Positive electrode material, electrochemical device, and electronic device

Abstract

Provided in the present application are a positive electrode material, an electrochemical device and an electronic device. The positive electrode material comprises lithium cobalt oxide and a coating layer formed on the lithium cobalt oxide, wherein the coating layer comprises a sodium superionic conductor and a boron-containing compound; the lithium cobalt oxide has a crystal structure belonging to the space group P63mc; and the lithium cobalt oxide further contains an element M1, M1 comprising at least one of Ni or Mn. The positive electrode material provided by the present application can reduce direct contact between the lithium cobalt oxide and an electrolyte while maintaining a relatively high ionic conductivity, and therefore the cycle performance of the positive electrode material under high voltages is improved.

Description

Cathode materials, electrochemical devices, and electronic devices Technical Field

[0001] The present application relates to the field of electrochemical energy storage, and in particular to a positive electrode material, an electrochemical device using the positive electrode material, and an electronic device using the electrochemical device. Background Art

[0002] Currently, the crystal structure of commercial lithium cobalt oxide is extremely unstable at voltages above 4.6V, and is accompanied by severe capacity attenuation, which makes it unable to exert its theoretical capacity at high voltages and difficult to achieve stable cycle performance, limiting the commercial application of lithium cobalt oxide. Summary of the Invention

[0003] The present application provides a positive electrode material capable of improving cycle performance.

[0004] In addition, the present application also provides an electrochemical device using the positive electrode material and an electronic device using the electrochemical device.

[0005] In a first aspect, the present application provides a positive electrode material, comprising lithium cobalt oxide and a coating layer formed on the lithium cobalt oxide, wherein the coating layer comprises a sodium superion conductor and a boron-containing compound, the lithium cobalt oxide has a P63mc crystal structure, and the lithium cobalt oxide further contains an M1 element, wherein M1 comprises at least one of Ni or Mn.

[0006] In the present application, the solid electrolyte of the sodium superionic conductor can increase the ionic conductivity of the interface, which is beneficial to the ion transport between the lithium cobalt oxide and the electrolyte, and is also beneficial to reducing the interface impedance. At the same time, it can also reduce the side reaction between the surface of the lithium cobalt oxide and the electrolyte, thereby improving the cycle performance of the electrochemical device. Moreover, the sodium superionic conductor and the boron-containing compound jointly coat the surface of the lithium cobalt oxide, further inhibiting the direct contact between the lithium cobalt oxide and the electrolyte, thereby reducing the interface side reaction between the lithium cobalt oxide and the electrolyte, and further improving the cycle performance of the electrochemical device. At the same time, the combination of the sodium superionic conductor and the boron-containing compound allows the positive electrode material to maintain a high ionic conductivity while also reducing the direct contact between the lithium cobalt oxide and the electrolyte, thereby allowing the positive electrode material to take into account both high conductivity and structural stability, and improve the cycle performance of the positive electrode material under high pressure. In addition, doping the M1 element into the lithium cobalt oxide can improve the stability of the positive electrode material and improve the first discharge capacity and cycle performance of the electrochemical device.

[0007] Based on the first aspect, in some possible embodiments, the sodium superion conductor is Li 1+x Al x Ti 2-x (PO4)3 or Li 1+y Al y Ge2-y (PO4)3, where 0 ≤ x ≤ 0.5 and 0 ≤ y ≤ 1. The above sodium superionic conductor has high ionic conductivity and chemical stability. Coating the lithium cobalt oxide with the sodium superionic conductor can increase the ionic conductivity of the lithium cobalt oxide and the electrolyte, thereby reducing the interfacial side reactions between the lithium cobalt oxide and the electrolyte and improving the cycling performance of the electrochemical device.

[0008] Based on the first aspect, in some possible embodiments, 0 < m1 / m2 ≤ 15%, where m1 is the amount of substance of M1 and m2 is the sum of the amount of substance of M1 and the amount of substance of Co element. This is beneficial for the cathode material to have better initial charge-discharge specific capacity and cycling performance.

[0009] Based on the first aspect, in some possible embodiments, the cathode material further contains an M2 element, and the M2 element includes at least one of Mg, Ca, La, Y, Ti, and Zr. The mass fraction of the M2 element in the lithium cobalt oxide is n, where 0 < n ≤ 1%. The M2 element can slow down the rapid change of the layer spacing during the insertion and extraction of active ions, thereby stabilizing the layered lithium cobalt oxide. At the same time, the M2 element can also reduce the oxygen activity of the cathode material, thereby improving the stability of the cathode material and further enhancing the safety and cycling life of the electrochemical device.

[0010] Based on the first aspect, in some possible embodiments, the boron-containing compound includes at least one of boron-containing oxides or borates. The boron-containing oxides include at least one of B2O3, BO, HBO3, and H3BO3, and the borates include at least one of Na2B4O7, NH4H2BO3, CaB2O4, and Mg(B(OH)4)2. The above boron-containing oxides can uniformly coat the surface of the lithium cobalt oxide, block the direct contact between the electrolyte and the lithium cobalt oxide, reduce side reactions, and thereby improve the cycling performance of the electrochemical device.

[0011] Based on the first aspect, in some possible embodiments, based on the mass of the cathode material, the mass ratio of the sodium superionic conductor is ω1, where 0 < ω1 ≤ 1%. This is beneficial for increasing the ionic conductivity of the cathode material while the cathode material has good specific capacity and low impedance, thereby improving the cycling performance and rate performance of the electrochemical device.

[0012] Based on the first aspect, in some possible embodiments, the mass ratio of boron element in the boron-containing compound is ω2, where 0 < ω2 ≤ 0.5%. This is beneficial for minimizing the impact on the interfacial impedance after coating with the boron-containing compound on the premise of reducing the direct contact between the lithium cobalt oxide and the electrolyte as much as possible.

[0013] Based on the first aspect, in some possible embodiments, 0<ω1+ω2≤1.5%. This is beneficial for increasing the ionic conductivity of the positive electrode material and improving the energy density of the electrochemical device. It can also reduce the interfacial impedance while reducing the side reaction between lithium cobalt oxide and the electrolyte, thereby improving the cycle performance of the positive electrode material.

[0014] Based on the first aspect, in some possible embodiments, the lithium cobalt oxide is a single-crystal particle having cracks. The presence of the cracks can reduce and release stress generated by lattice expansion and contraction during charge and discharge, thereby inhibiting the rapid expansion of lattice defects, thereby improving the structural stability of the positive electrode material.

[0015] Based on the first aspect, in some possible embodiments, the median particle size D of the sodium superion conductor is 50 The particle size is 50 nm to 100 nm. This helps improve the uniformity of the sodium superion conductor coating the lithium cobalt oxide. At this particle size, it also helps increase the contact area between the sodium superion conductor and the lithium cobalt oxide, reducing the risk of the sodium superion conductor falling off the lithium cobalt oxide, thereby improving the stability of the sodium superion conductor formed on the surface of the lithium cobalt oxide and improving the stability of the positive electrode material.

[0016] A second aspect of the present application provides an electrochemical device comprising a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet comprises a current collector and a positive electrode material layer disposed on the current collector, wherein the positive electrode material layer comprises a positive electrode material. The surface of the lithium cobalt oxide in the positive electrode material is coated with a sodium superion conductor and a boron-containing compound, which can reduce interfacial impedance and side reactions between the lithium cobalt oxide and the electrolyte, thereby improving the cycle performance of the positive electrode material under high voltage, thereby increasing the cycle life and charge and discharge rate of the electrochemical device.

[0017] A third aspect of the present application provides an electronic device comprising an electrochemical device. The electrochemical device provides power to the electronic device, and the electrochemical device comprises a positive electrode material, wherein the surface of the lithium cobalt oxide in the positive electrode material is coated with a sodium superion conductor and a boron-containing compound, thereby increasing the cycle life of the electrochemical device and thereby increasing the service life and charge and discharge rate of the electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0019] FIG1 is an X-ray diffraction pattern of lithium cobalt oxide prepared in Example 1.

[0020] FIG2 is a scanning electron microscope image of the lithium cobalt oxide prepared in Example 1.

[0021] FIG3 is a surface EDS spectrum of the lithium cobalt oxide prepared in Example 1.

[0022] FIG4 is a scanning electron microscope image of a cross section of the lithium cobalt oxide prepared in Example 1.

[0023] FIG5 is a scanning electron microscope image of the lithium cobalt oxide prepared in Comparative Example 2. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application are described clearly and in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0025] An embodiment of the present application provides an electrochemical device, which includes a housing, an electrode assembly, and an electrolyte. The electrode assembly and the electrolyte are both located in the housing.

[0026] The housing can be a packaging bag encapsulated with a packaging film (such as an aluminum-plastic film), such as a soft-pack electrochemical device. In other embodiments, the electrochemical device can also be a steel-shell electrochemical device, an aluminum-shell electrochemical device, or the like.

[0027] The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator, with the separator being disposed between the positive and negative electrode sheets. The electrode assembly can be a laminated structure, formed by stacking the positive electrode sheet, separator, and negative electrode sheet. In other embodiments, the electrode assembly can also be a wound structure, formed by stacking the positive electrode sheet, separator, and negative electrode sheet and then winding them.

[0028] Positive electrode

[0029] The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer, and the positive electrode material layer includes a positive electrode material, a binder and a conductive agent.

[0030] According to some embodiments of the present application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil or nickel foil may be used. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer substrate.

[0031] The present application provides a positive electrode material comprising lithium cobalt oxide and a coating layer formed on the lithium cobalt oxide, the coating layer comprising a sodium superion conductor and a boron-containing compound, the lithium cobalt oxide having a P63mc crystal structure. The lithium cobalt oxide further contains an M1 element, wherein the M1 element comprises at least one of nickel and manganese.

[0032] In the present application, a sodium superionic conductor and a boron-containing compound are formed on the surface of the lithium cobalt oxide. The solid electrolyte of the sodium superionic conductor can increase the ionic conductivity of the interface, facilitate the ion transport between the lithium cobalt oxide and the electrolyte, and also help reduce the interface impedance. At the same time, it can also reduce the side reaction between the surface of the lithium cobalt oxide and the electrolyte, thereby helping to improve the cycle performance of the electrochemical device. Moreover, the sodium superionic conductor and the boron-containing compound jointly coat the surface of the lithium cobalt oxide, further inhibiting the direct contact between the lithium cobalt oxide and the electrolyte, thereby reducing the interface side reaction between the lithium cobalt oxide and the electrolyte, and further improving the cycle performance of the electrochemical device. At the same time, the combination of the sodium superionic conductor and the boron-containing compound can not only reduce the interface impedance, but also reduce the side reaction between the lithium cobalt oxide and the electrolyte, and improve the cycle performance of the positive electrode material under high pressure. Doping the M1 element into the lithium cobalt oxide can improve the stability of the positive electrode material and improve the first discharge capacity and cycle performance of the electrochemical device.

[0033] In this application, the sodium superionic conductor (NaSICON) itself has high ionic conductivity and chemical stability. It is formed on the surface of lithium cobalt oxide and can increase the ion transmission between the positive electrode material and the electrolyte. However, since the sodium superionic conductor is not easy to completely cover the surface of the lithium cobalt oxide, and combined with the low melting point of the boron-containing compound, it is easy to evenly adhere to the surface of the lithium cobalt oxide to reduce the defect sites exposed by the lithium cobalt oxide, reduce the specific surface area of ​​the positive electrode material, and thus reduce the occurrence of interfacial side reactions. The combination of the sodium superionic conductor and the boron-containing compound allows the positive electrode material to maintain a high ionic conductivity while also helping to reduce the direct contact between the lithium cobalt oxide and the electrolyte, thereby allowing the positive electrode material to have both high conductivity and structural stability to improve the cycle performance of the positive electrode material.

[0034] In some embodiments, the sodium superion conductor is Li 1+x Al x Ti 2-x (PO4)3 (abbreviated as LATP) or Li 1+y Al y Ge 2-y (PO4)3 (abbreviated as LAGP), where 0≤x≤0.5, 0≤y≤1. Sodium superionic conductors have high ionic conductivity, low toxicity, and high chemical stability. Sodium superionic conductors coated on the surface of lithium cobalt oxide can significantly increase the ionic conductivity of lithium cobalt oxide and electrolyte, thereby reducing the interface side reaction between lithium cobalt oxide and electrolyte and improving the cycle performance of electrochemical devices. For example, sodium superionic conductors can be Li 1.4 Al 0.4 Ti 1.6 (PO4)3 and Li 1.5 Al 0.5 Ge 1.5At least one of (PO4)3.

[0035] In some embodiments, 0 < m1 / m2 ≤ 15%, where m1 is the amount of substance of M1 and m2 is the sum of the amount of substance of M1 and the amount of substance of Co element. When the doping amount of M1 in lithium cobalt oxide is within the above range, it is beneficial for the cathode material to have better first charge-discharge specific capacity and cycling performance. If the value of m1 / m2 is relatively large, such as a relatively high content of Mn element, Mn is doped in lithium cobalt oxide in the form of Mn 4+ and is electrochemically inert and stable during charge-discharge, which will reduce the discharge specific capacity of the cathode material; if the content of Ni element is relatively large, it increases the probability of Ni element mixing and reduces the structural stability of the cathode material, thus affecting the cycling performance of the cathode material. In some embodiments, the ratio of m1 / m2 can be 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15% or any value within the range composed of any two of the above values.

[0036] In some embodiments, the cathode material further contains M2 element, and M2 element includes at least one of Mg, Ca, La, Y, Ti or Zr. The mass ratio of M2 element in lithium cobalt oxide is n, and 0 < n ≤ 1%. Adding M2 element to the cathode material can slow down the rapid change of the layer spacing during the insertion and extraction of active ions, thereby stabilizing the layered lithium cobalt oxide. At the same time, the doped M2 element can also reduce the oxygen activity of the cathode material, thereby improving the stability of the cathode material and further enhancing the safety and cycling life of the electrochemical device. If there is too much M2 element doped in lithium cobalt oxide, it will generate resistance to the insertion and extraction of active ions and affect the insertion and extraction and transmission of active ions. In some embodiments, n can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or any value within the range composed of any two of the above values.

[0037] In some embodiments, the boron-containing compound includes at least one of boron-containing oxides or borates. The boron-containing oxides include at least one of B2O3, BO, HBO3, H3BO3, and the borates include at least one of Na2B4O7, NH4H2BO3, CaB2O4, Mg(B(OH)4)2. The above boron-containing oxides can be uniformly coated on the surface of lithium cobalt oxide to block the direct contact between the electrolyte and lithium cobalt oxide, reduce side reactions, and thus improve the cycling performance of the electrochemical device.

[0038] In some embodiments, based on the mass of the positive electrode material, the mass ratio of the sodium superion conductor is ω1, 0<ω1≤1%. The sodium superion conductor in the lithium cobalt oxide is within the above range, which can increase the ionic conductivity of the positive electrode material while the positive electrode material has a good gram capacity and low impedance, thereby improving the cycle performance and rate performance of the electrochemical device. If the mass ratio of the sodium superion conductor in the positive electrode material is large, that is, there are more sodium superion conductors formed on the surface of the lithium cobalt oxide, it will not only reduce the gram capacity of the positive electrode material, but also increase the impedance of the positive electrode material because the sodium superion conductor does not have electrochemical properties, affecting the cycle performance and rate performance of the positive electrode material. In some embodiments, ω1 can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or any value within the range formed by any two of the above values.

[0039] In some embodiments, based on the mass of the positive electrode material, the mass ratio of the boron element in the boron-containing compound is ω2, 0<ω2≤0.5%. The electrical conductivity of the boron-containing compound is poor, and the effect on improving the electrical performance of the positive electrode material is not obvious. The mass ratio of the boron element in the boron-containing compound is within the above range, and the impact of the boron-containing compound on the interface impedance is minimized as much as possible under the premise of reducing the direct contact between the lithium cobalt oxide and the electrolyte. If the mass ratio of the boron element in the boron-containing compound is large, the mass of the boron-containing compound will increase, which will significantly increase the interface impedance between the positive electrode material and the electrolyte, thereby worsening the impedance of the electrochemical device. In some embodiments, ω2 can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or any value within the range composed of any two of the above values.

[0040] In some embodiments, 0 < ω1 + ω2 ≤ 1.5%. In the positive electrode material, the sodium superion conductor and the boron-containing compound are within the above range, which is beneficial to increasing the ionic conductivity of the positive electrode material and improving the energy density of the electrochemical device; it can also reduce the interfacial impedance while reducing the side reactions between lithium cobalt oxide and the electrolyte, thereby improving the cycle performance of the positive electrode material. If ω1 + ω2 is large, the content of at least one of the sodium superion conductor and the boron-containing compound is high, which will reduce the specific capacity of the positive electrode material and increase the interfacial impedance, thereby affecting the cycle performance of the electrochemical device. In some embodiments, ω1 + ω2 can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, or any value within the range formed by any two of the above values.

[0041] In some embodiments, the lithium cobalt oxide is a single crystal particle, and the lithium cobalt oxide has cracks, as shown in Figure 4. The lithium cobalt oxide has a layered structure with cracks inside, some of which are located inside the grains, and some extend from the interior of the grains to the surface of the grains. The direction of the cracks is parallel to the transition metal layer (Co layer). The presence of these cracks can reduce and release the stress generated by the lattice expansion and contraction process during the charge and discharge process, thereby inhibiting the rapid expansion of lattice defects, thereby improving the structural stability of the positive electrode material and improving the electrochemical performance.

[0042] In some embodiments, the median particle size D of the sodium superion conductor is 50 The sodium superion conductor is 50nm to 100nm. The sodium superion conductor in the above nanometer range is conducive to improving the uniformity of the sodium superion conductor coating the lithium cobalt oxide, and at this particle size, it is also conducive to increasing the contact area between the sodium superion conductor and the lithium cobalt oxide, reducing shedding, thereby improving the stability of the sodium superion conductor formed on the surface of the lithium cobalt oxide and improving the stability of the positive electrode material. In some embodiments, the median particle size D of the sodium superion conductor is 50 It can be 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or any value within the range formed by any two of the above values.

[0043] The present application also provides a method for preparing a positive electrode material, comprising the following steps:

[0044] (1) Refinement of NaSICON solid electrolyte.

[0045] The NaSICON solid electrolyte is ball-milled to refine the particle size of the NaSICON solid electrolyte, which is more conducive to the coating of the NaSICON solid electrolyte on the lithium cobalt oxide.

[0046] (2) The refined NaSICON solid electrolyte and lithium cobalt oxide are mixed and dispersed in a solvent to obtain a suspension.

[0047] The solid-liquid mass ratio of the suspension is 1:0.5 to 1:5, which is beneficial to improving the uniformity of the NaSICON solid electrolyte coating on the lithium cobalt oxide.

[0048] (3) Drying the suspension so that the NaSICON solid electrolyte is coated on the surface of the lithium cobalt oxide to obtain an intermediate; uniformly mixing the intermediate and the boron-containing compound, and performing an annealing treatment.

[0049] The method for drying the suspension includes spray drying or rotary evaporation drying.

[0050] The annealing temperature is 180-250° C., preferably 190-220° C. The annealing time is 6-24 hours, preferably 8-12 hours.

[0051] The boron-containing compound includes at least one of a boron-containing oxide or a borate. The boron-containing oxide includes at least one of B2O3, BO, HBO3, and H3BO3. The borate includes at least one of Na2B4O7, NH4H2BO3, CaB2O4, and Mg(B(OH)4)2. When boric acid is used as the coating material, it has a low melting point (approximately 171°C). During preparation, the boric acid melts to form a liquid and evenly adheres to the surface of the lithium cobalt oxide. Furthermore, during the coating process, the boric acid can remove residual lithium from the surface of the lithium cobalt oxide, thereby optimizing the capacity and cycle life of the electrochemical device and improving the stability of the coated lithium cobalt oxide.

[0052] (4) Screening and dispersing the annealed material to obtain a positive electrode material.

[0053] The binder in the positive electrode material layer is used to bond the positive electrode material particles to facilitate the formation of a film layer, and can also improve the bonding force between the positive electrode material layer and the positive electrode current collector. In some embodiments, the binder may include, but is not limited to, a binder polymer, such as polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, modified polyvinylidene fluoride, modified SBR rubber, or polyurethane. In some embodiments, the polyolefin binder includes at least one of polyethylene, polypropylene, polyolefin ester, polyolefin alcohol, or polyacrylic acid.

[0054] In some embodiments, the conductive agent includes a carbon-based material, a metal-based material, a conductive polymer, or a mixture thereof. Carbon-based materials include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, or carbon fiber; metal-based materials include metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; and conductive polymers include polyphenylene derivatives.

[0055] Negative electrode

[0056] The present application has no particular limitation on the negative electrode sheet, as long as the purpose of the present application can be achieved. For example, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector.

[0057] In the present application, the negative electrode material layer can be provided on one surface of the negative electrode current collector in the thickness direction, or on both surfaces of the negative electrode current collector in the thickness direction. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or a portion of the negative electrode current collector. This application is not particularly limited, as long as the purpose of this application can be achieved.

[0058] The present application has no particular restrictions on the negative electrode current collector, as long as it can achieve the purpose of the present application. For example, it may include but is not limited to copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collectors (such as carbon copper composite current collectors, nickel copper composite current collectors, titanium copper composite current collectors, etc.).

[0059] In this application, there is no particular limitation on the thickness of the negative electrode current collector and the negative electrode material layer, as long as the purpose of this application can be achieved. For example, the thickness of the negative electrode current collector is 6 μm to 12 μm, and the thickness of the negative electrode material layer is 30 μm to 130 μm. In this application, there is no particular limitation on the thickness of the negative electrode sheet, as long as the purpose of this application can be achieved. For example, the thickness of the negative electrode sheet is 50 μm to 280 μm.

[0060] The negative electrode material layer of the present application includes a negative electrode material, which may include but is not limited to graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiOx (0.5<x<1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structure lithium titanate lithiated TiO2-Li4Ti5O 12 , at least one of Li-Al alloy and metallic lithium.

[0061] The negative electrode material layer in the present application may further include a negative electrode binder and a negative electrode conductor, or the negative electrode material layer may further include a negative electrode binder, a negative electrode conductor and a thickener. The present application has no particular restrictions on the types of negative electrode binders and negative electrode conductors, as long as the purpose of the present application can be achieved. For example, the negative electrode binder may include but is not limited to at least one of the above-mentioned positive electrode binders, and the negative electrode conductor may include but is not limited to at least one of the above-mentioned positive electrode conductors. The present application has no particular restrictions on the type of thickener, as long as the purpose of the present application can be achieved. For example, the thickener may include but is not limited to at least one of sodium carboxymethyl cellulose or carboxymethyl cellulose.

[0062] In some embodiments, the binder includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin or nylon, etc.

[0063] 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 material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0064] Isolation film

[0065] The material and shape of the separator used in the electrochemical device of the present application are not particularly limited and can be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance formed of a material that is stable to the electrolyte of the present application.

[0066] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, film, or composite film having a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, polypropylene porous film, polyethylene porous film, polypropylene non-woven fabric, polyethylene non-woven fabric, or polypropylene-polyethylene-polypropylene porous composite film may be used.

[0067] A surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer, an inorganic layer, or a layer formed by a mixture of a polymer and an inorganic material. The inorganic layer includes inorganic particles and a binder. The inorganic particles are selected from at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.

[0068] The binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyvinylpyrrolidone, polyethylene alkoxy, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer comprises a polymer, and the polymer material is selected from at least one of polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, polyacrylate salt, polyvinylpyrrolidone, polyethylene alkoxy, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0069] electrolyte

[0070] According to some embodiments of the present application, the electrolyte includes an organic solvent, a lithium salt, and optional additives.

[0071] The organic solvent in the electrolyte of the present application may be any organic solvent known in the prior art that can be used as a solvent for the electrolyte. The electrolyte used in the electrolyte according to the present application is not limited, and it can be any electrolyte known in the prior art. The additive of the electrolyte according to the present application may be any additive known in the prior art that can be used as an electrolyte additive. In some embodiments, the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) or ethyl propionate.

[0072] In some embodiments, the organic solvent includes an ether solvent, for example, at least one of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME). In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFI), lithium bis(oxalatoborate) LiB(C2O4)2 (LiBOB), or lithium difluorooxalatoborate LiBF2(C2O4) (LiDFOB). In some embodiments, the additive includes at least one of fluoroethylene carbonate and adiponitrile.

[0073] According to some embodiments of the present application, the electrochemical device of the present application includes, but is not limited to: a lithium ion electrochemical device. In some embodiments, the electrochemical device includes a lithium ion electrochemical device.

[0074] This application also applies an electrochemical device to an electronic device, where the electrochemical device powers a load in the electronic device. The electrochemical device in the electronic device includes a positive electrode material, wherein a sodium superion conductor and a boron-containing compound are formed on the surface of the lithium cobalt oxide in the positive electrode material, thereby reducing the interfacial impedance of the positive electrode material and reducing side reactions between the lithium cobalt oxide and the electrolyte, thereby improving the cycle performance and charging efficiency of the electrochemical device, and further increasing the service life and charging efficiency of the electronic device.

[0075] The electronic devices or devices of the present application are not particularly limited. In some embodiments, the electronic devices of the present application include, but are not limited to, laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

[0076] The present application is described below by way of specific examples and comparative examples. It should be understood by those skilled in the art that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0077] Example 1

[0078] (1) Preparation of NaSICON solid electrolyte

[0079] Preparation of Li by solid-phase reaction method 1.4 Al 0.4 Ti 1.6 (PO4)3(LATP) and Li 1.5 Al 0.5 Ge 1.5 (PO4)3(LAGP)NaSICON solid electrolyte powder. The preparation process is as follows:

[0080] Preparation of Li 1.4 Al 0.4 Ti 1.6 (PO4)3(LATP): According to Li 1.4 Al 0.4 Ti 1.6 The raw materials Li₂C₂O₄, Al(NO₃)·9H₂O, TiO₂, and NH₄H₂PO₄ were weighed in a stoichiometric ratio of (PO₄)₃. These materials were placed in a ball mill and milled to ensure thorough mixing. The mixed materials were then placed in a high-temperature furnace and held at 400°C for 2 hours for thermal decomposition, which promotes chemical reactions. The sample was then heated to 800°C for 10 hours to promote reactions and crystal formation. After cooling, LATP solid electrolyte powder was obtained.

[0081] Preparation of Li 1.5 Al 0.5 Ge 1.5 (PO4)3(LAGP): Preparation of Li 1.5 Al 0.5Ge 1.5 (PO4)3(LAGP) method and preparation of Li 1.4 Al 0.4 Ti 1.6 The steps of (PO4)3(LATP) are the same except that the TiO2 is replaced by GeO2.

[0082] (2) Preparation of lithium cobalt oxide

[0083] Cobalt sulfate, nickel sulfate, and manganese sulfate were weighed in a molar ratio of 90:5:5 and added to deionized water for rapid stirring and dissolution. After mixing thoroughly, ammonium carbonate was added to adjust the pH of the solution to 8-9 to allow for a complete reaction and produce a uniform carbonate precipitate. The precipitate was sintered at 650°C for 12 hours, and the sintered product was then crushed and sieved to obtain a metal oxide precursor. Sodium carbonate and the metal oxide precursor were mixed in a molar ratio of 0.45:1 and maintained at 850°C for 48 hours. After cooling, the mixture was crushed and sieved to obtain a sodium cobalt oxide precursor. The sodium cobalt oxide precursor, lithium nitrate, and lithium hydroxide were mixed in a molar ratio of 1:2:3 and reacted at 250°C for 6 hours. After cooling, a mixture containing lithium cobalt oxide was obtained. The mixture was then crushed and washed multiple times with deionized water to remove soluble sodium and lithium salts. After washing with deionized water until the conductivity of the supernatant is less than 200 uS / cm, the residual solid is centrifuged, dried and classified to finally obtain layered lithium cobalt oxide.

[0084] The element content was tested by inductively coupled plasma mass spectrometry (ICP), and the chemical formula of the obtained layered lithium cobalt oxide was Li 0.9 Na 0.003 Co 0.9 Ni 0.05 Mn 0.05 Figure 1 shows the XRD pattern of the obtained layered lithium cobalt oxide. Comparison with the standard PDF card shows that the material is a pure phase material with a P63mc (No. 186) crystal structure.

[0085] (3) Preparation of positive electrode materials

[0086] The LATP powder is ball-milled in a ball mill to obtain a median particle size of 50 to 100 nm, such as 73 nm, to improve the uniformity of the LATP coating. The refined LATP material is mixed with the lithium cobalt oxide prepared above, wherein the mass proportion of LATP in the positive electrode material is 0.3%. Deionized water is added at a solid-liquid mass ratio of 1:1 and stirred evenly to obtain a suspension. The mass ratio of the suspension is 1:2. The suspension is spray-dried to remove moisture and ensure that the LATP is evenly distributed on the surface of the layered lithium cobalt oxide material.

[0087] The spray-dried lithium cobalt oxide and boric acid (boron source) are weighed and mixed in a certain mass ratio, wherein the boron element accounts for 0.3% by mass in the positive electrode material. The mixed material is placed in a box furnace and annealed at 200°C. During the annealing process, the boric acid melts and evenly coats the surface of the material. After cooling, the annealed product is sieved through a 200-mesh sieve to obtain the positive electrode material.

[0088] Scanning electron microscopy (SEM) analysis of the cathode material prepared in Example 1 reveals clearly visible LATP-coated particles on the cathode material's surface, as shown in Figure 2. Figure 3 shows the surface EDS results of the cathode material in Example 1. Scanning along the dotted arrows reveals that LATP is primarily coated on the material surface in a dotted pattern, while boron is uniformly coated across the entire surface.

[0089] Furthermore, the material was cut by a plasma beam and the morphology of the grain cross section was observed by SEM. The test results are shown in Figure 4. There are cracks in the lithium cobalt oxide single crystal particles in Figure 4 (such as the elliptical dotted line in Figure 4). Some cracks are located inside the grains, and some cracks extend from the inside of the grains to the surface of the grains. The direction of the cracks is parallel to the transition metal layer (Co layer). The presence of the cracks can reduce and release the stress generated by the lattice expansion and contraction process during the charge and discharge process, thereby inhibiting the rapid expansion of lattice defects, thereby improving the structural stability of the positive electrode material and improving the electrochemical performance of the electrochemical device.

[0090] Preparation of lithium-ion batteries:

[0091] The battery cell design size is 5 mm × 32 mm × 77 mm, and the design capacity is 2Ah.

[0092] Preparation of the positive electrode sheet: The positive electrode material prepared in Example 1, conductive carbon (SP), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.6:1.1:1.3 and thoroughly stirred in an N-methylpyrrolidone solvent system to prepare a positive electrode slurry. The prepared positive electrode slurry was coated on the positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode sheet.

[0093] Preparation of the negative electrode sheet: Commercial graphite, conductive carbon (SP), sodium carboxymethyl cellulose (CMC), and styrene butadiene rubber (SBR) were mixed in a weight ratio of 96:1:1.5:1.5. An appropriate amount of water was added to adjust the slurry viscosity to 4000-6000 Pa·s to prepare the negative electrode slurry. The prepared negative electrode slurry was coated on the negative electrode current collector copper foil, dried, and cold pressed to obtain the negative electrode sheet.

[0094] The unit area capacity of the positive electrode and the negative electrode is about 2.6 mAh cm -2 and 2.7 mAh cm -2 , corresponding to a negative / positive electrode capacity ratio (N / P) of approximately 1.045. The above-mentioned positive and negative electrode sheets are separated by a winding process using a 7um polyethylene (PE) separator. Among them, ethyl carbonate / propyl carbonate / diethyl carbonate / propyl propionate (EC / PC / DEC / PP) with a volume ratio of 1:1:1:1 is mixed, and 1M LiPF6 is added to the solvent and mixed evenly. Then, 5wt.% of fluoroolefin carbonate (FEC) and 2wt.% of 1,3,6-hexanitrile (HTCN) are added as electrolyte additives. The electrolyte retention coefficient is 1.6g / Ah. After aging, formation, capacity separation and other processes, a lithium-ion battery is made.

[0095] Example 2

[0096] The difference between Example 2 and Example 1 is that LATP is replaced with an equal amount of LAGP, and the rest of the preparation process is exactly the same as that of Example 1.

[0097] Example 3 to Example 8

[0098] The difference from Example 1 is that in the preparation step of layered lithium cobalt oxide, sodium carbonate and the precursor are evenly mixed in a molar ratio of 0.45:1, and 0.2% Ca is added in the form of Ca(OH)2, and the boron coating amount in LATP and the boron-containing compound is adjusted according to Table 1. The rest of the preparation process is exactly the same as in Example 1.

[0099] Example 9 to Example 14

[0100] The difference from Example 1 is that the Ni and Mn doping concentrations in the co-precipitated precursor material are adjusted, 0.3% La is added in the form of nano-La2O3 during the sintering process at 850°C, and the coating amount of boron element in LAGP and boron-containing compounds is adjusted. The specific material composition is shown in Table 1.

[0101] Example 15 to Example 24

[0102] The difference from Example 1 is that the Ni and Mn doping concentrations in the co-precipitated precursor material are adjusted, and doping elements other than Ni and Mn are introduced during the sintering process at 850°C. Among them, Mg, Y, Ti and Zr element doping are introduced in the form of nano-MgO, nano-Y2O3, nano-TiO2 and nano-ZrO2, respectively, and the coating amount of LATP and boric acid is adjusted. The specific material composition is shown in Table 1.

[0103] Comparative Example 1

[0104] The difference from Example 1 is that, during the preparation of lithium cobalt oxide, the metal oxide precursor is not doped with metal elements other than Co, such as Ni and Mn, and the lithium cobalt oxide is not subjected to any coating treatment. The specific material composition is shown in Table 1.

[0105] Comparative Example 2

[0106] The difference from Example 1 is that, during the preparation of lithium cobalt oxide, the metal oxide precursor is doped with Ni and Mn elements, but is not subjected to any coating treatment. The specific material composition is shown in Table 1.

[0107] Scanning electron microscopy (SEM) testing of the positive electrode material of Comparative Example 2 shows that the surface of the lithium cobalt oxide material is relatively smooth, as shown in FIG5 , while the surface of Example 1 ( FIG2 ) has obvious coated particles attached, indicating that LATP has been coated on the lithium cobalt oxide.

[0108] Comparative Examples 3 to 5

[0109] The difference from Example 1 is that the precursor is doped with Ni and Mn elements, and the surface of the lithium cobalt oxide is only coated with one of the NaSICON solid electrolyte or the boron-containing compound. The specific material composition is shown in Table 1.

[0110] Performance Testing

[0111] The XRD test method includes: using an X-ray powder diffractometer (XRD, instrument model: Bruker D8 ADVANCE) to test the positive electrode material, wherein the target material is Cu Kα, the test voltage is 40 kV, the test current is 35 mA, the scanning angle range is 10° to 90°, and the scanning rate is 0.02° / s.

[0112] The inductively coupled plasma mass spectrometry (ICP) testing method involves using an inductively coupled plasma mass spectrometer (PE Optima 7000DV) to measure the content of elements such as lithium and transition metals in the cathode material. First, an appropriate amount of powder sample is weighed, and approximately 10 mL of aqua regia is added. The sample is heated on a flat-plate heating device at approximately 185°C for 30 to 50 minutes to fully digest the sample before testing.

[0113] The SEM test method includes: taking material powder, observing it using a ZEISS SEM (Sigma-02-33), and performing elemental composition testing through EDS linear scanning.

[0114] To observe defects within the grains, the positive electrode sheet must be sliced ​​using a microtome to obtain a cross-section perpendicular to the positive current collector surface. This cross-sectional backscatter image is then captured using a scanning electron microscope. Cracks within the grains can be observed in the cross-sectional image. In the cross-sectional image, closed areas with a different color from the surrounding area represent cracks.

[0115] The performance of the lithium secondary batteries prepared in Examples 1 to 24 and Comparative Examples 1 to 5 was evaluated using the following method. The specific test results are listed in Table 1.

[0116] The test steps for the first charge and discharge efficiency include:

[0117] At 25°C, charge the lithium-ion battery at 1.3C to 4.4V, then further charge it at 0.7C to 4.55V. Maintain a constant voltage of 4.55V until the current drops to 0.05C. Then, discharge it at 0.5C to 3.0V. Repeat this step twice, and use the second discharge capacity to calculate the gram capacity of the positive electrode material.

[0118] The test steps for battery cycle performance include:

[0119] At room temperature of 25°C, the lithium-ion battery was charged to 4.4V at 2C, and then further charged to 4.55V at 1.3C. The voltage was then maintained at a constant 4.55V until the current dropped to 0.05C. The battery was then discharged to 3.0V at 1C. The charge and discharge process was repeated 300 times, and the discharge capacity of the battery after 300 cycles was recorded. C represents the current rate, 1C = 2A, and the capacity retention rate of the battery was calculated according to the following formula: Capacity retention rate = (discharge capacity of the 300th cycle / discharge capacity of the third cycle) * 100%.

[0120] Table 1

[0121] It can be seen from Table 1 above that compared with the uncoated lithium cobalt oxide in Comparative Example 1, the cycle performance of the lithium ion batteries assembled with the positive electrode materials coated with sodium superion conductors and boron-containing compounds in Examples 1 to 24 are all improved. This shows that the sodium superion conductor and the boron-containing compound are co-coated on the surface of the lithium cobalt oxide, which is beneficial to improving the cycle performance of the positive electrode material.

[0122] Compared with Comparative Example 1, the lithium cobalt oxide in Comparative Example 2 is doped with Ni and Mn elements. The first discharge gram capacity and 300-cycle cycle retention rate of Comparative Example 2 are both improved, which indicates that Ni and Mn elements affect the first discharge gram capacity and cycle performance of the positive electrode material.

[0123] Compared with Comparative Examples 3 to 5 in which only one of the sodium superion conductor and the boron-containing compound is coated on the lithium cobalt oxide, Examples 1 and 2 use a sodium superion conductor and a boron-containing compound to co-coat the lithium cobalt oxide. As can be seen from Table 1, single coating and co-coating have little effect on the first discharge capacity of the positive electrode material, but the difference in cycle stability is very obvious. After 300 cycles, the capacity retention rate of the single-coated sample is only about 60%, while that of the co-coated sample is greatly increased to more than 75%. This also shows that when NaSICON solid electrolyte (LATP and LAGP) and boron-containing compound (H3BO3) are co-coated, the cycle stability of the material can be significantly improved.

[0124] NaSICON solid electrolyte material has relatively stable physical and chemical properties and high electrical conductivity, and is an excellent material for coating lithium cobalt oxide. However, since it is not easy to form a uniform coating layer on the surface of lithium cobalt oxide, it is not easy to completely coat it, resulting in the existence of locally exposed defect sites of lithium cobalt oxide, affecting the coating effect. When H3BO3 in a boron-containing compound is used for coating, the melting point of H3BO3 is relatively low (about 171°C). When the coating temperature exceeds its melting point, H3BO3 will melt into a liquid and evenly adhere to the surface of the material, thereby reducing the number of exposed defect sites on the surface of the material, reducing the specific surface area of ​​the material, and further reducing the direct contact between the positive electrode material and the electrolyte, thereby avoiding the occurrence of interfacial side reactions. And the present application has found through statistics that the specific surface area of ​​the lithium cobalt oxide material coated with H3BO3 is reduced by an average of 0.2 to 0.4 m2 compared with the uncoated material. 2 / g. The coating layer includes both NaSICON and a boron-containing compound. NaSICON has a higher electrical conductivity, which can improve the problem of increased interfacial impedance of the positive electrode material due to the poor electrical conductivity of H3BO3. H3BO3 easily forms a uniform adhesion on the surface of the lithium cobalt oxide positive electrode material, which can improve the problem of NaSICON's difficulty in forming a uniform coating on the surface of the lithium cobalt oxide. This gives the positive electrode material the advantages of higher electrical conductivity and stability, thereby improving the cycle stability of the positive electrode material.

[0125] In particular, when 0<ω1≤1% or 0<ω2≤0.5% or 0<ω1+ω2≤1.5%, it is beneficial to ion transport, suppressing the increase in the impedance of the positive electrode material, thereby improving the cycle stability of the positive electrode material.

[0126] In Examples 9 to 14, the doping amounts of Ni and Mn also affect the first discharge specific capacity and cycling performance of the cathode material. The doping amount of Ni has a relatively small negative impact on the first discharge specific capacity of the cathode material, but the doping of Mn will reduce the specific capacity of the material. In the cathode material, Mn is doped into the lattice in the form of Mn 4+ and cannot change during the charge-discharge process, showing electrochemical inertness. As the total doping amount of Ni and Mn increases, the cycling capacity retention rate of the cathode material first increases and then decreases. When the total doping amount of Ni and Mn is less than 15%, the cathode material still has good first discharge specific capacity and cycling stability.

[0127] In Examples 15 to 18, on the basis of doping Ni and Mn in lithium cobalt oxide, M2 element is also doped. When 0 < n ≤ 1%, the comprehensive electro-performance improvement effect of lithium cobalt oxide is better.

[0128] In Examples 19 to 24, on the basis of doping Ni and Mn in lithium cobalt oxide, different M2 elements or multiple metal elements are co-doped, and the corresponding cathode materials all have good cycling capacity retention rates.

[0129] The above-disclosed are only the preferred embodiments of the present application. Of course, the present application cannot be limited thereby. Therefore, equivalent changes made in accordance with the present application still fall within the scope covered by the present application.

Claims

1. A positive electrode material, wherein It includes lithium cobalt oxide and a coating layer formed on the lithium cobalt oxide. The coating layer includes a sodium superionic conductor and a boron-containing compound. The lithium cobalt oxide has a P63mc crystal structure, and the lithium cobalt oxide further contains an element M1, where M1 includes at least one of Ni or Mn.

2. The positive electrode material according to claim 1, wherein The sodium superion conductor is Li 1+x Al x Ti 2-x (PO4)3 or Li 1+y Al y Ge 2-y (PO4)3, where 0≤x≤0.5, 0≤y≤1.

3. The positive electrode material according to claim 1 or 2, wherein 0 < m1 / m2 ≤ 15%, where m1 is the amount of substance of M1 and m2 is the sum of the amount of substance of M1 and the amount of substance of Co element.

4. The positive electrode material according to any one of claims 1 to 3, wherein The positive electrode material further contains an element M2, where the element M2 includes at least one of Mg, Ca, La, Y, Ti, Zr. The mass ratio of the element M2 in the lithium cobalt oxide is n, and 0 < n ≤ 1%.

5. The positive electrode material according to any one of claims 1 to 4, wherein The boron-containing compound includes at least one of boron-containing oxides or borates. The boron-containing oxides include at least one of B2O3, BO, HBO3, H3BO3. The borates include at least one of Na2B4O7, NH4H2BO3, CaB2O4, Mg(B(OH)4)2.

6. The positive electrode material according to any one of claims 1 to 5, wherein Based on the mass of the positive electrode material, the mass ratio of the sodium superionic conductor is ω1, and the mass ratio of boron element in the boron-containing compound is ω2. The positive electrode material satisfies at least one of the following conditions: (1) 0 < ω1 ≤ 1%; (2) 0 < ω2 ≤ 0.5%; (3) 0 < ω1 + ω2 ≤ 1.5%.

7. The positive electrode material according to any one of claims 1 to 6, wherein The lithium cobalt oxide is single crystal particles, and the lithium cobalt oxide has cracks.

8. The positive electrode material according to any one of claims 1 to 7, wherein The median particle size D of the sodium superion conductor 50 50nm to 100nm.

9. An electrochemical device comprising a positive electrode sheet and a negative electrode sheet, wherein: The positive electrode sheet includes a current collector and a positive electrode material layer provided on the current collector. The positive electrode material layer includes the positive electrode material according to any one of claims 1 to 8.

10. An electronic device, wherein: An electrochemical device including the one according to claim 9.

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