A positive electrode sheet, a secondary battery, and an electrical device

Abstract

The present invention relates to the field of electrochemistry technology, and specifically discloses a positive electrode plate, a secondary battery and an electrical device using the same. The positive active material of the positive electrode plate of the present invention comprises a manganese-containing phosphate material; the positive electrode plate satisfies the following relational expression: 0.08 ≤ (A×H) / I Al ≤ 27; wherein, A is the manganese content in the positive active material; H is the growth rate of the hydrogen ion content when the positive electrode plate is immersed in the mixed solution; I Al is the difference in the peak intensity of the aluminum element characteristic peak in the XPS spectrum when the positive electrode plate is analyzed by XPS at different depths. By comprehensively controlling the manganese element content in the positive active material, the hydrogen ion growth characteristics of the positive electrode plate and the Al peak intensity at different depths of the electrode plate, the present invention greatly improves the gas generation problem of the secondary battery containing the positive electrode plate, and the internal resistance growth rate of the battery after cycling is low.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a positive electrode plate, a secondary battery, and an electrical device. Background Art

[0002] Lithium iron manganese phosphate (LMFP) cathode materials have received extensive attention in the fields of electric vehicles and portable electronic devices due to their high energy density. Compared with lithium iron phosphate (LFP), LMFP improves the theoretical energy density of the battery by introducing manganese element, enabling the battery to have a longer endurance.

[0003] However, the increase in manganese content brings about the problem of manganese dissolution. Especially in a high-temperature environment, the dissolution of manganese ions may be aggravated. Manganese dissolution not only causes gas generation inside the battery, increasing the risk of battery swelling, but also forms deposits, which are formed inside the battery, increasing the internal resistance of the battery and reducing the charge and discharge efficiency and lifespan of the battery.

[0004] Therefore, it is necessary to provide a positive electrode plate that can improve the gas generation problem and reduce the internal resistance. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a positive electrode plate, a secondary battery, and an electrical device. By comprehensively controlling the manganese element content in the positive electrode active material, the hydrogen ion growth characteristics of the positive electrode plate, and the Al peak intensity at different depths of the electrode plate, the gas generation problem of the secondary battery containing the positive electrode plate is greatly improved, and the internal resistance growth rate of the battery after cycling is low.

[0006] To achieve the above purpose, in the first aspect of the present invention, the present invention provides a positive electrode plate, including a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a manganese-containing phosphate material;

[0007] The positive electrode plate satisfies the following relational expression:

[0008] 0.08 ≤ (A × h) / I Al ≤ 27;

[0009] Wherein, A is the molar content of manganese element in the positive electrode active material accounting for the transition metal element, with the unit of mol%;

[0010] H is the hydrogen ion content growth rate of the positive electrode plate when impregnated in a mixed solution at 60 °C for T1 h to T2 h, T2 - T1 = 72, T1 > 0; the mixed solution contains an organic solvent and a lithium salt, and the unit of H is %;

[0011] I Al= I2 - I1, where I1 is the peak intensity of the characteristic peak of aluminum element in the XPS spectrum when performing X-ray photoelectron spectroscopy (XPS) analysis on the surface of the positive electrode sheet; I2 is the peak intensity of the characteristic peak of aluminum element in the XPS spectrum after etching the positive electrode sheet with an etching depth of 50 nm and then performing XPS analysis; the units of I1, I2, and I Al are all counts / s.

[0012] As a preferred embodiment of the present invention, the positive electrode sheet satisfies the following relationship: 0.16 ≤ (A × h) / I Al ≤ 4.5.

[0013] As a preferred embodiment of the present invention, the range of A is 50 - 95 mol%.

[0014] As a further preferred embodiment of the present invention, the range of A is 55 - 85 mol%.

[0015] As a preferred embodiment of the present invention, the range of H is 12 - 42%.

[0016] As a further preferred embodiment of the present invention, the range of H is 15 - 35%.

[0017] As a preferred embodiment of the present invention, the range of I Al is 100 - 9000 counts / s.

[0018] As a further preferred embodiment of the present invention, the range of I Al is 600 - 7000 counts / s.

[0019] As a preferred embodiment of the present invention, the range of I1 is 100 - 12800 counts / s.

[0020] As a preferred embodiment of the present invention, the positive electrode active material includes lithium iron manganese phosphate materials.

[0021] As a preferred embodiment of the present invention, the average particle size of the lithium iron manganese phosphate materials is 30 - 400 nm.

[0022] As a preferred embodiment of the present invention, the mixed solution includes ethylene carbonate, ethyl methyl carbonate, and lithium perchlorate, where the volume ratio of ethylene carbonate to ethyl methyl carbonate is 3:7, and the molar concentration of lithium perchlorate in the mixed solution is 1 mol / L.

[0023] In the second aspect of the present invention, the present invention provides a secondary battery, including a positive electrode sheet, a negative electrode sheet, and an electrolyte, wherein the positive electrode sheet is the above-mentioned positive electrode sheet.

[0024] In a third aspect of the present invention, the present invention provides an electrical device including the above secondary battery.

[0025] The beneficial effects of the present invention are as follows:

[0026] The present invention develops a positive electrode plate, a secondary battery and an electrical device. By comprehensively controlling the manganese element content in the positive active material, the hydrogen ion growth characteristics of the positive electrode plate and the Al peak intensity at different depths of the electrode plate, the gas generation problem of the secondary battery containing the positive electrode plate is greatly improved, and the internal resistance growth rate of the battery after cycling is low. Description of the Drawings

[0027] Figure 1 It is an XPS diagram of the positive electrode plate of Example 6. Detailed Embodiments

[0028] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] In the present invention, among the technical features described in an open-ended manner, a closed technical solution composed of the listed features is included, and an open technical solution including the listed features is also included.

[0030] In the present invention, regarding the numerical range, unless otherwise specified, the above numerical range is considered continuous and includes the minimum value and the maximum value of the range, as well as each value between such minimum value and maximum value. Further, when the range refers to an integer, each integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0031] In the present invention, there is no particular limitation on the specific dispersion and stirring treatment methods.

[0032] The reagents or instruments used in the present invention that are not specified by the manufacturer can all be conventional products obtained through commercial purchase.

[0033] Positive Electrode Plate

[0034] An embodiment of the present invention provides a positive electrode plate, which includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a manganese-containing phosphate material;

[0035] The positive electrode plate satisfies the following relationship:

[0036] 0.08 ≤ (A × H) / I Al ≤ 27;

[0037] Wherein, A is the molar content of manganese element in the positive electrode active material accounting for the transition metal element, and the unit is mol%;

[0038] H is the hydrogen ion content growth rate of the positive electrode plate when impregnated in the mixed solution at 60 °C for T1 h to T2 h, T2 - T1 = 72, T1 > 0; the mixed solution contains an organic solvent and a lithium salt, and the unit of H is %;

[0039] I Al = I2 - I1, where I1 is the peak intensity of the aluminum element characteristic peak in the XPS spectrum when performing XPS analysis on the surface of the positive electrode plate; I2 is the peak intensity of the aluminum element characteristic peak in the XPS spectrum after etching the positive electrode plate with an etching depth of 50 nm and then performing XPS analysis; the units of I1, I2, and I Al are all counts / s.

[0040] By comprehensively controlling the manganese element content in the positive electrode active material, the hydrogen ion growth rate of the positive electrode plate, and the Al peak intensity at different depths of the positive electrode plate, the present invention greatly improves the gas generation problem of the secondary battery containing the positive electrode plate, and the internal resistance growth rate of the battery after cycling is low.

[0041] The present invention studies and finds that a certain amount of aluminum element (Al) in the positive electrode plate helps to improve the gas generation phenomenon inside the battery. During the first charge process of the battery, Al in the positive electrode plate will participate in the chemical reaction earlier than manganese element (Mn), promoting the formation of a solid electrolyte interface film (CEI film) on the surface of the positive electrode plate. The rapid formation of the CEI film can effectively protect the positive electrode before manganese dissolution, thus greatly reducing the side reaction between the positive electrode active material and the electrolyte and reducing the generation of gas inside the battery. However, the content of Al in the surface layer of the positive electrode plate (mainly the CEI film) should not be too high. Al located in the surface layer of the positive electrode plate may dissolve into the negative electrode plate and participate in the formation of the negative electrode solid electrolyte interface film (SEI film). When the Al content is too high, it may lead to an increase in the film impedance of the negative electrode SEI film, and then increase the internal resistance of the battery.

[0042] In XPS analysis, the characteristic peak position of an element is mainly judged by the binding energy. The position of the characteristic peak is generally related to the element type, valence state, structure, and test environment. For the positive electrode sheet of the present invention, the characteristic peak of aluminum element generally appears in the XPS spectrum with a binding energy of 60 - 90 eV. The peak intensity of the aluminum element characteristic peak in the XPS spectrum can reflect the relative content of Al at that position. I Al For the difference in the peak intensity of the Al peak at different etching depths of the positive electrode sheet, the present invention adjusts I Al to control the content distribution of Al at different depth positions of the positive electrode sheet, so as to improve the gas generation phenomenon of the battery while keeping the internal resistance of the battery low.

[0043] H is the growth rate of hydrogen ion content when the positive electrode sheet is impregnated in a mixed solution containing lithium perchlorate. When the positive electrode sheet is impregnated in a mixed solution containing a lithium salt, an interfacial reaction occurs between the positive electrode active material and the mixed solution, generating hydrogen ions. The greater the growth rate of hydrogen ion content during the impregnation process, the higher the degree of interfacial reaction. The degree of particle passivation of the positive electrode active material is an important factor affecting the above reaction degree. Therefore, the hydrogen ion growth rate in the present invention reflects to a certain extent the degree of particle passivation of the positive electrode active material. By controlling the value of H and adjusting the degree of passivation, and using the passivation effect to reduce the oxidizing property of the positive electrode active material, the protection of the positive electrode sheet can be achieved, reducing manganese dissolution, improving the gas generation situation of the battery, and also reducing the internal resistance of the battery. However, the value of H should not be too low. Too low a value of H may mean excessive passivation, resulting in hindered electron transport inside the positive electrode sheet and an increase in the internal resistance of the battery.

[0044] The value of H is related to various factors, such as the particle structure of the positive electrode active material, the particle coating situation, the additive composition of the battery electrolyte, and the doping elements and content of the positive electrode active material. That is to say, the contents of Al and Mn in the positive electrode sheet will both affect the value of H. Therefore, the present invention comprehensively controls the content of manganese element in the positive electrode active material, the hydrogen ion growth rate of the positive electrode sheet, and the Al peak intensity at different depths of the positive electrode sheet, and by controlling it to satisfy 0.08 ≤ (A × H) / I Al ≤ 27, the gas generation problem of the secondary battery containing this positive electrode sheet is improved, and the internal resistance growth rate of the battery is low after cycling.

[0045] When the value of (A × H) / I Al is too small, less than 0.08, there may be a situation of excessive passivation or too high an aluminum element content in the surface layer of the positive electrode sheet, resulting in too high an internal resistance growth rate of the battery; when the value of (A × H) / I Al is too high, greater than 27, it may lead to serious gas generation in the battery and a relatively high internal resistance growth rate.

[0046] Exemplarily, in the present invention, (A × H) / IAl The value can be 0.08, 0.10, 0.15, 0.20, 0.50, 1.0, 2.0, 5.0, 10.0, 15.0, 20.0, 25.0, 25.5, 26.0, 26.5, 26.8, 26.85, 26.90, 26.95, 27.0, or it can also be the range formed by any two of the above numerical values.

[0047] In one embodiment, the positive electrode plate satisfies the following relational expression: 0.16 ≤ (A × h) / I Al ≤ 4.5.

[0048] Further research in the present invention has found that when the positive electrode plate is within the above preferred range, the gas generation situation and the internal resistance growth rate of the battery are comprehensively better.

[0049] In one embodiment, the range of A is 50 - 95 mol%, for example, A can be 50 mol%, 55 mol%, 60 mol%, 70 mol%, 80 mol%, 90 mol%, 95 mol%.

[0050] In one preferred embodiment, the range of A is 55 - 85 mol%.

[0051] In the present invention, it is preferred to use a positive electrode active material with a relatively high manganese element content, which helps the battery to have a better energy density. However, the value of A should not be too high. If the value of A is too high, on the one hand, it will lead to an increased possibility of manganese dissolution, and on the other hand, it will also affect the passivation effect of the positive electrode, deteriorate the gas generation situation of the battery, and also increase the internal resistance of the battery.

[0052] Regarding the detection method of A, the present invention does not make any limitations. Those skilled in the art can detect the molar content of manganese element in the phosphate-based material according to conventional technical means, such as ICP testing.

[0053] Exemplarily, A can be detected by the following method:

[0054] Disassemble the battery in the empty state to obtain the positive electrode plate. After treatment, obtain the positive electrode active material powder, and through ICP testing, obtain the molar content of manganese element in the positive electrode active material accounting for the transition metal elements.

[0055] In one embodiment, the range of H is 12 - 42%, for example, H can be 12%, 15%, 18%, 25%, 30%, 35%, 38%, 40%, 42%.

[0056] In one preferred embodiment, the range of H is 15 - 35%.

[0057] The magnitude of the H value reflects the passivation degree of the positive electrode active material, which is affected by various factors, such as the particle structure, particle size, coating layer thickness, coating integrity, coating amount of the positive electrode active material; the additive composition of the battery electrolyte, whether it contains additives that promote film formation and passivation; the doping elements and their contents in the bulk phase of the positive electrode active material, etc. When the H value is within the above-preferred range, it indicates that the passivation effect of the positive electrode active material is appropriate, which can not only effectively improve the gas generation situation of the battery but also will not cause excessive increase in the internal resistance of the battery.

[0058] In one of the embodiments, the mixed solution includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and lithium perchlorate, where the volume ratio of ethylene carbonate to ethyl methyl carbonate is 3:7, and the molar concentration of lithium perchlorate in the mixed solution is 1 mol / L.

[0059] When the above mixed solution is used, the positive electrode plate is immersed in the mixed solution, and the lithium salt reacts with the solvents (EC, EMC) to form a solvation structure, which promotes the interfacial reaction between the solvent and the positive electrode active material. The solvent reacts to dehydrogenate and produce hydrogen ions. As the immersion time prolongs, the hydrogen ion content in the mixed solution increases. Lithium perchlorate, as a lithium salt with relatively stable properties, helps to make the detection of the H value more accurate.

[0060] Exemplarily, H can be detected by the following method:

[0061] Disassemble the battery in the fully charged state to obtain the positive electrode plate in the fully charged state. After drying at 80 °C for 4 h, the positive electrode plate is obtained. Cut the positive electrode plate into a test electrode plate of 7 cm × 7 cm;

[0062] At a test temperature of 60 °C, immerse the test electrode plate in 20 ml of the mixed solution, which is composed of ethylene carbonate, ethyl methyl carbonate, and lithium perchlorate, where the volume ratio of ethylene carbonate to ethyl methyl carbonate is 3:7, and the molar concentration of lithium perchlorate in the mixed solution is 1 mol / L;

[0063] When the test electrode plate is immersed in the mixed solution for 48 h, detect the hydrogen ion content in the mixed solution and record it as H1 ppm; when the test electrode plate continues to be immersed in the mixed solution for 72 h, detect the hydrogen ion content in the mixed solution again and record it as H2 ppm;

[0064] Among them, the hydrogen ion content can be tested by the acid-base titration method;

[0065] Calculate the growth rate of the hydrogen ion content H = (H2 - H1) / H1 × 100% when the positive electrode plate is immersed in the mixed solution containing perchloric acid. The hydrogen ion content when the test electrode plate is immersed in the mixed solution for 48 h is used as the initial hydrogen ion content, which is considered for the process of full wetting of the mixed solution and the positive electrode plate.

[0066] In one embodiment, the I Al ranges from 100 to 9000 counts / s. For example, the I Al can be 100 counts / s, 200 counts / s, 500 counts / s, 1000 counts / s, 3000 counts / s, 5000 counts / s, 8000 counts / s, 8500 counts / s, 9000 counts / s.

[0067] In one preferred embodiment, the I Al ranges from 600 to 7000 counts / s.

[0068] In one embodiment, the range of I1 is 100 to 12800 counts / s.

[0069] I Al value greater than 0 indicates that Al exists more in the positive electrode active material layer rather than in the CEI film layer. When I Al is within the above preferred range, the distribution of Al is more suitable. There is a sufficient amount of aluminum element in the positive electrode active material layer at the middle position (etching depth 50 nm) of the positive electrode plate, which helps to effectively improve the gas generation situation of the battery, and the aluminum element content in the surface layer (etching depth 0 nm) of the positive electrode plate is low, avoiding the deterioration of the battery internal resistance.

[0070] Since neither I1 nor I2 can be negative, it can be inferred that when the I Al value is too low, it means that the value of I2 is very small (the value of I1 is relatively even smaller), or the values of I1 and I2 are very close. Too small values of I1 and I2 indicate a low Al content in the positive electrode plate, and the improvement of the gas generation problem of the battery is not obvious enough; very close values of I1 and I2 indicate too small a difference in the Al content between the middle position and the surface layer position of the positive electrode plate, which may lead to a relatively high battery internal resistance. When the I Al value is higher than 9000 counts / s, it means that the Al content (i.e., I2) at the middle position of the positive electrode plate is not less than 9000 counts / s, and the overall Al content of the positive electrode plate is too high, which may lead to a relatively large increase rate of the internal resistance of the battery during cycling.

[0071] I Al value can be controlled by adding doping elements during the preparation of the positive electrode active material or adding aluminum elements during the preparation of the positive electrode plate.

[0072] Exemplarily, the I Al can be detected by the following method:

[0073] Disassemble the battery to obtain the positive electrode sheet, dry the positive electrode sheet to obtain the test electrode sheet; perform XPS analysis on the surface of the test electrode sheet and under the condition of an etching depth of 50 nm to obtain the difference in peak intensity of the aluminum element characteristic peak.

[0074] In one of the embodiments, the positive electrode active material includes lithium iron manganese phosphate materials.

[0075] The lithium iron manganese phosphate materials include at least one of lithium iron manganese phosphate (LMFP), lithium iron manganese phosphate containing doping elements, and lithium iron manganese phosphate with a coating layer.

[0076] In one of the embodiments, the average particle size of the lithium iron manganese phosphate materials is 30 - 400 nm.

[0077] The lithium iron manganese phosphate materials can be single particles or aggregates composed of primary particles. When the lithium iron manganese phosphate materials are single particles, the average particle size of the lithium iron manganese phosphate materials refers to the average particle size of the single particles; when the lithium iron manganese phosphate materials are aggregates, the average particle size of the lithium iron manganese phosphate materials refers to the average particle size of the primary particles.

[0078] The doping element can be aluminum.

[0079] The coating layer coats the surface of the LMFP particles, and the coating layer can be a carbon layer.

[0080] In the present invention, the preparation method of LMFP is not limited, and those skilled in the art can prepare LMFP according to conventional technical means.

[0081] Exemplarily, the preparation method of LMFP can include the following steps:

[0082] Mix a manganese source, an iron source, a phosphorus source, and a lithium source in a certain molar ratio and grind them.

[0083] After spray-drying the above-ground product, sinter it in an atmosphere with an oxygen concentration of less than 150 ppm to obtain LMFP.

[0084] According to needs, the process of grinding - spray-drying - sintering can be carried out multiple times when preparing LMFP. For example, after mixing the manganese source, the iron source, the phosphorus source, and the lithium source, perform one grinding, one spray-drying treatment, and then sinter it in an atmosphere with an oxygen concentration of less than 150 ppm; then perform secondary grinding on the product of the first sintering, perform secondary spray-drying treatment, and then sinter it in an atmosphere with an oxygen concentration of less than 150 ppm; then perform post-treatment to obtain LMFP.

[0085] The lithium source may include at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, lithium dihydrogen phosphate, lithium citrate, or lithium acetate.

[0086] The phosphorus source may include at least one of diammonium hydrogen phosphate, lithium dihydrogen phosphate, ammonium phosphate, or lithium phosphate.

[0087] The iron source may include at least one of ferrous oxalate, iron(III) hydroxide, iron(II) hydroxide, iron(III) phosphate, iron(II) phosphate, iron(III) acetate, iron(II) acetate, iron(III) carbonate, iron(II) carbonate, iron(III) oxide, iron(II,III) oxide, or iron(III) oxalate.

[0088] The manganese source may include at least one of manganese carbonate, manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, or manganese acetate.

[0089] Manganese iron phosphate can be selected to serve as both the manganese source, the iron source, and the phosphorus source; iron phosphate can be selected to serve as both the iron source and the phosphorus source.

[0090] When LMFP further contains doping elements, a certain amount of the doping element source can be weighed and mixed with the manganese source, the iron source, the phosphorus source, and the lithium source, and then ball-milled.

[0091] When the doping element is aluminum, the doping element source is an aluminum source. The aluminum source may include at least one of aluminum formate, aluminum acetate, aluminum glycolate, aluminum lactate, aluminum tartrate, aluminum oxalate, aluminum phosphate, aluminum hydrogen phosphate, aluminum dihydrogen phosphate, aluminum carbonate, aluminum oxide, aluminum hydroxide, aluminum fluoride, aluminum chloride, aluminum nitrate, aluminum sulfate, or aluminum bromide.

[0092] When LMFP further contains a coating layer, a certain amount of the coating layer raw material can be weighed and mixed with the manganese source, the iron source, the phosphorus source, and the lithium source, and then ball-milled.

[0093] When the coating layer is a carbon layer, the coating layer raw material is a carbon source. The carbon source may include at least one of glucose, sucrose, or polydiethanol.

[0094] In one embodiment, the positive electrode active material further includes at least one of lithium iron phosphate and lithium nickel cobalt manganese oxide.

[0095] When lithium manganese iron phosphate material is compounded with other types of positive electrode materials (such as lithium iron phosphate or lithium nickel cobalt manganese oxide) as the positive electrode active material, when the positive electrode plate satisfies 0.08 ≤ (A × H) / I Al ≤ 27, secondary batteries using this positive electrode plate all have less gas generation and a lower growth rate of cycle internal resistance.

[0096] In addition to the above positive electrode active material, the positive electrode active material layer may further contain a conductive agent and a binder.

[0097] The conductive agent only needs to have appropriate electronic conductivity and not cause adverse chemical changes in the battery, and the type of the conductive agent is not particularly limited in the present invention. Specifically, at least one of carbon nanotubes, carbon black, or graphene can be used as the conductive agent.

[0098] The binder is used to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. In the present invention, the binder can be a conventional choice in the battery field. Specifically, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylate, polyolefin, sodium carboxymethyl cellulose (CMC), or sodium alginate can be used as the binder.

[0099] The present invention places no particular restrictions on the positive electrode current collector, as long as it has conductivity and does not cause adverse chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, fired carbon; or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc. can be used.

[0100] In the present invention, the positive electrode plate can be prepared according to the conventional methods in the art. For example, the positive electrode active material, the conductive agent, and the binder are dispersed in a solvent to form a uniform positive electrode slurry, and the positive electrode slurry is coated on the positive electrode current collector, and after processes such as drying and rolling, the positive electrode plate is obtained.

[0101] Secondary battery

[0102] An embodiment of the present invention provides a secondary battery including the positive electrode plate described above.

[0103] In addition to the positive electrode plate, the electrochemical device further includes a negative electrode plate, a separator, and an electrolyte.

[0104] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material. For the negative electrode active material, the type of the negative electrode active material is not specifically limited in the embodiments of the present invention and can be selected according to actual needs. As an example, the negative electrode active material can be natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, or a silicon-carbon composite.

[0105] The separator is located between the positive electrode plate and the negative electrode plate, and is used to separate the positive electrode plate and the negative electrode plate to prevent the positive electrode plate and the negative electrode plate from contacting and short - circuiting. The separator can be materials of various types suitable for the separator of electrochemical energy storage devices in the art. Specifically, the separator includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fiber.

[0106] The electrolyte of the present invention can be electrolytes of various types suitable for electrochemical energy storage devices in the art. The electrolyte includes an electrolyte and a solvent, and the electrolyte usually includes a lithium salt.

[0107] Specifically, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluoro(dioxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP). The concentration of the electrolyte in the electrolyte can be 0.5 - 5 mol / L.

[0108] Specifically, the solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4 - butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0109] Power - consuming device

[0110] One embodiment of the present invention provides a power - consuming device, which includes the secondary battery described above.

[0111] The power - consuming device serves as the power supply of the power - consuming device.

[0112] The electrical device refers to any device that can utilize electrical energy and convert it into other forms of energy such as mechanical energy, thermal energy, and light energy, such as electric motors, electrothermal machines, and electric light sources. Specifically, it can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc. Mobile devices can be mobile phones, laptops, drones, floor cleaning robots, electronic cigarettes, etc.; electric vehicles can be pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.

[0113] The following further elaborates the present invention with specific embodiments:

[0114] Embodiment 1

[0115] This embodiment provides a lithium-ion battery, and the specific preparation method is as follows:

[0116] (1) Preparation of the positive electrode sheet

[0117] S1. According to the molar ratio n(Li):n(Mn + Fe):n(P)=1:1:1, and n(Mn):n(Fe)=75:25, accurately weigh Mn3O4, FePO4, and LiH2PO4 for mixing to obtain a mixed material;

[0118] Then weigh a carbon source (75 wt.% glucose and 25 wt.% polyethylene glycol), and an aluminum source (Al2O3), add them to the mixed material and carry out the first ball milling, the first spraying, and the first sintering together to obtain a first-sintered precursor;

[0119] Among them: weigh the aluminum source according to the molar ratio n(Al) / n(Mn)=6000 ppm;

[0120] Among them: weigh the carbon source according to 5 wt.% of the weight of the mixed material;

[0121] The conditions for the first ball milling are: 500 rpm, 25 °C, 22 h;

[0122] The conditions for the first spraying are: spraying pressure 0.65 MPa;

[0123] The conditions for the first sintering are: 500 °C, 10 h;

[0124] S2. Then weigh a certain amount of carbon source (75 wt.% glucose and 25 wt.% polyethylene glycol), mix it with the first-sintered precursor, carry out the second ball milling, the second spraying, and the second sintering together, and then through crushing, sieving, and removing impurities, obtain a lithium iron manganese phosphate material with an average particle size of 85.2 nm (lithium iron manganese phosphate coated with a carbon material layer), and the lithium iron manganese phosphate material is the positive electrode active material;

[0125] Among them: adjust the amount of carbon source to control the carbon coating amount of lithium iron manganese phosphate (the mass ratio of carbon material to lithium iron manganese phosphate material) to 2.8 wt.%;

[0126] The conditions for the second ball milling are: 500 rpm, 25 °C, 22 h;

[0127] The conditions for the second spraying are: spraying pressure 0.65 MPa;

[0128] The conditions for the second sintering are: 600 °C, 10 h.

[0129] S3. Mix the positive electrode active material, binder (PVDF), and conductive agent (SP) according to a mass ratio of 96:3:1, disperse them in NMP to obtain a positive electrode slurry. Subsequently, evenly coat the mixed positive electrode slurry on the aluminum foil, dry it in a vacuum furnace at 100 °C, perform rolling and cutting, and then bake to obtain a positive electrode plate.

[0130] (2) Preparation of the negative electrode plate

[0131] Mix the negative electrode active material (artificial graphite), conductive agent (SP), and binder (carboxymethyl cellulose, CMC) according to a mass ratio of 92:4:4, disperse them in deionized water to obtain a negative electrode slurry, evenly coat the negative electrode slurry on the negative electrode current collector (copper foil), transfer the negative electrode current collector coated with the negative electrode slurry to a vacuum environment in an oven and dry it at 100 °C, perform rolling and cutting, and then bake to obtain a negative electrode plate.

[0132] (3) Preparation of the electrolyte

[0133] Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent. Then, dissolve the fully dried lithium salt LiPF6 in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0134] (4)Preparation of the separator

[0135] Use a polyethylene (PE) separator.

[0136] (5)Preparation of the battery

[0137] Wind the positive electrode plate, separator, and negative electrode plate prepared above to obtain an un-injected bare battery cell; place the bare battery cell in an outer packaging foil, inject the prepared electrolyte into the dried bare battery cell, and obtain a lithium-ion battery through processes such as vacuum packaging, standing, formation, shaping, and sorting.

[0138] Examples 2 - 9, Examples 11 - 18, and Comparative Examples 1 and 2

[0139] Examples 2 to 9, Examples 11 to 18 and Comparative Examples 1 and 2 each provide a lithium-ion battery. The specific preparation method is similar to that of Example 1, except that in the preparation of the positive electrode sheet:

[0140] In S1, the values of n(Mn):n(Fe) and n(Al) / n(Mn) are shown in Table 1;

[0141] The time of the first ball milling is shown in Table 1;

[0142] In S2, after pulverization and sieving, the average particle size of the lithium iron manganese phosphate material is adjusted to meet the requirements shown in Table 1; the amount of the carbon source is adjusted to control the carbon coating amount of the lithium iron manganese phosphate material to meet the requirements shown in Table 1; the time of the second ball milling is shown in Table 1;

[0143] For Example 3, there is also the following difference in step S2: after obtaining the lithium iron manganese phosphate material, the lithium iron manganese phosphate material and lithium iron phosphate are mixed at a mass ratio of 8:2 to obtain the positive electrode active material;

[0144] For Example 15, there is also the following difference in step S2: after obtaining the lithium iron manganese phosphate material, the lithium iron manganese phosphate material and the ternary material (LiNi 0.6 Co 0.2 Mn 0.2 O2) are mixed at a mass ratio of 2:8 to obtain the positive electrode active material;

[0145] For Example 16, there is also the following difference in step S2: after obtaining the lithium iron manganese phosphate material, the lithium iron manganese phosphate material and the ternary material (LiNi 0.8 Co 0.1 Mn 0.1 O2) are mixed at a mass ratio of 2:8 to obtain the positive electrode active material.

[0146] Example 10

[0147] Example 10 provides a lithium-ion battery. The specific preparation method is similar to that of Example 1, except that in the preparation of the positive electrode sheet, the following method is adopted:

[0148] According to the molar ratio n(Li):n(Mn + Fe):n(P) = 1:1:1, and n(Mn):n(Fe) = 56:44, Mn3O4, FePO4, and LiH2PO4 are accurately weighed and mixed to obtain a mixed material;

[0149] Weigh the carbon source (75 wt.% glucose and 25 wt.% polyethylene glycol) and the aluminum source (Al2O3) again, add them to the mixture, and conduct the first ball milling, the first spray drying, and the first sintering together to obtain the lithium iron manganese phosphate material with an average particle size of 210 nm (lithium iron manganese phosphate coated with a carbon material layer); (no multiple ball milling or multiple sintering is carried out), and this lithium iron manganese phosphate material is the positive electrode active material;

[0150] Among them: weigh the aluminum source according to the molar ratio n(Al) / n(Mn) = 7600 ppm;

[0151] Adjust the amount of the carbon source to control the carbon coating amount of the lithium iron manganese phosphate (the mass ratio of the carbon material to the lithium iron manganese phosphate material) to be 2.0 wt.%;

[0152] The conditions for the first ball milling are: 500 rpm, 25 °C, 24 h;

[0153] The conditions for the first spray drying are: spray pressure 0.65 MPa;

[0154] The conditions for the first sintering are: 600 °C, 10 h;

[0155] Then, mix the positive electrode active material, the binder (PVDF), and the conductive agent (SP) according to the mass ratio of 96:3:1, disperse them in NMP to obtain the positive electrode slurry. Subsequently, uniformly coat the mixed positive electrode slurry on the aluminum foil, dry it in a vacuum furnace at 100 °C, roll press and cut it, and then bake it to obtain the positive electrode plate.

[0156] Comparative Example 3

[0157] Comparative Example 3 provides a lithium-ion battery. The specific preparation method is similar to that of Example 1, except that in the preparation of the positive electrode plate:

[0158] In S1, no aluminum source is added, and the value of n(Mn):n(Fe) is shown in Table 1; the time for the first ball milling is shown in Table 1;

[0159] In S2, after pulverization and sieving, adjust the average particle size of the lithium iron manganese phosphate material to meet the requirements shown in Table 1; adjust the amount of the carbon source to control the carbon coating amount of the positive electrode active material to meet the requirements shown in Table 1; the time for the second ball milling is shown in Table 1;

[0160] S3 is the following steps:

[0161] S3. Mix the positive electrode active material, the binder (PVDF), and the conductive agent (SP) according to the mass ratio of 96:3:1, disperse them in NMP to obtain the first positive electrode slurry; add 1.2 wt.% of Al2O3 to the first positive electrode slurry to obtain the second positive electrode slurry;

[0162] The second positive electrode slurry is evenly coated on the aluminum foil, dried in a vacuum furnace at 100°C, rolled, cut, and then baked to obtain the positive electrode plate.

[0163] The carbon coating amount of the lithium iron manganese phosphate material is determined by the following method:

[0164] The sample is weighed by an electronic balance and then enters the combustion reaction cell. Under the condition of sufficient oxygen, it is heated and burned at high temperature by a high-frequency furnace to oxidize carbon into carbon dioxide. After this gas is filtered and dried, it enters the corresponding absorption cell to absorb the corresponding infrared radiation spectrum (carbon dioxide 4200nm), and then is converted into a corresponding electrical signal by a detector. This signal is collected by a computer, linearly corrected and then converted into a value proportional to carbon dioxide. Then, the values of the entire analysis process are accumulated. After the analysis is completed, this accumulated value is divided by the weighed value in the computer and then multiplied by the correction coefficient to obtain the mass fraction of carbon in the sample, which is the carbon coating amount (unit: wt.%).

[0165] Table 1

[0166]

[0167] For the positive electrode plates A, h, and I in the lithium-ion batteries prepared in the above-mentioned examples and comparative examples Al are detected. The detection method is as follows, and the test results are shown in Table 2.

[0168] Detection method:

[0169] A: Disassemble the lithium-ion battery in the empty battery state to obtain the positive electrode plate. After the positive electrode plate is dried at 80°C for 4h, it is placed in a sintering furnace at 400°C and sintered for 4h, and then the positive electrode active material powder is scraped off with a ceramic knife;

[0170] Accurately weigh 0.5g of the positive electrode active material powder, disperse it in 20ml of water, then add 10ml of nitric acid, mix evenly and then heat it. After the positive electrode active material powder is dissolved, the material is made up to 100mL with water to obtain the test solution;

[0171] Perform ICP test on the test solution. ICP test conditions: Select the detection spectral wavelength of the element (Mn wavelength 257.61nm), and set the appropriate working conditions of the ICP instrument according to the characteristics of the sample and the element to be detected, including a gas flow rate of 0.5L / min and a power of 1150W; measure the Mn content of the element in it by ICP to obtain the molar content of manganese element in the positive electrode active material accounting for the transition metal element, which is the value of A, and the unit is mol%.

[0172] H: First, discharge the lithium-ion battery at a rate of 0.33C; then charge it at a rate of 0.33C until the cut-off voltage of 4.25V, with a cut-off current of 0.05C. When the battery reaches 100% SOC, i.e., the fully charged state; disassemble the fully charged battery to obtain the positive electrode plate in the fully charged state. After drying at 80°C for 4 hours, obtain the positive electrode plate, and cut the positive electrode plate into a test electrode plate of 7 cm × 7 cm;

[0173] Under the condition of 60°C, immerse the test electrode plate in 20 ml of a mixed solution composed of ethylene carbonate, ethyl methyl carbonate, and lithium perchlorate. The volume ratio of ethylene carbonate to ethyl methyl carbonate is 3:7, and the molar concentration of lithium perchlorate in the mixed solution is 1 mol / L;

[0174] When the test electrode plate is immersed in the mixed solution for 48 hours, detect the hydrogen ion content in the mixed solution and record it as H1 ppm; when the test electrode plate continues to be immersed in the mixed solution for another 72 hours, detect the hydrogen ion content in the mixed solution again and record it as H2 ppm;

[0175] The hydrogen ion content (H1, H2) in the mixed solution is detected by the following method:

[0176] Prepare a 0.05 mol / L triethylamine titrant with triethylamine and ethyl methyl carbonate (EMC); take the mixed solution impregnating the positive electrode plate as the test solution, add 10 - 30 drops of methyl red as an indicator to it, and drip the triethylamine titrant into the test solution containing methyl red. Record the consumption of the triethylamine titrant when the test solution turns orange; then obtain the hydrogen ion content according to the formula:

[0177] Hydrogen ion content = M × V × 20010 / m, and the unit of hydrogen ion content is ppm;

[0178] In the formula: M is the concentration of the triethylamine titrant, with the unit mol / L,

[0179] V is the volume of the titrant consumed by triethylamine, with the unit mL,

[0180] m is the mass of the test solution, with the unit g,

[0181] 20010 = 20.01 × 10 3 , 20.01 is the molecular mass of HF. The fully charged positive electrode plate contains the electrolyte component LiPF6. The positive electrode active material reacts with EC and EMC to dehydrogenate and produce HF in the presence of LiPF6. The hydrogen ions are represented by the amount of HF.

[0182] Calculate the growth rate of hydrogen ion content H = (H2 - H1) / H1 × 100% when the positive electrode plate is immersed in the mixed solution containing lithium perchlorate.

[0183] I Al : Disassemble the battery to obtain the positive electrode sheet. After drying the positive electrode sheet at 80 °C for 4 h, obtain the test electrode sheet;

[0184] Perform XPS analysis on the surface of the test electrode sheet. The peak intensity of the characteristic peak of aluminum element in the obtained XPS spectrum is I1 counts / s;

[0185] After etching the test electrode sheet with an etching depth of 50 nm, perform XPS analysis again. The peak intensity of the characteristic peak of aluminum element in the obtained XPS spectrum is I2 counts / s;

[0186] Among them, the conditions for XPS analysis are as follows: use a 120 W monochromatic Al Kα X-ray source; the energy resolution is less than or equal to 0.48 eV; the test beam spot is 400 microns, and the instrument automatically supplements the test pass energy range according to the element to be tested; the conditions for etching treatment are as follows: use Ar ions for etching, and control the etching depth to be 50 nm by adjusting the etching rate or etching time, etc.;

[0187] After the XPS analysis test is completed, the instrument will automatically give the test results, and I1 and I2 can be read out;

[0188] Calculate to obtain I Al = I2 - I1, and the units of I1, I2, and I Al are all counts / s.

[0189] Figure 1 is the XPS spectrum of the positive electrode sheet of Example 6. Among them, the lower line is the XPS spectrum obtained by performing XPS analysis on the surface of the test electrode sheet; the upper line is the XPS spectrum obtained by performing XPS analysis after etching the test electrode sheet with an etching depth of 50 nm. In Figure 1 , the position of the characteristic peak of aluminum element is at a binding energy of 84 ± 1 eV.

[0190] Table 2

[0191]

[0192] Test the gas generation performance of the positive electrode sheets prepared in the above examples and comparative examples, as well as the growth rate of the internal resistance (DCR) of the lithium-ion batteries prepared in the examples and comparative examples. The specific test method is as follows, and the test results are shown in Table 3.

[0193] (1) Gas generation performance:

[0194] Prepare soft-pack batteries by the processes of roll cutting, assembling, drying, and injecting electrolyte for the positive electrode sheets, separators, and negative electrode sheets of each example and comparative example;

[0195] Install a special container, an electronic scale, a soft-pack battery, wires, a bracket, and a formation device. Inject water into the special container until water overflows from the opening of the special container, and fully immerse the soft-pack battery in the water;

[0196] When the overflow stops, zero the electronic scale; perform formation (formation process: charge at 0.02C to 2.4V, let it stand for 10 minutes, then discharge at 0.02C to 2V, and let it stand for 10 minutes again. Repeat this three times. Then charge at 0.02C to 3.5V, let it stand for 10 minutes, and then charge at 0.1C to 4.25V). During the formation process, gas is generated inside the soft-pack battery, causing the volume of the battery to continuously expand, and the liquid in the special container to continuously overflow. As a result, the reading of the electronic scale changes simultaneously, and the volume of the overflowed water is the volume of the generated gas;

[0197] After the formation is completed, read the value shown on the electronic scale, which is the mass of the lost liquid. The density of water is known; then the gas production volume = mass of the lost liquid / density of water, with the unit of milliliters (ml);

[0198] The soft-pack battery is subjected to constant volume testing (constant current charge at 1 / 3C rate to 4.25V, constant voltage charge until the current is less than 0.05C, perform more than 3 steps, record the capacity of the battery, and obtain the actual capacity of the soft-pack battery (unit: Ah);

[0199] Evaluate the gas production performance of the positive electrode plate through the gas production volume per unit capacity of the battery. The gas production volume per unit capacity = gas production volume / actual capacity (unit: ml / Ah).

[0200] (2)DCR growth rate:

[0201] Constantly volume the lithium-ion battery, fully charge it at 0.33C to 4.25V, with a constant voltage cut-off current of 0.05C, discharge and regulate the charge at 0.33C to 50% SOC, let it stand for 2 hours, and then discharge at 1C under 50% SOC to measure the initial internal resistance of the battery and obtain DCR1;

[0202] Place the lithium-ion battery in a 55°C constant temperature oven, discharge the lithium-ion battery at a constant current of 0.33C until it is empty, and then, in the constant temperature oven, under the conditions of a charge-discharge test rate of 1C / 1C and a cyclic voltage range of 2.5 - 4.25V, perform cycling for a total of 300 cycles;

[0203] After 300 cycles, discharge and regulate the charge at 0.33C to 50% SOC, let it stand for 2 hours, and then discharge at 1C under 50% SOC to test the internal resistance of the battery after cycling and obtain DCR2;

[0204] Among them, the method for testing the internal resistance of the battery: Take the voltage at the last second of standing as V0, the voltage after discharging in 18s as V1, and the current during the discharging process as I. DCR = (V0 - V1) / I;

[0205] Calculate the DCR growth rate = (DCR2 - DCR1) / DCR1 × 100%.

[0206] Table 3

[0207]

[0208] According to the test results in Table 3, the lithium-ion batteries using the positive electrode sheets prepared in the embodiments of the present invention all have excellent gas generation performance (gas generation per unit capacity ≤ 24.1 ml / Ah), and the internal resistance growth rate of the lithium-ion batteries after cycling is low (DCR growth rate ≤ 65%).

[0209] It can be seen from Examples 1 to 6 and Examples 10 to 11 that when the positive electrode sheet further satisfies 0.16 ≤ (A × H) / I Al ≤ 4.5, the comprehensive performance of the battery is better, the gas generation is relatively lower, and the internal resistance growth is relatively less.

[0210] It can be seen from Comparative Examples 1 to 3 that when the positive electrode sheet exceeds the technical solution of the present invention and does not satisfy 0.08 ≤ (A × H) / I Al ≤ 27, it is difficult for the lithium-ion battery using this positive electrode sheet to balance good gas generation performance and a low internal resistance growth rate.

[0211] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, characterized in that: The positive electrode active material includes a lithium iron manganese phosphate material, the lithium iron manganese phosphate material is a single particle, and the average particle size of the lithium iron manganese phosphate material is 30 to 400 nm; The positive electrode sheet satisfies the following relationship: 0.08≤(A×H) / I Al ≤27; Wherein, A is the molar content of manganese element in the positive electrode active material to the transition metal element, in mol%, and the range of A is 50 to 95 mol%; H is the growth rate of hydrogen ion content of the positive electrode plate from T1 h to T2 h when immersed in the mixed solution at 60°C, T2-T1=72, T1>0; the mixed solution contains an organic solvent and a lithium salt, the unit of H is %, and the range of H is 12-42%; I Al =I2-I1, wherein I1 is the peak intensity of the characteristic peak of aluminum element in the XPS diagram when the surface of the positive electrode is subjected to XPS analysis; wherein I2 is the peak intensity of the characteristic peak of aluminum element in the XPS diagram after the positive electrode is etched to a depth of 50 nm and then subjected to XPS analysis; I1, I2 and I Al The units are all counts / s; the range of I1 is 1302~12202counts / s.

2. The positive electrode sheet according to claim 1, characterized in that: The positive electrode sheet satisfies the following relationship: 0.16≤(A×H) / I Al ≤4.

5.

3. The positive electrode sheet according to claim 1 or 2, characterized in that: The range of A is 55 to 85 mol%.

4. The positive electrode sheet according to claim 1 or 2, characterized in that: The range of H is 15-35%.

5. The positive electrode sheet according to claim 1 or 2, characterized in that: I Al The range is 100~9000counts / s.

6. The positive electrode sheet according to claim 5, characterized in that: I Al The range is 600~7000counts / s.

7. The positive electrode sheet according to claim 1, characterized in that: The mixed solution comprises ethylene carbonate, ethyl methyl carbonate and lithium perchlorate, wherein the volume ratio of ethylene carbonate to ethyl methyl carbonate is 3:7, and the molar concentration of lithium perchlorate in the mixed solution is 1 mol / L.

8. A secondary battery, comprising a positive electrode sheet, a negative electrode sheet and an electrolyte, characterized in that: The positive electrode sheet is the positive electrode sheet according to any one of claims 1 to 7.

9. An electrical device, characterized in that: Comprising the secondary battery as claimed in claim 8.

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