Rapid screening method for positive electrode precursor based on sodium embedding mode
The rapid screening method for cathode precursors using sodium intercalation, which evaluates the structural integrity and electrochemical performance of cathode precursors through electrochemical testing, solves the problem of inaccurate prediction of precursor structural defects and finished product electrochemical performance in existing technologies. This enables rapid screening of high-quality samples, reduces production costs, and shortens the R&D cycle.
Patent Information
- Application Number
- CN202511850273.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-03-03
AI Technical Summary
Existing technologies cannot accurately predict the structural defects of cathode material precursors and the electrochemical performance of finished products, resulting in high production costs and long R&D cycles.
A rapid screening method for positive electrode precursors based on sodium intercalation was adopted. The sodium battery positive electrode precursor was mixed with a conductive agent and a binder, coated on an aluminum foil current collector, and then assembled into a coin cell. Electrochemical tests were performed to obtain the sodium intercalation specific capacity and voltage-sodium intercalation specific capacity curves, and the structural integrity and electrochemical performance were judged in a graded manner.
It enables precise evaluation of the cathode precursor structure, prediction of the electrochemical performance of the finished product, shortens the R&D cycle, and reduces production costs.
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Figure CN121595668A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sodium battery cathode precursor detection technology, and more specifically, to a rapid screening method for cathode precursors based on sodium intercalation. Background Technology
[0002] Currently, sodium-ion batteries have attracted widespread attention due to their high theoretical capacity and low cost. Cathode materials are a crucial component of sodium-ion batteries, and the structural integrity and chemical properties of the cathode material precursor directly affect the electrochemical performance of the battery. Traditional performance evaluation of cathode material precursors mainly relies on conventional physicochemical testing methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), BET method for specific surface area determination, and ICP-MS composition analysis. While these methods can provide basic information such as crystal phase composition, particle size distribution, specific surface area, and chemical composition, they struggle to reveal in-depth crystal defects within the material (such as dislocations and interlayer disorder). Furthermore, even cathode material precursors with comparable physicochemical properties can exhibit significant differences in electrochemical performance (such as specific capacity, cycle stability, and rate performance) after sintering to produce the final product. Existing cathode material precursor characterization techniques cannot effectively predict the relationship between precursor quality and final product performance. Therefore, at present, electrochemical performance testing of cathode materials is still largely necessary to screen for high-performance cathode materials; however, this method is costly to produce and has a long development cycle. Summary of the Invention
[0003] The main objective of this invention is to provide a rapid screening method for cathode precursors based on sodium intercalation, in order to solve the problem in the prior art that it is impossible to accurately predict precursor structural defects and the electrochemical performance of the finished product.
[0004] To achieve the above objectives, according to one aspect of the present invention, a rapid screening method for positive electrode precursors based on sodium intercalation is provided, comprising the following steps:
[0005] A sodium battery positive electrode precursor, a conductive agent, a binder, and a first solvent are mixed to obtain a slurry; the slurry is coated onto the surface of an aluminum foil current collector, and after drying and rolling, a negative electrode sheet is obtained; the negative electrode sheet is used as the working electrode to assemble a coin cell.
[0006] After static aging, the coin cell was subjected to electrochemical testing to obtain the sodium intercalation specific capacity and voltage-sodium intercalation specific capacity curve of the coin cell under the test range of current density of 0.01C~0.1C and voltage of 0.01V~3.0V.
[0007] Based on the sodium intercalation specific capacity and the voltage-sodium intercalation specific capacity curve, the structural integrity of the sodium battery cathode precursor and the electrochemical performance of the sodium battery cathode material are classified and predicted.
[0008] The sodium battery cathode precursor is screened based on the classification and prediction results.
[0009] Furthermore, based on the percentage of the sodium intercalation specific capacity relative to the theoretical capacity and the smoothness of the voltage-sodium intercalation specific capacity curve, the structural integrity of the sodium battery cathode precursor and the electrochemical performance of the sodium battery cathode material are graded and predicted.
[0010] Furthermore, the tiered prediction is carried out in the following manner:
[0011] Excellent level: The sodium intercalation specific capacity of the coin cell reaches more than 75% of the theoretical capacity, and the voltage-sodium intercalation specific capacity curve of the coin cell is smooth without abnormal plateau, indicating that there is no impurity phase reaction in the sodium battery cathode precursor and the electrochemical performance of the sodium battery cathode material is excellent.
[0012] Medium level: The sodium intercalation specific capacity of the coin cell is 60%~75% of the theoretical capacity, and the abnormal plateau in the voltage-sodium intercalation specific capacity curve of the coin cell indicates that the structure of the sodium battery cathode precursor is basically complete, and the electrochemical performance of the sodium battery cathode material is medium.
[0013] Poor grade: The sodium intercalation specific capacity of the coin cell is less than 60% of the theoretical capacity, or the voltage-sodium intercalation specific capacity curve of the coin cell shows an abnormal plateau, indicating that the sodium battery cathode precursor contains impurity phase reaction, and the electrochemical performance of the sodium battery cathode material is poor.
[0014] The abnormal platform refers to the voltage-sodium intercalation specific capacity curve having zero specific capacity within the voltage range of 1.0V to 2.0V.
[0015] Furthermore, the step of screening the sodium battery cathode precursor based on the classification prediction results includes: screening out sodium battery cathode precursors corresponding to coin cells that meet the requirements of sodium intercalation capacity reaching more than 75% of the theoretical capacity and having a smooth voltage-sodium intercalation capacity curve, based on the classification prediction results, for use in preparing sodium battery cathode materials.
[0016] Furthermore, the electrochemical tests include: 0.1C discharge to 0.01V, 0.05C discharge to 0.01V, and 0.01C discharge to 0.01V.
[0017] Furthermore, the mass ratio of the sodium battery positive electrode precursor, the conductive agent, and the binder is (70~90):(5~20):(5~10).
[0018] Furthermore, the general chemical formula of the sodium battery cathode precursor includes M(OH)2, where M is one or more of Ni, Fe, Mn, and Cu.
[0019] Furthermore, the particle size of the sodium battery cathode precursor is 1 μm to 10 μm; and / or,
[0020] The drying temperature is 80℃~90℃; and / or,
[0021] The pressure of the roller is 0.25MPa~0.35MPa.
[0022] Furthermore, the conductive agent includes at least one of acetylene black, Ketjen black, and Super P; and / or,
[0023] The adhesive comprises at least one of polyvinylidene fluoride, carboxymethyl cellulose, and styrene-butadiene rubber; and / or
[0024] The first solvent includes N-methylpyrrolidone and / or water.
[0025] Further, the step of assembling the negative electrode as the working electrode into the coin cell includes: stacking the negative electrode, the separator, and the sodium metal sheet to obtain an electrode assembly; placing the electrode assembly and electrolyte into a coin cell casing in an argon-filled glove box and assembling them into a CR2032 type coin cell; wherein the separator is a glass fiber separator, the electrolyte includes an electrolyte and a second solvent, the electrolyte is NaClO4, and the second solvent is a mixed solvent of ethylene carbonate, propylene carbonate, and diethyl carbonate; and / or,
[0026] The static aging time is >18h.
[0027] By applying the technical solution of this invention, the structural integrity of the sodium battery cathode precursor can be accurately assessed through electrochemical testing, and the electrochemical performance of the finished product can be effectively predicted. This invention can screen high-quality samples at the precursor stage, avoiding unnecessary subsequent sintering and full-cell testing, which helps to shorten the R&D cycle of sodium battery cathode materials and reduce production costs. Attached Figure Description
[0028] Figure 1 This is a voltage-sodium intercalation specific capacity curve of the sodium battery positive electrode precursor in Example 1;
[0029] Figure 2 The voltage-specific capacity discharge curve of the cathode material prepared from the sodium battery cathode precursor of Example 1;
[0030] Figure 3 This is a voltage-sodium intercalation specific capacity curve of the sodium battery positive electrode precursor in Example 2;
[0031] Figure 4 The voltage-specific capacity discharge curve of the cathode material prepared from the sodium battery cathode precursor of Example 2;
[0032] Figure 5 This is a voltage-sodium intercalation specific capacity curve of the sodium battery positive electrode precursor in Example 3;
[0033] Figure 6 The voltage-specific capacity discharge curve of the cathode material prepared from the sodium battery cathode precursor of Example 3;
[0034] Figure 7 This is a voltage-sodium intercalation specific capacity curve of the sodium battery positive electrode precursor in Example 4;
[0035] Figure 8 The voltage-specific capacity discharge curve of the cathode material prepared from the sodium battery cathode precursor of Example 4;
[0036] Figure 9 This is a schematic diagram of a rapid screening method for positive electrode precursors based on sodium intercalation in one embodiment of the present invention. Detailed Implementation
[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0038] As described in the background section of this invention, existing technologies suffer from the problem of being unable to accurately predict precursor structural defects and the electrochemical performance of the finished product. To address these issues, such as... Figure 9 As shown, in a typical embodiment of the present invention, a rapid screening method for positive electrode precursors based on sodium intercalation is provided, comprising the following steps:
[0039] A sodium battery positive electrode precursor, conductive agent, binder and first solvent are mixed to obtain a slurry; the slurry is coated on the surface of an aluminum foil current collector, and after drying and rolling, a negative electrode sheet is obtained; the negative electrode sheet is used as the working electrode to assemble a coin cell.
[0040] After static aging, the coin cells were subjected to electrochemical tests to obtain the sodium intercalation specific capacity and voltage-sodium intercalation specific capacity curves of the coin cells under the test range of current density of 0.01C~0.1C and voltage of 0.01V~3.0V.
[0041] Based on the sodium intercalation specific capacity and voltage-sodium intercalation specific capacity curves, the structural integrity of the sodium battery cathode precursor and the electrochemical performance of the sodium battery cathode material are classified and predicted.
[0042] The sodium battery cathode precursors are screened based on the classification and prediction results.
[0043] Specifically, sodium-ion battery cathode materials are prepared by sintering sodium-ion battery cathode precursors. The electrochemical performance (such as capacity and cycle stability) of sodium-ion battery cathode materials is closely related to their crystal structure. In layered sodium-ion battery cathode materials, the insertion and extraction of sodium ions mainly occur along two-dimensional paths between layers. Materials with complete crystal structures, suitable interlayer spacing, and few interlayer defects can provide smoother ion transport channels, thus exhibiting higher electrochemical activity and stability during sodium insertion. The ion transport performance of sodium-ion battery cathode precursors is closely related to their structural integrity; unobstructed ion transport channels indicate structural integrity, while the opposite indicates defects. Microscopic defects in sodium-ion battery cathode precursors, such as dislocations, vacancies, and interlayer disorder, can hinder sodium ion migration and affect the specific capacity of sodium-ion battery cathode materials. These defects are not easily detected by conventional XRD or SEM characterization, but they are directly reflected in the electrochemical response of the sodium insertion process, such as abnormal fluctuations, plateau effects, or slope changes in the voltage-capacity curve.
[0044] The structural integrity of the sodium battery cathode precursor directly affects the electrochemical performance of the resulting sodium battery cathode material. A complete structure implies reasonable interlayer spacing, unobstructed ion transport pathways, and the absence of significant crystal defects, leading to a more efficient and stable sodium intercalation process. This results in higher sodium intercalation specific capacity and a smoother voltage-sodium intercalation specific capacity curve in electrochemical tests.
[0045] Electrochemical tests simulated the insertion and extraction of sodium ions in the cathode precursor of a sodium-ion battery. By obtaining the sodium insertion specific capacity and voltage-intercalation specific capacity curves, the efficiency and stability of the ion transport pathways in the sodium-ion battery cathode material can be evaluated. Specifically, the voltage-intercalation specific capacity curve not only reflects the sodium insertion specific capacity but also provides important information about the electrochemical stability and reaction kinetics of the sodium-ion battery cathode precursor, such as the shape, slope, and plateau effect of the curve. This allows for the revelation of the rate and stability of the sodium insertion reaction at different potentials in the sodium-ion battery cathode precursor, thereby evaluating the electrochemical performance of the sodium-ion battery cathode material.
[0046] Traditional characterization methods (such as XRD, SEM, and BET) can provide basic information, but they are difficult to accurately predict the electrochemical behavior of sodium battery cathode materials. This invention directly simulates the battery's operating environment by conducting electrochemical tests on coin half-cells assembled from sodium battery cathode precursors. On the one hand, this helps provide test data that more closely approximates real electrochemical reactions, thereby reducing the uncertainty in the performance of sodium battery cathode materials and facilitating accurate assessment of the structural integrity of sodium battery cathode precursors, effectively predicting the electrochemical performance of the finished product. On the other hand, by conducting electrochemical tests at the precursor stage, samples with structural problems or poor ion transport performance can be identified early in the processing of sodium battery cathode materials, avoiding wasted resources in subsequent sintering, finished product preparation, and full-cell testing, and facilitating rapid screening and optimization of sodium battery cathode materials.
[0047] In some embodiments, the structural integrity of the sodium battery cathode precursor and the electrochemical performance of the sodium battery cathode material are graded and predicted based on the percentage of sodium intercalation specific capacity relative to the theoretical capacity and the smoothness of the voltage-sodium intercalation specific capacity curve. By refining the percentage relationship between sodium intercalation specific capacity and theoretical capacity and the consideration criteria for the smoothness of the voltage-sodium intercalation specific capacity curve, an accurate assessment of the structural integrity of the sodium battery cathode precursor can be achieved, and the electrochemical performance level of the sodium battery cathode material can be predicted accordingly. First, the ratio of sodium intercalation specific capacity to theoretical capacity is used as one of the core indicators, which can intuitively reflect whether the sodium ion transport channels inside the precursor are unobstructed and whether there are defects or disorder in the crystal structure. The higher this ratio, the more perfect the structure of the precursor and the better the electrochemical performance of the sodium battery cathode material. Second, the morphological characteristics of the voltage-sodium intercalation specific capacity curve provide additional structural information. Good curve smoothness means that the sodium ion intercalation process in the precursor is stable and does not encounter significant resistance or obstacles, indicating that the sodium battery cathode material exhibits good stability and consistency during charge and discharge. Combining these two indicators can effectively distinguish the quality of precursors, providing a scientific basis for subsequent performance evaluation of finished materials.
[0048] In some embodiments, the grading prediction is performed as follows: Excellent level: The sodium intercalation specific capacity of the coin cell reaches more than 75% of the theoretical capacity, and the voltage-sodium intercalation specific capacity curve of the coin cell is smooth without abnormal plateaus, indicating that the sodium battery cathode precursor has no impurity phase reaction and the electrochemical performance of the sodium battery cathode material is excellent; Medium level: The sodium intercalation specific capacity of the coin cell is 60%~75% of the theoretical capacity, and the voltage-sodium intercalation specific capacity curve of the coin cell shows an abnormal plateau, indicating that the structure of the sodium battery cathode precursor is basically intact and the electrochemical performance of the sodium battery cathode material is moderate; Poor level: The sodium intercalation specific capacity of the coin cell is less than 60% of the theoretical capacity, or the voltage-sodium intercalation specific capacity curve of the coin cell shows an abnormal plateau, indicating that the sodium battery cathode precursor contains impurity phase reactions and the electrochemical performance of the sodium battery cathode material is poor. An abnormal plateau refers to a voltage-sodium intercalation specific capacity curve where the specific capacity is zero in the voltage range of 1.0V~2.0V.
[0049] Specifically, a sodium intercalation specific capacity of a coin cell exceeding 75% of its theoretical capacity, coupled with a smooth voltage-sodium intercalation specific capacity curve, indicates a complete precursor structure. This suggests the finished product will exhibit excellent electrochemical performance, with the expected sodium intercalation specific capacity reaching over 75% of the theoretical capacity. This standard effectively distinguishes high-quality cathode precursors, ensuring the finished battery possesses high energy density and stable cycle characteristics. Conversely, when the sodium intercalation specific capacity is between 60% and 75% of the theoretical capacity, and an abnormal plateau appears in the voltage-sodium intercalation specific capacity curve, it indicates a basically complete precursor structure. The performance of the finished product is predicted to be at a moderate level, with the expected sodium intercalation specific capacity reaching 60% to 75% of the theoretical capacity. This classification helps identify precursor samples that can be further optimized to improve the performance of the finished product. When the sodium intercalation specific capacity is lower than 60% of the theoretical value, or when the voltage-sodium intercalation specific capacity curve shows significant fluctuations and abnormal plateaus, it indicates that there are structural defects in the precursor, and the electrochemical performance of the expected finished product is poor. The expected sodium intercalation specific capacity of the finished product is lower than 60% of the theoretical capacity. This judgment standard can identify unqualified raw materials in the early stage, avoiding subsequent ineffective R&D investment and production waste.
[0050] In some embodiments, the step of screening sodium battery cathode precursors based on the classification prediction results includes: screening sodium battery cathode precursors that meet the requirement of achieving a sodium intercalation specific capacity of more than 75% of the theoretical capacity and having a smooth voltage-sodium intercalation specific capacity curve, for use in the preparation of sodium battery cathode materials. This method can accurately identify precursor materials with excellent structural integrity, thereby significantly improving the electrochemical performance of the finished sodium battery cathode material, avoiding resource waste due to poor material performance during subsequent preparation, and reducing R&D and production costs.
[0051] In some embodiments, the electrochemical test includes: discharging at 0.1C to 0.01V, discharging at 0.05C to 0.01V, and discharging at 0.01C to 0.01V.
[0052] In some embodiments, the mass ratio of the sodium battery positive electrode precursor, the conductive agent, and the binder is (70~90):(5~20):(5~10). By controlling the mass ratio of the sodium battery positive electrode precursor, the conductive agent, and the binder, the sodium battery positive electrode precursor can be effectively encapsulated in the conductive agent and binder during the preparation of the negative electrode sheet, forming a tight and uniform structure, which helps to improve the accuracy of testing.
[0053] This invention does not limit the specific types of the sodium battery positive electrode precursor, conductive agent, binder, and first solvent described above, and can be adjusted according to actual conditions. For example, in some embodiments, the general chemical formula of the sodium battery positive electrode precursor includes M(OH)2, where M is one or more of Ni, Fe, Mn, and Cu; and / or, the conductive agent includes at least one of acetylene black, Ketjen black, and Super P; and / or, the binder includes at least one of polyvinylidene fluoride, carboxymethyl cellulose, and styrene-butadiene rubber; and / or, the first solvent includes N-methylpyrrolidone and / or water.
[0054] In some embodiments, the particle size of the sodium battery cathode precursor is 1 μm to 10 μm. By controlling the particle size of the sodium battery cathode precursor to 1 μm to 10 μm, it is beneficial to improve the reactivity of the sodium battery cathode precursor, effectively balance the activity and stability of the sodium battery cathode precursor, reduce the test error caused by particle size inhomogeneity, and further improve the reliability of the characterization results.
[0055] The present invention does not limit the preparation process of the negative electrode sheet, and conventional methods in the art can be used. For example, in some embodiments, the drying temperature is 80°C to 90°C; and / or the rolling pressure is 0.25MPa to 0.35MPa.
[0056] This invention does not limit the assembly process of the coin cell and can employ conventional methods in the art. For example, the steps of assembling a coin cell with a negative electrode as the working electrode include: stacking the negative electrode, the separator, and the sodium metal sheet to obtain an electrode assembly; placing the electrode assembly and electrolyte into a coin cell casing in an argon-filled glove box and assembling them into a CR2032 type coin cell; wherein the separator is a glass fiber separator, the electrolyte includes an electrolyte and a second solvent, the electrolyte is NaClO4, and the second solvent is a mixed solvent of ethylene carbonate, propylene carbonate, and diethyl carbonate, preferably with a mass ratio of ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) of 1:4:5; and / or, the static aging time is >18h.
[0057] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.
[0058] Example 1
[0059] This embodiment is based on a rapid screening method for positive electrode precursors using a sodium intercalation method, and includes the following steps:
[0060] S1, a sodium battery positive electrode precursor with a particle size of 3μm~5μm, Super P, and PVDF are mixed at a mass ratio of 85:10:5, and NMP is added and mixed evenly to obtain a slurry; the slurry is coated onto a 15μm aluminum foil current collector, dried at 100℃ for 18h, and rolled at 10MPa for 12mm to obtain a negative electrode sheet; wherein, the preparation method of the sodium battery positive electrode precursor used in this embodiment includes the following steps: nickel sulfate hexahydrate, manganese sulfate monohydrate, and ferrous sulfate heptahydrate are mixed at a molar ratio of 0.33:0.33:0.33 to form a mixed salt solution with a metal element concentration of 1.5mol / L, which is pumped into a 50L reactor at a feed rate of 50mL / min, while a 32% sodium hydroxide solution and a 25% ammonia solution are pumped in simultaneously, and nitrogen gas is introduced at a rate of 5L / min for protection, and Ni is co-precipitated to form Ni. 0.33 Fe 0.33 Mn 0.33 (OH)2;
[0061] S2, using a negative electrode as the working electrode, a sodium sheet with a thickness of 0.8 mm as the counter electrode, a glass fiber membrane with a thickness of 15 μm (13 mm) as the separator, 80 μL of electrolyte (electrolyte is 1 mol / L NaClO4, solvent is ethylene carbonate, propylene carbonate and diethyl carbonate in a mass ratio of 1:4:5, additive is 3% fluoroethylene carbonate)), sealed at 25 MPa, and assembled into a CR2032 coin cell;
[0062] S3. Let the CR2032 coin cell stand for 18 hours, then discharge it to 0.01V at 0.1C, 0.05C, and 0.01C to 0.01V. Obtain the sodium intercalation specific capacity and voltage-sodium intercalation specific capacity curves (e.g., ...). Figure 1 (as shown)
[0063] The measured sodium intercalation specific capacity was 168 mAh / g (the theoretical specific capacity is 200 mAh / g), which is 84% of the theoretical capacity. The voltage-sodium intercalation specific capacity curve was smooth without any abnormal plateaus.
[0064] Preliminary assessment: The precursor structure of the sodium battery cathode is determined to be intact, and the electrochemical performance of the sodium battery cathode material is at an excellent level.
[0065] Verification: The sodium battery cathode precursor was sintered at 800℃ for 10 hours to obtain the sodium battery cathode material; the specific capacity of the sodium battery cathode material was tested, and the voltage-sodium intercalation specific capacity curve of the cathode material was obtained (e.g., Figure 2 As shown in the figure, the charge-discharge regime is 0.1C constant current charging to 4.0V, standing for 5 min, and 0.1C constant current discharging to 2.0V. The calculated sodium intercalation specific capacity at 0.1C is 155mAh / g, which is 77.5% of the theoretical capacity. The electrochemical performance of the prepared sodium battery cathode material is excellent, consistent with the prediction.
[0066] Example 2
[0067] This embodiment is based on a rapid screening method for positive electrode precursors using a sodium intercalation method, and includes the following steps:
[0068] S1, a sodium battery positive electrode precursor with a particle size of 1μm~3μm, acetylene black, and CMC+SBR are mixed at a mass ratio of 80:15:5, and water is added and mixed evenly to obtain a slurry; the slurry is coated onto a 20μm aluminum foil current collector, dried at 80℃ for 24h, and rolled at 15MPa for 12mm to obtain a negative electrode sheet; wherein, the preparation method of the sodium battery positive electrode precursor used in this embodiment includes the following steps: nickel sulfate hexahydrate, manganese sulfate monohydrate, and ferrous sulfate heptahydrate are mixed at a molar ratio of 0.33:0.33:0.33 to form a mixed salt solution with a metal element concentration of 1.5mol / L, which is pumped into a 50L reactor at a feed rate of 70mL / min, while a 32% sodium hydroxide solution and a 25% ammonia solution are pumped in simultaneously, and nitrogen gas is introduced at a rate of 5L / min for protection, and Ni is co-precipitated to form Ni. 0.33 Fe 0.33 Mn 0.33 (OH)2;
[0069] S2, using a negative electrode as the working electrode, a sodium sheet with a thickness of 0.8 mm as the counter electrode, a glass fiber membrane with a thickness of 15 μm (13 mm) as the separator, 70 μL of electrolyte (electrolyte is 1 mol / L NaClO4, solvent is ethylene carbonate, propylene carbonate and diethyl carbonate in a mass ratio of 1:4:5, additive is 3% fluoroethylene carbonate)), sealed at 25 MPa, and assembled into a CR2032 coin cell;
[0070] S3. Allow the CR2032 coin cell to stand for 18 hours, then discharge it to 0.01V at 0.1C, 0.05C, and 0.01C to 0.01V. Obtain the sodium intercalation specific capacity and voltage-sodium intercalation specific capacity curves (e.g., ...). Figure 3 (as shown)
[0071] The measured sodium intercalation specific capacity was 160 mAh / g (the theoretical specific capacity is 200 mAh / g), which is 80% of the theoretical capacity. The voltage-sodium intercalation specific capacity curve was smooth without any abnormal plateaus.
[0072] Graded prediction: The precursor structure of the sodium battery cathode is determined to be intact, and the electrochemical performance of the sodium battery cathode material is excellent.
[0073] Verification: The sodium battery cathode precursor was sintered at 800℃ for 10 hours to obtain the sodium battery cathode material; the specific capacity of the sodium battery cathode material was tested, and the voltage-sodium intercalation specific capacity curve of the cathode material was obtained (e.g., Figure 4 As shown in the figure, the charge-discharge regime is 0.1C constant current charging to 4.0V, standing for 5 min, and 0.1C constant current discharging to 2.0V. The calculated sodium intercalation specific capacity at 0.1C is 151mAh / g, which is 75.5% of the theoretical capacity. The electrochemical performance of the prepared sodium battery cathode material is excellent, consistent with the prediction.
[0074] Example 3
[0075] This embodiment is based on a rapid screening method for positive electrode precursors using a sodium intercalation method, and includes the following steps:
[0076] S1, a sodium battery positive electrode precursor with a particle size of 1μm~3μm, acetylene black, and CMC+SBR are mixed at a mass ratio of 80:15:5, and water is added and mixed evenly to obtain a slurry; the slurry is coated onto a 20μm aluminum foil current collector, dried at 80℃ for 24h, and rolled at 15MPa for 12mm to obtain the working electrode; wherein, the preparation method of the sodium battery positive electrode precursor used in this embodiment includes the following steps: nickel sulfate hexahydrate, manganese sulfate monohydrate, and ferrous sulfate heptahydrate are mixed at a molar ratio of 0.2:0.4:0.4 to form a mixed salt solution with a metal element concentration of 1.5mol / L, which is pumped into a 50L reactor at a feed rate of 50mL / min, while a 32% sodium hydroxide solution and a 25% ammonia solution are pumped in simultaneously, and nitrogen gas is introduced at a rate of 5L / min for protection, and Ni is co-precipitated to form Ni. 0.2 Fe 0.4 Mn 0.4 (OH)2;
[0077] S2, using a 0.8 mm thick sodium sheet as the counter electrode, a 15 μm thick glass fiber membrane (13 mm) as the separator, 70 μL of electrolyte (electrolyte is 1 mol / L NaClO4, solvent mass ratio is ethylene carbonate: propylene carbonate: diethyl carbonate = 1:4:5, additive is 3% fluoroethylene carbonate), sealed at 25 MPa, and assembled into a CR2032 coin cell;
[0078] S3, after allowing the CR2032 coin cell to stand for 18 hours, perform sodium intercalation according to the discharge schedule of 0.1C to 0.01V, 0.05C to 0.01V, and 0.01C to 0.01V, and obtain the sodium intercalation specific capacity and voltage-sodium intercalation specific capacity curves (e.g.) Figure 5 (as shown)
[0079] The measured sodium intercalation specific capacity was 130 mAh / g (the theoretical specific capacity is 180 mAh / g), which is 72.2% of the theoretical capacity. The voltage-sodium intercalation specific capacity curve shows a plateau in the range of 1.5V to 2.0V.
[0080] Preliminary assessment: The precursor structure of the sodium battery cathode is basically intact, and the electrochemical performance of the sodium battery cathode material is moderate.
[0081] Verification: The sodium battery cathode precursor was sintered at 800℃ for 10 hours to obtain the sodium battery cathode material; the sodium battery cathode material was tested for specific capacity, and the voltage-sodium intercalation specific capacity curve of the cathode material was obtained (e.g., ...). Figure 6 As shown in the figure, the charge-discharge regime is 0.1C constant current charging to 4.0V, standing for 5 min, and 0.1C constant current discharging to 2.0V. The calculated sodium intercalation specific capacity at 0.1C is 132.4mAh / g, which is 73.5% of the theoretical capacity. The electrochemical performance of the prepared sodium battery cathode material is at a medium level, consistent with the prediction.
[0082] Example 4
[0083] This embodiment is based on a rapid screening method for positive electrode precursors using a sodium intercalation method, and includes the following steps:
[0084] S1, a sodium battery positive electrode precursor with a particle size of 1μm~3μm, acetylene black, and CMC+SBR are mixed at a mass ratio of 80:15:5, and water is added and mixed evenly to obtain a slurry; the slurry is coated onto a 20μm aluminum foil current collector, dried at 80℃ for 24h, and rolled at 15MPa for 12mm to obtain the working electrode; wherein, the preparation method of the sodium battery positive electrode precursor used in this embodiment includes the following steps: nickel sulfate hexahydrate, manganese sulfate monohydrate, and ferrous sulfate heptahydrate are mixed at a molar ratio of 0.2:0.4:0.4 to form a mixed salt solution with a metal element concentration of 1.5mol / L, which is pumped into a 50L reactor at a feed rate of 70mL / min, while a 32% sodium hydroxide solution and a 25% ammonia solution are pumped in simultaneously, and nitrogen gas is introduced at a rate of 5L / min for protection, and Ni is co-precipitated to form Ni. 0.2 Fe 0.4 Mn 0.4 (OH)2;
[0085] S2, using a 0.8 mm thick sodium sheet as the counter electrode, a 15 μm thick glass fiber membrane (13 mm) as the separator, 70 μL of electrolyte (electrolyte is 1 mol / L NaClO4, solvent mass ratio is ethylene carbonate: propylene carbonate: diethyl carbonate = 1:4:5, additive is 3% fluoroethylene carbonate), sealed at 25 MPa, and assembled into a CR2032 coin cell;
[0086] S3. After allowing the CR2032 button cell to stand for 18 hours, perform sodium intercalation on a 5V 5mA testing cabinet according to the following discharge procedures: 0.1C to 0.01V, 0.05C to 0.01V, and 0.01C to 0.01V. Obtain the sodium intercalation specific capacity and voltage-sodium intercalation specific capacity curves (e.g., ...). Figure 7 (as shown)
[0087] The measured sodium intercalation specific capacity was 105 mAh / g (the theoretical specific capacity is 180 mAh / g), which is 58% of the theoretical capacity. The voltage-sodium intercalation specific capacity curve shows a plateau in the range of 1.5V to 2.0V.
[0088] Graded prediction: It is determined that the precursor structure of the sodium battery cathode has defects, and the electrochemical performance of the sodium battery cathode material is poor.
[0089] Verification: The sodium battery cathode precursor was sintered at 800℃ for 10 hours to obtain the sodium battery cathode material; the specific capacity of the sodium battery cathode material was tested, and the voltage-sodium intercalation specific capacity curve of the cathode material was obtained (e.g., Figure 8 As shown in the figure, the charge-discharge regime is 0.1C constant current charging to 4.0V, standing for 5 min, and 0.1C constant current discharging to 2.0V. The calculated sodium intercalation specific capacity at 0.1C is 90mAh / g, which is 50% of the theoretical capacity. The electrochemical performance of the prepared sodium battery cathode material is poor, which is consistent with the prediction.
[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A rapid screening method for cathode precursors based on sodium intercalation, characterized in that, Includes the following steps: A sodium battery positive electrode precursor, a conductive agent, a binder, and a first solvent are mixed to obtain a slurry; the slurry is coated onto the surface of an aluminum foil current collector, and after drying and rolling, a negative electrode sheet is obtained; the negative electrode sheet is used as the working electrode to assemble a coin cell. After static aging, the coin cell was subjected to electrochemical testing to obtain the sodium intercalation specific capacity and voltage-sodium intercalation specific capacity curve of the coin cell under the test range of current density of 0.01C~0.1C and voltage of 0.01V~3.0V. Based on the sodium intercalation specific capacity and the voltage-sodium intercalation specific capacity curve, the structural integrity of the sodium battery cathode precursor and the electrochemical performance of the sodium battery cathode material are classified and predicted. The sodium battery cathode precursor is screened based on the classification and prediction results.
2. The method according to claim 1, characterized in that, Based on the percentage of the sodium intercalation specific capacity relative to the theoretical capacity and the smoothness of the voltage-sodium intercalation specific capacity curve, the structural integrity of the sodium battery cathode precursor and the electrochemical performance of the sodium battery cathode material are graded and predicted.
3. The method according to claim 1 or 2, characterized in that, The hierarchical prediction is performed in the following manner: Excellent level: The sodium intercalation specific capacity of the coin cell reaches more than 75% of the theoretical capacity, and the voltage-sodium intercalation specific capacity curve of the coin cell is smooth without abnormal plateau, indicating that there is no impurity phase reaction in the sodium battery cathode precursor and the electrochemical performance of the sodium battery cathode material is excellent. Medium level: The sodium intercalation specific capacity of the coin cell is 60%~75% of the theoretical capacity, and the abnormal plateau in the voltage-sodium intercalation specific capacity curve of the coin cell indicates that the structure of the sodium battery cathode precursor is basically complete, and the electrochemical performance of the sodium battery cathode material is medium. Poor grade: The sodium intercalation specific capacity of the coin cell is less than 60% of the theoretical capacity, or the voltage-sodium intercalation specific capacity curve of the coin cell shows an abnormal plateau, indicating that the sodium battery cathode precursor contains impurity phase reaction, and the electrochemical performance of the sodium battery cathode material is poor. The abnormal platform refers to the voltage-sodium intercalation specific capacity curve having zero specific capacity within the voltage range of 1.0V to 2.0V.
4. The method according to any one of claims 1 to 3, characterized in that, The step of screening the sodium battery cathode precursor according to the classification prediction results includes: screening out the sodium battery cathode precursors corresponding to coin cells that meet the requirements of sodium intercalation specific capacity reaching more than 75% of the theoretical capacity and having a smooth voltage-sodium intercalation specific capacity curve, and using them to prepare sodium battery cathode materials.
5. The method according to any one of claims 1 to 4, characterized in that, The electrochemical tests include: discharging at 0.1C to 0.01V, discharging at 0.05C to 0.01V, and discharging at 0.01C to 0.01V.
6. The method according to any one of claims 1 to 5, characterized in that, The mass ratio of the sodium battery positive electrode precursor, the conductive agent and the binder is (70~90):(5~20):(5~10).
7. The method according to any one of claims 1 to 6, characterized in that, The general chemical formula of the sodium battery cathode precursor includes M(OH)2, where M is one or more of Ni, Fe, Mn, and Cu.
8. The method according to any one of claims 1 to 7, characterized in that, The particle size of the sodium battery cathode precursor is 1 μm to 10 μm; and / or, The drying temperature is 80℃~90℃; and / or, The pressure of the roller is 0.25MPa~0.35MPa.
9. The method according to any one of claims 1 to 8, characterized in that, The conductive agent includes at least one of acetylene black, Ketjen black, and Super P; and / or, The adhesive comprises at least one of polyvinylidene fluoride, carboxymethyl cellulose, and styrene-butadiene rubber; and / or The first solvent includes N-methylpyrrolidone and / or water.
10. The method according to any one of claims 1 to 9, characterized in that, The steps of assembling the negative electrode as the working electrode into the coin cell include: stacking the negative electrode, the separator, and the sodium metal sheet to obtain an electrode assembly; placing the electrode assembly and electrolyte into a coin cell casing in an argon-filled glove box and assembling them into a CR2032 type coin cell; wherein the separator is a glass fiber separator, and the electrolyte includes an electrolyte and a second solvent, the electrolyte being NaClO4, and the second solvent being a mixed solvent of ethylene carbonate, propylene carbonate, and diethyl carbonate; and / or, The static aging time is >18h.