Modified positive electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a modified positive electrode material, a preparation method and application thereof, a positive electrode plate and an all-solid-state battery. The modified positive electrode material comprises a positive electrode material matrix, a singlet oxygen quencher serving as an inner coating layer and a conductive polymer serving as an outer coating layer, wherein the quenching rate constant of the singlet oxygen quencher is greater than or equal to 1 * 10 < 6 > M <-1 >. S <-1 >. The modified positive electrode material provided by the invention adopts double-layer coating, so that the problem of interface stability caused by oxygen evolution on the surface of the positive electrode material is solved; meanwhile, the modified positive electrode material is applied to the lithium ion battery, especially an all-solid-state battery, so that the cycling stability and safety of the lithium ion battery at high temperature and high pressure are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a modified cathode material, a preparation method of a modified cathode material, a cathode electrode sheet, an application of a modified cathode material, and a all-solid-state battery. Background Art

[0002] As a frontier research hotspot in the field of power batteries, all-solid-state batteries have the potential to solve the problems of "safety hazards" and "range anxiety" of batteries because they use non-flammable solid electrolytes to replace traditional liquid electrolytes and can be matched with high specific energy anode and cathode material systems. However, achieving high performance and high safety of all-solid-state batteries faces many challenges, especially the interfacial stability problem between the cathode material and the solid electrolyte. Currently, traditional layered oxide cathode materials, such as lithium-rich manganese-based oxides, high-nickel ternary materials, etc., are prone to release highly reactive oxygen in the oxidized state (such as singlet oxygen 1 O2) during cycling and storage, especially under high cut-off voltage and high-temperature test conditions. These reactive oxygen molecules can trigger strong interfacial reactions with inorganic solid electrolytes, especially sulfide solid electrolytes, generating gases such as SO2 and a large amount of heat, resulting in interface instability and exacerbating battery aging and capacity decay.

[0003] At the same time, the intrinsic chemical instability of sulfide solid electrolytes and their reactivity with high-nickel cathode materials further reduce the safety performance of the batteries, seriously restricting the commercialization process of sulfide all-solid-state batteries.

[0004] In liquid battery systems, the prior art focuses on adding antioxidants to the slurry / electrolyte or coating antioxidants on the surface of the cathode electrode sheet to solve the problems of oxygen evolution and gas generation in the battery. These antioxidants mainly target intermediate-state oxygen free radicals or superoxide anions, and have limited absorption capacity for singlet oxygen molecules. However, these compounds may form coordination compounds with lithium ions, reducing the migration rate of lithium ions in the electrolyte. More importantly, during battery cycling, the singlet oxygen ( 1 O2) evolved from the lattice oxygen of the layered oxide cathode material has an extremely short lifespan, only at the picosecond level, and existing methods cannot effectively locate and capture it in a timely manner, unable to fundamentally solve the gas generation problem. In addition, since most of these antioxidants are organic compounds, they have poor electrical conductivity, high solubility in the electrolyte in liquid batteries, and poor interaction with the cathode, resulting in failure.

[0005] Therefore, there is an urgent need to develop a cathode modification material that can effectively inhibit the release of singlet oxygen and interfacial side reactions to improve the interfacial stability, electrochemical performance, and safety of lithium-ion batteries, especially all-solid-state batteries. Summary of the Invention

[0006] The object of the present invention is to overcome the above technical problems, and to provide a modified cathode material, a preparation method and application thereof, a cathode electrode sheet, and a all-solid-state battery. The modified cathode material is coated with a double layer of a singlet oxygen quencher and a conductive polymer to solve the interfacial stability problem caused by oxygen evolution ( 1 O2) on the surface of the cathode material; meanwhile, the modified cathode material is applied to a lithium ion battery, especially an all-solid-state battery, to improve its cycle stability and safety at high temperature and high pressure.

[0007] To achieve the above object, the first aspect of the present invention provides a modified cathode material, which includes a cathode material matrix, a singlet oxygen quencher as an inner coating layer, and a conductive polymer as an outer coating layer;

[0008] Wherein, the quenching rate constant of the singlet oxygen quencher ≥ 1×10 6 M -1 ·s -1 .

[0009] In the present invention, without special description, the modified cathode material has a core-shell structure, including a cathode material matrix as the inner core, an inner coating layer loaded on the surface of the cathode material matrix, and an outer coating layer loaded on the surface of the inner coating layer.

[0010] In the present invention, without special description, both the inner coating layer and the outer coating layer are successively laminated and coated relative to the surface of the cathode material matrix from the inside to the outside.

[0011] In the present invention, the singlet oxygen quencher is also called 1 O2 quencher.

[0012] The inventors of the present invention have found through research that: by constructing a double-layer coating layer containing a singlet oxygen quencher and a conductive polymer on the surface of the cathode material, wherein the singlet oxygen quencher in the inner coating layer utilizes its excellent oxygen quenching ability to achieve the directional capture of 1 O2 released from the surface of the layered oxide cathode material, so as to improve the oxygen framework and interfacial stability of the cathode material; the conductive polymer in the outer coating layer is tightly combined with the inner coating layer through hydrogen bonds, and the conductive polymer has a high electronic conductivity. On the one hand, it can make up for the problem of poor conductivity of the singlet oxygen quencher in the inner coating layer and improve the overall charge transfer ability of the coating layer. On the other hand, it can inhibit the side reaction and heat generation between the singlet oxygen quencher in the inner coating layer and the electrolyte, change the failure reaction path of the battery under high temperature and high pressure conditions, and play a role in stabilizing the inner coating layer. Therefore, the interfacial stability problem caused by 1 O2 precipitation on the surface of the layered oxide cathode material is solved from the root, thereby significantly improving the cycle stability and safety of all-solid-state batteries, especially sulfide all-solid-state batteries.

[0013] In this regard, the cathode material modified by double-layer coating based on singlet oxygen quencher and conductive polymer can inhibit the side reactions and heat generation with the sulfide solid electrolyte, and change the failure reaction path of all-solid-state batteries under high temperature and high pressure conditions. This method is expected to break through the limitations of existing technologies and pave the way for the commercialization of all-solid-state batteries.

[0014] The second aspect of the present invention provides a method for preparing a modified cathode material, and the preparation method includes:

[0015] (1) Sequentially performing first mixing and first drying on the cathode material matrix dispersion liquid and a singlet oxygen quencher with a quenching rate constant ≥ 1×10 6 M -1 ·s -1 to load the singlet oxygen quencher on the surface of the cathode material matrix, thereby obtaining an intermediate;

[0016] (2) Sequentially performing second mixing and second drying on the conductive polymer dispersion liquid and the intermediate to load the conductive polymer on the surface of the intermediate, thereby obtaining a modified cathode material.

[0017] The third aspect of the present invention provides a positive electrode sheet, which includes the modified cathode material provided by the first aspect, or the modified cathode material prepared by the preparation method provided by the second aspect.

[0018] The fourth aspect of the present invention provides an application of the modified cathode material provided by the first aspect, or the modified cathode material prepared by the preparation method provided by the second aspect, or the positive electrode sheet provided by the third aspect in a lithium-ion battery.

[0019] The fifth aspect of the present invention provides an all-solid-state battery, and the all-solid-state battery includes: a positive electrode sheet, a negative electrode sheet, and an electrolyte layer;

[0020] wherein, the positive electrode sheet includes the modified cathode material provided by the first aspect, or the modified cathode material prepared by the preparation method provided by the second aspect;

[0021] or, the positive electrode sheet is selected from the positive electrode sheet provided by the third aspect.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The modified cathode material provided by the present invention adopts a double-layer composite coating structure of an inner-layer singlet oxygen quencher and an outer-layer conductive polymer, which can not only achieve the directional capture of 1 O2 released from the surface of the layered oxide cathode material, inhibit 1Subsequent intense interfacial side reactions between O2 and the electrolyte can also improve the electron transport performance through the outer conductive polymer; meanwhile, through the synergistic effect of the singlet oxygen quencher and the conductive polymer, the thermal stability and electrochemical performance of the interface between the modified cathode material and the electrolyte are enhanced;

[0024] (2) The preparation method provided by the present invention uses a liquid-phase method for step-by-step coating, which not only obtains a modified cathode material with dense and uniform coating, but also simplifies the process flow and facilitates industrial production;

[0025] (3) Applying the modified cathode material provided by the present invention to a lithium-ion battery, especially a all-solid-state battery, can not only solve the gas generation problem, but also improve the cycle life, safety performance and rate performance of the battery, meeting the requirements of high energy density and high power output. Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram of the modified cathode material S1 prepared in Example 1.

[0027] Figure 2 It is the first-cycle charge-discharge curve of the all-solid-state battery assembled with the modified cathode material S1 prepared in Example 1. Detailed Embodiments

[0028] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0029] In the present invention, without special circumstances, "first" and "second" neither represent the order nor limit each material or step, but are only used to distinguish or illustrate that these are not the same material or step. For example, "first mixing" and "second mixing" are only used to illustrate that these are not the same mixing.

[0030] The first aspect of the present invention provides a modified cathode material, which includes a cathode material matrix, a singlet oxygen quencher as the inner coating layer, and a conductive polymer as the outer coating layer;

[0031] Among them, the quenching rate constant of the singlet oxygen quencher ≥ 1×10 6 M -1 ·s -1 .

[0032] In the present invention, the above-mentioned quenching rate parameter is measured by high performance liquid chromatography. The specific test method is as follows: using methanol as the solvent, a tungsten halogen lamp as the light source, and potassium dichromate as the color filter solution; before measurement, the photosensitizer, singlet oxygen acceptor, and singlet oxygen quencher are subjected to a light reaction on a rotating light excitation device for 3 minutes, and the solution after light irradiation is analyzed by liquid chromatography. The quenching rate constant can be calculated from the concentration change of the singlet oxygen acceptor and the peak area.

[0033] In some embodiments of the present invention, preferably, the quenching rate constant of the singlet oxygen quencher is 1×10 6 -5×10 10 M -1 ·s -1 , for example, 1×10 6 M -1 ·s -1 、5×10 6 M -1 ·s -1 、8×10 6 M -1 ·s -1 、1×10 7 M -1 ·s -1 、2×10 7 M -1 ·s -1 、5×10 7 M -1 ·s -1 、8×10 7 M -1 ·s -1 、1×10 8 M -1 ·s -1 、2×10 8 M -1 ·s -1 、3×10 8 M -1 ·s -1 、5×10 8 M -1 ·s -1 、8×10 8 M -1 ·s -1 、1×10 9 M -1 ·s -1 、2.2×10 9 M -1 ·s -1 、3×10 9 M -1 ·s -1 、5×109 M -1 ·s -1 、8.2×10 9 M -1 ·s -1 、9×10 9 M -1 ·s -1 、1×10 10 M -1 ·s -1 、2×10 10 M -1 ·s -1 、5×10 10 M -1 ·s -1 , and any value within the range formed by any two of these values, preferably 1×10 8 -1×10 10 M -1 ·s -1 。

[0034] In the present invention, the singlet oxygen quencher satisfying the above range, on the premise of satisfying the directional capture of the O2 released from the surface of the positive electrode material, also realizes rapid, efficient, and timely directional capture, further optimizing the oxygen framework and interface stability of the positive electrode material. 1 O2's directional capture prerequisite, and also realizes rapid, efficient, and timely directional capture, further optimizing the oxygen framework and interface stability of the positive electrode material.

[0035] In the present invention, there is a relatively wide selection range for the type of the singlet oxygen quencher, as long as the above-mentioned quenching rate constant limit is satisfied. Preferably, the singlet oxygen quencher is selected from compounds containing a conjugated structure and / or a polar group, and the polar group is selected from at least one of a hydroxyl group, a mercapto group, a carbonyl group, and an amino group.

[0036] In the present invention, in the singlet oxygen quencher, the conjugated structure system determines the energy absorption and transfer efficiency, that is, the length and number of the conjugated structures directly affect the quenching efficiency. For example, astaxanthin has a longer conjugated double bond and contains a hydroxyl group and a keto group, enhancing its ability to interact with singlet oxygen and making its quenching rate constant (2.2×10 9 M-1·s-1) significantly higher than that of β-carotene.

[0037] In the present invention, without special circumstances, the conjugated structure refers to the existence of a conjugation effect between two adjacent conjugated double bonds in a molecule or between adjacent double bonds in a ring, forming an extended π-electron system.

[0038] In some embodiments of the present invention, preferably, the singlet oxygen quencher is selected from at least one of compounds containing a conjugated double bond system, carboxylic acid compounds containing a mercapto group, phthalocyanine compounds containing a conjugated structure, and derivatives generated by grafting or doping modification of the above compounds.

[0039] In some specific embodiments of the present invention, the compound and its derivatives containing a conjugated double bond system are selected from carotenoids, including but not limited to astaxanthin, α-carotene, β-carotene, lutein, lycopene, canthaxanthin, tunaxanthin, etc.

[0040] In some specific embodiments of the present invention, the mercapto-containing carboxylic acid compounds and their derivatives include but are not limited to glutathione, lipoic acid, etc.

[0041] In some specific embodiments of the present invention, the phthalocyanine compounds and their derivatives containing a conjugated structure include but are not limited to phthalocyanine, copper phthalocyanine, nickel phthalocyanine, cobalt phthalocyanine, etc.

[0042] In some embodiments of the present invention, more preferably, the singlet oxygen quencher is selected from at least one of astaxanthin, glutathione, and copper phthalocyanine.

[0043] In the present invention, without special instructions, the mechanism of the singlet oxygen quencher is mainly based on two pathways: physical quenching and chemical quenching, with physical quenching being the dominant one. Specifically:

[0044] Physical quenching (main mechanism) - Energy transfer process. Singlet oxygen (1O) is an excited state oxygen molecule with relatively high energy. The long conjugated double bond system in carotenoid molecules (for example, β-carotene has 11 conjugated double bonds and astaxanthin has 13 conjugated double bonds) can absorb the energy of singlet oxygen through electron resonance, converting it into its own excited state (3Carotenoid*). Subsequently, the carotenoid releases the energy in the form of heat through non-radiative decay (such as vibrational relaxation), and itself returns to the ground state, while the singlet oxygen returns to the ground state (3O). This process does not consume carotenoids, so it can act repeatedly.

[0045] Chemical quenching (secondary mechanism) - Direct chemical reaction. Carotenoids can undergo an oxidation reaction with singlet oxygen to form adducts (such as epoxides or carbonyl compounds). For example, β-carotene may be oxidized to β-carotene oxide. This process consumes carotenoid molecules, but the efficiency is usually lower than that of physical quenching, and it is not the main pathway at physiological concentrations.

[0046] In some embodiments of the present invention, preferably, the conductivity of the conductive polymer is ≥10 -7 S / cm. For example, 1×10 -7 S / cm, 2×10 -7 S / cm, 5×10 -7 S / cm, 8×10 -7 S / cm, 1×10 -6 S / cm, 2×10-6 S / cm, 5×10 -6 S / cm, 8×10 -6 S / cm, 1×10 -5 S / cm, 2×10 -5 S / cm, 5×10 -5 S / cm, 8×10 -5 S / cm, 1×10 -4 S / cm, and any value within the range formed by any two of these values, preferably 10 -7 -10 -4 S / cm.

[0047] In the present invention, the conductivity of the conductive polymer refers to the electronic conductivity of the conductive polymer; both the conductivity parameter and the electronic conductivity parameter are measured using a powder resistivity meter, and are measured at 25 ± 2°C respectively.

[0048] In the present invention, preferably, the number average molecular weight of the conductive polymer is 2000 - 200000 g / mol. For example, 2000 g / mol, 5000 g / mol, 8000 g / mol, 10000 g / mol, 20000 g / mol, 50000 g / mol, 80000 g / mol, 100000 g / mol, 120000 g / mol, 150000 g / mol, 180000 g / mol, 200000 g / mol, and any value within the range formed by any two of these values.

[0049] In some embodiments of the present invention, preferably, the conductive polymer is selected from at least one of polyacetylene, polypyrrole, poly(p - phenylene vinylene), polythiophene, poly(3,4 - ethylenedioxythiophene), polyvinylpyrrolidone, polydopamine, and polytannic acid, preferably polydopamine and / or poly(3,4 - ethylenedioxythiophene).

[0050] In some embodiments of the present invention, preferably, the D of the positive electrode material matrix 50 is 1 - 20 μm. For example, 1 μm, 3 μm, 3.5 μm, 4.5 μm, 5 μm, 6 μm, 8 μm, 10 μm, 13 μm, 15 μm, 20 μm, and any value within the range formed by any two of these values, preferably 3 - 13 μm.

[0051] In the present invention, the D 50 parameter is measured using a scanning electron microscope (SEM).

[0052] In some embodiments of the present invention, preferably, the positive electrode material matrix is selected from LiCoO2, LiNiO2, LiM2O4, LiNi x Co y M1-x-y At least one of O2, zLi2MnO3·(1-z)LiM’O2, and the doping modification of the above materials and composite materials, wherein M is selected from Mn and / or Al, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, 0 < z < 1, and M’ is selected from at least one of Fe, Ni, Co, Mn, Cr, and V.

[0053] In the present invention, LiM2O4 is selected from LiMn2O4, LiAl2O4; LiNi x Co y M 1-x-y O2 is selected from LiNi x Co y Mn 1-x-y O2, LiNi x Co y Al 1-x-y O2; zLi2MnO3·(1-z)LiM’O2 is selected from zLi2MnO3·(1-z)LiFeO2, zLi2MnO3·(1-z)LiNiO2, zLi2MnO3·(1-z)LiCoO2, zLi2MnO3·(1-z)LiMnO2, zLi2MnO3·(1-z)LiCrO2, zLi2MnO3·(1-z)LiVO2.

[0054] In a specific embodiment of the present invention, the positive electrode material includes, but is not limited to, LiNi 0.8 Co 0.1 Mn 0.1 O2, Li 1.2 [Ni 0.13 Co 0.13 Mn 0.54 O2, LiCoO2, Li[Ni 0.89 Co 0.05 Mn 0.05 Al 0.01 O2, etc.

[0055] In some embodiments of the present invention, preferably, in the modified positive electrode material, the mass ratio of the positive electrode material matrix to the singlet oxygen quencher is 100:0.01 - 5, for example, 100:0.01, 100:0.02, 100:0.05, 100:0.1, 100:0.2, 100:0.4, 100:0.5, 100:0.6, 100:0.8, 100:1, 100:1.2, 100:2, 100:3, 100:4.5, 100:5, and any value within the range composed of any two values, preferably 100:0.1 - 1.

[0056] In the present invention, when the mass ratio of the positive electrode material matrix to the singlet oxygen quencher is less than 100:0.01, due to the low content of the singlet oxygen quencher, the inner coating layer is relatively thin, and it is difficult to form an effective and uniform coating on the surface of the positive electrode material matrix, resulting in limited quenching ability for capturing singlet oxygen and affecting the electrical performance and safety performance; when the mass ratio is greater than 100:1, due to the relatively thick inner coating layer and the poor conductivity of the singlet oxygen quencher itself, the specific capacity of the positive electrode material will be reduced.

[0057] In some embodiments of the present invention, preferably, in the modified positive electrode material, the mass ratio of the positive electrode material matrix to the conductive polymer is 100:0.3 - 5, for example, 100:0.3, 100:0.4, 100:0.5, 100:0.6, 100:0.8, 100:1, 100:1.2, 100:1.5, 100:1.8, 100:2, 100:0.8, 100:1, 100:2, 100:3, 100:4, 100:4.5, 100:5, and any value within the range composed of any two numerical values, preferably 100:0.5 - 2.

[0058] In the present invention, when the mass ratio of the positive electrode material matrix to the conductive polymer is less than 100:0.3, due to the too thin outer coating layer, it is difficult to form a continuous and uniform conductive network, resulting in uncovered areas still existing on the material surface and unable to effectively improve the electron conductivity, thus limiting the high-rate performance; when the mass ratio is higher than 100:5, the too thick conductive polymer layer will increase the lithium ion diffusion path, resulting in a significant increase in the interfacial impedance.

[0059] In some embodiments of the present invention, preferably, the thickness of the inner coating layer is 5 - 100 nm, for example, 5 nm, 8 nm, 10 nm, 20 nm, 25 nm, 30 nm, 50 nm, 60 nm, 75 nm, 80 nm, 90 nm, 100 nm, and any value within the range composed of any two numerical values, preferably 10 - 60 nm.

[0060] In the present invention, the thickness parameter is measured by a transmission electron microscope (TEM).

[0061] In some embodiments of the present invention, preferably, the thickness of the outer coating layer is 10 - 200 nm, for example, 10 nm, 20 nm, 40 nm, 50 nm, 60 nm, 80 nm, 85 nm, 100 nm, 130 nm, 150 nm, 180 nm, 200 nm, and any value within the range composed of any two numerical values, preferably 50 - 100 nm.

[0062] The modified positive electrode material provided by the present invention not only has a high electron conductivity but also has excellent thermal stability.

[0063] In the present invention, preferably, the electronic conductivity of the modified cathode material is 5×10 -6 -5×10 -2 S / cm, for example, 5×10 -6 S / cm, 7×10 -6 S / cm, 9×10 -6 S / cm, 1×10 -5 S / cm, 2×10 -5 S / cm, 5×10 -5 S / cm, 7×10 - 5 S / cm, 9×10 -5 S / cm, 1×10 -4 S / cm, 2×10 -4 S / cm, 3×10 -4 S / cm, 5×10 -4 S / cm, 8×10 -4 S / cm, 1×10 -3 S / cm, 2×10 -3 S / cm, 5×10 -3 S / cm, 8×10 -3 S / cm, 1×10 -2 S / cm, 2×10 -2 S / cm, 5×10 -2 S / cm, and any value within the range composed of any two of these values.

[0064] In the present invention, preferably, the ratio of the total heat release of the modified cathode material in the fully charged state to the total heat release of the cathode material matrix in the fully charged state is ≤70%, for example, 70%, 68%, 67%, 65%, 63%, 60%, 59%, 57%, 55%, 52%, 51%, 50%, 49%, 45%, 42%, 40%, and any value within the range composed of any two of these values.

[0065] The second aspect of the present invention provides a preparation method of a modified cathode material, and the preparation method includes:

[0066] (1) Mixing the cathode material matrix dispersion liquid and a singlet oxygen quencher with a quenching rate constant ≥1×10 6 M -1 ·s -1 in sequence for the first mixing and the first drying to load the singlet oxygen quencher on the surface of the cathode material matrix and obtain an intermediate;

[0067] (2) The conductive polymer dispersion and the intermediate are successively subjected to second mixing and second drying to load the conductive polymer on the surface of the intermediate, thereby obtaining a modified cathode material.

[0068] In the present invention, without special instructions, the types of the singlet oxygen quencher, the cathode material matrix, and the conductive polymer are all defined as above, and are not elaborated herein.

[0069] In some embodiments of the present invention, preferably, in step (1), the mass ratio of the cathode material matrix to the singlet oxygen quencher is 100:0.01 - 5, for example, 100:0.01, 100:0.02, 100:0.05, 100:0.1, 100:0.2, 100:0.4, 100:0.5, 100:0.6, 100:0.8, 100:1, 100:1.2, 100:2, 100:3, 100:4.5, 100:5, and any value within the range composed of any two of these values, preferably 100:0.1 - 1.

[0070] In the present invention, the first mixing aims to uniformly mix the cathode material matrix dispersion and the singlet oxygen quencher, and the singlet oxygen quencher is uniformly adsorbed on the surface of the cathode material matrix to obtain a first mixed solution. Preferably, the conditions for the first mixing include: a rotation speed of 200 - 500 rpm and a time of 0.5 - 5 h.

[0071] In the present invention, the first drying aims to remove the solvent in the above-mentioned first mixed solution. Preferably, the conditions for the first drying include: a temperature of 80 - 200 °C and a time of 1 - 6 h.

[0072] In the present invention, preferably, the solid content of the cathode material matrix dispersion is 5 - 35 wt%.

[0073] In the present invention, preferably, the cathode material matrix dispersion is prepared by first dispersing the cathode material matrix and a first organic solvent.

[0074] In the present invention, the first dispersion method has a wide selection range, including but not limited to ultrasonic dispersion, etc. Among them, the frequency of the ultrasonic wave is 10 - 50 kHz and the time is 5 - 30 min.

[0075] In the present invention, preferably, the first organic solvent is selected from at least one of ethanol, isopropanol, acetone, methyl ether, ethyl ether, N - methylpyrrolidone (NMP), and N,N - dimethylformamide (DMF), preferably selected from at least one of ethanol, isopropanol, N - methylpyrrolidone (NMP), and N,N - dimethylformamide (DMF).

[0076] In some embodiments of the present invention, preferably, in step (2), the mass ratio of the cathode material matrix to the singlet oxygen quencher is 100:0.3 - 5. For example, 100:0.3, 100:0.4, 100:0.5, 100:0.6, 100:0.8, 100:1, 100:1.2, 100:1.5, 100:1.8, 100:2, 100:0.8, 100:1, 100:2, 100:3, 100:4, 100:4.5, 100:5, and any value within the range composed of any two of these values. Preferably, it is 100:0.5 - 2.

[0077] In the present invention, the second mixing aims to uniformly mix the conductive polymer dispersion with the intermediate, and the conductive polymer is uniformly adsorbed on the surface of the intermediate to obtain a second mixed solution. Preferably, the conditions for the second mixing include: the rotation speed is 100 - 300 rpm, and the time is 0.5 - 3 h.

[0078] In the present invention, the second drying aims to remove the solvent of the above-mentioned second mixed solution. Preferably, the conditions for the second drying include: the temperature is 80 - 300 °C, and the time is 1 - 6 h.

[0079] In the present invention, preferably, the solid content of the conductive polymer dispersion is 10 - 50 wt%.

[0080] In the present invention, preferably, the conductive polymer dispersion is prepared by dissolving the conductive polymer in a second organic solvent or a buffer solution and then performing a second dispersion.

[0081] In the present invention, the method of the second dispersion has a wide selection range, including but not limited to ultrasonic dispersion, etc. Among them, the frequency of ultrasonic is 10 - 50 kHz, and the time is 5 - 30 min.

[0082] In the present invention, preferably, the second organic solvent is selected from at least one of ethanol, isopropanol, acetone, methyl ether, ethyl ether, N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF), and preferably selected from at least one of ethanol, isopropanol, N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF).

[0083] In the present invention, preferably, the pH of the buffer solution is 6 - 9, and it is preferably selected from at least one of phosphate buffer solution, acetate buffer solution, and tris(hydroxymethyl)aminomethane hydrochloride buffer solution (Tris buffer solution), and more preferably selected from Tris buffer solution with pH = 8.5.

[0084] The third aspect of the present invention provides a positive electrode plate, and the positive electrode plate includes the modified positive electrode material provided in the first aspect, or the modified positive electrode material prepared by the preparation method provided in the second aspect.

[0085] In the present invention, without special description, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode current collector includes but is not limited to metal foil (aluminum foil), composite current collector, etc.

[0086] In the present invention, preferably, in the positive electrode plate, the content of the modified positive electrode material is 50-99 wt%, for example, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 99 wt%, and any value within the range composed of any two values. In the present invention, the content of the modified positive electrode material is based on the total mass of the positive electrode active material layer.

[0087] In the present invention, preferably, the active material layer of the positive electrode plate is composed of the modified positive electrode material, a solid electrolyte, a conductive agent, and an optional binder.

[0088] In the present invention, when the solid electrolyte is selected from sulfide electrolytes or halide electrolytes, the positive electrode plate may not contain a binder.

[0089] In some embodiments of the present invention, preferably, the solid electrolyte is selected from at least one of sulfide electrolytes, oxide electrolytes, halide electrolytes, polymer electrolytes, and borohydride electrolytes.

[0090] In some specific embodiments of the present invention, the solid electrolyte includes but is not limited to wLi2S·(100-w)P2S5 (0≤w≤100), Li3PS4, Li7P3S 11 、Li6PS5X (X is selected from Cl, Br, I) and its derivative systems, Li 10 M”P2S 12 (M” is selected from Ge and / or Sn), Li 3.25 Ge 0.25 P 0.75 S4, Li4GeS4, Li 11 Sn2PS 12 、Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 、Li3InCl6 and its derivative systems, Li 0.388 Ta 0.238 La 0.475 Cl3 and its derivative systems, Li5X3M”’2O 12(M''' is selected from Ta and / or Nb), Li7La3Zr2O 12 and its derivative systems, La 2 / 3-x’ Li 3x’ TiO3 (0 < x' < 2 / 3) and its derivative systems, NaZr2(PO4)3 and its derivative systems, PEO (polyethylene oxide) and its derivatives, PPC (poly(ethylene carbonate)), PAN (polyacrylonitrile), PDMS (polydimethylsiloxane), PVDF (polyvinylidene fluoride), PMMA (polymethyl methacrylate) and its derivative systems, and at least one of LiBH4.

[0091] In the present invention, the conductive agent is selected from at least one of acetylene black, conductive carbon black, carbon fiber, carbon nanotube, and Ketjen black. In the present invention, the conductive carbon black includes, but is not limited to, Super P, Super S, etc.

[0092] In the present invention, the binder is selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyamide-imide (PAI), polyethyleneimine (PEI), polyimide (PI), and tert-butyl acrylate-triethoxyvinylsilane (TBATEVS).

[0093] The fourth aspect of the present invention provides an application of the modified cathode material provided in the first aspect, or the modified cathode material prepared by the preparation method provided in the second aspect, or the cathode electrode sheet provided in the third aspect, in a lithium-ion battery.

[0094] In the present invention, without special instructions, lithium-ion batteries include, but are not limited to, liquid batteries, hybrid solid-liquid batteries / semi-solid batteries, all-solid-state batteries, etc.

[0095] The modified cathode material provided by the present invention is applied to an all-solid-state battery, which reduces interface aging and capacity attenuation caused by side reactions, thereby improving the cycle life of the battery; reduces gas release and heat generation under high temperature and high pressure conditions, thereby improving the safety performance of the battery; and improves the rate performance of the all-solid-state battery by optimizing the interface conductivity, meeting the requirements of high energy density and high power output.

[0096] The fifth aspect of the present invention provides an all-solid-state battery, which includes: a positive electrode sheet, a negative electrode sheet, and an electrolyte layer;

[0097] wherein, the positive electrode sheet includes the modified cathode material provided in the first aspect, or the modified cathode material prepared by the preparation method provided in the second aspect;

[0098] Alternatively, the positive electrode sheet is selected from the positive electrode sheets provided in the third aspect.

[0099] In some embodiments of the present invention, preferably, the electrolyte layer is selected from at least one of sulfide electrolytes, oxide electrolytes, halide electrolytes, polymer electrolytes, and borohydride electrolytes.

[0100] The present invention will be described in detail below through examples.

[0101] Example 1

[0102] (1) 5 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 (D 50 = 3.5 μm) was used as the positive electrode material matrix and ultrasonically dispersed in 100 mL of absolute ethanol at an ultrasonic frequency of 20 kHz for 10 min to obtain a uniform dispersion of the positive electrode material matrix;

[0103] 0.02 g of astaxanthin (quenching rate constant of 2.2×10 9 M -1 ·s -1 ) was weighed and added to the above-mentioned dispersion of the positive electrode material matrix, and the stirring speed was 200 rpm and the stirring time was 0.5 h to uniformly adsorb astaxanthin on the surface of the positive electrode material matrix. The obtained first mixture was placed in a forced-air drying oven at a drying temperature of 100 °C for 5 h to coat astaxanthin on the surface of the positive electrode material matrix to obtain an intermediate;

[0104] (2) 0.05 g of polydopamine (conductivity of 1.35×10 -4 S / cm and number-average molecular weight of 5000 g / mol) was dissolved in 100 mL of Tris buffer solution with pH = 8.5 and ultrasonically dispersed at an ultrasonic frequency of 20 kHz for 10 min to form a uniform dispersion of polydopamine;

[0105] The above-mentioned intermediate was slowly added to the polydopamine dispersion, and the stirring speed was 150 rpm and the stirring time was 1 h. The obtained second mixture was placed in a forced-air drying oven and dried at 250 °C for 5 h to coat polydopamine on the surface of the above-mentioned intermediate to obtain a modified positive electrode material S1.

[0106] Among them, the structural schematic diagram of the above-mentioned modified positive electrode material S1 is as Figure 1 shown, including a positive electrode material matrix, astaxanthin as the inner coating layer, and polydopamine as the outer coating layer.

[0107] Example 2

[0108] According to the method of Example 1, the difference is that

[0109] In step (1), replace 0.02 g of astaxanthin (quenching rate constant of 2.2×10 9 M -1 ·s -1 ) with 0.02 g of glutathione (quenching rate constant of 3×10 8 M -1 ·s -1 );

[0110] Under the same other conditions, the modified cathode material S2 is obtained.

[0111] Example 3

[0112] According to the method of Example 1, the difference is that

[0113] In step (1), replace 0.02 g of astaxanthin (quenching rate constant of 2.2×10 9 M -1 ·s -1 ) with 0.02 g of copper phthalocyanine (quenching rate constant of 8.2×10 9 M -1 ·s -1 );

[0114] Under the same other conditions, the modified cathode material S3 is obtained.

[0115] Example 4

[0116] According to the method of Example 1, the difference is that

[0117] In step (1), replace the dosage of astaxanthin with 0.005 g;

[0118] Under the same other conditions, the modified cathode material S4 is obtained.

[0119] Example 5

[0120] According to the method of Example 1, the difference is that

[0121] In step (1), replace the dosage of astaxanthin with 0.15 g;

[0122] Under the same other conditions, the modified cathode material S5 is obtained.

[0123] Example 6

[0124] According to the method of Example 1, the difference is that

[0125] In step (2), replace 0.05 g of polydopamine (conductivity of 1.35×10 -4S / cm, with a number-average molecular weight of 5000 g / mol) was replaced with 0.05 g of polypyrrole (conductivity 1.12×10 -5 S / cm, with a number-average molecular weight of 7000 g / mol);

[0126] Under the same other conditions, the modified cathode material S6 was obtained.

[0127] Example 7

[0128] According to the method of Example 1, the difference is that

[0129] In step (2), 0.05 g of polydopamine (conductivity 1.35×10 -4 S / cm, with a number-average molecular weight of 5000 g / mol) was replaced with 0.05 g of polytannic acid (conductivity 2.45×10 -7 S / cm, with a number-average molecular weight of 10000 g / mol);

[0130] Under the same other conditions, the modified cathode material S7 was obtained.

[0131] Example 8

[0132] According to the method of Example 1, the difference is that

[0133] In step (2), 0.05 g of polydopamine (conductivity 1.35×10 -4 S / cm, with a number-average molecular weight of 5000 g / mol) was replaced with 0.05 g of polyethylene terephthalate (conductivity 6.87×10 -10 S / cm, with a number-average molecular weight of 40000 g / mol);

[0134] Under the same other conditions, the modified cathode material S8 was obtained.

[0135] Example 9

[0136] According to the method of Example 1, the difference is that

[0137] In step (2), the dosage of polydopamine was replaced with 0.015 g;

[0138] Under the same other conditions, the modified cathode material S9 was obtained.

[0139] Example 10

[0140] According to the method of Example 1, the difference is that

[0141] In step (2), the dosage of polydopamine was replaced with 0.15 g;

[0142] Under the same other conditions, the modified cathode material S10 was obtained.

[0143] Example 11

[0144] According to the method of Example 1, except that

[0145] in step (1), 5 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 (D 50 = 3.5 μm) was replaced with 5 g of Li 1.2 [Ni 0.13 Co 0.13 Mn 0.54 O2 (D 50 = 4.5 μm); the dosage of astaxanthin was adjusted to 0.001 g; the stirring speed was replaced with 220 rpm; the drying temperature was replaced with 85 °C;

[0146] in step (2), 0.05 g of polydopamine (conductivity 1.35×10 -4 S / cm, number-average molecular weight 5000 g / mol) was replaced with 0.025 g of poly(3,4-ethylenedioxythiophene) (conductivity 8.35×10 -3 S / cm, number-average molecular weight 6500 g / mol); the stirring speed was replaced with 200 pm; the drying temperature was replaced with 280 °C;

[0147] Under the same other conditions, the modified cathode material S11 was obtained.

[0148] Example 12

[0149] According to the method of Example 1, except that

[0150] in step (1), 5 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 (D 50 = 3.5 μm) was replaced with 5 g of LiCoO2 (D 50 = 5 μm); 0.02 g of astaxanthin (quenching rate constant 2.2×10 9 M -1 ·s -1 ) was replaced with 0.06 g of copper phthalocyanine (quenching rate constant 8.2×10 9 M -1 ·s -1 ); the stirring speed was replaced with 350 rpm; the drying temperature was replaced with 90 °C;

[0151] in step (2), 0.05 g of polydopamine (conductivity 1.35×10 -4S / cm, number-average molecular weight is 5000 g / mol) is replaced with 0.04 g of polythiophene (conductivity is 1×10 -5 S / cm, number-average molecular weight is 4500 g / mol); the stirring speed is replaced with 150 rpm; the drying temperature is replaced with 180 °C;

[0152] Under the same other conditions, the modified cathode material S12 is obtained.

[0153] Example 13

[0154] According to the method of Example 1, the difference is that

[0155] In step (1), 5 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 (D 50 = 3.5 μm) is replaced with 5 g of Li[Ni 0.89 Co 0.05 Mn 0.05 Al 0.01 O2 (D 50 = 6 μm); 0.02 g of astaxanthin (quenching rate constant is 2.2×10 9 M -1 ·s -1 ) is replaced with 0.225 g of lutein (quenching rate constant is 1.2×10 8 M -1 ·s -1 ); the stirring speed is replaced with 450 rpm; the drying temperature is replaced with 100 °C;

[0156] In step (2), 0.05 g of polydopamine (conductivity is 1.35×10 -4 S / cm, number-average molecular weight is 5000 g / mol) is replaced with 0.2 g of poly(phenylethylene) (conductivity is 1×10 -6 S / cm, number-average molecular weight is 20000 g / mol); the stirring speed is replaced with 280 rpm; the drying temperature is replaced with 220 °C;

[0157] Under the same other conditions, the modified cathode material S13 is obtained.

[0158] Comparative Example 1

[0159] According to the method of Example 1, the difference is that the coating order is different, that is,

[0160] In step (1), 0.05 g of polydopamine (conductivity is 1.35×10 -4 S / cm, number-average molecular weight is 5000 g / mol) is first mixed and dried with the above-mentioned cathode material matrix dispersion to obtain an intermediate;

[0161] In step (2), 0.02 g of astaxanthin (quenching rate constant is 2.2×10 9 M -1 ·s -1 ) is dissolved in 100 mL of Tris buffer solution with pH = 8.5 to obtain an astaxanthin dispersion liquid, and then it is mixed with the above intermediate for the second time and dried;

[0162] Under the same other conditions, the modified cathode material DS1 is obtained.

[0163] Comparative Example 2

[0164] According to the method of Example 1, the difference is that

[0165] directly weigh 0.02 g of astaxanthin (quenching rate constant is 2.2×10 9 M -1 ·s -1 ) and 0.05 g of polydopamine (conductivity is 1.35×10 -4 S / cm, number-average molecular weight is 5000 g / mol), add them to the above cathode material matrix dispersion liquid for the first mixing and drying, and directly obtain the modified cathode material DS2.

[0166] Comparative Example 3

[0167] According to the method of Example 1, the difference is that no conductive polymer is added, that is,

[0168] directly use the intermediate prepared in step (1) as the modified cathode material DS3.

[0169] Comparative Example 4

[0170] According to the method of Example 1, the difference is that no singlet oxygen quencher is added, that is,

[0171] directly mix the above polydopamine dispersion liquid and the above cathode material matrix dispersion liquid for the second time and dry them to obtain the modified cathode material DS4.

[0172] Comparative Example 5

[0173] According to the method of Example 1, the difference is that two-step dry coating is adopted, that is,

[0174] In step (1), the above cathode material matrix and astaxanthin are mixed for the first time and dried to obtain an intermediate;

[0175] In step (2), the above intermediate and polydopamine are mixed for the second time and dried to obtain the modified cathode material DS5.

[0176] Comparative Example 6

[0177] According to the method of Example 1, except that

[0178] 0.02 g of astaxanthin (quenching rate constant is 2.2×10 9 M -1 ·s -1 ) is replaced with 0.02 g of benzidine (quenching rate constant is 5.65×10 5 M -1 ·s -1 );

[0179] Under the same other conditions, the modified cathode material DS6 is obtained.

[0180] Comparative Example 7

[0181] According to the method of Example 1, except that

[0182] 0.02 g of astaxanthin (quenching rate constant is 2.2×10 9 M -1 ·s -1 ) is replaced with 0.02 g of phenol (quenching rate constant is 4.32×10 5 M -1 ·s -1 );

[0183] Under the same other conditions, the modified cathode material DS7 is obtained.

[0184] Comparative Example 8

[0185] According to the method of Example 1, except that

[0186] In step (2), 0.05 g of polydopamine (conductivity is 1.35×10 -4 S / cm, molecular weight is 5000 g / mol) is replaced with 0.05 g of conductive carbon black (conductivity is 10 S / cm);

[0187] Under the same other conditions, the modified cathode material DS8 is obtained.

[0188] Comparative Example 9

[0189] According to the method of Example 1, except that no conductive polymer and singlet oxygen quencher are added, that is,

[0190] The cathode material matrix dispersion liquid prepared in step (1) is directly dried to obtain the modified cathode material DS9.

[0191] Table 1

[0192]

[0193] Note: 1 - mass ratio of the cathode material matrix, singlet oxygen quencher, and conductive polymer.

[0194] From the results in Table 1, it can be seen that compared with Comparative Examples 1 - 9, the modified cathode materials prepared by the method provided in the present invention in Examples 1 - 13 have better coating effects and higher electronic conductivity. From the data of Example 1 and Examples 4 - 5, it is known that due to the poor electronic conductivity of the singlet oxygen quencher, different contents of the singlet oxygen quencher were used in Examples 4 - 5, and by regulating the thickness of the inner coating layer, the charge transport ability was affected, thereby affecting the electronic conductivity. From the data of Example 1 and Examples 6 - 8, it is known that compared with Examples 6 - 8 using conductive polymers with relatively low conductivity as the outer coating layer, the overall conductivity and the effect of the conductive transport network of their modified cathode materials are lower than those of the modified cathode material in Example 1.

[0195] From the data of Example 1 and Examples 9 - 10, it is known that compared with Example 9 using a lower content of the conductive polymer, an effective electron transport network cannot be constructed, reducing the conductivity of the modified cathode material; Example 10 using a higher content of the conductive polymer as the outer coating layer will result in a higher coating layer thickness, which will also limit and affect the interfacial charge transport performance of the modified cathode material.

[0196] Compared with Comparative Example 1 for regulating the coating sequence, Comparative Example 2 for mixed coating, and Comparative Example 5 for dry coating, Example 1 uses the liquid phase method for coating, coating the singlet oxygen quencher and the conductive polymer separately. The singlet oxygen quencher in the inner coating layer can capture the singlet oxygen molecules generated on the surface of the cathode material matrix in real time and in a directional manner. The conductive polymer in the outer coating layer can not only effectively improve the electronic conductivity of the cathode material, but also improve the interfacial contact with the electrolyte, thereby achieving a higher conductivity.

[0197] Compared with Comparative Examples 3 - 4 using single - layer coating of the singlet oxygen quencher and the conductive polymer respectively, Example 1 uses double - layer coating, which can avoid problems such as poor conductivity caused by a poor electron transport network in a single coating layer or poor interfacial stability caused by the inability to improve the oxygen evolution on the surface of the cathode material, thereby affecting the conductivity and comprehensive performance of the modified cathode material.

[0198] Compared with Comparative Example 8 using conductive carbon black, the liquid phase method in Example 1 can achieve a more uniform and dense coating effect on the surface of the cathode material matrix. Comparative Example 8 using conductive carbon black as a conductive agent for coating can only achieve an effect similar to dot - like coating, the coating layer is discontinuous, and the coating degree of the outer coating layer is lower than that in Example 1, easily forming a discontinuous electron transport effect, resulting in its conductivity being lower than that in Example 1.

[0199] Test Example

[0200] The modified cathode materials prepared in the above examples and comparative examples were respectively subjected to electrochemical performance tests.

[0201] Preparation of all-solid-state battery:

[0202] The above modified cathode materials, Li 10 GeP2S 12 solid electrolyte, and Super P were sufficiently ground and mixed in a mass ratio of 7:2:1 for 30 min, and then pressed into a composite cathode of the all-solid-state battery.

[0203] Lithium metal foil (50 μm) and indium metal foil (50 μm) were weighed in a molar ratio of 0.5:1. The two metal foils were stacked under a press, and an aluminum-plastic film was used to isolate the metal foils from the metal press head to prevent adhesion. A pressure of 100 MPa was applied and maintained for 20 min to prepare the anode of the all-solid-state battery.

[0204] Weigh 70 mg of Li 10 GeP2S 12 sulfide solid electrolyte and pour it into the all-solid-state battery mold. Apply a pressure of 100 MPa and maintain it for 10 min to press the solid electrolyte into a sheet.

[0205] The composite cathode with a diameter of 7 mm was attached to one side of the electrolyte film, and the indium-lithium alloy (In-Li) with a diameter of 6 mm was attached to the other side of the electrolyte film. The sandwich structure was placed in a CR2025 coin cell, and then pressed with a hydraulic press at a pressure of 40 MPa to prepare an all-solid-state half-cell with a three-layer composite structure. All the above processes were carried out in a glove box filled with argon, and the H2O and O2 contents were kept below 0.01 ppm.

[0206] The assembled all-solid-state battery was subjected to constant current charge-discharge tests and cycling performance tests at 2.0 - 3.8 V (V vs. Li / In-Li) using a Land-CT 2001A type blue electrochemical test system. The test results are listed in Table 2.

[0207] Among them, as Figure 2 shown, the initial discharge specific capacity of the all-solid-state battery assembled with the modified cathode material S1 prepared in Example 1 was 206.4 mAh g -1 .

[0208] The DSC detection method for the electrode sheet is as follows:

[0209] The above assembled all-solid-state battery was charged at a constant current and constant voltage at a rate of 0.1C to the cut-off voltage at a constant temperature of 25°C, then discharged. After two charge-discharge cycles according to this procedure, it was charged to the cut-off voltage, left standing for 2 h, and the test was stopped. The battery was disassembled in a glove box, the composite positive electrode sheet was taken out, and transferred to a sample holder to start DSC testing. The temperature was raised at a rate of 5°C / min to 500°C, and the test results were marked with the starting exothermic temperature, exothermic peak temperature, heat release amount, etc.

[0210] Among them, the ratio of the DSC heat release amount = the total DSC heat release amount of the modified positive electrode material in the fully charged state / the total DSC heat release amount of the positive electrode material matrix in the fully charged state * 100%.

[0211] Table 2

[0212]

[0213] Note: * - The ratio of the total DSC heat release amount of the modified positive electrode material in the fully charged state to the total DSC heat release amount of the positive electrode material matrix in the fully charged state.

[0214] It can be seen from the data in Table 2 that compared with Comparative Examples 1-9, Examples 1-13 using the modified positive electrode material of the present invention have higher specific capacity utilization, cycle performance and thermal stability.

[0215] (1) Influence of the quenching rate constant of the singlet oxygen quencher in the modified positive electrode material on the battery performance

[0216] It can be seen from the data of Examples 1-3 and Comparative Examples 6-7 that compared with Comparative Examples 6-7 using singlet oxygen quenchers with lower quenching rate constants, the effective capture of singlet oxygen on the surface of the positive electrode material matrix cannot be achieved. Examples 1-3 using singlet oxygen quenchers with higher oxygen quenching rate constants can effectively inhibit the interfacial side reactions between the positive electrode material and the electrolyte, improve the cycle performance and reduce heat generation.

[0217] (2) Influence of the mass ratio of the singlet oxygen quencher in the modified positive electrode material on the battery performance

[0218] It can be seen from the data of Examples 4-5 and Example 1 that the mass ratio of the singlet oxygen quencher will affect the battery performance. If the mass ratio of the singlet oxygen quencher is too small, its quenching effect on singlet oxygen molecules will be affected, resulting in limited improvement in the battery cycle performance and thermal stability; if the mass ratio of the singlet oxygen quencher is too high, its conductivity is poor, which will affect the capacity utilization. Therefore, when its ratio is within the scope of the present invention, it can not only ensure its quenching ability for singlet oxygen molecules, but also ensure its conductivity, thereby improving the cycle performance and reducing heat generation.

[0219] (3) Influence of the conductivity of the conductive polymer in the modified cathode material on battery performance

[0220] Comparing Examples 6 - 8 with Example 1, the conductivity of the outer - coated conductive polymer affects battery performance. If the conductivity of the outer - coated conductive polymer is too low, it will affect the construction of the conductive transport network on the surface of the cathode material, resulting in a relatively low conductivity of the modified cathode material, thereby reducing the battery capacity and affecting the cycle performance.

[0221] (4) Influence of the mass ratio of the conductive polymer in the modified cathode material on battery performance

[0222] From the data of Examples 9 - 10 and Example 1, when the mass ratio of the outer - coated conductive polymer is too small or too large, the outer - coated layer is too thin or too thick, which affects the interfacial charge kinetic transport process of the cathode material, affects the battery capacity, and results in limited improvement in the cycle performance and thermal stability of the battery.

[0223] (5) Influence of the synergistic effect of the inner and outer coating layers in the modified cathode material on battery performance

[0224] From the data of Comparative Examples 1 - 4 and Example 1, compared with Comparative Example 1 for regulating the coating sequence, Comparative Example 2 for mixed coating, Comparative Example 3 for simply coating the singlet oxygen quencher, and Comparative Example 4 for simply coating the conductive polymer, Example 1 uses the liquid - phase method for coating, coating the singlet oxygen quencher on the inner layer and the conductive polymer on the outer layer respectively. The inner - layer singlet oxygen quencher can achieve directional capture of singlet oxygen molecules generated on the surface of the cathode material matrix, and the outer - layer conductive polymer can not only effectively improve the electronic conductivity of the cathode material, but also improve the interfacial contact with the electrolyte. Therefore, the best capacity, cycle performance and the lowest heat generation are obtained.

[0225] (6) Influence of the coating method of the modified cathode material on battery performance

[0226] From the data of Comparative Example 5 and Example 1, compared with Comparative Example 5 using the dry - coating method, it is impossible to form a nanoscale coating layer on the surface of the cathode material, and the distribution is uneven. The overall conductivity and thermal stability of the modified cathode material formed in this dry - mixing form are lower than those of Example 1, resulting in a decrease in the capacity, battery cycle performance and thermal stability of the cathode material.

[0227] (7) Influence of the type of the outer - coated conductive agent in the modified cathode material on battery performance

[0228] From the data of Comparative Example 8 and Example 1, it can be seen that in Comparative Example 8, using conductive carbon black as a conductive agent for coating can only achieve an effect similar to dot-like coating. In Example 1, the liquid-phase method can achieve a more uniform and thinner conductive polymer coating effect on the surface of the cathode material matrix, forming a continuous electron transport network, further improving the electrode process kinetics of the cathode material, enhancing the capacity utilization and cycle performance, and significantly improving the interfacial side reactions and heat generation between singlet oxygen and the solid electrolyte.

[0229] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A modified cathode material, characterized in that, The modified positive electrode material comprises a positive electrode material matrix, a singlet oxygen quencher as an inner coating layer and a conductive polymer as an outer coating layer; Wherein, the quenching rate constant of the singlet oxygen quencher is ≥1×10 6 M -1 ·s -1 .

2. The modified positive electrode material according to claim 1, wherein The quenching rate constant of the singlet oxygen quencher is 1×10 6 -5×10 10 M -1 ·s -1 ; And / or, the singlet oxygen quencher is selected from compounds containing a conjugated structure and / or a polar group, and the polar group is selected from at least one of a hydroxyl group, a thiol group, a carbonyl group and an amino group; Preferably, the singlet oxygen quencher is selected from at least one of compounds containing a conjugated double bond system, carboxylic acid compounds containing a thiol group, phthalocyanine compounds containing a conjugated structure, and derivatives of the above compounds modified by grafting or doping; Preferably, the singlet oxygen quencher is at least one selected from astaxanthin, α-carotene, β-carotene, lutein, lycopene, canthaxanthin, tuna xanthocyanin, glutathione, lipoic acid, phthalocyanine, copper phthalocyanine, nickel phthalocyanine and cobalt phthalocyanine.

3. The modified positive electrode material according to claim 1 or 2, wherein The conductivity of the conductive polymer ≥ 10 -7 S / cm, preferably 10 -5 -10 -2 S / cm; and / or, the number average molecular weight of the conductive polymer is 2000-200000 g / mol; Preferably, the conductive polymer is selected from at least one of polyacetylene, polypyrrole, poly(p-phenylene vinylene), polythiophene, poly(3,4-ethylenedioxythiophene), polyvinylpyrrolidone, polydopamine and polytannic acid, preferably polydopamine and / or poly(3,4-ethylenedioxythiophene); And / or, the D of the positive electrode material matrix 50 1-20 μm, preferably 3-13 μm; And / or, the positive electrode material matrix is selected from LiCoO2, LiNiO2, LiM2O4, LiNi x Co y M 1-x-y O2, zLi2MnO3·(1-z)LiM’O2, and at least one of the doping modification and composite materials of the above materials, where M is selected from Mn and / or Al, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, 0 < z < 1, and M’ is selected from at least one of Fe, Ni, Co, Mn, Cr, and V.

4. The modified cathode material according to any one of claims 1-3, wherein, In the modified positive electrode material, the mass ratio of the positive electrode material matrix to the singlet oxygen quencher is 100:0.01-5, preferably 100:0.1-1; And / or, in the modified positive electrode material, the mass ratio of the positive electrode material matrix to the conductive polymer is 100:0.3-5, preferably 100:0.5-2; and / or, the thickness of the inner coating layer is 5-100 nm, preferably 10-60 nm; And / or, the thickness of the outer coating layer is 10-200 nm, preferably 50-100 nm.

5. The modified positive electrode material according to any one of claims 1 to 4, wherein The electronic conductivity of the modified cathode material is 5×10 -6 -5×10 -2 S / cm.

6. A preparation method of a modified cathode material, characterized in that, The preparation method comprises: (1) The positive electrode material matrix dispersion is mixed with a quenching rate constant ≥ 1×10 6 M -1 ·s -1 The singlet oxygen quencher is sequentially subjected to a first mixing and a first drying to load the singlet oxygen quencher on the surface of the positive electrode material matrix to obtain an intermediate; (2) The conductive polymer dispersion and the intermediate are sequentially subjected to a second mixing and a second drying to load the conductive polymer on the surface of the intermediate to obtain a modified positive electrode material.

7. The preparation method according to claim 6, wherein In step (1), The mass ratio of the positive electrode material matrix to the singlet oxygen quencher is 100:0.01-5, preferably 100:0.1-1; And / or, the first mixing conditions include: a rotation speed of 200-500 rpm and a time of 0.5-5 h; And / or, the first drying conditions include: temperature of 80-200° C., time of 1-6 h; And / or, the positive electrode material matrix dispersion liquid is prepared by first dispersing the positive electrode material matrix and a first organic solvent; In step (2), The mass ratio of the positive electrode material matrix to the singlet oxygen quencher is 100:0.3-5, preferably 100:0.5-2; And / or, the second mixing conditions include: a rotation speed of 100-300 rpm and a time of 0.5-3 h; And / or, the second drying conditions include: temperature of 80-300° C., time of 1-6 h; And / or, the conductive polymer dispersion is prepared by dissolving the conductive polymer in a second organic solvent or a buffer solution and performing a second dispersion.

8. A positive electrode plate, characterized in that: The positive electrode sheet comprises the modified positive electrode material according to any one of claims 1 to 5, or the modified positive electrode material prepared by the preparation method according to claim 6 or 7; Preferably, in the positive electrode sheet, the content of the modified positive electrode material is 50-99 wt%.

9. Use of the modified positive electrode material according to any one of claims 1 to 5, or the modified positive electrode material prepared by the preparation method according to claim 6 or 7, or the positive electrode sheet according to claim 8 in a lithium-ion battery; Preferably, the lithium-ion battery is selected from a liquid battery, a hybrid solid-liquid battery or an all-solid-state battery; Preferably used in all-solid-state batteries.

10. A all-solid-state battery, characterized in that, The all-solid-state battery comprises: a positive electrode sheet, a negative electrode sheet and an electrolyte layer; Wherein, the positive electrode sheet comprises the modified positive electrode material according to any one of claims 1 to 5, or the modified positive electrode material prepared by the preparation method according to claim 6 or 7; Alternatively, the positive electrode sheet is selected from the positive electrode sheet according to claim 8; Preferably, the electrolyte layer is selected from at least one of a sulfide electrolyte, an oxide electrolyte, a halide electrolyte, a polymer electrolyte and a borohydride electrolyte.

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