Positive electrode active material and preparation method therefor, positive electrode sheet, and battery
By controlling the exposure of specific crystal faces and the formation of rock salt phase in lithium nickel manganese oxide materials, the problems of slow lithium-ion transport and manganese dissolution in lithium nickel manganese oxide materials were solved, and the high-rate performance and stability were improved.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-09-26
- Publication Date
- 2026-04-02
AI Technical Summary
The existing lithium nickel manganese oxide cathode active material has a slow lithium-ion transport rate on the (111) facet and is prone to manganese dissolution, which affects its rate performance and stability.
By controlling the exposure of the (110), (100) and (311) crystal planes of the positive electrode active material and combining the formation of the rock salt phase, a lithium nickel manganese oxide material with a specific composition was prepared. The surface composition was adjusted by using acetate solution to promote the exposure of the (110) and (100) planes, form a surface reconstructed shell, improve the lithium ion conduction rate and passivate the surface.
It significantly improves the rate performance and cycle stability of lithium nickel manganese oxide batteries, reduces manganese leaching, and meets the needs of different application scenarios.
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Figure CN2025124288_02042026_PF_FP_ABST
Abstract
Description
A positive electrode active material, a preparation method thereof, a positive electrode sheet and a battery
[0001] The present application claims priority to the Chinese patent application No. 202411361195.2, filed on September 26, 2024, and entitled "A positive electrode active material, a preparation method thereof, a positive electrode sheet and a battery", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD
[0002] The present application relates to the field of battery materials, in particular to a positive electrode active material, a preparation method thereof, a positive electrode sheet and a battery. BACKGROUND
[0003] Lithium nickel manganese oxide is a lithium ion battery positive electrode active material with a spinel structure. Compared with other spinel structure positive electrode active materials (such as lithium manganate and lithium iron phosphate), lithium nickel manganese oxide has a higher working voltage and energy density, and thus has a wide application prospect in the fields of electric vehicles, energy storage systems and portable electronic devices.
[0004] Common lithium nickel manganese oxide materials have a typical octahedral morphology of spinel materials, which usually exhibit (111) surface exposed outside to form an octahedral morphology. However, the lithium ion transmission rate of the (111) surface is slow, and the manganese dissolution phenomenon is prone to occur, which is not conducive to the rate capability and stability of lithium nickel manganese oxide as a positive electrode active material. Therefore, how to control the exposure degree of other crystal faces of lithium nickel manganese oxide to improve the rate capability and stability of lithium nickel manganese oxide battery is an urgent problem to be solved.
[0005] SUMMARY
[0006] The present application provides a positive electrode active material, which can significantly improve the rate capability and cycle stability of the corresponding battery by limiting the exposure degree of a specific crystal face.
[0007] The present application also provides a preparation method of the above-mentioned positive electrode active material, which can prepare the above-mentioned positive electrode active material and has a simple process.
[0008] The present application also provides a positive electrode sheet, which has the advantages of fast ion transmission rate and good stability due to the inclusion of the above-mentioned positive electrode active material.
[0009] The present application also provides a battery, which has high rate capability and cycle stability due to the inclusion of the above-mentioned positive electrode sheet.
[0010] In a first aspect, the present application provides a positive electrode active material, which satisfies the following formula 1: I1+I2+I3≤10.20 Formula 1.
[0011] I1 is I(111) / I(311) in the XRD pattern of the positive electrode active material, I2 is I(111) / I(400) in the XRD pattern of the positive electrode active material, I3 is I(111) / I(440) in the XRD pattern of the positive electrode active material, and I1, I2, and I3 are all not 0.
[0012] Further, the XRD pattern of the positive electrode active material further includes a diffraction peak of rock salt phase Li x Ni 1-x O.
[0013] Further, the chemical composition of the positive electrode active material includes Li 1+x Ni 0.5+y Mn 1.5+z M u N v O w , -0.1≤y≤0.1, -0.3≤z≤0.3, 0≤u≤0.2, 0
[0014] Further, the positive electrode active material satisfies the following formula 2: 0.0005≤y / x≤0.0100 Formula 2.
[0015] , wherein x is the particle size of the positive electrode active material, in units of μm, and y is the thickness at which the concentration of N is 0 when extending in the direction from the surface of the positive electrode active material to the core, in units of μm.
[0016] Further, 0.001 μm≤y≤0.020 μm.
[0017] Further, the Dv50 of the positive electrode active material is 1-15 μm.
[0018] In a second aspect, the present application provides a preparation method of the positive electrode active material according to the first aspect, comprising the following steps:
[0019] 1) preparing a first precursor material, the chemical composition of the first precursor material being Li 1+x Ni 0.5+y Mn 1.5+z M u O wwherein -0.1≤x≤0.2, -0.1≤y≤0.1, -0.3≤z≤0.3, 0≤u≤0.2, 3.8≤w≤4.3; M comprises at least one of Al, Sc, Ti, V, Cr, Fe, Cu, Ga, Sr, Y, Zr, Nb, Mo, Ru, Ta, W, B, Si, Ge, Sb, Te, P, S, F;
[0020] 2) The first precursor material is mixed with a soluble salt solution of N, and sequentially subjected to stirring, filtration and drying treatment to obtain a second precursor material;
[0021] 3) The second precursor material is subjected to sintering treatment at 700-1000°C to obtain the positive electrode active material.
[0022] Further, the first precursor material is prepared by a method comprising the following processes:
[0023] A precursor with a molecular formula of Ni 0.5 Mn 1.5 (OH)4, a lithium source and an M source are mixed to obtain a mixture, which is sintered at 900-1100°C for 5-30h, and then subjected to cooling treatment at a cooling rate of 0.1-3°C / min to 600-800°C, and kept at the temperature for 1-10h to obtain the first precursor material.
[0024] Further, in the soluble salt solution of N, the concentration of element N is 0.01-1mol / L.
[0025] In a third aspect, the present application provides a positive electrode sheet, comprising a current collector and a positive electrode active layer arranged on at least one surface of the current collector; the positive electrode active layer comprises the positive electrode active material according to the first aspect.
[0026] In a fourth aspect, the present application provides a battery comprising the positive electrode sheet according to the third aspect.
[0027] The positive electrode active material provided by the present application can improve the lithium ion conduction rate and reduce the occurrence of manganese dissolution by limiting the exposure degree of the (110) plane, (100) plane and (311) plane of formula 1, and thus can significantly improve the rate performance and cycle stability of the corresponding battery. BRIEF DESCRIPTION OF DRAWINGS
[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and serve to explain the principles of the present application together with the specification.
[0029] FIG. 1 is an SEM image of the positive electrode active material of Example 1;
[0030] FIG. 2 is an SEM image of the positive electrode active material of Example 2;
[0031] Fig. 3 is an SEM image of the positive electrode active material of Comparative Example 1.
[0032] Fig. 4 is an XRD comparison chart of the positive electrode active materials of Example 1 and Comparative Example 1. DETAILED DESCRIPTION
[0033] In order for those skilled in the art to better understand the scheme of the present application, the present application is further described in detail below. The following specific embodiments are only used to describe the principles and characteristics of the present application, and the examples are used to explain the present application, but not to limit the scope of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.
[0034] In order to expose other crystal faces in addition to the lithium nickel manganese oxide (111) crystal face, so as to improve the rate performance and stability of the battery, the following technical scheme is adopted in the present application:
[0035] In a first aspect, the present application provides a positive electrode active material, which satisfies the following formula 1: I1+I2+I3≤10.20 Formula 1;
[0036] wherein I1 is I(111) / I(311) in the XRD pattern of the positive electrode active material, I2 is I(111) / I(400) in the XRD pattern of the positive electrode active material, and I3 is I(111) / I(440) in the XRD pattern of the positive electrode active material, and I1, I2 and I3 are all not 0.
[0037] It should be noted that in formula 1, I(111) refers to the diffraction peak intensity of the (111) crystal face in the XRD pattern of the positive electrode active material, and the intensity is counted as the height of the diffraction peak. Further, I(111) / I(311) refers to the ratio of the diffraction peak intensity of the (111) crystal face and the diffraction peak intensity of the (311) crystal face in the XRD pattern of the positive electrode active material, and I(111) / I(400) and I(111) / I(440) are the same.
[0038] In the present application, the total exposure degree of the (440) plane, the (400) plane and the (311) plane relative to the (111) crystal plane can be defined by formula 1 (440), which helps to improve the rate performance and stability of the positive electrode material. The reason is that different crystal planes of the positive electrode active material have different atomic arrangements and surface characteristics, so the exposure of different crystal planes has different effects on the electrochemical performance of the positive electrode active material. In detail, under the influence of surface energy, lithium nickel manganese oxide tends to form a regular octahedron to expose the (111) plane to reduce the surface energy. However, the lithium ion transmission of the (111) plane is slow and easy to cause Mn dissolution. The (110) plane is aligned with the lithium ion transmission direction (8a-16C-8a), and the (100) plane and the (110) plane have higher lithium ion density, so the (100) plane and the (110) plane have faster ion transmission speed. By controlling the exposure ratio of the (110) plane, the (100) plane and the (311) crystal plane, the rate performance and cycle stability of lithium nickel manganese oxide can be improved to meet the needs of different application scenarios. In addition, in the XRD pattern, the (110) and (100) planes are low-index crystal planes and are at a lower 2-Theta angle, so they are difficult to identify. The (440) and (400) planes are parallel to the (100) and (100) planes, so the present application selects (440) and (400) to replace (100) and (100) for definition, which also shows the reduction of the (111) plane in the material system from the side.
[0039] In a specific embodiment, 7≤I1+I2+I3≤10.20, 7.5≤I1+I2+I3≤10.20, 8≤I1+I2+I3≤10.
[0040] In an optional embodiment, the XRD pattern of the positive electrode active material further includes the diffraction peak of the rock salt phase Li x Ni 1-x O. Wherein, the generation of the rock salt phase helps to passivate the surface of lithium nickel manganese oxide, further reduce the oxidizability of lithium nickel manganese oxide surface, reduce the surface side reaction, hinder Mn dissolution, thereby further improving the cycle stability of the positive electrode active material.
[0041] In a specific embodiment, the diffraction peak of the rock salt phase Li x Ni 1-x O corresponds to 2θ of 37.5° and 43.5°.
[0042] In an optional embodiment, the chemical composition of the positive electrode active material includes Li 1+x Ni 0.5+y Mn 1.5+z M u N v O wwherein -0.1≤x≤0.2, -0.1≤y≤0.1, -0.3≤z≤0.3, 0≤u≤0.2, 0
[0043] In an optional embodiment, the positive electrode active material satisfies the following formula 2: 0.0005≤y / x≤0.0100 Formula 2.
[0044] wherein x is the particle size of the positive electrode active material, unit: μm, y is the thickness of the positive electrode active material from the surface to the core in the direction of the concentration of N being 0, unit: μm.
[0045] In the above embodiment, N only exists in the surface of the positive electrode active material within a specific thickness range, which can be understood as a surface reconstruction shell, and the inside opposite to the surface reconstruction shell does not contain element N, which can be understood as a core opposite to the surface reconstruction shell, and the surface reconstruction shell is the main factor for regulating the positive electrode active material to satisfy formula 1.
[0046] The particle size x of the above positive electrode active material refers to the specific particle size value of a single positive electrode active material, which can be measured by SEM, and the thickness y of the positive electrode active material from the surface to the core in the direction can be measured by linear scanning EDS of high-precision transmission electron microscopy section.
[0047] In a specific embodiment, 1 nm≤y≤20 nm.
[0048] In an optional embodiment, the Dv50 of the positive electrode active material is 1-15 μm. Illustratively, the Dv50 of the positive electrode active material is 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, or any range consisting of any two of them.
[0049] The above Dv50 represents the particle size value corresponding to the cumulative amount of 50% (by volume) in the particle size cumulative distribution curve, which is generally tested by a laser diffraction particle size distribution instrument.
[0050] In a second aspect, the application provides a preparation method of the positive electrode active material according to the first aspect, comprising the following steps:
[0051] 1) preparing a first precursor material, the chemical composition of the first precursor material being Li 1+x Ni 0.5+y Mn 1.5+z M u O w , wherein -0.1≤x≤0.2, -0.1≤y≤0.1, -0.3≤z≤0.3, 0≤u≤0.2, 3.8≤w≤4.3; M comprises at least one of Al, Sc, Ti, V, Cr, Fe, Cu, Ga, Sr, Y, Zr, Nb, Mo, Ru, Ta, W, B, Si, Ge, Sb, Te, P, S, F;
[0052] 2) mixing the first precursor material with a soluble salt solution of N, sequentially performing stirring, filtering, and drying treatment to obtain a second precursor material;
[0053] 3) performing sintering treatment on the second precursor material at 700-1000℃ to obtain the positive electrode active material.
[0054] In the above preparation method, after the first precursor material and the soluble salt solution of N are mixed and stirred, a small amount of N salt is uniformly left on the surface of the first precursor material after washing and drying, and then the N ion induces the surface reconstruction of the first precursor material through secondary sintering, so as to expose more (110), (100), and (311) surfaces in addition to (111) surface, which helps to improve the rate performance and stability of lithium nickel manganese oxide. In addition, the N element has low oxidation and is not easy to increase the valence, and these elements can also promote the generation of rock salt phase, which is beneficial to passivate the surface of lithium nickel manganese oxide, reduce the oxidation of lithium nickel manganese oxide, and reduce the surface side reaction, thereby further improving the stability of lithium nickel manganese oxide.
[0055] Taking the acetate salt of N as an example, the reasons for promoting the generation of (110) and (100) surfaces and rock salt phase through the above preparation method include: using the acetate salt of N to wash the lithium nickel manganese oxide, the acetate ion in the acetate salt solution is acidic after ionization, H + and Li + in the lithium nickel manganese oxide perform lithium-hydrogen exchange to wash out the lithium ions on the surface of the lithium nickel manganese oxide into the solution, and the N ions in the acetate salt solution remain on the surface of the lithium nickel manganese oxide, so that the surface of the lithium nickel manganese oxide is in a state of lithium-poor and transition metal-rich, and the surface of the lithium nickel manganese oxide which deviates significantly from the equilibrium state is reconstructed in the subsequent sintering process, so that more (110) and (100) surfaces are exposed and rock salt phase is formed.
[0056] In some embodiments, when N is Ni, it cannot be detected by high-precision transmission electron microscopy, and the chemical composition of the positive electrode active material and the concentration of N can be calculated according to the chemical composition of the first precursor material during preparation and the total content of Ni of the obtained positive electrode active material.
[0057] In some embodiments, the above preparation method can achieve the following effects:
[0058] In the XRD pattern of the first precursor material, I(111) / I(311) is denoted as T1, I(111) / I(400) is denoted as T2, and I(111) / I(440) is denoted as T3. The value of [(T 1+ T 2+ T3)-(I1+I2+I3)] / (T 1+ T 2+ T3)≥5%.
[0059] The soluble salt solution of N includes, but is not limited to, acetate, oxalate, citrate, nitrate, etc. of element N, and is preferably acetate.
[0060] It should be noted that the first precursor material is a conventional lithium nickel manganese oxide material without a restructured shell, which can be commercially purchased or prepared according to a conventional method. In an optional embodiment, the first precursor material is prepared by a method comprising the following processes:
[0061] A precursor with a molecular formula of Ni 0.5 Mn 1.5 (OH)4, a lithium source, and an M source are mixed and treated to obtain a mixture, which is sintered at 900-1100°C for 5-30h, and then cooled at a cooling rate of 0.1-3°C / min to 600-800°C, and kept at this temperature for 1-10h to obtain the first precursor material.
[0062] For example, the M source can be a compound of M, and is preferably an oxide of M.
[0063] In an optional embodiment, the concentration of element N in the soluble salt solution of N is 0.01-1mol / L. If the concentration of element N is too low, the improvement effect is not significant. If the concentration is too high, the reconstruction depth is too large, the internal structure is reconstructed, and the capacity is affected.
[0064] More preferably, the concentration of element N in the soluble salt solution of N is 0.01-0.2mol / L. For example, the concentration of element N is 0.05mol / L, 0.1mol / L, 0.12mol / L, 0.15mol / L, 0.17mol / L, or a range consisting of any two of them.
[0065] In a third aspect, the present application provides a positive electrode sheet, comprising a current collector and a positive electrode active layer arranged on at least one surface of the current collector; the positive electrode active layer comprises the positive electrode active material according to the first aspect.
[0066] It can be understood that the positive electrode active layer further comprises a conductive agent and a binder.
[0067] Exemplarily, the material of the current collector is not specifically limited in the present application, for example, it can be selected from any one or several of copper foil, titanium foil, tin foil, chromium foil, and composite foil of the above metals; the conductive agent can be selected from any known carbon material having conductive properties, for example, it can be at least one of carbon black, acetylene black, graphene, ketjen black, and carbon fiber; the binder can be at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, oxirane-containing polymer, polyvinylpyrrolidone, and polyurethane.
[0068] The thickness, area density, and thickness of the positive electrode active material layer of the positive electrode sheet are not specifically limited in the present application, but in order to balance the battery capacity, cycle life, and energy density, in a specific embodiment, the thickness of the positive electrode sheet is 40-120 μm, specifically including but not limited to 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, etc.; the area density of the positive electrode sheet is 3-10 mg / cm 2 , specifically including but not limited to 3.5 mg / cm 2 , 4 mg / cm 2 , 4.5 mg / cm 2 , 5 mg / cm 2 , 5.5 mg / cm 2 , 6 mg / cm 2 , 6.5 mg / cm 2 , 7 mg / cm 2 , 7.5 mg / cm 2 , 8 mg / cm 2 , 8.5 mg / cm 2 , 9 mg / cm 2 , 9.5 mg / cm 2 , etc.; and the thickness of the positive electrode active material layer is 20-60 μm, specifically including but not limited to 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, etc.
[0069] In a fourth aspect, the present application provides a battery comprising the positive electrode sheet according to the third aspect.
[0070] It can be understood that the battery of the present application can also include a negative electrode sheet, a separator, and an electrolyte.
[0071] The separator of the present application is not particularly limited and can be any known porous structure separator having electrochemical stability and chemical stability, for example, can be at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator can be single-layer or multi-layer.
[0072] The electrolyte of the present application is not particularly limited and can be, for example, an electrolyte including an organic solvent and an electrolyte salt. Among them, the organic solvent as a medium for transmitting ions in electrochemical reaction can use the organic solvent known in the art for battery electrolyte, for example: one or more of fluorinated carbonate, fluorinated carboxylate, non-fluorinated carbonate, fluorinated carbonate, non-fluorinated carboxylate, fluorinated carboxylate, fluorinated ether, non-fluorinated ether, tetrahydrofuran; the electrolyte salt as a source of ions can use the electrolyte salt known in the art for battery electrolyte, for example: one or more of lithium hexafluorophosphate, bis-trifluoromethylsulfonylimide, lithium bis(fluorosulfonyl)imide.
[0073] The battery of the present application can be prepared according to conventional methods in the art, for example, the positive electrode sheet, the separator, and the negative electrode sheet can be stacked in sequence, and then assembled into an electric core by winding process or stacking process, and then packaged and baked, and then injected with electrolyte, and then subjected to heat pressing and formation, to obtain the battery.
[0074] The present application is further described below in conjunction with specific examples:
[0075] Example 1
[0076] This example provides a positive electrode active material C1, which has a chemical composition of Li 1.0078 Ni 0.4990 Mn 1.4966 N 0.0044 O 3.9785 , N=Ni, and the positive electrode active material is a single-crystal positive electrode active material.
[0077] The preparation method thereof includes the following steps:
[0078] 1) 2 kg of precursor Ni 0.5 Mn 1.5 (OH)4, 415.19 g of lithium carbonate are added to a high-speed mixer, mixed and stirred until uniform, the mixture is sintered at 1050°C for 10 h, then cooled to 700°C at a cooling rate of 0.5°C / min and kept for 5 h, and then naturally cooled, crushed, and sieved to obtain a first precursor material A1.
[0079] 2) The first precursor material is added into 0.1 mol / L nickel acetate solution, the water-to-material mass ratio is 1:5, and stirring is performed at a speed of 500 rpm for 5 min. After stirring, centrifugation is performed to remove the excess nickel acetate aqueous solution, and drying is performed at 100°C to obtain the nickel acetate-coated second precursor material.
[0080] 3) The second precursor material is sintered at 900°C for 10 h, and the positive electrode active material C1 is obtained after natural cooling.
[0081] Examples 2-10
[0082] A positive electrode active material C2-C10 is provided, and the differences from Example 1 are shown in Table 1.
[0083] The preparation method is referred to Example 1.
[0084] Comparative Example 1
[0085] A positive electrode active material D1 is provided, and the differences from Example 1 are shown in Table 1.
[0086] The preparation method is referred to Example 1, and the difference is that only step 1) is performed.
[0087] Comparative Example 2
[0088] A positive electrode active material D2 is provided, and the differences from Example 1 are shown in Table 1.
[0089] The preparation method is different from Example 1 in that;
[0090] 2) The first precursor material A1 is added into deionized water, the water-to-material mass ratio is 1:5, and stirring is performed at a speed of 500 rpm for 5 min. After stirring, centrifugation is performed to remove the excess water, and drying is performed at 100°C. After drying, sintering is performed at 900°C for 10 h, and the positive electrode active material D2 is obtained after natural cooling.
[0091] Example 11
[0092] A positive electrode active material C11 is provided, and the differences from Example 1 are shown in Table 1. The preparation method is referred to Example 1, and the difference is that, in step 1), 2 kg of the precursor Ni 0.5 Mn 1.5 (OH)4, 463.54 g of lithium carbonate, and 62.75 g of ammonium dihydrogen phosphate are added into a high-speed mixer, and mixing and stirring are performed until uniform. The mixture is sintered at 1050°C for 10 h, and then cooled to 700°C at a cooling rate of 0.5°C / min and kept at 700°C for 5 h. After natural cooling, crushing and sieving are performed to obtain the first precursor material A2. In step 2), the nickel acetate aqueous solution is replaced by the solution shown in Table 1.
[0093] Examples 12-13
[0094] A positive electrode active material C11 is provided, which is different from Example 11 as shown in Table 1; and its preparation method is referred to Example 11.
[0095] Comparative Example 3
[0096] A positive electrode active material D3 is provided, which is different from Example 11 as shown in Table 1; and its preparation method is referred to Example 11.
[0097] Its preparation method is referred to Example 11, except that only step 1) is performed.
[0098] Example 14
[0099] A positive electrode active material C14 is provided, which is different from Example 1 as shown in Table 1; and its preparation method is referred to Example 1, except that: 2 kg of the precursor Ni 0.5 Mn 1.5 (OH)4, 425.66 g of lithium carbonate and 25.43 g of Ta2O5 are added into a high-speed mixer, mixed and stirred until uniform, the mixture is sintered at 1050°C for 10 h, then cooled to 700°C at a cooling rate of 0.5°C / min and kept for 5 h, and then naturally cooled, crushed and sieved to obtain a first precursor material A3; the aqueous nickel acetate solution of step 2) is replaced by the solution shown in Table 1.
[0100] Examples 15-16
[0101] A positive electrode active material C15-16 is provided, which is different from Example 14 as shown in Table 1; and its preparation method is referred to Example 14.
[0102] Comparative Example 4
[0103] A positive electrode active material D4 is provided, which is different from Example 14 as shown in Table 1; and its preparation method is referred to Example 14.
[0104] Its preparation method is referred to Example 1, except that only step 1) is performed.
[0105] Example 17
[0106] A positive electrode active material C17 is provided, which is different from Example 1 as shown in Table 1; and its preparation method is referred to Example 1, except that: 2 kg of the precursor Ni 0.5 Mn 1.5(OH)4, 471.08 g of lithium carbonate and 63.62 g of ammonium dihydrogen phosphate, 8.63 g of Ta2O5, 10.12 g of Nb2O5, 8.92 g of WO3 were added into a high-speed mixer, mixed and stirred until uniform, the mixture was sintered at 1050°C for 10 h, then cooled to 700°C at a cooling rate of 0.5°C / min and kept for 5 h, and then crushed and sieved after natural cooling to obtain a first precursor material A4; the aqueous solution of nickel acetate in step 2) was replaced by the solution shown in Table 1.
[0107] Examples 19-20
[0108] A positive electrode active material C18-20 was provided, which was different from Example 17 as shown in Table 1; and the preparation method thereof referred to Example 17.
[0109] Comparative Example 5
[0110] A positive electrode active material D5 was provided, which was different from Example 17 as shown in Table 1;
[0111] The preparation method thereof referred to Example 1, except that only step 1) was performed.
[0112] The positive electrode active materials of the above examples and comparative examples were tested as follows:
[0113] 1. The microstructure of the positive electrode active materials of the above examples and comparative examples was observed by SEM, wherein FIG. 1 shows the SEM picture of the positive electrode active material of Example 1, FIG. 2 shows the SEM picture of the positive electrode active material of Example 3, and FIG. 3 shows the SEM picture of the positive electrode active material of Comparative Example 1. By comparing FIGS. 1-3, it can be seen that the octahedral morphology of the lithium nickel manganese oxide positive electrode active materials of Examples 1-2 has changed significantly, with truncated corners and edges, exposing the (100) and (110) planes, while the lithium nickel manganese oxide positive electrode active material of Comparative Example 1 has a typical octahedral morphology.
[0114] 2. The crystal structure of the positive electrode active material powder of the above examples and comparative examples was tested by XRD, wherein I(111) / I(311) in the XRD spectrum of the first precursor material was denoted as T1, I(111) / I(400) was denoted as T2, and I(111) / I(440) was denoted as T3, and T-I = [(T 1+ T 2+ T3)-(I1+I2+I3)] / (T 1+ T 2+ T3)×100%.
[0115] FIG. 4 is the XRD diffraction spectrum of Example 1 and Comparative Example 1. As can be seen from the figure, both Comparative Example 1 and Example 1 are consistent with LiNi 0.5 Mn 1.5Standard diffraction pattern of O4. Comparative Example 1 has a flat curve around 2-Theta = 37.6 and 43.6°, and no rock salt phase Li x Ni 1-x O diffraction peaks. In Example 1, there are obvious diffraction peaks, which prove that after surface reconstruction, the lithium nickel manganese oxide produces rock salt phase Li x Ni 1-x O.
[0116] Some structural parameters and preparation parameters of the positive electrode active materials of the examples and comparative examples are summarized in Table 1.
[0117] Table 1: In the table, " / " represents that the result is not recorded, and the sintering conditions of the examples refer only to the sintering conditions of step 3), and the sintering conditions of the comparative examples refer to the sintering conditions of step 1).
[0118] Application Example 1
[0119] The positive electrode active materials of the above examples and comparative examples are used to prepare positive electrode sheets, including the following steps:
[0120] The positive electrode materials of the above examples and comparative examples are added to an appropriate amount of NMP in a ratio of positive electrode material: conductive agent (Super P): binder (PVDF) = 94.5:3:2.5, and mixed with a defoaming machine. The mixed slurry is coated on an aluminum foil to obtain a positive electrode sheet, and the positive electrode active material surface loading of the electrode sheet is 8 mg / cm 2 .
[0121] Application Example 2
[0122] The above positive electrode sheets are used to prepare batteries, including the following steps:
[0123] The above positive electrode sheets are used to prepare button-type half-cells, including the following steps: the positive electrode sheet obtained in Application Example 1 is punched into a 15 mm diameter electrode sheet, and a CR2430 button-type battery is assembled in an argon glove box, and the counter electrode is a metal lithium sheet.
[0124] Performance test:
[0125] The following electrical properties of each battery assembled in Application Example 2 are tested respectively (the results are shown in Table 2):
[0126] Electrochemical performance test: nominal capacity 150 mAh / g, electrochemical window 3.5-4.95 V. The capacity test procedure is to charge the assembled button-type battery to 4.95 V at a set rate, then charge to a current density of 0.05 C, then discharge to 3.5 V at a set rate (0.33 C, 2 C), and the obtained discharge specific capacity is the discharge specific capacity at the rate.
[0127] Mn dissolution test: the prepared lithium nickel manganese oxide positive electrode was prepared into a full cell, the negative electrode was graphite, and the NP ratio was 1.15. After the assembled full cell was formed, the cycle test was carried out, and the specific test conditions were as follows: the nominal capacity was 150 mAh / g, the electrochemical window was 3.4-4.85 V, 45℃, 1C cycle 200 cycles (1C constant current charging to 4.95V, then constant voltage charging to current density 0.05C, then 1C constant current discharging to 3.5V as a cycle), the cycle retention rate was recorded, and after the cycle, the negative electrode sheet was taken out, and the negative electrode sheet was subjected to ICP-OES test, and the obtained Mn content was the Mn dissolution amount.
[0128] Table 2:
[0129] As can be seen from Table 2, compared with the positive electrode active materials D1 and D2, the positive electrode active materials C1-C10 used in the battery can significantly reduce the dissolution of manganese and improve the rate performance and cycle stability of the corresponding battery; further, compared with the positive electrode active material D3, the positive electrode active materials C11-C13 used in the battery can reduce the dissolution of manganese and significantly improve the rate performance and cycle stability of the corresponding battery; further, compared with the positive electrode active material D4, the positive electrode active materials C14-C16 used in the battery can reduce the dissolution of manganese and improve the rate performance and cycle stability of the corresponding battery; further, compared with the positive electrode active material D5, the positive electrode active materials C17-C20 used in the battery can reduce the dissolution of manganese and significantly improve the rate performance and cycle stability of the corresponding battery.
[0130] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. A positive electrode active material, characterized by, The positive electrode active material satisfies the following formula 1: I1+I2+I3≤10.20 Formula 1; Wherein, I1 is I(111) / I(311) in the XRD pattern of the positive electrode active material, I2 is I(111) / I(400) in the XRD pattern of the positive electrode active material, I3 is I(111) / I(440) in the XRD pattern of the positive electrode active material, and I1, I2, I3 are all not 0.
2. The positive electrode active material according to claim 1, characterized by The XRD pattern of the positive electrode active material further includes a diffraction peak of a rock salt phase Li x Ni 1-x O.
3. The positive electrode active material according to claim 1 or 2, characterized by The chemical composition of the positive electrode active material includes Li 1+x Ni 0.5+y Mn 1.5+z M u N v O w wherein -0.1≤x≤0.2, -0.1≤y≤0.1, -0.3≤z≤0.3, 0≤u≤0.2, 0 M includes at least one of Al, Sc, Ti, V, Cr, Fe, Cu, Ga, Sr, Y, Zr, Nb, Mo, Ru, Ta, W, B, Si, Ge, Sb, Te, P, S, F; and N includes at least one of Mg, Ca, Co, Ni, Zn, Sr, Y, Sn, Ba, La, Ce, Nd.
4. The positive electrode active material according to claim 3, characterized by The positive electrode active material satisfies the following formula 2: 0.0005≤y / x≤0.0100 Formula 2; Wherein, x is the particle size of the positive electrode active material, unit: μm, y is the thickness when the concentration of N is 0, which is extended from the surface of the positive electrode active material to the core, unit: μm.
5. The positive electrode active material according to claim 4, characterized by 0.001 μm≤y≤0.02 μm; And / or, the Dv50 of the positive electrode active material is 1-15 μm.
6. A method for producing the positive electrode active material according to any one of claims 1 to 5, characterized by, Comprising the following steps: 1) preparing a first precursor material, the first precursor material having a chemical composition of Li 1+x Ni 0.5+y Mn 1.5+z M u O w wherein -0.1≤x≤0.2, -0.1≤y≤0.1, -0.3≤z≤0.3, 0≤u≤0.2, 3.8≤w≤4.3; M includes at least one of Al, Sc, Ti, V, Cr, Fe, Cu, Ga, Sr, Y, Zr, Nb, Mo, Ru, Ta, W, B, Si, Ge, Sb, Te, P, S, F; 2) The first precursor material is mixed with a soluble salt solution of N, and stirring, filtering and drying are sequentially performed to obtain a second precursor material; 3) The second precursor material is sintered at 700-1000 ℃ to obtain the positive electrode active material.
7. The production method according to claim 6, characterized by, The first precursor material is prepared by a method comprising the following process: The precursor of the molecular formula Ni 0.5 Mn 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 1.5 The precursor of the molecular formula Ni 8. The preparation method according to claim 6, characterized in that, In the soluble salt solution of N, the concentration of element N is 0.01-1 mol / L.
9. A positive electrode sheet characterized by comprising: Comprising a current collector and a positive electrode active layer arranged on at least one surface of the current collector; the positive electrode active layer comprises the positive electrode active material according to any one of claims 1-5.
10. A battery, characterized by Comprising the positive electrode sheet according to claim 9.