Mixed positive electrode material and manufacturing method thereof, positive electrode sheet, battery, and electric device

Abstract

The application discloses a mixed positive electrode material, a manufacturing method thereof, a positive electrode sheet, a battery and an electric device. The mixed positive electrode material comprises a lithium cobaltate material and a ternary positive electrode material. The particle size of the lithium cobaltate material is greater than that of the ternary positive electrode material. The mass proportion of the lithium cobaltate material in the mixed positive electrode material is greater than or equal to the mass proportion of the ternary positive electrode material in the mixed positive electrode material. The mixed positive electrode material can solve the problem of poor material structure stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a mixed positive electrode material, a manufacturing method thereof, a positive electrode sheet, a battery and an electric device. BACKGROUND

[0002] With the rising price of lithium cobaltate material, the cost of lithium ion batteries gradually increases, and in view of environmental protection, the use of cobalt is also constantly called for. The ternary positive electrode material lithium ion battery has a certain advantage in cost due to its low cobalt content. The prior art provides a scheme of mixing lithium cobaltate material and ternary positive electrode material, but the ternary positive electrode material will collapse after long-term use. How to combine the advantages of lithium cobaltate material and ternary positive electrode material to provide a mixed positive electrode material with good material structure stability and good cycle stability has become the key. SUMMARY

[0003] The purpose of the present application is to provide a mixed positive electrode material, a manufacturing method thereof, a positive electrode sheet, a battery and an electric device, to solve the problem of poor material structure stability.

[0004] To achieve the purpose of the present application, the present application provides the following technical solutions:

[0005] In a first aspect, the present application provides a mixed positive electrode material, comprising lithium cobaltate material and ternary positive electrode material, the particle size of the lithium cobaltate material is larger than the particle size of the ternary positive electrode material, and the mass fraction of the lithium cobaltate material in the mixed positive electrode material is greater than or equal to the mass fraction of the ternary positive electrode material in the mixed positive electrode material.

[0006] In an embodiment, the particles of the plurality of lithium cobaltate materials have inter-particle gaps, and part of the ternary positive electrode material is filled in the inter-particle gaps.

[0007] In an embodiment, the particle size Dv50 of the lithium cobaltate material is greater than the particle size Dv100 of the ternary positive electrode material.

[0008] In an embodiment, the particle size Dv50 of the lithium cobaltate material is A, and A satisfies 16 < A < 20 < m.

[0009] In an embodiment, the particle size Dv90 of the ternary positive electrode material is B, and B satisfies 0 < A < 10 < m.

[0010] In an embodiment, the particle size Dv100 of the ternary positive electrode material is C, and C satisfies 0 < C < 16 < m.

[0011] In an embodiment, the ternary positive electrode material is a single crystal particle.

[0012] In an embodiment, the mass ratio of the lithium cobaltate material and the ternary cathode material in the mixed cathode material is (50-90):(10-50).

[0013] In an embodiment, the outer surface of the lithium cobaltate material is coated with a first coating layer, and the first coating layer is an inorganic ceramic material.

[0014] In an embodiment, the thickness of the first coating layer is 10-300 nm.

[0015] In an embodiment, the mass ratio of the first coating layer and the lithium cobaltate material is (1-10):(90-99).

[0016] In an embodiment, the material of the first coating layer comprises at least one of an oxide, a sulfide, and an inorganic solid-state electrolyte.

[0017] In an embodiment, the outer surface of the ternary cathode material is coated with a second coating layer, and the second coating layer is an inorganic ceramic material.

[0018] In an embodiment, the thickness of the second coating layer is 5-200 nm.

[0019] In an embodiment, the mass ratio of the second coating layer and the ternary cathode material is (0.2-3):(97-99.8).

[0020] In an embodiment, the material of the second coating layer comprises at least one of an oxide, a sulfide, and an inorganic solid-state electrolyte.

[0021] In a second aspect, the application further provides a method for manufacturing a mixed cathode material, comprising: mixing a lithium cobaltate material and a ternary cathode material to obtain the mixed cathode material; wherein the particle size of the lithium cobaltate material is greater than the particle size of the ternary cathode material, and the mass proportion of the lithium cobaltate material in the mixed cathode material is greater than or equal to the mass proportion of the ternary cathode material in the mixed cathode material.

[0022] In a third aspect, the application further provides a cathode sheet, comprising a current collector and a cathode active material layer arranged on the current collector, and the cathode active material layer comprises the mixed cathode material of the first aspect.

[0023] In an embodiment, the compaction density of the cathode active material layer satisfies the relationship: (G1*4.15+G2*3.5)-0.1; wherein G1 is the mass proportion of the lithium cobaltate material, G2 is the mass proportion of the ternary cathode material, and the unit of the compaction density of the cathode sheet is g / cm 3 .

[0024] In a fourth aspect, the application further provides a battery, which comprises an electrolyte, a separator, a negative electrode sheet and the positive electrode sheet provided in the third aspect, the separator is arranged between the positive electrode sheet and the negative electrode sheet, and the separator, the negative electrode sheet and the positive electrode sheet are all soaked in the electrolyte.

[0025] In a fifth aspect, the application further provides a power consumption device, which comprises a power consumption component and the battery provided in the fourth aspect, and the battery supplies power to the power consumption component.

[0026] Compared with lithium cobaltate material, ternary positive electrode material has the advantages of low price and high capacity per gram. Therefore, mixing ternary positive electrode material into lithium cobaltate material can reduce the manufacturing cost of the positive electrode sheet. At the same time, the upper limit voltage of the mixed positive electrode material (including lithium cobaltate material and ternary positive electrode material) can be increased to 4.45V. By mixing large-particle lithium cobaltate material with small-particle ternary positive electrode material, and by using the small particle size characteristics of the ternary positive electrode material, in the sheet pressing process, the large-particle lithium cobaltate material serves as the main force-bearing body, thereby reducing the structural collapse of the ternary positive electrode material caused by sheet pressing. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0028] Figure 1 It is a schematic diagram of the cross-sectional structure of the positive electrode sheet of an embodiment. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] Unless otherwise defined, all technical and scientific terms used in the present application have the same meanings as commonly understood by those skilled in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used in the present application includes any and all combinations of one or more related listed items.

[0031] Some embodiments of the present application will be described in detail with reference to the drawings. The following examples and features in the examples can be combined with each other in the case of no conflict.

[0032] The following are explanations of the terms used in the text:

[0033] Particle size Dv50: the particle size corresponding to the cumulative particle size distribution percentage of 50% of a sample, that is, it can be understood as the median particle size or median particle size.

[0034] Particle size Dv90: the particle size corresponding to the cumulative particle size distribution percentage of 90% of a sample. Its physical meaning is that particles with a particle size smaller (or larger) than it account for 90%.

[0035] Particle size Dv100: the particle size corresponding to the cumulative particle size distribution percentage of 100% of a sample, that is, it can be understood as the maximum particle size.

[0036] The particle size of the particles involved in the specification is detected by Mastersizer3000 laser particle size distribution instrument according to GB / T 41949-2022; the coating layer of the particles is measured by transmission electron microscope (TEM).

[0037] K value = voltage drop / time, the smaller the K value, the smaller the self-discharge of the battery, and the better the performance of the battery.

[0038] Capacity refers to the actual discharge capacity, and capacity distribution refers to the uniformity of the capacity of the batch of batteries, and the narrower the capacity distribution, the better.

[0039] The present application provides a positive electrode sheet, which comprises a mixed positive electrode material, please refer to Figure 1 , comprising a lithium cobaltate material 10 and a ternary positive electrode material 20, the particle size of the lithium cobaltate material 10 is larger than that of the ternary positive electrode material 20, and the mass fraction of the lithium cobaltate material 10 in the mixed positive electrode material is greater than or equal to the mass fraction of the ternary positive electrode material 20 in the mixed positive electrode material.

[0040] Specifically, the mixed positive electrode material is used to make a positive electrode sheet, and the mixed positive electrode material can be a positive electrode material slurry. In the positive electrode sheet, the mass fraction of the lithium cobaltate material 10 is greater than that of the ternary positive electrode material 20, that is, the ternary positive electrode material 20 is mixed in the lithium cobaltate material 10.

[0041] Ternary cathode materials 20 are mainly composed of nickel-cobalt-manganese oxides and nickel-cobalt-aluminum oxides. Based on the proportion of nickel content, they can be classified into 5-series, 6-series, 7-series, and 8-series ternary cathode materials, etc. Currently, mass-produced ternary cathode materials 20 are mainly 5-series and 6-series. Ternary cathode materials 20 have high specific capacity, but their operating voltage is relatively low, resulting in a lower overall energy density of the battery. In existing technologies, the upper limit voltage of ternary cathode material batteries is lower than that of lithium cobalt oxide material batteries, thus resulting in a lower volumetric energy density for ternary cathode material lithium batteries compared to high-voltage lithium cobalt oxide material batteries.

[0042] Compared to lithium cobalt oxide material 10, ternary cathode material 20 has the advantages of lower price and higher specific capacity. Therefore, mixing ternary cathode material 20 into lithium cobalt oxide material 10 can reduce the manufacturing cost of the cathode sheet. At the same time, it can also increase the upper limit voltage of the mixed cathode material (including lithium cobalt oxide material 10 and ternary cathode material 20) to 4.45V.

[0043] Furthermore, due to the prolonged high-voltage period (4.45V) in the high-voltage system, the ternary cathode material 20 eventually suffers structural instability and framework collapse during cycling due to excessive delithiation. Moreover, the final compaction density of the cathode sheet exceeds the compaction limit of the ternary cathode material 20, leading to excessive stress and breakage of the ternary cathode material 20 particles. Therefore, this invention employs a mixture of large-particle lithium cobalt oxide material 10 and small-particle ternary cathode material 20, utilizing the small particle size of the ternary cathode material 20 to reduce particle breakage and structural collapse caused by excessive pressure on the ternary cathode material 20.

[0044] In one embodiment, there are interparticle gaps between the particles of the plurality of lithium cobalt oxide materials 10, and a portion of the ternary cathode material 20 fills the interparticle gaps.

[0045] like Figure 1 As shown, because the lithium cobalt oxide material 10 has a larger particle size, a larger interparticle gap is formed between multiple lithium cobalt oxide material 10 particles, and the smaller ternary cathode material 20 can fill this interparticle gap. The advantages of this structure are that, on the one hand, it can increase the compaction density of the cathode active layer in the cathode sheet, thereby obtaining a cathode sheet with higher energy density; on the other hand, the lithium cobalt oxide material 10, which has better structural stability, forms a supporting skeleton, preventing the ternary cathode material 20 from being directly subjected to force, which could lead to particle breakage, structural instability, pulverization, and peeling off after breakage.

[0046] In one embodiment, the particle size Dv50 of the lithium cobaltate material is greater than the particle size Dv100 of the ternary cathode material. It can be understood that in the case where the particle size Dv100 (the largest particle size) of the ternary cathode material is less than the particle size Dv50 of the lithium cobaltate material, that is, the particle size of the ternary cathode material is less than the particle size of the lithium cobaltate material.

[0047] The particle size of the mixed cathode material is matched, the particle size distribution of the lithium cobaltate cathode material and the ternary cathode material is controlled, and it is ensured that the Dv100 of the ternary cathode material is lower than the Dv50 of the lithium cobaltate material. The large-particle lithium cobaltate material matched with the small-particle ternary cathode material can avoid damage of the ternary cathode material under high compaction, and the small-size ternary cathode material as a gap-filling particle in the present application can avoid direct pressure to the greatest extent.

[0048] In one embodiment, the particle size Dv50 of the lithium cobaltate material is A, and A satisfies 16 μm≤A≤20 μm. Optionally, the particle size Dv50 of the lithium cobaltate material can be 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, or 20 μm. It needs to be explained that the particle size Dv50 of the lithium cobaltate material is its total particle size, and when the lithium cobaltate material has a coating layer, the particle size Dv50 includes the thickness of the coating layer.

[0049] In one embodiment, the particle size Dv90 of the ternary cathode material is B, and B satisfies 0<A≤10 μm. Optionally, the particle size Dv90 of the ternary cathode material can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. It needs to be explained that the particle size Dv90 of the ternary cathode material is its total particle size, and when the ternary cathode material has a coating layer, the particle size Dv90 includes the thickness of the coating layer.

[0050] In one embodiment, the particle size Dv100 of the ternary cathode material is C, and C satisfies 0<C<16 μm. Optionally, the particle size Dv100 of the ternary cathode material can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or 15.5 μm. It needs to be explained that the particle size Dv100 of the ternary cathode material is its total particle size, and when the ternary cathode material has a coating layer, the particle size Dv100 includes the thickness of the coating layer.

[0051] The positive plate provided by the application carries out strict particle size control on the lithium cobaltate material and the ternary positive material before selection, and the particle size Dv50 of the lithium cobaltate material is controlled in the range of 16-20 μm through particle size screening treatment, and the particle size Dv90 of the ternary positive material is less than 10 μm, and the Dv100 is less than the Dv50 of the lithium cobaltate material.

[0052] In an embodiment, the ternary positive material is a single crystal particle. Specifically, the ternary positive material can be a single crystal particle or a polycrystal particle. The single crystal refers to a single dispersed or single-like dispersed particle, and the polycrystal refers to a secondary spherical particle formed by agglomeration of primary particles. The ternary positive material prepared in the application is a single crystal particle, which can reduce the structure damage of the ternary positive material after transition discharge, reduce the exposure of the grain boundary in the ternary positive material, and thus reduce the reaction between the electrolyte and the ternary positive material.

[0053] In an embodiment, in the mixed positive material, the mass ratio of the lithium cobaltate material to the ternary positive material is (50-90):(10-50). Alternatively, the mass ratio of the lithium cobaltate material to the ternary positive material can be 90:10, 85:15, 80:20, 75:25, 70:30, 65:35, 60:40, 55:45 or 50:50.

[0054] Satisfying the mass ratio of the lithium cobaltate material to the ternary positive material in the above range can ensure that the system of the mixed positive material is a lithium cobaltate material dominant system, and the ternary positive material is a mixed material. When the mass ratio of the lithium cobaltate material to the ternary positive material satisfies the above range, the cost of the mixed positive material is lower, and the cycle performance is better. In an embodiment, the outer surface of the lithium cobaltate material is coated with a first coating layer; and / or, the outer surface of the ternary positive material is coated with a second coating layer, and the first coating layer and the second coating layer are both inorganic ceramic materials.

[0055] Specifically, in the mixed positive material provided by the application, the lithium cobaltate material and / or the ternary positive material can be coated, wherein the first coating layer is coated on the lithium cobaltate material, the second coating layer is coated on the ternary positive material, and the materials of the first coating layer and the second coating layer are both inorganic ceramic materials.

[0056] Since the electronic conductivity and ionic conductivity of the negative side are much better than those of the positive side, the embedding of lithium ions into the lithium cobaltate material is extremely critical during discharge. When high-rate discharge, the increase of polarization resistance caused by the ion concentration difference of the positive side is an important factor for temperature rise. Therefore, reducing the transmission resistance and transmission distance of lithium ions in the mixed positive material is the key.

[0057] In order to reduce the resistance of lithium ion transmission of the positive electrode during discharging, the mixed positive electrode material with a suitable particle size is configured, the conductivity of the electrode sheet is ensured by optimizing the content of the conductive agent, and the mixed positive electrode material is further provided by a surface coating treatment, especially the lithium cobaltate material coated by the first coating layer. By coating the lithium cobaltate material by the first coating layer, the ion transmission kinetics of the large-particle lithium cobaltate material can be improved, the charging and discharging temperature rise is reduced, and the further deterioration of the ternary positive electrode material due to the excessively high temperature rise under high-temperature cycling is avoided.

[0058] Moreover, the ternary positive electrode material is easy to absorb water on the surface to form lithium hydroxide and lithium carbonate, so that the positive electrode impedance is increased, the capacity is reduced, and the structural stability is damaged. With the increase of the nickel content ratio, the preparation process requirement of the ternary positive electrode material is increased, and the water control requirement of the battery production is also increased. Therefore, by coating the ternary positive electrode material by the second coating layer, the water absorption on the surface of the ternary positive electrode material can be reduced, and the side reaction of the material in the electrolyte can be reduced.

[0059] There are many impedance control design methods for the positive electrode material, and the stability, operability, cost and other factors need to be considered; therefore, in the present application, the lithium cobaltate material and the ternary positive electrode material coated by the inorganic ceramic material are used on the basis of the suitable particle size, so that the oxidation of the electrolyte at the positive electrode is greatly reduced, and therefore, the high-temperature long-cycle retention rate is improved, and the expansion is also reduced.

[0060] In an embodiment, the material of the first coating layer and / or the material of the second coating layer comprises at least one of an oxide, a sulfide, and an inorganic solid-state electrolyte. The inorganic solid-state electrolyte can be lithium aluminum titanium phosphate (LATP) or lithium lanthanum zirconium oxide (LLZO).

[0061] Specifically, the first coating layer and the second coating layer can both have a doping element, including but not limited to Al, W, Ti, Y, Zr, F, etc. The types of inorganic ceramic materials include but are not limited to inorganic particles such as metal oxides or metal sulfides, and can also be solid-state electrolytes (including but not limited to LATP / LLZO). The coating layer (the first coating layer and the second coating layer) mainly plays a role in protecting the mixed positive electrode material, improving the cycle performance of the battery, and enhancing the interface ion conductivity. The material selection of the coating layer should have the characteristics of chemical stability, high ion conductivity, and good compatibility with the positive electrode material. Among them, the oxides such as aluminum oxide and zirconium oxide have the characteristics of high chemical stability and moderate ion conductivity; and the sulfides such as lithium sulfide also have high ion conductivity and can supplement the lithium capacity.

[0062] Optionally, the ternary cathode material requires high structural stability, and the second coating layer is designed not to select a fast ion conductor, but to select an oxide as a coating material, mainly to stabilize the crystal structure during high temperature cycling. Due to the small particle size of the ternary cathode material, the transmission distance of lithium ions is short, so the transmission of lithium ions in the ternary cathode material is not the rate-determining step. The design of the ternary part mainly reflects the structural stability.

[0063] In an embodiment, the thickness of the first coating layer is 10 nm to 300 nm. Optionally, the thickness of the first coating layer can be 10 nm, 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm. Optionally, the thickness of the first coating layer is 50 nm to 200 nm.

[0064] In an embodiment, the mass ratio of the first coating layer to the lithium cobalt oxide material is (1-10):(90-99). Optionally, the mass ratio of the first coating layer to the lithium cobalt oxide material can be 1:99, 2:98, 3:97, 4:96, 5:95, 6:94, 7:93, 8:92, 9:91, 10:90. Optionally, the mass ratio of the first coating layer to the lithium cobalt oxide material is (1-5):(95-99).

[0065] In an embodiment, the thickness of the second coating layer is 5 nm to 200 nm. Optionally, the thickness of the second coating layer can be 5 nm, 8 nm, 10 nm, 15 nm, 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm. Optionally, the thickness of the second coating layer is 20 nm to 100 nm.

[0066] In an embodiment, the mass ratio of the second coating layer to the ternary cathode material is (0.2-3):(97-99.8). Optionally, the mass ratio of the second coating layer to the lithium cobalt oxide material can be 0.2:99.8, 0.5:99.5, 1:99, 1.5:98.5, 2:98, 2.5:97.5, 3:97. Optionally, the mass ratio of the first coating layer to the lithium cobalt oxide material is (0.5-3):(97-99.5).

[0067] In an embodiment, the positive electrode sheet includes a current collector and a positive electrode active material layer disposed on the current collector, and the positive electrode active material layer includes the mixed cathode material in the above-mentioned embodiments.

[0068] In an embodiment, the compaction density of the positive active material layer satisfies the relationship: (G1*4.15+G2*3.5)-0.1; wherein G1 is the mass percentage of the lithium cobaltate material, G2 is the mass percentage of the ternary positive material, and the compaction density of the positive plate is g / cm 3 .

[0069] Specifically, because the particle sizes of the lithium cobaltate material and the ternary material are different, the compaction densities of the two are also different. The theoretical upper limit compaction density of the lithium cobaltate material is about 4.2 g / cm 3 , and the theoretical upper limit compaction density of the ternary positive material is about 3.7 g / cm 3 . In a specific embodiment, the upper limit of the compaction density of the positive material mixed in a mass ratio of 6:4 is about 4 g / cm 3 . When the compaction density is used to design the positive active material layer, the ternary positive material part may be broken under pressure, especially the larger particles in the ternary positive material are more likely to be broken. Therefore, the upper limit compaction density of the lithium cobaltate material is adjusted to about 4.15 g / cm 3 , and the upper limit compaction density of the ternary positive material is about 3.5 g / cm 3 .

[0070] The compaction density of the positive active material layer calculated by the above relationship can avoid the situation that the ternary positive material part is broken under pressure. Of course, the actual use can be appropriately reduced by 0.5, so the actual compaction can be between (G1*4.15+G2*3.5)-0.5 and (G1*4.15+G2*3.5). Of course, the energy density of the positive plate satisfying the above compaction density is missing, so the missing energy density caused by compaction can be compensated by reducing the number of winding turns and increasing the area density.

[0071] In an embodiment, the application also provides a battery, which includes an electrolyte, a separator, a negative plate, and the positive plate provided in the above embodiment. The separator is arranged between the positive plate and the negative plate, and the separator, the negative plate, and the positive plate are all soaked in the electrolyte.

[0072] In an embodiment, the electrolyte includes an electrolyte, and the lithium salt of the electrolyte is LiPF6 (lithium hexafluorophosphate). The concentration of the lithium salt in the electrolyte is a mixture of multiple solvents (ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate, etc.).

[0073] In an embodiment, the electrolyte includes an additive, which includes but is not limited to one or more of 1,3-propane sultone, vinylene carbonate, tris(2,2,2-trifluoroethyl)phosphite (TTFEP), vinyl sulfate, vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, nitriles, etc.

[0074] In a specific embodiment, the formula of the electrolyte includes: electrolyte lithium salt (LiPF6), the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of EC\PC\DEC\PP; the additives are 1,3-propane sultone (PS), vinyl sulfite (DTD), vinylene carbonate (VC), fluoroethylene carbonate (FEC), tris(2,2,2-trifluoroethyl)phosphite (TTFEP), lithium difluorophosphate (LiPO2F2), HTCN, SN, and the mass fractions of the additives are 3%, 0.6%, 0.3%, 7%, 0.3%, 0.3%, 2%, and 1.5% of the total mass of the lithium salt and the ester solvent, respectively.

[0075] By matching the appropriate electrolyte formula, the excessive oxidation of the positive electrode to the electrolyte can be avoided, and the manganese dissolution is inhibited, and the stable SEI film is beneficial to high-temperature cycling. The electrolyte determines the high and low temperature, high rate, cycle, and safety performance of the battery. In a low temperature environment, the conductivity of the electrolyte will be greatly reduced, the solvation of Li+ is enhanced, the impedance of the SEI film is increased, and the solvent and lithium salt will be precipitated; while the temperature is higher, various complex side reactions will occur between the electrolyte itself and the electrode and the electrolyte. The electrolyte used for the mixed positive electrode material is mainly suitable for lithium cobaltate material in composition, and the protection of the positive electrode is mainly optimized by nitrile additives. The nitrile additive with a wide voltage window can be covered on the lithium cobaltate material through chelation to form an interface protection layer, preventing the oxidation of the electrolyte by the high-valence cobalt ion with high surface activity. In the mixed positive electrode material, the introduction of part of the transition metals nickel and manganese in the ternary positive electrode material makes the oxidation-reduction characteristics of the positive electrode change significantly.

[0076] On the basis of the above-mentioned embodiments, in the mixed positive electrode material, the ternary positive electrode material part preferentially de-lithiates, at a high voltage of 4.45V, the high-valence nickel and manganese will have obvious oxidation to the electrolyte, and conversely, the oxidation of the electrolyte will also cause the stability of the ternary positive electrode material to deteriorate, the film impedance of the surface of the ternary positive electrode material increases, and finally abnormal de-lithiation and cycle retention rate decrease are shown. At the same time, due to the lower oxidation potential of nickel, at the same charging current, as the voltage rises, the ternary positive electrode material part will preferentially de-lithiate, causing the oxidation potential of nickel and manganese to rapidly increase, therefore, in the electrolyte matching of the mixed positive electrode material, the structural characteristics of the pure ternary positive electrode material part should be fully considered. In summary, the electrolyte in the battery provided by the present application has the following advantages: 1) has an interface protection effect on the mixed positive electrode material, reduces the electrolyte oxidation caused by the interface reaction; 2) the additives of the electrolyte can form a high-stability SEI film by reacting on the negative electrode, and the SEI film should have the characteristics of Li + fast conduction speed, dense and not easy to dissolve; the SEI film should have good high-temperature resistance and not be easy to decompose at high temperature, and at the same time, it will not dissolve in the electrolyte, so as to inhibit the electrode / electrolyte interface side reaction of the high-voltage mixed positive electrode material battery at high temperature and high pressure, reduce the consumption of reversible / irreversible Li + , and improve the interface stability.

[0077] In one embodiment, the present application also provides a kind of electric equipment, including the battery and electric device as described in the above embodiment, and the battery supplies power to electric device. The electric equipment can be energy storage power station or new energy vehicle.

[0078] In one embodiment, the present application also provides a kind of preparation method of mixed positive electrode material, comprising the following steps:

[0079] Step S1, mix lithium cobaltate material and ternary positive electrode material to obtain mixed positive electrode material.

[0080] Wherein, the particle size of the lithium cobaltate material is larger than the particle size of the ternary positive electrode material, and the mass fraction of the lithium cobaltate material in the mixed positive electrode material is greater than or equal to the mass fraction of the ternary positive electrode material in the mixed positive electrode material. The particle size of the lithium cobaltate material and the ternary positive electrode material can refer to the range provided in the above-mentioned embodiments; and the mixing ratio of the lithium cobaltate material and the ternary positive electrode material can also refer to the range provided in the above-mentioned embodiments, which will not be repeated here.

[0081] Optionally, the mixed positive electrode material prepared by the method can be mixed positive electrode slurry. The mixed positive electrode slurry can further include a conductive agent and a binder. The mass ratio of the lithium cobaltate material, the ternary positive electrode material, the conductive agent and the binder can be (50-90):(10-50):(0.4-1):(0.4-1).

[0082] Optionally, the ternary positive electrode material can be NCM (nickel-cobalt-manganese ternary positive electrode material) or NCA (nickel-cobalt-aluminum ternary positive electrode material), and the ratio of the three transition metal elements is not limited, wherein the nickel can be 5 series, 6 series, 7 series, 8 series, 9 series, etc., and the cobalt content in the ternary positive electrode material can be 0.

[0083] Optionally, the conductive agent can be CNT (carbon nanotube), conductive carbon black or a mixture of the two. The adhesive can be PVDF (polyvinylidene fluoride). The amount of the adhesive is determined according to the actual molecular weight of PVDF to meet the positive electrode sheet peeling strength of 1.5 N / m or more.

[0084] In one embodiment, the present application also provides a method for manufacturing a positive electrode sheet, comprising the following steps:

[0085] Step S10, mixing and dispersing the lithium cobaltate material, the ternary positive electrode material, the conductive agent and the adhesive in the solvent in proportion to obtain a mixed positive electrode slurry.

[0086] Step S20, coating the mixed positive electrode slurry on the surface of the current collector, drying and rolling to obtain the positive electrode sheet.

[0087] Optionally, the solvent in step S10 can be NMP (N-methyl pyrrolidone).

[0088] Optionally, the positive electrode sheet manufacturing in step S20 needs to meet the preset compaction density, and the specific compaction density can be calculated by the formula: (G1*4.15+G2*3.5)-0.1; wherein G1 is the mass ratio of the lithium cobaltate material, G2 is the mass ratio of the ternary positive electrode material, and the compaction density of the positive electrode sheet is g / cm 3 .

[0089] In one embodiment, the present application also provides a method for manufacturing a battery, comprising the following steps:

[0090] Step S100, manufacturing a positive electrode sheet and a negative electrode sheet.

[0091] Step S200, manufacturing the battery by winding or stacking the sliced positive electrode sheet, the negative electrode sheet and the separator.

[0092] The method for manufacturing the positive electrode sheet in step S100 is as provided in the above embodiment, which is not repeated here. The method for manufacturing the negative electrode sheet comprises: dispersing the artificial graphite, Super-P, the adhesive and the thickening agent in the solvent, and the mass ratio of the four meets 100:(0-1):(0-2):(0-2) to obtain a negative electrode slurry; uniformly coating the negative electrode slurry on the two side surfaces of the copper foil, drying, pressing, and slicing to obtain the negative electrode sheet.

[0093] The optional adhesive includes, but is not limited to, styrene butadiene rubber and / or SBR. The thickening agent includes, but is not limited to, sodium carboxymethyl cellulose, CMCNa, CMC Li, etc. The solvent is deionized water.

[0094] The optional diaphragm in step S200 includes, but is not limited to, an oil-based acetone diaphragm, an oil-based DMAC diaphragm, a water-based diaphragm, etc.

[0095] In one embodiment, after the battery is injected, the battery is aged at 45°C for 36h-48h, and then is subjected to formation. The formation temperature can be adjusted according to the type of the diaphragm used, wherein the formation temperature of the oil-based acetone diaphragm is 60°C-78°C, and the formation temperature of the oil-based DMAC diaphragm and the water-based diaphragm is 70°C-90°C.

[0096] In one embodiment, the battery is formed in two steps, the first step is charging at a small current of 0.05-0.2C to 20% SOC, and the second step is charging at a current of 0.1C-0.8C to 40% SOC. The two-step formation pressure is 0.7MPa-0.9MPa (acetone oil-based diaphragm), or 1.0MPa-1.2MPa (DMAC diaphragm and water-based diaphragm).

[0097] In one embodiment, after the formation is completed, the battery is continuously kept at temperature and pressure for 20min, the battery is cooled to 45°C, the pressure is adjusted to the target pressure (the upper limit pressure of the formation minus 0.2MPa-0.4MPa), then 0.5C charging is performed to the target voltage (the upper limit voltage minus 30mV-80mV), 0.02C cutoff, and 0.5C discharging is performed to 3.0V. Such a cycle is performed twice, then vacuum sealing is performed, and secondary aging is performed at room temperature or 45°C for 4h-24h, then the battery is subjected to capacity distribution, and after the capacity distribution, the battery is left for 24h to test OCV1, and after seven days, OCV2 is tested, and the self-discharge K value is calculated. Through the above formation process, a more compact and uniform SEI film can be formed. Unlike the formation step of the lithium cobaltate material, the mixed cathode material battery needs to reduce the formation current, and the formation current before 30% SOC capacity should be ≤0.5C. In this scheme, a segmented formation method is adopted, the first segment is charged at a small current, the SEI film is mainly thin, compact and organic lithium compound, the second segment is charged at a larger current to 60% SOC, and the SEI is mainly thick, loose and porous inorganic lithium salt. After charging to 60% SOC, the battery is continuously kept at the original pressure and temperature for 20min. The segmented formation is beneficial to the full reaction of the electrode and electrolyte interface side reaction, improves the capacity consistency and self-discharge screening consistency, the constant temperature and pressure keeping after the formation can make the SEI film more uniform and stable, and is beneficial to the improvement of the high-temperature cycle retention rate.

[0098] The technical solutions of the present application are described in detail below through specific embodiments.

[0099] Example 1

[0100] The embodiment provides a battery, a positive plate of the battery comprising a lithium cobaltate material and a ternary positive material. The mass ratio of the lithium cobaltate material and the ternary positive material is 60:40; the particle size Dv50 of the lithium cobaltate material is 16.5 microns (including a coating layer), the material of the coating layer is fast ion conductor lithium aluminum titanium phosphate (LATP), and the coating thickness is 100 nm; the particle size Dv50 of the ternary positive material (NCM613) is 3.92 microns, the particle size Dv90 is 7.1 microns, the particle size Dv100 is 15.45 microns (including a coating layer), the material of the coating layer is aluminum oxide and zirconium oxide (the mass ratio of the aluminum oxide and the zirconium oxide is 9:1), and the coating thickness is 50 nm.

[0101] The manufacturing process of the battery is as follows:

[0102] 1) The lithium cobaltate material, the ternary positive material, the conductive agent (CNT) and the adhesive (PVDF5130) are mixed according to the mass ratio 60:40:0.7:0.8 to obtain a mixed positive electrode slurry.

[0103] 2) The mixed positive electrode slurry is coated on the surface of the current collector, dried, and rolled (the compaction density is 3.78 g / cm 3 ) to obtain a positive plate.

[0104] 3) The artificial graphite, Super-P, the adhesive (styrene butadiene rubber and SBR) and the thickening agent (carboxymethyl cellulose lithium and CMCLi) are mixed according to the mass ratio 100:0.5:1:1.1 to obtain a negative electrode slurry.

[0105] 4) The negative electrode slurry is uniformly coated on the two side surfaces of the copper foil, dried, and pressed (the compaction density is 1.68 g / cm 3 ), cut, to obtain a negative plate.

[0106] 5) The cut positive plate, the negative plate, the separator (oil-based DMAC separator) are prepared into an electric core in the form of winding, and then packaged into a to-be-liquid-injected electric core through an aluminum plastic film.

[0107] 6) Inject electrolyte, electrolyte formula: electrolyte lithium salt (LiPF6), the concentration of lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of EC\PC\DEC\PP; the additives are 1,3-propane sulfone lactone (PS), ethylene sulfite (DTD), vinylene carbonate (VC), fluoroethylene carbonate (FEC), tris (2,2,2-trifluoroethyl) phosphite (TTFEP), lithium difluorophosphate (LiPO2F2), HTCN (1,3,6-hexane trinitrile), SN (butanedinitrile), and the mass fraction of the additives is 3%, 0.6%, 0.3%, 7%, 0.3%, 0.3%, 2% and 1.5% of the total mass of lithium salt and ester solvent respectively. The amount of FEC per unit area of the negative electrode is 0.05 g / m 2 .

[0108] 7) After injecting the liquid, the battery is sealed, aged at 45℃ for 48h, and then formed. The formation temperature is 80℃, and the battery is formed in two steps, the first step is small current 0.1C charging to 20% SOC, and the second step is current 0.2C charging to 40% SOC, and the pressure after formation is 1.1MPa (DMAC diaphragm).

[0109] 8) After the formation is completed, the battery is kept at constant temperature and constant pressure for 20min, the battery is cooled to 45℃, the pressure is adjusted to the target pressure (0.8MPa), and then 0.5C charging is carried out to the target voltage (4400mV), 0.02C cutoff, 0.5C discharging to 3.0V, and such cycle is carried out twice, finally vacuum sealing, 45℃ secondary aging for 24h, and then performing the capacity distribution. The capacity distribution is 0.5C charging to 4.45V, 0.05C cutoff, and 0.2C discharging to 3.0V. After the capacity distribution, the battery is left for 24h to test OCV1, and OCV2 is tested after seven days, and the self-discharge K value is calculated.

[0110] Example 2

[0111] The present embodiment provides a battery, the positive electrode sheet of the battery includes lithium cobaltate material and ternary positive electrode material. The mass ratio of the lithium cobaltate material and the ternary positive electrode material is 60:40; the particle size Dv50 of the lithium cobaltate material is 20μm (including the coating layer), the material of the coating layer is fast ion conductor lithium aluminum titanium phosphate (LATP), and the coating thickness is 100nm; the particle size Dv50 of the ternary positive electrode material (NCM613) is 3.92μm, the particle size Dv90 is 7.1μm, and the particle size Dv100 is 15.45μm (including the coating layer), the material of the coating layer is aluminum oxide and zirconium oxide (the mass ratio of aluminum oxide and zirconium oxide is 9:1), and the coating thickness is 50nm.

[0112] The manufacturing method of the battery provided in Example 2 is the same as that in Example 1.

[0113] The difference between Example 2 and Example 1 is that the particle size Dv50 of the lithium cobalt oxide material is 20 μm (including the coating layer).

[0114] Example 3

[0115] The present embodiment provides a battery, the positive electrode sheet of which comprises a lithium cobalt oxide material and a ternary positive electrode material. The mass ratio of the lithium cobalt oxide material and the ternary positive electrode material is 90:10; the particle size Dv50 of the lithium cobalt oxide material is 16.5 μm (including the coating layer), the material of the coating layer is fast ion conductor lithium aluminum titanium phosphate (LATP), and the coating thickness is 100 nm; the particle size Dv50 of the ternary positive electrode material (NCM613) is 3.92 μm, the particle size Dv90 is 7.1 μm, the particle size Dv100 is 15.45 μm (including the coating layer), the material of the coating layer is aluminum oxide and zirconium oxide (the mass ratio of aluminum oxide and zirconium oxide is 9:1), and the coating thickness is 50 nm.

[0116] The manufacturing method of the battery provided in Example 3 is the same as that in Example 1.

[0117] The difference between Example 3 and Example 1 is that the mass ratio of the lithium cobalt oxide material and the ternary positive electrode material is 90:10.

[0118] Example 4

[0119] The present embodiment provides a battery, the positive electrode sheet of which comprises a lithium cobalt oxide material and a ternary positive electrode material. The mass ratio of the lithium cobalt oxide material and the ternary positive electrode material is 60:40; the particle size Dv50 of the lithium cobalt oxide material is 16.5 μm (including the coating layer), the material of the coating layer is fast ion conductor lithium aluminum titanium phosphate (LATP), and the coating thickness is 20 nm; the particle size Dv50 of the ternary positive electrode material (NCM613) is 3.92 μm, the particle size Dv90 is 7.1 μm, the particle size Dv100 is 15.45 μm (including the coating layer), the material of the coating layer is aluminum oxide and zirconium oxide (the mass ratio of aluminum oxide and zirconium oxide is 9:1), and the coating thickness is 50 nm.

[0120] The manufacturing method of the battery provided in Example 4 is the same as that in Example 1.

[0121] The difference between Example 4 and Example 1 is that the thickness of the coating layer (the first coating layer) on the surface of the lithium cobalt oxide material is 20 nm.

[0122] Example 5

[0123] The embodiment provides a battery, and the positive plate of the battery comprises lithium cobaltate material and ternary positive material. The mass ratio of the lithium cobaltate material and the ternary positive material is 60:40; the particle size Dv50 of the lithium cobaltate material is 16.5 microns (including a coating layer), the material of the coating layer is fast ion conductor lithium aluminum titanium phosphate (LATP), and the coating thickness is 100 nm; the particle size Dv50 of the ternary positive material (NCM613) is 3.92 microns, the particle size Dv90 is 7.1 microns, the particle size Dv100 is 15.45 microns (including a coating layer), the material of the coating layer is aluminum oxide and zirconium oxide (the mass ratio of the aluminum oxide and the zirconium oxide is 9:1), and the coating thickness is 10 nm.

[0124] The manufacturing method of the battery provided in the embodiment 5 is the same as that in the embodiment 1.

[0125] The difference between the embodiment 5 and the embodiment 1 is that the thickness of the coating layer (the second coating layer) on the surface of the ternary positive material is 10 nm.

[0126] Embodiment 6

[0127] The embodiment provides a battery, and the positive plate of the battery comprises lithium cobaltate material and ternary positive material. The mass ratio of the lithium cobaltate material and the ternary positive material is 60:40; the particle size Dv50 of the lithium cobaltate material is 16.5 microns (including a coating layer), the material of the coating layer is fast ion conductor lithium aluminum titanium phosphate (LATP), and the coating thickness is 100 nm; the particle size Dv50 of the ternary positive material (NCM613) is 3.92 microns, the particle size Dv90 is 7.1 microns, the particle size Dv100 is 15.45 microns (including a coating layer), the material of the coating layer is aluminum oxide and zirconium oxide (the mass ratio of the aluminum oxide and the zirconium oxide is 9:1), and the coating thickness is 10 nm.

[0128] The manufacturing method of the battery provided in the embodiment 6 is the same as that in the embodiment 1.

[0129] The difference between the embodiment 6 and the embodiment 1 is that the lithium cobaltate material does not contain a coating layer (the first coating layer).

[0130] Embodiment 7

[0131] The embodiment provides a battery, and the positive plate of the battery comprises lithium cobaltate material and ternary positive material. The mass ratio of the lithium cobaltate material and the ternary positive material is 60:40; the particle size Dv50 of the lithium cobaltate material is 16.5 microns (including a coating layer), the material of the coating layer is fast ion conductor lithium aluminum titanium phosphate (LATP), and the coating thickness is 100 nm; the particle size Dv50 of the ternary positive material (NCM613) is 3.92 microns, the particle size Dv90 is 7.1 microns, the particle size Dv100 is 15.45 microns (including a coating layer), the material of the coating layer is aluminum oxide and zirconium oxide (the mass ratio of the aluminum oxide and the zirconium oxide is 9:1), and the coating thickness is 10 nm.

[0132] The manufacturing method of the battery provided in the embodiment 7 is the same as that in the embodiment 1.

[0133] Example 7 and Example 1 differ in that the ternary positive electrode material does not contain a coating layer (second coating layer).

[0134] Example 8

[0135] This example provides a battery, the positive electrode sheet of the battery includes lithium cobaltate material and ternary positive electrode material. Among them, the mass ratio of lithium cobaltate material and ternary positive electrode material is 60:40; the particle size Dv50 of lithium cobaltate material is 16.5μm (including coating layer), the material of the coating layer is aluminum oxide and zirconium oxide (the mass ratio of aluminum oxide and zirconium oxide is 9:1), and the coating thickness is 100nm; the particle size Dv50 of ternary positive electrode material (NCM613) is 3.92μm, the particle size Dv90 is 7.1μm, and the particle size Dv100 is 15.45μm (including coating layer), the material of the coating layer is aluminum oxide and zirconium oxide (the mass ratio of aluminum oxide and zirconium oxide is 9:1), and the coating thickness is 50nm.

[0136] The manufacturing method of the battery provided in Example 8 is the same as that in Example 1.

[0137] Example 8 and Example 1 differ in that the coating layer materials of lithium cobaltate material and ternary positive electrode material are the same.

[0138] Example 9

[0139] This example provides a battery, the positive electrode sheet and the negative electrode sheet of the battery provided in Example 9 are the same as those in Example 1.

[0140] The manufacturing method of the battery provided in Example 9 is the same as that in Example 1.

[0141] Example 9 and Example 1 differ in that in the step 2) in the manufacturing process of the battery, the compaction density of the positive electrode sheet (positive electrode active material layer) is 4.1g / cm 3 .

[0142] Comparative Example 1

[0143] This comparative example provides a battery, the positive electrode sheet of the battery includes lithium cobaltate material and ternary positive electrode material. Among them, the mass ratio of lithium cobaltate material and ternary positive electrode material is 60:40; the particle size Dv50 of lithium cobaltate material is 13μm (including coating layer), the material of the coating layer is fast ion conductor lithium titanium aluminum phosphate (LATP), and the coating thickness is 100nm; the particle size Dv50 of ternary positive electrode material (NCM613) is 5μm, the particle size Dv90 is 10.15μm, and the particle size Dv100 is 18μm (including coating layer), the material of the coating layer is aluminum oxide and zirconium oxide (the mass ratio of aluminum oxide and zirconium oxide is 9:1), and the coating thickness is 50nm.

[0144] The manufacturing method of the battery provided in Comparative Example 1 is the same as that in Example 1.

[0145] Comparative Example 2

[0146] The present comparative example provides a battery, which includes a lithium cobaltate material and a ternary positive electrode material in the positive electrode sheet of the battery. The mass ratio of the lithium cobaltate material and the ternary positive electrode material is 40:60; the particle size Dv50 of the lithium cobaltate material is 16.5 μm (including a coating layer), the material of the coating layer is fast ion conductor lithium titanium aluminum phosphate (LATP), and the coating thickness is 100 nm; the particle size Dv50 of the ternary positive electrode material (NCM613) is 3.92 μm, the particle size Dv90 is 7.1 μm, the particle size Dv100 is 15.45 μm (including a coating layer), the material of the coating layer is aluminum oxide and zirconium oxide (the mass ratio of aluminum oxide and zirconium oxide is 9:1), and the coating thickness is 50 nm.

[0147] The battery provided by Comparative Example 2 is manufactured in the same manner as Example 1.

[0148] The batteries obtained in Examples 1-9 and Comparative Examples 1-2 are tested as follows.

[0149] (1) Cycle performance test

[0150] (1-1) Normal temperature cycle test: under the condition of 25±1℃, the battery is charged at 0.7C and discharged at 0.5CP to perform charge-discharge cycle test. The steps are as follows: stand for 10 min; 0.5C constant current charging to 4.45V, constant voltage charging to 0.05C cutoff; stand for 10 min; 0.5CP constant power discharging to 3.0V, which is 1 cycle. Repeat the steps, and test the capacity retention rate of the battery after 1000 cycles.

[0151] (1-2) High temperature cycle test: under the condition of 45±1℃, the battery is charged at 0.7C and discharged at 0.5CP to perform charge-discharge cycle test. The steps are as follows: stand for 10 min; 0.7C constant current charging to 4.45V, constant voltage charging to 0.05C cutoff; stand for 10 min; 0.5CP constant power discharging to 3.0V, which is 1 cycle. Repeat the steps, and test the capacity retention rate of the battery after 700 cycles.

[0152] (1-3) Low temperature cycle test: under the condition of 10±1℃, the battery is charged at 0.7C and discharged at 0.5CP to perform charge-discharge cycle test. The steps are as follows: stand for 10 min; 0.7C constant current charging to 4.45V, constant voltage charging to 0.05C cutoff; stand for 10 min; 0.5CP constant power discharging to 3.0V, which is 1 cycle. Repeat the steps, and test the capacity retention rate of the battery after 300 cycles.

[0153] (2) High temperature storage performance test

[0154] The battery prepared in each of the above examples and comparative examples was charged at 0.7C constant current and constant voltage to 4.45V at 25°C, cut off at 0.05C, and then left for 30 min, and then discharged at 0.2C constant current to 3.0V, and the discharge capacity was taken as the initial capacity Co. The thickness H0 of the battery before storage was measured, and the battery was transferred to a high-temperature test cabinet and stored at 60°C for 30 days. After storage, the battery was taken out and the thickness H1 of the battery immediately after storage was measured, and then the battery was cooled to room temperature and discharged at 0.2C constant current to 3.0V. The discharge capacity C1 was recorded, and then the battery was charged at 0.7C constant current and constant voltage to 4.45V, cut off at 0.05C, and left for 30 min, and then discharged at 0.2C constant current to 3.0V. The discharge capacity C2 was recorded.

[0155] The capacity retention rate (%) = C1 / C0 x 100%;

[0156] The capacity recovery rate (%) = C2 / C0 x 100%;

[0157] The battery thickness expansion rate (%) = [(H1-H0) / H0] x 100%; and the test results are summarized in Table 1.

[0158] Table 1

[0159]

[0160]

[0161] In Example 1, by reasonably matching the particle size of the lithium cobaltate material and the ternary positive electrode material in the positive electrode, and by using a suitable electrolyte and by controlling the formation step, a uniform and dense SEI film can be obtained. The ternary positive electrode material has a large amount of lithium extraction and insertion, and the crystal framework changes significantly, which can easily lead to the rupture of the positive electrode particles after long cycle. This is particularly evident in polycrystalline ternary positive electrode materials, and defects are easily generated at the grain boundaries under stress. Therefore, the small particle single-crystal ternary positive electrode material introduced in this embodiment can better compensate for the structural defects of the material. At the same time, the protective effect of the electrolyte on the lithium cobaltate material and the ternary positive electrode material avoids the oxidation and decomposition of the electrolyte by the high-activity transition metal at the positive electrode rupture site in the high oxidation state, thereby avoiding the drying of the electrolyte, local lithium precipitation, and cycle performance degradation.

[0162] In Comparative Example 1, unlike Example 1, when a large particle ternary positive electrode material is used, the overall performance decreases. The reason may be that the large particles of the ternary positive electrode material are broken during tabletting due to overpressure stress, and such microscopic damage is often not directly reflected in the initial stage, but becomes apparent in the later cycle or long-term high-temperature storage, resulting in decreased retention rate and increased expansion.

[0163] In Comparative Example 2, different from Example 1, the mass ratio of the ternary positive electrode material is larger, and since the performance of the ternary positive electrode material is slightly lower than that of the lithium cobaltate material, the battery performance obtained is lower than that of Example 1.

[0164] In Examples 4 to 8, different from Example 1, the thickness of the coating layer, the presence or absence of the coating layer, and the material of the coating layer can obviously affect the battery performance, so the parameters of the coating layer can be adjusted to control the battery performance.

[0165] In Example 9, the compaction density of the positive electrode sheet does not meet the formula provided by the present application, and the compaction is too large, so that the ternary particles and lithium cobaltate particles may be broken at the same time during the pressing process of the positive electrode sheet, thereby the battery performance is reduced. This also illustrates the superiority of the formula provided by the present application.

[0166] In the description of the embodiments of the present application, it should be noted that the terms “center”, “upper”, “lower”, “left”, “right”, “vertical”, “horizontal”, “inner”, “outer” and the like refer to the orientation or positional relationship based on the drawings, and are only used to facilitate the description of the present application and simplify the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0167] The above disclosure is only one preferred embodiment of the present application, and of course cannot limit the scope of the present application. Those skilled in the art can understand that the above-mentioned all or part of the processes can be implemented, and equivalent changes made according to the claims of the present application still belong to the scope covered by the present application.

Claims

1. A hybrid cathode material, characterized in that, The mixture includes lithium cobalt oxide material and ternary cathode material, wherein the particle size of the lithium cobalt oxide material is larger than that of the ternary cathode material, and the mass percentage of the lithium cobalt oxide material in the mixed cathode material is greater than or equal to the mass percentage of the ternary cathode material in the mixed cathode material. The particle size Dv50 of the lithium cobalt oxide material is greater than the particle size Dv100 of the ternary cathode material, and the particle size Dv100 of the ternary cathode material is C, where C satisfies 0 < C < 16 μm.

2. The hybrid cathode material according to claim 1, characterized in that, There are interparticle gaps between the multiple lithium cobalt oxide material particles, and a portion of the ternary cathode material fills the interparticle gaps.

3. The hybrid cathode material according to claim 1, characterized in that, The particle size Dv50 of the lithium cobalt oxide material is A, where A satisfies 16μm≤A≤20μm; and / or The particle size Dv90 of the ternary cathode material is B, where B satisfies 0 < A ≤ 10 μm; and / or The ternary cathode material is a single crystal particle.

4. The hybrid cathode material according to claim 1, characterized in that, In the hybrid cathode material, the mass ratio of the lithium cobalt oxide material to the ternary cathode material is (50~90):(10~50).

5. The hybrid cathode material according to claim 1, characterized in that, The outer surface of the lithium cobalt oxide material is covered with a first coating layer, which is an inorganic ceramic material.

6. The hybrid cathode material according to claim 5, characterized in that, The thickness of the first coating layer is 10 nm to 300 nm; and / or The mass ratio of the first coating layer to the lithium cobalt oxide material is (1~10):(90~99); and / or The material of the first coating layer includes at least one of oxides, sulfides, and inorganic solid electrolytes.

7. The hybrid cathode material according to claim 1, characterized in that, The outer surface of the ternary cathode material is covered with a second coating layer, which is an inorganic ceramic material.

8. The hybrid cathode material according to claim 7, characterized in that, The thickness of the second coating layer is 5 nm to 200 nm; and / or The mass ratio of the second coating layer to the ternary cathode material is (0.2~3):(97~99.8); and / or The material of the second coating layer includes at least one of oxides, sulfides, and inorganic solid electrolytes.

9. A method for fabricating a hybrid cathode material, characterized in that, The manufacturing method is used to prepare the hybrid cathode material as described in any one of claims 1-8, and the manufacturing method includes: The mixed cathode material is obtained by mixing lithium cobalt oxide material and ternary cathode material; Wherein, the particle size of the lithium cobalt oxide material is larger than that of the ternary cathode material, and the mass percentage of the lithium cobalt oxide material in the mixed cathode material is greater than or equal to the mass percentage of the ternary cathode material in the mixed cathode material.

10. A positive electrode plate, characterized in that, The positive electrode sheet includes a current collector and a positive electrode active material layer disposed on the current collector, wherein the positive electrode active material layer includes a mixed positive electrode material as described in any one of claims 1-8.

11. The positive electrode sheet according to claim 10, characterized in that, The compaction density of the positive electrode active material layer satisfies the following formula: (G1*4.15+G2*3.5)-0.1; where G1 is the mass percentage of the lithium cobalt oxide material, G2 is the mass percentage of the ternary positive electrode material, and the unit of the compaction density of the positive electrode sheet is g / cm³. 3 .

12. A battery, characterized in that, It includes an electrolyte, a separator, a negative electrode, and a positive electrode as described in claim 10 or 11, wherein the separator is disposed between the positive electrode and the negative electrode, and the separator, the negative electrode, and the positive electrode are all immersed in the electrolyte.

13. An electrical appliance, characterized in that, It includes an electrical device and a battery as described in claim 12, wherein the battery supplies power to the electrical device.

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