Single-crystal lithium nickel manganese oxide material, preparation method thereof and lithium ion battery
Single-crystal lithium nickel manganese oxide material was prepared by a two-stage sintering and doping method with high-valence metal elements, which solved the problem of insufficient cycle performance and overall performance of lithium nickel manganese oxide material in lithium-ion batteries and achieved a high-efficiency improvement in battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGZHOU TINCI MATERIALS TECH
- Filing Date
- 2024-11-29
- Publication Date
- 2026-05-29
AI Technical Summary
Existing lithium nickel manganese oxide materials have shortcomings in cycle performance, energy density, thermal stability and durability in lithium-ion batteries, and high-temperature sintering or the use of large amounts of molten salt will increase costs.
Single-crystal lithium nickel manganese oxide material was prepared by using a two-stage sintering process and doping with high-valence metal elements. By controlling the impurity phase content, large particle size and surface coating were formed. Combined with a low-temperature lithium replenishment process, a material with high solid density and low specific surface area was formed.
It improves the battery's cycle stability, energy density, thermal stability, and mechanical properties, reduces the risk of electrolyte decomposition, enhances the battery's overall performance, and lowers production costs.
Smart Images
Figure CN122117825A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery materials technology, specifically relating to single-crystal lithium nickel manganese oxide materials and their preparation. Background Technology
[0002] In lithium-ion batteries, the cathode material accounts for approximately 40% of the battery cost. Lithium nickel manganese oxide (LNMO), also known as spinel-type lithium nickel manganese oxide, is a high-performance cathode material widely used in lithium-ion batteries. It is renowned for its high voltage platform (approximately 4.7V), high energy density, long cycle life, and excellent safety performance, making it an ideal choice for next-generation battery materials. However, LNMO materials still face challenges in improving cycle performance, and improvements in the battery's overall performance, including energy density, thermal stability, mechanical properties, and durability, also need to be considered. Summary of the Invention
[0003] To address the problems existing in the prior art, the first objective of this invention is to provide a single-crystal lithium nickel manganese oxide material and its preparation method; the second objective of this invention is to provide a battery.
[0004] To achieve the above objectives, the present invention provides the following specific technical solutions.
[0005] First, this invention provides a single-crystal lithium nickel manganese oxide material, wherein Li in the single-crystal lithium nickel manganese oxide material x Ni 2-x The percentage content of O2 is C≤1.6%, C=(I LixNi2-xO2 / (I LixNi2-xO2 +I LiNi0.5Mn1.5O4 ))×100%, I LixNi2-xO2 For Li in the XRD refinement results x Ni 2-x The diffraction peak intensity corresponding to O2, I LixNi2-xO2 +I LiNi0.5Mn1.5O4 LiNi was superimposed in the XRD refinement results 0.5 Mn 1.5 O4 and Li x Ni 2-x The diffraction peak intensities of the O2 two-phase model, where 0 ≤ x ≤ 0.6 and the grain size is 5~11 μm.
[0006] In a further preferred embodiment, the single-crystal lithium nickel manganese oxide material has at least one of the following characteristics (1) to (3): (1) Octahedral morphology; (2) The compacted density is 3.1~3.4 g / cm³. 3 ; (3) Specific surface area is 0.2~0.4 m² 2 / g.
[0007] In a further preferred embodiment, the single-crystal lithium nickel manganese oxide material contains a dopant element, wherein the dopant element is at least one selected from Nb, Zr, Mo, Sb, Ta, and W. More preferably, the molar ratio of the dopant element to Ni is 0.001~0.005:0.5.
[0008] In a further preferred embodiment, the single-crystal lithium nickel manganese oxide material contains a coating layer, wherein the coating layer contains at least one element selected from P, F, and Al.
[0009] Secondly, this invention provides a method for preparing single-crystal lithium nickel manganese oxide material, comprising: Step S1: After the precursor and lithium salt are mixed evenly, they are sintered in an oxygen atmosphere to obtain lithium-deficient lithium nickel manganese oxide material. The precursor is Ni 0.5 Mn 1.5 (OH)4 or a mixture of Mn2O3 and MnNiO3; The ratio of the total molar amount of transition metals Ni and Mn in the precursor to the molar amount of Li in the lithium salt is 1:0.15~0.45; The sintering is a two-stage sintering process, firstly at 1000~1200℃, and then at 650~750℃. Step S2: After the lithium-deficient lithium nickel manganese oxide material and lithium salt are mixed evenly, they are sintered in an oxygen atmosphere to obtain single-crystal lithium nickel manganese oxide material. The ratio of the total molar amount of transition metals Ni and Mn to the molar amount of Li in the lithium salt in the lithium-deficient nickel manganese oxide material is 1:0.05~0.35; The sintering process is a two-stage sintering: first, a first-stage sintering is carried out at 900~1000℃, and then a second-stage sintering is carried out at 650~750℃.
[0010] In a further preferred embodiment, the lithium salt is at least one selected from Li₂CO₃, LiOH, LiCl, and Li₂SO₄.
[0011] In a further preferred embodiment, in step S1, the sintering time for the first stage is 5-20 hours; and the sintering time for the second stage is 3-10 hours.
[0012] In a further preferred embodiment, in step S1, a flux is added and mixed with the precursor and lithium salt; the flux is at least one of oxides or salts of Nb, Zr, Mo, Sb, Ta, and W.
[0013] In a further preferred embodiment, the amount of flux added is determined based on the ratio of the total molar amount of Nb, Zr, Mo, Sb, Ta, and W to the molar amount of Ni being 0.001 to 0.005:0.5.
[0014] In a further preferred embodiment, in step S2, the sintering time for the first stage is 10-20 hours; and the sintering time for the second stage is 5-10 hours.
[0015] In a further preferred embodiment, in step S2, a coating material is added and mixed with lithium-deficient nickel manganese oxide material and lithium salt; more preferably, the coating material is at least one of NH4H2PO4, Al2O3, and NH4F.
[0016] In a further preferred embodiment, the oxygen volume content in the sintering atmosphere is 50-100%.
[0017] Based on the same inventive concept, the present invention also provides a lithium-ion battery, comprising the aforementioned single-crystal lithium nickel manganese oxide material or the single-crystal lithium nickel manganese oxide material obtained by the aforementioned preparation method.
[0018] Compared with the prior art, one or more technical solutions of the present invention can achieve at least one of the following beneficial effects: This invention provides Li x Ni 2-x Single-crystal lithium nickel manganese oxide materials with low O2 content avoid the generation of HF and Li₂ through electrolyte decomposition under high voltage. x Ni 2-x O2 reaction can effectively improve the cycle stability of the battery.
[0019] The single-crystal lithium nickel manganese oxide material provided by this invention has a grain size of 5~11μm. The large particle size and relatively small specific surface area can reduce contact with the electrolyte, reduce electrolyte decomposition, and effectively improve the cycle performance of the battery.
[0020] The high-density single-crystal lithium nickel manganese oxide material provided by this invention can effectively improve the energy density, thermal stability, mechanical properties and durability of batteries.
[0021] This invention further involves doping single-crystal lithium nickel manganese oxide materials with high-valence metals such as Nb, Zr, Mo, Sb, Ta, and W to suppress Ni. 3+ The reduction of Ni 2+ The content of Ni is reduced, thereby reducing the Ni content. 2+ The migration of these elements further improves the uniformity of nickel and manganese, resulting in low-impurity lithium nickel manganese oxide. Furthermore, high-valence metals such as Nb, Zr, Mo, Sb, Ta, and W form a lithium composite transition metal oxide layer on the surface of the final single-crystal lithium nickel manganese oxide material. This lithium composite metal oxide effectively isolates the electrolyte from the cathode material, increasing the battery's cycle stability.
[0022] The present invention further forms a coating layer of phosphate, fluoride, alumina, etc. on the surface of the single crystal lithium nickel manganese oxide material to inhibit or reduce the contact between the electrolyte and the positive electrode material, and effectively inhibit the decomposition of the electrolyte.
[0023] The method for preparing single-crystal lithium nickel manganese oxide materials according to the present invention is relatively simple, reliable, effective, and can utilize existing production lines. Attached Figure Description
[0024] Figure 1 The lithium-deficient lithium nickel manganese oxide cathode material (Li) prepared in step S1 of Example 1 0.35 Ni 0.5 Mn 1.5 SEM image of O4).
[0025] Figure 2 LiNi prepared in step S2 of Example 1 0.5 Mn 1.5 SEM of O4.
[0026] Figure 3 The image shows the SEM image of the lithium nickel manganese oxide cathode material obtained in Comparative Example 1.
[0027] Figure 4 The image shows the SEM image of the lithium nickel manganese oxide cathode material obtained in Comparative Example 2.
[0028] Figure 5 The image shows the SEM image of the lithium nickel manganese oxide cathode material obtained in Comparative Example 3.
[0029] Figure 6 The image shows the SEM image of the lithium-deficient nickel-manganese oxide cathode material obtained in step S1 of Example 2.
[0030] Figure 7 The image shows the SEM image of the lithium nickel manganese oxide cathode material obtained in step S2 of Example 2.
[0031] Figure 8 This is a SEM image of the lithium nickel manganese oxide cathode material obtained in Example 3.
[0032] Figure 9 shows the refined XRD patterns of lithium nickel manganese oxide cathode materials obtained in Examples 1 to 3 and Comparative Example 1. Figure 9(a) is the refined pattern of Example 1, Figure 9(b) is the refined pattern of Example 2, Figure 9(c) is the refined pattern of Example 3, and Figure 9(d) is the refined pattern of Comparative Example 1.
[0033] Figure 10 This is an enlarged view of the 37.4°~37.8° and 43.9°~44.1° areas in Figure 9.
[0034] Figure 11 shows the electrochemical performance of the lithium nickel manganese oxide cathode material obtained in Example 1. Detailed Implementation
[0035] To prepare large-size single-crystal lithium nickel manganese oxide materials, current technologies either increase the sintering temperature or use large amounts of molten salt. The higher the temperature, the more Ni... 2+ Than Ni 3+ More stable and migrating faster, it easily aggregates to form impurity phases. Impurity phases (Li x Ni 2-x The presence of O2 (0≤x≤0.6) will exacerbate the corrosion of materials by HF generated from electrolyte decomposition, reducing the cycle stability of the battery, while the use of large amounts of molten salt will result in higher production costs.
[0036] Based on this, in a first aspect, some embodiments of the present invention provide a single-crystal lithium nickel manganese oxide material, wherein Li in the single-crystal lithium nickel manganese oxide material x Ni 2-x The percentage content of O2 is C≤1.6%, C=(I LixNi2-xO2 / (I LixNi2-xO2 +I LiNi0.5Mn1.5O4 ))×100%, I LixNi2-xO2 For Li in the XRD refinement results x Ni 2-x The diffraction peak intensity corresponding to O2, I LixNi2-xO2 +I LiNi0.5Mn1.5O4 LiNi was superimposed in the XRD refinement results 0.5 Mn 1.5 O4 and Li x Ni 2-x The diffraction peak intensities of the O2 two-phase model, where 0 ≤ x ≤ 0.6.
[0037] Li x Ni 2-x The O2 impurity phase lacks electrochemical activity, which leads to a decrease in the reversibility of the charge-discharge capacity of the cathode material. Furthermore, under high voltage, the electrolyte decomposes to produce HF, which readily reacts with the impurity phase, thereby damaging the surface structure of the cathode material, accelerating electrolyte decomposition, and causing a decrease in the cycle stability of the cathode material.
[0038] The single-crystal lithium nickel manganese oxide material provided by this invention contains Li x Ni 2-x The low percentage of O2, meaning fewer impurities, avoids the decomposition of the electrolyte under high voltage, which produces HF and Li. x Ni 2-x O2 reaction can effectively improve the cycle stability of the battery.
[0039] The single-crystal lithium nickel manganese oxide material has a grain size of 5~11μm. The large particle size and relatively small specific surface area can reduce contact with the electrolyte, reduce electrolyte decomposition, and effectively improve the cycle performance of the battery.
[0040] In some embodiments of the present invention, the single-crystal lithium nickel manganese oxide material further has at least one of the following characteristics (1) to (3): (1) Octahedral morphology; (2) The compacted density is 3.1~3.4 g / cm³. 3 ; (3) Specific surface area is 0.2~0.4 m² 2 / g.
[0041] The high compaction density of single-crystal lithium nickel manganese oxide materials can improve the energy density, thermal stability, mechanical properties and durability of batteries.
[0042] In some embodiments of the present invention, the single-crystal lithium nickel manganese oxide material contains a dopant element, wherein the dopant element is at least one selected from Nb, Zr, Mo, Sb, Ta, and W. More preferably, the molar ratio of the dopant element to Ni is 0.001~0.005:0.5.
[0043] Further doping of single-crystal lithium nickel manganese oxide materials with high-valence metals such as Nb, Zr, Mo, Sb, Ta, and W can suppress Ni 3+ The reduction of Ni 2+ The content of Ni is reduced, thereby reducing the Ni content. 2+ The migration of these elements further improves the uniformity of nickel and manganese, resulting in low-impurity lithium nickel manganese oxide. Furthermore, high-valence metals such as Nb, Zr, Mo, Sb, Ta, and W form a lithium composite transition metal oxide layer on the surface of the final single-crystal lithium nickel manganese oxide material. This lithium composite metal oxide effectively isolates the electrolyte from the cathode material, increasing the battery's cycle stability.
[0044] In some embodiments of the present invention, the single-crystal lithium nickel manganese oxide material contains a coating layer, wherein the coating layer contains at least one element selected from P, F, and Al.
[0045] A coating layer of phosphate, fluoride, and alumina is formed on the surface of the single-crystal lithium nickel manganese oxide material to inhibit or reduce the contact between the electrolyte and the positive electrode material, thereby effectively suppressing electrolyte decomposition.
[0046] Secondly, some embodiments of the present invention provide a method for preparing single-crystal lithium nickel manganese oxide materials, including: Step S1: After the precursor and lithium salt are mixed evenly, they are sintered in an oxygen atmosphere to obtain lithium-deficient lithium nickel manganese oxide material. The precursor is Ni 0.5 Mn 1.5 (OH)4 or a mixture of Mn2O3 and MnNiO3; The ratio of the total molar amount of transition metals Ni and Mn in the precursor to the molar amount of Li in the lithium salt is 1:0.15~0.45; The sintering process is a two-stage process. First, a first-stage sintering is performed at 1000~1200℃, followed by a second-stage heat-holding sintering at 650~750℃. The first high-temperature sintering improves structural stability, while the second low-temperature heat-holding sintering reduces internal stress in the material.
[0047] Step S2: After the lithium-deficient lithium nickel manganese oxide material and lithium salt are mixed evenly, they are sintered in an oxygen atmosphere to obtain single-crystal lithium nickel manganese oxide material. The ratio of the total molar amount of transition metals Ni and Mn to the molar amount of Li in the lithium salt in the lithium-deficient nickel manganese oxide material is 1:0.05~0.35; The sintering process consists of two stages: first, a first-stage sintering is performed at 900~1000℃, followed by a second-stage heat preservation sintering at 650~750℃.
[0048] In this invention, the mixture of Mn2O3 and MnNiO3 is composed of Ni 0.5 Mn 1.5 (OH)4 was obtained by sintering at 700°C for 5 hours under an oxygen atmosphere.
[0049] Relatively speaking, the sintering in step S1 is high-temperature sintering, while the sintering in step S2 is low-temperature sintering. In step S1, a small amount of lithium salt is mixed with the precursor, and high-temperature sintering is beneficial for the growth of single-crystal particles, resulting in large-particle lithium nickel manganese oxide with a lithium-deficient phase, and the nickel and manganese elements are uniformly distributed in the material. In step S2, low-temperature sintering replenishes lithium, avoiding the generation of impurity phases, and simultaneously promoting secondary particle growth to form complete large-sized single-crystal lithium nickel manganese oxide material. The material has a low specific surface area, thereby reducing contact with the electrolyte and reducing electrolyte decomposition. During the sintering process in step S2, when the temperature is below 900℃, lithium salt cannot be embedded in the lithium-deficient lithium nickel manganese oxide cathode material; when the temperature is above 1000℃, the amount of impurity phase in the lithium nickel manganese oxide cathode material will increase.
[0050] Lithium nickel manganese oxide exhibits decreased stability and is prone to Li formation above 1000℃. x Ni 2-x The O2 impurity phase is present, and the growth thermal motive force for single crystals below 1000℃ is insufficient to form large single crystals. Therefore, by reducing the lithium content, lithium nickel manganese oxide with a lithium-deficient phase and large particle size is grown at high temperature (≥1000℃), and then lithium is replenished by low-temperature sintering to obtain lithium nickel manganese oxide with a low impurity phase.
[0051] In both steps S1 and S2, the present invention employs a two-stage sintering process and a two-stage heat preservation sintering process, which can reduce the internal stress of the material, reduce the generation of oxygen vacancies, and thus improve the structural stability of the material, thereby obtaining a single-crystal lithium nickel manganese oxide material with large particle size and low impurity phase content.
[0052] In some specific embodiments of the present invention, the lithium salt is at least one selected from Li₂CO₃, LiOH, LiCl, and Li₂SO₄. Those skilled in the art may also use other conventional lithium salts of the present invention.
[0053] In some specific embodiments of the present invention, in step S1, the sintering time for the first stage is 5-20 hours; the sintering time for the second stage is 3-10 hours. The sintering time can be adjusted adaptively according to the sintering temperature and sintering conditions.
[0054] In some specific embodiments of the present invention, in step S1, a flux is also added and mixed with the precursor and lithium salt; the flux is at least one of oxides or salts of Nb, Zr, Mo, Sb, Ta, and W.
[0055] Adding flux not only lowers the sintering temperature, but also enables the doping of high-valence metals such as Nb, Zr, Mo, Sb, Ta, and W into single-crystal lithium nickel manganese oxide materials.
[0056] In some specific embodiments of the present invention, the amount of flux added is determined based on the ratio of the total molar amount of Nb, Zr, Mo, Sb, Ta, and W to the molar amount of Ni of 0.001 to 0.005:0.5.
[0057] In some specific embodiments of the present invention, in step S2, the sintering time of the first stage is 10-20 hours; the sintering time of the second stage is 5-10 hours.
[0058] In some specific embodiments of the present invention, in step S2, a coating material is further added and mixed with lithium-deficient lithium nickel manganese oxide material and lithium salt; more preferably, the coating material is at least one of NH4H2PO4, Al2O3, and NH4F. The amount of coating material used is the conventional amount used in the art, for example, the mass of the coating material is 0.1~1wt% of the mass of the lithium nickel manganese oxide material.
[0059] In some specific embodiments of the present invention, the oxygen volume content in the sintering atmosphere is 50-100%.
[0060] Thirdly, some embodiments of the present invention also provide a lithium-ion battery, including the aforementioned single-crystal lithium nickel manganese oxide material or the single-crystal lithium nickel manganese oxide material obtained by the aforementioned preparation method.
[0061] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.
[0062] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.
[0063] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.
[0064] Example 1 Step S1: 1 mol of precursor Ni 0.5 Mn 1.5 After thoroughly mixing (OH)4 and 0.175 mol of Li2CO3, the mixture was calcined at 1050℃ for 20 h in an oxygen atmosphere for the first stage of sintering, followed by a second stage of sintering at 650℃ for 5 h. The high-purity oxygen flow rate was 100 sccm, the heating rate was 5℃ / min, and the cooling rate was 2℃ / min. This yielded a lithium-deficient lithium nickel manganese oxide cathode material (Li...). 0.35 Ni 0.5 Mn 1.5 O4).
[0065] Step S2: Lithium-deficient lithium nickel manganese oxide cathode material (Li 0.35 Ni 0.5 Mn 1.5 O4) was then mixed with 0.325 mol of Li2CO3. After thorough mixing, the mixture was sintered in an oxygen atmosphere. The first stage of sintering was carried out at 950℃ for 10 h, followed by the second stage of sintering at 700℃ for 5 h. The high-purity oxygen flow rate was 100 sccm, the heating rate was 5℃ / min, and the cooling rate was 2℃ / min. This yielded a single-crystal lithium nickel manganese oxide material (LiNi). 0.5 Mn 1.5 O4).
[0066] Comparative Example 1 1 mol of precursor Ni 0.5 Mn 1.5 (OH)4 and 0.5 mol of Li2CO3 were thoroughly mixed and calcined at 1000℃ for 20 h in an oxygen atmosphere, followed by holding at 650℃ for 5 h; the high-purity oxygen flow rate was 100 sccm, the heating rate was 5℃ / min, and the cooling rate was 2℃ / min; thus, lithium nickel manganese oxide cathode material (LiNi) was obtained. 0.5 Mn 1.5 O4).
[0067] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the sintering in step S2 is "sintering at 850°C for 10 hours, and then holding at 700°C for 5 hours".
[0068] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the sintering in step S2 is "sintering at 1030°C for 10 hours, and then holding at 700°C for 5 hours".
[0069] Example 2 The difference between Example 2 and Example 1 is as follows: In step S1, 1 mol of the precursor Ni 0.5 Mn 1.5 (OH)4 and 0.325 mol of Li2CO3 are thoroughly mixed; In step S2, lithium-deficient lithium nickel manganese oxide cathode material (Li 0.65 Ni 0.5 Mn 1.5 O4) is then mixed with 0.175 mol of Li2CO3.
[0070] Example 3 The difference between Example 3 and Example 1 is as follows: In step S1, 0.003 mol of flux WO3 and 1 mol of precursor Ni are added. 0.5 Mn 1.5 (OH)4 and 0.175 mol of Li2CO3 are thoroughly mixed.
[0071] Examples 4-18 Based on Example 1, the process parameters were adjusted to obtain Examples 4 to 18.
[0072] Specifically, the process conditions and stoichiometric coefficients for Examples 1-18 are shown in Table 1.
[0073] Table 1 Example 19 The only difference between Example 19 and Example 1 is that the precursor material used is 1 mol of Ni. 0.5 Mn 1.5 A mixture of Mn2O3 and MnNiO3 was obtained by calcining (OH)4 at 700℃ for 5h.
[0074] In this invention: (1) Li x Ni 2-x The percentage content of O2 is determined in the following way: XRD analysis of single-crystal lithium nickel manganese oxide (LiNiManganese Oxide) was performed using a Cu target. The measurement range was 10–80°, with a step size of 0.01° / step and a scan rate of 2° / min. Diffraction peaks were refined using FullProf software with Pseudo-Voigt as the peak shape function. Rietveld refinement was applied to the single-crystal LiNiManganese Oxide samples, and the results were obtained through mathematical calculations and superposition of LiNi... 0.5 Mn 1.5 O4 and Li x Ni 2-x The diffraction peaks of the O2 two-phase model were analyzed and compared with actual test results until the weighted fitting factor R was calculated. wp When the percentage is ≤15%, a refined result is obtained. Based on the refined result, Li... x Ni 2-x The diffraction peak intensity corresponding to O2 and the superimposed LiNi 0.5 Mn 1.5 O4 and Li x Ni 2-x The ratio of diffraction peak intensities in the O2 two-phase model was used to calculate Li. x Ni 2-x The percentage content C of the O2 impurity phase, where C = (I LixNi2-xO2 / (I LixNi2-xO2 +I LiNi0.5Mn1.5O4 ))×100%, I LixNi2-xO2 For Li in the XRD refinement results x Ni 2-x The diffraction peak intensity corresponding to O2, I LixNi2-xO2 +I LiNi0.5Mn1.5O4 LiNi was superimposed in the XRD refinement results 0.5 Mn 1.5 O4 and Li x Ni 2-x The diffraction peak intensities of the O2 two-phase model. Adjusted parameters include: phase content, cell parameters, atomic coordinates, occupancy, full width at half maximum (FWHM) function, and asymmetry function.
[0075] (2) The grain size of lithium nickel manganese oxide material was determined by the following method: Malvern laser particle size distribution method according to GB / T 19077.
[0076] (3) The morphology of lithium nickel manganese oxide material was obtained by SEM images.
[0077] (4) The specific surface area of lithium nickel manganese oxide material was determined by the nitrogen adsorption method according to GB / T 13390.
[0078] (5) The compaction density of lithium nickel manganese oxide material shall be determined by the following method: the compaction density tester method shall be used in accordance with GB / T 24533.
[0079] (6) The electrical properties of lithium nickel manganese oxide materials were determined by the following methods: Using the prepared single-crystal lithium nickel manganese oxide material as the active material, the active material: carbon black: PVDF were weighed according to a mass ratio of 8:1:1. After mixing, the mixture was manually ground or thoroughly mixed using a mixer. The mixture was then sieved through a 325# sieve, coated onto carbon-coated aluminum foil, dried, cut into sheets, and weighed to obtain the positive electrode sheet. Using lithium sheets as the negative electrode, Celgard 2320 as the separator, and a mixture of x% FEC, 87%-x% FEMC, and 13% LiPF6 (mass content) as the electrolyte (where x = 15~20%), button cells were assembled and allowed to stand for 5 hours before subsequent electrochemical performance testing. 1CC / 1CD charge / discharge capacity: With the ambient temperature maintained at 25℃, the device was first charged at a constant current of 0.1C (1C=140mA / g) to 4.95V, allowed to stand for 3 minutes, and then discharged at a constant current of 0.1C to 3.5V. This cycle was repeated 3 times for activation. After that, the device was charged at a constant current and constant voltage of 1C to 4.95V, with a cutoff current of 0.1C. After standing for 3 minutes, the device was discharged at a constant current of 1C to 3.5V to obtain the 1C charge / discharge specific capacity.
[0080] 2CC / 2CD Cyclic Stability Test: With the ambient temperature maintained at 25℃, the capacitor was first charged to 4.95V at a constant current of 0.1C (1C=140mA / g), allowed to stand for 3 minutes, and then discharged to 3.5V at a constant current of 0.1C. After 3 cycles for activation, the capacitor was charged to 4.95V at a constant current and voltage of 2C, with a cutoff current of 0.1C. After standing for 3 minutes, the capacitor was discharged to 3.5V at a constant current of 2C. After 200 cycles, the capacity retention rate was calculated.
[0081] Rate performance test: The ambient temperature was maintained at 25℃. Within the voltage window of 3.5-4.95V, constant current and constant voltage charging (cutoff current 0.1C) and constant current discharging were performed 5 times at 0.1C, 1C, 2C, 3C, 5C and 1C respectively to end the test. The discharge capacity at each rate was recorded.
[0082] The lithium-deficient lithium nickel manganese oxide cathode material (Li) prepared in step S1 of Example 1 0.35 Ni 0.5 Mn 1.5 The morphology of O4 is as follows Figure 1 As shown, it has a spherical structure. LiNi prepared in step S2 of Example 1 0.5 Mn 1.5 O4 as Figure 2 As shown, it is an octahedral single crystal with a grain size of about 6.5 μm.
[0083] Figure 3 The image shows a SEM image of the lithium nickel manganese oxide cathode material obtained in Comparative Example 1. As can be seen from the image, the lithium nickel manganese oxide cathode material contains a large number of small particles.
[0084] Figure 4 The image shows the SEM image of the lithium nickel manganese oxide cathode material obtained in Comparative Example 2. It can be seen that the surface of lithium nickel manganese oxide is relatively rough and the crystal growth is incomplete.
[0085] Figure 5 The image shows the SEM image of the lithium nickel manganese oxide cathode material obtained in Comparative Example 3. It can be seen that the lithium nickel manganese oxide particles are of uneven size.
[0086] Figure 6 This is a SEM image of the lithium-deficient lithium nickel manganese oxide cathode material obtained in step S1 of Example 2. Figure 7 This is a SEM image of the lithium nickel manganese oxide cathode material obtained in step S2 of Example 2. (Comparison) Figure 2 and Figure 7 It is not difficult to find that the higher the lithium content in the first replenishment, the larger the size of the lithium-deficient nickel manganese oxide particles, and the lower the uniformity of the obtained nickel manganese oxide cathode material particles.
[0087] Figure 8 The image shows the SEM image of the lithium nickel manganese oxide cathode material obtained in Example 3. It can be seen that the material has an octahedral morphology and a large grain size.
[0088] Figure 9 shows the refined XRD patterns of lithium nickel manganese oxide cathode materials obtained in Examples 1 to 3 and Comparative Example 1, where Figure 9(a) is the refined pattern of Example 1, Figure 9(b) is the refined pattern of Example 2, Figure 9(c) is the refined pattern of Example 3, and Figure 9(d) is the refined pattern of Comparative Example 1.
[0089] Further magnification of the 37.4°~37.8° and 43.9°~44.1° regions in Figure 9 yields... Figure 10 .
[0090] Figure 11 shows the electrochemical performance of the lithium nickel manganese oxide cathode material obtained in Example 1. Figure 11(a) shows the 1C charge-discharge curve, Figure 11(b) shows the rate performance, and Figure 11(c) shows the 2C charge-2C discharge cycle performance. 1C is calculated at 140 mA / g. The battery assembled from the lithium nickel manganese oxide cathode material obtained in Example 1 has a 1C discharge capacity of 134 mAh / g, a 5C discharge capacity of 114 mAh / g, and a capacity retention of 93.3% after 200 cycles of 2C charge-2C discharge.
[0091] Table 2 summarizes the relevant performance parameters of the lithium nickel manganese oxide materials obtained in Examples 1-19 and Comparative Examples 1-3.
[0092] Table 2 As can be seen from Table 2: Comparative Example 1 uses a single-stage high-temperature sintering process in the existing technology. The resulting lithium nickel manganese oxide material has a high impurity phase content, severe agglomeration, and small primary particle size. The assembled battery has low discharge capacity, low capacity retention, and low compaction density. The presence of the impurity phase (LixNi2-xO2) exacerbates the corrosion of the material by HF generated from electrolyte decomposition, reducing the cycle stability of the battery.
[0093] In Comparative Example 2, the sintering temperature used in step S2 is low, which prevents lithium salts from intercalating into the lithium-deficient lithium nickel manganese oxide cathode material. The particle size is large, requiring a higher activation energy for lithium intercalation. Due to the excessively low sintering temperature, the crystal growth is incomplete, resulting in poor material conductivity and consequently poor electrochemical performance.
[0094] In Comparative Example 3, step S2 uses a higher sintering temperature, which further increases the impurity phase content, resulting in poor electrochemical performance. The single-crystal lithium nickel manganese oxide material provided by this invention contains the impurity phase Li. x Ni 2-x The low O2 content and large particle size result in batteries with high discharge capacity and very high capacity retention. The monocrystalline lithium nickel manganese oxide material provided by this invention has high compaction density and low specific surface area, which can further improve the overall performance of the battery, including energy density, thermal stability, mechanical properties, and durability.
[0095] By using high-priced metal elements for doping and surface coating modification, the electrical properties of materials can be further improved, and the overall performance of batteries can be further enhanced.
[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A single-crystal lithium nickel manganese oxide material, characterized in that, In the single-crystal lithium nickel manganese oxide material, Li x Ni 2-x The percentage content of O2 is C≤1.6%, C=(I LixNi2-xO2 / (I LixNi2-xO2 +I LiNi0.5Mn1.5O4 ))×100%, I LixNi2-xO2 For Li in the XRD refinement results x Ni 2-x The diffraction peak intensity corresponding to O2, I LixNi2-xO2 +I LiNi0.5Mn1.5O4 LiNi was superimposed in the XRD refinement results 0.5 Mn 1.5 O4 and Li x Ni 2-x The diffraction peak intensities of the O2 two-phase model, where 0 ≤ x ≤ 0.6 and the grain size is 5~11 μm.
2. The single-crystal lithium nickel manganese oxide material as described in claim 1, characterized in that, The single-crystal lithium nickel manganese oxide material has at least one of the following characteristics (1) to (3): (1) Octahedral morphology; (2) The compacted density is 3.1~3.4 g / cm³. 3 ; (3) Specific surface area is 0.2~0.4 m² 2 / g.
3. The single-crystal lithium nickel manganese oxide material as described in claim 1 or 2, characterized in that, The single-crystal lithium nickel manganese oxide material contains a doping element, which is at least one of Nb, Zr, Mo, Sb, Ta, and W; the molar ratio of the amount of the doping element to the amount of Ni is 0.001~0.005:0.
5.
4. The single-crystal lithium nickel manganese oxide material as described in claim 1 or 2, characterized in that, The single-crystal lithium nickel manganese oxide material contains a coating layer; the coating layer contains at least one element selected from P, F, and Al.
5. A method for preparing a single-crystal lithium nickel manganese oxide material, characterized in that, include: Step S1: After the precursor and lithium salt are mixed evenly, they are sintered in an oxygen atmosphere to obtain lithium-deficient lithium nickel manganese oxide material. The precursor is Ni 0.5 Mn 1.5 (OH)4 or a mixture of Mn2O3 and MnNiO3; The ratio of the total molar amount of transition metals Ni and Mn in the precursor to the molar amount of Li in the lithium salt is 1:0.15~0.45; The sintering is a two-stage sintering process, firstly at 1000~1200℃, and then at 650~750℃. Step S2: After the lithium-deficient lithium nickel manganese oxide material and lithium salt are mixed evenly, they are sintered in an oxygen atmosphere to obtain single-crystal lithium nickel manganese oxide material. The ratio of the total molar amount of transition metals Ni and Mn to the molar amount of Li in the lithium salt in the lithium-deficient nickel manganese oxide material is 1:0.05~0.35; The sintering process is a two-stage sintering: first, a first-stage sintering is carried out at 900~1000℃, and then a second-stage sintering is carried out at 650~750℃.
6. The preparation method according to claim 5, characterized in that, The lithium salt is at least one of Li2CO3, LiOH, LiCl, and Li2SO4.
7. The preparation method according to claim 5, characterized in that, In step S1, the sintering time for the first stage is 5-20 hours; the sintering time for the second stage is 3-10 hours.
8. The preparation method according to any one of claims 5 to 7, characterized in that, In step S1, a flux is added and mixed with the precursor and lithium salt; the flux is at least one of oxides or salts of Nb, Zr, Mo, Sb, Ta, and W; the amount of flux added is determined according to the ratio of the total molar amount of Nb, Zr, Mo, Sb, Ta, and W to the molar amount of Ni is 0.001 to 0.005:0.
5.
9. The preparation method according to claim 5, characterized in that, In step S2, the sintering time for the first stage is 10-20 hours; the sintering time for the second stage is 5-10 hours.
10. The preparation method according to claim 5 or 9, characterized in that, In step S2, a coating material is added and mixed with lithium-deficient nickel manganese oxide material and lithium salt; the coating material is at least one of NH4H2PO4, Al2O3, and NH4F.
11. The preparation method according to claim 5, characterized in that, The oxygen volume content in the sintering atmosphere is 50-100%.
12. A lithium-ion battery, characterized in that, The material includes the single-crystal lithium nickel manganese oxide material according to any one of claims 1 to 4 or the single-crystal lithium nickel manganese oxide material obtained by the preparation method according to any one of claims 5 to 11.