A positive electrode material, an electrode sheet, and a secondary battery

Abstract

The application discloses a positive electrode material, a pole piece and a secondary battery, and belongs to the technical field of batteries. The positive electrode material is based on the introduction of specific doping elements in a lithium cobaltate material, and a hybrid coated conductive shell layer is constructed on the surface of the material. When applied to a secondary battery, the positive electrode material can exhibit ideal capacity effect, and has excellent structural stability and excellent cycle performance under high working voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a positive electrode material, a pole piece and a secondary battery. BACKGROUND

[0002] The lithium cobaltate system positive electrode material has been used as a popular material for consumer secondary batteries due to its high energy density and good structural stability. With the gradual increase of the capacity requirement of the positive electrode material of consumer batteries, people try to set a higher working voltage when using the lithium cobaltate system positive electrode material. However, the degree of capacity improvement of the lithium cobaltate system material is low when the working voltage is further increased after 4.55V, and the structural stability is extremely affected. Such materials are currently in a bottleneck state, and modification methods such as doping and coating commonly used in positive electrode materials cannot effectively improve the electrochemical performance of the lithium cobaltate system positive electrode material at high working voltage. SUMMARY

[0003] The purpose of the present application is to overcome the deficiencies in the prior art and provide a doped lithium cobaltate system positive electrode material with a core-shell structure. The material is based on the introduction of specific doping elements into the lithium cobaltate material, and a hybrid coated conductive shell layer is constructed on the surface of the material. When applied in a secondary battery, it can achieve ideal capacity effect, and has excellent structural stability, and can achieve excellent cycle performance at high working voltage.

[0004] To achieve the above purpose, in the first aspect of the present application, the present application provides a positive electrode material, comprising a composite particle, the composite particle comprising an active material and a coating material arranged on the surface of the active material.

[0005] The active material comprises Li(Co a Ni b Al c Mg d B e )O2, wherein 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤d≤1, 0≤e≤1.

[0006] The coating material comprises LiTi2O4 and LiBO2.

[0007] As an embodiment of the present application, a=0.9-0.98.

[0008] As an embodiment of the present application, b=0.01-0.07.

[0009] As an embodiment of the present application, c=0.005-0.01.

[0010] As an embodiment of the present application, d=0.002-0.008.

[0011] As an embodiment of the present application, the e is 0.002-0.008.

[0012] As an embodiment of the present application, the mass content of the coating material in the composite particle is 0.2-0.8%.

[0013] As an embodiment of the present application, the molar ratio of Ti element and B element in the coating material is (2:8)-(8:2).

[0014] In a second aspect of the present application, the present application provides a positive electrode tab, comprising the positive electrode material.

[0015] In a third aspect of the present application, the present application provides a secondary battery, comprising the positive electrode tab.

[0016] In a fourth aspect of the present application, the present application provides an electric device, comprising the secondary battery as a power supply of the electric device.

[0017] The present application has the following beneficial effects:

[0018] The present application provides a positive electrode material of a doped lithium cobalt oxide system with a core-shell structure, which is based on introducing specific doping elements into a lithium cobalt oxide material, and constructing a hybrid coated conductive shell layer on the surface of the material. When applied in a secondary battery, the material can exhibit ideal capacity effect, and has excellent structural stability, and can achieve excellent cycle performance at high working voltage. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0020] In the present application, the technical features described in an open manner include both the closed technical scheme consisting of the listed features and the open technical scheme containing the listed features.

[0021] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0022] The present application is further illustrated below with specific embodiments:

[0023] This application provides a positive electrode material, including composite particles, wherein the composite particles include an active material and a coating material disposed on the surface of the active material;

[0024] The active material includes Li(Co) a Ni b Al c Mg d B e O2, where 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤d≤1, 0≤e≤1;

[0025] The coating materials include LiTi2O4 and LiBO2.

[0026] In some implementations, a+b+c+d+e>0.

[0027] The lithium cobaltate system positive electrode material has obvious irreversible phase change when lithium is deintercalated at high working voltage, the structural stability is significantly reduced, thus a large volume effect is generated and eventually leads to cracks of the crystal particles, which is difficult to improve the charge and discharge capacity, and seriously reduces the cycle life. Therefore, some existing processes select doping or coating to inhibit the structural damage, but this method not only does not significantly improve the capacity of the material, but also reduces the capacity. In order to overcome the bottleneck of the existing lithium cobaltate system positive electrode material at high working voltage, the doping method is adopted in the technical scheme to uniformly dope the lithium cobaltate crystal through multiple lattice sites, effectively inhibiting the generation of cracks of the crystal lattice at high voltage, and among the specific doping elements, the ionic radius of trivalent Ni is similar to that of trivalent Co in lithium cobaltate, which can replace Co site in large quantities without damaging the crystal structure, and since the redox potential of Ni is lower than that of Co, Ni doping can enable the active material to achieve higher capacity at the same cutoff voltage; the ionic radius of trivalent Al is also close to that of trivalent Co, which can effectively replace Co in lithium cobaltate, and it has electrochemical inertness and can serve as a support point to improve the structural stability of the overall material. The ionic radius of divalent Mg is similar to that of Li in lithium cobaltate, and its doping can occupy the Li site, playing a supporting role in the material charging and discharging process and further preventing the collapse of the crystal lattice when lithium is deeply deintercalated. In addition, the incorporation of divalent Mg also introduces electron holes, which can further improve the conductivity of the material in cooperation with Ni. The ionic radius of trivalent B is significantly smaller than that of the above-mentioned doping elements and Co, which occupies the tetrahedral interstitial position and does not affect the normal deintercalation of Li ions, but the bond energy of the B-O bond formed by B and O reaches 802 kJ / mol, which helps to stabilize the crystal structure and prevent oxygen evolution. Through the design of multiple doping points, the phase change reversibility of the active material during the deep lithium deintercalation process at high working voltage can be effectively improved, ensuring that it has high structural stability and improved cycle performance. On the other hand, the application also designs a coating material containing LiTi2O4 and LiBO2 on the surface of the active material. This material not only improves the ion diffusion rate and conductivity of the active material surface, but also inhibits the tendency of the active material to directly contact the electrolyte and react during lithium deintercalation, reducing the probability of corrosion of the active material, and further improving the electrochemical performance of the positive electrode material.

[0028] In some embodiments, a = 0.9-0.98.

[0029] Further preferably, a = one of 0.9, 0.91, 0.914, 0.92, 0.93, 0.95, 0.97, 0.98 or a range value of any two thereof.

[0030] In some embodiments, b = 0.01-0.07.

[0031] Further preferably, the b = one of 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07 or a range value of any two thereof.

[0032] In some embodiments, the c = 0.005-0.01.

[0033] Further preferably, the c = one of 0.005, 0.006, 0.007, 0.008, 0.009, 0.01 or a range value of any two thereof.

[0034] In some embodiments, the d = 0.002-0.008.

[0035] Further preferably, the d = one of 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008 or a range value of any two thereof.

[0036] In some embodiments, the e = 0.002-0.008.

[0037] Further preferably, the e = one of 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008 or a range value of any two thereof.

[0038] Further preferably, the a = 0.93-0.96 and the b = 0.03-0.05.

[0039] The doping ratio of trivalent nickel as the doping element of the lithium cobalt oxide positive electrode material has an influence on the capacity of the obtained positive electrode material and the structural stability at high working voltage, and when the unit doping molar ratio is preferably in the above range, the positive electrode material can achieve more optimal comprehensive electrochemical performance.

[0040] In some embodiments, the mass content of the coating material in the composite particles is 0.2-0.8%.

[0041] Further preferably, the mass content of the coating material in the composite particles is one of 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or a range value of any two thereof.

[0042] Further preferably, the mass content of the coating material in the composite particles is 0.4-0.6%.

[0043] With the proportion of the coating material gradually increasing, the conductivity and ion conduction efficiency of the overall positive electrode material will also be improved, and the side reaction caused by the direct contact between the active material and the electrolyte will also be effectively inhibited. Under high working voltage conditions, the coating material will also have certain side reactions, so within the above preferred range, the coating material can play a more optimal protective role while improving the lithium ion deintercalation efficiency of the overall positive electrode material.

[0044] In some embodiments, the molar ratio of Ti element and B element in the coating material is (2:8) to (8:2).

[0045] Further preferably, the molar ratio of Ti element and B element is one of 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2 or a range value of any two thereof.

[0046] Further preferably, the molar ratio of Ti element and B element in the coating material is (4:6) to (6:4).

[0047] Compared with LiBO2, the higher the molar proportion of LiTi2O4 in the coating material, the higher the capacity level of the overall positive electrode material, but relatively, the proportion of the two coating substances will also affect the structural stability of the positive electrode material during the cycle process to a certain extent, and when the molar ratio of Ti and B in the two substances is preferably within the above range, the positive electrode material can achieve a more optimal electrochemical performance level.

[0048] In some embodiments, the positive electrode material is prepared by the following method:

[0049] (1) mixing a cobalt source, a nickel source, an aluminum source, a magnesium source, and a boron source to prepare a metal ion solution;

[0050] (2) mixing a carbon source and the metal ion solution and adding water to perform a chemical reaction to obtain a doped cobalt carbonate seed;

[0051] (3) mixing the doped cobalt carbonate seed with a carbon source and water, continuously adding the metal ion solution to perform a chemical reaction, and when the doped cobalt carbonate reaches a predetermined size, washing, drying, and sintering to obtain a doped precursor;

[0052] (4) mixing the doped precursor and a lithium source, sintering to obtain an active material;

[0053] (5) once grinding the coating material, mixing the active material after sieving, and performing secondary grinding, sieving, and sintering to obtain a positive electrode material.

[0054] It should be noted that the positive electrode material described in the present application can be prepared by selecting the preparation of the above-mentioned conventional lithium cobaltate system positive electrode material, or other conventional preparation methods, such as high-energy ball milling, sol-gel method, CVD method, etc. For example, the materials are directly ball milled and calcined to obtain a doped precursor, then mixed with a lithium source and high-energy ball milled to obtain an active material, and finally mixed with a coating material according to the similar steps of the above-mentioned preparation method to prepare a positive electrode material, as long as it does not affect the doping ratio of each doping element and the subsequent coating effect of the coating material.

[0055] The present application also provides a positive electrode tab, which comprises the positive electrode material.

[0056] In some embodiments, the positive electrode tab comprises a current collector and an active layer, wherein the active layer comprises the positive electrode material, a binder and a conductive agent.

[0057] The mass ratio of the positive electrode material, the conductive agent and the binder is (94-96):(2-4):(1-3).

[0058] The present application also provides a secondary battery comprising the positive electrode tab.

[0059] In some embodiments, the secondary battery further comprises a separator and a negative electrode tab, wherein the negative electrode tab comprises a current collector and an active layer, and the active layer comprises a negative electrode material.

[0060] Further preferably, the negative electrode material comprises at least one of carbon-based materials, silicon-based materials, and silicon-carbon composite materials.

[0061] The positive electrode material described in the present application has ideal electrochemical performance at high working voltage. In the conventional use field or in the device application pursuing long service life, the person skilled in the art can select common carbon-based materials to prepare a secondary battery. In some high-voltage high-energy density demand fields, the person skilled in the art can also select silicon-based materials or silicon-carbon composite materials to prepare a secondary battery product that meets the requirements.

[0062] The present application is further described in the following specific embodiments, which cannot be understood as limiting the scope of the present application:

[0063] Example 1

[0064] An embodiment of a positive electrode material, a tab and a secondary battery, wherein the preparation method of the positive electrode material comprises the following steps:

[0065] (1) Cobalt chloride, nickel chloride, aluminum sulfate, magnesium chloride and boric acid are mixed and prepared into a metal ion solution; wherein the concentration of cobalt chloride is 100 g / L, and other materials are compounded according to the metering ratio concentration;

[0066] (2) Ammonium bicarbonate with a concentration of 130 g / L is added to water, the temperature is set to 35℃, pH=10, and the metal ion solution is added for combination reaction under stirring at a speed of 450 rpm. Sodium carbonate is added during the reaction, and the pH of the reaction solution is controlled to be 8. The average particle size of the generated particle precipitate is 10 μm, and a doped cobalt carbonate seed is obtained;

[0067] (3) The doped cobalt carbonate seed is mixed with sodium carbonate and water, the solution pH is controlled to be 8.25, and the solution is stirred at a speed of 280 rpm and heated to 45℃. The metal ion solution is continuously added at a flow rate of 6 L / h for combination reaction, and the pH is controlled to be 7 during the reaction. After the average particle size of the generated doped cobalt carbonate reaches 20 μm, it is washed, dried at 90℃ for 12 h, and sintered at 680℃ for 13 h in O2 atmosphere to obtain a doped precursor;

[0068] (4) The doped precursor and lithium carbonate are mixed and sintered at 500℃ for 5 h in O2 atmosphere, and then heated to 750℃ for 15 h to obtain an active material LiCo 0.934 Ni 0.05 Al 0.008 Mg 0.005 B 0.005 O2;

[0069] (5) LiTi2O4 and LiBO2 are mixed and ground according to the Ti:B molar ratio in the material = 5:5, and then sieved through a 400 mesh screen to obtain a coated material. Then, the active material is mixed with the coated material according to the mass ratio of active material:coated material = 99.4:0.6, and then subjected to secondary grinding and sieving through a 400 mesh screen. The positive electrode material is obtained by sintering the mixture at 750℃ for 10 h in O2 atmosphere.

[0070] Example 2

[0071] An embodiment of a positive electrode material, a pole piece and a secondary battery, which is different from example 1 only in that in step (5), the mass ratio of active material:coated material = 99.8:0.2.

[0072] Example 3

[0073] An embodiment of a positive electrode material, a pole piece and a secondary battery, which is different from example 1 only in that in step (5), the mass ratio of active material:coated material = 99.6:0.4.

[0074] Example 4

[0075] An embodiment of a positive electrode material, an electrode sheet, and a secondary battery differs from that of Example 1 only in that in the step (5), the mass ratio of active material:coating material = 99.2:0.8.

[0076] Example 5

[0077] An embodiment of a positive electrode material, an electrode sheet, and a secondary battery differs from that of Example 1 only in that in the step (5), LiTi2O4 and LiBO2 are combined in a Ti:B molar ratio of 2:8 in the material.

[0078] Example 6

[0079] An embodiment of a positive electrode material, an electrode sheet, and a secondary battery differs from that of Example 1 only in that in the step (5), LiTi2O4 and LiBO2 are combined in a Ti:B molar ratio of 4:6 in the material.

[0080] Example 7

[0081] An embodiment of a positive electrode material, an electrode sheet, and a secondary battery differs from that of Example 1 only in that in the step (5), LiTi2O4 and LiBO2 are combined in a Ti:B molar ratio of 6:4 in the material.

[0082] Example 8

[0083] An embodiment of a positive electrode material, an electrode sheet, and a secondary battery differs from that of Example 1 only in that in the step (5), LiTi2O4 and LiBO2 are combined in a Ti:B molar ratio of 8:2 in the material.

[0084] Comparative Example 1

[0085] A positive electrode material, a method for preparing the positive electrode material, and a secondary battery are provided.

[0086] (1) Cobalt chloride is prepared into a metal ion solution; the concentration of the cobalt chloride is 100 g / L;

[0087] (2) Ammonium bicarbonate with a concentration of 130 g / L is added to water, the temperature is set to 35°C, and the pH is set to 10; the metal ion solution is added to the solution while stirring at a speed of 450 rpm to perform a combination reaction; sodium carbonate is added to the solution during the reaction to control the pH of the solution to 8; after the average particle size of the generated cobalt carbonate seed reaches 10 μm, the seed is obtained;

[0088] (3) The cobalt carbonate seed is mixed with sodium carbonate and water, the pH of the solution is controlled to 8.25, the solution is stirred at a speed of 280 rpm and heated to 45°C; the metal ion solution is continuously added to the solution at a flow rate of 6 L / h to perform a combination reaction; the pH of the solution is controlled to 7 during the reaction; after the average particle size of the generated cobalt carbonate reaches 20 μm, the cobalt carbonate is washed, dried at 90°C for 12 h, and sintered at 680°C for 13 h in an O2 atmosphere to obtain a precursor.

[0089] (4) The precursor and lithium carbonate are mixed, sintered at 500°C for 5h under O2 atmosphere, then heated to 750°C and sintered for 15h to obtain the active material LiCoO2.

[0090] Comparative Example 2

[0091] A positive electrode material, which is different from Example 1 only in that the LiBO2 is replaced by Li2WO4, LiTi2O4 and Li2WO4 are in a Ti:W molar ratio of 5:5 in the material.

[0092] Comparative Example 3

[0093] A positive electrode material, which is different from Example 1 only in that the coating material is only LiTi2O4 which is ground and passed through a 400-mesh sieve.

[0094] Comparative Example 4

[0095] A positive electrode material, which is different from Example 1 only in that the coating material is only LiBO2 which is ground and passed through a 400-mesh sieve.

[0096] Example 1

[0097] In order to verify the use effect of the positive electrode material described in the present application, the positive electrode materials of each example and comparative example are used to prepare button cells and secondary batteries, wherein the preparation of the secondary battery comprises the following steps:

[0098] (1) Preparation of positive electrode sheet: the positive electrode material obtained in each example or comparative example is mixed with conductive agent acetylene black, binder polyvinylidene fluoride in a mass ratio of 95:3:2 in N-methylpyrrolidone solvent to prepare a slurry, which is coated on an aluminum foil, dried, cold-pressed, slitted, and welded to obtain a positive electrode sheet;

[0099] (2) Preparation of negative electrode sheet: artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber, thickening agent sodium carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.5:1.5 in water to prepare a slurry, which is coated on a copper foil, dried, cold-pressed, slitted, and welded to obtain a negative electrode sheet;

[0100] (3) Preparation of electrolyte: lithium salt LiPF6 is mixed with non-aqueous organic solvent (mass ratio of ethylene carbonate: diethyl carbonate: propylene carbonate: propionic acid propyl ester: vinylene carbonate = 20:30:20:28:2) in a mass ratio of 8:92 to prepare an electrolyte;

[0101] (4) Preparation of the secondary battery: a commercially available porous polyethylene separator was used as a separator, and the positive electrode sheet, the separator, and the negative electrode sheet were stacked in order, and the two electrode sheets were led out by spot welding, and then the secondary battery was obtained by winding, packaging, injecting an electrolyte, and forming and dividing.

[0102] The preparation of the button cell comprises the following steps:

[0103] (1) Preparation of the positive electrode sheet: the positive electrode material obtained in each example or the comparative example was mixed with acetylene black as a conductive agent and polyvinylidene fluoride as a binder at a mass ratio of 95:3:2 in N-methylpyrrolidone solvent to prepare a slurry, which was coated on an aluminum foil, and then the positive electrode sheet was obtained by drying, cold pressing, and cutting;

[0104] (3) Preparation of the electrolyte: LiPF6 and non-aqueous organic solvents (mass ratio of ethylene carbonate: diethyl carbonate: propylene carbonate: propyl propionate: vinylene carbonate = 20:30:20:28:2) were mixed at a mass ratio of 8:92 to prepare an electrolyte;

[0105] (4) Preparation of the secondary battery: a commercially available porous polyethylene separator was used as a separator, and the positive electrode sheet, the separator, and the negative electrode sheet were stacked in order, and the two electrode sheets were led out by spot welding, and then the secondary battery was obtained by winding, packaging, injecting an electrolyte, and forming and dividing.

[0106] Subsequently, the electrochemical performance test was performed:

[0107] (1) Gram capacity test: the button cell was subjected to charge and discharge tests at 45°C, and then was charged at 0.1C constant current and constant voltage to 4.55V, the cutoff current was 0.05C, and then was left to stand for 5min, and then was discharged at 0.1C constant current to 3.0V to obtain the gram capacity of the button cell;

[0108] (2) Cycle performance test: five secondary batteries obtained from each group of examples and comparative examples were taken, and the lithium ion secondary battery was repeatedly charged and discharged 500 times by the following steps, and the cycle capacity retention rate of the secondary battery was calculated: the secondary battery was left to stand for 60min at 45°C to reach a constant temperature, and then was charged at 1.0C constant current and constant voltage to 4.55V, the cutoff current was 0.05C, and then was left to stand for 5min, and then was discharged at 1.0C constant current to 3.0V.

[0109] The test results are shown in Table 1.

[0110] Table 1

[0111]

[0112]

[0113] As can be seen from Table 1, the positive electrode material described in the application can exert ideal electrochemical performance when applied to a battery, not only has a higher gram capacity, which can reach 201 mAh / g at 0.1C, and the capacity retention rate can still reach more than 81% after 500 charge-discharge cycles at 1C rate, which is mainly due to the multi-element doping of the active material in the material and the shell construction of the coating material. Compared with the comparative example 1 product of pure lithium cobalt oxide material, the gram capacity is increased by more than 5 mAh / g, and the cycle capacity retention rate is increased by more than 10%.

[0114] As the coating material, LiTi2O4 and LiBO2 are very critical, the ratio of the two will directly affect the electrochemical performance of the product, as shown in Examples 1 and 5-8, and if one of the coating materials is missing, as shown in Comparative Examples 3 and 4, the product cannot guarantee high cycle stability, the capacity retention rate is less than 80%, and the gram capacity cannot be guaranteed. If one of the substances is replaced, as shown in Comparative Example 2, the protective effect of the coating material on the active material may be reduced, and the cycle stability of the product is obviously not as good as that of the product of the example, and the capacity retention rate after 500 cycles is only 76.7%.

[0115] Example 2

[0116] In order to verify the influence of the doping elements and doping content of the active material in the positive electrode material described in the application on the performance of the active material, the active material LiCo 0.934 Ni 0.05 Al 0.008 Mg 0.005 B 0.005 O2 was prepared according to the method described in Example 1, and the complex concentration of cobalt chloride, nickel chloride, aluminum sulfate, magnesium chloride and boric acid during preparation was adjusted, and the same method was used to prepare:

[0117] The active material LiCo 0.974 Ni 0.01 Al 0.008 Mg 0.005 B 0.005 O2;

[0118] The active material LiCo 0.954 Ni 0.03 Al 0.008 Mg 0.005 B 0.005 O2;

[0119] The active material LiCo 0.914 Ni 0.07 Al 0.008 Mg 0.005 B 0.005 O2;

[0120] Furthermore, the active material was prepared according to the method described in Example 1, with the only difference from Example 1 being the method for preparing the metal ion solution:

[0121] Cobalt chloride, nickel chloride, aluminum sulfate, magnesium chloride, boric acid, and manganese chloride were mixed and prepared into a metal ion solution; the concentration of cobalt chloride was 100 g / L, and the concentrations of the other materials were compounded according to the stoichiometric ratio.

[0122] The method ultimately prepares the active material LiCo. 0.939 Ni 0.05 Al 0.008 Mg 0.005 B 0.005 Mn 0.005 O2;

[0123] The active material was prepared according to the method described in Example 1, with the only difference being the method for preparing the metal ion solution:

[0124] Cobalt chloride, nickel chloride, aluminum sulfate, magnesium chloride, and zirconium chloride were mixed and prepared into a metal ion solution; the concentration of cobalt chloride was 100 g / L, and the concentrations of the other materials were compounded according to the stoichiometric ratio.

[0125] The method ultimately prepares the active material LiCo. 0.932 Ni 0.05 Al 0.008 Mg 0.005 Zr 0.01 O2;

[0126] The active material was prepared according to the method described in Example 1, with the only difference being the method for preparing the metal ion solution:

[0127] Cobalt chloride, nickel chloride, aluminum sulfate, magnesium chloride, and niobium chloride were mixed and prepared into a metal ion solution; the concentration of cobalt chloride was 100 g / L, and the concentrations of the other materials were compounded according to the stoichiometric ratio.

[0128] The method ultimately prepares the active material LiCo. 0.93 Ni 0.05 Al 0.008 Mg 0.005 Nb 0.01 O2.

[0129] Subsequently, the above-mentioned active materials were subjected to the same tests as described in Effect Example 1, and the results are shown in Table 2.

[0130] Table 2

[0131]

[0132] From the test results can be clearly seen, the doping elements and content in the active material has a greater impact on its specific capacity and cycle stability, when Co, Ni, Al, Mg and B these five elements lack or be replaced, not only will directly affect the intrinsic specific capacity of the active material, the most important is compared to the lithium cobaltate material of comparative example 1, the cycle stability of the active material greatly reduced degree of increase, the minimum increase is less than 3%, it is not any doping can improve the structural stability of the material at high working voltage, compared to the product of example 1, the active material alone as the positive material when the specific capacity decreases, and the cycle stability is not enough, fully illustrates that the coating material is important to the modification of the active material.

[0133] In the process of doping, the content of Ni doping has a greater impact on the electrochemical performance of the active material, the main reason is that the trivalent Ni can effectively replace the Co site in the material without destroying the structure, and the improvement of the specific capacity is most obvious, however, after the doping content reaches a certain degree, the overall structural stability decreases, therefore, the unit molar amount of Ni in the active material is most suitable for 0.03-0.05 mol.

[0134] The above active material is further coated with a coating material according to the method described in example 1, and the obtained positive material is tested in the same way, the results are similar to table 2, which shows that the influence of the doping elements and content on the electrochemical performance of the active material will not change because of the coating material, and therefore will not be repeated here.

Claims

1. A positive electrode material, characterized by, The composite particle comprises an active material and a coating material arranged on the surface of the active material. The active material includes Li(Co a Ni b Al c Mg d B e )O2, wherein a = 0.9 ~ 0.98, b = 0.01 ~ 0.07, c = 0.005 ~ 0.01, d = 0.002 ~ 0.008, e = 0.002 ~ 0.008; The coating material comprises LiTi2O4 and LiBO2, and the mass content of the coating material in the composite particle is 0.2-0.8%.

2. The cathode material of claim 1, wherein, The a=0.93-0.96, and the b=0.03-0.

05.

3. The cathode material of claim 1, wherein, The mass content of the coating material in the composite particle is 0.4-0.6%.

4. The cathode material of claim 1, wherein, In the coating material, the molar ratio of Ti element to B element is (2:8)-(8:2).

5. The cathode material of claim 4, wherein, In the coating material, the molar ratio of Ti element to B element is (4:6)-(6:4).

6. A positive electrode sheet characterized by comprising: The positive electrode material according to any one of claims 1-5.

7. A secondary battery characterized by comprising: The positive electrode plate according to claim 6.

8. An electrical device, characterized by The secondary battery according to claim 7, which serves as a power supply for the electric device.

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