Double-layer-coated lithium-ion positive electrode material, and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of lithium batteries. Disclosed are a double-layer-coated lithium-ion positive electrode material, and a preparation method therefor and the use thereof. The double-layer-coated lithium-ion positive electrode material sequentially comprises a positive electrode active material, an ion transport coating layer and an interstitial inert material coating layer at a mass ratio of 100:(0.05-5):(0.02-3) from inside to outside, wherein the components of the ion transport coating layer comprise a first component and a second component, the first component comprising at least one of Li2CO3 and Li2O, and the second component being a lithium-containing metallic compound; and the interstitial inert material coating layer is at least one of a non-Al metallic oxide and an Al-containing compound. The interstitial inert material coating layer can play a role in protecting the surface of the material during the process of cycling; moreover, since the interstitial inert material coating layer is in an interstitial state, the transport of lithium ions is not hindered, the impedance of the material is not significantly increased, ion dissolution from the surface of the material is significantly reduced, and the performance of the positive electrode material is significantly improved.

Description

A double-layer coated lithium ion positive electrode material and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to Chinese patent application number 2024103667627, filed with the Patent Office of China on March 28, 2024, entitled “A double-layer coated lithium ion positive electrode material, its preparation method and application”, the entire contents of which are incorporated by reference into this disclosure. Technical Field

[0003] The present disclosure relates to the technical field of lithium batteries, and in particular to a double-layer coated lithium ion positive electrode material and a preparation method and application thereof. Background Art

[0004] Lithium-ion batteries, with their ultra-high energy density and extremely long lifespan, are increasingly replacing fossil fuels and gaining wider use in daily life. Mobile phones and electric vehicles are particularly integral to our lives. Therefore, for safety reasons, lithium-ion battery stability must meet even higher standards. Cathode materials are a crucial component of lithium-ion batteries, and improvements in these materials can significantly impact the performance of the finished battery. Therefore, there is an urgent need to improve the safety of lithium-ion batteries by addressing the cathode material preparation process and developing highly safe lithium-ion batteries.

[0005] Conventionally prepared cathode materials have a coating on their surface that can slow down side reactions between the electrolyte and the material during lithium battery cycling, improving the material's cycling performance. The efficient and energy-saving construction of lithium ion surface coatings has attracted extensive research. However, it is currently difficult to completely and evenly coat the surface with the coating material. Low coating amounts can expose the uncoated substrate to the electrolyte. However, thicker coatings can severely hinder lithium ion transport, significantly increasing the material's impedance. Research is ongoing on new coating methods to further enhance lithium battery performance.

[0006] In view of this, the present disclosure is proposed.

[0007] Public content

[0008] The purpose of the present disclosure is to provide a double-layer coated lithium ion positive electrode material, a preparation method thereof, and applications thereof.

[0009] The present disclosure is achieved as follows:

[0010] In a first aspect, the present disclosure provides a double-layer coated lithium ion positive electrode material, which comprises, from the inside to the outside, a positive electrode active material, an ion transport coating layer, and a gap-shaped inert material coating layer in a mass ratio of 100:0.05-5:0.02-3;

[0011] The composition of the ion transport coating layer includes a first component and a second component, the first component includes at least one of Li2CO3 and Li2O, and the second component is a lithium-containing metal compound;

[0012] The interstitial inert material coating layer is at least one of a non-Al metal oxide and an Al-containing compound.

[0013] In an optional embodiment, the mass of the ion transport coating layer accounts for 0.1%-0.3% of the total mass of the positive electrode active material, and the mass of the interstitial inert material coating layer accounts for 0.05%-0.15% of the total mass of the positive electrode active material.

[0014] In an optional embodiment, the lithium-containing metal compound includes at least one of LiAlO2, LiY2O3, Li2ZrO3 and Li2TiO3.

[0015] In an optional embodiment, the interstitial shapes in the interstitial inert material coating layer are mesh-shaped.

[0016] In an optional embodiment, the non-Al metal oxide includes at least one of La2O3 and ZrO2;

[0017] Preferably, the Al-containing compound includes at least one of Al2O3, LiAlO2, and Al(OH)3.

[0018] In a second aspect, the present disclosure provides a method for preparing a double-layer coated lithium ion positive electrode material as described in any one of the aforementioned embodiments, comprising:

[0019] ball-milling a positive electrode active material and an ion transport coating layer raw material, and sintering to obtain a first sintered material having an ion transport coating layer coated on the surface of the positive electrode active material, wherein the ion transport coating layer raw material comprises a metal oxide;

[0020] Mixing a raw material for an interstitial inert material coating layer, a coating additive, and a solvent to form a mixed solution, wherein the raw material for the interstitial inert material coating layer includes a compound containing a metal element;

[0021] The first sintered material is added to the mixed solution, the pH is adjusted to 11-12, stirred and mixed, dried, and sintered to obtain a second sintered material having an interstitial inert material coating layer on the surface of the ion transport coating layer, i.e., a double-layer coated lithium ion positive electrode material.

[0022] In an optional embodiment, the amount of the coating additive is 0.1%-2% of the total mass of the positive electrode active material.

[0023] In an optional embodiment, the coating additive includes at least one of hydroxypropyl methylcellulose, gelatin, starch and polyethylene glycol.

[0024] In an optional embodiment, the sintering temperature of the first sintering material and the second sintering material are both 700-900°C.

[0025] In a third aspect, the present disclosure provides a double-layered lithium-ion positive electrode material as described in any of the aforementioned embodiments or a double-layered lithium-ion positive electrode material prepared by the preparation method of the double-layered lithium-ion positive electrode material as described in any of the aforementioned embodiments in the preparation of lithium-ion batteries.

[0026] The present disclosure has the following beneficial effects:

[0027] The double-layer coated lithium ion positive electrode material provided by the present disclosure is first coated with an ion transport coating layer on the surface of the positive electrode active material, and then coated with an interstitial inert material coating layer on the surface of the ion transport coating layer, wherein the interstitial inert material coating layer can play a role in protecting the surface of the material during the cycle, and at the same time, due to its interstitial state, it will not prevent the transmission of lithium ions, so that the material impedance will not increase significantly. The coating layer can also significantly reduce the ion dissolution from the surface of the positive electrode material, preventing the negative impact of ion dissolution on the battery. The preparation method of the double-layer coated lithium ion positive electrode material provided by the present disclosure is to introduce a coating additive to achieve the interstitial inert material coating layer raw material under the adhesion effect of the coating additive, which can be interstitially attached and fixed on the surface of the first sintered material without displacement, and the coating material is more tightly combined with the substrate during sintering, so as to achieve good adhesion of the interstitial inert material coating layer, effectively avoiding contact between the positive electrode active material and the electrolyte, while also ensuring the transmission of lithium ions, and the cycle performance of the positive electrode material is better. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0029] FIG1 is a SEM image of a double-layer coated lithium ion positive electrode material provided in an embodiment of the present disclosure;

[0030] FIG2 is a SEM image of another double-layer coated lithium ion positive electrode material provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0031] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0032] The present disclosure provides a double-layer coated lithium ion positive electrode material, which includes a positive electrode active material, an ion transport coating layer and an interstitial inert material coating layer.

[0033] In the present disclosure, an ion transport coating layer is configured to facilitate lithium ion transport. The ion transport coating layer is coated on the surface of the positive electrode active material and comprises a first component and a second component. The first component comprises at least one of Li2CO3 and Li2O, and the second component is a lithium-containing metal compound; the lithium-containing metal compound comprises at least one of LiAlO2, LiY2O3, Li2ZrO3, and Li2TiO3. The first component is an unavoidable residual substance remaining during the preparation of the positive electrode active material, while the second component is primarily formed by the metal compound reacting with lithium and intercalating lithium. The second component is the functional component of the ion transport coating layer primarily configured to facilitate lithium ion transport. The mass of the ion transport coating layer accounts for 0.05% to 5% of the total mass of the positive electrode active material, preferably 0.1% to 0.5% of the total mass of the positive electrode active material. By limiting the mass proportion of the ion transport coating layer, the present disclosure achieves good coating while also providing excellent lithium ion transport capabilities.

[0034] The interstitial inert material coating layer is coated as the outermost layer, and is coated on the surface of the ion transport coating layer. The interstitial inert material coating layer can effectively prevent the positive electrode active material from being exposed to the electrolyte; at the same time, since the interstitial inert material coating layer is an interstitial coating, it will not hinder the transmission of lithium ions. In the present disclosure, the interstitial inert material coating layer is at least one of a non-Al metal oxide and an Al-containing compound. The non-Al metal oxide includes at least one of La2O3 and ZrO2; the Al-containing compound includes at least one of Al2O3, LiAlO2, and Al(OH)3. Since the state of the material formed during the coating process is uncertain, it is speculated from the raw materials that Al2O3 is mainly formed, and LiAlO2 material may be formed. Some moisture absorption may form Al(OH)3. The shapes of the gaps in the interstitial inert material coating layer are various, for example, it can be a mesh, spaced dots, strips, etc. The mass of the interstitial inert material coating layer accounts for 0.02% to 3% of the total mass of the positive electrode active material; preferably, the mass of the interstitial inert material coating layer accounts for 0.04% to 0.2% of the total mass of the positive electrode active material.

[0035] In the present disclosure, a layer of interstitial inert material coating is applied to the surface of the ion transport coating. This coating is distributed interstitially on the material surface and, after a sintering step, is tightly bonded to the substrate. This protects the material surface during cycling. Furthermore, due to its interstitial state, it does not impede lithium ion transport, preventing a significant increase in material impedance. This coating also significantly reduces ion dissolution from the positive electrode material surface, preventing the negative impact of ion dissolution on the battery.

[0036] In addition, the present disclosure provides a method for preparing the above-mentioned double-layer coated lithium ion positive electrode material, which comprises the following steps:

[0037] S1. Ball-milling the positive electrode active material and the raw material for the ion transport coating layer, and sintering to obtain a first sintered material having the ion transport coating layer coated on the surface of the positive electrode active material, wherein the raw material for the ion transport coating layer comprises a metal oxide, including but not limited to Al2O3, Y2O3, La2O3, ZrO2, and TiO2. During the ball-milling process with the positive electrode active material, the above-mentioned metal oxides can achieve lithium ion embedding, and after sintering at a sintering temperature of 700-900°C, a lithium-containing metal compound (at least one of LiAlO2, LiY2O3, Li2ZrO3, and Li2TiO3) can be formed, which serves as the ion transport coating layer.

[0038] S2. Mixing a raw material for the interstitial inert material coating layer, a coating additive, and a solvent to form a mixed solution, wherein the raw material for the interstitial inert material coating layer includes a compound containing a metal element.

[0039] The amount of the coating additive is 0.1% to 0.3% of the mass of the raw material of the interstitial inert material coating layer. The coating additive includes at least one of hydroxypropyl methylcellulose, gelatin, starch and polyethylene glycol.

[0040] In the present disclosure, by pre-mixing the raw material of the interstitial inert material coating layer and the coating additive, it is advantageous for the subsequent coating additive to coat the raw material of the interstitial inert material coating layer on the surface of the first sintered material.

[0041] S3. Add the first sintered material to the mixed solution, adjust the pH to 11-12, stir and mix, dry, and sinter to obtain a second sintered material having an interstitial inert material coating layer on the surface of the ion transport coating layer, i.e., a double-layer coated lithium ion positive electrode material.

[0042] In the present disclosure, by adjusting the pH value to 11-12, the adhesion effect of the coating additive is more favorable under alkaline conditions. Under the action of the coating additive, the interstitial inert material coating layer raw material can be fixed on the surface of the first sintered material without displacement. However, due to the small amount of coating additive, it can only be attached to the surface gap of the first sintered material. When sintered at a subsequent sintering temperature of 700-900°C, the coating material is more tightly combined with the substrate, which can play a role in protecting the surface of the material during the cycle. At the same time, due to the state of its gaps, it will not hinder the transmission of lithium ions, so that the material impedance will not increase significantly. This coating layer can also significantly reduce the dissolution of ions on the surface of the positive electrode material, preventing the negative impact of ion dissolution on the battery.

[0043] In addition, the present disclosure also provides the use of the above-mentioned double-layer coated lithium ion positive electrode material in the preparation of lithium ion batteries, and the lithium ion battery prepared therefrom has good cycle performance.

[0044] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0045] In the first embodiment, this embodiment provides a double-layer coated lithium ion positive electrode material, the preparation method of which is as follows:

[0046] S1: 1 kg of lithium cobalt oxide semi-finished material, 4 g of Y2O3 and 2 g of TiO2, raw materials for the ion transport coating layer, were placed in a ball mill and mixed at a ball mill speed of 25 Hz for 3 hours to obtain a first mixed material; the first mixed material was sintered at 800°C for 12 hours to obtain a first sintered material;

[0047] S2: Add 10 g of aluminic acid as Al raw material to 2 L of deionized water solution, add 2 g of hydroxypropyl methylcellulose (HPMC) as coating additive, and stir for 10 min to obtain a mixed solution;

[0048] S3: Add the first sintering material to the mixed solution, adjust the pH to 12, continue stirring for 20 minutes, filter and dry to obtain the second mixed material, and sinter at 800°C for 8 hours to obtain a double-layer coated lithium battery positive electrode material.

[0049] After testing, it was found that the core layer of the double-layer coated lithium battery positive electrode material is lithium cobalt oxide, and its surface is coated with an ion transport coating layer with a mass percentage of about 0.3%. The ion transport coating layer contains Li2CO3, Li2O, LiYO2 and Li4Ti5O, and the surface of the ion transport coating layer is coated with an interstitial inert material coating layer Al2O3 with a mass percentage of about 0.15%.

[0050] Please refer to FIG. 1 . It can be seen from FIG. 1 that the interstitial coating layer is coated on the surface of the lithium cobalt oxide material in a grid shape.

[0051] The second embodiment and the third embodiment are basically the same as the first embodiment, and the only difference is that the amount of the raw material for the ion transport coating layer and the raw material for the interstitial inert material coating layer is different.

[0052] In the second embodiment, the amount of Y2O3 added as the raw material for the ion transport coating layer is 2g, the amount of TiO2 added is 1g, and the amount of aluminate added is 5g. As shown in Figure 2, after testing, the core layer of the double-layer coated lithium battery positive electrode material is lithium cobalt oxide, and its surface is coated with an ion transport coating layer with a mass fraction of approximately 0.15%. The ion transport coating layer contains Li2CO3, Li2O, LiYO2, and Li4Ti5O. The surface of the ion transport coating layer is coated with an interstitial inert material coating layer with a mass fraction of approximately 0.08% Al2O3.

[0053] In the third embodiment, the amount of Y2O3 added as the raw material for the ion transport coating layer is 2g, and the amount of aluminate added is 3g. Testing revealed that the core layer of the double-layer coated lithium battery positive electrode material is lithium cobalt oxide, coated with an ion transport coating layer comprising approximately 0.1% by weight. The ion transport coating layer contains Li2CO3, Li2O, and LiYO2, and the surface of the ion transport coating layer is coated with an interstitial inert material coating layer comprising approximately 0.05% by weight of Al2O3.

[0054] The fourth embodiment is basically the same as the first embodiment, except that the raw material of the ion transport coating layer in this embodiment is La2O3, and the specific preparation method is as follows:

[0055] S1: 1 kg of lithium cobalt oxide semi-finished material and 4 g of La2O3, a raw material for the ion transport coating layer, were placed in a ball mill and mixed at a ball mill speed of 25 Hz for 3 hours to obtain a first mixed material; the first mixed material was sintered at 800°C to obtain a first sintered material;

[0056] S2: Add 10 g of aluminic acid as Al raw material to 2 L of deionized water solution, add 2 g of hydroxypropyl methylcellulose (HPMC) as coating additive, and stir for 10 min to obtain a mixed solution;

[0057] S3: Add the first sintering material to the mixed solution, adjust the pH to 12, continue stirring for 20 minutes, filter and dry to obtain the second mixed material, and sinter at 800° C. to obtain a double-layer coated lithium battery positive electrode material.

[0058] After testing, it was found that the core layer of the double-layer coated lithium battery positive electrode material is lithium cobalt oxide, and its surface is coated with an ion transport coating layer with a mass percentage of about 0.3%. The ion transport coating layer contains Li2CO3, Li2O and La2O3, and the surface of the ion transport coating layer is coated with an interstitial inert material coating layer Al2O3 with a mass percentage of about 0.15%.

[0059] The fifth embodiment is basically the same as the first embodiment, except that the raw materials of the ion transport coating layer in this embodiment are ZrO2 and TiO2, and the specific preparation method is as follows:

[0060] This embodiment provides a double-layer coated lithium ion positive electrode material, the preparation method of which is as follows:

[0061] S1: 1 kg of lithium cobalt oxide semi-finished material and 4 g of ZrO2 and 0.6 g of TiO2, raw materials for the ion transport coating layer, were placed in a ball mill and mixed at a ball mill speed of 25 Hz for 3 hours to obtain a first mixed material; the first mixed material was sintered at 800°C to obtain a first sintered material;

[0062] S2: Add 10 g of aluminic acid as Al raw material to 2 L of deionized water solution, add 2 g of hydroxypropyl methylcellulose (HPMC) as coating additive, and stir for 10 min to obtain a mixed solution;

[0063] S3: Add the first sintering material to the mixed solution, adjust the pH to 12, continue stirring for 20 minutes, filter and dry to obtain the second mixed material, and sinter at 800° C. to obtain a double-layer coated lithium battery positive electrode material.

[0064] After testing, it was found that the core layer of the double-layer coated lithium battery positive electrode material is lithium cobalt oxide, and its surface is coated with an ion transport coating layer with a mass percentage of about 0.3%. The ion transport coating layer contains Li2CO3, Li2O, Li2ZrO3 and Li4Ti5O, and the surface of the ion transport coating layer is coated with an interstitial inert material coating layer Al2O3 with a mass percentage of about 0.15%.

[0065] The sixth embodiment is substantially the same as the first embodiment, with the only difference being that the raw materials for the interstitial inert material coating layer in this embodiment are Y2O3 and TiO2, and the specific preparation method is as follows:

[0066] S1: 1 kg of lithium cobalt oxide semi-finished material, 4 g of Y2O3 and 2 g of TiO2, raw materials for the ion transport coating layer, were placed in a ball mill and mixed at a ball mill speed of 25 Hz for 3 hours to obtain a first mixed material; the first mixed material was sintered at 800°C to obtain a first sintered material;

[0067] S2: Add 10 g of lanthanum nitrate as La raw material to 2 L of deionized water solution, add 2 g of hydroxypropyl methylcellulose (HPMC) as coating additive, and stir for 10 min to obtain a mixed solution;

[0068] S3: Add the first sintering material to the mixed solution, adjust the pH to 12, continue stirring for 20 minutes, filter and dry to obtain the second mixed material, and sinter at 800° C. to obtain a double-layer coated lithium battery positive electrode material.

[0069] After testing, it was found that the core layer of the double-layer coated lithium battery positive electrode material is lithium cobalt oxide, and its surface is coated with an ion transport coating layer with a mass percentage of about 0.3%. The ion transport coating layer contains Li2CO3, Li2O, LiYO2 and Li4Ti5O, and the surface of the ion transport coating layer is coated with an interstitial inert material coating layer La2O3 with a mass percentage of about 0.1%.

[0070] The seventh embodiment is substantially the same as the first embodiment, except that the raw materials for the interstitial inert material coating layer in this embodiment are Y2O3 and TiO2, and the specific preparation method is as follows:

[0071] S1: 1 kg of lithium cobalt oxide semi-finished material, 4 g of Y2O3 and 2 g of TiO2, raw materials for the ion transport coating layer, were placed in a ball mill and mixed at a ball mill speed of 25 Hz for 3 hours to obtain a first mixed material; the first mixed material was sintered at 800°C to obtain a first sintered material;

[0072] S2: Add 10 g of zirconium nitrate as a Zr raw material to 2 L of deionized water solution, add 2 g of hydroxypropyl methylcellulose (HPMC) as a coating additive, and stir for 10 min to obtain a mixed solution;

[0073] S3: Add the first sintering material to the mixed solution, adjust the pH to 12, continue stirring for 20 minutes, filter and dry to obtain the second mixed material, and sinter at 800° C. to obtain a double-layer coated lithium battery positive electrode material.

[0074] After testing, it was found that the core layer of the double-layer coated lithium battery positive electrode material is lithium cobalt oxide, and its surface is coated with an ion transport coating layer with a mass percentage of about 0.3%. The ion transport coating layer contains Li2CO3, Li2O, LiYO2 and Li4Ti5O, and the surface of the ion transport coating layer is coated with an interstitial inert material coating layer ZrO2 with a mass percentage of about 0.1%.

[0075] The preparation methods of the lithium cobalt oxide semi-finished materials of the above seven embodiments are conventional preparation methods and are not limited herein.

[0076] During the preparation of lithium cobalt oxide, it is inevitable that Li2CO3 and Li2O will remain on the surface of the lithium cobalt oxide. Therefore, this part of the residue will enter the ion transport coating layer as its first component, but the above-mentioned residual substances do not play a functional role in ion transport.

[0077] In addition, the positive electrode active material can be other than the positive electrode active material, the positive electrode active material can also be Li x Co i Ni j Mn k M m O 2-x, 0.6<x≤1, 0≤i≤0.4, 0≤j≤0.5, 0≤k≤0.6, 0≤m≤0.2, and i+j+k+m+x=1, M is B 3+ Mg 2+ , K + , Ca 2+ 、V 3+ 、V 4+ Cr 3+ 、Cu 2+ 、Zn 2+ 、Zr 4+ 、Nb 5+ or Sn 4+ The preparation method thereof can be prepared by referring to conventional preparation methods and is not limited in this application.

[0078] The first comparative example is basically the same as the first embodiment, with the only difference being that the hydroxypropyl methylcellulose in the first embodiment is omitted. In this case, the outermost coating of the double-layer coated lithium battery positive electrode material prepared is an Al2O3 coating layer, which is a layered coating rather than a gap-shaped coating.

[0079] The second comparative example provides a double-layer coated lithium ion positive electrode material, which includes sequentially depositing LiAlO2 and Al2O3 on the surface of a lithium cobalt oxide semi-finished material by chemical vapor deposition.

[0080] The third comparative example is substantially the same as the first example, except that, in this comparative example, the amount of Y2O3, the raw material for the ion transport coating layer, accounts for 8% of the lithium cobalt oxide semi-finished material, and the amount of aluminic acid, the raw material for the interstitial inert material coating layer, accounts for 5% of the lithium cobalt oxide semi-finished material.

[0081] The fourth comparative example is basically the same as the first embodiment, except that, in this comparative example, the amount of Al2O3, the raw material for the ion transport coating layer, accounts for 0.01% of the lithium cobalt oxide semi-finished material, and the amount of aluminic acid, the raw material for the interstitial inert material coating layer, accounts for 0.01% of the lithium cobalt oxide semi-finished material.

[0082] Experimental example

[0083] The performance of the double-layer coated lithium-ion cathode materials prepared in the seven examples and four comparative examples was tested using DCR, surface Co ion dissolution under acidic conditions, and 50 cycles at 45°C. The test results are as follows:

[0084] As can be seen from the table above, all seven embodiments of this application achieved lower DCR and Co 3+Dissolution amount, where DCR represents the discharge / charge power capability of the battery. The smaller the DCR value, the stronger the power capability and the better the rate performance of the battery. In the first comparative example, hydroxypropyl methylcellulose was not added. At this time, the outermost layer of the double-layer coated lithium battery positive electrode material prepared was a layered Al2O3 coating layer. The complete layered coating would hinder the transmission of lithium ions, resulting in a significant increase in DCR and a significant decrease in cycle performance. In the second comparative example, LiAlO2 and Al2O3 were deposited in sequence by chemical vapor deposition, and the layered coating still obtained had an effect similar to that of comparative example 1, with a significant increase in DCR and a significant decrease in cycle performance. In the third comparative example, the amount of raw material added to the coating layer was large, which would significantly affect the performance of the material, resulting in an extremely significant increase in DCR and an extremely significant decrease in cycle performance. And Co 3+ The dissolution amount is within 200-400ppm, which is a normal dissolution amount. Therefore, the first comparative example - the third comparative example are for Co 3+ The dissolution amount was not significantly affected, while in the fourth comparative example, due to the low amount of coating layer, effective coating could not be formed, resulting in a significant increase in the dissolution amount. Therefore, the seven examples of this application can effectively protect the lithium cobalt oxide matrix through the interstitial inert material coating layer constructed on the surface, significantly improving the cycle performance.

[0085] In summary, the double-layer coated lithium ion positive electrode material provided by the present disclosure is first coated with an ion transport coating layer on the surface of the positive electrode active material, and then coated with a gap-shaped inert material coating layer on the surface of the ion transport coating layer, wherein the gap-shaped inert material coating layer can play a role in protecting the surface of the material during the cycle, and at the same time, due to its gap state, it will not prevent the transmission of lithium ions, so that the material impedance will not increase significantly. The coating layer can also significantly reduce the dissolution of ions on the surface of the positive electrode material, preventing the negative impact of ion dissolution on the battery. The preparation method of the double-layer coated lithium ion positive electrode material provided by the present disclosure is to introduce a coating additive to achieve the interstitial inert material coating layer raw material. Under the action of the coating additive, it can be interstitially attached and fixed on the surface of the first sintered material without displacement. During sintering, the coating material is more tightly combined with the substrate, achieving good adhesion of the interstitial inert material coating layer, effectively avoiding contact between the positive electrode active material and the electrolyte, while also ensuring the transmission of lithium ions, and the cycle performance of the positive electrode material is better.

[0086] The foregoing description is merely a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present disclosure shall be included within the scope of protection of the present disclosure. Industrial Applicability

[0087] By adopting the above scheme, by introducing the coating additive, the raw material of the interstitial inert material coating layer can be interstitially attached and fixed on the surface of the first sintered material without displacement under the adhesion effect of the coating additive. During sintering, the coating material and the substrate are closely combined, achieving good adhesion of the interstitial inert material coating layer, effectively avoiding contact between the positive electrode active material and the electrolyte, while also ensuring the transmission of lithium ions, and the cycle performance of the positive electrode material is better.

Claims

1. A double-layer coated lithium ion positive electrode material, characterized in that: It includes, from the inside to the outside, a positive electrode active material, an ion transport coating layer, and a gap-shaped inert material coating layer in a mass ratio of 100:0.05-5:0.02-3; The composition of the ion transport coating layer includes a first component and a second component, the first component includes at least one of Li2CO3 and Li2O, and the second component is a lithium-containing metal compound; The interstitial inert material coating layer is at least one of a non-Al metal oxide and an Al-containing compound.

2. The double-layer coated lithium ion positive electrode material according to claim 1, characterized in that The mass of the ion transport coating layer accounts for 0.1%-0.3% of the total mass of the positive electrode active material, and the mass of the interstitial inert material coating layer accounts for 0.05%-0.15% of the total mass of the positive electrode active material.

3. The double-layer coated lithium ion positive electrode material according to claim 1 or 2, characterized in that The lithium-containing metal compound includes at least one of LiAlO2, LiY2O3, Li2ZrO3 and Li2TiO3.

4. The double-layer coated lithium ion positive electrode material according to any one of claims 1 to 3, characterized in that The gaps in the gap-shaped inert material coating layer are in a mesh shape.

5. The double-layer coated lithium ion positive electrode material according to any one of claims 1 to 4, characterized in that The non-Al metal oxide includes at least one of La2O3 and ZrO2; Preferably, the Al-containing compound includes at least one of Al2O3, LiAlO2, and Al(OH)3.

6. A method for preparing a double-layer coated lithium ion positive electrode material according to any one of claims 1 to 5, characterized in that: It includes: ball-milling a positive electrode active material and an ion transport coating layer raw material, and sintering to obtain a first sintered material having an ion transport coating layer coated on the surface of the positive electrode active material, wherein the ion transport coating layer raw material comprises a metal oxide; Mixing a raw material for an interstitial inert material coating layer, a coating additive, and a solvent to form a mixed solution, wherein the raw material for the interstitial inert material coating layer includes a compound containing a metal element; The first sintered material is added to the mixed solution, the pH is adjusted to 11-12, stirred and mixed, dried, and sintered to obtain a second sintered material having an interstitial inert material coating layer on the surface of the ion transport coating layer, i.e., a double-layer coated lithium ion positive electrode material.

7. The method for preparing a double-layer coated lithium ion positive electrode material according to claim 6, characterized in that: The amount of the coating additive is 0.1%-2% of the total mass of the positive electrode active material.

8. The method for preparing a double-layer coated lithium ion positive electrode material according to claim 6 or 7, characterized in that: The coating additive includes at least one of hydroxypropyl methylcellulose, gelatin, starch and polyethylene glycol.

9. The method for preparing a double-layer coated lithium ion positive electrode material according to any one of claims 6 to 8, characterized in that: The sintering temperatures of the first sintering material and the second sintering material are both 700-900°C.

10. Use of the double-layer coated lithium ion positive electrode material according to any one of claims 1 to 5 or the double-layer coated lithium ion positive electrode material prepared by the method for preparing the double-layer coated lithium ion positive electrode material according to any one of claims 6 to 9 in preparing a lithium ion battery.

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