Battery and power consuming device

Abstract

The application relates to a battery and a power utilization device, and belongs to the technical field of batteries. The battery comprises an electrolyte and a positive pole piece, wherein the positive pole piece comprises a positive pole current collector and a positive pole active material layer arranged on at least one surface of the positive pole current collector, the positive pole active material layer comprises a positive pole active material, the positive pole active material comprises lithium iron phosphate, and the electrolyte comprises tris(dimethylvinylsilyl) phosphate; by regulating the mass ratio a of the tris(dimethylvinylsilyl) phosphate in the electrolyte, the contact angle b of the positive pole active material layer and the solution and the powder resistivity c of the positive pole active material layer to satisfy a specific relationship, the battery has less side reactions, low gas production, high ion and electron conductivity of the positive pole piece during the cycle process, and can have low gas production and low DCR.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery and a power utilization device. BACKGROUND

[0002] Lithium iron phosphate battery has the advantages of high working voltage, large energy density, good safety performance, small self-discharge rate and no memory effect. However, the lithium iron phosphate battery has serious gas production. The addition of phosphate ester additives in the electrolyte can inhibit gas production, but this will increase the DCR of the battery, especially in the lithium supplement system (i.e. the positive plate contains lithium supplement additives). SUMMARY

[0003] The purpose of the present application is to overcome the shortcomings of the prior art and provide a battery and a power utilization device, so that the lithium iron phosphate battery has low gas production and low DCR.

[0004] To achieve the above purpose, in a first aspect, the present application provides a battery, comprising an electrolyte and a positive plate, the positive plate comprising a positive current collector and a positive active material layer arranged on at least one surface of the positive current collector, the positive active material layer comprising a positive active material, the positive active material comprising lithium iron phosphate, the electrolyte comprising tris(dimethylvinylsilyl) phosphate;

[0005] The battery satisfies the following relationship: 0.3 < a x b x c < 124,

[0006] Wherein, a is the mass fraction of tris(dimethylvinylsilyl) phosphate in the electrolyte;

[0007] b is the contact angle of the positive active material layer with the solution, in °, the solution consisting of ethylene carbonate, methyl ethyl carbonate and lithium hexafluorophosphate, wherein the mass ratio of ethylene carbonate and methyl ethyl carbonate is 3:7, and the concentration of lithium hexafluorophosphate in the solution is 1 mol / L;

[0008] c is the powder resistivity of the positive active material layer, in Ω·cm.

[0009] In a second aspect, the present application provides a power utilization device comprising the battery.

[0010] Compared with the prior art, the present application has the following beneficial effects: by adjusting the mass fraction of tris(dimethylvinylsilyl) phosphate in the electrolyte, the contact angle of the positive active material layer with the solution and the powder resistivity of the positive active material layer to satisfy a specific relationship, the battery has less side reactions, low gas production and high ion and electron conductivity of the positive plate during the cycle process, so that it can have low gas production and low DCR. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 Figure for testing the contact angle b of the positive electrode active material layer with the solution for Example 1. DETAILED DESCRIPTION

[0012] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0013] In the present application, the technical features described in an open form include a closed technical solution consisting of the listed features, and also an open technical solution containing the listed features.

[0014] In the present application, if no special description is made, the numerical range is regarded as continuous and includes the minimum value and the maximum value of the range and each value between the minimum value and the 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 a feature or a property, 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.

[0015] In the present application, the specific dispersion and stirring treatment method is not particularly limited.

[0016] The reagents or instruments used in the present application are all conventional products that can be obtained by purchase in the market, if no manufacturer is specified.

[0017] Battery

[0018] The present application provides a positive electrode sheet, including an electrolyte and a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, the positive electrode active material layer contains a positive electrode active material, the positive electrode active material includes lithium iron phosphate, and the electrolyte contains tris(dimethylvinylsilyl) phosphate (DMVSP);

[0019] The battery satisfies the following relationship: 0.3 < a x b x c < 124,

[0020] Wherein, a is the mass ratio of the tris(dimethylvinylsilyl) phosphate in the electrolyte;

[0021] b is the contact angle between the positive electrode active material layer and the solution, in degrees. The solution is composed of ethylene carbonate, methyl ethyl carbonate and lithium hexafluorophosphate, wherein the mass ratio of ethylene carbonate to methyl ethyl carbonate is 3:7, and the concentration of lithium hexafluorophosphate in the solution is 1 mol / L.

[0022] c represents the powder resistivity of the positive electrode active material layer, in Ω·cm.

[0023] By rationally controlling the mass ratio of DMVSP in the electrolyte, the contact angle between the positive electrode active material layer and the solution, and the powder resistivity of the positive electrode active material layer, the battery exhibits fewer side reactions and lower gas production during cycling, while maintaining high ionic and electronic conductivity of the positive electrode sheet. This allows the battery to achieve both low gas production and low DCR.

[0024] The mass percentage (a) of DMVSP in the electrolyte affects the battery's gas production and DCR (discharge rate). Increasing the mass percentage (a) of DMVSP in the electrolyte helps improve gas production, but it leads to an increase in the battery's DCR. The mass percentage (a) of DMVSP in the electrolyte can be adjusted by changing the ratio of electrolyte to DMVSP.

[0025] The present invention does not limit the method for detecting the mass percentage (a) of DMVSP in the electrolyte. Those skilled in the art can detect the mass percentage (a) of DMVSP in the electrolyte using conventional techniques. For example, the mass percentage (a) of DMVSP in the electrolyte can be detected using the following method:

[0026] Use a battery charging and discharging device to discharge the battery completely. Discharge conditions: current 0.33C, cutoff voltage 2.5V, and record the battery number / barcode.

[0027] The battery was disassembled and the electrolyte was collected in a glove box (with internal environment meeting the following conditions: H2O≤0.1ppm, O2≤0.1ppm);

[0028] The presence of DMVSP in the electrolyte was tested using nuclear magnetic resonance spectroscopy. If it was found, the mass percentage of DMVSP in the electrolyte was tested using gas chromatography.

[0029] The disassembly of the battery and collection of the electrolyte can be carried out using the following three methods:

[0030] ① After removing the battery cover, if there is a sufficient amount (i.e., more than 10 mL, the same below) of free electrolyte, use a pipette to collect the electrolyte into the sample tube and seal it with sealing film;

[0031] ② After removing the battery cover, if there is no sufficient free electrolyte, a hydraulic press (such as the FY-30 hydraulic press from Beijing Hengaode Technology Co., Ltd.) can be used to continuously pressurize until free electrolyte appears. Collect the electrolyte into a sample tube and seal it with sealing film.

[0032] ③ After opening the battery cover, if insufficient electrolyte cannot be collected using methods ① and ②, an extraction experiment is required. The specific operation is as follows: Add a mixture of 2-5 g / Ah dichloromethane and cyclohexylbenzene (volume ratio of 1:9) to the battery as an extractant and record the amount of extractant used. Then, put the battery into an aluminum-plastic bag and seal it with a heat sealer. Let it stand at room temperature (25°C) for 4 days to allow the electrolyte in the electrode to mix thoroughly with the dichloromethane. Then, use a pipette to draw the mixture of extractant and electrolyte into a 5 mL sample tube and seal the sample tube with sealing film.

[0033] The mass percentage of DMVSP in the electrolyte can be determined using a gas chromatograph (Thermo Fisher Scientific Trace-1610) as follows: The collected electrolyte sample is injected into a 2 mL sample vial using a microsyringe. The response curve of the electrolyte sample is tested and compared with the DMVSP standard curve (the same test is performed using pure DMVSP to obtain the standard curve) to obtain the mass percentage of DMVSP in the electrolyte.

[0034] The method for testing the presence of DMVSP in electrolyte using nuclear magnetic resonance spectroscopy is as follows: 1 mL of the collected electrolyte sample is placed in a sample tube, and 0.5 mL of CDCl3 (deuterated chloroform) is injected into the sample tube using a syringe to fully dissolve the sample. The NMR spectrum of the electrolyte is then measured using a nuclear magnetic resonance spectrometer (Brook 400MHz NMR spectrometer) and compared with a DMVSP standard curve (obtained by performing the same test with pure DMVSP) to help confirm the presence of DMVSP in the electrolyte.

[0035] Lithium iron phosphate batteries commonly use a mixed solution of ethylene carbonate and methyl ethyl carbonate with added lithium hexafluorophosphate as the electrolyte. The contact angle (b) between the positive electrode active material layer and this solution reflects the wettability of the positive electrode to the electrolyte. A decrease in the contact angle (b) improves the wettability of the positive electrode to the electrolyte, which helps reduce the ionic impedance of the positive electrode, thus lowering the battery's damping coefficient (DCR). It also increases the contact area between the electrolyte and the positive electrode. The contact angle (b) between the positive electrode active material layer and the solution can be adjusted by modifying the type and / or amount of carbon source during the carbon coating process of the positive electrode active material, and by adjusting the compaction density of the positive electrode.

[0036] The present invention does not limit the method for detecting the contact angle (b) between the positive electrode active material layer and the solution. Those skilled in the art can detect the contact angle (b) using conventional techniques. For example, the contact angle (b) between the positive electrode active material layer and the solution can be measured using a contact angle measuring instrument (Beijing Zhongyi Kexin Technology Co., Ltd. JC2000D2M). The specific testing method is as follows:

[0037] 1) Positive electrode pretreatment: After disassembling the empty battery, use ceramic scissors to cut a positive electrode sheet with a size of about 8.5*8cm. After placing the positive electrode sheet at room temperature of 25℃ for 6 to 10 hours, the two ends of the electrode sheet can be fixed on the test fixture to start the test.

[0038] 2) Place the device for fixing the electrode on the sample placement stage of the contact angle measuring instrument;

[0039] 3) The solution is dripped onto the electrode using a syringe, and the contact angle of the solution within 0.01 to 0.05 s is measured. The contact angle is calculated using the five-point fitting method and image analysis method. The solution is prepared by mixing ethylene carbonate EC and methyl ethyl carbonate EMC at a mass ratio of 3:7, adding lithium hexafluorophosphate, and adjusting the concentration of lithium hexafluorophosphate to 1 mol / L.

[0040] The powder resistivity (c) of the positive electrode active material layer is related to the electronic conductivity of the positive electrode and its wettability to the electrolyte. Reducing the powder resistivity (c) of the positive electrode active material layer can improve the electronic conductivity of the positive electrode, thus improving the battery's direct current carrying capacity (DCR), and also improve the wettability of the positive electrode to the electrolyte. The powder resistivity (c) of the positive electrode active material layer can be adjusted by modifying the particle size of the positive electrode powder and the ratio of conductive agent to binder in the positive electrode slurry.

[0041] The present invention does not limit the method for detecting the powder resistivity (c) of the positive electrode active material layer. Those skilled in the art can detect the powder resistivity (c) of the positive electrode active material layer using conventional techniques. For example, the powder resistivity (c) of the positive electrode active material layer can be detected using the following method:

[0042] Discharge the battery to 0.33C, disassemble it, and place the positive electrode in a fume hood for 24 hours. Then, collect 1g of positive electrode powder with a scraper. Ball mill the scraped positive electrode powder at a speed of 300r / min using 0.6mm diameter zirconia balls with a ball-to-powder ratio of 5:1 for 20-40 minutes. After ball milling, place the powder on a four-probe resistivity tester (such as the ST2722 semiconductor powder resistivity tester from Suzhou Jingge Electronics Co., Ltd.) to test the powder resistivity. The specific operation method is as follows: place the powder on the electrode, apply pressure to the powder with the other electrode, and read the powder resistivity value.

[0043] The mass percentage of DMVSP in the electrolyte, the contact angle between the positive electrode active material layer and the solution, and the powder resistivity of the positive electrode active material layer all affect the battery's DCR and gas production to varying degrees, and these factors have a certain degree of mutual influence. Controlling a single variable makes it difficult to achieve a battery with both low DCR and low gas production. This invention adjusts the mass percentage of DMVSP in the electrolyte, the contact angle between the positive electrode active material layer and the solution, and the powder resistivity of the positive electrode active material layer to satisfy the above-mentioned specific relationships. This results in fewer side reactions and lower gas production during battery cycling, while maintaining high ionic and electronic conductivity of the positive electrode sheet, thus enabling the battery to achieve both low gas production and low DCR.

[0044] For example, the value of a×b×c can be selected as 0.4, 0.6, 0.8, 1.0, 1.1, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 115, 120, 123 or any range formed by any two of the above values.

[0045] In one preferred embodiment, the battery satisfies the following relationship: 0.5 ≤ a × b × c ≤ 16. The value of a × b × c is controlled within this range to result in a lower DCR, fewer side reactions, and lower gas production.

[0046] In some embodiments, the positive electrode active material layer also includes lithium supplementation additives.

[0047] In one preferred embodiment, the lithium replenishing additive comprises lithium iron ferrite (LFO). When the lithium replenishing additive comprises lithium iron ferrite, after disassembling the empty battery, the positive electrode is removed, cleaned with DMC (dimethyl carbonate) for 4-5 hours, and then left to stand at 45°C for 3 hours. XPS (X-ray photoelectron spectroscopy) analysis can detect the presence of Fe. 4+ .

[0048] In one embodiment, the lithium-replenishing additive has a mass percentage of 0.001 to 0.05 in the positive electrode active material layer. For example, the mass percentage of the lithium-replenishing additive in the positive electrode active material layer is 0.001, 0.003, 0.005, 0.007, 0.01, 0.02, 0.03, 0.04, 0.05, or any range formed by two of the above values.

[0049] In some embodiments, the positive electrode active material further includes at least one of lithium manganese iron phosphate and ternary materials. When the positive electrode active material includes at least one of lithium manganese iron phosphate and ternary materials, the upper limit voltage of the positive electrode sheet can be increased. The sum of the mass percentages of the lithium manganese iron phosphate and the ternary materials in the positive electrode active material layer is 0.02 to 0.5, such as 0.02, 0.05, 0.07, 0.1, 0.2, 0.3, 0.4, 0.5, or any range formed by two of the above values.

[0050] The mass percentage of lithium manganese iron phosphate in the positive electrode active material layer can be selected from 0.02 to 0.5, such as 0.02, 0.05, 0.07, 0.1, 0.2, 0.3, 0.4, 0.5, or any range formed by two of the above values; the chemical formula of the lithium manganese iron phosphate is LiMn. e Fe 1-e PO4, 0 < e < 1, such as 0.01, 0.03, 0.05, 0.07, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.93, 0.96, 0.99, or any range formed by two of the above values; the particle size Dv50 of the lithium manganese iron phosphate is 2-3 μm, such as 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, or any range formed by two of the above values. This invention does not limit the method for detecting the particle size Dv50 of lithium manganese iron phosphate; those skilled in the art can detect the particle size Dv50 of lithium manganese iron phosphate using conventional techniques. For example, the particle size Dv50 of lithium manganese iron phosphate can be detected by the following method: Discharge the battery at 0.33C to a voltage of 2.5V, disassemble it, place the positive electrode sheet in a fume hood for 24 hours, then collect 0.1-0.2g of positive electrode powder with a scraper, and photograph the obtained positive electrode powder with a scanning electron microscope (SEM). Measure the particle size of lithium manganese iron phosphate in the SEM image using MEARSURE NANO software, and collect the particle size of lithium manganese iron phosphate using the diagonal tracing method. After collecting more than 100 samples, statistically analyze the particle size distribution and calculate the particle size-related parameter of lithium manganese iron phosphate: Dv50.

[0051] The mass percentage of the ternary material in the positive electrode active material layer can be selected from 0.02 to 0.5, such as 0.02, 0.05, 0.07, 0.1, 0.2, 0.3, 0.4, 0.5, or any range formed by two of the above values; the ternary material is LiNi. x Co y Mn (1-x-y) O2, where 0 < x < 1 (e.g., 0.01, 0.03, 0.05, 0.07, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.93, 0.96, 0.99, or any interval formed by two of the above values), and 0 < y < 1 (e.g., 0.01, 0.03, 0.05, 0.07, 0.1, 0.2, 0. The particle size Dv50 of the ternary material is 3–20 μm, such as 3 μm, 5 μm, 7 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, or any two of the above values. This invention does not limit the method for detecting the particle size Dv50 of the ternary material; those skilled in the art can detect the particle size Dv50 of the ternary material using conventional techniques. For example, the particle size Dv50 of ternary materials can be detected by the following method: Discharge the battery at 0.33C to a voltage of 2.5V, disassemble it, place the positive electrode sheet in a fume hood for 24 hours, then collect 0.1-0.2g of positive electrode powder with a scraper, and photograph the obtained positive electrode powder with a scanning electron microscope (SEM). Measure the particle size of the ternary material in the positive electrode powder in the SEM image using MEARSURE NANO software. Collect the particle size of the ternary material using the diagonal tracing method. After collecting more than 100 samples, statistically analyze the particle size distribution and calculate the particle size-related parameter of the ternary material: Dv50.

[0052] In some embodiments, c is 1 to 200 Ω·cm. For example, c is 1 Ω·cm, 3 Ω·cm, 5 Ω·cm, 7 Ω·cm, 10 Ω·cm, 15 Ω·cm, 20 Ω·cm, 25 Ω·cm, 30 Ω·cm, 35 Ω·cm, 40 Ω·cm, 45 Ω·cm, 50 Ω·cm, 60 Ω·cm, 70 Ω·cm, 80 Ω·cm, 90 Ω·cm, 100 Ω·cm, 110 Ω·cm, 120 Ω·cm, 130 Ω·cm, 140 Ω·cm, 150 Ω·cm, 160 Ω·cm, 170 Ω·cm, 180 Ω·cm, 190 Ω·cm, 200 Ω·cm, or a range formed by any two of the above values.

[0053] When c is in the range of 1 to 200 Ω·cm, not only is the wettability of the positive electrode to the electrolyte within a more reasonable range, but there are also fewer side reactions between the positive electrode and the electrolyte, less gas production, and higher electronic conductivity of the positive electrode, resulting in a lower DCR of the battery.

[0054] In one preferred embodiment, c is 5 to 50 Ω·cm. When c is within this range, it is more beneficial to balance the gas production and DCR of the battery.

[0055] In some embodiments, b is 10° to 40°. For example, b is 10°, 13°, 15°, 17°, 20°, 22°, 25°, 28°, 30°, 32°, 35°, 37°, 40° or a range formed by any two of the above values.

[0056] When b is in the range of 10° to 40°, the wetting rate of the positive electrode to the electrolyte is within a more reasonable range. Not only is it less likely for the positive electrode to undergo side reactions with the electrolyte, but the ionic impedance inside the battery is also lower, and the battery's DCR is also lower.

[0057] In some embodiments, 'a' is 0.0001 to 0.05. For example, 'a' is 0.0001, 0.0005, 0.001, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, or a range formed by any two of the above values.

[0058] When a is in the range of 0.0001 to 0.05, the battery produces less gas and has a lower DCR.

[0059] In one preferred embodiment, 'a' is 0.001 to 0.01. When 'a' is within this range, it is more conducive to balancing the gas production of the battery with the DCR.

[0060] In some embodiments, the particle size Dv50 of the lithium iron phosphate is 0.1–2 μm, such as 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 1 μm, 1.2 μm, 1.5 μm, 1.7 μm, 2 μm, or any range formed by two of the above values. Controlling the particle size Dv50 of the lithium iron phosphate within this specific range ensures that the contact angle of the solution on the surface of the positive electrode is within a suitable range, while maintaining good porosity in the positive electrode active material layer, increasing the wetting rate of the electrolyte on the positive electrode, and reducing ionic impedance. This invention does not limit the method for detecting the particle size Dv50 of lithium iron phosphate; those skilled in the art can detect the particle size Dv50 of lithium iron phosphate using conventional techniques. For example, the particle size Dv50 of lithium iron phosphate can be detected by the following method: Discharge the battery at 0.33C to a voltage of 2.5V, disassemble it, place the positive electrode sheet in a fume hood for 24 hours, then collect 0.1-0.2g of positive electrode powder with a scraper, and photograph the obtained positive electrode powder with a scanning electron microscope (SEM). Measure the size of lithium iron phosphate particles in the SEM image using MEARSURE NANO software, and collect the lithium iron phosphate particle size using the diagonal tracing method. After collecting more than 100 samples, statistically analyze the particle size distribution and calculate the relevant parameter of lithium iron phosphate: Dv50.

[0061] In some embodiments, the compaction density of the positive electrode sheet is 2.0–3.0 g / cm³. 3 For example, 2.0g / cm 3 2.2g / cm 3 2.4g / cm 3 2.6g / cm 3 2.8g / cm 3 3.0g / cm 3 Or any two of the above values ​​within a range. When the compaction density of the positive electrode sheet is controlled within this specific range, the surface of the positive electrode sheet has good wetting performance with the electrolyte, which can reduce the ion impedance of the entire battery. At the same time, because the areal density is within a suitable range, the energy density of the battery is well guaranteed.

[0062] This invention does not limit the method for detecting the compaction density of the positive electrode sheet. Those skilled in the art can detect the compaction density of the positive electrode sheet using conventional techniques. For example, the compaction density of the positive electrode sheet can be detected using the following method:

[0063] Discharge the battery at 0.33C, with a cutoff voltage of 2.5V. After disassembling the battery, remove the positive electrode sheet and place it in a fume hood for 24 hours. Cut the positive electrode sheet into a circular piece with a diameter of 4cm. Record the original sheet's mass as m1 and area as s1. Measure the mass of the same size positive electrode foil as m2. Calculate the areal density d using the formula d = (m1 - m2) / s1. Measure the thickness of the positive electrode active material layer in the positive electrode circular piece as h1. Calculate the compaction density using the formula compaction density = d / h1.

[0064] In some embodiments, the mass percentage of the positive electrode active material in the positive electrode active material layer is 0.95 to 0.998, such as 0.95, 0.955, 0.96, 0.965, 0.97, 0.975, 0.98, 0.985, 0.99, 0.995, 0.998, or any range formed by two of the above values.

[0065] In addition to the positive electrode active material, the positive electrode active material layer also includes a conductive agent and a binder.

[0066] The conductive agent in the positive electrode active material layer is used to provide conductivity. Any conductive agent can be used without particular limitation, as long as it has suitable electronic conductivity and does not significantly cause adverse chemical changes in the battery. For example, the conductive agent in the positive electrode active material layer includes, but is not limited to, at least one of carbon nanotubes, carbon black, graphite, carbon fibers, activated carbon, mesoporous carbon, and fullerenes, wherein carbon fibers are, for example, carbon nanofibers; and carbon black is, for example, acetylene black, Ketjen black, SuperP (i.e., SP), etc.

[0067] In some embodiments, the mass percentage of the conductive agent in the positive electrode active material layer is 0.001 to 0.02, such as 0.001, 0.003, 0.005, 0.007, 0.01, 0.012, 0.015, 0.017, 0.02, or any range formed by two of the above values.

[0068] The binder in the positive electrode active material layer is used to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Any binder can be used without particular limitation, as long as it has suitable adhesive properties and does not significantly cause adverse chemical changes in the battery. For example, the binder in the positive electrode active material layer includes, but is not limited to, fluorinated polyolefin binders, including but not limited to polyvinylidene fluoride (PVDF), PVDF copolymers, or their modified derivatives (e.g., modified with carboxylic acids, acrylic acid, acrylonitrile, etc.).

[0069] In some embodiments, the mass percentage of the binder in the positive electrode active material layer is 0.001 to 0.05, such as 0.001, 0.003, 0.005, 0.007, 0.01, 0.02, 0.03, 0.04, 0.05, or any range formed by two of the above values.

[0070] The present invention does not impose any particular restrictions on the positive electrode current collector, as long as it is conductive and will not cause adverse chemical changes in the battery, and can be made of, for example: aluminum, nickel, titanium, stainless steel, sintered carbon; or aluminum or stainless steel that has been surface treated with one of carbon, nickel, titanium, silver, etc.

[0071] The preparation method of the positive electrode active material is not particularly limited in this invention, and those skilled in the art can use conventional means to prepare the positive electrode active material.

[0072] For example, the positive electrode active material can be prepared by the following method:

[0073] Iron phosphate, a carbon source, and lithium carbonate are mixed in an organic solvent at a mass ratio of 1:(0.15–0.35):0.09. After spray drying, the raw material is obtained. The raw material is then sintered at a temperature of 650–800°C for 1–5 hours to obtain the positive electrode active material. The carbon source can be at least one of glucose, sucrose, and polyethylene glycol. The organic solvent can be at least one of methanol and ethanol. After sintering, the material can be ground, or ground and sieved.

[0074] For example, the preparation method of the positive electrode active material can also be carried out by the following method: Iron phosphate and lithium carbonate are mixed in an organic solvent at a mass ratio of 1:0.09, spray-dried to obtain raw materials, and then sintered at a temperature of 650–800°C for 1–5 hours to obtain the positive electrode active material. The organic solvent can be at least one of methanol and ethanol. After sintering, grinding or sieving can be performed. The positive electrode active material can also be commercially available lithium iron phosphate, such as lithium iron phosphate from Beijing DangSheng Materials Technology Co., Ltd.

[0075] The positive electrode active material can also be prepared by mixing lithium iron phosphate with at least one of lithium manganese iron phosphate and ternary materials. The lithium iron phosphate used here can be commercially available lithium iron phosphate, such as that from Beijing Dangsheng Materials Technology Co., Ltd., or it can be prepared using the method described in the example above.

[0076] The preparation method of the positive electrode sheet is not particularly limited in the present invention, and those skilled in the art can obtain the positive electrode sheet by conventional means. For example, the preparation method of the positive electrode sheet includes the following steps:

[0077] Disperse the positive electrode active material, conductive agent and binder in a solvent. The solvent can be N-methylpyrrolidone (NMP) or deionized water to form a uniform positive electrode slurry. Coating the positive electrode slurry on the positive electrode current collector and after processes such as roll pressing, the positive electrode sheet is obtained.

[0078] The battery of the present invention further includes a negative electrode sheet, and the negative electrode sheet 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.

[0079] The present invention has no particular limitation on the negative electrode active material. Exemplarily, the negative electrode active material includes but is not limited to natural graphite, artificial graphite, mesophase microbeads (MCMB), hard carbon, soft carbon, silicon, SiO g (0 < g < 2, such as g = 1), silicon carbide, Li4Ti5O 12 and at least one of them.

[0080] In some embodiments, the mass ratio of the negative electrode active material in the negative electrode active material layer is 0.93 to 0.998, such as 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 0.993, 0.995, 0.998 or the range formed by any two of the above values.

[0081] In some embodiments, the negative electrode active material includes graphite, and the particle size Dv50 of the graphite is 5 to 20 μm, such as 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 20 μm, 22 μm, 25 μm or the range formed by any two of the above values.

[0082] The negative electrode active material layer may further contain a conductive agent and / or a binder.

[0083] The conductive agent in the negative electrode active material layer is used to provide conductivity, and any conductive agent can be used without particular limitation as long as it has suitable electronic conductivity and does not significantly cause adverse chemical changes in the battery. Exemplarily, the conductive agent in the negative electrode active material layer includes but is not limited to at least one of carbon nanotubes, carbon black, graphite, carbon fiber, activated carbon, mesoporous carbon, fullerenes, etc. Among them, carbon fiber such as carbon nanofiber, etc.; carbon black such as acetylene black, Ketjen black, Super P (i.e., SP), etc.

[0084] In some embodiments, based on the weight of the negative electrode active material layer, the mass percentage of the conductive agent in the negative electrode active material layer is 0.001 to 0.02, such as 0.001, 0.003, 0.005, 0.007, 0.01, 0.012, 0.014, 0.016, 0.018, 0.02, or any range formed by two of the above values.

[0085] The binder in the negative electrode active material layer is used to improve the adhesion between negative electrode active material particles and the adhesion between the negative electrode active material and the negative electrode current collector. Any binder can be used without particular limitation, as long as it has suitable adhesive properties and does not significantly cause adverse chemical changes in the battery. For example, the binder in the negative electrode active material layer includes, but is not limited to, at least one of carboxymethyl cellulose (CMC), styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl butyral, and aqueous acrylic resin.

[0086] In some embodiments, based on the weight of the negative electrode active material layer, the mass percentage of the binder in the negative electrode active material layer is 0.001 to 0.05, such as 0.001, 0.003, 0.005, 0.007, 0.01, 0.02, 0.03, 0.04, 0.05, or any range formed by any two of the above values.

[0087] The present invention does not impose any particular restrictions on the negative electrode current collector, as long as it is conductive and will not cause adverse chemical changes in the battery, and can be made of, for example: copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel surface-treated with at least one of carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy.

[0088] The method for preparing the negative electrode sheet is not particularly limited in this invention, and those skilled in the art can obtain the negative electrode sheet using conventional methods. For example, the method for preparing the negative electrode sheet includes the following steps:

[0089] The negative electrode active material, conductive agent and binder are dispersed in a solvent, which can be N-methylpyrrolidone (NMP) or deionized water, to form a uniform negative electrode slurry. The negative electrode slurry is coated on the negative electrode current collector, and after processes such as rolling, the negative electrode sheet is obtained.

[0090] The electrolyte of this invention further comprises a solvent. Exemplarily, the solvent includes, but is not limited to, at least one of ethylene carbonate (EC), methylene disulfonate (MMDS), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl 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), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0091] The mass percentage of the solvent in the electrolyte can be selected from 0.65 to 0.98889, such as 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 0.98, 0.9889, or any range formed by two of the above values.

[0092] In some embodiments, the electrolyte further comprises methylene methane disulfonate, wherein the mass percentage of methylene methane disulfonate in the electrolyte is 0.00001 to 0.05, such as 0.00001, 0.00005, 0.0001, 0.0005, 0.001, 0.005, 0.01, 0.03, 0.05, or any range formed by two of the above values. Adding the specific amount of methylene methane disulfonate described above can reduce the amount of DMVSP used, further reducing ion impedance.

[0093] The electrolyte further comprises an electrolyte, which typically includes lithium salts. Exemplary examples include, but are not limited to, 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 difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). The mass percentage of the electrolyte in the electrolyte can be selected from 0.01 to 0.2, such as 0.01, 0.03, 0.05, 0.07, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, or any range formed by two of the above values.

[0094] In addition, the electrolyte may also contain other additives. For example, the other additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery high-temperature performance, additives that improve battery overcharge performance, additives that improve battery low-temperature performance, etc.

[0095] The preparation method of the electrolyte is not particularly limited in this invention, and those skilled in the art can use conventional methods to prepare the negative electrode sheet. For example, the preparation method of the electrolyte includes the following steps:

[0096] The solvent, lithium salt, DMVSP, and other additives (if any) are mixed to obtain the electrolyte.

[0097] The battery may further include a separator located between the positive and negative electrode plates to separate them and prevent short circuits caused by contact. The separator can be any suitable battery separator material in the art. Exemplarily, the separator includes, but is not limited to, at least one of polypropylene (PP) and polyethylene (PE).

[0098] Electrical appliances

[0099] The present invention also provides an electrical device comprising the battery. The battery serves as the power supply for the electrical device.

[0100] The term "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. The converted energy can be one or more forms. For example, the electrical device includes at least one of the following: electric vehicles, electric trains, mobile devices, ships and satellites, and energy storage systems. For instance, electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, and electric trucks; mobile devices include, but are not limited to, mobile phones, laptops, drones, and robotic vacuum cleaners.

[0101] The present invention will be further illustrated below with specific embodiments.

[0102] Example 1

[0103] Example 1 provides a battery, the preparation method of which is as follows:

[0104] (1) Preparation of positive electrode sheet

[0105] (1.1) Preparation of lithium iron phosphate

[0106] Iron phosphate, carbon source, and lithium carbonate were mixed in methanol at a mass ratio of 1:0.25:0.09 and spray-dried to obtain raw material. The raw material was sintered at 700℃ for 3 hours, then ball-milled (using 0.6mm diameter zirconia balls, a ball-to-material ratio of 5:1, and a rotation speed of 300r / min), and sieved to obtain carbon-coated lithium iron phosphate, i.e., lithium iron phosphate, in which glucose was the carbon source.

[0107] (1.2) Preparation of positive electrode sheet

[0108] The obtained lithium iron phosphate was used as the positive electrode active material. The positive electrode active material, conductive agent acetylene black and binder PVDF were mixed at a mass ratio of 96.3:0.7:3.0 and then dispersed in NMP to obtain a positive electrode slurry. The positive electrode slurry was coated on both sides of an aluminum foil, and the wet film thickness of the positive electrode slurry coated on one side of the aluminum foil was controlled to be 120 μm. After rolling and cutting, the positive electrode sheet was obtained. The compaction density of the obtained positive electrode sheet is shown in Table 1.

[0109] (2) Preparation of negative electrode sheet

[0110] Artificial graphite, carboxymethyl cellulose binder, and conductive carbon black conductive agent were dispersed in deionized water at a mass ratio of 95.8:1.2:3.0 to prepare a negative electrode slurry. The negative electrode slurry was coated on both sides of a copper foil, and the wet film thickness of the negative electrode slurry coated on one side of the copper foil was controlled to be 180 μm. Then, the negative electrode sheet was obtained by rolling and cutting.

[0111] (3) Preparation of electrolyte

[0112] The solvent, tris(dimethylvinylsilyl) phosphate, and lithium hexafluorophosphate were mixed in a mass ratio of 0.9599:0.0051:0.035 to obtain the electrolyte.

[0113] The solvent is prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 3:4:3 to obtain the solvent.

[0114] (4) Preparation of the separating membrane

[0115] PE diaphragm is used.

[0116] (5) Assembly and formation

[0117] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0118] Examples 2-17 and Comparative Examples 1-4

[0119] Examples 2-17 and Comparative Examples 1-4 each provide a battery, the preparation method of which is similar to that of Example 1, the difference being that...

[0120] In step (1.1), the mass ratio of iron phosphate, carbon source and lithium carbonate and the ball milling and sieving process are adjusted. The mass ratio of iron phosphate, lithium carbonate and carbon source and the particle size Dv50 of the resulting lithium iron phosphate are shown in Table 1.

[0121] In step (1.2), the mass ratio of the positive electrode active material, the conductive agent and the binder and the compaction density of the obtained positive electrode sheet are shown in Table 1;

[0122] In step (3), the mass ratio of DMVSP in the electrolyte is adjusted, and the mass ratio of solvent in the electrolyte is adjusted accordingly. The mass ratio of DMVSP in the electrolyte is shown in Table 1.

[0123] Example 18 and Comparative Examples 7-8

[0124] Example 18 and Comparative Examples 7-8 each provide a battery prepared using a method similar to that of Example 1, the difference being that...

[0125] In step (1.1), the ball milling and sieving process was adjusted, and the particle size Dv50 of the resulting lithium iron phosphate is shown in Table 1.

[0126] In step (1.2), the obtained lithium iron phosphate is used together with lithium manganese iron phosphate as the positive electrode active material. The weight of lithium manganese iron phosphate is 5% of the weight of lithium iron phosphate, and the chemical formula of the lithium manganese iron phosphate used is LiMn. 0.4 Fe 0.6 The PO4 has a particle size Dv50 of 2.6 μm. The mass ratio of the positive electrode active material, conductive agent and binder and the compaction density of the obtained positive electrode sheet are shown in Table 1.

[0127] In step (3), the mass ratio of DMVSP in the electrolyte is adjusted, and the mass ratio of solvent in the electrolyte is adjusted accordingly. The mass ratio of DMVSP in the electrolyte is shown in Table 1.

[0128] Example 19 and Comparative Examples 9-10

[0129] Example 19 and Comparative Examples 9-10 each provide a battery prepared using a method similar to that of Example 1, the difference being that...

[0130] In step (1.1), the ball milling and sieving process was adjusted, and the particle size Dv50 of the resulting lithium iron phosphate is shown in Table 1.

[0131] In step (1.2), the obtained lithium iron phosphate is used together with the ternary material as the positive electrode active material. The weight of the ternary material is 5% of the weight of the lithium iron phosphate, and the chemical formula of the ternary material used is LiNi.0.2 Co 0.3 Mn 0.5 O2 with a particle size Dv50 of 13 μm, the mass ratio of positive electrode active material, conductive agent and binder and the compaction density of the obtained positive electrode sheet are shown in Table 1;

[0132] In step (3), the mass ratio of DMVSP in the electrolyte is adjusted, and the mass ratio of solvent in the electrolyte is adjusted accordingly. The mass ratio of DMVSP in the electrolyte is shown in Table 1.

[0133] Examples 20-21 and Comparative Examples 5-6

[0134] Examples 20-21 and Comparative Examples 5-6 each provide a battery prepared using a method similar to that of Example 1, the difference being that...

[0135] In step (1.1), the ball milling and sieving process was adjusted, and the particle size Dv50 of the resulting lithium iron phosphate is shown in Table 1.

[0136] In step (1.2), the positive electrode active material, lithium supplementing additive, conductive agent acetylene black and binder PVDF are mixed to prepare positive electrode slurry. The mass ratio of positive electrode active material, lithium supplementing additive, conductive agent and binder and the compaction density of the obtained positive electrode sheet are shown in Table 1. Among them, the lithium supplementing additive is lithium iron ferrite rich in lithium.

[0137] In step (3), the mass ratio of DMVSP in the electrolyte is adjusted, and the mass ratio of solvent in the electrolyte is adjusted accordingly. The mass ratio of DMVSP in the electrolyte is shown in Table 1.

[0138] Example 22

[0139] Example 22 provides a battery prepared in a method similar to that of Example 1, except that...

[0140] In step (1.1), the ball milling and sieving process was adjusted, and the particle size Dv50 of the resulting lithium iron phosphate is shown in Table 1.

[0141] In step (1.2), the compaction density of the obtained positive electrode sheet is shown in Table 1;

[0142] In step (3), the solvent, tris(dimethylvinylsilyl) phosphate, lithium hexafluorophosphate and methylene disulfonate are mixed to prepare the electrolyte. The mass percentage of DMVSP in the electrolyte is shown in Table 1. The mass percentage of methylene disulfonate in the electrolyte is 0.003, and the mass percentage of lithium hexafluorophosphate in the electrolyte remains unchanged.

[0143] Examples 23-27 and Comparative Examples 11-12

[0144] Examples 23-27 and Comparative Examples 11-12 each provide a battery, the preparation method of which is similar to that of Example 1, the difference being that...

[0145] In step (1.1), no carbon source was used. The ball milling and sieving process was adjusted. The mass ratio of iron phosphate to lithium carbonate and the particle size Dv50 of the resulting lithium iron phosphate are shown in Table 1.

[0146] In step (1.2), the mass ratio of the positive electrode active material, the conductive agent and the binder and the compaction density of the obtained positive electrode sheet are shown in Table 1;

[0147] In step (3), the mass ratio of DMVSP in the electrolyte is adjusted, and the mass ratio of solvent in the electrolyte is adjusted accordingly. The mass ratio of DMVSP in the electrolyte is shown in Table 1.

[0148] The following methods were used to detect the mass percentage (a) of DMVSP in the electrolyte, the contact angle (b) between the positive electrode active material layer and the solution, and the powder resistivity (c) of the positive electrode active material layer in each embodiment and comparative example. The test results are shown in Table 1.

[0149] (1) The mass percentage of DMVSP in the electrolyte, a

[0150] Perform a full discharge procedure on the battery under the following conditions: current 0.33C, discharge cut-off voltage 2.5V. Record the battery number / barcode. Disassemble the battery in a glove box (internal environment meets the following requirements: H2O≤0.1ppm, O2≤0.1ppm). After removing the battery cover, collect the electrolyte according to methods ①~③.

[0151] ① If there is enough free electrolyte (i.e., more than 10 mL, the same below), collect the electrolyte into the sample tube with a pipette and seal it with sealing film;

[0152] ② If sufficient electrolyte cannot be collected by method ①, use a hydraulic press (such as the FY-30 hydraulic press from Beijing Hengaode Technology Co., Ltd.) to continuously pressurize until free electrolyte appears, collect the electrolyte into the sample tube and seal it with sealing film;

[0153] ③ If sufficient electrolyte cannot be collected by methods ① and ②, an extraction experiment is required. The specific operation is as follows: Add a mixture of 5g / Ah dichloromethane and cyclohexylbenzene (volume ratio of 1:9) to the battery as an extractant and record the amount of extractant used. Then, put the battery into an aluminum-plastic bag and seal it with a heat sealer. Let it stand at room temperature (25℃) for 4 days to allow the electrolyte in the electrode to mix thoroughly with the dichloromethane. Then, use a pipette to draw the mixture of extractant and electrolyte into a 5mL sample tube and seal the sample tube with sealing film.

[0154] The method for testing the presence of DMVSP in the electrolyte using nuclear magnetic resonance spectroscopy is as follows: 1 mL of the collected electrolyte sample is placed in a sample tube, and 0.5 mL of CDCl3 (deuterated chloroform) is injected into the sample tube using a syringe to fully dissolve the sample. The NMR spectrum of the electrolyte is then tested using a nuclear magnetic resonance spectrometer (Brook 400MHz NMR spectrometer) and compared with the DMVSP standard curve (obtained by performing the same test with pure DMVSP) to help confirm the presence of DMVSP in the electrolyte.

[0155] If the presence of DMVSP in the electrolyte is detected by nuclear magnetic resonance spectroscopy, the mass percentage of DMVSP in the electrolyte is determined by gas chromatography (Thermo Fisher Scientific Trace-1610) as follows: the collected electrolyte sample is injected into a 2 mL sample vial using a microsyringe, the response curve of the electrolyte sample is tested, and the result is compared with the DMVSP standard curve (obtained by performing the same test with pure DMVSP) to obtain the mass percentage of DMVSP in the electrolyte.

[0156] (2) The contact angle b between the positive electrode active material layer and the solution

[0157] The contact angle was measured using a contact angle measuring instrument (Beijing Zhongyi Kexin Technology Co., Ltd. JC2000D2M). The specific test method is as follows:

[0158] 1) Positive electrode pretreatment: After disassembling the empty battery (using the empty battery method of testing the mass percentage a of DMVSP in the electrolyte), cut a positive electrode sheet of approximately 8.5*8cm using ceramic scissors. After placing the positive electrode sheet at room temperature (25℃) for 8 hours, the two ends of the electrode sheet can be fixed on the test fixture to start the test.

[0159] 2) Place the device for fixing the electrode on the sample placement stage of the contact angle measuring instrument;

[0160] 3) The electrolyte is dripped onto the electrode using a syringe, and the contact angle of the solution when it falls onto the electrode for 0.05 s is measured. The contact angle is calculated using the five-point fitting method and image analysis method. The solution is prepared by mixing ethylene carbonate EC and methyl ethyl carbonate EMC at a mass ratio of 3:7, and adding lithium hexafluorophosphate to adjust the concentration of lithium hexafluorophosphate to 1 mol / L.

[0161] (3) Powder resistivity c of the positive electrode active material layer

[0162] Discharge the battery to 0.33C, disassemble it, and place the positive electrode in a fume hood for 24 hours. Then, collect 1g of positive electrode powder with a scraper. Ball mill the scraped positive electrode powder at a speed of 300r / min using 0.6mm diameter zirconia balls with a ball-to-powder ratio of 5:1 for 20 minutes. After ball milling, place the powder on a four-probe resistivity tester (ST2722 semiconductor powder resistivity tester from Suzhou Jingge Electronics Co., Ltd.) to test the powder resistivity. The specific operation method is as follows: place the powder on the electrode, apply pressure to the powder with the other electrode, and match the pressure intensity according to the material. The pressure intensity is 10MPa, and the powder resistivity value is read.

[0163] The performance of the batteries obtained in each embodiment and comparative example was tested, and the test results are shown in Table 1. The specific test methods are as follows:

[0164] High-temperature gas production: Charge the battery at a constant current of 0.33C to the upper limit voltage of 3.65V, then charge at a constant voltage until the current is less than or equal to 0.05C. After full charging, test the battery volume using the water displacement method and record it as V0. Then, place the battery in a 60℃ oven for 48 hours. After the battery temperature drops to room temperature (25℃), test the battery volume again using the water displacement method and record it as V1. Calculate the gas production at 60℃ using the following formula:

[0165] Gas production at 60℃ = (V1-V0) / battery capacity.

[0166] The specific method for testing battery volume using the water displacement method is as follows:

[0167] 1) Add an appropriate amount of pure water to the container and test its density ρ with a hydrometer and record it;

[0168] 2) Place the aforementioned container on a balance and tare it (tare the container before testing each cell);

[0169] 3) Submerge the battery cell body along with the tabs in pure water, ensuring that the battery cell does not contact the container wall. After stabilization, take a reading and record the data. Before the battery is placed in the oven for storage, this data is recorded as T0. After the battery is placed in the oven for storage, this data is recorded as T0.

[0170] 4) Turn off the balance and seal the container to prevent the reagent from evaporating.

[0171] Calculate V1-V0 using the following formula: V1-V0=T1 / ρ-T0 / ρ.

[0172] DCR: Charge the battery at a constant current and constant voltage of 0.33C to 3.65V with a cutoff current of 0.05C; let it rest for 10 minutes, then discharge it at a constant current of 0.33C to 2.5V. Repeat this cycle twice. Let it rest for 10 minutes, then charge it at a constant current and constant voltage of 0.33C to 3.65V. Discharge it to 50% of the discharge capacity of the second cycle and let it rest for 2 hours. (Discharge capacity of the second cycle) Discharge at 1C for 18 seconds. Record the starting discharge voltage as V3, the voltage after the 18-second discharge as V4, and the 18-second discharge current as I1. RDCR discharge (I1, 18s) = |V3-V4| / I1.

[0173] Table 1

[0174]

[0175]

[0176]

[0177] For the batteries prepared in the various embodiments of the present invention, their DCR ≤ 73Ω and their gas production at 60℃ ≤ 1.52mL / Ah are shown to be low. It can be seen that the batteries containing the positive electrode of the present invention have both low DCR and low gas production.

[0178] Comparing Examples 1-5 with Examples 6-9, and Examples 10-11 with Examples 12-15, it can be seen that when the mass percentage 'a' of DMVSP in the electrolyte and the powder resistivity 'c' of the positive electrode active material layer meet the preferred ranges described in this invention, it is more conducive to balancing the DCR and low gas production of the battery.

[0179] Comparing Examples 1-9 with Examples 10-17, it can be seen that when the battery satisfies 0.5≤a×b×c≤16, the balance between the battery's DCR and low gas production is better.

[0180] According to Comparative Examples 1 to 12, even if the mass percentage of DMVSP in the electrolyte (a), the contact angle between the positive electrode active material layer and the solution (b), and the powder resistivity (c) of the positive electrode active material layer are all within a suitable range, the DCR and gas production of the battery are relatively high when the value of a×b×c exceeds the range of 0.3 to 124 (excluding the two endpoint values).

[0181] As can be seen from the comparison between Example 22 and Example 3, adding methylene methane disulfonate to the electrolyte can reduce the amount of DMVSP while obtaining similar DCR and gas production.

[0182] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this article and are not intended to limit the scope of protection of this article. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this article without departing from the essence and scope of the technical solutions of this article.

Claims

1. A battery comprising an electrolyte and a positive electrode, the positive electrode comprising a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer comprising a positive active material, the positive active material comprising lithium iron phosphate, characterized in that, The electrolyte contains tris(dimethylvinylsilyl)phosphate; The battery satisfies the following relationship: 0.3 < a × b × c < 124. Wherein, a is the mass percentage of the tris(dimethylvinylsilyl)phosphate in the electrolyte; b is the contact angle between the positive electrode active material layer and the solution, in degrees. The solution is composed of ethylene carbonate, methyl ethyl carbonate and lithium hexafluorophosphate, wherein the mass ratio of ethylene carbonate to methyl ethyl carbonate is 3:7, and the concentration of lithium hexafluorophosphate in the solution is 1 mol / L. c is the powder resistivity of the positive electrode active material layer, in Ω·cm; a is 0.0001~0.05, b is 10°~40°, and c is 1~200Ω·cm; The compaction density of the positive electrode sheet is 2.0~3.0 g / cm³. 3 .

2. The battery as described in claim 1, characterized in that, The battery satisfies the following relationship: 0.5≤a×b×c≤16.

3. The battery as described in claim 1, characterized in that, The positive electrode active material layer also contains lithium supplementation additives.

4. The battery as described in claim 3, characterized in that, The lithium supplement additive includes lithium iron ferrite rich in lithium.

5. The battery as described in claim 1, characterized in that, The positive electrode active material also includes at least one of lithium manganese iron phosphate and ternary materials.

6. The battery as claimed in claim 1, characterized in that, The value of c is 5~50 Ω·cm.

7. The battery as claimed in claim 1, characterized in that, The value of a is 0.001 to 0.

01.

8. The battery as claimed in claim 1, characterized in that, The battery satisfies at least one of the following conditions: S1. The particle size Dv50 of the lithium iron phosphate is 0.1~2μm; S2. The electrolyte further comprises methylene methane disulfonate, wherein the mass percentage of methylene methane disulfonate in the electrolyte is 0.00001~0.

05. S3. The battery further includes a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, the negative active material layer comprising graphite, the graphite having a particle size Dv50 of 5~20μm.

9. An electrical device, characterized in that, Includes the battery as described in any one of claims 1 to 8.

Images