Positive electrode material, secondary battery and electric device

Abstract

Provided in the present application are a positive electrode material, a secondary battery, and an electric device. The positive electrode material of the present application comprises positive electrode active material particles. The positive electrode active material particles comprise a compound having a chemical formula of LizV(1-z)Mx[MnyFe(1-y)]1-xPO4, wherein 0.027≤x≤0.1, 0.1≤y≤0.9, 0.70≤z≤0.92, V is a lithium hole, and M comprises a metal element having a valence of at least +5. The positive electrode material of the present application contains lithium holes and high-valence metal ions, and the contents of the lithium holes and the high-valence metal ions in the positive electrode material are controlled, so that the prepared secondary battery has an excellent electrochemical performance.

Description

Cathode material, secondary battery and electric device

[0001] The present application claims priority to the Chinese patent application No. 202410865352.7, filed on June 28, 2024, and entitled "Cathode material, secondary battery and electric device", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of cathode materials, in particular to a cathode material, a secondary battery and an electric device. BACKGROUND

[0003] Lithium manganese iron phosphate has a high voltage platform, so the secondary battery using lithium manganese iron phosphate as a cathode active material has a high energy density, and the cost of lithium manganese iron phosphate is basically the same as that of lithium iron phosphate, thereby attracting widespread attention in the industry, but lithium manganese iron phosphate has a Jiang Taylor effect, and Mn ions are easy to dissolve out, which can cause a series of problems such as fast cycle decay and gas production of the secondary battery. SUMMARY

[0004] The purpose of the present application is to provide a cathode material, a secondary battery and an electric device to improve the electrochemical performance of the existing lithium manganese iron phosphate secondary battery.

[0005] To achieve the above-mentioned purpose, the first aspect of the present application provides a cathode material, which comprises cathode active material particles, the cathode active material particles comprise a compound with a chemical formula of Li z V (1-z) M x [Mn y Fe (1-y) ] 1-x PO4, wherein 0.027≤x≤0.1, 0.1≤y≤0.9, 0.70≤z≤0.92, V is a lithium vacancy, and M comprises a metal element with an oxidation value of at least +5.

[0006] As an embodiment of the present application, at least part of the surface of the cathode active material particles has a coating layer, and the coating layer comprises M elements.

[0007] As an embodiment of the present application, at least part of the surface of the cathode active material particles has a coating layer, and the coating layer comprises a metal oxide with a chemical formula of M2O5.

[0008] As an embodiment of the present application, M comprises at least one of Sb, Bi, Nb and Ta.

[0009] As an embodiment of the present application, the unit cell parameter b of the positive electrode active material particle is b1, and the unit cell parameter b of the metal oxide is b2, satisfying: 0.97≤b2 / b1≤1.03.

[0010] As an embodiment of the present application, the unit cell parameter b of the positive electrode active material particle is b1, satisfying: 1.014nm≤b1≤1.064nm.

[0011] As an embodiment of the present application, the unit cell parameter b of the metal oxide is b2, satisfying: 1.013nm≤b2≤1.073nm.

[0012] As an embodiment of the present application, the thickness of the coating layer is Tnm, satisfying: 0.36≤T*(1-z)≤1.80.

[0013] As an embodiment of the present application, the T satisfies: 2≤T≤10.

[0014] In a second aspect of the present application, a secondary battery is provided, which comprises the positive electrode material of the first aspect of the present application.

[0015] In a third aspect of the present application, an electric device is provided, which comprises the secondary battery of the second aspect of the present application.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] The present application provides a positive electrode material, which comprises positive electrode active material particles, the positive electrode active material particles comprising a compound with a chemical formula of Li z V (1-z) M x [Mn y Fe (1-y) ] 1-x PO4, wherein 0.027≤x≤0.1, 0.1≤y≤0.9, 0.70≤z≤0.92, V is a lithium vacancy, and M comprises a metal element with an oxidation state of at least +5. The positive electrode material of the present application contains a lithium vacancy and a high-valence metal ion, and the content of the lithium vacancy and the high-valence metal ion in the positive electrode material is controlled, so that the prepared secondary battery has excellent electrochemical performance. DETAILED DESCRIPTION

[0018] To better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in conjunction with specific examples, but the examples do not limit the present application in any form. Unless otherwise specified, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field. Unless otherwise specified, the reagents and materials used in the present application are commercially available.

[0019] In the present application, the technical features described in an open way include both a closed technical solution consisting of the listed features and an open technical solution including the listed features.

[0020] In the present application, when a numerical interval is involved, the numerical interval is considered to be continuous and includes the minimum value and the maximum value of the range and each value between the minimum value and the maximum value of the range, unless otherwise specified. Further, when a range is referred to as an integer, each integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0021] In one embodiment of the present application, the present application provides a positive electrode material, which comprises positive electrode active material particles, the positive electrode active material particles comprising a compound of formula Li z V (1-z) M x [Mn y Fe (1-y) ] 1-x PO4, wherein 0.027≤x≤0.1, 0.1≤y≤0.9, 0.70≤z≤0.92, V is a lithium vacancy, and M comprises a metal element with a valence of at least +5.

[0022] The present application has found that the electrochemical performance of a lithium iron manganese phosphate secondary battery is closely related to the lithium vacancy and the doped metal ion contained in the positive electrode material lithium iron manganese phosphate. By controlling the content of the lithium vacancy, the valence and content of the doped metal ion in the lithium iron manganese phosphate within a specific range, the oxidation of Mn 2+ ions to Mn 3+ can be inhibited, the deintercalation efficiency of lithium ions can be improved, and thus the electrochemical performance of the secondary battery can be improved.

[0023] It should be noted that the lithium vacancy described in the present application can be obtained by a spherical aberration-corrected scanning transmission electron microscopy test.

[0024] In some embodiments, at least part of the surface of the positive electrode active material particles has a coating layer comprising the M element. The further coating layer comprising the M element on the surface of the positive electrode active material particles can further reduce the dissolution of manganese and improve the electrochemical performance of the secondary battery.

[0025] In some embodiments, at least part of the surface of the positive electrode active material particle has a coating layer, and the coating layer comprises a metal oxide with a chemical formula of M2O5. The surface of the positive electrode active material particle further having a metal oxide with a chemical formula of M2O5 can further reduce manganese elution and improve the electrochemical performance of the secondary battery.

[0026] In some embodiments, M comprises at least one of Sb, Bi, Nb, and Ta.

[0027] Exemplarily, the metal oxide can be one or more of Sb2O5, Bi2O5, Nb2O5, and Ta2O5.

[0028] In some embodiments, the unit cell parameter b of the positive electrode active material particle is b1, the unit cell parameter b of the metal oxide is b2, and the following relationship is satisfied: 0.97≤b2 / b1≤1.03.

[0029] Exemplarily, the unit cell parameter b of the positive electrode active material particle is b1, the unit cell parameter b of the metal oxide is b2, and b2 / b1 can be any point value or a range value between any two points within the range of 0.97-1.03. For example, b2 / b1 can be 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, etc.

[0030] The present application has found that when the unit cell parameter b of the positive electrode active material particle and the unit cell parameter b of the metal oxide satisfy the above relationship, the coating layer material and the internal material can be fused in crystallography, the coating effect is improved, the manganese elution of the internal material is inhibited, and thus the electrochemical performance of the secondary battery is further improved.

[0031] In some embodiments, the unit cell parameter b of the positive electrode active material particle is b1, and the following relationship is satisfied: 1.014 nm≤b1≤1.064 nm. Exemplarily, b1 can be any point value or a range value between any two points within the range of 1.014-1.064 nm. For example, b1 can be 1.014 nm, 1.024 nm, 1.034 nm, 1.044 nm, 1.054 nm, 1.064 nm, etc.

[0032] In some embodiments, the unit cell parameter b of the metal oxide is b2, and the following relationship is satisfied: 1.013 nm≤b2≤1.073 nm. Exemplarily, b2 can be any point value or a range value between any two points within the range of 1.013-1.073 nm. For example, b2 can be 1.013 nm, 1.023 nm, 1.033 nm, 1.043 nm, 1.053 nm, 1.063 nm, 1.073 nm, etc.

[0033] It should be noted that the cell parameters of the positive electrode active material and the metal oxide described in the present application can be obtained by XRD (X-Ray Diffraction) testing on the material, and the structure is refined by the Rietveld method on the test pattern.

[0034] In some embodiments, the thickness of the coating layer is Tnm, and satisfies: 0.36≤T*(1-z)≤1.80.

[0035] Illustratively, when the thickness of the coating layer is Tnm, T*(1-z) can be any point value or a range value of any two points between 0.36 and 1.80. For example, T*(1-z) can be 0.36, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.70, 1.80, etc. When T*(1-z) is in the above range, the electrochemical performance of the secondary battery can be further improved.

[0036] In some embodiments, the T satisfies: 2≤T≤10.

[0037] Illustratively, the T is any point value or a range value of any two points between 2 and 10. For example, T can be 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. The thickness T of the coating layer in the above range can further reduce the dissolution of manganese.

[0038] In one embodiment of the present application, the present application provides a secondary battery, which comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, and the positive electrode active material layer comprises the positive electrode material described in the present application.

[0039] In some embodiments, the secondary battery further comprises a negative electrode sheet, a separator and an electrolyte.

[0040] In some embodiments, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector; and the negative electrode active material layer comprises a negative electrode active material. The present application does not limit the negative electrode active material, and any known negative electrode active material can be used.

[0041] The present application does not limit the composition of the electrolyte, and any known electrolyte composition can be used to prepare the electrolyte.

[0042] In an embodiment, the separator of the secondary battery is arranged between the positive electrode and the negative electrode.

[0043] In one embodiment of the present application, the present application provides an electric device, which comprises the secondary battery described in the present application.

[0044] For example, the above-mentioned electric device can include a mobile device (e.g., a mobile phone, a notebook computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0045] The following are specific embodiments of the present application, and the technical solutions of the present application are further described in conjunction with the embodiments. However, the present application is not limited to these embodiments. The reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field unless otherwise specified.

[0046] Embodiment 1

[0047] The present embodiment provides a lithium ion battery, and the preparation method comprises the following steps:

[0048] (1) Preparation of the positive electrode material:

[0049] S1. Mix Li2CO3, Sb2O5, FePO4, MnPO4 according to the molar ratio of 0.41:0.03:0.376:0.564, ball mill for 6 hours at 200 rpm, then take out the powder and press into a sheet, calcine at 1200℃ in oxygen for 6 hours, and naturally cool to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0050] S2. Dissolve appropriate amounts of Sb(NO3)5·9H2O and NH4HCO3 in deionized water to prepare solutions, add polyethylene glycol to the NH4HCO3 solution, then disperse the product obtained in S1 in the NH4HCO3 solution, magnetically stir to form a uniform dispersion, and drop the Sb(NO3)5 solution into the dispersion under the condition of a 90℃ water bath and continuous stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5·9H2O is 100:1, continue stirring for 4h, then filter, wash and dry, and finally calcine the product in a tube furnace at 400℃ in an oxygen atmosphere for 5h to obtain a positive electrode material sample coated with Sb2O5.

[0051] (2) Preparation of the positive electrode sheet:

[0052] The positive electrode material, conductive agent carbon black, and binder PVDF are mixed in a mass ratio of 96.5:2:1.5, a solvent NMP is added, and stirring is performed under the action of a vacuum stirrer to obtain a positive electrode slurry; the positive electrode slurry is uniformly coated on a positive electrode current collector aluminum foil, dried at room temperature, then transferred to an oven for continuous drying, and then subjected to rolling, slitting, and cutting to obtain a positive electrode sheet.

[0053] (3) Preparation of a negative electrode sheet:

[0054] The negative electrode active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber, and dispersant sodium carboxymethyl cellulose are mixed in a mass ratio of 96.5:1.5:1.5:0.5, a solvent deionized water is added, and stirring is performed under the action of a vacuum stirrer to obtain a negative electrode slurry; the negative electrode slurry is uniformly coated on a negative electrode current collector copper foil, dried at room temperature, then transferred to an oven for continuous drying, and then subjected to rolling, slitting, and cutting to obtain a negative electrode sheet.

[0055] (4) Preparation of an electrolyte:

[0056] Vinyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 1:1:1, then LiPF6 is added, and mixed uniformly to prepare an electrolyte with a LiPF6 concentration of 1 mol / L.

[0057] (5) Preparation of a lithium ion battery:

[0058] The positive electrode sheet, separator (polyethylene), and negative electrode sheet are sequentially stacked with the separator exactly between the positive electrode and the negative electrode to play a role of isolating the two electrodes, then wound into a bare cell and placed in an aluminum plastic film, baked at 80°C to remove moisture, then injected with electrolyte, and then subjected to sealing, hot and cold pressing, secondary sealing, formation, and capacity distribution to obtain a finished battery.

[0059] Example 2

[0060] The difference between Example 2 and Example 1 lies in the preparation method of the positive electrode material. In this embodiment, the preparation method of the positive electrode material is as follows:

[0061] S1. Li2CO3, Bi2O3, FePO4, and MnPO4 are mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball milled at a speed of 200 revolutions per minute for 6 hours, then pressed into a sheet, calcined at 1200°C in an oxygen atmosphere for 6 hours, and naturally cooled to obtain Li 0.82 V 0.18 Bi 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0062] S2. An appropriate amount of Bi(NO3)3.5H2O and NH4HCO3 were dissolved in deionized water to prepare solutions, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and magnetic stirring was performed to obtain a uniform dispersion liquid. The Bi(NO3)3 solution was added dropwise into the dispersion liquid under the condition of a 90°C water bath and continuous stirring, the molar ratio of the product obtained in S1 to Bi(NO3)3.5H2O was 100:1, and the stirring was continued for 4 h, then the product was filtered, washed and dried. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a positive electrode material sample coated with Bi2O5.

[0063] Example 3

[0064] Example 3 differs from Example 1 in that the preparation method of the positive electrode material is different. In this embodiment, the preparation method of the positive electrode material is as follows:

[0065] S1. Li2CO3, Nb2O5, FePO4 and MnPO4 were mixed according to a molar ratio of 0.41:0.03:0.376:0.564, ball-milling was performed at a speed of 200 revolutions per minute for 6 hours, then the powder was taken out and pressed into a sheet, and the sheet was calcined in oxygen at 1200°C for 6 hours, and then naturally cooled to obtain Li 0.82 V 0.18 Nb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0066] S2. An appropriate amount of niobium oxalate (C 10 H5NbO 20 ) and NH4HCO3 were dissolved in deionized water to prepare solutions, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and magnetic stirring was performed to obtain a uniform dispersion liquid. The niobium oxalate (C 10 H5NbO 20 ) solution was added dropwise into the dispersion liquid under the condition of a 90°C water bath and continuous stirring, the molar ratio of the product obtained in S1 to niobium oxalate (C 10 H5NbO 20 ) was 100:1, and the stirring was continued for 4 h, then the product was filtered, washed and dried. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a positive electrode material sample coated with Nb2O5.

[0067] Example 4

[0068] Example 4 differs from Example 1 in that the preparation method of the positive electrode material is different. In this embodiment, the preparation method of the positive electrode material is as follows:

[0069] S1. Li2CO3, Ta2O5, FePO4, MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled for 6 hours at 200 rpm, then the powder was taken out and pressed into a sheet, calcined in oxygen at 1200°C for 6 hours, and then naturally cooled to obtain Li 0.82 V 0.18 Ta 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0070] S2. A proper amount of tantalum oxalate (C 10 H5TaO 20 ) and NH4HCO3 were dissolved in deionized water to prepare a solution, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and magnetic stirring was performed to obtain a uniform dispersion liquid, the tantalum oxalate (C 10 H5TaO 20 ) solution was added dropwise to the dispersion liquid under the condition of a 90°C water bath and continuous stirring, the molar ratio of the product obtained in S1 to the tantalum oxalate (C 10 H5TaO 20 ) was 100:1, stirring was continued for 4 hours, then filtration, washing and drying were performed, and finally the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 hours to obtain a positive electrode material sample coated with Ta2O5.

[0071] Example 5

[0072] The difference between Example 5 and Example 1 is that the preparation method of the positive electrode material is different. In this embodiment, the preparation method of the positive electrode material is as follows:

[0073] S1. Li2CO3, Sb2O5, FePO4, MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled for 6 hours at 200 rpm, then the powder was taken out and pressed into a sheet, calcined in oxygen at 1400°C for 6 hours, and then naturally cooled to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0074] S2. An appropriate amount of Sb(NO3)5-9H2O and NH4HCO3 were dissolved in deionized water to prepare a solution, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and a uniform dispersion was obtained by magnetic stirring. The Sb(NO3)5 solution was added dropwise to the dispersion under the condition of a 90°C water bath and continuous stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5-9H2O was 100:1, and the stirring was continued for 4 h before filtration, washing and drying. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a sample of the Sb2O5-coated positive electrode material.

[0075] Example 6

[0076] Example 6 differs from Example 1 in that the preparation method of the positive electrode material is different. In this example, the preparation method of the positive electrode material is as follows:

[0077] S1. Li2CO3, Sb2O5, FePO4, and MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled at 200 rpm for 6 hours, then the powder was taken out and pressed into a sheet, calcined at 1100°C for 6 hours in oxygen, and naturally cooled to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0078] S2. An appropriate amount of Sb(NO3)5-9H2O and NH4HCO3 were dissolved in deionized water to prepare a solution, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and a uniform dispersion was obtained by magnetic stirring. The Sb(NO3)5 solution was added dropwise to the dispersion under the condition of a 90°C water bath and continuous stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5-9H2O was 100:1, and the stirring was continued for 4 h before filtration, washing and drying. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a sample of the Sb2O5-coated positive electrode material.

[0079] Example 7

[0080] Example 7 differs from Example 1 in that the preparation method of the positive electrode material is different. In this example, the preparation method of the positive electrode material is as follows:

[0081] S1. Li2CO3, Sb2O5, FePO4, MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled for 6 hours at a speed of 200 rpm, then the powder was taken out and pressed into a sheet, calcined in oxygen at 1300°C for 6 hours, and then naturally cooled to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0082] S2. A proper amount of Sb(NO3)5.9H2O and NH4HCO3 were dissolved in deionized water to prepare solutions, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and the mixture was stirred magnetically to form a uniform dispersion liquid, the Sb(NO3)5 solution was added dropwise into the dispersion liquid under the condition of a water bath at 90°C and continuous stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5.9H2O was 100:1. After continuous stirring for 4 hours, the mixture was filtered, washed and dried, and finally the product was calcined in a tube furnace at 400°C in an oxygen atmosphere for 5 hours to obtain a sample of the positive electrode material coated with Sb2O5.

[0083] Example 8

[0084] The difference between Example 8 and Example 1 is the preparation method of the positive electrode material. In this example, the preparation method of the positive electrode material is as follows:

[0085] S1. Li2CO3, Sb2O5, FePO4, MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled for 6 hours at a speed of 200 rpm, then the powder was taken out and pressed into a sheet, calcined in oxygen at 1300°C for 6 hours, and then naturally cooled to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0086] S2. An appropriate amount of Sb(NO3)5-9H2O and NH4HCO3 were dissolved in deionized water to prepare a solution, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and the mixture was stirred magnetically to form a uniform dispersion. The Sb(NO3)5 solution was added dropwise to the dispersion under the condition of a 90°C water bath and constant stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5-9H2O was 100:1, and the stirring was continued for 4 h before filtration, washing and drying. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a sample of the Sb2O5-coated positive electrode material.

[0087] Example 9

[0088] Example 9 differs from Example 1 in the method of preparing the positive electrode material. In this example, the method of preparing the positive electrode material is as follows:

[0089] S1. Li2CO3, Sb2O5, FePO4 and MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled at 200 rpm for 6 hours, then the powder was taken out and pressed into a sheet, and calcined in oxygen at 1200°C for 4 hours. After natural cooling, Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0090] S2. An appropriate amount of Sb(NO3)5-9H2O and NH4HCO3 were dissolved in deionized water to prepare a solution, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and the mixture was stirred magnetically to form a uniform dispersion. The Sb(NO3)5 solution was added dropwise to the dispersion under the condition of a 90°C water bath and constant stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5-9H2O was 100:1, and the stirring was continued for 4 h before filtration, washing and drying. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a sample of the Sb2O5-coated positive electrode material.

[0091] Example 10

[0092] Example 10 differs from Example 1 in the method of preparing the positive electrode material. In this example, the method of preparing the positive electrode material is as follows:

[0093] S1. Li2CO3, Sb2O5, FePO4, MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled for 6 hours at a rotation speed of 200 rpm, then the powder was taken out and pressed into a sheet, calcined at 1200°C in oxygen for 8 hours, and then cooled naturally to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0094] S2. A proper amount of Sb(NO3)5.9H2O and NH4HCO3 were dissolved in deionized water to prepare solutions, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and the mixture was stirred magnetically to form a uniform dispersion liquid, the Sb(NO3)5 solution was added dropwise to the dispersion liquid under the condition of a water bath at 90°C and continuous stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5.9H2O was 100:1, the stirring was continued for 4 hours, then the product was filtered, washed and dried, and finally the product was calcined in a tube furnace at 400°C in an oxygen atmosphere for 5 hours to obtain a sample of the positive electrode material coated with Sb2O5.

[0095] Example 11

[0096] Example 11 differs from Example 1 in that the preparation method of the positive electrode material is different. In this example, the preparation method of the positive electrode material is as follows:

[0097] S1. Li2CO3, Sb2O5, FePO4, MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled for 6 hours at a rotation speed of 200 rpm, then the powder was taken out and pressed into a sheet, calcined at 1200°C in oxygen for 8 hours, and then cooled naturally to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0098] S2. An appropriate amount of Sb(NO3)5-9H2O and NH4HCO3 were dissolved in deionized water to prepare a solution, polyethylene glycol was added to the NH4HCO3 solution, and then the product obtained in S1 was dispersed in the NH4HCO3 solution, which was stirred magnetically to form a uniform dispersion. The Sb(NO3)5 solution was added dropwise to the dispersion under the condition of a 90°C water bath and constant stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5-9H2O was 100:1, and the stirring was continued for 4 h before filtration, washing and drying. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a sample of the Sb2O5-coated positive electrode material.

[0099] Example 12

[0100] Example 12 differs from Example 1 in the method of preparing the positive electrode material. In this example, the method of preparing the positive electrode material is as follows:

[0101] S1. Li2CO3, Sb2O5, FePO4 and MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled at 200 rpm for 6 hours, and then the powder was taken out and pressed into a sheet, which was calcined in oxygen at 1200°C for 7 hours, and then naturally cooled to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0102] S2. An appropriate amount of Sb(NO3)5-9H2O and NH4HCO3 were dissolved in deionized water to prepare a solution, polyethylene glycol was added to the NH4HCO3 solution, and then the product obtained in S1 was dispersed in the NH4HCO3 solution, which was stirred magnetically to form a uniform dispersion. The Sb(NO3)5 solution was added dropwise to the dispersion under the condition of a 90°C water bath and constant stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5-9H2O was 100:1, and the stirring was continued for 4 h before filtration, washing and drying. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a sample of the Sb2O5-coated positive electrode material.

[0103] Example 13

[0104] Example 13 differs from Example 1 in the method of preparing the positive electrode material. In this example, the method of preparing the positive electrode material is as follows:

[0105] (1) Preparation of the positive electrode material:

[0106] S1. Li2CO3, Sb2O5, FePO4, MnPO4 were mixed in a molar ratio of 0.35:0.05:0.36:0.54, ball-milled for 6 hours at a speed of 200 rpm, then the powder was taken out and pressed into a sheet, calcined in oxygen at 1200°C for 6 hours, and then naturally cooled to obtain Li 0.7 V 0.3 Sb 0.1 [Mn 0.6 Fe 0.4 ] 0.9 PO4.

[0107] S2. A proper amount of Sb(NO3)5.9H2O and NH4HCO3 were dissolved in deionized water to prepare solutions, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and the mixture was stirred magnetically to form a uniform dispersion liquid, the Sb(NO3)5 solution was added dropwise to the dispersion liquid under the condition of a water bath at 90°C and continuous stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5.9H2O was 100:1, the stirring was continued for 4 hours, then the product was filtered, washed and dried, and finally the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 hours to obtain a sample of the positive electrode material coated with Sb2O5.

[0108] Example 14

[0109] The difference between Example 14 and Example 1 is that the preparation method of the positive electrode material is different. In this example, the preparation method of the positive electrode material is as follows:

[0110] (1) Preparation of the positive electrode material:

[0111] S1. Li2CO3, Sb2O5, FePO4, MnPO4 were mixed in a molar ratio of 0.35:0.05:0.36:0.54, ball-milled for 6 hours at a speed of 200 rpm, then the powder was taken out and pressed into a sheet, calcined in oxygen at 1200°C for 6 hours, and then naturally cooled to obtain Li 0.92 V 0.08 Sb 0.027 [Mn 0.6 Fe 0.4 ] 0.973 PO4.

[0112] S2. An appropriate amount of Sb(NO3)5-9H2O and NH4HCO3 were dissolved in deionized water to prepare a solution, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and magnetic stirring was performed to obtain a uniform dispersion liquid. The Sb(NO3)5 solution was added dropwise into the dispersion liquid under the condition of a 90°C water bath and continuous stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5-9H2O was 100:1, and the stirring was continued for 4 h, then the product was filtered, washed and dried. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a sample of the positive electrode material coated with Sb2O5.

[0113] Example 15

[0114] Example 15 differs from Example 1 in that the preparation method of the positive electrode material is different. In this example, the preparation method of the positive electrode material is as follows:

[0115] (1) Preparation of the positive electrode material:

[0116] S1. Li2CO3, Sb2O5, FePO4, and MnPO4 were mixed according to a molar ratio of 0.41:0.03:0.376:0.564, ball-milled at a speed of 200 revolutions per minute for 6 hours, then the powder was taken out and pressed into a sheet, and calcined at 1200°C in oxygen for 6 hours, and then naturally cooled to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0117] S2. An appropriate amount of Sb(NO3)5-9H2O and NH4HCO3 were dissolved in deionized water to prepare a solution, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and magnetic stirring was performed to obtain a uniform dispersion liquid. The Sb(NO3)5 solution was added dropwise into the dispersion liquid under the condition of a 90°C water bath and continuous stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5-9H2O was 100:0.6, and the stirring was continued for 4 h, then the product was filtered, washed and dried. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a sample of the positive electrode material coated with Sb2O5.

[0118] Example 16

[0119] Example 16 differs from Example 1 in that the preparation method of the positive electrode material is different. In this example, the preparation method of the positive electrode material is as follows:

[0120] (1) Preparation of the positive electrode material:

[0121] S1. Li2CO3, Sb2O5, FePO4, MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled for 6 hours at a speed of 200 rpm, then the powder was taken out and pressed into a sheet, calcined in oxygen at 1200°C for 6 hours, and then naturally cooled to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0122] S2. A proper amount of Sb(NO3)5.9H2O and NH4HCO3 were dissolved in deionized water to prepare solutions, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and the mixture was stirred magnetically to form a uniform dispersion liquid, the Sb(NO3)5 solution was added dropwise into the dispersion liquid under the condition of a water bath at 90°C and continuous stirring, the molar ratio of the product obtained in S1 to Sb(NO3)5.9H2O was 100:0.4, the stirring was continued for 4 hours, then the product was filtered, washed and dried, and finally the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 hours to obtain a sample of the positive electrode material coated with Sb2O5.

[0123] Example 17

[0124] Example 17 differs from Example 1 in that the preparation method of the positive electrode material is different. In this example, the preparation method of the positive electrode material is as follows:

[0125] (1) Preparation of the positive electrode material:

[0126] S1. Li2CO3, Sb2O5, FePO4, MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled for 6 hours at a speed of 200 rpm, then the powder was taken out and pressed into a sheet, calcined in oxygen at 1200°C for 6 hours, and then naturally cooled to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0127] S2. An appropriate amount of Sb(N03)5-9H20 and NH4HCO3 were dissolved in deionized water to prepare a solution, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and magnetic stirring was performed to obtain a uniform dispersion liquid. The Sb(N03)5 solution was added dropwise into the dispersion liquid under the condition of a 90°C water bath and continuous stirring, the molar ratio of the product obtained in S1 to Sb(N03)5-9H20 was 100:1.2, and the stirring was continued for 4 h, then the product was filtered, washed and dried. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a sample of the positive electrode material coated with Sb205.

[0128] Example 18

[0129] Example 18 differs from Example 1 in that the preparation method of the positive electrode material is different. In this example, the preparation method of the positive electrode material is as follows:

[0130] (1) Preparation of the positive electrode material:

[0131] S1. Li2CO3, Sb205, FePO4, and MnPO4 were mixed according to a molar ratio of 0.41:0.03:0.376:0.564, ball-milled at a speed of 200 revolutions per minute for 6 hours, then the powder was taken out and pressed into a sheet, and calcined at 1200°C in oxygen for 6 hours, and then naturally cooled to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0132] S2. An appropriate amount of Sb(N03)5-9H20 and NH4HCO3 were dissolved in deionized water to prepare a solution, polyethylene glycol was added to the NH4HCO3 solution, then the product obtained in S1 was dispersed in the NH4HCO3 solution, and magnetic stirring was performed to obtain a uniform dispersion liquid. The Sb(N03)5 solution was added dropwise into the dispersion liquid under the condition of a 90°C water bath and continuous stirring, the molar ratio of the product obtained in S1 to Sb(N03)5-9H20 was 100:1.2, and the stirring was continued for 4 h, then the product was filtered, washed and dried. Finally, the product was calcined in a tube furnace under an oxygen atmosphere at 400°C for 5 h to obtain a sample of the positive electrode material coated with Sb205.

[0133] Example 19

[0134] Example 19 differs from Example 1 in that the preparation method of the positive electrode material is different. In this example, the preparation method of the positive electrode material is as follows:

[0135] Li2CO3, Sb2O5, FePO4, MnPO4 were mixed in a molar ratio of 0.41:0.03:0.376:0.564, ball-milled for 6 hours at 200 rpm, then the powder was taken out and pressed into a sheet, calcined in oxygen at 1200°C for 6 hours, and then naturally cooled to obtain Li 0.82 V 0.18 Sb 0.06 [Mn 0.6 Fe 0.4 ] 0.94 PO4.

[0136] Comparative Example 1

[0137] Comparative Example 1 provides a lithium ion battery, which differs from Example 1 in the preparation method of the positive electrode material. In Comparative Example 1, the preparation method of the positive electrode material is as follows:

[0138] Li2CO3, FePO4 and MnPO4 were mixed in a molar ratio of 0.5:0.4:0.6, ball-milled for 6 hours at 200 rpm, then the powder was taken out and pressed into a sheet, calcined in oxygen at 1200°C for 6 hours, and then naturally cooled to obtain LiMn 0.6 Fe 0.4 PO4.

[0139] The parameters of the positive electrode materials obtained in Examples 1-19 and Comparative Example 1 are shown in Table 1.

[0140] Table 1

[0141] The performance of the secondary batteries obtained in the examples and comparative examples was tested, and the specific testing methods were as follows:

[0142] 1) Gas production performance test: connect the injection port of the secondary battery to a pressure gauge and adjust to zero. Place the battery in a charge-discharge test cabinet, maintain a constant temperature of 25°C, voltage range of 2.5-4.25V, charge rate of 1C, discharge rate of 1C, and cycle test. When the test number is 100, stop the test and read the pressure of the pressure gauge.

[0143] 2) Rate performance test: place a fresh secondary battery that has not undergone electrochemical testing on a charge-discharge tester in a room temperature environment, charge at 0.33C to 4.25V, discharge at 0.33C to 2.5V, and the capacity is Q1. Charge at 0.33C to 4.25V, discharge at 6C to 2.5V, and the capacity is Q2. Rate performance = Q2 / Q1*100%.

[0144] 3) Cycle performance test: the secondary battery was placed in a charge-discharge test cabinet, 25℃ constant temperature, voltage range 2.5-4.25V, charge rate 1C, discharge rate 1C, cycle test. When the capacity dropped to 80% of the initial capacity, the test was stopped, and the cycle number was recorded.

[0145] The test results of the secondary batteries obtained in Examples 1-19 and Comparative Example 1 are shown in Table 2

[0146] Table 2

[0147] From the above examples and comparative examples, it can be seen that, by controlling the lithium vacancies and high-valence metal ions in the positive electrode material, and controlling the content of lithium vacancies and high-valence metal ions in the positive electrode material, the secondary battery prepared has excellent electrochemical performance.

[0148] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not a limitation on the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A cathode material, wherein, The positive electrode material comprises positive electrode active material particles, and the positive electrode active material particles contain the chemical formula Li. z V (1-z) M x [Mn y Fe (1-y) ] 1-x A compound of PO4, wherein 0.027≤x≤0.1, 0.1≤y≤0.9, 0.70≤z≤0.92, V is a lithium hole, and M contains a metallic element with a valence of at least +5.

2. The cathode material according to claim 1, wherein, At least a portion of the surface of the positive electrode active material particles has a coating layer, the coating layer containing the element M.

3. The cathode material according to claim 1, wherein, At least a portion of the surface of the positive electrode active material particles has a coating layer comprising a metal oxide with the chemical formula M2O5.

4. The cathode material according to any one of claims 1 to 3, wherein, M includes at least one of Sb, Bi, Nb, and Ta.

5. The cathode material according to claim 3, wherein, The metal oxide is one or more of Sb2O5, Bi2O5, Nb2O5, and Ta2O5.

6. The cathode material according to claim 3, wherein, The cell parameter b of the positive electrode active material particles is b1, and the cell parameter b of the metal oxide is b2, satisfying: 0.97≤b2 / b1≤1.

03.

7. The cathode material according to claim 6, wherein, b2 / b1 is 0.97, 0.98, 0.99, 1.00, 1.01, 1.02 or 1.

03.

8. The cathode material according to claim 6, wherein, The cell parameter b of the positive electrode active material particles is b1, which satisfies: 1.014nm≤b1≤1.064nm; And / or, the cell parameter b of the metal oxide is b2, satisfying: 1.013nm≤b2≤1.073nm.

9. The cathode material according to claim 8, wherein, b1 can be 1.014nm, 1.024nm, 1.034nm, 1.044nm, 1.054nm, or 1.064nm.

10. The cathode material according to claim 8, wherein, b2 can be 1.013nm, 1.023nm, 1.033nm, 1.043nm, 1.053nm, 1.063nm, or 1.073nm.

11. The cathode material according to claim 2 or 3, wherein, The thickness of the coating layer is T nm, which satisfies: 0.36≤T*(1-z)≤1.

80.

12. The cathode material according to claim 11, wherein, T*(1-z) is 0.36, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.70 or 1.

80.

13. The cathode material according to claim 11, wherein, The condition T satisfies: 2≤T≤10.

14. The cathode material according to claim 13, wherein, T is 2, 3, 4, 5, 6, 7, 8, 9 or 10.

15. A secondary battery, wherein, It includes a positive electrode sheet, wherein the positive electrode sheet comprises the positive electrode material according to any one of claims 1 to 14.

16. The secondary battery according to claim 15, wherein, The secondary battery also includes a negative electrode, a separator, and an electrolyte.

17. The secondary battery according to claim 16, wherein, The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector; the negative active material layer includes a negative active material.

18. An electrical appliance, wherein, The electrical device includes the secondary battery as described in any one of claims 15-17.

19. The electrical appliance according to claim 18, wherein, The electrical devices include mobile devices, electric vehicles, electric trains, ships, and satellites or energy storage systems.

20. The electrical appliance according to claim 19, wherein, The mobile device includes a mobile phone, a laptop computer; and / or The electric vehicles include pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, or electric trucks.

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