Modified lithium titanium aluminum phosphate material, its preparation method, modified ternary cathode material, its preparation method, cathode and lithium ion battery

Abstract

The present invention provides a modified lithium titanium aluminum phosphate material and a preparation method thereof, a modified ternary cathode material and a preparation method thereof, a cathode and a lithium ion battery. The modified lithium titanium aluminum phosphate material includes a lithium titanium aluminum phosphate material and a first coating layer semi-embedded on the surface of the lithium titanium aluminum phosphate material, wherein the material of the first coating layer is iron phthalocyanine. On the one hand, more liquid phase is introduced by the addition of urea during the preparation process of the lithium titanium aluminum phosphate (LATP) material, and the three-dimensional active sites formed during the sintering process are conducive to the landing reaction of iron phthalocyanine, thereby constructing a composite barrier layer on the surface of the LATP material matrix. Without affecting ion transport, the side reactions of the ternary cathode material during charge and discharge are minimized, and its structural stability is improved. On the other hand, the three-dimensional channels in the composite barrier layer are conducive to the transport of lithium ions under high-rate charge and discharge, thereby realizing a mechanism with excellent rate and cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular, to a modified lithium titanium aluminum phosphate material and a preparation method thereof, a modified ternary cathode material and a preparation method thereof, a cathode and a lithium-ion battery. Background Art

[0002] NASICON-type phosphate compounds have good structural stability and high ionic conductivity. Lithium ions or sodium ions can easily complete rapid insertion and extraction in the crystal. These excellent physical and electrochemical properties have made them widely studied in the fields of lithium-ion and sodium-ion energy storage. Among them, the lithium titanium aluminum phosphate material LATP is widely used in the field of lithium-ion batteries due to its high ionic conductivity.

[0003] The ternary nickel cobalt manganese cathode material is a lithium-ion battery cathode material that has gradually emerged in recent years. It is widely used in the field of power batteries due to its important advantages such as relatively low cost, good environmental protection, high capacity, and good cycle performance. However, with the increase in the content of nickel element and the improvement of energy density, the thermal stability and cycle stability are insufficient, and the safety and life cannot meet the requirements of power batteries. Therefore, it is necessary to modify the ternary material, especially the high-nickel ternary cathode material, to improve its structural stability and rate cycle capacity performance during charge and discharge. Summary of the Invention

[0004] The main object of the present invention is to provide a modified lithium titanium aluminum phosphate material and a preparation method thereof, a modified ternary cathode material and a preparation method thereof, a cathode and a lithium-ion battery, so as to solve the problem of poor thermal stability and cycle stability of the high-nickel ternary cathode material in the prior art.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided a modified lithium titanium aluminum phosphate material, which includes a lithium titanium aluminum phosphate material and a first coating layer semi-embedded on the surface of the lithium titanium aluminum phosphate material, wherein the material of the coating layer is iron phthalocyanine.

[0006] Further, the mass of the above iron phthalocyanine is 0.6-2.6 wt% of the total mass of the lithium titanium aluminum phosphate material, and preferably the D50 particle size of the lithium titanium aluminum phosphate material is 100-200 nm.

[0007] According to another aspect of the present invention, there is provided a method for preparing the aforementioned modified lithium titanium aluminum phosphate material, the preparation method comprising: Step S1, first mixing a first material including a lithium source, an aluminum source, a titanium source, and a phosphorus source with urea to obtain a first mixture; Step S2, pre-sintering the first mixture to obtain a pre-sintered material; Step S3, second mixing a second material including the pre-sintered material and iron phthalocyanine to obtain a second mixture; Step S4, sintering the second mixture in an oxygen-containing atmosphere to obtain the modified lithium titanium aluminum phosphate material.

[0008] Further, the process of the above-mentioned first mixing includes: low-speed stirring of the first material and urea followed by high-speed stirring. Preferably, the rotation speed of the low-speed stirring is 80 - 150 r / min, and the time of the low-speed stirring is preferably 5 - 10 min; preferably, the rotation speed of the high-speed stirring is 300 - 400 r / min, and the time of the high-speed stirring is preferably 5 - 30 min; the mass of urea is 0.2 - 1.8 wt% of the total mass of the first material; calculated by lithium atoms for the lithium source, by aluminum atoms for the aluminum source, by titanium atoms for the titanium source, and by phosphorus atoms for the phosphorus source, the molar ratio of the lithium source, the aluminum source, the titanium source, and the phosphorus source is 1.3 - 1.5:0.3 - 0.5:1.5 - 1.7:3; preferably, the lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, and lithium dihydrogen phosphate; preferably, the aluminum source is selected from any one or two mixtures of aluminum oxide and aluminum hydroxide; preferably, the titanium source is titanium dioxide; preferably, the phosphorus source is selected from any one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and lithium dihydrogen phosphate.

[0009] Further, the temperature of the above-mentioned pre-sintering is 280 - 500 °C, preferably the time of the pre-sintering is 3 - 5 h, and the D50 particle size of the pre-sintered material is 300 - 500 nm.

[0010] Further, in the above-mentioned Step S3, the mass of iron phthalocyanine is 1 - 3 wt% of the total mass of the first material. Preferably, the stirring rotation speed of the second mixing is 300 - 400 r / min, and the stirring time of the second mixing is preferably 15 - 30 min.

[0011] Further, in the above-mentioned Step S4, the sintering temperature is 700 - 800 °C, preferably the sintering time is 4 - 6 h.

[0012] According to still another aspect of the present invention, there is provided a modified ternary cathode material, which includes a ternary cathode material and a second coating layer coated on the surface of the ternary cathode material. Among them, the second coating layer includes the aforementioned modified lithium titanium aluminum phosphate material, or the second coating layer includes the modified lithium titanium aluminum phosphate material obtained by the above preparation method.

[0013] Further, the D50 particle size of the above-mentioned modified lithium titanium aluminum phosphate material is 150 - 300 nm.

[0014] Furthermore, the mass ratio of the ternary cathode material to the second coating layer is 1:6 to 10. Preferably, the D50 particle size of the ternary cathode material is 600 to 1000 nm. Further preferably, the ternary cathode material is a Ni88 system.

[0015] According to another aspect of the present invention, a method for preparing a modified ternary cathode material is provided. The preparation method includes: under the condition of heating in the dark, stirring and mixing raw materials including a ternary cathode material, a modified lithium titanium aluminum phosphate material, and a solvent to obtain a modified ternary cathode material.

[0016] Furthermore, the rotation speed of the above stirring and mixing is 100 to 800 r / min. Preferably, the temperature of the stirring and mixing is 50 to 80 °C. Preferably, the time of the stirring and mixing is 2 to 3.5 h. Preferably, the volume ratio of the ternary cathode material to the solvent is 1:2.5 to 5. Preferably, the solvent is ethanol and / or deionized water.

[0017] According to another aspect of the present invention, a cathode is provided, including a cathode material, and the cathode material is the aforementioned modified ternary cathode material or the modified ternary cathode material obtained by the above preparation method.

[0018] According to another aspect of the present invention, a lithium-ion battery is provided, including a cathode and an anode, and the cathode is the above-mentioned cathode.

[0019] Applying the technical solution of the present invention, when the above-mentioned modified lithium titanium aluminum phosphate material is used as the coating material of the ternary cathode material, on the one hand, more liquid phase is introduced by the addition of urea during the preparation process of the lithium titanium aluminum phosphate (LATP) material, which improves the mass transfer rate and reduces the reaction phase formation temperature. The three-dimensional active sites formed during the sintering process are beneficial to the landing reaction of iron phthalocyanine, thereby constructing a composite barrier layer on the surface of the LATP material matrix. Without affecting ion transport, the side reactions of the ternary cathode material during charge and discharge are minimized to the greatest extent, and its structural stability is improved. On the other hand, the three-dimensional channels in the composite barrier layer are beneficial to the transport of lithium ions under high-rate charge and discharge, thereby realizing the mechanism of excellent rate and cycle performance. Specific Embodiments

[0020] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0021] "Semi-embedded coating" means that during the sintering process, a part of the iron phthalocyanine molecular chain is embedded inside the LATP particles, and the other part is exposed outside the LATP particles.

[0022] As analyzed in the background art of the present application, the high-nickel ternary cathode materials in the prior art have problems of poor thermal stability and cycling stability. To solve this problem, the present application provides a modified lithium titanium aluminum phosphate material and its preparation method, a modified ternary cathode material and its preparation method, a cathode and a lithium-ion battery.

[0023] In a typical embodiment of the present application, a modified lithium titanium aluminum phosphate material is provided. The modified lithium titanium aluminum phosphate material includes a lithium titanium aluminum phosphate material and a first coating layer semi-embedded on the surface of the lithium titanium aluminum phosphate material. Among them, the material of the first coating layer is iron phthalocyanine.

[0024] When the above-mentioned modified lithium titanium aluminum phosphate material is used as the coating material of the ternary cathode material, on the one hand, more liquid phase is introduced by adding urea during the preparation process of the lithium titanium aluminum phosphate (LATP) material, which improves the mass transfer rate and reduces the reaction phase formation temperature. The three-dimensional active sites formed during the sintering process are conducive to the landing reaction of iron phthalocyanine, so as to construct a composite barrier layer on the surface of the LATP material matrix. Without affecting ion transport, the side reactions of the ternary cathode material during charge and discharge are minimized, and its structural stability is improved. On the other hand, the three-dimensional channels in the composite barrier layer are conducive to the transport of lithium ions under high-rate charge and discharge, thus realizing the mechanism of excellent rate and cycling performance.

[0025] Preferably, the mass of the above-mentioned iron phthalocyanine is 0.6-2.6 wt% of the total mass of the lithium titanium aluminum phosphate material. Preferably, the D50 particle size of the lithium titanium aluminum phosphate material is 100-200 nm, which is conducive to the synergistic cooperation between the lithium titanium aluminum phosphate material and iron phthalocyanine, and further helps to exert the excellent ion conductivity of the lithium titanium aluminum phosphate material and the inhibitory effect on side reactions during charge and discharge.

[0026] In another typical embodiment of the present application, a preparation method of the above-mentioned modified lithium titanium aluminum phosphate material is provided. The preparation method includes: Step S1, first mixing a first material including a lithium source, an aluminum source, a titanium source, and a phosphorus source with urea to obtain a first mixture; Step S2, pre-sintering the first mixture to obtain a pre-sintered material; Step S3, second mixing a second material including the pre-sintered material and iron phthalocyanine to obtain a second mixture; Step S4, sintering the second mixture in an oxygen-containing atmosphere to obtain a modified lithium titanium aluminum phosphate material.

[0027] The above-mentioned pre-sintering makes the first mixture basically shaped, and by adding urea, the reaction phase formation temperature is reduced, more liquid phase is provided, the mass transfer rate is increased, and the reaction phase formation temperature is reduced. The three-dimensional active sites formed during the sintering process are conducive to the landing reaction of iron phthalocyanine. After sintering, iron phthalocyanine is firmly coated on the surface of the lithium titanium aluminum phosphate material to alleviate the occurrence of side reactions during charge and discharge.

[0028] In one embodiment of the present application, in the above step S1, the process of the first mixing includes: low-speed stirring of the first material and urea followed by high-speed stirring. Preferably, the rotation speed of the low-speed stirring is 80 - 150 r / min, and the time of the low-speed stirring is preferably 5 - 10 min; preferably, the rotation speed of the high-speed stirring is 300 - 400 r / min, and the time of the high-speed stirring is preferably 5 - 30 min; the mass of urea is 0.2 - 1.8 wt% of the total mass of the first material; calculated by lithium atoms for the lithium source, by aluminum atoms for the aluminum source, by titanium atoms for the titanium source, and by phosphorus atoms for the phosphorus source, the molar ratio of the lithium source, aluminum source, titanium source and phosphorus source is 1.3 - 1.5:0.3 - 0.5:1.5 - 1.7:3; preferably, the lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate; preferably, the aluminum source is aluminum oxide and / or aluminum hydroxide; preferably, the titanium source is titanium dioxide; preferably, the phosphorus source is selected from any one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium dihydrogen phosphate.

[0029] Low-speed stirring and high-speed stirring are beneficial to the uniformity of the mixing of the first material and urea, laying a foundation for urea to exert its performance. Preferably, urea with the above content is beneficial to constructing certain reaction protection channels in the modified lithium titanium aluminum phosphate material and creating appropriate reaction active sites for the addition of iron phthalocyanine, thereby alleviating the occurrence of side reactions during charge and discharge.

[0030] Preferably, in the above step S2, the temperature of the pre-sintering is 280 - 500 °C, the time of the pre-sintering is preferably 3 - 5 h, and the D50 particle size of the pre-sintered material is 300 - 500 nm, so as to enable a certain degree of shaping of the first material and form reaction protection channels for urea.

[0031] Preferably, in the above step S3, the mass of iron phthalocyanine is 1 - 3 wt% of the total mass of the first material. Preferably, the stirring rotation speed of the second mixing is 300 - 400 r / min, and the stirring time of the second mixing is preferably 15 - 30 min, so as to enable iron phthalocyanine to be more uniformly coated on the surface of the lithium titanium aluminum phosphate material.

[0032] Preferably, in the above step S4, the temperature of the sintering is 700 - 800 °C, and the time of the sintering is preferably 4 - 6 h, which is beneficial to the shaping of the second mixture and the more firmly coating of iron phthalocyanine on the surface of the lithium titanium aluminum phosphate material.

[0033] In another typical embodiment of the present application, a modified ternary cathode material is provided. The modified ternary cathode material includes a ternary cathode material and a second coating layer coated on the surface of the ternary cathode material. Among them, the second coating layer includes the aforementioned modified lithium titanium aluminum phosphate material, or the second coating layer includes the modified lithium titanium aluminum phosphate material obtained by the aforementioned preparation method.

[0034] When the above modified lithium titanium aluminum phosphate material is used as the coating material for the ternary cathode material, due to the iron phthalocyanine in it, under the condition of not affecting ion transport, it can minimize the side reactions of the ternary cathode material during charge and discharge, improve its structural stability. At the same time, the special protection channels existing in the modified lithium titanium aluminum phosphate material are beneficial to the transport of lithium ions under high-rate charge and discharge, thus realizing the dual optimization of rate cycling performance.

[0035] Preferably, the D50 particle size of the above modified lithium titanium aluminum phosphate material is 150 - 300 nm, which helps to exert the modification effect of the modified lithium titanium aluminum phosphate material on the ternary cathode material and minimize its impact on ion transport as much as possible, so that the modified ternary cathode material has both high ion transportability and fewer side reactions during charge and discharge.

[0036] In an embodiment of the present application, the mass ratio of the above ternary cathode material to the second coating layer is 1:6 - 10. Preferably, the D50 particle size of the ternary cathode material is 600 - 1000 nm. Further, preferably, the ternary cathode material is the Ni88 system.

[0037] Preferably, the above ternary cathode material itself has excellent capacity. The mass ratio of the preferably ternary cathode material to the second coating layer is more conducive to the synergistic cooperation between the two, resulting in a modified ternary cathode material with excellent comprehensive performance.

[0038] In another typical embodiment of the present application, a preparation method of the aforementioned modified ternary cathode material is provided. The preparation method includes: under the condition of heating in the dark, stirring and mixing raw materials including the ternary cathode material, the modified lithium titanium aluminum phosphate material and a solvent to obtain the modified ternary cathode material.

[0039] Through the above wet coating, the modified lithium titanium aluminum phosphate material can be uniformly coated on the surface of the ternary cathode material to optimize its performance.

[0040] Preferably, the rotation speed of heating in the dark is 100 - 800 r / min, the temperature of stirring and mixing is preferably 50 - 80 °C, the time of stirring and mixing is preferably 2 - 3.5 h, the volume ratio of the ternary cathode material to the solvent is preferably 1:2.5 - 5, and the solvent is preferably ethanol and / or deionized water, which helps to uniformly coat the modified lithium titanium aluminum phosphate material on the surface of the ternary cathode material while minimizing the interference of the solvent, etc. on the ternary cathode material during the coating process.

[0041] In another typical embodiment of the present application, a cathode is provided, including a cathode material, and the cathode material is the aforementioned modified ternary cathode material or the modified ternary cathode material obtained by the aforementioned preparation method.

[0042] The positive electrode including the above-mentioned modified ternary positive electrode material has excellent structural stability, rate performance and cycling performance.

[0043] In another typical embodiment of the present application, a lithium-ion battery is provided, which includes a positive electrode and a negative electrode, and the positive electrode is the aforementioned positive electrode.

[0044] The lithium-ion battery including the above positive electrode has excellent structural stability, cycling performance and thermal stability.

[0045] The beneficial effects of the present application will be further described below in conjunction with embodiments.

[0046] Example 1

[0047] (1) Weigh the first materials of lithium carbonate, aluminum oxide, titanium dioxide and ammonium dihydrogen phosphate according to the stoichiometric ratio of Li:Al:Ti:P = 1.4:0.4:1.6:3, and preferentially add lithium carbonate and aluminum oxide to the stirring tank of the high-speed mixer. First, stir at a low speed of 100 r / min for 8 min, then add urea accounting for 1 wt% of the mass of the first materials. After stirring at a low speed of 100 r / min for 8 min, add titanium dioxide and ammonium dihydrogen phosphate, stir at a low speed of 100 r / min for 8 min and then at a high speed of 350 r / min for 25 min, and then collect the materials to obtain the first mixture.

[0048] (2) Place the first mixture in a graphite crucible, pre-bake it at 400 °C for 4 h to obtain a pre-baked material. After natural cooling, crush the pre-baked material to D50 = 400 nm, add iron phthalocyanine accounting for 2 wt% of the mass of the first materials, and mix and stir in the high-speed mixer at a rotation speed of 350 r / min for 20 min to obtain the second mixture; then sinter the second mixture at 780 °C for 5 h, and obtain the modified lithium aluminum titanium phosphate material after natural cooling.

[0049] (3) Nanometerize the modified lithium aluminum titanium phosphate material to D50 = 200 nm, and use ethanol as a solvent. Heat and react it in the dark at 65 °C for 3 h to coat the modified lithium aluminum titanium phosphate material on the ternary Ni88 positive electrode material (the volume ratio of the ternary Ni88 positive electrode material to ethanol is 1:3.5, the mass ratio of the ternary positive electrode material to the modified lithium aluminum titanium phosphate material is 1:8, and the D50 particle size of the ternary positive electrode material is 800 nm) to obtain the modified ternary positive electrode material.

[0050] Example 2

[0051] (1) Weigh the first materials of lithium carbonate, aluminum oxide, titanium dioxide and ammonium dihydrogen phosphate according to the stoichiometric ratio of Li:Al:Ti:P = 1.3:0.3:1.7:3. First, add lithium carbonate and aluminum oxide preferentially into the stirring tank of the high-speed mixer. Stir at a low speed of 80 r / min for 5 min, then add urea accounting for 0.2 wt% of the mass of the first materials. After stirring at a low speed of 80 r / min for 5 min, add titanium dioxide and ammonium dihydrogen phosphate. After stirring at a low speed of 80 r / min for 5 min and then at a high speed of 300 r / min for 15 min, collect the materials to obtain the first mixture.

[0052] (2) Place the obtained first mixture in a graphite crucible. First, pre-sinter at 280 °C for 3 h to obtain a pre-sintered material. After natural cooling, crush the pre-sintered material to D50 = 300 nm, add iron phthalocyanine accounting for 1 wt% of the mass of the first materials, and mix and stir in the high-speed mixer at a rotation speed of 300 r / min for 15 min to obtain a second mixture. Then, sinter the second mixture at 700 °C for 4 h, and obtain the modified lithium aluminum titanium phosphate material after natural cooling.

[0053] (3) Nanoscale the modified lithium aluminum titanium phosphate material to D50 = 150 nm, and use ethanol as a solvent. Heat and react in the dark at 50 °C for 2 h to coat the modified lithium aluminum titanium phosphate material on the ternary Ni88 cathode material (the volume ratio of the ternary Ni88 cathode material to ethanol is 1:2.5, the mass ratio of the ternary cathode material to the modified lithium aluminum titanium phosphate material is 1:6, and the D50 particle size of the ternary cathode material is 600 nm) to obtain the modified ternary cathode material.

[0054] Example 3

[0055] (1) Weigh the first materials of lithium carbonate, aluminum oxide, titanium dioxide and ammonium dihydrogen phosphate according to the stoichiometric ratio of Li:Al:Ti:P = 1.5:0.5:1.5:3. First, add lithium carbonate and aluminum oxide preferentially into the stirring tank of the high-speed mixer. Stir at a low speed of 150 r / min for 10 min, then add urea accounting for 1.8 wt% of the mass of the first materials. After stirring at a low speed of 150 r / min for 10 min, add titanium dioxide and ammonium dihydrogen phosphate. After stirring at a low speed of 150 r / min for 10 min and then at a high speed of 400 r / min for 30 min, collect the materials to obtain the first mixture.

[0056] (2) Place the first mixture in a graphite crucible. First, pre-sinter at 500 °C for 5 h to obtain a pre-sintered material. After natural cooling, crush the pre-sintered material to D50 = 500 nm, add iron phthalocyanine accounting for 3 wt% of the mass of the first materials, and mix and stir in the high-speed mixer at a rotation speed of 400 r / min for 30 min to obtain a second mixture. Then, sinter the second mixture at 800 °C for 6 h, and obtain the modified lithium aluminum titanium phosphate material after natural cooling.

[0057] (3) Nanoscale the modified lithium titanium aluminum phosphate material to D50 = 300 nm, and use ethanol as the solvent. Heat and react it in the dark at 80 °C for 3.5 h to coat the modified lithium titanium aluminum phosphate material on the ternary Ni88 cathode material (the volume ratio of the ternary Ni88 cathode material to ethanol is 1:5, the mass ratio of the ternary cathode material to the modified lithium titanium aluminum phosphate material is 1:10, and the D50 particle size of the ternary cathode material is 1000 nm) to obtain a modified ternary cathode material.

[0058] Example 4

[0059] The difference from Example 1 is that urea in the first mixture accounts for 0.2 wt% of the mass of the first material, and finally a modified ternary cathode material is obtained.

[0060] Example 5

[0061] The difference from Example 1 is that urea in the first mixture accounts for 1.8 wt% of the mass of the first material, and finally a modified ternary cathode material is obtained.

[0062] Example 6

[0063] The difference from Example 1 is that urea in the first mixture accounts for 0.1 wt% of the mass of the first material, and finally a modified ternary cathode material is obtained.

[0064] Example 7

[0065] The difference from Example 1 is that iron phthalocyanine in the first mixture accounts for 1 wt% of the mass of the first material, and finally a modified ternary cathode material is obtained.

[0066] Example 8

[0067] The difference from Example 1 is that iron phthalocyanine in the first mixture accounts for 3 wt% of the mass of the first material, and finally a modified ternary cathode material is obtained.

[0068] Example 9

[0069] The difference from Example 1 is that iron phthalocyanine in the first mixture accounts for 0.5 wt% of the mass of the first material, and finally a modified ternary cathode material is obtained.

[0070] Example 10

[0071] The difference from Example 1 is that the pre-sintering temperature is 280 °C, and finally a modified ternary cathode material is obtained.

[0072] Example 11

[0073] The difference from Example 1 is that the pre-sintering temperature is 500 °C, and finally a modified ternary cathode material is obtained.

[0074] Example 12

[0075] The difference from Example 1 is that the pre-sintering temperature is 200 °C, and finally the modified ternary cathode material is obtained.

[0076] Example 13

[0077] The difference from Example 1 is that the modified lithium titanium aluminum phosphate material is nano-sized to D50 = 150 nm, and finally the modified ternary cathode material is obtained.

[0078] Example 14

[0079] The difference from Example 1 is that the modified lithium titanium aluminum phosphate material is nano-sized to D50 = 100 nm, and finally the modified ternary cathode material is obtained.

[0080] Example 15

[0081] The difference from Example 1 is that the pre-sintered material is crushed to D50 = 300 nm, and finally the modified ternary cathode material is obtained.

[0082] Example 16

[0083] The difference from Example 1 is that the modified lithium titanium aluminum phosphate material is nano-sized to D50 = 200 nm, and finally the modified ternary cathode material is obtained.

[0084] Example 17

[0085] The difference from Example 1 is that the volume ratio of the ternary Ni88 cathode material to ethanol is 1:4, and finally the modified ternary cathode material is obtained.

[0086] Example 18

[0087] The difference from Example 1 is that the mass ratio of the ternary cathode material to the modified lithium titanium aluminum phosphate material is 1:6, and finally the modified ternary cathode material is obtained.

[0088] Example 19

[0089] The difference from Example 1 is that the mass ratio of the ternary cathode material to the modified lithium titanium aluminum phosphate material is 1:10, and finally the modified ternary cathode material is obtained.

[0090] Example 20

[0091] The difference from Example 1 is that the mass ratio of the ternary cathode material to the modified lithium titanium aluminum phosphate material is 1:12, and finally the modified ternary cathode material is obtained.

[0092] Example 21

[0093] The difference from Example 1 is that the stirring speed of the second mixing is 320 r / min, the volume ratio of the ternary Ni88 cathode material to ethanol is 1:4, the mass ratio of the ternary cathode material to the modified lithium titanium aluminum phosphate material is 1:9, the D50 particle size of the ternary cathode material is 900 nm, and finally the modified ternary cathode material is obtained.

[0094] Comparative Example 1

[0095] (1) Weigh the first materials of lithium carbonate, aluminum oxide, titanium dioxide and ammonium dihydrogen phosphate according to the stoichiometric ratio of Li:Al:Ti:P = 1.4:0.4:1.6:3. First add lithium carbonate and aluminum oxide to the stirring tank of the high-speed mixer. Stir at a low speed of 100 r / min for 8 min, then add titanium dioxide and ammonium dihydrogen phosphate, stir at a low speed of 100 r / min for 8 min and then stir at a high speed of 350 r / min for 25 min, and then collect the material to obtain the first mixture.

[0096] (2) Place the first mixture in a graphite crucible, pre-burn it at 400 °C for 4 h to obtain a pre-burned material. After natural cooling, crush the pre-burned material to D50 = 400 nm to obtain the second mixture; then sinter the second mixture at 780 °C for 5 h, and obtain the modified lithium titanium aluminum phosphate material after natural cooling.

[0097] (3) Nanometerize the modified lithium titanium aluminum phosphate material to D50 = 200 nm, and use ethanol as a solvent to heat and react it for 3 h in the dark at 65 °C to coat the modified lithium titanium aluminum phosphate material on the ternary Ni88 cathode material (the volume ratio of the ternary Ni88 cathode material to ethanol is 1:3.5) to obtain the modified ternary cathode material.

[0098] Use the modified ternary cathode materials obtained from the above Examples 1 to 21 and Comparative Example 1 as the cathode materials respectively, use battery-grade lithium sheets as the anode materials, and use lithium hexafluorophosphate as the main component as the electrolyte to assemble simulated batteries, and conduct relevant performance tests. Test the initial charge and discharge capacity at 0.2C, and test the discharge capacity at 0.33C, 1C, 2C, and 5C in turn. Under the condition of 1C charge and discharge, test the capacity retention rate after 100 times, and list the test results in Table 1.

[0099] Table 1

[0100]

[0101]

[0102] As can be seen from Table 1, the rate capacity and cycle stability of the lithium-ion battery obtained after coating the ternary cathode material with the modified lithium titanium aluminum phosphate material are significantly better than those of the ternary cathode material coated with the ordinary lithium titanium aluminum phosphate material, indicating that the construction of a good material system plays a crucial role in improving the performance of the high-nickel ternary cathode material.

[0103] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0104] When the above modified lithium titanium aluminum phosphate material is used as the coating material for the ternary cathode material, on the one hand, more liquid phase is introduced during the preparation of the lithium titanium aluminum phosphate (LATP) material by adding urea, which improves the mass transfer rate and reduces the reaction phase formation temperature. The three-dimensional active sites formed during the sintering process are beneficial to the landing reaction of iron phthalocyanine, thereby constructing a composite barrier layer on the surface of the LATP material matrix. Under the condition of not affecting ion transport, the side reactions of the ternary cathode material during charge and discharge are minimized, and its structural stability is improved. On the other hand, the three-dimensional channels in the composite barrier layer are beneficial to the transport of lithium ions under high-rate charge and discharge, thus realizing the mechanism of double excellent rate and cycle performance.

[0105] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A modified lithium titanium aluminum phosphate material, characterized in that, The modified lithium titanium aluminum phosphate material includes a lithium titanium aluminum phosphate material and a first coating layer semi-embedded on the surface of the lithium titanium aluminum phosphate material. Among them, the material of the first coating layer is iron phthalocyanine; The mass of the iron phthalocyanine is 0.6-2.6 wt% of the total mass of the lithium titanium aluminum phosphate material, and the D50 particle size of the lithium titanium aluminum phosphate material is 100-200 nm; The semi-embedded coating means that a part of the molecular chain of the iron phthalocyanine is embedded inside the particles of the lithium titanium aluminum phosphate material, and the other part is exposed outside the particles of the lithium titanium aluminum phosphate material.

2. The preparation method of the modified lithium titanium aluminum phosphate material according to claim 1, characterized in that, The preparation method includes: Step S1, first mixing a first material including a lithium source, an aluminum source, a titanium source, and a phosphorus source with urea to obtain a first mixture; Step S2, pre-sintering the first mixture to obtain a pre-sintered material; Step S3, second mixing a second material including the pre-sintered material and iron phthalocyanine to obtain a second mixture; Step S4, sintering the second mixture in an oxygen-containing atmosphere to obtain the modified lithium titanium aluminum phosphate material; The first material and the urea are stirred at a low speed and then at a high speed; The mass of the urea is 0.2-1.8 wt% of the total mass of the first material; The temperature of the pre-sintering is 280-500 °C.

3. The preparation method according to claim 2, characterized in that, In the step S1, the process of the first mixing includes: The rotation speed of the low-speed stirring is 80-150 r / min; Based on lithium atoms for the lithium source, aluminum atoms for the aluminum source, titanium atoms for the titanium source, and phosphorus atoms for the phosphorus source, the molar ratio of the lithium source, the aluminum source, the titanium source, and the phosphorus source is 1.3-1.5:0.3-0.5:1.5-1.7:

3.

4. The preparation method according to claim 2, wherein, The time of the low-speed stirring is 5-10 min.

5. The preparation method according to claim 2, characterized in that, The rotation speed of the high-speed stirring is 300-400 r / min.

6. The preparation method according to claim 2, characterized in that, The time of the high-speed stirring is 5-30 min.

7. The preparation method according to claim 3, characterized in that, The lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, and lithium dihydrogen phosphate.

8. The preparation method according to claim 3, characterized in that, The aluminum source is aluminum oxide and / or aluminum hydroxide.

9. The preparation method according to claim 3, characterized in that, The titanium source is titanium dioxide.

10. The preparation method according to claim 2, characterized in that, The phosphorus source is selected from any one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and lithium dihydrogen phosphate.

11. The preparation method according to any one of claims 2 to 10, characterized in that, In the step S2, the time of the pre-sintering is 3-5 h, and the D50 particle size of the pre-sintered material is 300-500 nm.

12. The preparation method according to any one of claims 2 to 10, characterized in that, In the step S3, the mass of the iron phthalocyanine is 1-3 wt% of the total mass of the first material.

13. The preparation method according to any one of claims 2 to 10, characterized in that, The stirring rotation speed of the second mixing is 300-400 r / min.

14. The preparation method according to any one of claims 2 to 10, characterized in that, The stirring time of the second mixing is 15-30 min.

15. The preparation method according to any one of claims 2 to 10, characterized in that, In the step S4, the temperature of the sintering is 700-800 °C.

16. The preparation method according to any one of claims 2 to 10, characterized in that, The time of the sintering is 4-6 h.

17. A modified ternary cathode material, characterized in that, The modified ternary cathode material includes a ternary cathode material and a second coating layer coated on the surface of the ternary cathode material. Among them, the second coating layer includes the modified lithium titanium aluminum phosphate material of claim 1, or the second coating layer includes the modified lithium titanium aluminum phosphate material obtained by the preparation method of any one of claims 2 to 16.

18. The modified ternary cathode material according to claim 17, wherein The D50 particle size of the modified lithium titanium aluminum phosphate material is 150-300 nm.

19. The modified ternary cathode material according to claim 17, wherein, The mass ratio of the ternary cathode material to the second coating layer is 1:6 to 10.

20. The modified ternary cathode material according to claim 17, wherein, The D50 particle size of the ternary cathode material is 600 to 1000 nm.

21. The modified ternary cathode material according to claim 20, wherein The ternary cathode material is a Ni88 system.

22. A method for preparing the modified ternary cathode material according to any one of claims 17 to 21, characterized in that, The preparation method includes: Under the condition of heating in the dark, the raw materials including the ternary cathode material, the modified lithium titanium aluminate phosphate material and the solvent are stirred and mixed to obtain the modified ternary cathode material.

23. The preparation method according to claim 22, characterized in that, The rotation speed of the stirring and mixing is 100 to 800 r / min.

24. The preparation method according to claim 22, wherein The temperature of the stirring and mixing is 50 to 80 °C.

25. The preparation method according to claim 22, characterized in that, The time of the stirring and mixing is 2 to 3.5 h.

26. The preparation method according to claim 22, characterized in that, The volume ratio of the ternary cathode material to the solvent is 1:2.5 to 5.

27. The preparation method according to claim 22, characterized in that, The solvent is ethanol and / or deionized water.

28. A positive electrode includes a positive electrode material, characterized in that, The cathode material is the modified ternary cathode material described in any one of claims 17 to 21 or the modified ternary cathode material obtained by the preparation method described in claim 22 or 27.

29. A lithium-ion battery, comprising a positive electrode and a negative electrode, characterized in that, The cathode is the cathode described in claim 28.

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