Composite modified lithium nickel manganese oxide positive electrode material as well as preparation method and application thereof
By doping high-valence and low-valence metals into lithium nickel manganese oxide cathode material and coating it with fast-ion conductors, the problem of structural and interface instability of lithium nickel manganese oxide under high voltage was solved, achieving excellent cycle performance and long life under high voltage.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANDONG CHUANGNENG NEW MATERIALS CO LTD
- Filing Date
- 2026-03-05
- Publication Date
- 2026-05-08
AI Technical Summary
Lithium nickel manganese oxide, an existing cathode material for lithium-ion batteries, is prone to oxidation and decomposition under high voltage, leading to surface corrosion and interface instability, which affects cycle stability and lifespan. Existing modification methods are difficult to improve both structural and interface stability at the same time.
Composite modified lithium nickel manganese oxide cathode materials were prepared by co-doping with high-valence and low-valence metal elements and combining them with fast-ion conductor coating. The lithium-ion diffusion channels were expanded and the lattice structure was strengthened by doping, and the interface stability was improved by using fast-ion conductor as a shell coating.
It significantly improves the structural and interfacial stability of lithium nickel manganese oxide cathode materials under high voltage, extends cycle life, achieves an initial efficiency of over 80%, and maintains a capacity retention rate of no less than 94.9% after 500 cycles.
Smart Images
Figure CN122000336A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrode material technology, specifically relating to a composite modified lithium nickel manganese oxide cathode material, its preparation method, and its application. Background Technology
[0002] Lithium-ion batteries are widely used in mobile electronic devices, electric vehicles, and large-scale energy storage devices due to their high energy density and long cycle life.
[0003] Currently available commercial cathode materials include LiCoO2, LiFePO4, and LiNi. x Mn y O4, LiNi x Co y Mn 1-x-y While these methods perform well across various performance dimensions, they still have limitations in high power output and long-cycle stability, making it difficult to meet the needs of electric transportation and energy storage systems.
[0004] Spinel-structured lithium nickel manganese oxide (LiNi) x Mn y O₄(x+y=2) has become a high-voltage cathode material with great application potential due to its advantages such as three-dimensional lithium-ion diffusion channels, excellent rate performance, and low cost. This material operates at around 4.7V, providing high energy density, making it suitable for power batteries and high-rate applications. However, this material also faces technical bottlenecks in practical applications: First, under high voltage, the electrolyte is prone to oxidative decomposition, generating corrosive substances such as hydrofluoric acid, leading to continuous erosion of the material surface, damaging the surface structure, and inducing transition metal dissolution; second, high-voltage-induced interfacial side reactions (such as instability of the negative electrode interface layer and solvent oxidation) exacerbate capacity decay during cycling, significantly affecting the material's cycle stability and lifespan.
[0005] To overcome the aforementioned problems, existing technologies employ modification methods such as element doping or surface coating. Element doping can reduce phase transitions and volume changes during cycling, helping to stabilize the crystal structure and improve material stability; however, element doping often struggles to balance structural stability and surface corrosion resistance, resulting in limited improvement. Surface coating involves coating the surface of the cathode material with lithium-based compounds such as LiNbO3 and Li3PO4 to construct a protective layer that prevents direct contact between the electrolyte and the active material, thereby improving interfacial stability. While surface coating improves interfacial stability, the coating layer is susceptible to stress damage during long-term cycling, leading to failure. Furthermore, surface coating cannot optimize the bulk structure of the material and cannot directly improve the material's inherent stability. Summary of the Invention
[0006] The purpose of this invention is to provide a composite modified lithium nickel manganese oxide cathode material, its preparation method, and its applications. The composite modified lithium nickel manganese oxide cathode material provided by this invention can simultaneously improve the structural stability and interfacial stability of the material, making it suitable for high-rate, high-voltage, and long-life lithium-ion batteries.
[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a composite modified lithium nickel manganese oxide cathode material, comprising a co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; The doping elements in the co-doped lithium nickel manganese oxide cathode material include high-valence metals and low-valence metals; the high-valence metals are one or more metals with a valence of +5; the low-valence metals are one or more metals with a valence of any value from +1 to +4. The fast ion conductor is a compound with the structural formula LiMO3, wherein M is a high-valence metal in the co-doped lithium nickel manganese oxide cathode material.
[0008] Preferably, the thickness of the fast ion conductor is 5~30 nm.
[0009] Preferably, based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the doping amount of the high-valence metal is 0.2~1%, and the doping amount of the low-valence metal is 0.1~0.5%.
[0010] Preferably, the high-valence metal includes niobium, vanadium, or tantalum; the low-valence metal includes aluminum, indium, magnesium, titanium, zirconium, or iron.
[0011] Preferably, the high-valence metal is niobium; the low-valence metal is aluminum or magnesium.
[0012] This invention also provides a method for preparing the composite modified lithium nickel manganese oxide cathode material described in the above technical solution, comprising: A precursor is obtained by mixing a high-valence metal oxalate complex, an oxide containing a low-valence metal, and a lithium nickel manganese oxide cathode material. The precursor is sintered to obtain a composite modified lithium nickel manganese oxide cathode material; the sintering temperature is 500~700℃ and the holding time is 3~8h.
[0013] Preferably, the total mass of the oxalic acid complex of the high-valence metal and the oxide containing the low-valence metal is 1.5 to 5% of the mass of the lithium nickel manganese oxide cathode material.
[0014] Preferably, the mass ratio of the oxalic acid complex of the high-valence metal to the oxide containing the low-valence metal is (1~5):1.
[0015] Preferably, the mixing method is ball milling.
[0016] The present invention also provides a lithium-ion battery cathode, wherein the active material in the lithium-ion battery cathode is the composite modified lithium nickel manganese oxide cathode material described in the above technical solution.
[0017] This invention provides a composite modified lithium nickel manganese oxide cathode material, comprising a co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated outside the co-doped lithium nickel manganese oxide cathode material; the doping elements in the co-doped lithium nickel manganese oxide cathode material include high-valence metals and low-valence metals; the high-valence metals are one or more metals with a valence of +5; the low-valence metals are one or more metals with a valence of +1 to +4; the fast ion conductor is a compound with the structural formula LiMO3, wherein M is the high-valence metal in the co-doped lithium nickel manganese oxide cathode material. This invention expands lithium-ion diffusion channels and improves rate performance by doping low-valence metals into lithium nickel manganese oxide cathode materials. It also suppresses lattice distortion and enhances structural stability. Doping with high-valence metals strengthens the MO bond, stabilizes the lattice structure, and further improves the structural stability of the cathode material. High-valence metals also maintain the valence stability of manganese and reduce side reactions. Simultaneously, using lithium salts of high-valence metals grown in situ on the surface of the co-doped lithium nickel manganese oxide cathode material as a shell not only provides fast ion conductivity and corrosion resistance, improving the interfacial stability and electrochemical performance of the cathode material, but also enhances the bonding stability between the coating layer and the cathode material, extending the coating layer's lifespan. Elemental doping and fast ion conductor coating synergistically improve the material's structural stability and cycle life under high voltage. The results of the embodiments show that the composite modified lithium nickel manganese oxide cathode material provided by this invention, when used in lithium-ion batteries, exhibits a 1C first-cycle efficiency exceeding 80% in the 3.5–4.9V voltage range and a capacity retention rate of no less than 94.9% after 500 cycles. Attached Figure Description
[0018] Figure 1 This is a SEM image of the composite modified lithium nickel manganese oxide cathode material of Example 1 of the present invention; Figure 2 The diagram shows the cycle performance of batteries assembled with the composite modified lithium nickel manganese oxide cathode material and the unmodified lithium nickel manganese oxide cathode material, respectively, according to Example 1 of the present invention. Detailed Implementation
[0019] All raw materials used in this invention are not particularly restricted in their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.
[0020] The purity of all raw materials used in this invention is not particularly limited, but high-purity or conventionally pure raw materials used in the field of electrode materials are preferred.
[0021] This invention provides a composite modified lithium nickel manganese oxide cathode material, comprising a co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; The doping elements in the co-doped lithium nickel manganese oxide cathode material include high-valence metals and low-valence metals; the high-valence metals are one or more metals with a valence of +5; the low-valence metals are one or more metals with a valence of any value from +1 to +4. The fast ion conductor is a compound with the structural formula LiMO3, wherein M is a high-valence metal in the co-doped lithium nickel manganese oxide cathode material.
[0022] The composite modified lithium nickel manganese oxide cathode material provided by this invention includes co-doped lithium nickel manganese oxide cathode material.
[0023] In this invention, the doping elements in the co-doped lithium nickel manganese oxide cathode material include high-valence metals and low-valence metals; the high-valence metals are one or more metals with a valence of +5, preferably including niobium, vanadium, or tantalum, and more preferably niobium; the low-valence metals are one or more metals with valences of +1 to +4, preferably including aluminum, indium, magnesium, titanium, zirconium, or iron, and more preferably aluminum or magnesium. Doping with high-valence metals can improve the interfacial stability of the material, while doping with low-valence metals can improve the structural stability of the material.
[0024] In this invention, based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the doping amount of the high-valence metal is preferably 0.2-1%, more preferably 0.5-0.8%. As one embodiment of this invention, the doping amount of the high-valence metal can be 0.3%, 0.4%, 0.6%, 0.7%, or 0.9%. Doping amounts of the high-valence metal within the above ranges can further improve the interfacial stability of the material.
[0025] In this invention, based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the doping amount of the low-valence metal is preferably 0.1~0.5%, more preferably 0.2~0.3%. Doping amounts of the low-valence metal within the above range can further improve the structural stability of the material.
[0026] In one embodiment of the present invention, the lithium nickel manganese oxide cathode material can be a spinel-structured lithium nickel manganese oxide cathode material with the chemical formula LiNi. x Mn y O4, x+y=2, x is 0.4~0.6, y is 1.4~1.6; specifically, x=0.5, y=1.5.
[0027] In one embodiment of the present invention, the co-doped lithium nickel manganese oxide cathode material can be co-doped with niobium and aluminum, and has the chemical formula LiNi. 0.5 Mn 1.5-a-b Al a Nb b O4; it can also be co-doped with niobium and magnesium, with the chemical formula LiNi. 0.5 Mn 1.5-a-b Mg a Nb b O4; it can also be co-doped with vanadium and aluminum, with the chemical formula LiNi. 0.5 Mn 1.5-a-b Al a V b O4; it can also be co-doped with vanadium and magnesium, with the chemical formula LiNi. 0.5 Mn 1.5-a-b Mg a V b O4; it can also be co-doped with tantalum and aluminum, with the chemical formula LiNi. 0.5 Mn 1.5-a-b Al a Ta b O4; it can also be co-doped with tantalum and magnesium, with the chemical formula LiNi. 0.5 Mn 1.5-a-b Mg a Ta b O4; it can also be co-doped with tantalum and titanium, with the chemical formula LiNi. 0.5 Mn 1.5-a-b Ti a Ta b O4; it can also be co-doped with tantalum and zirconium, with the chemical formula LiNi. 0.5 Mn 1.5-a-b Ti a Zr b O4; it can also be co-doped with vanadium and titanium, with the chemical formula LiNi. 0.5 Mn 1.5-a-b Ti a V b O4; where a and b represent the doping amount.
[0028] The composite modified lithium nickel manganese oxide cathode material provided by the present invention includes a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material.
[0029] In this invention, the fast ion conductor is a compound with the structural formula LiMO3, where M is a high-valence metal in the co-doped lithium nickel manganese oxide cathode material. The compound with the above structure possesses excellent ion conductivity and corrosion resistance, which can improve the corrosion resistance and ion conduction rate of the material; the high-valence metal is also a doping element of the lithium nickel manganese oxide cathode material, and in-situ coating can further improve the bonding stability between the coating layer and the cathode material.
[0030] In this invention, the thickness of the fast ion conductor is preferably 5-30 nm, more preferably 10-20 nm; as one embodiment of this invention, the thickness of the fast ion conductor can be 8 nm, 12 nm, 15 nm, 18 nm, 24 nm, or 27 nm. A thickness within the above range can further improve the material's corrosion resistance and ion conduction rate.
[0031] This invention expands lithium-ion diffusion channels and improves rate performance by doping low-valence metals into lithium nickel manganese oxide cathode materials. It also suppresses lattice distortion and enhances structural stability. Doping with high-valence metals strengthens the MO bond, stabilizes the lattice structure, and further improves the structural stability of the cathode material. High-valence metals also maintain the valence of manganese and reduce side reactions. Simultaneously, using lithium salts of high-valence metals grown in situ on the surface of the co-doped lithium nickel manganese oxide cathode material as a shell not only provides fast ion conductivity and corrosion resistance, improving the interfacial stability and electrochemical performance of the cathode material, but also enhances the bonding stability between the coating layer and the cathode material, extending the coating layer's lifespan. Elemental doping and fast ion conductor coating synergistically improve the material's structural stability and cycle life under high voltage.
[0032] This invention also provides a method for preparing the composite modified lithium nickel manganese oxide cathode material described in the above technical solution, comprising: A precursor is obtained by mixing a high-valence metal oxalate complex, an oxide containing a low-valence metal, and a lithium nickel manganese oxide cathode material. The precursor is sintered to obtain a composite modified lithium nickel manganese oxide cathode material; the sintering temperature is 500~700℃ and the holding time is 3~8h.
[0033] This invention mixes a high-valence metal oxalic acid complex, an oxide containing a low-valence metal, and a lithium nickel manganese oxide cathode material to obtain a precursor.
[0034] In this invention, the preferred mass ratio of the high-valence metal oxalic acid complex to the oxide containing the low-valence metal is (1~5):1, more preferably (2~4):1. As one embodiment of this invention, the mass ratio of the high-valence metal oxalic acid complex to the oxide containing the low-valence metal can be 1:1, 2:1, 3:1, 4:1, or 5:1. Maintaining the mass ratio of the high-valence metal oxalic acid complex to the oxide containing the low-valence metal within the above range can improve the dispersion effect of the raw materials while ensuring the material's performance.
[0035] In this invention, the total mass of the high-valence metal oxalic acid complex and the oxide containing the low-valence metal is preferably 1.5-5% of the mass of the lithium nickel manganese oxide cathode material, more preferably 2-4%. As one embodiment of this invention, the total mass of the high-valence metal oxalic acid complex and the oxide containing the low-valence metal is 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or 4.5% of the mass of the lithium nickel manganese oxide cathode material. Using the amounts of the high-valence metal oxalic acid complex and the oxide containing the low-valence metal within the above range can improve the dispersion effect while ensuring material performance.
[0036] In one embodiment of the present invention, the oxalic acid complex of the high-valence metal can be a niobium ammonium oxalate complex, a vanadium oxalate complex, a sodium vanadium metaoxide complex, or a tantalum ammonium oxalate complex; the oxide containing the low-valence metal can be aluminum oxide, magnesium oxide, titanium oxide, or zirconium oxide.
[0037] In this invention, the mixing method is preferably ball milling. As one embodiment of the invention, the ball milling can be dry milling or wet milling. The ball milling speed can be 200-600 rpm, the milling time can be 2-8 hours, the ball-to-material ratio can be (5-15):1, and the milling balls can be any one of zirconium oxide balls, alumina balls, or silicon nitride balls. For wet milling, anhydrous ethanol can be added as a dispersant, with an amount of 30-50% of the mass of the mixture. Ball milling can uniformly attach the oxalic acid complex of high-valence metals and oxides containing low-valence metals to the particle surface of lithium nickel manganese oxide cathode material, further improving the material's stability and electrochemical performance.
[0038] In one embodiment of the present invention, the ball milling apparatus can be a high-energy ball mill.
[0039] As one embodiment of the present invention, the material can be dried after ball milling to remove moisture and / or dispersant from the material; the drying temperature can be 80~95℃, and the drying time can be 6~8h; the drying temperature within the above range can remove moisture and / or dispersant from the material, and can also prevent premature decomposition of high-valence metal oxalic acid complexes; the drying atmosphere can be air.
[0040] After obtaining the precursor, the present invention sinters the precursor to obtain a composite modified lithium nickel manganese oxide cathode material.
[0041] In this invention, the sintering temperature is 500~700℃, preferably 550~650℃; as one embodiment of this invention, the sintering temperature can be 530℃, 560℃, 590℃, 600℃, 630℃, 660℃, or 680℃. During the sintering process, the high-valence metal ions generated by the decomposition of the oxalic acid complex of the high-valence metal partially react with lithium ions on the material surface to form lithium salts of the high-valence metal, which act as fast ion conductor shells covering the outer layer of the material, while the remaining portion enters the lithium nickel manganese oxide lattice for doping; oxides containing low-valence metals release low-valence metal ions to dope into the lithium nickel manganese oxide lattice; sintering temperatures within the above range can ensure the reaction proceeds, avoiding incomplete reactions due to excessively low temperatures, or disproportionation reactions of manganese in lithium nickel manganese oxide due to excessively high temperatures, which would affect the intrinsic properties of the material.
[0042] In this invention, the sintering holding time is 3-8 hours, preferably 4-6 hours; as one embodiment of this invention, the sintering holding time can be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours. Holding the sintering within the above range ensures complete reaction, avoids incomplete reaction leading to incomplete coating, and also balances the thickness and doping amount of the coating, improving the electrochemical performance and corrosion resistance of the material.
[0043] As one embodiment of the present invention, the heating rate of the sintering can be 2~8℃ / min, or 4~6℃ / min, specifically 5℃ / min; within the above range, the heating rate can make the reaction uniform and stable, and further improve the structural stability of the cathode material.
[0044] In one embodiment of the present invention, the sintering can be carried out in a flowing atmosphere to remove the gas produced by the reaction; the gas source of the flowing atmosphere can be an inert gas or air; the sintering apparatus can be a muffle furnace.
[0045] The preparation method provided by this invention is simple, easy to control, and conducive to obtaining products with stable quality.
[0046] The present invention also provides a lithium-ion battery cathode, wherein the active material in the lithium-ion battery cathode is the composite modified lithium nickel manganese oxide cathode material described in the above technical solution.
[0047] The present invention does not impose any particular limitation on the preparation process of the lithium-ion battery cathode; conventional preparation processes in the art can be used.
[0048] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0049] Example 1 A composite modified lithium nickel manganese oxide cathode material is composed of niobium and aluminum co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the doping amount of niobium is 0.25% and the doping amount of aluminum is 0.25%; The fast ion conductor is LiNbO3 with a thickness of 10 nm.
[0050] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5 O4 cathode material was mixed with 1.5g of niobium ammonium oxalate complex (C4H4NNbO9·nH2O, Aladdin reagent) and 0.5g of alumina in a high-energy ball mill for 3h. The grinding balls were zirconia balls with a ball-to-material ratio of 10:1 and a rotation speed of 500rpm. The mixture was dried in air at 80℃ for 5h. The temperature was then increased from room temperature to 600℃ at a rate of 5℃ / min, held for 4h, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0051] The scanning electron microscope (SEM) image of the obtained composite modified lithium nickel manganese oxide cathode material is shown below. Figure 1 As shown. From Figure 1 It can be seen that the composite modified lithium nickel manganese oxide cathode material provided by the present invention is granular with a particle size of about 10 μm, indicating that the modification did not change the morphology of the lithium nickel manganese oxide cathode material.
[0052] Example 2 A composite modified lithium nickel manganese oxide cathode material is composed of niobium and magnesium co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the doping amount of niobium is 0.2% and the doping amount of magnesium is 0.3%; The fast ion conductor is LiNbO3 with a thickness of 8 nm.
[0053] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5O4 cathode material was mixed with 1.0 g of niobium ammonium oxalate complex (C4H4NNbO9·nH2O, Aladdin reagent) and 0.5 g of magnesium oxide in a high-energy ball mill for 3 h. The grinding balls were zirconia balls with a ball-to-material ratio of 10:1 and a rotation speed of 500 rpm. The mixture was dried in air at 80 °C for 5 h. The temperature was then increased from room temperature to 450 °C at a rate of 5 °C / min, held for 5 h, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0054] Example 3 A composite modified lithium nickel manganese oxide cathode material is composed of vanadium and aluminum co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the vanadium doping amount is 0.25% and the aluminum doping amount is 0.25%; The fast ion conductor is LiVO3 with a thickness of 12 nm.
[0055] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5 O4 cathode material was mixed with 1.5g of vanadium oxalate complex and 0.5g of alumina in a high-energy ball mill for 3 hours. The grinding balls were zirconia balls with a ball-to-material ratio of 10:1 and a rotation speed of 500 rpm. The mixture was dried in air at 80℃ for 5 hours. The temperature was then increased from room temperature to 500℃ at a rate of 5℃ / min, held for 5 hours, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0056] Example 4 A composite modified lithium nickel manganese oxide cathode material is composed of vanadium and magnesium co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the vanadium doping amount is 0.31% and the magnesium doping amount is 0.3%; The fast ion conductor is LiVO3 with a thickness of 15 nm.
[0057] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5 O4 cathode material was mixed with 2g of vanadium oxalate complex and 0.5g of magnesium oxide in a high-energy ball mill for 3h. The grinding balls were zirconia balls with a ball-to-material ratio of 10:1 and a rotation speed of 500rpm. The mixture was dried in air at 80℃ for 5h. The temperature was then increased from room temperature to 600℃ at a rate of 5℃ / min, held for 6h, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0058] Example 5 A composite modified lithium nickel manganese oxide cathode material is composed of tantalum and aluminum co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the doping amount of tantalum is 0.4% and the doping amount of aluminum is 0.25%; The fast ion conductor is LiTaO3 with a thickness of 20 nm.
[0059] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5 O4 cathode material was mixed with 2.5g of ammonium tantalate oxalate complex ((NH4)3TaO(C2O4)3·xH2O, synthesized in the laboratory) and 0.5g of alumina in a high-energy ball mill for 3h. The grinding balls were zirconia balls with a ball-to-material ratio of 10:1 and a rotation speed of 500rpm. The mixture was dried in air at 80℃ for 5h. The temperature was then increased from room temperature to 700℃ at a rate of 5℃ / min, held for 6h, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0060] The synthesis method of (NH4)3TaO(C2O4)3·xH2O is as follows: Dissolving oxalic acid: Oxalic acid was dissolved in deionized water to prepare a 0.75 mol / L oxalic acid solution. Under magnetic stirring, weighed tantalum pentachloride solid powder (molar ratio of oxalate ions to tantalum ions is 3:1) is added and stirred continuously to allow it to react fully. Oxalate ions and tantalum ions undergo a coordination reaction to form a tantalum oxalate complex. Add ammonium source: To neutralize the acidity in the solution and provide ammonium ions, 1 mol / L ammonia water was added dropwise under stirring to adjust the pH of the solution to 6-7; the ammonium ions formed ammonium salts with oxalate ions, and further formed ammonium tantalum oxalate complexes with tantalum oxalate complexes. Formation of hydrates: The reaction mixture was heated to 60°C and maintained at that temperature for 1 hour; as the water gradually evaporated, the ammonium tantalum oxalate hydrate began to crystallize. Crystallization can be promoted by slowly evaporating the water in the solution; the amount of hydrate (x) depends on the crystallization conditions. After crystallization, the solid is filtered out and washed with deionized water to remove excess chloride or unreacted oxalic acid; Drying and collecting: The crystallized ammonium tantalate oxalate hydrate is dried at a low temperature (70°C) to remove moisture; if necessary, it can be dried under vacuum to ensure better hydration.
[0061] Example 6 A composite modified lithium nickel manganese oxide cathode material is composed of tantalum and magnesium co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the doping amount of tantalum is 0.4% and the doping amount of magnesium is 0.18%; The fast ion conductor is LiTaO3 with a thickness of 15 nm.
[0062] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5 O4 cathode material was mixed with 1.2g of ammonium tantalum oxalate complex ((NH4)3TaO(C2O4)3·xH2O, synthesized in the laboratory, same as in Example 5) and 0.3g of magnesium oxide in a high-energy ball mill for 3h. The grinding balls were zirconia balls with a ball-to-material ratio of 10:1 and a rotation speed of 500rpm. The mixture was dried in air at 80℃ for 5h. The temperature was then increased from room temperature to 450℃ at a rate of 5℃ / min, held for 4h, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0063] Example 7 A composite modified lithium nickel manganese oxide cathode material is composed of vanadium and aluminum co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the vanadium doping amount is 0.35% and the aluminum doping amount is 0.3%; The fast ion conductor is LiVO3 with a thickness of 12 nm.
[0064] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5 O4 cathode material was mixed with 1.8g of sodium meta-vanadium complex and 0.6g of alumina in a high-energy ball mill for 3h. The grinding balls were zirconia balls with a ball-to-material ratio of 10:1 and a rotation speed of 500rpm. The mixture was dried in air at 80℃ for 5h. The temperature was then increased from room temperature to 550℃ at a rate of 5℃ / min, held for 4h, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0065] Example 8 A composite modified lithium nickel manganese oxide cathode material is composed of tantalum and titanium co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the doping amount of tantalum is 1% and the doping amount of titanium is 0.36%; The fast ion conductor is LiTaO3 with a thickness of 30 nm.
[0066] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5 O4 cathode material was mixed with 3.0 g of ammonium tantalate oxalate complex ((NH4)3TaO(C2O4)3·xH2O, synthesized in the laboratory, same as in Example 5) and 0.6 g of titanium oxide in a high-energy ball mill for 3 h. The grinding balls were zirconia balls with a ball-to-material ratio of 10:1 and a rotation speed of 500 rpm. The mixture was dried in air at 80 °C for 5 h. The temperature was then increased from room temperature to 650 °C at a rate of 5 °C / min, held for 6 h, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0067] Example 9 A composite modified lithium nickel manganese oxide cathode material is composed of tantalum and zirconium co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the doping amount of tantalum is 0.2% and the doping amount of zirconium is 0.25%; The fast ion conductor is LiTaO3 with a thickness of 10 nm.
[0068] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5 O4 cathode material was mixed with 0.8g of tantalum oxalate complex ((NH4)3TaO(C2O4)3·xH2O, synthesized in the laboratory, same as in Example 5) and 0.4g of zirconium oxide in a high-energy ball mill for 3h. The grinding balls were aluminum nitride balls with a ball-to-material ratio of 10:1 and a rotation speed of 500rpm. The mixture was dried in air at 80℃ for 5h. The temperature was then increased from room temperature to 550℃ at a rate of 5℃ / min, held for 6h, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0069] Example 10 A composite modified lithium nickel manganese oxide cathode material is composed of vanadium and titanium co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the co-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the doping amount of vanadium is 0.25% and the doping amount of titanium is 0.25%. The fast ion conductor is LiVO3 with a thickness of 10 nm.
[0070] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5O4 cathode material was mixed with 0.8g of vanadium oxalate complex and 0.4g of titanium dioxide in a high-energy ball mill for 3 hours. The grinding balls were zirconium oxide balls with a ball-to-material ratio of 10:1 and a rotation speed of 500 rpm. The mixture was dried in air at 80℃ for 5 hours. The temperature was then increased from room temperature to 550℃ at a rate of 5℃ / min, held for 5 hours, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0071] Comparative Example 1 A modified lithium nickel manganese oxide cathode material is composed of niobium-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated on the niobium-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the niobium doping amount is 0.5%, and the fast ion conductor is LiNbO3 with a thickness of 20 nm.
[0072] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5 O4 cathode material was mixed with 2g of niobium ammonium oxalate complex (C4H4NNbO9·nH2O, Aladdin reagent) in a high-energy ball mill for 3h. The grinding balls were zirconia balls with a ball-to-material ratio of 10:1 and a rotation speed of 500rpm. The mixture was dried in air at 80℃ for 5h. The temperature was then increased from room temperature to 600℃ at a rate of 5℃ / min, held for 4h, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0073] Comparative Example 2 A modified lithium nickel manganese oxide cathode material is an aluminum-doped lithium nickel manganese oxide cathode material; based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the aluminum doping amount is 1.2%.
[0074] The preparation method is as follows: Take 100g of spinel-type LiNi 0.5 Mn 1.5 O4 cathode material was mixed with 2g of alumina in a high-energy ball mill for 3h. The grinding balls were zirconia balls with a ball-to-material ratio of 10:1 and a rotation speed of 500rpm. The mixture was dried in air at 80℃ for 5h. The temperature was then increased from room temperature to 600℃ at a rate of 5℃ / min, held for 4h, and then cooled to room temperature to obtain the composite modified lithium nickel manganese oxide cathode material.
[0075] Test case The modified lithium nickel manganese oxide cathode materials provided in Examples 1-10 and Comparative Examples 1-2, along with the raw materials for the lithium nickel manganese oxide cathode materials, were used to prepare electrodes: 270g of cathode material, 15g of conductive carbon black, and 15g of polyvinylidene fluoride were mixed with N-methylpyrrolidone solvent, the solid content was adjusted to 50%, and after stirring evenly, the mixture was coated onto aluminum foil with a coating amount of 30mg / cm². 2Vacuum drying at 120℃ and roller pressing are used to obtain electrodes.
[0076] Using the aforementioned electrode as the positive electrode and graphite as the negative electrode, a battery was assembled using a polyethylene separator and LiPF6 / EC (1 mol / L) electrolyte. Electrochemical tests were conducted. The first cycle was performed with a charge-discharge cycle at a current density of 1C (20 mA / g) within a voltage range of 3.5–4.9V. Subsequent charge-discharge cycle tests were performed at a rate of 1C within the same voltage range of 3.5–4.9V. Electrochemical data for batteries assembled using different materials are shown in Table 1. The cycle performance graphs of batteries assembled using the composite modified lithium nickel manganese oxide positive electrode material and the lithium nickel manganese oxide positive electrode material provided in Example 1 are shown below. Figure 2 As shown, Figure 2 In the text, "Comparative Example" refers to the unmodified lithium nickel manganese oxide cathode material, and "Example 1" refers to the modified lithium nickel manganese oxide cathode material provided in Example 1.
[0077] Table 1 Electrochemical Test Records for Different Materials
[0078] From Table 1 and Figure 2 It can be seen that the composite modified lithium nickel manganese oxide cathode material provided by the present invention has better first-efficiency and cycle performance than the unmodified or metal-modified lithium nickel manganese oxide cathode material.
[0079] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A composite modified lithium nickel manganese oxide cathode material, comprising a co-doped lithium nickel manganese oxide cathode material and a fast ion conductor in situ coated outside the co-doped lithium nickel manganese oxide cathode material; The doping elements in the co-doped lithium nickel manganese oxide cathode material include high-valence metals and low-valence metals; the high-valence metals are one or more metals with a valence of +5; the low-valence metals are one or more metals with a valence of +1 to +4. The fast ion conductor is a compound with the structural formula LiMO3, wherein M is a high-valence metal in the co-doped lithium nickel manganese oxide cathode material.
2. The composite modified lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The thickness of the fast ion conductor is 5~30 nm.
3. The composite modified lithium nickel manganese oxide cathode material according to claim 1, characterized in that, Based on the mass of the lithium nickel manganese oxide cathode material in the co-doped lithium nickel manganese oxide cathode material, the doping amount of the high-valence metal is 0.2~1%, and the doping amount of the low-valence metal is 0.1~0.5%.
4. The composite modified lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The high-valence metals include niobium, vanadium, or tantalum; the low-valence metals include aluminum, indium, magnesium, titanium, zirconium, or iron.
5. The composite modified lithium nickel manganese oxide cathode material according to claim 4, characterized in that, The high-valence metal is niobium; the low-valence metal is aluminum or magnesium.
6. The method for preparing the composite modified lithium nickel manganese oxide cathode material according to any one of claims 1 to 5, characterized in that, include: A precursor is obtained by mixing a high-valence metal oxalate complex, an oxide containing a low-valence metal, and a lithium nickel manganese oxide cathode material. The precursor is sintered to obtain a composite modified lithium nickel manganese oxide cathode material; the sintering temperature is 500~700℃ and the holding time is 3~8h.
7. The preparation method according to claim 6, characterized in that, The total mass of the oxalic acid complex of the high-valence metal and the oxide containing the low-valence metal is 1.5 to 5% of the mass of the lithium nickel manganese oxide cathode material.
8. The preparation method according to claim 7, characterized in that, The mass ratio of the oxalic acid complex of the high-valence metal to the oxide containing the low-valence metal is (1~5):
1.
9. The preparation method according to claim 6, characterized in that, The mixing method is ball milling.
10. A lithium-ion battery positive electrode, characterized in that, The active material in the positive electrode of the lithium-ion battery is the composite modified lithium nickel manganese oxide positive electrode material according to any one of claims 1 to 5 or the composite modified lithium nickel manganese oxide positive electrode material prepared by the preparation method according to any one of claims 6 to 9.