An electronic cigarette battery with long cycle life and a manufacturing method thereof

Abstract

The application discloses a long-cycle-life electronic cigarette battery and a manufacturing method thereof, and comprises the following steps: laminating a positive electrode sheet, a diaphragm and a negative electrode sheet on a winding needle to form a winding core; during the winding process, a soluble functional cylindrical rod is inserted into the interlayer gap between the electrode sheet and the diaphragm along the direction parallel to the axis of the winding needle; the winding core is placed in a shell and electrolyte is injected; after a preset time, the cylindrical rod is dissolved in the electrolyte to form a longitudinal through infiltration channel in situ in the battery; after formation and sealing, an electronic cigarette battery is obtained; wherein the cylindrical rod is arranged in a non-uniform gradient with a dense inner part and a sparse outer part. The application forms pores in situ by pre-embedding a soluble cylindrical rod inside, thereby avoiding the risk of active material falling off and diaphragm damage caused by traditional mechanical kneading; the exponential gradient arrangement makes the central region densely porous and the outer layer sparse, thereby achieving almost full-area infiltration while ensuring the stability of the battery structure and significantly improving the cycle life of the electronic cigarette battery.

Description

Technical Field

[0001] This invention belongs to the field of electronic cigarette cell manufacturing technology, and particularly relates to an electronic cigarette cell with long cycle life and its manufacturing method. Background Technology

[0002] In recent years, the market demand for e-cigarettes has continued to grow due to their portability and unique user experience. E-cigarette cells typically use ultra-small diameter cylindrical pouches or steel shell structures (such as models 08400 and 13400). Due to the limited size of e-cigarettes, the cells must employ a compact winding process with extremely high tension to achieve high energy density.

[0003] However, the high-tension, tight winding results in extremely low porosity inside the cell (especially in the central region). After injection, the electrolyte is constrained by capillary resistance and gas resistance, making it very difficult to penetrate to the center of the cell, leading to the formation of "wetting dead zones." Insufficient wetting directly causes problems such as low battery capacity utilization, increased internal resistance, and shortened cycle life.

[0004] Existing technologies attempt to use external physical methods such as "mechanical kneading" and "ultrasonic vibration" to weaken the compactness of the core, thereby increasing the internal gaps. However, these methods have the following drawbacks: 1) High risk of structural damage: Repeated physical rubbing can easily cause the active material on the ultra-thin electrode to fall off, or even cause microscopic tearing of the diaphragm, creating a safety hazard of internal micro-short circuit.

[0005] 2) Unable to solve the central dead zone: The deformation from external kneading is difficult to transmit to the deepest part of the core, resulting in a loose outer layer and a still compact inner layer, and the uniformity of wetting is still very poor.

[0006] 3) Low cycle life: Due to the low cell wettability and the easy shedding of active materials, the cycle life of electronic cigarette cells is greatly shortened.

[0007] Therefore, there is an urgent need to develop a new process that can effectively improve the wettability and cycle life of electronic cigarette cells while avoiding physical damage to the cell structure. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for manufacturing an electronic cigarette cell with a long cycle life. This method involves pre-embedding soluble functional cylindrical rods between layers during the winding process. After electrolyte injection, the cylindrical rods dissolve to form a continuous wetting channel, achieving efficient wetting of the electrolyte. This also effectively avoids physical damage caused by traditional mechanical rubbing, thereby significantly improving the structural stability and cycle life of the cell.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A method for manufacturing an electronic cigarette cell with a long cycle life includes the following steps: S1. The positive electrode, separator and negative electrode are sequentially stacked on the winding needle and wound to form a core; S2. During the winding process, soluble functional cylindrical rods are inserted intermittently into the interlayer gaps between the electrode and the diaphragm along a direction parallel to the axis of the winding needle; the soluble functional cylindrical rods are soluble in the electrolyte. S3. Place the core in the outer casing and inject electrolyte; S4. Allow the soluble functional cylindrical rod to stand for a preset time to dissolve in the electrolyte and form a longitudinally penetrating wetting channel in situ inside the battery cell. S5. After formation and sealing, the electronic cigarette cell is obtained; The soluble functional cylindrical rods are arranged in a non-uniform gradient along the winding layer direction, with a denser inner layer and a sparser outer layer. On the i-th winding layer, the arc length distance Li between two adjacent soluble functional cylindrical rods satisfies the following relationship: L i =d×K×e^(α×D i / D max ) Among them, D i D is the diameter of the i-th winding layer, in mm; max d is the maximum outer diameter of the core, in mm; d is the diameter of the soluble functional cylindrical rod, in mm; K is the pore compensation constant, with a value range of 1.5≤K≤4.0; α is the gradient divergence coefficient, with a value range of 1.0≤α≤3.0.

[0010] Preferably, the diameter d of the soluble functional cylindrical rod satisfies: d ≤ 0.3 × T, where T is the sum of the thicknesses of the positive electrode, negative electrode, and separator. This dimensional constraint ensures that the cylindrical rod will not break the electrode or puncture the separator under high winding tension, thus guaranteeing the safety of the winding process.

[0011] Preferably, the diameter of the soluble functional cylindrical rod is 15μm to 40μm, and the length of the soluble functional cylindrical rod is equal to the width of the coating area of ​​the electrode. This size range can form an effective wetting channel without significantly affecting the energy density of the cell.

[0012] Preferably, the soluble functional cylindrical rod is formed by co-extrusion molding of a soluble polymer matrix and a film-forming additive; wherein, by mass percentage, the content of the soluble polymer matrix is ​​60%~80%, and the content of the film-forming additive is 20%~40%. This ratio ensures that the cylindrical rod dissolves at a moderate rate in the electrolyte while releasing a sufficient concentration of film-forming additive.

[0013] Preferably, the soluble polymer matrix is ​​selected from one or more of polyethylene oxide (PEO), polymethyl methacrylate (PMMA), or polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP). These materials have excellent solubility in carbonate electrolytes, and their dissolution can improve the electrolyte's liquid retention capacity.

[0014] Preferably, the film-forming additive is selected from one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), or lithium bis(oxalato)borate (LiBOB). These additives can participate in the formation of a stable SEI film on the electrode surface, improving interfacial stability.

[0015] Preferably, the pore compensation constant K ranges from 2.0 to 3.0, and the gradient divergence coefficient α ranges from 1.5 to 2.5. This preferred range achieves the best balance between wetting efficiency and structural stability.

[0016] Preferably, the soluble functional cylindrical rod is inserted into the interlayer gap between the separator and the negative electrode sheet. A relatively large gap between the separator and the negative electrode sheet facilitates the stable placement of the cylindrical rod and subsequent dissolution.

[0017] Preferably, in step S4, the preset settling time is 1-4 hours, and the settling temperature is 20-30°C. These conditions ensure that the cylindrical rod is fully dissolved while avoiding the impact of excessively high temperatures on the electrolyte performance.

[0018] Preferably, in step S2, a feeding mechanism is set on the winding machine to automatically insert the soluble functional cylindrical rods; the feeding mechanism automatically cuts and attaches the soluble functional cylindrical rods into the interlayer gaps according to the arc length spacing calculated in real time by the PLC controller. This automation scheme ensures production efficiency and layout accuracy.

[0019] Furthermore, the present invention also provides an electronic cigarette cell manufactured by the method described above for producing an electronic cigarette cell with a long cycle life.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: 1) This invention pre-embeds soluble functional cylindrical rods during the winding process. After electrolyte injection, the cylindrical rods dissolve in situ to form longitudinally continuous wetting channels. The capillary effect is used to directly introduce the electrolyte into the central area of ​​the cell, fundamentally eliminating the problem of "wetting dead zone". Compared with the traditional mechanical kneading method, the method of this invention does not apply external mechanical stress at all, effectively avoiding the risk of electrode active material falling off and diaphragm micro-tears, and ensuring the integrity and safety of the cell structure.

[0021] 2) This invention employs an exponential gradient arrangement formula (L... i =d×K×e^(α×Di / D max The cylindrical rods are arranged in a non-uniform pattern with a dense inner layer and a sparse outer layer, perfectly matching the physical laws of fluid permeation in a circular wound body: the central region D of the battery cell i Small, the calculated spacing L i Extremely small size, densely packed apertures, significantly improving wetting in the central dead zone; outer layer D of the battery cell i Approaching D max The spacing increases exponentially, and the pores are sparse, ensuring the structural compactness of the outer electrode and preventing structural collapse due to excessive internal voids. Optimal balance between wetting efficiency and structural stability is achieved through the coordinated control of the porosity compensation constant K and the gradient divergence coefficient α.

[0022] 3) After the soluble functional cylindrical rod of the present invention is dissolved, it not only forms a physical channel, but also releases film-forming additives, which generate a robust SEI film in situ on the electrode surface of the inner wall of the channel, making up for the electrochemical reaction interface at the pores and further improving the cycle stability of the battery cell. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0025] This invention provides a method for manufacturing a long-cycle-life electronic cigarette cell. The core concept is as follows: during the winding of the positive electrode, separator, and negative electrode, functional cylindrical rods soluble in electrolyte are simultaneously embedded between the layers. After electrolyte injection, the cylindrical rods dissolve in the electrolyte, leaving interconnected capillary channels inside the cell, enabling high-speed electrolyte wetting. Simultaneously, the film-forming additives released from the dissolved cylindrical rods form an SEI film in situ on the inner wall of the channels, improving interfacial stability. This method effectively avoids the physical damage caused by traditional mechanical kneading, achieving a significant improvement in cell structural stability and cycle life.

[0026] The arrangement and placement of the cylindrical bars in this invention employs an exponential gradient formula: L i =d×K×e^(α×D i / D max ).

[0027] The physical meaning of this formula is as follows: (1) D i / D max This indicates the relative radial position of the current wound layer within the entire core, with a value ranging from 0 to 1. When the wound layer is located at the center of the core, D... i / D max Approaching 0; when the winding layer is located outside the core, D i / D max Close to 1.

[0028] (2) Exponential function e^(α×D) i / D max This causes the spacing to increase non-linearly with radial position. In the central region, the exponent value is close to e^0=1, the spacing is the smallest, and the pore formation is the most dense; in the outer region, the exponent value is close to e^α, the spacing is the largest, and the pore formation is the sparsest.

[0029] (3) The pore compensation constant K is used as a reference value to adjust the overall spacing. The larger the value of K, the larger the overall spacing and the lower the pore density; the smaller the value of K, the smaller the overall spacing and the higher the pore density. The value of K is 1.5~4.0, preferably 2.0~3.0.

[0030] (4) The gradient divergence coefficient α controls the degree of difference in the spacing between inner and outer layers. The larger the value of α, the greater the difference in the spacing between inner and outer layers, and the more significant the gradient effect; the smaller the value of α, the smaller the difference in the spacing between inner and outer layers, and the more uniform the arrangement. The value of α ranges from 1.0 to 3.0, preferably from 1.5 to 2.5.

[0031] This design, with its dense inner layer and sparse outer layer, perfectly aligns with the physical laws of fluid permeation in a circular winding: the central region of the cell is the most difficult to wet, requiring dense channels to overcome capillary resistance and air resistance; while the outer region is relatively easy to wet, and needs to maintain sufficient structural compactness to preserve the cell's mechanical strength.

[0032] Among them, the diameter d of the soluble functional cylindrical rod must satisfy: d≤0.3×T.

[0033] Where T represents the sum of the thicknesses of the positive electrode, negative electrode, and separator. The physical significance of this constraint lies in the fact that during winding, the electrodes and separator are tightly bonded under tension, resulting in extremely limited interlayer gaps. If the diameter of the cylindrical rod is too large, under the winding tension, it will cause localized stress concentration on adjacent electrodes and separators, potentially leading to cracking of the electrode coating or puncture of the separator. Limiting the diameter to within 30% of the total interlayer thickness ensures that the presence of the cylindrical rod between layers does not cause destructive stress to adjacent materials.

[0034] The preferred diameter of the cylindrical rod is 15μm to 40μm. Taking a typical electronic cigarette cell as an example, the thickness of the positive electrode is about 60 to 80μm, the thickness of the negative electrode is about 70 to 90μm, the thickness of the separator is about 12 to 20μm, T is about 142 to 190μm, and 0.3×T is about 42 to 57μm. Therefore, the diameter range of 15 to 40μm fully meets the safety constraints.

[0035] The length of the cylindrical rod is set to be equal to the width of the coating area of ​​the electrode to ensure that the formed wetting channel runs through the entire axial length of the cell, thereby achieving a uniform distribution of electrolyte in the axial direction.

[0036] The soluble functional cylindrical rod is formed by extruding a soluble polymer matrix (60%~80%) and film-forming additives (20%~40%) through melt spinning or solution spinning processes.

[0037] The role of the soluble polymer matrix: (1) Polyethylene oxide (PEO): Molecular weight selected from 100,000 to 1,000,000. It has good solubility in carbonate electrolytes (such as mixed solvents of EC, DMC and EMC). After dissolution, its ether oxygen group can coordinate with lithium ions, thereby improving the ionic conductivity and liquid retention capacity of the electrolyte.

[0038] (2) Polymethyl methacrylate (PMMA): The molecular weight is selected from 50,000 to 500,000. It has a moderate dissolution rate in carbonate solvents (completely dissolves in about 13 hours). The solution formed after dissolution has a certain viscosity, which helps to maintain the electrolyte in the channel.

[0039] (3) Polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP): The HFP content is selected from 10% to 30%. It can swell or dissolve in carbonate solvents. After dissolution, its fluorinated segments help to improve the electrochemical stability window of the electrolyte.

[0040] The role of film-forming additives: (1) Vinyl carbonate (VC): It preferentially reduces and decomposes on the negative electrode surface to form an SEI film with polyvinyl carbonate as the main component. This film is dense and flexible and can effectively inhibit the continuous decomposition of the electrolyte.

[0041] (2) Fluoroethylene carbonate (FEC): The decomposition products contain LiF, and the SEI film formed has higher mechanical strength and ion conductivity, making it particularly suitable for silicon-based anode systems.

[0042] (3) Lithium bis(oxalateborate) (LiBOB): It can form a protective film on both the positive and negative electrode surfaces, improving high-temperature cycling stability.

[0043] The dual effects of the cylindrical rod after dissolution: (1) Physical effect: leaving a through channel with a diameter of 15~40μm, which can quickly introduce the electrolyte into the center of the battery cell through the capillary effect; (2) Chemical effect: the released high-concentration film-forming additives directly act on the electrode surface of the inner wall of the channel, generating a strong SEI film in situ, which compensates for the electrochemical reaction interface at the pores and improves the cycle stability.

[0044] This invention adds a feeding mechanism to an automated winding machine to achieve precise automatic insertion of soluble functional cylindrical bars; this mechanism mainly includes: (1) Feeding device: including material reel and tension controller, which supplies continuous soluble functional cylindrical bar wire with constant tension.

[0045] (2) Precision cutting device: using laser cutting or ultrasonic cutting, according to the instructions of the PLC controller, the continuous wire is cut into lengths equal to the width of the electrode coating area.

[0046] (3) Attachment mechanism: The cut cylindrical rod is precisely attached to the designated position between the diaphragm and the negative electrode by vacuum adsorption or electrostatic adsorption.

[0047] (4) PLC controller: Real-time acquisition of the number of winding layers and the current winding diameter D i Based on the information, the arc length spacing L of the current layer is calculated according to the gradient arrangement formula. i And control the timing of cutting and attaching.

[0048] The working process is as follows: During the winding process, the encoder provides real-time feedback on the winding angle and number of layers. The PLC then calculates the winding angle and number of layers based on the diameter D of the current layer. i Substitute into the formula to calculate the spacing L i When the winding arc length reaches L i At this time, the cutting and attaching actions are triggered, placing a cylindrical rod between the separator and the negative electrode sheet, and then the winding continues. The entire process is synchronized with the winding and does not affect the production cycle.

[0049] The present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0050] Example 1

[0051] This embodiment provides a method for manufacturing a long-cycle-life electronic cigarette cell, which includes the following steps: S1. Material preparation and winding: Positive electrode sheet: Aluminum foil current collector (12μm thick), double-sided coated with positive electrode active material layer, the positive electrode active material layer includes 96wt% lithium cobalt oxide (LiCoO2), 2wt% conductive agent (SuperP) and 2wt% binder (PVDF), single-sided coating thickness is 30μm, and the total thickness of the positive electrode sheet is 72μm.

[0052] Negative electrode sheet: Copper foil current collector (thickness 8μm), double-sided coated with negative electrode active material layer, the negative electrode active material layer includes graphite 95wt%, conductive agent (conductive carbon black) 2wt% and binder (SBR / CMC) 3wt%, single-sided coating thickness 35μm, total thickness of negative electrode sheet 78μm.

[0053] Diaphragm: A 16μm thick polyethylene (PE) microporous diaphragm.

[0054] T = 72 + 78 + 16 = 166 μm.

[0055] Core specifications: Type 08400, D max =8mm.

[0056] The positive electrode, separator, and negative electrode are sequentially stacked on a winding needle and wound to form a core.

[0057] S2. Preparation and insertion of soluble functional cylindrical rods: Preparation of soluble functional cylindrical rods: 70 wt% PMMA (molecular weight 200,000) and 30 wt% VC were co-extruded using a twin-screw extruder at 160°C, and then melt-spun to obtain cylindrical rods with a diameter d = 30 μm (satisfying the constraint d ≤ 0.3 × 166 μm = 49.8 μm). The length of the cylindrical rods was cut to be equal to the width of the electrode coating area.

[0058] Set the gradient arrangement parameters: K=2.5, α=2.0.

[0059] During the winding process, a cylindrical rod is inserted into the interlayer gap between the separator and the negative electrode sheet via a feeding mechanism. The arc length spacing of each layer is calculated according to formula L. i =30×2.5×e^(2.0×D i / 8) Calculation: Inner layer (D) i =2mm): L i =75×e^0.5=123.7μm (dense arrangement) Middle layer (D) i =4mm): L i =75×e^1.0=203.9μm Outer layer (D) i =7mm): L i =75×e^1.75=431.6μm (sparse arrangement) S3. Filling the casing with liquid: The core is inserted into a 08400 type steel shell, and the electrolyte is injected under vacuum. The electrolyte is a mixed solvent of 1M LiPF6 dissolved in EC / DMC / EMC (volume ratio 1:1:1).

[0060] S4. Allow to dissolve by standing: The cells were left to stand at 25°C for 2 hours. The PMMA matrix gradually dissolved in the carbonate electrolyte, and the cylindrical rod completely disappeared, leaving a longitudinally penetrating wetting channel with a diameter of approximately 30 μm inside the cell. The electrolyte rapidly penetrated to the central region of the cell through the capillary effect. Simultaneously, the released VC additive participated in the formation of the SEI film on the negative electrode surface.

[0061] S5. Formation and Sealing: The battery cell is charged to 3.0V using a constant current of 0.05C, left to stand for 12 hours, and then charged to 4.2V using a constant current of 0.1C to complete the formation process. After formation, the cell is sealed to obtain the electronic cigarette battery cell.

[0062] Example 2

[0063] Unlike Example 1, the soluble functional cylindrical rod in this example is extruded from a blend of 70 wt% PEO (molecular weight 600,000) and 30 wt% FEC, with a diameter d = 30 μm. All other aspects are the same as in Example 1.

[0064] PEO dissolves slightly faster than PMMA in carbonate electrolytes, and its ether radical groups can coordinate with lithium ions after dissolution, which helps to improve the ionic conductivity of the electrolyte. FEC decomposition products contain LiF, resulting in a SEI film with higher mechanical strength.

[0065] The rest is the same as in Example 1, and will not be repeated here.

[0066] Example 3

[0067] Unlike Example 1, the soluble functional cylindrical rod in this example is composed of 60 wt% PMMA and 40 wt% VC. The increased content of film-forming additives (40%) results in a higher concentration of released VC, which is beneficial for forming a thicker SEI film.

[0068] The rest is the same as in Example 1, and will not be repeated here.

[0069] Example 4

[0070] Unlike Example 1, the soluble functional cylindrical rod in this example is composed of 80 wt% PMMA and 20 wt% VC. With the soluble polymer matrix content increased to 80%, the cylindrical rod has higher mechanical strength and is less prone to breakage during winding.

[0071] The rest is the same as in Example 1, and will not be repeated here.

[0072] Example 5

[0073] Unlike Example 1, the gradient arrangement parameters in this example are K=2.0 and α=1.5. Compared to Example 1, the overall spacing is reduced, the pore density is increased, and the wetting channels are more densely packed.

[0074] The arc length spacing of each layer is calculated according to formula L. i =30×2.0×e^(1.5×D i / 8) Calculation: Inner layer (D) i =2mm): L i =60×e^0.375=87.3μm Middle layer (D) i =4mm): L i =60×e^0.75=127.0μm Outer layer (D) i =7mm): L i =60×e^1.3125=222.9μm The rest is the same as in Example 1, and will not be repeated here.

[0075] Example 6

[0076] Unlike Example 1, the gradient arrangement parameters in this example are K=3.0 and α=2.5. Compared to Example 1, the overall spacing is increased and the pore density is decreased, but the gradient difference between the inner and outer layers is more significant.

[0077] The arc length spacing of each layer is calculated according to formula L. i =30×3.0×e^(2.5×D i / 8) Calculation: Inner layer (D) i =2mm): L i =90×e^0.625=168.1μm Middle layer (D) i =4mm): L i =90×e^1.25=314.1μm Outer layer (D) i =7mm): L i =90×e^2.1875=802.2μm The rest is the same as in Example 1, and will not be repeated here.

[0078] Example 7

[0079] Unlike Example 1, the soluble functional cylindrical rod in this example has a diameter d = 15 μm. The smaller diameter results in finer channels, which has a smaller impact on the cell's energy density, but a stronger capillary effect.

[0080] The rest is the same as in Example 1, and will not be repeated here.

[0081] Example 8

[0082] Unlike Example 1, the soluble functional cylindrical rod in this example has a diameter d = 40 μm. The increased diameter results in a wider channel and lower resistance to electrolyte flow, but has a slightly greater impact on the cell structure.

[0083] The rest is the same as in Example 1, and will not be repeated here.

[0084] Example 9

[0085] Unlike Example 1, in this example, the standing time in step S4 is 4 hours, and the standing temperature is 25°C. Extending the standing time ensures that the cylindrical rod is completely dissolved and the electrolyte is fully absorbed.

[0086] The rest is the same as in Example 1, and will not be repeated here.

[0087] Example 10

[0088] Unlike Example 1, the soluble functional cylindrical rod in this example is formed by extrusion of a blend of 70 wt% PMMA, 15 wt% VC, and 15 wt% LiBOB. The combination of these two film-forming additives allows for the simultaneous formation of protective films on both the positive and negative electrode surfaces.

[0089] The rest is the same as in Example 1, and will not be repeated here.

[0090] Comparative Example 1 (Traditional Mechanical Kneading Method) The same positive electrode, negative electrode, and separator materials as in Example 1 were used for normal winding (without adding soluble functional cylindrical rods). After winding, a mechanical kneading process was performed: the core was placed horizontally in the positioning groove of the positioning fixture, and three kneading rollers (stainless steel, 30mm in diameter) were set above the core. The kneading rollers rotated at 70 rpm in the opposite direction to the core's rotation, applying a pressure of 12 N / cm. 2 Knead continuously for 5 seconds. The core rotation speed is 60 rpm. Then, fill the casing with liquid and let it stand for 2 hours. Other conditions are the same as in Example 1.

[0091] Comparative Example 2 (uniformly arranged cylindrical rods) Unlike Example 1, the soluble functional cylindrical rods in this comparative example are arranged with uniform spacing, and the spacing between each layer is 200 μm (without using a gradient arrangement formula). Everything else is the same as in Example 1.

[0092] Comparative Example 3 (cylindrical rod without film-forming additives) Unlike Example 1, the soluble functional cylindrical rod in this comparative example is made of 100 wt% PMMA and contains no film-forming additives. Everything else is the same as in Example 1.

[0093] Comparative Example 4 (Cylindrical rod with excessively large diameter) Unlike Example 1, the soluble functional cylindrical rod in this comparative example has a diameter d = 60 μm (exceeding the constraint of 0.3 × T = 49.8 μm). Everything else is the same as in Example 1.

[0094] Comparative Example 5 (Cylindrical rod diameter is too small) Unlike Example 1, the soluble functional cylindrical rod in this comparative example has a diameter d = 8 μm. Everything else is the same as in Example 1.

[0095] Comparative Example 6 (K value too small) Unlike Example 1, the pore compensation constant K in this comparative example is 1.0 (below the lower limit of 1.5). Everything else is the same as in Example 1.

[0096] Comparative Example 7 (K value is too large) Unlike Example 1, the pore compensation constant K in this comparative example is 5.0 (higher than the upper limit of 4.0). Everything else is the same as in Example 1.

[0097] Comparative Example 8 (α value is too small) Unlike Example 1, the gradient divergence coefficient α in this comparative example is 0.5 (below the lower limit of 1.0). Everything else is the same as in Example 1.

[0098] Comparative Example 9 (α value is too large) Unlike Example 1, the gradient divergence coefficient α in this comparative example is 4.0 (higher than the upper limit of 3.0). Everything else is the same as in Example 1.

[0099] Comparative Example 10 (Conventional process without adding cylindrical rods) The same positive electrode, negative electrode, and separator materials as in Example 1 were used for normal winding, without adding soluble functional cylindrical rods or performing any post-processing. The material was directly packaged, injected with liquid, and allowed to stand for 2 hours. Other conditions were the same as in Example 1.

[0100] The following performance tests were performed on the electronic cigarette cells prepared in each embodiment and comparative example: 1. Cell center area wetting rate test: 1) The prepared battery cell was subjected to destructive dissection after being allowed to stand for a period of time following liquid injection; 2) Unwind the core along the axial direction of the cell and take an electrode sample from the central area (within 0~2mm from the center of the core); 3) Observe the electrolyte wetting on the surface of the electrode. The wet and black areas are the wetting areas, and the dry and white areas are the unwetting areas. 4) Use image analysis software to calculate the percentage of the infiltrated area to the total area, which is the infiltration rate of the central area.

[0101] 2. Electrode active material shedding test: 1) Dissect the prepared battery cell, remove the core and unfold it; 2) Use a precision balance (accuracy 0.01mg) to weigh the mass difference of the electrode before and after processing; 3) Amount of active material detachment = mass of electrode sheet before treatment - mass of electrode sheet after treatment.

[0102] 3. Initial charge / discharge efficiency test: 1) The prepared battery cell was charged to 4.2V at a constant current of 0.2C at 25℃, and then charged to the cutoff current of 0.02C at a constant voltage. 2) After standing for 10 minutes, discharge at a constant current of 0.2C to 3.0V; 3) Initial charge / discharge efficiency = (initial discharge capacity / initial charge capacity) × 100%.

[0103] 4. Capacity retention test after 300 cycles: 1) Under 25℃ conditions, perform charge-discharge cycles at a 1C rate (charging: 1C constant current to 4.2V, constant voltage to 0.05C; discharging: 1C constant current to 3.0V). 2) Record the discharge capacity for the 1st and 300th discharges; 3) Capacity retention rate after 300 cycles = (300th discharge capacity / 1st discharge capacity) × 100%.

[0104] 5. Rate performance (3C / 0.5C capacity ratio) test: 1) Perform a complete charge and discharge cycle at a 0.5C rate (charging: constant current at 0.5C to 4.2V, constant voltage to 0.02C; discharging: constant current at 0.5C to 3.0V), and record the discharge capacity; 2) Then perform a complete charge and discharge cycle at a 3C rate (charging: 0.5C constant current to 4.2V, constant voltage to 0.02C; discharging: 3C constant current to 3.0V), and record the discharge capacity; 3) 3C / 0.5C capacity ratio = (discharge capacity at 3C rate / discharge capacity at 0.5C rate) × 100%.

[0105] The specific test results are shown in Table 1 below.

[0106] Table 1

[0107] Example 1 99.2 <0.1 92.5 96.0 88.5 Example 2 99.0 <0.1 92.8 95.5 88.0 Example 3 99.1 <0.1 93.5 97.0 89.0 Example 4 99.0 <0.1 91.8 94.5 87.5 Example 5 99.5 <0.1 92.8 95.8 89.2 Example 6 97.5 <0.1 91.5 94.8 86.5 Example 7 97.8 <0.1 91.8 95.2 87.0 Example 8 99.5 <0.1 92.0 94.0 88.8 Example 9 99.5 <0.1 92.6 96.2 88.6 Example 10 99.3 <0.1 93.0 96.8 89.0 Comparative Example 1 88.0 2.5 87.0 86.0 78.0 Comparative Example 2 93.5 <0.1 90.5 92.0 84.0 Comparative Example 3 99.0 <0.1 90.0 91.5 85.5 Comparative Example 4 99.5 0.8 89.5 88.0 86.0 Comparative Example 5 90.0 <0.1 89.0 92.5 81.0 Comparative Example 6 99.8 <0.1 91.0 89.5 87.0 Comparative Example 7 92.0 <0.1 89.5 93.0 82.5 Comparative Example 8 95.0 <0.1 90.5 93.5 84.5 Comparative Example 9 99.5 <0.1 90.0 87.0 87.5 Comparative Example 10 76.0 0 85.0 79.0 71.0

[0108] The test results in Table 1 above are analyzed as follows: 1. Comparative analysis between the examples and comparative examples: (1) A comparison between Example 1 and Comparative Example 10 shows that: The wetting rate of the central region in Example 1 was 99.2%, significantly higher than the 76.0% of Comparative Example 10 (conventional process), representing an improvement of 23.2 percentage points. This fully demonstrates that the method of forming wetting channels by pre-embedding soluble cylindrical rods in this invention can fundamentally solve the problem of the "wetting dead zone" in the center of the battery cell. The capacity retention rate of Example 1 after 300 cycles was 96.0%, significantly higher than the 79.0% of Comparative Example 10, representing an improvement of 17 percentage points, demonstrating the crucial role of adequate wetting in cycle life.

[0109] (2) A comparison between Example 1 and Comparative Example 1 shows that: The central region wetting rate of Example 1 was significantly higher than that of Comparative Example 1 (traditional mechanical kneading method), indicating that the internal pore-forming method of the present invention is more effective than the external kneading method in solving the central wetting problem. The amount of active material detached in Example 1 was <0.1mg, while that in Comparative Example 1 was as high as 2.5mg, proving that the present invention completely avoids the physical damage caused by mechanical kneading. The capacity retention rate of Example 1 after 300 cycles (96.0%) was much higher than that of Comparative Example 1 (86.0%), an increase of 10 percentage points, fully demonstrating the advantages of the present invention in terms of cycle life.

[0110] (3) A comparison between Example 1 and Comparative Example 2 shows that: Example 1, employing a gradient arrangement, achieved a central region wetting rate of 99.2%, higher than the 93.5% of Comparative Example 2 (uniform arrangement). This is because the uniform arrangement resulted in insufficient pore density in the central region, failing to effectively overcome the high capillary resistance. The gradient arrangement, with its denser inner and sparser outer design, concentrates pore formation in the central region, significantly improving the central wetting effect. Furthermore, Example 1 exhibited a higher capacity retention rate after 300 cycles compared to Comparative Example 2, indicating that the gradient arrangement also outperforms the uniform arrangement in ensuring structural stability.

[0111] (4) A comparison between Example 1 and Comparative Example 3 shows that: The capacity retention rate of Example 1 after 300 cycles was 96.0%, higher than that of Comparative Example 3 (without film-forming additives) at 91.5%. The central region wettability of both examples was similar, indicating that the film-forming additives had little effect on wettability but significantly contributed to cycle life. This demonstrates the effectiveness of the "pore-forming + film-forming" dual-effect design of the film-forming additives in the cylindrical rod: after the additives dissolve and are released, an SEI film is formed in situ on the inner wall of the channel, compensating for the electrochemical interface at the pores and improving cycle stability.

[0112] (5) A comparison between Example 1 and Comparative Example 4 shows that: In Comparative Example 4, the diameter of the cylindrical rod (60 μm) exceeded the safety constraint (0.3 × T = 49.8 μm). Although the wettability was as high as 99.5%, the amount of active material detached reached 0.8 mg, the initial charge-discharge efficiency dropped to 89.5%, and the capacity retention rate after 300 cycles was only 88.0%. This is because the excessively large cylindrical rod caused local stress concentration on the electrode under winding tension, leading to coating cracking and active material detachment, demonstrating the necessity of diameter safety constraints.

[0113] (6) A comparison between Example 1 and Comparative Example 5 shows that: The cylindrical rod in Comparative Example 5 had a diameter of only 8 μm, and the wettability in the central region was only 90.0%, far lower than the 99.2% in Example 1. This is because the excessively narrow channel has too much capillary resistance, obstructing the flow of electrolyte and preventing effective wetting of the central region. Simultaneously, the rate performance was only 81.0%, lower than the 88.5% in Example 1, indicating that the narrow channel limited the rapid transport of the electrolyte.

[0114] (7) A comparison between Example 1 and Comparative Example 6 shows that: The K value (K=1.0) of Comparative Example 6 is below the lower limit, resulting in an excessively high overall pore density. Although the wettability is extremely high (99.8%), the capacity retention rate after 300 cycles is only 89.5%, lower than the 96.0% of Example 1. This is because excessive pores weaken the structural integrity of the cell, leading to poor contact between electrodes, increasing interfacial impedance, and affecting cycle stability.

[0115] (8) A comparison between Example 1 and Comparative Example 7 shows that: The K value (K=5.0) of Comparative Example 7 was higher than the upper limit, resulting in an overall low pore density. The wettability in the central region was only 92.0%, lower than 99.2% in Example 1. The rate performance was also only 82.5%, indicating that insufficient pore density resulted in insufficient electrolyte transport channels, affecting the wettability and rate performance.

[0116] (9) A comparison between Example 1 and Comparative Example 8 shows that: In Comparative Example 8, the α value (α=0.5) is below the lower limit, resulting in insignificant differences in the spacing between the inner and outer layers, tending towards a uniform arrangement. The central region wetting rate is 95.0%, lower than 99.2% in Example 1. This indicates that when the gradient effect is insufficient, the pore density in the central region is not concentrated enough, failing to adequately address the central wetting problem.

[0117] (10) A comparison between Example 1 and Comparative Example 9 shows that: The α value (α=4.0) of Comparative Example 9 is higher than the upper limit, resulting in an excessive difference in the spacing between the inner and outer layers. Although the wettability is high (99.5%), the capacity retention rate after 300 cycles is only 87.0%, far lower than the 96.0% of Example 1. This is because when α is too large, the pores in the inner layer are too dense, which seriously weakens the structural strength of the central region, causing local collapse inside the core and affecting the cycling performance.

[0118] 2. Comparative analysis between different embodiments: (1) Influence of cylindrical rod material (Examples 1, 2, 10): The central region wetting rates of Examples 1 (PMMA+VC), 2 (PEO+FEC), and 10 (PMMA+VC+LiBOB) were all above 99.0%, indicating that different soluble polymer matrices could effectively dissolve and form channels. Regarding cycle performance, Example 10 (96.8%) was slightly better than Examples 1 (96.0%) and 2 (95.5%), demonstrating that the compound film-forming additive (VC+LiBOB) could form a protective film at both the positive and negative electrodes, further improving cycle stability.

[0119] (2) Effect of film-forming additive content (Examples 1, 3, 4): Example 3 (40% VC) exhibited a capacity retention of 97.0% after 300 cycles, higher than Example 1 (30% VC, 96.0%) and Example 4 (20% VC, 94.5%). This indicates that within a polymer matrix range of 60%–80%, appropriately increasing the content of film-forming additives is beneficial for forming a more complete SEI film and improving cycle performance. However, the initial charge-discharge efficiency of Example 4 (91.8%) was slightly lower than that of Example 3 (93.5%), suggesting that insufficient additive content results in inadequate SEI film quality, while a moderate content yields the best results.

[0120] (3) The influence of gradient parameters K and α (Examples 1, 5, 6): The central region wetting rate of Example 5 (K=2.0, α=1.5) was 99.5%, slightly higher than that of Example 1 (K=2.5, α=2.0, 99.2%) and Example 6 (K=3.0, α=2.5, 97.5%). This is because decreasing the K and α values ​​both increase the pore density. However, the cycle capacity retention rate of Example 6 (94.8%) was slightly lower than that of Example 1 (96.0%) and Example 5 (95.8%), indicating that within the preferred range, the combination of K=2.0~2.5 and α=1.5~2.0 achieves the best balance between wetting efficiency and structural stability.

[0121] (4) Influence of cylindrical rod diameter (Examples 1, 7, 8): The central region wetting rate of Example 7 (d=15μm) was 97.8%, slightly lower than that of Example 1 (d=30μm, 99.2%) and Example 8 (d=40μm, 99.5%). This is because while finer channels provide stronger capillary driving force, they also result in greater flow resistance, limiting the overall wetting rate. Example 8 had the highest wetting rate, but its cycle capacity retention (94.0%) was slightly lower than that of Example 1 (96.0%), indicating that excessively thick channels have a certain impact on the cell structure. Overall, a diameter of 30μm achieves the best balance between wetting efficiency and structural stability.

[0122] (5) Effect of settling time (Examples 1 and 9): The performance of Example 9 (4 hours of standing) is similar to that of Example 1 (2 hours of standing), with a slight increase in the wettability of the central area. This indicates that the 2-hour standing time is sufficient to ensure the complete dissolution of the cylindrical rod and the full wettability of the electrolyte. Extending it to 4 hours can further ensure the completeness of the wettability, but the improvement is limited.

[0123] In summary, the present invention, by pre-embedding soluble functional cylindrical rods during the winding process and employing an exponential gradient arrangement, has the following advantages: 1) The central area wetting rate has been increased from 76.0% in conventional processes to over 99%, fundamentally eliminating the problem of "wetting dead zone"; 2) The amount of active substance detached is <0.1mg, which completely avoids the physical damage caused by the traditional mechanical kneading method (comparative example 1 detached 2.5mg). 3) The capacity retention rate after 300 cycles is increased from 79.0% in conventional processes to 94%~97%, which significantly extends the cycle life of electronic cigarette cells; 4) The rate performance has been improved from 71.0% in conventional processes to 86%~89%, and the establishment of electrolyte transmission channels has effectively reduced the internal resistance of the cells.

[0124] Therefore, this invention replaces the "external mechanical kneading" with a novel concept of "internal pre-embedding-in-situ dissolution pore-forming", combines an exponential gradient arrangement formula to achieve the optimal channel distribution with dense inner and sparse outer channels, and achieves synergistic optimization of physical channels and electrochemical interfaces through a dual-effect material design of "pore-forming + film formation".

[0125] It should be noted that the contents not described in detail in this specification are existing technologies known to those skilled in the art, and will not be elaborated here.

[0126] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for manufacturing a long-cycle-life electronic cigarette cell, characterized in that, Includes the following steps: S1. The positive electrode, separator and negative electrode are sequentially stacked on the winding needle and wound to form a core; S2. During the winding process, soluble functional cylindrical rods are inserted intermittently into the interlayer gaps between the electrode and the diaphragm along a direction parallel to the axis of the winding needle; the soluble functional cylindrical rods are soluble in the electrolyte. S3. Place the core in the outer casing and inject electrolyte; S4. Allow the soluble functional cylindrical rod to stand for a preset time to dissolve in the electrolyte and form a longitudinally penetrating wetting channel in situ inside the battery cell. S5. After formation and sealing, the electronic cigarette cell is obtained; The soluble functional cylindrical rods are arranged in a non-uniform gradient along the winding layer direction, with a denser inner layer and a sparser outer layer; on the i-th winding layer, the arc length distance L between two adjacent soluble functional cylindrical rods is... i The following relationship must be satisfied: L i =d×K×e^(α×D i / D max ) Among them, D i D is the diameter of the i-th winding layer, in mm; max d is the maximum outer diameter of the core, in mm; d is the diameter of the soluble functional cylindrical rod, in mm; K is the pore compensation constant, with a value range of 1.5≤K≤4.0; α is the gradient divergence coefficient, with a value range of 1.0≤α≤3.

0.

2. The method for manufacturing a long-cycle-life electronic cigarette cell according to claim 1, characterized in that: The diameter d of the soluble functional cylindrical rod satisfies: d≤0.3×T, where T is the sum of the thicknesses of the positive electrode, negative electrode and separator.

3. The method for manufacturing a long-cycle-life electronic cigarette cell according to claim 2, characterized in that: The diameter of the soluble functional cylindrical rod is 15μm~40μm, and the length of the soluble functional cylindrical rod is equal to the width of the coating area of ​​the electrode.

4. The method for manufacturing a long-cycle-life electronic cigarette cell according to claim 1, characterized in that: The soluble functional cylindrical rod is formed by co-extrusion molding of a soluble polymer matrix and a film-forming additive; wherein, by mass percentage, the content of the soluble polymer matrix is ​​60%~80%, and the content of the film-forming additive is 20%~40%.

5. The method for manufacturing a long-cycle-life electronic cigarette cell according to claim 4, characterized in that: The soluble polymer matrix is ​​selected from one or more of polyethylene oxide, polymethyl methacrylate, or polyvinylidene fluoride-hexafluoropropylene copolymer; And / or, the film-forming additive is selected from one or more of vinylene carbonate, fluoroethylene carbonate, or lithium bis(oxalato)borate.

6. The method for manufacturing a long-cycle-life electronic cigarette cell according to claim 1, characterized in that: The pore compensation constant K has a value range of 2.0 ≤ K ≤ 3.0, and the gradient divergence coefficient α has a value range of 1.5 ≤ α ≤ 2.

5.

7. The method for manufacturing a long-cycle-life electronic cigarette cell according to claim 1, characterized in that: The soluble functional cylindrical rod is inserted into the interlayer gap between the separator and the negative electrode sheet.

8. The method for manufacturing a long-cycle-life electronic cigarette cell according to claim 1, characterized in that: In step S4, the preset settling time is 1 to 4 hours, and the settling temperature is 20 to 30°C.

9. The method for manufacturing a long-cycle-life electronic cigarette cell according to claim 1, characterized in that: In step S2, the soluble functional cylindrical rod is automatically inserted by setting a feeding mechanism on the winding machine; the feeding mechanism automatically cuts and attaches the soluble functional cylindrical rod in the interlayer gap according to the arc length spacing calculated in real time by the PLC controller.

10. A long-cycle-life electronic cigarette cell, characterized in that: It is prepared by the method of manufacturing a long cycle life electronic cigarette cell according to any one of claims 1 to 9.