Positive electrode material and preparation method thereof, positive plate and battery

Abstract

The invention discloses a positive electrode material and a preparation method thereof, a positive plate and a battery. The positive electrode material is a modified lithium iron phosphate positive electrode material co-doped with an antimony element and a chlorine element. According to the preparation method, the modified lithium iron phosphate positive electrode material is prepared from the lithium iron phosphate positive electrode material, an antimony-containing compound and chloride through a one-step hydrothermal synthesis reaction. The lithium iron phosphate positive electrode material is doped and modified by the antimony element and the chlorine element at the same time, so that the modification of the antimony element and the modification of the chlorine element form advantage cooperation, the structure of the positive electrode material is optimized, the electrochemical and dynamic performance of the positive electrode material is improved, and the rate capability of the battery is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a positive electrode material and a preparation method thereof, a positive electrode sheet and a battery. Background Art

[0002] With the rapid development of the new energy industry, battery cell companies are paying more and more attention to the performance modification of existing positive electrode materials to improve the electrochemical performance of battery cells and even energy storage devices. Positive electrode materials are the decisive factor in the electrochemical performance of batteries, directly determining the energy density, cycle performance and safety of batteries. Common positive electrode materials include: lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, ternary materials, etc.

[0003] Among them, lithium iron phosphate material (LFP) is a popular cathode material at present. It is rich in raw materials, low in price, environmentally friendly, has good cycle performance and high safety, and is very popular among consumers. However, it also has the advantages of poor conductivity, Li + Defects such as slow diffusion rate are problems that still need to be solved. Summary of the invention

[0004] The object of the present invention is to provide a positive electrode material and a preparation method thereof, a positive electrode sheet and a battery in view of the above problems.

[0005] To achieve the above purpose, the technical solution provided by the present invention is:

[0006] A first aspect of the present application provides a positive electrode material, wherein the positive electrode material is a modified lithium iron phosphate positive electrode material, and the modified lithium iron phosphate positive electrode material is co-doped with antimony and chlorine.

[0007] Furthermore, the antimony element is Sb 3+ Ion; the chlorine element is Cl - ion.

[0008] The second aspect of the present application provides a method for preparing a positive electrode material, wherein a lithium iron phosphate positive electrode material is prepared into a modified lithium iron phosphate positive electrode material through a one-step hydrothermal synthesis reaction with an antimony-containing compound and a chloride.

[0009] In order to optimize the above technical solutions, the specific limitations adopted also include:

[0010] The antimony-containing compound is selected from at least one of antimony trioxide, antimony trisulfide, indium antimonide and silver antimonide; the chloride is selected from at least one of calcium chloride, potassium chloride and sodium chloride.

[0011] The molar ratio of the lithium iron phosphate positive electrode material to the antimony element in the antimony-containing compound is 65-80:1.

[0012] The molar ratio of the lithium iron phosphate positive electrode material to the chlorine element in the chloride is 120-135:1.

[0013] Preferably, the reaction temperature of the one-step hydrothermal synthesis reaction is 180-200° C., and the reaction time is 16-18 h.

[0014] In a disclosed scheme of the present invention, the reaction process is specifically as follows: after mixing the lithium iron phosphate positive electrode material with the antimony-containing compound and chloride, placing the mixture in a hydrothermal reactor, placing the mixture in a forced air drying oven for baking reaction, and then filtering, washing, and vacuum drying to obtain the modified lithium iron phosphate positive electrode material.

[0015] The third aspect of the present application provides a positive electrode sheet, comprising a positive electrode material prepared by the method of the first aspect of the present application or the second aspect of the present application.

[0016] The fourth aspect of the present application provides a battery, comprising the positive electrode sheet provided in the third aspect of the present application.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention introduces antimony and chlorine elements into conventional lithium iron phosphate materials, and obtains modified lithium iron phosphate materials through a one-step hydrothermal synthesis method, filtering, washing, and vacuum drying. The modified lithium iron phosphate material is used as a positive electrode material for a battery, which can achieve significant improvement in rate performance.

[0019] Due to Sb 3+ With Li + The ionic radius of Sb 3+ After doping the Li site, Sb 3+ It can smoothly enter the lattice of lithium iron phosphate material, Sb 3+ The high valence of Cl will promote the formation of more holes, which is beneficial to the transmission of lithium ions, thereby improving the rate performance. - O 2- The ionic radius is larger, and the Cl-doped - After that, it will cause the lithium iron phosphate material lattice to expand, thereby increasing the diffusion rate of lithium ions and the internal conductivity, which is manifested in the battery end as an improvement in rate performance. Due to the combined influence of these effects, the Sb 3+ With Cl - The co-doping changes the morphology of traditional lithium iron phosphate particles and realizes the radially arranged microstructure of lithium iron phosphate particles, which not only allows the rapid transmission of lithium ions during the charge and discharge process to effectively improve the battery's rate performance, but also helps to reduce the shrinkage and expansion of lithium iron phosphate particles after a long battery cycle and reduce the formation of defects.

[0020] In the present invention, calcium chloride is preferably used as the doping reactant of chlorine element, because Ca 2+ Ions can change the ion diffusion path in lithium iron phosphate, which is beneficial to the deintercalation of lithium ions under high current charging and discharging conditions, thereby playing a synergistic optimization role in the enhanced rate performance of antimony and chlorine doping. DETAILED DESCRIPTION

[0021] The above contents of the present invention are further described in detail below in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the above contents of the present invention belong to the scope of the present invention.

[0022] The experimental methods used in the following examples are all conventional methods unless otherwise specified, and the reagents, methods and equipment used are all conventional reagents, methods and equipment in the technical field unless otherwise specified.

[0023] For the sake of simplicity, this document only specifically discloses some numerical values ​​and optional ranges. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range. Similarly, any upper limit can be combined with any other upper limit to form an unambiguous range; the optional items in the optional range can also be combined arbitrarily.

[0024] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art.

[0025] The invention provides a positive electrode material, which is a modified lithium iron phosphate positive electrode material. The modified lithium iron phosphate positive electrode material contains antimony element and chlorine element doped together.

[0026] In a preferred embodiment, the antimony element is Sb 3+ Ion; chlorine is Cl - ion.

[0027] The present application also provides a method for preparing a positive electrode material, wherein a lithium iron phosphate positive electrode material is prepared into a modified lithium iron phosphate positive electrode material through a one-step hydrothermal synthesis reaction with an antimony-containing compound and a chloride.

[0028] In some embodiments, the antimony-containing compound is selected from at least one of antimony trioxide, antimony trisulfide, indium antimonide, and silver antimonide; and the chloride is selected from at least one of calcium chloride, potassium chloride, and sodium chloride.

[0029] The molar ratio of the lithium iron phosphate positive electrode material to the antimony element in the antimony-containing compound is 65-80:1.

[0030] The molar ratio of the lithium iron phosphate positive electrode material to the chlorine element in the chloride is 120-135:1.

[0031] Preferably, the reaction temperature of the one-step hydrothermal synthesis reaction is 180-200° C., and the reaction time is 16-18 h.

[0032] In some embodiments, the reaction process is specifically as follows: after mixing the lithium iron phosphate positive electrode material with the antimony-containing compound and the chloride, placing it in a hydrothermal reactor, putting it into a forced air drying oven for baking reaction, and after the reaction, filtering, washing, and vacuum drying to obtain the modified lithium iron phosphate positive electrode material.

[0033] The above specific reaction process is only an example of a commonly used device method, and the one-step hydrothermal synthesis reaction of the present application is not limited to the use of the above reaction device.

[0034] The solvent used for filtering and washing after the reaction can be pure water or alcohol; filtering and washing are performed multiple times; the vacuum drying conditions can be 100-140°C and 10-16h;

[0035] The present application also provides a positive electrode sheet comprising the above-mentioned positive electrode material.

[0036] When using the positive electrode material of the present application to prepare positive electrode sheets, conventional preparation methods can be used, using binders and conductive agents used in the art. The ratio of positive electrode material to binder and conductive agent can be obtained by technicians in this field through experiments and is not limited to the scheme involved in the embodiments.

[0037] The present application also provides a battery comprising the above-mentioned positive electrode sheet.

[0038] In some embodiments, the batteries of the present application may be assembled into a battery module. The number of batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0039] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0040] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments:

[0041] Embodiment 1:

[0042] 1. Preparation of Modified LFP Materials

[0043] A certain amount of traditional LFP material, Sb 2 O 3 , CaCl 2Put it in a beaker, add deionized water, stir it evenly, transfer it to a reactor, put it in a blast drying oven, bake it at 190℃ for 17h, filter, wash and vacuum dry to obtain the modified LFP material. 2 O 3 The molar ratio of traditional LFP material and CaCl is 145:1. 2 The molar ratio is 255:1.

[0044] 2. Preparation of positive electrode slurry:

[0045] The positive electrode active material is the product modified LFP material obtained in step 1, the binder is PVDF (KF1100), and the conductive agent is Super P (Swiss Termeco); the active material: binder: conductive agent = 96:2:2 are stirred and mixed, and after mixing evenly, coated on a 15um aluminum foil, and dried in a vacuum drying oven at 140°C for 12h.

[0046] 3. Assembly of button batteries:

[0047] The button battery shell uses the CR2032 model, the diaphragm uses a 20um diaphragm, and the electrode uses a positive electrode with a uniform coating. In a glove box filled with argon, the button battery is assembled in the following order: battery shell - place the positive electrode - drip the electrolyte - place the diaphragm - drip the electrolyte - place the lithium sheet - place the gasket spring - battery shell.

[0048] 4. Rate performance test:

[0049] A button battery charge and discharge tester (Wuhan Blue Electric, CT3002A) was used to perform charge and discharge tests on button batteries at 0.2C, 0.5C, 1C, and 3C, with a voltage range of 2.0-3.5V. The test results are shown in the table.

[0050] Embodiment 2:

[0051] It is basically the same as Example 1, except that: the traditional LFP material and Sb 2 O 3 The molar ratio is 125:1.

[0052] Embodiment 3:

[0053] It is basically the same as Example 1, except that: the traditional LFP material and Sb 2 O 3 The molar ratio is 135:1.

[0054] Embodiment 4:

[0055] It is basically the same as Example 1, except that: the traditional LFP material and Sb 2 O3 The molar ratio is 155:1.

[0056] Embodiment 5:

[0057] It is basically the same as Example 1, except that: the traditional LFP material and Sb 2 O 3 The molar ratio is 165:1.

[0058] Embodiment 6:

[0059] It is basically the same as Example 1, except that: the traditional LFP material and CaCl 2 The molar ratio is 235:1.

[0060] Embodiment 7:

[0061] It is basically the same as Example 1, except that: the traditional LFP material and CaCl 2 The molar ratio is 245:1.

[0062] Embodiment 8:

[0063] It is basically the same as Example 1, except that: the traditional LFP material and CaCl 2 The molar ratio is 265:1.

[0064] Embodiment 9:

[0065] It is basically the same as Example 1, except that: the traditional LFP material and CaCl 2 The molar ratio is 275:1.

[0066] Comparative Example 1:

[0067] It is basically the same as Example 1, except that: there is no Sb in step 1 2 O 3 Introduction.

[0068] Comparative Example 2:

[0069] The same as Example 1, except that: there is no CaCl in step 1 2 Material introduction.

[0070] Comparative Example 3:

[0071] It is basically the same as Example 1, except that traditional LFP is used as the positive electrode material.

[0072] The examples and comparative examples were tested and the results are shown in Table 1:

[0073] Table 1 Comparison of test results of various embodiments and comparative examples

[0074] serial number 0.2C capacity retention rate 0.5C capacity retention rate 1C capacity retention rate 3C capacity retention rate Example 1 99.5％ 97.1％ 93.4％ 88.9％ Example 2 96.1％ 94.1％ 89.1％ 81.6％ Example 3 96.5％ 94.5％ 89.3％ 82.3％ Example 4 96.9％ 94.4％ 89.7％ 82.4％ Example 5 96.4％ 94.5％ 89.1％ 81.2％ Example 6 97.6％ 94.8％ 88.8％ 80.9％ Example 7 97.8％ 95.2％ 89.3％ 82.4％ Example 8 97.2％ 95.3％ 89.8％ 82.5％ Example 9 97.1％ 94.8％ 88.3％ 81.7％ Comparative Example 1 95.9％ 91.9％ 82.2％ 73.2％ Comparative Example 2 95.3％ 90.1％ 80.7％ 70.9％ Comparative Example 3 93.1％ 87.4％ 75.1％ 61.7％

[0075] From the test results, we can know that:

[0076] The capacity retention test results of Examples 1-9 of the present invention are compared with those of Comparative Examples 1-3. 2 O 3 Introduced or no CaCl 2 When the material was introduced, the test results were worse than those in the embodiment. 2 O 3 , CaCl 2 In comparative example 3, there is no Sb 2 O 3 Introduced without CaCl 2 When the material is introduced, the comparison of the test results is more obvious. The present application optimizes the structure of the positive electrode material by modifying the lithium iron phosphate positive electrode material by doping it with antimony and chlorine elements at the same time, thereby improving its electrochemical kinetic performance.

[0077] The experimental measurements of each embodiment in Examples 1-9 are compared and it can be seen that the traditional LFP material and Sb 2 O 3 , CaCl 2 By using a certain appropriate ratio, the modification of antimony and chlorine can form an advantageous combination, significantly improving the rate performance of the battery. 2 O 3 The molar ratio of CaCl is in the range of 130-160:1. 2 When the molar ratio is in the range of 240-270:1, the test effect is better.

[0078] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, according to the technical essence of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the present invention.

Claims

1. A positive electrode material, characterized in that: The positive electrode material is a modified lithium iron phosphate positive electrode material, and the modified lithium iron phosphate positive electrode material contains antimony element and chlorine element co-doped and modified.

2. The positive electrode material according to claim 1, characterized in that: The antimony element is Sb 3+ Ion; the chlorine element is Cl - ion.

3. A method for preparing a positive electrode material, characterized in that: The modified lithium iron phosphate positive electrode material is prepared by a one-step hydrothermal synthesis reaction of a lithium iron phosphate positive electrode material, an antimony-containing compound and a chloride.

4. The method for preparing the positive electrode material according to claim 3, characterized in that: The antimony-containing compound is selected from at least one of antimony trioxide, antimony trisulfide, indium antimonide and silver antimonide; the chloride is selected from at least one of calcium chloride, potassium chloride and sodium chloride.

5. The method for preparing the positive electrode material according to claim 3, characterized in that: The molar ratio of the lithium iron phosphate positive electrode material to the antimony element in the antimony-containing compound is 65-80:

1.

6. The method for preparing the positive electrode material according to claim 3, characterized in that: The molar ratio of the lithium iron phosphate positive electrode material to the chlorine element in the chloride is 120-135:

1.

7. The method for preparing the positive electrode material according to claim 3, characterized in that: The reaction temperature of the one-step hydrothermal synthesis reaction is 180-200° C., and the reaction time is 16-18 hours.

8. The method for preparing the positive electrode material according to claim 3, characterized in that: The specific reaction process is as follows: after mixing the lithium iron phosphate positive electrode material with the antimony-containing compound and chloride, placing the mixture in a hydrothermal reactor, placing the mixture in a forced air drying oven for baking reaction, and then filtering, washing, and vacuum drying to obtain the modified lithium iron phosphate positive electrode material.

9. A positive electrode sheet, characterized in that: A positive electrode material comprising the positive electrode material described in claim 1 or 2 or prepared by the method described in any one of claims 3 to 8.

10. A battery, characterized in that: A positive electrode sheet comprising the positive electrode sheet according to claim 9.