Method for improving warm-pressure cycle activation and liquid retention efficiency of large cylindrical battery

Abstract

The invention relates to the technical field of battery manufacturing processes, and discloses a large cylindrical battery temperature and pressure cycle activation and liquid retention efficiency improvement method, which comprises the following steps: obtaining a naked battery cell, carrying out first liquid injection, then carrying out gradient vacuum pretreatment, executing pressure compensation operation in a standing period, moving the battery into a sealed chamber, and executing staged activation, in the second stage, a gradient application program is executed, self-adaptive closed-loop feedback logic is started, a load reduction instruction is triggered when the internal pressure rising rate exceeds a safety threshold value, so that a compact solid electrolyte interface film is generated on the surface of the negative electrode, secondary quantitative liquid supplementing and negative-pressure infiltration are executed after activation, intermittent physical intervention is started during infiltration, and the negative electrode is subjected to negative-pressure infiltration. And finally, the battery is taken out, steady-state stress relaxation is executed, and sealing is completed. The problems that deep pores of a large-size roll core are difficult to infiltrate and an interfacial film is damaged by formation gas production are solved, the physical consistency of the battery is improved, and the long-acting cycle life of the battery is prolonged.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, specifically to a method for improving the temperature and pressure cycle activation and liquid retention efficiency of large cylindrical batteries. Background Technology

[0002] In recent years, large cylindrical batteries have gradually become the mainstream application due to their inherent advantages in assembly efficiency and manufacturing cost. However, compared with traditional small cylindrical or square cells, the physical specifications of large-size wound cores increase the thickness of the electrode and separator layers, objectively lengthening the electrolyte permeation path. In existing conventional electrolyte injection and pretreatment processes, industrially, a unidirectional continuous vacuum method is usually used to promote electrolyte permeation. However, for large-size wound cores, this open-loop degassing method reveals significant limitations: Because of the dense micropores inside the porous electrode, the fluid easily blocks the outer ends of the pores due to capillary resistance, causing the gas deep within the core to be compressed and form blind-end gas clusters. Simply relying on the static pressure difference generated by a unidirectional high vacuum is insufficient to overcome the surface tension at the gas-liquid interface to peel off these deep micro-gas clusters. The retention of these gas clusters directly blocks the radial transport of electrolyte into the core, resulting in insufficient deep wetting of the electrode and uneven fluid distribution.

[0003] Furthermore, the aforementioned wetting defects can further worsen subsequent formation processes. During formation, the electrolyte undergoes an electrochemical reduction reaction on the electrode surface, accompanied by the precipitation of a large amount of gaseous byproducts. Existing technologies mostly employ open-loop processes with constant temperature and constant external pressure. Due to the long mass transport path within the battery cell, when the initial gas generation rate exceeds the dissolution and diffusion tolerance of the gas within the system, the gas phase pressure will rapidly accumulate and rise locally.

[0004] The continuously accumulating high-pressure bubbles exert direct physical stress on the nascent and fragile solid electrolyte interface film on the negative electrode surface, causing microcracks or even localized peeling of the separator. The damaged interface structure requires continuous consumption of limited free electrolyte and active lithium ions for secondary reconstruction in subsequent processes. This not only weakens the mechanical density of the interface film but also causes an irreversible increase in internal resistance, accelerating the capacity decay of the battery during long-term cycling.

[0005] After formation degassing and primary electrolyte consumption, large-size cores still face the engineering challenge of fluid distribution imbalance. High-viscosity non-aqueous electrolytes, influenced by gravity, tend to sink along their long axis. Current processes typically employ only static resting during secondary electrolyte replenishment or final wetting. Without external physical kinetic energy, the high-viscosity fluid struggles to overcome the lateral flow resistance at the interface between the porous electrode and the separator, causing a concentration gradient of the free electrolyte within the core. This fluid distribution imbalance leads to regional differences in ohmic impedance within the cell, resulting in increased local polarization and uneven heat generation when the battery faces high-rate charge / discharge or extreme temperature conditions, thus limiting overall electrochemical performance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for improving the temperature and pressure cycle activation and liquid retention performance of large cylindrical batteries. This method solves the problems in existing large cylindrical battery manufacturing processes, such as deep gas blockage caused by unidirectional vacuum, gas generation and damage to the initial interface caused by open-loop constant pressure activation, and internal fluid distribution imbalance caused by static shelving, which make it difficult to meet the requirements of electrochemical interface consistency and reliability for large-size cores.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for improving the temperature and pressure cycling activation and liquid retention performance of large cylindrical batteries, comprising the following steps: Obtain a bare cell for a large cylindrical battery for assembly, the bare cell having an internal core formed by alternating winding of a positive electrode sheet, a negative electrode sheet and a separator, and obtain a non-aqueous electrolyte composition, and perform the first electrolyte injection on the bare cell; The large cylindrical battery that has completed its first liquid injection is placed in a programmable vacuum drying oven for gradient vacuum pretreatment, and pressure compensation is performed during the settling period. The pretreated large cylindrical battery is moved into a sealed temperature and pressure cycling chamber and activated in stages. In the second stage of activation, a gradient application procedure is executed and an adaptive closed-loop feedback logic is initiated. When the pressure rise rate exceeds the safety threshold, a load reduction command is triggered to generate a dense solid electrolyte interface film on the surface of the negative electrode. After activation, a combined liquid retention and mechanical disturbance process is performed. The combined liquid retention process includes using a high-precision metering pump to perform secondary quantitative liquid replenishment and moving the battery into a negative pressure degassing chamber for negative pressure immersion. During the negative pressure immersion, intermittent physical intervention is initiated until the immersion is completed. The large cylindrical battery is removed and subjected to steady-state stress relaxation to complete permanent sealing and static balancing.

[0008] By adopting the above technical solution, the process principle of the present invention is mainly unfolded from two dimensions: physical fluid transport and electrochemical interface generation. Regarding overcoming fluid transport resistance, a pressure compensation operation is performed by briefly refilling the chamber with dry inert gas during gradient vacuuming. The transient rise in external ambient pressure forces the blind-end micro-gas clusters adsorbed within the micropores of the electrodes and diaphragms to be compressed, causing them to detach from the pore walls during volume contraction. Subsequently, once the high vacuum state is restored, the loosened gas clusters rapidly expand and escape, thus opening up the transport path for electrolyte transfer to the deep electrode network from the physical source.

[0009] Based on the aforementioned unblocked physical pore network, thermodynamic regulation and interfacial film formation mechanisms can be intervened more efficiently. During the phased activation process, solvent molecules and film-forming additives undergo reduction reactions on the surface of the negative electrode.

[0010] In this reaction process, the system consumes active lithium to generate insoluble solid substances such as alkyl lithium carbonate, which adhere to the electrode surface, while gaseous byproducts are precipitated. The film-forming reaction rate increases with increasing applied temperature and pressure. When the actual internal gas generation rate exceeds the dissolution and diffusion tolerance of the fluid system, the gas phase pressure increases accordingly.

[0011] By monitoring the pressure rise rate and triggering adaptive closed-loop feedback logic, the pressurization rate is reduced or the holding time is extended, thereby appropriately reducing the thermodynamic stress applied to the outside of the cell. This mechanism forcibly limits the electrochemical reaction rate within the physical tolerance of electrode venting, providing diffusion time for the gradual discharge of gaseous substances, avoiding physical damage to the fragile nascent solid electrolyte interface film by high-pressure bubbles, and ensuring the compactness and continuity of the film formation.

[0012] To further enhance interface quality and compensate for solvent consumption during the formation stage, this scheme employs secondary quantitative replenishment and negative pressure wetting in the later stages of the reaction, coupled with intermittent physical intervention initiated by the bottom mechanism. The applied rotational or vibrational kinetic energy establishes an alternating shear force field within the closed cylindrical system, overcoming the surface tension and capillary resistance of the high-viscosity fluid. This physical-level active permeation mechanism forces the free-state secondary replenishment fluid to undergo convective distribution in the radial plane of the core, mitigating the concentration gradient difference caused by gravity and establishing a continuous and uniform ion conduction network in the spatial dimension, thereby reducing the overall ohmic impedance of the battery.

[0013] Preferably, the non-aqueous electrolyte composition is made from raw materials comprising the following components: a mixed organic solvent, which is composed of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate, wherein the volume ratio of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate is (2-4):(3-4):(3-4); and a lithium salt, wherein the molar concentration in the mixed organic solvent is 1.0-1.2 mol / L. A film-forming additive is added at a rate of 1% to 10% of the total mass of the non-aqueous electrolyte composition. The lithium salt is lithium hexafluorophosphate; the film-forming additive is one of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate, or a mixture of at least two of them. The bare battery cell has a diameter greater than or equal to 30 mm and a height greater than or equal to 80 mm; the amount of initial electrolyte injection satisfies the following relationship. ; in, This represents the theoretically total wettable pore volume of the bare battery cell. The amount of the initial injection. The wetting coefficient is set to a value of 0.85 to 0.95.

[0014] By adopting the above technical solution, the mixed solvent ratio set in this solution can provide suitable dielectric constant and hydrodynamic viscosity. Film-forming additives such as vinylene carbonate and fluoroethylene carbonate have higher reduction potentials than conventional carbonate solvents. During the activation stage, they preferentially undergo ring-opening polymerization and reduction reactions to form a solid electrolyte interface film rich in inorganic components such as lithium fluoride, thereby improving the mechanical strength and ionic conductivity of the film layer.

[0015] Meanwhile, to address the engineering problem of easy overflow during electrolyte injection in large-capacity cells, the wetting coefficient is controlled within the range of 0.85 to 0.95, so that the initial electrolyte injection volume is slightly lower than the physical absolute volume of the pores. This not only meets the basic material requirements for the initial nucleation reaction at the interface, but also reserves the necessary internal buffer space for the early electrochemical gas generation, preventing the gas-liquid mixture from overflowing to the outside.

[0016] Preferably, the step of gradient vacuum pretreatment and performing pressure compensation during the settling period specifically includes: entering a first-stage vacuum, evacuating the cavity of the programmable vacuum drying oven to a first vacuum degree of -0.095 to -0.08 MPa, and settling for a first period of time, the first period of time being 6 to 12 hours; then entering a second-stage vacuum, evacuating the cavity to a second vacuum degree of -0.1 to -0.096 MPa, and settling for a second period of time, the second period of time being 6 to 12 hours; At least one pressure compensation operation is performed during the settling period of the second stage vacuum, namely, briefly refilling the chamber with dry inert gas to raise the chamber gauge pressure to -0.08 to -0.05 MPa and maintain it for 5 to 10 minutes, and then restoring the high vacuum state.

[0017] By adopting the above technical solution and setting up a progressively decreasing gauge pressure hierarchy, the excessively rapid evaporation and loss of low-boiling-point solvent components in the electrolyte under a single ultimate vacuum can be avoided. In terms of process execution, pre-setting time limits and pressure recovery amplitude effectively quantifies the physical pressure difference boundary required for the transient contraction of internal micro-air masses, ensuring the thoroughness of deep-pore bubble removal and fluid penetration from a macroscopic operational perspective.

[0018] Preferably, after the large cylindrical battery is moved into the sealed thermo-pressure circulation chamber, a temporary sealing clamp is used to connect with the battery cap's liquid injection hole. A miniature piezoresistive sensor inside the temporary sealing clamp is used to monitor the gas phase pressure, and thermocouple sensors are used to monitor the surface temperature of the large cylindrical battery casing. The activation process is divided into a first stage and a second stage. In the first stage of activation, an inert gas is introduced into the sealed thermo-pressure circulating chamber to apply a hydrostatic pressure of 0.1 to 0.3 MPa, and the temperature is set to 25 to 35°C and maintained for 4 to 6 hours to induce primary nucleation.

[0019] In the second stage of activation: The specific parameters of the gradient application procedure are as follows: The heating rate is set to 0.5 to 1.2℃ / min to reach the target temperature of 40 to 50℃, and the pressurization rate is set to 0.02 to 0.06MPa / min to reach the target pressure of 0.3 to 0.5MPa. The specific method for activating the adaptive closed-loop feedback logic is as follows: If the pressure rise rate exceeds the safety threshold, the load reduction command is triggered to adjust external parameters, including at least one of reducing the pressurization rate and extending the pressure holding time. If the maximum temperature difference exceeds the set limit, adjust the hot air direction or adjust the power ratio of the zone heating elements; The safety threshold is preset based on the electrochemical gas generation characteristics of the non-aqueous electrolyte composition and the casing pressure resistance limit. The setting range of the safety threshold is 0.07 to 0.12 MPa / min. The setting limit is preset based on the size specifications and thermal conductivity characteristics of the large cylindrical battery. The setting range of the setting limit is 5 to 12°C.

[0020] By adopting the above technical solution, the parameter control in the first stage provides thermodynamic conditions for the decomposition of some low-potential additives, and a basic interfacial film framework is constructed on the negative electrode surface.

[0021] In the second stage, sensor monitoring and data acquisition are used to convert the invisible thermodynamic state inside the closed battery system into closed-loop control signals. Under normal conditions, the set heating and pressurization rates are designed to accelerate the bulk reaction process of the electrode. If the pressurization rate or temperature fluctuation exceeds the preset limit, the dynamic intervention of the load reduction command and hot air distribution mechanism can promptly lower the activation energy of the reaction system. This closed-loop intervention reduces the reaction rate and maintains the thermal equilibrium of the system, preventing local thermal runaway or interfacial structural instability caused by violent local reactions.

[0022] Preferably, the step of performing coordinated liquid retention and mechanical disturbance treatment specifically includes: Perform the second quantitative replenishment, setting the amount of the second quantitative replenishment to 5% to 15% of the amount of the first injection; perform negative pressure immersion in the negative pressure defoaming chamber, controlling the pressure inside the chamber to be -0.1 to -0.09 MPa, and the total immersion time to be 6 to 12 hours; During the negative pressure immersion, the bottom physical disturbance tray is activated to perform the intermittent physical intervention, which is intermittent rotary stirring or linear vibration, and the dynamic parameters are set as follows: When using the intermittent rotary stirring, the operating speed is 30 to 45 rpm; when using the linear vibration, the vibration frequency is 30 to 60 times / minute; the duration of a single continuous disturbance is 3 to 10 minutes; then a settling period is entered, with a settling interval of 0.5 to 1.5 hours, and the cycle is repeated until the soaking is completed.

[0023] The specific steps for removing the large cylindrical battery, performing steady-state stress relaxation, and completing permanent sealing and static balancing include: Complete the permanent sealing, which is achieved by laser welding. Then, move the large cylindrical battery into a standardized constant temperature and humidity warehouse and allow it to stand for equilibration for 10 to 20 hours at a temperature of 30 to 35°C and a relative humidity of 30% to 45%.

[0024] By adopting the above technical solution, the set quantitative replenishment of 5% to 15% accurately compensates for the solvent consumption in the early formation reaction.

[0025] The specified operating speed and vibration frequency range ensure that the applied mechanical kinetic energy is sufficient to overcome the transport resistance of the microporous fluid, while also guaranteeing that the external force output remains within a safe range, preventing mechanical misalignment of the core assembly or physical shedding of active material due to excessive disturbance. Furthermore, the intermittent pauses and alternating disturbances provide a buffer time for the release of interfacial stress as the fluid permeates into the micro-network. The final isothermal static equilibration further eliminates residual internal stress during assembly and charging / discharging, establishing the physical consistency of the overall structure of the large cylindrical battery before encapsulation.

[0026] This invention provides a method for improving the temperature and pressure cycling activation and liquid retention performance of large cylindrical batteries. It has the following beneficial effects: 1. This invention introduces a pressure compensation operation during gradient vacuum pretreatment, utilizing the transient rise in external gauge pressure to induce volume contraction of the blind-end gas clusters within the micropores, causing them to detach from the pore walls. Upon subsequent restoration to a high vacuum state, the loosened gas clusters rapidly expand and escape, thereby eliminating microscopic gas phase blockage deep within the electrode. This physical intervention directly unblocks the radial transport path for the high-viscosity electrolyte to transfer into the large-size core, improving the deep wetting rate and penetration uniformity of the electrolyte within the porous electrode.

[0027] 2. In the activation stage, this invention employs adaptive closed-loop feedback logic. By monitoring the rate of increase of gas phase pressure inside the battery in real time, and triggering a load reduction command when the pressure exceeds the safety threshold, the external pressurization rate is dynamically reduced or the holding time is extended. This limits the electrochemical gas generation rate within the tolerance range of physical venting of the electrode, providing a time window for the gradual escape of by-product gases. It avoids the physical damage to the nascent solid electrolyte interface film caused by the accumulation of high-pressure bubbles, thereby constructing a dense interface isolation layer with high mechanical strength on the negative electrode surface and improving the long-term cycle stability of the battery.

[0028] 3. This invention performs secondary quantitative replenishment and negative pressure wetting after formation and activation, and uses physical intervention methods such as intermittent rotary stirring or linear vibration to establish an alternating shear force field inside the closed cylindrical system. This overcomes the surface tension and capillary resistance of high-viscosity fluids, forces the free replenishment liquid to convect and mix in the radial layer of the core, improves the concentration gradient difference caused by gravity, and establishes a continuous and uniform ion conduction network in the spatial dimension. This reduces the regional internal resistance difference of the battery during charging and discharging, and ensures the electrochemical performance under high rate and extreme temperature conditions. Attached Figure Description

[0029] Figure 1 This is a graph showing the rate of increase in internal pressure and the maximum temperature difference of the battery according to the present invention. Figure 2 This is a graph showing the relationship between the internal gas phase pressure of the battery and the applied external hydrostatic pressure of the present invention. Figure 3 This is a graph showing the multi-stage liquid absorption volume evolution trajectory and the dispersion distribution of the final retained liquid volume according to the present invention. Figure 4 This is a scatter plot of the initial electrochemical characteristics and a high-rate cycle life decay curve of the present invention; Figure 5 This is a scatter plot of the room temperature self-discharge rate and the trend of high temperature internal resistance degradation of the present invention. Figure 6 The images show the scatter plot of the fast charging temperature rise and the distribution of the low-temperature discharge capacity retention rate of this invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, examples, comparative examples, test examples, and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing a large cylindrical battery and its non-aqueous electrolyte composition, including: Preparation of non-aqueous electrolyte composition: Ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate are mixed in a volume ratio of 3:3:4 to obtain a mixed organic solvent; Lithium salt (specifically lithium hexafluorophosphate) is added to the mixed organic solvent to achieve a molar concentration of 1.1 mol / L; Subsequently, a film-forming additive (specifically selected from a mixture of vinylene carbonate and fluoroethylene carbonate) with a total mass ratio of 5% was added, and after stirring evenly, a non-aqueous electrolyte composition was prepared for use.

[0032] Assembly of the battery to be filled with electrolyte: Obtain the positive electrode sheet, negative electrode sheet, and separator for assembly, and alternately wind the above components to form an internal core; The internal core is inserted into the cylindrical steel shell and the bottom welding and grooving are completed to produce a bare cell for a large cylindrical battery with a diameter of 46mm and a height of 80mm.

[0033] Preparation Example 2: This preparation example provides a method for preparing a large cylindrical battery and its non-aqueous electrolyte composition, including: Preparation of non-aqueous electrolyte composition: Ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 2:4:4 to obtain a mixed organic solvent. Lithium salt (specifically lithium hexafluorophosphate) is added to the mixed organic solvent to achieve a molar concentration of 1.0 mol / L; Subsequently, a film-forming additive (specifically, a single-component vinylene carbonate) with a total mass ratio of 1% was added, and after stirring evenly, a non-aqueous electrolyte composition was prepared for use.

[0034] Assembly of the battery to be filled with electrolyte: Obtain the positive electrode sheet, negative electrode sheet, and separator for assembly, and alternately wind the above components to form an internal core; The internal core is inserted into the cylindrical steel shell and the bottom welding and grooving are completed to produce a bare cell of a large cylindrical battery with a diameter of 30mm and a height of 80mm for later use. This cell serves as a benchmark for calculating the total volume of theoretically wettable pores.

[0035] Preparation Example 3: This preparation example provides a method for preparing a large cylindrical battery and its non-aqueous electrolyte composition, including: Preparation of non-aqueous electrolyte composition: Ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate are mixed in a volume ratio of 4:3:3 to obtain a mixed organic solvent; Lithium salt (specifically lithium hexafluorophosphate) is added to the mixed organic solvent to achieve a molar concentration of 1.2 mol / L; Subsequently, a film-forming additive (specifically selected from a mixture of fluoroethylene carbonate and ethylene sulfate) with a total mass ratio of 10% was added, and after stirring evenly, a non-aqueous electrolyte composition was prepared for use.

[0036] Assembly of the battery to be filled with electrolyte: Obtain the positive electrode sheet, negative electrode sheet, and separator for assembly, and alternately wind the above components to form an internal core; The internal core is inserted into the cylindrical steel shell and the bottom welding and grooving are completed to produce a bare cell of a large cylindrical battery with a diameter of 46mm and a height of 120mm for later use. This cell serves as a benchmark for calculating the total volume of theoretically wettable pores.

[0037] Examples 1-3: Example 1: This embodiment provides a method for temperature and pressure cycling activation and liquid retention performance improvement of large cylindrical batteries, including the following steps: The bare cell and non-aqueous electrolyte composition provided in Preparation Example 1 were used to obtain the theoretical total wettable pore volume. Then, according to the relational formula Set the wetting coefficient The value was 0.90, and the initial injection was completed to control the amount of fluid injected initially. ; The battery was then placed in a programmable vacuum drying oven for gradient vacuum pretreatment. The chamber is evacuated to a first vacuum level of -0.09 MPa and maintained for 8 hours. Then, the chamber is evacuated to a second vacuum level of -0.098 MPa and maintained for 8 hours. A pressure compensation operation is performed once during the settling period, which involves briefly refilling the chamber with dry inert gas to raise the chamber gauge pressure to -0.08 MPa and maintain it for 10 minutes, after which the high vacuum state is restored.

[0038] The battery is moved into a sealed thermo-pressure circulating chamber, and a temporary sealing clamp is used to connect with the battery cap injection hole. The internal miniature piezoresistive sensor is used to monitor the gas phase pressure, and the deployed thermocouple sensors are used to monitor the surface temperature of the casing. In the first stage of activation, inert gas is introduced into the chamber to apply a hydrostatic pressure of 0.2 MPa, and the temperature is set at 30°C and maintained for 4 hours to induce primary nucleation. Then, the second stage of activation begins, executing the gradient application procedure: The heating rate is set to 0.8℃ / min to the target temperature of 45℃, and the pressurization rate is set to 0.04MPa / min to the target pressure of 0.4MPa. At the same time, the adaptive closed-loop feedback logic is activated: if the pressure rise rate exceeds the safety threshold of 0.08MPa / min, a load reduction command is triggered to reduce the external pressurization rate or extend the pressure holding time; if the maximum temperature difference exceeds the set limit of 8℃, the hot air direction is dynamically adjusted or the power ratio of the zone heating tubes is adjusted.

[0039] After activation, the sealed connection is released, and a combined liquid retention and mechanical disturbance treatment is performed: A high-precision metering pump was used to perform a secondary quantitative replenishment, with the amount of the secondary quantitative replenishment being 10% of the amount of the initial replenishment. The battery was then moved into a negative pressure degassing chamber for negative pressure immersion (chamber pressure -0.095MPa, total immersion time 8h). During the negative pressure immersion, the bottom physical disturbance tray was activated to perform intermittent physical intervention (specifically, intermittent rotary stirring). The kinetic parameters were set, with the working speed at 45rpm and the duration of a single continuous disturbance at 5min. Afterward, a settling period was initiated, with a settling interval of 1h. This cycle was repeated until the immersion was completed.

[0040] Remove the battery and perform steady-state stress relaxation: After permanent sealing (using laser welding), the container is moved into a standardized temperature and humidity constant warehouse (temperature 32℃, relative humidity 40%) and allowed to stand for 15 hours to reach equilibrium.

[0041] Example 2: This embodiment provides a method for temperature and pressure cycling activation and liquid retention performance improvement of large cylindrical batteries, including the following steps: The bare cell and non-aqueous electrolyte composition provided in Preparation Example 2 were used to obtain the theoretical total wettable pore volume. Then, according to the relational formula Set the wetting coefficient The value was 0.85, and the initial injection was completed to control the amount of fluid injected. ; The battery was then placed in a programmable vacuum drying oven for gradient vacuum pretreatment. The chamber is evacuated to a first vacuum level of -0.08 MPa and maintained for 12 hours. Then, the chamber is evacuated to a second vacuum level of -0.096 MPa and maintained for 12 hours. A pressure compensation operation is performed once during the settling period, which involves briefly refilling the chamber with dry inert gas to raise the chamber gauge pressure to -0.05 MPa and maintain it for 10 minutes, after which the high vacuum state is restored.

[0042] The battery is moved into a sealed thermo-pressure circulating chamber, and a temporary sealing clamp is used to connect with the battery cap injection hole. The internal miniature piezoresistive sensor is used to monitor the gas phase pressure, and the deployed thermocouple sensors are used to monitor the surface temperature of the casing. In the first stage of activation, inert gas is introduced into the chamber to apply a hydrostatic pressure of 0.1 MPa, and the temperature is set at 25°C and maintained for 6 hours to induce primary nucleation. Then, the second stage of activation begins, executing the gradient application procedure: The heating rate is set to 0.5℃ / min to the target temperature of 40℃, and the pressurization rate is set to 0.02MPa / min to the target pressure of 0.3MPa. At the same time, the adaptive closed-loop feedback logic is activated: if the pressure rise rate exceeds the safety threshold of 0.07MPa / min, a load reduction command is triggered to reduce the external pressurization rate or extend the pressure holding time; if the maximum temperature difference exceeds the set limit of 6℃, the hot air direction is dynamically adjusted or the power ratio of the zone heating tubes is adjusted.

[0043] After activation, the sealed connection is released, and a combined liquid retention and mechanical disturbance treatment is performed: A high-precision metering pump was used to perform a secondary quantitative replenishment, with the amount of the secondary quantitative replenishment being 5% of the amount of the initial replenishment. The battery was then moved into a negative pressure degassing chamber for negative pressure immersion (chamber pressure -0.09 MPa, total immersion time 6 hours). During the negative pressure immersion, the bottom physical disturbance tray was activated to perform intermittent physical intervention (specifically, intermittent rotary stirring). The kinetic parameters were set, with the working speed at 30 rpm and the duration of a single continuous disturbance at 3 minutes. Afterward, a settling period was initiated, with a settling interval of 0.5 hours. This cycle was repeated until the immersion was completed.

[0044] Remove the battery and perform steady-state stress relaxation: After completing the permanent sealing (using laser welding for airtightness), it is moved into a standardized constant temperature and humidity warehouse (temperature 30℃, relative humidity 30%) and left to stand for 10 hours to achieve equilibrium.

[0045] Example 3: This embodiment provides a method for temperature and pressure cycling activation and liquid retention performance improvement of large cylindrical batteries, including the following steps: Using the bare cell and non-aqueous electrolyte composition provided in Preparation Example 3, the theoretical total wettable pore volume of the inner electrode and separator of the large cylindrical battery was obtained. Then, according to the relational formula Set the wetting coefficient The value was 0.95, and the initial injection was completed to control the amount of fluid injected initially. ; The battery was then placed in a programmable vacuum drying oven for gradient vacuum pretreatment. The chamber is evacuated to a first vacuum level of -0.095 MPa and maintained for 6 hours. Then, the chamber is evacuated to a second vacuum level of -0.1 MPa and maintained for 6 hours. A pressure compensation operation is performed once during the settling period, which involves briefly refilling the chamber with dry inert gas to raise the chamber gauge pressure to -0.08 MPa and maintain it for 5 minutes, after which the high vacuum state is restored.

[0046] The battery is moved into a sealed thermo-pressure circulating chamber, and a temporary sealing clamp is used to connect with the battery cap injection hole. The internal miniature piezoresistive sensor is used to monitor the gas phase pressure, and the deployed thermocouple sensors are used to monitor the surface temperature of the casing. In the first stage of activation, inert gas is introduced into the chamber to apply a hydrostatic pressure of 0.3 MPa, and the temperature is set at 35°C and maintained for 4 hours to induce primary nucleation. Then, the second stage of activation begins, executing the gradient application procedure: The heating rate is set to 1.2℃ / min to the target temperature of 50℃, and the pressurization rate is set to 0.06MPa / min to the target pressure of 0.5MPa. At the same time, the adaptive closed-loop feedback logic is activated: if the pressure rise rate exceeds the safety threshold of 0.10MPa / min, a load reduction command is triggered to reduce the external pressurization rate or extend the pressure holding time; if the maximum temperature difference exceeds the set limit of 10℃, the hot air direction is dynamically adjusted or the power ratio of the zone heating tubes is adjusted.

[0047] After activation, the sealed connection is released, and a combined liquid retention and mechanical disturbance treatment is performed: A high-precision metering pump was used to perform a secondary quantitative replenishment, with the amount of the secondary quantitative replenishment being 15% of the amount of the initial replenishment. The battery was then moved into a negative pressure degassing chamber for negative pressure immersion (chamber pressure -0.1 MPa, total immersion time 12 hours). During the negative pressure immersion, the bottom physical disturbance tray was activated to perform intermittent physical intervention (specifically linear vibration). The dynamic parameters were set, with a vibration frequency of 60 times / minute (equivalent to 60 rpm) and a single continuous disturbance duration of 10 minutes. Afterward, a settling period was initiated, with a settling interval of 1.5 hours. This cycle was repeated until the immersion was completed.

[0048] Remove the battery and perform steady-state stress relaxation: After permanent sealing (using laser welding), the container is moved into a standardized temperature and humidity constant warehouse (temperature 35℃, relative humidity 45%) and left to stand for 20 hours to reach equilibrium.

[0049] Comparative Examples 1-4: Comparative Example 1: Compared with Example 1, the difference is that only ambient temperature and pressure natural immersion is performed, without gradient vacuum pretreatment, staged temperature and pressure activation, adaptive closed-loop feedback logic, and intermittent physical intervention; all other aspects are the same.

[0050] Comparative Example 2: Compared with Example 1, the difference is that in the pretreatment, only the second vacuum degree is continuously extracted and maintained, and no dry inert gas is introduced to perform the pressure compensation operation to restore the gauge pressure. All other aspects are the same.

[0051] Comparative Example 3: Compared with Example 1, the difference is that a constant high temperature and hydrostatic pressure (open-loop control) are used in the activation stage, ignoring the sudden change in the pressure rise rate and not triggering any load reduction command, that is, the adaptive closed-loop feedback logic is missing, but everything else is the same.

[0052] Comparative Example 4: The difference from Example 1 is that the negative pressure immersion period is always in a static state, and no intermittent physical intervention is applied by activating the bottom physical disturbance tray; otherwise, they are the same.

[0053] Test Examples 1-5: Test Example 1: Verification of the Process Response of Adaptive Closed-Loop Feedback Logic This test case aims to verify whether the adaptive closed-loop feedback logic in the sealed temperature and pressure cycling chamber responds as expected to the dynamic changes in the internal pressure of the battery and the temperature difference on the surface of the casing during the activation stage of the large cylindrical battery in Example 1.

[0054] Ten large cylindrical batteries (46mm in diameter and 80mm in height) from the same batch were selected and were in the dynamic regulation and accelerated activation stage.

[0055] A sealed temperature and pressure circulation chamber with an integrated high-frequency data acquisition module has a sampling frequency of 1Hz.

[0056] The temporary sealing clamp has a built-in miniature piezoresistive sensor with a range of 0 to 5 MPa to monitor real-time gauge pressure.

[0057] Thermocouple sensors are placed at the top, middle and bottom of the battery casing to calculate the maximum temperature difference.

[0058] The initial heating rate was set to 0.8℃ / min, and the initial pressurization rate was set to 0.04MPa / min.

[0059] The safety threshold is 0.08 MPa / min, and the set limit (temperature difference) is set to 8℃.

[0060] When the monitored rate of pressure rise If the pressure exceeds 0.08 MPa / min for two consecutive minutes, reduce the external pressurization rate. If the maximum temperature difference exceeds the set limit, adjust the hot air direction and the power ratio of the zone heating tubes.

[0061] Test data recording (basic pressure gauge): For ease of analysis, a representative data point was extracted every 5 minutes from the collected 1Hz high-frequency data. Due to the nonlinearity of the response and the slight noise of the sensor, reasonable fluctuations are expected in the data.

[0062] Table 1. Record of changes in key parameters during the activation phase over time.

[0063] Figure 1 The graph shows the changes in the rate of increase of internal battery pressure and the maximum temperature difference over time. The safety threshold, set limit, and key time points that trigger feedback are marked in the graph. Figure 2 The diagram shows the correspondence between the internal gas phase gauge pressure and the external fluid static pressure gauge pressure. The vertical line in the diagram reflects the intervention node where the external pressurization rate is reduced.

[0064] in conclusion: According to Table 1 and Figure 1 , Figure 2 The records show that during the initial stage of the activation process (0 to 15 minutes), the internal gas phase gauge pressure of the battery rises gradually, and the rate of pressure increase remains between 0.042 and 0.069 MPa / min, which is below the safety threshold; at the same time, the maximum temperature difference on the core surface is also at a low level. During this period, the external hydrostatic pressure rises steadily according to the initially set pressurization rate, indicating that the film formation reaction is in the initial nucleation stage, the electrochemical gas production is low, and the system is at the baseline thermodynamic input state.

[0065] As the activation process progressed to 20 minutes, the internal chemical reaction intensified, and the rapid release of byproduct gases caused the internal gauge pressure to rise. Data monitoring showed that at the 25-minute sampling point, the pressure rise rate climbed to 0.095 MPa / min, exceeding the safety threshold of 0.08 MPa / min. Simultaneously, due to the heat generated by the reaction and the thermal inertia of the large-sized core, the maximum temperature difference reached 8.5℃, exceeding the set limit of 8℃. The instantaneous exceeding of these two limits activated the adaptive feedback logic, and the system immediately implemented intervention measures, reducing the external fluid static pressure increase rate from 0.04 MPa / min to 0.02 MPa / min and dynamically adjusting the hot air direction to optimize heat distribution.

[0066] After implementing load reduction and thermal regulation intervention, the slope of the external pressure growth curve slowed significantly after 25 minutes, providing a buffer for the diffusion and dissolution of internal gases. As a result, the rate of increase in internal pressure dropped back to the safe zone of 0.068 MPa / min after 30 minutes, and the maximum temperature difference also decreased accordingly. The gradual convergence of the indicators indicates that the internal electrochemical reaction has returned to stability, and the solid electrolyte interfacial film can continue to grow under suitable temperature and pressure conditions, effectively avoiding physical damage to the interfacial film structure caused by excessively rapid gas production.

[0067] Based on the aforementioned dynamic response characteristics, it can be proven that the dynamic control mechanism based on dual closed-loop feedback of internal pressure and temperature difference proposed in this scheme can be effectively triggered in actual equipment operation. This mechanism, through precise process control, ensures the smooth implementation of the temperature-pressure cycle synergy mechanism, and verifies the feasibility of improving the interface consistency of large cylindrical batteries from an engineering perspective.

[0068] Test Example 2: Verification of Staged Liquid Absorption Volume in Multi-Stage Physically Assisted Infiltration

[0069] This test case aims to verify the substantial driving effect of pressure compensation operation in gradient vacuum pretreatment and mechanical disturbance in synergistic liquid retention on deep wetting of large cylindrical batteries by observing the evolution of macroscopic quality with process nodes.

[0070] Five bare cells from each of the large cylindrical batteries in the preparation stage in Example 1, Comparative Example 2, and Comparative Example 4 were selected as experimental samples. The initial dry weight of each cell was measured and recorded using a high-precision analytical balance in a drying room.

[0071] The first liquid injection was completed according to the wetting coefficient set for each group. After each group of samples completed the gradient vacuum pretreatment process independently, the residual liquid on the outside of the battery casing and the injection hole was cleaned with a lint-free cloth, the total weight was weighed again and the initial dry weight was deducted, and the absolute liquid absorption volume at the first node (after vacuum degassing) was recorded.

[0072] The sample was transferred to a sealed thermo-pressure circulating chamber for staged adaptive thermo-pressure cyclic activation. Immediately after activation, a second quantitative liquid replenishment was performed. After cleaning up the residual liquid, the sample was weighed, and the absolute liquid volume at the second node (after activation replenishment) was calculated.

[0073] Each group of samples was placed in a negative pressure degassing chamber for negative pressure immersion. In Example 1, intermittent rotary stirring was applied using a bottom physical disturbance tray, while in Comparative Example 4, the samples were kept completely still. After immersion, permanent sealing was performed, the shell was cleaned, and the final weight was measured. The standard weight of the bare battery cell and the sealing structure was deducted, and the effective residual liquid volume at the third node (after final equilibration) was calculated.

[0074] Test data record: Table 2. Evolution of Absolute Liquid Absorption in Large Cylindrical Batteries at Different Process Nodes

[0075] Figure 3 Subplot (a) shows the evolution trajectory of liquid absorption of samples from Example 1, Comparative Example 2 and Comparative Example 4 from the first node (after gradient vacuum pretreatment and degassing), the second node (after temperature and pressure activation and secondary quantitative liquid replenishment) to the third node (after negative pressure immersion and static sealing). The broken lines in the figure represent the mean data of each group.

[0076] Figure 3 Subplot (b) shows the scatter distribution of the final effective residual liquid volume at the end of the preparation process for the three test groups. Different geometric scatter points in the figure represent the actual test values ​​of individuals within the group, and the horizontal lines indicate the corresponding mean level within the group.

[0077] in conclusion: Based on Table 2 and Figure 3 It can be observed that under conventional process systems, large-size cores face significant physical resistance bottlenecks in deep fluid transport. Microchannels in industrial production environments are prone to capillary blockage, and the use of unidirectional continuous deep vacuum often exacerbates the surface tension lock-up phenomenon at the gas-liquid interface.

[0078] Based on this physical mechanism, Comparative Example 2, due to the removal of pressure compensation during the pretreatment stage, exhibited a generally low liquid absorption rate at the first node, with a sample mean of only 12.2 grams. This quality deficiency indirectly confirms that relying solely on ultimate vacuum cannot effectively expel the blind-end gas clusters. The blocked electrode network traps a large amount of liquid phase material on the outer layer of the core, causing early permeation stagnation. In contrast, Example 1 introduced a brief gauge pressure rebound intervention during vacuum settling, utilizing the slight pressure fluctuations in the external environment to force the trapped micro-gas clusters inside to undergo transient contraction and loosening. This loosened gas was effectively extracted during the secondary vacuuming, increasing the liquid absorption rate at the first node of Example 1 to approximately 13.45 grams, thus opening up the transport path for electrolyte transfer to deeper pores from the source.

[0079] With the completion of the activation reaction and the second quantitative replenishment, all groups showed an increase in mass at the second node. However, the actual challenge in determining the batch consistency of the cells often lies in the liquid phase retention capacity during the static sealing stage. After entering the negative pressure wetting stage, the imbalance of gravity distribution of the high-viscosity non-aqueous electrolyte along its long axis becomes apparent.

[0080] Although Comparative Example 4 received a sufficient amount of replenishing fluid, it remained in a static relaxation state throughout the process due to the lack of a bottom physical disturbance tray. Without external intervention, the liquid phase could not spontaneously overcome the lateral flow resistance between the porous membrane layers, resulting in a large amount of free electrolyte remaining near the injection port or at the bottom of the shell, and physically leaking out during the final sealing process. This led to a decrease in the effective retained fluid volume of Comparative Example 4 at the third node, a corresponding increase in the dispersion of samples within the group, and an inter-individual difference as high as 0.73 grams.

[0081] To address the aforementioned fluid retention problem, Example 1 employs intermittent rotary stirring applied in the same stage. By continuously introducing an alternating shear force field within the enclosed space of the cylindrical system, the original static distribution is disrupted. This mechanical kinetic energy effectively overcomes the resistance caused by fluid surface tension, forcing the electrolyte to undergo convective mixing in the radial plane.

[0082] The kinetic intervention not only weakened the concentration gradient caused by gravity, but also retained the free liquid more uniformly within the micropores of the electrode, stabilizing the final retained liquid volume of Example 1 at 14.8 grams. The evolution trajectory of the macroscopic weighing data, based on the above testing process, corroborates the practical effectiveness of pressure compensation and mechanical disturbance in improving deep wetting rate and maintaining system consistency in this scheme.

[0083] Test Example 3: Initial Electrochemical Characteristics and High-Rate Long-Term Cycle Life Assessment

[0084] This test case aims to verify the substantial impact of the physical intervention and dynamic feedback mechanism introduced in the activation and wetting stage on the interface quality and long-term reliability of large cylindrical batteries by analyzing the evolution of electrochemical performance parameters.

[0085] Four finished cylindrical batteries from Examples 1, 2, 1, and 3 that have undergone stabilization post-treatment were selected and transferred into a constant temperature explosion-proof test chamber, and then connected to a high-precision battery testing system.

[0086] At room temperature of 25°C, the initial AC internal resistance of all samples was measured at a frequency of 1kHz using an AC internal resistance tester to quantitatively evaluate the overall basic state of the porous electrode ohmic impedance and interfacial impedance after deep electrolyte wetting.

[0087] The sample underwent formation and standard capacity testing. It was charged at a constant current of 0.1C to the preset cutoff voltage and allowed to stand. Then it was discharged at a constant current of 0.1C to the lower limit voltage. The initial charge and discharge capacity data were recorded, and the initial coulombic efficiency was calculated based on this data.

[0088] The ambient temperature was raised to 45°C to simulate the heat accumulation and accelerated aging environment under actual working conditions. The charge / discharge rate was set to 1C / 1C, and continuous high-rate charge / discharge cycles were performed. At specific nodes of 500, 1000, 1500, and 2000 cycles, the discharge capacity data was extracted and its retention rate relative to the initial rated capacity was calculated.

[0089] Test data record: Table 3. Initial electrochemical characteristics and cycle life records of large cylindrical batteries in each group.

[0090] Figure 4 Subplot (a) shows the electrochemical interface characteristics established during constant current formation of battery samples from Examples 1, 2, Comparative Example 1 and Comparative Example 3. The influence of each process route on the internal penetration uniformity is mapped by a two-dimensional scatter plot with the initial AC internal resistance (mΩ) as the x-axis and the initial coulombic efficiency (%) as the y-axis. Figure 4 Subplot (b) shows the evolution of capacity retention (%) of each group of representative battery samples with the number of cycles under 45°C and 1C charge / discharge rate conditions. The figure marks the 80% life warning line to reflect the impact of different activation mechanisms on cycle life.

[0091] in conclusion: Based on Table 3 and Figure 4It is known that the capacity decay trajectory of large-size cylindrical batteries during long-term cycling is correlated with the quality of early interfacial film formation. As a direct mapping of the microscopic wetting state to the macroscopic electrochemical level, AC internal resistance can often expose dry defects deep within the electrode in advance.

[0092] Test results show that Comparative Example 1, using traditional natural wetting and conventional formation processes, not only saw its internal resistance rise to over 3.6 mΩ overall, but also exhibited significant dispersion among samples, with some reaching a high impedance level of 4.1 mΩ. This structural deficiency at the fundamental physical interface forces the consumption of a large amount of active lithium during the formation stage to repeatedly fill the structural pores in the unwetted areas, resulting in an initial coulombic efficiency that is generally difficult to reach 89%. Furthermore, in subsequent 1C high-rate penetration tests, due to electrode breathing expansion leading to an increase in the dry area and the accompanying vicious cycle of microscopic lithium deposition, the capacity of batteries constructed using the traditional method rapidly declines after 1000 cycles, failing to meet the application requirements of long-life energy storage systems.

[0093] In engineering practice, to shorten production cycle time, a compromise solution of applying forced pressure in one direction is often adopted, and Comparative Example 3 represents the actual effect of this open-loop process. Although the constant external hydrostatic pressure forces liquid phase permeation, reducing internal resistance to some extent, the high-pressure environment of the open loop prevents gaseous byproducts from dissipating in time due to the intense electrochemical gas generation behavior in the early stages of formation. The nascent fragile interfacial film is locally damaged by the continuously rising internal bubbles, causing this solid electrolyte interfacial film containing microcracks to continuously consume limited free electrolyte for reconstruction during subsequent long-term cycles. This process triggers an irreversible increase in system impedance, resulting in a capacity retention rate of only around 73% after 2000 cycles, failing to fundamentally extend cycle life.

[0094] In comparison, the data matrix of the example samples exhibits better consistency and improved overall performance. The internal pressure feedback mechanism precisely triggers load reduction intervention during peak gas production, providing a time window for the smooth escape of gaseous substances and effectively avoiding damage to the electrode interface. Combined with intermittent physical intervention at specific rotation speeds in the later stages, the replenishing fluid is stably retained deep within the pore network. This dense and uniform physicochemical dual interface not only stabilizes the internal resistance at around 2.2 mΩ but also improves the first-efficiency to an industry-leading level of 92.5%, endowing the example samples with extremely strong thermodynamic stability and anti-polarization capability. Based on the above optimizations, this group of samples maintained above 80% capacity retention after undergoing 2000 high-intensity destructive cycles, thus truly transforming laboratory mechanistic assumptions into industrial-grade product reliability.

[0095] Test Example 4: Evaluation of Static Self-Discharge Rate and High-Temperature Interface Stability

[0096] This test case aims to examine the intrinsic physical integrity and resistance to side reactions of a solid electrolyte interface membrane constructed through adaptive closed-loop feedback logic under long-term static storage and high-temperature thermal stress.

[0097] Five large cylindrical batteries from Examples 1, 2, 1, and 3, which had undergone stabilization and were fully charged to 100% state of charge, were selected as experimental subjects and placed in a standard explosion-proof test environment at 25°C for 24 hours to eliminate the initial polarization voltage.

[0098] The initial open-circuit voltage of each sample was tested and recorded using a high-precision multimeter. The batteries were then transferred to a 25°C insulated and dry environment and left to stand for 14 consecutive days. After the standing period, the open-circuit voltage was measured again. The physical self-discharge rate (K value, in mV / day) was calculated by the ratio of the initial and final voltage differences to the standing time. This indicator is mainly used to evaluate the insulation passivation and micro-leakage prevention performance of the electrode interface at room temperature.

[0099] The samples that completed the room temperature self-discharge test were directly transferred to a 60°C high-temperature explosion-proof constant temperature chamber for extreme thermal storage testing, with a continuous storage time set at 30 days. During storage, the appearance of the battery casing was inspected regularly to check for abnormal expansion. After storage, all samples were removed and allowed to stand at 25°C for 48 hours.

[0100] The battery samples after high-temperature recovery were retested with 1kHz AC internal resistance. The final impedance data was recorded and compared with the initial internal resistance after full charge before testing. The AC internal resistance growth rate was calculated to quantify the degree of degradation of the internal structure of the porous electrode under high-temperature thermal stress.

[0101] Test data record: Table 4. Record of self-discharge rate at room temperature and degradation of internal resistance at high temperature for large cylindrical batteries in each group.

[0102] Figure 5 Subplot (a) shows the distribution of self-discharge rate K values ​​(mV / day) of battery samples from Examples 1, 2, Comparative Examples 1 and 3 under 14-day room temperature static conditions. The geometric scatter points in the figure represent the test values ​​of individuals in each group, and the group mean trajectory connected by solid lines reflects the average self-discharge level under different process systems. Figure 5 Subplot (b) shows the distribution of the AC internal resistance growth rate (%) of the battery after 30 days of storage at 60°C. Different geometric scatter points are used to identify the individual test values ​​of Example 1, Example 2, Comparative Example 1 and Comparative Example 3. The group mean trajectory connected by the dashed line reflects the internal resistance change trend of each group under high temperature environment.

[0103] in conclusion: Based on Table 4 and Figure 5 It is evident that the slight voltage decay at room temperature and the significant increase in impedance at high temperatures are closely related in an electrochemical dimension. Together, they reflect the inherent defects of the solid electrolyte interface film in terms of density and mechanical toughness. Based on actual experience in the manufacturing of large-size cores, it can be found that the microscopic side reactions in the early stages of formation are often easily masked by the seemingly normal macroscopic voltage performance, causing potential interface hazards to flow into subsequent use stages.

[0104] The test results show that Comparative Example 1, using a conventional natural wetting system, exhibited uneven electrolyte penetration, resulting in numerous exposed graphite areas at the interface that were not effectively covered by film-forming additives. In these microscopic blind spots, the free electrolyte continuously underwent a slow reduction reaction, constantly consuming the active lithium ions within the system, leading to an abnormally high self-discharge rate at room temperature. Some samples even exceeded 0.6 mV / day. When these inherently defective samples were placed in a high-temperature catalytic environment of 60°C, the previously incomplete passivation layer failed to provide effective physical protection. The accompanying solvent co-intercalation and by-reaction product accumulation caused the internal resistance growth rate to generally climb to over 39%.

[0105] In engineering practice, attempts to improve the interface by simply applying external physical constraints revealed limitations in the data feedback of Comparative Example 3. Although constant external hydrostatic pressure compacted the core layers to some extent, during the core stage of formation where intense gas generation occurred, the continuously expanding gas could not be effectively buffered and released due to the lack of adaptive closed-loop feedback logic for gas phase pressure. The accumulated gas pressure stress locally damaged the nascent and fragile interface film, leading to repeated alternations of reconstruction and rupture on the negative electrode surface. This damaged film with microcracks, while suppressing early leakage to some extent and reducing the average K value to around 0.36 mV / day, still experienced rapid expansion of microcracks under continuous high-temperature thermal stress. The influx of fresh electrolyte into the cracks caused further interface thickening, resulting in a persistently high rate of internal resistance degradation.

[0106] In contrast, the data matrix of the embodiments verifies the positive improvement effect of dynamic thermodynamic intervention on the electrode film structure. Embodiment 1, relying on precise monitoring of the pressure rise rate and real-time coordination of unloading commands, provides sufficient physical unloading space for the gradual escape of gaseous byproducts. Under this feedback mechanism, the external physical extrusion pressure and the internal chemical expansion force achieve a dynamic equilibrium, enabling the film-forming additives to crystallize and grow a dense, complete interface layer with good mechanical properties on the electrode surface. This high-quality intrinsic isolation barrier effectively blocks the electron tunneling leakage path, controlling the self-discharge K value to an excellent range of 0.15 mV / day.

[0107] Even during a month-long high-temperature test, the protective film constructed using temperature and pressure synergistic control technology maintained high physical integrity, effectively isolating the continuous consumption of electrolyte and the spread of side reactions. Based on the above structural advantages, the final AC internal resistance growth rate of the embodiment was controlled within the aging threshold of approximately 10%, thus confirming the core engineering value of the present invention in improving the long-term reliability of large cylindrical batteries from the perspective of microscopic interface stability.

[0108] Test Example 5: Evaluation of Temperature Rise During High-Rate Fast Charging and Low-Temperature Wide-Range Discharge Performance

[0109] This test case aims to verify the profound impact of physical intervention mechanisms in the pretreatment and immersion stages on the uniformity of fluid distribution and ion transport dynamics inside a large cylindrical battery through extreme full life cycle application conditions.

[0110] Five large cylindrical batteries that had completed standard capacity testing and were in a 100% state of charge from Examples 1, 3, 1, and 4 were selected as experimental samples. All samples were placed in a constant temperature explosion-proof test chamber at 25°C and left to stand for 3 hours to ensure initial thermal equilibrium.

[0111] High-precision K-type thermocouples were attached to the geometric center height of the cylindrical steel casing of the battery and to the positive and negative electrode leads. The testing equipment was started, and all samples were subjected to 3C high-rate constant current charging to the upper limit cutoff voltage. During this period, the surface temperature data of the casing was recorded in real time at a sampling rate of 1Hz. The highest surface temperature during the charging process was extracted, and the absolute value of the temperature rise during high-rate fast charging was calculated. ).

[0112] After the charging test, the sample was discharged to a depleted state at a standard rate of 0.3C and then fully charged. It was then transferred to a high and low temperature alternating damp heat test chamber. The ambient temperature was set to -20℃, and the sample was continuously immersed at this constant temperature for 12 hours to ensure that the internal temperature of the large-size core was completely cooled and reached the set low temperature steady state.

[0113] In an extremely cold environment of -20℃, the control test cabinet performs constant current discharge at a discharge rate of 1C on the constant-temperature sample until the lower cutoff voltage. The actual discharge capacity under low-temperature conditions is recorded, and its ratio with the nominal capacity at room temperature of 25℃ is calculated to obtain low-temperature discharge capacity retention data, which is used to evaluate the ion conduction hysteresis at the interface under extreme operating conditions.

[0114] Test data record: Table 5. Record of Fast Charging Temperature Rise and Low-Temperature Discharge Performance of Large Cylindrical Batteries in Each Group

[0115] Figure 6 Subplot (a) shows the surface temperature rise (°C) distribution of the battery under 3C fast charging at 25°C. Hollow geometric scatter points correspond to the individual test values ​​of Example 1, Example 3, Comparative Example 1 and Comparative Example 4. The mean trajectory connected by solid lines marks the average heat accumulation level of each group. Figure 6 Subplot (b) shows the low-temperature capacity retention (%) of the battery at -20°C. Different geometric scatter points are used to identify the individual test results of Example 1, Example 3, Comparative Example 1 and Comparative Example 4. The mean trajectory connected by the dashed line reflects the physical effect of internal fluid wetting uniformity on suppressing low-temperature polarization.

[0116] in conclusion: Based on Table 5 and Figure 6 It can be seen that the macroscopic electrochemical performance of large cylindrical batteries at extreme rates and extreme temperatures is essentially a concentrated mapping of the connectivity and uniformity of the internal fluid pore network.

[0117] Based on the test results, Comparative Example 1, manufactured under conventional conditions, exhibited a significant tendency for heat accumulation when faced with high-intensity charging currents (3C). Due to the lack of vacuum assistance and physical electrolyte retention, a large number of unwetted dead zones existed within its core. These dry zones hindered the electrochemical reaction while forcing the wetted areas that actually participated in the reaction to bear localized ultra-high current densities far exceeding those of 3C.

[0118] This localized current convergence triggered Joule heating and polarization heat generation, causing the surface temperature of Comparative Example 1 to rise to over 30°C, with the highest individual temperature even approaching the safety threshold of 60°C. Furthermore, when the test environment was switched to -20°C, the electrolyte's viscosity increased dramatically and its ionic conductivity plummeted. The originally incomplete liquid phase transport path in Comparative Example 1 was significantly blocked under low-temperature stress, resulting in a decrease in discharge capacity retention to below 50%, thus limiting the battery's wide-temperature-range operating capability.

[0119] Engineering practice shows that if only the total amount of liquid replenishment is considered while neglecting the intervention of fluid distribution, it is difficult to eliminate the radial transmission bottleneck of large-size cores. For example, although Comparative Example 4 completed the secondary liquid replenishment operation, it was in a static state during the wetting stage, eliminating the physical disturbance intervention at the bottom. Under these conditions, the high-viscosity secondary replenishment liquid is trapped at the complex interface between the porous electrode and the diaphragm, and accumulates in large quantities in the outer winding area under the action of capillary resistance, making the deep electrode still relatively liquid-deficient. This spatial distribution imbalance directly leads to regional differences in internal resistance. In fast charging tests, its temperature rise data reached a relatively high level of about 24°C, and in -20°C discharge, it lost nearly 40% of the usable capacity due to the lag in the transport of deep ions.

[0120] In contrast, the example group improved this static rheological limitation by introducing mechanical intervention during the negative pressure wetting stage. Example 1 employed intermittent rotary stirring, which created a continuous alternating inertial force field within the closed cylindrical cavity. This effectively overcame the surface tension of the fluid through weak shear force, forcing the electrolyte to penetrate deeply into the pore network at the deepest point of the core. This active penetration mechanism at the physical level not only established a highly uniform and continuous ion conduction network within the three-dimensional space of the electrode but also fundamentally reduced the local density of the reaction current.

[0121] Based on the above structural optimizations, in terms of macroscopic performance, the high-rate temperature rise of the sample was stably controlled within a safe range of around 15°C; even at a low temperature of -20°C, the robust conduction network still ensured more than 72% capacity release. The comprehensive test data further demonstrates the practical engineering significance of this physical-synergistic liquid retention process in improving the intrinsic safety and all-climate adaptability of the battery.

Claims

1. A method for temperature and pressure cycling activation and improving liquid retention performance of large cylindrical batteries, characterized in that, Includes the following steps: Obtain a bare cell for a large cylindrical battery for assembly, the bare cell having an internal core formed by alternating winding of a positive electrode sheet, a negative electrode sheet and a separator, and obtain a non-aqueous electrolyte composition, and perform the first electrolyte injection on the bare cell; The large cylindrical battery that has completed its first liquid injection is placed in a programmable vacuum drying oven for gradient vacuum pretreatment, and pressure compensation is performed during the settling period. The pretreated large cylindrical battery is moved into a sealed temperature and pressure cycling chamber and activated in stages. In the second stage of activation, a gradient application procedure is executed and an adaptive closed-loop feedback logic is initiated. When the pressure rise rate exceeds the safety threshold, a load reduction command is triggered to generate a dense solid electrolyte interface film on the surface of the negative electrode. After activation, a combined liquid retention and mechanical disturbance process is performed. The combined liquid retention process includes using a high-precision metering pump to perform secondary quantitative liquid replenishment and moving the battery into a negative pressure degassing chamber for negative pressure immersion. During the negative pressure immersion, intermittent physical intervention is initiated until the immersion is completed. The large cylindrical battery is removed and subjected to steady-state stress relaxation to complete permanent sealing and static balancing.

2. The method for temperature and pressure cycling activation and liquid retention performance improvement of a large cylindrical battery according to claim 1, characterized in that, The non-aqueous electrolyte composition is made from raw materials comprising the following components: A mixed organic solvent, which is composed of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate, wherein the volume ratio of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate is (2-4):(3-4):(3-4). The lithium salt has a molar concentration of 1.0-1.2 mol / L in the mixed organic solvent; Film-forming additives are added in an amount of 1% to 10% of the total mass of the non-aqueous electrolyte composition.

3. The method for temperature and pressure cycling activation and liquid retention performance improvement of a large cylindrical battery according to claim 2, characterized in that, The lithium salt is lithium hexafluorophosphate; The film-forming additive is one or a combination of several of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate.

4. The method for temperature and pressure cycling activation and liquid retention performance improvement of a large cylindrical battery according to claim 1, characterized in that, The diameter of the bare battery cell is greater than or equal to 30 mm and the height is greater than or equal to 80 mm; The amount of liquid injected initially is equal to the product of the theoretically wettable total volume of the bare cell and the wetting coefficient. The value of the wetting coefficient is set to be between 0.85 and 0.

95.

5. The method for temperature and pressure cycling activation and liquid retention performance improvement of a large cylindrical battery according to claim 1, characterized in that, The steps of gradient vacuum pretreatment and performing pressure compensation during the settling period specifically include: Entering the first stage of vacuum, the cavity of the programmable vacuum drying oven is evacuated to a first vacuum degree of -0.095 to -0.08 MPa, and left to stand for a first period of time, which is 6 to 12 hours; The second stage of vacuum is then initiated, in which the cavity is evacuated to a second vacuum level of -0.1 to -0.096 MPa and left to stand for a second period of 6 to 12 hours. At least one pressure compensation operation is performed during the settling period of the second stage vacuum, namely, briefly refilling the chamber with dry inert gas to raise the chamber gauge pressure to -0.08 to -0.05 MPa and maintain it for 5 to 10 minutes, and then restoring the high vacuum state.

6. The method for temperature and pressure cycling activation and liquid retention performance improvement of a large cylindrical battery according to claim 1, characterized in that, After the large cylindrical battery is moved into the sealed temperature and pressure circulation chamber, a temporary sealing clamp is used to connect with the liquid injection hole of the battery cap. The gas phase pressure is monitored by a miniature piezoresistive sensor inside the temporary sealing clamp, and the surface temperature of the large cylindrical battery casing is monitored by a thermocouple sensor.

7. The method for temperature and pressure cycling activation and liquid retention performance improvement of a large cylindrical battery according to claim 6, characterized in that, The activation is divided into a first stage and a second stage; In the first stage of activation, an inert gas is introduced into the sealed thermo-pressure circulating chamber to apply a hydrostatic pressure of 0.1 to 0.3 MPa, and the temperature is set to 25 to 35°C and maintained for 4 to 6 hours to induce primary nucleation.

8. The method for temperature and pressure cycling activation and liquid retention performance improvement of a large cylindrical battery according to claim 7, characterized in that, In the second stage of activation: The specific parameters of the gradient application procedure are as follows: The heating rate is set to 0.5 to 1.2℃ / min to reach the target temperature of 40 to 50℃, and the pressurization rate is set to 0.02 to 0.06MPa / min to reach the target pressure of 0.3 to 0.5MPa. The specific method for activating the adaptive closed-loop feedback logic is as follows: If the pressure rise rate exceeds the safety threshold, the load reduction command is triggered to adjust external parameters, including at least one of reducing the pressurization rate and extending the pressure holding time. If the maximum temperature difference exceeds the set limit, adjust the hot air direction or adjust the power ratio of the zone heating elements; The safety threshold is preset based on the electrochemical gas generation characteristics of the non-aqueous electrolyte composition and the casing pressure resistance limit. The setting range of the safety threshold is 0.07 to 0.12 MPa / min. The setting limit is preset based on the size specifications and thermal conductivity characteristics of the large cylindrical battery. The setting range of the setting limit is 5 to 12°C.

9. The method for temperature and pressure cycling activation and liquid retention performance improvement of a large cylindrical battery according to claim 1, characterized in that, The steps for performing coordinated liquid retention and mechanical disturbance treatment specifically include: The second quantitative fluid replacement is performed, and the amount of the second quantitative fluid replacement is set to 5% to 15% of the amount of the first fluid injection. Negative pressure immersion is performed in the negative pressure degassing chamber, with the chamber pressure controlled at -0.1 to -0.09 MPa and the total immersion time being 6 to 12 hours. During the negative pressure immersion, the bottom physical disturbance tray is activated to perform the intermittent physical intervention, which is intermittent rotary stirring or linear vibration, and the dynamic parameters are set as follows: When using the intermittent rotary stirring method, the operating speed is 30 to 45 rpm; When the linear vibration is used, the vibration frequency is 30 to 60 times per minute; The duration of a single continuous disturbance is 3 to 10 minutes; Then a settling period is initiated, with the settling interval set at 0.5 to 1.5 hours, and this cycle is repeated until the soaking process is complete.

10. The method for temperature and pressure cycling activation and liquid retention performance improvement of a large cylindrical battery according to claim 1, characterized in that, The specific steps for removing the large cylindrical battery, performing steady-state stress relaxation, and completing permanent sealing and static balancing include: The permanent seal is completed using laser welding. The large cylindrical battery is moved into a standardized constant temperature and humidity warehouse and placed for static equilibration for 10 to 20 hours at a temperature of 30 to 35°C and a relative humidity of 30% to 45%.

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