Positive electrode lithium supplementing material and preparation method thereof, positive electrode plate and battery cell

Abstract

The invention provides a positive electrode lithium supplementing material and a preparation method thereof, a positive electrode plate and a battery cell. The positive electrode lithium supplementing material can comprise an organic framework material and a lithium-containing compound, wherein the lithium-containing compound at least partially fills the organic framework material; the organic framework material is added into the lithium-containing compound, the organic framework material is a crystalline porous polymer with a long-range ordered structure and has the structural characteristics of high conjugation, modifiability, large specific surface area and porosity and excellent crystallinity and stability, the organic framework material and the lithium-containing compound are compounded, and the lithium-containing compound can be used for preparing a lithium battery. The obtained positive electrode lithium supplementing material has excellent structural stability, ionic conductivity and electronic conductivity, and is beneficial to improving the long cycle performance of a battery cell when being applied to the battery cell.

Description

Technical Field

[0001] This invention relates to the technical field of batteries, specifically to a positive electrode lithium replenishment material and its preparation method, a positive electrode sheet, and a battery cell. Background Technology

[0002] Currently, the most commonly used batteries for electrochemical energy storage are high-capacity lithium iron phosphate batteries, mainly including 280Ah, 300Ah, 305Ah, 320Ah and 380Ah batteries, with a cycle life requirement of 8,000 to 12,000 charge-discharge cycles.

[0003] In related technologies, to obtain high-capacity batteries with long cycle life, a certain amount of lithium replenishing agent can be added to the positive electrode. The role of the lithium replenishing agent is to provide more lithium ions to be inserted into and stored in the negative electrode. This facilitates the gradual release of lithium ions stored in the negative electrode during charge-discharge cycles, allowing them to participate in the reaction and thus ensuring a high cycle life for the battery cell. Common lithium replenishing agents include ternary lithium compounds, which also have high capacity and can release lithium ions to be inserted into and stored in the negative electrode even at relatively low charging voltages.

[0004] However, ternary lithium compounds have poor stability in air and are prone to side reactions with the electrolyte under high voltage, affecting the long-cycle performance of the battery cell. Summary of the Invention

[0005] The embodiments of the present invention provide a positive electrode lithium replenishment material and its preparation method, a positive electrode sheet and a battery cell, aiming to improve the problem of poor stability of the lithium replenishment material affecting the long cycle life of the battery cell.

[0006] In a first aspect, embodiments of the present invention provide a positive electrode lithium replenishment material, characterized in that...

[0007] The positive electrode lithium replenishment material includes organic framework materials and lithium-containing compounds;

[0008] The organic framework material has a porous structure, and the lithium-containing compound is at least partially filled in the porous structure of the organic framework material.

[0009] Optionally, in some embodiments of this application, a portion of the lithium-containing compound fills the porous structure of the organic framework material, and another portion of the lithium-containing compound is deposited on the surface of the organic framework material.

[0010] Optionally, in some embodiments of this application, the mass ratio of the lithium-containing compound to the organic framework material ranges from 0.03 to 0.05.

[0011] Optionally, in some embodiments of this application, the organic framework material satisfies at least one of the following conditions:

[0012] The porosity of the organic framework material ranges from 30% to 80%.

[0013] The specific surface area of ​​the organic framework material ranges from 300 m². 3 / g to 700m 3 / g;

[0014] The pore size of the organic framework material ranges from 0.1 nm to 1 nm.

[0015] Optionally, in some embodiments of this application, the lithium-containing compound includes at least one selected from Li4FeO5, Li6CoO4, Li2NiO2, Li2MnO3, and Li2MoO3; and / or

[0016] The organic framework material is a COF material.

[0017] Secondly, embodiments of the present invention provide a method for preparing a positive electrode lithium replenishment material, the preparation method comprising:

[0018] The positive electrode lithium replenishment material is obtained by dispersing organic framework materials and lithium-containing compounds in a solvent;

[0019] The organic framework material has a porous structure, and the lithium-containing compound is at least partially filled in the porous structure of the organic framework material.

[0020] Optionally, in some embodiments of this application, the step of dispersing the organic framework material and the lithium-containing compound in a solvent to obtain the positive electrode lithium replenishment material includes:

[0021] Preparation of organic framework materials;

[0022] The organic framework material and the lithium-containing compound are dispersed in a solvent to obtain the positive electrode lithium replenishment material.

[0023] Optionally, in some embodiments of this application, the reaction temperature for preparing the organic framework material is 80°C to 150°C; and / or

[0024] The reaction time for preparing the organic framework material is 12 h to 40 h.

[0025] Thirdly, embodiments of the present invention provide a positive electrode sheet, the positive electrode sheet comprising the aforementioned positive electrode lithium replenishment material.

[0026] Fourthly, embodiments of the present invention provide a battery cell, the battery cell comprising the positive electrode, negative electrode and separator as described above.

[0027] The beneficial effects of the embodiments of the present invention are as follows:

[0028] The positive electrode lithium replenishment material of this application embodiment includes an organic framework material and a lithium-containing compound. The organic framework material is a crystalline porous polymer with a long-range ordered structure, which has the structural characteristics of high conjugation, modifiability, large specific surface area and porosity, as well as excellent crystallinity and stability. By compounding the organic framework material with the lithium-containing compound, the resulting positive electrode lithium replenishment material has excellent structural stability, ionic conductivity and electronic conductivity. When applied to the battery cell, it helps to improve the long cycle performance of the battery cell. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a detection diagram of organic framework materials and lithium-containing compounds provided in an embodiment of the present invention;

[0031] Figure 2 This is a flowchart of a method for preparing a positive electrode lithium replenishment material according to an embodiment of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention. In the present invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0033] Currently, to obtain high-capacity batteries, a common practice is to add a lithium replenishing agent to the positive electrode. This agent allows more lithium ions to be inserted into and stored in the negative electrode. As the number of charge-discharge cycles increases, the lithium ions stored in the negative electrode gradually participate in the reaction and are inserted into the positive electrode, replenishing the lithium ions lost by the positive electrode during charge-discharge. Furthermore, the lithium ions stored in the negative electrode can replenish the lithium ions needed for SEI film recombination during long cycles, thus giving the cell a long cycle life.

[0034] In related technologies, there are two main types of positive electrode lithium replenishing agents: 1) binary lithium-containing compounds, such as Li2O, Li2O2, LiF, Li2S, etc. When used, the binary lithium-containing compounds are carbon-coated or combined with metal nanoparticles to catalyze the release of lithium ions from the binary lithium-containing compounds; 2) ternary lithium-containing compounds, such as Li4FeO5, Li6CoO4, Li2NiO2, Li2MnO3, Li2MoO3, etc. Among them, Li2NiO2 is the main material. The theoretical specific capacity of this lithium replenishing agent is 486mAh / g, the actual first-cycle lithium insertion capacity is 340mAh / g, and the delithiation capacity can reach 80mAh / g. When the charging voltage reaches above 3.5V, lithium ions can be released and inserted into the negative electrode for storage.

[0035] However, Li2NiO2 material has poor stability in air and an unstable structure. In particular, it is prone to side reactions with the electrolyte at high potentials (>4.4V), which affects the long cycle life of the battery cell.

[0036] In view of this, embodiments of this application provide a positive electrode lithium replenishment material and its preparation method, a positive electrode sheet and a battery cell, aiming to improve the problem of poor stability of the lithium replenishment material affecting the long cycle life of the battery cell.

[0037] According to a first aspect of the embodiments of this application, a positive electrode lithium replenishment material is provided, which may include an organic framework material and a lithium-containing compound; wherein the lithium-containing compound at least partially fills the organic framework material.

[0038] By adopting the above scheme, the positive electrode lithium replenishment material of this application embodiment includes an organic framework material and a lithium-containing compound. The organic framework material is a crystalline porous polymer with a long-range ordered structure, which has the structural characteristics of high conjugation, modifiability, large specific surface area and porosity, as well as excellent crystallinity and stability. By compounding the organic framework material with the lithium-containing compound, the resulting positive electrode lithium replenishment material has excellent structural stability, ionic conductivity and electronic conductivity. When applied to the battery cell, it helps to improve the long cycle performance of the battery cell.

[0039] Understandably, organic framework materials, as stable supporting structures, can effectively improve the structural stability of cathode lithium replenishment materials. Furthermore, organic framework materials possess conjugated structures and excellent conductivity. Combining organic framework materials with lithium-containing compounds can effectively reduce the reaction resistance of cathode lithium replenishment materials, thus improving the lithium extraction and insertion capabilities and the total amount of lithium stored.

[0040] It should be noted that the organic framework material has a porous structure. This porous structure provides more storage space and reaction sites for lithium-rich nickel oxide, which is beneficial for lithium-rich nickel oxide to partially or completely fill the porous structure of the organic framework material. In addition, the porous structure of the organic framework material facilitates better wetting with the electrolyte, thereby providing channels for lithium-ion migration and providing more active sites for electrochemical reactions. This allows lithium-rich nickel oxide (Li2NiO2) to release more lithium ions into the negative electrode, effectively replenishing the lithium ion loss during charge-discharge cycles.

[0041] In some embodiments of this application, reference is made to Figure 1 One portion of the lithium-containing compound fills the porous structure of the organic framework material, while another portion of the lithium-containing compound is deposited on the surface of the organic framework material.

[0042] By employing the above-mentioned scheme, the portion of the lithium-containing compound filled within the porous structure of the organic framework material can isolate the lithium-containing compound from direct contact with air / electrolyte, inhibiting its oxidative decomposition and reducing side reactions. Furthermore, the organic framework material provides mechanical support for the lithium-containing compound, mitigating volume expansion during charging and discharging and maintaining the structural integrity of the material. Another portion of the lithium-containing compound is deposited on the surface of the organic framework material, meaning that a portion of the lithium-containing compound is directly exposed to the electrolyte. This facilitates the rapid release of lithium ions from the lithium-containing compound, shortens the ion migration path, and thus reduces the initial internal resistance of the cathode lithium replenishment material.

[0043] In some embodiments of this application, the mass ratio of the lithium-containing compound to the organic framework material ranges from 0.03 to 0.05. Exemplarily, the mass ratio of the lithium-containing compound to the organic framework material can be 0.03, 0.032, 0.035, 0.038, 0.04, 0.042, 0.045, 0.048, 0.05, or any value between two adjacent values ​​mentioned above.

[0044] By employing the above-mentioned scheme, within the specified range, lithium-containing compounds can be uniformly dispersed within the porous structure of the organic framework material. If the proportion of lithium-containing compounds is too low, it will affect the ion transport pathway; if the proportion is too high, it will lead to a lower overall initial efficiency of the cell. From a cell design perspective, a higher content of lithium-containing compounds (lithium replenishment agents) requires corresponding space for lithium storage in the negative electrode, resulting in relatively high redundancy in the negative electrode design and lower initial efficiency. Furthermore, as charge-discharge cycles progress, the formation and decomposition of the SEI film accelerate, leading to a significant increase in the SEI film thickness and affecting the cell's DCR internal resistance. Simultaneously, the temperature rise during charge-discharge processes also increases, further increasing the cell's energy loss; therefore, it is necessary to maintain the proportions within a suitable range.

[0045] In some embodiments of this application, the porosity of the organic framework material ranges from 30% to 80%. Further, the porosity of the organic framework material ranges from 40% to 65%. Exemplarily, the porosity of the organic framework material can be 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 63%, 65%, or any value between two adjacent values.

[0046] By adopting the above scheme and limiting the porosity to a suitable range, it is beneficial to make the proportion of porous structures on the organic framework material moderate, so that the organic framework material has both moderate storage space and active sites as well as excellent load-bearing performance. The optimal porosity range is 40% to 65%.

[0047] In some embodiments of this application, the specific surface area of ​​the organic framework material ranges from 300 m². 3 / g to 700m 3 / g. Furthermore, the specific surface area of ​​the organic framework material ranges from 400m². 3 / g to 600m 3 / g. For example, the specific surface area of ​​an organic framework material can be 400 m². 3 / g、420m 3 / g、450m 3 / g、470m 3 / g、500m 3 / g、520m 3 / g、540m 3 / g、560m 3 / g、580m 3 / g、600m 3 / g and any value between the two adjacent values ​​mentioned above.

[0048] Understandably, the high porosity of organic framework materials indicates a large specific surface area, which provides more storage space and active sites, allowing for the loading of more lithium-containing compounds. This ensures that the cathode lithium replenishment material possesses excellent lithium delithiation and insertion capabilities and a large total lithium storage capacity. Furthermore, the larger specific surface area facilitates better wetting of the organic framework material with the electrolyte, providing channels for ion migration. This allows lithium-rich lithium nickel oxide to release more lithium ions into the anode, effectively replenishing the lithium ion losses during charge-discharge cycles.

[0049] In some embodiments of this application, the pore size of the organic framework material ranges from 0.1 nm to 1 nm. Further, the pore size of the organic framework material ranges from 0.3 nm to 0.8 nm. Exemplarily, the pore size of the organic framework material can be 0.3 nm, 0.35 nm, 0.4 nm, 0.45 nm, 0.5 nm, 0.55 nm, 0.6 nm, 0.65 nm, 0.7 nm, 0.75 nm, 0.8 nm, or any value between two adjacent values ​​mentioned above.

[0050] By adopting the above-described scheme, the organic framework material of this application has a smaller pore size. The pore size of the organic framework material depends on the size of the monomers. In order to form a highly ordered crystalline structure, it is usually necessary to select monomers with relatively simple structures and moderate sizes. Since the physical size of these monomers is small, the size of the pores they can form is limited. Moreover, the short length of the bonds (such as imine bonds, borate ester bonds, hydrazone bonds, enamine bonds, amide bonds, etc.) of these monomers also helps to reduce the pore size of the organic framework material. In addition, since the contact between the lithium compound and the organic framework material is a balance between van der Waals forces and π-π interactions, the pores are also relatively narrow in the vertical direction.

[0051] In some embodiments of this application, the lithium-containing compound includes at least one of Li4FeO5, Li6CoO4, Li2NiO2, Li2MnO3, Li2MoO3, Li2C2O4, Li2CO3, Li4SiO4, and Li3PO4.

[0052] By adopting the above scheme, the lithium-containing compounds mentioned above are all lithium-rich materials. They can all provide a large number of lithium ions to be inserted into and stored in the negative electrode. As the number of charge and discharge cycles increases, the lithium ions stored in the negative electrode gradually participate in the reaction and are inserted into the positive electrode, which helps to make up for the loss of lithium ions caused by charging and discharging, thereby ensuring the long cycle performance of the battery cell.

[0053] In some embodiments of this application, the organic framework material is a COF material.

[0054] By adopting the above scheme, organic framework materials can be made into COFs materials. COFs materials meet the principles and requirements of green environmental protection and have the potential for sustainable development.

[0055] It should be noted that when applying COFs materials, the COFs structure can be built according to the functional requirements of the battery cell. For example, if long-cycle battery cell performance is required, the ratio of lithium-containing compounds to COFs materials can be changed to compensate for the lithium-ion loss during the charging and discharging process of the battery cell.

[0056] In addition, it should be noted that the redox energy storage process of the organic active functional groups in COFs materials only involves the reversible transformation of chemical bonds. The structure is not easily collapsed during the reaction, and the intermediate products are stable and not easily dissolved, which helps the battery cell to obtain better cycle performance and rate performance.

[0057] According to a second aspect of the embodiments of this application, a method for preparing a positive electrode lithium replenishment material is provided, the method comprising the following steps:

[0058] Organic framework materials and lithium-containing compounds are placed in a solvent and dispersed to obtain positive electrode lithium replenishment materials;

[0059] The organic framework material has a porous structure, and the lithium-containing compound is at least partially filled in the porous structure of the organic framework material.

[0060] By adopting the above scheme, the organic framework material and the lithium-containing compound are placed in a solvent and fully dispersed so that the lithium-containing compound at least partially fills the porous structure of the organic framework material, thereby obtaining a positive electrode lithium replenishment material. The prepared positive electrode lithium replenishment material has excellent structural stability, ionic conductivity and electronic conductivity.

[0061] In some embodiments of this application, the step of dispersing an organic framework material and a lithium-containing compound in a solvent to obtain a positive electrode lithium replenishment material is described in the following reference. Figure 2 ,include:

[0062] S100, Preparation of organic framework materials;

[0063] S200: Disperse organic framework materials and lithium-containing compounds in a solvent to obtain positive electrode lithium replenishment materials.

[0064] By adopting the above scheme, the organic framework material is made in-house, and the process parameters can be adjusted according to the requirements, which is more conducive to the mutual matching of the organic framework material and the lithium-containing compound, so that the prepared cathode lithium replenishment material has better electrochemical performance.

[0065] In some embodiments of this application, the organic framework material is prepared by the following method:

[0066] Tris(4-aminophenyl)amine, tris(4-formylphenyl)amine, a 1 mol / L aqueous solution of acetic acid and o-xylene were added to a reaction vessel and ultrasonically dispersed for 8 to 20 hours to obtain a mixed solution.

[0067] An aqueous acetic acid solution was slowly added dropwise to the above mixed solution. The reaction vessel was sealed and transferred to a microwave reaction device. The microwave reaction temperature was set to 80–150 °C, and the microwave reaction time was 12–40 h. The product was then filtered and washed with N,N-dimethylformamide (DMF), acetone, and ethanol, respectively. The washed material was then dried under vacuum at 60–100 °C for 12–36 h to obtain the organic framework material.

[0068] Understandably, microwave heating can accelerate the reaction, thereby shortening the preparation cycle.

[0069] By coordinating and controlling the reaction temperature and reaction time, cross-scale pore design from micropores to mesopores can be achieved.

[0070] In some embodiments of this application, the microwave reaction temperature is between 100°C and 140°C. Exemplarily, the microwave reaction temperature is 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, and any value between two adjacent values.

[0071] It is understandable that the higher the microwave reaction temperature, the faster the polymerization reaction, resulting in smaller pore sizes in the porous structure; conversely, the lower the microwave reaction temperature, the slower the polymerization reaction, resulting in larger pore sizes in the porous structure.

[0072] In some embodiments of this application, the microwave response time is 16h to 36h. Exemplarily, the microwave response time can be 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 36h, or any value between two adjacent values.

[0073] By adopting the above scheme, the longer the microwave reaction time, the larger the pore size of the porous structure, and the easier it is for the organic framework material to collapse; the shorter the microwave reaction time, the more inconsistent the pore size of the porous structure, and the less likely it is to function as an organic framework material.

[0074] It is important to note that when preparing organic framework materials, it is necessary to simultaneously control the microwave reaction temperature and reaction time to effectively adjust the pore size of the porous structure of the organic framework material. If the pore size is too small, lithium-containing compounds may not be able to enter the organic framework material, resulting in a low loading and insufficient improvement in electrical performance; if the pore size is too large, lithium-containing compounds may aggregate in the organic framework material, failing to provide confinement and thus preventing them from achieving their effective performance.

[0075] In some embodiments of this application, the step of dispersing the organic framework material and the lithium-containing compound in a solvent includes:

[0076] Preparation of organic solvents;

[0077] Organic framework materials and lithium-containing compounds were placed in an organic solvent and ultrasonically dispersed.

[0078] By adopting the above scheme, in order to mix the organic framework material and the lithium-containing compound more evenly, an organic solvent is first prepared, and then the organic framework material and the lithium-containing compound are placed in the organic solvent. By using ultrasonic dispersion, it is helpful to fully fill the lithium-containing compound into the organic framework material.

[0079] In some embodiments of this application, the preparation method further includes washing and drying steps.

[0080] Understandably, organic framework materials and lithium-containing compounds are dispersed in a solvent, then washed and dried to obtain positive electrode lithium replenishment materials for later use.

[0081] In some embodiments of this application, the drying step includes freeze-drying. Specifically, the freeze-drying temperature is between -20°C and -60°C, which helps to reduce the impact of thermal stress on the material structure, thereby maintaining the pore integrity of the organic framework material and the chemical stability of the lithium-containing compound; in addition, the solid-state sublimation process of freeze-drying can preserve the porous structure of the organic framework material, facilitating the rapid transport of lithium ions during subsequent battery charging and discharging.

[0082] According to a third aspect of the embodiments of this application, a positive electrode sheet is provided, the positive electrode sheet comprising the positive electrode lithium replenishment material as described above.

[0083] By adopting the above scheme, it is beneficial to improve the cycle performance and rate performance of the positive electrode.

[0084] According to a fourth aspect of the embodiments of this application, a battery cell is provided, the battery cell including a positive electrode, a negative electrode, and a separator as described above.

[0085] By adopting the above scheme, the resulting battery cell has low DC resistance and excellent cycle performance and rate performance.

[0086] In some embodiments of this application, the DC internal resistance of the battery cell ranges from 1.718 mΩ to 1.853 mΩ. Further, the DC internal resistance of the battery cell ranges from 1.768 mΩ to 1.853 mΩ. Exemplarily, the DC internal resistance of the battery cell can be 1.768 mΩ, 1.831 mΩ, 1.853 mΩ, or any value between two adjacent values.

[0087] By adopting the above scheme, the lower the DC internal resistance of the battery cell, the more favorable it is for electrochemical polarization during charging and discharging, resulting in lower heat generation. This is beneficial for improving the charging and discharging efficiency, rate performance, cycle life of the battery cell, and reducing lithium-ion side reactions.

[0088] In some embodiments of this application, the rate discharge capacity retention rate of the battery cell under 3C conditions ranges from 92.58% to 96.89%. Further, the rate discharge capacity retention rate of the battery cell under 3C conditions ranges from 94.63% to 96.89%. Exemplarily, the rate discharge capacity retention rate of the battery cell under 3C conditions can be 94.63%, 94.99%, 95.43%, 95.86%, 96.02%, 96.89%, or any value between two adjacent values.

[0089] By adopting the above scheme, the battery cell has better capacity retention at high rates, less capacity loss, and fewer side reactions, which is conducive to meeting the needs of fast charging and discharging.

[0090] In some embodiments of this application, the capacity retention rate of the battery cell after 2000 1C charge-discharge cycles ranges from 83.85% to 87.93%. Further, the capacity retention rate of the battery cell after 2000 1C charge-discharge cycles ranges from 85.27% to 87.93%. Exemplarily, the capacity retention rate of the battery cell after 2000 1C charge-discharge cycles can be 85.27%, 85.57%, 86.59%, 86.61%, 86.86%, 87.93%, or any value between two adjacent values.

[0091] By adopting the above scheme, the capacity retention rate remains at a high level after 2000 cycles under 1C fast charging conditions.

[0092] The present application will be specifically described below through specific embodiments. These embodiments are only some embodiments of the present application and are not intended to limit the present application. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0093] Example 1

[0094] A positive electrode lithium supplement material is prepared using the following steps:

[0095] S100, Preparation of organic framework materials:

[0096] S110. Take 1 mmol of tris-(4-aminophenyl)amine, 1 mmol of tris-(4-formylphenyl)amine, 1 mL of acetic acid aqueous solution (solution of 1 mol / L) and 2 mL of o-xylene and add them to the reaction vessel. Disperse by ultrasonication for 30 min to obtain the first mixed solution.

[0097] S120. Slowly add 5 drops of acetic acid aqueous solution (solution of 1 mol / L) to the first mixed solution, seal the reaction vessel and transfer it to a microwave reaction device, set the microwave reaction temperature to 120℃, and microwave react for 36 h. After that, filter and wash the product with N,N-dimethylformamide, acetone and ethanol respectively. After washing, dry the product at 80℃ under vacuum for 24 h to obtain the organic framework material.

[0098] S200, Preparation of cathode lithium supplementation materials:

[0099] An organic solvent was prepared by mixing ethanol and deionized water at a volume ratio of 1:1.

[0100] An organic framework material and lithium-rich nickel oxide (Li2NiO2) were added to an organic solvent and ultrasonically dispersed for 12 h to obtain a second mixed solution; wherein the concentration of the organic framework material in the organic solvent was 0.45 g / mL and the mass ratio of the organic framework material to the lithium-rich nickel oxide was 100:3.

[0101] The second mixed solution was washed with ethanol and deionized water, filtered, and then dried in a freeze dryer at -50°C for 48 hours to obtain the positive electrode lithium replenishment material.

[0102] A battery cell is prepared using the following method:

[0103] S300, Prepare materials:

[0104] The material system of the positive electrode includes lithium iron phosphate (LiFePO4, abbreviated as LFP), conductive carbon black (Super P Li, abbreviated as SP), carbon nanotubes (CNTs), polyvinylidene fluoride (PVDF), and the aforementioned positive electrode lithium supplementation material, formulated in weight percentages of 95.7%, 1.5%, 0.5%, 2.0%, and 0.3%, respectively, with N-methylpyrrolidone as the solvent;

[0105] The material system of the negative electrode sheet includes artificial graphite, thickener CMC, conductive carbon black and styrene-butadiene rubber (SBR) binder formulated in mass percentages of 95.8%, 1.2%, 1.0% and 2.0%, respectively, with deionized water as the solvent.

[0106] The electrolyte consists of a mixture of ethylene carbonate EC, dimethyl carbonate DMC, and ethyl methyl carbonate EMC in a volume ratio of 3:5:2. The functional additives are 2.5% vinylene carbonate VC and 0.5% fluoroethylene carbonate FEC. The molar concentration of lithium hexafluorophosphate LiPF6 is 1.2 mol / L.

[0107] The diaphragm is a PE diaphragm (Shenzhen Xingyuan Material, 9μm base film + 3μm Al2O3 ceramic coating);

[0108] S400, Cell fabrication:

[0109] A positive electrode slurry with a solid content of 61% was prepared according to the material system of the positive electrode sheet. The positive electrode slurry was coated on aluminum foil, dried, and die-cut to obtain the positive electrode sheet.

[0110] A negative electrode slurry with a solid content of 50% was prepared according to the material system of the negative electrode sheet. The negative electrode slurry was coated on copper foil, dried, and die-cut to obtain the negative electrode sheet.

[0111] The positive electrode, separator, and negative electrode are stacked together, and then packaged, injected with electrolyte, formed, and tested for capacity to produce a battery cell.

[0112] Example 2

[0113] A battery cell differs from Example 1 in that it uses a different positive electrode lithium replenishment material. In this example, the positive electrode lithium replenishment material is prepared using the following method:

[0114] S100, Preparation of organic framework materials:

[0115] S110. Take 1 mmol of tris-(4-aminophenyl)amine, 1 mmol of tris-(4-formylphenyl)amine, 1 mL of acetic acid aqueous solution (solution of 1 mol / L) and 2 mL of o-xylene and add them to the reaction vessel. Disperse by ultrasonication for 30 min to obtain the first mixed solution.

[0116] S120. Slowly add 5 drops of acetic acid aqueous solution (solution of 1 mol / L) to the first mixed solution, seal the reaction vessel and transfer it to a microwave reaction device, set the microwave reaction temperature to 120℃, and microwave react for 36 h. After that, filter and wash the product with N,N-dimethylformamide, acetone and ethanol respectively. After washing, dry the product at 80℃ under vacuum for 24 h to obtain the organic framework material.

[0117] S200, Preparation of cathode lithium supplementation materials:

[0118] An organic solvent was prepared by mixing ethanol and deionized water at a volume ratio of 1:1.

[0119] An organic framework material and lithium-rich nickel oxide (Li2NiO2) were added to an organic solvent and ultrasonically dispersed for 12 h to obtain a second mixed solution; wherein the concentration of the organic framework material in the organic solvent was 0.45 g / mL and the mass ratio of the organic framework material to the lithium-rich nickel oxide was 100:4.

[0120] The second mixed solution was washed with ethanol and deionized water, filtered, and then dried in a freeze dryer at -50°C for 48 hours to obtain the positive electrode lithium replenishment material.

[0121] Example 3

[0122] A battery cell differs from Example 1 in that it uses a different positive electrode lithium replenishment material. In this example, the positive electrode lithium replenishment material is prepared using the following method:

[0123] S100, Preparation of organic framework materials:

[0124] S110. Take 1 mmol of tris-(4-aminophenyl)amine, 1 mmol of tris-(4-formylphenyl)amine, 1 mL of acetic acid aqueous solution (solution of 1 mol / L) and 2 mL of o-xylene and add them to the reaction vessel. Disperse by ultrasonication for 30 min to obtain the first mixed solution.

[0125] S120. Slowly add 5 drops of acetic acid aqueous solution (solution of 1 mol / L) to the first mixed solution, seal the reaction vessel and transfer it to a microwave reaction device, set the microwave reaction temperature to 120℃, and microwave react for 36 h. After that, filter and wash the product with N,N-dimethylformamide, acetone and ethanol respectively. After washing, dry the product at 80℃ under vacuum for 24 h to obtain the organic framework material.

[0126] S200, Preparation of cathode lithium supplementation materials:

[0127] An organic solvent was prepared by mixing ethanol and deionized water at a volume ratio of 1:1.

[0128] An organic framework material and lithium-rich nickel oxide (Li2NiO2) were added to an organic solvent and ultrasonically dispersed for 12 h to obtain a second mixed solution; wherein the concentration of the organic framework material in the organic solvent was 0.45 g / mL and the mass ratio of the organic framework material to the lithium-rich nickel oxide was 100:5.

[0129] The second mixed solution was washed with ethanol and deionized water, filtered, and then dried in a freeze dryer at -50°C for 48 hours to obtain the positive electrode lithium replenishment material.

[0130] Example 4

[0131] A battery cell differs from Example 1 in that it uses a different positive electrode lithium replenishment material. In this example, the positive electrode lithium replenishment material is prepared using the following method:

[0132] S100, Preparation of organic framework materials:

[0133] S110. Take 1 mmol of tris-(4-aminophenyl)amine, 1 mmol of tris-(4-formylphenyl)amine, 1 mL of acetic acid aqueous solution (solution of 1 mol / L) and 2 mL of o-xylene and add them to the reaction vessel. Disperse by ultrasonication for 30 min to obtain the first mixed solution.

[0134] S120. Slowly add 5 drops of acetic acid aqueous solution (solution of 1 mol / L) to the first mixed solution, seal the reaction vessel and transfer it to a microwave reaction device, set the microwave reaction temperature to 120℃, and microwave react for 36 h. After that, filter and wash the product with N,N-dimethylformamide, acetone and ethanol respectively. After washing, dry the product at 80℃ under vacuum for 24 h to obtain the organic framework material.

[0135] S200, Preparation of cathode lithium supplementation materials:

[0136] An organic solvent was prepared by mixing ethanol and deionized water at a volume ratio of 1:1.

[0137] An organic framework material and lithium-rich nickel oxide (Li2NiO2) were added to an organic solvent and ultrasonically dispersed for 12 h to obtain a second mixed solution; wherein the concentration of the organic framework material in the organic solvent was 0.45 g / mL and the mass ratio of the organic framework material to the lithium-rich nickel oxide was 100:10.

[0138] The second mixed solution was washed with ethanol and deionized water, filtered, and then dried in a freeze dryer at -50°C for 48 hours to obtain the positive electrode lithium replenishment material.

[0139] Example 5

[0140] A battery cell differs from Example 1 in that it uses a different positive electrode lithium replenishment material. In this example, the positive electrode lithium replenishment material is prepared using the following method:

[0141] S100, Preparation of organic framework materials:

[0142] S110. Take 1 mmol of tris-(4-aminophenyl)amine, 1 mmol of tris-(4-formylphenyl)amine, 1 mL of acetic acid aqueous solution (solution of 1 mol / L) and 2 mL of o-xylene and add them to the reaction vessel. Disperse by ultrasonication for 30 min to obtain the first mixed solution.

[0143] S120. Slowly add 5 drops of acetic acid aqueous solution (solution of 1 mol / L) to the first mixed solution, seal the reaction vessel and transfer it to a microwave reaction device, set the microwave reaction temperature to 120℃, and microwave react for 36 h. After that, filter and wash the product with N,N-dimethylformamide, acetone and ethanol respectively. After washing, dry the product at 80℃ under vacuum for 24 h to obtain the organic framework material.

[0144] S200, Preparation of cathode lithium supplementation materials:

[0145] An organic solvent was prepared by mixing ethanol and deionized water at a volume ratio of 1:1.

[0146] An organic framework material and lithium-rich nickel oxide (Li2NiO2) were added to an organic solvent and ultrasonically dispersed for 12 h to obtain a second mixed solution; wherein the concentration of the organic framework material in the organic solvent was 0.45 g / mL and the mass ratio of the organic framework material to lithium-rich nickel oxide was 100:2.

[0147] The second mixed solution was washed with ethanol and deionized water, filtered, and then dried in a freeze dryer at -50°C for 48 hours to obtain the positive electrode lithium replenishment material.

[0148] Example 6

[0149] A battery cell differs from Example 1 in that the preparation process of the organic framework material is different. In this example, the organic framework material is prepared using the following method:

[0150] S110. Take 1 mmol of tris-(4-aminophenyl)amine, 1 mmol of tris-(4-formylphenyl)amine, 1 mL of acetic acid aqueous solution (solution of 1 mol / L) and 2 mL of o-xylene and add them to the reaction vessel. Disperse by ultrasonication for 30 min to obtain the first mixed solution.

[0151] S120. Slowly add 5 drops of acetic acid aqueous solution (solution of 1 mol / L) to the first mixed solution, seal the reaction vessel and transfer it to a microwave reaction device, set the microwave reaction temperature to 100℃, and microwave react for 46 h. After that, filter and wash the product with N,N-dimethylformamide, acetone and ethanol respectively. After washing, dry the product at 80℃ under vacuum for 24 h to obtain the organic framework material.

[0152] Example 7

[0153] A battery cell differs from Example 1 in that the preparation process of the organic framework material is different. In this example, the organic framework material is prepared using the following method:

[0154] S110. Take 1 mmol of tris-(4-aminophenyl)amine, 1 mmol of tris-(4-formylphenyl)amine, 1 mL of acetic acid aqueous solution (solution of 1 mol / L) and 2 mL of o-xylene and add them to the reaction vessel. Disperse by ultrasonication for 30 min to obtain the first mixed solution.

[0155] S120. Slowly add 5 drops of acetic acid aqueous solution (solution of 1 mol / L) to the first mixed solution, seal the reaction vessel and transfer it to a microwave reaction device, set the microwave reaction temperature to 140℃, and microwave react for 24 h. After that, filter and wash the product with N,N-dimethylformamide, acetone and ethanol respectively. After washing, dry the product at 80℃ under vacuum for 24 h to obtain the organic framework material.

[0156] Example 8

[0157] A battery cell differs from Example 1 in that the preparation process of the organic framework material is different. In this example, the organic framework material is prepared using the following method:

[0158] S110. Take 1 mmol of tris-(4-aminophenyl)amine, 1 mmol of tris-(4-formylphenyl)amine, 1 mL of acetic acid aqueous solution (solution of 1 mol / L) and 2 mL of o-xylene and add them to the reaction vessel. Disperse by ultrasonication for 30 min to obtain the first mixed solution.

[0159] S120. Slowly add 5 drops of acetic acid aqueous solution (solution of 1 mol / L) to the first mixed solution, seal the reaction vessel and transfer it to a microwave reaction device, set the microwave reaction temperature to 80℃, and microwave react for 52 h. After that, filter and wash the product with N,N-dimethylformamide, acetone and ethanol respectively. After washing, dry the product under vacuum at 80℃ for 24 h to obtain the organic framework material.

[0160] Example 9

[0161] A battery cell differs from Example 1 in that the preparation process of the organic framework material is different. In this example, the organic framework material is prepared using the following method:

[0162] S110. Take 1 mmol of tris-(4-aminophenyl)amine, 1 mmol of tris-(4-formylphenyl)amine, 1 mL of acetic acid aqueous solution (solution of 1 mol / L) and 2 mL of o-xylene and add them to the reaction vessel. Disperse by ultrasonication for 30 min to obtain the first mixed solution.

[0163] S120. Slowly add 5 drops of acetic acid aqueous solution (solution of 1 mol / L) to the first mixed solution. Seal the reaction vessel and transfer it to a microwave reaction device. Set the microwave reaction temperature to 160℃. After microwave reaction for 18 hours, filter and wash the product with N,N-dimethylformamide, acetone and ethanol respectively. After washing, dry the product at 80℃ under vacuum for 24 hours to obtain the organic framework material.

[0164] Comparative Example 1:

[0165] A battery cell is prepared using the following method:

[0166] S100, Prepare materials:

[0167] The positive electrode material system includes lithium iron phosphate (LiFePO4, abbreviated as LFP), conductive carbon black (Super P Li, abbreviated as SP), carbon nanotubes (CNTs), polyvinylidene fluoride (PVDF), and commercially available lithium-rich nickel oxide, formulated in weight percentages of 95.7%, 1.5%, 0.5%, 2.0%, and 0.3%, respectively, with N-methylpyrrolidone as the solvent.

[0168] The material system of the negative electrode sheet includes artificial graphite, sodium carboxymethyl cellulose (CMC), conductive carbon black and styrene-butadiene rubber (SBR) binder formulated in weight percentages of 95.8%, 1.2%, 1.0% and 2.0%, respectively, with deionized water as the solvent;

[0169] The electrolyte consists of a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 3:5:2. The functional additives are 2.5% VC (ethylene carbonate) and 0.5% FEC (fluoroethylene carbonate), and the molar concentration of LiPF6 (lithium hexafluorophosphate) is 1.2 mol / L.

[0170] The diaphragm is a PE diaphragm (Shenzhen Xingyuan Material, 9μm base film + 3μm Al2O3 ceramic coating);

[0171] S200. Prepare a positive electrode slurry with a solid content of 61% according to the material system of the positive electrode sheet. Coat the positive electrode slurry onto aluminum foil, and obtain the positive electrode sheet by drying and die cutting.

[0172] S300. Prepare a negative electrode slurry with a solid content of 50% according to the material system of the negative electrode sheet. Coat the negative electrode slurry onto copper foil, and obtain the negative electrode sheet by drying and die cutting.

[0173] S400: The positive electrode, separator, and negative electrode are stacked together, and the battery cell is produced through packaging, liquid injection, formation, and capacity testing.

[0174] Performance testing:

[0175] I. The organic framework material of the embodiment was tested for the following indicators, and the test results are shown in Table 1:

[0176] 1. Sample pretreatment: Degas under high vacuum / high temperature (130~150℃) to remove adsorbed moisture or impurities;

[0177] 2. Adsorption process: N2 gas was gradually introduced at 77K (liquid nitrogen temperature), and the pressure and adsorption amount were recorded;

[0178] 3. Desorption process: Reduce gas pressure and record the N2 release process;

[0179] 4. Data Processing:

[0180] BET method: Calculate the specific surface area in the 5-30% relative pressure zone;

[0181] The BJH method (Barrett-Joyner-Halenda): used for mesopore size distribution;

[0182] DFT (Density Functional Theory) Model: Micropore COF Pore Size Analysis.

[0183] II. The following performance tests were conducted on the battery cells of the embodiments and comparative examples. The performance testing equipment used was the HRCDS-5V200A-8CH charging and discharging equipment of Shenzhen Ruineng Industrial Co., Ltd. The test results are shown in Table 2.

[0184] (1) DC internal resistance: The DCR internal resistance was tested at 25℃ and 50% SOC for 10s under 2C discharge;

[0185] (2) Rate performance: Test the rate discharge capacity retention rate under 3C conditions;

[0186] (3) Cyclic performance: Under high temperature of 45℃, the capacity retention rate was tested after 2000 cycles of 1C / 1C charge and discharge.

[0187] Table 1

[0188] Sample Porosity (%) <![CDATA[Specific surface area (m 2 / g)]]> Aperture (nm) Example 1 55 500 0.5 Example 6 30 350 0.8 Example 7 80 620 0.3 Example 8 15 150 1.5 Example 9 85 830 0.08

[0189] Table 2

[0190] Sample DC internal resistance (mΩ) Ratio performance (%) Cyclic performance (%) Example 1 1.718 96.89 87.93 Example 2 1.732 95.43 86.59 Example 3 1.742 94.63 85.27 Example 4 1.768 94.99 83.85 Example 5 1.853 92.58 84.96 Example 6 1.739 95.86 86.61 Example 7 1.726 96.02 86.86 Example 8 1.831 93.95 85.57 Example 9 1.749 94.35 85.06 Comparative Example 1 1.982 91.36 82.05

[0191] Compared with Examples 1-5 and the comparative example, Examples 1-5 added organic framework materials to lithium-rich nickel oxide, which significantly improved the stability of lithium-rich nickel oxide, resulting in a cell with lower DC internal resistance and optimal rate and cycle performance. Table 2 shows that a moderate mass ratio of lithium-rich nickel oxide is beneficial for improving the cell's initial efficiency, reducing reaction byproducts, and lowering the cell's internal resistance and capacity decay. The cell's DC internal resistance is 1.718–1.742 mΩ, the rate discharge capacity retention rate under 3C conditions is 94.63–96.89%, and the capacity retention rate after 2000 1C charge-discharge cycles is 85.27–87.93%. If the mass ratio of lithium-rich nickel oxide is low, the improvement in cell internal resistance, capacity, and rate performance is limited; if the mass ratio of lithium-rich nickel oxide is high, the cell's initial efficiency is low, and the capacity and rate performance deteriorate, mainly because excessive lithium additives generate more gas in the initial reaction, leading to more side reactions with the electrolyte.

[0192] Compared to Examples 1 and 6-9, Examples 6-9 altered the reaction conditions for preparing organic framework materials, thereby achieving the preparation of organic framework materials with different pore sizes. As shown in Tables 1-2, Examples 6-9 exhibit lower internal resistance, higher rate performance, and better cycling performance. This is mainly due to the reasonable control of the reaction temperature and time in the COF preparation. If the reaction temperature is too high, the polymerization reaction is too fast, resulting in smaller pore sizes in the COFs. In this case, the pore structure is non-uniform, failing to utilize the COFs' function. Conversely, if the reaction temperature is too low, the reaction time is too long, resulting in larger pore sizes in the COFs material. This situation can lead to the collapse of the lithium-containing material's structure. Therefore, controlling the reaction temperature and time is necessary to facilitate the synergistic effect between COFs and lithium-containing compounds.

[0193] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A positive electrode lithium replenishment material, characterized in that, The positive electrode lithium replenishment material includes organic framework materials and lithium-containing compounds; The organic framework material has a porous structure, and the lithium-containing compound is at least partially filled in the porous structure of the organic framework material.

2. The positive electrode lithium replenishment material according to claim 1, characterized in that, A portion of the lithium-containing compound fills the porous structure of the organic framework material, and another portion of the lithium-containing compound is deposited on the surface of the organic framework material.

3. The positive electrode lithium replenishment material according to claim 1 or 2, characterized in that, The mass ratio of the lithium-containing compound to the organic framework material ranges from 0.03 to 0.

05.

4. The positive electrode lithium replenishment material according to any one of claims 1 to 3, characterized in that, The organic framework material must satisfy at least one of the following conditions: The porosity of the organic framework material ranges from 30% to 80%. The specific surface area of ​​the organic framework material ranges from 300 m². 3 / g to 700m 3 / g; The pore size of the organic framework material ranges from 0.1 nm to 1 nm.

5. The positive electrode lithium replenishment material according to claim 1, characterized in that, The lithium-containing compound includes at least one of Li4FeO5, Li6CoO4, Li2NiO2, Li2MnO3, and Li2MoO3; and / or The organic framework material is a COF material.

6. A method for preparing a positive electrode lithium replenishment material, characterized in that, The preparation method includes the following steps: The positive electrode lithium replenishment material is obtained by dispersing organic framework materials and lithium-containing compounds in a solvent; The organic framework material has a porous structure, and the lithium-containing compound is at least partially filled in the porous structure of the organic framework material.

7. The method for preparing the positive electrode lithium replenishment material according to claim 6, characterized in that, The step of dispersing the organic framework material and the lithium-containing compound in a solvent to obtain the positive electrode lithium replenishment material includes: Preparation of organic framework materials; The organic framework material and the lithium-containing compound are dispersed in a solvent to obtain the positive electrode lithium replenishment material.

8. The method for preparing the positive electrode lithium replenishment material according to claim 7, characterized in that, The reaction temperature for preparing the organic framework material is 80°C to 150°C; and / or The reaction time for preparing the organic framework material is 12 h to 40 h.

9. A positive electrode sheet, characterized in that, The positive electrode sheet includes the positive lithium replenishment material as described in any one of claims 1 to 5.

10. A battery cell, characterized in that, The battery cell includes a positive electrode, a negative electrode, and a separator as described in claim 9; wherein the active material of the positive electrode includes one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, and lithium-rich manganese-based materials.

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