Lithium-rich manganese-based precursor, lithium-rich manganese-based positive electrode material and lithium ion secondary battery
By using a core-shell structured carbonate-hydroxide composite precursor to prepare lithium-rich manganese-based cathode materials, the problems of low compaction density and poor electrochemical performance were solved, and high energy density and good electrochemical performance were achieved.
Patent Information
- Application Number
- CN202410960356.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-17
- Publication Date
- 2026-01-20
AI Technical Summary
In existing technologies, lithium-rich manganese-based cathode materials have low compaction density, resulting in insufficient energy density and poor electrochemical performance, making it difficult to effectively utilize them in full-cell systems.
A core-shell carbonate-hydroxide composite precursor with hydroxide as the core and carbonate as the shell was used to prepare lithium-rich manganese-based cathode material by high-temperature sintering, thereby improving the material's compaction density and lithium-ion transport performance.
This improved the compaction density and discharge capacity of lithium-rich manganese-based cathode materials, enhancing the energy density utilization and capacity retention of the materials in the full battery system.
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Figure CN121361847A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of lithium batteries, and in particular to a lithium-rich manganese-based precursor, a lithium-rich manganese-based positive electrode material and a lithium ion secondary battery. BACKGROUND
[0002] Co-precipitation is the best choice for large-scale preparation of positive electrode precursors. From the type of precipitants, co-precipitation mainly has two categories of carbonates and hydroxides. Due to the high content of manganese in the lithium-rich manganese-based precursor material, only using hydroxide co-precipitation process to prepare the precursor material will cause the precursor material to nucleate too fast in the precipitation process, the shape is not easy to control, resulting in poor morphology of the precursor material, so that the specific capacity of the finally prepared lithium-rich manganese-based positive electrode material is relatively low. The precursor of the lithium-rich manganese-based positive electrode material usually adopts the synthesis route of carbonates, however, the lithium-rich manganese-based positive electrode material prepared by the carbonates route exhibits a relatively low tap density in the subsequent electrode sheet preparation process, usually less than 2.8 g / cm 3 , which seriously restricts the energy density of the lithium-rich manganese-based positive electrode material in the full battery system. The lithium-rich manganese-based positive electrode material mainly faces the problems of serious energy density recession caused by voltage recession and low tap density in the commercialization process. SUMMARY
[0003] The present application aims to overcome the above-mentioned problems existing in the prior art, and provides a lithium-rich manganese-based precursor, a lithium-rich manganese-based positive electrode material prepared from the lithium-rich manganese-based precursor and a lithium ion secondary battery comprising the lithium-rich manganese-based positive electrode material. The lithium-rich manganese-based precursor is a carbonate-hydroxide composite precursor with a core-shell structure. Compared with the lithium-rich manganese-based material prepared from a carbonate precursor, the lithium-rich manganese-based material prepared from the composite precursor of the present application has a higher tap density, which improves the energy density of the lithium-rich manganese-based positive electrode material in the full battery system. Compared with the lithium-rich manganese-based material prepared from a hydroxide precursor, the lithium ion secondary battery prepared from the composite precursor of the present application has a higher discharge capacity and capacity retention rate.
[0004] To achieve the above-mentioned purpose, the first aspect of the present application provides a lithium-rich manganese-based precursor, the chemical formula of which is a[Ni x1 Co y1 Mn z1 CO3]·b[Ni x2 Co y2 Mn z2 (OH)2], wherein 0.1 < x1+x2 < 0.4, 0 ≤ y1+y2 < 0.2, 0.5 < z1 < 1, 0.5 < z2 < 1, 0 < a < 1, 0 < b < 1; the lithium-rich manganese-based precursor comprises a hydroxide-carbonate composite core-shell structure, the hydroxide Ni x2 Co y2Mn z2 (OH)2 as a core layer, and carbonate Ni x1 Co y1 Mn z1 CO3 as a shell layer;
[0005] The lithium-rich manganese-based precursor has a 001 crystal face diffraction peak at 2theta = 18-20°.
[0006] The lithium-rich manganese-based precursor has a 104 crystal face diffraction peak at 2theta = 30-32°.
[0007] The second aspect of the present application provides a lithium-rich manganese-based positive electrode material, which is obtained by high-temperature sintering reaction of the lithium-rich manganese-based precursor of the first aspect of the present application and a lithium source.
[0008] The third aspect of the present application provides a lithium-rich manganese-based positive electrode material, which has a molecular formula of Li 1+δ Ni x Co y Mn z O2, wherein 0 < delta < 0.5, 0 < x < 0.4, 0 <= y < 0.3, and z > 0.5; and the lithium-rich manganese-based positive electrode material comprises a core-shell structure.
[0009] The fourth aspect of the present application provides a lithium ion secondary battery comprising the lithium-rich manganese-based positive electrode material of the second aspect of the present application or the lithium-rich manganese-based positive electrode material of the third aspect of the present application.
[0010] The technical scheme of the present application has the following beneficial effects:
[0011] The lithium-rich manganese-based precursor provided by the present application is a carbonate-hydroxide composite precursor with a core-shell structure. Compared with the lithium-rich manganese-based material prepared by a carbonate precursor, the lithium-rich manganese-based material prepared by the composite precursor of the present application has a higher compaction density, which improves the energy density of the lithium-rich manganese-based positive electrode material in the full battery system. Compared with the lithium-rich manganese-based material prepared by a hydroxide precursor, the lithium ion secondary battery prepared by the composite precursor of the present application has a higher discharge capacity and capacity retention rate.
[0012] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values should be interpreted as approximately between the stated values. Values between the endpoints of the ranges and values within the stated ranges are also contemplated as being within the scope of the ranges. In this document, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or variations thereof do not indicate a quantity of integers; a composition of matter; a step or steps of a process; an interaction between components; or a description applicable to, consisting of or consisting essentially of, but rather specifies occurrences of the following features and rules out the presence of other features or steps. BRIEF DESCRIPTION OF DRAWINGS
[0013] Figure 1 SEM image of the lithium-rich manganese-based composite precursor obtained in Example 1-1 is shown.
[0014] Figure 2 XRD image of the lithium-rich manganese-based composite precursor obtained in Example 1-1 is shown.
[0015] Figure 3 XRD image of the lithium-rich manganese-based composite precursor obtained in Comparative Example 1 is shown.
[0016] Figure 4 SEM image of the lithium-rich manganese-based positive electrode material obtained in Example 1-1 is shown.
[0017] Figure 5 Energy density cycle performance curve of the lithium-rich manganese-based positive electrode material obtained in Example 1-1 is shown.
[0018] Figure 6 Concentration change curve of the ammonia ion in the reaction system during the preparation process of Example 1-1 is shown.
[0019] Figure 7 Concentration change curve of the ammonia ion in the reaction system during the preparation process of Comparative Example 1 is shown. DETAILED DESCRIPTION
[0020] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.
[0021] Unless otherwise defined, all scientific and technical terms used in the present application have the same meanings as commonly understood by one of ordinary skill in the art to which the present application pertains.
[0022] The hydroxide precursor makes the material more resistant to compaction due to the large sheet layer characteristics of the primary particles, and the compaction density is larger, but the too large primary particles of the material increase the Li transmission path on the active surface of the lithium transmission, so that the electrochemical performance of the lithium-rich manganese-based material is poor. Although the decomposition of the carbonate precursor is easy to form spherical nanoparticles, the diffusion path of the Li ion of the nano-ion is shorter, but the lithium-rich manganese-based positive electrode material prepared by the carbonate precursor shows a lower compaction density in the subsequent electrode sheet preparation process, which restricts the energy density of the lithium-rich manganese-based positive electrode material in the full battery system.
[0023] The first aspect of the present application provides a lithium-rich manganese-based precursor, the chemical formula of the lithium-rich manganese-based precursor is a[Ni x1 Co y1 Mn z1 CO3]·b[Ni x2 Co y2 Mnz2 (OH)2], wherein 0.1 < x1+x2 < 0.4, 0≤y1+y2<0.2, 0.5<z1<1, 0.5<z2<1, 0<a<1, 0<b<1; the chemical formula of the lithium-rich manganese-based precursor satisfies the chemical valence balance, for example, a+b = 1;
[0024] The lithium-rich manganese-based precursor comprises a hydroxide-carbonate composite core-shell structure, the hydroxide Ni x2 Co y2 Mn z2 (OH)2 is a core layer, and the carbonate Ni x1 Co y1 Mn z1 CO3 is a shell layer;
[0025] The lithium-rich manganese-based precursor has a 001 crystal face diffraction peak at 2θ = 18-20°;
[0026] The lithium-rich manganese-based precursor has a 104 crystal face diffraction peak at 2θ = 30-32°.
[0027] In the present application, the lithium-rich manganese-based precursor is a carbonate-hydroxide composite precursor, the 001 crystal face diffraction peak at 2θ = 18-20° is the main peak of the crystalline hydroxide precursor in space group, the 104 crystal face diffraction peak at 2θ = 30-32° is the main peak of the carbonate precursor in space group, is the typical space group structure of the crystalline hydroxide precursor precipitation, The space group appears 104 crystal face diffraction peak, which proves that the lithium-rich manganese-based precursor of the application is a carbonate-hydroxide composite precursor. On the one hand, the hydroxide in the core layer has a sheet structure, has a larger porosity structure, and presents a three-dimensional network stacking structure. In the process of being extruded by external force, the high porosity provides the space required for deformation, and the three-dimensional network stacking structure inside can disperse stress in all directions under external force to provide stronger support properties and compression resistance, thereby avoiding the breakage of particles under external force, relieving the micro stress suffered by the lithium-rich manganese-based material obtained from the composite precursor during electrochemical cycling, avoiding the breakage of particles of the lithium-rich manganese-based material during long cycling, improving the cycling stability of the material, and reducing the energy density decay of the battery.
[0028] In some embodiments, the ratio of the intensity of the 104 crystal face diffraction peak to the intensity of the 001 crystal face diffraction peak of the lithium-rich manganese-based precursor satisfies: 0.05≤I 104 / I 001 ≤1.0, for example, the ratio can be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, preferably 0.1≤I 104 / I 001 ≤0.8.
[0029] On the basis that the lithium-rich manganese-based carbonate-hydroxide composite precursor has the above-mentioned shell structure and characteristic peaks, the ratio of the intensity of the 104 crystal face diffraction peak to the intensity of the 001 crystal face diffraction peak is adjusted, which is equivalent to adjusting the thickness ratio of the core layer to the shell layer in the composite precursor. Because the carbonate and the hydroxide belong to different space groups and have different symmetries, the XRD diffraction peak intensity does not interfere with each other, so the thickness ratio of the core layer to the shell layer can be determined by the peak intensity ratio. When the peak intensity ratio is in the above-mentioned range, the lithium-rich manganese-based carbonate-hydroxide composite precursor can have both physical properties and electrochemical properties, so that the composite precursor has both high compaction density and high lithium ion transport performance and high capacity.
[0030] In some embodiments, the half peak width FWHM(104) of the 104 crystal face diffraction peak of the lithium-rich manganese-based precursor is 0.15-0.3°, that is, the carbonate precursor of the shell layer in the composite precursor has a half peak width FWHM(104) of 0.15-0.3°. The half-peak width of the main peak of the space group can be 0.15°, 0.18°, 0.20°, 0.22°, 0.25°, 0.28°, 0.30°.
[0031] In some embodiments, the lithium-rich manganese-based precursor has a half-peak width FWHM(001) of the 001 crystal plane diffraction peak of 0.5-1.0°, i.e., the crystalline hydroxide precursor in the core layer of the composite precursor has a half-peak width FWHM(001) of the 001 crystal plane diffraction peak of 0.5-1.0°. The half-peak width of the main peak of the space group can be 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, 1.0°.
[0032] On the basis of the lithium-rich manganese-based carbonate-hydroxide composite precursor having the above-mentioned shell structure and characteristic peaks, further adjusting the half-peak width of the 104 crystal plane diffraction peak and the 001 crystal plane diffraction peak can further improve the crystallinity of the composite precursor, and the impurities and defects are less, thereby reducing the impurities that can be introduced in the preparation process of the lithium-rich manganese-based positive electrode material, improving the purity of the lithium-rich manganese-based positive electrode material, and helping to improve the stability of the positive electrode material, reduce the particle breakage caused by the structural change in the charging and discharging process, and further reduce the energy density decay of the battery.
[0033] In some embodiments, the lithium-rich manganese-based precursor has a 101 crystal plane diffraction peak at 2θ = 38-40°, i.e., the crystalline hydroxide precursor in the core layer of the composite precursor has a 101 crystal plane diffraction peak at 2θ = 38-40°. The space group also includes a secondary strong peak of the 101 crystal plane.
[0034] In some embodiments, the lithium-rich manganese-based precursor has a 102 crystal plane diffraction peak at 2θ = 24-25°, i.e., the carbonate precursor in the shell layer of the composite precursor has a 102 crystal plane diffraction peak at 2θ = 24-25°. The space group also includes a secondary strong peak of the 102 crystal plane.
[0035] The petal-shaped hydroxide inner core in the composite precursor mainly plays a structural support role, but too large a sheet layer and too much hydroxide primary particle can cause poor electrochemical performance of the material, which mainly affects the release of capacity in Li2MnO3; however, too few sheet layers and too few contents of hydroxide primary particles are difficult to resist the damage of external pressure to the particles themselves, and therefore the proportion of the sheet structure of the hydroxide inner core should be limited. On the basis of the lithium-rich manganese-based carbonate-hydroxide composite precursor having the above-mentioned shell structure and characteristic peaks, further adjusting the 104 crystal plane diffraction peak and the 101 crystal plane diffraction peak of the composite precursor can further improve the electrochemical performance and structural stability of the composite precursor. The space group and The secondary strong peak position of the space group can make the content of the hydroxide inner core and the hydroxide primary particle be in a suitable range, improve the electrochemical performance and structural stability of the composite precursor, and enable the synthesized positive electrode material to have the advantages of high compaction density and good structural stability.
[0036] In some embodiments, the core layer comprises petal-shaped particles, and the shell layer comprises fiber bundles. Preferably, the petal-shaped particles and fiber bundles are nanoscale.
[0037] In some implementations, such as Figure 1 As shown, the core layer comprises a three-dimensional network stacked structure formed by nano-petal-shaped primary particles, and the shell layer comprises a fiber bundle structure formed by the stacking of nanoparticles. Based on the aforementioned shell structure and characteristic peaks of the lithium-rich manganese-based carbonate-hydroxide composite precursor, the structures of the core and shell layers are further adjusted. The three-dimensional network stacked structure of the core layer helps alleviate external compressive stress, reduces particle breakage, and improves the cycling stability of the material. The fiber bundle nano-ions of the shell layer help provide a larger specific surface area, improving the uniformity of mixing with the lithium source and shortening the Li-Li cycle time. + Diffusion pathways enhance the rate performance of lithium-rich manganese-based materials.
[0038] In some embodiments, the petal-shaped particles have a thickness of 100nm-500nm and a diameter of 200nm-1000nm. In some embodiments, the fiber bundle has a length of 10nm-200nm and a top diameter of 50nm-500nm.
[0039] Based on the core-shell structure and characteristic peaks of the lithium-rich manganese-based carbonate-hydroxide composite precursor, the structure of the core layer as a three-dimensional network stacked structure and the shell layer as a fiber bundle structure are adjusted. Further adjustments to the thickness and diameter of the nano-petal-shaped primary particles in the core layer reduce the Li transport path, improve the lithium-ion transport performance of the lithium-rich manganese-based material, disperse lattice pressure during long cycles, and effectively disperse external pressure to improve the cycle life of the lithium-rich manganese-based material. Simultaneously, adjusting the length of the fiber bundles in the shell layer allows the nanofiber bundles to form spherical primary particles during cathode material preparation. Appropriate fiber bundle lengths ensure that the particle size of the spherical particles is within a suitable range, increasing the specific surface area of the spherical particles. This is beneficial for increasing the wettability of the lithium-rich manganese-based cathode material at the electrolyte interface, reducing the Li-ion diffusion barrier on the surface, and enhancing the electrochemical activity of the lithium-rich manganese-based cathode material.
[0040] In some embodiments, the thickness of the shell layer in the lithium-rich manganese-based precursor is 20% to 80%, for example, the thickness percentage can be 20%, 30%, 40%, 50%, 60%, 70%, or 80%.
[0041] On the basis that the lithium-rich manganese-based carbonate-hydroxide composite precursor has the shell structure and characteristic peaks described above, while the core layer is limited to a three-dimensional network stacking structure and the shell layer is limited to a fiber bundle structure, and the thickness ratio of the shell layer is adjusted to be within the above range, the appropriate proportion of carbonate and the network structure of the hydroxide core inside can improve the stability of the composite precursor, so that the composite precursor has both physical properties and electrochemical properties. The composite precursor has a high compaction density and also has good lithium ion transport performance, improving the stability of the precursor material while improving its morphology.
[0042] In some embodiments, the thickness of the core layer is 0.5 μm to 8 μm, for example, it can be 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, preferably 1 μm to 5 μm.
[0043] In some embodiments, the thickness of the shell layer is 0.5 μm to 10 μm, for example, it can be 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, preferably 1 μm to 8 μm.
[0044] A too large core layer thickness ratio can better improve the compaction density of the positive electrode material, but can significantly reduce the electrochemical performance of the material. A too small core layer thickness ratio does not significantly improve the mechanical properties of the positive electrode material. On the basis that the lithium-rich manganese-based carbonate-hydroxide composite precursor has the shell structure and characteristic peaks described above, while the core layer is limited to a three-dimensional network stacking structure and the shell layer is limited to a fiber bundle structure, and the thickness ratio of the shell layer is adjusted to be within the above range, further adjusting the thickness of the core layer and the thickness of the shell layer within the above range can better improve the compaction density of the positive electrode material, so that the positive electrode material can have both electrochemical and mechanical performance stability.
[0045] In some embodiments, the precursor satisfies at least one of the following conditions:
[0046] (i) the compaction density is 2.7 g / cm 3 - 3.1 g / cm 3 ;
[0047] (ii) the tap density is 1.0 g / cm 3 - 2.7 g / cm 3 ;
[0048] (iii) the specific surface area is 50 m 2 / g to 100 m 2 / g;
[0049] (iv) (Dv90-Dv10) / Dv50 = 0.5-1.8, Dv10 is 0.5-8 μm, Dv50 is 3-20 μm, Dv90 is 8-25 μm;
[0050] (v) S content is lower than 900 ppm.
[0051] (i) The tap density of the lithium-rich manganese-based precursor can be, for example, 2.7 g / cm 3 , 2.8 g / cm 3 , 2.9 g / cm 3 , 3.0 g / cm 3 , 3.1 g / cm 3 . On the basis of the lithium-rich manganese-based carbonate-hydroxide composite precursor having the shell structure and the characteristic peaks described above, adjusting the tap density of the lithium-rich manganese-based precursor in the range described above can improve the tap density of the lithium-rich manganese-based positive electrode material prepared from the lithium-rich manganese-based precursor, and is conducive to realizing the scale application of the lithium-rich manganese-based material.
[0052] (ii) The tap density of the lithium-rich manganese-based precursor can be, for example, 1.0 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 , 1.3 g / cm 3 , 1.4 g / cm 3 , 2.5 g / cm 3 , 1.6 g / cm 3 , 2.2 g / cm 3 , 2.5 g / cm 3 , 2.6 g / cm 3 , 2.7 g / cm 3 . A lower tap density (for example, lower than 1.0 g / cm 3 ) means that the particle consistency of the lithium-rich manganese-based precursor is poor, and a higher tap density (for example, higher than 2.7 g / cm 3 ) is difficult to achieve by the current process. On the basis of the lithium-rich manganese-based carbonate-hydroxide composite precursor having the shell structure and the characteristic peaks described above, adjusting the tap density of the lithium-rich manganese-based precursor in the range described above can well balance the tap density and the energy density.
[0053] (iii) The specific surface area of the lithium-rich manganese-based precursor can be, for example, 50 m 2 / g, 60 m 2 / g, 70 m 2 / g, 80 m 2 / g, 90 m 2 / g, 100 m 2g. On the basis of the above-mentioned shell structure and characteristic peaks of the lithium-rich manganese-based carbonate-hydroxide composite precursor, when the specific surface area of the composite precursor is adjusted to be within the above-mentioned range, the specific surface area is relatively large, which can make the specific surface area of the prepared lithium-rich manganese-based positive electrode material also relatively large, so that the lithium-rich manganese-based positive electrode material is more fully in contact with the electrolyte, the lithium ion diffusion efficiency is improved, and the energy density and capacity of the battery are improved.
[0054] (iv) The Span of the lithium-rich manganese-based precursor is 0.5-1.8, for example, the ratio can be 0.5, 0.6, 0.8, 1.0, 1.2, 1.4, 1.5, 1.8, and preferably the Span is 0.8-1.5. Preferably, Dv10 is 0.5-8 μm, Dv50 is 3-20 μm, and Dv90 is 8-25 μm. On the basis of the above-mentioned shell structure and characteristic peaks of the lithium-rich manganese-based carbonate-hydroxide composite precursor, when the particle size distribution width and particle size of the lithium-rich manganese-based positive electrode material meet the above-mentioned conditions, the consistency of the composite precursor particles is better, the composite precursor has more excellent compaction characteristics, and thus the compaction density of the lithium-rich manganese-based positive electrode material is improved, and the energy density of the lithium-rich manganese-based positive electrode material in the full battery system is improved.
[0055] (v) The S content in the lithium-rich manganese-based precursor is less than 900 ppm. On the basis of the above-mentioned shell structure and characteristic peaks of the lithium-rich manganese-based carbonate-hydroxide composite precursor, adjusting the low S content in the composite precursor can avoid the generation of waste gas in the subsequent sintering process and reduce environmental pollution.
[0056] The application also provides a preparation method of the above-mentioned lithium-rich manganese-based precursor, comprising:
[0057] (1) preparing a mixed salt solution A containing Ni, Co and Mn;
[0058] (2) preparing a mixed alkali solution containing carbonate and hydroxide as a precipitant solution B;
[0059] (3) preparing a complexing agent solution C containing ammonia ions;
[0060] (4) preparing a surfactant solution and adding it to the bottom liquid in the reaction kettle;
[0061] (5) adding the alkali solution to the reaction kettle to adjust the pH of the bottom liquid to be alkaline;
[0062] (6) adding the salt solution A, the precipitant solution B and the complexing agent solution C to the reaction kettle at a certain rate, and linearly reducing the flow rate of the complexing agent solution C.
[0063] In some embodiments, in step (1), the total concentration of the salt solution A is 0.5-2 mol / L. The soluble Ni salt includes one of nickel sulfate, nickel chloride, nickel nitrate, and nickel acetate; the soluble Co salt includes one of cobalt sulfate, cobalt chloride, cobalt nitrate, and cobalt acetate; and the soluble Mn salt includes one of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride.
[0064] In some embodiments, in step (2), the total concentration of the precipitant solution B is 1-8 mol / L, and the molar ratio of carbonate is 70-95%. Adjusting the molar ratio of carbonate in the precipitant solution B is conducive to adjusting the CO3 2- The concentration of OH- can be adjusted, which can avoid the formation of hydroxide-carbonate composite precipitation caused by excessive concentration of OH-, and is conducive to obtaining the lithium-rich manganese-based precursor with a core-shell structure of hydroxide-carbonate composite.
[0065] In some embodiments, in step (2), the precipitant includes at least one of sodium carbonate, potassium hydroxide, lithium hydroxide, sodium bicarbonate, ammonium bicarbonate, and ammonium carbonate.
[0066] In some embodiments, in step (3), the total concentration of the ammonia radical ion is 0.1-2 mol / L. The complexing agent solution containing ammonia radical includes one or two of ammonium sulfate, ammonium bicarbonate, ammonia water, ammonium oxalate, and ammonium carbonate.
[0067] In some embodiments, in step (4), the concentration of the surfactant solution is 0.01-0.2 mol / L. The surfactant includes one or two of citric acid, polypyrrole, carboxymethyl cellulose, ethylene glycol, sodium dodecyl sulfonate, sodium citrate, sodium polystyrene sulfonate, and monolauryl phospholipid. The solubility product (Ksp) of the hydroxide is smaller than that of the carbonate, which makes the hydroxide preferentially nucleate to the carbonate. The pre-addition of the surfactant to the bottom solution can avoid the agglomeration of the hydroxide nucleus, so that the particle size distribution of the composite precursor is narrower and more uniform, and the composite precursor has more excellent compaction characteristics, thereby improving the compaction density of the lithium-rich manganese-based positive electrode material.
[0068] In some embodiments, the purpose of step (5) is to adjust the pH of the bottom solution in the reaction kettle to 10-12 to maintain an alkaline environment of the bottom solution. For example, the concentration of the alkali solution can be 0.001-0.5 mol / L.
[0069] In some embodiments, in step (6), the flow rate of the salt solution A is 2-50 L / h, the flow rate of the alkali solution B is 2-50 L / h, and the flow rate of the complexing agent solution C is linearly reduced from an initial 1-5 L / h to 0.5 L / h. Preferably, the linear coefficient of the reduction of the complexing agent solution C is -0.01 to -0.3.
[0070] The linear change of the amount of ammonia in the solution system is a key link for obtaining the composite precursor of the application by one-step method. The ammonia radical mainly balances the nucleation and growth rate through complexation. In the hydroxide precipitation system, the hydroxide has a small solubility product, so it is less sensitive to the amount of ammonia. In the carbonate system, it is just the opposite. Therefore, by linearly changing the amount of ammonia, the volume change of the total solution is superimposed, and then the nucleation and growth rate in the reaction kettle is controlled. In the early stage of the reaction, the concentration of the ammonia radical ion is large, which can better avoid the precipitation of the carbonate and is conducive to the formation of the inner core of the hydroxide. As the reaction proceeds, the amount of ammonia radical gradually decreases, which is conducive to inducing the precipitation of the carbonate to form a shell, and finally the hydroxide-carbonate composite precursor is obtained.
[0071] The second aspect of the application provides a lithium-rich manganese-based positive electrode material, which is obtained by high-temperature sintering reaction of the lithium-rich manganese-based precursor of the first aspect of the application and a lithium source.
[0072] In some embodiments, the molar ratio of lithium element in the lithium source to transition metal element in the lithium-rich manganese-based precursor is (1-2):1, which can be 1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2.0:1. If the molar ratio of lithium element to transition metal element is too high (for example, greater than 2:1), the excessive Li content cannot effectively enter the layered lattice, which will cause the surface residual alkali content to increase sharply, and thus cause gas production and battery bulging during the charging and discharging process, which will seriously affect the performance and safety of the battery. In addition, if the molar ratio of lithium element to transition metal element is too low (for example, less than 1:1), the low Li content cannot effectively form a layered phase, mainly forming a composite phase of spinel and layered, which will seriously reduce the specific capacity of the material and thus reduce the energy density of the material.
[0073] In some embodiments, the lithium-rich manganese-based precursor and the lithium source are subjected to high-temperature sintering to generate the lithium-rich manganese-based positive electrode material. The temperature of the high-temperature sintering reaction is 700-1000℃, for example, the temperature can be 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, or 1000℃, preferably 800-900℃. The time of the high-temperature sintering reaction is 8-30h, preferably 10-20h.
[0074] In some embodiments, the lithium source is one or more of lithium oxide, lithium nitrate, lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium chloride, and lithium peroxide.
[0075] A third aspect of this invention provides a lithium-rich manganese-based cathode material, wherein the molecular formula of the lithium-rich manganese-based cathode material is Li. 1+δ Ni x Co y Mn z O2, where 0 < δ < 0.5, 0 <x<0.4,0≤y<0.3,z> 0.5. In the lithium-rich manganese-based chemical formula, δ, x, y, and z satisfy valence equilibrium. Preferably, the core layer comprises plate-like particles, and / or the shell layer comprises primary particles.
[0076] The lithium-rich manganese-based cathode material of this invention is obtained by high-temperature sintering of a hydroxide-carbonate composite precursor with a core-shell structure, such as... Figure 4 As shown, lithium-rich manganese-based cathode materials also possess a core-shell structure. The core layer comprises a three-dimensional network structure of stacked sheet-like particles, while the shell layer comprises a structure of stacked spherical primary particles. The relatively loose three-dimensional network structure of stacked sheet-like particles helps alleviate external stress, improves the compressive strength of the lithium-rich manganese-based cathode material, and helps maintain its integrity under high pressure conditions. The structure of stacked spherical primary particles in the shell layer increases the specific surface area of the lithium-rich manganese-based cathode material, enhances the wettability of the interface between the lithium-rich manganese-based cathode material and the electrolyte, and reduces the surface Li-ion diffusion barrier, which is beneficial to improving the electrochemical activity of the lithium-rich manganese-based cathode material. In summary, in lithium-rich manganese-based cathode materials, the three-dimensional sheet-like stacking structure of the core layer (i.e., the three-dimensional network structure of stacked sheet-like particles) is beneficial to improving the physical properties of the lithium-rich manganese-based cathode material, while the spherical nanoparticle stacking structure of the shell layer is beneficial to the electrochemical performance of the lithium-rich manganese-based cathode material, thus comprehensively improving the physicochemical properties of the lithium-rich manganese-based cathode material.
[0077] In some embodiments, the thickness of the sheet-like particles is 200nm-500nm, and the diameter is 1μm-5μm; and / or, the Dv50 of the primary particles (spherical or near-spherical) is 200nm-500nm. Based on the core-shell structure of the lithium-rich manganese-based cathode material, adjusting the thickness and diameter of the sheet-like particles in the core layer within the above range can reduce the Li transport path, improve the lithium-ion transport performance of the lithium-rich manganese-based material, and enhance the physical properties of the lithium-rich manganese-based cathode material. Simultaneously, adjusting the Dv50 of the primary particles within the above range can further increase the specific surface area of the lithium-rich manganese-based material, which is beneficial for increasing the wettability of the lithium-rich manganese-based cathode material at the electrolyte interface, reducing the Li-ion diffusion barrier on the surface, and enhancing the electrochemical activity of the lithium-rich manganese-based cathode material.
[0078] In some embodiments, the lithium-rich manganese-based positive electrode material has an amorphous diffraction peak of 020 crystal face (main diffraction) at 2θ = 20-25°. This amorphous diffraction peak (bulging diffraction peak) is a typical characteristic peak of Li2MnO3 and can also be considered as a typical characteristic peak of lithium-rich material, i.e., the presence of the amorphous diffraction peak proves that the lithium-rich manganese-based positive electrode material is provided.
[0079] In some embodiments, the ratio of the diffraction peak intensity of the 020 crystal face to the diffraction peak intensity of the 003 crystal face of the lithium-rich manganese-based positive electrode material satisfies: I 020 / I 003 ≤0.01, and the lithium-rich manganese-based positive electrode material has a diffraction peak of 003 crystal face at 2θ = 18-19°. A weaker bulging diffraction peak means that the crystallinity of Li2MnO3 is poorer, and more disordered Li2MnO3 means better lattice oxygen activity and higher capacity. Thus, on the basis of the lithium-rich manganese-based positive electrode material having the above core-shell structure, adjusting the ratio of the main peak intensity of the bulging diffraction peak to the main peak intensity of the 003 crystal face to be less than 0.01 can improve the lattice oxygen activity of the lithium-rich manganese-based positive electrode material and better improve the capacity of the lithium-rich manganese-based positive electrode material.
[0080] In some embodiments, the lithium-rich manganese-based material has a first diffraction peak at 2θ = 18-19°, and the peak intensity is denoted as I 003 , the lithium-rich manganese-based material has a second diffraction peak at 2θ = 44-46°, and the peak intensity is denoted as I 104 , and the ratio of I 003 to I 104 satisfies: 1.5≤I 003 / I 104 ≤2.2, for example, can be 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, preferably 1.6≤I 003 / I 104 ≤2.0. Preferably, the half-peak width FWHM (003) of the first diffraction peak is 0.01-0.02°. The first diffraction peak corresponds to the (003) crystal face, and the second diffraction peak corresponds to the (104) crystal face. On the basis of the lithium-rich manganese-based positive electrode material having the above core-shell structure, adjusting the ratio of I 003 / I 104 and the half-peak width of the first diffraction peak in the above range can improve the crystallinity of the lithium-rich manganese-based positive electrode material, better the stability of the layered structure, improve the cycle stability of the lithium-rich manganese-based material, and further improve the capacity of the lithium-rich manganese-based positive electrode material. However, too high a ratio of I 003 / I 104 may reduce the Li ion channel due to the preferred growth of the 003 crystal face, which is not conducive to the capacity of the lithium-rich manganese-based positive electrode material.
[0081] In some embodiments, in the DQ / DV curve of the lithium-rich manganese-based material, the peak intensity in the range of 3.6V-4.0V is denoted as I a , the peak intensity in the range of 4.5V-4.6V is denoted as I b , and the ratio of I a and I b satisfies: 1.4≤I a / I b ≤2.8, for example, can be 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, preferably 1.5≤I a / I b ≤2.5. The oxidation peak of Ni / Co appears in the range of 3.6-4.0V, and the oxidation peak of lattice oxygen appears in the range of 4.5-4.6V (typical characteristic sharp peak), and the integral area surrounded by the DQ / DV curve corresponds to the capacity of the lithium-rich manganese-based material, and the higher the capacity means the stronger the redox peaks of DQ / DV, and the higher the oxidation peak of lattice oxygen means the higher activity of lattice oxygen and the higher capacity of the positive electrode material. On the basis of the lithium-rich manganese-based positive electrode material having the above-mentioned core-shell structure, adjusting the ratio of I a / I b in the above range can improve the activity of lattice oxygen in the lithium-rich manganese-based positive electrode material and improve the capacity of the lithium-rich manganese-based positive electrode material.
[0082] In some embodiments, the compaction density of the lithium-rich manganese-based positive electrode material is 2.8-3.5g / cm 3 . On the basis of the lithium-rich manganese-based positive electrode material having the above-mentioned core-shell structure, adjusting the compaction density of the lithium-rich manganese-based positive electrode material in the above range can improve the capacity of the lithium-rich manganese-based positive electrode material and improve the energy density of the battery.
[0083] In some embodiments, the discharge specific capacity of the lithium-rich manganese-based positive electrode material is 220-300mAh / g at a current density of 20mA / g. On the basis of the lithium-rich manganese-based positive electrode material having the above-mentioned core-shell structure, adjusting the discharge specific capacity of the lithium-rich manganese-based positive electrode material can improve the energy density of the lithium-rich manganese-based positive electrode material in the full battery system.
[0084] The application also provides a positive electrode sheet comprising the lithium-rich manganese-based positive electrode material of the second aspect of the application or the lithium-rich manganese-based positive electrode material of the third aspect of the application. The lithium-rich manganese-based positive electrode material is prepared from the lithium-rich manganese-based precursor, the positive electrode sheet is prepared from the lithium-rich manganese-based positive electrode material, and the lithium secondary battery is assembled from the positive electrode sheet.
[0085] In some embodiments, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer comprises the above-mentioned lithium-rich manganese-based positive electrode material, and further comprises a conductive agent and a binder. The positive electrode current collector comprises, but is not limited to, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy. The conductive agent comprises at least one of conductive carbon black (SP), acetylene black, ketjen black, graphene, conductive carbon fiber, 350G, carbon nanotube (CNT), amorphous carbon, metal powder and carbon fiber; and the binder comprises at least one of sodium carboxymethyl cellulose, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyethylene oxide.
[0086] The fourth aspect of the present application provides a lithium ion secondary battery comprising the lithium-rich manganese-based positive electrode material of the second aspect of the present application, or the lithium-rich manganese-based positive electrode material prepared by the method of the third aspect of the present application.
[0087] In some embodiments, the lithium ion secondary battery can be a power lithium battery, a consumer lithium battery or an energy storage lithium battery. The lithium-rich manganese-based positive electrode material provided by the present application has the advantage of high compaction density, and can exhibit higher energy density in a full battery system, so that the lithium battery comprising the lithium-rich manganese-based positive electrode material has the advantage of higher capacity.
[0088] In some embodiments, the battery further comprises a negative electrode sheet. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on one side or both sides of the negative electrode current collector. The negative electrode current collector comprises copper, stainless steel, aluminum, nickel, titanium, carbon cloth or a composite of the above-mentioned materials. The negative electrode active material layer comprises a negative electrode active material, a conductive agent and a binder. Exemplarily, the negative electrode active material comprises at least one of artificial graphite, natural graphite, hard carbon, mesocarbon microbeads, lithium titanate, silicon-carbon, silicon monoxide, silicon alloy.
[0089] In some embodiments, the battery further comprises an electrolyte; the electrolyte comprises a non-aqueous organic solvent, a conductive lithium salt and an additive. Exemplarily, the non-aqueous organic solvent comprises at least one of cyclic carbonates, and at least one of linear carbonates and linear carboxylates. Exemplarily, the conductive lithium salt comprises one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide salt, lithium bis-trifluoromethylsulfonylimide, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium difluoro oxalate borate, lithium tetrafluoro oxalate phosphate, lithium difluoro bis-oxalate phosphate, lithium bis-oxalate borate, lithium 4,5-dicyano-2-trifluoromethyl-imidazole, lithium di(trifluoromethylsulfonyl)imide, lithium di(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methide and lithium di(trifluoromethylsulfonyl)imide. Exemplarily, the additive comprises one or more of nitrile compounds, vinylene carbonate and 1,3-propylene sulfite.
[0090] In some embodiments, the battery further comprises a separator. The separator substrate comprises at least one of polyethylene, polypropylene, polyethylene, polypropylene, polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and aramid. The separator further comprises a ceramic layer coated on one or both sides of the substrate. The ceramic material in the ceramic layer comprises, but is not limited to, one or more of alumina, boehmite, magnesium hydroxide, CeO2, MgAl2O4, ZrO, TiO2.
[0091] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.
[0092] The materials, reagents, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.
[0093] The present application will be described in detail below in conjunction with specific examples, which are used for understanding rather than limiting the present application.
[0094] The batteries of the examples and comparative examples in the present application are prepared according to the following preparation method. The differences from Example 1-1 are described below.
[0095] Example 1-1
[0096] 1. Preparation of lithium-rich manganese-based composite precursor
[0097] (1) Preparation stage: dissolve nickel sulfate, cobalt sulfate, and manganese sulfate in deionized water according to the chemical molar ratio of Ni:Co:Mn=0.2:0.1:0.7 to form a salt solution A, wherein the total concentration of metal ions is 1.5 mol / L; dissolve sodium carbonate and sodium hydroxide in deionized water to prepare a precipitant solution B with a total concentration of 2.2 mol / L, wherein the molar ratio of carbonate is 75%; disperse the mixed solution of ammonia and ammonium sulfate in deionized water to prepare a complexing agent solution C; add 0.02 mol / L concentration of ethylene glycol solution as dispersant and surfactant in the reaction kettle, and add appropriate amount of ammonia to control the pH of the bottom liquid to 11.
[0098] (2) Reaction stage: pump the salt solution A into the reaction kettle at a feed rate of 8 L / h, and control the amount of alkali solution B through the automatic feedback program of the reaction kettle. The pH in the reaction process is gradually adjusted from 11 of the bottom liquid to 8.2; the initial amount of complexing agent solution C is 3 L / h, and the linear coefficient is -0.18. Adjust the change of ammonia ion concentration (such as Figure 6(As shown). The reaction was stopped after 48 hours and aged for 12 hours. The obtained precursor was washed by sedimentation and dried at 100℃ for 12 hours to obtain the target lithium-rich manganese-based composite precursor with the chemical formula 0.75[Ni]. 0.2 Co 0.1 Mn 0.7 CO3]·0.25[Ni 0.2 Co 0.1 Mn 0.7 (OH)2]. Figure 1 The image shown is a SEM image of the lithium-rich manganese-based composite precursor obtained in Example 1-1. Figure 2 The image shown is the XRD pattern of the lithium-rich manganese-based composite precursor obtained in Example 1-1.
[0099] 2. Preparation of lithium-rich manganese-based cathode materials
[0100] The composite precursor obtained in step 1 above was mixed with lithium carbonate, wherein the molar ratio of lithium element in lithium carbonate to transition metal element in the composite precursor was 1.5:1. The mixture was then sintered at 800℃ for 15 hours to obtain the product with the chemical formula Li. 1.5 Ni 0.2 Co 0.1 Mn 0.7 O 2.5 .
[0101] 3. Preparation of positive electrode sheet
[0102] The lithium-rich manganese-based material, binder PVDF, and conductive agent Super P obtained above are mixed in a ratio of 8:1:1 and stirred at high speed to obtain a uniform positive electrode slurry. The positive electrode slurry is uniformly coated on at least one surface of aluminum foil. After coating, it is dried, rolled, and slit to obtain a positive electrode sheet.
[0103] 4. Preparation of negative electrode: 8mm thick Li sheet.
[0104] 3. Preparation of the diaphragm: A ceramic layer (the ceramic material is MgAl2O4, and the thickness of the ceramic layer is 3μm) is coated on one side of a polypropylene diaphragm with a thickness of 5μm.
[0105] 4. Assemble the battery by combining the above positive electrode, separator, and negative electrode, and inject the electrolyte (the electrolyte is 1M LiPF6, EC / DMC / EMC (V / V / V) = 1 / 1 / 1)).
[0106] The batteries obtained in the following embodiments and comparative examples were subjected to the following performance tests:
[0107] (1) Compacted density test
[0108] The electrode sheet is calculated by the compaction density method, two plane probes are arranged at the upper and lower ends of the vertical hollow cylinder, the powder sample is filled between the upper and lower probes, the distance between the probes is changed by applying pressure to the probes, and the distance H between the upper and lower probes is measured by the displacement sensor under appropriate pressure. According to ρ = mg / (S*H), the compaction density of the sample under the corresponding conditions can be calculated. The pressure of 0MPa is pressed, the positive electrode is measured, the active material load is measured, and the active mass on the positive electrode side after pressing is measured.
[0109] (2) Tap density test
[0110] Refer to GB / T 5162-2021 Determination of tap density of metal powders.
[0111] (3) Specific surface area test
[0112] Refer to GB / T 13390-2008 Determination of specific surface area of metal powders - Nitrogen adsorption method.
[0113] (4) 0.1C discharge capacity test
[0114] The first discharge specific capacity of the product is determined according to the provisions of GB / T 23365 to make the battery, and the test environment temperature is 25℃±1℃. The charge and discharge system is as follows:
[0115] a) Constant current charging current: 0.1C;
[0116] b) Charging limit voltage: 4.6V
[0117] c) Constant voltage charging termination current: 0.01C;
[0118] d) Standby for 10min;
[0119] e) Constant current discharge current: 0.1C;
[0120] f) Discharge termination voltage: 2.0V; a) Constant current charging current: 0.1C;
[0121] g) Charging limit voltage: 4.8V
[0122] h) Constant voltage charging termination current: 0.01C;
[0123] i) Standby for 10min;
[0124] j) Constant current discharge current: 0.1C;
[0125] k) Discharge termination voltage: 2.0V.
[0126] (5) Capacity retention rate test
[0127] The product cycle life is determined according to the provisions of GB / T 23366. The battery is made and formed, and the ambient temperature of the cycle life test is 25℃±1℃. The charging and discharging system is as follows:
[0128] a) Constant current charging current: 0.2C;
[0129] b) Charging limit voltage: 4.6V
[0130] c) Constant voltage charging termination current: 0.02C;
[0131] d) Constant current discharging current: 0.2C;
[0132] e) Discharge termination voltage: 2.0V;
[0133] f) The ratio of the specific capacity of the last cycle to the specific capacity of the first cycle is the capacity retention rate.
[0134] The results of the performance test of the above battery are recorded in Table 5.
[0135] (6) Mechanical properties
[0136] The positive electrode material sample is accurately weighed 2g of powder material into the mold, and a certain pressure is applied by the press to obtain the compacted block material. The interface material is obtained by crushing, and the particle-free crushing is observed by SEM. The pressure value is recorded as the basis for judging the mechanical properties of the powder material.
[0137] Examples 1-4, 5-6, and Comparative Examples 1-2 are carried out according to Example 1-1, with the main difference being that the raw material components, the ratio, or the preparation conditions of the lithium-rich manganese-based precursor or the lithium-rich manganese-based positive electrode material are different. The specific different characteristics are shown in Table 1.
[0138] In Example Group 1, the molar proportion of carbonate in the precipitation solution B is changed (in Example 1-2, the molar proportion of carbonate is 50%; in Example 1-3, the molar proportion of carbonate is 90%), so that the chemical formula of the composite precursor is changed. In Example 1-1, the chemical formula of the lithium-rich manganese-based composite precursor is 0.75[Ni 0.2 Co 0.1 Mn 0.7 CO3]·0.25[Ni 0.2 Co 0.1 Mn 0.7 (OH)2], and the chemical formula of the lithium-rich manganese-based positive electrode material is Li 1.5 Ni 0.2 Co 0.1 Mn 0.7 O 2.5 ; in Example 1-2, the chemical formula of the lithium-rich manganese-based composite precursor is 0.5[Ni0.2 Co 0.1 Mn 0.7 CO3]·0.5[Ni 0.2 Co 0.1 Mn 0.7 [(OH)2], the chemical formula of the lithium-rich manganese-based cathode material is the same as that in Examples 1-1; in Examples 1-3, the chemical formula of the lithium-rich manganese-based composite precursor is 0.9[Ni 0.2 Co 0.1 Mn 0.7 CO3]·0.1[Ni 0.2 Co 0.1 Mn 0.7 [(OH)2], the chemical formula of the lithium-rich manganese-based cathode material is the same as that in Example 1-1.
[0139] In Example 2, the half-width at half maximum (FWHM) of the 001 crystal plane diffraction peak and the half-width at half maximum (FWHM) of the 104 crystal plane diffraction peak of the composite precursor were controlled by adjusting the linear coefficient of the change in ammonia ion concentration. In Example 2, the chemical formula of the lithium-rich manganese-based composite precursor was the same as that in Example 1-1, and the chemical formula of the lithium-rich manganese-based cathode material was the same as that in Example 1-1.
[0140] In Example 3, by adjusting the sintering temperature, the higher the sintering temperature, the higher the ratio of I003 / I104. In Example 3-1, the sintering temperature was 700 degrees, and in Example 3-2, the sintering temperature was 900 degrees.
[0141] In Example 4, the chemical formula of the cathode material was changed by adjusting the molar ratio of Li in the lithium source to the transition metal in the composite precursor. In Example 4-1, the molar ratio of Li to the transition metal was 1.2:1, and the chemical formula of the lithium-rich manganese-based cathode material was Li. 1.2 Ni 0.2 Co 0.1 Mn 0.7 O 2.2 In Example 4-1, the molar ratio of Li to transition metal is 1.4:1, and the chemical formula of the lithium-rich manganese-based cathode material is Li. 1.4 Ni 0.2 Co 0.1 Mn 0.7 O 2.4 .
[0142] In Example 5, Co was removed from salt solution A, and the chemical formula of the lithium-rich manganese-based composite precursor was 0.75[Ni]. 0.25 Mn 0.75 CO3]·0.25[Ni 0.25 Mn 0.75 [(OH)2], the chemical formula of lithium-rich manganese-based cathode material is Li 1.5 Ni0.25 Mn 0.75 O 2.5 .
[0143] In Example 6, Ni was removed from salt solution A, and the chemical formula of the lithium-rich manganese-based composite precursor was 0.75[Co]. 0.25 Mn 0.75 CO3]·0.25[Co 0.25 Mn 0.75 [(OH)2], the chemical formula of lithium-rich manganese-based cathode material is Li 1.5 Co 0.25 Mn 0.75 O 2.5 .
[0144] In Comparative Example 1, the precipitant solution B does not contain sodium hydroxide, and the concentration change curve of ammonia ions in the reaction system during the preparation process is shown in Figure 1. Figure 7 As shown, the chemical formula of the lithium-rich manganese-based composite precursor is Ni. 0.2 Co 0.1 Mn 0.7 CO3, the chemical formula of lithium-rich manganese-based cathode material is Li 1.5 Ni 0.2 Co 0.1 Mn 0.7 O 2.5 . Figure 3 The image shown is the XRD pattern of the lithium-rich manganese-based composite precursor obtained in Comparative Example 1.
[0145] In Comparative Example 2, the precipitant solution B does not contain sodium carbonate, and the chemical formula of the lithium-rich manganese-based composite precursor is Ni. 0.2 Co 0.1 Mn 0.7 (OH)3, the chemical formula of lithium-rich manganese-based cathode material is Li 1.5 Ni 0.2 Co 0.1 Mn 0.7 O 2.5 .
[0146] Table 1
[0147]
[0148]
[0149] Note: "*" indicates that the corresponding parameters in this embodiment or comparative example are the same as those in Embodiment 1-1.
[0150] The test results of Examples 1-4, Examples 5-6, and Comparative Examples 1-2 are shown in Table 2.
[0151] Table 2.
[0152]
[0153]
[0154] As can be seen from Table 2, compared with the lithium-rich manganese-based material prepared from the carbonate precursor, the lithium-rich manganese-based material prepared from the composite precursor of the application has higher compaction density; compared with the lithium-rich manganese-based material prepared from the hydroxide precursor, the lithium ion secondary battery prepared from the composite precursor of the application has higher discharge capacity and capacity retention rate.
[0155] Figure 5 The energy density cycle performance curve of the lithium-rich manganese-based positive electrode material obtained in Example 1-1 is shown, which proves that the lithium-rich manganese-based material prepared by using the composite precursor of the application has higher energy density.
[0156] Example 7 group refers to Example 1-1, the main difference is that the thickness and diameter of the petal-shaped particles and the length of the fiber bundle in the lithium-rich manganese-based composite precursor are adjusted by changing the molar ratio of carbonate, and the thickness and diameter of the flaky particles and the Dv50 of the spherical primary particles in the lithium-rich manganese-based material are different. The main difference is shown in Table 3.
[0157] Table 3
[0158]
[0159] As can be seen from Table 3, the thickness and diameter of the nanometer petal-shaped primary particles in the core layer of the lithium-rich manganese-based composite precursor are within the protection scope of the application, and the lithium ion secondary battery prepared from the lithium-rich manganese-based composite precursor has higher discharge capacity and capacity retention rate.
[0160] Example 8 group refers to Example 1-1, the main difference is that the shell thickness, core layer thickness and shell thickness ratio of the lithium-rich manganese-based composite precursor are adjusted by changing the molar ratio of carbonate, and the shell thickness ratio is related to the value of a in the chemical formula of the lithium-rich manganese-based precursor, a = 75, and the shell thickness ratio is 75%. The main difference is shown in Table 4.
[0161] Table 4
[0162]
[0163] As can be seen from Table 4, the thickness of the core layer and the thickness of the shell of the lithium-rich manganese-based composite precursor of the application are within the protection scope of the application, which can increase the compaction density of the lithium-rich manganese-based positive electrode material, so that the lithium-rich manganese-based positive electrode material can have stable electrochemical and mechanical properties.
[0164] The above merely provides the preferred embodiment of the present application, and not intended to limit the present application. Accordingly, any modification, equivalent replacement, and the like made within the spirit and principle of the present application shall fall within the scope of protection of the present application.
Claims
1. A lithium-rich manganese-based precursor, characterized in that, The lithium-rich manganese-based precursor has a chemical formula of a[Ni x1 Co y1 Mn z1 CO3]·b[Ni x2 Co y2 Mn z2 (OH)2, wherein 0.1 < x1 + x2 < 0.4, 0 ≤ y1 + y2 < 0.2, 0.5 < z1 < 1, 0.5 < z2 < 1, 0 < a < 1, 0 < b < 1. The lithium-rich manganese-based precursor comprises a hydroxide-carbonate composite core-shell structure, a hydroxide Ni x2 Co y2 Mn z2 (OH)2is the core layer, a carbonate Ni x1 Co y1 Mn z1 CO3is the shell layer; the lithium-rich manganese-based precursor has a 001 crystal face diffraction peak at 2θ = 18-20°; the lithium-rich manganese-based precursor has a 104 crystal face diffraction peak at 2θ = 30-32°.
2. The lithium-rich manganese-based precursor of claim 1, wherein the ratio of the intensity of the 104 crystal face diffraction peak to the intensity of the 001 crystal face diffraction peak of the lithium-rich manganese-based precursor satisfies: 0.05≤I 104 / I 001 ≤1.0, preferably 0.1≤I 104 / I 001 ≤0.8; Preferably, the lithium-rich manganese-based precursor has a 104 crystal face diffraction peak with a half-peak width FWHM(104) of 0.15-0.3°. Preferably, the lithium-rich manganese-based precursor has a 001 crystal face diffraction peak with a half-peak width FWHM(001) of 0.5-1.0°. Preferably, the lithium-rich manganese-based precursor has a 101 crystal face diffraction peak at 2θ = 38-40°. Preferably, the lithium-rich manganese-based precursor has a 102 crystal face diffraction peak at 2θ = 24-25°.
3. The lithium-rich manganese-based precursor of claim 1, wherein, the core layer comprises petal-shaped particles, and the shell layer comprises fiber bundles; Preferably, the petal-shaped particles have a thickness of 100-500 nm and a diameter of 200-2000 nm; and / or, the fiber bundles have a length of 10-200 nm and a top diameter of 50-500 nm. Preferably, in the lithium-rich manganese-based precursor, the thickness ratio of the shell layer is 20-80%. Preferably, the core layer has a thickness of 0.5-8 μm, and / or the shell layer has a thickness of 0.5-10 μm.
4. The lithium-rich manganese-based precursor according to any one of claims 1 to 3, characterized in that, The lithium-rich manganese-based precursor satisfies at least one of the following conditions: (i) a compacted density of 2.7 g / cm 3 - 3.1 g / cm 3 ; (ii) a tap density of 1.0 g / cm3 3 - 2.7 g / cm3 3 ; (iii) a specific surface area of 50 m 2 / g-100 m 2 / g; (iv) Span = (Dv90-Dv10) / Dv50 is 0.5-1.8, Dv10 is 0.5-8 μm, Dv50 is 3-20 μm, and Dv90 is 8-25 μm; (v) S content is less than 900 ppm.
5. A lithium-rich manganese-based positive electrode material, characterized in that, The lithium-rich manganese-based positive electrode material is obtained by high-temperature sintering reaction of the lithium-rich manganese-based precursor of any one of claims 1-4 with a lithium source. Preferably, the molar ratio of lithium in the lithium source to transition metal elements in the lithium-rich manganese-based precursor is (1-2):
1.
6. A lithium-rich manganese-based positive electrode material, characterized in that, The lithium-rich manganese-based positive electrode material has a molecular formula of Li 1+δ Ni x Co y Mn z O2, wherein 0<δ<0.5, 0 The lithium-rich manganese-based positive electrode material comprises a core-shell structure. Preferably, the core layer of the core-shell structure comprises flaky particles, and / or the shell layer of the core-shell structure comprises primary particles. Preferably, the flaky particles have a thickness of 200-500 nm and a diameter of 1-5 μm; and / or, the primary particles have a Dv50 of 200-500 nm.
7. The lithium-rich manganese-based positive electrode material according to claim 5 or 6, characterized in that, The ratio of the diffraction peak intensity of the 020 crystal face of the lithium-rich manganese-based positive electrode material to the diffraction peak intensity of the 003 crystal face satisfies: I 020 ≤0.01 003 ≤0.01 Preferably, the lithium-rich manganese-based positive electrode material has a first diffraction peak at 2θ = 18-19°, the peak intensity being denoted as I 003 , the lithium-rich manganese-based positive electrode material has a second diffraction peak at 2θ = 44-46°, the peak intensity being denoted as I 104 , the ratio of I 003 and I 104 satisfies: 1.5≤I 003 / I 104 ≤2.
2. Preferably, the first diffraction peak has a half-peak width FWHM(003) of 0.01-0.02°. 8.The lithium-rich manganese-based cathode material of claim 5 or 6, characterized in that, The peak intensity in the range of 3.6V-4.0V in the DQ / DV curve of the lithium-rich manganese-based positive electrode material is denoted as I a The peak intensity in the range of 4.5V-4.6V is denoted as I b The ratio of I a and I b satisfies: 1.4≤I a / I b ≤2.
8. 9.The lithium-rich manganese-based cathode material of claim 5 or 6, characterized in that, The compaction density of the lithium-rich manganese-based positive electrode material is 2.8-3.5 g / cm 3 ; Preferably, the lithium-rich manganese-based positive electrode material has a discharge specific capacity of 220-300 mAh / g at a current density of 20 mA / g.
10. A lithium-ion secondary battery, characterized by comprising: The lithium-rich manganese-based positive electrode material of claim 5, or the lithium-rich manganese-based positive electrode material of any one of claims 6-9.