Cathode materials, electrochemical devices and electronic devices

Abstract

To provide a cathode material, an electrochemical device using the cathode material, and an electronic device, the cathode material having a stable crystal structure, and the electrochemical device being capable of holding a relatively high capacity and excellent cycle characteristics at high voltage.SOLUTION: A cathode material includes particles having a P63mc crystal phase structure, and a particle size distribution curve diagram includes a first peak and a second peak. The cathode material includes a first particle and a second particle, and the first particle is a particle represented by the first peak, while the second particle is a particle represented by the second peak. Both the first particle and the second particle have the P63mc crystal phase structure. The average particle diameter of the first particle is 3 μm to 12 μm. The average particle diameter of the second particle is 15 μm to 30 μm. The particle diameter of the particle represented by the first peak is smaller than the particle diameter of the particle represented by the second peak. When the peak area of the first peak is represented by S1 and the peak area of the second peak is represented by S2, S1 and S2 satisfy 0<S1 / S2<1, and there are holes and gaps inside the particles of the cathode material.SELECTED DRAWING: None

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application was filed on December 11, 2020, and is related to the invention entitled "Positive electrode material, electrochemical device Priority based on Chinese Patent Application No. 202011460086.8 for "Devices and Electronic Apparatuses" The entire contents of this Chinese patent application are incorporated herein by reference. [Technical Field]

[0002] The present invention relates to the field of electrochemical technology, specifically to cathode materials, electrochemical devices and electronic devices. It is related to. [Background technology]

[0003] With the development and advancement of electrochemical devices (e.g., lithium-ion batteries), the demand for their capacity is One of the key ways to improve the capacity of electrochemical devices is through the use of electrochemical The goal is to increase the voltage of electrochemical devices, but the positive electrode material in high-voltage electrochemical devices has a crystalline structure. The capacity is unstable, the capacity fades rapidly, and the cycle characteristics are significantly reduced.

[0004] Currently, the common cores used in electrochemical devices (e.g., lithium-ion batteries) The lithium baltic oxide cathode material has an R-3m crystalline phase structure and its theoretical capacity is 273.8mA. h / g, which has good cycle characteristics and safety properties, and holds an important position in the positive electrode material market. To obtain higher specific energy, the lithium cobalt oxide material is developed in the direction of high voltage. Currently, when the charging voltage of lithium cobalt oxide material is 4.5V, the capacity is To improve the capacity of the lithium cobalt oxide material, cobalt Attempts have been made to release more lithium ions from the crystalline structure of lithium nitrate, but As the voltage increases, lithium ions are released from the crystalline structure of the lithium cobalt oxide. When this happens, a series of irreversible phase changes occur, and the cycleability and The storage characteristics are significantly reduced, and the interfacial side reactions increase under high voltage, causing the elution of cobalt metal. This leads to increased electrolyte decomposition and severe capacity decay of lithium cobalt oxide materials. is. Summary of the Invention

[0005] The present invention provides a cathode material, an electrochemical device, and an electronic device, and the cathode material in the present invention is a stable The cathode material has a stable crystal structure, and electrochemical devices using the cathode material have relatively high capacity and and excellent cycle characteristics can be maintained.

[0006] In some embodiments, the present invention provides particles having a P63mc crystalline phase structure, A positive electrode material is provided in which the particle size distribution curve of the material includes a first peak and a second peak. The present invention provides a cathode material consisting of particles with different particle sizes, while the P63mc phase compound The material has a special oxygen structure, is stable enough at a high voltage of 4.6V, and is gentle on the electrolyte. On the other hand, by designing the particles of the positive electrode material with different particle sizes, It can fully play the role of particles of different diameters, improve the processing properties of materials, and reduce the mixing sedimentation Solves the problem of low compaction density when the temperature is high, improving rate characteristics The P63mc crystal phase structure has a unique lithium-deficient structure, which is advantageous for lithium During the lithium absorption and release process, there are lithium vacancies in the crystal structure, and excess Its ability to accommodate lithium ions prevents capacity fade and allows for different particles When particles of different diameters are mixed, the kinetics performance of the cathode material is improved. As a result, the P63mc crystal phase structure has a stronger lithium storage capacity, better capacity and better cycle performance.

[0007] In some embodiments, the particle diameter of the particles represented by the first peak is smaller than that of the particles represented by the second peak. Let the peak area of the first peak be S1 and the peak area of the second peak be S2. Then, S1 and S2 satisfy the relational expression 0 < S1 / S < 1. In some embodiments S1 and S2 respectively represent the contents of two types of particles with different particle diameters, and 0 < S 1 / S2 < 1 indicates that the percentage of particles with a smaller particle diameter is less than 50%. If the percentage of particles with a smaller particle diameter is too high, the cycle performance may decrease. In some embodiments, when there are no particles with a smaller particle diameter, it is disadvantageous for improving the compression density and for improving the kinetics performance of the cathode material.

[0008] In some embodiments, the chemical compositions of the first particles and the second particles are different. The first particles are L i x Na z Co 1-y1 M 1 y1 O2, where 0.6 < x < 0.95, 0 ≤ y1 < 0.15, 0 ≤ z < 0.05, and M 1 is at least one of Al, Mg, Ti, Zr, La, Ca, Ge, N b, Sn, and Y. The second particles are Li x Na z Co 1-y2 M 2 y2 O2, where 0.6 < x < 0.95, 0 ≤ y2 < 0.15, 0 ≤ z < 0 .05, M 2 The alloy contains at least one of Ni, Mn, Zn and Fe. The characteristics of the particles differ, with smaller particle sizes having relatively poor cycle characteristics, and larger particles having poor cycle characteristics. Since the rate performance of particles with larger particle sizes is relatively poor, in some embodiments of the present invention The chemical composition of the first particle and the second particle is different, and depending on the defects of the characteristics of particles with different particle sizes, By selecting the corresponding chemical composition, the shortcomings of the properties can be compensated for.

[0009] In some embodiments, the first particles have an average particle size of 3 μm to 12 μm, The average particle size of the second particles is 15 μm to 30 μm. If the average particle size of the first and second particles is too small, the consumption of the electrolyte increases and the cathode material In some other embodiments, the average of the first particles and the second particles is If the average particle size is too large, the rate characteristics may be reduced.

[0010] In some embodiments, the particles of the positive electrode material have holes and interstices therein. The particles can be in sufficient contact with the electrolyte, and the positive electrode material expands during the charge and discharge process. When the holes and gaps are formed, they can reduce the internal stress of the positive electrode material, thereby improving the crystalline structure. This is advantageous for improving the stability of the structure. In some embodiments, the specific surface area of ​​the positive electrode material is 0. 1m 2 / g~2m 2 / g. If the specific surface area is too small, it is disadvantageous to the rate characteristics. If the specific surface area is too large, the cycle characteristics may be reduced.

[0011] Some embodiments of the present invention provide a cathode material, the cathode material having a P63mc crystalline phase structure. and the particle size distribution curve of the positive electrode material includes a first peak and a second peak. The positive electrode material is Li x Na z Co 1-y M y O2, where 0.6 <x<0.95 , 0≦y<0.15, 0≦z<0.05, M is Al, Mg, Ti, Mn, Fe, Ni, Z containing at least one of n, Cu, Nb, Cr, Y and Zr, and having a P63mc crystalline phase structure The average particle size of the particles having the structure is 3 μm to 30 μm. The electrode material may be doped or undoped lithium cobalt oxide. Although doping elements in lithium cobalt oxide can improve the structural stability, However, if the content of the doping element is too high, the capacity loss may be too large, and the present invention This allows the capacity to be guaranteed within a limited range while improving the structural stability.

[0012] In some embodiments, the particles of the positive electrode material have holes and interstices therein. The particles can be in sufficient contact with the electrolyte, and the positive electrode material expands during the charge and discharge process. When the holes and gaps are formed, they can reduce the internal stress of the positive electrode material, thereby improving the crystalline structure. This is advantageous for improving the stability of the structure. In some embodiments, the specific surface area of ​​the positive electrode material is 0. 1m 2 / g~2m 2 / g. If the specific surface area is too small, it is disadvantageous to the rate characteristics. If the specific surface area is too large, the cycle characteristics may be reduced.

[0013] Some embodiments of the present invention include a positive electrode, a negative electrode, an electrolyte, and a cell disposed between the positive electrode and the negative electrode. The positive electrode is provided on a current collector and a positive electrode active material disposed on the current collector. The positive electrode active material layer includes any one of the positive electrode materials described above.

[0014] In some embodiments, the positive electrode active material layer of the electrochemical device has a compressed density of 3 g / cm 3 ~4 .35g / cm 3 In some embodiments, the positive electrode material is made of two types of particles with different particle sizes. The particles are advantageous in improving the compression density of the positive electrode active material layer. If the degree is too high, the particles may be crushed.

[0015] In some embodiments, the electrolyte solution includes a compound having 2 to 3 cyano groups. Compounds having one cyano group include dinitrile compounds, trinitrile compounds, ether dinitrile compounds, and It contains at least one of a tolyl compound and an ether trinitrile compound. In the example, the carbon-nitrogen triple bond of the cyano group has a very high bond energy, and oxidation It is difficult to be broken down, has a relatively high stability, and the coordination ability of the cyano group is very strong, making it suitable for use as a cathode material. It can coordinate with high-valent metal ions in the material, thereby reducing the decomposition It is possible to reduce the amount of cyano compounds containing 2 to 3 cyano groups compared to monocyano compounds. The material of the present invention can more effectively reduce the reaction between the positive electrode and the electrolyte and suppress gas generation. can.

[0016] In some embodiments, the compound having 2-3 cyano groups is glutaronitrile, sulfonyl nitrile, or the like. Kushinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, 1,3, 5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, and 1, 2,3-tris(2-cyanoethoxy)propane, The content of compounds having 2 to 3 cyano groups is 0.01 wt% to 15 wt% of the weight of the Some embodiments of the present invention are directed to an electronic device comprising any of the electrochemical devices described above. to provide.

[0017] In some embodiments, the electrolyte is ethylene carbonate, diethyl carbonate , propylene carbonate, propyl propionate, and vinylene carbonate The organic solvent contains at least one of the above-mentioned organic solvents, which is compatible with the cathode material of the present invention. This creates a synergistic effect and stabilizes the crystal structure, improving cycle characteristics.

[0018] The cathode material provided in the present embodiment comprises particles having a P63mc crystalline phase structure, and P6 The 3mc crystal phase structure is unique HCP (hexagonal closest packing) g, hexagonal close-packed) oxygen structure, and cycling at high voltages (e.g., 4.6 V or higher) In this invention, the oxygen structure is stable, the electrolyte is gentle, and the cycle characteristics are excellent. Therefore, the particle size distribution curve of the positive electrode material includes the first and second peaks. It means that two types of particles with different particle sizes are contained, thereby improving the processing characteristics of the material. This solves the problem of high compound settling and low compaction density, and the P63mc crystalline phase structure The battery itself is a lithium-deficient material, and during the charging process, it needs to release lithium ions to open up a pathway. In addition to accommodating the lithium ions released from itself during the discharge process, It has the electrochemical lithium absorption ability to absorb lithium ions. As a positive electrode material, it has a large When particles and small particles are mixed, the dynamic properties of the cathode material are improved, The material has a stronger lithium absorption capacity, and exhibits better capacity and cycle characteristics. vinegar. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention can be realized in various ways. and should not be construed as being limited to the embodiments described herein, but rather These examples are provided to provide a more detailed and complete understanding of the present invention. be.

[0020] In the prior art, lithium cobalt oxide positive electrode materials having the R-3m phase have been used for high voltage applications of 4.6 V or more. The crystal structure undergoes an irreversible phase transition (from O3 to H1-3, and from H1-3 to O1) This significantly reduces the cycle and safety characteristics of the material. The R-3m phase is generally used as a cathode material to enhance the structural stability of the R-3m phase lithium cobalt oxide cathode material. The doping of most elements slows down irreversible phase transitions, improving the material's However, this method does not improve the structural stability when the voltage is greater than 4.6V. The effect of increasing the doping amount is unclear, and the loss of theoretical capacity increases as the doping amount increases. Therefore, in the related art, it is possible to maintain the crystal structure stability at a high voltage of 4.6V or more while maintaining the capacity. The amount and cycle characteristics cannot be maintained.

[0021] In order to solve at least some of the above problems, some embodiments of the present invention include a P63 The positive electrode material is a particle having an mc crystalline phase structure, and the particle size distribution curve of the positive electrode material is This indicates that the positive electrode material contains two types of P with different particle sizes. It can be seen that particles having a 63mc crystal phase structure are included.

[0022] The present invention provides a positive electrode material composed of particles having different particle sizes. On the other hand, P63mc phase compound has a special HCP oxygen structure, is sufficiently stable at a high voltage of 4.6V, and is friendly to the electrolyte and has excellent cycle characteristics. On the other hand, by designing the particles of the positive electrode material with different particle sizes, the roles of the particles with different particle sizes can be fully played, the processing characteristics of the material can be improved, and the problem that the compression density is low when the blending sedimentation is high can be solved, which is advantageous for improving the rate characteristics. More importantly, the P63mc crystal phase structure has a unique lithium-deficient structure and has lithium vacancies in the crystal structure during the process of lithium release and absorption, and has the ability to accommodate extra lithium ions, so that capacity decay can be prevented. When particles with different particle sizes are mixed, the kinetic characteristics of the positive electrode material are improved, so that the P63mc crystal phase structure has a stronger lithium absorption capacity and exhibits better capacity and better cycle characteristics. That is. In some embodiments of the present invention, the particle size of the particles represented by the first peak is smaller than the particle size of the particles represented by the second peak. Let the peak area of the first peak be S1 and the peak area of the second peak be S2. Then, S1 and S2 satisfy the relational expression 0 < S1 / S2 < 1. In some embodiments, S1 and S2 respectively represent the contents of two types of particles with different particle sizes, and 0 < S1 / S2 < 1 represents that the percentage of particles with a smaller particle size is less than 50%.

[0023] If the percentage of particles with a smaller particle size is too high, the cycle characteristics may be low. In some embodiments, there are no particles with a smaller particle size. When the peak area of the second peak is S2, S1 and S2 satisfy the relational expression 0 < S1 / S2 < 1. In some embodiments, S1 and S2 respectively represent the contents of two types of particles with different particle sizes, and 0 < S1 / S2 < 1 represents that the percentage of particles with a smaller particle size is less than 50%. In some embodiments, S1 and S2 respectively represent the contents of two types of particles with different particle sizes, and 0 < S1 / S2 < 1 represents that the percentage of particles with a smaller particle size is less than 50%. That is, the percentage of particles with a smaller particle size is less than 50%. If the percentage of particles with a smaller particle size is too high, the cycle characteristics may be low. In some embodiments, there are no particles with a smaller particle size. If the temperature is too low, it is disadvantageous to improve the compaction density and the dynamic properties of the positive electrode material. .

[0024] In some embodiments of the present invention, the positive electrode material comprises first particles and second particles, and the first particles In some embodiments of the present invention, the first particles have a different chemical composition from the second particles. i x Na z Co 1-y1 M 1 y1 O2, where 0.6 <x<0.95、0≦y1 <0.15, 0≦z<0.05, M 1 is Al, Mg, Ti, Zr, La, Ca, Ge, N The second particles contain at least one of Li, Sn, and Y. x Na z Co 1-y2 M 2 y2 O2, where 0.6 <x<0.95、0≦y2<0.15、0≦z<0 .05, M 2 The alloy contains at least one of Ni, Mn, Zn, and Fe. In the examples, the properties of particles with different particle sizes are different, and the size of particles with smaller particle sizes is The cycle characteristics of particles with a large particle size are relatively poor, and the rate characteristics of particles with a large particle size are relatively poor. Therefore, in some embodiments of the present invention, the chemical composition of the first particles and the second particles is different, and the particles By selecting the corresponding chemical composition according to the characteristic defects of particles with different particle sizes, the characteristic defects can be reduced. For example, the first particles with a small particle diameter are doped with an element that improves cycle characteristics, and the second particles with a small particle diameter are doped with an element that improves cycle characteristics. By doping the large secondary particles with elements that enhance the rate capability, the cathode material as a whole The average particle size of the first particles is 3 μm to 12 μm. μm, and the average particle size of the second particles is 15 μm to 30 μm. In this case, if the average particle diameter of the first particles and the second particles is too small, the consumption of the electrolyte increases, and and is detrimental to the cycle characteristics of the positive electrode material. If the average particle size of the second particles is too large, the rate characteristics may be reduced. In this embodiment, the first particles are particles represented by a first peak and the second particles are particles represented by a second peak. Both the first particle and the second particle have a P63mc crystal phase structure. .

[0025] In some embodiments of the present invention, there are holes and interstices within the particles of the positive electrode material. In some embodiments, the particles have holes and interstices that allow sufficient contact with the electrolyte, and When the positive electrode material expands during the charge and discharge process, the holes and gaps reduce the internal stress of the positive electrode material. This is advantageous in improving the stability of the crystal structure. The number of holes and gaps on one particle is 50 or less. If the number is too large, the positive electrode material The mechanical strength of the material may become insufficient, making it more susceptible to crystal collapse.

[0026] Some embodiments of the present invention provide a cathode material, the cathode material having a P63mc crystalline phase structure. the particle size distribution curve of the positive electrode material includes a first peak and a second peak, The electrode material is Li x Na z Co 1-y M y O2, where 0.6 <x<0.95、0≦ y<0.15, 0≦z<0.05, M is Al, Mg, Ti, Mn, Fe, Ni, Zn, C containing at least one of u, Nb, Cr, Y and Zr, and having a P63mc crystal phase structure. The average particle size of the particles is 3 μm to 30 μm.

[0027] In some embodiments, the cathode material is doped or undoped cobalt. Doped lithium cobalt oxide may also be used. However, if the content of doping elements is too high, the capacity loss will be large. Therefore, it is necessary to improve the structural stability while ensuring the capacity within the range limited by the present invention. It can be raised.

[0028] In some embodiments, the particle size of the particles affects the structural stability and rate performance of the cathode material. In some embodiments, the first particles have a smaller particle size than the second particles. The second particles, which have a larger particle size, have poorer rate characteristics than the first particles. Therefore, the first particle is provided with M, which helps to improve the structural stability of the first particle. 1 The second particle is doped with 2M helps improve the rate characteristics of particles 2 can be doped.

[0029] In some embodiments of the present invention, there are holes and interstices within the particles of the positive electrode material. In some embodiments, the particles have holes and interstices that allow sufficient contact with the electrolyte, and When the positive electrode material expands during the charge and discharge process, the holes and gaps reduce the internal stress of the positive electrode material. This is advantageous for improving the stability of the crystal structure. In the example, the number of holes and gaps on one particle is 50 or less. If the number is too large, the positive electrode The mechanical strength of the material may become insufficient, and crystal collapse may become more likely to occur.

[0030] In some embodiments of the present invention, the specific surface area of ​​the positive electrode material is 0.1 m 2 / g~2m 2 / g In some embodiments, the specific surface area is 2 m 2 / g, electrolyte consumption This accelerates the rate of destabilization of the crystal structure, which may result in a deterioration in cycle characteristics. On the other hand, the specific surface area is 0.1 m 2 If the density is less than / g, the rate characteristics will be poor. There is a risk of this happening.

[0031] Some embodiments of the present invention further comprise a positive electrode, a negative electrode, an electrolyte, and a battery disposed between the positive electrode and the negative electrode. a separator, a positive electrode, a current collector, and a separator disposed on the current collector; and a positive electrode active material layer comprising the positive electrode material of any of the above embodiments. .

[0032] In some embodiments of the present invention, the positive electrode active material layer of the electrochemical device has a compressed density of 3 g / cm m 3 ~4.35g / cm 3 In some embodiments, the positive electrode material has different particle sizes. The presence of two types of particles is advantageous in increasing the compression density of the positive electrode active material layer. In one example, the compressed density of the positive electrode active material layer when compressed at a pressure of 150 MPa was 3. .80g / cm 3 The above is the compression of the positive electrode active material layer when compressed at a pressure of 250 MPa. Density is 4g / cm 3 The pressure of the positive electrode active material layer when compressed at a pressure of 500 MPa is equal to or greater than that. The shrinkage density is 4.2g / cm 3 (c) The electrochemical device has a discharge capacity of 200 mAh. If the value is greater than or equal to 1 / g, the electrochemical device is cycled 20 times at a rate of 1 C, and the electrochemical device In some embodiments, the increase in DC resistance is 2% or less. Since the increase rate of the DC resistance after the cycle is 2% or less, the positive electrode of the electrochemical device of the present invention can be The polar material has better structural stability and no obvious structural changes occur during cycling. It can be seen that there is no obvious increase in DC resistance.

[0033] In some embodiments of the present invention, the electrolyte solution contains a compound having two to three cyano groups. Compounds having 2 to 3 cyano groups include dinitrile compounds, trinitrile compounds, ether compounds, etc. The compound contains at least one of an ether trinitrile compound and an ether trinitrile compound. In some examples, the bond energy of the carbon-nitrogen triple bond of the cyano group is very high. , it is difficult to oxidize, has a relatively high stability, and the coordination ability of the cyano group is very strong. It can coordinate with high-valent metal ions in the positive electrode material, thereby Compared with monocyano compounds, the decomposition of The compound having the above structure can effectively reduce the reaction between the positive electrode and the electrolyte and suppress gas generation. can be done.

[0034] In some embodiments of the present invention, the compound having 2-3 cyano groups is glutaronite. nitrile, succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, and 1,2,3-tris(2-cyanoethoxy)propane The content of the compound having 2 to 3 cyano groups is 0.01 wt% based on the weight of the electrolyte. ~15wt%.

[0035] In some embodiments, the positive electrode current collector may be an Al foil, but it is generally used in the art. Of course, other positive electrode current collectors used in the prior art may also be used. In some embodiments, the thickness of the positive electrode current collector may be 1 μm to 200 μm. In this case, the positive electrode active material layer may be applied only to a partial area of ​​the positive electrode current collector. In the embodiment, the thickness of the positive electrode active material layer may be 10 μm to 500 μm. Please note that these are examples only and other suitable thicknesses may be used.

[0036] In some embodiments, the separator is made of polyethylene, polypropylene, polyvinyl fluoride, or the like. At least one of ethylenediamine, polyethylene terephthalate, polyimide and aramid For example, polyethylene includes high density polyethylene, low density polyethylene, and ultra- High molecular weight polyethylene. Polypropylene has excellent short circuit prevention and shutdown effect. In some embodiments, the thickness of the separator is about 5 μm. It is in the range of 500µm to 500µm.

[0037] In some embodiments, the surface of the separator further comprises at least one The substrate may include a porous layer disposed on the surface, the porous layer including inorganic particles and a binder. The organic particles are aluminum oxide (Al2O3), silicon oxide (SiO2), magnesium oxide MgO, titanium oxide (TiO2), hafnium dioxide (HfO2), tin oxide (S nO2), cerium oxide (CeO2), nickel oxide (NiO), zinc oxide (ZnO), Calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (YO 3), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, At least one selected from calcium hydroxide and barium sulfate. In an embodiment, the pore diameter of the separator is in the range of about 0.01 μm to 1 μm. The binder is polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer. Polymers, polyamides, polyacrylonitrile, polyacrylates, polyacrylic acids , polyacrylate, sodium carboxymethylcellulose, polyvinylpyrrolidone, Polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyethylene The porous surface of the separator is at least one selected from the group consisting of fluoroethylene, fluoroisopropyl ether ... The layer enhances the separator's heat resistance, oxidation prevention, and electrolyte wetting properties, and This can strengthen the adhesion between the pieces.

[0038] In some embodiments of the present invention, the electrochemical device is of a rolled or stacked type.

[0039] In some embodiments, the electrochemical device comprises a lithium ion battery, which is In some embodiments, the electrochemical device may further include an electrolyte. The electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolytic solution. It contains a lithium salt and a non-aqueous solvent. The lithium salt is LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN( SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB and Diflu For example, the lithium orthoborate may be one or more selected from the group consisting of lithium orthoborate, ... LiPF6 is used as the lithium salt to improve cycle characteristics.

[0040] The non-aqueous solvent may be a carbonate ester compound, a carboxylic acid ester compound, an ether compound, or other organic solvent. The solvent may be an organic solvent or a combination thereof.

[0041] Carbonate compounds include chain carbonate compounds, cyclic carbonate compounds, and fluorocarbon compounds. It may also be an acid ester compound or a combination thereof.

[0042] Examples of chain carbonate ester compounds are diethyl carbonate (DEC), dimethyl carbonate, Dimethyl methacrylate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (M PC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (MEC) and combinations thereof. Examples of the cyclic carbonate ester compound include ethylene carbonate, ester (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl carbonate ethylene carbonate (VEC), or a combination thereof. Examples of ester compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate (FDCO), 1,1-Difluoroethylene carbonate, 1,1,2-Trifluoroethylene carbonate Fluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate , 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene Carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2- Trifluoro-2-methylethylene carbonate, Trifluoromethylethylene carbonate or a combination thereof.

[0043] Examples of carboxylic acid ester compounds are methyl acetate, ethyl acetate, n-propyl acetate, acetic acid tert-butyl, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone , methyl formate, or a combination thereof.

[0044] Examples of ether compounds are dibutyl ether, tetraethylene glycol dimethyl ether, Diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethylene glycol ethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydro furan or a combination thereof.

[0045] Examples of other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl Thilsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolide Formamide, dimethylmethylamide, acetonitrile, trimethyl phosphate, phosphate triethyl, trioctyl phosphate, and phosphate esters or combinations thereof.

[0046] Embodiments of the present invention further provide electronic devices that include the electrochemical devices described above. The electrochemical device is not particularly limited and may be used in any electronic device known in the prior art. In some embodiments, the electrochemical device of the present application can be used in a notebook computer, a pen Input type computers, mobile computers, e-book players, mobile phones, Band-type facsimile, portable copier, portable printer, stereo headset, video Recorders, LCD TVs, portable cleaners, portable CD players, minidiscs , walkie-talkies, electronic notebooks, calculators, memory cards, portable tape records Damper, radio, backup power supply, motor, automobile, motorcycle, auxiliary bicycle, bicycle , lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage This includes, but is not limited to, storage batteries and lithium-ion capacitors. .

[0047] Some embodiments of the present invention further comprise a cathode material prepared using the cathode materials in the above embodiments. A method for preparing a material is provided, the method comprising the steps of:

[0048] (1) Li x Na z Co 1-y M y O2 was prepared, where 0.6 <x<0.95、0≦ y<0.15, 0≦z<0.05, M is Al, Mg, Ti, Mn, Fe, Ni, Zn, C It is at least one selected from the group consisting of u, Nb, Cr and Zr.

[0049] (2) M with different particle sizes obtained by the liquid phase deposition method and the sintering method 1 Doped with elements (Co 1- y1 M 1 y1 )3O4 and M 2 Doped with elements (Co 1-y2 M 2 y2 )3O4 precursor Prepare the solution: soluble cobalt salts (e.g., cobalt chloride, cobalt acetate, cobalt sulfate) , cobalt nitrate, etc.) and M salt (e.g., sulfate, etc.) in a molar ratio of Co to M of (1-y1) :y1 and (1-y2):y2 in a solvent (e.g., deionized water), and Precipitants (e.g., sodium carbonate, sodium hydroxide) and and a complexing agent (e.g., aqueous ammonia solution), and the molar ratio of the complexing agent to the precipitating agent is 0.1 to 1. Then, the pH value is adjusted (for example, the pH value is adjusted to 5 to 9) to cause precipitation. The precipitate is sintered in air at 400℃~800℃ for 5h~20h, and the sintered product is polished and then subjected to different Particle size M 1 Doped with elements (Co 1-y1 M 1 y1 )3O4 and M 2 The elements Doped (Co 1-y2 M 2 y2 )3O4 precursor is obtained. M 1 are Al, Mg, and T at least one of i, Zr, La, Ca, Ge, Nb, Sn and Y, 2 teeth It contains at least one of Ni, Mn, Zn and Fe.

[0050] (3) Na by solid-phase sintering m Co 1-y M y Synthesize O2: As a precursor, M 1 The element is Grouped (Co 1-y1 M 1 y1 )3O4 and M 2 Doped with elements (Co 1-y2 M 2 y2 )3O4 powder and Na2CO3 powder are used in a molar ratio of Na to Co of 0. Mix the powders in a ratio of 7:1 to a maximum of 0.74:1. Place the powders in an oxygen gas atmosphere until they are uniform. Sintering was carried out at 700℃ to 1000℃ for 36 to 56 hours in an atmosphere, and the Na of P63mc structure was obtained. mCo 1-y1 M 1 y1 O2 and Na m Co 1-y2 M 2 y2 O2 is obtained, where 0 .6 < m < 1.

[0051] (4) Synthesize the Li x Na z Co 1-y M y O2 cathode material by ion exchange method: Na m Co 1-y1 M 1 y1 O2 or Na m Co 1-y2 M 2 y2 O2, and a lithium -containing molten salt (such as lithium nitrate, lithium chloride, lithium hydroxide, etc.) are mixed until the molar ratio of Na to Li becomes uniform at a ratio of 0.01 - 0.2, and reacted in an air atmosphere at 200°C - 400°C for 2 h - 8 h. The product is washed several times with deionized water to remove the molten salt , and then the powder is dried to obtain Li x Na z Co 1-y1 M 1 y1 O2, where 0.6 < x < 0.95, 0 ≤ y1 < 0.15, 0 ≤ z < 0.05, and the second particles contain Li Na x Na z Co 1-y2 M 2 y2 O2, where 0.6 < x < 0.9 5, 0 ≤ y2 < 0.15, 0 ≤ z < 0.05.

[0052] (5) Li x Na z [[ID=8l]]Co 1-y1 1 M y1 x O2 and Li xNa z Co 1-y2 M 2 y2 O2 and are mixed in a certain ratio, where Li x Na z Co 1-y2 M 2 y2 The number of O2 is Li x Na z Co 1-y1 M 1 y1 Less than O2.

[0053] In the following, several examples and comparative examples will be given to further explain the present invention. Here, a lithium-ion battery is taken as an example.

[0054] Preparation of positive electrode pieces: positive electrode material, conductive carbon black as a conductive agent, and poly(ethylene glycol) as a binder. Vinylidene fluoride was mixed with N-methylpyrrolidone (NMP) in a weight ratio of 97:1.4:1.6. The aluminum foil was used as a positive electrode current collector, and the positive electrode slurry was prepared. The slurry was applied to the positive electrode current collector at a coating weight of 17.2 mg / cm 2 and then dried and cold rolled After cutting, a positive electrode piece was obtained.

[0055] Preparation of negative electrode pieces: The negative electrode material was artificial graphite. Negative electrode material, acrylic resin, conductive carbon Black and sodium carboxymethyl cellulose in a weight ratio of 94.8:4.0:0.2 : 1.0 in deionized water to form a negative electrode active material layer slurry, The weight percentage of the element was 10%. A copper foil with a thickness of 10 μm was used as the negative electrode current collector, and the negative electrode slurry was applied to the negative electrode current collector, with a coating weight of 6.27 mg / cm 2 and the water content of the negative electrode piece is 3 The negative electrode active material layer was obtained by cutting the negative electrode pieces. was obtained.

[0056] Preparation of separator: The separator substrate is polyethylene (PE) with a thickness of 8 μm. A 2 μm layer of aluminum oxide ceramic is applied to both sides of the substrate, and finally The binder polyvinylidene fluoride (PVDF) was applied to both sides of the ceramic layer. ) 2.5 mg was applied and allowed to dry.

[0057] Preparation of electrolyte: In an environment with a water content of less than 10 ppm, lithium hexafluorophosphate and non-aqueous Organic solvent (weight ratio: ethylene carbonate (EC): diethyl carbonate (DEC) : Propylene carbonate (PC): Propyl propionate (PP): Vinylene carbonate The electrolyte solution was prepared by mixing the cellulose acetate (VC) and the cellulose acetate (VC) in a weight ratio of 8:92. Successful.

[0058] Preparation of Lithium-ion Battery: The separator acts as an insulator between the positive and negative electrode pieces. The positive electrode piece, separator, and negative electrode piece were stacked in this order and wound up to obtain an electrode assembly. The object is placed on an aluminum plastic film exterior, and after removing moisture at 80°C, The electrolyte is poured, packaged, and then subjected to formation, degassing, and After going through a process flow including trimming, a lithium-ion battery was obtained.

[0059] The preparation steps of the lithium ion batteries of the Examples and Comparative Examples are similar, and The only difference is the cathode material used. The specific cathode materials used are listed in Table 1 below. ~As shown in Table 8.

[0060] The method for measuring each parameter of the present invention will be described below.

[0061] Particle volume distribution measurement: An appropriate amount of powder is dispersed using ultrasonic waves, and the dispersion is measured using a laser particle size measuring device (Mastersize r 3000) and measured by particle size distribution laser diffraction method GB / T19077 -2016, 1, measurement range is 0.02μm~2000μm (MS2000), 0 The range was 0.01 μm to 3500 μm (MS3000), and the detection limit was 20 nm. Finally, the volume distribution curve of the powder was obtained. The particle size distribution percentage is the particle size distribution percentage corresponding to 50% of the cumulative particle size distribution percentage. Refers to the diameter of the tube.

[0062] Capacity retention measurement: The first charge and discharge is performed in a 25°C environment, and the theoretical capacity is fully discharged within 0.5C (i.e., 2 hours). The battery was charged at a constant current (the current value that discharges the battery to the full potential) until the upper limit voltage reached 4.8V. Discharge at a constant current of 0.5C until the final voltage reaches 3V. (initial discharge capacity) was recorded, and then the 100th charge and discharge cycle was carried out. The discharge capacity of the lithium-ion battery was recorded using the following formula: The capacity retention rate at the 1st cycle was calculated.

[0063] 100 cycle capacity retention rate = 100th cycle discharge capacity / first cycle discharge capacity × 100% .

[0064] Hole and Gap Measurement: The cathode material was processed using an ion milling machine (JEOL-IB-09010CP) and the cross section The cross section was photographed using a scanning electron microscope at a magnification of 5.0 K or higher. In the cross-sectional image, holes and gaps are visible, and in the particle cross-sectional image, the color is different from the surrounding area. The closed areas were holes and gaps.

[0065] Hole selection criteria: Holes that meet the counting requirements must be aligned along the longest axis of a single particle. The ratio of the longest axis of the closed region to the longest axis of the closed region is between 2% and 10%, and the longest axis of the closed region is the maximum The difference in the minor axes is less than 0.5 micrometers.

[0066] Requirements for selecting gaps: A gap that meets the counting requirements must be the smallest gap in a single particle. The ratio of the longest axis of the occluded area to the major axis is 70% or more.

[0067] How to select the long and short axes: Connect any two points on the closed curve and choose the longest axis. The axis with the shortest distance was taken as the shortest axis.

[0068] A closed area is a region surrounded by a closed curve in a figure, and any part of the inside of the closed area A line segment connecting a point in the region with any point outside the region intersects the boundary of the region.

[0069] Elemental composition determination: The elemental composition of the positive electrode material powder was measured using an iCAP7000 ICP measurement device.

[0070] The electrode pieces carrying the positive electrode material are dissolved in NMP, filtered, and the powder is dried. Elemental composition measurements were performed using a CAP7000 ICP analyzer.

[0071] X-ray diffraction measurement: XRD diffraction patterns of cathode materials measured with Bruker D8 ADVANCE If the powder cannot be removed, dissolve the positive electrode pieces in NMP, filter, and remove the powder. The body was dried and the powder was measured by XRD.

[0072] Specific surface area (BET) measurement method: Measurement device: BSD-BET400, measurement process: The pipe is placed in a gas system filled with N2, and the surface of the material is physically adsorbed at the temperature of liquid nitrogen. When the physical adsorption is in equilibrium, the adsorption pressure and the flow rate of the adsorbed gas are measured. By determining the surface area, the amount of monolayer adsorption of the material can be calculated, and thus the specific surface area of ​​the sample can be calculated. I calculated.

[0073] Compressed density measurement: Lithium-ion battery is set to 0 SOC% (SOC: State of Charge) Discharge the battery to 1000 kJ / hour (state of charge), disassemble it, clean it, dry it, and measure the battery temperature using an electronic balance. A positive electrode piece (a positive electrode current collector coated with a positive electrode active material layer on both sides) having a certain area A is weighed. Weigh the positive electrode, and let its weight be W1. Then, using a one-tenth micrometer, measure the positive electrode. The thickness T1 was measured. The positive electrode active material layer was washed off with a solvent, dried, and the weight of the positive electrode current collector was Measure and call it W2, and use a ten-thousandth micrometer to determine the thickness of the positive electrode current collector. The weight W of the positive electrode active material layer disposed on one side of the positive electrode current collector was calculated using the following formula: The thickness T0, the density of the positive electrode active material layer, and the compressed density of the positive electrode active material layer were calculated as follows: W0=(W1-W2) / 2 T0=(T1-T2) / 2 Compressed density = W0 / (T0 x A).

[0074] [Table 1-1] [Table 1-2]

[0075] From Table 1, the total initial discharge capacity and cycle capacity in Examples 1-1 to 1-17 It can be seen that the performance is superior to that of Comparative Examples 1-1 to 1-8. Li with 3mc crystal phase structure a1 Na c1 Co 1-b1 M 1 b1 O2 and Li a2 Na c2 C o 1-b2 M 2 b2 O2 is also included, and Li a1 Na c1 Co 1-b1 M 1 b1 O 2 and Li a2 Na c2 Co 1-b2 M 2 b2 When the size of O2 particles is different, Therefore, it is possible to improve the capacitance and cycle capacity of some of the present invention. In some embodiments, the positive electrode material includes particles having a P63mc crystalline phase structure, and the positive electrode The particle size distribution curve of the material is limited to include a first peak and a second peak.

[0076] Comparing Examples 1-1 to 1-17 with Comparative Examples 1-9 and 1-10, The particle size is in the range of 3 μm to 12 μm, and the secondary particle size is in the range of 15 μm to 30 μm. If the initial discharge capacity of the lithium-ion battery is within the range of 239 mAh / g or more, The capacity retention rate at 100 cycles is 88% or more, while the size of the first particle When the size of the second particles is 13 μm or more and the size of the second particles is 32 μm or more, the initial discharge capacity and It can be seen that the cycle capacity retention rate decreases. The average particle size of the first particles is 3 μm to 12 μm, and the average particle size of the second particles is 15 μm to 30 μm. It is restricted to m.

[0077] Comparing Examples 1-1 to 1-17, Example 1-1 is M 1 or M 2 Dope it up On the other hand, all of Examples 1-2 to 1-17 were doped, and Example 1-2 The initial discharge capacity and 100 cycle capacity retention rate in Examples 1-17 are Therefore, in some embodiments of the present invention, The polar material is M 1 or M 2 It has the following characteristics.

[0078] From Examples 1-18 and 1-19, Zn was used in Example 1-18, and Zn was used in Example 1-19. It is doped with Al, and large and small particles with similar chemical composition exist simultaneously. Therefore, the initial discharge capacity and the 100th cycle capacity in Examples 1-18 and 1-19 were It can be seen that the retention rates are all superior to those of Example 1-1. In some examples, the particle size distribution curve of the positive electrode material includes a first peak and a second peak. There are.

[0079] In the examples and comparative examples shown in Table 2, the positive electrode material used was Li x Na z Co 1-y M y O2, and the crystalline phase of the positive electrode material in each example and comparative example in Table 2 The structure of each was P63mc.

[0080] [Table 2]

[0081] Comparing Example 2-1 with Comparative Examples 2-1 to 2-3, it is clear that there are no holes or gaps in the positive electrode material. In contrast to Comparative Example 2-3, when the positive electrode material has either holes or gaps, the initial discharge capacity and The capacity retention rate at 100 cycles can be improved, and when the positive electrode material has both holes and gaps, In this case, the lithium-ion battery has a higher initial discharge capacity and a higher 100-cycle capacity retention rate. Therefore, in some embodiments of the present invention, the inside of the particles of the positive electrode material The presence of holes and gaps is limited.

[0082] In the examples and comparative examples shown in Table 3, the positive electrode material used was Li x Na z Co 1-y M y O2, and the crystalline phase of the positive electrode material in each example and comparative example in Table 3 The structure of each was P63mc.

[0083] [Table 3]

[0084] Comparing Example 3-1, Example 3-2, Comparative Example 3-1, and Comparative Example 3-2, the positive electrode material Specific surface area is 2m 2 When the content exceeds 1 / g, the initial discharge capacity of the lithium ion battery is small, and The 100-cycle capacity retention rate is low, and the specific surface area of ​​the positive electrode material is 2m 2 / g or less, lithium The initial discharge capacity of the lithium-ion battery is high, and the capacity retention rate is good over 100 cycles. Therefore, in some embodiments of the present invention, the specific surface area of ​​the positive electrode material is 0.1 m 2 / g~2m 2 / g.

[0085] In the examples and comparative examples shown in Table 4, the positive electrode material used was Li x Na z Co 1-y M y O2, and the crystalline phase of the positive electrode material in each example and comparative example in Table 4 The structure of each was P63mc. The main peak range in Table 4 is the X of the positive electrode material. This refers to the diffraction angle of the diffraction peak with the strongest intensity in the X-ray diffraction pattern, and is the full half-maximum value in Table 4. The width refers to the full width at half maximum of the main diffraction peak.

[0086] [Table 4]

[0087] When comparing Example 4-1, Example 4-2, Comparative Example 4-1, and Comparative Example 4-2, When the angle is in the 18°-19° range, the FWHM is shorter than when the FWHM is greater than 0.5°. When the width is within the range of 0° to 0.5°, the initial discharge capacity and 100 The cycle capacity retention rate is high in both cases, and the X-ray diffraction pattern of the positive electrode material shows the highest intensity. The diffraction angle of the strong diffraction peak is in the range of 18° to 19°, and the half of the strongest diffraction peak The full width of the value is in the range of 0° to 0.5°.

[0088] In the examples and comparative examples shown in Table 5, the positive electrode material used was Li x Na z Co 1-y M y O2, and the crystalline phase of the positive electrode material in each example and comparative example in Table 5 The structure of each was P63mc.

[0089] [Table 5]

[0090] Comparing Examples 5-1 to 5-6 with Comparative Examples 5-1 and 5-2, The initial discharge capacity and 100 cycle capacity retention rate of Examples 5-1 to 5-6 are all the same as those of Comparative Examples. It can be seen that the compression density of the positive electrode active material layer is higher than that of Comparative Example 5-1 and Comparative Example 5-2. g / cm 3 ~4.35g / cm 3 If so, the discharge characteristics and cycle This is advantageous for improving the characteristics of the film.

[0091] [Table 6]

[0092] Comparing Examples 7-1 to 7-8 with Comparative Examples 7-1 and 7-2, A compound with 2-3 cyano groups is added to the electrolyte of a lithium-ion battery, and The mass content of compounds having a cyano group is controlled within the range of 0.01 wt% to 15 wt%. In this case, the initial discharge capacity and 100-cycle capacity retention rate of the lithium-ion battery can be improved. This can be done.

[0093] The foregoing is merely an illustration of the preferred embodiments of the present invention and the technical principles applied thereto. It should be understood by those skilled in the art that the scope of the disclosure contained in the present invention does not necessarily include the specific combination of the above technical features. The technical solution is not limited to a combination of the above technical features or any combination of features equivalent thereto. Other technical solutions that are combinations of the above features and similar features disclosed in the present invention are also included. It is a technical solution that is a modification of the technical features having the same functions.

Claims

1. A positive electrode material, Used in lithium-ion batteries, P6 ３ particles having an mc crystalline phase structure, the particle size distribution curve of the positive electrode material includes a first peak and a second peak; the positive electrode material includes first particles and second particles; The first particles are particles represented by the first peak, the second particles are particles represented by the second peak, and both the first particles and the second particles are P6 ３ It has an mc crystalline phase structure, the first particles are doped with M 1 , the second particles are doped with M 2 , M 1 includes at least one of Al, Mg, Ti, Zr, La, Ca, Ge, Nb, Sn, and Y, and M 2 includes at least one of Ni, Mn, Zn, and Fe; The first particles have an average particle size of 3 μm to 12 μm, and the second particles have an average particle size of 15 μm to 30 μm. the particle size of the particles represented by the first peak is smaller than the particle size of the particles represented by the second peak, and when the peak area of ​​the first peak is S1 and the peak area of ​​the second peak is S2, S1 and S2 satisfy the relationship 0<S1 / S2<1; A positive electrode material characterized in that there are holes and gaps inside the particles of the positive electrode material.

2. The first particles are Li ｘ Na ｚ Co １－ｙ１ M １ ｙ１ O ２ where 0.6<x<0.95, 0<y1<0.15, 0≦z<0.05, M １ The positive electrode material according to claim 1 , wherein the element is at least one of Al, Mg, Ti, Zr, La, Ca, Ge, Nb, Sn, and Y.

3. The second particles are Li ｘ Na ｚ Co １－ｙ２ M ２ ｙ２ O ２ where 0.6<x<0.95, 0<y2<0.15, 0≦z<0.05, M ２ The positive electrode material according to claim 1 , wherein the metal oxide contains at least one of Ni, Mn, Zn, and Fe.

4. The specific surface area of ​​the positive electrode material is 0.1 m ２ / g to 2m ２ The positive electrode material according to claim 1, wherein the Cr content is 1 / g.

5. An electrochemical device, comprising: the electrochemical device is a lithium ion battery; a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode; The positive electrode 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 positive electrode material according to any one of claims 1 to 4. An electrochemical device.

6. The compressed density of the positive electrode active material layer is 3 g / cm ３ ~4.35g / cm ３ 6. The electrochemical device according to claim 5, wherein

7. 6. The electrochemical device according to claim 5, wherein the electrolytic solution contains a compound having two to three cyano groups, and the content of the compound having two to three cyano groups is 0.01 wt % to 15 wt % relative to the weight of the electrolytic solution.

8. 8. The electrochemical device according to claim 7, wherein the compound having two to three cyano groups includes at least one of a dinitrile compound, a trinitrile compound, an ether dinitrile compound, and an ether trinitrile compound.

9. The electrochemical device according to claim 7, wherein the compound having two to three cyano groups includes at least one of glutaronitrile, succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, and 1,2,3-tris(2-cyanoethoxy)propane.

10. An electronic device comprising the electrochemical device according to any one of claims 5 to 9.

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