A modified lithium battery positive electrode material coated with a polymer and a two-dimensional inorganic compound, and a preparation method and application thereof

Abstract

The application discloses a modified lithium battery positive electrode material coated by a polymer and a two-dimensional inorganic compound, and a preparation method and application thereof. The application adopts a two-dimensional inorganic compound to cooperatively coat an ultra-high nickel positive electrode material with a polymer. The two-dimensional inorganic compound (Ti3C2) has high conductivity, which is beneficial to the rapid transmission of lithium ions and electrons. Meanwhile, the two-dimensional inorganic compound (Ti3C2) acts as an artificial CEI layer to avoid excessive growth of the CEI layer. However, the two-dimensional inorganic compound (Ti3C2) has a lamellar morphology, is easy to aggregate and stack, and the method of the composite polymer makes the two-dimensional inorganic compound more uniform, dense and orderly coated on the surface of the ternary ultra-high nickel material. In addition, the selected polymer has good chemical stability, thermal stability and conductivity, and further improves the cycle stability, capacity and rate performance of the composite ultra-high nickel lithium battery modified positive electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery positive electrode materials, and in particular to a modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound, and a preparation method and application thereof. Background Art

[0002] Fuel-powered vehicles are being phased out in favor of environmentally friendly electric vehicles (EVs) with low greenhouse gas emissions. However, they have not yet gained enough market share to replace internal combustion engine vehicles (ICEVs). This is mainly due to the lack of satisfactory performance of electric vehicles. The driving range, charge rate capability, power performance and life cycle characteristics are mainly determined by lithium-ion batteries (LIBs). In batteries, the positive electrode is one of the most important components because it mainly determines the performance and price of lithium-ion batteries. Currently, Li[Ni x Co y (Mn or Al) 1-x-y ]O2 (Mn=NCM or Al=NCA) cathode materials are used as typical cathodes in electric vehicle batteries, accounting for more than 65%-75% of electric vehicle batteries. However, due to the relatively low nickel content of the current layered oxide cathode series, they can only extract a limited reversible capacity (210 mAh g -1 ), which limits the range of driving electric vehicles.

[0003] In order to achieve higher energy density, many studies have focused on increasing the average Ni content in NCM or NCA cathodes to more than 90%. Increasing the Ni ratio can maximize the reversible capacity of the positive electrode; however, the insertion and extraction of a large number of lithium ions will cause structural collapse, and the cycle life and thermal safety will be severely affected by the rapid deterioration. These reliability issues are caused by the inherent structural and chemical instability of high-nickel layered positive electrodes. With the increase of nickel content in the cathode, the degree of anisotropic unit cell volume change gradually increases, leading to the formation of intergranular cracks and intragranular cracks. Microcracks provide channels for electrolyte penetration and increase the internal surface area exposed to the electrolyte, accelerating the unstable Ni 4+ Parasitic reactions between ions and the electrolyte form a NiO-like rock salt layer around the particles. This inert layer severely impacts the transport pathways for lithium ions, compromising the overall battery performance. Furthermore, this structural degradation can trigger oxygen evolution within the main structure, causing structural degradation, leading to battery expansion, and potentially compromising battery safety. Summary of the Invention

[0004] In response to the problems of short cycle life and poor high-rate performance of ultra-high nickel ternary materials, the purpose of the present invention is to provide a modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound, as well as its preparation method and application, so as to solve the problems of cycle stability, structural stability, capacity attenuation and rate performance of the positive electrode materials of lithium-ion batteries in the prior art.

[0005] In order to solve the problems of the prior art, the technical solution adopted by the present invention is:

[0006] A method for modifying a lithium battery positive electrode material by composite coating with a polymer and a two-dimensional inorganic compound comprises the following steps:

[0007] (1) Dispersing the ultra-high nickel cathode material in 10-30 ml of anhydrous ethanol and fully dispersing it under the action of ultrasound to form a cathode dispersion;

[0008] (2) Grinding the pre-freeze-dried Ti3C2 and slowly adding it to the cathode dispersion to obtain a mixed dispersion, with the addition amount being 1-5 wt%;

[0009] (3) slowly adding the polymer to the mixed dispersion in step (2) to a final concentration of 1-3%, placing it on a stirring heating table until the solvent evaporates, and drying to obtain a composite-coated ultra-high nickel material;

[0010] (4) The ultra-high nickel material after composite coating is centrifuged, excess residual lithium and coating material are cleaned, and then sieved to obtain a modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound.

[0011] As an improvement, in step (1), the chemical formula of the ultra-high nickel positive electrode material is LiMO2, wherein M refers to NixCoyMnz, wherein x≥0.6-0.9, y+z≤0.4, and x+y+z=1, 0 <x<1,0<y<1,0<z<1。

[0012] As an improvement, the ultra-high nickel positive electrode material is LiNi 0.9 Co 0.05 Mn 0.05 O2.

[0013] As an improvement, in step (1), the frequency of the ultrasound is 20 KHz, the ultrasound time is 20-30 min, and the action temperature of the ultrasound is below 25°C.

[0014] As an improvement, in step (2), the Ti3C2 is nano-scale multi-layered, and the thickness after grinding is less than 50 nm, and the speed of slowly adding the ground Ti3C2 is 1 mg / min.

[0015] As an improvement, in step (3), the final concentration of the polymer solution is 1%-2%, the temperature of the stirring heating table is 35° C., the stirring speed is 380 rpm, and the stirring time is controlled within 6 h.

[0016] As an improvement, in step (3), the polymer is polymethyl methacrylate (PMMA), polyethyleneimine (PEI), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE) or polyethylene glycol (PEG).

[0017] As an improvement, in step (4), the centrifugal speed is 5000 rpm and the centrifugal time is 5 min.

[0018] As an improvement, in step (5), the sieve sizes are 50, 100, and 300 meshes, respectively.

[0019] Any of the above-mentioned modified lithium battery positive electrode materials compositely coated with a polymer and a two-dimensional inorganic compound is characterized in that the modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound includes an ultra-high nickel positive electrode material, and a modified layer composed of a polymer and a two-dimensional inorganic compound (Ti3C2) coated on the ultra-high nickel positive electrode material, wherein the thickness of the modification is 10 to 50 nm.

[0020] Application of the modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound in lithium-ion batteries.

[0021] Ultra-high nickel ternary positive electrode materials have a large theoretical specific capacity and high energy density, but as the nickel content increases, their cycle stability and structural stability will decrease. The two-dimensional inorganic compound (Ti3C2) itself has high conductivity. It is used as a coating layer to coat the surface of the ultra-high nickel material, thereby improving the capacity of the ultra-high nickel ternary positive electrode material at high rates. At the same time, the two-dimensional inorganic compound (Ti3C2) serves as an intermediate layer to reduce the loss of active materials due to severe side reactions and improve the cycle life of the material. The polymer polyvinyl alcohol (PVA) synergistically enhances the adhesion between the two-dimensional inorganic compound and the ultra-high nickel ternary material, making the two-dimensional inorganic compound more uniformly, densely and orderly coated on the surface of the ultra-high nickel ternary material. In addition, the polymer itself has good chemical stability, thermal stability and conductivity, which further improves the cycle stability and capacity of the composite modified positive electrode material.

[0022] Beneficial effects:

[0023] Compared with the existing technology, the present invention provides a modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound, and a preparation method and application thereof. Based on the sol-gel method combined with the action of an ultrasonic external field, polyvinyl alcohol (PVA) and a two-dimensional inorganic compound (Ti3C2) are compositely coated on the surface of an ultra-high nickel ternary material as the core to reduce the loss of active materials due to severe side reactions and improve the cycle life of the material. At the same time, the high conductivity of the two-dimensional inorganic compound (Ti3C2) is used to accelerate the lithium ion deintercalation process to improve the high-rate performance of the material. The obtained modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound effectively improves the cycle life and high-rate performance of the positive electrode material.

[0024] In addition, the present invention utilizes polyvinyl alcohol (PVA) with good chemical stability, thermal stability, and electrical conductivity to further improve the cycle stability and capacity of the composite modified cathode material. Simultaneously, during the coating process, the two-dimensional inorganic compound (Ti3C2) forms a certain Ti-doped layer on the surface of the ultra-high nickel ternary cathode, ensuring the structural stability of the ultra-high nickel ternary cathode material and thus ensuring stable capacity during the cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 XRD patterns of modified lithium battery positive electrode materials compositely coated with polymers and two-dimensional inorganic compounds prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 5;

[0026] Figure 2 The polyvinyl alcohol (PVA) & two-dimensional inorganic compound (Ti3C2) / composite ultra-high nickel material (Li[Ni 0.9 Co 0.05 Mn 0.05 ]O2@Ti3C2&PVA) energy spectrum;

[0027] Figure 3 The polyvinyl alcohol (PVA) & two-dimensional inorganic compound (Ti3C2) / composite ultra-high nickel material (Li[Ni 0.9 Co 0.05 Mn 0.05 ]TEM image of O2@Ti3C2&PVA);

[0028] Figure 4 Cycle diagrams of modified lithium battery positive electrode materials compositely coated with polymers and two-dimensional inorganic compounds prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 5;

[0029] Figure 5 These are rate diagrams of modified lithium battery positive electrode materials compositely coated with polymers and two-dimensional inorganic compounds prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 5. DETAILED DESCRIPTION

[0030] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0031] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0032] An embodiment of the present invention provides a method for modifying lithium battery positive electrode materials by composite coating with polymers and two-dimensional inorganic compounds, including an ultra-high nickel ternary positive electrode Li[Ni0.9Co0.05Mn0.05]O2@Ti3C2&PVA material compositely coated with polymer polyvinyl alcohol (PVA) and a two-dimensional inorganic compound (Ti3C2).

[0033] Example 1

[0034] The first ultra-high nickel (Li[Ni 0.9 Co 0.05 Mn 0.05 ]O2) The amount of the ternary positive electrode material added is 3g, and the amount of the two-dimensional inorganic compound (Ti3C2) added is 1wt%.

[0035] Under the action of an ultrasonic field with a frequency of 20KHz, 3g of high nickel ternary cathode material (Li[Ni 0.9 Co 0.05 Mn 0.05 ]O2), control the high nickel ternary material Li[Ni 0.9 Co 0.05 Mn 0.05 ]O2 was added at a rate of 1 g / min. After the addition was completed, ultrasonication was continued for 20 min to fully disperse it. The temperature was controlled at 25°C to obtain solution 1.

[0036] Transfer solution 1 to a stirring heating table and continue stirring for 0.5 h, controlling the temperature at 35 °C and the stirring speed at 380 rpm.

[0037] 30 mg (1 wt%) of freeze-dried two-dimensional inorganic compound (Ti3C2) was placed in a mortar and ground thoroughly into fine flake particles, i.e., dispersed nanoscale multilayers with a thickness of less than 50 nm. To ensure thorough grinding, 3 ml of deionized water was added during grinding, and the grinding time was 30 minutes. The temperature was controlled within 25°C during grinding.

[0038] The ground two-dimensional inorganic compound (Ti3C2) is slowly added to solution 1 to obtain a mixed dispersion, thereby obtaining solution 2.

[0039] A polyvinyl alcohol (PVA) solution with a concentration of 1% was slowly added to solution 2, and the amount of the polyvinyl alcohol (PVA) solution was controlled to be 3 ml to form solution 3.

[0040] Solution 3 was stirred on a stirring heating table for 6 h until the solvent evaporated, the temperature was controlled at 35° C., the stirring speed was 380 rpm, and after drying, a mixed material that had not yet been completely coated was obtained. The mixed material was placed in a vacuum oven at 60° C. for drying, and the mixed material that had not yet been completely coated was obtained as the oven cooled.

[0041] The obtained mixed material that has not yet been coated is centrifugally cleaned at a centrifugal speed of 5000rpm for 5 minutes to remove residual lithium and residual coating on the surface. After the centrifugal cleaning is completed, it is placed in a 60°C vacuum oven for drying, and the mixed material that has not yet been coated is obtained as the oven cools. It is then sieved, and the sieve sizes are 50 mesh, 100 mesh, and 300 mesh, respectively. After the sieving is completed, a polymer and a two-dimensional inorganic compound composite coated modified lithium battery positive electrode material is obtained, that is, a high nickel ternary composite positive electrode Li[Ni 0.9 Co 0.05 Mn 0.05 ]O2@Ti3C2&PVA-1% material.

[0042] Example 2

[0043] The addition amount of the two-dimensional inorganic compound (Ti3C2) was changed to 3wt%, and the rest was the same as in Example 1. Finally, an ultra-high nickel ternary composite positive electrode Li[Ni 0.9 Co 0.05 Mn 0.05 ]O2@Ti3C2&PVA-3% material.

[0044] Example 3

[0045] The addition amount of the two-dimensional inorganic compound (Ti3C2) was changed to 5wt%, and the rest was the same as in Example 1. Finally, a high nickel ternary composite positive electrode Li[Ni 0.9 Co 0.05 Mn 0.05 ]O2@Ti3C2&PVA-5% material.

[0046] The amount of two-dimensional inorganic compound (Ti3C2) added directly affects the coating effect. When the Ti3C2 coating amount is too low, the protective layer formed on the cathode material surface may be discontinuous or incomplete. This will result in significant contact between the electrolyte and the electrode material, failing to effectively prevent surface erosion and structural damage to the electrode material. Due to the insufficient protective layer, the battery may experience high interfacial impedance during charge and discharge, directly affecting the battery's charging efficiency and cycle life. Furthermore, if the coating layer fails to effectively cover the surface of the high-nickel material, nickel may dissolve, reducing the battery's chemical stability and safety. When the Ti3C2 coating amount is too high, while it more effectively blocks contact between the electrolyte and the electrode material, an excessively thick coating layer may hinder lithium ion migration. Excessive coating material may reduce the activity of the electrode material by hindering effective lithium ion exchange between the electrode surface and the electrolyte. An excessively thick protective layer may also increase the battery's internal resistance, affecting its energy density and power output. The optimal coating amount should be able to form a uniform, continuous protective layer without affecting the electrochemical activity of the material itself. An appropriate amount of Ti3C2 coating can effectively isolate the contact between the electrode material and the electrolyte, reducing interfacial corrosion during charge and discharge, thereby improving the battery's cycle performance and electrochemical stability. At the same time, an appropriate coating amount also helps provide more conductive paths and improve the battery's rate performance.

[0047] It can be seen from the above results that when the addition amount of the two-dimensional inorganic compound (Ti3C2) in the present invention is 3wt%, the structure of the obtained material is stable and the material is excellent.

[0048] Comparative Example 1

[0049] The same procedures as in Example 1 were followed except that 300 mg (10 wt %) of a two-dimensional inorganic compound (Ti3C2) was added for coating modification.

[0050] If too much two-dimensional inorganic compound (Ti3C2) is added, the ultra-high nickel ternary cathode material Li[Ni 0.9 Co 0.05 Mn 0.05 ]O2 surface accumulates a large amount of two-dimensional inorganic compounds (Ti3C2), which makes the lithium ion transmission path excessively long, causing serious obstruction to the deintercalation process and resulting in a significant increase in impedance. At the same time, since the concentration and addition amount of polyvinyl alcohol (PVA) are much smaller than the amount of two-dimensional inorganic compounds (Ti3C2), this will make the two-dimensional inorganic compounds (Ti3C2) unable to fit tightly on the ultra-high nickel ternary positive electrode material Li[Ni 0.9 Co 0.05 Mn 0.05]The surface of O2 causes the two-dimensional inorganic compound (Ti3C2) to accumulate or disperse in the electrode piece, which reduces the proportion of active materials in the electrode, resulting in a decrease in capacity and an increase in rate performance, thus failing to meet performance requirements.

[0051] Comparative Example 2

[0052] The same procedures as in Example 1 were followed except that the concentration of polyvinyl alcohol (PVA) added was changed from 1% to 5%.

[0053] If the concentration of polyvinyl alcohol (PVA) is too high, it may cause the high nickel ternary cathode Li[Ni 0.9 Co 0.05 Mn 0.05 ] An overly thick polymer coating is formed on the surface of the O2 material. Due to the general conductivity of the polymer, an overly thick polymer layer will reduce the conductivity of the surface of the ultra-high nickel positive electrode material and increase its interfacial transfer impedance (Rct), which will seriously hinder the insertion and extraction process of lithium ions on the positive electrode surface, thereby affecting the overall rate performance and capacity of the material, resulting in problems such as performance not meeting the requirements.

[0054] Comparative Example 3

[0055] The same procedures as in Example 2 were followed except that only 90 mg (3 wt %) of the two-dimensional inorganic compound (Ti3C2) was added and polyvinyl alcohol (PVA) was not added.

[0056] If only the two-dimensional inorganic compound (Ti3C2) is added during the coating process without the auxiliary coating agent (polyvinyl alcohol (PVA), the coating effect will not meet the expectations. The two-dimensional inorganic compound (Ti3C2) may be free from the surface of the ultra-high nickel cathode material, causing the coating to fail, thereby failing to achieve the desired effect of improving the ultra-high nickel cathode material's rate capability, capacity, and interfacial stability during cycling.

[0057] Comparative Example 4

[0058] Except for not adding the two-dimensional inorganic compound (Ti3C2) and polyvinyl alcohol (PVA), the remaining steps are the same as those in Example 1, that is, the bare high nickel ternary positive electrode material Li[Ni 0.9 Co 0.05 Mn 0.05 ]O2.

[0059] If the ultra-high nickel ternary cathode material is not subjected to any coating modification, its capacity will drop rapidly and the voltage decay will accelerate during long-term cycling at high voltage. 4+The high chemical activity of the battery will react with the electrolyte, causing structural degradation, dissolution of transition metal elements, and escape of oxygen atoms to produce oxygen, which will cause serious consequences such as high temperature, flatulence, and failure of the battery, making it unable to achieve the expected life.

[0060] Figure 1 These are the XRD spectra of Example 1, Example 2, Comparative Example 1, Comparative Example 4, and the two-dimensional inorganic compound (Ti3C2). It can be observed that with the increase of the coating content of the two-dimensional inorganic compound (Ti3C2), the characteristic peak of the two-dimensional inorganic compound (Ti3C2) in the XRD spectrum is also continuously enhanced. The uncoated Comparative Example 4 has no characteristic peak of the two-dimensional inorganic compound (Ti3C2). The amount of two-dimensional inorganic compound (Ti3C2) added in Comparative Example 1 is the largest, and its characteristic peak of the two-dimensional inorganic compound (Ti3C2) is also stronger. At the same time, Example 1, Example 2, Comparative Example 1, and Comparative Example 4 show typical structural characteristics of LiNiO2 positive electrode materials, and their diffraction peaks are characteristic peaks of a-NaFeO2 layered structure, belonging to the hexagonal system, R-3m space group, and the two pairs of diffraction peaks (006) / (012) and (018) / (110) are obviously split, forming a better layered structure. The diffraction peaks of the materials before and after coating do not change significantly, and there are no impurity peaks. The peak intensity ratio of (003) to (104) is similar to that of the layered positive electrode material Li + / Ni 2+ The peak intensity ratio I(003) / I(104) is related to the degree of cation mixing. The larger the peak intensity ratio I(003) / I(104), the lower the degree of cation mixing. The peak intensity ratio I(003) / I(104) of Comparative Example 1 and Comparative Example 4 is smaller than that of Example 1 and Example 2, indicating that the Li + / Ni 2+ This is because during the coating process, the Ti element in the two-dimensional inorganic compound (Ti3C2) will be doped into the surface of the ultra-high nickel ternary positive electrode material, inhibiting the Ni 2+ The generation of Li + / Ni 2+ However, with the increase of two-dimensional inorganic compounds (Ti3C2), the doping of Ti will also increase accordingly, which will aggravate the Li+ / Ni 2+ Mixed arrangement.

[0061] Figure 2-3 The EDS and TEM images of Example 2 clearly show that with the help of 1% polyvinyl alcohol (PVA), the two-dimensional inorganic compound (Ti3C2) is tightly and evenly coated on the surface of the ultra-high nickel ternary material. The EDS image also shows that the Ti element is doped into the bulk of the ultra-high nickel ternary material during the coating process, and these surface two-dimensional inorganic compounds (Ti3C2) and polyvinyl alcohol (PVA) are successfully coated on the ultra-high nickel ternary material.

[0062] Figure 4 It is a cycle diagram of Example 1, Example 2, Comparative Example 1, and Comparative Example 4 at 25°C and 2.7-4.5V. Among them, the capacity retention rates of Example 1 and Example 2 are 83.75% and 96.75%, respectively, showing excellent cycle retention rates and high capacity improvement. This is because the two-dimensional inorganic compound (Ti3C2) serves as an excellent lithium ion and electron transport layer, which can ensure that the lithium ion extraction and embedding process is smooth, thereby ensuring the capacity improvement. At the same time, the two-dimensional inorganic compound (Ti3C2) has excellent chemical stability, which can ensure that the ultra-high nickel cathode material is not corroded by the electrolyte, thereby ensuring the integrity of the surface structure of the material.

[0063] Figure 5 The rate graphs of Example 1, Example 2, Comparative Example 1, and Comparative Example 4 at 25°C and 2.7-4.5V are shown. Among them, under the high rate condition of 10C, Example 1 and Example 2 show 130mAh·g -1 and 148mAh·g -1 The capacity of Comparative Example 1 and Comparative Example 4 is only 110 mAh g -1 and 118mAh·g -1 . This is because at high rates, the reaction will be more rapid and cannot be fully carried out, which will cause the side reactions to intensify and the lithium ions to be unable to be fully embedded and removed, resulting in lower capacity. However, the presence of the two-dimensional inorganic compound (Ti3C2) can ensure that the ultra-high nickel material can still exert its capacity at high rates. The specific addition ratio further promotes the use of capacity. As shown in Example 2, after forming a suitable coating amount of two-dimensional inorganic compound (Ti3C2) and a polyvinyl alcohol (PVA) coating layer at a suitable concentration, it will be beneficial to the transmission of lithium ions and ensure that the capacity is fully utilized.

[0064] The above description is merely a specific embodiment of the present application. Any person skilled in the art may easily conceive of variations or substitutions within the technical scope disclosed in this application, and such variations or substitutions shall be within the scope of protection of this application. The scope of protection of this application shall be subject to the scope of protection of the claims.

Claims

1. A method for preparing a modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound, characterized in that: The following steps are involved: (1) Disperse the ultra-high nickel cathode material in 10-30 mL of anhydrous ethanol and fully disperse it under the action of ultrasound to form a cathode dispersion liquid, wherein the ultra-high nickel cathode material is LiNi 0.9 Co 0.05 Mn 0.05 O2; (2) Grinding the pre-freeze-dried Ti3C2 and slowly adding it to the positive electrode dispersion to obtain a mixed dispersion, wherein the amount of the added Ti3C2 is 1-5 wt%, wherein the Ti3C2 is nano-scale multilayered and the thickness after grinding is less than 50 nm, and the speed of slowly adding the ground Ti3C2 is 1 mg / min; (3) Prepare a polyvinyl alcohol solution with a concentration of 1% and slowly add it to the mixed dispersion in step (2), controlling the amount of the polyvinyl alcohol solution to 3 mL, and then place it on a stirring heating table until the solvent evaporates, and dry it to obtain the composite coated ultra-high nickel material; (4) The ultra-high nickel material after composite coating is centrifuged to clean the excess residual lithium and coating material, and then sieved to obtain a modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound.

2. The method for preparing a modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound according to claim 1, characterized in that: In step (1), the frequency of the ultrasound is 20 kHz, the ultrasound time is 20-30 min, and the action temperature of the ultrasound is 25 °C.

3. The method for preparing a modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound according to claim 1, characterized in that: In step (3), the temperature of the stirring heating table is 35° C., the stirring speed is 380 rpm, and the stirring time is controlled within 6 h.

4. The method for preparing a modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound according to claim 1, characterized in that: In step (4), the centrifugal speed is 5000 rpm and the centrifugal time is 5 min.

5. The method for preparing a modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound according to claim 1, characterized in that: In step (4), the sieve sizes are 50, 100, and 300 meshes, respectively.

6. A modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The modified lithium battery positive electrode material compositely coated with a polymer and a two-dimensional inorganic compound includes an ultra-high nickel positive electrode material and a modification layer composed of a polymer and a two-dimensional inorganic compound coated on the ultra-high nickel positive electrode material, wherein the thickness of the modification is 10 to 50 nm.

7. Application of the modified lithium-ion cathode material compositely coated with the polymer and two-dimensional inorganic compound according to claim 6 in lithium-ion batteries.

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