Preparation method of high-performance lithium cobalt oxide positive electrode material
By synthesizing single-crystal lithium cobalt oxide cathode materials through a high-temperature solid-state method doped with F and Mg, the problems of material stability and rate performance under high voltage were solved, achieving high efficiency in cycle stability and low-cost industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-03-27
AI Technical Summary
Lithium cobalt oxide cathode materials exhibit rapid capacity decay under high voltage and high rate conditions, mainly due to instability of grain boundaries, interfaces and bulk phase leading to particle cracking, side reactions and uneven lithium-ion insertion/extraction.
Single-crystal lithium cobalt oxide particles were synthesized by high-temperature solid-state method using F and Mg doping. A Mg-rich nano-modified layer was formed on the surface, and the (003), (102) and (104) crystal planes were selectively exposed. The bulk phase was doped with elements such as Al, Mg, Ti, and Zr to form a stable structure.
It improves the cycle stability and rate performance of lithium cobalt oxide cathode materials under high voltage, reduces cracks and twinning defects, and enhances the chemical and electrochemical stability of the materials, making them suitable for industrial production.
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Figure CN121748338A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of lithium ion battery cathode materials, and particularly relates to a preparation method of high-performance lithium cobaltate cathode material. BACKGROUND
[0002] As a kind of energy storage device with excellent performance, lithium ion battery has the advantages of high energy density, high average working voltage, good cycle stability, etc., and is widely used in mobile electronic devices, electric vehicles, energy storage facilities and other fields. Lithium cobaltate has high energy density and good rate performance, and is widely used in mobile electronic devices. With the continuous development of such products towards miniaturization and thinness, it is necessary to further improve the energy density of lithium ion battery. In order to meet this demand, it is necessary to develop lithium cobaltate cathode material with higher high-voltage resistance, higher specific capacity and higher rate performance.
[0003] The capacity of lithium cobaltate cathode material declines rapidly under high voltage and high rate charge and discharge. Studies have shown that lithium cobaltate will produce a series of problems when working under high voltage and high rate, including: 1. Phase transition under high voltage is accompanied by drastic change of lattice size, generating internal stress, leading to particle cracking and even breaking, among which, a large number of grain boundaries in lithium cobaltate are important sites for inducing cracks; 2. Side reactions between interface and electrolyte, lattice oxygen precipitation and cobalt dissolution under high voltage lead to surface interface degradation; 3. Inhomogeneous lithium ion deintercalation leads to body phase defects and aggravation of surface interface degradation. Therefore, synthesizing lithium cobaltate without grain boundaries (twin crystal), stable interface and body phase is the key to improving its performance.
[0004] Based on this, the application provides a preparation method of high-performance lithium cobaltate cathode material, which has the advantages of simple process, low cost and low energy consumption. The synthesized lithium cobaltate has excellent discharge specific capacity, rate performance and cycle stability under high voltage (~4.6 V), and has important application value. SUMMARY
[0005] The application synthesizes a single crystal particle lithium cobaltate mainly composed of three exposed surfaces (003), (102) and (104), without twin crystal and regular particle shape (14-hedron) by selecting F and Mg as two kinds of doping elements, Co2O3 precursor and using high-temperature solid phase method. There is F element doping and a small amount of Mg element doping in the body phase, and Mg element is mainly enriched on the surface of the material. A Mg-rich shell layer is formed on the surface, with a thickness of 1-5 nm, and the structure has the characteristics of spinel structure or rock salt structure.
[0006] The synthesis of the high-performance lithium cobaltate cathode material specifically includes the following steps: the precursor, lithium source, Mg doping source compound, F doping source compound and M doping element compound are mixed according to the following chemical formula: The stoichiometric ratio of each element is uniformly mixed, and solid-phase sintering is carried out in an air or oxygen atmosphere, wherein, , , , M is a metal element such as Ti, Al, Zr, Ni, etc., sintering is carried out at a rate of 2-10 ℃ / min to 600-1100 ℃, and the temperature is kept for 5-20 h, and after cooling with the furnace, the high-performance lithium cobalt oxide positive electrode material is obtained.
[0007] In the above steps, the lithium source can be selected from LiOH·H2O and Li2CO3, etc.; the doping source of Mg is Mg(COOCH3)2, MgO or MgF2, etc. containing Mg element compounds; the doping source of F is one or more of polyvinylidene fluoride (PVDF), LiF or MgF2, etc. containing F element compounds. The cobalt precursor is selected from one or more of Co3O4, Co2O3, CoO, Co(OH)2 and CoCO3 with a grain size of 0.05-2 μm.
[0008] The principle of the lithium cobalt oxide positive electrode material prepared by the preparation method in the application has excellent performance:
[0009] (1) The Mg element is enriched on the surface of the material to form a nano-surface modification layer with uniform thickness, the modification layer has stable cycle performance at high voltage, and the high-efficiency kinetic characteristics of the positive electrode material surface interface are ensured;
[0010] (2) The lithium cobalt oxide positive electrode material particle is complete, regular in shape, free of defects such as twinning, layer slip, cracks, etc., and is a single crystal particle, which reduces the stress concentration sites and crack nucleation sites in the cycle process, and does not produce local failure and inactivation in the high-voltage cycle process;
[0011] (3) Selective exposure of (003), (102) and (104) and other high-chemical-stability crystal surfaces provides uniform, efficient and stable reaction sites, and improves the interface chemical and electrochemical stability;
[0012] (4) Al, Mg, Ti, Zr, F and other elements can be used to dope the bulk phase of the material, which can improve the structural stability of the bulk phase and inhibit Co mixing, spinel phase change, intracrystalline crack and other degradation;
[0013] The application has the following beneficial effects:
[0014] (1) The lithium cobalt oxide positive electrode material prepared by the method of the application is a single crystal free of cracks, twin boundaries, grain boundary domains, layer slip and other defects, which effectively inhibits cycle cracks; the surface modification layer is thin and uniform in thickness, which can greatly improve the stability of the material in high-voltage cycle;
[0015] (2) The method of the present application can obtain a lithium cobaltate positive electrode material with excellent cycle stability and rate performance through solid phase mixing sintering, and the preparation process is simple, low in cost, low in energy consumption and easy for industrialized production. BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1 SEM (Scanning Electron Microscopy, SEM) images of the lithium cobaltate positive electrode materials in (a) Comparative Example 1 and (b) Example 2;
[0017] Figure 2 XRD (X-Ray Diffraction) pattern of the lithium cobaltate positive electrode material in Example 1;
[0018] Figure 3 (a) particle morphology schematic diagram and (b) particle exposed crystal face orientation schematic diagram of the high-performance lithium cobaltate positive electrode material described in the present patent;
[0019] Figure 4 (a) STEM-HAADF (Scanning Transmission Electron Microscopy-High Angle Annular Dark Field) image and EDS-mapping (Energy Dispersive Spectroscopy-mapping) image of the corresponding region of the positive electrode material in Example 1 (b) high-magnification STEM-HAADF image of the surface with orientation (102) and (104) and EDS-mapping of the corresponding region Mg element;
[0020] Figure 5 STEM-HAADF image of the surface spinel structure Mg-rich area and FFT (Fast Fourier Transform) image of the corresponding region;
[0021] Figure 6 Electrochemical performance comparison chart of Comparative Example 1 and Example 1 material, wherein (a) is a discharge specific capacity attenuation chart (capacity retention rate after 200 cycles is marked behind the legend) under the conditions of 3.0-4.6 V cutoff voltage and 1.0 C rate (1 C=140 mA / g) charging and discharging cycle (b) is the rate performance test result of 3.0-4.6 V cutoff voltage. DETAILED DESCRIPTION
[0022] The present application will be further described below in combination with examples, but the present application is not limited to the following examples.
[0023] Example 1
[0024] Li, Co, Mg, F in the chemical formula LiOH-H2O, Co2O3, Mg(COOCH3)2, PVDF were weighed according to the molar ratio of Li, Co, Mg, F in the chemical formula
[0025] Example 2
[0026] Li, Co, Mg, F in the chemical formula LiOH-H2O, Co2O3, Mg(COOCH3)2, PVDF were weighed according to the molar ratio of Li, Co, Mg, F in the chemical formula
[0027] Example 3
[0028] Li, Co, Mg, F in the chemical formula LiOH-H2O, Co2O3, Mg(COOCH3)2, PVDF were weighed according to the molar ratio of Li, Co, Mg, F in the chemical formula
[0029] Example 4
[0030] Li, Co, Mg, F in the chemical formula LiOH-H2O, Co2O3, Mg(COOCH3)2, PVDF were weighed according to the molar ratio of Li, Co, Mg, F in the chemical formula
[0031] Example 5
[0032] According to chemical formula The molar ratio of Li, Co, and Mg in the mixture was measured as LiOH·H2O, Co2O3, and Mg(COOCH3)2, and an additional 2% LiOH·H2O was added to compensate for the loss on ignition. The mixture was then ground evenly using an agate mortar and pestle. The mixed material was then heated to 800 ℃ in air at a rate of 5 ℃ / min and held for 12 h. Subsequently, it was cooled to room temperature in the furnace and ground evenly to obtain Mg-doped lithium cobalt oxide cathode material M1-LCO-800.
[0033] Example 6
[0034] According to chemical formula The molar ratios of Li, Co, Al, Mg, and F in the mixture were weighed as follows: LiOH·H2O, Co2O3, Al(COOCH3)3, Mg(COOCH3)2, and PVDF. An additional 2% of LiOH·H2O was added to compensate for loss on ignition. The mixture was then ground uniformly using an agate mortar. The mixed material was then heated to 800 ℃ in air at a rate of 5 ℃ / min and held for 12 h. Subsequently, it was cooled to room temperature in the furnace and ground uniformly to obtain Al, Mg, and F co-doped lithium cobalt oxide cathode material A0.5M1F2-LCO-800.
[0035] Comparative Example 1
[0036] Weigh LiOH·H2O and Co2O3 according to the molar ratio of Li and Co in the chemical formula LiCoO2, and add an additional 5% LiOH·H2O to compensate for the loss on ignition. Then grind them evenly using an agate mortar. The mixed material is then heated to 1000 ℃ in air at a rate of 5℃ / min and held for 10 h. After that, it is cooled to room temperature in the furnace and ground evenly to obtain the lithium cobalt oxide cathode material P-LCO-1000.
[0037] Depend on Figure 1 As shown in (a), the lithium cobalt oxide cathode material synthesized in Comparative Example 1 has an irregular morphology, with many fragments and numerous defects; (b) shows the regular shape of the lithium cobalt oxide cathode material synthesized in Example 2.
[0038] Figure 3 The diagram shows the distribution of the three crystal planes selectively exposed in the lithium cobalt oxide cathode materials synthesized in Examples 1-6. The upper and lower surfaces are (003) planes, and the side surfaces in each direction are mainly composed of two oriented crystal planes, (102) and (104). The whole is a 14-sided single crystal particle.
[0039] Depend on Figure 4In (a), we can see that Mg is enriched on the surface of the particles. In (b), we selected two surfaces (102) and (104) that have a greater impact on the performance of the cathode material, and we can see the thickness of the Mg enrichment layer.
[0040] Figure 5 The structure of the phase transition layer on the material surface is shown. Spinel spots can be seen in the FFT image, indicating the presence of a phase transition layer with a spinel structure on the surface.
[0041] Figure 6 The examples demonstrate the excellent cycle stability, high specific capacity, and superior rate performance of the synthesized lithium cobalt oxide cathode material. Performance tests were conducted in a 25 °C constant temperature chamber, with rate tests performed four cycles at each different rate. The same rate was used for both charging and discharging within the same cycle, and the specific rate is indicated above the corresponding cycle data point.
Claims
1. A high-performance lithium cobalt oxide cathode material, characterized in that, It has the following chemical formula: ,in, , , , M represents metallic elements such as Ti, Al, Zr, and Ni.
2. A high-performance lithium cobalt oxide cathode material according to claim 1, characterized in that, The lithium cobalt oxide cathode material has a Mg-rich shell on its surface, with a regular shape, and is a single crystal particle.
3. The high-performance lithium cobalt oxide cathode material according to claim 1, characterized in that, The Mg-rich shell on the surface is 1-5 nm thick and exists throughout the entire particle surface. The Mg-rich shell has the characteristics of spinel or rock salt structure.
4. The high-performance lithium cobalt oxide cathode material according to claim 1, characterized in that, It is mainly composed of three exposed surfaces (003), (102), and (104). The grains have regular shapes and are free from defects such as cracks, twin boundaries, domain boundaries, and layer slip. It is a single crystal morphology.
5. The high-performance lithium cobalt oxide cathode material according to claim 1, characterized in that, The particle size of high-performance lithium cobalt oxide cathode materials is between 0.3 and 5 μm, and their final form is single crystal or secondary particle form.
6. A method for preparing a high-performance lithium cobalt oxide cathode material according to any one of claims 1-5, characterized in that, Specifically, the following steps are included: The precursor, lithium source, Mg dopant source compound, F dopant source compound, and M dopant compound are defined according to the following chemical formulas: The stoichiometric ratios of all elements are uniformly mixed, and solid-state sintering is carried out under an air or oxygen atmosphere; among which, , , , M represents metallic elements such as Ti, Al, Zr, and Ni; the sintering temperature is increased to 600-1100℃ at a rate of 2-10℃ / min, held for 5-20 h, and then cooled in the furnace to obtain the high-performance lithium cobalt oxide cathode material.
7. The method according to claim 6, characterized in that, The lithium source can be LiOH·H2O or Li2CO3, etc.; the Mg doping source is Mg(COOCH3)2, MgO or MgF2 or other Mg-containing compounds; the F doping source is one or more of polyvinylidene fluoride (PVDF), LiF or MgF2 or other F-containing compounds; the cobalt precursor is one or more of Co3O4, Co2O3, CoO, Co(OH)2 or CoCO3 with a grain size between 0.05 and 2 μm.