Doped and coated lithium nickel manganese oxide positive electrode material, preparation method thereof and lithium ion battery

Abstract

The invention provides a doped and coated lithium nickel manganese oxide positive electrode material, a preparation method thereof and a lithium ion battery. The lithium nickel manganese oxide positive electrode material comprises lithium nickel manganese oxide particles, the coating layer contains an F and P double-doped carbon material, and the coating layer is positioned on the outer side of the lithium nickel manganese oxide particle; wherein the coating layer contains F and P, the electron withdrawing effect of F is relatively strong, the electron activity of the coating layer can be reduced, and electrolyte decomposition and Mn < 2 + > oxidation can be inhibited; meanwhile, the compactness of the coating layer can be improved through P doping, Mn < 2 + > on the surface of the coating layer is balanced through charge compensation, and the situation of manganese dissolution is reduced, so that the cycle life of the battery is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a doped coated lithium nickel manganese oxide cathode material, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] Spinel lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4, LNMO) as the third generation of lithium ion battery cathode material, because of its unique 4.7V (vs. Li / Li + ) high discharge platform and high theoretical energy density of 650Wh / kg, becomes the key research object in the field of high energy density power battery.

[0003] But in practical application, lithium nickel manganese oxide, due to the poor intrinsic dynamics of the material, is prone to disproportionation reaction in the process of high voltage cycle, affecting the cycle performance and charge-discharge performance of the battery. SUMMARY

[0004] The embodiments of the present application provide a doped coated lithium nickel manganese oxide cathode material, a preparation method thereof and a lithium ion battery, which can improve the technical problem of affecting the cycle performance and charge-discharge performance due to disproportionation reaction.

[0005] In a first aspect, the embodiments of the present application provide a doped coated lithium nickel manganese oxide cathode material, which comprises:

[0006] Lithium nickel manganese oxide particles;

[0007] A coating layer containing F and P doped carbon material, the coating layer is located on the outside of the lithium nickel manganese oxide particles.

[0008] In an embodiment, the mass percentage of the carbon material in the cathode material is in the range of 1% to 10%;

[0009] Preferably, the mass percentage of the carbon material in the cathode material is in the range of 3% to 8%. In an embodiment, the doping amount of F is in the range of 300ppm to 5000ppm; and / or

[0010] The doping amount of P is in the range of 200ppm to 3000ppm.

[0011] In an embodiment, the molecular formula of the lithium nickel manganese oxide particles is LiNi x Mn 2-x O4, wherein 0.49≤x≤0.51; and / or

[0012] The particle size of the lithium nickel manganese oxide particles is in the range of 0.8μm to 5μm.

[0013] In a second aspect, the embodiments of the present application provide a preparation method of a doped and coated lithium nickel manganese oxide positive electrode material, the preparation method comprising the following steps:

[0014] providing carbon-coated lithium nickel manganese oxide;

[0015] subjecting the carbon-coated lithium nickel manganese oxide to gas crushing, and then mixing the carbon-coated lithium nickel manganese oxide with a fluorine source and a phosphorus source to obtain a mixture;

[0016] subjecting the mixture to calcination to obtain the doped and coated lithium nickel manganese oxide positive electrode material.

[0017] In an embodiment, the carbon-coated lithium nickel manganese oxide is prepared by the following steps:

[0018] mixing a carbon source, a lithium source, a nickel source, and a manganese source with a solvent to obtain a mixed slurry;

[0019] subjecting the mixed slurry to spray granulation to obtain precursor particles;

[0020] subjecting the precursor particles to sintering to obtain the carbon-coated lithium nickel manganese oxide.

[0021] In an embodiment, in the step of mixing the carbon source, the lithium source, the nickel source, and the manganese source with the solvent, one of the following conditions is met:

[0022] the lithium source comprises at least one of lithium carbonate and lithium hydroxide;

[0023] the nickel source is at least one of nickel oxide, nickel hydroxide, and nickel acetate;

[0024] the manganese source is at least one of manganese dioxide and trimanganese tetroxide;

[0025] the carbon source is at least one of glucose, sucrose, and citric acid.

[0026] In an embodiment, in the step of preparing the carbon-coated lithium nickel manganese oxide, one of the following conditions is met:

[0027] the average particle size of the mixed slurry ranges from 0.3 μm to 0.5 μm;

[0028] the average particle size of the precursor particles ranges from 20 μm to 40 μm;

[0029] the temperature of the sintering ranges from 400 °C to 900 °C.

[0030] In an embodiment, the fluorine source comprises at least one of polyvinylidene fluoride and ammonium fluoride; and / or

[0031] the phosphorus source comprises at least one of triphenyl phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0032] In an embodiment, the temperature of the calcination ranges from 400℃ to 700℃.

[0033] In a third aspect, the embodiments of the present application provide a lithium ion battery, which comprises the doped coated lithium nickel manganese oxide cathode material as described above.

[0034] In an embodiment, the lithium ion battery satisfies one of the following conditions:

[0035] The lithium ion battery has a discharge specific capacity of 141.6-144.9 mAh·g -1 at 0.1C rate.

[0036] The lithium ion battery has a discharge specific capacity of 138.2-141.5 mAh·g -1 at 0.5C rate.

[0037] The lithium ion battery has a discharge specific capacity of 134.6-137.8 mAh·g -1 at 1C rate.

[0038] The lithium ion battery has a discharge specific capacity of 128.3-133.1 mAh·g -1 at 3C rate.

[0039] The lithium ion battery has a discharge specific capacity of 122.6-128.3 mAh·g -1 at 5C rate.

[0040] The lithium ion battery has a discharge specific capacity of 126.36-132.23 mAh·g -1 after 100 cycles at 1C rate.

[0041] The lithium ion battery has a manganese elution amount of 20.29-40.29 ppm after 100 cycles at 1C rate.

[0042] The embodiments of the present application have the following advantages:

[0043] In the embodiments of the present application, the cathode material comprises a coating layer, and the coating layer contains F and P. The electron-withdrawing effect of F is strong, which can reduce the electron activity of the coating layer, and help to inhibit the decomposition of the electrolyte and the oxidation of Mn 2+ . At the same time, P doping can improve the compactness of the coating layer, and balance the Mn 2+ on the surface of the coating layer through charge compensation, which helps to reduce the elution of manganese, thereby improving the cycle life of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to make the technical solutions in the embodiments of the present application clearer, the accompanying drawings needed in the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present application, and all other embodiments obtained by those skilled in the art without creative efforts based on the accompanying drawings also belong to the protection scope of the present application.

[0045] Figure 1 Flow chart of the preparation method in the embodiments of the present application. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, and specifically refer to the direction of the drawing surface in the accompanying drawings; and "inner" and "outer" refer to the outline of the device.

[0047] In practical applications, the electronic conductivity of lithium nickel manganese oxide is low (about 10 -6 S / cm), and the diffusion rate of lithium ions is slow (10 -12 ~ 10 -13 cm 2 / s), which leads to serious capacity attenuation during high-rate charging and discharging, and it is difficult to meet the demand for fast charging and discharging of power batteries. Moreover, under high-voltage working conditions above 4.7V, the electrolyte is prone to oxidative decomposition, and the Mn 3+ on the surface of lithium nickel manganese oxide will undergo disproportionation reaction (Mn 3+ → Mn 2+ + Mn 4+ ), which leads to the dissolution of manganese ions (Mn 2+ dissolved into the electrolyte and migrated to the negative electrode and deposited), which not only aggravates the loss of active material, but also destroys the interface stability of the electrode / electrolyte, significantly reducing the cycle life.

[0048] In the related art, the improvement of the above problems can be: 1) by doping a single element, although the electrical conductivity can be partially improved, but the inhibition effect on manganese dissolution is limited; 2) by a traditional carbon coating layer, although the electrical conductivity can be improved, but the coating layer is easy to fail due to the penetration of the electrolyte or loose structure, and cannot effectively block the dissolution of manganese.

[0049] In view of this, the embodiments of the present application provide a doped and coated lithium nickel manganese oxide positive electrode material, a preparation method thereof, and a lithium ion battery, aiming to obtain a positive electrode material having both high electrical conductivity and low manganese dissolution.

[0050] According to a first aspect of the present application, a doped and coated lithium nickel manganese oxide positive electrode material is provided, wherein the lithium nickel manganese oxide positive electrode material comprises:

[0051] lithium nickel manganese oxide particles;

[0052] The coating layer contains a carbon material doped with F and P, and is located on the outside of the lithium nickel manganese oxide particles.

[0053] By adopting the above scheme, the positive electrode material of the embodiment of the present application includes a coating layer, the coating layer contains F and P, F has a strong electron-withdrawing effect, which can reduce the electronic activity of the coating layer, and help to inhibit the decomposition of the electrolyte and the formation of Mn. 2+ At the same time, P doping can improve the density of the coating layer and balance the Mn on the surface of the coating layer through charge compensation. 2+ , which helps to reduce manganese dissolution and thus improve the cycle life of the battery.

[0054] In some embodiments of the present application, the mass percentage of the carbon material in the positive electrode material ranges from 1% to 10%. Further, the mass percentage of the carbon material in the positive electrode material ranges from 3% to 8%. For example, the mass percentage of the carbon material in the positive electrode material can be 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, and any value between two adjacent values ​​mentioned above.

[0055] By adopting the above solution, the mass percentage of carbon material in the positive electrode material is within an appropriate range, which helps to improve the conductivity of the positive electrode material and significantly enhances the cycle stability. At the same time, the increased density of the carbon layer helps to reduce the amount of manganese dissolution. However, if the mass percentage of carbon material in the positive electrode material is relatively small, the coating layer may lack continuity, the risk of electrolyte penetration is high, and the effect of inhibiting manganese dissolution is limited. If the mass percentage of carbon material in the positive electrode material is relatively large, the interfacial impedance may increase, resulting in a decrease in rate performance.

[0056] In some embodiments of the present application, the doping amount of F ranges from 300 ppm to 5000 ppm. Further, the doping amount of F ranges from 580 ppm to 4200 ppm. For example, the doping amount of F is 580 ppm, 600 ppm, 650 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1700 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4200 ppm, or any value between any two adjacent values of the above.

[0057] By using the above scheme, the doping amount of F is relatively large, the electron-withdrawing effect of F is relatively strong, the electron activity of the coating layer can be reduced, which helps to inhibit the decomposition of the electrolyte and the oxidation of Mn 2+ .

[0058] In some embodiments of the present application, the doping amount of P ranges from 200 ppm to 3000 ppm. Further, the doping amount of P ranges from 310 ppm to 2100 ppm. For example, the doping amount of P is 310 ppm, 350 ppm, 400 ppm, 430 ppm, 480 ppm, 520 ppm, 570 ppm, 650 ppm, 720 ppm, 800 ppm, 850 ppm, 900 ppm, 1000 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, or any value between any two adjacent values of the above.

[0059] By using the above scheme, P doping can improve the compactness of the coating layer, and balance the Mn 2+ on the surface of the coating layer through charge compensation, which helps to reduce the dissolution of manganese, thereby improving the cycle life of the battery.

[0060] It can be understood that, as the content of the carbon material increases, the doping amount of F increases relatively more, and the doping amount of P increases relatively less.

[0061] In some embodiments of the present application, the molecular formula of the lithium nickel-manganese oxide particles is LiNi x Mn 2-x O4, wherein 0.49≤x≤0.51.

[0062] By adopting the above scheme, when x slightly fluctuates in the range of 0.49-0.51, the ratio of nickel to manganese is close to 1:3, the nickel content is moderate, and the high-capacity rate performance is ensured; moreover, x in the above range helps to improve the high orderliness of the crystal structure, avoiding the lattice defects or local stress concentration caused by the deviation of the ratio; in addition, when x is in the above range, the Mn 3+ content is the lowest, which helps to reduce the manganese dissolution caused by disproportionation reaction. However, if the value of x is too large, nickel is excessive, and the lattice distortion is aggravated; if the value of x is too small, the capacity is reduced due to the lack of nickel.

[0063] In some embodiments of the present application, the particle size of the lithium nickel manganese oxide particles ranges from 0.8 μm to 5 μm. Exemplarily, the particle size of the lithium nickel manganese oxide particles is 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, and any value between any two adjacent values.

[0064] By adopting the above scheme, the particle size of the lithium nickel manganese oxide particles is small, which is beneficial to shorten the diffusion path of lithium ions and improve the high-rate performance of the positive electrode material; at the same time, the small particle size also helps to achieve uniform distribution through the process, which is beneficial to improve the compactness of electrode coating and thus increase the compaction density. However, if the particle size of the lithium nickel manganese oxide particles is too small, the positive electrode material is prone to agglomeration during processing, and the interface impedance is increased; if the particle size of the lithium nickel manganese oxide is too large, the specific surface area is reduced, the lithium ion diffusion path is lengthened, and the rate performance may be reduced.

[0065] In a second aspect, the embodiments of the present application provide a preparation method of the doped and coated lithium nickel manganese oxide positive electrode material, which is described with reference to Figure 1 The preparation method comprises the following steps:

[0066] S100, providing carbon-coated lithium nickel manganese oxide;

[0067] S200, performing gas crushing on the carbon-coated lithium nickel manganese oxide, and then mixing the carbon-coated lithium nickel manganese oxide with a fluorine source and a phosphorus source to obtain a mixture;

[0068] S300, calcining the mixture to obtain the doped and coated lithium nickel manganese oxide positive electrode material.

[0069] By adopting the above scheme, the carbon-coated lithium nickel manganese oxide can form a continuous conductive network, which helps to improve the electrical conductivity and is suitable for supporting high-rate charge and discharge. The carbon-coated lithium nickel manganese oxide is then gas-crushed to help increase the specific surface area, helping to ensure that the gas-crushed lithium nickel manganese oxide is fully mixed with the fluorine source and phosphorus source, ensuring that the fluorine and phosphorus precursors are evenly adsorbed on the surface of the carbon layer, which helps to improve the uniformity of subsequent doping reactions. After calcination, fluorine and phosphorus are embedded in the carbon layer in the form of CF and CP bonds, which helps to accelerate the diffusion of lithium ions, thereby achieving the preparation of a battery with both high electrical conductivity and low manganese dissolution. In addition, the dense doped carbon layer helps to protect the lithium nickel manganese oxide particles, making it suitable for high-voltage power batteries.

[0070] In some embodiments of the present application, carbon-coated lithium nickel manganese oxide can be prepared by the following steps:

[0071] mixing a carbon source, a lithium source, a nickel source, and a manganese source with a solvent to prepare a mixed slurry;

[0072] The mixed slurry is spray-granulated to obtain precursor particles;

[0073] The precursor particles are then sintered to obtain carbon-coated lithium nickel manganese oxide.

[0074] By adopting the above scheme, the raw materials are mixed, spray granulated and then sintered to prepare carbon-coated lithium nickel manganese oxide, which is helpful to prepare carbon-coated lithium nickel manganese oxide with a uniform and dense coating layer.

[0075] In some embodiments of the present application, the lithium source may include at least one of lithium carbonate and lithium hydroxide.

[0076] By adopting the above scheme, the decomposition temperature of lithium carbonate is higher, and in the high-temperature solid-phase reaction, it decomposes later, which helps to release lithium ions more slowly, thereby being more conducive to the formation of a uniform spinel structure; the strong alkalinity of lithium hydroxide is conducive to adjusting the pH value during the formation of the carbon layer, promoting the uniformity of fluorine and phosphorus doping, and thus inhibiting manganese dissolution.

[0077] In some embodiments of the present application, the nickel source is at least one of nickel oxide, nickel hydroxide, and nickel acetate.

[0078] By adopting the above scheme, the decomposition temperature of nickel oxide is high, and nickel ions are gradually released in the high-temperature solid-phase reaction, which helps to form a uniform spinel structure; the decomposition temperature of nickel hydroxide is low, which helps to release nickel ions early, accelerates the reaction with manganese source and lithium source, and shortens the process time; the pyrolysis of nickel acetate is synchronized with the pyrolysis process of the carbon source, which helps to optimize the uniformity of the carbon coating layer.

[0079] In some embodiments of the present application, the manganese source is at least one of manganese dioxide and trimanganese tetraoxide.

[0080] By adopting the above scheme, the manganese dioxide has high oxidation state stability, and the high oxidation state manganese is combined more densely in the crystal lattice, and the fluorine and phosphorus doped carbon layer plays an effective passivation effect, thereby reducing the manganese dissolution in the cycle process; the mixed valence manganese ions exist in the trimanganese tetroxide, the mixed valence manganese ions can accelerate the reaction with the lithium source, and the mixed valence can optimize the electron conduction path in the crystal lattice, and improve the rate performance.

[0081] In some embodiments of the present application, the carbon source is at least one of glucose, sucrose, and citric acid.

[0082] By adopting the above scheme, the glucose coating helps to form a network structure, providing a faster electron transmission channel, and the conductivity is significantly improved; and the network structure covers the active sites on the surface of the lithium nickel manganese oxide, which helps to reduce direct contact with the electrolyte and inhibit the occurrence of side reactions. The sucrose coating helps to form a dense structure after calcination, thereby forming stable C-F and C-P bonds; and the dense layer helps to block the penetration of the electrolyte, thereby reducing the amount of manganese dissolution.

[0083] In some embodiments of the present application, the average particle size of the mixed slurry can be in the range of 0.3 μm to 0.5 μm. For example, the average particle size of the mixed slurry can be 0.3 μm, 0.31 μm, 0.32 μm, 0.33 μm, 0.34 μm, 0.35 μm, 0.36 μm, 0.37 μm, 0.38 μm, 0.39 μm, 0.40 μm, 0.41 μm, 0.42 μm, 0.43 μm, 0.44 μm, 0.45 μm, 0.46 μm, 0.47 μm, 0.48 μm, 0.49 μm, 0.50 μm, and any value between any two adjacent values.

[0084] By adopting the above scheme, the average particle size of the mixed slurry is in a suitable range, which helps to ensure the fluidity of the mixed slurry, thereby ensuring the uniformity of the carbon coating layer; and the average particle size in a suitable range helps to optimize the ion diffusion path, thereby significantly improving the rate performance, cycle stability and manganese dissolution inhibition performance.

[0085] In some embodiments of the present application, the average particle size of the precursor particles is in the range of 20 μm to 40 μm. For example, the average particle size of the precursor particles can be 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 33 μm, 35 μm, 37 μm, 40 μm, and any value between any two adjacent values.

[0086] By adopting the above scheme, the average particle size of the precursor particles is moderate, which can ensure that the mixed slurry forms uniform secondary particles in the spray granulation process; moreover, the heat conduction of the secondary particles is relatively uniform during high-temperature sintering, reducing local stress concentration, and cooperating with the passivation effect of fluorine-phosphorus co-doped carbon layer, significantly prolonging the cycle life. In addition, the average particle size of the precursor particles is within a suitable range, which is conducive to the moderate roughness of the surface of the precursor particles, thereby facilitating uniform adsorption of the carbon source.

[0087] In some embodiments of the present application, the sintering temperature can be in the range of 400-900℃. Illustratively, the sintering temperature can be 400-500℃, with a holding time of 3-6h; then continue to sinter at 800-900℃, with a holding time of 8-12h; and then reduce the temperature to 700-800℃, and anneal for 4-6h.

[0088] By adopting the above scheme, the sintering temperature is within the above range, which is conducive to optimizing the carbon layer. For example, at 400-500℃, the carbon source pyrolyzes to form amorphous carbon at this temperature interval, and a coating layer is initially formed. Then, the coating layer forms spinel at a higher temperature interval, such as 800-900℃, which is conducive to improving the high-voltage stability of the material. Moreover, high temperature can promote the densification of the structure of the carbon layer, while improving the electrical conductivity and reducing manganese dissolution. In addition, high temperature is also conducive to optimizing the lattice arrangement of lithium nickel manganese oxide, reducing oxygen vacancies and grain boundary defects.

[0089] In some embodiments of the present application, the fluorine source can include at least one of polyvinylidene fluoride and ammonium fluoride.

[0090] By adopting the above scheme, polyvinylidene fluoride gradually releases fluorine elements during high-temperature decomposition, forming uniform C-F bonds embedded in the carbon layer; moreover, polyvinylidene fluoride may leave part of the skeleton after pyrolysis, which is conducive to improving the mechanical strength of the coating layer and inhibiting the peeling of the carbon layer during the cycle process. Ammonium chloride decomposes to generate NH3 and HF at a certain temperature, and active HF can quickly react with the carbon layer, which is conducive to achieving high-concentration fluorine doping.

[0091] In some embodiments of the present application, the phosphorus source can include at least one of triphenyl phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0092] By adopting the above scheme, triphenyl phosphate can decompose at high temperature to form C-P bonds embedded in the carbon layer, and triphenyl phosphate can assist the densification of the carbon layer, which is conducive to reducing manganese dissolution. Ammonium dihydrogen phosphate can decompose at a lower temperature, which is conducive to the rapid embedding of phosphorus elements in the carbon layer. Moreover, the released PO4 3- can be balanced by charge compensation to reduce Mn 2+ dissolution, thereby significantly reducing manganese dissolution. The PO4 3-The high content is helpful for high-concentration phosphorus element doping; and in the carbon source pyrolysis temperature range, the diammonium hydrogen phosphate also partially overlaps with the carbon source pyrolysis, thereby optimizing the pore structure of the carbon layer.

[0093] In some embodiments of the present application, the calcination temperature ranges from 400 to 700℃. Exemplarily, the calcination temperature can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, and any value between any two adjacent values.

[0094] By adopting the above scheme, the sintering temperature is in the above range, which is helpful for improving the fluorine-phosphorus doping efficiency, and also optimizes the carbon layer structure and enhances the diffusion efficiency of lithium ions.

[0095] According to a third aspect of the embodiments of the present application, a lithium ion battery is provided, which comprises the doped coated lithium nickel manganese oxide positive electrode material as described above.

[0096] By adopting the above scheme, the lithium ion battery has a higher discharge specific capacity, a higher cycle retention rate, and a lower manganese elution amount.

[0097] In some embodiments of the present application, the discharge specific capacity of the lithium ion battery at 0.1C rate can be 141.6-144.9 mAh·g -1 .

[0098] In some embodiments of the present application, the discharge specific capacity of the lithium ion battery at 0.5C rate can be 138.2-141.5 mAh·g -1 .

[0099] In some embodiments of the present application, the discharge specific capacity of the lithium ion battery at 1C rate can be 134.6-137.8 mAh·g -1 .

[0100] In some embodiments of the present application, the discharge specific capacity of the lithium ion battery at 3C rate can be 128.3-133.1 mAh·g -1 .

[0101] In some embodiments of the present application, the discharge specific capacity of the lithium ion battery at 5C rate can be 122.6-128.3 mAh·g -1 .

[0102] In some embodiments of the present application, the cycle discharge specific capacity of the lithium ion battery at 1C for 100 cycles can be 126.36-132.23 mAh·g -1 .

[0103] In some embodiments of the present application, the amount of manganese elution of the lithium ion battery after 100 cycles at 1C rate can be 20.29 ppm to 40.29 ppm.

[0104] The present application will be described in detail below with specific examples. The following examples are only part of the embodiments of the present application, and are not a limitation of the present application. The raw materials used in the following examples are commercially available products, unless otherwise specified.

[0105] Example 1

[0106] A positive electrode material is prepared by the following method:

[0107] Preparation of carbon-coated lithium nickel manganese oxide:

[0108] Lithium carbonate, nickel oxide, manganese dioxide and glucose are proportionally put into a sand mill stirring tank, and sand milling is performed until the D50 is 0.4 μm and the solid content is 35%, to prepare a mixed slurry;

[0109] The mixed slurry is subjected to secondary granulation in a spray drying tower, with an inlet air temperature of 210°C, an outlet air temperature of 90°C, and a centrifugal frequency of 310 Hz, to prepare precursor particles with a spray particle size D50 of 30 μm;

[0110] The precursor particles are then sintered in a sintering furnace under a nitrogen atmosphere, with a heating rate of 2.5°C / min, a sintering temperature of 400°C for 4 h, a sintering temperature of 900°C for 10 h, and then annealing at 700°C for 5 h with a cooling rate of 1.5°C / min, and finally natural cooling, to obtain 1wt% of carbon-coated lithium nickel manganese oxide.

[0111] Preparation of doped coated lithium nickel manganese oxide positive electrode material:

[0112] The carbon-coated lithium nickel manganese oxide is subjected to gas crushing, with a gas crushing D50 of 1.8 μm, and then mixed with triphenyl phosphate and ammonium fluoride in a ratio of 8:1:1 in a super mixer for 1 h to obtain a mixture;

[0113] The mixture is calcined under a nitrogen atmosphere, with a heating rate of 2.5°C / min and a calcination temperature of 450°C for 4 h, and then natural cooling, and grinding and screening to obtain a doped coated lithium nickel manganese oxide positive electrode material.

[0114] Example 2

[0115] A positive electrode material is prepared by the following method:

[0116] Preparation of carbon-coated lithium nickel manganese oxide:

[0117] Lithium carbonate, nickel oxide, trimanganese tetraoxide and citric acid are proportionally put into a sand mill stirring tank, and sand milling is performed until the D50 is 0.38 μm and the solid content is 30%, to prepare a mixed slurry;

[0118] The mixed slurry is subjected to secondary granulation in a spray drying tower, the inlet air temperature is 210℃, the outlet air temperature is 90℃, and the centrifugal frequency is 330Hz, to obtain precursor particles with a spray particle size D50 of 26μm;

[0119] The precursor particles are then sintered in a sintering furnace under a nitrogen atmosphere, the heating rate is 2.5℃ / min, the sintering temperature is 400℃ for 4h, 900℃ for 10h, then the temperature is reduced to 700℃ for annealing for 5h, the cooling rate is 1.5℃ / min, and finally natural cooling is performed, to obtain 3wt% carbon-coated lithium nickel manganese oxide.

[0120] Preparation of doped and coated lithium nickel manganese oxide positive electrode material:

[0121] The carbon-coated lithium nickel manganese oxide is subjected to gas crushing, and the gas crushing is performed to D50 of 1.1μm, then the gas crushing product is mixed with triphenyl phosphate and polyvinylidene fluoride in a ratio of 8:1:1 in a super mixer for 1.5h, to obtain a mixture;

[0122] The mixture is calcined under a nitrogen atmosphere, the heating rate is 2.5℃ / min, the calcination temperature is 500℃ for 5h, and then natural cooling is performed, and the mixture is ground and sieved to obtain the doped and coated lithium nickel manganese oxide positive electrode material.

[0123] Example 3

[0124] A positive electrode material is prepared by the following method:

[0125] Preparation of carbon-coated lithium nickel manganese oxide:

[0126] Lithium hydroxide, nickel acetate, trimanganese tetraoxide and sucrose are put into a sand mill stirring tank in a certain proportion, and sand milling is performed to D50 of 0.45μm and solid content of 26%, to obtain a mixed slurry;

[0127] The mixed slurry is subjected to secondary granulation in a spray drying tower, the inlet air temperature is 230℃, the outlet air temperature is 95℃, and the centrifugal frequency is 350Hz, to obtain precursor particles with a spray particle size D50 of 22μm;

[0128] The precursor particles are then sintered in a sintering furnace under a nitrogen atmosphere, the heating rate is 2.5℃ / min, the sintering temperature is 400℃ for 4h, 900℃ for 10h, then the temperature is reduced to 700℃ for annealing for 5h, the cooling rate is 1.5℃ / min, and finally natural cooling is performed, to obtain 5wt% carbon-coated lithium nickel manganese oxide.

[0129] Preparation of doped and coated lithium nickel manganese oxide positive electrode material:

[0130] The carbon-coated lithium nickel manganese oxide is gas-atomized to have a D50 of 2.5 μm, and then mixed with ammonium dihydrogen phosphate and ammonium fluoride in a ratio of 8:1:1 in a super mixer for 2 h to obtain a mixture;

[0131] The mixture is calcined under a nitrogen atmosphere at a temperature increasing rate of 2.5 ℃ / min and a calcination temperature of 400 ℃ for 8 h, and then naturally cooled, and ground and screened to obtain the doped and coated lithium nickel manganese oxide positive electrode material.

[0132] Example 4

[0133] A positive electrode material is prepared by the following method:

[0134] The carbon-coated lithium nickel manganese oxide is prepared by the following method:

[0135] Lithium carbonate, nickel hydroxide, trimanganese tetraoxide and glucose are put into a sand mill stirring tank in a certain proportion, and sand-milled to have a D50 of 0.32 μm and a solid content of 33%, to obtain a mixed slurry;

[0136] The mixed slurry is subjected to secondary granulation in a spray drying tower, with an inlet air temperature of 210 ℃, an outlet air temperature of 90 ℃ and a centrifugal frequency of 300 Hz, to obtain precursor particles with a spray particle size D50 of 35 μm;

[0137] The precursor particles are then sintered in a sintering furnace under a nitrogen atmosphere, at a temperature increasing rate of 2.5 ℃ / min and a sintering temperature of 400 ℃ for 4 h and 900 ℃ for 10 h, and then annealed at 700 ℃ for 5 h at a temperature decreasing rate of 1.5 ℃ / min, and finally naturally cooled, to obtain 8 wt% of the carbon-coated lithium nickel manganese oxide.

[0138] The doped and coated lithium nickel manganese oxide positive electrode material is prepared by the following method:

[0139] The carbon-coated lithium nickel manganese oxide is gas-atomized to have a D50 of 4 μm, and then mixed with ammonium dihydrogen phosphate and ammonium fluoride in a ratio of 8:1:1 in a super mixer for 3 h to obtain a mixture;

[0140] The mixture is calcined under a nitrogen atmosphere at a temperature increasing rate of 2.5 ℃ / min and a calcination temperature of 650 ℃ for 6 h, and then naturally cooled, and ground and screened to obtain the doped and coated lithium nickel manganese oxide positive electrode material.

[0141] Example 5

[0142] A positive electrode material is prepared by the following method:

[0143] The carbon-coated lithium nickel manganese oxide is prepared by the following method:

[0144] Lithium carbonate, nickel oxide, trimanganese tetraoxide and sucrose are put into a sand mill stirring tank in a certain proportion, and sand-milled to have a D50 of 0.36 μm and a solid content of 32%, to obtain a mixed slurry;

[0145] The mixed slurry is subjected to secondary granulation in a spray drying tower, the inlet air temperature is 210°C, the outlet air temperature is 90°C, and the centrifugal frequency is 300 Hz, to obtain precursor particles with a spray particle size D50 of 30 μm;

[0146] The precursor particles are then placed in a sintering furnace and sintered under a nitrogen atmosphere, the heating rate is 2.5°C / min, the sintering temperature is 400°C for 4 h, 900°C for 10 h, then cooled to 700°C for annealing for 5 h, the cooling rate is 1.5°C / min, and finally naturally cooled to obtain 10wt% carbon-coated lithium nickel manganese oxide.

[0147] Preparation of doped coated lithium nickel manganese oxide positive electrode material:

[0148] The carbon-coated lithium nickel manganese oxide is subjected to air crushing, the air crushing is to D50 of 1.9 μm, then mixed with triphenyl phosphate and ammonium fluoride in a ratio of 8:1:1 in a super mixer for 2.5 h to obtain a mixture;

[0149] The mixture is calcined under a nitrogen atmosphere, the heating rate is 2.5°C / min, the calcination temperature is 600°C for 5.5 h, and then naturally cooled, and ground and sieved to obtain the doped coated lithium nickel manganese oxide positive electrode material.

[0150] Comparative Example 1

[0151] A positive electrode material, which is different from Example 2 in that a single doping is used.

[0152] The positive electrode material in this comparative example is prepared by the following steps:

[0153] Preparation of carbon-coated lithium nickel manganese oxide:

[0154] Lithium carbonate, nickel oxide, trimanganese tetraoxide and citric acid are put into a sand mill stirring tank in a certain proportion, and sand milling is performed to obtain a mixed slurry with a D50 of 0.39 μm and a solid content of 31%;

[0155] The mixed slurry is subjected to secondary granulation in a spray drying tower, the inlet air temperature is 210°C, the outlet air temperature is 90°C, and the centrifugal frequency is 330 Hz, to obtain precursor particles with a spray particle size D50 of 27 μm;

[0156] The precursor particles are then placed in a sintering furnace and sintered under a nitrogen atmosphere, the heating rate is 2.5°C / min, the sintering temperature is 400°C for 4 h, 900°C for 10 h, then cooled to 700°C for annealing for 5 h, the cooling rate is 1.5°C / min, and finally naturally cooled to obtain 3wt% carbon-coated lithium nickel manganese oxide.

[0157] Preparation of doped coated lithium nickel manganese oxide positive electrode material:

[0158] The carbon-coated lithium nickel manganese oxide was gas-atomized to a D50 of 0.8 pm, and then mixed with triphenyl phosphate at a ratio of 8:2 in a super mixer for 0.5 h to obtain a mixture;

[0159] The mixture was calcined under a nitrogen atmosphere at a heating rate of 2.5°C / min, and the calcination temperature was 500°C for 5 h, and then naturally cooled, and then ground and sieved to obtain the doped and coated lithium nickel manganese oxide positive electrode material.

[0160] Comparative Example 2

[0161] A positive electrode material, which is different from Example 2 in that it is not doped with fluorine and phosphorus elements.

[0162] The positive electrode material in the present comparative example was prepared by the following steps:

[0163] The carbon-coated lithium nickel manganese oxide was prepared by the following steps:

[0164] Lithium carbonate, nickel oxide, trimanganese tetraoxide, and citric acid were put into a sand mill stirring tank in a certain proportion, and sand-milled to a D50 of 0.38 pm and a solid content of 31%, to obtain a mixed slurry;

[0165] The mixed slurry was subjected to secondary granulation in a spray drying tower, with an inlet air temperature of 210°C, an outlet air temperature of 90°C, and a centrifugal frequency of 330 Hz, to obtain precursor particles with a spray particle size D50 of 27 pm;

[0166] The precursor particles were then sintered in a sintering furnace under a nitrogen atmosphere, at a heating rate of 2.5°C / min, a sintering temperature of 400°C for 4 h, and 900°C for 10 h, and then cooled to 700°C for annealing for 5 h at a cooling rate of 1.5°C / min, and finally naturally cooled to obtain 3wt% carbon-coated lithium nickel manganese oxide.

[0167] The doped and coated lithium nickel manganese oxide positive electrode material was prepared by the following steps:

[0168] The carbon-coated lithium nickel manganese oxide was gas-atomized to a D50 of 3.6 pm, and then mixed with ammonium fluoride at a ratio of 8:2 in a super mixer for 1.5 h to obtain a mixture;

[0169] The mixture was calcined under a nitrogen atmosphere at a heating rate of 2.5°C / min, and the calcination temperature was 550°C for 5 h, and then naturally cooled, and then ground and sieved to obtain the doped and coated lithium nickel manganese oxide positive electrode material.

[0170] Comparative Example 3

[0171] A positive electrode material, which is different from Example 2 in that it is not doped with fluorine and phosphorus elements.

[0172] Lithium carbonate, nickel oxide, trimanganese tetraoxide and citric acid were proportionally put into a sand mill stirring tank, and sand-milled to a D50 of 0.4 μm and a solid content of 30%, to prepare a mixed slurry;

[0173] The mixed slurry was subjected to secondary granulation in a spray drying tower, with an inlet air temperature of 210 ℃, an outlet air temperature of 90 ℃, and a centrifugal frequency of 330 Hz, to prepare precursor particles with a spray particle size D50 of 26 μm;

[0174] The precursor particles were then sintered in a sintering furnace under a nitrogen atmosphere, with a heating rate of 2.5 ℃ / min, a sintering temperature of 400 ℃ for 4 h, a sintering temperature of 900 ℃ for 10 h, annealing at 700 ℃ for 5 h at a cooling rate of 1.5 ℃ / min, and finally natural cooling, to obtain 3wt% carbon-coated lithium nickel-manganese oxide, i.e. a positive electrode material.

[0175] Performance test:

[0176] (1) Electrical performance: 0.1C, 0.5C, 1C, 3C and 5C rate performance tests were carried out at 25 ℃, with five cycles at each rate, and a nominal capacity of 140 mAh / g, with results as shown in Table 2;

[0177] After 0.1C activation for one cycle at 25 ℃, 1C charge-discharge cycle tests were carried out for 100 cycles, with a voltage range of 3.0V-4.95V, and the discharge specific capacity of the 1st cycle, 20th cycle, 40th cycle, 60th cycle, 80th cycle and 100th cycle and the capacity retention rate of the 100th cycle were calculated, with test results as shown in Table 3;

[0178] (2) Manganese elution: the positive electrode materials of the examples and comparative examples were cycled for 100 cycles at 25 ℃ and 1C rate, then discharged to the lower limit voltage, and the battery was disassembled, the negative electrode powder was scraped off and subjected to ICP test for negative electrode Mn deposition, i.e. manganese elution test results, with test results as shown in Table 4;

[0179] (3) Carbon material content: determined by a carbon-sulfur instrument;

[0180] (4) P content and F content: determined by an inductively coupled plasma emission spectrometer (ICP).

[0181] Table 1

[0182] Carbon material content P content F content Units ％ ppm ppm Example 1 1.19 310.53 598.66 Example 2 3.17 1291.74 1718.95 Example 3 5.25 1674.57 2435.11 Example 4 7.93 2094.84 3573.31 Example 5 9.92 2546.13 4194.77 Comparative Example 1 3.11 2694.15 9.73 Comparative Example 2 3.08 3.67 4829.43 Comparative Example 3 3.26 2.12 4.7

[0183] Table 2

[0184]

[0185] Table 3

[0186]

[0187] Table 4

[0188]

[0189]

[0190] Compared with Examples 1-5, the content of carbon material is changed in Examples 1-5, and it can be known from Table 1 that more F can be doped with the increase of the content of carbon material, and the doping amount of P is relatively small, and it can be known from Tables 2-4 that the utilization efficiency of active substances can be reduced by too high content of carbon material, and part of active sites are shielded, that is, excessive P and F doping can reduce the ion conduction rate and increase the interface impedance, and in general, the performance of the positive electrode material coated with 3wt% carbon material is the best.

[0191] Compared with Examples 1-5, different nickel sources, lithium sources, manganese sources and carbon sources are used in Examples 1-5, and it can be known from Tables 2-4 that the positive electrode materials prepared have relatively high discharge specific capacity measured at 0.1C, 0.5C, 1C, 3C and 5C current density; and have relatively high capacity retention rate after 100 cycles at 1C. In addition, the manganese dissolution amount of Examples 1-5 is small after the manganese dissolution test. This is because the coating layer contains F and P, the electron-withdrawing effect of F is strong, which can reduce the electron activity of the coating layer, help to inhibit the decomposition of electrolyte and the oxidation of Mn 2+ ; at the same time, P doping can improve the density of the coating layer and balance the Mn 2+ on the surface of the coating layer through charge compensation, which helps to reduce the manganese dissolution, so as to improve the cycle life of the battery.

[0192] Compared with Comparative Examples 1-3 and Example 2, the coating layer of Example 2 is doped with fluorine element and phosphorus element, the coating layer of Comparative Example 1 is only doped with phosphorus element, the coating layer of Comparative Example 2 is only doped with fluorine element, and the coating layer of Comparative Example 3 is not doped with fluorine element or phosphorus element, and it can be known from Tables 2-4 that the discharge specific capacity of Example 2 is relatively high, the capacity retention rate after 100 cycles at 1C is relatively high, and the manganese dissolution amount is relatively low.

[0193] The above describes the embodiments of the present application in detail, and the specific examples are applied to describe the principles and implementation modes of the present application, and the above description of the embodiments is only used to help understand the method of the present application and its core idea; at the same time, according to the idea of the present application, the specific implementation mode and application range can be changed by those skilled in the art, and in summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A doped and coated lithium nickel manganese oxide positive electrode material, characterized in that: The lithium nickel manganese oxide positive electrode material comprises: lithium nickel manganese oxide particles; The coating layer contains a carbon material doped with F and P, and the coating layer is located outside the lithium nickel manganese oxide particles.

2. The doped and coated lithium nickel manganese oxide positive electrode material according to claim 1, characterized in that: The mass percentage of the carbon material in the positive electrode material is in the range of 1% to 10%; Preferably, the mass percentage of the carbon material in the positive electrode material is in the range of 3% to 8%.

3. The doped and coated lithium nickel manganese oxide positive electrode material according to claim 2, characterized in that: The doping amount of F is in the range of 300ppm to 5000ppm; and / or The doping amount of P ranges from 200 ppm to 3000 ppm.

4. The doped and coated lithium nickel manganese oxide positive electrode material according to any one of claims 1 to 3, characterized in that: The molecular formula of the lithium nickel manganese oxide particles is LiNi x Mn 2-x O4, where 0.49≤x≤0.51; and / or The particle size of the lithium nickel manganese oxide particles ranges from 0.8 μm to 5 μm.

5. A method for preparing a doped and coated lithium nickel manganese oxide positive electrode material, characterized in that: The preparation method comprises the following steps: Provide carbon-coated lithium nickel manganese oxide; Gas-crushing the carbon-coated lithium nickel manganese oxide, and then mixing it with a fluorine source and a phosphorus source to obtain a mixture; The mixture is calcined to obtain the doped and coated lithium nickel manganese oxide positive electrode material.

6. The method for preparing the doped and coated lithium nickel manganese oxide positive electrode material according to claim 5, characterized in that: The carbon-coated lithium nickel manganese oxide is prepared by the following steps: mixing a carbon source, a lithium source, a nickel source, and a manganese source with a solvent to prepare a mixed slurry; The mixed slurry is subjected to spray granulation to obtain precursor particles; The precursor particles are then sintered to obtain the carbon-coated lithium nickel manganese oxide.

7. The method for preparing the doped and coated lithium nickel manganese oxide positive electrode material according to claim 6, characterized in that: In the step of mixing the carbon source, lithium source, nickel source and manganese source with the solvent, one of the following conditions is met: The lithium source includes at least one of lithium carbonate and lithium hydroxide; The nickel source is at least one of nickel oxide, nickel hydroxide, and nickel acetate; The manganese source is at least one of manganese dioxide and manganese tetraoxide; The carbon source is at least one of glucose, sucrose and citric acid.

8. The method for preparing the doped and coated lithium nickel manganese oxide positive electrode material according to claim 6, characterized in that: In the preparation step of the carbon-coated lithium nickel manganese oxide, one of the following conditions is met: The average particle size of the mixed slurry ranges from 0.3 μm to 0.5 μm; The average particle size of the precursor particles ranges from 20 μm to 40 μm; The sintering temperature ranges from 400°C to 900°C.

9. The method for preparing the doped and coated lithium nickel manganese oxide positive electrode material according to claim 5, characterized in that: The fluorine source includes at least one of polyvinylidene fluoride and ammonium fluoride; and / or The phosphorus source includes at least one of triphenyl phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

10. The method for preparing the doped and coated lithium nickel manganese oxide positive electrode material according to claim 5, characterized in that: The calcination temperature ranges from 400°C to 700°C.

11. A lithium-ion battery, characterized in that: The lithium-ion battery comprises the doped and coated lithium nickel manganese oxide positive electrode material according to any one of claims 1 to 4.

12. The lithium-ion battery according to claim 11, wherein The lithium-ion battery satisfies one of the following conditions: The lithium-ion battery has a discharge capacity of 141.6 to 144.9 mAh·g at a 0.1C rate. -1 ; The lithium-ion battery has a discharge capacity of 138.2 to 141.5 mAh·g at a 0.5C rate. -1 ; The lithium-ion battery has a discharge capacity of 134.6 to 137.8 mAh·g at a 1C rate. -1 ; The lithium-ion battery has a discharge capacity of 128.3 to 133.1 mAh·g at a 3C rate. -1 ; The lithium-ion battery has a discharge capacity of 122.6 to 128.3 mAh·g at a 5C rate. -1 ; The lithium-ion battery has a cyclic discharge capacity of 126.36 to 132.23 mAh·g after 100 cycles at 1C. -1 ; The manganese dissolution amount of the lithium ion battery after 100 cycles at a 1C rate is 20.29 ppm to 40.29 ppm.

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