Preparation method of single-crystal high-crystallinity lithium nickel manganese oxide material and application thereof

Abstract

The application belongs to the technical field of lithium ion batteries, and discloses a preparation method of single-crystal high-crystallinity lithium nickel manganese oxide material and application thereof, wherein the preparation method comprises the following steps: (1) according to the nominal chemical dosage ratio of lithium nickel manganese oxide material, solid lithium source, nickel source and manganese source are proportioned, and solid-phase dispersion depolymerization treatment is performed to obtain dispersed particles with a particle size of less than 50 microns, thereby obtaining a raw material powder mixture; (2) the raw material powder mixture is subjected to step-by-step heat treatment under an oxygen-containing atmosphere to obtain single-crystal high-crystallinity lithium nickel manganese oxide material. Through improvement of the overall process of the preparation method, the single-crystal high-crystallinity lithium nickel manganese oxide material is prepared by means of one-step step-by-step heat treatment, has good morphology, and the crystallinity is obviously higher than that of the material obtained by the traditional lithium nickel manganese oxide preparation method, and has excellent electrochemical performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and more particularly relates to a preparation method of a single-crystal high-crystallinity lithium nickel manganese oxide material and application thereof. BACKGROUND

[0002] Since being commercially applied, lithium ion batteries have been widely used in consumer electronic devices, energy storage, transportation and other fields. Under the trend of lightweight electronic devices, the demand for battery materials with high energy density is increasing. Since the battery cathode material is a key factor determining the energy density of the battery, the battery industry attaches great importance to the development of cathode materials with high energy density. However, the nickel-cobalt-manganese ternary cathode material, which accounts for the majority of the market share of cathode materials, is facing serious supply chain problems due to the low abundance of cobalt and the geopolitical factors of cobalt mining. Therefore, it is an urgent need in the industry to seek low-cobalt or cobalt-free cathode materials with high energy density.

[0003] Lithium nickel manganese oxide material (LiNi x Mn (2-x) O y , wherein x can be 0.1 to 0.5, and y is 3.3 to 4) has a very high working voltage platform (~4.7V vs. Li + / Li), and has an ideal high theoretical specific capacity (146mAh g -1 ), so the theoretical energy density can reach 650Wh kg -1 . Moreover, the raw material prices of manganese and nickel elements are much lower than those of cobalt elements, so the lithium nickel manganese oxide material can achieve similar energy density to the nickel-cobalt-manganese ternary cathode material at a much lower theoretical preparation cost.

[0004] However, in the actual preparation process, the traditional preparation method of lithium nickel manganese oxide needs to first prepare a nickel-manganese precursor using a coprecipitation method or a sol-gel method: soluble nickel and manganese compounds are added to a liquid dispersant such as water, ethanol, propylene glycol, etc., so that the raw materials are mixed in a liquid state, and an alkaline solution or an organic polymer is added to produce a precipitate or a gel. The obtained precipitate or gel is dried and then heat treated to obtain a nickel-manganese precursor; then the precursor is mixed with a lithium-containing compound and then heat treated at a constant temperature to obtain a lithium nickel manganese oxide material. The liquid phase process in the above process is difficult to carry out on a large scale and the results are relatively uncontrollable. The use of soluble metal compounds, solvents and polymers in the process will greatly increase the production cost. The drying process of the solvent will produce a large amount of waste pollution to the environment, and the volatilization of flammable solvents will greatly increase the safety hazards in the production process.

[0005] The nickel-manganese precursor prepared by the traditional method has agglomeration, and the lithium nickel-manganese oxide material particles obtained by heat treatment of the nickel-manganese precursor have a polycrystalline morphology, which has overlapping grain boundaries, thereby affecting the electrochemical performance of the material. In addition, in order to obtain a lithium nickel-manganese oxide with good crystallinity, a constant temperature heat treatment at a high temperature of 800 DEG C or above is usually performed, but the lithium nickel-manganese oxide material will undergo oxygen loss reaction at a high temperature to generate oxygen defects, and too many oxygen defects will cause the generation of a large amount of trivalent manganese ions, and the Jahn-Teller effect generated will seriously destroy the material stability of the lithium nickel-manganese oxide, thereby causing the rapid decay of the cycle capacity of the lithium nickel-manganese oxide material.

[0006] Therefore, the traditional preparation method has defects such as complex process, high cost, uncontrollable waste liquid, low repeatability, not suitable for large-scale production, and poor electrochemical performance of the finished product. Therefore, it is of great significance and value to develop a lithium nickel-manganese oxide material (especially a single crystal lithium nickel-manganese oxide material) with simple preparation process, low cost, environmental friendliness, easy large-scale production and excellent electrochemical performance. SUMMARY

[0007] In view of the above defects or improvement needs of the prior art, the purpose of the present application is to provide a preparation method of a single crystal high crystallinity lithium nickel-manganese oxide material and its application, wherein the overall process of the preparation method is improved, the solid lithium source, the solid nickel source and the solid manganese source are directly subjected to solid phase dispersion treatment to obtain a mixture powder, and then the mixture powder is subjected to a segmented heat treatment with segmented temperature control and oxygen content control in an oxygen-containing atmosphere. In this way, the single crystal high crystallinity lithium nickel-manganese oxide material is prepared by one-step segmented heat treatment, which has a good morphology and a crystallinity significantly higher than that of the material prepared by the traditional lithium nickel-manganese oxide preparation method, and has excellent electrochemical performance. In addition, compared with the traditional lithium nickel-manganese oxide material preparation method, the present application does not need to prepare the traditional nickel-manganese precursor, which can effectively improve the problems of low repeatability, high cost, solvent waste, environmental pollution and inconvenience for large-scale production caused by the preparation of the nickel-manganese precursor in the traditional preparation process, and effectively reduce the time, material and energy cost in the manufacturing process.

[0008] To achieve the above-mentioned purpose, according to one aspect of the present application, a preparation method of a single crystal high crystallinity lithium nickel-manganese oxide material is provided, characterized in that it comprises the following steps:

[0009] (1) taking a solid lithium-containing compound as a lithium source, a solid nickel-containing compound as a nickel source, and a solid manganese-containing compound as a manganese source, and according to the nominal chemical dosage ratio of lithium, nickel and manganese in the lithium nickel-manganese oxide material LiNi x Mn (2-x) O y , the lithium source, the nickel source and the manganese source are proportioned, and then they are subjected to solid phase dispersion depolymerization treatment to obtain dispersed particles with a particle size of less than 50 microns, thereby obtaining a raw material powder mixture;

[0010] wherein 0.1≤x≤0.5, 3.3≤y≤4;

[0011] (2) subjecting the raw material powder mixture obtained in step (1) to a segmented heat treatment under an oxygen-containing atmosphere to prepare a single-crystal high-crystallinity lithium nickel manganese oxide material;

[0012] wherein the segmented heat treatment comprises at least two holding stages in sequence, and the two holding stages are denoted as a first holding stage and a second holding stage in sequence, the temperature of the first holding stage is higher than that of the second holding stage, and the oxygen content of the oxygen-containing atmosphere used in the first holding stage is lower than that of the oxygen-containing atmosphere used in the second holding stage; the first holding stage is used for crystal growth, and the second holding stage is used for reducing crystal defects.

[0013] As a further preferred embodiment of the present application, in step (1), the equipment used for the solid-phase dispersion treatment comprises at least one of a ball mill, a grinder, a mixer, a pulverizer, a crusher, and an air mill.

[0014] Preferably, when a ball mill is used, the weight ratio of balls to material is 2:1-10:1, the rotation speed is 200-400 rpm, and the treatment time is 6-12 hours.

[0015] When a grinder, a mixer, a pulverizer, a crusher, or an air mill is used, the rotation speed is 1000-25000 rpm, and the treatment time is 30 seconds-1 hour.

[0016] As a further preferred embodiment of the present application, in step (2), the holding temperature of the first holding stage is 800-1100℃, and the holding time is 6-24 hours; preferably, the heating rate for heating to the temperature of the first holding stage is 0.5-5℃ per minute.

[0017] The holding temperature of the second holding stage is 650-750℃, and the holding time is 12-48 hours.

[0018] As a further preferred embodiment of the present application, in step (1), the solid-state lithium-containing compound is selected from lithium carbonate, lithium hydroxide, lithium oxide, lithium nitrate, and organic compounds of lithium.

[0019] The solid-state nickel-containing compound is selected from nickel carbonate, nickel oxide, nickel protoxide, nickel protoxide, nickel hydroxide, nickel oxide hydroxide, nickel nitrate, and organic compounds of nickel.

[0020] The solid-state manganese-containing compound is selected from manganese carbonate, manganese protoxide, manganese dioxide, manganese hydroxide, manganese oxide, manganese nitrate, and organic compounds of manganese.

[0021] As a further preferred embodiment of the present application, the oxygen-containing atmosphere in step (2) comprises air, pure oxygen or oxygen-containing mixed gas.

[0022] According to another aspect of the present application, the present application provides the single-crystal high-crystallinity lithium nickel manganese oxide material prepared by the above method.

[0023] According to still another aspect of the present application, the present application provides the use of the single-crystal high-crystallinity lithium nickel manganese oxide material as a positive electrode material of a lithium ion battery.

[0024] According to still another aspect of the present application, the present application provides a lithium ion battery, characterized in that the positive electrode sheet of the lithium ion battery is made of the single-crystal high-crystallinity lithium nickel manganese oxide material as an active material.

[0025] By means of the above technical scheme according to the present application, the following beneficial effects can be achieved compared with the prior art:

[0026] 1. The preparation method of the present application is to first directly perform solid-phase dispersion treatment on solid-state lithium source, solid-state nickel source and solid-state manganese source to obtain raw material powder which is fully dispersed and uniformly mixed, wherein the particles in the raw material powder are dispersed particles (for example, independent soft agglomerates) with a particle size of less than 50 microns, which are depolymerized by solid-phase dispersion; then, the single-crystal high-crystallinity lithium nickel manganese oxide material is prepared by means of one-step segmented heat treatment in combination with segmented temperature control and oxygen content control of the oxygen-containing atmosphere. The process of preparing the lithium nickel manganese oxide material does not need to prepare a nickel manganese precursor, and the process is simple, which can effectively reduce the time consumption in the preparation process and reduce energy consumption.

[0027] The segmented heat treatment can include two or more different temperature stages, at least two stages corresponding to a crystal growth temperature and a defect removal temperature, the crystal growth temperature being higher than the defect removal temperature, wherein the crystal growth is performed first and the defect removal is performed later; and the oxygen content in the oxygen-containing atmosphere at the defect removal temperature is higher than the oxygen content in the oxygen-containing atmosphere at the crystal growth temperature, so that in the defect removal stage, the material will undergo an oxygen absorption reaction, which can reduce oxygen defects.

[0028] 2. The solid-phase dispersion treatment in the present application can be performed by using ball milling or stirring mixing to depolymerize the large-particle-size agglomerates, so that the material reaches a uniformly dispersed state, and the particle size of the dispersed particles is less than 50 microns. Compared with the preparation method in which a liquid-phase dispersant is used to disperse the raw materials, the use of solvents and additional raw materials can be effectively reduced, thereby reducing the production cost.

[0029] Due to the use of solid-phase dispersion treatment, there will be no serious agglomeration phenomenon in the subsequent heat treatment process, and the dispersion is better, which can reduce the loss caused by screening the material particles in the traditional preparation process.

[0030] The solid phase dispersion treatment in the present application can particularly adopt high-speed dispersion. High dispersion speed is conducive to breaking the raw materials, reducing the particle size of the raw materials (for example, the cutting action of air at high dispersion speed can depolymerize large-particle agglomerates in the raw materials), and fully mixing different raw materials; in the process of depolymerization of large-particle agglomerates, small-particle soft agglomerate particles will be self-assembled again under the action of surface energy, the small-particle particles can promote the growth of independent single crystal particles, avoid the agglomeration of single crystal particles to form polycrystals, reduce the particle size, and improve the morphology of the lithium nickel manganese oxide material.

[0031] 3. In the segmented heat treatment process of the preparation method of the present application, the depolymerized raw materials are first generated into single crystal particles at a relatively high crystal growth temperature, and then the temperature is lowered to a relatively low defect removal temperature; in the lower temperature and high oxygen content atmosphere environment in the defect removal stage, the spontaneous oxygen absorption reaction of the lithium nickel manganese oxide material can reduce the oxygen defect content generated at high temperature and regulate the crystal structure, which can effectively improve the crystallinity of the prepared lithium nickel manganese oxide material and further improve the electrochemical performance of the material.

[0032] 4. The present application can obtain lithium nickel manganese oxide material with good morphology and excellent electrochemical performance, and avoid the problems of complex process, high cost, environmental pollution and low repeatability caused by traditional liquid phase synthesis method, which is conducive to large-scale preparation of the material. The preparation method of the present application has simple process, easy to control production process, low cost, suitable for large-scale production, and the prepared lithium nickel manganese oxide material has excellent electrochemical performance, especially can be used as a high specific energy lithium ion battery positive electrode material, and has practical value.

[0033] The single crystal high-crystallinity lithium nickel manganese oxide material prepared by the method of the present application has excellent electrochemical performance, high specific capacity, high rate and long cycle life. For example, compared with the traditional preparation technology of coprecipitation (such as Comparative Example 1 in the following), the lithium nickel manganese oxide material prepared based on the preparation method of the present application presents a single crystal octahedral morphology, while the lithium nickel manganese oxide material prepared by the traditional method presents a relatively irregular secondary particle morphology, which specifically presents a large particle morphology formed by mutual adhesion of a large number of single crystal octahedral particles, and has defects such as low electrochemical performance caused by crystal boundary overlap and easy breakage of particles between the particles. The lithium nickel manganese oxide material prepared by the present application has excellent electrochemical performance and material stability. For example, in Example 1 in the following, the specific capacity of the prepared lithium nickel manganese oxide material can reach 135.2 mAh g -1 at a high rate of 0.5 C, and can be stably cycled at 0.5 C for up to 500 cycles. -1 The specific capacity of the lithium nickel manganese oxide material prepared in Comparative Example 1 in the following is only 103.2 mAh g -1, and material failure is prone to occur, and obvious capacity attenuation occurs after 50 cycles, and stable cycling cannot be achieved.

[0034] How to prepare a lithium nickel manganese oxide material with single crystal morphology and high crystallinity and excellent electrochemical performance has always been a technical difficulty. In the preparation process of traditional lithium nickel manganese oxide materials, in order to solve the problem of uniformity of raw materials, the method of mixing soluble nickel and manganese compounds in a liquid environment is generally used to obtain a precursor with uniformly mixed raw materials, and then a lithium compound is added for reaction. Although this method can achieve uniform mixing of raw materials, the nickel-manganese precursor obtained under the action of liquid surface tension is in the form of a large-volume spherical agglomerate. The product obtained after the reaction of the precursor with the lithium-containing compound is in the form of a large-volume spherical agglomerated polycrystalline morphology. The overlap of grain boundaries under polycrystalline morphology will cause the increase of ion migration energy barrier, thereby causing the deterioration of electrochemical performance; the material-electrolyte interface under polycrystalline morphology is unstable, which easily induces decomposition reaction of electrolyte on the surface and generates harmful by-products to the material; further, in the cycle process, intergranular stress will be generated in the polycrystalline particles due to the volume expansion of the material, thereby causing particle breakage and failure. In addition, the traditional preparation technology needs to use a large amount of high-cost soluble organic salt and organic solvent, resulting in high cost of the traditional preparation method. The present application uses the surface energy characteristics of the material to uniformly disperse the raw materials and spontaneously assemble the raw material particles into small-particle-size agglomerates with a particle size of less than 50 microns under the driving of surface energy, which is small in volume and more suitable for single crystal particle growth. Generally, in the heat treatment process of the material, higher temperature and longer treatment time can provide more energy required for crystal growth of the material, thereby obtaining better crystallinity. However, due to the characteristics of lithium nickel manganese oxide material itself, too high heat treatment temperature and too long heat treatment time will cause oxygen ions in the lattice of lithium nickel manganese oxide material to escape, thereby reducing the crystallinity of the material, damaging the structure of the material and causing deterioration of the electrochemical performance. The present application is very suitable for crystal growth of lithium nickel manganese oxide material by at least including two holding stages of segmented heat treatment (for example, the holding temperature of the first holding stage can be controlled to 800-1100℃, and the holding time can be controlled to 6-24 hours, the holding temperature of the second holding stage can be controlled to 650-750℃, and the holding time can be controlled to 12-48 hours), and the oxygen content in the oxygen-containing atmosphere is controlled, which can effectively repair the oxygen defects caused by the escape of oxygen ions at high temperature, regulate the material structure, and improve the electrochemical performance of the material, so that the lithium nickel manganese oxide material has extremely high crystallinity and excellent electrochemical performance.

[0035] In conclusion, the preparation method in the application has the advantages of simple and rapid preparation process, high preparation efficiency, low production cost, and easy large-scale production; and the prepared single-crystal high-crystallinity lithium nickel manganese oxide material has excellent electrochemical performance, high specific capacity, high rate, and long cycle life. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Figure 1 is a scanning electron microscope (SEM) image of Li2CO3 raw material without crushing treatment; the scale in the figure is 50 μm.

[0037] Figure 2 Figure 2 is a scanning electron microscope (SEM) image of NiCO3 raw material without crushing treatment; the scale in the figure is 10 μm.

[0038] Figure 3 Figure 3 is a scanning electron microscope (SEM) image of MnO2 raw material without crushing treatment; the scale in the figure is 10 μm.

[0039] Figure 4 Figure 4 is a schematic diagram of the morphology of raw materials before and after air cutting self-assembly.

[0040] Figure 5 Figure 5 is a scanning electron microscope (SEM) image of small-particle-size soft agglomerate particles of Li2CO3, NiCO3 and MnO2 raw materials obtained by solid-phase dispersion depolymerization treatment in Example 1 constructed according to the application; the scale in the figure is 5 μm.

[0041] Figure 6 Figure 6 is an X-ray diffraction (XRD) pattern of the lithium nickel manganese oxide material prepared in Example 1 constructed according to the application.

[0042] Figure 7 Figure 7 is a 30000 times scanning electron microscope (SEM) image of the lithium nickel manganese oxide material prepared in Example 1 constructed according to the application; the scale in the figure is 4 μm.

[0043] Figure 8 Figure 8 is a 60000 times scanning electron microscope (SEM) image of the lithium nickel manganese oxide material prepared in Example 1 constructed according to the application; the scale in the figure is 2 μm.

[0044] Figure 9 Figure 9 is a graph of the first three charge-discharge capacity performance of the lithium nickel manganese oxide material prepared in Example 1 constructed according to the application at a 0.1C rate.

[0045] Figure 10 Figure 10 is a cycle performance graph of the lithium nickel manganese oxide material prepared in Example 1 constructed according to the application.

[0046] Figure 11is a cycle performance graph of the lithium nickel manganese oxide material prepared in Example 2 and Example 3 constructed according to the present application.

[0047] Figure 12 is a 5000 times scanning electron microscope (SEM) graph of the lithium nickel manganese oxide material prepared in Comparative Example 1 constructed according to the present application; the scale in the graph is 10 μm.

[0048] Figure 13 is a cycle performance graph of the lithium nickel manganese oxide material prepared in Comparative Example 1 constructed according to the present application.

[0049] Figure 14 is an X-ray diffraction (XRD) graph of the lithium nickel manganese oxide material prepared in Comparative Example 3 constructed according to the present application.

[0050] Figure 15 is an X-ray diffraction (XRD) graph of the lithium nickel manganese oxide material prepared in Comparative Example 4 constructed according to the present application. DETAILED DESCRIPTION

[0051] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0052] In the following examples and comparative examples, the crystal phase structure of the prepared electrode material is characterized by an X-ray diffractometer and analyzed to determine the molecular formula and crystal structure integrity of the material. In addition, the microstructure of the sample is observed by a scanning electron microscope.

[0053] Example 1

[0054] 1.943 g of Li2CO3, 3.04 g of NiCO3, and 6.66 g of MnO2 raw materials were weighed into a ball milling jar, ball milling beads were added to a ball-to-charge mass ratio of 2:1, and the mixture was ball milled at a speed of 300 rpm for 6 hours to obtain a mixed powder for standby use. The SEM graphs of Li2CO3, NiCO3, and MnO2 before treatment are shown in Figure 1 、 Figure 2 、 Figure 3

[0055] ​The mixed Li2CO3, NiCO3 and MnO2 powders were further dispersed in a pulverizer and pulverized for 2 minutes at a speed of 25000 rpm to obtain small-size soft agglomerated particles of the raw materials of Li2CO3, NiCO3 and MnO2. Figure 4 As shown in Figure 2, the obtained small-size soft agglomerated particles are as follows: Figure 5 As shown, the particle size is about 5 microns and is formed by self-assembly under the action of surface energy.

[0056] The obtained powder mixture was placed in an atmosphere box furnace, heated to 900°C at 5°C / min under air conditions and kept warm for 8 hours, then an oxygen-containing mixed gas with an oxygen content of 50 vol% (the oxygen-containing mixed gas is an oxygen / nitrogen mixture, the same below) was introduced into the atmosphere box furnace and cooled to 700°C at 5°C / min and kept warm for 12 hours, and then naturally cooled to room temperature to obtain lithium nickel manganese oxide material.

[0057] The obtained LiNi 0.5 Mn 1.5 The O4 material was tested by XRD, and the results were as follows Figure 6 As shown in the figure, it can be seen that the diffraction characteristic peaks appearing in the sample are LiNi 0.5 Mn 1.5 The X-ray diffraction peak of O4 has a narrow peak width and high peak intensity, indicating that the prepared LiNi 0.5 Mn 1.5 O4 has a single crystal phase, no impurities and excellent crystallinity.

[0058] The obtained LiNi 0.5 Mn 1.5 The O4 material was characterized by SEM, and the results were as follows Figure 7 and Figure 8 As shown. Figure 7 、 8 It can be seen that the prepared LiNi 0.5 Mn 1.5 The O4 material particles are all independent octahedral particles with a particle size in the range of 2-4 microns, uniform size and good crystallinity.

[0059] Furthermore, using the above-mentioned LiNi 0.5 Mn 1.5 LiNi made of O4 material 0.5 Mn 1.5 O4 electrode sheet, the active material mass ratio of the electrode sheet is 93%, the conductive agent mass ratio is 4%, the binder mass ratio is 3%, and the electrode surface loading is 5.5 mg / cm 2 Then, using this LiNi 0.5 Mn 1.5O4 electrode sheet to make a half battery, and the half battery is specifically composed of a working electrode LiNi 0.5 Mn 1.5 O4, a counter electrode metal lithium, and a PP diaphragm.

[0060] The half battery is detected, and its charge-discharge capacity performance at 0.1C rate is as shown in the following figure. Figure 9 As can be seen from the figure, the LiNi 0.5 Mn 1.5 O4 has a discharge capacity as high as 135.2 mAh·g -1 at a current density of 0.1C in a voltage range of 3.0-4.95V, and a discharge platform of about 4.7V. This shows that the LiNi 0.5 Mn 1.5 O4 material constructed according to the application has excellent electrochemical performance.

[0061] The half battery is detected for cycle performance, and the results are as shown in the following figure. Figure 10 As can be seen from the figure, when the battery is charged and discharged at a current density of 0.5C, its cycle specific capacity can be as high as 126.7 mAh·g -1 , the discharge specific capacity can be as high as 117 mAh·g -1 after 160 cycles, and the discharge specific capacity is still as high as 108.1 mAh·g -1 after 500 cycles. This shows that the LiNi 0.5 Mn 1.5 O4 material prepared has good cycle performance.

[0062] Example 2

[0063] 1.943g of LiOH·H2O was weighed and placed in a pulverizer, pulverized at a high speed for 1 min, and a pulverization speed of 20000 rpm was used to obtain uniformly dispersed LiOH·H2O powder for standby.

[0064] 4.34g of NiO was weighed and placed in a stirrer, broken and stirred for 30 min, and a stirring speed of 2000 rpm was used to obtain uniformly dispersed NiO powder for standby.

[0065] 10.25g of MnCO3 was weighed and placed in a gas mill, broken and stirred for 10 min, and a stirring speed of 5000 rpm was used to obtain uniformly dispersed MnCO3 powder for standby.

[0066] The obtained uniformly dispersed LiOH·H2O, NiO and MnCO3 powders were placed in a ball mill, ball milling beads were added to a ball-to-material ratio of 10:1, and ball milling was carried out at a speed of 200 rpm for 12 hours to obtain a uniformly mixed LiOH·H2O, NiO and MnCO3 powder mixture.

[0067] The obtained powder mixture was placed in an atmosphere tube furnace, heated to 800°C at 0.5°C / min under air atmosphere and kept at this temperature for 24 hours, then introduced into pure oxygen and cooled to 750°C and kept at this temperature for 12 hours, and then cooled naturally to room temperature to obtain LiNi 0.5 Mn 1.5 O4 material.

[0068] Further, similar to Example 1, the LiNi prepared in this example 0.5 Mn 1.5 LiNi made of O4 material 0.5 Mn 1.5 O4 electrode sheet, the active material mass ratio of the electrode sheet is 93%, the conductive agent mass ratio is 4%, the binder mass ratio is 3%, and the electrode surface loading is 5.5 mg / cm 2 Then, using this LiNi 0.5 Mn 1.5 O4 electrode sheet to make a half-cell, the half-cell is specifically composed of the working electrode LiNi 0.5 Mn 1.5 It is composed of O4, metal lithium counter electrode and PP separator.

[0069] The cycle performance test of the half-battery is as follows Figure 11 As shown in Figure 2, when the battery is charged and discharged at a rate of 0.5C, the first cycle discharge capacity is 119.7 mAh g -1 After 100 cycles, there was no significant capacity attenuation, and the capacity was still 91 mAh g -1 , indicating that the LiNi prepared in Example 2 is 0.5 Mn 1.5 O4 material has excellent performance and is suitable for use as a positive electrode material for lithium-ion batteries with high electrochemical performance.

[0070] Example 3

[0071] Weigh 3.76g Li2O, 4.08g Ni(OH)2, and 6.92g Mn3O4, respectively, and place them in a blender. Stir and mix them at 1000 rpm for 1 hour to obtain uniformly mixed Li2O, Ni(OH)2, and Mn3O4 powders for use.

[0072] The obtained powder mixture was placed in an atmosphere box furnace, heated to 1100°C at 5°C / min in an oxygen-containing mixed gas atmosphere with an oxygen content of 10 vol%, and kept warm for 6 hours. Then, air was introduced and the temperature was lowered to 650°C and kept warm for 48 hours. The mixture was naturally cooled to room temperature to obtain LiNi 0.5 Mn 1.5 O4 material.

[0073] Further, similar to Example 1, the LiNi prepared in this example0.5 Mn 1.5 O4 material to LiNi 0.5 Mn 1.5 O4 electrode sheet, the active material mass ratio is 93%, the conductive agent mass ratio is 4%, the binder mass ratio is 3%, and the electrode sheet surface load is 5.5 mg / cm 2 . Then, the LiNi 0.5 Mn 1.5 O4 electrode sheet is used to make a half battery, and the half battery is specifically composed of a working electrode LiNi 0.5 Mn 1.5 O4 and a counter electrode metal lithium, and a PP separator.

[0074] The half battery is subjected to cycle performance detection, and the results are shown in Table 1. Figure 11 As shown in Table 1, when the battery is charged and discharged at a rate of 0.5C, the first cycle specific discharge capacity is 121.4 mAh·g -1 . And after 100 cycles, there is no obvious capacity decay, still 97.7 mAh·g -1 , indicating that the LiNi 0.5 Mn 1.5 O4 material prepared in Example 3 has excellent performance and is suitable for use as a high electrochemical performance lithium ion battery positive electrode material.

[0075] Comparative Example 1

[0076] The traditional lithium nickel manganese oxide preparation method is used in this comparative example, and the specific operation is as follows:

[0077] 2.48 g of C4H 14 NiO8 and 8.01 g of C6H 13 MnO8 are weighed, dissolved in 100 ml of deionized water, and continuously stirred for 6 hours at a stirring speed of 600 rpm to obtain a uniformly mixed solution. After stirring is completed, ammonia water is added to adjust the pH to produce a precipitate, and the obtained precipitate after suction filtration and washing is placed in a drying oven for drying for 24 hours to obtain a mixed powder of Ni and Mn compounds.

[0078] The obtained powder is placed in a box furnace, heated to 600°C at a rate of 3°C / min under an air atmosphere, and naturally cooled to room temperature to obtain a nickel-manganese precursor powder.

[0079] The obtained precursor powder is placed in a high-speed stirrer, 1.98 g of Li2CO3 is added, and broken and stirred for 5 min at a stirring speed of 10,000 rpm to obtain a uniformly dispersed mixed powder of nickel-manganese precursor and lithium-containing compound for standby use.

[0080] The obtained uniformly dispersed mixed powder was placed in a box furnace, and heated to 850°C at 3°C / min under air atmosphere, and then held for 24 hours, and then cooled to 650°C and held for 48 hours, and then naturally cooled to room temperature to obtain LiNi 0.5 Mn 1.5 O4 material.

[0081] Further, similar to Example 1, the LiNi 0.5 Mn 1.5 O4 electrode sheet was prepared using the LiNi 0.5 Mn 1.5 O4 material obtained in this comparative example, and the active material mass ratio in the electrode sheet was 93%, the conductive agent mass ratio was 4%, the binder mass ratio was 3%, and the electrode sheet surface loading was 5.5 mg / cm 2 . Then, a half battery was prepared using the LiNi 0.5 Mn 1.5 O4 electrode sheet, and the half battery was specifically composed of the working electrode LiNi 0.5 Mn 1.5 O4 and the counter electrode metal lithium, and a PP separator.

[0082] The LiNi 0.5 Mn 1.5 O4 material obtained was subjected to SEM characterization, and the results are shown in Figure 12 . Since the nickel-manganese precursor prepared by the traditional method has a agglomeration condition, the LiNi 0.5 Mn 1.5 O4 material particles obtained after heat treatment of the nickel-manganese precursor exhibit a block-like morphology composed of a large number of octahedral particles bonded together, which is a typical polycrystalline morphology. Under this morphology, the crystal growth interface is incomplete and has defects, and the mutual connection between the crystal grains will cause the mutual dislocation of the crystal boundaries, hinder the conduction of lithium ions in the material bulk phase, and generate stress between the crystal grains due to the volume expansion of the crystal grains under long cycle, resulting in material breakage and failure, which seriously affects the capacity development, rate performance, and long cycle stability of the material.

[0083] The half battery was subjected to cycle performance detection, and the results are shown in Figure 13 . As can be seen from the figure, when the battery is charged and discharged at a rate of 0.5C, the first cycle specific discharge capacity is only 103.2 mAh·g -1 . And after about 50 cycles, the capacity obviously decreases, which indicates that the LiNi 0.5 Mn 1.5 O4 material prepared in Comparative Example 1 has poor performance and is not suitable for use as a high electrochemical performance lithium ion battery positive electrode material.

[0084] Comparative Example 2

[0085] The comparative example adopts a solid phase dispersion treatment + constant temperature heat treatment at a fixed temperature to prepare lithium nickel manganese oxide, and the specific operation is as follows:

[0086] 1.943 g of LiOH·H2O, 4.48 g of NiO and 9.67 g of MnCO3 were weighed and placed in a ball mill jar, ball milling beads were added to a ball-to-material ratio of 6:1, and ball milling was performed at a speed of 400 rpm for 12 hours to obtain a uniformly mixed raw material powder.

[0087] The obtained powder was placed in a box furnace, and the temperature was raised to 1000℃ at a rate of 3℃ / min under air atmosphere, and then the temperature was kept for 6 hours, and then the temperature was naturally lowered to room temperature to obtain LiNi 0.5 Mn 1.5 O4 material.

[0088] Further, the LiNi 0.5 Mn 1.5 O4 material obtained by the comparative example was used to prepare a LiNi 0.5 Mn 1.5 O4 electrode sheet, and the active material mass ratio in the electrode sheet was 93%, the conductive agent mass ratio was 4%, the binder mass ratio was 3%, and the electrode sheet surface loading was 3.2 mg / cm 2 . Then, the LiNi 0.5 Mn 1.5 O4 electrode sheet was used to prepare a half battery, and the half battery was specifically composed of a working electrode LiNi 0.5 Mn 1.5 O4 and a counter electrode metal lithium, and a PP separator.

[0089] The rate performance of the half battery was detected, and when the battery was charged and discharged at a rate of 0.5C, the specific capacity was only 105.7 mAh·g -1 . This shows that the LiNi 0.5 Mn 1.5 O4 material prepared by the comparative example 2 has poor performance and is not suitable for use as a high electrochemical performance lithium ion battery positive electrode material.

[0090] Comparative example 3

[0091] The comparative example adopts a solid phase dispersion treatment + segmented heat treatment to prepare lithium nickel manganese oxide, but the oxygen content of the segmented heat treatment is kept fixed, and the specific operation is as follows:

[0092] 1.943 g of LiOH·H2O, 4.48 g of NiO and 9.67 g of MnCO3 were weighed and placed in a ball mill jar, ball milling beads were added to a ball-to-material ratio of 6:1, and ball milling was performed at a speed of 400 rpm for 12 hours to obtain a uniformly mixed raw material powder.

[0093] The obtained powder mixture was placed in an atmosphere box furnace, heated to 800°C at 5°C / min in an oxygen-containing mixed gas atmosphere with an oxygen content of 10 vol%, and kept warm for 24 hours, then cooled to 750°C and kept warm for 6 hours, and naturally cooled to room temperature to obtain LiNi 0.5 Mn 1.5 O4 material.

[0094] The LiNi obtained in this comparative example 0.5 Mn 1.5 The O4 material was tested by XRD, and the results were as follows Figure 14 As shown in the figure, it can be seen that the diffraction characteristic peaks appearing in the sample are LiNi 0.5 Mn 1.5 O4, but its peak intensity is lower than that of Example 1, which indicates that the LiNi prepared in Comparative Example 3 0.5 Mn 1.5 The crystallinity of the O4 material is worse than that of Example 1, which has a certain negative impact on the electrochemical performance.

[0095] Comparative Example 4

[0096] This comparative example adopts a solid phase dispersion treatment + staged heat treatment method to prepare lithium nickel manganese oxide, but the change in the oxygen content of the atmosphere in the staged heat treatment is opposite to that required by the present invention. The specific operation is as follows:

[0097] Weigh 1.943 g of Li2O, 4.48 g of NiO, and 6.67 g of MnO2 into a ball mill, add ball mill beads to a ball-to-material ratio of 6:1, and ball mill at 400 rpm for 12 h to obtain uniformly mixed raw material powders.

[0098] The obtained powder mixture was placed in an atmosphere box furnace, heated to 900°C at 5°C / min under pure oxygen and kept warm for 8 hours, then introduced with argon and cooled to 700°C and kept warm for 12 hours, and then cooled naturally to room temperature to obtain lithium nickel manganese oxide material.

[0099] The LiNi obtained in this comparative example 0.5 Mn 1.5 The O4 material was tested by XRD, and the results were as follows Figure 15 As shown in the figure, it can be seen that the diffraction characteristic peaks appearing in the sample are LiNi 0.5 Mn 1.5 The X-ray diffraction peak of O4 has a very low peak intensity, which indicates that the LiNi prepared in Comparative Example 4 is 0.5 Mn 1.5 The crystallinity of O4 material is extremely poor, which has a serious negative impact on the electrochemical performance.

[0100] The above embodiments are only examples. For example, when the lithium nickel manganese oxide material (such as LiNi0.5 Mn 1.5 When the electrode sheet is made using the active material (Li4Mn5O12 material) as the active material, the active material mass ratio in the electrode sheet can be 80-95%, the conductive agent mass ratio can be 3-10%, and the binder mass ratio can be 2-10%, and the electrode sheet surface loading can be 1-15 mg / cm 2 The stirring speed of the ball mill, the blender, the pulverizer, and the air mill can be 200-30000 rpm (of course, the actual speed used cannot exceed the rated speed of the equipment), and the time can be 30 seconds to 12 hours; the higher the stirring speed, the shorter the processing time that can be used. In addition, the stepwise heat treatment can be performed in an atmosphere tube furnace, an atmosphere box furnace, a muffle furnace, and all other equipment that can be used to perform high-temperature heat treatment by introducing an oxygen-containing gas. In addition, the lithium source, the nickel source, and the manganese source can be solid-phase raw materials, and can be corresponding inorganic salts, oxides, hydroxides, or corresponding organic salts (such as formate, acetate, oxalate, etc.).

[0101] Those skilled in the art will readily understand that the above description is only preferred embodiments of the present application and is not intended to limit the present application, and any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a single crystal high-crystalline lithium nickel manganese oxide material, characterized in that: The steps include: (1) Using solid lithium-containing compounds as lithium source, solid nickel-containing compounds as nickel source, and solid manganese-containing compounds as manganese source, according to the lithium nickel manganate material LiNi x Mn (2-x) O y A lithium source, a nickel source, and a manganese source are mixed in a nominal chemical dosage ratio of lithium, nickel, and manganese, and then solid-phase dispersed and deagglomerated to obtain dispersed particles having a particle size of less than 50 microns to obtain a raw material powder mixture; Among them, 0.1≤x≤0.5, 3.3≤y≤4; (2) subjecting the raw material powder mixture obtained in step (1) to a staged heat treatment in an oxygen-containing atmosphere to prepare a single crystal high-crystalline lithium nickel manganese oxide material; The staged heat treatment adopts two insulation stages, one after the other. The two insulation stages are respectively referred to as the first insulation stage and the second insulation stage in order. The temperature of the first insulation stage is higher than that of the second insulation stage, and the oxygen content of the oxygen-containing atmosphere used in the first insulation stage is lower than that of the oxygen-containing atmosphere used in the second insulation stage. The first insulation stage is used for crystal growth, and the second insulation stage is used for reducing crystal defects. Wherein, in the step (1), the equipment used for the solid phase dispersion deagglomeration treatment includes at least one of a ball mill, a stirrer, and an air mill; When using a ball mill, the ball-to-material weight ratio is 2:1-10:1, the rotation speed is 200-400 rpm, and the processing time is 6-12 hours; When a mixer or air mill is used, the rotation speed is 1000-25000 rpm and the processing time is 30 seconds to 1 hour; In the step (2), the first insulation stage has an insulation temperature of 800-1100°C and an insulation time of 6-24 hours; The second insulation stage has an insulation temperature of 650-750° C. and an insulation time of 12-48 hours.

2. The preparation method according to claim 1, wherein In the step (2), the heating rate used to heat the temperature to the first insulation stage is 0.5-5°C per minute.

3. The preparation method according to claim 1, wherein In the step (1), the solid lithium-containing compound is selected from lithium carbonate, lithium hydroxide, lithium oxide, lithium nitrate, and organic lithium compounds; The solid nickel-containing compound is selected from nickel carbonate, nickelous oxide, nickel trioxide, nickel hydroxide, nickel nitrate, and organic nickel compounds; The solid manganese-containing compound is selected from manganese carbonate, manganese trimanganese tetraoxide, manganese dioxide, manganese hydroxide, manganese nitrate, and organic manganese compounds.

4. The preparation method according to claim 1, wherein In the step (2), the oxygen-containing atmosphere includes pure oxygen or an oxygen-containing mixed gas.

5. The preparation method according to claim 4, wherein: The oxygen-containing mixed gas is air.

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