Positive electrode slurry, positive electrode sheet, lithium ion battery, electric device

Abstract

The present application relates to the technical field of lithium ion batteries, in particular to a positive electrode slurry, a positive electrode sheet, a lithium ion battery and an electric device, the positive electrode slurry comprises: a positive electrode active material, a conductive agent and an oxidizing agent; wherein the oxidizing agent in the positive electrode slurry releases oxygen in the formation stage. The positive electrode slurry optimizes the SEI structure of the negative electrode surface, reduces the battery impedance; at the same time, the positive electrode slurry is applied to the lithium ion battery, effectively improves the low-temperature discharge capacity and cycle life of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a positive electrode slurry, a positive electrode sheet containing the positive electrode slurry, a lithium ion battery containing the positive electrode sheet, and an electric device containing the lithium ion battery. BACKGROUND

[0002] Lithium ion batteries are widely used in consumer electronics, electric vehicles, and energy storage systems. Improving the overall performance of lithium ion batteries continues to drive the development of the lithium ion battery industry. During the first formation of a lithium ion battery, an SEI film is formed on the surface of the negative electrode. Research shows that the SEI film has an important influence on the electrochemical performance of the battery. Optimizing and designing the SEI film can improve the cycle life and low-temperature discharge performance of the lithium ion battery.

[0003] Currently, most methods for optimizing the SEI film involve adding specific functional electrolyte additives to the electrolyte. However, there are many types of additives, and single-function additives cannot simultaneously solve the cycle life or low-temperature performance. Complex formula combinations of additives can also cause system compatibility problems, which can affect the application of the battery.

[0004] Therefore, there is an urgent need to develop a new scheme for optimizing the negative electrode SEI film to improve the cycle life and low-temperature discharge performance of the lithium ion battery. SUMMARY

[0005] The purpose of the present application is to overcome the deficiencies in the prior art of optimizing the negative electrode SEI film by adding electrolyte additives to improve the cycle life and low-temperature discharge performance of the lithium ion battery. The present application provides a new positive electrode slurry, a positive electrode sheet containing the positive electrode slurry, a lithium ion battery containing the positive electrode sheet, and an electric device containing the lithium ion battery.

[0006] To achieve the above-mentioned purpose, the first aspect of the present application provides a positive electrode slurry, which comprises: a positive electrode active material, a conductive agent, and an oxidizing agent.

[0007] Preferably, the positive electrode slurry further comprises a positive electrode lithium supplement material.

[0008] Preferably, the weight ratio of the positive electrode lithium supplement material to the oxidizing agent is 5-20:1, preferably 7-15:1.

[0009] Preferably, the positive electrode lithium supplement material is selected from lithium compounds and / or lithium-containing composite oxides.

[0010] Preferably, the positive electrode lithium supplement material is selected from lithium compounds and / or lithium-containing composite oxides.

[0011] Preferably, the lithium compound is selected from at least one of Li2O, Li2O2, LiF, Li3N, Li2S, Li2CO3, Li2C2O4, Li2C4O4 and Li2C3O6.

[0012] Preferably, the lithium-containing composite oxide is selected from at least one of LiMO2, Li2MO2, Li2MO3, Li2MO4, Li3MO4, Li5MO4 and Li6MO4, wherein M is selected from Ni, Co, Mn, Fe.

[0013] Preferably, the oxidizing agent is selected from permanganate and / or chlorate.

[0014] Preferably, the permanganate is selected from at least one of LiMnO4, NaMnO4, KMnO4, NH4MnO4, Ca(MnO4)2, Ba(MnO4)2, Zn(MnO4)2, Mg(MnO4)2, Cu(MnO4)2, Fe(MnO4)3 and Al(MnO4)3.

[0015] Preferably, the chlorate is selected from at least one of NH4ClO3, LiClO3, NaClO3, KClO3, Mg(ClO3)2 and Al(ClO3)3.

[0016] The second aspect of the present application provides a positive electrode tab, comprising a positive electrode current collector and a positive electrode coating layer on the surface of the positive electrode current collector, wherein the positive electrode coating layer is prepared from the positive electrode slurry provided by the first aspect.

[0017] Preferably, the impedance of the positive electrode tab is 10-100 Ω·cm, preferably 15-60 Ω·cm.

[0018] Preferably, the thickness of the positive electrode coating layer is 1-1000 μm, preferably 5-500 μm.

[0019] The third aspect of the present application provides a lithium ion battery, comprising the positive electrode tab provided by the second aspect, and a negative electrode tab and a separator.

[0020] Preferably, the lithium ion battery is subjected to formation to form an SEI film on the surface of the negative electrode tab.

[0021] Preferably, the conditions of the formation include: temperature of 40-70 ℃, preferably 45-60 ℃; vacuum degree of -95 kPa to -25 kPa, preferably -85 kPa to -45 kPa.

[0022] More preferably, the formation process includes: a first formation stage, a second formation stage, and a third formation stage; wherein, the first formation stage includes: charging to 2-3.4V at 0.02-0.2C; the second formation stage includes: charging to 3.6-4V at a constant current and constant voltage of 0.2-0.5C; and the third formation stage includes: charging to 4.3-4.5V at a constant current and constant voltage of 0.02-0.1C.

[0023] A fourth aspect of the present invention provides an electrical device, the electrical device comprising the lithium-ion battery provided in the third aspect.

[0024] Compared with the prior art, the present invention has the following advantages: The positive electrode slurry provided by the present invention adds an oxidant, which releases oxygen during the formation stage, thereby optimizing the SEI composition and content of each component of the negative electrode, thereby reducing the battery impedance, especially the battery impedance at low temperature, and increasing the battery's low-temperature discharge capability; at the same time, the optimized SEI film structure is stable and can block the side reactions between the electrolyte and the electrode, thereby increasing the battery's cycle life. Detailed Implementation

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] In this invention, unless otherwise specified, "first," "second," and "third" do not indicate a sequence or limit on any step or material; they are merely used to indicate that these are not the same material or step. For example, in "first mix," "second mix," and "third mix," "first," "second," and "third" are used only to indicate that these are not the same mix.

[0027] The first aspect of the present invention provides a positive electrode slurry, the positive electrode slurry comprising: a positive electrode active material, a conductive agent, and an oxidant;

[0028] In the positive electrode slurry, the oxidant releases oxygen during the formation stage.

[0029] The inventors discovered that by adding an oxidant to the positive electrode slurry, which releases oxygen during the formation stage, the SEI composition and content of each component on the negative electrode side are optimized, thereby reducing battery impedance, especially at low temperatures, and increasing the battery's low-temperature discharge capability. At the same time, the optimized SEI film structure is stable and can block side reactions between the electrolyte and the electrode, increasing the battery's cycle life.

[0030] In some embodiments of the present application, preferably, the positive electrode slurry further comprises a positive electrode lithium supplementing material. According to the present application, the addition of the positive electrode lithium supplementing material in the positive electrode slurry can compensate for the consumption of lithium ions in the formation of SEI film during the formation reaction, provide sufficient lithium ions for the battery, and further increase the cycle life of the lithium ion battery.

[0031] According to the present application, the simultaneous addition of the oxidizing agent (e.g., permanganate and / or chlorate) and the positive electrode lithium supplementing material during the preparation of the positive electrode of the battery optimizes the SEI structure on the negative electrode surface, reduces the impedance of the battery, especially at low temperatures, and improves the low-temperature discharge capacity of the battery at low temperatures. At the same time, the oxidizing agent can also increase the utilization rate of the positive electrode lithium supplementing material, further improving the energy density, power density, and cycle life of the battery.

[0032] In some embodiments of the present application, preferably, the weight ratio of the positive electrode lithium supplementing material and the oxidizing agent is 5-20:1, for example, 5:1, 7:1, 10:1, 12:1, 15:1, 20:1, and any value in the range formed by any two numerical values, preferably 7-15:1. By adjusting the above weight ratio range, the utilization rate of the positive electrode lithium supplementing material is improved, thereby effectively improving the electrochemical performance of the lithium ion battery. When the weight ratio of the positive electrode material and the oxidizing agent is less than 5:1, the oxidizing agent is added too much, which reduces the energy density of the battery; when the weight ratio of the positive electrode lithium supplementing material and the oxidizing agent is greater than 20:1, the oxidizing agent is added too little, which cannot sufficiently optimize the SEI film on the negative electrode and cannot well improve the utilization rate of the lithium supplementing material.

[0033] In some embodiments of the present application, preferably, the weight ratio of the positive electrode active material, the conductive agent, the oxidizing agent, and the positive electrode lithium supplementing material is 100:0.1-5:0.1-2:0.5-10, for example, 100:1:0.1:0.5, 100:1:0.2:0.8, 100:1:0.2:1, 100:1:0.2:4, 100:1:0.3:2, 100:1:0.3:3, 100:1:0.4:2.5, 100:1:0.4:4, 100:1:1:5, 100:3:1:5, and any value in the range formed by any two numerical values, preferably 100:0.5-3:0.2-1:1-5. The use of the preferred weight ratio can maximize the energy density of the battery, and the addition of the oxidizing agent in the preferred range can maximize the energy density of the battery and reduce the impedance of the battery.

[0034] In the present application, unless otherwise specified, the weight ratio of the positive electrode active material, the conductive agent, the oxidizing agent, and the positive electrode lithium supplementing material is 100:0.1-5:0.1-2:0.5-10 means that, relative to 100 parts by weight of the positive electrode active material, the conductive agent is used in an amount of 0.1-5 parts by weight, the oxidizing agent is used in an amount of 0.1-2 parts by weight, and the positive electrode lithium supplementing material is used in an amount of 0.5-10 parts by weight.

[0035] In the present application, the type of the positive electrode lithium supplementing material has a wide selection range, as long as the positive electrode lithium supplementing material releases lithium ions during high-voltage decomposition. Preferably, the positive electrode lithium supplementing material is selected from lithium compounds and / or lithium-containing composite oxides.

[0036] In some embodiments of the present application, preferably, the lithium compound is selected from at least one of Li2O, Li2O2, LiF, Li3N, Li2S, Li2CO3, Li2C2O4, Li2C4O4, and Li2C3O6.

[0037] In some embodiments of the present application, preferably, the lithium-containing composite oxide is selected from at least one of LiMO2, Li2MO2, Li2MO3, Li2MO4, Li3MO4, Li5MO4, and Li6MO4, wherein M is selected from Ni, Co, Mn, Fe. In the present application, the lithium-containing composite oxide includes, but is not limited to, LiNiO2, Li2MnO3, Li2NiO3, Li5FeO4, Li6CoO4, etc.

[0038] In the present application, the type of the oxidizing agent has a wide selection range. Preferably, the oxidizing agent is selected from permanganates and / or chlorates.

[0039] In some embodiments of the present application, preferably, the permanganate is selected from at least one of LiMnO4, NaMnO4, KMnO4, NH4MnO4, Ca(MnO4)2, Ba(MnO4)2, Zn(MnO4)2, Mg(MnO4)2, Cu(MnO4)2, Fe(MnO4)3, and Al(MnO4)3.

[0040] In some embodiments of the present application, preferably, the chlorate is selected from at least one of NH4ClO3, LiClO3, NaClO3, KClO3, Mg(ClO3)2, and Al(ClO3)3.

[0041] In the present application, the positive electrode slurry includes a binder and a dispersant in addition to the positive electrode active material, the conductive agent, the oxidizing agent, and the positive electrode lithium supplementing material. Further preferably, the weight ratio of the positive electrode active material, the binder, and the dispersant is 100:0.1-5:0.1-5. In the present application, the weight ratio of each component is equivalent to the feeding ratio of each component unless otherwise specified.

[0042] In some embodiments of the present application, preferably, the positive electrode active material is selected from at least one of lithium iron phosphate LiFePO4, LiCoO2, LiMn2O4, LiNi 0.5 Mn 1.5 O4, LiMn x Fe 1-x O4(0 y Co z M’ 1-y-z (0.6≤y≤0.95, 0.01≤z≤0.2, y+z<1, M’ is selected from Mn and / or Al).

[0043] In some embodiments of the present application, preferably, the conductive agent is selected from at least one of graphite, carbon black, acetylene black, and graphene.

[0044] In some embodiments of the present application, preferably, the binder is selected from at least one of fluorine-containing resin and / or polyolefin, further preferably polyvinylidene fluoride, polyvinylidene difluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose, and butadiene-styrene latex.

[0045] In some embodiments of the present application, preferably, the dispersant includes, but is not limited to, polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), sodium polyacrylate (PAANa), ammonium polyacrylate (PAA-NH4), polystyrene sulfonic acid (PSSA), polyacrylamide (PAMA), polyethylenimine (PEI), polyethylene glycol octylphenyl ether, polyoxyethylene ether, and the like.

[0046] In the present application, the positive electrode slurry also contains a solvent unless otherwise specified, as long as the solvent uniformly disperses the positive electrode active material, the conductive agent, the positive electrode lithium supplementing material, the oxidizing agent, the binder, and the dispersant. Preferably, the solvent includes, but is not limited to, N-methylpyrrolidone, toluene, xylene, n-heptane, and the like.

[0047] In some embodiments of the present application, preferably, the solid content of the positive electrode slurry is 40-80 wt%, for example, 40 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 80 wt%, and any value in the range between any two of these values, preferably 50-70 wt%, more preferably 55-65 wt%.

[0048] In some embodiments of the present application, preferably, the viscosity of the positive electrode slurry is 1000-6000 mPa·s, for example, 1000 mPa·s, 1500 mPa·s, 2500 mPa·s, 3000 mPa·s, 3500 mPa·s, 4000 mPa·s, 4500 mPa·s, 5000 mPa·s, 6000 mPa·s, and any value in the range between any two of these values, preferably 2500-5000 mPa·s. In the present application, the viscosity parameter is tested by a rheometer, and the viscosity is 50 s -1 The following viscosity values.

[0049] In a specific embodiment of the present application, the positive electrode slurry comprises: positive electrode active material, conductive agent, oxidizing agent, positive electrode lithium supplement material, binder, dispersant and solvent; wherein the weight ratio of the positive electrode active material, conductive agent, oxidizing agent, positive electrode lithium supplement material, binder, dispersant is 100:0.1-5:0.1-2:0.5-10:0.1-5:0.1-5, preferably 100:0.5-3:0.2-1:1-5:0.1-5:0.1-5; the solid content of the positive electrode slurry is 40-80 wt%, preferably 50-70 wt%, more preferably 55-65 wt%.

[0050] The second aspect of the present application provides a positive electrode tab, which comprises a positive electrode current collector and a positive electrode coating on the surface of the positive electrode current collector, and the positive electrode coating is prepared from the positive electrode slurry provided by the first aspect.

[0051] In an embodiment of the present application, the positive electrode tab comprises: a positive electrode current collector and a positive electrode coating loaded on the positive electrode current collector, wherein the positive electrode coating comprises: positive electrode active material, conductive agent and oxidizing agent, and the weight ratio of the positive electrode active material, conductive agent and oxidizing agent is 100:0.1-5:0.1-2, preferably 100:0.5-3:0.2-1.

[0052] In one embodiment of the present application, the positive electrode coating further comprises a binder and a dispersant. The weight ratio of the positive electrode active material, the conductive agent, the oxidant, the positive electrode lithium supplement material, the binder and the dispersant is 100:0.1-5:0.1-2:0.5-10:0.1-5:0.1-5, preferably 100:0.5-3:0.2-1:0.5-3:1-5:0.1-5.

[0053] In another embodiment of the present application, the positive electrode tab comprises a positive electrode current collector and the positive electrode coating loaded on the positive electrode current collector, wherein the positive electrode coating comprises the positive electrode active material, the conductive agent, the oxidant and the positive electrode lithium supplement material, and the weight ratio of the positive electrode active material, the conductive agent, the oxidant and the positive electrode lithium supplement material is 100:0.1-5:0.1-2:0.5-10, preferably 100:0.5-3:0.2-1:1-5.

[0054] In one embodiment of the present application, the positive electrode coating further comprises a binder and a dispersant. The weight ratio of the positive electrode active material, the conductive agent, the oxidant, the positive electrode lithium supplement material, the binder and the dispersant is 100:0.1-5:0.1-2:0.5-10:0.1-5:0.1-5, preferably 100:0.5-3:0.2-1:0.5-3:1-5:0.1-5.

[0055] In the present application, the positive electrode current collector includes, but is not limited to, aluminum foil and the like, unless otherwise specified.

[0056] In some embodiments of the present application, preferably, the impedance of the positive electrode tab is 10-100 Ω·cm, for example, 10 Ω·cm, 15 Ω·cm, 20 Ω·cm, 30 Ω·cm, 35 Ω·cm, 40 Ω·cm, 50 Ω·cm, 60 Ω·cm, 100 Ω·cm, and any value in the range between any two of the numerical values, preferably 15-60 Ω·cm. In the present application, the impedance parameter is measured by the four-probe method.

[0057] In some embodiments of the present application, preferably, the thickness of the positive electrode coating is 1-1000 μm, for example, 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 800 μm, 1000 μm, and any value in the range between any two of the numerical values, preferably 5-500 μm. In the present application, the thickness parameter is measured by a micrometer or a micrometer gauge.

[0058] In the present application, the preparation method of the positive electrode tab has a wide range of choices. Preferably, the positive electrode slurry provided in the first aspect is coated on the positive electrode current collector, and then dried, rolled and die-cut to obtain the positive electrode tab.

[0059] In the present application, the physical property parameters of the positive electrode slurry are defined as above, and the present application does not repeat here.

[0060] In an embodiment of the present application, the positive electrode slurry is prepared by mixing the positive electrode active material, the conductive agent, the oxidizing agent, the binder, the dispersing agent and the solvent.

[0061] In another embodiment of the present application, the positive electrode slurry is prepared by mixing the positive electrode active material, the conductive agent, the oxidizing agent, the positive electrode lithium supplement material, the binder, the dispersing agent and the solvent.

[0062] In the present application, the types of the positive electrode active material, the conductive agent, the oxidizing agent, the positive electrode lithium supplement material, the binder, the dispersing agent and the solvent are defined as above, and the present application does not repeat here without special circumstances.

[0063] In the present application, the mixing process has a wide range of choices, as long as the positive electrode active material, the conductive agent, the oxidizing agent, the positive electrode lithium supplement material, the binder, the dispersing agent and the solvent are mixed uniformly. Preferably, the mixing conditions include: temperature of 15-40℃, preferably 20-30℃; time of 0.1-5h, preferably 0.5-2h.

[0064] In some embodiments of the present application, preferably, the coating conditions include: controlling the area density of the positive electrode slurry on the positive electrode current collector to be 200-800g / m 2 , for example, 200g / m 2 , 300g / m 2 , 350g / m 2 , 400g / m 2 , 450g / m 2 , 500g / m 2 , 600g / m 2 , 800g / m 2 , and any value in the range between any two values, preferably 300-600g / m 2 . In the present application, the positive electrode slurry by dry weight refers to the slurry after removing the solvent from the positive electrode slurry.

[0065] In the present application, by controlling the area density of the positive electrode slurry coated on the positive electrode current collector to be 200-800g / m 2 and the viscosity of the positive electrode slurry to be 1000-6000mPa·s, the impedance of the positive electrode sheet satisfies 10-100Ω·cm.

[0066] In some embodiments of the present application, preferably, the drying condition comprises a temperature of 60-150℃, preferably 80-120℃, and a time of 5-20h, preferably 8-15h. In the embodiments of the present application, the drying is performed in an oven, but the present application is not limited thereto.

[0067] In some embodiments of the present application, preferably, the rolling condition comprises a pressure of 0.1-20MPa, preferably 0.5-15MPa, and a rotating speed of 0.1-20rpm, preferably 0.1-10rpm. Further preferably, the rolling is performed in a rolling machine, but the present application is not limited thereto.

[0068] The third aspect of the present application provides a lithium ion battery, which comprises the positive electrode sheet provided by the second aspect, and a negative electrode sheet and a separator.

[0069] In some embodiments of the present application, preferably, the lithium ion battery is subjected to formation to form a SEI film on the surface of the negative electrode sheet.

[0070] In some embodiments of the present application, preferably, the formation temperature is 40-70℃, for example, 40℃, 45℃, 50℃, 55℃, 60℃, 70℃, and any value in the range consisting of any two of them, preferably 45-60℃. In the present application, when the formation temperature is in the above range, it is beneficial to promote the decomposition of the oxidizing agent and increase the optimization effect of the negative electrode SEI film.

[0071] In some embodiments of the present application, preferably, the vacuum degree of the formation is -95kPa to -25kPa, for example, -95kPa, -85kPa, -75kPa, -65kPa, -55kPa, -45kPa, -35kPa, -25kPa, and any value in the range consisting of any two of them, preferably -85kPa to -45kPa. In the present application, when the formation process is performed under the above vacuum degree, it is beneficial to remove the unreacted oxygen in the battery system and prevent excessive oxygen from having an adverse effect on the battery system.

[0072] In some embodiments of the present application, preferably, the formation process comprises a first formation stage, a second formation stage and a third formation stage; wherein the first formation stage comprises constant current constant voltage charging at 0.02-0.2C to 2-3.4V; the second formation stage comprises constant current constant voltage charging at 0.2-0.5C to 3.6-4V; and the third formation stage comprises constant current constant voltage charging at 0.02-0.1C to 4.3-4.5V. In the present application, the first formation stage aims to form SEI film on the surface of the negative electrode sheet; the second formation stage aims to charge to near full state without causing negative effects on the battery, thereby shortening the formation process time; and the third formation stage decomposes the oxidizing agent to release oxygen.

[0073] In a specific embodiment of the present application, the first formation stage comprises constant current constant voltage charging at 0.05C to 3V; the second formation stage comprises constant current constant voltage charging at 0.33C to 3.8V; and the third formation stage comprises constant current constant voltage charging at 0.05C to 4.4V.

[0074] In some embodiments of the present application, preferably, in the SEI film, the content of Li2CO3 is 40-80wt%, for example, 40wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 80wt%, and any value in the range between any two numerical values, preferably 50-70wt%; and the content of Li2O is 10-40wt%, for example, 10wt%, 15wt%, 25wt%, 35wt%, 40wt%, and any value in the range between any two numerical values, preferably 15-35wt%.

[0075] In the present application, unless otherwise specified, the content of Li2CO3 and the content of Li2O in the SEI film are tested by XPS (X-ray photoelectron spectroscopy), and the characteristic peaks of Li2CO3 and Li2O are peak-fitted.

[0076] In the present application, in addition to Li2CO3 and Li2O, the SEI film also comprises organic lithium salt.

[0077] In some embodiments of the present application, preferably, the thickness of the SEI film is 2-200nm, for example, 2nm, 10nm, 20nm, 50nm, 80nm, 100nm, 150nm, 200nm, and any value in the range between any two numerical values, preferably 10-100nm.

[0078] In the present application, unless otherwise specified, the thickness of the SEI film is obtained by TEM (transmission electron microscope) test.

[0079] In some embodiments of the present application, preferably, the working temperature of the lithium ion battery is -20℃ to 65℃, for example, -20℃, -10℃, 0℃, 10℃, 20℃, 25℃, 30℃, 50℃, 65℃, and any value in the range between any two of the values, preferably 20-30℃.

[0080] The fourth aspect of the present application provides a power consuming device, which comprises the lithium ion battery provided in the third aspect.

[0081] In the present application, the power consuming device includes, but is not limited to, a mobile phone, a car, and the like, unless otherwise specified.

[0082] According to a particularly preferred embodiment of the present application, a positive electrode slurry comprises: a positive electrode active material, a conductive agent, an oxidizing agent, and a positive electrode lithium supplementing material; wherein, during the formation stage of the lithium ion battery, the oxidizing agent in the positive electrode slurry releases oxygen;

[0083] The weight ratio of the positive electrode active material, the conductive agent, the oxidizing agent, and the positive electrode lithium supplementing material is 100:0.5-3:0.2-1:1-5; the weight ratio of the positive electrode lithium supplementing material and the oxidizing agent is 7-15:1.

[0084] The positive electrode lithium supplementing material is selected from a lithium compound and / or a lithium-containing composite oxide; the lithium compound is selected from at least one of Li2O, Li2O2, LiF, Li3N, Li2S, Li2CO3, Li2C2O4, Li2C4O4, and Li2C3O6; the lithium-containing composite oxide is selected from at least one of LiMO2, Li2MO2, Li2MO3, Li2MO4, Li3MO4, Li5MO4, and Li6MO4, wherein M is selected from Ni, Co, Mn, and Fe; the oxidizing agent is selected from a permanganate and / or a chlorate.

[0085] The present application will be described in detail below through examples.

[0086] The impedance parameter is measured by the four-probe method; the thickness parameter is measured by a micrometer or a micrometer.

[0087] The Li2CO3 content and the Li2O content in the SEI film are both tested by XPS (X-ray photoelectron spectroscopy), and the characteristic peaks corresponding to Li2CO3 and Li2O are peak-fitted.

[0088] The thickness parameter of the SEI film is obtained by TEM (transmission electron microscope) testing.

[0089] Capacity retention test method at different temperatures: (1) At 25±5℃, charge to the upper limit voltage of the battery (0.05C current cutoff) at 1 / 3C (C is the rated capacity of the battery), stand for 10 min, then discharge to the lower limit voltage of the battery at 1 / 3C, the obtained capacity is C0; (2) Charge to the upper limit voltage of the battery (0.05C current cutoff) at 1 / 3C, transfer the battery to the constant temperature oven, set the temperature of the constant temperature oven to the temperature to be tested, stand for 12h to make the temperature of the battery reach the temperature to be tested; (3) Discharge to the lower limit voltage of the battery at 1 / 3C, the obtained capacity is C1, C1 / C0 is the capacity retention at this temperature. Repeat steps (1)-(3) as above to obtain the capacity retention of the battery at different temperatures.

[0090] 25℃ cycle 1000 times capacity retention test method: (1) At 25±5℃, charge to the upper limit voltage of the battery (0.05C current cutoff) at 0.5C (C is the rated capacity of the battery), stand for 10 min; (2) Discharge to the lower limit voltage of the battery at 0.5C, the obtained capacity is C0, stand for 10 min; Repeat steps (1)-(2) 1000 times, the discharge capacity of the 1000th cycle is C1000, C1000 / C0 is the 25℃ cycle 1000 times capacity retention.

[0091] Example 1

[0092] (1) Dissolve the binder (PVDF) in the solvent (NMP), add the conductive agent (carbon nanotube) and disperse uniformly, then add the positive electrode active material (LiFePO4), stir uniformly, then add the positive electrode lithium supplement material (Li2O), stir uniformly, then add the oxidizing agent (KMnO4) to obtain the positive electrode slurry P1 with a solid content of 60.1wt% (viscosity is 3500mPa·s);

[0093] The weight ratio of the positive electrode active material, the conductive agent, the binder, the oxidizing agent and the positive electrode lithium supplement material is 100:1:2.5:0.2:1.

[0094] (2) Filter the above positive electrode slurry P1 through a 200 mesh screen and coat on the aluminum foil, control the surface density to be 420g / m 2 , after baking, rolling, die cutting, form a positive electrode coating with a thickness of 172μm on the aluminum foil to obtain the positive electrode sheet S1;

[0095] The positive electrode coating is composed of the positive electrode active material, the conductive agent, the binder, the oxidizing agent and the positive electrode lithium supplement material with a weight ratio of 100:1:2.5:0.2:1; the impedance of the above positive electrode sheet S1 is 20.8Ω·cm;

[0096] (3) Assembling the above positive electrode sheet S1, negative electrode sheet and separator to obtain a lithium ion battery;

[0097] The above lithium ion battery is subjected to formation at 45±5℃, first charged to 3V at 0.05C, then charged to 3.8V at 0.33C constant current and constant voltage, then charged to 4.4V (0.005C cut-off) at 0.05C constant current and constant voltage, the formation process maintains negative pressure pumping, the negative pressure is-65kPa, then after secondary injection, aging, capacity distribution, self-discharge detection and sealing, a finished lithium ion battery Q1 is obtained, and battery performance test is carried out, and the test results are shown in Table 1.

[0098] Example 2

[0099] (1) The binder (PVDF) is dissolved in the solvent (NMP), the conductive agent (carbon nanotube) is uniformly dispersed, then the positive electrode active material (LiFePO4) is added, the positive electrode lithium supplement material (Li5FeO4) is added after stirring, the oxidizing agent (KMnO4) is added after stirring, and a positive electrode slurry P2 with a solid content of 61.2wt% (viscosity of 3600mPa·s) is obtained;

[0100] The weight ratio of the positive electrode active material, the conductive agent, the binder, the oxidizing agent and the positive electrode lithium supplement material is 100:1:2.5:0.3:2.

[0101] (2) The above positive electrode slurry P2 is filtered through a 200 mesh screen and coated on an aluminum foil, and the surface density is controlled to be 420g / m 2 , after baking, rolling and die cutting, a positive electrode coating with a thickness of 172μm is formed on the aluminum foil, and a positive electrode sheet S2 is obtained;

[0102] The positive electrode coating is composed of the positive electrode active material, the conductive agent, the binder, the oxidizing agent and the positive electrode lithium supplement material in a weight ratio of 100:1:2.5:0.3:2; the impedance of the above positive electrode sheet S2 is 17.6Ω·cm;

[0103] (3) Assembling the above positive electrode sheet S2, negative electrode sheet and separator to obtain a lithium ion battery;

[0104] The above lithium ion battery is subjected to formation at 45±5℃, first charged to 3V at 0.05C, then charged to 3.8V at 0.33C constant current and constant voltage, then charged to 4.4V (0.005C cut-off) at 0.05C constant current and constant voltage, the formation process maintains negative pressure pumping, the negative pressure is-65kPa, then after secondary injection, aging, capacity distribution, self-discharge detection and sealing, a finished lithium ion battery Q1 is obtained, and battery performance test is carried out, and the test results are shown in Table 1.

[0105] Example 3

[0106] (1) Dissolve the binder (PVDF) in the solvent (NMP), add the conductive agent (carbon nanotube) and disperse uniformly, then add the positive electrode active material (LiFePO4), stir uniformly, then add the positive electrode lithium supplement material (Li2C2O4), stir uniformly, then add the oxidizing agent (KClO3), to obtain a positive electrode slurry P3 with a solid content of 59.3wt% (viscosity of 4000mPa·s);

[0107] Among them, the weight ratio of the positive electrode active material, the conductive agent, the binder, the oxidizing agent and the positive electrode lithium supplement material is 100:1:2.5:0.3:3;

[0108] (2) The above positive electrode slurry P3 is filtered through a 200 mesh screen and coated on an aluminum foil, with the surface density controlled at 420g / m 2 After baking, rolling, and die cutting, a positive electrode coating with a thickness of 171μm is formed on the aluminum foil, to obtain a positive electrode sheet S3;

[0109] Among them, the above positive electrode coating is composed of the positive electrode active material, the conductive agent, the binder, the oxidizing agent and the positive electrode lithium supplement material in a weight ratio of 100:1:2.5:0.3:3; the impedance of the above positive electrode sheet S3 is 18.2Ω·cm;

[0110] (3) The above positive electrode sheet S3, negative electrode sheet and separator are assembled to obtain a lithium ion battery;

[0111] The above lithium ion battery is subjected to formation at 50±5℃, first charged to 3V at 0.05C constant current and constant voltage, then charged to 3.8V at 0.33C constant current and constant voltage, then charged to 4.4V (0.005C cutoff) at 0.04C constant current and constant voltage, the formation process is kept under negative pressure and air extraction, the negative pressure is-65kPa, then sealed after secondary liquid injection, aging, capacity distribution and self-discharge detection, to obtain a finished lithium ion battery Q3, which is subjected to battery performance test, and the test results are shown in Table 1.

[0112] Example 4

[0113] (1) Dissolve the binder (PVDF) in the solvent (NMP), add the conductive agent (carbon nanotube) and disperse uniformly, then add the positive electrode active material (LiFePO4), stir uniformly, then add the positive electrode lithium supplement material (Li2CO3), stir uniformly, then add the oxidizing agent (LiClO3), to obtain a positive electrode slurry P4 with a solid content of 60.4wt% (viscosity of 3600mPa·s);

[0114] Among them, the weight ratio of the positive electrode active material, the conductive agent, the binder, the oxidizing agent and the positive electrode lithium supplement material is 100:1:2.5:0.2:2.5;

[0115] (2) The positive electrode slurry P4 is filtered through a 200-mesh screen and coated on an aluminum foil, with a surface density of 420 g / m 2 After baking, rolling, and die cutting, a positive electrode coating with a thickness of 171 μm is formed on the aluminum foil, and a positive electrode tab S4 is obtained;

[0116] The positive electrode coating consists of positive electrode active material, conductive agent, binder, oxidizing agent, and positive electrode lithium supplement material in a weight ratio of 100:1:2.5:0.2:2.5; the impedance of the positive electrode tab S4 is 18.7 Ω·cm;

[0117] (3) The positive electrode tab S4, negative electrode tab, and separator are assembled to obtain a lithium ion battery;

[0118] The lithium ion battery is subjected to formation at 50±5℃, first charged to 3V at 0.05C constant current and constant voltage, then charged to 3.8V at 0.33C constant current and constant voltage, and then charged to 4.35V (0.005C cutoff) at 0.05C constant current and constant voltage. The formation process maintains negative pressure and the negative pressure is-65 kPa. After secondary injection, aging, capacity distribution, and self-discharge detection, the product lithium ion battery Q4 is sealed and subjected to battery performance test. The test results are shown in Table 1.

[0119] Example 5

[0120] (1) The binder (PVDF) is dissolved in the solvent (NMP), the conductive agent (carbon nanotube) is uniformly dispersed, and then the positive electrode active material (LiFePO4) is added. After stirring, the positive electrode lithium supplement material (Li2NiO2) is added, and then the oxidizing agent (NaMnO4) is added to obtain a positive electrode slurry P5 with a solid content of 62.4wt% (viscosity of 3300 mPa·s);

[0121] The weight ratio of the positive electrode active material, conductive agent, binder, oxidizing agent, and positive electrode lithium supplement material is 100:1:2.5:0.4:6;

[0122] (2) The positive electrode slurry P5 is filtered through a 200-mesh screen and coated on an aluminum foil, with a surface density of 420 g / m 2 After baking, rolling, and die cutting, a positive electrode coating with a thickness of 172 μm is formed on the aluminum foil, and a positive electrode tab S5 is obtained;

[0123] The positive electrode coating consists of positive electrode active material, conductive agent, binder, oxidizing agent, and positive electrode lithium supplement material in a weight ratio of 100:1:2.5:0.4:6; the impedance of the positive electrode tab S5 is 20.4 Ω·cm;

[0124] (3) The positive electrode tab S5, negative electrode tab, and separator are assembled to obtain a lithium ion battery;

[0125] The above lithium ion battery was subjected to formation at 45±5°C, first charged to 3V at 0.05C constant current and constant voltage, then charged to 3.8V at 0.33C constant current and constant voltage, and then charged to 4.3V at 0.05C constant current and constant voltage (0.005C cutoff), the formation process was kept under negative pressure pumping, the negative pressure was-65kPa, then after twice liquid injection, aging, distribution, self-discharge detection, the lithium ion battery Q5 was sealed to obtain a finished product, and the battery performance test was carried out, and the test results are shown in Table 1.

[0126] Example 6

[0127] According to the method of Example 1, except that,

[0128] In step (1), the weight ratio of the positive electrode active material, the conductive agent, the binder, the oxidant and the positive electrode lithium supplement material was replaced by 100:1:2.5:0.2:4, and the remaining conditions were the same, to obtain a positive electrode slurry P6 with a solid content of 59.8wt% (viscosity of 3900mPa·s);

[0129] In step (2), a positive electrode coating with a thickness of 172μm was formed on the aluminum foil to obtain a positive electrode sheet S6;

[0130] The positive electrode coating is composed of the positive electrode active material, the conductive agent, the binder, the oxidant and the positive electrode lithium supplement material in a weight ratio of 100:1:2.5:0.2:4; the impedance of the positive electrode sheet S6 is 21.2Ω·cm;

[0131] In step (3), a finished product lithium ion battery Q6 was obtained, and the test results are shown in Table 1.

[0132] Example 7

[0133] According to the method of Example 1, except that,

[0134] In step (1), the weight ratio of the positive electrode active material, the conductive agent, the binder, the oxidant and the positive electrode lithium supplement material was replaced by 100:1:2.5:0.2:0.8, and the remaining conditions were the same, to obtain a positive electrode slurry P7 with a solid content of 61.4wt% (viscosity of 3700mPa·s);

[0135] In step (2), a positive electrode coating with a thickness of 172μm was formed on the aluminum foil to obtain a positive electrode sheet S7;

[0136] The positive electrode coating is composed of the positive electrode active material, the conductive agent, the binder, the oxidant and the positive electrode lithium supplement material in a weight ratio of 100:1:2.5:0.2:0.8; the impedance of the positive electrode sheet S7 is 24.2Ω·cm;

[0137] In step (3), a finished lithium ion battery Q7 was obtained, and the test results are shown in Table 1.

[0138] Example 8

[0139] According to the method of Example 1, except that,

[0140] In step (1), the oxidant was replaced by LiMnO4 and NH4ClO3 with a weight ratio of 1:1, and the other conditions were the same, to obtain a positive electrode slurry P8 with a solid content of 61.3wt% (viscosity of 3400mPa·s);

[0141] In step (2), a positive electrode coating with a thickness of 172μm was formed on the aluminum foil to obtain a positive electrode sheet S8;

[0142] The positive electrode coating consists of positive electrode active material, conductive agent, binder, oxidant and positive electrode lithium supplement material in a weight ratio of 100:1:2.5:0.2:1; the impedance of the positive electrode sheet S8 is 25.6Ω·cm;

[0143] In step (3), a finished lithium ion battery Q8 was obtained, and the test results are shown in Table 1.

[0144] Example 9

[0145] According to the method of Example 1, except that,

[0146] In step (1), the oxidant was replaced by Na2Cr2O7, and the other conditions were the same, to obtain a positive electrode slurry P9 with a solid content of 60.2wt% (viscosity of 3500mPa·s);

[0147] In step (2), a positive electrode coating with a thickness of 172μm was formed on the aluminum foil to obtain a positive electrode sheet S9;

[0148] The positive electrode coating consists of positive electrode active material, conductive agent, binder, oxidant and positive electrode lithium supplement material in a weight ratio of 100:1:2.5:0.2:1; the impedance of the positive electrode sheet S9 is 32.6Ω·cm;

[0149] In step (3), a finished lithium ion battery Q9 was obtained, and the test results are shown in Table 1.

[0150] Example 10

[0151] According to the method of Example 1, except that,

[0152] In step (3), the temperature of formation was replaced by 40±5℃, and the other conditions were the same, to obtain a finished lithium ion battery Q10, and the test results are shown in Table 1.

[0153] Example 11

[0154] According to the method of Example 2, no positive electrode lithium supplement material is added, i.e.,

[0155] (1) The binder (PVDF) is dissolved in the solvent (NMP), the conductive agent (carbon nanotube) is uniformly dispersed, and then the positive electrode active material (LiFePO4) is added, and the positive electrode slurry P11 with a solid content of 60.5wt% (viscosity of 3600 mPa·s) is obtained after uniform stirring and the addition of the oxidizing agent (KMnO4);

[0156] The weight ratio of the positive electrode active material, the conductive agent, the binder and the oxidizing agent is 100:1:2.5:0.3.

[0157] (2) The positive electrode slurry P11 is filtered through a 200-mesh screen and coated on an aluminum foil, and the surface density is controlled to be 420 g / m 2 After baking, rolling, and die cutting, the positive electrode coating with a thickness of 172 μm is formed on the aluminum foil, and the positive electrode sheet S11 is obtained.

[0158] The positive electrode coating is composed of the positive electrode active material, the conductive agent, the binder and the oxidizing agent in a weight ratio of 100:1:2.5:0.3; and the impedance of the positive electrode sheet S11 is 42.4 Ω·cm.

[0159] (3) The positive electrode sheet S11, the negative electrode sheet and the separator are assembled to obtain a lithium ion battery.

[0160] The lithium ion battery is formed at 25±5℃, first charged to 3V at 0.05C constant current and constant voltage, then charged to 3.8V at 0.33C constant current and constant voltage, and then charged to 4.4V (0.005C cutoff) at 0.05C constant current and constant voltage. The formation process maintains negative pressure and air exhaust, and the negative pressure is-65kPa. After secondary injection, aging, capacity distribution and self-discharge detection, the finished lithium ion battery Q11 is sealed, and the battery performance test is carried out. The test results are shown in Table 1.

[0161] Comparative Example 1

[0162] According to the method of Example 2, no positive electrode lithium supplement material and oxidizing agent are added, i.e.,

[0163] (1) The binder (PVDF) is dissolved in the solvent (NMP), the conductive agent (carbon nanotube) is uniformly dispersed, and then the positive electrode active material (LiFePO4) is added, and the positive electrode slurry DP1 with a solid content of 61wt% (viscosity of 3300 mPa·s) is obtained;

[0164] The weight ratio of the positive electrode active material, the conductive agent and the binder is 100:1:2.5.

[0165] (2) The positive electrode slurry DP1 is filtered through a 200-mesh screen and coated on an aluminum foil, with the surface density controlled at 420 g / m 2 After baking, rolling, and die cutting, a positive electrode coating with a thickness of 172 μm is formed on the aluminum foil to obtain a positive electrode sheet DS1.

[0166] The positive electrode coating is composed of the positive electrode active material, the conductive agent, and the binder in a weight ratio of 100:1:2.5; and the impedance of the positive electrode sheet DS1 is 114 Ω·cm.

[0167] (3) The positive electrode sheet DS1, the negative electrode sheet, and the separator are assembled to obtain a lithium ion battery.

[0168] The lithium ion battery is subjected to formation at 25±5℃, first charged to 3V at 0.05C constant current and constant voltage, and then charged to 3.8V (0.05C cutoff) at 0.33C constant current and constant voltage. The formation process is carried out under negative pressure extraction, with the negative pressure being -65 kPa. After secondary injection, aging, capacity distribution, and self-discharge detection, the product lithium ion battery DQ1 is sealed and subjected to battery performance testing. The test results are shown in Table 1.

[0169] Comparative Example 2

[0170] According to the method of Example 2, no oxidizing agent is added, i.e.,

[0171] (1) The binder (PVDF) is dissolved in the solvent (NMP), the conductive agent (carbon nanotube) is uniformly dispersed, and then the positive electrode active material (LiFePO4) is added. After stirring, the positive electrode lithium supplement material (Li5FeO4) is added to obtain a positive electrode slurry DP2 with a solid content of 60.2wt% (viscosity of 3600 mPa·s);

[0172] The weight ratio of the positive electrode active material, the conductive agent, the binder, and the positive electrode lithium supplement material is 100:1:2.5:2.

[0173] (2) The positive electrode slurry DP2 is filtered through a 200-mesh screen and coated on an aluminum foil, with the surface density controlled at 420 g / m 2 After baking, rolling, and die cutting, a positive electrode coating with a thickness of 172 μm is formed on the aluminum foil to obtain a positive electrode sheet DS1.

[0174] The positive electrode coating is composed of the positive electrode active material, the conductive agent, the binder, and the positive electrode lithium supplement material in a weight ratio of 100:1:2.5:2; and the impedance of the positive electrode sheet DS2 is 102 Ω·cm.

[0175] (3) The positive electrode sheet DS2, the negative electrode sheet, and the separator are assembled to obtain a lithium ion battery.

[0176] The above lithium ion battery was subjected to formation at 25±5℃, first charged to 3V at 0.05C constant current and constant voltage, then charged to 3.8V at 0.33C constant current and constant voltage, then charged to 4.4V (0.005C cutoff) at 0.05C constant current and constant voltage, the formation process was kept under negative pressure, the negative pressure was-65kPa, then the battery was subjected to secondary liquid injection, aging, distribution, self-discharge detection and sealing to obtain finished lithium ion battery DQ2, the battery performance test was carried out, and the test results are shown in Table 1.

[0177] Comparative Example 3

[0178] According to the method of Comparative Example 2, except that,

[0179] In step (3), the lithium ion battery was not subjected to formation, and the other conditions were the same, to obtain lithium ion battery DQ3, and the test results are shown in Table 1.

[0180] Table 1

[0181]

[0182] Table 1 (continued)

[0183]

[0184] As can be seen from the results in Table 1, compared with Comparative Examples 1-3, the lithium ion battery prepared from the positive electrode slurry provided by the application in Examples 1-11 has higher low-temperature discharge capacity and capacity retention rate, that is, the lithium ion battery prepared from the positive electrode slurry provided by the application has synergistic optimization of power and life.

[0185] The preferred embodiments of the application are described in detail above, but the application is not limited thereto. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the application and fall within the protection scope of the application.

Claims

1. A positive electrode slurry, characterized by, The positive electrode slurry comprises: a positive electrode active material, a conductive agent, a positive electrode lithium supplement material, and an oxidizing agent; the weight ratio of the positive electrode lithium supplement material and the oxidizing agent is 5-20:

1. The oxidizing agent in the positive electrode slurry releases oxygen in the formation stage; the oxidizing agent is selected from permanganate and / or chlorate; The positive electrode slurry has a surface density of 200-800 g / m 2 2 on the positive electrode current collector, and a viscosity of 1000-6000 mPa·s.

2. The positive electrode slurry according to claim 1, characterized by, The weight ratio of the positive electrode lithium supplement material and the oxidizing agent is 7-15:

1.

3. The positive electrode slurry according to claim 1, wherein The weight ratio of the positive electrode active material, the conductive agent, the oxidizing agent, and the positive electrode lithium supplement material is 100:0.1-5:0.1-2:0.5-10.

4. The positive electrode slurry according to claim 3, characterized by, The weight ratio of the positive electrode active material, the conductive agent, the oxidizing agent, and the positive electrode lithium supplement material is 100:0.5-3:0.2-1:1-5.

5. The positive electrode slurry of claim 1, wherein The positive electrode lithium supplement material is selected from lithium compounds and / or lithium-containing composite oxides; The lithium compound is selected from at least one of Li2O, Li2O2, LiF, Li3N, Li2S, Li2CO3, Li2C2O4, Li2C4O4, and Li2C3O6; The lithium-containing composite oxide is selected from at least one of LiMO2, Li2MO2, Li2MO3, Li2MO4, Li3MO4, Li5MO4, and Li6MO4, wherein M is selected from Ni, Co, Mn, Fe.

6. The positive electrode slurry according to any one of claims 1 to 5, wherein The permanganate is selected from at least one of LiMnO4, NaMnO4, KMnO4, NH4MnO4, Ca(MnO4)2, Ba(MnO4)2, Zn(MnO4)2, Mg(MnO4)2, Cu(MnO4)2, Fe(MnO4)3, and Al(MnO4)3; The chlorate is selected from at least one of NH4ClO3, LiClO3, NaClO3, KClO3, Mg(ClO3)2, and Al(ClO3)3.

7. A positive electrode sheet comprising a positive electrode current collector and a positive electrode coating on a surface thereof, characterized by, The positive electrode coating is prepared from the positive electrode slurry of any one of claims 1-6.

8. The cathode electrode of claim 7, wherein, The impedance of the positive electrode tab is 10-100 Ω·cm; And / or, the thickness of the positive electrode coating is 1-1000 μm.

9. The cathode electrode of claim 8, wherein, The impedance of the positive electrode tab is 15-60 Ω·cm; And / or, the thickness of the positive electrode coating is 5-500 μm.

10. A lithium-ion battery, characterized by, The lithium ion battery contains the positive electrode tab of any one of claims 7-9, and a negative electrode tab and a separator.

11. The lithium-ion battery of claim 10, wherein, The lithium ion battery is subjected to formation to form an SEI film on the surface of the negative electrode tab.

12. The lithium-ion battery of claim 11, wherein, The conditions of the formation include: a temperature of 40-70°C; a vacuum degree of -95 kPa to -25 kPa.

13. The lithium-ion battery of claim 12, wherein, The conditions of the formation include: a temperature of 45-60°C; a vacuum degree of -85 kPa to -45 kPa.

14. The lithium-ion battery of claim 11, wherein, The process of the formation includes: a first formation stage, a second formation stage, and a third formation stage; wherein the first formation stage includes: constant current constant voltage charging to 2-3.4 V at 0.02-0.2 C; the second formation stage includes: constant current constant voltage charging to 3.6-4 V at 0.2-0.5 C; and the third formation stage includes: constant current constant voltage charging to 4.3-4.5 V at 0.02-0.1 C.

15. The lithium-ion battery of claim 11, wherein, The SEI film has a content of Li2CO3 of 40-80 wt%; and a content of Li2O of 10-40 wt%; And / or, the SEI film has a thickness of 2-200 nm; And / or, the lithium ion battery has a working temperature of-20℃ to 65℃.

16. The lithium-ion battery of claim 15, wherein, The SEI film has a content of Li2CO3 of 50-70 wt%; and a content of Li2O of 15-35 wt%; And / or, the SEI film has a thickness of 10-100 nm; And / or, the lithium ion battery has a working temperature of 20-30℃.

17. An electrical device, characterized by The electric device comprises the lithium ion battery according to any one of claims 10-16.

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