Positive electrode composite, method for producing the same, positive electrode, and lithium-ion secondary battery

Abstract

The present application provides a positive electrode composite, a method for preparing the same, a positive electrode, and a lithium ion secondary battery. The positive electrode composite includes: a positive electrode active material; a coating layer coating the positive electrode active material, the coating layer including one or more of a polysaccharide organic polymer, polyvinyl alcohol, and polypropylene alcohol. Through the positive electrode composite of the present application, the method for preparing the same, and the positive electrode and lithium ion secondary battery including the same, the side reaction between the positive electrode active material and the electrolyte in the lithium ion secondary battery can be effectively inhibited, the dissolution of transition metals in the positive electrode active material can be reduced, the breakage of the positive electrode active material particles can be prevented, and the first coulomb efficiency and the cycle performance of the lithium ion secondary battery can be improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion secondary batteries, and more specifically, to a positive electrode composite material, a method for preparing the positive electrode composite material, and a positive electrode and a lithium-ion secondary battery comprising the positive electrode composite material. Background Technology

[0002] In recent years, with the continuous development of electronic technology, the demand for battery devices to support the energy supply of electronic devices has been increasing. Currently, there is a need for batteries capable of storing more electricity and outputting higher power. Traditional lead-acid and nickel-metal hydride batteries can no longer meet the needs of new electronic products such as mobile devices like smartphones and stationary devices such as energy storage systems. Therefore, lithium-ion rechargeable batteries have attracted widespread attention. In the development of lithium-ion rechargeable batteries, their capacity and performance have been effectively improved.

[0003] Lithium-ion secondary batteries consist of a positive electrode containing a positive electrode active material, a negative electrode, and an electrolyte. During the charge and discharge process of a lithium-ion secondary battery, the electrolyte dissolves transition metals in the positive electrode active material, leading to poor cycle performance and unstable electrochemical performance. Currently, a common solution is to coat the surface of the positive electrode active material with inorganic materials such as fluorides, alumina, or manganese dioxide. However, due to their low conductivity, these coating methods are not ideal. Existing technologies also disclose a method for coating the positive electrode sheet with metaphosphates. However, this method does not effectively improve the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries. Therefore, there is a need to develop a new positive electrode composite material, a method for preparing this positive electrode composite material, and a positive electrode and lithium-ion secondary battery incorporating this positive electrode composite material. Summary of the Invention

[0004] The main objective of this invention is to provide a positive electrode composite material, a method for preparing the positive electrode composite material, and a positive electrode and a lithium-ion secondary battery containing the positive electrode composite material, so as to solve the problem that it is difficult to effectively improve the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries in the prior art.

[0005] To achieve the above objectives, according to one aspect of the present invention, a positive electrode composite material is provided, comprising: a positive electrode active material; and a coating layer covering the positive electrode active material, the coating layer comprising one or more of polysaccharide organic polymers, polyvinyl alcohol, and polyacryl alcohol.

[0006] Furthermore, in the above-mentioned positive electrode composite material, the positive electrode active material includes materials with the general formula LiNi. x Co y M zO2 is a high-nickel cathode material, wherein x+y+z=1, 0.8≤x≤1, 0≤y≤0.2, 0≤z≤0.1, and M is selected from one or more of Mn, Al, Mg, Ti, Fe, Cu, Zn, Ga, Zr, Mo, Nb, W and Si.

[0007] Furthermore, in the above-mentioned positive electrode composite material, the polysaccharide organic polymer is selected from one or more of sodium alginate, gum arabic, and guar gum.

[0008] Furthermore, in the above-mentioned positive electrode composite material, based on 100 parts by mass of positive electrode active material, the amount of coating layer is in the range of 0.01 parts by mass to 3.5 parts by mass, preferably in the range of 0.01 parts by mass to 2.5 parts by mass.

[0009] Furthermore, in the above-mentioned cathode composite material, the thickness of the coating layer is in the range of 1 nm to 100 nm.

[0010] According to another aspect of the present invention, a method for preparing a positive electrode composite material is provided, the method comprising: a first step: adding water to a coating agent comprising one or more of a polysaccharide organic polymer, polyvinyl alcohol, and polyacryl alcohol to obtain a first mixture, and then stirring the first mixture to obtain a coating solution; and a second step: adding a positive electrode active material to the coating solution to obtain a second mixture, then stirring the second mixture, adding an organic solvent during stirring to obtain a third mixture, filtering the third mixture, and drying the filtered material to obtain the positive electrode composite material.

[0011] According to another aspect of the present invention, a method for preparing a positive electrode composite material is provided, the method comprising: a first step: adding water to a coating agent comprising one or more of a polysaccharide organic polymer, polyvinyl alcohol, and polyacryl alcohol to obtain a first mixture, and then stirring the first mixture to obtain a coating solution; and a second step: adding a positive electrode active material to the coating solution to obtain a second mixture, then placing the second mixture in a water bath and stirring, and after the water in the second mixture evaporates, drying the remaining material to obtain the positive electrode composite material.

[0012] Furthermore, in the above-mentioned method for preparing positive electrode composite materials, in the first step, the stirring speed is in the range of 100-500 rpm and the stirring time is in the range of 1-12 h.

[0013] Furthermore, in the above-described method for preparing the positive electrode composite material, in the first step, based on 100 parts by mass of the coating solution, the amount of coating agent is in the range of 0.01 parts by mass to 3.5 parts by mass, preferably, the amount of coating agent is in the range of 0.01 parts by mass to 2.5 parts by mass.

[0014] Furthermore, in the above-described method for preparing the cathode composite material, in the second step, the stirring speed is in the range of 100-500 rpm.

[0015] Furthermore, in the above-described method for preparing the cathode composite material, in the second step, based on the total weight of the second mixture, the content of the cathode active material in the second mixture is in the range of 4.0 wt% to 60 wt%.

[0016] Furthermore, in the above-described method for preparing the cathode composite material, in the second step, the organic solvent is selected from ethanol, isopropanol, and ethylene glycol.

[0017] Furthermore, in the above-mentioned method for preparing positive electrode composite materials, the amount of organic solvent added is 50%-100% of the mass of the coating solution.

[0018] Furthermore, in the above-described method for preparing positive electrode composite materials, in the second step, the drying temperature is in the range of 80-120°C, and the drying time is in the range of 4-12 hours.

[0019] Furthermore, in the above-described method for preparing positive electrode composite materials, in the second step, the temperature of the water bath is in the range of 60-100°C.

[0020] Furthermore, in the above-described method for preparing the cathode composite material, the cathode active material comprises a material with the general formula LiNi. x Co y M z O2 is a high-nickel cathode material, wherein x+y+z=1, 0.8≤x≤1, 0≤y≤0.2, 0≤z≤0.1, and M is selected from one or more of Mn, Al, Mg, Ti, Fe, Cu, Zn, Ga, Zr, Mo, Nb, W and Si.

[0021] Furthermore, in the above-mentioned method for preparing cathode composite materials, the polysaccharide organic polymer is selected from one or more of sodium alginate, gum arabic, and guar gum.

[0022] Furthermore, in the above-described method for preparing the positive electrode composite material, based on 100 parts by mass of the positive electrode active material, the amount of the coating agent is in the range of 0.01 parts by mass to 3.5 parts by mass, preferably in the range of 0.01 parts by mass to 2.5 parts by mass.

[0023] According to another aspect of the present invention, a lithium-ion secondary battery positive electrode is provided, the lithium-ion secondary battery positive electrode comprising the positive electrode composite material described above.

[0024] According to another aspect of the present invention, a lithium-ion secondary battery is provided, comprising: a positive electrode, a negative electrode, and a separator, wherein the positive electrode comprises the positive electrode composite material described above.

[0025] The positive electrode composite material, the method for preparing the positive electrode composite material, and the positive electrode and lithium-ion secondary battery containing the positive electrode composite material of the present invention can effectively suppress the side reactions between the positive electrode active material and the electrolyte in the lithium-ion secondary battery, reduce the dissolution of transition metals in the positive electrode active material, prevent the breakage of positive electrode active material particles, and improve the first coulombic efficiency and cycle performance of the lithium-ion secondary battery. Attached Figure Description

[0026] Figure 1 The 100-cycle performance of the batteries in Example 2 and Comparative Example 1 is shown.

[0027] Figure 2 A schematic diagram of the structure of a cathode composite material including high-nickel cathode material is shown. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the various embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments. The following embodiments are merely exemplary and are not intended to limit the scope of protection of the present invention.

[0029] As explained in the background section, it is difficult to effectively improve the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries in the prior art. To address the problems in the prior art, a typical embodiment of the present invention provides a positive electrode composite material, comprising: a positive electrode active material; and a coating layer covering the positive electrode active material, the coating layer comprising one or more of polysaccharide organic polymers, polyvinyl alcohol, and polyacryl alcohol.

[0030] In the positive electrode composite material of the present invention, by coating the positive electrode active material with a coating layer containing one or more of polysaccharide organic polymers, polyvinyl alcohol and polyacryl alcohol, it is possible to effectively prevent the contact between the positive electrode active material and the electrolyte in the lithium-ion secondary battery, effectively suppress the side reactions between the positive electrode active material and the electrolyte in the lithium-ion secondary battery, reduce the dissolution of transition metals in the positive electrode active material, prevent the breakage of positive electrode active material particles, and improve the initial coulombic efficiency and cycle performance of the lithium-ion secondary battery.

[0031] The positive electrode active material in the present invention can adopt the conventional positive electrode active materials in the art. Preferably, in some embodiments of the present invention, the positive electrode active material can be a lithium-containing compound. Examples of such lithium-containing compounds include lithium-transition metal composite oxides and lithium-transition metal phosphate compounds, etc. The lithium-transition metal composite oxide is an oxide containing Li and one or two or more transition metal elements as constituent elements. The lithium-transition metal phosphate compound is a phosphate compound containing Li and one or two or more transition metal elements as constituent elements. The transition metal element is advantageously one or more of Co, Ni, Mn, Ti, and Fe, etc. Examples of the lithium-transition metal composite oxide can include, for example, lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel oxide (LiNiO2), and lithium titanate, etc. Examples of the lithium-transition metal phosphate compound can include, for example, lithium iron phosphate (LiFePO4) and LiFe 1-u Mn u PO4(0 < u < 1), etc.

[0032] In some embodiments of the present invention, in the above positive electrode composite material, the positive electrode active material contains a high-nickel positive electrode material with the general formula LiNi x Co y M z O2, where x + y + z = 1, 0.8 ≤ x ≤ 1, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 0.1, and M is selected from one or more of Mn, Al, Mg, Ti, Fe, Cu, Zn, Ga, Zr, Mo, Nb, W, and Si. Preferably, in the above positive electrode composite material, the positive electrode active material is the high-nickel positive electrode material of the above general formula.

[0033] In the positive electrode composite material of the present invention, by coating the positive electrode active material containing the above high-nickel positive electrode material with a coating layer containing one or more of polysaccharide organic polymers, polyvinyl alcohol, and polypropylene alcohol, it can effectively prevent the contact between the positive electrode active material and the electrolyte in the lithium-ion secondary battery, effectively inhibit the side reaction between the positive electrode active material and the electrolyte in the lithium-ion secondary battery, reduce the dissolution of transition metals in the positive electrode active material, prevent the fragmentation of positive electrode active material particles, improve the first Coulomb efficiency and cycling performance of the lithium-ion secondary battery, and can also reduce the residual alkali on the surface of the high-nickel positive electrode material. At the same time, the excess Ni ions (Ni 2+ ) on the surface of the high-nickel positive electrode material can crosslink with the coating layer containing one or more of polysaccharide organic polymers, polyvinyl alcohol, and polypropylene alcohol, and the coating layer will not decompose when the charging voltage Ec > 4.1V (relative to Li + ), which can not only improve the structural stability and conductivity of the coating layer, but also reduce the lithium nickel (Li + / Ni 2+The phenomenon of mixed arrangement. Figure 2 A schematic diagram of a cathode composite material including a high-nickel cathode material is shown. According to... Figure 2 It can be clearly seen that the excess Ni ions (Ni) on the surface of the high-nickel cathode material 2+ The coating layer forms a Ni ion crosslink.

[0034] The intensity ratio (I003) of the diffraction peaks on the (003) plane to that on the (104) plane can be obtained from the results of X-ray diffraction (XRD). 003 / 104 If the obtained I 003 / 104 A larger value indicates that lithium nickel (Li) + / Ni 2+ The degree of mixing is relatively small.

[0035] In some embodiments of the present invention, in order to more effectively suppress the side reactions between the positive electrode active material and the electrolyte in the lithium-ion secondary battery and to more effectively improve the first coulombic efficiency and cycle performance of the lithium-ion secondary battery, the polysaccharide organic polymer may be selected from one or more of sodium alginate, gum arabic and guar gum.

[0036] In some embodiments of the present invention, in the cathode composite material of the present invention, based on 100 parts by mass of the cathode active material, the amount of the coating layer is in the range of 0.01 parts by mass to 3.5 parts by mass, preferably in the range of 0.01 parts by mass to 2.5 parts by mass, and more preferably in the range of 0.01 parts by mass to 0.1 parts by mass. By controlling the amount of the coating layer within the above range, a good coating effect of the coating layer on the cathode active material can be achieved, which can further improve the initial coulombic efficiency and capacity retention rate after 100 cycles of the lithium-ion secondary battery. When the cathode active material contains the above-mentioned high-nickel cathode material, by controlling the amount of the coating layer within the above range, in addition to improving the initial coulombic efficiency and capacity retention rate after 100 cycles of the lithium-ion secondary battery, residual alkali on the surface of the high-nickel cathode material and lithium nickel (Li) can also be reduced. + / Ni 2+ The phenomenon of mixed arrangement.

[0037] Specifically, based on 100 parts by weight of the positive electrode active material, the amount of the coating layer can be within the following ranges: 0.01 parts by weight to 3.5 parts by weight, 0.01 parts by weight to 3.3 parts by weight, 0.01 parts by weight to 3.1 parts by weight, 0.01 parts by weight to 2.9 parts by weight, 0.01 parts by weight to 2.7 parts by weight, 0.01 parts by weight to 2.5 parts by weight, 0.01 parts by weight to 2.3 parts by weight, 0.01 parts by weight to 2.1 parts by weight, 0.01 parts by weight to 1.9 parts by weight, 0.01 parts by weight to 1.7 parts by weight, 0.01 parts by weight to 1.5 parts by weight, 0.01 parts by weight to 1.3 parts by weight, 0.01 parts by weight to 1.1 parts by weight, 0.01 parts by weight to 0.9 parts by weight, 0.01 parts by weight to 0.7 parts by weight, 0.01 parts by weight to 0.5 parts by weight. Parts, 0.01 to 0.3 parts by mass, 0.01 to 0.1 parts by mass, 0.1 to 3.5 parts by mass, 0.1 to 3.3 parts by mass, 0.1 to 3.1 parts by mass, 0.1 to 2.9 parts by mass, 0.1 to 2.7 parts by mass, 0.1 to 2.5 parts by mass, 0.1 to 2.3 parts by mass, 0.1 to 2.1 parts by mass, 0.1 to 1.9 parts by mass, 0.1 to 1.7 parts by mass, 0.1 to 1.5 parts by mass, 0.1 to 1.3 parts by mass, 0.1 to 1.1 parts by mass, 0.1 to 0.9 parts by mass, 0.1 to 0.7 parts by mass, 0.1 to 0.5 parts by mass, or 0.1 to 0.3 parts by mass.

[0038] In some embodiments of the present invention, the thickness of the coating layer in the cathode composite material is in the range of 1 nm to 100 nm, preferably in the range of 1 nm to 80 nm, and more preferably in the range of 1 nm to 60 nm. By controlling the thickness of the coating layer within the above range, the initial coulombic efficiency and capacity retention after 100 cycles of the lithium-ion secondary battery can be improved.

[0039] Specifically, the thickness of the coating layer can be in the following ranges: 1nm to 100nm, 1nm to 90nm, 1nm to 80nm, 1nm to 70nm, 1nm to 60nm, 1nm to 50nm, 1nm to 40nm, 1nm to 30nm, 1nm to 20nm, 1nm to 10nm, 5nm to 100nm, 5nm to 90nm, 5nm to 80nm, 5nm to 70nm, 5nm to 60nm, 5nm to 50nm, 5nm to 40nm, 5nm to 30nm, 5nm to 20nm, or 5nm to 10nm.

[0040] In another typical embodiment of the present invention, a method for preparing a positive electrode composite material is provided, the method comprising: a first step: adding water to a coating agent comprising one or more of polysaccharide organic polymers, polyvinyl alcohol and polyacryl alcohol to obtain a first mixture, and then stirring the first mixture to obtain a coating solution; and a second step: adding a positive electrode active material to the coating solution to obtain a second mixture, then stirring the second mixture, adding an organic solvent during stirring to obtain a third mixture, filtering the third mixture, and drying the filtered material to obtain the positive electrode composite material.

[0041] The first step yields a uniform coating solution, while the second step allows a coating agent comprising one or more of polysaccharide organic polymers, polyvinyl alcohol, and polyacryl alcohol to uniformly coat the surface of the positive electrode active material. The positive electrode composite material obtained by the method of this invention effectively prevents contact between the positive electrode active material and the electrolyte in lithium-ion secondary batteries, effectively suppresses side reactions between the positive electrode active material and the electrolyte, reduces the dissolution of transition metals in the positive electrode active material, prevents particle breakage of the positive electrode active material, and improves the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries. Furthermore, in the positive electrode composite material obtained by the method of this invention, the coating layer covering the positive electrode active material is water-soluble, while an oil-based slurry system is typically used in the preparation of positive electrode sheets. The water-soluble coating layer of the positive electrode composite material prepared by the method of this invention can maintain its structural integrity well within oil-based slurry and electrode systems. Compared with existing methods for coating positive electrode sheets, the method of the present invention has a better coating effect on positive electrode active materials, thereby significantly improving the first coulombic efficiency and cycle performance of lithium-ion secondary batteries.

[0042] In some embodiments of the present invention, in the above-described method for preparing positive electrode composite materials, in the second step, the filtered material can be dried under vacuum conditions. Alternatively, the filtered material can be dried by drying. Preferably, the filtered material can be dried under vacuum conditions.

[0043] In another typical embodiment of the present invention, a method for preparing a positive electrode composite material is provided, the method comprising: a first step: adding water to a coating agent comprising one or more of polysaccharide organic polymers, polyvinyl alcohol and polyacryl alcohol to obtain a first mixture, and then stirring the first mixture to obtain a coating solution; and a second step: adding a positive electrode active material to the coating solution to obtain a second mixture, then placing the second mixture in a water bath and stirring, and after the water in the second mixture evaporates, drying the remaining material to obtain the positive electrode composite material.

[0044] Similarly, a uniform coating solution can be obtained through the first step, and the second step can uniformly coat the surface of the positive electrode active material with a coating agent containing one or more of polysaccharide organic polymers, polyvinyl alcohol, and polyacryl alcohol. The positive electrode composite material obtained by the above method of the present invention can effectively prevent contact between the positive electrode active material and the electrolyte in lithium-ion secondary batteries, effectively suppress side reactions between the positive electrode active material and the electrolyte in lithium-ion secondary batteries, reduce the dissolution of transition metals in the positive electrode active material, prevent the breakage of positive electrode active material particles, and improve the initial coulombic efficiency and cycle performance of lithium-ion secondary batteries. Moreover, in the positive electrode composite material obtained by the above method of the present invention, the coating layer covering the positive electrode active material is water-soluble, while an oil-based slurry system is usually used in the preparation of positive electrode sheets. The water-soluble coating layer of the positive electrode composite material prepared by the method of the present invention can maintain its structural integrity well in oil-based slurry and electrode systems. Compared with existing methods for coating positive electrode sheets, the method of the present invention has a better coating effect on positive electrode active materials, thereby significantly improving the first coulombic efficiency and cycle performance of lithium-ion secondary batteries.

[0045] In some embodiments of the present invention, in the above-described method for preparing positive electrode composite materials, in the second step, the remaining material can be dried under vacuum conditions. Alternatively, the remaining material can be dried by a drying method. Preferably, the remaining material can be dried under vacuum conditions.

[0046] In some embodiments of the present invention, in the above-described method for preparing the cathode composite material, in the first step, the stirring speed is in the range of 50-500 rpm and the stirring time is in the range of 0.5-12 h. Preferably, the stirring speed is in the range of 100-500 rpm and the stirring time is in the range of 1-12 h. More preferably, the stirring speed is in the range of 200-400 rpm and the stirring time is in the range of 1-8 h. Most preferably, the stirring speed is in the range of 250-350 rpm and the stirring time is in the range of 1-6 h. By controlling the stirring speed and stirring time in the first step within the above ranges, a uniform coating solution can be obtained, achieving a good coating effect of the coating layer on the cathode active material, and further improving the initial coulombic efficiency and capacity retention rate after 100 cycles of the lithium-ion secondary battery. When the cathode active material contains a high-nickel cathode material, by controlling the stirring speed and stirring time in the first step within the above ranges, in addition to obtaining the effects mentioned above, the lithium nickel (Li) content can also be significantly reduced. + / Ni 2+ The phenomenon of mixed arrangement.

[0047] In some embodiments of the present invention, in the above-described method for preparing positive electrode composite materials, in order to obtain a coating solution of suitable concentration and achieve a good coating effect, in the first step, based on 100 parts by mass of the coating solution, the amount of coating agent is in the range of 0.01 parts by mass to 3.5 parts by mass, preferably, the amount of coating agent is in the range of 0.01 parts by mass to 2.5 parts by mass, and more preferably, the amount of coating agent is in the range of 0.01 parts by mass to 0.1 parts by mass.

[0048] In some embodiments of the present invention, in the above-described method for preparing positive electrode composite materials, in order to achieve a good coating effect, in the second step, the stirring speed is in the range of 100-500 rpm, preferably in the range of 200-500 rpm, and more preferably in the range of 300-500 rpm. Specifically, in the second step, the stirring speed can be in the following ranges: 100-450 rpm, 100-400 rpm, 100-350 rpm, 100-300 rpm, 100-250 rpm, 100-200 rpm, 100-150 rpm, 150-450 rpm, 150-400 rpm, 150-350 rpm, 150-300 rpm, 150-250 rpm, or 150-200 rpm.

[0049] In some embodiments of the present invention, in the above-described method for preparing the cathode composite material, in the second step, based on the total weight of the second mixture, the content of the cathode active material in the second mixture is in the range of 4.0 wt%-60 wt%, preferably, based on the total weight of the second mixture, the content of the cathode active material in the second mixture is in the range of 35 wt%-55 wt%, more preferably, based on the total weight of the second mixture, the content of the cathode active material in the second mixture is in the range of 45 wt%-50 wt%. By controlling the content of the cathode active material in the second mixture within the above range, a good coating effect can be ensured, and the initial coulombic efficiency and capacity retention after 100 cycles of the lithium-ion secondary battery can be improved. When the cathode active material contains a high-nickel cathode material, by controlling the content of the cathode active material in the second mixture within the above range, in addition to ensuring the above-mentioned effects, it is also possible to ensure a reduction in residual alkali on the surface of the high-nickel cathode material and a reduction in lithium nickel (Li) content. + / Ni 2+ The phenomenon of mixed arrangement.

[0050] Specifically, in the second step, based on the total weight of the second mixture, the content of the positive electrode active material in the second mixture can be within the following ranges: 10wt%-60wt%, 15wt%-60wt%, 20wt%-60wt%, 25wt%-60wt%, 30wt%-60wt%, 35wt%-60wt%, 40wt%-60wt%, 45wt%-60wt%, 50wt%-60wt%, 55wt%-60wt%, 10wt%-50wt%, 15wt%-50wt%, 20wt%-50wt%, 25wt%-50wt%, 30wt%-50wt%, 35wt%-50wt%, 40wt%-50wt%, or 45wt%-55wt%.

[0051] In some embodiments of the present invention, in the above-described method for preparing the cathode composite material, in the second step, the organic solvent is selected from ethanol, isopropanol, and ethylene glycol. The organic solvent can displace the water in the second mixture, thereby ensuring that the washed-out residual alkali remains in the water and is removed during filtration, thus significantly reducing the residual alkali content of the cathode composite material obtained after coating.

[0052] In some embodiments of the present invention, in the above-described method for preparing the positive electrode composite material, the amount of organic solvent added can be 50%-100% of the mass of the coating solution, or 60%-90% of the mass of the coating solution, or 70%-80% of the mass of the coating solution, or 90%-100% of the mass of the coating solution. The more organic solvent added, the more significant the effect of water replacement by the organic solvent. Preferably, the amount of organic solvent added is consistent with the mass of the coating solution, that is, most preferably, the amount of organic solvent added is 100% of the mass of the coating solution.

[0053] In some embodiments of the present invention, in the above-described method for preparing the cathode composite material, in the second step, the drying temperature is in the range of 60-120°C and the drying time is in the range of 2-12 hours. Preferably, the drying temperature is in the range of 80-120°C and the drying time is in the range of 4-12 hours. More preferably, the drying temperature is in the range of 90-120°C and the drying time is in the range of 8-12 hours. Even more preferably, the drying temperature is in the range of 100-120°C and the drying time is in the range of 8-10 hours. Most preferably, the drying temperature is in the range of 110-120°C and the drying time is in the range of 6-8 hours. By controlling the drying temperature and drying time in the second step within the above ranges, a good coating effect can be obtained, and the charging capacity, initial coulombic efficiency, and capacity retention after 100 cycles of the lithium-ion secondary battery can be improved. When the positive electrode active material includes a high-nickel positive electrode material, by controlling the drying temperature and drying time in the second step within the aforementioned range, in addition to achieving the effects mentioned above, it is also possible to reduce the residual alkali on the surface of the high-nickel positive electrode material and reduce lithium nickel (Li) content. + / Ni 2+ The phenomenon of mixed arrangement.

[0054] In some embodiments of the present invention, in the above-described method for preparing the positive electrode composite material, in order to achieve a good coating effect, in the second step, the temperature of the water bath is in the range of 60-100°C, preferably in the range of 70-90°C, and more preferably in the range of 70-80°C. The above-mentioned water bath temperature ensures that the water in the second mixture evaporates at a uniform rate, not too quickly, thereby allowing the coating agent to uniformly coat the surface of the positive electrode active material during the water evaporation process.

[0055] In some embodiments of the present invention, in the above-described method for preparing cathode composite materials, the cathode active material comprises a material with the general formula LiNi. x Co y M z The high-nickel cathode material of O2, wherein x+y+z=1, 0.8≤x≤1, 0≤y≤0.2, 0≤z≤0.1, and M is selected from one or more of Mn, Al, Mg, Ti, Fe, Cu, Zn, Ga, Zr, Mo, Nb, W, and Si. Preferably, in the above-described method for preparing the cathode composite material, the cathode active material is a high-nickel cathode material of the above-described general formula. In the method for preparing the cathode composite material of the present invention, when the cathode active material includes a high-nickel cathode material, the same effect as in the above-described cathode composite material can be obtained.

[0056] In some embodiments of the present invention, in the above-described method for preparing the cathode composite material, the polysaccharide organic polymer is selected from one or more of sodium alginate, gum arabic, and guar gum. In this case, the same effect as in the above-described cathode composite material can be obtained.

[0057] In some embodiments of the present invention, in the above-described method for preparing the cathode composite material, based on 100 parts by mass of the cathode active material, the amount of coating agent is in the range of 0.01 parts by mass to 3.5 parts by mass, preferably in the range of 0.01 parts by mass to 2.5 parts by mass, and more preferably in the range of 0.01 parts by mass to 0.1 parts by mass. By controlling the amount of coating agent within the above range, a good coating effect of the coating agent on the cathode active material can be achieved, which can further improve the initial coulombic efficiency and capacity retention rate after 100 cycles of the lithium-ion secondary battery. When the cathode active material includes the above-described high-nickel cathode material, by controlling the amount of coating agent within the above range, in addition to further improving the initial coulombic efficiency and capacity retention rate after 100 cycles of the lithium-ion secondary battery, residual alkali on the surface of the high-nickel cathode material and lithium nickel (Li) can also be reduced. + / Ni 2+ The phenomenon of mixed arrangement.

[0058] In another typical embodiment of the present invention, a lithium-ion secondary battery positive electrode is provided, which comprises the positive electrode composite material described above. Because the lithium-ion secondary battery positive electrode of the present invention comprises the positive electrode composite material described above, it can effectively suppress side reactions between the positive electrode active material and the electrolyte in the lithium-ion secondary battery, reduce the dissolution of transition metals in the positive electrode active material, prevent the breakage of positive electrode active material particles, and improve the initial coulombic efficiency and cycle performance of the lithium-ion secondary battery.

[0059] In another typical embodiment of the present invention, a lithium-ion secondary battery is provided, comprising: a positive electrode, a negative electrode, and a separator, wherein the positive electrode comprises the positive electrode composite material described above. Because the lithium-ion secondary battery of the present invention comprises the positive electrode composite material described above, it can effectively suppress side reactions between the positive electrode active material and the electrolyte in the lithium-ion secondary battery, reduce the dissolution of transition metals in the positive electrode active material, prevent the breakage of positive electrode active material particles, and improve the initial coulombic efficiency and cycle performance of the lithium-ion secondary battery.

[0060] The positive electrode of the present invention includes a positive current collector and a positive active material layer containing a positive electrode composite material. The positive active material layer is formed on both surfaces of the positive current collector. Metal foil such as aluminum foil, nickel foil, or stainless steel foil can be used as the positive current collector.

[0061] The negative electrode of the present invention comprises a negative current collector and a negative active material layer containing a negative active material. The negative active material layer is formed on both surfaces of the negative current collector. A metal foil such as copper (Cu) foil, nickel foil, or stainless steel foil can be used as the negative current collector.

[0062] The negative electrode active material layer contains one or more negative electrode materials capable of inserting and extracting lithium ions as negative electrode active materials, and may contain other materials, such as negative electrode binders and / or negative electrode conductive agents, if necessary. The negative electrode active material may be selected from one or more of lithium metal, lithium alloys, carbon materials, silicon or tin and their oxides.

[0063] The separator of the present invention is used to separate the positive and negative electrodes in a battery and allow lithium ions to pass through while preventing short circuits caused by contact between the positive and negative electrodes. The separator is, for example, a porous membrane formed of synthetic resin or ceramic, and may be a laminated membrane in which two or more porous membranes are laminated. Examples of synthetic resins include, for example, polytetrafluoroethylene, polypropylene, and polyethylene.

[0064] In embodiments of the present invention, when the lithium-ion secondary battery is charged, for example, lithium ions are extracted from the positive electrode and embedded in the negative electrode through the electrolyte impregnated in the separator. When the lithium-ion secondary battery is discharged, for example, lithium ions are extracted from the negative electrode and embedded in the positive electrode through the electrolyte impregnated in the separator.

[0065] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0066] Example 1

[0067] 1. Weigh 0.01g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.01wt% sodium alginate solution;

[0068] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0069] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0070] Example 2

[0071] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0072] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0073] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0074] Example 3

[0075] 1. Weigh 2.5g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 2.5wt% sodium alginate solution;

[0076] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0077] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0078] Example 4

[0079] 1. Weigh 3.5g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 3.5wt% sodium alginate solution;

[0080] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0081] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0082] Example 5

[0083] 1. Weigh 0.1g of polyvinyl alcohol, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% polyvinyl alcohol solution;

[0084] 2. Weigh 100g of lithium cobalt oxide (LiCoO2) and add it to the solution in step 1. Place it in a water bath and stir until the water in the solution evaporates. Dry the remaining material to obtain coated lithium cobalt oxide. The stirring speed is 200rpm, the water bath temperature is 100℃, the drying temperature is 120℃, and the drying time is 8 hours.

[0085] 3. Take 97g of the material prepared by the process, 1.5g of conductive carbon black as a conductive agent and 1.5g of polyvinylidene fluoride (PVDF) as a binder to make an electrode sheet, and use the above electrode sheet to make a half cell. The results are shown in Table 1.

[0086] Example 6

[0087] 1. Weigh 0.01g of gum arabic, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.01wt% gum arabic solution;

[0088] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0089] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0090] Example 7

[0091] 1. Weigh 0.1g of gum arabic, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% gum arabic solution;

[0092] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0093] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0094] Example 8

[0095] 1. Weigh 2.5g of gum arabic, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 2.5wt% gum arabic solution;

[0096] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0097] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0098] Example 9

[0099] 1. Weigh 3.5g of gum arabic, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 3.5wt% gum arabic solution;

[0100] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0101] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0102] Example 10

[0103] 1. Weigh 0.1g of guar gum, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% guar gum solution;

[0104] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0105] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0106] Example 11

[0107] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 50rpm for half an hour to obtain a 0.1wt% sodium alginate solution;

[0108] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0109] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0110] Example 12

[0111] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0112] 2. Weigh 150g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0113] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0114] Example 13

[0115] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0116] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 60℃, and the drying time was 2 hours.

[0117] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0118] Example 14

[0119] 1. Weigh 0.1g of polyacrylol, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% polyacrylol solution;

[0120] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0121] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0122] Example 15

[0123] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0124] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) is added to the solution in step 1, placed in a water bath and stirred until the water in the solution evaporates. The remaining material is dried to obtain the coated high-nickel cathode material. The stirring speed is 200 rpm, the water bath temperature is 100℃, the drying temperature is 120℃, and the drying time is 8 hours.

[0125] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0126] Example 16

[0127] 1. Weigh 0.1g of polyvinyl alcohol, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% polyvinyl alcohol solution;

[0128] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) is added to the solution in step 1, and the mixture is placed in a water bath and stirred until the water in the solution evaporates. The remaining material is dried to obtain the coated high-nickel cathode material. The stirring speed is 200 rpm, the water bath temperature is 60°C, the drying temperature is 120°C, and the drying time is 8 hours.

[0129] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0130] Example 17

[0131] 1. Weigh 0.1g of gum arabic, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% gum arabic solution;

[0132] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1O2) is added to the solution in step 1, placed in a water bath and stirred until the water in the solution evaporates. The remaining material is dried to obtain the coated high-nickel cathode material. The stirring speed is 200 rpm, the water bath temperature is 100℃, the drying temperature is 120℃, and the drying time is 12 hours.

[0133] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0134] Example 18

[0135] 1. Weigh 0.1g of guar gum, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% guar gum solution;

[0136] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) is added to the solution in step 1, and the mixture is placed in a water bath and stirred until the water in the solution evaporates. The remaining material is dried to obtain the coated high-nickel cathode material. The stirring speed is 200 rpm, the water bath temperature is 100℃, the drying temperature is 80℃, and the drying time is 8 hours.

[0137] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0138] Example 19

[0139] 1. Weigh 0.1g of polyacrylol, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% polyacrylol solution;

[0140] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1O2) is added to the solution in step 1, and the mixture is placed in a water bath and stirred until the water in the solution evaporates. The remaining material is dried to obtain the coated high-nickel cathode material. The stirring speed is 200 rpm, the water bath temperature is 100℃, the drying temperature is 120℃, and the drying time is 4 hours.

[0141] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0142] Example 20

[0143] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 100rpm for 12 hours to obtain a 0.1wt% sodium alginate solution;

[0144] 2. Weigh 4.2g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 100rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0145] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 Electrode sheets were fabricated using 3.6g of the prepared material, 0.2g of conductive carbon black as a conductive agent, and 0.2g of polyvinylidene fluoride (PVDF) as a binder. Half cells were fabricated using the electrode sheets, and the results are shown in Table 1.

[0146] Example 21

[0147] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 500rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0148] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of isopropanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 100rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0149] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0150] Example 22

[0151] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0152] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 50g of ethylene glycol was added dropwise during the process. The mixture was then filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500 rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0153] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0154] Example 23

[0155] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0156] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al 0.05 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0157] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0158] Example 24

[0159] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0160] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Mn 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0161] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0162] Example 25

[0163] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0164] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Mn 0.05 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0165] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0166] Example 26

[0167] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0168] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al 0.03 Mg 0.02 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0169] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0170] Example 27

[0171] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0172] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al 0.03 Ti 0.02 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0173] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0174] Example 28

[0175] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0176] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al 0.03 Fe 0.02 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0177] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0178] Example 29

[0179] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0180] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al 0.03 Cu 0.02 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0181] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0182] Example 30

[0183] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0184] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al0.03 Zn 0.02 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0185] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0186] Example 31

[0187] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0188] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al 0.03 Ga 0.02 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0189] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0190] Example 32

[0191] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0192] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al 0.03 Zr 0.02O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0193] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0194] Example 33

[0195] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0196] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al 0.03 Mo 0.02 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0197] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0198] Example 34

[0199] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0200] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al 0.03 Nb 0.02O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0201] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0202] Example 35

[0203] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0204] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al 0.03 W 0.02 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0205] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0206] Example 36

[0207] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0208] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.9 Co 0.05 Al 0.03 Si 0.02O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0209] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0210] Example 37

[0211] 1. Weigh 0.05g sodium alginate and 0.05g guar gum, put them into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate / guar gum solution;

[0212] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2) was added to the solution in step 1, and stirring was continued for half an hour. 100g of ethanol was added dropwise during the process. The mixture was filtered and dried to obtain the coated high-nickel cathode material. The stirring speed was 500rpm, the drying temperature was 120℃, and the drying time was 8 hours.

[0213] 3. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0214] Comparative Example 1

[0215] 1. Use high-nickel cathode material (LiNi) 0.8 Co 0.1 Al 0.1 O2), residual alkali was tested using acid-base titration, and I was obtained from the XRD results. 003 / 104 An electrode sheet was fabricated using 90g of the high-nickel cathode material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was fabricated using the electrode sheet, and the results are shown in Table 1.

[0216] Comparative Example 2

[0217] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add water to 100g, stir at 300rpm for 1 hour to obtain a 0.1wt% sodium alginate solution;

[0218] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2), mix 5.6g of conductive carbon black as a conductive agent and 5.6g of polyvinylidene fluoride (PVDF) as a binder to form an electrode sheet, and then dry the electrode sheet;

[0219] 3. Take the above electrode sheet, use a coating rod to apply the coating solution prepared in step 1 to the electrode sheet, and dry the coated electrode sheet to obtain an electrode sheet with a coating layer.

[0220] 4. The above electrode sheets were used to make a half cell, and then the test was carried out. The results are shown in Table 1.

[0221] Comparative Example 3

[0222] 1. Weigh 0.1g of sodium alginate, put it into a beaker, add maleic acid and acrylic acid copolymer to 100g, stir at 300rpm for 1 hour to obtain 0.1wt% sodium alginate resin solution;

[0223] 2. Weigh 100g of high-nickel cathode material (LiNi). 0.8 Co 0.1 Al 0.1 O2), put it into a mixer and mix for 30 minutes at a speed of 300 rpm;

[0224] 3. Take the sodium alginate resin solution prepared in step 1 and add it dropwise to the high nickel cathode material in step 2. Heat the mixture to 80°C while stirring and keep it at that temperature for 1 hour to obtain the high nickel cathode material coated with sodium alginate.

[0225] 4. Take the material prepared by the above process, test the residual alkali using acid-base titration, and obtain I based on the XRD results. 003 / 104 An electrode sheet was made using 90g of the prepared material, 5g of conductive carbon black as a conductive agent, and 5g of polyvinylidene fluoride (PVDF) as a binder. A half-cell was then made using the electrode sheet. The results are shown in Table 1.

[0226] Battery performance testing

[0227] The half-cells from Examples 1-37 and Comparative Examples 1-3 were subjected to charge-discharge tests at room temperature and voltages between 2.5 and 4.25 V. The half-cells from the above examples and comparative examples were first subjected to one cycle test at 0.1C at 25°C to determine the initial charge capacity and initial coulombic efficiency. Then, they were subjected to 100 cycles of 1C charge and 5C discharge at 60°C to determine the capacity retention after 100 cycles. The experimental results are shown in Table 1 and below. Figure 1 As shown in the image.

[0228] Table 1. Test results of material physical properties and electrochemical performance.

[0229]

[0230]

[0231] The test results above show that the embodiments of the present invention achieve the following technical effects:

[0232] By comparing the results of Examples 1-37 with those of Comparative Example 1, it can be seen that, compared with Comparative Example 1 which does not have a coating layer covering the positive electrode active material, the batteries in Examples 1-37, which include a coating layer covering the positive electrode active material in the positive electrode composite material, have higher initial coulombic efficiency and significantly higher capacity retention after 100 cycles.

[0233] By comparing the results of Examples 1-4 and 6-37 with those of Comparative Example 1, it can be seen that, when using a high-nickel cathode material, compared with Comparative Example 1 which does not have a coating layer covering the high-nickel cathode material, the high-nickel cathode materials prepared in Examples 1-4 and 6-37, which include a coating layer covering the high-nickel cathode material, have less residual alkali (wt%) on the surface and I 003 / 104 The larger value indicates that the residual alkali on the surface of the high-nickel cathode material in Examples 1-4 and 6-37 is reduced and the lithium-nickel mixing phenomenon is reduced. Moreover, the battery prepared using this cathode composite material has a higher initial coulombic efficiency and a significantly higher capacity retention rate after 100 cycles.

[0234] By comparing the results of Examples 2 and 15 with those of Comparative Example 2, it can be seen that the methods in Examples 2 and 15 of the present invention have a better coating effect on the positive electrode active material than the method of coating the electrode sheet in Comparative Example 2, which improves the initial coulombic efficiency of the battery and significantly improves the capacity retention rate after 100 cycles.

[0235] By comparing the results of Examples 2, 13, 15 and 22 with those of Comparative Example 3, it can be seen that, compared with the method in Comparative Example 3, the methods in Examples 2, 13, 15 and 22 of the present invention have a better coating effect on the positive electrode active material, improve the initial coulombic efficiency of the battery, significantly improve the capacity retention rate after 100 cycles, and reduce the phenomenon of residual alkali and lithium-nickel mixing on the surface of the high-nickel positive electrode material.

[0236] By comparing the results of Examples 1-3 with Example 4 and by comparing the results of Examples 6-8 with Example 9, it can be seen that, based on 100 parts by mass of positive electrode active material, when the amount of coating agent is in the range of 0.01 parts by mass to 2.5 parts by mass, the capacity retention rate after 100 cycles is further improved.

[0237] The battery performance test results above show that the positive electrode composite material of the present invention, the method for preparing the positive electrode composite material, and the positive electrode and lithium-ion secondary battery containing the positive electrode composite material can effectively suppress the side reactions between the positive electrode active material and the electrolyte in the lithium-ion secondary battery, reduce the dissolution of transition metals in the positive electrode active material, prevent the breakage of positive electrode active material particles, and improve the first coulombic efficiency and cycle performance of the lithium-ion secondary battery.

[0238] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a positive electrode composite material, characterized in that, The method includes: First step: Water is added to a coating agent containing one or more of polysaccharide organic polymers, polyvinyl alcohol, and polyacryl alcohol to obtain a first mixture; then the first mixture is stirred to obtain a coating solution; and The second step involves adding the positive electrode active material to the coating solution to obtain a second mixture, then stirring the second mixture and adding an organic solvent during the stirring process to obtain a third mixture. The third mixture is then filtered, and the filtered material is dried to obtain the positive electrode composite material.

2. The method for preparing a positive electrode composite material according to claim 1, characterized in that, In the first step, the stirring speed is in the range of 100-500 rpm and the stirring time is in the range of 1-12 h.

3. The method for preparing a positive electrode composite material according to claim 1, characterized in that, In the first step, based on 100 parts by weight of the coating solution, the amount of the coating agent is in the range of 0.01 parts by weight to 3.5 parts by weight.

4. The method for preparing a positive electrode composite material according to claim 1, characterized in that, In the second step, the stirring speed is in the range of 100-500 rpm.

5. The method for preparing a positive electrode composite material according to claim 1, characterized in that, In the second step, based on the total weight of the second mixture, the content of the positive electrode active material in the second mixture is in the range of 4.0 wt% to 60 wt%.

6. The method for preparing a positive electrode composite material according to claim 1, characterized in that, In the second step, the organic solvent is selected from ethanol, isopropanol, and ethylene glycol.

7. The method for preparing a positive electrode composite material according to claim 1, characterized in that, The amount of organic solvent added is 50%-100% of the mass of the coating solution.

8. The method for preparing a positive electrode composite material according to claim 1, characterized in that, In the second step, the drying temperature is in the range of 80-120°C, and the drying time is in the range of 4-12 hours.

9. The method for preparing a positive electrode composite material according to claim 1, characterized in that, The positive electrode active material comprises LiNi x Co y M z O2 is a high-nickel cathode material, wherein x+y+z=1, 0.8≤x≤1, 0≤y≤0.2, 0≤z≤0.1, and M is selected from one or more of Mn, Al, Mg, Ti, Fe, Cu, Zn, Ga, Zr, Mo, Nb, W and Si.

10. The method for preparing a positive electrode composite material according to claim 1, characterized in that, The polysaccharide organic polymer is selected from one or more of sodium alginate, gum arabic, and guar gum.

11. The method for preparing a positive electrode composite material according to claim 1, characterized in that, Based on 100 parts by weight of the positive electrode active material, the amount of the coating agent is in the range of 0.01 parts by weight to 3.5 parts by weight.

12. A positive electrode composite material, characterized in that, The positive electrode composite material includes: Positive electrode active material; The coating layer covering the positive electrode active material comprises one or more of polysaccharide organic polymers, polyvinyl alcohol, and polyacryl alcohol. The positive electrode composite material is prepared by any one of the methods for preparing positive electrode composite materials according to claims 1 to 11.

13. The positive electrode composite material according to claim 12, characterized in that, The positive electrode active material comprises LiNi x Co y M z O2 is a high-nickel cathode material, wherein x+y+z=1, 0.8≤x≤1, 0≤y≤0.2, 0≤z≤0.1, and M is selected from one or more of Mn, Al, Mg, Ti, Fe, Cu, Zn, Ga, Zr, Mo, Nb, W and Si.

14. The positive electrode composite material according to claim 12 or 13, characterized in that, The polysaccharide organic polymer is selected from one or more of sodium alginate, gum arabic, and guar gum.

15. The positive electrode composite material according to claim 12 or 13, characterized in that, Based on 100 parts by weight of the positive electrode active material, the amount of the coating layer is in the range of 0.01 parts by weight to 3.5 parts by weight.

16. The positive electrode composite material according to claim 12 or 13, characterized in that, The thickness of the coating layer is in the range of 1 nm to 100 nm.

17. A positive electrode for a lithium-ion secondary battery, characterized in that, The positive electrode of the lithium-ion secondary battery comprises the positive electrode composite material according to any one of claims 12 to 16.

18. A lithium-ion secondary battery, characterized in that, The lithium-ion secondary battery includes: positive electrode, Negative electrode, and Diaphragm, The positive electrode is characterized in that it comprises a positive electrode composite material according to any one of claims 12 to 16.

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