A lithium nickel manganese oxide material, its preparation method and application

Abstract

This invention provides a lithium nickel manganese oxide material, its preparation method, and its application. The lithium nickel manganese oxide material includes a core and a coating layer covering the surface of the core. The core includes a first lithium nickel manganese oxide material; the coating layer includes a first coating layer and a second coating layer; the first coating layer includes a second lithium nickel manganese oxide material; the second coating layer includes at least one of Al, Zr, Ti, Si, Li, P, and La; the lithium nickel manganese oxide material satisfies: 0.5 ≤ (a-1) × c × b ≤ 45; where a is the ratio of the Ni element content in the first lithium nickel manganese oxide material to the Ni element content in the second lithium nickel manganese oxide material; b is the thickness of the second coating layer, in μm; and c is the Dv50 of the lithium nickel manganese oxide material, in μm. The lithium nickel manganese oxide material provided by this invention can balance the energy density and cycle performance of batteries.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and particularly relates to a lithium nickel manganese oxide material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are widely used in applications with extremely high energy efficiency requirements, such as new energy vehicles, energy storage systems, consumer electronics (such as smartphones and laptops), and aerospace, due to their high energy density, long cycle life, and lightweight characteristics.

[0003] In the field of new energy vehicles, the performance of cathode materials directly determines the specific capacity, safety, and cost of batteries. Lithium nickel manganese oxide, due to its high nickel content (Ni...),... 3+ / Ni 4+ The high specific capacity (>180mAh / g) and low cobalt dependence of nickel-containing materials make them an important supplement and alternative to current high-nickel ternary materials (such as NCM811 and NCA). However, the highly active Ni on its surface... 3+ / Ni 4 + Lithium nickel manganese oxide (LiNO3) readily undergoes side reactions with the electrolyte, leading to capacity decay, which has become a key technical bottleneck restricting its large-scale application. Therefore, developing a lithium nickel manganese oxide material that can balance battery energy density and cycle performance has become an urgent technical problem to be solved at this stage. Summary of the Invention

[0004] The main objective of this invention is to provide a lithium nickel manganese oxide material, its preparation method, and its application, which can balance the energy density and cycle performance of batteries.

[0005] In a first aspect, the present invention provides a lithium nickel manganese oxide material, comprising a core and a coating layer covering the surface of the core, wherein the core comprises a first lithium nickel manganese oxide material; the coating layer comprises a first coating layer covering the surface of the core and a second coating layer covering the surface of the first coating layer; the first coating layer comprises a second lithium nickel manganese oxide material; the second coating layer comprises at least one of Al, Zr, Ti, Si, Li, P, and La;

[0006] The molar ratio of Ni to Mn in the first lithium nickel manganese oxide material is A > 25 / 75;

[0007] The molar ratio of Ni to Mn in the second lithium nickel manganese oxide material is B≤25 / 75;

[0008] The lithium nickel manganese oxide material satisfies the following:

[0009] 0.5 ≤ (a-1) × c × b ≤ 45;

[0010] Wherein, a is the ratio of the Ni content in the first lithium nickel manganese oxide material to the Ni content in the second lithium nickel manganese oxide material; b is the thickness of the second coating layer, in μm; and c is the Dv50 of the lithium nickel manganese oxide material, in μm.

[0011] Secondly, the present invention provides a method for preparing the lithium nickel manganese oxide material as described above, comprising the following steps:

[0012] 1) Form a first system by combining a first nickel source, a first manganese source, and a complexing agent, wherein the pH of the first system is 10-11, to obtain a nickel-manganese hydroxide matrix precursor;

[0013] 2) Using a second nickel source and a second manganese source, nickel-manganese hydroxide is deposited on the surface of the nickel-manganese hydroxide matrix precursor to obtain an intermediate;

[0014] 3) The second system, including the intermediate and the lithium source, is subjected to gradient annealing to obtain the lithium nickel manganese oxide material precursor;

[0015] 4) The third system, including the lithium nickel manganese oxide material precursor and the coating agent, is coated to obtain the lithium nickel manganese oxide material; the coating agent accounts for 0.1~1% of the mass percentage of the lithium nickel manganese oxide material precursor.

[0016] Thirdly, the present invention provides a positive electrode sheet comprising the lithium nickel manganese oxide material as described above or the lithium nickel manganese oxide material prepared by the preparation method described above.

[0017] Fourthly, the present invention provides a battery comprising the positive electrode sheet as described above.

[0018] Fifthly, the present invention provides an electrical device comprising the battery as described above.

[0019] The lithium nickel manganese oxide material provided by the present invention, by limiting the molar ratio of Ni and Mn elements in the first lithium nickel manganese oxide material and the second lithium nickel manganese oxide material, and by limiting the relationship between the ratio of Ni element content in the first lithium nickel manganese oxide material to the Ni element content in the second lithium nickel manganese oxide material, the thickness of the second coating layer, and the Dv50 of the lithium nickel manganese oxide material, enables the lithium nickel manganese oxide material to balance the energy density and cycle performance of the battery. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 XRD pattern of lithium nickel manganese oxide material in Example 1 provided by the present invention;

[0022] Figure 2 This is a schematic diagram of the structure of lithium nickel manganese oxide material. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] Modification schemes for lithium nickel manganese oxide materials mainly include the following two categories:

[0025] Composition gradient design: By adjusting the molar ratio of Ni and Mn elements in the lithium nickel manganese oxide matrix, Ni... 3+ / Ni 4 + The concentration gradually decreases from the center to the outer layer of the lithium nickel manganese oxide matrix to suppress surface side reactions. For example, some schemes employ a fully or partially gradient lithium nickel manganese oxide matrix, and the composition distribution is controlled by elemental doping (such as Al, Mg, Zr, etc.) or synthesis process. However, such schemes usually rely on complex synthesis processes (such as co-precipitation combined with multi-step calcination), and the uniformity of the gradient distribution is difficult to control precisely, resulting in limited overall material capacity and limited improvement in surface stability.

[0026] Surface coating technology: A layer of low-activity elements (such as Al2O3, MgO, Li2ZrO3, etc.) is coated onto the surface of lithium nickel manganese oxide materials to prevent contact between the electrolyte and the lithium nickel manganese oxide material. Existing coating schemes mostly employ a single-layer coating structure, and the composition of the coating material differs significantly from the lithium nickel manganese oxide matrix. This easily leads to stress concentration or lattice mismatch at the interface, causing the coating layer to crack or detach, thus failing to achieve long-term stable interface protection. Furthermore, the thickness control precision of existing coating layers is insufficient; excessively thick coating layers can hinder lithium-ion transport and reduce the specific capacity of the material.

[0027] In summary, while existing technologies can improve the surface stability of lithium nickel manganese oxide materials, they cannot simultaneously guarantee their high capacity characteristics. Furthermore, they still have significant shortcomings in terms of coating layer structure design, composition gradient control, and compatibility of preparation processes.

[0028] The inventors of this application have discovered through research that the molar ratio of Ni to Mn in the first lithium nickel manganese oxide material, the molar ratio of Ni to Mn in the second lithium nickel manganese oxide material, the ratio of Ni content in the first lithium nickel manganese oxide material to Ni content in the second lithium nickel manganese oxide material, the thickness of the second coating layer, and the Dv50 of the lithium nickel manganese oxide material have a significant impact on the energy density and cycle performance of the battery.

[0029] Based on this, in a first aspect, the present invention provides a lithium nickel manganese oxide material, comprising a core and a coating layer covering the surface of the core, wherein the core comprises a first lithium nickel manganese oxide material; the coating layer comprises a first coating layer covering the surface of the core and a second coating layer covering the surface of the first coating layer; the first coating layer comprises a second lithium nickel manganese oxide material; the second coating layer comprises at least one of Al, Zr, Ti, Si, Li, P, and La; the molar ratio A of Ni to Mn in the first lithium nickel manganese oxide material is greater than 25 / 75; the molar ratio B of Ni to Mn in the second lithium nickel manganese oxide material is less than 25 / 75; the lithium nickel manganese oxide material satisfies:

[0030] 0.5 ≤ (a-1) × c × b ≤ 45;

[0031] Where a is the ratio of Ni content in the first lithium nickel manganese oxide material to Ni content in the second lithium nickel manganese oxide material; b is the thickness of the second coating layer, μm; and c is the Dv50 of the lithium nickel manganese oxide material, μm.

[0032] For example, A can be a range consisting of 26 / 74, 27 / 73, 28 / 72, 29 / 71, 30 / 70, 35 / 65, 40 / 60, 50 / 50 or any two of them; B can be a range consisting of 10 / 90, 15 / 85, 20 / 80, 21 / 79, 22 / 78, 23 / 77, 24 / 76, 25 / 75 or any two of them; (a-1)×c×b can be a range consisting of 0.5, 1, 2, 4, 8, 12, 20, 30, 40, 45 or any two of them.

[0033] The lithium nickel manganese oxide material provided by this invention achieves a balance between battery energy density and cycle performance by limiting the molar ratio of Ni and Mn elements in the first and second lithium nickel manganese oxide materials, as well as limiting the relationship between the ratio of Ni content in the first and second lithium nickel manganese oxide materials, the thickness of the second coating layer, and the Dv50 of the lithium nickel manganese oxide material. This is because the molar ratio of Ni to Mn elements A in the first lithium nickel manganese oxide material is greater than 25 / 75, which is a high-nickel core design, and its Ni content is significantly higher than that of traditional low-nickel lithium nickel manganese oxide. In lithium nickel manganese oxide, the capacity is mainly determined by Ni. 2+ / Ni 4+ The redox pair provides Mn, which has a stable +4 valence state, acting as a "structural pillar" to stabilize the spinel framework. Therefore, increasing the Ni content can improve the specific capacity and thus the energy density of the battery. Furthermore, the first coating layer and the core are made of the same lithium nickel manganese oxide material, differing only in the molar ratio of Ni and Mn. Their crystal structures and lattice parameters are similar, avoiding the high interfacial impedance problem introduced by heterogeneous coating layers. This ensures rapid insertion and extraction of lithium ions at the core-first coating layer interface, without sacrificing energy density efficiency due to the coating structure.

[0034] Furthermore, in the second lithium nickel manganese oxide material, the molar ratio of Ni to Mn is B≤25 / 75, resulting in a low-nickel, high-manganese coating layer. Mn in the lithium nickel manganese oxide material primarily exists as stable Mn. 4+ It exists but hardly participates in redox reactions, and can act as a "structural pillar" to suppress lattice expansion or contraction during charging and discharging, reducing the risk of particle cracking and improving cycle stability. Furthermore, the low-nickel design significantly reduces the Ni content on the surface of the first coating layer. 3+ / Ni 4+ The presence of active sites reduces the probability of side reactions with the electrolyte, thereby improving battery cycle performance. Simultaneously, the low-nickel, high-manganese layer exhibits higher chemical stability than the high-nickel core, delaying the dissolution of active metal ions and improving high-temperature cycle performance. Furthermore, the compositional gradient design within the same system (high-nickel core → low-nickel first coating layer) creates a gradual change in lattice parameters at the interface, avoiding interface defects and increased impedance caused by lattice mismatch, thus ensuring efficient lithium-ion transport.

[0035] The second coating layer can block the contact between the electrolyte and the first coating layer and the core, further reducing irreversible reactions such as electrolyte decomposition and metal ion dissolution, significantly reducing the capacity decay rate during cycling, and improving the capacity retention rate after high-temperature storage. Furthermore, under abuse conditions such as overcharging and short circuits, the second coating layer can delay the violent exothermic reaction between the electrolyte and the high-nickel core; simultaneously, its physical barrier function can prevent the rapid diffusion of gases and heat generated by the reaction, increasing the thermal decomposition temperature of the material and reducing the probability of thermal runaway.

[0036] If (a-1) is large, the Ni content in the first coating layer is low, which is not conducive to improving the overall capacity of the lithium nickel manganese oxide material. By reducing the Dv50 of the lithium nickel manganese oxide material, the diffusion path of lithium ions from the electrolyte to the core is shortened. Even if the lithium ion insertion / extraction rate of the low-nickel first coating layer is slightly lower, the overall lithium ion migration efficiency can be improved through the "short path effect," avoiding the actual discharge capacity decay caused by the capacity limitation of the first coating layer. However, if Dv50 is too small, it will increase the specific surface area of ​​the lithium nickel manganese oxide material, resulting in an increased contact area with the electrolyte and an increase in side reactions. This further controls the thickness of the second coating layer, reduces the side reactions between the electrolyte and the core, and the elements in the second coating layer can reduce the lithium ion transport resistance, avoiding further capacity sacrifice due to an excessively thick second coating layer. This application balances the energy density and cycle performance of the battery by comprehensively controlling the molar ratio of Ni and Mn elements in the core and the first coating layer, the ratio of Ni content in the first lithium nickel manganese oxide material to Ni content in the second lithium nickel manganese oxide material, the thickness of the second coating layer, and the Dv50 of the lithium nickel manganese oxide material.

[0037] Therefore, the lithium nickel manganese oxide material provided by the present invention limits the molar ratio of Ni and Mn elements in the first lithium nickel manganese oxide material and the second lithium nickel manganese oxide material, and limits the relationship between the ratio of Ni element content in the first lithium nickel manganese oxide material to the Ni element content in the second lithium nickel manganese oxide material, the thickness of the second coating layer, and the Dv50 of the lithium nickel manganese oxide material, so that the lithium nickel manganese oxide material can take into account both the energy density and cycle performance of the battery.

[0038] In some embodiments of the present invention, 2≤(a-1)×c×b≤11, for example, it can be a range consisting of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or any two of them.

[0039] As a preferred option, the energy density and cycle performance of the battery can be further improved.

[0040] In some embodiments of the present invention, 16≤a≤50, for example, a can be a range of 16, 20, 30, 40, 45, 50 or any two of them.

[0041] In some embodiments, 0.01μm≤b≤0.1μm, for example, b can be a range of 0.01μm, 0.03μm, 0.05μm, 0.07μm, 0.09μm, 0.1μm or any two of these.

[0042] In some embodiments, 3μm≤c≤10μm, for example, c can be a range of 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or any two of these.

[0043] The ranges of a, b, and c mentioned above can achieve (a-1)×c×b within the range of 0.5 to 45, thus enabling the battery to balance energy density and cycle performance.

[0044] The present invention does not limit the adjustment of 'a', but can specifically adjust it through the content of Ni and Mn elements in the core and the first coating layer, the mass ratio of the core and the first coating layer, etc.

[0045] The present invention does not limit the adjustment of b, but can specifically adjust it through annealing temperature, annealing time, etc.

[0046] The present invention does not limit the adjustment of c, but can specifically adjust it by the content of the coating agent, the number of deposited layers, etc.

[0047] In some embodiments of the present invention, 18≤a≤33, for example, a can be a range consisting of 18, 20, 22, 25, 27, 30, 33 or any two of them.

[0048] In some embodiments, 0.02μm≤b≤0.05μm, for example, b can be a range of 0.02μm, 0.03μm, 0.04μm, 0.05μm or any two of them.

[0049] In some embodiments, 5μm≤c≤8μm, for example, c can be a range of 5μm, 6μm, 7μm, 8μm or any two of them.

[0050] As a preferred option, the energy density and cycle performance of the battery can be further improved.

[0051] In some embodiments, 25 / 75 < A ≤ 30 / 70, for example, it can be a range consisting of 26 / 74, 27 / 73, 28 / 72, 29 / 71, 30 / 70 or any two of them.

[0052] It is understandable that Ni is the main source of capacity. The increased Ni content in the first nickel manganese oxide material leads to more active sites, more reversible electron transfer, greater lithium ion insertion / extraction, higher voltage platform, and higher specific capacity, thereby further improving the battery's energy density and cycle performance.

[0053] In some embodiments, 20 / 80 < B ≤ 25 / 75, for example, it can be a range consisting of 21 / 79, 22 / 78, 23 / 77, 24 / 76, 25 / 75 or any two of them.

[0054] As a preferred option, the energy density and cycle performance of the battery can be further improved.

[0055] In some embodiments of the present invention, the molar ratio of Ni and Mn elements in the first coating layer decreases gradually along the direction from the core to the second coating layer; the value of the gradient change of the molar ratio of Ni and Mn elements in the first coating layer is 0.01 to 0.08, for example, it can be a range of 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08 or any combination thereof.

[0056] The first cladding layer, located near the core, has a relatively high Ni content, a high degree of lattice parameter matching with the core, low lattice mismatch stress, and fewer interface defects. This region, with its high Ni content, retains certain lithium-ion insertion / extraction active sites, serving as a "conduction bridge" for the high capacity of the core. This prevents the low-nickel cladding layer from completely blocking the core's capacity, ensuring that the high-nickel core's capacity can be fully released.

[0057] In the first cladding layer, furthest from the core and closer to the second cladding layer, the Ni content gradually decreases while the Mn content gradually increases, resulting in a smooth decrease in lattice parameters. Finally, at the surface of the first cladding layer, the molar ratio of Ni and Mn is low, achieving a smooth transition with the second cladding layer. In this region, the Ni content gradient decreases to a low-nickel level, and the Mn content... 4+ The "structural pillar" role is dominant, and the highly active Ni on the surface 3+ / Ni 4+ The site density decreased significantly, suppressing side reactions with the electrolyte (electrolyte decomposition, metal ion dissolution). Simultaneously, Mn... 4+ The increasing content gradient can gradually enhance the structural rigidity of the first coating layer, resist lattice expansion or contraction during charging and discharging, reduce the risk of particle cracking, and improve cycle stability.

[0058] In some embodiments of the present invention, the thickness of the first coating layer is 50-100 nm, for example, it can be a range of 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or any two of them.

[0059] The thickness of the first coating layer is within the aforementioned range, providing sufficient thickness to achieve a smooth transition from high nickel in the core to low nickel in the first coating layer, thereby improving the energy density and cycle performance of the battery.

[0060] In some embodiments, the lithium nickel manganese oxide material has a spinel structure.

[0061] It is understandable that the space group of the spinel structure is Fd-3m. This is a highly symmetrical, open three-dimensional framework structure that provides an ideal channel for the rapid migration of lithium ions.

[0062] from Figure 2The structural diagram of lithium nickel manganese oxide shows that its space group is Fd-3m.

[0063] Spinel-structured lithium nickel manganese oxide materials exhibit high structural stability, reducing the risk of phase transitions and material collapse, thereby improving battery cycle performance. Furthermore, the first coating layer is a homogeneous spinel structure (different only in the molar ratio of nickel and manganese), with a lattice parameter difference of less than 0.3% from the core. This avoids introducing lattice mismatch stress into the heterogeneous coating layer, enabling rapid lithium-ion transport at the core-first coating layer interface and preventing capacity loss.

[0064] In some embodiments of the present invention, the core further includes a dopant element. The dopant element includes at least one selected from Al, Mg, Zr, Ti, Cr, Fe, Cu, and Co.

[0065] Doping elements in the core can enhance lattice rigidity, suppress volume expansion, reduce internal stress of particles, and prevent particle cracking and coating peeling during cycling, thereby improving the cycle performance of the battery.

[0066] In some embodiments, the dopant element accounts for 0.05 to 0.5% of the mass percentage of the lithium nickel manganese oxide material, for example, it can be a range of 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any two of these.

[0067] The content of the aforementioned doping elements can further stabilize the lattice parameters of the core, reduce the lattice difference between the core and the first coating layer, reduce the interface impedance, and ensure the rapid transport of lithium ions at the core-first coating layer interface.

[0068] Lithium nickel manganese oxide (LNMO) is a positive electrode active material with a spinel structure and high voltage characteristics. Its chemical composition is Li. 1+x Ni y M z Mn 2-y-z O 4-k , where 0≤x≤0.1, 0.4≤y≤0.6, 0≤z≤0.1, 0≤k≤0.1, and M is a dopant element.

[0069] In some embodiments of the present invention, the second coating layer includes Al2O3, ZrO2, TiO2, SiO2, Li3PO4, and Li4Ti5O. 12 At least one of LiAlO2, Li2ZrO3, LLZO, and LATP.

[0070] The inorganic oxides in the second coating layer, such as Al₂O₃, ZrO₂, TiO₂, and SiO₂, are highly chemically inert and can isolate the substrate from the electrolyte, reducing the occurrence of side reactions. Lithium-based compounds, such as Li₃PO₄, and fast ion conductors, such as Li₄Ti₅O₂, are also used. 12 LLZO and LATP can improve lithium-ion conductivity, thereby improving the rate performance of the battery.

[0071] Secondly, the present invention provides a method for preparing the lithium nickel manganese oxide material as described above, comprising the following steps:

[0072] 1) Form a first system by combining a first nickel source, a first manganese source, and a complexing agent. The pH of the first system is 10-11, and a nickel-manganese hydroxide matrix precursor is obtained.

[0073] 2) Using a second nickel source and a second manganese source, nickel-manganese hydroxide is deposited on the surface of the nickel-manganese hydroxide matrix precursor to obtain an intermediate;

[0074] 3) The second system, including the intermediate and the lithium source, is subjected to gradient annealing to obtain the lithium nickel manganese oxide material precursor;

[0075] 4) The third system, including lithium nickel manganese oxide material precursor and coating agent, is coated to obtain lithium nickel manganese oxide material; the coating agent accounts for 0.1%~1% of the mass percentage of lithium nickel manganese oxide material precursor.

[0076] For example, the pH of the first system can be a range of 10, 10.1, 10.3, 10.5, 10.7, 10.9, 11 or any two of these; the mass percentage of the coating agent in the lithium nickel manganese oxide precursor can be a range of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or any two of these.

[0077] Specifically, in step 1), the first nickel source can be at least one of nickel sulfate, nickel acetate, and nickel nitrate; the first manganese source can be at least one of manganese sulfate, manganese acetate, and manganese nitrate. The nickel salt solution, manganese salt solution, and complexing agent are mixed to form a first system. By adjusting the amount of complexing agent added, the pH of the first system is adjusted to 10-11, and a nickel-manganese hydroxide matrix precursor is obtained through co-precipitation. During the co-precipitation process, precipitating agents NaOH and / or KOH can be added to the first system.

[0078] In step 2), the second nickel source can be at least one of nickel sulfate, nickel acetate, and nickel nitrate; the second manganese source can be at least one of manganese sulfate, manganese acetate, and manganese nitrate; nickel-manganese hydroxide is deposited on the surface of the nickel-manganese hydroxide matrix precursor to form the precursor of the first coating layer. Specifically, the second nickel source, the second manganese source, the complexing agent, and the nickel-manganese hydroxide matrix precursor can be mixed, and the pH of the system can be controlled to be 10-11, so that the second nickel source and the second manganese source are deposited on the surface of the nickel-manganese hydroxide matrix precursor in the form of nickel-manganese hydroxide to obtain an intermediate.

[0079] In step 3), the lithium source can be at least one of lithium carbonate, lithium hydroxide, lithium oxalate, and lithium oxide. The intermediate is mixed with the lithium source to obtain a second system. The second system is subjected to gradient annealing treatment, which causes the nickel-manganese hydroxide matrix precursor to form a core and the precursor of the first coating layer to form a first coating layer. That is, the nickel-manganese hydroxide forms lithium nickel manganese oxide, thus obtaining the lithium nickel manganese oxide material precursor.

[0080] In step 4), the lithium nickel manganese oxide precursor is mixed with a coating agent to obtain a third system. This third system is then coated to form a second coating layer on the surface of the lithium nickel manganese oxide precursor, resulting in lithium nickel manganese oxide material. The thickness of the second coating layer is controlled by adjusting the mass percentage of the coating agent in the intermediate.

[0081] The method for preparing lithium nickel manganese oxide provided by the present invention can prepare the above-mentioned lithium nickel manganese oxide material, and the lithium nickel manganese oxide material can take into account both the energy density and cycle performance of the battery.

[0082] In some embodiments of the present invention, the complexing agent includes at least one of ammonia, citric acid, oxalic acid, urea, polyvinylpyrrolidone, ammonium carbonate, and ammonium bicarbonate.

[0083] The aforementioned complexing agents can form stable complexes with nickel and manganese ions, and by adjusting the pH of the system, Ni can be slowly released. 2+ Mn 2+ The ions precipitate to form nickel-manganese hydroxide.

[0084] In some embodiments, the total mass of the second nickel source and the second manganese source accounts for 2 to 10% of the mass percentage of the nickel-manganese hydroxide matrix precursor, for example, it can be a range of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any two of these.

[0085] When the total mass percentage of the second nickel source and the second manganese source relative to the mass of the nickel-manganese hydroxide matrix precursor is within the aforementioned range, the thickness of the first coating layer can be adjusted to a suitable range, enabling the first coating layer to provide sufficient thickness to achieve a smooth transition from high nickel in the core to low nickel in the first coating layer, thereby improving the energy density and cycle performance of the battery.

[0086] In some embodiments, the number of nickel-manganese hydroxide deposition layers is n layers, where 1 ≤ n ≤ 6, for example, it can be a range of 1, 2, 3, 4, 5, 6 or any two of them.

[0087] In this invention, the number of nickel-manganese hydroxide deposition layers allows the molar ratio of Ni and Mn elements in the first coating layer to decrease gradually along the direction from the core to the second coating layer, thereby improving the energy density and cycle stability of the battery.

[0088] In some embodiments of the present invention, the gradient annealing process includes: heating at 5~10℃ / min (e.g., a range of 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 10℃ / min or any two thereof) to 850~1000℃ (e.g., a range of 850℃, 870℃, 900℃, 950℃, 970℃, 1000℃ or any two thereof), holding at that temperature for 6~12h (e.g., a range of 6h, 7h, 8h, 9h, 10h, 11h, 12h or any two thereof), and then heating at 3~5℃ / min (e.g., a range of 3℃, 3.5℃, 4℃, 4.5℃, 5℃ or any two thereof). The temperature is lowered to 700-800℃ (e.g., a range of 700℃, 720℃, 740℃, 760℃, 780℃, 800℃ or any two thereof), held for 3-6 hours (e.g., a range of 3 hours, 4 hours, 5 hours, 6 hours or any two thereof), and then lowered to 500-600℃ at a rate of 3-5℃ / min (e.g., a range of 3℃, 3.5℃, 4℃, 4.5℃, 5℃ or any two thereof), held for 3-6 hours (e.g., a range of 3 hours, 4 hours, 5 hours, 6 hours or any two thereof).

[0089] The first stage of the gradient annealing process, namely the high-temperature stage of 850~1000℃, promotes the formation of the spinel phase, namely the formation of lithium nickel manganese oxide crystals in the core and the first coating layer. Furthermore, the first coating layer forms a chemical bond with the core surface through atomic diffusion, achieving a firm anchoring between the first coating layer and the core, preventing the first coating layer from peeling off during subsequent cycles.

[0090] The second stage, cooling to 700-800℃, guides Ni atoms within the first coating layer to diffuse towards the core, and Mn atoms to diffuse towards the surface of the first coating layer, ultimately forming a stable structure with a decreasing Ni / Mn molar ratio gradient along the direction from the core to the second coating layer. This avoids lattice quenching distortion caused by rapid cooling.

[0091] The third stage, which involves cooling to 500-600℃, allows the spinel lattice to relax slowly during the shrinkage process: the lattice formed at high temperatures is in a "stretched state" due to thermal expansion, and slow cooling allows the lattice to shrink gradually, avoiding intragranular stress and grain boundary cracks caused by rapid shrinkage.

[0092] In some embodiments of the present invention, the first system includes a dopant, which includes at least one selected from Al2(SO4)3, MgSO4, Zr(SO4)2, Ti(SO4)2, Cr2(SO4)3, FeSO4, CuSO4, and CoSO4.

[0093] The addition of dopants in the first system allows the core to contain doped elements, which can enhance the lattice rigidity of the core, suppress volume expansion, reduce internal stress of the particles, prevent particle cracking and coating layer detachment during cycling, and improve the cycle performance of the battery.

[0094] In some embodiments, the dopant accounts for 0.05% to 0.5% of the mass percentage of the first system, for example, it can be a range of 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any two of these.

[0095] The mass percentage of the dopant in the first system is within the above range, which can control the mass percentage of the doping element in the lithium nickel manganese oxide material. This can further stabilize the lattice parameters of the core, reduce the lattice difference between the core and the first coating layer, reduce the interface impedance, and ensure the rapid transport of lithium ions at the core-first coating layer interface.

[0096] In some embodiments, the coating treatment temperature is 600~800°C, for example, it can be a range of 600°C, 650°C, 700°C, 750°C, 800°C or any two of them; the time is 6~12h, for example, it can be a range of 6h, 7h, 8h, 9h, 10h, 11h, 12h or any two of them.

[0097] The temperature of the above coating process can effectively form a second coating layer, making the second coating layer more firmly attached, preventing it from falling off, and improving the cycle performance of the battery.

[0098] In some embodiments, the coating agent includes Al2O3, ZrO2, TiO2, SiO2, Li3PO4, and Li4Ti5O.12 At least one of LiAlO2, Li2ZrO3, LLZO, and LATP.

[0099] The aforementioned coating agents can effectively form a second coating layer on the surface of the first coating layer, isolating the core from the electrolyte and reducing the occurrence of side reactions; or they can improve lithium-ion conductivity, thereby improving the rate performance of the battery.

[0100] Thirdly, the present invention provides a positive electrode sheet comprising the lithium nickel manganese oxide material as described above or the lithium nickel manganese oxide material prepared by the preparation method described above.

[0101] The positive electrode sheet of the present invention can be prepared using conventional techniques in the art. Specifically, the above-mentioned lithium nickel manganese oxide material, conductive agent, and binder can be uniformly dispersed in a solvent to obtain a positive electrode slurry. The positive electrode slurry is then coated onto at least one functional surface of the positive electrode current collector, followed by rolling and cutting to obtain the positive electrode sheet of the present invention. The areal density of the positive electrode sheet can be 300~400 g / m³. 2 The compaction density can be 2.8~3.2 g / cm³. 3 .

[0102] This invention does not specifically limit the categories of conductive agents and adhesives. The conductive agents, adhesives and other components can all be conventional substances in the art. For example, the conductive agent may include one or more of conductive carbon black, carbon nanotubes, conductive graphite and graphene, and the adhesive may include one or more of polyvinylidene fluoride (PVDF), acrylic modified PVDF, polyacrylate polymers, polyimide, styrene-butadiene rubber and styrene-acrylic rubber.

[0103] The present invention does not specifically limit the coating method, and any coating method such as gravure coating, extrusion coating, spraying, screen printing, etc. can be used to achieve the coating of the positive electrode active layer slurry.

[0104] The positive electrode provided by the present invention includes the above-mentioned lithium nickel manganese oxide material. Therefore, when the positive electrode is applied to a battery, the battery can take into account energy density, cycle performance, storage performance and safety performance.

[0105] Fourthly, the present invention provides a battery comprising the positive electrode sheet as described above, which has advantages corresponding to the positive electrode sheet described above, and will not be elaborated further.

[0106] In addition to the positive electrode, the battery of the present invention also includes a separator, a negative electrode, and an electrolyte. The separator can be a conventionally used separator in the art, such as a PP film or a PE film.

[0107] The electrolyte can be any electrolyte conventionally used in the art, and may include solvents, additives, and lithium salts. Solvents may include at least one of ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), propylene carbonate (PC), methyl formate (MF), and methyl acetate (MA). Additives may include at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene ethylene carbonate (VEC), trimethyl phosphate (TMP), triethyl phosphate (TEP), propylene sulfonate lactone (PS), and vinyl sulfate (DTD). Lithium salts may include at least one of LiPF6, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate borate) (LiBOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium difluorophosphate (LiPO2F2).

[0108] The negative electrode sheet of the present invention can be prepared using conventional techniques in the art. Specifically, the negative electrode active material, conductive agent, and binder are uniformly dispersed in a solvent to obtain a negative electrode slurry. The negative electrode slurry is then coated onto at least one functional surface of the negative electrode current collector, followed by rolling and cutting to obtain the negative electrode sheet of the present invention. The areal density of the negative electrode sheet can be 58~78 g / m³. 2 The compaction density can be 1.4~1.6 g / cm³. 3 The negative electrode active material may include at least one of the following: artificial graphite, natural graphite, hard carbon, soft carbon, silicon-based negative electrode, and graphite-based composite material.

[0109] The battery of the present invention can be prepared using conventional methods in the art. Specifically, the positive electrode, separator and negative electrode can be stacked in sequence, and the cell can be obtained by stacking or winding. Then, the battery can be obtained by baking, liquid injection, formation and packaging.

[0110] The battery of the present invention can be a single cell, a battery pack, a battery stack, or a cylindrical cell formed by connecting single cells. These cells can be electrically connected by conventional methods in the art, such as series connection, parallel connection, or a hybrid connection including these connection methods, etc., without particular limitation.

[0111] Fifthly, the present invention provides an electrical device including the battery as described above, which has advantages corresponding to the positive electrode plate described above, and will not be elaborated further.

[0112] The electrical device of the present invention can be a conventional electrical device in the art, such as a power device (e.g., an electric vehicle), an electronic device (e.g., a computer, mobile phone, digital camera, printer, fax machine, etc.), a wearable device (e.g., a watch, bracelet, VR glasses, etc.), a home appliance (e.g., an air conditioner, refrigerator, washing machine, microwave oven, etc.), etc., and there is no particular limitation thereto.

[0113] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0114] Example 1

[0115] The preparation method of lithium nickel manganese oxide material in this embodiment includes the following steps:

[0116] 1) Nickel sulfate (first nickel source), manganese sulfate (first manganese source, molar ratio of Ni to Mn 3:7), dopant Al2(SO4)3, MgSO4, and ammonia water are complexed to form a first system. The pH of the first system is adjusted to 10.5, and the lithium nickel manganese oxide matrix precursor Ni is co-precipitated. 0.3 Mn 0.7 (OH)₂. The dopant accounts for 0.1% of the mass percentage of the first system.

[0117] 2) Using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 25:75), complex with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.25 Mn 0.75 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.9% of the total mass of the first nickel source and the first manganese source;

[0118] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 24:76) to adjust the pH of the system to 10.5. 0.25 Mn 0.75 Ni deposition on (OH)2 surface 0.24 Mn 0.76 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.9% of the total mass of the first nickel source and the first manganese source;

[0119] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 23:77) to adjust the pH of the system to 10.5. 0.24 Mn 0.76 Ni deposition on (OH)2 surface 0.23 Mn 0.77 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.9% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0120] 3) After mixing the intermediate with lithium carbonate, a second system is obtained. The second system is heated to 1000℃ at 10℃ / min in an oxygen atmosphere and held for 12h. Then it is cooled to 750℃ at 5℃ / min and held for 6h. Then it is cooled to 600℃ at 5℃ / min and held for 3h, which is a gradient annealing treatment to obtain the lithium nickel manganese oxide material precursor.

[0121] 4) The lithium nickel manganese oxide material precursor is mixed with coating agents Al2O3 and LATP to obtain a third system. The third system is coated at 800℃ for 6 hours to obtain the final lithium nickel manganese oxide material. The coating agent accounts for 1% of the mass of the lithium nickel manganese oxide material precursor.

[0122] The lithium nickel manganese oxide material comprises a core and a coating layer covering the surface of the core. The core includes a first lithium nickel manganese oxide material; the coating layer includes a first coating layer covering the surface of the core and a second coating layer covering the surface of the first coating layer; the first coating layer includes the second lithium nickel manganese oxide material; the molar ratio gradient of Ni and Mn elements in the first coating layer is 0.01. The core also includes doping elements, including Al and Mg. The second coating layer includes Al₂O₃ and LATP, i.e., the second coating layer includes Al, Ti, Li, and P. The lithium nickel manganese oxide material has a spinel structure.

[0123] Example 2

[0124] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 25:75) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.25 Mn 0.75 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 2.36% of the total mass of the first nickel source and the first manganese source;

[0125] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 24:76) to adjust the pH of the system to 10.5. 0.25 Mn 0.75 Ni deposition on (OH)2 surface 0.24 Mn 0.76 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 2.36% of the total mass of the first nickel source and the first manganese source;

[0126] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 23:77) to adjust the pH of the system to 10.5. 0.24 Mn 0.76 Ni deposition on (OH)2 surface 0.23 Mn 0.77 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 2.36% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0127] In step 3), the second system is heated to 850°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 6 hours.

[0128] In step 4), the coating agent accounts for 0.1% of the mass percentage of the lithium nickel manganese oxide precursor.

[0129] Example 3

[0130] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 25:75) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.25 Mn 0.75 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.9% of the total mass of the first nickel source and the first manganese source;

[0131] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 24:76) to adjust the pH of the system to 10.5. 0.25 Mn 0.75 Ni deposition on (OH)2 surface 0.24 Mn 0.76 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.9% of the total mass of the first nickel source and the first manganese source;

[0132] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 23:77) to adjust the pH of the system to 10.5. 0.24 Mn 0.76 Ni deposition on (OH)2 surface 0.23 Mn 0.77 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.9% of the total mass of the first nickel source and the first manganese source;

[0133] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 22:78) to adjust the pH of the system to 10.5. 0.23 Mn 0.77 Ni deposition on (OH)2 surface 0.22 Mn 0.78 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.9% of the total mass of the first nickel source and the first manganese source;

[0134] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 21:79) to adjust the pH of the system to 10.5. 0.22 Mn 0.78 Ni deposition on (OH)2 surface 0.21 Mn 0.79 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.9% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0135] In step 3), the second system is heated to 950°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 10 hours.

[0136] In step 4), the coating agent accounts for 0.5% of the mass percentage of the lithium nickel manganese oxide precursor.

[0137] Example 4

[0138] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 25:75) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.25 Mn 0.75 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.25% of the total mass of the first nickel source and the first manganese source;

[0139] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 24:76) to adjust the pH of the system to 10.5. 0.25 Mn 0.75 Ni deposition on (OH)2 surface 0.24 Mn 0.76 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.25% of the total mass of the first nickel source and the first manganese source;

[0140] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 23:77) to adjust the pH of the system to 10.5. 0.24 Mn 0.76 Ni deposition on (OH)2 surface 0.23 Mn 0.77 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.25% of the total mass of the first nickel source and the first manganese source;

[0141] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 22:78) to adjust the pH of the system to 10.5. 0.23 Mn 0.77 Ni deposition on (OH)2 surface 0.22 Mn 0.78 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.25% of the total mass of the first nickel source and the first manganese source;

[0142] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 21:79) to adjust the pH of the system to 10.5. 0.22 Mn 0.78 Ni deposition on (OH)2 surface 0.21 Mn 0.79 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.25% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0143] In step 3), the second system is heated to 950°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 6 hours.

[0144] In step 4), the coating agent accounts for 0.2% of the mass percentage of the lithium nickel manganese oxide precursor.

[0145] Example 5

[0146] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 25:75) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.25 Mn 0.75 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 7.41% of the total mass of the first nickel source and the first manganese source, and an intermediate is obtained.

[0147] In step 3), the second system is heated to 1000℃ in an oxygen atmosphere at a rate of 10℃ / min and held at that temperature for 10h.

[0148] In step 4), the coating agent accounts for 0.8% of the mass percentage of the lithium nickel manganese oxide precursor.

[0149] Example 6

[0150] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 25:75) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.25 Mn 0.75 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 2.4% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0151] In step 3), the second system is heated to 850°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 7 hours.

[0152] In step 4), the coating agent accounts for 0.15% of the mass percentage of the lithium nickel manganese oxide precursor.

[0153] Example 7

[0154] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 24:76) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.24 Mn 0.76 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.5% of the total mass of the first nickel source and the first manganese source;

[0155] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 23:77) to adjust the pH of the system to 10.5. 0.24 Mn 0.76 Ni deposition on (OH)2 surface 0.23 Mn 0.77 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.5% of the total mass of the first nickel source and the first manganese source;

[0156] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 22:78) to adjust the pH of the system to 10.5. 0.23 Mn 0.77 Ni deposition on (OH)2 surface 0.22 Mn 0.78 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.5% of the total mass of the first nickel source and the first manganese source;

[0157] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 21:79) to adjust the pH of the system to 10.5. 0.22 Mn 0.78 Ni deposition on (OH)2 surface 0.21 Mn 0.79 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.5% of the total mass of the first nickel source and the first manganese source;

[0158] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 20:80) to adjust the pH of the system to 10.5. 0.21 Mn 0.79 Ni deposition on (OH)2 surface 0.2 Mn 0.8 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.5% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0159] In step 3), the second system is heated to 950°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 10 hours.

[0160] In step 4), the coating agent accounts for 0.43% of the mass percentage of the lithium nickel manganese oxide precursor.

[0161] Example 8

[0162] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 24:76) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.24 Mn 0.76 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.828% of the total mass of the first nickel source and the first manganese source;

[0163] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 23:77) to adjust the pH of the system to 10.5. 0.24 Mn 0.76 Ni deposition on (OH)2 surface 0.23 Mn 0.77 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.828% of the total mass of the first nickel source and the first manganese source;

[0164] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 22:78) to adjust the pH of the system to 10.5. 0.23 Mn 0.77 Ni deposition on (OH)2 surface 0.22 Mn 0.78 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.828% of the total mass of the first nickel source and the first manganese source;

[0165] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 21:79) to adjust the pH of the system to 10.5. 0.22 Mn 0.78 Ni deposition on (OH)2 surface 0.21 Mn 0.79 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.828% of the total mass of the first nickel source and the first manganese source;

[0166] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 20:80) to adjust the pH of the system to 10.5. 0.21 Mn 0.79 Ni deposition on (OH)2 surface 0.2 Mn 0.8 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.828% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0167] In step 3), the second system is heated to 950°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 8 hours.

[0168] In step 4), the coating agent accounts for 0.25% of the mass percentage of the lithium nickel manganese oxide precursor.

[0169] Example 9

[0170] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 22:78) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.22 Mn 0.78 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.18% of the total mass of the first nickel source and the first manganese source;

[0171] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 21:79) to adjust the pH of the system to 10.5. 0.22 Mn 0.78 Ni deposition on (OH)2 surface 0.21 Mn 0.79 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.18% of the total mass of the first nickel source and the first manganese source;

[0172] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 20:80) to adjust the pH of the system to 10.5. 0.21 Mn 0.79 Ni deposition on (OH)2 surface 0.2 Mn 0.8 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.18% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0173] In step 3), the second system is heated to 950°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 9 hours.

[0174] In step 4), the coating agent accounts for 0.76% of the mass percentage of the lithium nickel manganese oxide precursor.

[0175] Example 10

[0176] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 20:80) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.2 Mn 0.8(OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 2.49% of the total mass of the first nickel source and the first manganese source, and an intermediate is obtained.

[0177] In step 3), the second system is heated to 800°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 6 hours.

[0178] In step 4), the coating agent accounts for 1.05% of the mass percentage of the lithium nickel manganese oxide precursor.

[0179] Example 11

[0180] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 20:80) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.2 Mn 0.8 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 14.28% of the total mass of the first nickel source and the first manganese source, and an intermediate is obtained.

[0181] In step 3), the second system is heated to 1000℃ in an oxygen atmosphere at a rate of 10℃ / min and held at that temperature for 14 hours.

[0182] In step 4), the coating agent accounts for 0.095% of the mass percentage of the lithium nickel manganese oxide precursor.

[0183] Example 12

[0184] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 25:75) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.25 Mn 0.75 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.468% of the total mass of the first nickel source and the first manganese source;

[0185] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 24:76) to adjust the pH of the system to 10.5. 0.25 Mn 0.75 Ni deposition on (OH)2 surface 0.24 Mn 0.76(OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.468% of the total mass of the first nickel source and the first manganese source;

[0186] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 23:77) to adjust the pH of the system to 10.5. 0.24 Mn 0.76 Ni deposition on (OH)2 surface 0.23 Mn 0.77 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.468% of the total mass of the first nickel source and the first manganese source;

[0187] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 22:78) to adjust the pH of the system to 10.5. 0.23 Mn 0.77 Ni deposition on (OH)2 surface 0.22 Mn 0.78 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.468% of the total mass of the first nickel source and the first manganese source;

[0188] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 21:79) to adjust the pH of the system to 10.5. 0.22 Mn 0.78 Ni deposition on (OH)2 surface 0.21 Mn 0.79 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.468% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0189] In step 3), the second system is heated to 1000℃ in an oxygen atmosphere at a rate of 10℃ / min and held at that temperature for 12 hours.

[0190] In step 4), the coating agent accounts for 1% of the mass percentage of the lithium nickel manganese oxide precursor.

[0191] Example 13

[0192] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 25:75) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.25 Mn 0.75(OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.47% of the total mass of the first nickel source and the first manganese source;

[0193] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 24:76) to adjust the pH of the system to 10.5. 0.25 Mn 0.75 Ni deposition on (OH)2 surface 0.24 Mn 0.76 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.47% of the total mass of the first nickel source and the first manganese source;

[0194] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 23:77) to adjust the pH of the system to 10.5. 0.24 Mn 0.76 Ni deposition on (OH)2 surface 0.23 Mn 0.77 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.47% of the total mass of the first nickel source and the first manganese source;

[0195] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 22:78) to adjust the pH of the system to 10.5. 0.23 Mn 0.77 Ni deposition on (OH)2 surface 0.22 Mn 0.78 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.47% of the total mass of the first nickel source and the first manganese source;

[0196] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 21:79) to adjust the pH of the system to 10.5. 0.22 Mn 0.78 Ni deposition on (OH)2 surface 0.21 Mn 0.79 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.47% of the total mass of the first nickel source and the first manganese source, and an intermediate is obtained.

[0197] In step 3), the second system is heated to 850°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 6 hours.

[0198] In step 4), the coating agent accounts for 0.1% of the mass percentage of the lithium nickel manganese oxide precursor.

[0199] Example 14

[0200] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 25:75) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.25 Mn 0.75 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.712% of the total mass of the first nickel source and the first manganese source;

[0201] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 24:76) to adjust the pH of the system to 10.5. 0.25 Mn 0.75 Ni deposition on (OH)2 surface 0.24 Mn 0.76 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.712% of the total mass of the first nickel source and the first manganese source;

[0202] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 23:77) to adjust the pH of the system to 10.5. 0.24 Mn 0.76 Ni deposition on (OH)2 surface 0.23 Mn 0.77 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.712% of the total mass of the first nickel source and the first manganese source;

[0203] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 22:78) to adjust the pH of the system to 10.5. 0.23 Mn 0.77 Ni deposition on (OH)2 surface 0.22 Mn 0.78 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.712% of the total mass of the first nickel source and the first manganese source;

[0204] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 21:79) to adjust the pH of the system to 10.5. 0.22 Mn 0.78 Ni deposition on (OH)2 surface 0.21 Mn 0.79(OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.712% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0205] In step 3), the second system is heated to 950°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 10 hours.

[0206] In step 4), the coating agent accounts for 0.5% of the mass percentage of the lithium nickel manganese oxide precursor.

[0207] Example 15

[0208] The preparation method of lithium nickel manganese oxide material in this embodiment is basically the same as that in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate) (molar ratio of Ni to Mn 25:75) are complexed with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.25 Mn 0.75 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.468% of the total mass of the first nickel source and the first manganese source;

[0209] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 24:76) to adjust the pH of the system to 10.5. 0.25 Mn 0.75 Ni deposition on (OH)2 surface 0.24 Mn 0.76 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.468% of the total mass of the first nickel source and the first manganese source;

[0210] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 23:77) to adjust the pH of the system to 10.5. 0.24 Mn 0.76 Ni deposition on (OH)2 surface 0.23 Mn 0.77 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.468% of the total mass of the first nickel source and the first manganese source;

[0211] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 22:78) to adjust the pH of the system to 10.5. 0.23 Mn 0.77 Ni deposition on (OH)2 surface 0.22 Mn 0.78(OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.468% of the total mass of the first nickel source and the first manganese source;

[0212] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 21:79) to adjust the pH of the system to 10.5. 0.22 Mn 0.78 Ni deposition on (OH)2 surface 0.21 Mn 0.79 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.468% of the total mass of the first nickel source and the first manganese source, and an intermediate is obtained.

[0213] In step 3), the second system is heated to 950°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 6 hours.

[0214] In step 4), the coating agent accounts for 0.2% of the mass percentage of the lithium nickel manganese oxide precursor.

[0215] Comparative Example 1

[0216] The preparation method of this comparative example is basically the same as that of the lithium nickel manganese oxide material in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 16:84) are used to complex with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.16 Mn 0.84 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 5.14% of the total mass of the first nickel source and the first manganese source;

[0217] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 15:85) to adjust the pH of the system to 10.5. 0.16 Mn 0.84 Ni deposition on (OH)2 surface 0.15 Mn 0.85 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 5.14% of the total mass of the first nickel source and the first manganese source;

[0218] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 14:86) to adjust the pH of the system to 10.5. 0.15 Mn 0.85 Ni deposition on (OH)2 surface 0.14 Mn 0.86(OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 5.14% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0219] In step 3), the second system is heated to 800°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 6 hours.

[0220] In step 4), the coating agent accounts for 0.09% of the mass percentage of the lithium nickel manganese oxide precursor.

[0221] Comparative Example 2

[0222] The preparation method of this comparative example is basically the same as that of the lithium nickel manganese oxide material in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 16:84) are used to complex with ammonia water to adjust the pH of the system to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.16 Mn 0.84 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.54% of the total mass of the first nickel source and the first manganese source;

[0223] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 15:85) to adjust the pH of the system to 10.5. 0.16 Mn 0.84 Ni deposition on (OH)2 surface 0.15 Mn 0.85 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.54% of the total mass of the first nickel source and the first manganese source;

[0224] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 14:86) to adjust the pH of the system to 10.5. 0.15 Mn 0.85 Ni deposition on (OH)2 surface 0.14 Mn 0.86 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 1.54% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0225] In step 3), the second system is heated to 1000℃ in an oxygen atmosphere at a rate of 10℃ / min and held at that temperature for 14 hours.

[0226] In step 4), the coating agent accounts for 1.02% of the mass percentage of the lithium nickel manganese oxide precursor.

[0227] Comparative Example 3

[0228] The preparation method of this comparative example is basically the same as that of the lithium nickel manganese oxide material in Example 1, except that in step 2), a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 29:71) are used to complex with ammonia water, and the pH of the system is adjusted to 10.5. 0.3 Mn 0.7 Ni deposition on (OH)2 surface 0.29 Mn 0.71 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.714% of the total mass of the first nickel source and the first manganese source;

[0229] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 28:72) to adjust the pH to 10.5. In the Ni... 0.29 Mn 0.71 Ni deposition on (OH)2 surface 0.28 Mn 0.72 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.714% of the total mass of the first nickel source and the first manganese source;

[0230] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 27:73) to adjust the pH of the system to 10.5. 0.28 Mn 0.72 Ni deposition on (OH)2 surface 0.27 Mn 0.73 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.714% of the total mass of the first nickel source and the first manganese source;

[0231] The system was complexed with ammonia using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 26:74) to adjust the pH of the system to 10.5. 0.27 Mn 0.73 Ni deposition on (OH)2 surface 0.26 Mn 0.74 (OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.714% of the total mass of the first nickel source and the first manganese source;

[0232] The system was complexed with ammonia water using a second nickel source (nickel sulfate) and a second manganese source (manganese sulfate, with a molar ratio of Ni to Mn of 25:75) to adjust the pH of the system to 10.5. 0.26 Mn 0.74 Ni deposition on (OH)2 surface 0.25 Mn 0.75(OH)2, in this step, the total mass of the second nickel source and the second manganese source accounts for 0.714% of the total mass of the first nickel source and the first manganese source, to obtain an intermediate.

[0233] In step 3), the second system is heated to 950°C at a rate of 10°C / min in an oxygen atmosphere and held at that temperature for 6 hours.

[0234] In step 4), the coating agent accounts for 0.2% of the mass percentage of the lithium nickel manganese oxide precursor.

[0235] Experimental example:

[0236] Preparation of the positive electrode sheet: The prepared lithium nickel manganese oxide material, the binder polyvinylidene fluoride (PVDF), the conductive agent carbon black, and carbon nanotubes were dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 95:2.5:1.5:1 to obtain a positive electrode slurry; the positive electrode slurry was coated on the upper and lower surfaces of an aluminum foil; then rolled and cut to obtain the positive electrode sheet; the areal density of the positive electrode sheet was 350 g / m³. 2 The compacted density is 3.0 g / cm³. 3 .

[0237] Preparation of the negative electrode sheet: Artificial graphite, conductive agent carbon black (SP), thickener carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) were mixed and uniformly dispersed in deionized water at a mass ratio of 96:1:0.6:2.4 to obtain a negative electrode slurry. This negative electrode slurry was coated onto both the upper and lower surfaces of a copper foil. After rolling and cutting, the negative electrode sheet was obtained. The areal density of the negative electrode sheet was 68 g / m³. 2 The compacted density is 1.5 g / cm³. 3 .

[0238] Preparation of electrolyte: Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0239] Preparation of the diaphragm: PP and PE were selected as the diaphragm.

[0240] Assembly and Formation: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for isolation. They are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a lithium-ion battery is obtained. Formation Steps: Charge at 0.02C for 5 hours, then at 0.05C for 4 hours.

[0241] 1. Test methods for Ni and Mn element content:

[0242] Pretreatment: Discharge the battery at 0.33C to the lower limit voltage of 3.5V, disassemble the empty battery to obtain the positive electrode sheet, soak the positive electrode sheet in dimethyl carbonate (DMC) solution at room temperature for 60 minutes, take it out and air dry at room temperature with humidity ≤15%.

[0243] Sample preparation: The positive electrode is precisely cut into an ideal observation cross section using an ion beam, and the positive electrode is fixed on the sample stage with the cross section facing upward.

[0244] Ten points from the core to the coating layer on the cross-section of the particle were sampled for EDS energy dispersive spectroscopy. The morphology and size of the material were observed under a scanning electron microscope (SEM) at 15k magnification. The elemental types and contents (normalized atomic percentages) of particles of different shapes and sizes in the field of view were measured by sampling points on the cross-section of the particle using EDS point-scan signal acquisition. Three similar particles were selected for testing, and the average value was taken to obtain accurate parallel sample test results. The material type was identified based on this data, and the average molar ratio of each transition metal element to the total transition metal elements was obtained.

[0245] 2. Dv50:

[0246] The particle size of lithium nickel manganese oxide material can be measured using a laser particle size distribution measuring instrument (Mastersizer 3000). The particle size distribution is determined by laser diffraction of particle size distribution (specific steps refer to GB / T19077-2016). The particle size corresponding to the cumulative particle size distribution percentage reaching 50% is Dv50.

[0247] 3. Types and amounts of doping elements:

[0248] The lithium nickel manganese oxide powder sample was dispersed in 20 mL of water, and then 10 mL of nitric acid (HNO3 mass percentage 66%) was added. The mixture was then heated until the lithium nickel manganese oxide powder was completely dissolved. The solution was then diluted to 100 mL with water to obtain the test solution. ICP testing was performed on the test solution to confirm the type and content of the doping element. The ICP instrument operating conditions were designed as follows: gas flow rate 0.5 L / min, power 1150 W.

[0249] 4. Thickness of the first and second coating layers, and type of the second coating layer:

[0250] Pretreatment: Discharge the battery at 0.33C to the lower limit voltage of 3.5V, disassemble the empty battery to obtain the positive electrode sheet, soak the positive electrode sheet in dimethyl carbonate (DMC) solution at room temperature for 60 minutes, take it out and air dry at room temperature with humidity ≤15%.

[0251] Sample preparation: The positive electrode is precisely cut into an ideal observation cross section using an ion beam, and the positive electrode is fixed on the sample stage with the cross section facing upward.

[0252] The thickness of the first and second coating layers was measured at three different locations using a transmission electron microscope (TEM), and the average value was taken to obtain the thickness of the first and second coating layers, respectively.

[0253] The elements of the second coating layer were tested using EDS to determine the types of substances in the second coating layer.

[0254] 5. XRD test:

[0255] The lithium nickel manganese oxide powder sample is loaded into the sample well and the surface is flattened with a glass slide to ensure that the sample surface is flat and smooth.

[0256] Place the prepared sample into the XRD sample stage, start the instrument to scan, the scanning range is 10~80°, the scanning speed is 2° / min, and the step size is 0.02°; the instrument automatically records the diffraction intensity at different diffraction angles (2θ) and generates X-ray diffraction patterns.

[0257] Phase identification: The measured diffraction pattern is compared with a standard PDF card (such as the ICDD database) to determine the crystal structure type of lithium nickel manganese oxide material (such as layered structure, spinel structure, olivine structure, etc.).

[0258] Lattice parameter calculation: The lattice constants a, b, and c are calculated by the diffraction peak positions to assess the degree of lattice distortion.

[0259] Figure 1 The image shows the XRD pattern of the lithium nickel manganese oxide material from Example 1.

[0260] from Figure 1 It can be seen that the lithium nickel manganese oxide material in Example 1 has a spinel structure.

[0261] 7. Cycling Performance: Under 25℃ conditions, the battery is discharged at 0.33C to the lower limit voltage of 3.5V, charged at 0.33C constant current and constant voltage to 4.8V, and then discharged at 0.33C to 3.5V, cycled twice to obtain the constant capacity C1; then charged at 1C1 constant current and constant voltage to 4.8V, and discharged at 1C1 to 3.5V, repeating this cycle 1000 times. The discharge capacity Q1 at the first cycle and the discharge capacity Q at the 1000th cycle are measured. 1000 The capacity retention rate Q after 1000 cycles is Q = Q 1000 / Q1×100%.

[0262] 8. Energy Density: The battery was charged at 25℃ with a constant current rate of 0.1C until the voltage reached 4.8V, then charged at 4.8V with a constant voltage until the current equals 0.05C. After resting for 5 minutes, it was discharged at a constant current rate of 0.1C until the voltage reached 3.5V. The initial discharge capacity Q of the battery was recorded. 放and the first discharge energy E 放 Weigh the battery and record the mass as W. Calculate the mass energy density ED = E. 放 / W.

[0263] Table 1

[0264]

[0265] As shown in Table 1, compared with the comparative example, the lithium nickel manganese oxide material provided by the present invention, by limiting the molar ratio of Ni and Mn elements in the first lithium nickel manganese oxide material and the second lithium nickel manganese oxide material, and by limiting the relationship between the ratio of Ni element content in the first lithium nickel manganese oxide material to the Ni element content in the second lithium nickel manganese oxide material, the thickness of the second coating layer, and the Dv50 of the lithium nickel manganese oxide material, enables the lithium nickel manganese oxide material to balance the energy density and cycle performance of the battery.

[0266] As can be seen from Examples 1-15 and Comparative Examples 1-3, when the range of (a-1)×c×b is 0.5~45, the energy density and cycle performance of the battery are better. Specifically, the energy density of the battery is greater than or equal to 164Wh / kg, and the cycle capacity retention rate is above 76%. Further controlling the range of (a-1)×c×b to 2~11 can further improve the energy density and cycle performance of the battery.

[0267] As can be seen from Examples 1-15 and Comparative Examples 1-3, when a ranges from 16 to 50, b ranges from 0.01 to 0.1 μm, and c ranges from 3 to 10 μm, the energy density and cycle performance of the battery are superior. Further controlling a range to 18 to 33, b ranges from 0.02 to 0.05 μm, and c ranges from 5 to 8 μm can further improve the energy density and cycle performance of the battery.

[0268] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A lithium nickel manganese oxide material, characterized in that, The system includes a core and a coating layer covering the surface of the core. The core includes a first lithium nickel manganese oxide material. The coating layer includes a first coating layer covering the surface of the core and a second coating layer covering the surface of the first coating layer. The first coating layer includes a second lithium nickel manganese oxide material. The second coating layer includes at least one of Al, Zr, Ti, Si, Li, P, and La. The molar ratio of Ni to Mn in the first lithium nickel manganese oxide material is A > 25 / 75; The molar ratio of Ni to Mn in the second lithium nickel manganese oxide material is B≤25 / 75; The lithium nickel manganese oxide material satisfies the following: 0.5 ≤ (a-1) × c × b ≤ 45; Wherein, a is the ratio of the Ni content in the first lithium nickel manganese oxide material to the Ni content in the second lithium nickel manganese oxide material; b is the thickness of the second coating layer, in μm; and c is the Dv50 of the lithium nickel manganese oxide material, in μm.

2. The lithium nickel manganese oxide material according to claim 1, characterized in that, 2≤(a-1)×c×b≤11.

3. The lithium nickel manganese oxide material according to claim 1, characterized in that, 16≤a≤50； And / or, 0.01μm≤b≤0.1μm; And / or, 3μm≤c≤10μm.

4. The lithium nickel manganese oxide material according to claim 3, characterized in that, 18≤a≤33； And / or, 0.02μm≤b≤0.05μm; And / or, 5μm≤c≤8μm.

5. The lithium nickel manganese oxide material according to claim 1, characterized in that, 25 / 75＜A≤30 / 70； And / or, 20 / 80≤B≤25 / 75.

6. The lithium nickel manganese oxide material according to claim 1, characterized in that, The molar ratio of Ni to Mn in the first coating layer decreases gradually along the direction from the core to the second coating layer. The molar ratio gradient of Ni and Mn elements in the first coating layer varies from 0.01 to 0.

08.

7. The lithium nickel manganese oxide material according to claim 1, characterized in that, The thickness of the first coating layer is 50~100nm.

8. The lithium nickel manganese oxide material according to claim 1, characterized in that, The lithium nickel manganese oxide material has a spinel structure.

9. The lithium nickel manganese oxide material according to claim 1, characterized in that, The core also includes doping elements; The doping element includes at least one of Al, Mg, Zr, Ti, Cr, Fe, Cu, and Co; And / or, the doping element accounts for 0.05~0.5% of the mass percentage of the lithium nickel manganese oxide material.

10. The lithium nickel manganese oxide material according to any one of claims 1-9, characterized in that, The second coating layer includes Al2O3, ZrO2, TiO2, SiO2, Li3PO4, and Li4Ti5O. 12 At least one of LiAlO2, Li2ZrO3, LLZO, and LATP.

11. A method for preparing lithium nickel manganese oxide material as described in any one of claims 1-10, characterized in that, Includes the following steps: 1) Form a first system by combining a first nickel source, a first manganese source, and a complexing agent, wherein the pH of the first system is 10-11, to obtain a nickel-manganese hydroxide matrix precursor; 2) Using a second nickel source and a second manganese source, nickel-manganese hydroxide is deposited on the surface of the nickel-manganese hydroxide matrix precursor to obtain an intermediate; 3) The second system, including the intermediate and the lithium source, is subjected to gradient annealing to obtain the lithium nickel manganese oxide material precursor; 4) The third system, including the lithium nickel manganese oxide material precursor and the coating agent, is coated to obtain the lithium nickel manganese oxide material; the coating agent accounts for 0.1~1% of the mass percentage of the lithium nickel manganese oxide material precursor.

12. The preparation method according to claim 11, characterized in that, The complexing agent includes at least one of ammonia, citric acid, oxalic acid, urea, polyvinylpyrrolidone, ammonium carbonate, and ammonium bicarbonate. And / or, the total mass of the second nickel source and the second manganese source accounts for 2-10% of the mass of the nickel-manganese hydroxide matrix precursor; And / or, the number of nickel-manganese hydroxide deposition layers is n layers, where 1≤n≤6.

13. The preparation method according to claim 11, characterized in that, The gradient annealing process includes: heating to 850-1000℃ at 5-10℃ / min, holding at that temperature for 6-12 hours, then cooling to 700-800℃ at 3-5℃ / min, holding at that temperature for 3-6 hours, and then cooling to 500-600℃ at 3-5℃ / min, holding at that temperature for 3-6 hours.

14. The preparation method according to claim 11, characterized in that, The first system further includes a dopant, which includes at least one of Al2(SO4)3, MgSO4, Zr(SO4)2, Ti(SO4)2, Cr2(SO4)3, FeSO4, CuSO4, and CoSO4.

15. The preparation method according to claim 14, characterized in that, The dopant accounts for 0.05% to 0.5% of the mass of the first system; And / or, the coating treatment is performed at a temperature of 600~800℃ for a time of 6~12h; And / or, the coating agent includes Al2O3, ZrO2, TiO2, SiO2, Li3PO4, Li4Ti5O 12 At least one of LiAlO2, Li2ZrO3, LLZO, and LATP.

16. A positive electrode plate, characterized in that, This includes lithium nickel manganese oxide materials according to any one of claims 1-10 or lithium nickel manganese oxide materials prepared by the preparation method according to any one of claims 11-15.

17. A battery, characterized in that, Includes the positive electrode sheet as described in claim 16.

18. An electrical appliance, characterized in that, Includes the battery as described in claim 17.

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