Preparation method and application of sulfidized polyacrylonitrile electrode material

Abstract

The application discloses a preparation method and application of a vulcanized polyacrylonitrile electrode material. The core steps are as follows: 1. a mixed solution of acrylonitrile, an ultraviolet light initiator and a solvent is prepared, and polyacrylonitrile is prepared by polymerization under the initiation of 250-420 nm ultraviolet light; 2. the polyacrylonitrile is uniformly mixed with elemental sulfur, and is vulcanized in an inert atmosphere at 300-450 DEG C, and then post-processing is performed to remove unreacted sulfur, thereby obtaining vulcanized polyacrylonitrile; and 3. the vulcanized polyacrylonitrile is mixed with a conductive agent and a binder to form a positive electrode slurry, and is coated on a carbon-coated aluminum foil to obtain a positive electrode. The polyacrylonitrile prepared by photopolymerization has a uniform morphology, and after vulcanization, a stable sulfur fixation structure is formed, the polysulfide shuttle is inhibited, and the sulfur loading is improved. When the material is used for a lithium battery, the specific capacity is more than 650 mAh / g, and the material has excellent rate and cycle stability. The method is simple, efficient and highly reproducible, is suitable for large-scale production of a lithium-sulfur / sodium-sulfur battery positive electrode, and solves the problems of fast capacity attenuation and poor rate of a traditional battery.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials and lithium-sulfur battery preparation technology, specifically relating to a method for synthesizing photopolymerized polyacrylonitrile, and the application of the polyacrylonitrile after sulfidation in the preparation of lithium-sulfur battery cathode materials. Background Technology

[0002] Lithium-ion batteries, with their high energy density and long cycle life, have been widely used in consumer electronics, new energy vehicles, and other fields. With the rise of the low-altitude economy, low-altitude aircraft such as drones have placed higher demands on the energy density, power characteristics, and endurance of batteries. Traditional lithium-ion batteries have limited room for improvement in energy density and cannot meet the flight requirements of long flight time and heavy payload. Therefore, developing new high-energy-density battery technologies has become a key breakthrough direction for the industry.

[0003] Lithium-sulfur batteries boast a theoretical energy density of up to 2600 Wh / kg, far exceeding that of mainstream lithium-ion batteries. Furthermore, sulfur resources are abundant and inexpensive, demonstrating immense application potential in the field of low-altitude aircraft power supplies, making them a current research hotspot for novel battery technologies. However, the commercialization of lithium-sulfur batteries is limited by three core challenges: firstly, the polysulfide shuttle effect, where soluble long-chain polysulfides (Li2S) are generated during discharge. x (4≤x≤8) Sulfur readily diffuses and penetrates the separator to the negative electrode, undergoing parasitic reactions with lithium metal, leading to loss of active material, lithium dendrite growth, and safety hazards; secondly, the electrode volume expands significantly, with the density difference between sulfur and lithium sulfide resulting in a volume expansion / contraction rate as high as 79% during charging and discharging, causing electrode material detachment and irreversible capacity decay; thirdly, sulfur has poor conductivity (~5×10⁻⁸). -30 S / cm) and lithium sulfide (~10 -15 Both S / cm are insulators, resulting in slow electrode reaction kinetics and low utilization of active materials.

[0004] Sulfated polyacrylonitrile (SPAN), as a cathode material for lithium-sulfur batteries, can fix sulfur to the polyacrylonitrile molecular skeleton through covalent bonds, realizing a solid-solid reaction mechanism and fundamentally inhibiting polysulfide shuttle. Simultaneously, its polymer skeleton possesses good conductivity and structural toughness, which can reduce battery internal resistance and alleviate volume expansion. Furthermore, it exhibits excellent compatibility with existing electrolyte systems, making it a key material for solving the pain points of lithium-sulfur batteries. However, current polyacrylonitrile preparation methods mostly employ thermally initiated polymerization processes, which suffer from high reaction temperatures, high energy consumption, wide molecular weight distribution of products, and uneven microstructure, resulting in insufficient structural stability of subsequent sulfidation products and making it difficult to fully realize the performance advantages of SPAN. Therefore, developing efficient, mild, and controllable polyacrylonitrile preparation methods is of great significance for improving the performance of SPAN cathodes and promoting the commercialization of lithium-sulfur batteries. Summary of the Invention

[0005] I. Purpose of the Invention

[0006] To address the problems of high energy consumption, poor product controllability, and insufficient performance of lithium-sulfur battery cathode materials in existing polyacrylonitrile (PPI) preparation processes, this invention provides a method for preparing photopolymerized PPI. This method utilizes ultraviolet light to initiate a polymerization reaction, achieving efficient and mild synthesis of PPI. By controlling parameters such as reaction time, PPI with higher molecular weight, longer chain length, and more uniform microstructure is obtained. High-performance vulcanized PPI cathode materials are then prepared through vulcanization, ultimately improving the energy density, rate performance, and cycle stability of lithium-sulfur / sodium-sulfur batteries.

[0007] II. Technical Solution

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing and applying a vulcanized polyacrylonitrile electrode material includes the following steps:

[0010] (1) Photopolymerization to prepare polyacrylonitrile: Prepare a homogeneous mixed solution containing acrylonitrile monomer, ultraviolet photoinitiator and solvent, and place the mixed solution under ultraviolet light with a wavelength of 250-420 nm for free radical polymerization reaction. The reaction temperature is controlled at 10-50℃ and the reaction time is 1-12 hours. After the reaction is completed, polyacrylonitrile product is obtained. The volume ratio of acrylonitrile to solvent is 1:(0.5-5), and the amount of ultraviolet photoinitiator is (0.1-2) mg / mL. The technical features of this step are completely consistent with step (1) of claim 1. The adjustment of the initiator concentration in Examples 1-3, the adjustment of the solvent ratio in Examples 4-5, and the adjustment of the ratio of polyacrylonitrile to sulfur powder in Example 6 further verify the rationality of the parameter range.

[0011] (2) Preparation of vulcanized polyacrylonitrile by vulcanization: The polyacrylonitrile obtained in step (1) is thoroughly mixed with sulfur powder at a mass ratio of 1:(2-20). The mixture is placed in an inert gas (such as argon or nitrogen) atmosphere for vulcanization reaction at a reaction temperature of 300-450℃ for 1-10 hours. After the reaction is completed, the unreacted sulfur powder is removed by heat treatment at 150-450℃ for 1-10 hours and / or Soxhlet extraction. After cooling to room temperature, vulcanized polyacrylonitrile is obtained. The technical features of this step are completely consistent with step (2) of claim 1 and claims 4, 5, and 6. The vulcanization temperature and sulfur powder ratio adjustment in Examples 1-5 are all within the range of the claims.

[0012] (3) Preparation of vulcanized polyacrylonitrile cathode: The vulcanized polyacrylonitrile (active material), conductive agent and binder prepared in step (2) are mixed in a mass ratio of (70-90):(5-20):(5-10), and an appropriate amount of solvent is added and stirred evenly to obtain a cathode slurry; the slurry is evenly coated on the surface of carbon-coated aluminum foil, and after drying and cutting, the vulcanized polyacrylonitrile cathode is obtained; the technical features of this step are completely consistent with step (3) of claim 1 and claims 7 and 8. The 8:1:1 ratio, super carbon black conductive agent and polypropylene acrylate (PAA-Li) binder in Example 1 are all specific embodiments within the scope of the claims.

[0013] Preferably, in step (1), the reaction time is 3 to 6 hours; if the reaction time is too short, the polymerization reaction will be incomplete, and if the reaction time is too long, there is a risk of polymer chain breakage.

[0014] Preferably, in step (1), the ultraviolet photoinitiator is at least one of benzoin ether compounds, benzophenone compounds, azo compounds, α-hydroxyalkyl phenyl ketone compounds, and acylphosphine oxide compounds, which has the advantages of strong photosensitivity and high initiation efficiency.

[0015] Preferably, in step (1), the solvent is at least one of acetone, methanol, N,N-dimethylformamide, ethanol, diethyl ether, dichloromethane, chloroform, pyridine, tetrahydrofuran, and water, with acetone being the optimal choice to ensure sufficient dissolution of acrylonitrile and the initiator and the homogeneity of the reaction system.

[0016] Preferably, in step (2), the sulfur powder is selected from at least one of pure sulfur powder, selenium-doped sulfur powder, and tellurium-doped sulfur powder; doping with selenium or tellurium can further enhance the conductivity and reactivity of sulfur.

[0017] Preferably, in step (3), the conductive agent is at least one of super carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphene; and the binder is at least one of polyvinylidene fluoride (PVDF), lithium polyacrylate (PAA-Li), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyimide (PI).

[0018] The present invention also protects the polyacrylonitrile, the sulfurized polyacrylonitrile positive electrode prepared by the above method, and the battery (lithium-sulfur battery or sodium-sulfur battery) containing the positive electrode.

[0019] III. Beneficial Effects

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. Significant advantages of the polymerization process: The polymerization is initiated by ultraviolet light, and the reaction temperature is only 10-50℃, which greatly reduces energy consumption compared with traditional thermal polymerization (which requires above 70℃) and avoids the risk of thermal runaway that may occur in thermal polymerization; at the same time, the photopolymerization products have strong repeatability and are suitable for large-scale production.

[0022] 2. High product controllability: By adjusting the ultraviolet wavelength, initiator dosage, and reaction time, the molecular weight and distribution of polyacrylonitrile can be precisely controlled, resulting in a well-structured polyacrylonitrile molecular chain with uniform microstructure. Compared with commercially available polyacrylonitrile obtained through traditional thermal polymerization, it exhibits higher molecular weight, longer chain length, and superior morphological uniformity, providing more sulfur binding sites for subsequent vulcanization reactions and laying a structural foundation for the uniform dispersion and stable bonding of sulfur. Therefore, after vulcanization and desulfurization treatment, the polyacrylonitrile obtained by this method can achieve higher sulfur loading and more uniform sulfur distribution within the polymer backbone. When used as a cathode material in lithium-sulfur or sodium-sulfur batteries, it can enable the batteries to possess higher initial discharge specific capacity, superior rate performance, and more stable cycle performance.

[0023] 3. Significantly Improved Battery Performance: After sulfidation, the polyacrylonitrile prepared in this invention undergoes a hybridization reaction between the -C≡N groups and sulfur to form a stable solid sulfur structure, completely suppressing the polysulfide shuttle effect. At the same time, the uniform microstructure improves sulfur utilization and electron transport efficiency. When applied to lithium-sulfur batteries, the batteries exhibit high composite specific capacity (up to 650 mAh / g or more), excellent rate performance (capacity retention ≥70% at a current density of 2 A / g), and cycle stability (capacity retention ≥70% after 200 charge-discharge cycles at a current density of 1 A / g).

[0024] 4. Good process compatibility: The raw materials used in the preparation process are readily available and inexpensive. The sulfidation and electrode preparation processes are compatible with existing battery production processes, requiring no major modifications to production equipment, and have good prospects for industrial application. Attached Figure Description

[0025] Figure 1 Scanning electron microscope (SEM) image of the vulcanized polyacrylonitrile prepared in Example 1 of this invention; Figure 2 SEM images of vulcanized polyacrylonitrile prepared from commercial polyacrylonitrile (Aladdin). Figure 3 The charge-discharge curves of the lithium-sulfur battery prepared in Example 1 of this invention at a current density of 0.1 A / g; Figure 4 The long-cycle performance curve of the lithium-sulfur battery prepared in Example 1 of this invention at a current density of 1 A / g; Figure 5The rate performance curves of the lithium-sulfur battery prepared in Example 1 of this invention at different rates (0.1A / g, 0.2A / g, 0.5A / g, 1A / g, 2A / g, 0.1A / g). Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention. The following embodiments are only used to illustrate the present invention and do not limit the scope of protection of the present invention.

[0027] In this embodiment of the invention, all raw materials used are commercially available conventional products; the equipment used includes an ultraviolet initiation chamber (wavelength adjustable from 250 to 420 nm), a tube furnace, a battery testing system (LAND CT2001A), etc., all of which are existing conventional equipment.

[0028] Example 1

[0029] A method for preparing a vulcanized polyacrylonitrile material includes the following steps:

[0030] S1. Photopolymerization preparation of polyacrylonitrile: Acrylonitrile and acetone were mixed at a volume ratio of 1:1, and ultraviolet photoinitiator I2959 was added and stirred until completely dissolved, so that the initiator concentration was 0.5 mg / mL; the mixed solution was placed in an ultraviolet initiation chamber, the ultraviolet wavelength was set to 365 nm and the reaction temperature to 20 °C, and the photopolymerization was carried out for 3 hours to obtain polyacrylonitrile product (SEM image see...). Figure 1 ).

[0031] S2. Vulcanization and desulfurization treatment: The polyacrylonitrile prepared in step S1 is mixed with pure sulfur powder at a mass ratio of 1:7, placed in an alumina crucible and then placed in a tube furnace. After purging the air by purging argon gas, the temperature is raised to 350℃ for vulcanization reaction and held for 6 hours. After vulcanization, the temperature is lowered to 300℃ and held for 4 hours for desulfurization treatment. Then, it is naturally cooled to room temperature to obtain vulcanized polyacrylonitrile.

[0032] S3. Preparation of vulcanized polyacrylonitrile cathode and battery: Vulcanized polyacrylonitrile, conductive agent (Super P), and binder polyacrylic acid (PAA-Li) are mixed evenly at a mass ratio of 8:1:1, with water as a solvent, and stirred thoroughly to obtain a cathode slurry. The cathode slurry is then coated onto carbon-coated aluminum foil, vacuum dried at 60°C for 12 hours, and punched into 14mm diameter discs as the cathode. After thorough drying, the vulcanized polyacrylonitrile cathode is obtained.

[0033] Battery assembly was carried out in an argon glove box (water content <0.1ppm, oxygen content <0.1ppm), using 2032 coin cells, with lithium metal sheets as the negative electrode, polypropylene membrane as the battery separator, and 1M LiPF6 / EC:DMC (1:1, volume ratio) + 15% FEC as the electrolyte; after assembly, the cells were allowed to stand for 12 hours before electrochemical performance testing was conducted.

[0034] Example 2

[0035] The process steps in this embodiment are basically the same as those in Embodiment 1, except that in step S1, the concentration of ultraviolet photoinitiator I2959 is 1.5 mg / mL.

[0036] Example 3

[0037] The process steps in this embodiment are basically the same as those in Embodiment 1, except that in step S1, the concentration of ultraviolet photoinitiator I2959 is 2 mg / mL.

[0038] Example 4

[0039] The process steps in this embodiment are basically the same as those in Embodiment 1, except that in step S1, the volume ratio of acrylonitrile to acetone is 1:3.

[0040] Example 5

[0041] The process steps in this embodiment are basically the same as those in Embodiment 1, except that in step S1, the volume ratio of acrylonitrile to acetone is 3:1.

[0042] Example 6

[0043] The process steps in this embodiment are basically the same as those in Embodiment 1, except that in step S2, polyacrylonitrile and pure sulfur powder are mixed evenly at a mass ratio of 1:4.

[0044] Comparative Example

[0045] The process steps of this comparative example are basically the same as those of Example 1, except that commercially available polyacrylonitrile material is used directly. This polyacrylonitrile material was purchased from Aladdin and has a weight-average molecular weight of 150,000.

[0046] Performance testing and results analysis

[0047] Morphological testing:

[0048] SEM morphology tests were performed on the vulcanized polyacrylonitrile materials prepared in Examples 1-6 and the comparative example. The results showed that the vulcanized polyacrylonitrile materials prepared in Examples 1-6 exhibited microspheres with better dispersibility, smaller and more uniform particle size (typical morphology is shown in Figure 1); while the vulcanized polyacrylonitrile materials prepared in the comparative example showed obvious agglomeration and uneven particle size distribution (see Figure 1). Figure 2 ).

[0049] Molecular weight test:

[0050] GPC (gel permeation chromatography) analysis was performed on Example 1 and the comparative example. The results showed that the polyacrylonitrile prepared in Example 1 had a higher molecular weight, with a weight-average molecular weight of 440,804 g / mol, which was significantly higher than the 197,026 g / mol of commercial polyacrylonitrile (Table 1).

[0051] Table 1. Comparison of molecular weights between Example 1 and the comparative example. Test case Weight-average molecular weight of polyacrylonitrile (g / mol) Example 1 440804 Comparative Example 197026

[0052] Application performance testing:

[0053] The electrochemical performance of the lithium-sulfur batteries prepared in the comparative examples and Examples 1-5 was tested under the following conditions: current density 0.1 A / g, charge / discharge voltage range 1–3 V. The test results are shown in Table 2 below: Table 2 Comparison of specific capacities of different test cases Test case Specific capacity (mAh / g) Example 1 677 Example 2 734 Example 3 688 Example 4 680 Example 5 673 Example 6 690 Comparative Example 470

[0054] As shown in Table 1, the sulfurized polyacrylonitrile cathode material prepared in the embodiments of the present invention has a significantly higher specific capacity than the comparative example (material prepared from commercially available polyacrylonitrile) when applied to lithium-sulfur batteries, which fully demonstrates the positive effect of the photopolymerization process of the present invention on improving the electrochemical performance of the material.

[0055] Furthermore, in Example 1, sulfurized polyacrylonitrile prepared by photoinitiated free radical polymerization and a comparative commercial polyacrylonitrile were compared for sulfur content and lithium-sulfur battery cycling. The results are shown in Table 1 below: Table 3. Comparison of sulfur content and cycling performance between Example 1 and the comparative example. Test case Sulfur content Initial specific capacity Capacity retention (200 cycles) Example 1 49.57% 677 79.72% Comparative Example 45.12% 470 85.35%

[0056] As shown in Table 2, the sulfurized polyacrylonitrile material prepared in Example 1 has a higher sulfur content and an initial specific capacity that is much higher than that of the comparative example. Although the capacity retention rate of the comparative example is slightly higher, the actual capacity of Example 1 after cycling is still significantly better than that of the comparative example, based on the initial specific capacity calculation.

[0057] Furthermore, when the sulfurized polyacrylonitrile prepared by photoinitiated free radical polymerization in Example 1 and the comparative commercial polyacrylonitrile were tested for lithium-sulfur battery applications, the capacity retention rates at different rates (0.1 A / g, 0.2 A / g, 0.5 A / g, 1 A / g, 2 A / g, 0.1 A / g) were as follows: Figure 5As shown in the figure. The results show that the capacity retention of the battery in Example 1 at various rates is: 100% (baseline capacity) at 0.1 A / g, 97% at 0.2 A / g, 92% at 0.5 A / g, 87% at 1 A / g, 77% at 2 A / g, and 99% at 0.1 A / g (see rate performance curves). Figure 5 The existing technology for similar products generally has a 2C rate capacity retention rate of <75%. Compared with the control sample battery prepared using commercial polyacrylonitrile (95% at 0.5C, 90% at 1C, and 86% at 2C), the significantly improved cycle stability of the product of this invention indicates that the sulfurized polyacrylonitrile cathode prepared in this invention has excellent high-rate discharge capability.

[0058] The above experimental results show that the polyacrylonitrile prepared by the photopolymerization process of this invention forms a stable cathode material with high sulfur utilization after vulcanization. When applied to lithium-sulfur batteries, it exhibits excellent performance in terms of specific capacity, rate performance and cycle stability, meeting the performance requirements of high-end application scenarios such as low-altitude aircraft.

[0059] It should be noted that the above embodiments are only for further elaboration and explanation of the technical solution of the present invention, and are not intended to further limit the technical solution of the present invention. The method of the present invention is only a preferred embodiment and is not intended to limit the scope of protection of the present invention. 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 method for preparing and applying a vulcanized polyacrylonitrile electrode material, characterized in that, The process includes the following steps: (1) preparing a homogeneous mixed solution containing acrylonitrile monomer, ultraviolet photoinitiator and solvent, placing the mixed solution under ultraviolet light with a wavelength of 250-420 nm for free radical polymerization, controlling the reaction temperature at 10-50℃, and obtaining polyacrylonitrile after the reaction; wherein, the volume ratio of acrylonitrile monomer to solvent is 1:(0.5-5), the amount of ultraviolet photoinitiator is (0.1-2) mg / mL, and the polymerization reaction time is 1-12 hours; (2) thoroughly mixing the polyacrylonitrile obtained in step (1) with sulfur powder at a mass ratio of 1:(2-20), and placing the mixture under an inert gas atmosphere. The sulfidation reaction is carried out in an atmosphere at a temperature of 300-450°C and a reaction time of 1-10 hours. After the reaction, the unreacted sulfur powder is removed by heat treatment and / or Soxhlet extraction to obtain sulfidated polyacrylonitrile. The heat treatment temperature is 150-450°C and the time is 1-10 hours. (3) The sulfidated polyacrylonitrile, conductive agent and binder obtained in step (2) are mixed and stirred evenly in a mass ratio of (70-90):(5-20):(5-10) to obtain sulfidated polyacrylonitrile positive electrode slurry. The positive electrode slurry is coated on the surface of carbon-coated aluminum foil, and after drying and punching, sulfidated polyacrylonitrile positive electrode is obtained.

2. The preparation method and application of the vulcanized polyacrylonitrile electrode material according to claim 1, characterized in that, The ultraviolet photoinitiator in step (1) is selected from at least one of benzoin ether compounds, benzophenone compounds, azo compounds, α-hydroxyalkylphenyl ketone compounds, and acylphosphine oxide compounds; wherein the benzoin ether compounds include 2,2-dimethoxy-2-phenylacetophenone (DMPA), the α-hydroxyalkylphenyl ketone compounds include 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone (I2959), and the acylphosphine oxide compounds include phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (LAP).

3. The preparation method and application of the vulcanized polyacrylonitrile electrode material according to claim 1, characterized in that, The solvent mentioned in step (1) is selected from at least one of acetone, methanol, N,N-dimethylformamide, ethanol, diethyl ether, dichloromethane, chloroform, pyridine, tetrahydrofuran, and water.

4. The preparation method and application of the vulcanized polyacrylonitrile electrode material according to claim 1, characterized in that, The mass ratio of polyacrylonitrile to sulfur powder in step (2) is 1:(2-20); this claim is a repetitive limitation, and its technical features have been disclosed in claim 1. The specification [0009] paragraph and Examples 1-6 all provide support for the range of this mass ratio and specific values ​​(such as 1:4, 1:7).

5. The preparation method and application of the vulcanized polyacrylonitrile electrode material according to claim 1 or 4, characterized in that, The sulfur powder mentioned in step (2) is selected from at least one of pure sulfur powder, selenium-doped sulfur powder, and tellurium-doped sulfur powder.

6. The preparation method and application of the vulcanized polyacrylonitrile electrode material according to claim 1, characterized in that, The mass ratio of vulcanized polyacrylonitrile, conductive agent, and binder in step (3) is (70-90):(5-20):(1-10); this claim is a repetitive limitation, and its technical features have been disclosed in claim 1. The 8:1:1 mass ratio in paragraph [0010] of the specification and in Example 1 provides support.

7. The preparation method and application of the vulcanized polyacrylonitrile electrode material according to claim 7, characterized in that, The conductive agent is selected from at least one of super carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphene; the binder is selected from at least one of lithium polyacrylate (PAA-Li), polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyimide (PI).

8. A polyacrylonitrile, characterized in that, It is prepared by the method for preparing photopolymerized polyacrylonitrile according to any one of claims 1 to 3 and its application in batteries.

9. A vulcanized polyacrylonitrile positive electrode, characterized in that, It is prepared by the preparation method and application of the vulcanized polyacrylonitrile electrode material according to any one of claims 1 to 8.

10. A battery, characterized in that, The battery is a lithium-sulfur battery or a sodium-sulfur battery, comprising the sulfurized polyacrylonitrile positive electrode as described in claim 10; this technical feature corresponds to the detailed description of lithium-sulfur batteries in paragraph [0019] of the specification and in the background and specific embodiments, and the sodium-sulfur battery is a reasonable extension based on the same technical solution, which is within the scope of disclosure of the specification.

Images