Antimony-modified lithium cobalt oxide material, and preparation method and application thereof

Abstract

The application belongs to the technical field of lithium ion batteries, and particularly relates to a kind of antimony modified lithium cobalt oxide material and its preparation method and application.The antimony modified lithium cobalt oxide material provided by the application comprises layered lithium cobalt oxide and an antimony layer wrapped on the surface of the layered lithium cobalt oxide;The antimony layer comprises an antimony oxide compound.The application adopts an antimony layer to wrap lithium cobalt oxide, enhances the interface stability of lithium cobalt oxide, makes it have good structural stability at high voltage, and has excellent cycle stability and rate performance as a positive electrode material.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to an antimony-modified lithium cobalt oxide material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries have become an indispensable part of people's lives. The development of high-quality cathode materials has become crucial for achieving performance optimization goals in lithium-ion batteries. Currently, especially with the advancement of 3C (computer, communication, and consumer electronics) electronic products, higher demands are being placed on the energy density of lithium-ion batteries. As the earliest commercially available cathode material, lithium cobalt oxide possesses high tap density and a relatively high theoretical capacity (274 mAh / g), making it the top choice for cathode materials in lithium-ion batteries for portable electronic devices. Currently, the commercial market mainly uses 4.45V LiCoO2, with an actual capacity of 180 mAh / g, which still has room for improvement compared to its theoretical capacity. Increasing the charging cutoff voltage of the lithium cobalt oxide cathode has become the preferred approach to further improve its capacity. In recent years, the academic community has adopted various strategies to improve the performance of high-voltage lithium cobalt oxide (LiCoO2) cathode materials, mainly focusing on surface optimization, bulk doping, and electrolyte engineering. The academic community generally believes that interfacial instability and the deep delithiation state of Li... + High-flux diffusion leading to undesirable phase transitions is a major problem faced by high-voltage lithium cobalt oxide cathode materials, for example, at voltages exceeding 4.5V (relative to Li / Li). + Under high voltage, lithium cobalt oxide undergoes multi-scale and multi-dimensional structural changes, involving changes in bulk phase and surface, which leads to structural damage and electrochemical performance degradation. Therefore, maintaining the structural stability of lithium cobalt oxide under high cutoff voltage remains an urgent problem to be solved. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide an antimony-modified lithium cobalt oxide material, its preparation method and application. The antimony-modified lithium cobalt oxide material provided by this invention has good structural stability under high voltage, thus enabling it to have excellent cycle stability and rate performance as a cathode material.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] The present invention provides an antimony-modified lithium cobalt oxide material, comprising layered lithium cobalt oxide and an antimony layer coating the surface of the layered lithium cobalt oxide; the antimony layer comprises an antimony oxide compound.

[0006] Preferably, the thickness of the antimony layer is 1–20 nm.

[0007] Preferably, the specific surface area of ​​the antimony-modified lithium cobalt oxide material is 0.2–0.5 m². 2 / g.

[0008] The present invention also provides a method for preparing the antimony-modified lithium cobalt oxide material described in the above technical solution, comprising the following steps:

[0009] An organic dispersion of lithium cobalt oxide, an organic dispersion of an antimony source, and water are mixed. After the antimony source undergoes a hydrolysis reaction, the mixture is dried to obtain a precursor material, wherein the precursor material is lithium cobalt oxide coated with antimony oxide and antimony hydroxide.

[0010] The precursor material was calcined in an oxygen atmosphere to obtain antimony-modified lithium cobalt oxide material.

[0011] Preferably, the antimony source is one or more of antimony acetate, antimony glycolate, antimony trichloride, antimony fluoride, and antimony trioxide.

[0012] Preferably, the calcination temperature is 350–450°C; and the calcination holding time is 3–5 hours.

[0013] Preferably, the heating rate to the calcination temperature is 3-5 °C / min.

[0014] Preferably, after calcination, the process further includes annealing; the annealing involves cooling the temperature from the calcination temperature to room temperature.

[0015] Preferably, the cooling rate is 3-5°C / min.

[0016] The present invention also provides the application of the antimony-modified lithium cobalt oxide material described in the above technical solution or the antimony-modified lithium cobalt oxide material prepared by the preparation method described in the above technical solution as a cathode material in lithium-ion batteries.

[0017] This invention provides an antimony-modified lithium cobalt oxide material, comprising layered lithium cobalt oxide and an antimony layer coating the surface of the layered lithium cobalt oxide; the antimony layer comprises an antimony oxide compound. This invention uses an antimony layer to coat lithium cobalt oxide, enhancing the interfacial stability of the lithium cobalt oxide and giving it good structural stability at high voltages. As a cathode material, it exhibits excellent electrochemical performance (cycle stability and rate performance) at a high voltage of 4.65V, retaining a high capacity after 200 cycles. Attached Figure Description

[0018] Figure 1 SEM images of the antimony-modified lithium cobalt oxide material (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Example 1;

[0019] Figure 2 The images show the XRD patterns of the antimony-modified lithium cobalt oxide material (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Example 1.

[0020] Figure 3EDS image of the antimony-modified lithium cobalt oxide material (Sb-LCO) prepared in Example 1;

[0021] Figure 4 The electrochemical performance diagrams are of the antimony-modified lithium cobalt oxide material (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Example 1.

[0022] Figure 5 Electrochemical performance diagrams of antimony-modified lithium cobalt oxide (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Comparative Example 1;

[0023] Figure 6 Electrochemical performance diagrams of antimony-modified lithium cobalt oxide (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Comparative Example 2;

[0024] Figure 7 The graph shows the rate performance of the antimony-modified lithium cobalt oxide material (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Example 1. Detailed Implementation

[0025] The present invention provides an antimony-modified lithium cobalt oxide material, comprising layered lithium cobalt oxide and an antimony layer coating the surface of the layered lithium cobalt oxide; the antimony layer comprises an antimony oxide compound.

[0026] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0027] The antimony-modified lithium cobalt oxide material provided by this invention includes layered lithium cobalt oxide.

[0028] The antimony-modified lithium cobalt oxide material provided by the present invention includes an antimony layer coated on the surface of the layered lithium cobalt oxide; the antimony layer includes antimony oxides.

[0029] In one embodiment, the thickness of the antimony layer in the antimony-modified lithium cobalt oxide material is 1–20 nm, and in a specific embodiment it is 10 nm.

[0030] In one embodiment, the specific surface area of ​​the antimony-modified lithium cobalt oxide material is 0.2–0.5 m². 2 / g, specifically 0.3m in the embodiment. 2 / g.

[0031] This invention uses an antimony layer to encapsulate lithium cobalt oxide, enhancing the interfacial stability of lithium cobalt oxide and giving it good structural stability at high voltage. As a cathode material, it exhibits excellent electrochemical performance (cycle stability and rate performance) at a high voltage of 4.65V, and still has a high capacity after 200 cycles.

[0032] The present invention also provides a method for preparing the antimony-modified lithium cobalt oxide material described in the above technical solution, comprising the following steps:

[0033] An organic dispersion of lithium cobalt oxide, an organic dispersion of an antimony source, and water are mixed. After the antimony source undergoes a hydrolysis reaction, the mixture is dried to obtain a precursor material, wherein the precursor material is lithium cobalt oxide coated with antimony oxide and antimony hydroxide.

[0034] The precursor material was calcined in an oxygen atmosphere to obtain antimony-modified lithium cobalt oxide material.

[0035] This invention involves mixing an organic dispersion of lithium cobalt oxide, an organic dispersion of an antimony source, and water. After the antimony source undergoes a hydrolysis reaction, the mixture is dried to obtain a precursor material, wherein the precursor material is lithium cobalt oxide coated with antimony oxide and antimony hydroxide.

[0036] In one embodiment, the antimony source is one or more of antimony acetate, antimony glycolate, antimony trichloride, antimony fluoride, and antimony trioxide. In a specific embodiment, it is antimony acetate, antimony glycolate, antimony trichloride, antimony fluoride, or antimony trioxide.

[0037] In this invention, the organic dispersion of lithium cobalt oxide is a suspension, and the lithium cobalt oxide is not dissolved in anhydrous ethanol. The purpose of this invention is to first stir the lithium cobalt oxide evenly. Therefore, there is no special limitation on the amount of organic dispersion added. It is sufficient to add an appropriate amount of organic solvent to stir the lithium cobalt oxide evenly in the mixture.

[0038] As one embodiment, the organic dispersion of lithium cobalt oxide is prepared by mixing lithium cobalt oxide and anhydrous ethanol and stirring to obtain an organic dispersion of lithium cobalt oxide. As one embodiment, the stirring rate is 200–500 r / min and the stirring time is 5–20 min; in a specific embodiment, the stirring rate is 300 r / min and the stirring time is 10 min.

[0039] In one embodiment, the mass percentage of antimony source in the organic dispersion of the antimony source is 0.8% to 1%, and in a specific embodiment it is 0.8%.

[0040] As one embodiment, the method for preparing the organic dispersion of the antimony source is as follows: mixing the antimony source and an organic solvent and then subjecting the mixture to ultrasonic treatment to obtain the organic dispersion of the antimony source. As one embodiment, the organic solvent is anhydrous ethanol and / or tartaric acid, and the ultrasonic treatment power is 300–800 W, the frequency is 28–60 kHz, and the time is 5–20 min; in a specific embodiment, the ultrasonic treatment power is 360 W, the frequency is 40 kHz, and the time is 10 min. When the organic solvent is anhydrous ethanol and tartaric acid, the volume ratio of anhydrous ethanol to tartaric acid is 2:1.

[0041] In one embodiment, the molar ratio of lithium cobalt oxide to antimony source is 1:0.0012 to 0.0028; in a specific embodiment, the molar ratio of lithium cobalt oxide to antimony source is 1:0.002.

[0042] In one implementation method, the water is deionized water.

[0043] The purpose of adding deionized water in this invention is to further promote the hydrolysis of the antimony source. Therefore, the amount of deionized water added is excessive relative to the antimony source, so there is no need for a specific antimony source to water mass ratio.

[0044] In one embodiment, the organic dispersion of lithium cobalt oxide, the organic dispersion of antimony source, and water are mixed by adding the organic dispersion of antimony source dropwise to the organic dispersion of lithium cobalt oxide, followed by the addition of water. In one embodiment, the dropping rate is 0.3–1 mL / min, and in a specific example, it is 0.5 mL / min.

[0045] In one implementation, the hydrolysis reaction takes 10 minutes to 2 hours; in a specific embodiment, the hydrolysis reaction takes 1 hour.

[0046] In one embodiment, the drying temperature is 40–70°C, and the drying is carried out under stirring conditions at a stirring rate of 200–500 r / min; in a specific embodiment, the drying temperature is 50°C, and the stirring rate is 300 r / min.

[0047] The present invention does not have a specific time limit for the drying process, which continues until the solvent evaporates completely.

[0048] After obtaining the precursor material, the present invention calcines the precursor material in an oxygen atmosphere to obtain antimony-modified lithium cobalt oxide material.

[0049] In one embodiment, the purity of the oxygen atmosphere is >99.5%.

[0050] In one embodiment, the calcination temperature is 350–450°C; the calcination holding time is 3–5 h; and the heating rate to the calcination temperature is 3–5°C / min. In a specific embodiment, the calcination temperature is 400°C; the calcination holding time is 5 h; and the heating rate to the calcination temperature is 3°C / min.

[0051] As a cathode material, lithium cobalt oxide has residual alkali on its surface, such as lithium carbonate (Li₂CO₃), lithium hydroxide (LiOH), or other lithium salts. When lithium cobalt oxide coated with antimony oxide and antimony hydroxide as the precursor material is calcined at high temperature, the hydroxide dehydrates into oxides, and finally forms antimony oxides under high temperature calcination in an oxygen atmosphere.

[0052] In one embodiment, the calcination process further includes annealing; the annealing involves cooling the temperature from the calcination temperature to room temperature at a rate of 3–5 °C / min; in a specific embodiment, the cooling rate is 3 °C / min.

[0053] The antimony surface modification strategy for lithium cobalt oxide provided by this invention is highly efficient, has a simple synthesis route, and uses readily available raw materials.

[0054] The present invention also provides the application of the antimony-modified lithium cobalt oxide material described in the above technical solution or the antimony-modified lithium cobalt oxide material prepared by the preparation method described in the above technical solution as a cathode material in lithium-ion batteries.

[0055] This invention does not impose any particular limitation on the application of the antimony-modified lithium cobalt oxide material prepared by the above preparation method as a cathode material in lithium-ion batteries; any application method known in the art can be used.

[0056] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0057] Example 1

[0058] First, weigh 2g of lithium cobalt oxide and place it in a beaker. Add anhydrous ethanol and then place it on a magnetic stirrer and stir at a constant speed of 300rpm for 10min to obtain an organic dispersion of lithium cobalt oxide.

[0059] Meanwhile, in another beaker, 12.22 mg of antimony acetate was weighed according to 0.2 mol% Sb (the molar ratio of antimony in lithium cobalt oxide and antimony source was 1:0.002), and anhydrous ethanol was added as a solvent. The mixture was ultrasonically treated for 10 min at 25 °C, 360 W power, and 40 kHz frequency to obtain an organic solution of antimony acetate (the mass percentage of antimony source was 0.8%).

[0060] The organic solution of antimony acetate was slowly added dropwise to the organic dispersion of lithium cobalt oxide at a rate of 0.5 mL / min, and 5 mL of deionized water was added to promote the hydrolysis reaction of antimony acetate for 60 min. The generated antimony oxide and antimony hydroxide coated the lithium cobalt oxide material. Finally, the mixture was continuously stirred under a heating mantle at 50 °C and 300 r / min until the solvent evaporated to dryness, and the dry precursor material was obtained.

[0061] The precursor material was placed in a tube furnace and heated to 400°C at a heating rate of 3°C / min in an oxygen atmosphere (purity > 99.5%), and calcined at 400°C for 5 hours. Then, it was annealed to room temperature at a rate of 3°C / min to obtain antimony-modified lithium cobalt oxide material (0.2 mol% Sb-LCO, antimony layer thickness of 10 nm).

[0062] Under these conditions, lithium cobalt oxide exhibits the best electrochemical performance (cycle stability and rate performance) at 4.65V.

[0063] Example 2

[0064] The difference from Example 1 is that antimony glycolate was weighed according to 0.2 mol% Sb, and the mass percentage of antimony source in the resulting organic solution of antimony source was 0.8%, thus obtaining antimony-modified lithium cobalt oxide material (Sb-LCO).

[0065] Example 3

[0066] The difference from Example 1 is that antimony trichloride was weighed according to 0.2 mol% Sb, and the mass percentage of antimony source in the resulting organic solution of antimony source was 0.8%, thus obtaining antimony-modified lithium cobalt oxide material (Sb-LCO).

[0067] Example 4

[0068] The difference from Example 1 is that antimony fluoride was weighed according to 0.2 mol% Sb, and the mass percentage of antimony source in the resulting organic solution of antimony source was 0.8%, thus obtaining antimony-modified lithium cobalt oxide material (Sb-LCO).

[0069] Example 5

[0070] The difference from Example 1 is that, firstly, 2g of lithium cobalt oxide was weighed and placed in a beaker, and a mixed solution of anhydrous ethanol and tartaric acid (volume ratio of anhydrous ethanol to tartaric acid was 2:1) was added and stirred at a constant speed to obtain an organic dispersion of lithium cobalt oxide; at the same time, 12.22mg of antimony acetate was weighed in another beaker according to 0.2mol% Sb, and tartaric acid was added as a solvent, and ultrasonic treatment was performed to obtain an organic solution of antimony acetate (mass percentage of antimony source was 0.8%), thus obtaining the antimony-modified lithium cobalt oxide material (Sb-LCO).

[0071] Comparative Example 1

[0072] The difference from Example 1 is that 6.11 mg of antimony acetate was weighed according to 0.1 mol% Sb (the molar ratio of antimony in lithium cobalt oxide and antimony source is 1:0.001), and the mass percentage of antimony source in the resulting organic solution of antimony source was 0.4%, thus obtaining antimony-modified lithium cobalt oxide material (0.1 mol% Sb-LCO).

[0073] Compared to lithium cobalt oxide, the insufficient Sb content under these conditions did not effectively improve the electrochemical performance of antimony-modified lithium cobalt oxide materials at high voltage.

[0074] Comparative Example 2

[0075] The difference from Example 1 is that 18.32 mg of antimony acetate was weighed according to 0.3 mol% Sb (the molar ratio of antimony in lithium cobalt oxide and antimony source is 1:0.003), and the mass percentage of antimony source in the resulting organic solution of antimony source was 1.2%, thus obtaining antimony-modified lithium cobalt oxide material (0.3 mol% Sb-LCO).

[0076] Under these conditions, the excessively high Sb content leads to a significant capacity loss in antimony-modified lithium cobalt oxide materials.

[0077] Comparative Example 3

[0078] The difference from Example 1 is that the material was heated to 500°C at a heating rate of 3°C / min in an oxygen atmosphere and calcined at 500°C for 5 hours to obtain antimony-modified lithium cobalt oxide material.

[0079] Comparative Example 4

[0080] The difference from Example 1 is that the material was heated to 300°C at a heating rate of 3°C / min in an oxygen atmosphere and calcined at 300°C for 5 hours to obtain antimony-modified lithium cobalt oxide material.

[0081] Performance testing

[0082] (1) Figure 1 SEM images of the antimony-modified lithium cobalt oxide material (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Example 1 are shown, where (a) and (b) are LCO, and (c) and (d) are Sb-LCO. Figure 1 As can be seen from the scanning electron microscope (SEM), the morphology of Sb-LCO and LCO particles remained almost unchanged before and after modification, indicating that surface optimization does not have an adverse effect on the morphology of the material.

[0083] (2) Figure 2 The images show the XRD patterns of the antimony-modified lithium cobalt oxide material (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Example 1. Figure 2 As can be seen from the XRD characterization of the crystal structures of Sb-LCO and LCO, although the surface optimization strategy was used, the results showed that the diffraction peaks of Sb-LCO were consistent with those of LCO, indicating that the surface optimization had no effect on the bulk structure of Sb-LCO.

[0084] (3) Figure 3 EDS images of the antimony-modified lithium cobalt oxide material (Sb-LCO) prepared in Example 1 are shown, where (a) is the SEM image of Sb-LCO, (b) is the O element distribution map of Sb-LCO, (c) is the Co element distribution map of Sb-LCO, and (d) is the Sb element distribution map of Sb-LCO. Figure 3 As can be seen from the figures, each figure shows the spatial distribution of a specific element in Sb-LCO.

[0085] (4) Figure 4 The images show the electrochemical performance of the antimony-modified lithium cobalt oxide material (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Example 1. (From...) Figure 4 As can be seen from the graph, the capacity retention rate is 94.14% after 100 cycles, and the capacity in the first cycle is 200.16 mAh / g. This is the electrochemical performance graph under optimal conditions.

[0086] (5) Figure 5 Electrochemical performance graphs of the antimony-modified lithium cobalt oxide material (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Comparative Example 1 are shown. Figure 5 As can be seen, the amount of antimony compound added under these conditions is insufficient, and it is not effective enough to improve the electrochemical performance of lithium cobalt oxide under high voltage. After 100 cycles, the capacity retention rate is 85.48%, which is lower than the cycle performance under optimal conditions.

[0087] (6) Figure 6 Electrochemical performance graphs of the antimony-modified lithium cobalt oxide material (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Comparative Example 2 are shown. Figure 6 As can be seen, although the capacity retention rate was 96.77% after 100 cycles under these conditions, the overall capacity was too low due to the excessive amount of antimony compound added. The capacity in the first cycle was 192.08 mAh / g, which is not the optimal performance.

[0088] (7) Figure 7 This is a rate performance graph of the antimony-modified lithium cobalt oxide material (Sb-LCO) and lithium cobalt oxide (LCO) prepared in Example 1. From... Figure 7 As can be seen, Sb-LCO has a significantly improved rate performance compared to LCO. At a high rate of 10C, Sb-LCO can still exhibit a capacity of 115mAh / g, which is higher than LCO's 70mAh / g.

[0089] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An antimony-modified lithium cobalt oxide cathode material, characterized in that, It includes layered lithium cobalt oxide and an antimony layer coating the surface of the layered lithium cobalt oxide; the antimony layer includes antimony oxides; The preparation method is as follows: First, weigh 2g of lithium cobalt oxide and place it in a beaker. Add anhydrous ethanol and then place it on a magnetic stirrer and stir at a constant speed of 300rpm for 10min to obtain an organic dispersion of lithium cobalt oxide. Meanwhile, in another beaker, 12.22 mg of antimony acetate was weighed according to 0.2 mol% Sb, the molar ratio of antimony in lithium cobalt oxide and antimony source was 1:0.002, and anhydrous ethanol was added as solvent. The mixture was ultrasonically treated for 10 min at 25 °C, 360 W power and 40 kHz frequency to obtain an organic solution of antimony acetate with a mass percentage of 0.8% antimony source. The organic solution of antimony acetate was slowly added dropwise to the organic dispersion of lithium cobalt oxide at a rate of 0.5 mL / min, and 5 mL of deionized water was added to promote the hydrolysis reaction of antimony acetate for 60 min. The generated antimony oxide and antimony hydroxide coated the lithium cobalt oxide material. Finally, the mixture was continuously stirred under a heating mantle at 50 °C and 300 r / min until the solvent evaporated to dryness, and the dry precursor material was obtained. The precursor material was placed in a tube furnace and heated to 400°C at a heating rate of 3°C / min in an oxygen atmosphere with a purity >99.5%, and calcined at 400°C for 5 hours. Then, it was annealed to room temperature at a rate of 3°C / min to obtain an antimony-modified lithium cobalt oxide cathode material with 0.2 mol% Sb-LCO and an antimony layer thickness of 10 nm.

2. The application of the antimony-modified lithium cobalt oxide cathode material according to claim 1 in lithium-ion batteries.

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