A lithium ion transmission function layer cooperated with coated modified lithium nickel manganese oxide positive electrode material, a preparation method and application thereof

Abstract

This invention provides a modified lithium nickel manganese oxide cathode material with synergistic coating of two lithium-ion transport functional layers, its preparation method, and its application, belonging to the field of electrode material technology. This invention improves the bonding stability of the composite coating layer and effectively enhances the cycle performance and rate performance of the cathode material by in-situ coating a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer onto the outer surface of the lithium nickel manganese oxide cathode material. The phosphate-based lithium-ion transport functional layer exhibits excellent corrosion resistance, reducing the erosion of the cathode material by the electrolyte; the niobium-based fast ion conductor possesses high ion conductivity, ensuring the lithium-ion transport rate and improving the electrochemical performance of the cathode material.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, specifically relating to a modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers and its preparation method and application. Background Technology

[0002] Lithium-ion batteries are widely used in mobile electronic devices, electric vehicles and other fields due to their high energy density and long lifespan.

[0003] Spinel-structured lithium nickel manganese oxide (LiNi) x Mn y O4 (Li₂O₄) possesses a three-dimensional lithium-ion diffusion channel, excellent rate performance, and a relatively good cost advantage, making it considered an ideal cathode material for high-voltage lithium-ion batteries. Its operating voltage is as high as 4.7V (relative to Li₂O₄). + / Li). However, under high voltage conditions, the electrolyte is prone to decomposition to generate hydrofluoric acid (HF), which leads to damage to the surface structure of the material and dissolution of transition metal ions, seriously affecting the cycle life and safety of the battery.

[0004] To improve the stability of lithium nickel manganese oxide cathode materials under high voltage, existing technologies employ inert coatings, such as phosphate coatings and metal oxide coatings. While single inert coatings offer some protection against electrolyte corrosion, they fail to maintain lithium-ion conductivity, leading to rapid capacity decay during long-term cycling.

[0005] The composite coating strategy combines inert coating and conductive layer coating. The inert coating effectively enhances the resistance to HF corrosion, while the conductive layer not only serves as a protective layer but also significantly improves the ion conduction rate, compensating for the low conductivity of the inert coating and achieving synergistic optimization of protection and conduction. However, in existing composite coatings, the inert coating and conductive layer are difficult to form a tightly bonded synergistic structure. The modified cathode material, after 40 cycles at a voltage of 3.5~4.9V and a current density of 20mA / g, does not achieve a capacity retention of 86% (compared to 82% for the unmodified material), indicating that further improvement is needed. Summary of the Invention

[0006] The purpose of this invention is to provide a lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers synergistically coated, its preparation method, and its applications. The lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers synergistically coated, provided by this invention, exhibits good cycle stability and rate performance under high voltage.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer comprises a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer arranged sequentially from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4; the material of the niobium-based fast ion conductor layer is LiNbO3.

[0008] This invention also provides a method for preparing the modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers synergistically coated as described in the above technical solution, comprising: Phosphate, niobium-containing compound and lithium nickel manganese oxide cathode material are mixed and then calcined in an inert atmosphere to obtain lithium nickel manganese oxide cathode material with dual lithium ion transport functional layer synergistic coating; The calcination temperature is 400~700℃, and the holding time is 2~12h.

[0009] Preferably, the mass ratio of the total mass of the phosphate and the niobium-containing compound to the mass of the lithium nickel manganese oxide cathode material is (0.2~3):100.

[0010] Preferably, the mass ratio of the phosphate to the niobium-containing compound is (1~3):1.

[0011] Preferably, the phosphate includes one or more of Li3PO4, Na3PO4, K3PO4 and AlPO4.

[0012] Preferably, the niobium-containing compound includes one or more of Nb2O5, Nb2O3, NbCl5, Nb(NO3)5, (NH4)3[NbO(C2O4)3]·H2O, K3[NbO(C2O4)3]·H2O, and (NH4)2[NbO(NO3)5].

[0013] Preferably, the calcination is a single-stage calcination or a segmented calcination.

[0014] Preferably, the segmented calcination is performed by holding the temperature at 400-550°C for 1-6 hours, then raising the temperature to 600-700°C and holding for 1-6 hours.

[0015] Preferably, the heating rate of the calcination is 1~10℃ / min.

[0016] The present invention also provides a lithium-ion battery cathode, wherein the active material of the lithium-ion battery cathode is the modified nickel-manganese oxide cathode material with dual lithium-ion transport functional layers as described in the above technical solution.

[0017] This invention provides a modified lithium nickel manganese oxide cathode material with a dual lithium-ion transport functional layer synergistic coating, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer includes a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer sequentially disposed from the inside out; the material of the phosphate-based lithium-ion transport functional layer is Li3PO4; and the material of the niobium-based fast ion conductor layer is LiNbO3. This invention improves the bonding stability of the composite coating layer by in-situ coating the outer surface of the lithium nickel manganese oxide cathode material with a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer, effectively enhancing the cycle performance and rate performance of the cathode material. The phosphate-based lithium-ion transport functional layer exhibits excellent corrosion resistance, reducing the erosion of the cathode material by the electrolyte; the niobium-based fast ion conductor has high ion conductivity, ensuring the lithium-ion transport rate and improving the electrochemical performance of the cathode material. The results of the embodiments show that the modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers provided by the present invention retains a capacity of more than 86% after 40 cycles at a voltage of 3.5~4.9V and a current density of 20mA / g. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers in an embodiment of the present invention; in the figure, 1 is a lithium nickel manganese oxide particle, 2 is a phosphate-based lithium-ion transport functional layer, and 3 is a niobium-based fast ion conductor layer. Figure 2 This is a SEM image of the modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers in Embodiment 1 of the present invention. Figure 3 The figures show the first charge-discharge curves of the modified lithium nickel manganese oxide cathode material and the unmodified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers in Embodiment 1 of the present invention. Figure 4 The diagram shows the cycle performance of the half-cell assembled with the modified lithium nickel manganese oxide cathode material and the unmodified lithium nickel manganese oxide cathode material, which are co-coated with dual lithium-ion transport functional layers in Example 1 of the present invention. Figure 5 The images show the XRD patterns of the modified lithium nickel manganese oxide cathode material and the unmodified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers in Embodiment 1 of the present invention. Figure 6 XRD patterns of the materials are provided for Embodiment 1 and Comparative Example 4 of the present invention; Figure 7 XRD patterns of materials are provided for Embodiment 1 and Comparative Example 5 of the present invention; Figure 8 This is a TEM image of the modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers in Embodiment 1 of the present invention. Detailed Implementation

[0019] For all raw materials of the present invention, there are no special restrictions on their sources, and they can be purchased on the market or prepared by conventional methods well-known to those skilled in the art.

[0020] For all raw materials of the present invention, there are no special restrictions on their purity. The present invention preferably uses raw materials of analytical purity or conventional purity in the field of electrode materials.

[0021] The present invention provides a lithium nickel manganese oxide cathode material modified by synergistic coating of a double lithium ion transport functional layer, which includes a lithium nickel manganese oxide cathode material and a composite coating layer in-situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer includes a phosphoric acid-based lithium ion transport functional layer and a niobium-based fast ion conductor layer arranged in sequence from the inside to the outside; the material of the phosphoric acid-based lithium ion transport functional layer is Li3PO4; the material of the niobium-based fast ion conductor layer is LiNbO3.

[0022] The lithium nickel manganese oxide cathode material modified by synergistic coating of a double lithium ion transport functional layer provided by the present invention includes a lithium nickel manganese oxide cathode material.

[0023] The lithium nickel manganese oxide cathode material is the basic material for modification, ensuring the intrinsic properties such as the energy density and rate performance of the cathode material. The chemical formula of lithium nickel manganese oxide is LiNi x Mn y O4, where 0 < x < 1, 0 < y ≤ 1.5, and x + y = 2. In the embodiments of the present invention, the lithium nickel manganese oxide cathode material with a spinel structure is used, and the chemical formula is LiNi 0.5 Mn 1.5 O4.

[0024] The lithium nickel manganese oxide cathode material modified by synergistic coating of a double lithium ion transport functional layer provided by the present invention further includes a composite coating layer in-situ coated on the outer surface of the lithium nickel manganese oxide cathode material.

[0025] In the present invention, the composite coating layer includes a phosphoric acid-based lithium ion transport functional layer and a niobium-based fast ion conductor layer arranged in sequence from the inside to the outside. The phosphoric acid-based lithium ion transport functional layer has excellent corrosion resistance and can reduce the erosion of the electrolyte on the cathode material; the niobium-based fast ion conductor has high ion conductivity, which can ensure the transport rate of lithium ions and improve the electrochemical performance of the cathode material; the in-situ formed double-layer coating can improve the binding stability of the composite coating layer and effectively enhance the cycle performance and rate performance of the cathode material.

[0026] This invention improves the bonding stability of the composite coating layer and effectively enhances the cycle performance and rate performance of the cathode material by in-situ coating a phosphate-based lithium ion transport functional layer and a niobium-based fast ion conductor layer on the outer surface of the lithium nickel manganese oxide cathode material. The phosphate-based lithium ion transport functional layer has excellent corrosion resistance, which can reduce the erosion of the cathode material by the electrolyte; the niobium-based fast ion conductor has high ion conductivity, which can ensure the lithium ion transport rate and improve the electrochemical performance of the cathode material.

[0027] This invention also provides a method for preparing the modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers synergistically coated as described in the above technical solution, comprising: Phosphate, niobium-containing compound and lithium nickel manganese oxide cathode material are mixed and then calcined in an inert atmosphere to obtain lithium nickel manganese oxide cathode material with dual lithium ion transport functional layer synergistic coating; The calcination temperature is 400~700℃, and the holding time is 2~12h.

[0028] In this invention, the phosphate preferably includes one or more of Li3PO4, Na3PO4, K3PO4, and AlPO4, more preferably Li3PO4; when multiple types of phosphate are used, they can be compounded in any proportion. During calcination, the aforementioned phosphate can react with lithium ions on the surface of the lithium nickel manganese oxide cathode material to form a phosphate-based lithium ion transport functional layer, further improving the electrochemical performance of the cathode material.

[0029] In this invention, the niobium-containing compound preferably includes one or more of Nb₂O₅, Nb₂O₃, NbCl₅, Nb(NO₃)₅, (NH₄)₃[NbO(C₂O₄)₃]·H₂O, K₃[NbO(C₂O₄)₃]·H₂O, and (NH₄)₂[NbO(NO₃)₅]. When there is one or more niobium-containing compounds, this invention does not limit the mass relationship of each niobium-containing compound, and any proportion is acceptable. During the calcination process, the above-mentioned niobium-containing compounds can decompose or react directly with lithium ions to generate niobium-based fast ion conductors with high lithium ion transference numbers, further improving the electrochemical performance of the cathode material.

[0030] In this invention, the mass ratio of the total mass of the phosphate and the niobium-containing compound to the lithium nickel manganese oxide cathode material is (0.2~3):100, more preferably (0.5~2):100. As one embodiment of this invention, the mass ratio of the total mass of the phosphate and the niobium-containing compound to the lithium nickel manganese oxide cathode material can be 0.2:100, 0.3:100, 0.4:100, 0.5:100, 1:100, or 2:100. A mass ratio of the total mass of the phosphate and the niobium-containing compound to the lithium nickel manganese oxide cathode material within the above range is beneficial for the protection of the lithium nickel manganese oxide cathode material by the composite coating layer, further improving the cycle stability of the battery.

[0031] In this invention, the preferred mass ratio of the phosphate to the niobium-containing compound is (1~3):1, more preferably (1.5~2.5):1; as one embodiment of this invention, the mass ratio of the phosphate to the niobium-containing compound can be 1:1, 1.5:1, 7:3, 2.5:1, 8:3, or 3:1. A mass ratio of phosphate to niobium-containing compound within the above range is beneficial to the bonding stability of the phosphate-based lithium-ion transport functional layer and the niobium-based fast-ion conductor layer, further improving the cycle stability of the battery.

[0032] The present invention does not have any particular limitation on the mixing method, as long as the raw materials can be mixed evenly.

[0033] In one embodiment of the present invention, after mixing, the mixture can be dried; the drying temperature can be 80°C, and the holding time can be 5 hours. Drying can remove moisture from the mixture and reduce side reactions during calcination.

[0034] In this invention, the calcination is preferably a one-stage calcination or a segmented calcination, and more preferably a segmented calcination.

[0035] In one embodiment of the present invention, the calcination is a one-stage calcination; the calcination temperature is 400~700℃, preferably 500~650℃, more preferably 550~600℃; the holding time is 2~12h, preferably 3~8h, more preferably 5~6h. If the calcination temperature is below 400℃, the reaction is incomplete, and the composite coating layer is incomplete; if the calcination temperature is too high, it will cause the Mn content in the cathode material to decrease. 3+ Jahn-Teller distortion or disproportionation reactions occur, damaging the material's bulk structure; one-stage calcination has a higher sintering rate, which can improve preparation efficiency.

[0036] In another embodiment of the present invention, the calcination is a segmented calcination; the segmented calcination is as follows: holding at 400~550℃ for 1~6 hours, then raising the temperature to 600~700℃ and holding for 1~6 hours; preferably, holding at 450~500℃ for 2~5 hours, then raising the temperature to 600~650℃ and holding for 2~4 hours; in an embodiment of the present invention, the segmented calcination is as follows: holding at 500℃ for 5 hours, then raising the temperature to 600℃ and holding for 3 hours; holding at 500℃ for 5 hours, then... The temperature was raised to 650℃ and held for 3 hours; then held at 500℃ for 5 hours, followed by raising to 700℃ and holding for 3 hours; then held at 450℃ for 4 hours, followed by raising to 620℃ and holding for 4 hours; then held at 520℃ for 6 hours, followed by raising to 680℃ and holding for 2 hours; then held at 480℃ for 5 hours, followed by raising to 700℃ and holding for 3 hours; then held at 550℃ for 4 hours, followed by raising to 640℃ and holding for 5 hours; or held at 460℃ for 6 hours, followed by raising to 660℃ and holding for 4 hours. The thermodynamic stability and phase formation temperature range of the phosphate system and the niobium oxide system at high temperatures differ significantly; phosphates (such as Li3PO4, AlPO4) can react with the Li on the surface of lithium nickel manganese oxide at 350~500℃. + An interfacial reaction occurs, forming a stable lithium-ion conductive phase based on phosphate. The driving force for its formation mainly comes from Li. + Surface diffusion and PO4 3- The rigid framework provides fixation, thus preferentially growing and fixing to the particle surface to form an inner layer structure during the first-stage low-temperature calcination process; in contrast, the conversion of niobium oxides (such as Nb₂O₅) into lithium niobate or amorphous Li-Nb-O fast ionic conductor phases requires higher reaction temperatures (typically above 600℃), depending on Li + The further diffusion and reconstruction process into the Nb-O network results in the formation and deposition of the phosphate layer only during the second-stage high-temperature calcination. Therefore, the thermodynamic reaction sequence determines the hierarchical distribution structure where the phosphate-based lithium-ion transport functional layer forms first, followed by the niobium-based fast-ion conductor layer. Segmented calcination facilitates the sequential formation of the phosphate-based lithium-ion transport functional layer and the niobium-based fast-ion conductor, further enhancing the modification effect.

[0037] In this invention, the heating rate of the calcination is preferably 1~10℃ / min, more preferably 2~5℃ / min; as one embodiment of this invention, the heating rate of the calcination can be 2.5℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, or 8℃ / min. A heating rate within the above range is beneficial to the reaction and further improves the cycle stability of the battery.

[0038] In one embodiment of the present invention, the cooling method after calcination can be furnace cooling.

[0039] The preparation method provided by this invention uses widely available raw materials, is low in cost, has a simple process, is easy to control, and is conducive to obtaining products with stable performance.

[0040] The present invention also provides a lithium-ion battery cathode, wherein the active material of the lithium-ion battery cathode is the modified nickel-manganese oxide cathode material with dual lithium-ion transport functional layers as described in the above technical solution.

[0041] The present invention does not impose any particular limitation on the preparation method of the lithium-ion battery cathode; conventional preparation processes in the art can be used.

[0042] In this invention, the structural schematic diagram of the modified nickel-manganese lithium cathode material with dual lithium-ion transport functional layers is shown below. Figure 1 As shown, it consists of a spinel-structured lithium nickel manganese oxide matrix and a phosphate-based lithium ion transport functional layer and a niobium-based fast ion conductor layer sequentially coated on it.

[0043] 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.

[0044] Example 1 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0045] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.3g Li3PO4, 0.3g (NH4)3[NbO(C2O4)3]·H2O were mixed and dried at 80℃ for 5h. Then, the temperature was increased to 500℃ at a heating rate of 2.5℃ / min and held for 5h. The temperature was increased to 600℃ at a heating rate of 5℃ / min and held for 3h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0046] Example 2 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0047] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.6g AlPO4, 0.3g Nb2O5, were mixed and dried at 80℃ for 5h. Then, the temperature was increased to 500℃ at a heating rate of 2.5℃ / min and held for 5h. The temperature was then increased to 650℃ at a heating rate of 5℃ / min and held for 3h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0048] Example 3 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0049] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.9g K3PO4, 0.3g Nb(NO3)5 were mixed and dried at 80℃ for 5h. Then, the temperature was increased to 500℃ at a heating rate of 2.5℃ / min and held for 5h. The temperature was increased to 700℃ at a heating rate of 5℃ / min and held for 3h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0050] Example 4 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0051] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 1.2g Li3PO4, 0.4g (NH4)3[NbO(C2O4)3]·H2O were mixed and dried at 80℃ for 5h. Then, the temperature was increased to 500℃ at a heating rate of 2.5℃ / min and held for 5h. The temperature was increased to 650℃ at a heating rate of 5℃ / min and held for 3h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0052] Example 5 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0053] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.5g Li3PO4, 0.25g Nb2O5, were mixed and dried at 80℃ for 5h. Then, the temperature was increased to 500℃ at a heating rate of 2.5℃ / min and held for 5h. The temperature was increased to 600℃ at a heating rate of 5℃ / min and held for 3h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0054] Example 6 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0055] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5O4 cathode material, 0.4g Li3PO4, 0.2g (NH4)3[NbO(C2O4)3]·H2O were mixed and dried at 80℃ for 5h. Then, the temperature was increased to 450℃ at a heating rate of 2.5℃ / min and held for 4h. The temperature was increased to 620℃ at a heating rate of 5℃ / min and held for 4h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0056] Example 7 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0057] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.7g Na3PO4, 0.3g Nb2O5, were mixed and dried at 80℃ for 5h. Then, the temperature was increased to 520℃ at a heating rate of 2.5℃ / min and held for 6h. The temperature was increased to 680℃ at a heating rate of 5℃ / min and held for 2h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0058] Example 8 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0059] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 1g K3PO4, 0.4g Nb(NO3)5, were mixed and dried at 80℃ for 5h. Then, the temperature was increased to 480℃ at a heating rate of 2.5℃ / min and held for 5h. The temperature was then increased to 700℃ at a heating rate of 5℃ / min and held for 3h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0060] Example 9 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0061] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.6g Li3PO4, 0.2g (NH4)3[NbO(C2O4)3]·H2O were mixed and dried at 80℃ for 5h. Then, the temperature was increased to 550℃ at a heating rate of 2.5℃ / min and held for 4h. The temperature was increased to 640℃ at a heating rate of 5℃ / min and held for 5h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0062] Example 10 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0063] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.8g Na3PO4, 0.3g Nb2O5, were mixed and dried at 80℃ for 5h. Then, the temperature was increased to 460℃ at a heating rate of 2.5℃ / min and held for 6h. The temperature was increased to 660℃ at a heating rate of 5℃ / min and held for 4h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0064] Example 11 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0065] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.3g Li3PO4, 0.3g (NH4)3[NbO(C2O4)3]·H2O were mixed and dried at 80℃ for 5h. The temperature was then increased to 550℃ at a rate of 5℃ / min and held for 6h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0066] Example 12 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0067] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.5g Li3PO4, 0.25g Nb2O5, were mixed and dried at 80℃ for 5h. The mixture was then heated to 600℃ at a heating rate of 3℃ / min and held for 5h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0068] Comparative Example 1 A phosphoric acid-based lithium-ion transport functional layer coated modified lithium nickel manganese oxide cathode material is composed of lithium nickel manganese oxide cathode material and a coating layer covering the outer surface of the lithium nickel manganese oxide cathode material. The coating layer is a phosphoric acid-based lithium-ion transport functional layer, and the material of the phosphoric acid-based lithium-ion transport functional layer is Li3PO4.

[0069] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.6g Li3PO4, were mixed and dried at 80℃ for 5h. Then, the temperature was increased to 500℃ at a heating rate of 2.5℃ / min and held for 5h. The temperature was then increased to 600℃ at a heating rate of 5℃ / min and held for 3h. After cooling to room temperature, fast ion conductor-coated modified lithium nickel manganese oxide cathode material was obtained.

[0070] Comparative Example 2 A fast ion conductor-coated modified lithium nickel manganese oxide cathode material is composed of a lithium nickel manganese oxide cathode material and a coating layer covering the outer surface of the lithium nickel manganese oxide cathode material. The coating layer is a niobium-based fast ion conductor layer, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0071] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.6 g (NH4)3[NbO(C2O4)3]·H2O, were mixed and dried at 80℃ for 5 h. Then, the temperature was increased to 500℃ at a heating rate of 2.5℃ / min and held for 5 h. The temperature was increased to 600℃ at a heating rate of 5℃ / min and held for 3 h. After cooling to room temperature, fast ion conductor-coated modified lithium nickel manganese oxide cathode material was obtained.

[0072] Comparative Example 3 A modified lithium nickel manganese oxide cathode material with a dual lithium-ion transport functional layer is disclosed, comprising a lithium nickel manganese oxide cathode material and a composite coating layer covering the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0073] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.3g Li3PO4, were mixed and dried at 80℃ for 5h, then heated to 600℃ at a heating rate of 2.5℃ / min and held for 3h, and cooled to room temperature to obtain a phosphate-coated intermediate product; 0.3g (NH4)3[NbO(C2O4)3]·H2O was added to the intermediate product, and the temperature was increased to 600℃ at a heating rate of 2.5℃ / min and held for 3h, and then cooled to room temperature to obtain a modified nickel manganese oxide cathode material with a double lithium-ion transport functional layer.

[0074] Comparative Example 4 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is composed of a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer is a phosphate-based lithium-ion transport functional layer and a niobium-based conductor layer. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4.

[0075] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5O4 cathode material, 0.3g Li3PO4, 0.3g (NH4)3[NbO(C2O4)3]·H2O were mixed and dried at 80℃ for 5h. The temperature was then increased to 350℃ at a rate of 2.5℃ / min and held for 8h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0076] Comparative Example 5 A modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers is disclosed, comprising a portion of lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material. The composite coating layer consists of a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer from the inside out. The material of the phosphate-based lithium-ion transport functional layer is Li3PO4, and the material of the niobium-based fast ion conductor layer is LiNbO3.

[0077] The preparation method is as follows: Take 100g of spinel-structured LiNi 0.5 Mn 1.5 O4 cathode material, 0.3g Li3PO4, 0.3g (NH4)3[NbO(C2O4)3]·H2O were mixed and dried at 80℃ for 5h. The temperature was then increased to 750℃ at a rate of 2.5℃ / min and held for 5h. After cooling to room temperature, a modified nickel manganese oxide cathode material with dual lithium-ion transport functional layers was obtained.

[0078] Test Example 1 The modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers in Example 1 was observed using a scanning electron microscope (SEM), and the SEM images were obtained as follows: Figure 2 As shown. From Figure 2 As can be seen, the particles maintain a complete spherical structure, and a continuous and dense composite coating layer is formed on the particle surface, with no obvious pores or shedding.

[0079] Test Example 2 Electrodes were prepared using unmodified lithium nickel manganese oxide cathode material and modified lithium nickel manganese oxide cathode materials provided in Examples 1-12 and Comparative Examples 1-5 as active materials, and assembled into half-cells to test their electrochemical performance: Using N-methylpyrrolidone as a solvent, the active material was ground and mixed with acetylene black and polyvinylidene fluoride at a ratio of 80:10:10 by weight of the feed materials. The slurry was then coated onto aluminum foil using a coating machine and dried in a vacuum oven at 80°C for 12 hours to form an electrode disc with a diameter of 10 mm. In an argon glove box (water content less than 0.1 ppm, oxygen content less than 0.1 ppm), the electrode disc was used as the working electrode, a lithium metal sheet as the counter electrode, and a polypropylene microporous membrane Celgard 2100 as the separator to assemble a CR2032 type button cell half-cell.

[0080] The assembled half-cells were charged and discharged using a Blue Electric Battery Tester. The voltage range was 3.5~4.9V, the initial current density was 10mA / g, and the current density was 20mA / g from the second cycle onwards, for a total of 40 cycles. The test results are recorded in Table 1. The initial charge and discharge curves of the battery assembled using Example 1 and unmodified lithium nickel manganese oxide cathode material are shown below. Figure 3 As shown in the figure, the cycle performance graph is as follows: Figure 4 As shown, Figure 3 , Figure 4 The “comparative example” in the text refers to unmodified lithium nickel manganese oxide cathode material.

[0081] Table 1 Electrochemical Test Records for Different Active Materials

[0082] From Table 1 and Figure 3 , Figure 4 It can be seen that the modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layer synergistic coating provided by the present invention is used as the active material to prepare the electrode and assemble the half cell. The cycle performance is better than that of the unmodified lithium nickel manganese oxide cathode material.

[0083] Comparing Example 1 and Comparative Examples 1-3, it can be seen that the lithium nickel manganese oxide cathode material modified by dual lithium-ion transport functional layer synergistic coating provided by the present invention has better cycle performance than the lithium nickel manganese oxide cathode material modified by single coating (Comparative Examples 1 and 2), and is also better than the modified material modified by sequentially coating with phosphate-based lithium-ion transport functional layer and niobium-based fast ion conductor (Comparative Example 3).

[0084] Comparing Example 1 and Example 11, it can be seen that step-by-step calcination can further improve the coating modification effect compared to single-stage calcination.

[0085] Comparing Example 1 with Comparative Examples 4 and 5, it can be seen that the calcination temperature is crucial to the coating modification effect. Under the same conditions, the modification effect will decrease when the calcination temperature is below 400℃ or above 700℃.

[0086] Test Example 3 X-ray diffraction (XRD) was used to observe the unmodified lithium nickel manganese oxide cathode material compared with the materials provided in Examples 1, 4, and 5, and the XRD patterns were obtained as follows: Figures 5-7 As shown. Figure 5 In the middle, the middle image is an enlarged view of the part marked by the dotted line in the left image, and the right image is an enlarged view of the two main peaks (311) and (400) in the left image; Figure 7 In the middle figure, the middle figure is an enlarged view of the part marked by the dotted line in the left figure, and the right figure is an enlarged view of the two main peaks (311) and (400) in the left figure.

[0087] from Figure 5It can be seen that the two main peaks (311) and (400) after coating are weaker than the main peaks of the comparative example, further indicating that the cation mixing of the coated material is suppressed. Figure 6 It can be seen that Comparative Example 4, calcined at only 350℃, showed no significant difference in new phase from Example 1 in XRD, but its electrochemical performance decreased significantly due to the lack of an effective coating layer (Table 1). Figure 7 It can be seen that the main peak of Comparative Example 5 is significantly higher than that of Example 1, indicating that the cation mixing is more severe and that the 750°C treatment will have an adverse effect on the performance.

[0088] Test Example 4 The material provided in Example 1 was observed using a high-magnification transmission electron microscope, and TEM images were obtained, as shown below. Figure 8 As shown. From Figure 8 As can be seen, a continuous coating layer has formed on the surface of the material (marked by the dashed line in the figure).

[0089] 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 modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers, comprising a lithium nickel manganese oxide cathode material and a composite coating layer in situ coated on the outer surface of the lithium nickel manganese oxide cathode material, wherein the composite coating layer comprises a phosphate-based lithium-ion transport functional layer and a niobium-based fast ion conductor layer arranged sequentially from the inside out; the material of the phosphate-based lithium-ion transport functional layer is Li3PO4; and the material of the niobium-based fast ion conductor layer is LiNbO3.

2. The preparation method of the modified lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layers as described in claim 1, comprising: Phosphate, niobium-containing compound and lithium nickel manganese oxide cathode material are mixed and then calcined in an inert atmosphere to obtain lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layer synergistic coating; The calcination temperature is 400~700℃, and the holding time is 2~12h.

3. The preparation method according to claim 2, characterized in that, The total mass ratio of the phosphate and niobium-containing compound to the lithium nickel manganese oxide cathode material is (0.2~3):

100.

4. The preparation method according to claim 2 or 3, characterized in that, The mass ratio of the phosphate to the niobium-containing compound is (1~3):

1.

5. The preparation method according to claim 2, characterized in that, The phosphate includes one or more of Li3PO4, Na3PO4, K3PO4 and AlPO4.

6. The preparation method according to claim 2, characterized in that, The niobium-containing compounds include one or more of Nb2O5, Nb2O3, NbCl5, Nb(NO3)5, (NH4)3[NbO(C2O4)3]·H2O, K3[NbO(C2O4)3]·H2O, and (NH4)2[NbO(NO3)5].

7. The preparation method according to claim 2, characterized in that, The calcination is either a single-stage calcination or a multi-stage calcination.

8. The preparation method according to claim 7, characterized in that, The segmented calcination process involves holding the temperature at 400-550℃ for 1-6 hours, then raising the temperature to 600-700℃ and holding it for another 1-6 hours.

9. The preparation method according to claim 2, 7 or 8, characterized in that, The heating rate of the calcination is 1~10℃ / min.

10. A lithium-ion battery positive electrode, characterized in that, The active material of the lithium-ion battery cathode is the lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layer synergistic coating as described in claim 1, or the lithium nickel manganese oxide cathode material with dual lithium-ion transport functional layer synergistic coating as described in any one of claims 2 to 9.

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