A method for evaluating the maximum sintering amount in a tube furnace based on laboratory-prepared electrode materials

Abstract

This invention discloses a method for evaluating the maximum sintering amount in a tube furnace for laboratory preparation of electrode materials, belonging to the field of battery material preparation technology. This invention uses Comsol Multiphysics to simulate the temperature gradient distribution during the preparation of active materials in a tube furnace, conveniently and quickly determining the maximum sintering amount and optimal position of the material that can be sintered in the sample boat within the tube furnace, effectively improving the stability and repeatability of the material. The measurement of this invention has good repeatability, and the measurement process is easy to control. The method of this invention is simple, easy to implement, and low in cost, making it suitable for widespread use.

Description

Technical Field

[0001] This invention belongs to the field of battery material preparation technology, specifically relating to a method for evaluating the maximum sintering amount in a tube furnace based on laboratory preparation of electrode materials. Background Technology

[0002] Tube furnaces are mainly used in industries such as metallurgy, glass, heat treatment, lithium battery cathode and anode materials, and new energy, as specialized equipment for measuring materials under specific temperature conditions. The furnace structure is simple, easy to operate and control, and allows for continuous production. In preliminary process design in the laboratory, tube furnaces can meet the requirement of uniform production of trace materials. However, the sintering amount cannot be well controlled during the preparation process. In actual production, heat conduction in the tube furnace becomes a limiting factor in material processing, making it impossible to obtain samples with uniform morphology, which affects the performance of the electrode materials. To solve these problems, the temperature gradient of the entire tube furnace should be analyzed to explore the maximum sinterable amount. Traditionally, the temperature gradient of the tube furnace is studied by connecting the thermocouple leads to a temperature controller via an adapter and recording the relevant data.

[0003] Contact testing of the temperature field in high-temperature furnaces is susceptible to interference from external factors, increasing the instability of thermocouple calibration. Providing a method for evaluating the maximum sintering yield of a tube furnace based on laboratory-prepared electrode materials is a technical problem that needs to be solved. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0005] As one aspect of the present invention, the present invention provides a method for evaluating the maximum sintering amount of a tube furnace for preparing electrode materials in a laboratory setting, wherein: the temperature gradient distribution during the preparation of active materials in a tube furnace is simulated using Comsol Multiphysics, including the following steps:

[0006] S1. Based on the working process of the tubular furnace in calcination, select the physical field and physical field interface in the COMSOL multiphysics simulation software.

[0007] S2. Based on the dimensional data of the heating and heat transfer components of the tubular furnace, a three-dimensional model of the heating and heat transfer components of the tubular furnace is established in the COMSOL multiphysics simulation software.

[0008] S3. In the COMSOL multiphysics simulation software, the established three-dimensional tubular furnace heating and heat transfer component models are divided into regions. The divided regions include the calcined material, the corundum semi-circular ceramic boat, the quartz tube, the heat source layer, the insulation layer, the external air domain, and the nitrogen flow domain inside the tube.

[0009] S4. Based on the properties of the heating and heat transfer components of the tubular furnace, set the material parameters, boundary values, and initial parameters of the heating and heat transfer components in the COMSOL multiphysics simulation software.

[0010] S5. Couple the solid-to-surface heat transfer and surface-to-surface radiative heat transfer models.

[0011] S6. Mesh the various regions of the tubular furnace, set the solver's solution method, and obtain simulation data;

[0012] S7. Visualize the simulation data to obtain temperature distribution data.

[0013] As a preferred embodiment of the evaluation method for the maximum sintering amount of a tube furnace based on laboratory-prepared electrode materials according to the present invention: in step S1, the physical field interface includes solid heat transfer and surface-to-surface radiation.

[0014] As a preferred embodiment of the evaluation method for the maximum sintering amount of a tubular furnace based on laboratory-prepared electrode materials described in this invention: In step S2, the three-dimensional tubular furnace heating component and heat transfer component model includes an insulation layer, a heat source layer, a vacuum quartz tube cavity, a corundum semi-circular ceramic boat, and calcination materials.

[0015] As a preferred embodiment of the evaluation method for the maximum sintering amount of the tube furnace based on laboratory-prepared electrode materials described in this invention: Step S4 includes setting the material of the corundum semi-circular ceramic boat to alumina, the material of the heat source layer to nickel-chromium alloy, and the material of the insulation layer to 50wt% alumina and 50wt% silicon dioxide, wherein the medium between the insulation layer and the heat source layer and the medium on the outer wall of the quartz tube are both set to air, the input heat source temperature is defined as 800℃, and the air domain temperature is the ambient temperature of 25℃;

[0016] As a preferred embodiment of the method for evaluating the maximum sintering amount of a tube furnace based on laboratory-prepared electrode materials as described in this invention: In step S5, the thermal resistance of the furnace chamber is mainly composed of the thermal resistance per unit area of ​​air and the thermal resistance per unit area of ​​thermocouples. The formula for calculating the total thermal resistance per unit area is:

[0017] R A =R air,A +R TC,A = λ air / δ air + λ TC / δ TC

[0018] Among them, R A R is the thermal resistance of the total surface area inside the furnace of a tubular furnace. air,A R is the thermal resistance per unit area of ​​air. TC,Aλ is the thermal resistance per unit area of ​​the thermocouple. air λ is the thermal conductivity of air. TC δ is the thermal conductivity of the thermocouple. air δ represents the thickness of the air layer. TC These are the characteristic dimensions of the thermocouple;

[0019] The steady-state solid heat transfer model inside the furnace of a tubular furnace is as follows:

[0020] ρC ρ u·▽T+▽·q=Q+Q ted

[0021] q=-k▽T

[0022] Where ρ is the density of the material, ▽T is the temperature gradient at a point inside the furnace of the tubular furnace, u is the velocity field, and C ρ Q is the specific heat capacity, and Q is the volumetric heat source. ted The heat source generated by the compression or expansion of a solid, k is the thermal conductivity of the heat transfer component material, q is the heat flux density per unit area, and ▽·q is the heat flux density gradient at a point inside the furnace of a tube furnace.

[0023] The convective heat flux is:

[0024] q o =h·(T ext – T)

[0025] Where, q o T represents the convective heat flux, h represents the heat transfer coefficient, and T represents the total heat transfer coefficient. ext T represents the external boundary condition temperature of the tubular furnace, and T represents the internal boundary condition temperature of the tubular furnace.

[0026] The fundamental equations of the surface-to-surface radiation model are:

[0027] Q radiation =σεAF (T1 4 -T2 4 )

[0028] E b (T)=n 2 σT 4

[0029] Among them, Q radiation Let σ be the radiative heat transfer rate, σ be the Stefan-Boltzmann constant, A be the radiative heat transfer area, T1 and T2 be the thermodynamic temperatures of the two object surfaces, T be the absolute temperature, ε be the surface emissivity, and E be the surface emissivity. b Let n be the total emission power of the blackbody, n be the refractive index of the transparent medium, and F be the viewing angle factor.

[0030] As a preferred embodiment of the evaluation method for the maximum sintering amount of a tube furnace based on laboratory-prepared electrode materials described in this invention: In step S6, the grid-divided region includes the calcined material, the corundum semi-circular ceramic boat, the quartz tube, the heat source layer, the insulation layer, and the physical field control grid.

[0031] A preferred embodiment of the method for evaluating the maximum sintering amount in a tube furnace based on laboratory-prepared electrode materials according to the present invention further includes: preparing electrode materials in a tube furnace; performing morphological scanning on the electrode materials; conducting electrochemical tests; and determining the maximum sintering amount range under optimal electrochemical performance based on the electrochemical test data.

[0032] As a preferred embodiment of the evaluation method for the maximum sintering amount of the tube furnace based on laboratory preparation of electrode materials described in this invention: the preparation of electrode materials using the tube furnace is as follows: a quartz tube is placed inside the furnace chamber of the tube furnace, and calcined materials containing 1 / 5, 3 / 5, 4 / 5, and 5 / 5 of the volume of the corundum semi-circular ceramic boat are pushed to the middle of the quartz tube and the furnace chamber, respectively. The working gas path is connected, so that the working gas flows in through the inlet valve and out through the outlet valve. The heating rate is set not to exceed 10°C / minute, the temperature is raised to 800°C, held for two hours, and then naturally cooled to obtain electrode materials 1 / 5VC, 3 / 5VC, 4 / 5VC, and 5 / 5VC, respectively.

[0033] As a preferred embodiment of the method for evaluating the maximum sintering amount of a tube furnace based on laboratory-prepared electrode materials according to the present invention: the electrochemical test includes cyclic voltammetry and constant current charge-discharge testing; wherein, the cyclic voltammetry test includes 1 mV s -1 The test was performed at a scanning speed of 1 A g, and the constant current charge-discharge test included 1 A g -1 The test was conducted at a current density of [value missing].

[0034] The beneficial effects of this invention are: the temperature gradient distribution method for simulating the tube furnace preparation process of active materials using Comsol Multiphysics is highly accurate and accurately determines the optimal maximum sintering amount. Furthermore, this invention offers good measurement repeatability and the measurement process is easy to control. The method is simple, easy to implement, and low in cost, making it suitable for widespread use. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, wherein:

[0036] Figure 1 The results are electrochemical tests for different sintering amounts, where (a) is a cyclic voltammetry test and (b) is a constant current charge-discharge test.

[0037] Figure 2The results are shown in the scanning electron microscopy characterization of different sintering amounts.

[0038] Figure 3 This represents the internal temperature gradient of the tubular furnace.

[0039] Figure 4 This is a temperature distribution diagram of the surface of the calcined material sample.

[0040] Figure 5 This is a cross-sectional view of the surface temperature of the calcined material sample. Detailed Implementation

[0041] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0042] This invention provides a method for evaluating the maximum sintering amount in a tube furnace based on laboratory-prepared electrode materials:

[0043] Step 1: Material preparation: Calcination materials with different sintering amounts are calcined in a tube furnace. The sintering amounts are 1 / 5V, 3 / 5V, 4 / 5V and 5 / 5V of the total volume of the corundum semi-circular ceramic boat, respectively, to obtain electrode materials of 1 / 5VC, 3 / 5VC, 4 / 5VC and 5 / 5VC.

[0044] The specific method is as follows: Place the quartz tube in the furnace chamber of the tube furnace, and push the ceramic boats with sintering amounts of 1 / 5V, 3 / 5V, 4 / 5V and 5 / 5V to the middle of the quartz tube respectively. Install the gas furnace flange, connect the working gas line, and continuously let the gas used flow in through the inlet valve and out through the outlet valve. Design the heating and cooling curves. The heating rate should not exceed 10℃ / minute. Heat to 800℃, hold for two hours, and cool naturally to obtain electrode materials of 1 / 5VC, 3 / 5VC, 4 / 5VC and 5 / 5VC respectively.

[0045] Step 2: Determine the electrochemical performance and surface morphology of electrode materials with different sintering amounts: Perform cyclic voltammetry and constant current charge-discharge tests on the above four electrode materials.

[0046] Specifically, the electrode materials are used as the positive and negative electrodes, respectively, and the battery is assembled inside a glove box. The electrolyte is an organic electrolyte. The assembly sequence is as follows: positive electrode shell, electrode material, electrolyte, separator, electrolyte, electrode material, gasket, spring, negative electrode shell.

[0047] The scan rate for cyclic voltammetry testing of the assembled battery is 1 mV / s. -1 The current density for the constant current charge-discharge test is 1 A g. -1 The four electrode materials were characterized by scanning electron microscopy at a magnification of 10000.

[0048] Step 3: Simulate the temperature gradient distribution during the preparation of active materials in a tube furnace using Comsol Multiphysics: Solid heat transfer in the heat transfer module of Comsol software is selected as the physical field interface. Steady-state studies are added. By establishing a simulation model consistent with the experiment, the material properties of the heating components and heat transfer components of the tube furnace are added. A coupled solid heat transfer and surface-to-surface radiation heat transfer model is constructed. The temperature gradient distribution inside the tube furnace is calculated using the mesh generation step. Based on the simulated temperature gradient distribution, the optimal sintering range is verified.

[0049] As a preferred embodiment of the preparation method described in this invention:

[0050] S1. Based on the working process of the tubular furnace in calcination, solid heat transfer is selected as the physical field interface in the COMSOL multiphysics simulation software, and steady-state studies are added.

[0051] S2. Based on the actual size data of the heating and heat transfer components of the tubular furnace, a 1:1 three-dimensional model of the heating components of the tubular furnace is established in the COMSOL multiphysics simulation software. The geometric model of the heating and heat transfer components of the tubular furnace is three-dimensional and mainly includes: insulation layer, heat source layer, vacuum quartz tube, corundum semi-circular ceramic boat, and pitch calcination material.

[0052] The specific specifications of the model are as follows: the corundum semi-circular ceramic boat has dimensions of a×b×c×d, where the long side a = 100 mm, the short side b = 40 mm, the height c = 20 mm, and the thickness 3 mm. The quartz tube has dimensions of a×b×c, where the long side a = 600 mm, the outer diameter b = 50 mm, and the wall thickness c = 2.5 mm. The heat source has a length of 300 mm and an arc length l = 32.75 mm. To better protect the heat source, a cylindrical insulating layer with a length of 350 mm is added to the heat source.

[0053] The calcined materials inside the corundum semi-circular porcelain boat are respectively set with dimensions of 1 / 5V, 3 / 5V, 4 / 5V and 5 / 5V.

[0054] S3. Divide the established three-dimensional tubular furnace heating and heat transfer component models into regions using COMSOL multiphysics simulation software.

[0055] The divided areas include the material, the corundum semi-circular ceramic boat, the quartz tube, the upper and lower effective heat source layers, the insulation layer, the external air zone, and the nitrogen flow zone inside the tube.

[0056] S4. Based on the properties of the heating and heat transfer components of the tubular furnace, set the material parameters, boundary values, and initial parameters of the heating and heat transfer components for this region in the COMSOL multiphysics simulation software.

[0057] The calcined material sample inside the corundum semi-circular ceramic boat was set to the parameters of asphalt. The material of the ceramic boat was set to 94% alumina. The medium inside the tube was set to a nitrogen atmosphere. The material of the horizontal long tube was set to quartz glass. The material of the heat source layer was nickel-chromium alloy. The material of the insulation layer was 50wt% alumina-50wt% silicon dioxide. The medium between the insulation layer and the heat source layer and the medium on the outer wall of the quartz tube were set to air. The input heat source temperature was defined as 800℃, and the air temperature was defined as the ambient temperature of 25℃.

[0058] S5. Construct a coupled model of solid-to-surface heat transfer and surface-to-surface radiative heat transfer.

[0059] The thermal resistance of a tubular furnace is mainly composed of the thermal resistance per unit area of ​​air and the thermal resistance per unit area of ​​thermocouples. The formula for calculating the total thermal resistance per unit area is:

[0060] R A =R air,A +R TC,A = λ air / δ air + λ TC / δ TC

[0061] Among them, R A R is the thermal resistance of the total surface area inside the furnace of a tubular furnace. air,A R is the thermal resistance per unit area of ​​air. TC,A λ is the thermal resistance per unit area of ​​the thermocouple. air λ is the thermal conductivity of air. TC δ is the thermal conductivity of the thermocouple. air δ represents the thickness of the air layer. TC These are the characteristic dimensions of the thermocouple;

[0062] The steady-state solid heat transfer model inside the furnace of a tubular furnace is as follows:

[0063] ρC ρ u·▽T+▽·q=Q+Q ted

[0064] q=-k▽T

[0065] Where ρ is the density of the material, ▽T is the temperature gradient at a point inside the furnace of the tubular furnace, u is the velocity field, and C ρ Q is the specific heat capacity, and Q is the volumetric heat source. ted The heat source generated by the compression or expansion of a solid, k is the thermal conductivity of the heat transfer component material, q is the heat flux density per unit area, and ▽·q is the heat flux density gradient at a point inside the furnace of a tube furnace.

[0066] The convective heat flux is:

[0067] qo =h·(T ext – T)

[0068] Where, q o T represents the convective heat flux, h represents the heat transfer coefficient, and T represents the total heat transfer coefficient. ext T represents the external boundary condition temperature of the tubular furnace, and T represents the internal boundary condition temperature of the tubular furnace.

[0069] The fundamental equations of the surface-to-surface radiation model are:

[0070] Q radiation =σεAF (T1 4 -T2 4 )

[0071] E b (T)=n 2 σT 4

[0072] Among them, Q radiation Let σ be the radiative heat transfer rate, σ be the Stefan-Boltzmann constant, A be the radiative heat transfer area, T1 and T2 be the thermodynamic temperatures of the two object surfaces, T be the absolute temperature, ε be the surface emissivity, and E be the surface emissivity. b Let n be the total emission power of the blackbody, n be the refractive index of the transparent medium, and F be the viewing angle factor.

[0073] Table 1 Material Properties

[0074]

[0075] S6. Mesh the various regions of the tubular furnace, set the solver's solution method, and obtain simulation data.

[0076] The meshed area includes the calcined material, the corundum semi-circular ceramic boat, the quartz tube, the upper and lower effective heat sources, the insulation layer, and the physical field controls the mesh. The cell size is selected to be coarse.

[0077] S7. Visualize the simulation data obtained from the solution to obtain temperature distribution data.

[0078] Example 1:

[0079] Step 1: Electrode Material Preparation

[0080] Place the quartz tube inside the tube furnace. Push the corundum semi-circular ceramic boats with a sintering weight of 1 / 5V to the middle of both the quartz tube and the furnace chamber. Install the furnace flange and check for airtightness. Connect the working gas line, allowing the gas to continuously flow in through the inlet valve and out through the outlet valve, controlling the flow rate. Design a heating and cooling curve, ensuring the heating rate does not exceed 10℃ / minute. Heat to 800℃, hold for two hours, and allow to cool naturally to obtain the electrode material 1 / 5VC.

[0081] Step 2: Determine the electrochemical performance and surface morphology of electrode materials with different sintering amounts.

[0082] Cyclic voltammetry and constant current charge-discharge tests were performed on four electrode materials.

[0083] As a preferred embodiment of the preparation method described in this invention: the electrode materials are used as the positive and negative electrodes, and the battery is assembled in a glove box. The electrolyte is an organic electrolyte. The assembly sequence is: positive electrode shell, electrode material, electrolyte, separator, electrolyte, electrode material, gasket, spring, and negative electrode shell.

[0084] The scan rate for cyclic voltammetry testing of the assembled battery is 1 mV / s. -1 The current density for the constant current charge-discharge test is 1 A g. -1 .

[0085] Four electrode materials were characterized by scanning electron microscopy at a magnification of 10,000.

[0086] Step 3: Simulate the temperature gradient distribution during the preparation of active materials in a tube furnace using Comsol Multiphysics.

[0087] Solid-state heat transfer was selected from the heat transfer module of Comsol software as the physical field interface. Steady-state studies were added, and a simulation model consistent with the experiment was established. The required material properties were added, and the volume of the calcined material inside the corundum semi-circular ceramic boat was set to 1 / 5V. A coupled solid-state heat transfer and surface-to-surface radiative heat transfer model was constructed, defining the input heat source temperature as 800℃ and the air domain temperature as the ambient temperature of 25℃. The temperature gradient distribution within the tubular furnace cavity was calculated using a mesh generation process. Based on the simulated temperature gradient distribution, the optimal sintering range was verified.

[0088] Example 2:

[0089] Step 1: Material Preparation

[0090] Place the quartz tube inside the tube furnace. Push the corundum semi-circular ceramic boats with a sintering weight of 3 / 5V to the middle of both the quartz tube and the furnace chamber. Install the furnace flange and check for airtightness. Connect the working gas line, allowing the gas to continuously flow in through the inlet valve and out through the outlet valve, controlling the flow rate. Design a heating and cooling curve, ensuring the heating rate does not exceed 10℃ / minute. Heat to 800℃, hold for two hours, and allow to cool naturally to obtain the 3 / 5VC electrode material.

[0091] Step 2: Determine the electrochemical performance and surface morphology of electrode materials with different sintering amounts.

[0092] Cyclic voltammetry and constant current charge-discharge tests were performed on four electrode materials.

[0093] As a preferred embodiment of the preparation method described in this invention: the electrode materials are used as the positive and negative electrodes, and the battery is assembled in a glove box. The electrolyte is an organic electrolyte. The assembly sequence is: positive electrode shell, electrode material, electrolyte, separator, electrolyte, electrode material, gasket, spring, and negative electrode shell.

[0094] The scan rate for cyclic voltammetry testing of the assembled battery was 1 mV s⁻¹, and the current density for constant current charge-discharge testing was 1 A g. -1 .

[0095] Four electrode materials were characterized by scanning electron microscopy at a magnification of 10,000.

[0096] Step 3: Use Comsol Multiphysics to simulate the temperature gradient distribution during the preparation of active materials in a tube furnace.

[0097] Solid-state heat transfer was selected from the heat transfer module of Comsol software as the physical field interface. Steady-state studies were added, and a simulation model consistent with the experiment was established. The required material properties were added, and the volume of the calcined material inside the corundum semi-circular ceramic boat was set to 3 / 5V. A coupled solid-state heat transfer and surface-to-surface radiative heat transfer model was constructed, defining the input heat source temperature as 800℃ and the air domain temperature as the ambient temperature of 25℃. The temperature gradient distribution within the tubular furnace cavity was calculated using a mesh generation process. Based on the simulated temperature gradient distribution, the optimal sintering range was verified.

[0098] Example 3:

[0099] Step 1: Material Preparation

[0100] Place the quartz tube inside the tube furnace. Push the corundum semi-circular ceramic boats with a sintering weight of 4 / 5V to the middle of both the quartz tube and the furnace chamber. Install the furnace flange and check for airtightness. Connect the working gas line, allowing the gas to continuously flow in through the inlet valve and out through the outlet valve, controlling the flow rate. Design a heating and cooling curve, ensuring the heating rate does not exceed 10℃ / minute. Heat to 800℃, hold for two hours, and allow to cool naturally to obtain the 4 / 5VC electrode material.

[0101] Step 2: Determine the electrochemical performance and surface morphology of electrode materials with different sintering amounts.

[0102] Cyclic voltammetry and constant current charge-discharge tests were performed on four electrode materials.

[0103] As a preferred embodiment of the preparation method described in this invention: the electrode materials are used as the positive and negative electrodes, and the battery is assembled in a glove box. The electrolyte is an organic electrolyte. The assembly sequence is: positive electrode shell, electrode material, electrolyte, separator, electrolyte, electrode material, gasket, spring, and negative electrode shell.

[0104] The scan rate for cyclic voltammetry testing of the assembled battery is 1 mV / s. -1 The current density for the constant current charge-discharge test is 1 A g. -1 .

[0105] Four electrode materials were characterized by scanning electron microscopy at a magnification of 10,000.

[0106] Step 3: Simulate the temperature gradient distribution during the preparation of active materials in a tube furnace using Comsol Multiphysics.

[0107] Solid-state heat transfer was selected from the heat transfer module of Comsol software as the physical field interface. Steady-state studies were added, and a simulation model consistent with the experiment was established. The required material properties were added, and the volume of the calcined material inside the corundum semi-circular ceramic boat was set to 4 / 5V. A coupled solid-state heat transfer and surface-to-surface radiative heat transfer model was constructed, defining the input heat source temperature as 800℃ and the air domain temperature as the ambient temperature of 25℃. The temperature gradient distribution within the tubular furnace cavity was calculated using a mesh generation process. Based on the simulated temperature gradient distribution, the optimal sintering range was verified.

[0108] Example 4:

[0109] Step 1: Material Preparation

[0110] Place the quartz tube inside the tube furnace. Push the corundum semi-circular ceramic boats with a sintering weight of 5 / 5V to the middle of both the quartz tube and the furnace chamber. Install the furnace flange and check for airtightness. Connect the working gas line, allowing the gas to continuously flow in through the inlet valve and out through the outlet valve, controlling the flow rate. Design a heating and cooling curve, ensuring the heating rate does not exceed 10℃ / minute. Heat to 800℃, hold for two hours, and allow to cool naturally to obtain the 5 / 5VC electrode material.

[0111] Step 2: Determine the electrochemical performance and surface morphology of electrode materials with different sintering amounts.

[0112] Cyclic voltammetry and constant current charge-discharge tests were performed on four electrode materials.

[0113] As a preferred embodiment of the preparation method described in this invention: the electrode materials are used as the positive and negative electrodes, and the battery is assembled in a glove box. The electrolyte is an organic electrolyte. The assembly sequence is: positive electrode shell, electrode material, electrolyte, separator, electrolyte, electrode material, gasket, spring, and negative electrode shell.

[0114] The scan rate for cyclic voltammetry testing of the assembled battery is 1 mV / s. -1 The current density for the constant current charge-discharge test is 1 A g. -1 .

[0115] Four electrode materials were characterized by scanning electron microscopy at a magnification of 10,000.

[0116] Step 3: Simulate the temperature gradient distribution during the preparation of active materials in a tube furnace using Comsol Multiphysics.

[0117] Solid-state heat transfer was selected from the heat transfer module of Comsol software as the physical field interface. Steady-state studies were added, and a simulation model consistent with the experiment was established. The required material properties were added, and the volume of the calcined material inside the corundum semi-circular ceramic boat was set to 5 / 5V. A coupled solid-state heat transfer and surface-to-surface radiative heat transfer model was constructed, defining the input heat source temperature as 800℃ and the air domain temperature as the ambient temperature of 25℃. The temperature gradient distribution within the tubular furnace cavity was calculated using a mesh generation process. Based on the simulated temperature gradient distribution, the optimal sintering range was verified.

[0118] By comparing the electrochemical test results and the morphological characteristics of the electrode materials, it was found that under the above experimental materials and conditions, the electrode material performance is stable when the sintering amount in the tube furnace reaches 3 / 5V. However, as the sintering amount continues to increase, the performance and morphology of the prepared electrode material deteriorate. Using Comsol simulation to evaluate the temperature distribution gradient within the tube furnace cavity, it was found that the target temperature at 3 / 5V achieves optimal performance, but the target temperature disappears above 3 / 5V. This conveniently and quickly determined that the maximum sinterable material position in the ceramic boat of the tube furnace is at 3 / 5V, effectively improving material stability and reducing sintering errors during experimental operations. The above experimental results show that the evaluation method for the maximum sintering amount in a tube furnace based on laboratory preparation of electrode materials provided by this invention is consistent with the actual experimental evaluation results, indicating that the temperature gradient distribution method using Comsol Multiphysics to simulate the tube furnace preparation process of active materials is highly accurate. Furthermore, this invention exhibits good measurement repeatability and the measurement process is easy to control. The method of this invention is simple, easy to implement, and low in cost, making it suitable for widespread use.

[0119] In this invention, Figure 1 The electrochemical test results are compared for Examples 1, 2, 3, and 4. Figure 1 It can be seen that the difference in sintering amount among the samples in different embodiments caused the performance differences. From Example 1 to Example 4, the electrochemical performance of the samples gradually decreased as the sintering amount in the tube furnace increased. The integral area and charge-discharge time of the cyclic voltammetry curves of the samples in Example 1 and Example 3 were not significantly different, indicating that the performance could be maintained when the sintering amount was kept at 3 / 5V as in Example 2. However, the performance of the sample in Example 3 was significantly different from that in Examples 1 and 2, further indicating that the sintering amount of the 3 / 5V calcined material sample loaded in Example 3 was the maximum preferred sintering amount. Figure 2 The scanning electron microscopy characterization results are for Examples 1, 2, 3, and 4. Figure 2 The scanning electron microscopy characterization results for different sintering amounts show that, from Example 1 to Example 4, the morphology of the prepared electrode materials becomes uneven as the sintering amount in the furnace increases. In particular, the electrode material in Example 4 exhibits disordered granular structure, indicating that the calcination is insufficient. Figure 3 The internal temperature gradient of the tubular furnace is achieved through thermal radiation, thermal conduction, and thermal convection. Figure 4 The surface temperature distribution of the sample is shown, and the bulk temperature cloud map of the material inside the ceramic boat is also presented. The calcined material is supported by a corundum semi-circular ceramic boat, and the heat flux is transferred through heat conduction, which increases the thermal resistance and makes the temperature gradient of the material more obvious. Figure 5This is a cross-sectional view of the sample surface temperature. Analysis of the cross-sectional contour plot shows that the temperature is highest in the lowest central region of the material, with a significant temperature drop along the longitudinal direction. This is because the contact between the material and the three-sided ceramic boat increases thermal resistance, resulting in the lowest temperature. Steady-state studies using COMSOL indicate that increasing the amount of calcined material within a limited calcination space leads to uneven temperature distribution, thus affecting the uniformity of the calcination process. Based on the required calcination temperature range, simulation results show that when the sintering amount is 3 / 5V, the temperature distribution remains within a certain fluctuation range and does not significantly affect the calcination process; therefore, 3 / 5V is considered the optimal maximum sintering amount.

[0120] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for evaluating the maximum sintering amount in a tube furnace based on laboratory-prepared electrode materials, characterized in that: The temperature gradient distribution during the preparation of active materials in a tube furnace was simulated using Comsol Multiphysics, including the following steps: S1. Based on the working process of the tubular furnace in calcination, select the physical field and physical field interface in the COMSOL multiphysics simulation software. S2. Based on the dimensional data of the heating and heat transfer components of the tubular furnace, a three-dimensional model of the heating and heat transfer components of the tubular furnace is established in the COMSOL multiphysics simulation software. S3. In the COMSOL multiphysics simulation software, the established three-dimensional tubular furnace heating and heat transfer component models are divided into regions. The divided regions include the calcined material, the corundum semi-circular ceramic boat, the quartz tube, the heat source layer, the insulation layer, the external air domain, and the nitrogen flow domain inside the tube. S4. Based on the properties of the heating and heat transfer components of the tubular furnace, set the material parameters, boundary values, and initial parameters of the heating and heat transfer components in the COMSOL multiphysics simulation software. S5. Couple the solid-to-surface heat transfer and surface-to-surface radiative heat transfer models. S6. Mesh the various regions of the tubular furnace, set the solver's solution method, and obtain simulation data; S7. Visualize the simulation data to obtain temperature distribution data; In step S5, the thermal resistance of the tubular furnace is composed of the thermal resistance per unit area of ​​air and the thermal resistance per unit area of ​​thermocouples. The formula for calculating the total area thermal resistance is: R A =R air,A +R TC,A =λ air / d air +λ TC / d TC Among them, R A R is the thermal resistance of the total surface area inside the furnace of a tubular furnace. air,A R is the thermal resistance per unit area of ​​air. TC,A λ is the thermal resistance per unit area of ​​the thermocouple. air λ is the thermal conductivity of air. TC δ is the thermal conductivity of the thermocouple. air δ represents the thickness of the air layer. TC These are the characteristic dimensions of the thermocouple; The steady-state solid heat transfer model inside the furnace of a tubular furnace is as follows: Where ρ is the density of the object. Let u be the temperature gradient at a point inside the furnace of the tubular furnace, and C be the velocity field. ρ Q is the specific heat capacity, and Q is the volumetric heat source. ted The heat source is generated by the compression or expansion of a solid, k is the thermal conductivity of the heat transfer component material, and q is the heat flux density per unit area. The heat flux density gradient at a point inside the furnace of a tubular furnace; The convective heat flux is: q o =h·(T ext –T) Where, q o T represents the convective heat flux, h represents the heat transfer coefficient, and T represents the total heat transfer coefficient. ext T represents the external boundary condition temperature of the tubular furnace, and T represents the internal boundary condition temperature of the tubular furnace. The fundamental equations of the surface-to-surface radiation model are: E b (T)=n 2 σT 4 Among them, Q radiation Let σ be the radiative heat transfer rate, σ be the Stefan-Boltzmann constant, A be the radiative heat transfer area, T1 and T2 be the thermodynamic temperatures of the two object surfaces respectively, T be the absolute temperature, ε be the surface emissivity, and E be the surface emissivity. b Let n be the total emission power of the blackbody, n be the refractive index of the transparent medium, and F be the viewing angle factor.

2. The method for evaluating the maximum sintering amount of a tube furnace based on laboratory-prepared electrode materials according to claim 1, characterized in that: In step S1, the physical field interface includes solid heat transfer and surface-to-surface radiation.

3. The method for evaluating the maximum sintering amount of a tube furnace based on laboratory-prepared electrode materials according to claim 1 or 2, characterized in that: In step S2, the model of the three-dimensional tubular furnace heating component and heat transfer component includes an insulation layer, a heat source layer, a vacuum quartz tube cavity, a corundum semi-circular ceramic boat, and calcination material.

4. The method for evaluating the maximum sintering amount of a tube furnace based on laboratory-prepared electrode materials according to claim 1, characterized in that: Step S4 includes setting the material of the corundum semi-circular ceramic boat to alumina, the material of the heat source layer to nickel-chromium alloy, and the material of the insulation layer to 50wt% alumina and 50wt% silicon dioxide. The medium between the insulation layer and the heat source layer and the medium on the outer wall of the quartz tube are both set to air. The input heat source temperature is defined as 800℃, and the air temperature is defined as the ambient temperature of 25℃.

5. The method for evaluating the maximum sintering amount of a tube furnace based on laboratory-prepared electrode materials according to claim 1 or 2, characterized in that: In step S6, the gridded area includes the calcined material, the corundum semi-circular ceramic boat, the quartz tube, the heat source layer, the insulation layer, and the physical field control grid.

6. The method for evaluating the maximum sintering amount of a tube furnace based on laboratory-prepared electrode materials according to claim 1 or 2, characterized in that: It also includes preparing electrode materials using a tube furnace; performing morphological scanning on the electrode materials; conducting electrochemical tests; and determining the maximum sintering amount range under optimal electrochemical performance based on the electrochemical test data.

7. The method for evaluating the maximum sintering amount of a tube furnace based on laboratory-prepared electrode materials according to claim 6, characterized in that: The preparation of electrode materials using a tube furnace is as follows: a quartz tube is placed inside the furnace chamber of the tube furnace, and calcined materials containing 1 / 5, 3 / 5, 4 / 5, and 5 / 5 of the volume of the corundum semi-circular ceramic boat are pushed to the middle of the quartz tube and the furnace chamber, respectively. The working gas path is connected, allowing the working gas to flow in through the inlet valve and out through the outlet valve. The heating rate is set to not exceed 10℃ / minute, and the temperature is raised to 800℃. The temperature is held for two hours and then naturally cooled to obtain electrode materials 1 / 5VC, 3 / 5VC, 4 / 5VC, and 5 / 5VC, respectively.

8. The method for evaluating the maximum sintering amount of a tube furnace based on laboratory-prepared electrode materials according to claim 7, characterized in that: The electrochemical tests include cyclic voltammetry and constant current charge-discharge testing; wherein, the cyclic voltammetry test includes a 1 mV / s test. -1 The test was conducted at a scanning speed of 1Ag, and the constant current charge-discharge test included 1Ag. -1 The test was conducted at a current density of [value missing].

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