Positive electrode sheet, and electrochemical device and electronic device containing same

Abstract

The application discloses a positive electrode sheet, an electrochemical device containing the same and electronic equipment. The positive electrode sheet comprises a positive electrode current collector; a positive electrode material layer is arranged on at least one surface of the positive electrode current collector; the positive electrode material layer comprises a positive electrode active material and an oxygen vacancy-containing metal oxide, and the oxygen vacancy-containing metal oxide is dispersed in the positive electrode active material. The membrane sheet resistance of the positive electrode sheet is low, the high-temperature gas generation of the electrochemical device (especially a lithium ion battery) prepared by using the positive electrode sheet is low, and excellent capacity performance and cycle stability can be considered.

Description

Technical Field

[0001] This invention relates to a positive electrode and an electrochemical device and electronic device containing the same. Background Technology

[0002] Lithium manganese iron phosphate (LiMnFePO4) is a lithium-ion battery cathode material with the same olivine-type structure as lithium iron phosphate (LiFePO4), exhibiting excellent structural stability and corresponding battery safety. Furthermore, its voltage plateau (4.1V) is 0.7V higher than that of lithium iron phosphate, which can increase battery energy density by 20% under the same battery design conditions. Therefore, it is a novel lithium battery material that can balance high energy density and high safety. However, lithium manganese phosphate has a lower intrinsic conductivity (<10⁻¹⁰ S / cm), and manganese exhibits a severe Jan-Taylor effect during charge and discharge, leading to structural distortion, hindering lithium-ion diffusion, and ultimately preventing its electrochemical performance from being fully realized.

[0003] Energy density, cycle stability, low impedance, and high-temperature gas generation during high-temperature storage have always been key areas of focus for improving the performance of lithium-ion battery cathode materials. However, it is difficult to achieve all of these in actual production applications. Therefore, how to improve the above-mentioned performance of lithium-ion battery cathode sheets has always been a key focus of the industry. Summary of the Invention

[0004] To address the aforementioned problems of lithium-ion batteries in the prior art, this invention provides a positive electrode and an electrochemical device and electronic device containing the same. This positive electrode has low film resistance, and electrochemical devices (especially lithium-ion batteries) made using this positive electrode exhibit low high-temperature gas generation growth, while also achieving excellent capacity performance and cycle stability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] In a first aspect, the present invention provides a positive electrode sheet comprising a positive current collector; a positive electrode material layer is disposed on at least one surface of the positive current collector; the positive electrode material layer comprises a positive electrode active material and a metal oxide containing oxygen vacancies, wherein the metal oxide containing oxygen vacancies is dispersed in the positive electrode active material.

[0007] In a second aspect, the present invention provides an electrochemical device comprising a positive electrode as described above.

[0008] Thirdly, the present invention provides an electronic device comprising the electrochemical device described above.

[0009] The positive and progressive effects of this invention are as follows:

[0010] In this invention, by introducing metal oxides containing oxygen vacancies into the positive electrode material layer and dispersing them in the positive electrode active material, the resulting positive electrode sheet has a low film resistance. Electrochemical devices (especially lithium-ion batteries) prepared using this positive electrode sheet exhibit low high-temperature gas generation growth and can also achieve excellent cycle stability and capacity performance. Detailed Implementation

[0011] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0012] Positive electrode film

[0013] In the positive electrode sheet provided in the first aspect of the present invention, it includes a positive electrode current collector; a positive electrode material layer is disposed on at least one surface of the positive electrode current collector; the positive electrode material layer includes a positive electrode active material and a metal oxide containing oxygen vacancies, wherein the metal oxide containing oxygen vacancies is dispersed in the positive electrode active material.

[0014] In this invention, by introducing oxygen-vacant metal oxides into the cathode material layer and dispersing these oxygen-vacant metal oxides in the cathode active material, the advantages are as follows: on the one hand, the oxygen-vacant metal oxides have ultra-high conductivity, which can improve the conductivity of the electrode, improve specific capacity utilization and cycle stability; on the other hand, the oxygen vacancies in the oxygen-vacant metal oxides can absorb oxygen anions generated by the cathode active material, reduce interfacial side reactions, reduce gas production, and improve battery stability.

[0015] In some embodiments, the oxygen-vacant metal oxide includes CeO. 2-a TiO 2-a WO 3-a Al2O 3-a and ZrO 2-a One or more of the following, preferably CeO 2-a Wherein, 0 < a ≤ 0.65, and a is preferably 0.1-0.2, and a is, for example, 0.4 or 0.65.

[0016] In some embodiments, the content of the oxygen-vacant metal oxide is 0.2%-2%, for example 0.5% or 1%, the percentage being the mass percentage of the cathode material layer.

[0017] In some specific embodiments, the oxygen-vacant metal oxide is CeO. 1.8 .

[0018] In some specific embodiments, the oxygen-vacant metal oxide is CeO. 1.4 .

[0019] In some specific embodiments, the oxygen-vacant metal oxide is CeO. 1.9 .

[0020] In some specific embodiments, the oxygen-vacant metal oxide is CeO. 1.35 .

[0021] In some specific embodiments, the oxygen-vacant metal oxide is CeO. 1.8 and TiO 1.8 .

[0022] In some specific embodiments, the oxygen-vacant metal oxide is WO. 2.8 .

[0023] In some specific embodiments, the oxygen-vacancy-containing metal oxide is TiO2. 1.8 .

[0024] In some specific embodiments, the oxygen-vacant metal oxide is CeO. 1.6 .

[0025] In this invention, the CeO 2-a The preparation method may include the following steps: dissolving cerium nitrate or cerium chloride in water to obtain an aqueous solution with a concentration of 0.5-2 mol / L, adjusting the pH of the aqueous solution to 2-3, filtering and drying to obtain a precipitate, and calcining the precipitate in air to obtain CeO. 2-a The calcination temperature is 400-600℃, the calcination time is 2-10h, and the oxygen partial pressure of the air atmosphere is 5-15kPa.

[0026] In this invention, the WO 2.8 The preparation method may include the following steps: dissolving ammonium tungstate in water to obtain a mixture, filtering and drying to obtain a precipitate, and calcining the precipitate in air to obtain WO3. 2.8 The concentration of the mixture is 1 mol / L, the calcination temperature is 1100℃, the calcination time is 4 h, and the oxygen partial pressure of the air atmosphere is 14 kPa.

[0027] In this invention, the TiO 1.8 The preparation method may include the following steps: dissolving titanium oxysulfate in water to obtain a mixture, filtering and drying to obtain a precipitate, and calcining the precipitate in air to obtain TiO2. 1.8 The concentration of the mixture is 1 mol / L, the calcination temperature is 1000℃, the calcination time is 4 h, and the oxygen partial pressure of the air atmosphere is 14 kPa.

[0028] In some alternative embodiments, the Dv50 particle size of the oxygen-vacancy-containing metal oxide is 5 nm-1 μm, for example 0.1-0.3 μm, for example 0.15 μm or 0.2 μm.

[0029] In some alternative embodiments, the mass ratio of the positive electrode active material to the oxygen-vacant metal oxide is (90-190):1, preferably (90-99.9):1, more preferably (96-99.5):1, for example 95:1.

[0030] In some alternative embodiments, the positive electrode active material includes lithium manganese iron phosphate and / or ternary positive electrode materials.

[0031] In some preferred embodiments, the positive electrode active material is lithium manganese iron phosphate and a ternary positive electrode material, and the mass ratio of the lithium manganese iron phosphate to the ternary positive electrode material is (40-60):(60-40).

[0032] In this invention, the chemical formula of the lithium manganese iron phosphate can be Li z Mn x Fe 1-x PO4, wherein z is 0.9-1.1, preferably 1.0-1.03, and x is 0-1, preferably 0.6-0.8.

[0033] In this invention, the lithium manganese iron phosphate may be doped with heteroatoms, which include one or more of Ti, Mg, Zr, V, Nb, Mo, W, Al, Ni and Co.

[0034] In this invention, the lithium manganese iron phosphate may further include an outer coating layer, which may be, for example, one or two of a carbon layer and a metal oxide layer; the metal oxide layer preferably includes one or more of aluminum oxide, tungsten oxide, titanium oxide, zirconium oxide, molybdenum oxide and zinc oxide.

[0035] In this invention, the Dv50 particle size of the lithium manganese iron phosphate can be 0.3-2 μm.

[0036] In this invention, the chemical formula of the ternary cathode material can be LiNi. x Co y Mn 1-x-y O2, where 0.6≤x<1, and y is 0-0.2.

[0037] In this invention, the ternary cathode material may be doped with heteroatoms, which include one or more of Ti, Mg, Zr, V, Nb, Mo, W and Al.

[0038] In this invention, the ternary cathode material may further include an outer coating layer, which may be, for example, one or two of a carbon layer and a metal oxide layer; the metal oxide layer preferably includes one or more of aluminum oxide, tungsten oxide, titanium oxide, zirconium oxide, molybdenum oxide and zinc oxide.

[0039] In this invention, the ternary cathode material can be a single-crystal material.

[0040] In this invention, the Dv50 particle size of the ternary cathode material can be 2-6 μm.

[0041] In some specific embodiments, the positive electrode active material includes LiMn 0.6 Fe 0.4 PO4 and LiNi 0.6 Co 0.1 Mn 0.3 O2, the LiMn 0.6 Fe 0.4 The Dv50 particle size of PO4 is 0.67 μm, and the LiNi 0.6 Co 0.1 Mn 0.3 The Dv50 particle size of O2 is 3.58 μm; the LiMn 0.6 Fe 0.4 PO4 and LiNi 0.6 Co 0.1 Mn 0.3 The mass ratio of O2 is 50:50, 40:60, or 60:40.

[0042] In some preferred embodiments, the content of the positive electrode active material is 80% or more, where the percentage is the mass percentage of the positive electrode material layer.

[0043] In some preferred embodiments, the cathode material layer comprises LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and oxygen-vacant metal oxides, such as CeO 1.8 CeO 1.4 CeO 1.9 CeO 1.6 CeO 1.35 TiO 1.8 and WO 2.8 One or more of them.

[0044] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The mass ratio is 47.5:47.5:1.

[0045] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The mass ratio is 47.5:47.5:0.5.

[0046] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.4 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.4 The mass ratio is 47.5:47.5:1.

[0047] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.9 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.9 The mass ratio is 47.5:47.5:1.

[0048] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.35 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.35 The mass ratio is 47.5:47.5:1.

[0049] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The mass ratio is 49.95:49.95:1.

[0050] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The mass ratio is 45:45:1.

[0051] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2, CeO 1.8 and TiO 1.8 The LiMn 0.6 Fe0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2, CeO 1.8 and TiO 1.8 The mass ratio is 47.5:47.5:0.8:0.2.

[0052] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and WO 2.8 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and WO 2.8 The mass ratio is 47.5:47.5:1.

[0053] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and TiO 1.8 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and TiO 1.8 The mass ratio is 47.5:47.5:1.

[0054] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.6 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.6 The mass ratio is 47.5:47.5:1.

[0055] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The mass ratio is 38:57:1.

[0056] In some specific embodiments, the cathode material layer includes LiMn. 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The LiMn 0.6 Fe 0.4 PO4, LiNi 0.6 Co 0.1 Mn 0.3 O2 and CeO 1.8 The mass ratio is 57:38:1.

[0057] In this invention, the positive electrode material layer may further include a conductive agent, the content of which is 1%-3%, for example 1.5%, and the percentage is the mass percentage of the positive electrode material layer.

[0058] In this invention, the conductive agent can be a conventional conductive material in the art, preferably including one or more of conductive carbon black (SuperP), acetylene black, carbon nanotubes (CNT), graphene and vapor-grown carbon fiber reinforcement (VGCF), such as CNT and SP.

[0059] In this invention, the positive electrode material layer may further include a binder, the content of which is 1%-4%, for example 2.5%, and the percentage is the mass percentage of the positive electrode material layer.

[0060] In this invention, the adhesive may be an adhesive conventionally used in the art, preferably including one or both of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), for example, PVDF.

[0061] In some embodiments, the mass ratio of the positive electrode active material, the oxygen-vacancy-containing metal oxide, the conductive agent and the binder in the positive electrode material layer is (90-99.9):(0.2-2):(1-3):(1-4).

[0062] In some embodiments, the positive electrode sheet is prepared by the following method: the positive electrode slurry obtained by thoroughly mixing the components of the positive electrode material layer in a solvent is coated onto at least one surface of the positive electrode current collector, dried, cold-pressed, and cut to obtain the positive electrode sheet.

[0063] The solid content of the positive electrode slurry is preferably 55%-60%.

[0064] The viscosity of the positive electrode slurry is preferably 2000-4000 Pa·s.

[0065] Electrochemical device

[0066] The electrochemical device provided in the second aspect of the present invention includes a positive electrode as described above.

[0067] In this invention, the electrochemical device is preferably a battery.

[0068] In some alternative embodiments, the electrochemical device is a lithium-ion battery; the lithium-ion battery further includes a negative electrode, a separator, and an electrolyte.

[0069] negative electrode sheet

[0070] In this invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer, wherein the negative electrode material layer is disposed on at least one surface of the negative electrode current collector.

[0071] In this invention, the negative electrode material in the negative electrode material layer can be a negative electrode material conventionally used in the art, preferably including one or more of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase carbon microspheres, silicon suboxide and silicon carbide materials, such as artificial graphite.

[0072] In some implementations, the negative electrode material layer also includes a thickener.

[0073] The addition of the thickener can increase the viscosity of the system of each component in the negative electrode slurry. It can be a thickener commonly used in the art to prepare negative electrode sheets, such as sodium carboxymethyl cellulose (CMC).

[0074] In some implementations, the negative electrode material layer further includes a conductive agent.

[0075] The conductive agent is not particularly limited, as long as it is conductive and does not cause chemical changes in the battery. For example, specific materials that can be used include: graphite, such as natural or artificial graphite; carbon-based materials, such as conductive carbon black (Super P), carbon nanotubes (CNTs), acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, or carbon fiber; metal powders or metal fibers, such as copper, nickel, aluminum, or silver; conductive whiskers, such as zinc oxide whiskers or potassium titanate whiskers; conductive metal oxides, such as titanium dioxide; or conductive polymers, such as polyphenylene derivatives.

[0076] In some specific implementations, the conductive agent in the negative electrode material layer is acetylene black.

[0077] In some implementations, the negative electrode material layer further includes a binder.

[0078] The type of adhesive is not particularly limited and can be selected from polyvinylidene fluoride, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid (PAA), ethylene-propylene-diene terpolymer and its sulfonates, styrene-butadiene rubber (SBR), fluororubber and various copolymers, such as SBR.

[0079] In some specific embodiments, the mass ratio of the negative electrode material, conductive agent, binder and thickener in the negative electrode material layer is 96.4:1:1.4:1.2.

[0080] In this invention, the negative electrode current collector can be a conventional negative electrode current collector in the art. As a substrate supporting the negative electrode material layer, the negative electrode current collector is typically a metal foil with a thickness of 3-500 micrometers. There are no particular restrictions on the material, as long as it has high conductivity and does not produce a chemical reaction in the secondary battery system. For example, it can be a foil formed by surface treatment of nickel, titanium, aluminum, silver, stainless steel, carbon, etc. The negative electrode current collector usually has a smooth surface, but fine textures can also be formed on its surface to improve the adhesion between the negative electrode material layer and the current collector. Besides foil, the negative electrode current collector can also be used in any one or more combinations of various forms such as film, mesh, porous, foam, or non-woven fabric. Generally, the negative electrode current collector is copper foil.

[0081] In some embodiments, the method for preparing the negative electrode sheet includes the following steps: coating the negative electrode slurry obtained by thoroughly mixing the components of the negative electrode material layer in a solvent onto at least one surface of the negative electrode current collector, drying, cold pressing, and slitting to obtain the final product.

[0082] diaphragm

[0083] In this invention, the diaphragm can be a diaphragm conventionally used in the art.

[0084] In some alternative embodiments, the diaphragm may be a polypropylene (PP) film, a polyethylene (PE) film, or a PP / PE / PP porous membrane, such as a PP / PE / PP porous membrane.

[0085] The air permeability of the diaphragm can be 180-380s / 100mL.

[0086] The porosity of the diaphragm can be 30%-50%.

[0087] The thickness of the diaphragm can be 9-18 μm.

[0088] In one specific embodiment, the diaphragm is a polyethylene film; the thickness of the diaphragm is 16 μm; the air permeability of the diaphragm is 230 s / 100 mL; and the porosity of the diaphragm is 40%.

[0089] electrolyte

[0090] In some embodiments, the electrolyte may be a conventional electrolyte used in batteries in the art, generally including non-aqueous solvents, lithium salts, and additives.

[0091] In some embodiments, the method for preparing the lithium-ion battery includes the following steps: stacking the positive electrode, separator, and negative electrode in sequence, with the separator positioned between the positive and negative electrodes to act as a separator; then wrapping with an aluminum-plastic film, drying, and injecting the electrolyte; and finally preparing a soft-pack battery through processes such as encapsulation, settling, and formation.

[0092] In some implementations, the capacity of the lithium-ion battery is, for example, 1 Ah.

[0093] electronic devices

[0094] The electronic device provided in the third aspect of the present invention includes an electrochemical device as described above.

[0095] For example, the electronic device described in this invention may be, but is not limited to, mobile devices (such as mobile phones, tablets, laptops, video recorders, portable printers / copiers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems and backup power supplies, etc.

[0096] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0097] The reagents and raw materials used in this invention are all commercially available.

[0098] In the following embodiments, the specific preparation method of the metal oxide containing oxygen vacancies is as follows:

[0099] (1) Metal oxides containing oxygen vacancies, CeO 1.8 The preparation method of (a = 0.2) includes the following steps:

[0100] Cerium nitrate was dissolved in water to obtain an aqueous solution (the concentration of the metal salt was 2 mol / L). Oxalic acid and... Ammonia water to adjust pH The concentration was 2.5. After separation and drying, a precipitate was obtained, which was then calcined at high temperature under a certain atmosphere. Obtain CeO 1.8 The calcination temperature was 600℃, the time was 5 hours, and the atmosphere was air with an oxygen partial pressure of 14 kPa.

[0101] (2) Metal oxides containing oxygen vacancies, CeO 1.4 CeO 1.9 CeO 1.35 and CeO 1.6 Preparation method: CeO metal oxide with oxygen vacancies as described above 1.8 Based on the preparation method of CeO 1.4 CeO 1.9 CeO 1.35 and CeO 1.6 In the preparation method, only the oxygen partial pressure was changed to 7 kPa, 16 kPa, 5 kPa and 10 kPa, and the other conditions were the same as CeO. 1.8 The preparation method remains consistent.

[0102] (3) Oxygen-containing metal oxides WO3 2.8 The preparation method of (a = 0.2) includes the following steps:

[0103] Ammonium tungstate was dissolved in water to obtain a mixture (metal salt concentration of 1 mol / L). After separation and drying, a precipitate was obtained, which was then calcined at high temperature under a certain atmosphere to obtain WO3. 2.8 The calcination temperature was 1100℃, the time was 4 hours, and the atmosphere was air with an oxygen partial pressure of 14 kPa.

[0104] (4) Metal oxides containing oxygen vacancies, TiO2 1.8 The preparation method of (a = 0.2) includes the following steps:

[0105] Titanium oxysulfate was dissolved in water to obtain a mixture (metal salt concentration of 1 mol / L). After separation and drying, a precipitate was obtained, which was then calcined at high temperature under a certain atmosphere to obtain TiO2. 1.8 The calcination temperature was 1000℃, the time was 4 hours, and the atmosphere was air with an oxygen partial pressure of 14 kPa.

[0106] Example 1

[0107] In this embodiment, the method for preparing the positive electrode sheet includes the following steps:

[0108] First, Super P, CNT, NMP, and PVDF were mixed in a mass ratio of 1:0.5:80:2.5 and dispersed and stirred at 1500 rpm / min for 2 hours to prepare a conductive slurry.

[0109] Subsequently, the positive electrode active material and the oxygen-vacant metal oxide CeO were combined. 1.8 The conductive slurry was stirred and mixed at 2000 rpm / min to prepare a positive electrode slurry (solid content 59%, viscosity 3570 Pa·s). The prepared slurry was then uniformly coated onto aluminum foil using a doctor blade and placed in a forced-air drying oven at 120°C for 30 minutes to obtain an electrode sheet, with the slurry forming the positive electrode material layer. Finally, the dried electrode sheet was rolled (rolled to a compaction of 2.9 g / cc) and cut to form the positive electrode sheet.

[0110] The positive electrode active material in the obtained positive electrode material layer is lithium manganese iron phosphate (LiMn). 0.6 Fe 0.4 PO4 and single-crystal ternary cathode material LiNi 0.6 Co 0.1 Mn 0.3 O2 (mass ratio 50:50), and the positive electrode active material is a metal oxide CeO containing oxygen vacancies. 1.8 The mass ratio of Super P, CNT, and PVDF is 95:1:1:0.5:2.5, along with lithium manganese iron phosphate, ternary cathode materials, and CeO. 1.8 The Dv50 particle sizes were 0.67 μm, 3.58 μm and 0.2 μm, respectively.

[0111] Example 2

[0112] The only difference between this embodiment and Embodiment 1 is that in the positive electrode material layer, the positive electrode active material and CeO are... 1.8 The mass ratio of SuperP, CNT and PVDF was 95:0.5:1:0.5:2.5, and the other conditions were the same as in Example 1.

[0113] Example 3

[0114] The difference between this embodiment and Embodiment 1 is that in the positive electrode material layer, only the CeO is changed. 1.8 CeO 1.4 (a is 0.6), CeO 1.4 The Dv50 particle size was 0.2 μm, and the other conditions were the same as in Example 1.

[0115] Example 4

[0116] The difference between this embodiment and Embodiment 1 is that in the positive electrode material layer, only the CeO is changed. 1.8 CeO 1.9 (a is 0.1), CeO 1.9 The Dv50 particle size was 0.2 μm, and the other conditions were the same as in Example 1.

[0117] Example 5

[0118] The difference between this embodiment and Embodiment 1 is that in the positive electrode material layer, only the CeO is changed. 1.8 CeO 1.35 (a is 0.65), CeO 1.35 The Dv50 particle size was 0.2 μm, and the other conditions were the same as in Example 1.

[0119] Example 6

[0120] The difference between this embodiment and Embodiment 1 is that in the positive electrode material layer, only the CeO is changed. 1.8 The Dv50 particle size was 1 μm, and the other conditions were the same as in Example 1.

[0121] Example 7

[0122] The difference between this embodiment and Embodiment 1 is that in the positive electrode material layer, only the CeO is changed. 1.8 The Dv50 particle size was 0.3 μm, and the other conditions were the same as in Example 1.

[0123] Example 8

[0124] The difference between this embodiment and Embodiment 1 is that in the positive electrode material layer, only the CeO is changed. 1.8 The Dv50 particle size was 0.1 μm, and the other conditions were the same as in Example 1.

[0125] Example 9

[0126] The only difference between this embodiment and Embodiment 1 is that in the positive electrode material layer, the positive electrode active material and CeO are... 1.8 The mass ratio of SuperP, CNT and PVDF was 99.9:1:1:0.5:2.5, and the other conditions were the same as in Example 1.

[0127] Example 10

[0128] The only difference between this embodiment and Embodiment 1 is that in the positive electrode material layer, the positive electrode active material and CeO are... 1.8 The mass ratio of SuperP, CNT and PVDF was 90:1:1:0.5:2.5, and the other conditions remained the same as in Example 1.

[0129] Example 11

[0130] The only difference between this embodiment and Embodiment 1 is that the metal oxide containing oxygen vacancies in the positive electrode material layer also includes TiO2. 1.8 (Dv50 particle size is 0.2μm), in which, in the positive electrode material layer, positive electrode active material, CeO 1.8 TiO 1.8 The mass ratio of Super P, CNT and PVDF was 95:0.8:0.2:1:0.5:2.5, and the other conditions were the same as in Example 1.

[0131] Example 12

[0132] The only difference between this embodiment and Embodiment 1 is that WO3 is used in the positive electrode material layer. 2.8 Replace CeO 1.8 WO 2.8 The Dv50 particle size is 0.15 μm, among which, the positive electrode active material, WO 2.8 The mass ratio of Super P, CNT and PVDF was 95:1:1:0.5:2.5, and the other conditions were the same as in Example 1.

[0133] Example 13

[0134] The only difference between this embodiment and Embodiment 1 is that TiO2 is used in the positive electrode material layer. 1.8 Replace CeO 1.8 TiO 1.8 The Dv50 particle size is 0.2 μm, and it is a positive electrode active material and TiO2. 1.8 The mass ratio of Super P, CNT and PVDF was 95:1:1:0.5:2.5, and the other conditions were the same as in Example 1.

[0135] Example 14

[0136] The only difference between this embodiment and Embodiment 1 is that in the cathode material layer, lithium manganese iron phosphate (LiMn) is used. 0.6 Fe 0.4 PO4 and ternary cathode material LiNi 0.6 Co 0.1 Mn 0.3 The mass ratio of O2 was 40:60, and the other conditions remained the same as in Example 1.

[0137] Example 15

[0138] The only difference between this embodiment and Embodiment 1 is that in the cathode material layer, lithium manganese iron phosphate (LiMn) is used. 0.6 Fe 0.4 PO4 and ternary cathode material LiNi0.6 Co 0.1 Mn 0.3 The mass ratio of O2 was 60:40, and the other conditions remained the same as in Example 1.

[0139] Example 16

[0140] The only difference between this embodiment and Embodiment 1 is that the positive electrode active material in the positive electrode material layer is only lithium manganese iron phosphate (LiMn). 0.6 Fe 0.4 PO4, with all other conditions remaining the same as in Example 1.

[0141] Example 17

[0142] The only difference between this embodiment and Embodiment 1 is that the positive electrode active material in the positive electrode material layer is only the ternary positive electrode material LiNi. 0.6 Co 0.1 Mn 0.3 O2, and the rest of the conditions are the same as in Example 1.

[0143] Example 18

[0144] The difference between this embodiment and Embodiment 1 is that in the positive electrode material layer, only the CeO is changed. 1.8 CeO 1.6 (a is 0.4), CeO 1.6 The Dv50 particle size was 0.2 μm, and the other conditions were the same as in Example 1.

[0145] Comparative Example 1

[0146] The only difference between this comparative example and Example 1 is that the cathode material layer does not contain CeO. 1.8 The mass ratio of the positive electrode active material, Super P, CNT and PVDF was 96:1:0.5:2.5, and the other conditions were the same as in Example 1.

[0147] Comparative Example 2

[0148] The only difference between this comparative example and Example 1 is that CeO2 is used instead of CeO in the positive electrode material layer. 1.8 The mass ratio of the positive electrode active material, CeO2, Super P, CNT and PVDF was 95:1:1:0.5:2.5, and the other conditions were the same as in Example 1.

[0149] The parameters of the positive electrode in Examples 1-18 and Comparative Examples 1-2 are shown in Table 1.

[0150] Example 1: Film resistance of the positive electrode

[0151] The film resistance of the positive electrode sheets used in Examples 1-18 and Comparative Examples 1-2 was measured. The specific test methods are as follows:

[0152] Three small φ14 discs were cut from the above positive electrode using a punching machine. The thickness of the small discs was measured and recorded. The small discs were tested using a film resistance meter, and the film resistance was recorded.

[0153] The test results are shown in Table 2.

[0154] Example 2: Preparation and electrochemical performance testing of lithium-ion batteries

[0155] Preparation of lithium-ion batteries (pouch cells)

[0156] (1) Preparation of negative electrode

[0157] Artificial graphite (anode material), acetylene black (conductive agent), CMC (thickener), and SBR (binder) were mixed in a mass ratio of 96.4:1:1.2:1.4. Deionized water was added as a solvent and the mixture was stirred thoroughly to obtain a cathode slurry. The cathode slurry was then uniformly coated onto a copper foil (anode current collector), and the cathode sheet was prepared by drying, cold pressing, and slitting.

[0158] (2) Preparation of electrolyte

[0159] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0160] (3) Diaphragm

[0161] A PP / PE / PP porous membrane with a thickness of 16μm was used as the separator.

[0162] The membrane has an air permeability of 230s / 100mL and a porosity of 40%.

[0163] (4) Assembly of lithium-ion batteries

[0164] Lithium-ion batteries were assembled using the positive electrode sheets from Examples 1-18 and Comparative Examples 1-2, respectively. The specific steps are as follows:

[0165] The prepared positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes to act as a separator. Then, an aluminum-plastic film is wrapped around the separator, dried, and injected with the electrolyte prepared above. After encapsulation, settling, formation, and aging processes, a 1Ah soft-pack battery, i.e., a lithium-ion battery, is finally produced.

[0166] Electrochemical performance testing

[0167] The electrochemical performance of the newly prepared lithium-ion battery was tested, as follows:

[0168] (1) Quantity and capacity retention rate after 500 cycles at 45°C

[0169] Specific capacity: Activated by three charge-discharge cycles with a current density of 0.33C and a voltage window of 2.8-4.4V, the discharge capacity of the third charge-discharge cycle is tested. Specific capacity = discharge capacity / mass of positive electrode active material.

[0170] High-temperature cycling test: The activated battery was charged and discharged at 1C for 500 cycles within the range of 2.8-4.4V at 45℃. The capacity ratio of the 500th cycle to the 1st cycle was recorded as its capacity retention rate.

[0171] (2) Gas production growth rate during 56 days of high temperature

[0172] High-temperature storage gas generation test:

[0173] The activated batteries were adjusted to 100% SOC, and the cell volume at room temperature was measured using the water displacement method, recorded as the cell volume V0 on day 0. The batteries were then stored in a 60°C constant-temperature oven. Every 7 days, the batteries were removed from the oven, allowed to stand and cool to room temperature, and the cell volume was measured again using the water displacement method. The cell volume (V0) after 56 days was recorded. 56 The formula for calculating the gas production growth rate over 56 days of high temperature is: (V 56 -V0) / V0×100%.

[0174] The test results are shown in Table 2.

[0175] Table 1

[0176]

[0177]

[0178] Table 2

[0179]

[0180] As can be seen from Tables 1 and 2 above, in Examples 1-18 of the present invention, the film resistance of the obtained positive electrode sheet can be lower than 23.5Ω, the 56-day high-temperature gas production growth rate of the prepared electrochemical device (especially lithium-ion battery) can be lower than 30%, and on this basis, the capacity retention rate after 500 cycles at 45°C can be higher than 88%, and the specific capacity can reach more than 135mAh / g.

[0181] In this invention, by introducing oxygen-vacant metal oxides into the cathode material layer, the cathode sheet containing these oxides exhibits better conductivity, and the prepared electrochemical device (especially the lithium-ion battery) shows lower high-temperature gas production growth after 56 days, while also achieving excellent cycle stability and capacity performance. However, if the cathode sheet does not contain oxygen-vacant metal oxides, the above-mentioned effects cannot be achieved.

[0182] Compared to Example 1, in Comparative Example 1, the positive electrode does not contain CeO. 1.8 The film resistance of the positive electrode is significantly increased, the 56-day high-temperature gas production growth rate of the prepared lithium-ion battery is significantly worse, and the capacity retention rate and specific capacity after 500 cycles at 45℃ are also poor.

[0183] Compared to Example 1, in Comparative Example 2, the positive electrode contains CeO2 but not CeO. 1.8 The film resistance of the positive electrode deteriorated significantly, the gas production growth rate of the prepared lithium-ion battery increased significantly at high temperature over 56 days, and the capacity retention rate and specific capacity were poor after 500 cycles at 45℃.

[0184] In Examples 16-17, either lithium iron phosphate or ternary cathode materials were used alone as the positive electrode active material. Although this method has advantages over the oxygen-vacant metal oxides used in Comparative Examples 1-2, it still results in lower film resistance for the obtained cathode sheets compared to Example 1, which used both lithium iron phosphate and ternary cathode materials simultaneously. Consequently, the lithium-ion batteries exhibited either a reduced capacity retention rate after 500 cycles at 45°C, a reduced gas production growth rate after 56 days at high temperature, or a decreased specific capacity. This may be because lithium manganese iron phosphate (LFP) alone has low electronic conductivity and good electrical conductivity, but its polarization is large, which is not conducive to the full utilization of battery capacity. Meanwhile, pure ternary cathode materials easily release oxygen anions, leading to significant gas generation in the battery, ultimately resulting in poor cycle performance and storage performance. However, when both LFP and ternary cathode materials are used as cathode active materials in Example 1, the advantages of both can be fully utilized on the basis of metal oxides containing oxygen vacancies, further improving the effect. It should be noted that although the above embodiments of the present invention do not show the presence of doping elements M (including one or more of Ti, Mg, Zr, V, Nb, Mo, W, Al, Ni, and Co) and / or the presence of an outer coating layer in the cathode active materials such as LFP and ternary cathode materials, the technical solution of the present invention is still applicable to LFP and ternary cathode materials with doping elements or outer coating layers, and the technical effects of the present invention can be achieved.

[0185] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A positive electrode plate, characterized in that, It includes a positive electrode current collector; a positive electrode material layer is disposed on at least one surface of the positive electrode current collector; the positive electrode material layer includes a positive electrode active material and a metal oxide containing oxygen vacancies, wherein the metal oxide containing oxygen vacancies is dispersed in the positive electrode active material; the metal oxide containing oxygen vacancies includes CeO. 2-a Wherein, 0.1≤a≤0.65; the Dv50 particle size of the oxygen-vacancy-containing metal oxide is 0.1-0.3μm; the mass ratio of the positive electrode active material to the oxygen-vacancy-containing metal oxide is (90-95):1; the positive electrode active material is lithium manganese iron phosphate and ternary positive electrode material.

2. The positive electrode sheet as described in claim 1, characterized in that, 0.2≤a≤0.65。 3. The positive electrode sheet as described in claim 1, characterized in that, The Dv50 particle size of the oxygen-vacancy-containing metal oxide is 0.1-0.2 μm.

4. The positive electrode sheet as described in claim 1, characterized in that, The content of the oxygen-vacant metal oxide is 0.2%-2%, and the percentage is the mass percentage of the positive electrode material layer.

5. The positive electrode sheet as described in claim 1, characterized in that, The mass ratio of lithium manganese iron phosphate to the ternary cathode material is (40-60):(60-40).

6. The positive electrode sheet as described in claim 1, characterized in that, The lithium manganese iron phosphate and the ternary cathode material satisfy one or more of the following conditions ai: a. The chemical formula of the lithium manganese iron phosphate is Li. z Mn x Fe 1-x PO4, where z is 0.9-1.1, 0 < x < 1; b. The lithium manganese iron phosphate is doped with heteroatoms, which include one or more of Ti, Mg, Zr, V, Nb, Mo, W, Al, Ni and Co; c. The lithium manganese iron phosphate also includes an outer coating layer; d. The Dv50 particle size of the lithium manganese iron phosphate is 0.3-2 μm; e. The chemical formula of the ternary cathode material is LiNi. x Co y Mn 1-x-y O2, where 0.6 ≤ x < 1, 0 < y ≤ 0.2; f. The ternary cathode material is doped with heteroatoms, which include one or more of Ti, Mg, Zr, V, Nb, Mo, W and Al; g. The ternary cathode material also includes an outer coating layer; h. The ternary cathode material is a single-crystal material; i. The Dv50 particle size of the ternary cathode material is 2-6 μm.

7. The positive electrode sheet as described in claim 1, characterized in that, The positive electrode material layer satisfies one or more of the following conditions: a. The content of the positive electrode active material is 80% or more, and the percentage is the mass percentage of the positive electrode material layer; b. The positive electrode material layer further includes a conductive agent, the content of which is 1%-3%, and the percentage is the mass percentage of the positive electrode material layer; c. The positive electrode material layer further includes a binder, the content of which is 1%-4%, and the percentage is the mass percentage of the positive electrode material layer.

8. An electrochemical device, characterized in that, It includes the positive electrode sheet as described in any one of claims 1-7.

9. An electronic device, characterized in that, It includes the electrochemical device as described in claim 8.

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