A cobalt-free novel high-rate ternary battery cathode material and a preparation method thereof

Abstract

The application discloses a cobalt-free novel high-rate ternary battery positive electrode material and a preparation method thereof. 0.9 Ce 0.05 Mn 0.05 (OH)2 precursor; the precursor is pre-calcined, and after cooling, the precursor is ball-milled with lithium hydroxide monohydrate at a molar ratio of 1:1.08, and then is subjected to secondary calcination, oxygen calcination, cooling, crushing, sieving and grinding. The cobalt-free novel high-rate ternary battery positive electrode material and the preparation method thereof can avoid serious capacity attenuation and cycle stability deterioration of the material under the premise of ensuring the content of nickel.

Description

Technical Field

[0001] This invention relates to a novel cobalt-free, high-rate ternary battery cathode material and its preparation method, belonging to the field of lithium battery technology. Background Technology

[0002] Cathode materials are a crucial component of lithium-ion batteries, directly impacting their performance. Among them, ternary materials like LiNi... x Co y Mn 1−x−y O2 (NCM) cathode materials combine the advantages of traditional layered cathode materials such as LiNiO2 and LiCoO2, and are currently widely used in commercial lithium-ion batteries. Increasing the nickel content in the cathode material can further improve the energy density of the battery. However, due to the scarcity of cobalt resources and its potential for water and soil pollution, lithium-ion batteries are currently developing towards high-nickel, low-nickel, and cobalt-free materials. However, increasing the nickel content can easily lead to severe capacity decay and deterioration in cycle stability. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a novel cobalt-free high-rate ternary battery cathode material and its preparation method, which can avoid severe capacity decay and deterioration of cycle stability of the material while ensuring nickel content.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a novel cobalt-free, high-rate ternary battery cathode material includes the following steps:

[0006] S01, add 1000mL of deionized water to a three-necked flask, assemble the three-necked flask with the condenser, seal all joints and ports with plastic wrap, and introduce nitrogen into the three-necked flask. At the same time, poke holes in the plastic wrap at the upper port of the condenser to remove oxygen from the deionized water. Prepare a salt solution by adding nickel nitrate hexahydrate, cerium nitrate hexahydrate, and manganese sulfate monohydrate according to a nickel:cerium:manganese molar ratio of 90:5:5. Add polyvinyl alcohol solid particles to the salt solution.

[0007] S02 is continuously heated and stirred. After the metal salt particles are completely dissolved in deionized water, polyacrylamide is added all at once. Then the reaction solution is sealed with plastic wrap. Nitrogen gas is introduced throughout the reaction, with only the small hole above the condenser for venting.

[0008] After transferring the reaction solution to a large beaker containing SO3 and sealing it with plastic wrap, the mixture was allowed to stand for a period of time to precipitate. The precipitate was then filtered, centrifuged, washed, and dried to obtain Ni. 0.9 Ce 0.05 Mn 0.05(OH)2 precursor;

[0009] S04, the obtained Ni 0.9 Ce 0.05 Mn 0.05 The (OH)₂ precursor was pre-calcined, cooled, and then ball-milled with lithium hydroxide monohydrate at a molar ratio of 1:1.08. This mixture was then subjected to a second calcination, followed by oxygen-assisted calcination after a period of time. Finally, it was cooled, removed, sieved, and ground to obtain the cathode material LiNi. 0.90 Ce 0.05 Mn 0.05 O2.

[0010] In S01, the total concentration of the salt solution is 50 mmol / L, the volume is 1L, and the polyvinyl alcohol solid particles are polyvinyl alcohol type 1788 with a mass of 3g.

[0011] In SO2, the stirring speed is 500 rpm, the stirring temperature is 120℃, the stirring reaction time is 6 h, and the amount of polyacrylamide added is 50 mL.

[0012] In SO3, the settling time is 12 hours, and the cleaning includes two deionized water washes and two alcohol washes.

[0013] In SO4, the pre-calcination temperature is 300℃ and the time is 4h; the secondary calcination temperature is 600℃ and the time is 6h; the oxygen-assisted calcination temperature is 800℃ and the time is 25h.

[0014] A novel cobalt-free high-rate ternary battery cathode material is prepared by the above-described preparation method.

[0015] The beneficial effects of this invention: This invention provides a novel cobalt-free, high-rate ternary battery cathode material and its preparation method. By completely replacing Co with the rare earth element Ce, a novel ternary cathode material, LiNi, is prepared. 0.90 Ce 0.05 Mn 0.05 O2 is used to reduce the environmental pollution caused by cobalt. Furthermore, Ce, a rare earth element, is cheaper than Co, reducing costs. The Ce-O chemical bond formed during the reaction is stronger, enhancing the structural stability of the cathode material during charge and discharge, improving cycle stability. The larger radius of cerium ions can increase interlayer spacing and improve the diffusion rate of lithium ions, thus improving electrochemical performance and avoiding the severe capacity decay problem caused by increasing nickel content. Additionally, this invention uses polyacrylamide as a precipitant and polyvinyl alcohol as a dispersant, preparing the precursor via a co-precipitation method. Polyacrylamide is a linear polymer compound that decomposes at high temperatures to generate ammonia gas. Ammonia gas reacts with water to form ammonia water, which hydrolyzes to provide OH-. -This invention provides a stable alkaline reaction condition, thereby accelerating particle aggregation and precipitation, avoiding uneven precipitation and difficulty in pH control. Polyvinyl alcohol, a water-soluble polymer surfactant, can reduce the surface tension between solid particles and has good hydrophilicity and dispersibility, allowing solid particles to be dispersed in the liquid and uniformly distributed. The use of polyacrylamide and polyvinyl alcohol in this invention not only provides a stable alkaline reaction condition but also allows metal salt particles to be better dispersed in deionized water to form flocs, thus accelerating particle aggregation. This is beneficial for preparing a precursor with dense and uniform particle distribution, improving the quality of the precursor, and ultimately preparing a cathode material with excellent electrochemical performance. Furthermore, this preparation method makes the wastewater generated during the reaction process easier to treat, reducing environmental pollution. Attached Figure Description

[0016] Figure 1 This is the XRD pattern of lithium nickel cerium manganese oxide (NCM-Ce) prepared by the method of this invention;

[0017] Figure 2 The first charge-discharge curves of lithium nickel cobalt manganese oxide (NCM-Co) and lithium nickel cerium manganese oxide (NCM-Ce) prepared by the method of this invention are shown at 0.1C.

[0018] Figure 3 The graph shows the cycling performance of lithium nickel cobalt manganese oxide (NCM-Co) and lithium nickel cerium manganese oxide (NCM-Ce) prepared by the method of this invention at 1C.

[0019] Figure 4 The graph shows the rate performance of lithium nickel cobalt manganese oxide (NCM-Co) and lithium nickel cerium manganese oxide (NCM-Ce) prepared by the method of this invention at different current densities. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention. Specific Implementation

[0021] This invention discloses a method for preparing a novel cobalt-free, high-rate ternary battery cathode material, comprising the following steps:

[0022] Step 1: Take 1000 mL of deionized water into a three-necked flask. Assemble the condenser at the middle port. Seal the condenser at the left and middle ports with plastic wrap to prevent heat dissipation. Insert a thermometer into the right port and set the temperature to 120℃ and the rotation speed to 500 rpm. When introducing nitrogen gas into the three-necked flask, poke small holes in the plastic wrap above the condenser to remove oxygen from the deionized water. After heating to the set temperature, add nickel nitrate hexahydrate, cerium nitrate hexahydrate, and manganese sulfate monohydrate in a nickel:cerium:manganese molar ratio of 90:5:5 to prepare a 1 L salt solution with a total concentration of 50 mmol / L. Add 3 g of polyvinyl alcohol 1788 solid granules to the salt solution.

[0023] Step 2: Continue heating and stirring until the metal salt particles are completely dissolved in the deionized water. Then, add 50 mL of polyacrylamide at once, ensuring that all joints are sealed with plastic wrap. Let the reaction proceed for 6 hours, with nitrogen gas introduced throughout the reaction, leaving only a small hole above the condenser for venting.

[0024] Step 3: After 6 hours, transfer the reaction solution to a large beaker, seal it with plastic wrap, and let it stand for a period of time to precipitate. Pour off the supernatant, filter, centrifuge, and wash the precipitate, and dry it to obtain Ni. 0.9 Ce 0.05 Mn 0.05 (OH)2 precursor. The settling time was 12 hours, and the washing process included two washes with deionized water and two washes with alcohol.

[0025] Step four, obtain Ni 0.9 Ce 0.05 Mn 0.05 After pre-calcining the (OH)₂ precursor for a period of time, it was ball-milled and mixed with lithium hydroxide monohydrate at a molar ratio of 1:1.08. Then, it underwent a second calcination, followed by oxygen-assisted calcination after a period of time. Finally, it was cooled, removed, pulverized, sieved, and ground to obtain LiNi. 0.9 Ce 0.05 Mn 0.05 The O2 ternary cathode material is denoted as NCM-Ce. The pre-calcination temperature is 300℃ for 4 hours; the secondary calcination temperature is 600℃ for 6 hours; and the oxygen-assisted calcination temperature is 800℃ for 25 hours. Example

[0026] Lithium nickel cobalt manganese oxide cathode materials were prepared according to the above preparation method, the only difference being that cerium nitrate hexahydrate in step one was replaced with cobalt nitrate hexahydrate in step one. The Ni alloy in step three was prepared using the same steps. 0.9 Co 0.05 Mn 0.05 (OH)2 precursor, finally the lithium nickel cobalt manganese oxide ternary cathode material (LiNi) in step four is prepared. 0.9 Co0.05 Mn 0.05 O2), denoted as NCM-Co.

[0027] like Figure 1 As shown, the diffraction peaks of lithium nickel cerium manganese oxide prepared in this invention match well with the standard card (PDF#09-0063) of layered LiNiO2, corresponding to hexagonal... a It has the R3m space group of the -NaFeO2 structure and no other impurity peaks.

[0028] like Figure 2 As shown, at 0.1C, the initial charge specific capacities of lithium nickel cobalt manganese oxide and lithium nickel cerium manganese oxide prepared in this invention are 189.57 mAh / g and 199.71 mAh / g, respectively, and the discharge specific capacities are 185.23 mAh / g and 191.15 mAh / g, respectively. Figure 3 As shown, at 1C, the initial discharge specific capacities of lithium nickel cobalt manganese oxide and lithium nickel cerium manganese oxide prepared according to the present invention are 148.47 mAh / g and 153.35 mAh / g, respectively. After 100 cycles, the discharge specific capacities are 129.79 mAh / g and 134.37 mAh / g, respectively, with corresponding capacity retention rates of 87.42% and 87.62%, respectively. The lithium nickel cerium manganese oxide prepared according to the present invention has better cycle performance.

[0029] like Figure 4 The figure shows the rate performance of lithium nickel cobalt manganese oxide and lithium nickel cerium manganese oxide prepared according to the present invention at different current densities. As can be seen from the figure, the discharge specific capacity decreases with increasing current density. However, at a high rate of 5C, the discharge specific capacity of lithium nickel cerium manganese oxide prepared according to the present invention is significantly higher than that of lithium nickel cobalt manganese oxide. The discharge specific capacities of lithium nickel cobalt manganese oxide and lithium nickel cerium manganese oxide are 71.51 mAh / g and 105.74 mAh / g, respectively. After returning to 0.2C from a high rate discharge, the discharge specific capacities are 166.11 mAh / g and 177.24 mAh / g, respectively. Compared with the initial discharge specific capacities at 0.2C (168.98 mAh / g and 177.65 mAh / g), the capacity recovery rates are 99.48% and 99.77%, respectively. The data comparison shows that lithium nickel cerium manganese oxide prepared according to the present invention has excellent rate performance. Therefore, by using polyacrylamide and polyvinyl alcohol to prepare precursors, a ternary cathode material with excellent performance and good stability at high rates was obtained.

[0030] Finally, the precursor prepared by polyacrylamide and polyvinyl alcohol in this invention has a mass of approximately 4.6-5.2g. When polyacrylamide is replaced with an equal volume of formamide, and other conditions remain unchanged, the mass of the final precursor is approximately 4-4.3g. It can be seen that the precursor prepared by polyacrylamide and polyvinyl alcohol in this invention has a more obvious dispersion and sedimentation effect than that prepared by polyethylene glycol and formamide, and the yield is also greater.

[0031] This invention prepares a novel cobalt-free, high-rate ternary battery cathode material, LiNi, by completely replacing cobalt with cerium. 0.9 Ce 0.05 Mn 0.05 O2 is used to reduce the environmental pollution caused by cobalt salts. At the same time, the ternary cathode material prepared by polyacrylamide and polyvinyl alcohol does not require strict control of pH and liquid inlet rate compared with the traditional preparation using aqueous solutions of ammonia and sodium hydroxide, simplifying the reaction process. In addition, the use of sulfate and ammonia in the reaction process will generate difficult-to-treat wastewater. However, the raw materials prepared by this invention use nitrate instead of sulfate, and the use of polyacrylamide and polyvinyl alcohol can improve the floc strength and sedimentation speed, making the wastewater generated in the reaction process easier to treat.

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a cobalt-free, high-rate ternary battery cathode material, characterized in that: Includes the following steps: S01, add deionized water to a three-necked flask, assemble the three-necked flask with the condenser, and seal all joints and ports with plastic wrap. Nitrogen gas is introduced into the three-necked flask throughout the reaction. At the same time, holes are punched in the plastic wrap at the upper port of the condenser to remove oxygen from the deionized water. Nickel nitrate hexahydrate, cerium nitrate hexahydrate, and manganese sulfate monohydrate are added to deionized water to prepare a salt solution according to the nickel:cerium:manganese molar ratio of 90:5:

5. Polyvinyl alcohol solid is then added to the salt solution. S02 is heated and stirred continuously until the metal salt particles are completely dissolved in deionized water. Then, polyacrylamide is added all at once, and the reaction solution is sealed with plastic wrap. After transferring the reaction solution to a large beaker containing SO3 and sealing it with plastic wrap, the mixture was allowed to stand for a period of time to precipitate. Following filtration, centrifugation, washing, and drying, Ni was obtained. 0.9 Ce 0.05 Mn 0.05 (OH)2 precursor; S04, the obtained Ni 0.9 Ce 0.05 Mn 0.05 The (OH)₂ precursor was pre-calcined, cooled, and then ball-milled with lithium hydroxide monohydrate at a molar ratio of 1:1.

08. This mixture was then subjected to a second calcination, followed by oxygen-assisted calcination. The pre-calcination temperature was 300℃ for 4 hours; the second calcination temperature was 600℃ for 6 hours; and the oxygen-assisted calcination temperature was 800℃ for 25 hours. Finally, the mixture was cooled, pulverized, sieved, and ground to obtain LiNi. 0.9 Ce 0.05 Mn 0.05 O2 ternary cathode material.

2. The method for preparing a cobalt-free, high-rate ternary battery cathode material according to claim 1, characterized in that: In S01, the total concentration of the salt solution is 50 mmol / L, the volume is 1L, and the polyvinyl alcohol solid particles are polyvinyl alcohol type 1788 with a mass of 3g.

3. The method for preparing a cobalt-free, high-rate ternary battery cathode material according to claim 2, characterized in that: In SO2, the stirring speed is 500 rpm, the stirring temperature is 120℃, the stirring reaction time is 6 h, and the amount of polyacrylamide added is 50 mL.

4. The method for preparing a cobalt-free, high-rate ternary battery cathode material according to claim 1, characterized in that: In SO3, the settling time is 12 hours, and the washing includes two washes with deionized water and two washes with alcohol.

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