Positive electrode material, electrochemical device, and electronic device

Abstract

The application provides a positive electrode material, an electrochemical device and an electronic device, a cross section of a particle of the positive electrode material comprises a first region and a second region; wherein, taking a midpoint of a longest diameter in the cross section as a center, a line connecting the center to any point on a surface of the particle in the cross section is a first line, the first line has a first demarcation point, a distance from the center to the first demarcation point is 3 / 5 of a length of the first line where the first demarcation point is located, and the first region is a region surrounded by the first demarcation point; the second region is a region other than the first region in the cross section; a porosity of the first region is Vc1, a porosity of the second region is Vc2, and 5%≤Vc2-Vc1≤30% is satisfied. The positive electrode material can improve the cycle performance and high-temperature storage performance of the electrochemical device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to a positive electrode material, and an electrochemical device and an electronic device comprising the same. BACKGROUND

[0002] With the increasing depletion of fossil energy, people pay more and more attention to the demand for clean energy, and lithium ion batteries play an important role in it. The ternary material has been widely used due to its low cost and high energy density, especially in the field of electric vehicles. However, the mechanical properties of the ternary polycrystalline material itself are poor and cracks between particles are prone to occur during the cycle charging and discharging process. These cracks will exacerbate the side reaction between the electrolyte and the positive electrode material, resulting in battery gas production and cycle life deterioration, and there is also a risk of causing cracks in the polycrystalline material particles during the cold pressing of the electrode sheet. SUMMARY

[0003] In view of the above problems existing in the prior art, the present application provides a positive electrode material, an electrochemical device and an electronic device, which solves the problems of poor mechanical properties of the positive electrode material and cracks prone to occur during the cycle process by regulating the internal pore structure distribution of the positive electrode material particles.

[0004] In a first aspect, the present application provides a positive electrode material, a cross section of a particle of the positive electrode material comprising a first region and a second region; wherein taking a midpoint of a longest diameter in the cross section as a center, a line from the center to any point on the surface of the particle of the positive electrode material in the cross section is a first line, the first line has a first demarcation point, a distance from the center to the first demarcation point is 3 / 5 of the length of the first line where the first demarcation point is located, the first region is a region enclosed by the first demarcation point; the second region is a region outside the first region in the cross section; the porosity of the first region is Vc1, the porosity of the second region is Vc2, and it satisfies: 5%≤Vc2-Vc1≤30%.

[0005] In some embodiments, the positive electrode material satisfies: 7%≤Vc2-Vc1≤18%.

[0006] In some embodiments, the positive electrode material satisfies: 3%≤Vc1≤30%.

[0007] In some embodiments, the positive electrode material satisfies: 10%≤Vc2≤35%.

[0008] In some embodiments, the second region comprises a hole, the length of the hole is L, and L≤5μm.

[0009] In some embodiments, the width of the hole is d, and d≤1.5μm.

[0010] In some embodiments, the length direction of the hole is consistent with the radial direction of the second region.

[0011] In some embodiments, the holes are distributed radially.

[0012] In some embodiments, the positive electrode material is assembled into a button cell with lithium metal, and when the button cell is charged and discharged at a current of 0.1C in a voltage interval of 2.8V to 4.5V, a capacity-voltage differential dQ / dV curve obtained has a first oxidation peak and a first reduction peak in an interval of 4.2V to 4.5V.

[0013] In some embodiments, the peak voltage of the first oxidation peak is Vo1, the peak voltage of the first reduction peak is Vr1, and |Vo1-Vr1|≤0.2V.

[0014] In some embodiments, the capacity-voltage differential dQ / dV curve has a second oxidation peak and a second reduction peak in an interval of 3.6V to 4.0V, the peak voltage of the second oxidation peak is Vo2, the peak voltage of the second reduction peak is Vr2, and |Vo2-Vr2|≤0.3V.

[0015] In some embodiments, the peak height of the first oxidation peak is in an interval of 2000mAh / g / V to 4000mAh / g / V based on the mass of the positive electrode material.

[0016] In some embodiments, the absolute value of the peak height of the first reduction peak is in an interval of 2000mAh / g / V to 4000mAh / g / V based on the mass of the positive electrode material.

[0017] In some embodiments, when the button cell is charged and discharged at a current of 0.1C in a voltage interval of 2.8V to 4.5V, a discharge curve in a voltage-capacity curve obtained has a platform in an interval of 4.2V to 4.5V.

[0018] In some embodiments, when the button cell is charged and discharged at a current of 0.1C in a voltage interval of 2.8V to 4.5V, a discharge curve in a voltage-capacity curve obtained has a capacity of Q1 in an interval of 4.2V to 4.5V, and a capacity of Qt in an interval of 2.8V to 4.5V, and satisfies: 0.2≤Q1 / Qt≤0.35.

[0019] In some embodiments, the cathode material comprises a lithium transition metal oxide, which includes a T element and an optional M element. The T element includes at least one of Ni, Co, or Mn, and the M element includes at least one of K, Ca, Sr, Y, Zr, Nb, Mo, In, Sn, Sb, Ba, La, Ce, Hf, Ta, W, Pb, Al, Mg, B, Si, P, S, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, or Ge.

[0020] In some embodiments, the molar percentage of Ni is 30% to 70% based on the total molar amount of T in the lithium transition metal oxide.

[0021] In some embodiments, the molar percentage of Mn is less than or equal to 70% based on the total molar amount of T in the lithium transition metal oxide; and / or, the molar percentage of Co is less than or equal to 50% based on the total molar amount of T in the lithium transition metal oxide.

[0022] In some embodiments, based on the total molar amount of T and M elements in the lithium transition metal oxide, the molar percentage of T element is 90% to 100%, and the molar percentage of M element is 0% to 10%.

[0023] In some embodiments, the ratio of the molar amount of Li to the total molar amount of T and M elements in the lithium transition metal oxide is 0.5 to 1.1.

[0024] In some embodiments, the lithium transition metal oxide further includes Na, and the molar percentage of Na is 0.1% to 20% based on the total molar amount of T and M elements in the lithium transition metal oxide.

[0025] In some embodiments, the lithium transition metal oxide further includes an element R, which includes at least one of F, Cl, Br, I, or N, and the molar percentage of the element R is 0.1% to 10% based on the total molar amount of elements T and M in the lithium transition metal oxide.

[0026] In some embodiments, the lithium transition metal oxide has a layered crystal structure.

[0027] In some embodiments, the lithium transition metal oxide includes Li x1 Na x2 Ni y1 Mn y2 Co y3 M z1 O 2±m Rm 0.5≤x1≤1.1, 0.001≤x2≤0.2, 0.3≤y1≤0.7, 0≤y2≤0.7, 0≤y3≤0.5, 0≤z1≤0.1, 0≤m≤0.1, wherein the R element comprises at least one of F, Cl, Br, I, or N.

[0028] In some embodiments, the X-ray diffraction pattern of the positive electrode material has diffraction peaks in the intervals of 16° to 20°, 34° to 38°, and 42° to 46°.

[0029] In a second aspect, the present application also provides an electrochemical device comprising a positive electrode, wherein the positive electrode comprises a positive electrode active material layer, and the positive electrode active material layer comprises the positive electrode material of the first aspect.

[0030] In a third aspect, the present application provides an electronic device comprising the electrochemical device of the second aspect.

[0031] Beneficial effects: By regulating the distribution of the internal pore structure of the positive electrode material particles, the present application can effectively reduce the influence of cold pressing and charge-discharge cycling on the stress between the polycrystalline particles, thereby improving the problem of particle cracking caused by cold pressing and cycling, and further improving the cycle performance and high-temperature storage performance of the electrochemical device. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 SEM photograph of the cross section of the positive electrode material particles of Example 1.

[0033] Figure 2 XRD pattern of the positive electrode material of Comparative Example 1 and Example 6.

[0034] Figure 3 Voltage capacity curve of the button cell of Comparative Example 1 and Example 6.

[0035] Figure 4 Capacity voltage differential dQ / dV curve of the button cell of Comparative Example 1 and Example 6. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions, and advantages of the present application clearer, the technical solutions of the present application will be described below in conjunction with embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of the present application. The embodiments of the present application should not be interpreted as a limitation of the present application.

[0037] For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any upper limit can be combined with any lower limit to create a range not expressly disclosed; and any lower limit can be combined with any other lower limit to create a range not expressly disclosed, and any upper limit can be combined with any other upper limit to create a range not expressly disclosed. Further, each individual disclosed point or single numerical value can be combined with any other point or single numerical value to create a range not expressly disclosed, either as a lower limit or an upper limit, or both.

[0038] In the description herein, the terms "above", "below" include the number itself, unless otherwise indicated.

[0039] Unless otherwise indicated, the terms used in this application have the meanings commonly understood by those of ordinary skill in the art. Unless otherwise indicated, the values of the parameters mentioned in this application can be measured using various measuring methods commonly used in the art (for example, can be tested according to the methods given in the examples of this application).

[0040] In the DETAILED DESCRIPTION and in the claims, a list of items joined by the term "at least one of" or "one or more of" can mean any combination of the listed terms. For example, if a list of items includes A, B, and C, then "at least one of A, B, and C" or "one or more of A, B, or C" can mean A alone; B alone; C alone; A and B together; A and C together; B and C together; or A, B, and C together. The item A can include an individual element or a plurality of elements. The item B can include an individual element or a plurality of elements. The item C can include an individual element or a plurality of elements.

[0041] In a first aspect, the application provides a positive electrode material, the cross section of the positive electrode material particle comprises a first region and a second region; wherein, taking the midpoint of the longest diameter in the cross section as the center, the line connecting the center to any point on the surface of the positive electrode material particle in the cross section is the first connecting line, the first connecting line has a first demarcation point, the distance from the center to the first demarcation point is 3 / 5 of the length of the first connecting line where the first demarcation point is located, the first region is the region enclosed by the first demarcation point; the second region is the region outside the first region in the cross section; the porosity of the first region is Vc1, the porosity of the second region is Vc2, which satisfies: 5%≤Vc2-Vc1≤30%. The positive electrode material particle satisfying the above conditions can effectively alleviate the influence of cold pressing and charge-discharge cycling of the electrode sheet on the stress between the particles, improve the problem of particle cracking caused by cold pressing and charge-discharge cycling, and further improve the cycle performance and high-temperature storage performance of the electrochemical device.

[0042] In some embodiments, Vc2-Vc1 can be 5%, 7%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or a range consisting of any two of these values. In some embodiments, the positive electrode material satisfies: 7%≤Vc2-Vc1≤18%.

[0043] In some embodiments, the positive electrode material satisfies: 3%≤Vc1≤30%. In some embodiments, Vc1 can be 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or a range consisting of any two of these values. In some embodiments, the positive electrode material satisfies: 10%≤Vc2≤35%. In some embodiments, Vc2 can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, or a range consisting of any two of these values. In the case of too high porosity, too many voids will cause electrons to flow difficultly in the material, making the electronic conductivity of the positive electrode material particles worse, thereby reducing the electrical conductivity of the material. In addition, too high porosity will increase the path of ion transmission, causing the diffusion rate of ions in the material to be slow, reducing the charge and discharge rate of the battery. Inevitably, too high porosity will also cause the structure of the material to be unstable, easily swelling, shrinking or structural damage, affecting the life and safety of the battery. In the case of too low porosity, it will limit the free diffusion of ions, causing the efficient transmission of ions in the material to be difficult, reducing the charge and discharge performance of the battery. In addition, the polycrystalline positive electrode material will swell in volume during the charging process. If the void is too small, it cannot accommodate the swelling material, which may cause the material to break or the battery to fail. Therefore, it is necessary to limit the porosity within a reasonable range.

[0044] In some embodiments, the second region includes a hole, the length of the hole being L, L≤5μm. In some embodiments, L can be 0.2μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, or a range consisting of any two of these values. In some embodiments, the width of the hole is d, d≤1.5μm. In some embodiments, d can be 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, or a range consisting of any two of these values. In order to obtain good electrochemical performance, the holes of the positive electrode material are controlled within the above suitable range, which can ensure good transmission of electrons and ions, and better accommodate the volume change of the material.

[0045] In some embodiments, the length direction of the holes is consistent with the radial direction of the second region. In some embodiments, the holes are distributed radially. The holes arranged in the above manner can better disperse stress during cold pressing and cycling, reduce particle cracking during cold pressing and cycling, and thus improve the cycling performance and high-temperature storage performance of the electrochemical device.

[0046] In some embodiments, the positive electrode material is assembled into a button cell with lithium metal, and when the button cell is charged and discharged at a current of 0.1C in a voltage range of 2.8V to 4.5V, a capacity-voltage differential dQ / dV curve obtained has a first oxidation peak and a first reduction peak in a range of 4.2V to 4.5V.

[0047] In some embodiments, the peak voltage of the first oxidation peak is Vo1, the peak voltage of the first reduction peak is Vr1, and |Vo1-Vr1|≤0.2V. This indicates that the positive electrode material has reversible charge and discharge capacity in a high voltage range of 4.2V to 4.5V, thereby making the positive electrode material have a higher energy density and good structural stability. In some embodiments, |Vo1-Vr1| can be 0.2V, 0.18V, 0.16V, 0.14V, 0.12V, 0.1V, 0.08V, 0.06V, 0.04V, 0.02V, 0.01V, or a range consisting of any two of these values.

[0048] In some embodiments, the capacity-voltage differential dQ / dV curve obtained when the button cell is charged and discharged at a current of 0.1C in a voltage range of 2.8V to 4.5V has a second oxidation peak and a second reduction peak in a range of 3.6V to 4.0V. The peak voltage of the second oxidation peak is Vo2, the peak voltage of the second reduction peak is Vr2, and |Vo2-Vr2|≤0.3V. In some embodiments, |Vo1-Vr1| can be 0.3V, 0.28V, 0.26V, 0.24V, 0.22V, 0.2V, 0.18V, 0.16V, 0.14V, 0.12V, 0.1V, 0.08V, 0.06V, 0.04V, 0.02V, 0.01V, or a range consisting of any two of these values.

[0049] In some embodiments, the peak height of the first oxidation peak is in a range of 2000mAh / g / V to 4000mAh / g / V based on the mass of the positive electrode material. This indicates that the positive electrode material can have a higher charge capacity in a high voltage range of 4.2V to 4.5V, thereby being able to improve the charge capacity of the electrochemical device.

[0050] In some embodiments, the absolute value of the peak height of the first reduction peak is in the range of 2000 mAh / g / V to 4000 mAh / g / V based on the mass of the positive electrode material. This indicates that the positive electrode material can have a higher reversible discharge capacity in the high voltage range of 4.2 V to 4.5 V, thereby increasing the energy density of the electrochemical device.

[0051] In some embodiments, the discharge curve in the voltage capacity curve obtained when the button cell is charged and discharged in the voltage range of 2.8 V to 4.5 V at a current of 0.1 C has a plateau in the range of 4.2 V to 4.5 V. This indicates that the positive electrode material can have a reversible discharge capacity in the high voltage range of 4.2 V to 4.5 V.

[0052] In some embodiments, the capacity of the discharge curve in the range of 4.2 V to 4.5 V is Q1, and the capacity of the discharge curve in the range of 2.8 V to 4.5 V is Qt, in the voltage capacity curve obtained when the button cell is charged and discharged in the voltage range of 2.8 V to 4.5 V at a current of 0.1 C, and 0.2≤Q1 / Qt≤0.35 is satisfied. At this time, the capacity of the positive electrode material in the high voltage range of 4.2 V to 4.5 V is high, thereby making the positive electrode material have a higher energy density.

[0053] In some embodiments, the positive electrode material includes a lithium transition metal oxide including T elements and optionally M elements, the T elements including at least one of Ni, Co, or Mn, and the M elements including at least one of K, Ca, Sr, Y, Zr, Nb, Mo, In, Sn, Sb, Ba, La, Ce, Hf, Ta, W, Pb, Al, Mg, B, Si, P, S, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, or Ge.

[0054] In some embodiments, the molar percentage content of Ni elements is 30% to 70% based on the total molar amount of T elements in the lithium transition metal oxide. For example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range consisting of any two of these values.

[0055] In some embodiments, the molar percentage content of Mn elements is less than or equal to 70% based on the total molar amount of T elements in the lithium transition metal oxide. For example, 0.5%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, or a range consisting of any two of these values.

[0056] In some embodiments, the lithium transition metal oxide further comprises a Na element, a molar percentage content of the Na element is 0.1% to 20%, for example 0.1%, 0.5%, 1%, 2%, 5%, 8%, 10%, 15%, 20%, or a range consisting of any two of these values, based on a total molar amount of T elements and M elements in the lithium transition metal oxide.

[0057] In some embodiments, a molar percentage content of the T elements is 90% to 100%, for example 90%, 92%, 95%, 96%, 98%, 99%, 100%, or a range consisting of any two of these values, based on a total molar amount of T elements and M elements in the lithium transition metal oxide; a molar percentage content of the M elements is 0% to 10%, for example 0%, 0.1%, 1%, 2%, 4%, 6%, 8%, 10%, or a range consisting of any two of these values.

[0058] In some embodiments, a ratio of a molar amount of Li elements to a total molar amount of the T elements and the M elements in the lithium transition metal oxide is 0.5 to 1.1, for example 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, or a range consisting of any two of these values.

[0059] In some embodiments, the lithium transition metal oxide further comprises a Na element, a molar percentage content of the Na element is 0.1% to 20%, for example 0.1%, 0.5%, 1%, 2%, 5%, 8%, 10%, 15%, 20%, or a range consisting of any two of these values, based on a total molar amount of T elements and M elements in the lithium transition metal oxide.

[0060] In some embodiments, the lithium transition metal oxide further comprises an R element, the R element comprises at least one of F, Cl, Br, I, or N, a molar percentage content of the R element is 0.1% to 10%, for example 0.1%, 0.5%, 1%, 2%, 5%, 8%, 10%, or a range consisting of any two of these values, based on a total molar amount of T elements and M elements in the lithium transition metal oxide.

[0061] In some embodiments, the lithium transition metal oxide has a layered crystal structure.

[0062] In some embodiments, the lithium transition metal oxide comprises Li x1 Na x2 Ni y1 Mn y2 Co y3 M z1 O2±mR m0.5 < x1 < 1.1, 0.001 < x2 < 0.2, 0.3 < y1 < 0.7, 0 < y2 < 0.7, 0 < y3 < 0.5, 0 < z1 < 0.1, 0 < m < 0.1, wherein the R element includes at least one of F, CI, Br, I, or N.

[0063] In some embodiments, the X-ray diffraction pattern of the positive electrode material has diffraction peaks in the intervals of 16° to 20°, 34° to 38°, and 42° to 46°.

[0064] In a second aspect, the present application also provides an electrochemical device, which includes a positive electrode, the positive electrode including a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer including the positive electrode material of the first aspect.

[0065] In some embodiments, the positive electrode active material layer further includes a conductive agent and a binder. In some embodiments, the binder includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, or vinylidene fluoride-hexafluoropropylene copolymer, etc. In some embodiments, the conductive agent includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based materials are selected from carbon black, acetylene black, ketjen black, carbon nanotubes, carbon fibers, graphene, or any combination thereof. In some embodiments, the metal-based materials are selected from metal powders or metal fibers. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0066] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, an aluminum foil can be used. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate.

[0067] The electrochemical device of the present application also includes a negative electrode, which includes a negative electrode active material layer and a negative electrode current collector.

[0068] In some embodiments, the negative active material layer includes a negative active material, a binder, and optionally a conductive agent. In some embodiments, the negative active material includes at least one of a carbon material or a silicon material. In some embodiments, the carbon material includes at least one of graphite, hard carbon, or soft carbon. In some embodiments, the silicon material includes at least one of silicon, silicon oxide, silicon carbide, or silicon alloy. In some embodiments, the binder includes at least one of polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, or styrene butadiene rubber. In some embodiments, the conductive agent can use any conductive material as long as it does not cause chemical changes. In some embodiments, the conductive agent includes at least one of conductive carbon black, acetylene black, carbon nanotube, ketjen black, carbon fiber, or graphene.

[0069] In some embodiments, the negative current collector can be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0070] In some embodiments, the electrochemical device further includes an electrolyte. In some embodiments, the electrolyte includes a lithium salt and a non-aqueous solvent. In some embodiments, the lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate. For example, the lithium salt can be LiPF6. In some embodiments, the non-aqueous solvent can be a carbonate compound, a carboxylic acid ester compound, an ether compound, or a combination thereof. The carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, or a combination thereof. Examples of the chain carbonate compound are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and a combination thereof. Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and a combination thereof. Examples of the carboxylic acid ester compound are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valerolactone, hexanolactone, and a combination thereof. Examples of the ether compound are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and a combination thereof.

[0071] According to some embodiments of the present application, a separator is provided between the positive electrode and the negative electrode to prevent short circuiting. The material and shape of the separator used in the embodiments of the present application are not particularly limited and can be any of the techniques disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance formed of a material stable to the electrolyte of the present application, and the like. For example, the separator can include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, a film, or a composite film having a porous structure, and the material of the substrate layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used. A surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed of a mixture of a polymer and an inorganic substance. The inorganic layer includes inorganic particles and a binder, and the inorganic particles include at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder includes at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polytetrafluoroethylene, or polyhexafluoropropylene. The polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or vinylidene fluoride-hexafluoropropylene copolymer.

[0072] According to some embodiments of the present application, the electrochemical device of the present application includes, but is not limited to, a primary battery or a secondary battery of all kinds. In some embodiments, the electrochemical device is a lithium secondary battery. In some embodiments, the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0073] In a third aspect, the electronic device of the present application can be any device using the electrochemical device of the second aspect of the present application.

[0074] In some embodiments, the electronic device includes, but is not limited to: laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries or lithium-ion capacitors, etc.

[0075] Examples and Comparative Examples

[0076] The following examples and comparative examples further illustrate this application in detail. It should be understood that this application is not limited to these examples.

[0077] 1. Preparation of cathode materials

[0078] Comparative Example 1

[0079] Step 1: In a 5L continuous reactor, a 2M metal salt solution was prepared by mixing nickel sulfate and manganese sulfate in an aqueous solution at a molar ratio of Ni:Mn = 50:50, and connected to the reactor. 3L of deionized water was added to the reactor, and nitrogen gas was introduced at a rate of 2L / min to remove dissolved oxygen. Then, a certain amount of 3M NaOH solution was introduced into the reactor, while the mixture was stirred uniformly at 1200 rpm at 60°C and the pH was adjusted to 12.0. Next, the 2M metal salt solution, 3M NaOH solution, and 10% NH4OH aqueous solution were gradually added at rates of 100 mL / h, 100 mL / h, and 8 mL / h, respectively, and allowed to react completely for 24 hours to obtain a dense Ni structure. 0.5 Mn 0.5 (OH)2 precursor;

[0080] Step 2: The obtained dense Ni structure 0.5 Mn 0.5 The (OH)2 precursor and lithium carbonate were thoroughly mixed in a (Ni+Mn):Li molar ratio of 1:1.02 and reacted in an air atmosphere at 800℃ for 20h. The mixture was then cooled to room temperature at a cooling rate of 10℃ / min, and finally crushed and sieved to obtain the cathode material.

[0081] Comparative Example 2

[0082] The difference from Comparative Example 1 is:

[0083] Step 2: The obtained dense Ni structure 0.5 Mn 0.5The intermediate product is mixed with a lithium source (a mixture of lithium hydroxide and lithium nitrate with a molar ratio of 1:1) at a mass ratio of 1:10, heated to 400°C at a heating rate of 10°C / min, kept at 400°C for 10h, then cooled to room temperature at a cooling rate of 50°C / min in Ar mixed with air (volume ratio of 1:1), and the product is soaked and stirred in deionized water, filtered, vacuum dried, crushed, and sieved to obtain the positive electrode material.

[0084] Step 3, the intermediate product is mixed with a lithium source (a mixture of lithium hydroxide and lithium nitrate with a molar ratio of 1:1) at a mass ratio of 1:10, heated to 400°C at a heating rate of 10°C / min, kept at 400°C for 10h, then cooled to room temperature at a cooling rate of 50°C / min in Ar mixed with air (volume ratio of 1:1), and the product is soaked and stirred in deionized water, filtered, vacuum dried, crushed, and sieved to obtain the positive electrode material.

[0085] Comparative Example 3

[0086] Step 1, a 2M metal salt solution is prepared by mixing nickel sulfate and manganese sulfate in a molar ratio of Ni:Mn=50:50 in an aqueous solution in a 5L continuous reactor, and the reactor is connected; in addition, a 3M metal salt solution is prepared by mixing nickel sulfate and manganese sulfate in a molar ratio of Ni:Mn=50:50, and the reactor is connected; a 3M NaOH solution and a 10% NH4OH aqueous solution are prepared respectively, and are connected to the reactor respectively; 3L deionized water is added to the reactor and nitrogen gas is passed in at a rate of 2L / min to remove dissolved oxygen, then a certain amount of 3M NaOH solution is passed into the reactor, while stirring uniformly at 1200rpm at 60°C and adjusting the pH to 12.0. Then, 2M metal salt solution, 3M NaOH solution and 10% NH4OH aqueous solution are gradually added at a rate of 100mL / h, 100mL / h and 8mL / h respectively. After the reaction of the 2M metal salt solution is completed, 3M metal salt solution, 3M NaOH solution and 10% NH4OH aqueous solution are gradually added at a rate of 100mL / h, 140mL / h and 13mL / h respectively, and the reaction is carried out for 24h to obtain a Ni 0.5 Mn 0.5 (OH)2precursor;

[0087] Step 2, the prepared Ni 0.5 Mn 0.5 (OH)2precursor is mixed with sodium carbonate at a molar ratio of (Ni+Mn):Na=1:1.05, reacted in an air atmosphere at 800°C for 20h, cooled to room temperature at a cooling rate of 10°C / min, and finally crushed and sieved to obtain a first product;

[0088] Step 3, mix the first product with lithium source (a mixture of lithium hydroxide and lithium nitrate with a molar ratio of 1:1) with a mass ratio of 1:10, heat to 400℃ at a heating rate of 10℃ / min, and keep constant temperature for 10h. Then cool to room temperature at a cooling rate of 50℃ / min in Ar mixed with air (volume ratio of 1:1); soak the product in deionized water and stir well, and then filter, vacuum dry, crush, and sieve to obtain the positive electrode material.

[0089] Example 1

[0090] Step 1, prepare a 2M metal salt solution by mixing nickel sulfate and manganese sulfate in a molar ratio of Ni:Mn=50:50 in an aqueous solution in a 5L continuous reactor, and connect the reactor; additionally, prepare a 3M metal salt solution by mixing nickel sulfate and manganese sulfate in a molar ratio of Ni:Mn=50:50, and connect the reactor; prepare a 3M NaOH solution and a 10% NH4OH aqueous solution respectively, and connect the reactors respectively; add 3L deionized water to the reactor and pass nitrogen gas at a rate of 2L / min to remove dissolved oxygen, then pass a certain amount of 3M NaOH solution into the reactor, while stirring uniformly at 1200rpm at 60℃ and adjusting the pH to 12.0. Then gradually add the 2M metal salt solution, the 3M NaOH solution, and the 10% NH4OH aqueous solution at rates of 100mL / h, 100mL / h, and 8mL / h respectively. After the reaction of the 2M metal salt solution is completed, then gradually add the 3M metal salt solution, the 3M NaOH solution, and the 10% NH4OH aqueous solution at rates of 100mL / h, 150mL / h, and 12mL / h respectively, and react for 24h to obtain a Ni 0.5 Mn 0.5 (OH)2 precursor with a hollow circular ring structure;

[0091] Step 2, mix the prepared Ni 0.5 Mn 0.5 (OH)2 precursor with sodium carbonate in a molar ratio of (Ni+Mn):Na=1:1.05, react in an air atmosphere at 800℃ for 20h, and then cool to room temperature at a cooling rate of 10℃ / min, and finally crush and sieve to obtain the first product;

[0092] Step 3, mix the first product with lithium source (a mixture of lithium hydroxide and lithium nitrate with a molar ratio of 1:1) with a mass ratio of 1:10, heat to 400℃ at a heating rate of 10℃ / min, and keep constant temperature for 10h. Then cool to room temperature at a cooling rate of 50℃ / min in Ar mixed with air (volume ratio of 1:1); soak the product in deionized water and stir well, and then filter, vacuum dry, crush, and sieve to obtain the positive electrode material.

[0093] Example 2-3

[0094] The difference from Example 1 is that the constant temperature time in step 3 is adjusted to 8 hours and 5.5 hours respectively.

[0095] Example 4-15

[0096] Example 4, Example 7, Example 10, Example 13 and Example 1 differ in that the calcium oxide or strontium hydroxide is mixed with the circular ring hollow structure Ni 0.5 Mn 0.5 (OH)2precursor and sodium carbonate in step 2 is different.

[0097] Example 5, Example 8, Example 11, Example 14 and Example 2 differ in that the calcium oxide or strontium hydroxide is mixed with the circular ring hollow structure Ni 0.5 Mn 0.5 (OH)2precursor and sodium carbonate in step 2 is different.

[0098] Example 6, Example 9, Example 12, Example 15 and Example 3 differ in that the calcium oxide or strontium hydroxide is mixed with the circular ring hollow structure Ni 0.5 Mn 0.5 (OH)2precursor and sodium carbonate in step 2 is different.

[0099] Table 1 shows the average diameter D of the positive electrode material particles, the length L of the pores, the width d of the pores, the void fraction Vc1, the void fraction Vc2, and the difference between Vc2 and Vc1 in Comparative Examples 1-3 and Examples 1-15.

[0100] Table 1

[0101]

[0102]

[0103] 2. Preparation of lithium ion battery:

[0104] (1) Preparation of lithium ion button cell:

[0105] The binder polyvinylidene fluoride (PVDF), the conductive agent conductive carbon black (Super P) and the positive electrode material in a weight ratio of 1.5:1.5:97 were mixed, added into N-methyl pyrrolidone (NMP) and mixed uniformly to prepare a positive electrode slurry with a solid content of 0.7. The mixed slurry was uniformly coated on an aluminum foil, dried and then roll-pressed to form the required electrode, wherein the electrode coating surface density was 14 mg / cm 2The positive electrode sheet was obtained after drying, and was punched into a circular sheet with a diameter of 14 mm to prepare a single-sided positive electrode sheet. The separator film was punched into a circular sheet with a diameter of 18 mm; the negative electrode used was a lithium metal sheet with a diameter of 18 mm; and an electrolyte was prepared by adding LiPF6 into a solvent prepared by mixing propylene carbonate (PC), ethylene carbonate (EC) and diethyl carbonate (DEC) at a weight ratio of 1:1:1 and uniformly mixing the same, wherein the mass concentration of LiPF6 was 12.5% based on the mass of the electrolyte. The positive electrode sheet, the separator film, the negative electrode sheet (lithium sheet), the electrolyte and other accessories such as the battery shell were moved into a glove box (the water content needed to be less than 11 ppm); the battery was assembled in the order of bottom to top and was injected with the electrolyte as follows: negative electrode shell > flat gasket > metal lithium sheet + appropriate amount of electrolyte > one layer of separator film + appropriate amount of electrolyte > positive electrode sheet + appropriate amount of electrolyte > flat gasket > spring > positive electrode shell; and the battery was packaged on a packaging machine to obtain a button cell.

[0106] (2) Preparation of a lithium ion soft package battery

[0107] Preparation of a positive electrode

[0108] A binder polyvinylidene fluoride (PVDF), a conductive agent conductive carbon black (Super P) and a positive electrode material were mixed at a weight ratio of 1.5:1.5:97, were added into N-methyl pyrrolidone (NMP) and were uniformly mixed to prepare a positive electrode slurry with a solid content of 0.7. The mixed positive electrode slurry was uniformly coated on one side surface of an aluminum foil, the above step was repeated on the other side surface of the aluminum foil after drying, and a double-sided coated positive electrode sheet was obtained; and the positive electrode was obtained after cold pressing, cutting and welding of the tabs.

[0109] Preparation of a negative electrode

[0110] Artificial graphite, butadiene styrene rubber and sodium carboxymethyl cellulose (CMC) were mixed with deionized water at a mass ratio of 96:2:2, and were uniformly stirred to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on one side surface of a copper foil, the above step was repeated on the other side surface of the copper foil after drying, and a double-sided coated negative electrode sheet was obtained; and the negative electrode was obtained after cold pressing, cutting and welding of the tabs.

[0111] Preparation of an electrolyte

[0112] In a dry argon environment, LiPF6 was added into a solvent prepared by mixing propylene carbonate (PC), ethylene carbonate (EC) and diethyl carbonate (DEC) at a weight ratio of 1:1:1 and uniformly mixing the same to obtain an electrolyte, wherein the mass concentration of LiPF6 was 12.5% based on the total weight of the electrolyte.

[0113] Preparation of a separator film

[0114] A porous polyethylene (PE) polymer film was used as the separator film.

[0115] Preparation of lithium ion soft package battery

[0116] The positive electrode, the separator and the negative electrode are stacked in sequence with the separator between the positive electrode and the negative electrode to play a separating role, and the naked battery is obtained by winding. The naked battery is placed in an outer packaging aluminum plastic film, electrolyte is injected, and the lithium ion soft package battery is obtained after packaging, formation, degassing, edge cutting and other process procedures.

[0117] Test method

[0118] 1. Test of porosity, average diameter D, hole length L and width d

[0119] The positive electrode sheet is cut longitudinally using ion polishing, and then a scanning electron microscope (instrument model: ZEISS SEM, acceleration voltage: 0.1KV-30KV) is used to observe the morphology of the positive electrode material particles in the cross section of the positive electrode sheet and take micrographs. In the cross section photograph, the midpoint of the longest diameter of the positive electrode material particles is taken as the center to determine the region surrounded by the first demarcation point as the first region, wherein the center to any point on the surface of the positive electrode material particle in the cross section is the first connecting line, and the distance from the center to the first demarcation point is 3 / 5 of the length of the first connecting line where the first demarcation point is located. The region outside the first region is the second region. The porosity of the first region and the porosity of the second region are counted by using image processing software. Randomly select 20 positive electrode material particles, take the average value of the porosity of the first region and the porosity of the second region as the porosity of the first region Vc1 and the porosity of the second region Vc2 of the positive electrode material, and take the average value of the longest diameter as the average diameter D of the positive electrode material. Wherein, the porosity Vc=(total area of pores in a certain region / total area of the certain region) x 100%. At the same time, 20 holes are randomly selected in the cross section photograph of the positive electrode material, the maximum length and the maximum width perpendicular to the maximum length of the holes are measured, and the average value of the maximum length is taken as the length L of the holes and the average value of the maximum width is taken as the width d of the holes.

[0120] 2. XRD test

[0121] The positive electrode material is tested by an X-ray powder diffractometer (instrument model: Bruker D8 ADVANCE, target material is Cu Kα; voltage and current are 40KV / 40mA, and the scanning angle range is 10° to 70°) to obtain the X-ray diffraction pattern of the positive electrode material.

[0122] 3. 85℃ storage thickness expansion rate test

[0123] The lithium ion soft package battery is charged at 0.5C to 4.35V at 25°C, then charged at 4.35V to 0.05C, and the thickness of the lithium ion battery at this time is tested and recorded by a micrometer, denoted as H1; then the lithium ion battery is placed in an 85°C oven for 12 hours, and the thickness of the lithium ion battery at this time is tested and recorded by a micrometer after 12 hours, denoted as H2.

[0124] The thickness expansion rate (%) of the lithium ion battery after 12 hours of storage at 85°C = (H2-H1) / H1x100%.

[0125] 4.45℃ cycle capacity retention rate test

[0126] The lithium ion soft package battery is placed in a 45°C constant temperature oven and allowed to stand for 30 minutes to allow the lithium ion battery to reach a constant temperature; the lithium ion battery that has reached a constant temperature is charged at 1.5C to 4.35V at 45°C, then charged at 4.35V to 0.02C; stand for 5 minutes, then discharge at 4C to 2.8V, stand for 5 minutes, test the discharge capacity this time, denoted as the first cycle discharge capacity; such charging and discharging cycle 300 times, test the discharge capacity of the 300th cycle of the battery, denoted as the 300th cycle discharge capacity.

[0127] The capacity retention rate (%) of the lithium ion battery after 300 cycles at 45°C = the 300th cycle discharge capacity / the first cycle discharge capacityx100%.

[0128] 5. Q1 / Qt, dQ / dV test

[0129] Using an electrochemical workstation, the charge-discharge curve of the lithium ion button cell in the voltage range of 2.8V to 4.5V is tested at 25°C; first charge at 0.1C to 4.5V, then charge at 4.5V to 0.02C; stand for 5min, then discharge at 0.1C to 2.8V, stand for 5min; calculate the discharge capacity in the voltage range of 4.2 to 4.5V as Q1, and the discharge capacity in the voltage range of 2.8V to 4.5V as Qt. At the same time, according to the dQ / dV curve, the peak position of the first oxidation peak Vo1(V), the peak position of the first reduction peak Vr1(V), the peak position of the second oxidation peak Vo2, the peak position of the second reduction peak Vr2(V), and the absolute value of the first reduction peak dQ / dV are obtained.

[0130] 6. First circle coulombic efficiency test

[0131] The lithium ion soft package battery is charged at 0.2C to 4.35V at 25°C, then charged at 4.35V to 0.02C; stand for 5 minutes, then discharge at 0.2C to 2.8V, stand for 5 minutes. The ratio of discharge capacity to charge capacity is the first circle coulombic efficiency.

[0132] 7. Capacity retention rate of the coin cell cycling

[0133] The coin cell was charged at 0.1C to 4.5V, then 4.5V constant voltage charging to the current of 0.02C at 25℃, and then rested for 5min, and discharged at 0.1C to 2.8V, and then rested for 5min. The discharge capacity of the first cycle was recorded as C1. The above cycle was repeated for 50 times. The discharge capacity of the 50th cycle was recorded as C50. The capacity retention rate of the coin cell cycling for 50 cycles = (C50 / C1) x 100%.

[0134] Test results

[0135] Table 2

[0136]

[0137] According to the analysis of the data of Examples 1-15 and Comparative Examples 1-3, by reasonably regulating the distribution of the internal pore structure of the positive electrode material particles, so that 5%≤Vc2-Vc1≤30%, the capacity retention rate of the positive electrode material in the coin cell cycling, the thickness expansion rate of the lithium ion battery at 85℃ storage, and the 45℃ cycle capacity retention rate and other performances are significantly improved, which shows that limiting the size and distribution of the porosity of the positive electrode material within a reasonable range can not only ensure the transmission of electrons and ions, but also accommodate the volume change of the material, which can effectively reduce the influence of cold pressing and charge-discharge cycling on the stress between the polycrystalline particles of the positive electrode material, thereby improving the problem of particle cracking caused by cold pressing and cycling, and further improving the cycle performance and high-temperature storage performance of the lithium ion battery.

[0138] At the same time, from the attached Figure 1 It can be seen that in the cross-sectional SEM photograph of the positive electrode material particles of Example 1 of the present application, the length direction of the holes is consistent with the radial direction of the cross section, and the holes are distributed in a radial manner. The above-mentioned arranged holes can better disperse the stress in the cold pressing and cycling process, reduce the particle cracking phenomenon in the cold pressing and cycling process, and thus better improve the cycle performance and high-temperature storage performance of the lithium ion battery.

[0139] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above-mentioned embodiments cannot be interpreted as a limitation of the present application, and changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A positive electrode material, a cross section of a particle of the positive electrode material comprising a first region and a second region; wherein a first connecting line being a line connecting a center of a longest diameter in the cross section to any point on a surface of the particle of the positive electrode material, the first connecting line having a first demarcation point, a distance from the center to the first demarcation point being 3 / 5 of a length of the first connecting line where the first demarcation point is located, the first region being a region enclosed by the first demarcation point, and the second region being a region other than the first region in the cross section; a porosity of the first region being Vc1 and a porosity of the second region being Vc2, satisfying 5%≤Vc2-Vc1≤30%, 11%≤Vc1≤30%, and 25%≤Vc2≤35%; the positive electrode material comprising a lithium transition metal oxide, the lithium transition metal oxide comprising a T element and an M element, the T element comprising at least one of Ni, Co, or Mn, and the M element comprising at least one of Ca or Sr; the positive electrode material being assembled into a button cell with lithium metal, the button cell being charged and discharged at a current of 0.1C in a voltage interval of 2.8V to 4.5V, a capacity-voltage differential dQ / dV curve obtained from the button cell having a first oxidation peak and a first reduction peak in an interval of 4.2V to 4.5V.

2. The positive electrode material of claim 1, wherein, the positive electrode material satisfying at least one of conditions (1) to (3) below: (1) 7%≤Vc2-Vc1≤18%; (2) 12%≤Vc1≤30%; (3) 28%≤Vc2≤35%.

3. The cathode material of claim 1, wherein, the second region comprising pores, the pores satisfying at least one of conditions (1) to (4) below: (1) a length of the pores being L, L≤5μm; (2) a width of the pores being d, d≤1.5μm; (3) a length direction of the pores being consistent with a radial direction of the second region; (4) the pores being distributed in a radial pattern.

4. The cathode material of claim 1, wherein, the positive electrode material satisfying at least one of conditions (1) to (6) below: (1) a peak height of the first oxidation peak being in an interval of 2000mAh / g / V to 4000mAh / g / V based on a mass of the positive electrode material; (2) an absolute value of a peak height of the first reduction peak being in an interval of 2000mAh / g / V to 4000mAh / g / V based on the mass of the positive electrode material; (3) a peak voltage of the first oxidation peak being Vo1, a peak voltage of the first reduction peak being Vr1, and |Vo1-Vr1|≤0.2V; (4) the capacity-voltage differential dQ / dV curve having a second oxidation peak and a second reduction peak in an interval of 3.6V to 4.0V, a peak voltage of the second oxidation peak being Vo2, a peak voltage of the second reduction peak being Vr2, and |Vo2-Vr2|≤0.3V; (5) a discharge curve in a voltage-capacity curve obtained from the button cell when the button cell is charged and discharged at a current of 0.1C in a voltage interval of 2.8V to 4.5V having a plateau in an interval of 4.2V to 4.5V. (6) When the button cell is charged and discharged at a current of 0.1C in a voltage range of 2.8V to 4.5V, a capacity of a discharge curve in a voltage capacity curve obtained is Q1 in a range of 4.2V to 4.5V, and a capacity of the discharge curve is Qt in a range of 2.8V to 4.5V, and 0.2≤Q1 / Qt≤0.35 is satisfied.

5. The positive electrode material according to any one of claims 1 to 4, wherein The lithium transition metal oxide satisfies at least one of the following conditions (1) to (4): (1) the molar percentage content of Ni element is 30% to 70% based on the total molar amount of T element in the lithium transition metal oxide; (2) the molar percentage content of Mn element is less than or equal to 70% based on the total molar amount of T element in the lithium transition metal oxide; and / or, the molar percentage content of Co element is less than or equal to 50% based on the total molar amount of T element in the lithium transition metal oxide; (3) the molar percentage content of the T element is 90% to 100% and the molar percentage content of the M element is 0% to 10% based on the total molar amount of the T element and the M element in the lithium transition metal oxide; (4) the ratio of the molar amount of Li element to the total molar amount of the T element and the M element in the lithium transition metal oxide is 0.5 to 1.

1.

6. The cathode material of claim 5, wherein, The lithium transition metal oxide satisfies at least one of the following conditions (1) to (4): (1) the lithium transition metal oxide further includes Na element, and the molar percentage content of the Na element is 0.1% to 20% based on the total molar amount of T element and M element in the lithium transition metal oxide; (2) the lithium transition metal oxide further includes R element, the R element includes at least one of F, Cl, Br, I or N, and the molar percentage content of the R element is 0.1% to 10% based on the total molar amount of T element and M element in the lithium transition metal oxide; (3) the lithium transition metal oxide has a layered crystal structure; (4) the lithium transition metal oxide includes Li x1 Na x2 Ni y1 Mn y2 Co y3 M z1 O2±mR m , 0.5≤x1≤1.1, 0.001≤x2≤0.2, 0.3≤y1≤0.7, 0≤y2≤0.7, 0≤y3≤0.5, 0≤z1≤0.1, 0≤m≤0.1, wherein the R element includes at least one of F, Cl, Br, I, or N.

7. The cathode material of claim 1, wherein, The X-ray diffraction pattern of the positive electrode material has diffraction peaks in the range of 16° to 20°, 34° to 38° and 42° to 46°.

8. An electrochemical device comprising a positive electrode, the positive electrode comprising a positive electrode active material layer, the positive electrode active material layer comprising the positive electrode material according to any one of claims 1 to 7.

9. An electronic device comprising the electrochemical device according to claim 8.

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