Cathode materials, electrochemical devices and electronic devices

Abstract

To provide a positive electrode material, an electrochemical device, and an electronic apparatus.SOLUTION: A positive electrode material includes a first active material and a second active material. The first active material includes a lithium transition metal oxide. A general chemical formula of the second active material is Li1+(a / (2+a))Mn2a / (2+a)M6 / (2+a)-2O2, where 0.5≤a≤1, M is selected from one or a plurality of Ni, Co, Mn, Mg, Al, Ti, Zr, Nb, La, Sr, and W, and the second active material produces a MnO2 coating layer when having a lithium potential higher than X volt (V), where 4.3≤X≤4.6. The positive electrode material of the present invention has higher high-temperature cycle stability when used in a battery.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a positive electrode material, an electrochemical device, and an electronic device. [Background technology]

[0002] With the development of technology and the increasing demand for mobile devices, the demand for secondary batteries as an energy source is growing rapidly. Among these secondary batteries, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0003] However, the positive electrode material used in lithium-ion batteries (lithium manganese oxide (LiNi 1.5 Mn 0.5 O 4 ), ternary materials (NCM / NCA), lithium iron manganese phosphate, lithium iron phosphate, lithium cobalt oxide, etc.) all have the disadvantage of poor high-temperature cycling performance. For example, when used at temperatures above 40°C, their cycling performance drops significantly, which severely limits the use of lithium-ion batteries. Summary of the Invention [Problem to be solved by the invention]

[0004] In order to overcome the problems such as low high-temperature cycle stability of the positive electrode material in the prior art, a positive electrode material, a positive electrode sheet, an electrochemical device and an electronic device are provided. The positive electrode material of the present invention is used in an electrochemical device, and can effectively improve the cycle performance of the electrochemical device at 45°C. [Means for solving the problem]

[0005] In order to achieve the above objectives, the technical solutions adopted in the present invention are as follows: In a first aspect, the present invention provides a cathode material comprising a first active material and a second active material. Here, the first active material includes a lithium transition metal oxide. Here, the general formula of the second active material is Li 1+(a / (2+a)) Mn 2a / (2+a) M 6 / (2+a)-2 O 2 where 0.5≦a≦1, M is selected from one or more of Ni, Co, Mn, Mg, Al, Ti, Zr, Nb, La, Sr, and W, and the second active material is MnO when it has a potential vs. lithium higher than X volts (V). 2 A coating layer is formed, where 4.3≦X≦4.6.

[0006] In a second aspect, the present invention also provides a positive electrode sheet comprising the positive electrode material described above.

[0007] In a third aspect, the present invention also provides an electrochemical device comprising the positive electrode sheet.

[0008] In a fourth aspect, the present invention also provides an electronic device comprising the electrochemical device described above.

[0009] Based on common knowledge in the art, the above preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention.

[0010] All reagents and raw materials used in the present invention are commercially available. Effect of the Invention

[0011] The advantageous effects of the present invention are as follows: The positive electrode material of the present invention is used in an electrochemical device, and compared with a solution using only the same first active material, the improvement in 45°C cycle capacity retention is 1.1% or more, the high temperature cycle capacity retention is improved, and the cycle performance of the entire battery cell is improved. [Brief description of the drawings]

[0012] [Figure 1] 1 is a graph showing cycle capacity retention rates after 500 cycles in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the scope of these examples. In the following examples, experimental methods for which conditions are not specified are selected according to conventional methods and conditions or product instructions.

[0014] Cathode Materials

[0015] The positive electrode material of the first aspect of the present invention includes a first active material and a second active material, the first active material including a lithium transition metal oxide. The general chemical formula of the second active material is Li 1+(a / (2+a)) Mn 2a / (2+a) M 6 / (2+a)-2 O 2 wherein 0.5≦a≦1 and M is selected from one or more of Ni, Co, Mn, Mg, Al, Ti, Zr, Nb, La, Sr, and W; Here, the second active material is MnO when the second active material has a potential relative to lithium higher than X volts (V). 2 A coating layer is formed, where 4.3≦X≦4.6.

[0016] In the present invention, the potential versus lithium is the potential of the working electrode obtained by testing with lithium metal as the reference electrode.

[0017] Preferably, the first active material is lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), nickel cobalt manganese ternary material (NCM), lithium cobalt oxide (LCO), lithium rich manganese oxide (LRMO), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O 4 ) is preferably included.

[0018] In some particular embodiments, the first active material is LiNi 0.9 Co 0.06 Mn 0.04 O 2 , LiCoO 2, LiNi 1.5 Mn 0.5 O 4 , LiMn 0.6 Fe 0.4 PO 4 , LiFePO 4 , and Li 1.1 Ni 0.4 Mn 0.6 O 2 It may be one or more of:

[0019] In some particular embodiments, the first active material comprises lithium iron phosphate and / or lithium manganese iron phosphate, and the lithium iron phosphate and / or lithium manganese iron phosphate are LiMn 0.6 Fe 0.4 PO 4 / 0.02C and / or LiFePO 4 Includes a carbon coating layer such as / 0.013C.

[0020] In the present invention, the introduction of the second active material improves the high temperature cycle performance of the first active material.

[0021] Preferably, the general formula of the second active material is Li 1+(a / (2+a)) Mn 2a / (2+a)-A M 6 / (2+a)-2 O 2-2A / AMnO 2 Here, 0≦A≦0.05 and 0.5≦a≦1.

[0022] In some particular embodiments, the second active material is Li 1.09 Mn 0.5 Ni 0.5 O 2 , Li 1.27 Mn 0.55 Ni 0.19 O 2 , Li 1.23 Mn 0.46 Ni 0.31 O 2 and Li 1.2 Mn 0.4 Ni 0.4 O 2 It may be one or more of:

[0023] Preferably, the mass percentage of the second active material is 1% to 30%. More preferably, it is 5% to 15%, and the percentage is the mass percentage of the second active material in the total mass of the first active material and the second active material. If the mass percentage of the second active material is too high, the cycle characteristics of the positive electrode sheet are deteriorated. If the mass percentage is too low, the effect of improving the cycle performance is not significant.

[0024] In some specific embodiments, the mass percentage of the second active material is 0.9%, 1%, 5%, 10%, 15%, 30%, or 31%, where the percentage is the mass of the second active material as a percentage of the combined mass of the first active material and the second active material.

[0025] Preferably, MnO 2 The coating layer is 5% to 30%, and more preferably 10% to 20%. The percentage of the coating amount is the ratio of MnO to the mass of the second active material. 2 The second active material is MnO to improve its stability during cycling, reduce its interface side reactions, and improve the cycling performance of the battery core. 2 It has a coating layer.

[0026] Preferably, MnO 2 is an amorphous form. Amorphous MnO 2 can suppress the dissolution of the precious metal in the second active material and improve the cycle stability of the positive electrode material.

[0027] Preferably, the primary particle diameter of the second active material is 40 nm to 600 nm. More preferably, it is 100 nm to 200 nm. Within the particle diameter range of the present invention, the capacity performance and cycle performance of the second active material are superior. The primary particle diameter is common knowledge in the technical field, and generally refers to the particle diameter of a single microcrystalline particle, and is also called the original particle diameter.

[0028] In some preferred embodiments, the first active material is LiFePO 4 and the second active material is Li 1.09 Mn0.5 Ni 0.5 O 2 and MnO 2 The coating amount of the coating layer is 10% to 20%.

[0029] In some preferred embodiments, the first active material is Li 1.1 Ni 0.4 Mn 0.6 O 2 and the second active material is Li 1.09 Mn 0.5 Ni 0.5 O 2 and MnO 2 The coating amount of the coating layer is 10% to 20%.

[0030] In some particular embodiments, the positive electrode material also includes a third active material, the third active material having a general formula of Li 6-x M 1-y N y O 4-z where 0≦x≦5.95, 0≦y≦1, and 0≦z≦2. M includes one or more of Fe, Ni, Co, and Cu, and N includes one or more of Al, Mn, Ti, and Si.

[0031] In particular, the third active material is Li 5 FeO 4 , Li 6 Chief of Staff 4 , Li 2 NiO 2 , and Li 2 Ni 0.5 Cu 0.5 O 2 It is preferred that the compound is one or more of the following:

[0032] Preferably, the mass percentage of the second active material and the third active material to the total mass is 1% to 30%, the percentage is the percentage of the total mass of the second active material and the third active material to the total mass of the first active material, the second active material, and the third active material, and the mass ratio of the second active material to the third active material is (2 to 20:1).

[0033] In some specific embodiments, the mass ratio of the second active material to the third active material is 4:1, 9:1, or 7:3.

[0034] In some specific embodiments, the mass ratio of the first active material, the second active material, and the third active material is 90:8:2, 90:9:1, or 90:7:3.

[0035] Positive electrode sheet

[0036] The positive electrode sheet provided in the second aspect of the present invention comprises a positive electrode material.

[0037] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. The positive electrode active material layer includes a positive electrode material, a conductive agent, and a binder.

[0038] In particular, the positive electrode current collector is not particularly limited as long as it does not undergo chemical changes in the battery and has electrical conductivity. For example, the positive electrode current collector may be made of stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel that has been surface-treated with carbon, nickel, titanium, silver, or the like, but is not limited thereto.

[0039] The positive electrode material is as described above, and therefore a detailed description thereof will be omitted here.

[0040] In particular, the conductive agent can be selected according to actual needs as long as it is conductive and does not cause chemical changes in the battery.For example, specifically, graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium dioxide; or conductive polymers such as polyphenylene derivatives.These may be used alone or in combination of two or more.

[0041] In particular, the binder plays a role in improving the adhesion between the positive electrode active material particles and between the positive electrode active material and the positive electrode current collector. The type of the binder is not particularly limited, and specific examples of the binder include polyvinylidene fluoride (PVDF), polyvinylidene fluoride hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and any one or a mixture of two or more of these.

[0042] In particular, the mass ratio of the conductive agent, the binder and the positive electrode material is preferably (95-98):(0.5-3):(1-3), and more preferably 97:1.5:1.5.

[0043] Electrochemical Equipment

[0044] A third aspect of the present invention provides an electrochemical device comprising the above positive electrode sheet.

[0045] In the present invention, the electrochemical device may be a battery including a positive electrode sheet, a negative electrode sheet disposed opposite the positive electrode sheet, a separator disposed between the positive electrode sheet and the negative electrode sheet, and an electrolyte, where the positive electrode sheet is as described above. The battery may also include a battery case that houses the positive electrode sheet, the negative electrode sheet, and the separator, and a sealing member that seals the battery case, as necessary.

[0046] In this battery, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, and optionally a conductive agent and a binder.

[0047] In particular, a compound capable of reversibly absorbing and releasing lithium can be used as the negative electrode active material. Specific examples of the negative electrode active material include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; (semi)metallic materials capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; SiO β (0<β<2), SnO 2 , vanadium oxide, or lithium vanadium oxide, which may be doped or undoped with lithium; composite materials containing (semi)metallic or carbonaceous materials, such as Si-C composite materials and Sn-C composite materials, which may be used alone or in combination of two or more.

[0048] In particular, the conductive agent is a reagent used to improve the charge / discharge performance of the electrode, and may be selected from graphite materials such as natural graphite and artificial graphite; carbon black materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; non-metal powders such as carbon fluoride powder; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium dioxide, and polyphenylene derivatives.

[0049] In particular, the binder is a component that promotes the binding between the active material and the conductive agent, and between the active material and the current collector, and may be selected from polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers.

[0050] In particular, the negative electrode current collector functions as a substrate supporting the electrode active material, and is usually a metal foil having a thickness of 3 microns to 500 microns. There is no particular limitation as long as the material has high conductivity and does not cause a chemical reaction in the secondary battery system. For example, the material may be a foil material surface-treated with nickel, titanium, aluminum, silver, stainless steel, carbon, or the like. The surface of the negative electrode current collector is usually smooth, but fine lines or the like may be formed on the surface to improve the adhesion between the positive electrode active material and the current collector. As the negative electrode current collector, in addition to foil materials, various forms such as films, meshes, porous materials, foams, and nonwoven fabrics may be used alone or in combination.

[0051] In the present invention, the separator is disposed between the positive electrode sheet and the negative electrode sheet, and is an insulating film having chemical resistance, hydrophobicity, ion permeability and high mechanical strength. The separator generally has a thickness of 9 μm to 18 μm. The pore size is 5 μm to 300 μm. The air permeability is 180 sec / 100 mL to 380 sec / 100 mL. The porosity is 30% to 50%. Examples of the separator include a sheet or nonwoven fabric made of an olefin polymer such as polypropylene. Glass fiber or polyethylene may also be used.

[0052] In the present invention, the electrolyte usually contains a non-aqueous solvent, a lithium salt, and an additive.

[0053] In particular, the non-aqueous solvent may be a conventional non-aqueous solvent in the art, preferably an ester solvent, more preferably a carbonate-based solvent, and in particular, the carbonate-based solvent is preferably one or more of ethylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0054] In particular, examples of lithium salts include LiPF 6 , LiBF 4 , LiN(SO 2 F) 2 (abbreviated as LiFSI), LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (abbreviated as LiBOB), LiBF 2 (C 2 O 4 ) (abbreviated as LiDFOB), LiN(SO 2 RF) 2 , LiN(SO 2 F)(SO 2 RF) in the electrolyte. The content of the electrolyte is preferably 5% to 20%.

[0055] In particular, the additive is preferably one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), ethylene sulfate (DTD), vinylene sulfate, 1,3-propane sultone (PS), 1-propene 1,3-sultone, and 1,4-butane sultone. Conventional amounts of additives in the electrolyte are 1% to 4% of the electrolyte, for example 2%.

[0056] The present invention is not particularly limited to the shape of the battery, which may be cylindrical, rectangular, or of other shapes.

[0057] electronic equipment

[0058] The electronic device of the present invention comprises the electrochemical device of the third aspect.

[0059] By way of example, the electronic device of the present invention may be, but is not limited to, a mobile device (e.g., a mobile phone, a tablet computer, a notebook computer, a video recorder, a portable printer / copier, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric locomotive, a marine vessel, a satellite, an energy storage system, a backup power source, etc.

[0060] Based on common knowledge in the art, the above preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention.

[0061] Example 1

[0062] In this embodiment, 85% LiMn 0.6 Fe 0.4 PO 4 / 0.02C and 15% Li 1.09 Mn 0.5 Ni 0.5 O 2 A positive electrode sheet is provided having a cathode material containing: At the same time, the positive electrode sheet contains conductive carbon black (Super P), and the mass ratio of polyvinylidene fluoride (PVDF) to the positive electrode material is 1.5:1.5:97.

[0063] (1) The method for producing a positive electrode sheet includes the following steps.

[0064] First, the positive electrode sheet, Super P, and PVDF were mixed in the above ratio, and nitrogen methylpyrrolidone (NMP) was gradually added while stirring at high speed to prepare a positive electrode slurry with a specified viscosity. Next, the prepared slurry was evenly applied onto aluminum foil and dried for 10 minutes in a 120°C air drying oven. Finally, the dried electrode sheet was rolled and cut to prepare a positive electrode sheet.

[0065] (2) Preparation of electrolyte:

[0066] The organic solvent was a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) and polycarbonate (PC), where the volume ratio of EC, EMC, DMC and PC was 30:35:30:5. A sufficiently dried lithium salt (LiPF 6 ) was dissolved in an organic solvent and mixed uniformly to obtain LiPF 6 An electrolyte solution with a concentration of 1 mol / L was obtained.

[0067] (3) Preparation of separator: A polypropylene separator with a thickness of 12 μm was used.

[0068] (4) Preparation of negative electrode sheet: The negative electrode active material graphite, the conductive agent acetylene black, the thickener sodium carboxymethylcellulose, and the adhesive styrene butadiene rubber were mixed in a mass ratio of 97:1:1:1. After adding deionized water, the negative electrode slurry was obtained under the action of a vacuum mixer. The negative electrode slurry was uniformly applied onto an 8 μm copper foil current collector. After drying at room temperature, the copper foil current collector was transferred to an oven for drying, cold pressed, and cut to obtain a negative electrode sheet.

[0069] (5) Battery preparation: The positive electrode sheet, separator, and negative electrode sheet prepared above were laminated in this order so that the separator was located between the positive electrode sheet and the negative electrode sheet to play an insulating role. Next, the product was wrapped in aluminum plastic film, transferred to a vacuum oven and dried at 120°C, and 3.0g / Ah of electrolyte was injected and the opening was sealed. After going through processes such as leaving, hot pressing, cold pressing, 4.5V formation, fixing, and grading, a soft pack battery (i.e., a lithium ion battery) with a capacity of 1Ah was finally produced.

[0070] The method of producing the positive electrode sheets in the other examples and comparative examples was the same as in Example 1. The preparation parameters set in Examples 2 to 23 and Comparative Examples 1 to 8 are shown in Table 1. The preparation parameters set in Examples 24 to 27 are shown in Table 2.

[0071] Examples of Effects

[0072] Capacity retention test method: In the desired voltage range, the maximum value of the voltage range was the charging voltage of the lithium-ion battery, and the minimum value was the discharging voltage. Charge and discharge were performed at 1C / 1C at 45°C, and the ratio of the discharge capacity at the 500th cycle to the 1st cycle was taken as the capacity retention. [Table 1] JPEG0007681087000002.jpg254165JPEG0007681087000003.jpg160165

[0073] From the data in Table 1, it can be seen that the technical solution of the present invention has a significantly higher increase in its 45° C. cycle capacity retention compared to the solution using only the same first active material.

[0074] Comparing Example 3 with Comparative Example 1, the first active material is LiNi 0.9 Co 0.06 Mn 0.04 O 2As shown in FIG. 1, when the second active material was not added, the capacity retention rate of the battery after 500 cycles at 45° C. was only 86.5%, but when the second active material was added, the cycle capacity retention rate of the battery at 45° C. increased to 88.4%.

[0075] Comparing Example 4 and Comparative Example 2, the first active material is LiCoO 2 In this case, the 45° C. cycle capacity retention of the battery without the addition of the second active material was only 84.8%, whereas when the second active material was added, the 45° C. cycle capacity retention of the battery was improved to 86.2%.

[0076] Comparing Example 5 with Comparative Example 3, the first active material was LiNi 1.5 Mn 0.5 O 4 In this case, the 45° C. cycle capacity retention rate of the battery without the second active material was only 78.8%, but when the second active material was added, the 45° C. cycle capacity retention rate of the battery increased to 81.9%, indicating that the effect of Example 5 was significantly improved.

[0077] The first active material is LiMn 0.6 Fe 0.4 PO 4 When combined with a specific second active material and other conditions, the 45°C cycle capacity retention of the battery was always 89.9% or more. Compared with Comparative Example 4, the high temperature capacity retention was improved to some extent. 0.6 Fe 0.4 PO 4 It has been shown that when LiMn is carbon-coated, the high-temperature capacity retention of the battery is more significantly improved. The capacity retention of Example 1 at 500 cycles is shown in FIG. 1, which can reach 93.1%. 0.6 Fe 0.4 PO 4 If the surface is not carbon-coated, it will be exposed to the electrolyte and will easily undergo side reactions with the electrolyte, consuming active lithium and causing cycle decay. Therefore, carbon coating can achieve better cycle stability.

[0078] Comparing Example 7 and Comparative Example 5, the first active material was LiFePO 4 In this case, the 45° C. cycle capacity retention of the battery without the addition of the second active material was only 93.3%, whereas when the second active material was added, the 45° C. cycle capacity retention of the battery was improved to 94.3%.

[0079] Comparing Example 8 with Comparative Example 6, the first active material is Li 1.1 Ni 0.4 Mn 0.6 O 2 In this case, the 45° C. cycle capacity retention rate of the battery without the second active material was only 86.5%, but in the case where the second active material was added, the 45° C. cycle capacity retention rate of the battery increased to 93.4%, indicating that the effect of Example 8 was significantly improved.

[0080] Compared with the solution using only the same first active material, the technical solution of the present invention had an improvement rate of 45°C cycle capacity retention rate, as shown in Table 2. The calculation formula of the improvement rate is improvement rate = (capacity retention rate of the embodiment - capacity retention rate of the comparative example) / capacity retention rate of the comparative example. [Table 2]

[0081] From the data in Table 2, it can be seen that the 45°C cycle capacity retention of the technical solution of the present invention can be increased by more than 1.1%, and in some preferred embodiments, can be increased by 8%, compared to a solution using only the same first active material. 2 MnO 3 etc.) activates the second active material in a long cycle, and at a low potential of less than 4.3 V to 4.4 V, there is an activation phenomenon in which lithium is slowly released, which can improve the cycle stability of the battery.

[0082] From Example 9 to Example 14, it can be seen that the mass percentage of the second active material had a certain effect on the high-temperature cycle stability of the battery. Within a certain range, as the second active material increased, the capacity retention rate of the battery increased. When the mass percentage of the second active material was 15%, the capacity retention rate could be 93%. The second active material played a role in replenishing lithium and compensating for thermodynamic losses during cycling. However, the introduction of the second active material led to an increase in the impedance of the positive electrode, which resulted in an increase in polarization during cycling, resulting in kinetic losses during cycling. Therefore, if the proportion of the second active material was within a certain range, the cycle performance could be improved.

[0083] From Examples 16 to 20, it can be seen that the primary particle diameter of the second active material also affects the high-temperature capacity retention rate of the battery. If the particle diameter is within an appropriate range, the capacity retention rate of the battery can be improved. If the primary particle diameter of the second active material is too large, the impedance of the second active material becomes large, the electrochemical activity is weak, and the lithium supplement effect is poor. If the primary particle diameter is too small, the electrochemical activity of the second active material is too strong. The lithium supplement effect is good, but the kinetic loss during cycling becomes large. Therefore, if the primary particle diameter of the second active material is within a certain range, the cycle characteristics can be improved.

[0084] In Examples 24 to 27, the positive electrode material also contained a third active material, and Table 3 shows the parameter settings and the effect on the cycle capacity retention rate. [Table 3]

[0085] The data in Table 3 show that when the positive electrode material also contains a third active material, the 45° C. cycle capacity retention increases to some extent. [Industrial Applicability]

[0086] Furthermore, the positive electrode material, electrochemical device, and electronic device of the present invention can be used in the electronics field, and have high industrial applicability.

[0087] The above description is only a specific embodiment of the present invention. However, the present invention is not limited to the specific details of the above embodiment. Within the technical spirit of the present invention, various simple modifications can be made to the technical solution of the present invention, and all of these simple modifications belong to the scope of the present invention.

[0088] It should also be noted that the specific technical features described in the specific embodiments can be combined in any suitable manner unless they are inconsistent, and in order to avoid unnecessary repetition, the present invention will not provide a more detailed description of the various possible combinations.

[0089] Furthermore, various different embodiments of the present invention can be combined in any combination, and as long as the various different embodiments of the present invention do not violate the concept of the present invention, the various different embodiments of the present invention should also be considered as disclosure of the present invention.

Claims

1. A positive electrode material comprising a first active material and a second active material, the first active material comprises a lithium transition metal oxide, the lithium transition metal oxide comprising one or more of a lithium manganese iron phosphate, a lithium rich manganese based material, and a lithium manganese nickel oxide; The general formula of the second active material is Li １＋（ａ／（２＋ａ）） Mn ２ａ／（２＋ａ） M ６／（２＋ａ）－２ O ２ wherein 0.5≦a≦1 and M is selected from one or more of Ni, Co, Mn, Mg, Al, Ti, Zr, Nb, La, Sr, W; When the second active material has a lithium potential higher than X volts (V), MnO ２ A coating layer is formed, wherein 4.3≦X≦4.

6.

2. The positive electrode material according to claim 1 , wherein the positive electrode material satisfies the following condition (b): (b) the general formula of the second active material is Li １＋（ａ／（２＋ａ）） Mn ２ａ／（２＋ａ）－Ａ M ６／（２＋ａ）－２ O ２－２Ａ / AMnO ２ In the formula, 0≦A≦0.05 and 0.5≦a≦1.

3. 10. The cathode material of claim 1, wherein the lithium transition metal oxide comprises a carbon coating layer.

4. The positive electrode material according to claim 1, wherein the positive electrode material satisfies one or more of the following conditions (c) to (e): (c) the mass percentage of the second active material is 1% to 30%, said mass percentage being the percentage of the mass of the second active material relative to the total mass of the first active material and the second active material; (d) The MnO ２ The coating amount of the coating layer is 5% to 30%, and the percentage of the coating amount is the ratio of the MnO ２ is the percentage of the mass of (e) The MnO ２ is the amorphous form.

5. The positive electrode material includes a third active material, and the third active material has a general formula of Li ６－ｘ M １－ｙ N ｙ O ４－ｚ 2. The cathode material of claim 1, wherein 0≦x≦5.95, 0≦y≦1, 0≦z≦2; M is selected from one or more of Fe, Ni, Co, and Cu; and N is selected from one or more of Al, Mn, Ti, and Si.

6. 6. The positive electrode material according to claim 5, wherein a mass percentage of the second active material and the third active material with respect to a total mass of the second active material and the third active material is 1% to 30%, the mass percentage being a percentage of a total mass of the second active material and the third active material with respect to a total mass of the first active material, the second active material, and the third active material, and a mass ratio of the second active material to the third active material is (2 to 20):

1.

7. The positive electrode material according to claim 1, wherein the primary particle size of the second active material is 40 nm to 600 nm.

8. An electrochemical device comprising a positive electrode sheet, a negative electrode sheet, and a separator, the positive electrode sheet comprising the positive electrode material according to any one of claims 1 to 7.

9. An electronic device comprising the electrochemical device of claim 8.

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