Positive electrode material, electrochemical apparatus, and electronic device

Abstract

The present application provides a positive electrode material. When a button cell fabricated with the positive electrode material versus a lithium metal sheet is charged and discharged at a rate of 0.04 C within a voltage range of 2.8 V to 4.5 V, the resulting differential capacity vs. voltage curve shows a first oxidation peak and a first reduction peak within the range of 3.6 V to 4.0 V, a second oxidation peak and a second reduction peak within the range of 4.1 V to 4.3 V, and a third oxidation peak and a third reduction peak within the range of 4.31 V to 4.5 V. The positive electrode material of the present application exhibits higher energy density and better cycling stability.

Description

Cathode materials, electrochemical devices and electronic equipment Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a cathode material, an electrochemical device, and an electronic device. Background Technology

[0002] With the widespread adoption of consumer electronics such as laptops, mobile phones, tablets, power banks, and drones, and the continuous growth of the electric vehicle market, there is a huge demand for high-power and high-energy-density electrochemical devices. In pursuit of higher energy density, secondary batteries have been developing towards increasing voltage and thus increasing the amount of lithium removed.

[0003] However, under high voltage and high lithium depletion conditions, the cycle stability of secondary batteries is poor. Therefore, it is necessary to improve the energy density of cathode materials and the cycle performance of batteries. Summary of the Invention

[0004] This application provides a cathode material, an electrochemical device, and an electronic device, aimed at improving the energy density of the cathode material.

[0005] In a first aspect, this application provides a positive electrode material, wherein the voltage-capacity differential curve obtained by charging and discharging a coin cell made of lithium sheet with the positive electrode material at a rate of 0.04C within a voltage range of 2.8V to 4.5V shows a first oxidation peak and a first reduction peak in the range of 3.6V to 4.0V, a second oxidation peak and a second reduction peak in the range of 4.1V to 4.3V, and a third oxidation peak and a third reduction peak in the range of 4.31V to 4.5V.

[0006] According to this application, the cathode material has two additional redox peaks in the two high voltage ranges of 4.1V to 4.3V and 4.31V to 4.5V compared to general cathode materials, indicating that it has charge and discharge capacity in the above two high voltage ranges, thus the cathode material has a higher energy density.

[0007] In some embodiments, the X-ray diffraction pattern of the cathode material has a single diffraction peak in the ranges of 16° to 20° and 42° to 46°, respectively.

[0008] In some of the above embodiments, the cathode material has only a single diffraction peak in the above-mentioned range, indicating that the cathode material is a homogeneous single material, rather than a mixture of multiple materials. That is, the cathode material is optimized in terms of its composition and structure, thereby adding two redox peaks in the two high-voltage ranges compared to general cathode materials. In this application, oxygen defects are introduced into the cathode material to enable the cathode material to have reversible charge-discharge capacity in the two high-voltage ranges. At the same time, oxygen defects can improve the oxygen resistance of the cathode material, thereby improving energy density while having good cycle stability.

[0009] In some embodiments, the cathode material comprises a plurality of cathode active particles, wherein the mass content of any element in any two cathode active particles in the cathode material is w1 and w2, respectively, satisfying |w1-w2| / w1≤10%.

[0010] In some of the above embodiments, the elemental composition of the cathode material is relatively similar, indicating that the cathode material is a homogeneous single material rather than a mixture of multiple materials, which is beneficial to improving the cycle stability of the cathode material.

[0011] In some embodiments, the peak height of the second oxidation peak is between 100 mAh / g / V and 1500 mAh / g / V. Based on the above embodiments, the charging capacity is higher in the high voltage range of 4.1V to 4.3V, at which point the cathode material has a higher energy density.

[0012] The peak height of the third oxidation peak ranges from 100 mAh / g / V to 1500 mAh / g / V. Based on the above embodiments, the charging capacity is higher in the high voltage range of 4.31V to 4.5V, at which point the cathode material exhibits a higher energy density.

[0013] In some embodiments, the peak voltage of the first oxidation peak is Vo1, and the peak voltage of the first reduction peak is Vr1, satisfying |Vo1-Vr1|≤0.3V. Based on the above embodiments, the polarization is small and the reversibility is good during charging and discharging in the voltage range of 3.6V to 4.0V, exhibiting good cycle stability.

[0014] In some embodiments, the peak voltage of the second oxidation peak is Vo2, and the peak voltage of the second reduction peak is Vr2, satisfying |Vo2-Vr2|≤0.3V. Based on the above embodiments, the polarization is small and the reversibility is good during charging and discharging within the voltage range of 4.1V to 4.3V, exhibiting good cycle stability.

[0015] In some embodiments, the peak voltage of the third oxidation peak is Vo3, and the peak voltage of the third reduction peak is Vr3, satisfying |Vo3-Vr3|≤0.3V. Based on the above embodiments, the polarization is small and the reversibility is good during charging and discharging within the voltage range of 4.31V to 4.5V, exhibiting good cycle stability.

[0016] The small difference in peak voltage between the two sets of redox peaks is due to the introduction of oxygen defects into the cathode material, which can improve the conductivity of lithium ions and electrons, enhance the kinetic performance of the cathode material, thereby reducing polarization and improving the cycle stability of the cathode material.

[0017] In some embodiments, the voltage-capacity curves of the coin cell made of lithium foil relative to the positive electrode material are obtained by charging and discharging at a rate of 0.04C within a voltage range of 2.8V to 4.5V. The discharge curves exhibit plateaus at 3.6V to 4.0V, 4.1V to 4.3V, and 4.31V to 4.5V, respectively. The specific capacity of the discharge curve at the 3.6V to 4.0V plateau is Q1, the capacity in the 4.1V to 4.3V voltage range is Q2, the capacity in the 4.31V to 4.5V voltage range is Q3, and the total capacity in the 2.8V to 4.5V voltage range is Q. t The condition is satisfied that: 0.13 ≤ Q² / Q t ≤0.5. Based on the above implementation method, it is shown that the discharge capacity of the cathode material is relatively high in the voltage range of 4.1V to 4.3V, which is beneficial to further improve the energy density of the cathode material.

[0018] In some implementations, 0.13 ≤ Q3 / Q t ≤0.5. Based on the above implementation method, it is shown that the discharge capacity of the cathode material is relatively high in the voltage range of 4.31V to 4.5V, which is beneficial to further improve the energy density of the cathode material.

[0019] In some implementations, 0.5 ≤ Q2 / Q3 ≤ 1.5. Based on the above implementations, it is shown that the discharge capacity of the cathode material is not significantly different in the two high-voltage ranges, and both can further improve the energy density of the cathode material.

[0020] In some embodiments, the cell parameter 'a' of the cathode material satisfies: Based on the above implementation method, the structure of the cathode material has good stability.

[0021] In some embodiments, the cell parameter c of the cathode material satisfies: Based on the above implementation method, the cathode material is more easily inserted and extracted by lithium ions, thus having a higher capacity.

[0022] In some implementations, 4.93 ≤ c / a ≤ 5.05. Based on the above implementations, the cathode material exhibits good cycle stability and capacity.

[0023] In some embodiments, the cathode material comprises a lithium transition metal composite oxide, which includes elements M and T. Element M includes at least one of Na, K, or Y, and element T includes at least one of Ni, Co, or Mn. Based on the above embodiments, doping the lithium layer with element M, which has a high ionic radius, can increase the lithium-oxygen interlayer spacing, thereby improving the kinetic performance of the cathode material.

[0024] In some embodiments, the mass content of Li element is greater than 5% based on the total mass of the lithium transition metal composite oxide;

[0025] In some implementations, the molar ratio of Li to T is 0.5 to 2;

[0026] In some embodiments, the molar content of Ni is 40% to 60% based on the total molar amount of element T.

[0027] In some embodiments, the molar content of Mn is 20% to 40% based on the total molar amount of element T;

[0028] In some embodiments, the molar content of Co is 10% to 30% based on the total molar amount of element T;

[0029] In some embodiments, the element M includes the element Na, and the molar content of the element Na is 1% to 10% based on the total molar amount of the element T;

[0030] In some embodiments, the lithium transition metal composite oxide further includes element M', which includes at least one selected from Ca, Sr, Ba, Al, Fe, B, Mg, Si, S, Ti, Cr, Fe, Cu, Zn, Ga, Zr, Mo, W, Nb, In, Sn, Pb, Sb, Ce, La, or Hf; the molar content of element M' is 0.5% to 5% based on the total molar amount of element T; preferably, element M' is at least one selected from Ca, Sr, and Zr.

[0031] In some embodiments, the lithium transition metal composite oxide further includes element M", which includes at least one of F, Cl, Br, I, N or P; the molar content of element M" is 1% to 10% based on the total molar amount of element T; preferably F.

[0032] In a second aspect, this application provides an electrochemical device including a positive electrode and an electrolyte, wherein the positive electrode includes a positive electrode film layer, and the positive electrode film layer includes a positive electrode material according to any embodiment of the first aspect.

[0033] According to this application, the positive electrode film layer of the positive electrode in the electrochemical device includes the positive electrode material of the first aspect, thus the electrochemical device has good cycle performance and high energy density.

[0034] In some embodiments, the electrolyte comprises succinic anhydride. In this case, the succinic anhydride in the electrolyte, in conjunction with the aforementioned cathode material, can enable the electrochemical device to have better cycle performance.

[0035] Thirdly, this application provides an electronic device including an electrochemical device according to any embodiment of the second aspect. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0037] Figure 1 shows the capacity-voltage differential curves of the button half-cells of Comparative Example 1 and Example 27 in this application.

[0038] Figure 2 is the XRD pattern of the cathode material of Comparative Example 1 and Example 27 in this application.

[0039] Figure 3 shows the voltage-capacity curves of the button half-cells of Comparative Example 1 and Example 27 in this application.

[0040] Figure 4 illustrates the specific capacity Q1 at 3.6V to 4.0V, Q2 at 4.1V to 4.3V, and Q3 at 4.31V to 4.5V, and the specific capacity Q at 2.8V to 4.5V for the coin half-cells of Comparative Example 1 and Example 27. t The ratio of . Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0042] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0043] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0044] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0045] The capacity of ternary cathode materials primarily arises from the valence changes of nickel and cobalt. Its capacity is related to the nickel content; higher nickel content results in higher capacity. However, manganese (Mn) exists in a +4 valence state and does not contribute to capacity, further limiting the material's energy density. Additionally, the low electrochemical activity of manganese leads to poor material kinetics. Under deep delithiation, the high activity of oxygen ions on the material surface easily leads to side reactions with the electrolyte, resulting in increased interfacial impedance or gas generation. Finally, the low lithium-oxygen interlayer spacing in ternary materials typically hinders lithium-ion diffusion at the end of discharge, causing sluggish material kinetics and lower capacity.

[0046] This application utilizes synthetic methods to control internal defects and lithium-oxygen interlayer spacing in ternary materials through elemental doping of the lithium layer. Introducing oxygen defects into the ternary material activates the redox properties of the transition metal, thereby creating two charge-discharge plateaus in the high-voltage range. This provides additional charge-discharge capacity and increases the plateau voltage of the lithium-ion battery, significantly improving the material's energy density. Furthermore, oxygen vacancies formed on the material surface reduce surface oxygen activity, stabilizing oxygen ions in the outer layer of the cathode material and preventing oxygen release and gas generation during high-temperature cycling. Simultaneously, doping the lithium layer with elements of high ionic radius increases the lithium interlayer spacing, enhancing the material's kinetic performance.

[0047] cathode materials

[0048] In a first aspect, this application discloses a cathode material. The voltage-capacity differential curve of the cathode material relative to a coin cell made of lithium sheet, obtained by charging and discharging at a rate of 0.04C within a voltage range of 2.8V to 4.5V, shows a first oxidation peak and a first reduction peak in the range of 3.6V to 4.0V, a second oxidation peak and a second reduction peak in the range of 4.1V to 4.3V, and a third oxidation peak and a third reduction peak in the range of 4.31V to 4.5V.

[0049] According to this application, the cathode material has two additional redox peaks in the two high voltage ranges of 4.1V to 4.3V and 4.31V to 4.5V compared to general cathode materials, indicating that it has charge and discharge capacity in the above two high voltage ranges, thus the cathode material has a higher energy density.

[0050] Specifically, this is because the introduction of oxygen defects within the cathode material activates the redox properties of the transition metal, thereby generating two charge-discharge plateaus in the high-voltage range. This provides additional charge-discharge capacity and increases the plateau voltage of the lithium-ion battery, significantly improving the material's energy density. Furthermore, the oxygen vacancies formed on the material surface by the synthesis method reduce the activity of oxygen on the material surface, stabilizing the oxygen ions in the outer layer of the cathode material and preventing oxygen release and gas production during high-temperature cycling, thus improving the cycle stability of the cathode material. As an example, Figure 1 shows the voltage-capacity differential curve of the cathode material in one embodiment of this application. It can be seen that there are first oxidation and first reduction peaks in the 3.6V to 4.0V range, second oxidation and second reduction peaks in the 4.1V to 4.3V range, and third oxidation and third reduction peaks in the 4.31V to 4.5V range. Figure 1 also shows the voltage-capacity differential curve of a typical cathode material, which only has redox peaks in the 3.6V to 4.0V range.

[0051] In some embodiments, the X-ray diffraction pattern of the cathode material exhibits single diffraction peaks in the ranges of 16° to 20° and 42° to 46°, respectively.

[0052] In some of the above embodiments, the cathode material exhibits only a single diffraction peak in the aforementioned range, indicating that the cathode material is a homogeneous single material, rather than a mixture of multiple materials. That is, the cathode material achieves this by optimizing its composition and structure, thereby adding two redox peaks in the two high-voltage ranges compared to general cathode materials. In this application, oxygen defects are introduced into the cathode material, enabling reversible charge-discharge capacity in both high-voltage ranges. Simultaneously, oxygen defects improve the oxygen resistance of the cathode material, thus increasing energy density while maintaining good cycle stability. As an example, Figure 2 shows the X-ray diffraction patterns of the cathode material and a general cathode material in one embodiment of this application. Both exhibit single diffraction peaks in the 16° to 20° and 42° to 46° ranges, respectively, indicating that the cathode material in this application, like general cathode materials, is a homogeneous single material and not a mixture of multiple materials.

[0053] In some embodiments, the cathode material includes a plurality of cathode active particles, wherein the mass content of any element in any two cathode active particles is w1 and w2, respectively, satisfying |w1-w2| / w1≤10%.

[0054] In some of the above embodiments, the elemental composition of the cathode material varies little, indicating that the cathode material is a homogeneous single material, rather than a mixture of multiple materials, and thus exhibits good cycle stability. For example, the value of |w1-w2| / w1 can be 0.1%, 0.2%, 1.4%, 2.2%, 3.0%, 3.8%, 3.9%, 5.1%, 5.8%, 6.5%, 7.5%, 7.7%, 8.5%, 9.4%, 10%, or any range of the above values.

[0055] It should be noted that any element can be any element included in the cathode material. This is to demonstrate that the material under test is a homogeneous, single-element material. Therefore, to ensure the accuracy of the results, an easily quantifiable element is generally selected as the representative element. For example, element Ni is used as the representative element, and the following method is employed: SEM / EDS (Energy Dispersive X-ray Spectroscopy) is used to analyze the elemental composition and content of the micro-area of ​​the material. By adjusting the SEM magnification to ensure that at least 10 cathode material particles appear in the field of view, two particles are randomly selected for EDS elemental scanning. The mass fraction of the same element in the SED scan results of the two particles, such as Ni, is w1(Ni) and w2(Ni), respectively, satisfying |w1(Ni)-w2(Ni)| / w1(Ni)≤10%.

[0056] In some embodiments, the peak height of the second oxidation peak is between 100 mAh / g / V and 1500 mAh / g / V. Based on the above embodiments, the charging capacity is higher in the high voltage range of 4.1V to 4.3V, at which point the cathode material has a higher energy density. For example, the peak height of the second oxidation peak can be 100 mAh / g / V, 138 mAh / g / V, 300 mAh / g / V, 358 mAh / g / V, 436 mAh / g / V, 543 mAh / g / V, 723 mAh / g / V, 782 mAh / g / V, 935 mAh / g / V, 972 mAh / g / V, 1159 mAh / g / V, 1187 mAh / g / V, 1361 mAh / g / V, 1470 mAh / g / V, 1500 mAh / g / V, or any of the above values.

[0057] The peak height of the third oxidation peak ranges from 100 mAh / g / V to 1500 mAh / g / V. Based on the above embodiments, the charging capacity is higher in the high voltage range of 4.31V to 4.5V, at which point the cathode material exhibits a higher energy density. For example, the peak height of the third oxidation peak can be 100 mAh / g / V, 138 mAh / g / V, 300 mAh / g / V, 358 mAh / g / V, 436 mAh / g / V, 543 mAh / g / V, 723 mAh / g / V, 782 mAh / g / V, 935 mAh / g / V, 972 mAh / g / V, 1159 mAh / g / V, 1187 mAh / g / V, 1361 mAh / g / V, 1470 mAh / g / V, 1500 mAh / g / V, or any of the above values.

[0058] In some embodiments, the peak voltage of the first oxidation peak is Vo1, and the peak voltage of the first reduction peak is Vr1, satisfying |Vo1-Vr1|≤0.3V. Based on the above embodiments, the polarization is small and the reversibility is good during charging and discharging within the voltage range of 3.6V to 4.0V, exhibiting good cycle stability. For example, |Vo1-Vr1| can be 0.3V, 0.27V, 0.25V, 0.23V, 0.20V, 0.17V, 0.16V, 0.15V, 0.14V, 0.13V, 0.12V, 0.11V, 0.10V, 0.09V, 0.08V, 0.07V, 0.06V, 0.05V, 0.04V, 0.03V, 0.02V, 0.01V, or any of the above values.

[0059] In some embodiments, the peak voltage of the second oxidation peak is Vo2, and the peak voltage of the second reduction peak is Vr2, satisfying |Vo2-Vr2|≤0.3V. Based on the above embodiments, the polarization is small and the reversibility is good during charging and discharging within the voltage range of 4.1V to 4.3V, exhibiting good cycle stability. For example, |Vo2-Vr2| can be 0.3V, 0.27V, 0.25V, 0.23V, 0.20V, 0.17V, 0.16V, 0.15V, 0.14V, 0.13V, 0.12V, 0.11V, 0.10V, 0.09V, 0.08V, 0.07V, 0.06V, 0.05V, 0.04V, 0.03V, 0.02V, 0.01V, or any of the above values.

[0060] In some embodiments, the peak voltage of the third oxidation peak is Vo3, and the peak voltage of the third reduction peak is Vr3, satisfying |Vo3-Vr3|≤0.3V. Based on the above embodiments, the polarization is small and the reversibility is good during charging and discharging within the voltage range of 4.31V to 4.5V, exhibiting good cycle stability. For example, |Vo3-Vr3| can be 0.3V, 0.27V, 0.25V, 0.23V, 0.20V, 0.17V, 0.16V, 0.15V, 0.14V, 0.13V, 0.12V, 0.11V, 0.10V, 0.09V, 0.08V, 0.07V, 0.06V, 0.05V, 0.04V, 0.03V, 0.02V, 0.01V, or any of the above values.

[0061] The small difference in peak voltage between the two sets of redox peaks is due to the introduction of oxygen defects into the cathode material, which can improve the conductivity of lithium ions and electrons, enhance the kinetic performance of the cathode material, thereby reducing polarization and improving the cycle stability of the cathode material.

[0062] In some embodiments, the voltage-capacity curves of a button cell made of lithium foil with positive electrode material are obtained by charging and discharging at a rate of 0.04C within a voltage range of 2.8V to 4.5V. The discharge curves exhibit plateaus at 3.6V to 4.0V, 4.1V to 4.3V, and 4.31V to 4.5V, respectively. The capacity of the discharge curve in the 3.6V to 4.0V range is Q1, the capacity in the 4.1V to 4.3V range is Q2, the capacity in the 4.31V to 4.5V range is Q3, and the total capacity in the 2.8V to 4.5V range is Q_0. t The condition is satisfied that: 0.13 ≤ Q² / Q t≤0.5. Based on the above implementation method, it is shown that the discharge capacity of the cathode material is relatively high in the voltage range of 4.1V to 4.3V, which is beneficial to further improve the energy density of the cathode material. For example, Q2 / Q t It can be 0.13, 0.14, 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 of the above values ​​within a range.

[0063] In some implementations, 0.13 ≤ Q3 / Q t ≤0.5. Based on the above implementation method, it is shown that the discharge capacity of the cathode material is relatively high in the voltage range of 4.31V to 4.5V, which is beneficial to further improve the energy density of the cathode material. For example, Q3 / Q t It can be 0.13, 0.14, 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 of the above values ​​within a range.

[0064] In some implementations, 0.5 ≤ Q2 / Q3 ≤ 1.5. Based on the above implementations, it is shown that the discharge capacity of the cathode material is not significantly different in the two high-voltage ranges, and both can further improve the energy density of the cathode material. For example, Q2 / Q3 can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or any range of the above values.

[0065] As an example, Figure 3 shows the voltage-capacity curve of the cathode material in one embodiment of this application. It can be seen that the discharge curve exhibits plateaus at 3.6V to 4.0V, 4.1V to 4.3V, and 4.31V to 4.5V, respectively. Figure 3 also shows the voltage-capacity curve of a typical cathode material, where the discharge curve only exhibits plateaus in the 3.6V to 4.0V range. Figure 4 shows the capacity ratio of the cathode material in one embodiment of this application and a typical cathode material at different voltage plateaus. It can be seen that the capacity ratio of the cathode material in this embodiment at the two high voltage plateaus is significantly higher than that of the typical cathode material, thus exhibiting a higher energy density.

[0066] It should be noted that the voltage-capacity curves and voltage-capacity differential curves of button batteries made with cathode materials relative to lithium sheets, charged and discharged at a rate of 0.04C within the voltage range of 2.8V to 4.5V, can be obtained through the following methods:

[0067] (1) A positive electrode slurry is prepared by adding a certain weight ratio (90∶5∶5) of positive electrode material, polyvinylidene fluoride (PVDF) and conductive carbon black (Super P) to N-methylpyrrolidone (NMP);

[0068] (2) Adjust the viscosity of the positive electrode slurry to 3000 mPa·s to 6000 mPa·s, and uniformly coat the mixed slurry onto aluminum foil with a coating thickness of 40 μm, coating one side only; after drying, roll press to form the required electrode. The humidity of the electrode processing and transportation environment is 45%. The areal density of the coated electrode is 14 mg / cm³. 2 The positive electrode sheet is obtained by drying and then punched into 14mm round sheets;

[0069] (3) Cut the separator into 18mm round pieces; the negative electrode used is a lithium metal sheet with a diameter of 18mm; add LiPF6 to a solvent made of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) (weight ratio 1:1:1) and mix evenly to obtain an electrolyte, wherein the mass concentration of LiPF6 is 12.5%; move the positive electrode, separator, negative electrode (lithium sheet), electrolyte, battery case and other accessories into a glove box (the water content must be less than 11ppm);

[0070] (4) Assemble the batteries in a stacking order from bottom to top and inject electrolyte. Then encapsulate them on a packaging machine to obtain button cells.

[0071] (5) At 25°C, the button cell was charged and discharged at a current of 0.04C within the voltage range of 2.8V to 4.5V to obtain the voltage-capacity curve and the voltage-capacity differential dQ / dV curve.

[0072] In some implementations, the cell parameter 'a' of the cathode material satisfies: Based on the above implementation method, the structure of the cathode material exhibits good stability. For example, 'a' can be... Or within the range of any of the above values.

[0073] In some implementations, the cell parameter c of the cathode material satisfies: Based on the above implementation method, the cathode material is more easily inserted and extracted by lithium ions, thus exhibiting higher capacity. For example, c can be... Or within the range of any of the above values.

[0074] In some implementations, 4.93 ≤ c / a ≤ 5.05. Based on the above implementations, the cathode material exhibits good cycle stability and capacity.

[0075] It should be noted that the X-ray diffraction pattern, unit cell parameters a and c of the cathode material can be obtained in the following way: The cathode material is tested using an X-ray powder diffractometer (XRD, instrument model: Bruker D8 ADVANCE), with Cu Kα as the target material; the voltage and current are 40KV / 40mA, and the scanning angle range is 10° to 70°. The X-ray diffraction pattern of the cathode material is obtained, and the values ​​of unit cell parameters a and c can be calculated.

[0076] In some embodiments, the cathode material includes a lithium transition metal composite oxide, which comprises elements M and T. Element M includes at least one of Na, K, or Y, and element T includes at least one of Ni, Co, or Mn. Based on the above embodiments, doping the lithium layer with element M, which has a high ionic radius, can increase the lithium-oxygen interlayer spacing, thereby improving the kinetic performance of the cathode material.

[0077] In some implementations, the mass content of Li element is greater than 5% based on the total mass of the lithium transition metal composite oxide;

[0078] In some implementations, the molar ratio of Li to T is 0.5 to 2;

[0079] In some embodiments, the molar content of Ni is 40% to 60% based on the total molar amount of element T. Based on the above embodiments, a moderate nickel content is beneficial for improving the cycle stability of the cathode material.

[0080] In some implementations, the molar content of Mn is 20% to 40% based on the total molar amount of element T;

[0081] In some implementations, the molar content of Co is 10% to 30% based on the total molar amount of element T;

[0082] In some implementations, element M includes element Na, and the molar content of element Na is 1% to 10% based on the total molar amount of element T.

[0083] In some embodiments, the lithium transition metal composite oxide further comprises element M', wherein element M' comprises at least one of Ca, Sr, Ba, Al, Fe, B, Mg, Si, S, Ti, Cr, Fe, Cu, Zn, Ga, Zr, Mo, W, Nb, In, Sn, Pb, Sb, Ce, La or Hf; based on the total molar amount of element T, the molar content of element M' is 0.5% to 5%; preferably, element M' is at least one of Ca, Sr and Zr;

[0084] In some embodiments, the lithium transition metal composite oxide further comprises element M'', wherein element M'' comprises at least one of F, Cl, Br, I, N or P; based on the total molar amount of element T, the molar content of element M'' is 1% to 10%; F is preferred.

[0085] In some embodiments, the positive electrode material satisfies the general formula Li x M y (Ni a Co b Mn c M' d )O e M'' f , wherein 0<x+y≤2, 0≤a, b, c, d≤1, and a, b, c, d are not 0 at the same time, 0<e≤3, 0≤f<1, M is at least one of Na, K and Y, M' is at least one of Ca, Sr, Ba, Al, Fe, B, Mg, Si, S, Ti, Cr, Fe, Cu, Zn, Ga, Zr, Mo, W, Nb, In, Sn, Pb, Sb, Ce, La and Hf, and M'' is at least one of F, Cl, Br, I, N and P.

[0086] In some embodiments, the preparation method of the cathode material includes the following steps: 1) under a first atmosphere, calcining the precursor with a lithium source, an element M source, an optional element M' source, and an optional element M” source at a first temperature for a first time; 2) cooling to a second temperature and maintaining it under a second atmosphere for a second time; 3) finally cooling to room temperature. The first atmosphere is selected from air, oxygen, or a mixture of air and oxygen; the precursor contains element T, which includes at least one of Ni, Co, or Mn; the element M includes at least one of Na, K, or Y; the element M' includes at least one of Ca, Sr, Ba, Al, Fe, B, Mg, Si, S, Ti, Cr, Fe, Cu, Zn, Ga, Zr, Mo, W, Nb, In, Sn, Pb, Sb, Ce, La, Ta, or Hf; the element M” includes at least one of F, Cl, Br, I, N, or P; the second atmosphere is selected from at least one of an inert atmosphere or a mixture of an inert gas and a reducing gas. This application introduces oxygen vacancies into the cathode material by introducing an inert gas or a mixture of inert and reducing gases during the cooling process after calcination and holding the material at that temperature for a period of time. This causes a change in the oxidation state of the transition metals in the cathode material. The reducing gas may include ammonia and / or hydrogen.

[0087] In some embodiments, the first temperature is 700°C to 1200°C; the first time is 10h to 48h. In some embodiments, the first temperature can be 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, or any range of the above values. In some embodiments, the first time can be 10h, 12h, 16h, 14h, 18h, 24h, 36h, 48h, or any range of the above values.

[0088] In some embodiments, the second temperature is 350°C to 600°C; the second time is 4 hours to 24 hours. In some embodiments, the second temperature can be 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, or any range of the above values. In some embodiments, the second time can be 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 16 hours, 18 hours, 24 hours, or any range of the above values.

[0089] In some embodiments, the inert gas is selected from at least one of N2, Ar, or He.

[0090] In some implementations, the cooling rate in step 3) is greater than or equal to 50°C / min.

[0091] In some embodiments, the volume content of H2 in the inert gas and H2 mixture is less than or equal to 10% based on the total volume of the inert gas and H2 mixture. In some embodiments, the volume content of H2 in the inert gas and H2 mixture can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any range of the above values, such as 1% to 3%, 5% to 10%, etc.

[0092] In some embodiments, the precursor comprises a hydroxide of element T.

[0093] In some embodiments, the lithium source includes at least one of lithium carbonate or lithium hydroxide.

[0094] In some embodiments, the source of element M includes at least one of the carbonates or hydroxides of element M.

[0095] In some embodiments, the source of element M' includes an oxide of element M'.

[0096] In some embodiments, the source of element M” includes at least one of an ammonium salt or a lithium salt of element M”.

[0097] In some embodiments, the molar content of Ni is 40% to 60% based on the total molar amount of element T.

[0098] In some embodiments, the molar content of Mn is 20% to 40% based on the total molar amount of element T.

[0099] In some embodiments, the molar content of Co is 10% to 30% based on the total molar amount of element T.

[0100] In some embodiments, the molar content of element M is 1% to 10% based on the total molar amount of element T.

[0101] In some embodiments, the molar content of element M' is 0.5% to 5% based on the total molar amount of element T.

[0102] In some embodiments, the molar content of element M” is 1% to 10% based on the total molar amount of element T.

[0103] Electrochemical device

[0104] In a second aspect, this application provides an electrochemical device including a positive electrode and an electrolyte, wherein the positive electrode includes a positive electrode film layer, and the positive electrode film layer includes a positive electrode material according to any embodiment of the first aspect.

[0105] According to this application, the positive electrode film layer of the positive electrode in the electrochemical device includes the positive electrode material of the first aspect, thus the electrochemical device has good cycle performance and high energy density.

[0106] Typically, electrochemical devices also include a negative electrode and a separator.

[0107]

Positive Electrode

[0108] In some embodiments, the positive electrode film layer further includes an adhesive. The adhesive improves the bonding between the positive electrode material particles and also improves the bonding between the positive electrode material and the positive electrode current collector.

[0109] In some embodiments, the adhesive includes at least one of styrene-butadiene rubber (SBR), waterborne acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), or polyvinyl alcohol (PVA), but is not limited thereto; the adhesive may be selected according to actual needs.

[0110] In some embodiments, the weight percentage of the binder is less than or equal to 5.0% based on the total weight of the positive electrode film. In some embodiments, the weight percentage of the binder is 5.0%, 4.0%, 3.0%, 2.0%, 1.5%, 1.0%, 0.5%, 0.3%, 0.1%, or any of the above values, based on the total weight of the positive electrode film.

[0111] In some embodiments, the positive electrode film layer further includes a conductive agent, which includes at least one of graphite, acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, and carbon nanofibers, but is not limited thereto. The conductive agent can be selected according to actual needs.

[0112] In some embodiments, the weight percentage of the conductive agent is greater than or equal to 0.5% based on the total weight of the positive electrode film. In some embodiments, the weight percentage of the conductive agent is greater than or equal to 1.0% or greater than or equal to 1.5% based on the total weight of the positive electrode film.

[0113] In some embodiments, the positive current collector may be a metal foil or a porous metal plate, such as a foil or porous plate of metals or alloys thereof, such as aluminum foil, copper, nickel, titanium or silver, but not limited thereto.

[0114] In some embodiments, the thickness of the positive current collector is from 5 μm to 20 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm or any of the above values.

[0115] In some embodiments, the positive electrode sheet can be prepared by methods known in the art. For example, the positive electrode sheet can be obtained by mixing a positive electrode material, a conductive agent, and a binder in a solvent to prepare a positive electrode slurry, coating the positive electrode slurry onto a positive electrode current collector, and obtaining the positive electrode sheet through processes such as drying and cold pressing. In some embodiments, the solvent may include, but is not limited to, N-methylpyrrolidone (NMP).

[0116] [Negative electrode plate]

[0117] In some embodiments, the negative electrode sheet may be a lithium metal sheet, or it may include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. In some embodiments, the negative electrode film layer includes a negative electrode active material, and optionally includes a conductive agent and a binder.

[0118] In some embodiments, the negative electrode active material may include one or more of natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn-O alloy, Li-Al alloy, and metallic lithium.

[0119] In some embodiments, the conductive agent may include one or more of acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, and carbon nanofibers.

[0120] In some embodiments, the adhesive may be one or more of styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl butyral, waterborne acrylic resin, or carboxymethyl cellulose.

[0121] The negative electrode in the electrochemical device of this application is not limited to the above materials. Other materials that can be used as negative electrode active materials, conductive agents, binders and thickeners in lithium-ion batteries may also be used.

[0122] The negative electrode current collector can be made of materials such as metal foil or porous metal plate, for example, using metals or alloys of metals such as copper, nickel, titanium or iron, or porous plates such as copper foil.

[0123] The negative electrode sheet can be prepared according to conventional methods in the art. Typically, the negative electrode active material and optional conductive agent and binder are dispersed in a solvent, which can be N-methylpyrrolidone or water, to form a uniform negative electrode slurry. The negative electrode slurry is then coated onto a negative electrode current collector, and the negative electrode sheet is obtained through processes such as drying and cold pressing.

[0124]

Isolation Film

[0125] The separator is positioned between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through. This application does not impose any particular restriction on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0126] In some embodiments, the material of the separator can be selected from one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited to these. Optionally, the material of the separator may include polyethylene and / or polypropylene. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different. In some embodiments, a ceramic coating or a metal oxide coating may also be provided on the separator.

[0127] Electrolyte

[0128] The electrolyte acts as a conductor of active ions between the positive and negative electrodes. The electrolyte used in the electrochemical device of this application can be any electrolyte known in the prior art.

[0129] In some embodiments, the electrolyte may include an organic solvent, an electrolyte salt, and optional additives. The types of organic solvents, lithium salts, and additives are not specifically limited and can be selected as needed.

[0130] In some embodiments, the electrochemical device is a lithium-ion battery, and the electrolyte salt may include a lithium salt. As examples, the lithium salt includes, but is not limited to, at least one of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dicoxalate borate), LiPO2F2 (lithium difluorophosphate), LiDODFP (lithium difluorodioxalate phosphate), and LiOTFP (lithium tetrafluorooxalate phosphate). One of the above lithium salts may be used alone, or two or more may be used simultaneously.

[0131] In some embodiments, as examples, the organic solvent includes, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE). One of the above organic solvents may be used alone, or two or more may be used simultaneously. Optionally, two or more of the above organic solvents may be used simultaneously.

[0132] In some embodiments, the additive includes succinic anionylene. In this case, the succinic anionylene in the electrolyte, in conjunction with the aforementioned cathode material, can improve the cycle performance of the electrochemical device.

[0133] In some embodiments, the additive may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0134] As an example, the additives include, but are not limited to, at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), vinyl sulfate (DTD), propylene sulfate, vinyl sulfite (ES), 1,3-propanesulfonate lactone (PS), 1,3-propylene sulfonate lactone (PST), sulfonate cyclic quaternary ammonium salts, succinic anhydride, succinic anhydride (SN), adiponitrile (AND), tris(trimethylsilane) phosphate (TMSP), and tris(trimethylsilane) borate (TMSB).

[0135] The electrolyte can be prepared according to conventional methods in the art. For example, an organic solvent, an electrolyte salt, and optional additives can be mixed evenly to obtain an electrolyte. There are no particular restrictions on the order of addition of the materials; for example, the electrolyte salt and optional additives can be added to the organic solvent and mixed evenly to obtain an electrolyte; or, the electrolyte salt can be added to the organic solvent first, and then the optional additives can be added to the organic solvent and mixed evenly to obtain an electrolyte.

[0136] electronic devices

[0137] Thirdly, this application provides an electronic device including an electrochemical device according to any embodiment of the second aspect.

[0138] Since the electronic device includes the electrochemical device of any embodiment of the second aspect, it has the beneficial effects of the second aspect.

[0139] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0140]

[0141] Example

[0142] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0143] Methods for preparing pouch cells:

[0144] (1) A positive electrode slurry is prepared by adding a certain weight ratio (96∶2∶2) of positive electrode material, polyvinylidene fluoride (PVDF) and conductive carbon black (SuperP) to N-methylpyrrolidone (NMP);

[0145] (2) Adjust the viscosity of the positive electrode slurry to 3000 mPa·s to 6000 mPa·s, and uniformly coat the mixed slurry onto aluminum foil. The coating thickness on one side is 40 μm, and double-sided coating is also possible. After drying, roll-press the slurry to form the desired electrode. The humidity of the electrode processing and transportation environment is 45%. The surface density of the coated electrode is 14 mg / cm³. 2 .

[0146] Preparation of negative electrode

[0147] Artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose (CMC) were mixed with deionized water at a mass ratio of 96:2:2 and stirred until homogeneous to obtain a negative electrode slurry. This negative electrode slurry was then coated onto a 12 μm thick copper foil. After drying and cold pressing, the foil was cut and tabs were welded to obtain the negative electrode.

[0148] Preparation of electrolyte

[0149] In a dry argon atmosphere, LiPF6 and succinate are added to a solvent composed of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a weight ratio of 1:1:1, and mixed evenly to obtain an electrolyte. The mass concentration of LiPF6 is 12.5%, and the mass concentration of succinate is 1%.

[0150] Preparation of the separating membrane

[0151] Polyethylene (PE) porous polymer film is used as the separator.

[0152] Preparation of pouch cells

[0153] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for isolation. This is then wound to obtain a bare cell. The bare cell is placed in outer packaging, electrolyte is injected, and it is sealed. After processes such as formation, degassing, and edge trimming, a lithium-ion battery is obtained.

[0154] Test section

[0155] 1. Thickness expansion rate test:

[0156] A lithium-ion battery was charged to 4.35V at 85℃ and stored for 24 hours. The thickness change of the lithium-ion battery was measured using a micrometer. The initial thickness of the lithium-ion battery before storage was defined as H0, and the thickness after storage was defined as H1. The thickness expansion rate was calculated as (H1-H0) / H0×100%.

[0157] 2. Cyclic capacity retention test:

[0158] The lithium-ion battery was placed in a 45°C constant temperature chamber and charged at a constant current rate of 1C to 4.35V. Then, it was charged at a constant voltage of 4.35V to a current of 0.05C. Finally, it was discharged at a constant current rate of 1C to 3.0V. This constitutes one charge-discharge cycle. The lithium-ion battery was subjected to 1000 charge-discharge cycles in the above manner. The discharge capacity of the lithium-ion battery in the first cycle and the discharge capacity in the 1000th cycle were recorded. The cycle capacity retention rate = discharge capacity in the 1000th cycle / discharge capacity in the first cycle × 100%.

[0159] 3. Specific capacity testing of cathode materials:

[0160] (1) A positive electrode slurry is prepared by adding a certain weight ratio (90∶5∶5) of positive electrode material, polyvinylidene fluoride (PVDF) and conductive carbon black (Super P) to N-methylpyrrolidone (NMP);

[0161] (2) Adjust the viscosity of the positive electrode slurry to 3000 mPa·s to 6000 mPa·s, and uniformly coat the mixed slurry onto aluminum foil with a coating thickness of 100 μm, coating one side only; after drying, roll press to form the required electrode. The humidity of the electrode processing and transportation environment is 45%. The areal density of the coated electrode is 14 mg / cm³. 2 The positive electrode sheet is obtained by drying and then punched into 14mm round sheets;

[0162] (3) Cut the separator into 18mm round pieces; the negative electrode used is a lithium metal sheet with a diameter of 18mm; add LiPF6 to a solvent made of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) (weight ratio 1:1:1) and mix evenly to obtain an electrolyte, wherein the mass concentration of LiPF6 is 12.5%; move the positive electrode, separator, negative electrode (lithium sheet), electrolyte, battery case and other accessories into a glove box (the water content must be less than 11ppm);

[0163] (4) Assemble the batteries in a stacking order from bottom to top and inject electrolyte. Then encapsulate them on a packaging machine to obtain button cells.

[0164] (5) At 25°C, the button cell is charged to 4.5V at a current of 0.04C, and then charged at a constant voltage of 4.5V to a current of 50μA. The capacity obtained by this charging process is the specific capacity of the positive electrode material.

[0165] Comparative Example 1

[0166] The positive electrode material is manufactured as follows:

[0167] 1) Prepare a mixed solution containing NiSO4, CoSO4, and MnSO4 according to the elemental molar ratio Ni:Co:Mn = 50:20:30. Mix this solution with a precipitant (NaOH solution) and a complexing agent (ammonia water) and react them. Control the reaction time to be 60 hours, the ammonia water concentration to be 1 mol / L, and the pH to be 12.2 to obtain the ternary precursor Ni. 0.5 Co 0.2 Mn 0.3 (OH)2;

[0168] 2) Grind and mix the precursor and lithium carbonate in the above steps at a molar ratio of 1.05 until uniform, calcine at 850°C in air for 10 hours, cool to room temperature at a rate of 20°C / min, and finally obtain the cathode material by crushing and sieving.

[0169]

[0170] Examples 1 to 23:

[0171] The positive electrode material is manufactured as follows:

[0172] Ternary precursor Ni 0.5 Co 0.2 Mn 0.3 (OH)2 is the same as in Comparative Example 1;

[0173] The precursor and lithium carbonate from the above steps were ground and mixed uniformly at a molar ratio of 1.02. The mixture was then calcined for 10 hours at the first temperature in air atmosphere as shown in Table 2, and cooled to room temperature at a rate of 10℃ / min. After crushing and sieving, an intermediate product was obtained. The intermediate product was heated to the second temperature shown in Table 2, and a mixture of N2, NH3, and H2 in a certain proportion was introduced according to Table 2. This mixture was maintained for 6 hours, and then quenched to room temperature at the cooling rate shown in Table 2, while keeping the atmosphere constant during the cooling process. Finally, the cathode material was obtained after crushing and sieving.

[0174] Examples 24 to 28:

[0175] The positive electrode material is manufactured as follows:

[0176] Ternary precursor Ni 0.5 Co 0.2 Mn 0.3 (OH)2 is the same as in Comparative Example 1;

[0177] The precursor and lithium carbonate from the above steps were ground and mixed uniformly at a molar ratio of 1.02. Sodium carbonate was then mixed uniformly with the precursor and lithium carbonate according to the Na doping concentration (molar percentage of Na to element T) in Table 1. The mixture was then calcined for 10 hours at the first temperature in air atmosphere as shown in Table 2, and cooled to room temperature at a rate of 10℃ / min. After crushing and sieving, an intermediate product was obtained. The intermediate product was heated to the second temperature shown in Table 2, and a mixture of N2, NH3, and H2 in a certain proportion was introduced according to Table 2. This mixture was maintained for 6 hours, and then quenched to room temperature at the cooling rate shown in Table 2, while keeping the atmosphere constant during the cooling process. Finally, the cathode material was obtained after crushing and sieving.

[0178] Examples 29 to 33:

[0179] The positive electrode material is manufactured as follows:

[0180] Ternary precursor Ni 0.5 Co 0.2 Mn 0.3 (OH)2 is the same as in Comparative Example 1;

[0181] The precursor and lithium carbonate from the above steps were ground and mixed uniformly at a molar ratio of 1.02. Vapor-phase nano-alumina was then mixed with the precursor and lithium carbonate according to the Al doping concentration (molar percentage of Al to element T) in Table 1, ground, and mixed uniformly. The mixture was then calcined for 10 hours at the first temperature in air atmosphere as shown in Table 2, and cooled to room temperature at a rate of 10℃ / min. After crushing and sieving, an intermediate product was obtained. The intermediate product was heated to the second temperature shown in Table 2, and a mixture of N2, NH3, and H2 in a certain proportion was introduced according to Table 2. This mixture was maintained for 6 hours, and then quenched to room temperature at the cooling rate shown in Table 2, while keeping the atmosphere constant during the cooling process. Finally, the cathode material was obtained after crushing and sieving.

[0182] Example 34:

[0183] The positive electrode material is manufactured as follows:

[0184] Ternary precursor Ni 0.5 Co 0.2 Mn 0.3 (OH)2 is the same as in Comparative Example 1;

[0185] The precursor and lithium carbonate from the above steps were ground and mixed uniformly at a molar ratio of 1.02. Sodium carbonate and fumed alumina were then mixed with the precursor and lithium carbonate at a Na doping concentration (molar percentage of Na to element T) of 2.5% and an Al doping concentration (molar percentage of Al to element T) of 2.5%, respectively. The mixture was then calcined for 10 hours at the first temperature in air atmosphere as shown in Table 2, and cooled to room temperature at a rate of 10℃ / min. After crushing and sieving, an intermediate product was obtained. The intermediate product was heated to the second temperature shown in Table 2, and a mixture of N2, NH3, and H2 in a certain proportion was introduced according to Table 2. This mixture was maintained for 6 hours, and then quenched to room temperature at the cooling rate shown in Table 2, while keeping the atmosphere constant during the cooling process. Finally, the cathode material was obtained after crushing and sieving.

[0186] Examples 35 and 36:

[0187] The positive electrode material is manufactured as follows:

[0188] Ternary precursor Ni 0.5 Co 0.2 Mn 0.3 (OH)2 is the same as in Comparative Example 1;

[0189] The precursor and lithium carbonate from the above steps were ground and mixed uniformly at a molar ratio of 1.02. The M” source was then mixed uniformly with the precursor and lithium carbonate according to the M” element doping concentration (molar percentage of M” to element T) in Table 1. The mixture was then calcined for 10 hours at the first temperature in air atmosphere as shown in Table 2, and cooled to room temperature at a rate of 10℃ / min. After crushing and sieving, an intermediate product was obtained. The intermediate product was heated to the second temperature in Table 2, and a mixture of N2, NH3, and H2 in a certain proportion was introduced according to Table 2. After maintaining this condition for 6 hours, it was quenched to room temperature at the cooling rate shown in Table 2, while keeping the atmosphere constant during the cooling process. Finally, the cathode material was obtained after crushing and sieving.

[0190] Examples 37 to 41:

[0191] The positive electrode material is manufactured as follows:

[0192] Ternary precursor Ni 0.5 Co 0.2 Mn 0.3 (OH)2 is the same as in Comparative Example 1;

[0193] The precursor and lithium carbonate from the above steps were ground and mixed uniformly at a molar ratio of 1.02. Sodium carbonate and M' source were then mixed uniformly with the precursor and lithium carbonate according to the Na doping concentration (molar percentage of Na to element T) and M' doping concentration (molar percentage of M' to element T) in Table 1. The mixture was then calcined for 10 hours at the first temperature in air atmosphere as shown in Table 2, and cooled to room temperature at a rate of 10℃ / min. After crushing and sieving, an intermediate product was obtained. The intermediate product was heated to the second temperature in Table 2, and a mixture of N2, NH3, and H2 in a certain proportion was introduced according to Table 2. After maintaining this condition for 6 hours, it was quenched to room temperature at the cooling rate shown in Table 2, while keeping the atmosphere constant during the cooling process. Finally, the cathode material was obtained after crushing and sieving.

[0194] Table 1

[0195] Table 2

[0196] The high-voltage plateau voltage data, plateau peak height, voltage plateau capacity ratio, plateau polarization |Vo-Vr|, coin cell half-cell capacity, pouch cell cycle retention rate and expansion rate of the cathode material obtained in the above embodiments and comparative examples are shown in Table 3.

[0197] Table 3

[0198] Continued from Table 3

[0199] As shown in Table 3, the voltage-capacity differential curves of the cathode materials prepared in each embodiment of this application exhibit a second oxidation peak and a second reduction peak in the 4.1V to 4.3V range, and a third oxidation peak and a third reduction peak in the 4.31V to 4.5V range. This indicates that the cathode material possesses reversible charge-discharge capacity in the aforementioned two high-voltage ranges, exhibiting a higher specific capacity compared to the comparative example. Simultaneously, the discharge curve satisfies Q2 / Q t The values ​​of both are between 0.13 and 0.5, indicating that the cathode material has a high capacity in the two high-voltage ranges mentioned above, thus resulting in a higher energy density. In addition, the pouch cell prepared using this cathode material has a lower cycle expansion rate and a higher cycle capacity retention rate compared to the comparative example, indicating that the cathode material also has high cycle stability.

[0200] In each embodiment, the difference between the peak oxidation voltage and the peak reduction voltage of the cathode material in the three voltage ranges is no greater than 0.3V, indicating that the cathode material has good kinetic performance and low polarization during the charging and discharging process.

[0201] Figure 1 shows the voltage-capacity differential curve of the cathode material in Example 27. It can be seen that there are first oxidation peaks and first reduction peaks in the range of 3.6V to 4.0V, second oxidation peaks and second reduction peaks in the range of 4.1V to 4.3V, and third oxidation peaks and third reduction peaks in the range of 4.31V to 4.5V. At the same time, Figure 1 also shows the voltage-capacity differential curve of the cathode material in Comparative Example 1, which only has redox peaks in the range of 3.6V to 4.0V.

[0202] Figure 2 shows the X-ray diffraction patterns of the cathode material in Example 27 and the cathode material in Comparative Example 1. Both have single diffraction peaks in the ranges of 16° to 20° and 42° to 46°, respectively, indicating that the cathode material of this application is a uniform single material, just like general cathode materials, and is not a mixture of multiple materials.

[0203] Figure 3 shows the voltage-capacity curves of the cathode material in Example 27. It can be seen that the discharge curves exhibit plateaus at 3.6V to 4.0V, 4.1V to 4.3V, and 4.31V to 4.5V, respectively. Figure 3 also shows the voltage-capacity curves of Comparative Example 1, where the discharge curves only exhibit plateaus in the 3.6V to 4.0V range. Figure 4 shows the capacity ratios of the cathode materials in Example 27 and Comparative Example 1 at different voltage plateaus. It can be seen that the capacity ratios of the cathode materials in this application at the two high voltage plateaus are significantly higher than those of typical cathode materials, thus exhibiting higher energy density.

[0204] Specifically, the cell parameters of the above-mentioned cathode material satisfy... and / or This can further improve the energy density of cathode materials and battery cycle performance.

[0205] In particular, the aforementioned cathode material, in combination with succinic acid in the electrolyte, can synergistically improve the battery's cycle performance.

[0206] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. Finally, it should be stated that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A positive electrode material, wherein the voltage-capacity differential curve of the positive electrode material relative to a coin cell made of lithium sheet, obtained by charging and discharging at a rate of 0.04C within a voltage range of 2.8V to 4.5V, exhibits a first oxidation peak and a first reduction peak in the range of 3.6V to 4.0V, a second oxidation peak and a second reduction peak in the range of 4.1V to 4.3V, and a third oxidation peak and a third reduction peak in the range of 4.31V to 4.5V.

2. The cathode material according to claim 1, wherein, The X-ray diffraction pattern of the cathode material shows a single diffraction peak in the ranges of 16° to 20° and 42° to 46°.

3. The cathode material according to claim 1 or 2, wherein, The cathode material comprises a plurality of cathode active particles, wherein the mass content of any element in any two cathode active particles in the cathode material is w1 and w2, respectively, satisfying |w1-w2| / w1≤10%.

4. The cathode material according to any one of claims 1 to 3, wherein, The peak height of the second oxidation peak is from 100 mAh / g / V to 1500 mAh / g / V; and / or The peak height of the third oxidation peak is from 100 mAh / g / V to 1500 mAh / g / V.

5. The cathode material according to any one of claims 1 to 4, wherein, The cathode material satisfies at least one of the following conditions: (1) The peak voltage of the first oxidation peak is Vo1, and the peak voltage of the first reduction peak is Vr1, satisfying: |Vo1-Vr1|≤0.3V; (2) The peak voltage of the second oxidation peak is Vo2, and the peak voltage of the second reduction peak is Vr2, satisfying: |Vo2-Vr2|≤0.3V; (3) The peak voltage of the third oxidation peak is Vo3 and the peak voltage of the third reduction peak is Vr3, satisfying: |Vo3-Vr3|≤0.3V.

6. The cathode material according to any one of claims 1 to 5, wherein, The voltage-capacity curves of the button cell made of the positive electrode material relative to the lithium sheet were obtained by charging and discharging at a rate of 0.04C within a voltage range of 2.8V to 4.5V. The discharge curves of the voltage-capacity curves show plateaus at 3.6V to 4.0V, 4.1V to 4.3V, and 4.31V to 4.5V, respectively. The discharge curve shows the following specific capacity: Q1 at the plateau between 3.6V and 4.1V; Q2 in the voltage range of 4.1V to 4.3V; Q3 in the voltage range of 4.31V to 4.5V; and Q' ... t It meets at least one of the following conditions: (1)0.13≤Q2 / Q t ≤0.5; (2)0.13≤Q3 / Q t ≤0.5; (3) 0.5 ≤ Q2 / Q3 ≤ 1.

5.

7. The cathode material according to any one of claims 1 to 6, wherein, The cell parameters a and c of the cathode material satisfy at least one of the following conditions: (1) (2) (3) 4.93≤c / a≤5.

05.

8. The cathode material according to any one of claims 1 to 7, wherein, The cathode material comprises a lithium transition metal composite oxide, which includes elements M and T. Element M includes at least one of Na, K, or Y, and element T includes at least one of Ni, Co, or Mn. The lithium transition metal composite oxide satisfies at least one of the following conditions: (1) Based on the total mass of the lithium transition metal composite oxide, the mass content of Li element is greater than 5%; (2) The molar ratio of Li to T is 0.5 to 2; (3) Based on the total molar amount of element T, the molar content of Ni is 40% to 60%; (4) Based on the total molar amount of element T, the molar content of element Mn is 20% to 40%; (5) Based on the total molar amount of element T, the molar content of element Co is 10% to 30%; (6) The element M includes the element Na, and the molar content of the element Na is 1% to 10% based on the total molar amount of the element T; (7) The lithium transition metal composite oxide further includes element M', which includes at least one of Sr, Ti, Zr, Mo or W; the molar content of element M' is 0.5% to 5% based on the total molar amount of element T; (8) The lithium transition metal composite oxide further includes element M”, which includes F and / or Cl; based on the total molar amount of element T, the molar content of element M” is 1% to 10%.

9. An electrochemical device comprising a positive electrode and an electrolyte, wherein the positive electrode comprises a positive electrode film layer, the positive electrode film layer comprising a positive electrode material according to any one of claims 1 to 8.

10. The electrochemical device according to claim 9, wherein, The electrolyte includes succinic acid.

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

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