A method for evaluating and controlling pressure consistency in a solid-state battery isostatic pressing process

Abstract

The present application relates to battery manufacturing quality detection technical field, propose a kind of solid-state battery isostatic pressing process pressure consistency evaluation and control method, comprising: S1, preparation built-in patterned pressure sensor's sample battery current collector;S2, preparation has the sample battery of multichannel pressure detection signal lead-out structure;S3, the sample battery is placed into isostatic pressing equipment with actual to-be-processed solid-state battery to obtain the pressure detection signal of each pressure detection area in the sample battery;S4, according to the pressure detection signal of each pressure detection area in the sample battery, obtain the pressure characteristics of each pressure detection area, and carry out isostatic pressing process pressure consistency evaluation;S5, the pressure consistency evaluation result is fed back to isostatic pressing equipment control system, and isostatic pressing process parameters are regulated and controlled.The present application realizes isostatic pressing process pressure consistency evaluation and the regulation and control optimization of isostatic pressing process parameters, improves battery performance consistency and production reliability.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing quality inspection technology, and in particular to a method for evaluating and controlling the pressure consistency during the isostatic pressing process of solid-state batteries. Background Technology

[0002] With the increasing demand for high-energy-density and high-safety batteries in fields such as new energy vehicles, energy storage power stations, low-altitude aircraft, and high-end consumer electronics, solid-state batteries, which use solid electrolytes instead of traditional liquid electrolytes, have advantages such as high safety, good thermal stability, and great potential for energy density improvement, and have become an important development direction for next-generation lithium batteries. However, the performance of solid-state batteries is highly dependent on the interfacial contact state between the electrodes and the solid electrolyte. Since solid electrolytes usually lack the wetting ability of liquid electrolytes, there are easily problems such as pores, interfacial gaps, or insufficient local contact between the positive electrode active material, negative electrode material, and solid electrolyte, resulting in discontinuous ion transport paths, increased interfacial impedance, insufficient battery capacity, and decreased cycle stability. In order to improve the contact state between particles, layers, and interfaces inside solid-state batteries, pressure processing processes such as hot pressing, rolling, molding, and isostatic pressing are usually introduced during cell manufacturing. Among them, the isostatic pressing process can apply relatively uniform external pressure to the battery or battery semi-finished product through a pressure medium, which is beneficial to improve the densification degree of solid electrolyte and the degree of interfacial adhesion, and is one of the important process methods in solid-state battery manufacturing.

[0003] In the isostatic pressing process of solid-state batteries, factors such as pressure magnitude, pressurization rate, holding time, depressurization rate, temperature conditions, pressure medium state, pressure-bearing fixture structure, and battery placement all affect the pressure state of different areas inside the battery. Even if the external pressure set by the equipment meets the process requirements, the actual pressure experienced by different areas inside the battery may not be consistent. For example, there may be pressure differences between the central and edge areas, the tab area and the main body area, and the upper and lower areas, resulting in uneven compaction of solid-state batteries, inconsistent interface contact, and performance fluctuations in batch products. Therefore, a method for pressure consistency assessment and control in the isostatic pressing process of solid-state batteries is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to assess the pressure consistency during isostatic pressing and optimize the control of isostatic pressing process parameters, thereby improving battery performance consistency and production reliability. To achieve the above objective, this invention provides a method for assessing and controlling the pressure consistency during the isostatic pressing process of solid-state batteries, with the following specific steps: S1. Preparation of a sample battery current collector with built-in patterned pressure sensors: Multiple patterned pressure sensors are pre-embedded in the positive electrode current collector, negative electrode current collector, or special detection current collector of the sample battery to form multiple pressure detection areas, wherein the patterned pressure sensor is a pressure sensor with a preset shape pattern. S2. Prepare a sample battery with a multi-channel pressure detection signal lead-out structure: independently lead out the patterned pressure sensors in different pressure detection areas inside the sample battery, so that each patterned pressure sensor corresponds to a set of independent detection lead-out terminals, and obtain a sample battery with a multi-channel pressure detection signal lead-out structure. S3. Place the sample battery and the actual solid-state battery to be processed together into an isostatic pressing device to obtain the pressure detection signals of each pressure detection area inside the sample battery. S4. Based on the pressure detection signals of each pressure detection area inside the sample battery, obtain the pressure characteristics of each pressure detection area, and perform a pressure consistency evaluation of the isostatic pressing process: Based on the pressure detection signals of each pressure detection area inside the sample battery, obtain the pressure characteristics of each pressure detection area in the isostatic pressing process, and compare and analyze the pressure characteristics of different pressure detection areas inside the sample battery to obtain a pressure consistency evaluation index, thereby quantitatively evaluating the consistency of the isostatic pressing process. S5. Feedback the pressure consistency assessment results to the isostatic pressure equipment control system to adjust the isostatic pressure process parameters: Use the pressure characteristics and the pressure consistency assessment index as feedback inputs, and automatically or manually adjust the isostatic pressure process parameters according to the pressure consistency assessment results.

[0005] Preferably, in step S1, the pressure detection area is set according to the pressure transmission path and potentially inconsistent pressure distribution of the sample battery during the isostatic pressing process. Multiple patterned pressure sensors are arranged in partitions corresponding to multiple pressure detection areas to convert the pressure state of the sample battery at different positions during the isostatic pressing process into collectable electrical signal changes. The partitioned arrangement of the multiple patterned pressure sensors includes: for sample batteries that need to evaluate the overall surface pressure uniformity, the patterned pressure sensors can be arranged as a combination of the center point, four corner points, and edge points of the sample battery; for sample batteries that need to evaluate the pressure condition of the tab area, the patterned pressure sensor can be set separately in the area near the tab of the sample battery; for sample batteries that need to evaluate the pressure transmission consistency of the stacked structure, multiple patterned pressure sensors can be set along the length direction, width direction, and / or thickness direction of the sample battery.

[0006] Preferably, in step S1, the patterned pressure sensor is calibrated for pressure-electrical signals after the sample battery is prepared, and the correspondence between the resistance change rate and pressure of each pressure detection area is established.

[0007] Preferably, in step S2, the sample battery and the actual solid-state battery to be processed are placed simultaneously in the same isostatic chamber, the same pressure medium, the same pressure-bearing fixture, and the same battery stacking unit with the same placement direction. This allows the sample battery and the actual solid-state battery to undergo the same or similar pressure increase rate, holding pressure, holding time, pressure release rate, temperature conditions, pressure medium flow state, and fixture constraint state. During the pressure increase, holding, and pressure release processes, the resistance changes of each patterned pressure sensor inside the sample battery are collected in real time and converted into pressure values ​​of the corresponding pressure detection areas. The pressure detection signals from each pressure detection area inside the sample battery are used to characterize the pressure state of the actual solid-state battery to be processed during the isostatic process.

[0008] Preferably, in step S2, the channels are electrically insulated from each other and electrically isolated from the positive and negative main circuits of the sample battery to ensure that the pressure detection signal is not interfered with by the electrochemical circuit of the sample battery or other channels; the form of the detection lead includes detection tabs, metal leads, flexible circuit boards, multi-channel connection terminals or other lead structures that can maintain conductivity under isostatic pressure conditions; before the sample battery enters the isostatic pressure equipment, the initial resistance, insulation resistance and conductivity of each channel are tested to confirm that the signals of each patterned pressure sensor are stable, there are no short circuits between the channels, and the detection circuit and the main circuit of the sample battery are electrically insulated.

[0009] Preferably, in step S3, the actual solid-state battery to be processed includes a finished solid-state battery or a semi-finished solid-state battery that has undergone isostatic pressing. The sample battery has the same or similar external dimensions, stacked structure, packaging form, thickness, material system, or mechanical response characteristics as the actual solid-state battery to be processed. The sample battery is placed at the center, edge, or multiple representative positions of the actual solid-state battery pack to be processed to evaluate the pressure consistency at different spatial positions within the isostatic pressing chamber.

[0010] Preferably, in step S4, the pressure characteristics include the real-time pressure value, maximum pressure value, minimum pressure value, average pressure value, pressure change rate, pressure response delay time, pressure fluctuation amplitude during the pressure holding stage, and pressure recovery time during the pressure release stage for each pressure detection area. The pressure consistency evaluation indicators include pressure range, pressure standard deviation, coefficient of variation, pressure gradient, and pressure change rate. When each of the pressure consistency evaluation indicators exceeds its set threshold, it is determined that there is a pressure inconsistency problem in the isostatic process. The pressure consistency assessment is conducted for the pressurization phase, the pressure holding phase, and the pressure relief phase to distinguish different types of problems, including uneven pressure transmission, insufficient pressure holding stability, and inconsistent pressure relief recovery.

[0011] Preferably, in step S5, adjusting the isostatic pressing process parameters includes adjusting the pressure curve, pressurization rate, holding pressure, holding time, depressurization rate, temperature conditions, tooling structure, pressure medium state, or the placement of the sample battery and the actual solid-state battery to be processed in the isostatic pressing equipment, so that the actual pressure distribution during the isostatic pressing process tends to be uniform; the specific adjustment method includes controlling the target holding pressure based on the average pressure, controlling pressure consistency based on the pressure range or pressure standard deviation, controlling the pressurization rate and depressurization rate based on the pressure change rate, and controlling the holding time and pressure compensation strategy based on the pressure fluctuation during the holding stage.

[0012] Preferably, in step S5, the static pressure equipment control system can use a neural network algorithm to output optimized isostatic pressure process parameters using isostatic pressure, pressure increase rate, pressure holding time, pressure release rate, temperature, sample battery position, pressure characteristics of each pressure detection area, and solid-state battery performance indicators after processing as input and training data.

[0013] Preferably, step S5 further includes establishing an isostatic pressing process database based on the pressure consistency evaluation results of sample batteries from different batches, for long-term monitoring of the isostatic pressing equipment status, identification of pressure field drift in the isostatic pressing equipment, and continuous optimization of the solid-state battery mass production process.

[0014] The beneficial effects of this invention are as follows: (1) This invention can convert the internal pressure state, which is difficult to obtain directly during the isostatic pressing process of solid-state batteries, into detectable, recordable, and analyzable electrical signals, thereby achieving in-situ evaluation of pressure consistency during the isostatic pressing process. In this way, this invention can directly obtain the actual pressure response of different regions inside the sample battery, thus more accurately evaluating the pressure uniformity of the solid-state battery in the isostatic pressing process. It can promptly detect and correct pressure unevenness during processing, resulting in a more consistent compaction effect in different regions of the solid-state battery. This improves the stability of the solid-state battery manufacturing process, reduces batch-to-batch differences, and enhances battery performance consistency and production reliability.

[0015] (2) The present invention can establish a quantitative pressure consistency evaluation index, which can quantitatively determine the pressure difference between different detection areas, and identify pressure inconsistency problems in the isostatic process according to the set threshold. It can directly form a quantifiable, comparable and traceable pressure consistency evaluation result in the isostatic process.

[0016] (3) This invention can promptly identify pressure inconsistencies caused by isostatic pressing equipment, pressure-bearing fixtures, pressure medium conditions, and battery placement. By placing the sample battery at the center, edge, or multiple representative locations of the actual solid-state battery pack to be processed, and collecting pressure signals from different areas inside the sample battery in real time, this invention can determine whether the pressure transmission at different spatial locations within the isostatic pressing chamber is consistent, and can also determine whether there are local pressure anomalies in the battery's central area, edge area, corner area, and near the tabs, providing a basis for isostatic pressing equipment maintenance, fixture optimization, and production layout optimization.

[0017] (4) This invention can feed back the pressure consistency assessment results to the isostatic pressing equipment control system, thereby realizing the regulation and optimization of isostatic pressing process parameters. This invention uses multi-point pressure signals inside the sample battery as feedback inputs, adjusting the target holding pressure based on the pressure average, adjusting pressure consistency based on the pressure range or standard deviation, adjusting the pressure increase and release rates based on the pressure change rate, and adjusting the holding time and pressure compensation strategy based on pressure fluctuations during the holding phase. In this way, this invention transforms the isostatic pressing process from open-loop control based solely on equipment settings to feedback control based on the actual pressure state inside the sample battery, thereby improving the accuracy and adaptability of isostatic pressing process parameter settings. Attached Figure Description

[0018] To more intuitively illustrate the technical solutions of the embodiments of the present invention, the key drawings involved in the implementation process will be briefly described below. The drawings listed below are only used to illustrate some typical verification embodiments of the present invention. For those skilled in the art, other equivalent graphic derivative expressions can be obtained based on these basic drawings without creative effort.

[0019] Figure 1 This is a simplified flowchart of the method for evaluating and controlling the pressure consistency during the isostatic pressing process of solid-state batteries according to the present invention.

[0020] Figure 2 This is the grid-patterned pressure sensor used in the embodiments of the present invention.

[0021] Figure 3 This is the serpentine patterned pressure sensor used in the embodiments of the present invention.

[0022] Figure 4 This is the interdigitated patterned pressure sensor used in the embodiments of the present invention.

[0023] Figure 5 This is a schematic diagram of the patterned pressure sensor arrangement in different pressure detection areas of the sample battery in an embodiment of the present invention.

[0024] Figure 6This is a schematic diagram of the arrangement of the sample battery inside the isostatic pressure device and its connection with the control device in an embodiment of the present invention.

[0025] Figure reference numerals: 1-Multi-channel flexible circuit board, 2-Soft-pack battery, 3-Flexible insulating mold, 4-Fixed bracket, 5-Pressure equipment, 6-Isostatic pressure equipment, 7-Liquid pressure transmission medium, 8-Pressure acquisition line, 9-Sealed wiring interface, 10-Pressure acquisition device, 11-Computer. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Those skilled in the art will understand that, unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as herein.

[0027] This embodiment provides a method for evaluating and controlling the pressure consistency during the isostatic pressing process of solid-state batteries. The method uses a sample battery with a built-in multi-point patterned pressure sensor as the monitoring carrier for the isostatic pressing process. This sample battery is placed together with actual solid-state batteries from the same batch to be processed in a cold isostatic pressing apparatus. Pressure signals from different regions inside the sample battery are collected in real time during the pressurization, holding, and depressurization processes. The pressure consistency during the isostatic pressing process is evaluated based on the multi-point pressure signals. Furthermore, the pressure consistency evaluation results are fed back to the isostatic pressing apparatus control system to regulate the pressurization rate, holding pressure, holding time, and depressurization rate.

[0028] Step 1: Prepare a sample battery for isostatic pressing process monitoring, and pre-embed multiple patterned pressure sensors in the current collector inside the sample battery. The sample battery refers to a monitoring battery used for isostatic pressing process pressure consistency assessment, whose external dimensions, stacked structure, packaging form, thickness, material system, or mechanical response characteristics are the same as or similar to the actual solid-state battery to be processed. The sample battery can be a complete solid-state battery or a process monitoring sample battery not intended for final shipment; its internal components may include a positive electrode, a negative electrode, a solid electrolyte layer, and a current collector, ensuring that its pressure state in the isostatic pressing equipment can represent the pressure state of the actual solid-state batteries in the same batch. The patterned pressure sensors can be strip-shaped, serpentine, interdigitated, grid-shaped, arrayed dot-shaped, ring-shaped, partitioned block-shaped, or a combination of the above patterns. Serpentine patterns can increase the effective conductive path length and improve pressure response sensitivity; interdigitated patterns can enhance the influence of interface contact changes on the electrical signal; grid-shaped patterns can sense the average pressure over a large area; arrayed dot-shaped or partitioned block-shaped patterns can achieve multi-location pressure distribution detection. By incorporating various pattern combinations within the sample cell, detection sensitivity, detection area, and spatial resolution can be balanced. Patterned pressure sensors can be made from carbon nanotubes and PDMS, graphene and PDMS, carbon black and PDMS, MXene and PVDF, graphene and PVDF, carbon nanotubes and PVDF, carbon nanotubes and PI, carbon black and PI, or other composite materials with piezoresistive response characteristics.

[0029] In this embodiment, the sample battery also measures 70mm × 50mm × 4mm. The sample battery internally includes a positive electrode, a negative electrode, a solid electrolyte layer, and a current collector structure, ensuring its mechanical response in the isostatic pressing equipment is similar to that of the actual solid-state battery to be processed. This sample battery is not intended for final shipment but serves as a process monitoring sample for the isostatic pressing process of the same batch of solid-state batteries.

[0030] In this embodiment, a dedicated detection current collector is disposed inside the sample battery, located near the middle layer of the sample battery, for arranging multiple patterned pressure sensors. The dedicated detection current collector uses a 10μm thick copper foil as a substrate, and a 5μm thick polyimide insulating layer is disposed on the surface of the copper foil. Multiple patterned pressure sensors are then formed on the surface of the insulating layer. The surface of the patterned pressure sensors is covered with a 3μm to 5μm thick PVDF encapsulation layer to avoid direct contact between the sensor material and the solid electrolyte or electrode material, while ensuring that the pressure during the isostatic pressing process can be transmitted to the pressure sensors.

[0031] In this embodiment, the patterned pressure sensor is prepared using a carbon nanotube (CNT) and polyimide (PI) piezoresistive composite material. Multi-walled carbon nanotubes are ultrasonically dispersed in N-methylpyrrolidone for 60 min, then mixed with a PI precursor solution to form a CNT and PI piezoresistive paste with a carbon nanotube mass fraction of 6 wt%. This piezoresistive paste is screen-printed onto the surface of a polyimide insulating layer and pre-baked at 120°C for 30 min, followed by heat treatment at 180°C for 60 min to form a patterned pressure sensor with a stable piezoresistive response. The thickness of each patterned pressure sensor is 8 μm to 12 μm, preferably 10 μm, and the initial resistance is controlled within the range of 1 kΩ to 50 kΩ. In this embodiment, the initial resistance of each sensor is 5 kΩ to 20 kΩ.

[0032] To evaluate the pressure consistency of different regions of the sample battery during the isostatic pressing process, this embodiment incorporates nine patterned pressure sensors inside the sample battery, such as... Figure 5 As shown, these correspond to the central region, upper edge region, lower edge region, left edge region, right edge region, upper left corner region, upper right corner region, lower left corner region, and lower right corner region, respectively. The pressure sensor in the central region uses a grid pattern, as shown below. Figure 2 As shown, the average pressure response in the central region of the sample battery is obtained; the four edge region pressure sensors adopt a serpentine pattern, as shown... Figure 3 As shown, this is used to improve the detection sensitivity of pressure changes in the edge region; the pressure sensors in the four corner regions adopt an interdigitated pattern, as shown... Figure 4 As shown, this is used to enhance the effect of local pressure changes at the corners on the resistance signal. By combining the center, edge, and corner arrangements, the overall pressure uniformity and local pressure differences of the sample battery during the isostatic pressing process can be evaluated.

[0033] In this embodiment, the detection area of ​​the grid pattern in the central region is 12mm × 12mm, the line width is 400μm, and the line spacing is 600μm; the detection area of ​​the serpentine pattern in the edge region is 10mm × 8mm, the line width is 300μm, and the line spacing is 500μm; the detection area of ​​the interdigitated pattern in the corner region is 8mm × 8mm, the interdigit width is 300μm, and the interdigit spacing is 300μm. An insulating gap of at least 2mm is provided between each pressure sensor to avoid electrical signal crosstalk between adjacent sensors. After fabrication, each pressure sensor undergoes initial resistance testing and pressure-resistance response pre-calibration.

[0034] Step two involves constructing a multi-channel pressure signal extraction structure, where each patterned pressure sensor corresponds to an independent set of detection tabs, to prepare a sample battery for pressure consistency detection during isostatic pressing. Multi-channel pressure detection signals are acquired through the multi-channel pressure signal extraction structure of the sample battery using an external acquisition device. This allows for simultaneous acquisition of pressure detection signals from multiple pressure detection areas during isostatic pressing, pressure holding, and pressure release, avoiding the problem of obtaining only a single average pressure value and failing to identify local pressure inconsistencies. When there are a large number of patterned pressure sensors, a flexible circuit board is used as the multi-channel extraction structure, connecting multiple pressure detection areas to a unified data acquisition interface. When the detection tabs protrude from the sample battery's encapsulation area, they can be encapsulated using tab adhesive, heat-sealing adhesive, polyimide film, insulating tape, epoxy sealant, or an elastic sealing structure to prevent the isostatic medium from entering the sample battery and to avoid short circuits between detection tabs or between the detection tabs and external pressure-bearing fixtures. The detection tabs can be made of nickel strip, nickel-plated copper strip, aluminum strip, flexible circuit board copper foil circuit, or other conductive materials that are pressure-resistant, bend-resistant, and encapsulation-resistant.

[0035] In this embodiment, nine patterned pressure sensors are led out through independent detection lines, and each sensor adopts a two-terminal resistor detection structure, thus the sample battery has a total of eighteen detection leads. To reduce the number of tabs and improve packaging reliability, a ten-channel lead structure can also be formed by using one common terminal and nine independent signal terminals. In this embodiment, a multi-channel flexible circuit board 1 is preferably used as the multi-channel lead structure, such as... Figure 5 As shown, nine pressure sensors are connected to the same flexible circuit board connection port.

[0036] The flexible circuit board uses a polyimide (PI) substrate with a thickness of 25 μm, copper foil lines with a thickness of 12 μm, line widths ranging from 200 μm to 500 μm, and line spacing of no less than 300 μm. One end of the flexible circuit board is connected to the detection pads of each patterned pressure sensor via conductive silver paste and low-temperature hot pressing. The other end extends from the edge of the sample battery package and connects to an external multi-channel resistance acquisition module. The detection pad area is locally encapsulated with epoxy insulating adhesive to improve mechanical stability and insulation reliability during isostatic pressing.

[0037] During sample battery encapsulation, the flexible circuit board extends from the edge of the aluminum-plastic film encapsulation. The extended area is fitted with tab adhesive, a polyimide reinforcing film, and a heat-sealing adhesive layer. The heat-sealing temperature is 150℃~180℃, the heat-sealing time is 3s~8s, and the heat-sealing pressure is 0.2MPa~0.5MPa. In this embodiment, the heat-sealing temperature is 165℃, the heat-sealing time is 5s, and the heat-sealing pressure is 0.3MPa. After encapsulation, an airtightness check is performed on the sample battery to confirm that the isostatic medium will not enter the sample battery from the flexible circuit board exit point.

[0038] Before the sample batteries enter the isostatic pressing equipment, continuity and insulation tests are performed on the nine pressure detection channels. The initial resistance of each channel should be within the preset range, the insulation resistance between adjacent detection channels should not be less than 10MΩ, and the insulation resistance between the detection channels and the main circuit of the positive and negative terminals of the sample battery should not be less than 100MΩ. If any detection channel has an open circuit, short circuit, or abnormal initial resistance, the sample battery is determined not to be used for monitoring the isostatic pressing process of this batch.

[0039] Step 3: Place the sample battery and the actual solid-state battery to be processed together in an isostatic pressing apparatus, placing them in the same or similar isostatic pressing environment. During the pressurization, holding, and depressurization processes, the resistance changes of various pressure sensors inside the sample battery are collected in real time. The pressurization, holding, and depressurization processes refer to the process by which the isostatic pressing apparatus applies pressure to the sample battery and the actual solid-state battery to be processed according to a set process curve. During the pressurization process, the synchronization of pressure responses in different regions can be detected; during the holding process, the stability of pressure in different regions and the presence of pressure drift can be detected; during the depressurization process, the consistency of pressure recovery in different regions and the presence of hysteresis can be detected. By monitoring the entire process in real time, richer process pressure information can be obtained than a single holding pressure setting. The actual solid-state battery to be processed can be a stacked solid-state battery, a wound solid-state battery, a pouch solid-state battery, a prismatic solid-state battery, or a solid-state battery of other structural forms. The actual solid-state battery to be processed can be in the process stages after stacking, before packaging, after packaging, after pre-pressing, after hot pressing, or before formation.

[0040] In this embodiment, as Figure 6 As shown, the isostatic pressing device 6 is a cold isostatic pressing device, and the liquid pressure medium 7 is hydraulic oil or water-based pressure medium, which is pressurized by the pressurizing device 5. The maximum working pressure of the isostatic pressing device 6 is 300MPa. The actual solid-state battery to be processed and the sample battery ( Figure 6 The soft-pack batteries 2 shown as sample batteries are all placed in the flexible insulating mold 3 by the fixed bracket 4 and placed in the same pressure-bearing fixture.

[0041] In this embodiment, each batch of isostatic pressing includes twenty actual solid-state batteries to be processed and one sample battery. The twenty actual solid-state batteries to be processed are stacked in parallel in the same direction, and the sample battery is placed in the middle of the battery stack unit to characterize the typical pressure state of the batch of batteries during the isostatic pressing process. For cases where it is necessary to evaluate the pressure consistency of the isostatic pressing chamber space, a sample battery can also be placed at the center, edge, and near the chamber wall of the battery stack unit to compare the pressure response differences at different spatial locations.

[0042] This embodiment employs the following isostatic pressing process parameters: pressurization rate of 5 MPa / min, target holding pressure of 180 MPa, holding time of 10 min, depressurization rate of 10 MPa / min, and isostatic pressing temperature of 25°C. Throughout the pressurization, holding, and depressurization processes, an external multi-channel resistance acquisition module collects the resistance values ​​of nine pressure sensors at a sampling frequency of 1 Hz, and simultaneously records the pressure displayed on the isostatic pressing equipment, equipment temperature, holding time, and process stage information. The resistance change rate of each pressure sensor is converted into the corresponding pressure value for the detection area based on a pre-established pressure-resistance calibration curve.

[0043] To establish calibration relationships, the sample batteries undergo flat plate compression calibration or low-pressure pre-calibration before the formal isostatic pressing test. The sample batteries are placed between two parallel pressure plates, and a preload pressure within the range of 0 MPa to 50 MPa is applied to obtain the preliminary pressure response curves of each pressure sensor. Subsequently, the sensor responses within the range of 50 MPa to 200 MPa are corrected by combining the standard pressure values ​​in the isostatic pressing apparatus. After calibration, a correspondence is established between pressure P and the rate of change of resistance ΔR / R0, where R0 is the initial resistance before isostatic pressing, and ΔR is the resistance change during the isostatic pressing process. In this embodiment, each pressure sensor exhibits a monotonic pressure response within the range of 20 MPa to 200 MPa, and the pressure detection repeatability error does not exceed ±8%.

[0044] Step four involves determining, based on the pressure characteristics of each testing area, whether the pressure in different regions of the solid-state battery is uniform under isostatic pressing equipment and process conditions, and identifying pressure inconsistencies during the isostatic pressing process. The pressure range can be expressed as the difference between the maximum and minimum pressure values ​​in each testing area; the pressure standard deviation indicates the degree to which the pressure in different testing areas deviates from the average pressure; the coefficient of variation represents the ratio of the pressure standard deviation to the average pressure; and the pressure gradient represents the spatial difference in pressure changes between adjacent testing areas.

[0045] In this embodiment, the pressure values ​​obtained from the nine detection areas are denoted as P1 to P9, and the average pressure Pavg = (P1 + P2 + P3 + P4 + P5 + P6 + P7 + P8 + P9) / 9, the pressure range Prange = Pmax - Pmin, and the pressure standard deviation σ are calculated during the pressure increase, pressure holding, and pressure release phases, respectively. The pressure variation coefficient CV = σ / Pavg, where Prange is the pressure range, representing the difference between the maximum pressure value Pmax and the minimum pressure value Pmin in the nine regions, and CV is the ratio of the pressure standard deviation to the pressure mean, i = 0, 1, 2, 4, 5, 6, 7, 8, 9.

[0046] During the pressurization phase, the response time differences of the nine pressure sensors when reaching 50%, 80%, and 95% of the target pressure were compared. If the time difference between any two detection areas reaching the same pressure ratio exceeded 30 seconds, it was determined that there was asynchronous pressurization response in different areas of the sample battery, which may indicate problems with isostatic medium transmission, tooling constraints, or battery stacking methods. During the pressure holding phase, pressure data from the 2nd to the 10th minute after the start of pressure holding were statistically analyzed. If the pressure range Prange during the pressure holding phase was greater than 8% of the target pressure holding pressure, or the pressure coefficient of variation CV during the pressure holding phase was greater than 5%, it was determined that there was an inconsistent pressure distribution problem in the isostatic pressing process. During the pressure relief phase, if the time difference between different areas recovering to near the initial pressure exceeded 60 seconds, it was determined that there was an inconsistent stress release problem in the pressure relief process.

[0047] In this embodiment, when the target holding pressure is 180 MPa, if the pressures of the nine detection areas during the holding stage are 176 MPa, 181 MPa, 179 MPa, 174 MPa, 183 MPa, 169 MPa, 185 MPa, 171 MPa, and 182 MPa respectively, the average pressure is approximately 177.8 MPa, the pressure range is 16 MPa, and the pressure variation coefficient is approximately 3.1%. Therefore, the pressure consistency of this isostatic pressing process is deemed to meet the requirements. However, if the pressures of the nine detection areas in a batch are 190 MPa, 186 MPa, 184 MPa, 162 MPa, 181 MPa, 155 MPa, 188 MPa, 158 MPa, and 180 MPa respectively, the pressure range reaches 35 MPa, and the pressure variation coefficient exceeds 6%. This indicates a significant pressure inconsistency problem in this batch, requiring adjustments to the tooling layout, sample placement, or isostatic pressing process parameters.

[0048] To visually evaluate the pressure distribution during isostatic pressing, this embodiment can also establish a two-dimensional pressure distribution map based on the location and pressure values ​​of the nine detection areas. The pressure distribution map can be used to determine the pressure differences in the central, edge, and corner regions of the sample battery. For example, when the pressure in the four corner regions is significantly lower than that in the central region, it indicates that there may be insufficient pressure transmission at the battery corners; when the pressure near the tabs is significantly higher than that in the main body region, it indicates that the tab structure or the edge of the packaging may have a local impact on pressure transmission; when there is a large pressure difference between the upper and lower regions, it indicates that there may be an off-center load on the battery placement or the pressure-bearing fixture.

[0049] Step five: Feedback the pressure consistency assessment results to the isostatic pressure equipment control system to adjust the isostatic pressure equipment parameters. In this embodiment, for example... Figure 6As shown, the multi-channel resistance acquisition module includes a multi-channel flexible circuit board 1 and multiple pressure acquisition lines 8. The pressure acquisition lines 8 pass through the sealed wiring interface 9 on the isostatic pressing device 6 and are connected to the pressure acquisition unit 10 and the computer 11 through the multi-channel flexible circuit board 1. The computer 11 inputs the calculated pressure mean, pressure range, pressure standard deviation, pressure coefficient of variation, and pressure rise response time difference into the isostatic pressing device control system. The control system adjusts the isostatic pressing process parameters according to preset rules to achieve feedback control or batch-to-batch parameter optimization of the isostatic pressing process.

[0050] When the average pressure during the holding phase is detected to be lower than the target holding pressure, the control system increases the target pressure setting or extends the holding time. When the pressure difference or pressure variation coefficient exceeds the set threshold, the control system reduces the pressurization rate to allow the pressure medium more time to equalize. When the pressure in the edge or corner region is detected to be consistently lower than the pressure in the center region, the control system prompts adjustments to the battery stacking method, increases the spacing support structure, or optimizes the pressure-bearing fixtures. When a significant difference in pressure recovery is detected during the depressurization phase, the control system reduces the depressurization rate to minimize inconsistencies in stress release between the sample battery and the actual solid-state battery to be processed.

[0051] In this embodiment, the first batch of isostatic pressure tests uses a pressure ramp rate of 5 MPa / min, a target pressure of 180 MPa, a holding time of 10 min, and a decompression rate of 10 MPa / min. If the sample battery test results show that the pressure in the corner area is more than 20 MPa lower than the pressure in the center area, the pressure ramp rate is reduced to 3 MPa / min and the holding time is extended to 15 min in the next batch of processes. If the pressure range of the nine test areas decreases from 35 MPa to 14 MPa after adjustment, and the pressure variation coefficient decreases from 6.5% to 3.0%, it is determined that the adjusted isostatic pressure parameters improve pressure consistency. In this way, the present invention can optimize the isostatic pressure parameters based on the actual pressure response inside the sample battery, rather than relying solely on the pressure displayed by the equipment or the performance of the processed battery to infer the values.

[0052] Furthermore, this embodiment can also employ a neural network algorithm to optimize isostatic pressing process parameters. The target holding pressure, boost rate, holding time, depressurization rate, isostatic pressing temperature, sample battery placement, average pressure, pressure range, standard deviation, boost response time difference, holding pressure fluctuation amplitude, and the thickness consistency, interface impedance, and capacity retention of the processed solid-state battery for each batch are used as training data to establish a correlation model between isostatic pressing process parameters, pressure consistency, and battery processing quality. The neural network model can employ a multilayer perceptron model, with the input layer including process parameters and multi-point pressure characteristics, the hidden layer consisting of two fully connected layers, and the output layer containing the recommended boost rate, holding pressure, holding time, and depressurization rate. After training with historical batch data, the model can predict better isostatic pressing process parameters for the next batch based on the current sample battery's pressure response.

[0053] This embodiment prepares a sample battery with nine built-in patterned pressure sensors and performs isostatic pressing on the sample battery along with the actual solid-state battery to be processed. This enables real-time acquisition and consistency evaluation of pressure signals from multiple regions within the sample battery throughout the entire isostatic pressing process, including pressurization, holding, and depressurization. By feeding back the pressure consistency evaluation results to the isostatic pressing equipment control system, the pressurization rate, holding pressure, holding time, depressurization rate, and tooling arrangement can be adjusted. This improves the pressure uniformity during the isostatic pressing process of the solid-state battery, enhancing interface compaction consistency and manufacturing reliability.

[0054] Finally, it should be noted that the above descriptions are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features within the technical scope disclosed in the present invention; and such modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for evaluating and controlling pressure consistency during the isostatic pressing process of a solid-state battery, characterized in that, The specific steps are as follows: S1. Preparation of a sample battery current collector with built-in patterned pressure sensors: Multiple patterned pressure sensors are pre-embedded in the positive electrode current collector, negative electrode current collector, or special detection current collector of the sample battery to form multiple pressure detection areas, wherein the patterned pressure sensor is a pressure sensor with a preset shape pattern. S2. Prepare a sample battery with a multi-channel pressure detection signal lead-out structure: independently lead out the patterned pressure sensors in different pressure detection areas inside the sample battery, so that each patterned pressure sensor corresponds to a set of independent detection lead-out terminals, and obtain a sample battery with a multi-channel pressure detection signal lead-out structure. S3. Place the sample battery and the actual solid-state battery to be processed together into an isostatic pressing device to obtain the pressure detection signals of each pressure detection area inside the sample battery. S4. Based on the pressure detection signals of each pressure detection area inside the sample battery, obtain the pressure characteristics of each pressure detection area, and perform a pressure consistency evaluation of the isostatic pressing process: Based on the pressure detection signals of each pressure detection area inside the sample battery, obtain the pressure characteristics of each pressure detection area in the isostatic pressing process, and compare and analyze the pressure characteristics of different pressure detection areas inside the sample battery to obtain a pressure consistency evaluation index, thereby quantitatively evaluating the consistency of the isostatic pressing process. S5. Feedback the pressure consistency assessment results to the isostatic pressure equipment control system to adjust the isostatic pressure process parameters: Use the pressure characteristics and the pressure consistency assessment index as feedback inputs, and automatically or manually adjust the isostatic pressure process parameters according to the pressure consistency assessment results.

2. The method for evaluating and controlling pressure consistency during the isostatic pressing process of a solid-state battery according to claim 1, characterized in that, In step S1, the pressure detection area is set according to the pressure transmission path and potentially inconsistent pressure distribution of the sample battery during the isostatic pressing process. Multiple patterned pressure sensors are arranged in partitions corresponding to multiple pressure detection areas to convert the pressure state of the sample battery at different positions during the isostatic pressing process into collectable electrical signal changes. The partitioned arrangement of the multiple patterned pressure sensors includes: for sample batteries that need to evaluate the overall surface pressure uniformity, the patterned pressure sensors are arranged as a combination of the center point, four corner points, and edge points of the sample battery; for sample batteries that need to evaluate the pressure condition of the tab area, the patterned pressure sensor is set separately in the area near the tab of the sample battery; for sample batteries that need to evaluate the pressure transmission consistency of the stacked structure, multiple patterned pressure sensors are set along the length direction, width direction, and / or thickness direction of the sample battery.

3. The method for evaluating and controlling pressure consistency during the isostatic pressing process of a solid-state battery according to claim 2, characterized in that, In step S1, the patterned pressure sensor is calibrated for pressure-electrical signals after the sample battery is prepared, and the correspondence between the resistance change rate and pressure of each pressure detection area is established.

4. The method for evaluating and controlling pressure consistency during the isostatic pressing process of a solid-state battery according to claim 3, characterized in that, In step S2, a sample battery and an actual solid-state battery to be processed are simultaneously placed in the same isostatic chamber, the same pressure medium, the same pressure-bearing fixture, and the same battery stacking unit, with the same placement direction. This allows the sample battery and the actual solid-state battery to undergo the same or similar pressure increase rate, holding pressure, holding time, pressure release rate, temperature conditions, pressure medium flow state, and fixture constraint state. During the pressure increase, holding, and pressure release processes, the resistance changes of each patterned pressure sensor inside the sample battery are collected in real time and converted into pressure values ​​of the corresponding pressure detection areas. The pressure detection signals from each pressure detection area inside the sample battery are used to characterize the pressure state of the actual solid-state battery to be processed during the isostatic process.

5. The method for evaluating and controlling pressure consistency during the isostatic pressing process of a solid-state battery according to claim 4, characterized in that, In step S2, each of the channels is electrically insulated from each other, and each of the channels is electrically isolated from the positive and negative main circuits of the sample battery to ensure that the pressure detection signal is not interfered with by the electrochemical circuit of the sample battery or other channels. The form of the detection lead includes detection tabs, metal leads, flexible circuit boards, multi-channel connection terminals, or other lead structures that can maintain conductivity under isostatic pressure. Before the sample battery enters the isostatic pressure equipment, the initial resistance, insulation resistance, and conductivity of each channel are tested to confirm that the signals of each patterned pressure sensor are stable, there are no short circuits between the channels, and the detection circuit is electrically insulated from the main circuit of the sample battery.

6. The method for evaluating and controlling pressure consistency during the isostatic pressing process of a solid-state battery according to claim 5, characterized in that, In step S3, the actual solid-state battery to be processed includes finished or semi-finished solid-state batteries subjected to isostatic pressing. The sample battery has the same or similar external dimensions, stacked structure, packaging form, thickness, material system, or mechanical response characteristics as the actual solid-state battery to be processed, or the sample battery is a standard battery capable of withstanding the maximum pressure of the isostatic pressing equipment. The sample battery is placed at the center, edge, or multiple representative positions of the actual solid-state battery pack to be processed to evaluate the pressure consistency at different spatial positions within the isostatic pressing chamber.

7. The method for evaluating and controlling pressure consistency during the isostatic pressing process of a solid-state battery according to claim 6, characterized in that, In step S4, the pressure characteristics include the real-time pressure value, maximum pressure value, minimum pressure value, average pressure value, pressure change rate, pressure response delay time, pressure fluctuation amplitude during the pressure holding phase, and pressure recovery time during the pressure release phase for each pressure detection area. The pressure consistency evaluation indicators include pressure range, pressure standard deviation, coefficient of variation, pressure gradient, and pressure change rate. When each of the pressure consistency evaluation indicators exceeds its set threshold, it is determined that there is a pressure inconsistency problem in the isostatic process. The pressure consistency assessment is conducted for the pressurization phase, the pressure holding phase, and the pressure relief phase to distinguish different types of problems, including uneven pressure transmission, insufficient pressure holding stability, and inconsistent pressure relief recovery.

8. The method for evaluating and controlling pressure consistency during the isostatic pressing process of a solid-state battery according to claim 7, characterized in that, In step S5, adjusting the isostatic pressing process parameters includes adjusting the pressure curve, pressurization rate, holding pressure, holding time, depressurization rate, temperature conditions, tooling structure, pressure medium state, or the placement of the sample battery and the actual solid-state battery to be processed in the isostatic pressing equipment, so that the actual pressure distribution during the isostatic pressing process tends to be uniform. The specific methods of adjustment include controlling the target holding pressure based on the average pressure, controlling pressure consistency based on the pressure range or standard deviation, controlling the pressurization rate and depressurization rate based on the pressure change rate, and controlling the holding time and pressure compensation strategy based on the pressure fluctuation during the holding stage.

9. The method for evaluating and controlling pressure consistency during the isostatic pressing process of a solid-state battery according to claim 8, characterized in that, In step S5, the static pressure equipment control system can use a neural network algorithm to output optimized isostatic pressure process parameters, taking isostatic pressure, pressure increase rate, pressure holding time, pressure release rate, temperature, sample battery position, pressure characteristics of each pressure detection area, and solid-state battery performance indicators after processing as input and training data.

10. The method for evaluating and controlling pressure consistency during the isostatic pressing process of a solid-state battery according to claim 9, characterized in that, Step S5 also includes establishing an isostatic pressing process database based on the pressure consistency evaluation results of sample batteries from different batches. This database is used for long-term monitoring of the isostatic pressing equipment status, identification of pressure field drift in the isostatic pressing equipment, and continuous optimization of the solid-state battery mass production process.

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