Conductive polymer-coated lithium ion battery cathode material and preparation method thereof

Abstract

The application relates to the technical field of lithium ion batteries, and discloses a conductive polymer-coated lithium ion battery positive electrode material and a preparation method thereof. 0.8 Co 0.1 Mn 0.1 O2 as a matrix, and the surface is coated with a polyaniline-polyethylene glycol copolymer, and the mass percentage of the copolymer is 0-5%. The positive electrode material can be prepared through an emulsion polymerization, a mixed ball milling, a low-temperature sintering and a grinding process. The conductive polymer-coated lithium ion battery positive electrode material can obviously improve the cycle performance of the lithium ion battery at a high voltage between 2.8-4.4V, optimizes the thermal stability of the positive electrode material itself, effectively improves the reversible capacity of the positive electrode material, helps to reduce the manufacturing cost and enhances the comprehensive performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a conductive polymer-coated lithium-ion battery cathode material and its preparation method. Background Technology

[0002] As research continues to advance in the field of lithium-ion battery cathode materials, in order to cater to market demand for lithium nickel cobalt manganese oxide (LiNiO2) 1-x-y Co x Mn y To meet the high standards of energy density and safety performance of O2 materials, researchers have proposed several innovative strategies. These strategies include: introducing new elements through doping or surface coating techniques to optimize the electrochemical performance of the material; adjusting the proportion of metal elements to enhance battery capacity; and improving the morphology and structure of the material to increase energy density. Previous researchers have explored different transition metal ratios in LiNi... 1-x-y Co x Mn y In-depth research on O2 cathode materials has revealed the patterns of their performance and structural variations. Studies show that high-nickel-content LiNi with a layered structure... 0.8 Co 0.1 Mn 0.1 O2 cathode materials, due to their excellent specific capacity, superior cycle stability, and economical cost-effectiveness, are gradually becoming one of the most promising cathode material choices for commercial applications.

[0003] Nevertheless, while high nickel content provides high energy density, it reduces the structural stability of the material, making it susceptible to phase transitions and structural damage during charge and discharge. LiNi 0.8 Co 0.1 Mn 0.1 O2 cathode materials have high surface chemical activity, making them prone to side reactions with the electrolyte, leading to capacity decay and shortened lifespan. Under high temperature or overcharge conditions, LiNi... 0.8 Co 0.1 Mn 0.1 O2 has relatively poor thermal stability, posing a safety hazard. As the number of cycles increases, LiNi... 0.8 Co 0.1 Mn 0.1 O2 cathode materials can experience microcrack propagation and internal structural degradation, affecting their cycle life.

[0004] To address this challenge, Chinese patent CN118619372A relates to a nickel-cobalt-manganese oxide material with a zirconate-cerate composite coating structure, aiming to improve the initial discharge specific capacity, rate performance, cycle performance, and high-temperature cycle stability of lithium-ion battery cathode materials. This patent effectively improves the electrochemical performance of the material by forming a composite coating layer on the surface of the nickel-cobalt-manganese oxide. Patent CN118630169A describes a method for coating conventional lithium nickel-cobalt-manganese cathode materials with a WC-W-2C heterostructure. This method can improve the rate performance of modified lithium nickel-cobalt-manganese cathode materials, suppress voltage decay, and provide excellent long-term cycle stability. Through this specific heterostructure coating, the electrochemical performance of the cathode material is significantly improved. Patent CN114784248B describes a method that forms a fast-ion conductor layer on the surface of ternary materials through a dry acid-base reaction. The dry coating avoids the electrochemically inactive layer generated by the material's contact with water in wet coating, reducing additional lithium loss and improving the material's cycle performance, rate performance, and low-temperature performance.

[0005] While current control methods can effectively improve the structural stability and cycle performance of nickel-cobalt-manganese-oxygen lithium-ion batteries, they still fall far short of practical application requirements due to their complex processes and high costs. Current cathode materials struggle to balance manufacturing costs, capacity, internal resistance, and other electrochemical properties with their inherent safety. Therefore, there is an urgent need to develop a lithium-ion battery cathode material with good structural stability, superior performance, and high safety. Summary of the Invention

[0006] The technical problem this invention aims to solve is the series of problems commonly encountered by ternary cathode materials during long-term cycling in existing technologies, such as structural reorganization, particle fragmentation, transition metal dissolution, and damage to the interface film between the cathode and electrolyte. Especially under high delithiation conditions, oxide cathode materials exhibit poor thermal stability and are prone to decomposition at high temperatures, releasing oxygen and causing severe oxidation reactions in the electrolyte, generating large amounts of heat and gas, which may lead to battery fires or explosions. To overcome these shortcomings, this invention provides a conductive polymer-coated lithium-ion battery cathode material and its preparation method. By optimizing the production cost of the cathode material, enhancing its crystal structure stability in high-voltage environments, reducing side reactions at the interface, improving the material's thermal stability, and lowering the risk of battery thermal runaway, this invention enhances the cycle life and safety of lithium-ion batteries.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] A conductive polymer-coated lithium-ion battery cathode material, comprising a polyaniline (PANI)-polyethylene glycol (PEG) copolymer and lithium nickel cobalt manganese oxide cathode material LiNi 1-x-y Cox Mn y O2 composite sintering was used to obtain the cathode material; among which, lithium nickel cobalt manganese oxide (LiNi) was used. 1-x-y Co x Mn y The O2 mass percentage is 97–99.5%, with the balance being polyaniline-polyethylene glycol copolymer.

[0009] Furthermore, the polyaniline-polyethylene glycol copolymer is prepared by emulsion polymerization or solution polymerization.

[0010] Furthermore, the sintering method is a tube furnace with an oxygen atmosphere or a muffle furnace with an air atmosphere.

[0011] Furthermore, the molecular weight of polyethylene glycol in the polyaniline-polyethylene glycol copolymer is 200 to 400.

[0012] Furthermore, the lithium nickel cobalt manganese oxide cathode material LiNi 1-x-y Co x Mn y In O2, x ranges from 0.05 to 0.2, and y ranges from 0.05 to 0.3.

[0013] A method for preparing a conductive polymer-coated lithium-ion battery cathode material as described above specifically includes the following steps:

[0014] Step S1: Weigh polyethylene glycol and aniline, mix them, add deionized water, then add dodecylbenzenesulfonic acid aqueous solution and ammonium persulfate. Polymerize at 0-5℃ for 6 hours, then clean with a centrifuge and dry to obtain polyaniline-polyethylene glycol copolymer.

[0015] Step S2: The polyaniline-polyethylene glycol copolymer and lithium nickel cobalt manganese oxide cathode material LiNi... 1-x-y Co x Mn y After mixing with O2, add anhydrous ethanol, then place the mixture in a mechanical mixing device and mix for 1 hour. After thorough mixing, a mixed powder is obtained.

[0016] Step S3: Place the mixed powder into the sample cell, then place it in the sintering furnace and sinter for 12 hours to obtain the initial product;

[0017] Step S4: Place the initial product into a mortar and grind it to obtain the finished conductive polymer-coated lithium-ion battery cathode material.

[0018] Furthermore, in step S1, the mass ratio of polyethylene glycol to aniline is (4-8):1.86.

[0019] Furthermore, in step S2, the mixing temperature is 80°C.

[0020] Furthermore, in step S3, the sintering temperature is 400°C.

[0021] The beneficial effects of this invention are as follows: This invention has a reasonable design and a simple preparation method, and has the following advantages:

[0022] (1) The conductive polymer-coated lithium-ion battery cathode material of the present invention can significantly improve the cycle performance of nickel manganese oxide lithium-ion batteries at high voltages of 2.8 to 4.4V. Compared with existing cathode materials, the specific capacity of the battery increases to 202.00 mA / g and the capacity retention rate increases to 75%.

[0023] (2) The conductive polymer coating of the lithium-ion battery cathode material of the present invention can improve the thermal stability of the cathode material itself, increase the thermal decomposition reaction temperature of the cathode material, and achieve the purpose of delaying the thermal runaway rate of the battery and improving the safety performance of the battery. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 The graph shows a comparison of the cycle efficiency curves of the half-cells assembled in Examples 1 to 3 of this invention and Comparative Example 1.

[0026] Figure 2 The above are comparative graphs of the thermal analysis test DSC curves of the cathode materials in Examples 1 to 3 of this invention and Comparative Example 1. Detailed Implementation

[0027] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0028] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] A conductive polymer-coated lithium-ion battery cathode material, comprising a copolymer polyaniline (PANI)-polyethylene glycol (PEG) and lithium nickel cobalt manganese oxide cathode material LiNi 1-x-y Co x Mn y O2 composite sintering was used to obtain the cathode material; among which, lithium nickel cobalt manganese oxide (LiNi) was used. 1-x-y Co x Mn y The O2 mass percentage is 97–99.5%, with the balance being polyaniline-polyethylene glycol copolymer.

[0031] The polyaniline-polyethylene glycol copolymer can be prepared by emulsion polymerization or solution polymerization.

[0032] The sintering method is a tube furnace with an oxygen atmosphere or a muffle furnace with an air atmosphere.

[0033] The molecular weight of polyethylene glycol in polyaniline-polyethylene glycol copolymers is 200-400.

[0034] LiNi nickel cobalt manganese oxide cathode material 1-x-y Co x Mn y In O2, x ranges from 0.05 to 0.2, and y ranges from 0.05 to 0.3.

[0035] A method for preparing the above-mentioned conductive polymer-coated lithium-ion battery cathode material specifically includes the following steps:

[0036] Step S1: Weigh polyethylene glycol and aniline, mix them, add deionized water, then add dodecylbenzenesulfonic acid aqueous solution and ammonium persulfate. Polymerize at 0-5℃ for 6 hours, then wash with a centrifuge and dry at 80℃ to obtain polyaniline-polyethylene glycol copolymer.

[0037] Step S2: The polyaniline-polyethylene glycol copolymer and lithium nickel cobalt manganese oxide cathode material LiNi... 1-x-y Co x Mn y After mixing with O2, add 100 ml of anhydrous ethanol, then place it in a mechanical mixing device and mix for 1 hour at a temperature of 80°C. After thorough mixing, a mixed powder is obtained.

[0038] Step S3: Place the mixed powder into the sample cell, then place it in the sintering furnace, sinter at 400℃ for 12 hours to obtain the initial product;

[0039] Step S4: Place the initial product into a mortar and grind for 5 minutes to obtain the finished conductive polymer-coated lithium-ion battery cathode material.

[0040] Example 1

[0041] A method for preparing a conductive polymer-coated positive electrode material for lithium-ion batteries specifically includes the following steps:

[0042] Step S1: Weigh 6g of polyethylene glycol and 1.86g of aniline, mix them, add 60ml of deionized water, then add dodecylbenzenesulfonic acid aqueous solution and ammonium persulfate. Polymerize at 5℃ for 6h, then wash with a centrifuge and dry at 80℃ to obtain polyaniline-polyethylene glycol copolymer; the molecular weight of polyaniline-polyethylene glycol copolymer is 300.

[0043] Step S2: Add 0.02g of polyaniline-polyethylene glycol copolymer and 1.98g of lithium nickel cobalt manganese oxide cathode material LiNi 0.8 Co 0.1 Mn 0.1 After mixing with O2, add 100 ml of anhydrous ethanol, then place it in a mechanical mixing device and mix for 1 hour at a temperature of 80°C. After thorough mixing, a mixed powder is obtained.

[0044] Step S3: Place the mixed powder into the sample cell, and then place it in a tube furnace under an oxygen atmosphere. The sintering temperature is 400℃, and the sintering time is 12 hours to obtain the initial product.

[0045] Step S4: Place the initial product into a mortar and grind for 5 minutes to obtain the finished conductive polymer-coated lithium-ion battery cathode material.

[0046] The manufacturing process of a positive electrode sheet is as follows: The positive electrode material of lithium-ion battery coated with conductive polymer, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of positive electrode material: acetylene black: PVDF = 8:1:1. After mixing, N-methylpyrrolidone (NMP) is added and stirred thoroughly to form a uniform positive electrode slurry. This slurry is then uniformly coated onto a 15μm thick aluminum foil and dried in a forced-air drying oven at 120℃ for 12 hours to obtain the positive electrode sheet for later use.

[0047] The manufacturing process of a positive electrode half-cell is as follows: the above positive electrode sheet is used as the positive electrode, the lithium metal sheet is used as the negative electrode, Celgard 2500 is used as the separator, electrolyte is added, and the cells are assembled into a button cell with battery model CR2032 in a glove box.

[0048] The battery cycle test procedure is as follows:

[0049] The assembled coin cells were left to stand at room temperature (25°C) for 12 hours, and then cycled at a charge / discharge voltage of 2.8–4.4V. The coin cells were first charged and discharged for three cycles at a current of C / 10, and then 50–100 cycles were performed at a current of C / 5.

[0050] The test procedure was as follows: constant current charging at C / 20 to 4.4V, followed by discharge at C / 20 to 2.8V. After fully activating the electrode material, the battery was cycled 100 times at C / 5 to evaluate its cycle stability.

[0051] The thermal analysis test process is as follows:

[0052] After cycling, the coin cell was disassembled in a glove box, the positive electrode was separated, and the positive electrode was cleaned with dimethyl carbonate solvent to remove residual electrolyte and allowed to dry. The electrode material was scraped off the aluminum sheet, and 5 mg ± 0.5 mg of the electrode was weighed and placed in the sample cell. Differential scanning calorimetry (DSC) experiments were performed on the conductive polymer-coated lithium-ion battery. As a comparison, DSC experiments were also performed individually on samples with different positive electrode materials.

[0053] Example 2

[0054] The difference from Example 1 is that in step S1 of this example, 4g of polyethylene glycol and 1.86g of aniline are weighed, mixed, and then 60ml of deionized water is added. Then, dodecylbenzenesulfonic acid aqueous solution and ammonium persulfate are added and polymerized at 5°C for 6 hours. After centrifugation and washing, the copolymer is dried at 80°C to obtain polyaniline-polyethylene glycol copolymer. The molecular weight of polyaniline-polyethylene glycol copolymer is 200.

[0055] The cathode material and coin cell were prepared using the same method as in Example 1, and their cycle performance and thermal analysis were tested.

[0056] Example 3

[0057] The difference from Example 1 is that in step S1 of this example, 8g of polyethylene glycol and 1.86g of aniline are weighed, mixed, and then 60ml of deionized water is added. Then, dodecylbenzenesulfonic acid aqueous solution and ammonium persulfate are added and polymerized at 5°C for 6 hours. After centrifugation and washing, the copolymer is dried at 80°C to obtain polyaniline-polyethylene glycol copolymer. The molecular weight of polyaniline-polyethylene glycol copolymer is 400.

[0058] The positive electrode material and coin half-cell were prepared using the same method as in Example 1, and thermal analysis tests were performed.

[0059] Comparative Example 1

[0060] The difference from Example 1 is that the cathode material of this comparative example is a ternary cathode material in the prior art.

[0061] The cathode material and cathode half-cell were prepared using the same method as in Example 1, and their cycle performance and thermal stability were tested.

[0062] from Figure 1 As can be seen, compared with Examples 1 to 3, adjusting the molecular weight of ethylene glycol to 300 significantly improved the cycle performance of the battery. The cycle performance results of the three coin half-cells show that the reversible capacity of the three cathode materials increases in a gradient. After long-cycle cycling, the capacity of Examples 1 to 3 and Comparative Example 1 decreased by 33%, 35%, 38%, and 42%, respectively. Therefore, Example 1 has a significant advantage in terms of cycle stability.

[0063] In terms of thermal safety performance, Figure 2 The DSC test results show that the conductive polymer-coated lithium-ion battery cathode material corresponding to Example 1 exhibits good thermal stability. The initial heat release temperatures of Examples 1 to 3 are all later than those of Comparative Example 1, with the initial heat release temperature of Example 2 being delayed by 25°C compared to Comparative Example 1. Figure 2 As shown, the heat release of Examples 1, 2, and 3 is significantly lower than that of Comparative Example 1. Calculations show that the heat release of Example 3 is 138.42 J, while that of Comparative Example 1 is 212.28 J. Therefore, the conductive polymer-coated cathode material prepared by this invention can maximize the stability of the material, thereby reducing the heat generation of the cathode material and effectively suppressing the initial reaction of battery thermal runaway.

[0064] In summary, the conductive polymer-coated lithium-ion battery cathode material of the present invention effectively improves the migration rate of lithium ions inside the cathode material and prevents structural degradation of the material during cycling, thereby enhancing the cycle stability of the battery under high voltage conditions and ensuring that the lithium-ion battery maintains high voltage cycle characteristics while possessing excellent safety performance.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a conductive polymer-coated lithium-ion battery cathode material, characterized by: Specifically comprising the following steps: Step S1, weigh the mass of polyethylene glycol and aniline, mix them, then add deionized water, and then add aqueous dodecylbenzenesulfonic acid and ammonium peroxydisulfate, and polymerize at 0-5℃ for 6h, then clean with a centrifuge, and dry to obtain a polyaniline-polyethylene glycol copolymer; Step S2, weigh the polyaniline-polyethylene glycol copolymer, nickel cobalt manganese lithium cathode material LiNi 1-x-y Co x Mn y O2, after mixing, add anhydrous ethanol, then put into a mechanical mixing device, the mixing time is 1h, after fully mixing, the mixed powder is obtained; Step S3, put the mixed powder into a sample cell, then put it into a sintering furnace, and sinter for 12h to obtain a primary product; Step S4, put the primary product into a mortar, grind, and obtain a finished product of a conductive polymer coated lithium ion battery positive electrode material; The conductive polymer-coated lithium ion battery positive electrode material is obtained by composite sintering of polyaniline-polyethylene glycol copolymer, lithium nickel cobalt manganese oxide positive electrode material LiNi 1-x-y Co x Mn y O2; wherein the lithium nickel cobalt manganese oxide positive electrode material LiNi 1-x-y Co x Mn y O2 is 97-99.5%, and the polyaniline-polyethylene glycol copolymer is the balance. The nickel cobalt manganese lithium cathode material LiNi 1-x-y Co x Mn y O2, x is 0.05-0.2, and y is 0.05-0.

3.

2. The method for preparing a conductive polymer-coated lithium ion battery cathode material according to claim 1, characterized in that: The sintering furnace is a tube furnace in an oxygen atmosphere or a muffle furnace in an air atmosphere.

3. The method according to claim 1, wherein the method is characterized by: The molecular weight of the polyethylene glycol in the polyaniline-polyethylene glycol copolymer is 200-400.

4. The method for preparing a conductive polymer-coated lithium-ion battery cathode material according to claim 1, characterized in that: In step S1, the mass ratio of polyethylene glycol to aniline is (4-8):1.

86.

5. The method for preparing a conductive polymer-coated lithium-ion battery cathode material according to claim 1, characterized in that: In step S2, the mixing temperature is 80℃.

6. The method for preparing a conductive polymer-coated lithium-ion battery cathode material according to claim 1, characterized in that: In step S3, the sintering temperature is 400℃.

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