Positive electrode material, electrochemical device and electronic device

Abstract

The present application relates to a positive electrode material, an electrochemical device and an electronic device, the positive electrode material comprising a lithium-containing transition metal oxide having a layered structure, the intensity I (003) of a (003) diffraction peak, the intensity I (104) of a (104) diffraction peak, and the intensity I (015) of a (015) diffraction peak in an X-ray diffraction spectrum of the positive electrode material satisfying: I (003) / I (104) < = 1.4, and I (104) / I (015) < = 6.8. The positive electrode material has relatively high lithium utilization rate and excellent cycling stability.

Description

Positive electrode material, electrochemical device and electronic device Technical Field

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

[0002] With the increasing popularity of consumer electronics such as laptops, mobile phones, tablets, power banks, and drones, the requirements for batteries inside them are becoming increasingly stringent. For example, batteries must not only be lightweight but also have high capacity and a long operating life. Lithium-ion batteries, with their outstanding advantages such as high energy density, excellent safety, no memory effect, and long operating life, have become the mainstream in the market.

[0003] To achieve higher energy density, lithium-ion batteries have been developing towards higher voltages and increased lithium removal rates. These high voltages and high lithium removal rates expose the problems of surface oxygen release and structural phase transitions in cathode materials, leading to battery cycle failures and gassing.

[0004] Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the first aspect of the present application provides a positive electrode material, which includes a lithium-containing transition metal oxide with a layered structure, wherein the intensity of the (003) diffraction peak in the X-ray diffraction spectrum of the positive electrode material is I(003), the intensity of the (104) diffraction peak is I(104) and the intensity of the (015) diffraction peak is I(015), satisfying: I(003) / I(104)≤1.4, I(104) / I(015)≤6.8.

[0006] Normally, positive electrode ternary materials mainly generate capacity through the valence change of two elements, nickel and cobalt. The capacity of the positive electrode material is related to the nickel content contained in the positive electrode material. The higher the nickel content, the higher the capacity of the positive electrode material. However, the Mn in the positive electrode material is in a +4 valence state, which does not provide capacity and further limits the energy density of the material. At the same time, the low electrochemical activity of manganese leads to poor kinetics of the material. Under deep delithiation, the oxygen ion activity on the surface of the material is high and it is easy to have side reactions with the electrolyte, resulting in increased interfacial impedance or gas production. In addition, when the lithium-oxygen interlayer spacing in the ternary material is low, it will hinder the diffusion of lithium ions at the end of discharge, resulting in kinetic hysteresis of the material and low capacity.

[0007] The inventors of this application have discovered that by adjusting the doping elements in the lithium layer and the sintering process, a layered positive electrode material in an extremely lithium-deficient state can be synthesized, and defects can be introduced into the layered positive electrode material by heat treatment. Such defects are reflected in the reduction of the ratio of the (003) peak to the (104) peak in the X-ray diffraction spectrum of the layered positive electrode material, which is conducive to the deintercalation of lithium ions in the layered structure. Doping the layered material with lithium layer elements can regulate the distance between the lithium-oxygen layers, improve the stability and kinetic properties of the material, and at the same time, introducing oxygen defects into the material can activate the redox properties of the transition metal and significantly increase the energy density of the material. Doping with lithium layer elements plays a role in stabilizing the material structure and can maintain the stability of the layered material structure in a highly delithiated state, thereby significantly improving the cycle stability of lithium-ion batteries. The setting of doping elements and oxygen defects ultimately allows the lithium element in the positive electrode material to be mostly deintercalated, thereby significantly improving its lithium utilization rate. In addition, the oxygen vacancies formed on the surface can reduce the activity of oxygen on the surface of the material, stabilize the oxygen ions on the outer layer of the material, avoid the release of oxygen during high-temperature cycling of the positive electrode material, and further improve the high-temperature cycling performance of lithium-ion batteries.

[0008] According to some embodiments of the present application, the positive electrode material comprises Li element, Na element, transition metal element T and optional M element, wherein the transition metal element T comprises at least one of Ni, Co or Mn, and the M element comprises at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, K, Ca, Sr, Ca, Ba, Ta, Hf or Ce; wherein the molar number of Li element is n Li , the number of moles of Na element is n Na The molar number of the transition metal element T is n T , the molar number of the element M is n M , in some embodiments, 0.55≤n Li / (n T +n M )≤0.9; in some embodiments, 0.001≤n Na / (n T +n M )≤0.1; in some embodiments, 0.55≤(n Li +n Na ) / (n T +n M )≤1.

[0009] According to some embodiments of the present application, an electrode comprising the positive electrode material and a lithium sheet are assembled into a button battery. When the button battery is charged to 4.5V at a current of 0.04C in a voltage range of 2.8V to 4.5V, the molar number of the Li element in the positive electrode material is n Li ', the molar number of the transition metal element T is n T 'And the molar number of the M element is n M ', satisfy: n Li ' / (n T '+n M Thus, in the charged state, lithium ions in the positive electrode material can be fully released, thereby improving the lithium utilization rate and the energy density of the electrochemical device.

[0010] According to some embodiments of the present application, the lithium utilization rate of the positive electrode material is R=1-(n Li ' / (n T '+n M ')) / (n Li / (n T +n M )), satisfying: R≥70%. Further, in some embodiments, R≥80%.

[0011] According to some embodiments of the present application, the molar number of Ni element in the positive electrode material is n Ni , 0.3≤n Ni / (n T +n M )≤0.7.

[0012] According to some embodiments of the present application, 0.01≤n M / (n T +n M )≤0.2.

[0013] According to some embodiments of the present application, the positive electrode material further comprises an R element, wherein the R element comprises at least one of F, Cl, Br, I or N, wherein the molar number of the R element is n R , 0.01≤n R / (n T +n M )≤0.1.

[0014] According to some embodiments of the present application, the cathode material satisfies the general formula Li x Na y (Ni a Co b Mn c M d )O 2±e R e, wherein, 0.55≤x / (a+b+c+d)≤0.9, 0.01≤y / (a+b+c+d)≤0.2; 0.3≤a / (a+b+c+d)≤0.7, 0≤b / (a+b+c+d)≤0.3, 0≤c / (a+b+c+d)≤0.3, 0≤d / (a+b+c+d)≤0.2, 0≤e≤0.1, and R includes at least one of F, Cl, Br, I or N.

[0015] According to some embodiments of the present application, the X-ray diffraction spectrum of the positive electrode material has diffraction peaks in the ranges of 16° to 20°, 42° to 46°, and 34° to 38°.

[0016] According to some embodiments of the present application, an electrode including the positive electrode material is assembled with a lithium sheet into a button battery. When the button battery is charged and discharged at a current of 0.04C in a voltage range of 2.8V to 4.5V, the obtained capacity-voltage differential dQ / dV curve has a first oxidation peak and a first reduction peak in the range of 4.2V to 4.5V and a second oxidation peak and a second reduction peak in the range of 3.6V to 4.0V.

[0017] According to some embodiments of the present application, based on the mass of the positive electrode material, the peak height of the first oxidation peak is 1500 mAh / g / V to 4000 mAh / g / V.

[0018] According to some embodiments of the present application, based on the mass of the positive electrode material, the absolute value of the peak height of the first reduction peak is 1500 mAh / g / V to 4000 mAh / g / V.

[0019] According to some embodiments of the present application, 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.

[0020] According to some embodiments of the present application, an electrode including the positive electrode material is assembled with a lithium sheet into a button battery. When the button battery is charged and discharged at a current of 0.04C in a voltage range of 2.8V to 4.5V, the discharge curve in the obtained voltage-capacity curve has a platform in the range of 4.2V to 4.5V.

[0021] In some embodiments, an electrode comprising the positive electrode material is assembled with a lithium sheet into a button battery. When the button battery is charged and discharged at a current of 0.04C in a voltage range of 2.8V to 4.5V, the discharge curve in the obtained voltage-capacity curve has a capacity of Q1 in the range of 4.2V to 4.5V, and a total capacity of Qt in the range of 3.0V to 4.5V, satisfying: 0.15≤Q1 / Qt≤0.35.

[0022] In a second aspect, the present application provides an electrochemical device comprising a positive electrode plate, wherein the positive electrode plate comprises the positive electrode material described in the first aspect of the present application.

[0023] In a third aspect, the present application provides an electronic device comprising the electrochemical device described in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 shows the charge and discharge curves of the button batteries of Comparative Example 1 and Example 10.

[0025] FIG2 shows the capacity-voltage differential curves of the button-type batteries of Comparative Example 1 and Example 10. DETAILED DESCRIPTION

[0026] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of this application, rather than all the embodiments. The relevant embodiments described herein are illustrative and are used to provide a basic understanding of this application. The embodiments of this application should not be interpreted as limiting this application.

[0027] For the sake of clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0028] In the description herein, unless otherwise specified, “above” and “below” include the number itself.

[0029] Unless otherwise specified, the terms used in this application have the commonly understood meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0030] A list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0031] 1. Cathode Materials

[0032] In a first aspect, the present application provides a positive electrode material, which includes a lithium-containing transition metal oxide with a layered structure, wherein the intensity of the (003) diffraction peak in the X-ray diffraction spectrum of the positive electrode material is I(003), the intensity of the (104) diffraction peak is I(104), and the intensity of the (015) diffraction peak is I(015), satisfying: I(003) / I(104)≤1.4, I(104) / I(015)≤6.8.

[0033] In some embodiments, I(003) / I(104) is 1.10, 1.12, 1.14, 1.16, 1.18, 1.20, 1.22, 1.24, 1.26, 1.28, 1.30, 1.32, 1.34, 1.36, 1.38, 1.40 or any interval therebetween.

[0034] In some embodiments, I(104) / I(015) is 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8 or any interval therebetween.

[0035] In some embodiments, the positive electrode material comprises Li element, Na element, transition metal element T and optional M element, wherein the transition metal element T comprises at least one of Ni, Co or Mn, and the M element comprises at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, K, Ca, Sr, Ca, Ba, Ta, Hf or Ce; wherein the molar number of Li element is n Li , the number of moles of Na element is n Na The molar number of the transition metal element T is n T, the molar number of the element M is n M .

[0036] In some embodiments, 0.55≤n Li / (n T +n M )≤0.9. In this way, the positive electrode material has a higher capacity, thereby improving the energy density of the electrochemical device.

[0037] In some embodiments, 0.001≤n Na / (n T +n M )≤0.1. In this way, the lithium layer structure can be better supported in the charging state, thereby promoting the full release of lithium ions while maintaining the stability of the crystal structure of the positive electrode material, thereby improving the cycle performance of the electrochemical device on the basis of improving the lithium utilization rate.

[0038] In some embodiments, 0.55≤(n Li +n Na ) / (n T +n M )≤1.

[0039] In some embodiments, n M It is 0.

[0040] In some embodiments, n Li / (n T +n M ) is 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90 or any interval therebetween.

[0041] In some embodiments, n Na / (n T +n M ) is 0.001, 0.003, 0.005, 0.008, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10 or any interval therebetween.

[0042] In some embodiments, (n Li +n Na ) / (n T +n M ) is 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0 or any interval therebetween.

[0043] In some embodiments, an electrode comprising the positive electrode material is assembled with a lithium sheet into a button battery. When the button battery is charged to 4.5V at a current of 0.04C in a voltage range of 2.8V to 4.5V, the molar number of the Li element in the positive electrode material is n Li ', the molar number of the transition metal element T is n T 'And the molar number of the M element is n M ', satisfy: n Li ' / (n T '+n M ')≤0.22.

[0044] In some embodiments, the lithium utilization rate of the positive electrode material is R=1-(n Li ' / (n T '+n M ')) / (n Li / (n T +n M )), satisfying: R≥70%.

[0045] In some embodiments, R is 70.0%, 75.0%, 80.0%, 85.0%, 85.5%, 86.0%, 86.5%, 87.0%, 87.5%, 88.0%, 88.5%, 89.0%, 89.5%, 90.0%, 90.5%, 91.0%, 91.5%, 92.0%, 92.5%, 93.0%, 93.5%, 94.0%, 94.5%, 95.0%, 95.5%, 96.0%, or any range therebetween. Further, in some embodiments, R is ≥ 80%.

[0046] In some embodiments, the molar number of Ni element in the positive electrode material is n Ni , 0.3≤n Ni / (n T +n M )≤0.7.

[0047] In some embodiments, n Ni / (n T +n M ) is 0.30, 0.35, 0.4, 0.45, 0.5, 0.55, 0.60, 0.65, 0.70 or any interval therebetween.

[0048] In some embodiments, 0.01≤n M / (n T +n M )≤0.2. In some embodiments, n M / (n T +n M) is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20 or any interval therebetween.

[0049] In some embodiments, the positive electrode material further comprises an R element, wherein the R element comprises at least one of F, Cl, Br, I, or N, wherein the molar number of the R element is n R , 0.01≤n R / (n T +n M )≤0.1.

[0050] In some embodiments, n R / (n T +n M ) is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10 or any interval therebetween.

[0051] In some embodiments, the cathode material satisfies the general formula Li x Na y (Ni a Co b Mn c M d )O 2±e R e , wherein, 0.55≤x / (a+b+c+d)≤0.9, 0.01≤y / (a+b+c+d)≤0.2; 0.3≤a / (a+b+c+d)≤0.7, 0≤b / (a+b+c+d)≤0.3, 0≤c / (a+b+c+d)≤0.3, 0≤d / (a+b+c+d)≤0.2, 0≤e≤0.1, and R includes at least one of F, Cl, Br, I or N.

[0052] In some embodiments, the X-ray diffraction spectrum of the positive electrode material has diffraction peaks in the ranges of 16° to 20°, 42° to 46°, and 34° to 38°.

[0053] In some embodiments, an electrode comprising the positive electrode material is assembled with a lithium sheet into a button battery. When the button battery is charged and discharged at a current of 0.04C 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 the range of 4.2V to 4.5V, and a second oxidation peak and a second reduction peak in the range of 3.6V to 4.0V.

[0054] In some embodiments, based on the mass of the positive electrode material, the peak height of the first oxidation peak is 1500mAh / g / V to 4000mAh / g / V, for example, 1500mAh / g / V, 1700mAh / g / V, 1900mAh / g / V, 2000mAh / g / V, 2100mAh / g / V, 2200mAh / g / V, 2300mAh / g / V, 2400mAh / g / V, 2500mAh / g / V, 2600mAh / g / V, 2700mAh / g / V, 2800mAh / g / V, 2900mAh / g / V, 3000mAh / g / V, 3100mAh / g / V, 3200mAh / g / V, 3300mAh / g / V, 3400mAh / g / V, 3500mAh / g / V, 3600mAh / g / V, 3700mAh / g / V, 3800mAh / g / V, 3900mAh / g / V, 4000mAh / g / V or any range therebetween.

[0055] In some embodiments, based on the mass of the positive electrode material, the absolute value of the peak height of the first reduction peak is 1500mAh / g / V to 4000mAh / g / V, for example, 1500mAh / g / V, 1700mAh / g / V, 1900mAh / g / V, 2000mAh / g / V, 2100mAh / g / V, 2200mAh / g / V, 2300mAh / g / V, 2400mAh / g / V , 2500mAh / g / V, 2600mAh / g / V, 2700mAh / g / V, 2800mAh / g / V, 2900mAh / g / V, 3000mAh / g / V, 3100mAh / g / V, 3200mAh / g / V, 3300mAh / g / V, 3400mAh / g / V, 3500mAh / g / V, 3600mAh / g / V, 3700mAh / g / V, 3800mAh / g / V, 3900mAh / g / V, 4000mAh / g / V or any range therebetween.

[0056] 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|≤0.2 V. In some embodiments, |Vo1-Vr1| is, for example, 0.01 V, 0.02 V, 0.03 V, 0.04 V, 0.05 V, 0.06 V, 0.07 V, 0.08 V, 0.09 V, 0.10 V, 0.11 V, 0.12 V, 0.13 V, 0.14 V, 0.15 V, 0.16 V, 0.17 V, 0.18 V, 0.19 V, 0.20 V, or any range therebetween.

[0057] In some embodiments, an electrode comprising the positive electrode material is assembled with a lithium sheet into a button battery. When the button battery is charged and discharged at a current of 0.04C in a voltage range of 2.8V to 4.5V, the discharge curve in the obtained voltage-capacity curve has a platform in the range of 4.2V to 4.5V.

[0058] In some embodiments, the discharge curve has a capacity of Q1 in the range of 4.2V to 4.5V, and a total capacity of Qt in the range of 3.0V to 4.5V, satisfying the following: 0.15≤Q1 / Qt≤0.35. In some embodiments, the value of Q1 / Qt is, for example, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, or any range therebetween.

[0059] 2. Electrochemical Device

[0060] The electrochemical device provided in the present application includes a positive electrode plate, which includes the positive electrode material described in the first aspect of the present application.

[0061] In some embodiments, the positive electrode plate 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 fluoride, 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 material is selected from carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotubes, graphene or any combination thereof. In some embodiments, the metal-based material is selected from metal powder or metal fiber. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0062] In some embodiments, the positive electrode further includes a positive electrode current collector. In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, aluminum foil can be used. The composite current collector can be formed by forming a metal material on a polymer substrate.

[0063] In some embodiments, the electrochemical device further comprises a negative electrode.

[0064] In some embodiments, the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. In some embodiments, the negative electrode active material layer includes a negative electrode active material. In some embodiments, the negative electrode active material includes at least one of a carbon material or a silicon material. The carbon material includes at least one of graphite and hard carbon, and the silicon material includes at least one of silicon, a silicon oxide, a silicon carbon compound, or a silicon alloy. In some embodiments, the negative electrode active material layer contains a binder. In some embodiments, the binder includes at least one of polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, a polyacrylate, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polyvinyl ether, or styrene-butadiene rubber. In some embodiments, the negative electrode active material layer further includes a conductive material to improve the conductivity of the electrode. In some embodiments, the conductive material includes at least one of conductive carbon black, acetylene black, carbon nanotubes, Ketjen black, or graphene.

[0065] In some embodiments, the electrochemical device further comprises an electrolyte or a solid electrolyte.

[0066] In some embodiments, the electrolyte that can be used in the embodiments of the present application can be an electrolyte known in the prior art.

[0067] In some embodiments, the electrolyte includes an organic solvent and a lithium salt. 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), propylene carbonate, or ethyl propionate. 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) (LiFSI), lithium bis(oxalatoborate) LiB(C2O4)2 (LiBOB), or lithium difluorooxalatoborate LiBF2(C2O4) (LiDFOB).

[0068] In some embodiments, in the electrochemical device, an isolation membrane is provided between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the isolation membrane used in the embodiments of the present application are not particularly limited, and it can be any technology disclosed in the prior art. In some embodiments, the isolation membrane includes a polymer or inorganic substance formed from a material that is stable to the electrolyte of the present application. For example, the isolation membrane may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with 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 non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be selected. 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 by a mixed polymer and an inorganic substance. The inorganic layer includes inorganic particles and a binder, wherein the inorganic particles include 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, or barium sulfate. The binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, a polyacrylic acid salt, polyvinylpyrrolidone, polyvinyl ether, polytetrafluoroethylene, or polyhexafluoropropylene. The polymer layer includes a polymer, and the polymer material includes at least one of polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, a polyacrylic acid salt, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or a copolymer of vinylidene fluoride and hexafluoropropylene.

[0069] In some embodiments, the electrochemical device of the present application includes, but is not limited to, all types of primary or secondary batteries. 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.

[0070] 3. Electronic Devices

[0071] The electronic device of the present application may be any device using the electrochemical device according to the second aspect of the present application.

[0072] In some embodiments, the electronic device includes, but is not limited to: a laptop computer, a pen-type computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery or a lithium-ion capacitor, etc.

[0073] Examples and Comparative Examples

[0074] Examples 1-4

[0075] Preparation of positive electrode materials

[0076] (1) A mixed solution containing NiSO4 and MnSO4 was prepared according to the element molar ratio of Ni:Mn=50:50, and the mixed solution was mixed with a precipitant (NaOH solution) and a complexing agent (ammonia solution) to react. The reaction time was controlled to be 60 hours, the ammonia concentration was 1 mol / L, and the pH was controlled to be 12.2 to obtain a nickel-manganese precursor TM(OH)2 (TM represents Ni / Mn) with an average particle size Dv50 of 11 μm;

[0077] (2) The nickel-manganese precursor, lithium carbonate and sodium carbonate are ground and mixed uniformly in proportion to obtain the molar ratio of Na element to transition metal element T (Ni and Mn) shown in Table 1. Na / n T And the molar ratio of Li element to transition metal element T (Ni and Mn) n Li / n T The product was calcined at 800°C in an air atmosphere for 20 hours, then cooled to 600°C at a rate of 10°C / min, and a mixture of air and hydrogen was introduced. The volume contents of air and hydrogen in the mixture were selected according to Table 1, based on the total volume of the mixture. After maintaining the mixture under these conditions for 6 hours, the product was quenched at 50°C / min to room temperature. After crushing and sieving, the product was calcined in a N2 atmosphere for 5 hours. The calcination temperature in the N2 atmosphere is shown in Table 1. The product was then crushed and sieved again to obtain the positive electrode material.

[0078] Production of button batteries

[0079] -Mix the positive electrode material, binder polyvinylidene fluoride (PVDF), and conductive carbon black (Super P) in a weight ratio of 90:5:5, add them to N-methylpyrrolidone (NMP), mix them evenly, and prepare a positive electrode slurry with a solid content of 0.7;

[0080] - The mixed positive electrode slurry is evenly coated on the aluminum foil with a coating thickness of 40 μm on one side; after drying, it is rolled to form the required electrode, wherein the electrode coating surface density is 14 mg / cm 2 , after drying, the positive electrode sheet is obtained, and then punched into 14 mm discs to obtain a single-sided positive electrode sheet;

[0081] - Punch the separator into 18mm discs; the negative electrode used is a lithium metal sheet with a diameter of 18mm; add LiPF6 to a solvent mixed with propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) (PC:EC:DEC weight ratio of 1:1:1) and mix well to obtain an electrolyte; the mass concentration of LiPF6 based on the total weight of the electrolyte is 12.5%; move the positive electrode sheet, separator paper, negative electrode sheet (lithium sheet), electrolyte, battery case and other accessories into a glove box (the water content must be less than 11ppm);

[0082] Assemble the battery and inject the electrolyte in the following stacking order from bottom to top: negative electrode shell > flat pad + appropriate amount of electrolyte > metal lithium sheet + appropriate amount of electrolyte > a layer of separator paper + appropriate amount of electrolyte > positive electrode sheet + appropriate amount of electrolyte > flat pad + appropriate amount of electrolyte > shrapnel > positive electrode shell; package on a packaging machine to obtain a button battery.

[0083] Production of lithium-ion soft-pack batteries

[0084] Preparation of the positive electrode: The positive electrode material, binder polyvinylidene fluoride (PVDF), and conductive agent conductive carbon black (Super P) in a weight ratio of 96:2:2 are mixed, added to N-methylpyrrolidone (NMP), mixed evenly, and prepared into a positive electrode slurry with a solid content of 0.7; the positive electrode slurry is evenly coated on one side of the aluminum foil, and after drying, the above steps are repeated on the other side of the aluminum foil to obtain a double-sided coated positive electrode sheet; after cold pressing, cutting, and welding the pole ears, the positive electrode is obtained.

[0085] Preparation of the negative electrode: Artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose (CMC) were mixed with deionized water in a mass ratio of 96:2:2 and stirred to form a negative electrode slurry. This negative electrode slurry was evenly coated on one surface of a copper foil. After drying, the above steps were repeated on the other surface of the copper foil to obtain a double-sided coated negative electrode sheet. The negative electrode was then cold pressed, cut, and the tabs were welded to obtain the negative electrode.

[0086] Preparation of electrolyte: Under a dry argon environment, LiPF6 was added to a solvent mixed with propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) (PC:EC:DEC weight ratio of 1:1:1) and mixed uniformly to obtain an electrolyte, wherein the mass concentration of LiPF6 based on the total weight of the electrolyte was 12.5%.

[0087] Preparation of isolation membrane: Polyethylene (PE) porous polymer film is used as the isolation membrane.

[0088] Assembly of a lithium-ion soft-pack battery: The positive electrode, separator, and negative electrode are stacked in order, with the separator positioned between the positive and negative electrodes to provide isolation. The resulting bare cell is then placed in an aluminum-plastic film wrapper, electrolyte is injected, and the battery is encapsulated. After formation, degassing, and trimming, the lithium-ion soft-pack battery is completed.

[0089] Example 5-22

[0090] The difference from Example 1 is that the following step (2) is performed:

[0091] (2) The nickel-manganese precursor, lithium carbonate and sodium carbonate are ground and mixed uniformly in proportion to obtain the molar ratio of Na element to transition metal element T (Ni and Mn) shown in Table 1. Na / n T And the molar ratio of Li element to transition metal element T (Ni and Mn) n Li / n T The product was calcined at 800°C in an air atmosphere for 20 hours, then cooled to 600°C at a rate of 10°C / min, and a mixture of air and hydrogen was introduced. The volume contents of air and hydrogen in the mixture were selected according to Table 1, based on the total volume of the mixture. After maintaining the mixture under these conditions for 6 hours, the product was quenched at 50°C / min to room temperature. After crushing and sieving, the product was calcined in a N2 atmosphere for 5 hours. The calcination temperature in the N2 atmosphere is shown in Table 1. The product was then crushed and sieved again to obtain the positive electrode material.

[0092] Table 1 “ / ” means it does not exist.

[0093] Comparative Example 1

[0094] The difference from Example 1 is that the positive electrode material is prepared according to the following steps:

[0095] (1) A mixed solution containing NiSO4 and MnSO4 was prepared according to the element molar ratio of Ni:Mn=50:50, and the mixed solution was mixed with a precipitant (NaOH solution) and a complexing agent (ammonia water) for reaction. The reaction time was controlled to be 60 hours, the ammonia concentration was 1 mol / L, and the pH was controlled to be 12.2 to obtain a nickel-manganese precursor Ni with an average particle size Dv50 of 11 μm. 0.5 Mn 0.5 (OH)2;

[0096] (2) The nickel-manganese precursor and lithium carbonate were ground and mixed uniformly at a molar ratio of Li:(Ni+Mn) of 1.02:1, and then calcined at 800°C in an air atmosphere for 20 hours, cooled to room temperature at a rate of 10°C / min, and crushed and sieved to obtain a positive electrode material.

[0097] Test Method

[0098] 1. X-ray diffraction test

[0099] For the initial positive electrode material, an X-ray powder diffractometer (XRD, instrument model: Bruker D8ADVANCE, target material: Cu Kα; voltage and current: 40 kV / 40 mA, scanning angle range: 10° to 70°, scanning speed: 3° / min) was used for testing. For the positive electrode material in the full battery, the full battery was first fully discharged, disassembled to obtain the positive electrode sheet, soaked and cleaned with dimethyl carbonate (DMC), and dried before the above XRD test was performed. The peak intensity I(003) of the (003) diffraction peak at 16° to 19°, the peak intensity I(104) of the (104) diffraction peak at 42° to 46°, and the peak intensity I(015) of the (015) diffraction peak at 34° to 38° were obtained.

[0100] 2. Element content, n Li / n T 、n Li ' / n T 'And lithium utilization R test

[0101] Dissolve the cathode material sample in a mixed solvent (for example, 0.4 g of sample is dissolved in a mixed solvent of 10 ml of aqua regia (nitric acid and hydrochloric acid mixed in a ratio of 1:1) and 2 ml of HF), dilute to 100 ml, and measure the content of each element in the cathode material using an inductively coupled plasma spectrometer (ICP). Li / n T The above element content is obtained by soaking and cleaning the initial positive electrode material or the positive electrode sheet obtained by disassembling the full battery, using dimethyl carbonate (DMC), and then drying the obtained positive electrode material. Li ' / n T The above-mentioned element content test was performed by charging button cells to 4.5V at a current of 0.04C in the voltage range of 2.8V to 4.5V, disassembling the positive electrode sheets, soaking and cleaning them with dimethyl carbonate (DMC), and drying the obtained positive electrode materials.

[0102] Lithium utilization rate R = 1-(n Li ' / (n T '+n M ')) / (n Li / (nT +n M )).

[0103] 3. 4.5V charging capacity test

[0104] Charge the button cell at a constant current of 0.04C over a voltage range of 2.8V to 4.5V to 4.5V. Then, charge at a constant voltage of 4.5V to a current of 50μA. Record the charge capacity. 4.5V charge capacity in grams = charge capacity / mass of positive electrode material.

[0105] 4. Cycle number test when the cycle capacity retention rate reaches 80% at 25℃: At 25℃, the lithium-ion soft-pack battery is charged to 4.35V with a constant current of 1.5C charging current to make the lithium-ion battery reach a fully charged state, and then discharged with a constant current of 4C discharge current to a voltage of 2.8V. The discharge capacity at this time is recorded as the first discharge capacity. Repeat the above charge and discharge cycle until the cycle capacity retention rate reaches 80%. Record the number of cycles at this time. Cycle capacity retention rate = discharge capacity of the Nth cycle / first discharge capacity.

[0106] 5. Cycle number test when the 45℃ cycle capacity retention rate reaches 80%: At 45℃, the lithium-ion soft-pack battery is charged to 4.35V with a constant current of 1.5C charging current to make the lithium-ion battery reach a fully charged state, and then discharged with a constant current of 4C discharge current to a voltage of 2.8V. The discharge capacity at this time is recorded as the first discharge capacity. Repeat the above charge and discharge cycle until the cycle capacity retention rate reaches 80%. Record the number of cycles at this time. Cycle capacity retention rate = discharge capacity of the Nth cycle / first discharge capacity.

[0107] Test results

[0108] The test results of the button cells and lithium-ion soft-pack batteries obtained in various embodiments and comparative examples are shown in Table 2.

[0109] Table 2

[0110] From the comparison of Examples 1-22 and Comparative Example 1 in Table 1, it can be seen that the positive electrode materials of the embodiments of the present application meet the following conditions: I(003) / I(104)≤1.4, I(104) / I(015)≤6.8, and the corresponding lithium-ion batteries have more excellent cycle performance, and the lithium utilization rate is greatly improved, thereby being able to give full play to the capacity of the positive electrode material and improve the energy density of the lithium-ion battery.

[0111] From the comparison between Example 10 and Examples 15-22, it can be seen that 0.001≤n Na / n T≤0.1, the corresponding lithium-ion battery has more excellent cycle performance and higher lithium utilization rate and charge capacity. The possible reason is that when the content of Na element is within the above range, it can better support the lithium layer structure in the charged state, thereby promoting the full release of lithium ions while maintaining the stability of the crystal structure of the positive electrode material, thereby improving the cycle performance of the lithium-ion battery on the basis of improving the lithium utilization rate.

[0112] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those skilled in the art will recognize that modifications and changes may be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims, and these modifications and changes also fall within the scope of protection of the present application.

Claims

1. A positive electrode material, characterized in that: The positive electrode material comprises a lithium-containing transition metal oxide having a layered structure, wherein the intensity of the (003) diffraction peak in the X-ray diffraction spectrum of the positive electrode material is I(003), the intensity of the (104) diffraction peak is I(104), and the intensity of the (015) diffraction peak is I(015), satisfying: I(003) / I(104)≤1.4, I(104) / I(015)≤6.

8.

2. The positive electrode material according to claim 1, characterized in that The positive electrode material comprises Li element, Na element, transition metal element T and optional M element, wherein the transition metal element T comprises at least one of Ni, Co or Mn, and the M element comprises at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, K, Ca, Sr, Ca, Ba, Ta, Hf or Ce; wherein the molar number of Li element is n Li , the number of moles of Na element is n Na The molar number of the transition metal element T is n T , the molar number of the element M is n M , satisfies at least one of the following conditions: (i) 0.55≤n Li / (n T +n M )≤0.9; (ii)0.001≤n Na / (n T +n M )≤0.1; (iii)0.55≤(n Li +n Na ) / (n T +n M )≤1.

3. The positive electrode material according to claim 2, characterized in that The electrode including the positive electrode material and the lithium sheet are assembled into a button battery. When the button battery is charged to 4.5V at a current of 0.04C in the voltage range of 2.8V to 4.5V, the molar number of the Li element in the positive electrode material is n Li ', the molar number of the transition metal element T is n T 'And the molar number of the M element is n M ', satisfying: n Li ' / (n T '+n M ')≤0.

22.

4. The positive electrode material according to claim 3, characterized in that The lithium utilization rate of the positive electrode material is R=1-(n Li ' / (n T '+n M ')) / (n Li / (n T +n M )), satisfying: R ≥ 70%.

5. The positive electrode material according to claim 2, characterized in that At least one of the following conditions is met: (1) The molar number of Ni element in the positive electrode material is n Ni , 0.3≤n Ni / (n T +n M )≤0.7; (2)0.01≤n M / (n T +n M )≤0.2; (3) The positive electrode material further comprises an R element, wherein the R element comprises at least one of F, Cl, Br, I or N, wherein the molar number of the R element is n R , 0.01≤n R / (n T +n M )≤0.1; (4) The positive electrode material satisfies the general formula Li x Na y (Ni a Co b Mn c M d ) 2±e R e , among them, 0.55≤x / (a+b+c+d)≤0.9, 0.01≤y / (a+b+c+d)≤0.2; 0.3≤a / (a+b+c+d)≤0.7, 0≤b / (a+b+c+d)≤0.3, 0≤ c / (a+b+c+d)≤0.3, 0≤d / (a+b+c+d)≤0.2, 0≤e≤0.1, and R includes at least one of F, Cl, Br, I or N.

6. The positive electrode material according to claim 1, characterized in that At least one of the following conditions is met: (1) The X-ray diffraction spectrum of the positive electrode material has diffraction peaks in the ranges of 16° to 20°, 42° to 46°, and 34° to 38°; (2) Assembling an electrode including the positive electrode material and a lithium sheet into a button battery, wherein when the button battery is charged and discharged at a current of 0.04C 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 the range of 4.2V to 4.5V, and a second oxidation peak and a second reduction peak in the range of 3.6V to 4.0V.

7. The positive electrode material according to claim 6, characterized in that The positive electrode material satisfies at least one of the following conditions: (1) Based on the mass of the positive electrode material, the peak height of the first oxidation peak is 1500 mAh / g / V to 4000 mAh / g / V; (2) Based on the mass of the positive electrode material, the absolute value of the peak height of the first reduction peak is 1500 mAh / g / V to 4000 mAh / g / V; (3) 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.

8. The positive electrode material according to claim 6, characterized in that The electrode including the positive electrode material and the lithium sheet are assembled into a button battery. When the button battery is charged and discharged at a current of 0.04C in a voltage range of 2.8V to 4.5V, the discharge curve in the obtained voltage-capacity curve satisfies at least one of the following conditions: (1) The discharge curve has a platform in the range of 4.2V to 4.5V; (2) The capacity of the discharge curve in the range of 4.2V to 4.5V is Q1, and the total capacity in the range of 3.0V to 4.5V is Qt, satisfying: 0.15≤Q1 / Qt≤0.

35.

9. An electrochemical device, characterized in that: The electrochemical device comprises a positive electrode sheet, and the positive electrode sheet comprises the positive electrode material according to any one of claims 1 to 8.

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

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