,294,3 Exemplary embodiment 1726,393,7 Exemplary embodiment 1827,195,3 Exemplary embodiment 1926,593,2 Exemplary embodiment 202795.8 Exemplary embodiment 2126,793,3 Exemplary embodiment 2227,493 Exemplary embodiment 2326,993,1 Example 242196 Comparative example 13390.4 Comparative example 23189.8 Comparative example 332,690,7 Comparative example 431,490 Comparative example 531,390,4 Comparative example 630,890,2 Table 5 shows that the secondary battery described in this application uses an olive-like phosphate and a lithium-containing oxide as active cathode materials and simultaneously regulates the charging behavior of the cathode and anode materials of the secondary battery as well as the ionic impedance of the cathode foil. By defining the relationship formula (a*b) / c for key parameters and adjusting the formula range between 0.6 and 5, the two active cathode materials achieve favorable synergistic effects. The secondary battery achieves both excellent fast-charging performance and high-temperature cycle performance. In fast-charging tests, the time required to charge from 10% to 80% state of charge (SOC) is reduced to less than 28 minutes. Furthermore, after 200 cycles at 45 °C, the secondary battery maintains a capacity retention rate of over 92%. As can be seen from embodiments 1 to 23, in secondary batteries, if (a*b) / c is designed, and the slope of the curve segment of the secondary battery's voltage transition region is too steep during charging, the balance between electron and ion transport changes, and the oxidation activity of the active cathode material can increase. Therefore, it is necessary to further regulate b and c to prevent a drop in cycle performance at high secondary battery temperatures. If a is too small, the overall efficiency of the secondary battery's lithium embedding decreases, and fast-charging capability is not guaranteed. Consequently, the ion impedance of the corresponding cathode foil and the charging behavior of the active anode material must be regulated.On the other hand, changes in b and c also affect the structural stability, interfacial stability, and lithium disembedding efficiency of the active cathode and anode materials. This means that the range of (a*b) / c has a direct influence on the electrochemical behavior of secondary batteries. Optimization within the range of (a*b) / c = 1.5 to 3.6 results in secondary batteries exhibiting higher overall lithium disembedding efficiency and improved material stability. Fast charging time can be further reduced to below 25.3 minutes, while high-temperature cycle capacity can be increased to over 94.5%. Since α, the slope of the charging curve segment in the voltage transition region between oxidation plateaus, is directly related to the cyclic interfacial stability of the secondary battery's active cathode material in a high-temperature environment, as well as to the ion transport efficiency, the entire secondary battery can be further optimized by regulating α to achieve a balance between charging behavior and cyclic stability, thereby improving the overall electrochemical performance level. The ion impedance β of the cathode foil is related to the ion transport rate during charging and the stability of the active cathode material on the cathode foil. The magnitude of the anode potential decay rate due to lithium embedding and polarization during charging leads to a change in (α × β) / β, which in turn affects the fast-charging performance and the cycle performance of the secondary battery.Optimizing the b and c ranges can also improve the overall electrochemical behavior of the secondary battery. If (a*b) / c is in the range of 1.5 to 3.6, and a is optimally chosen between 8 and 29 Ω, and / or b between 0.4 and 0.56 Ω, and / or c between 3.5 and 6 Ω, the performance of the secondary battery can be further improved. During fast charging, the shortest achievable charging time is only 18 minutes, while the capacity retention rate can reach a maximum of 97% per cycle. The present application discloses a secondary battery and relates to the technical field of batteries. The secondary battery of the present application uses a composite material consisting of an olivine-containing phosphate material and a lithium-containing oxide material as an active cathode material. By simultaneously regulating the charging behavior of both the cathode and anode materials, as well as a synergistic relationship created by the impedance of the cathode foil, high cycle performance at high temperatures and, at the same time, fast charging performance are ensured. QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature GB / T24533-2019

[0096]

Claims

Secondary battery, characterized in that the secondary battery comprises a cathode foil and an anode foil, wherein the cathode foil comprises an active cathode material, the active cathode material comprising an olive-like phosphate and a lithium-containing oxide; wherein the secondary battery satisfies the following: (a×b) / c = 0.6 to 5; where a denotes a slope of a curve segment between a first oxidation plateau and a second oxidation plateau on a charging curve with a unit of V, obtained at 25°C within an operating voltage range of 2.5 V to 4.25 V; wherein a voltage range of the first oxidation plateau is 3.3 to 3.5 V, while a voltage range of the second oxidation plateau is 4.0 to 4.1 V;where b Ω denotes a volume-phase lithium-ion transport impedance of the cathode foil in an EIS test at a SOC value corresponding to a minimum value between a first curve peak and a second curve peak of a dQdV-V curve at 25°C within the operating voltage range of 2.5 V to 4.25 V; where c denotes a decay rate of an anode potential during a charging process of the secondary battery at 25°C within the operating voltage range of 3.7 V to 4.25 V with a unit of V⁻¹. Secondary battery according to claim 1, characterized in that the secondary battery fulfills the following: (a×b) / c = 1.5 to 3.

6. Secondary battery according to claim 1, characterized in that a = 8 to 30, and / or that b = 0.35 Ω to 0.66 Ω, and / or that c = 2.8 to 7.

3. Secondary battery according to claim 3, characterized in that a = 13 to 27, and / or that b = 0.4 Ω to 0.56 Ω, and / or that c = 3.5 to 6. Secondary battery according to claim 1, characterized in that the olive-like phosphate comprises at least one of lithium manganese iron phosphate and doped lithium manganese iron phosphate. Secondary battery according to claim 5, characterized in that the molar content of a manganese element in total transition metal elements in the olive-like phosphate is 60% to 85%, and / or that the average primary particle size of the olive-like phosphate is 80 nm to 200 nm. Secondary battery according to claim 1, characterized in that the lithium-containing oxide comprises at least one of lithium nickel cobalt manganese oxide, doped lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel manganese oxide, manganese-rich lithium manganese oxide. Secondary battery according to claim 7, characterized in that the molar content of a nickel element in the total transition metal elements in the lithium-containing oxide is 60% to 92%, wherein the molar content of a cobalt element in the total transition metal elements is 2% to 35%, and / or that the average primary particle size of the lithium-containing oxide is 1.5 µm to 2.2 µm. Secondary battery according to claim 1, characterized in that the mass ratio of the olive-like phosphate and the lithium-containing oxide is (97:3) to (70:30). Secondary battery according to claim 1, characterized in that it fulfills at least one of the following conditions (a) to (f): (a) the cathode foil comprises an active cathode material layer, wherein the active cathode material layer comprises an active cathode material, wherein the porosity of the active cathode material layer is 10% to 20%; (b) the cathode foil comprises an active cathode material layer, wherein the active cathode material layer comprises a conductive means, wherein the conductive means comprises carbon nanotubes, wherein the average diameter of the carbon nanotubes is 8 nm to 15 nm, and wherein the specific surface area is 220 m² / g to 300 m² / g; (c) the secondary battery further comprises an anode foil, wherein the anode foil comprises an active anode material, wherein the degree of graphitization of the active anode material is 91% to 95%;(d) the secondary battery further comprises an anode foil, the anode foil comprising an active anode material layer, the active anode material layer comprising graphite, wherein the average particle diameter of the graphite is 8 µm to 13 µm; (e) the secondary battery further comprises an electrolyte solution, the electrolyte solution comprising a solvent, the solvent comprising a linear carbonate, wherein the mass fraction of the linear carbonate in the total mass of the electrolyte solution is 50% to 90%; (f) the secondary battery further comprises an electrolyte solution, the electrolyte solution comprising an additive, the additive comprising at least one of vinylidene carbonate and vinylidene sulfate, wherein the mass fraction of the vinylidene carbonate and the vinylidene sulfate in the total mass of the electrolyte solution is 0.2% to 1%. Power-consuming device, characterized in that it comprises a secondary battery according to one of claims 1 to 10, wherein the secondary battery is used as a power supply in the power-consuming device.

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