Implantable film pressure sensor and lithium battery

Abstract

The invention discloses an implantable film pressure sensor, which comprises a functional material layer and an electrode layer adjacent to the functional material layer, and is characterized in that the electrode layer comprises a flexible substrate and a metal electrode; the functional material layer comprises a polymer substrate and a functional film; the functional membrane is formed by compounding an ionic conductive material and a polymer matrix, and the surface of the functional membrane is provided with a plurality of microstructures arranged in an array; the ion conductive material is a material capable of stably existing in the lithium battery or a material used in the manufacturing process of the lithium battery; and the polymer matrix adopts a polymer material or a polymer precursor which is compatible with the ionic conductive material and has gel or polymer network forming capability. Furthermore, the invention also discloses a lithium battery integrated with the implantable thin film pressure sensor. Based on the implantable thin film pressure sensor, the internal pressure and pressure distribution change of the lithium battery can be obtained more accurately and sensitively.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to an implantable thin-film pressure sensor and a lithium battery. Background Technology

[0002] Lithium-ion batteries, as the core of new energy technologies, play a crucial role in electric vehicles, energy storage systems, and other fields. However, the state and safety monitoring of lithium-ion batteries remains a critical step in ensuring their performance and lifespan. Currently, commonly used battery state monitoring methods mainly include voltage, current, and temperature monitoring. While these methods provide some basic information, they often lack sensitivity to changes in battery state, such as state of charge (SOC) and state of health (SOH), and are highly dependent on external conditions. Voltage signals typically exhibit a relatively flat characteristic when battery state (such as lithium iron phosphate batteries) changes, making it difficult to accurately reflect state changes. Furthermore, voltage and current signals are significantly affected by external conditions such as charge / discharge rates and temperature, easily causing signal fluctuations and thus affecting the accuracy of state estimation. These factors make it difficult to provide stable and accurate state monitoring by relying solely on voltage and current signals. Therefore, traditional detection methods have significant limitations in state and safety monitoring, lacking accurate and effective signals that are strongly correlated with battery state.

[0003] The application of mechanical sensors in battery status and safety monitoring primarily involves assessing battery condition by measuring expansion force. Expansion force directly reflects changes in the battery's internal state. During charging and discharging, the electrode volume changes due to the insertion and extraction of lithium ions, exhibiting high sensitivity and stability compared to traditional voltage and current signals. Furthermore, changes in expansion force are related to the degree of lithium deposition in the electrodes. By effectively capturing these changes during battery charge-discharge cycles, the sensors can more accurately and in real-time reflect changes in the battery's state of charge (SOC) and state of health (SOH), thus improving the accuracy of state estimation and safety monitoring. In addition, mechanical sensors play a crucial role in early warning of battery thermal runaway. By monitoring expansion force in real-time, the accumulation and abnormal changes related to thermal runaway can be detected in advance. Analyzing these trends can effectively identify early warning signs of thermal runaway, improving the battery system's safety warning capabilities and reducing the risk of accidents.

[0004] While mechanical signals offer significant advantages, their application in accurately detecting battery expansion force still needs improvement. Due to the rigid external encapsulation of batteries, minute internal mechanical changes are difficult to detect. Therefore, implanted sensors within the battery can detect these minute changes earlier and more accurately. Currently, the most commonly used implanted pressure sensing solutions are fiber Bragg grating (FBG) sensors, strain gauges, and thin-film pressure sensors. However, while FBG sensors offer high accuracy and corrosion resistance, their materials are fragile and unsuitable for the high-stress scenarios of late-stage battery aging. Furthermore, they are difficult to array. Strain gauges, while also possessing good accuracy, are also difficult to array and are susceptible to corrosion in electrolyte environments, limiting their long-term operation. While ordinary thin-film pressure sensors offer advantages in detection accuracy and arrayability, they also fail to meet the corrosion resistance requirements of the battery's internal environment.

[0005] Chinese patent application CN118533333A discloses an implantable, unpackaged thin-film pressure sensor. This sensor employs an unpackaged sensing architecture and can operate directly in an electrolyte environment. Integrating this implantable, unpackaged thin-film pressure sensor into a battery cell creates an implantable sensing cell capable of in-situ pressure signal sensing. However, this technology relies on the electrolyte within the battery to establish the sensing function, requiring a sufficient and freely flowing amount of electrolyte around the sensor. This requirement is clearly difficult to meet in most batteries (such as semi-solid and all-solid electrolyte batteries). Furthermore, the future trend in battery development is to reduce electrolyte content to improve energy density and safety performance. Therefore, proposing novel battery implantable sensor solutions is urgently needed. Summary of the Invention

[0006] To address the aforementioned problems, this invention, based on the inherent material system within lithium-ion batteries and utilizing its corrosion-resistant properties that allow it to exist stably inside the battery, proposes an implantable thin-film pressure sensor for monitoring the expansion force of lithium-ion batteries. Furthermore, this invention also proposes a lithium battery integrating the implantable thin-film pressure sensor based on this material.

[0007] The first aspect of this invention discloses an implantable thin-film pressure sensor, comprising a functional material layer and an electrode layer adjacent to the functional material layer. The electrode layer includes a flexible substrate and a metal electrode formed on the flexible substrate. The functional material layer includes a polymer substrate and a functional membrane formed on the polymer substrate. The functional membrane is composed of an ion-conducting material and a polymer matrix, and has multiple arrayed microstructures on its surface. The ion-conducting material is a material that can exist stably inside a lithium battery or a material used in the manufacturing process of a lithium battery. The polymer matrix is ​​a polymer material or polymer precursor that is compatible with the ion-conducting material and has the ability to form gels or polymer networks.

[0008] Optionally, when the lithium battery is a liquid electrolyte battery, the ion-conducting material is composed of an organic electrolyte system. The organic electrolyte includes a combination of a carbonate organic solvent and a soluble lithium salt, wherein the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium trifluoromethanesulfonate (LiOTf); and the carbonate organic solvent is selected from one or a mixture of methyl carbonate (DMC), ethyl carbonate (EMC), and ethyl methyl carbonate (DEC).

[0009] When the lithium battery is a semi-solid electrolyte battery, the ion-conducting material is selected from the gel electrolyte material in the semi-solid electrolyte battery system; the gel electrolyte material is formed by a polymer matrix and an organic electrolyte.

[0010] When the lithium battery is a solid-state electrolyte battery, the ion-conducting material is selected from polymer solid-state electrolytes or inorganic solid-state electrolyte materials in the solid-state electrolyte battery system; the polymer solid-state electrolyte includes a composite formed by polyethylene oxide (PEO) or polymethyl methacrylate (PMMA) and lithium salt; the inorganic solid-state electrolyte material includes sulfide materials, oxide materials and halide materials.

[0011] Optionally, the polymer in the polymer material is a polymerized synthetic polymer, including any one of polyurethane, polyvinyl alcohol, polyvinylidene fluoride, and polyacrylate.

[0012] The polymer precursor is one or more composites of epoxy resin and organosilicon resin; the polymer precursor can form a flexible film or gel structure after treatment.

[0013] Optionally, the polymer substrate is any one of PET, PI, PP, CPP, and PDMS.

[0014] Optionally, the polymer substrate thickness is 50–150 μm.

[0015] Optionally, the metal electrode is copper.

[0016] Optionally, the surface of the metal electrode may also be provided with a gold plating layer.

[0017] Optionally, the flexible substrate is PI or PDMS.

[0018] Optionally, the implantable thin-film pressure sensor has a sandwich electrode structure or an interdigitated electrode structure; correspondingly, the electrode layer includes a positive electrode layer and a negative electrode layer, or the electrode layer is a single-layer interdigitated electrode layer.

[0019] The second aspect of the present invention discloses a lithium battery, including an outer encapsulation structure and an electrolyte, a positive electrode, a negative electrode, and a separator for isolating the positive and negative electrodes disposed within the outer encapsulation structure; it also includes an implantable thin-film pressure sensor as described in the first aspect and any optional embodiment; the implantable thin-film pressure sensor is disposed between the outer encapsulation structure and the outermost positive or negative electrode adjacent to the outer encapsulation structure.

[0020] A third aspect of the present invention discloses a lithium battery, comprising an outer encapsulation structure and an electrolyte, a positive electrode, a negative electrode, and a separator for isolating the positive and negative electrodes disposed within the outer encapsulation structure, wherein the inner side of the outer encapsulation structure is a polymer material; further comprising an implantable thin-film pressure sensor as described in the first aspect and any optional embodiment; the implantable thin-film pressure sensor is an interdigitated electrode structure and is disposed between the outer encapsulation structure and the outermost positive or negative electrode adjacent to the outer encapsulation structure; the polymer material on the inner side of the outer encapsulation structure constitutes the polymer substrate of the implantable thin-film pressure sensor.

[0021] The fourth aspect of this invention discloses a lithium battery, including an outer encapsulation structure and an electrolyte, a positive electrode, a negative electrode, and a separator for isolating the positive and negative electrodes disposed within the outer encapsulation structure; it also includes an implantable thin-film pressure sensor as described in the first aspect and any alternative embodiment; the implantable thin-film pressure sensor is disposed between the outer encapsulation structure and the outermost negative electrode adjacent to the outer encapsulation structure; the positive electrode and / or negative electrode of the implantable thin-film pressure sensor is made of copper foil on the side of the composite current collector in the outermost negative electrode near the outer encapsulation structure, and the side of the composite current collector in the outermost negative electrode near the outer encapsulation structure is insulated from the other side of the composite current collector in the outermost negative electrode and other electrodes.

[0022] The fifth aspect of this invention discloses a lithium battery, including an outer encapsulation structure and an electrolyte, a positive electrode, a negative electrode, and a separator for isolating the positive and negative electrodes disposed within the outer encapsulation structure. The inner side of the outer encapsulation structure is made of a polymer material. It also includes an implantable thin-film pressure sensor as described in the first aspect and any optional embodiment. The implantable thin-film pressure sensor has an interdigitated electrode structure and is disposed between the outer encapsulation structure and the outermost negative electrode adjacent to the outer encapsulation structure. The polymer material inside the outer encapsulation structure constitutes the polymer substrate of the implantable thin-film pressure sensor. The positive and negative electrodes of the implantable thin-film pressure sensor are made of copper foil on the side of the composite current collector in the outermost negative electrode near the outer encapsulation structure, and the side of the composite current collector in the outermost negative electrode near the outer encapsulation structure is insulated from the other side of the composite current collector in the outermost negative electrode and other electrodes.

[0023] Beneficial effects:

[0024] The implantable thin-film pressure sensor provided by this invention is based on the inherent material system of lithium-ion batteries, has excellent corrosion resistance, and is highly compatible with the internal environment of lithium batteries. It can work stably inside lithium batteries, and the electrolyte (including electrolyte solution) environment has almost no impact on its electrical and mechanical properties.

[0025] This invention can organically combine the sensor structure with the battery packaging structure or the composite current collector structure, achieving a high degree of integration between the sensor device and the lithium battery, and overcoming the problems of difficulty in integrating ordinary mechanical sensors with battery systems or the complexity of integration operations.

[0026] When the implantable thin-film pressure sensor provided by this invention is integrated inside a lithium battery, it can respond to pressure changes during charging and discharging. Because it is implanted inside the lithium battery, the influence of rigid packaging on pressure transmission can be avoided, and it can be easily arrayed, allowing for more accurate and sensitive acquisition of changes in the internal expansion force and expansion force distribution of the lithium battery.

[0027] The method for embedding a thin-film pressure sensor inside a battery proposed in this invention can not only achieve sensitive detection of internal pressure, but its process is also highly compatible with the battery manufacturing process. It does not require much modification to existing battery manufacturing lines, and the integration method and manufacturing process are simple and reliable, showing great application prospects.

[0028] This invention can construct integrated smart batteries with various structural forms based on implanted thin-film pressure sensors, enabling real-time perception of the internal expansion force and its distribution in lithium batteries. It can conduct systematic monitoring and analysis for lithium dendrite identification, thermal runaway early warning, and health status assessment, and can further regulate lithium battery aging, thus helping to extend the life of lithium batteries. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of an interdigital sensor, where 101 is the functional material layer, 102 is the electrode layer, 103 is the microstructure, and 104 is the double-sided adhesive.

[0030] Figure 2 This is a schematic diagram of a sandwich sensor, where 201 is the positive electrode layer, 202 is the functional material layer, 203 is the negative electrode layer, 204 is the microstructure, and 205 is the double-sided adhesive.

[0031] Figure 3 Schematic diagram of the internal structure of a lithium battery Figure 1 Among them, 301-functional material layer, 302-electrode (copper foil layer), 303-PI layer, 304-copper foil layer, 305-negative electrode active material, 301-303 constitute the sensor structure, and 302-304 constitute the composite negative electrode composite current collector.

[0032] Figure 4 Schematic diagram of the internal structure of a lithium battery Figure 2 Among them, 401-protective layer, 402-aluminum foil layer, 403-heat seal layer, 404-functional film, 405-electrode, 406-flexible substrate layer (electrode substrate layer), 401-403 constitute aluminum-plastic film, and 403-406 constitute sensor structure.

[0033] Figure 5 Schematic diagram of the internal structure of a lithium battery Figure 1 Among them, 501-functional material layer, 5021-interdigital electrode (copper foil), 5022-PI layer, 5023-copper foil layer, 503 negative electrode active material layer, 504-separator, 505-positive electrode active material, 506-composite positive electrode current collector, 507-aluminum-plastic film. Among them, 501 to 5022 together constitute the sensor with interdigital electrode structure, and 5021 to 5023 constitute the composite negative electrode composite current collector.

[0034] Figure 6 Schematic diagram of the internal structure of a lithium battery Figure 2 Among them, 601-flexible substrate layer (electrode substrate layer), 602-positive electrode, 603-functional membrane, 6041-negative electrode (copper foil layer), 6042-PI layer, 6043-copper foil layer, 605-negative electrode active material, 606-separator, 607-positive electrode active material, 608-composite positive electrode current collector, 609-aluminum-plastic film, wherein 601 to 6042 constitute the sensor with a sandwich electrode structure, and 6041 to 6043 constitute the negative electrode composite current collector 604.

[0035] Figure 7 This is a schematic diagram illustrating the working principle of the sensor.

[0036] Figure 8 This is a schematic diagram of the structure of an integrated smart battery, in which 801 is the battery encapsulation layer, 802 is the functional material layer, 803 is the electrode layer, 804 is the outermost negative electrode composite current collector, and 805 is the tab. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely 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 creative effort are within the scope of protection of the present invention.

[0038] In the description of this invention, the use of terms such as "upper," "lower," "inner," "outer," "top," and "bottom," indicating orientation or positional relationships, is based on the orientation or positional relationships shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Those skilled in the art can understand the specific meaning of the above terms in this invention in conjunction with the specific circumstances. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, but rather to include other units not explicitly listed or inherent to these products or devices.

[0039] like Figure 1 As shown, Embodiment 1 of the present invention discloses a thin-film pressure sensor: it adopts an interdigital electrode type, forming a double-layer structure consisting of an electrode layer and a functional material layer, which can be bonded together with double-sided adhesive. This type of sensor is also called a double-layer interdigital electrode sensor.

[0040] like Figure 2 As shown, in another optional embodiment 2, the thin-film pressure sensor adopts a sandwich structure, including three layers: a positive and negative electrode layer and a functional material layer. The functional material layer is sandwiched between the upper and lower positive and negative electrode layers and can be bonded together with double-sided adhesive. This type of sensor is also called a sandwich structure sensor.

[0041] The functional material layer includes a polymer substrate and a polymer thin film or gel-like thin film material (referred to as "functional film") formed on the polymer substrate, which is composed of an ion-conducting material and a polymer matrix. The ion-conducting material provides ion migration channels, while the polymer matrix imparts flexible film-forming properties and structural stability. The ion-conducting material can be derived from ion conduction systems widely used in lithium-ion battery technology to ensure the stable presence of the sensing functional material within the battery. For example, for traditional electrolyte systems, a combination of carbonate-based organic solvents and lithium salts can be used, suitable for traditional lithium-ion batteries; for gel electrolyte systems, a polymer matrix can be used to embed liquid electrolytes, commonly used in semi-solid-state electrolyte batteries; for solid-state electrolyte systems, polymer solid-state electrolytes or inorganic solid-state electrolytes can be used, suitable for all-solid-state electrolyte batteries.

[0042] The functional material surface has multiple arrays of microscopic protrusions (referred to as "microstructures"). Specifically, the microstructures can be hemispherical, conical, columnar, or other shapes. Specifically, the diameter of the hemispherical structure is 1–100 micrometers, preferably 10–50 micrometers, and the height is 0.5–80 micrometers, preferably 5–40 micrometers; the base diameter of the conical structure is 5–100 micrometers, and the height is 5–120 micrometers; the diameter of the columnar structure is 5–80 micrometers, and the height is 5–100 micrometers. The microstructures are distributed on the functional material surface in a two-dimensional periodic array, and the arrangement can be rectangular, circular, etc. The center-to-center distance (array period) between adjacent microstructures is 5–150 micrometers, preferably 20–100 micrometers.

[0043] The choice of ion-conducting materials is related to the type of battery into which the sensor needs to be implanted. When selecting ion-conducting materials, the chosen materials should either be able to exist stably inside the lithium battery, or be materials that are used in the lithium battery manufacturing process.

[0044] For traditional lithium-ion batteries (also known as liquid electrolyte lithium batteries), the ion-conducting material can be composed of organic electrolyte systems commonly used in traditional lithium-ion batteries. This organic electrolyte includes a combination of carbonate-based organic solvents and soluble lithium salts. The lithium salt can be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium trifluoromethanesulfonate (LiOTf); the carbonate-based organic solvent can be selected from one or a mixture of methyl carbonate (DMC), ethyl carbonate (EMC), and ethyl methyl carbonate (DEC).

[0045] For semi-solid electrolyte batteries, the ion-conducting material can be selected from gel electrolyte materials commonly used in semi-solid electrolyte battery systems. The gel electrolyte material can be formed by combining a polymer matrix with an organic electrolyte. The organic electrolyte includes a combination of carbonate-based organic solvents and lithium salts. The lithium salt can be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium trifluoromethanesulfonate (LiOTf). The carbonate-based organic solvent can be selected from one or a mixture of methyl carbonate (DMC), ethyl carbonate (EMC), and ethyl methyl carbonate (DEC).

[0046] For solid-state electrolyte batteries, the ion-conducting material can be selected from polymer solid-state electrolytes or inorganic solid-state electrolyte materials commonly used in solid-state electrolyte battery systems. Polymer solid-state electrolytes can include complexes formed by polyethylene oxide (PEO), polymethyl methacrylate (PMMA), etc., with lithium salts (such as LiTFSI, LiClO4). Inorganic solid-state electrolyte materials mainly include sulfide materials (such as Li6PS5Cl, Li...). 10 GeP2S 12 (etc.), oxide materials (such as Li7La3Zr2O) 12 Li 1.3 Al 0.3 Ti 1.7 (PO4)3, etc.), and halide materials (such as Li3InCl6, Li3YCl6, etc.).

[0047] The polymer matrix is ​​a polymeric material or polymeric precursor that is compatible with ion-conducting materials in the electrolyte system and has the ability to form gels or polymer networks. The polymeric materials include fully polymerized synthetic polymers such as polyurethane (PU), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), and polyacrylate (PNT). The polymeric precursor can be one or more composites of epoxy resin and silicone resin. Understandably, in practical applications, these polymeric precursors usually need to undergo polymerization, crosslinking, and film formation processes to form the final polymeric material.

[0048] It is worth noting that polymer precursors possess significant processing flexibility and functional tunability. During processing, the liquid or low-viscosity state of polymer precursors facilitates precise film formation and structural construction, making them suitable for various preparation methods such as blade coating, spin coating, printing, and injection molding. They are particularly well-suited for constructing micro / nano structures or flexible interfaces. In the preparation of functional materials, polymer precursors can be processed through polymerization, crosslinking, curing, and film formation, with the polymerization and crosslinking processes exhibiting excellent controllability. By rationally selecting the types of polymers in the precursor and adjusting their mass ratio and degree of crosslinking in the entire composite system, customized control over various indicators such as the mechanical properties, ionic conductivity, and adhesion of the final composite material can be achieved. For example, when it is necessary to improve the mechanical strength and structural stability of a material, the proportion of rigid polymer precursors, such as PMMA (polymethyl methacrylate) and PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer), can be increased, and a high-crosslinking thermosetting or photocuring process can be used to construct a high-strength polymer network structure. As another example, when it is necessary to achieve high ionic conductivity and flexible conformability of a material, polymer precursors with more flexible segments, such as PEGDA (polyethylene glycol diacrylate) and PEO (polyethylene oxide), can be introduced and the crosslinking density can be reduced to enhance the connectivity of ion migration channels and the deformability of the material.

[0049] Furthermore, polymer precursors exhibit good interfacial affinity with various substrate materials (e.g., polymer substrates such as PET, PI, PP, and PDMS), which is beneficial for integrated packaging and the construction of multilayer composite devices. Moreover, polymer precursor materials processed through polymerization, crosslinking, curing, and film formation can form flexible films or gel-like structures with stable mechanical and chemical properties, making them suitable for applications in complex structures or multi-physics environments.

[0050] Polymer precursors (such as EP (epoxy resin), silicone precursor solutions, etc.) or polymerized polymeric materials (such as PVA (polyvinyl alcohol), PU (polyurethane), etc.) can both be thoroughly mixed with ion-conducting materials (such as lithium salts, organic electrolytes, ionic liquids, etc.) to form a homogeneous composite system. Polymerized polymeric materials are typically solid or high-viscosity systems with poor bulk flowability, making them difficult to mix thoroughly with ion-conducting materials. They are suitable for film formation processes such as physical drying, hot pressing, or casting. To improve the film-forming properties and processing adaptability of such composite systems, adjustments can be made through electrolyte solution pretreatment, plasticizer introduction, or surface modification. For example, by pre-dissolving or dispersing the polymeric material in a mixed solution containing lithium salts, ionic liquids, or organic electrolytes, the conductive components can fully penetrate the polymeric network structure; or low-molecular-weight plasticizers such as glycerol or polyethylene glycol can be introduced to improve flexibility and spreadability; plasma treatment or silane coupling agent modification can also be used to improve interfacial wettability and adhesion.

[0051] In contrast, polymer precursors are mostly in a liquid or low-viscosity state, possessing good fluidity and crosslinking activity. They can achieve uniform dispersion with ion-conductive materials and are suitable for wet patterning processes such as screen printing, coating, and inkjet printing. This mixed system can be deposited on the surface of a flexible substrate, followed by solvent removal and crosslinking through drying, forced-air drying, thermosetting, or photosetting, thereby obtaining a composite functional film with stable structure, good adhesion, and ion-conductive properties. Furthermore, during the subsequent thermosetting or photocrosslinking process, the crosslinking density, chain segment arrangement, and microstructure of the polymer precursor can be finely controlled by adjusting process parameters such as curing temperature, time, light intensity, and photoinitiator concentration, thereby achieving dual optimization of the mechanical properties and ion conductivity of the composite film. Specifically, an appropriate crosslinking density helps to construct a three-dimensional polymer network with high toughness and high extensibility, improving the structural integrity and lifespan of the film under mechanical deformations such as bending and stretching. Simultaneously, reasonable inter-chain spacing and the introduction of ionophilic functional groups can construct continuous and efficient ion migration channels, significantly improving the ion mobility and overall conductivity of the film. Therefore, through the synergistic design of precursor formulations and crosslinking processes, multi-dimensional adaptation of the film to mechanical compliance, signal stability, and electrochemical response performance can be achieved in flexible electronic devices.

[0052] As the substrate for the functional material layer, the polymer substrate typically needs a certain degree of flexibility to ensure it can be bonded and integrated within the battery, while also possessing sufficient mechanical strength to guarantee the stability of the sensing structure. Simultaneously, it should exhibit a certain degree of stability to avoid affecting film quality and to ensure stable existence within the battery. Commonly used polymer substrates include polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), cast polypropylene (CPP), and polydimethylsiloxane (PDMS), with thicknesses typically ranging from 50 to 150 μm.

[0053] It is worth noting that the sensor structure is highly compatible with the battery manufacturing process, especially in the processing of the aluminum-plastic film encapsulation material. The aluminum-plastic film is typically composed of an outer protective layer (PA, PET, nylon, etc.), a middle barrier layer (usually an aluminum foil layer), and an inner heat-sealing layer (CPP, PP, etc.). The heat-sealing layer possesses good heat-sealing properties and electrolyte resistance, meeting the substrate property requirements of the functional material layer. Therefore, the CPP inner layer material of the aluminum-plastic film can be directly used as the polymer substrate for the functional material layer. When embedding a thin-film pressure sensor inside a lithium battery, the aluminum-plastic film of the lithium battery can be used as the substrate for the functional material layer, such as... Figure 4 As shown, functional materials can be prepared on the polypropylene (PP) / cast polypropylene (CPP) film material, i.e. the heat-sealing layer, on the inner side of the aluminum-plastic film through screen printing, coating and other methods, so as to achieve integrated integration with the battery encapsulation material.

[0054] Electrode Layer: The electrode layer consists of a flexible substrate layer and metal electrodes formed on the flexible substrate layer. Thin films of materials such as polyimide (PI) and polydimethylsiloxane (PDMS) can be used as the flexible substrate, exhibiting excellent mechanical flexibility, thermal stability, and chemical inertness, and maintaining good structural integrity under complex stress environments. The metal electrodes can be copper electrodes with excellent conductivity. By constructing micropatterned electrodes using copper (Cu), high conductivity and excellent charge transport performance can be achieved.

[0055] Furthermore, considering that copper is prone to oxidation and corrosion in electrochemical and high-humidity environments, gold (Au) plating can be applied to the electrode surface to significantly improve its oxidation resistance, corrosion resistance and long-term stability, while optimizing its electrochemical contact performance with ion-functionalized materials.

[0056] It is worth noting that the metal electrodes of the thin-film pressure sensor use the same copper foil material as the negative current collector of the lithium battery. The sensor structure is highly compatible with the battery manufacturing process in terms of design, especially in the processing technology of the negative electrode composite current collector (also known as "copper-based composite current collector"). Therefore, the thin-film pressure sensor can be applied to lithium batteries that use composite current collectors. The electrodes can be placed on the surface of the negative electrode composite current collector of the lithium battery. That is, the electrode structure required for the sensor is constructed using the negative electrode composite current collector in the outermost electrode of the lithium battery.

[0057] Understandably, composite current collectors, through "metal-polymer-metal" sandwich structures or metal-polymer composite structures, can significantly improve battery safety, energy density, and lifespan, making them one of the key technologies for next-generation batteries. Structurally, composite current collectors consist of an insulating substrate (such as PET, PP, PI, etc.) as the intermediate layer and conductive layers arranged on both sides of the intermediate layer. For negative electrode composite current collectors, the conductive layer is copper foil; for positive electrode composite current collectors, the conductive layer is aluminum foil. In lithium-ion battery electrodes, active materials (such as graphite, ternary materials) are coated and fixed onto the current collector surface in slurry form through the combined action of conductive agents and binders to achieve the charging and discharging functions of the lithium-ion battery. For sensor integration schemes using composite current collector structures, the copper foil-PI-copper foil composite current collector system commonly used in battery manufacturing is utilized to organically combine sensor functional materials with the battery current collector structure, achieving embedded construction of sensing functions. Specifically, one of the two copper foil layers can be patterned to create a usable electrode layer. The resulting composite current collector includes a PI dielectric layer, copper foil layers arranged on both sides of the PI dielectric layer (as the negative electrode composite current collector), and a patterned copper foil layer (used to construct the metal electrode of the sensor), such as... Figure 3As shown, patterning can be used to construct interdigitated or planar sensing electrodes through etching, laser engraving, or other methods. This approach offers significant advantages such as compact structure, good adhesion, stable sensing performance, and high degree of process integration, making it suitable for constructing flexible, scalable battery-embedded sensor systems. Figure 5 and Figure 6 The diagrams show two different sensing structures integrated inside a lithium battery.

[0058] When constructing the sensing electrode outside the negative electrode composite current collector, patterning can be performed on the entire surface or a portion of the copper foil as needed to construct the sensing electrode. For example, multiple arrayed electrode units can be designed on the entire surface of the copper foil to form a negative electrode layer with an interdigitated electrode structure or a sandwich electrode structure.

[0059] The thin-film pressure sensor proposed in this invention is based on the principle of ionization, and its functional material is an elastically conductive material in which ions act as charge carriers. Combined with... Figure 7 As shown, when the functional material comes into contact with the sensing electrode, a stable electrical double-layer structure can be established at the interface. When the external pressure changes, the contact area between the functional material and the sensing electrode changes, causing a rearrangement of ions and electrons on both sides of the double layer, resulting in a change in the double-layer capacitance, which is ultimately converted into a readable electrical signal. This mechanism has advantages such as high sensitivity, fast response, and good flexibility. Furthermore, regardless of whether it is a traditional lithium battery, a semi-solid electrolyte battery, or an all-solid electrolyte battery, it can be based on the ionization sensing principle, independent of the battery system. The sensing system proposed in this invention is applicable to all these battery systems without changing the sensing mechanism.

[0060] For thin-film pressure sensors with interdigitated electrode structures, only one electrode layer is present, with the electrode pattern arranged in a complementary interdigitated pattern. During fabrication, functional materials are directly deposited onto the surface of this electrode layer through methods such as printing and coating, and then subjected to heat drying or photocuring to form a stable and uniform film layer. Interdigitated electrode structure sensors offer advantages such as simple structural design, high sensitivity, fast response speed, and simplified processing, making them suitable for single-point or array-type pressure sensing applications. It is worth noting that, based on this interdigitated electrode structure, the polymer substrate can be used as the inner layer of the aluminum-plastic film used for battery encapsulation, namely the polypropylene (CPP) layer, achieving seamless integration with the battery encapsulation process.

[0061] For thin-film pressure sensors with a sandwich electrode structure, there are two electrode layers with a functional material sandwiched in between. During fabrication, the functional material is first deposited on the surface of the lower electrode using screen printing or inkjet printing, and then the upper electrode is stacked on top to form the sandwich structure. Sandwich electrode structure sensors exhibit high structural symmetry and response consistency, which helps improve signal uniformity, sensitivity, and long-term stability of the device. They are also suitable for single-point or array designs.

[0062] Embodiment 3 of this invention discloses a smart battery with an embedded thin-film pressure sensor. The fabricated thin-film pressure sensor is sandwiched between the aluminum-plastic film and the outermost electrode of a lithium battery, thus embedding it inside the lithium battery. The thin-film pressure sensor is directly encapsulated between the aluminum-plastic film and the outermost electrode of the lithium-ion battery, avoiding interference with the battery's normal charging and discharging function if placed between the positive and negative electrodes. One end of the sensor's signal line is connected to the sensing electrode, and the other end can be led out from the edge of the aluminum-plastic film. This solution, by utilizing the excellent encapsulation properties of the aluminum-plastic film, enables the sensor to have more stable and longer sensing performance. Furthermore, this method is applicable to lithium batteries using traditional current collector electrodes as well as lithium batteries using composite current collectors. The lithium battery is not limited to pouch, prismatic, or cylindrical structures.

[0063] During use, the battery undergoes reversible and irreversible expansion. During the expansion process, the thin-film pressure sensor structure is subjected to vertical compression, which in turn affects the redistribution of ions in the functional material layer. At the same time, the deformation caused by the expansion also changes the effective contact area between the functional material layer and the electrode, thereby causing a significant change in the electric double layer capacitance (EDLC), which in turn detects the change in pressure.

[0064] Embodiment 4 of this invention discloses an integrated smart battery. The main difference from Embodiment 3 is that the inner heat-sealing layer (PP, CPP, etc.) of the lithium battery aluminum-plastic film is directly used as the polymer substrate of the functional material layer of the thin-film pressure sensor, and the two are deeply integrated. For specific implementation details, please refer to the section on functional material layers of the thin-film pressure sensor.

[0065] Embodiment 5 of this invention discloses another integrated smart battery. The main difference from Embodiment 3 is that the outermost copper foil of the negative electrode composite current collector of the lithium battery is directly used to construct the sensing electrode, achieving deep integration between the two. For specific implementation details, please refer to the section on electrode layers in the thin-film pressure sensor description.

[0066] Embodiment 6 of the present invention discloses yet another integrated smart battery, which combines the solutions of Embodiments 4 and 5, such as... Figure 8 As shown, the inner heat-sealing layer (PP, CPP, etc.) of the lithium battery aluminum-plastic film is used as the polymer substrate of the functional material layer of the thin-film pressure sensor, and the outermost copper foil of the negative electrode composite current collector of the lithium battery is used to construct the sensing electrode. In other words, in terms of structural composition, only one functional film needs to be made on the inner heat-sealing layer of the aluminum-plastic film. Without affecting the charging and discharging function of the lithium battery, the internal structure of the lithium battery is fully utilized to realize an integrated smart battery with sensing function.

[0067] Understandably, for solutions using a polymer substrate with the inner heat-sealing layer of the lithium-ion battery aluminum-plastic film as the functional material layer of the sensor, the sensor structure is a single-layer interdigitated electrode structure. (This is because in a sandwich structure, the functional material layer is located between two electrode layers, making it impossible to use the polymer material inside the aluminum-plastic film as the functional material layer substrate.)

[0068] It's worth noting that the conductive layers on both sides of the composite current collector are not physically connected; current is typically drawn out through tabs. Based on this, for the scheme using a composite current collector with a negative electrode to construct the metal electrode of the sensor, one side of the composite current collector serves as the normal lithium-ion battery negative electrode composite current collector, while the other side is used to construct the electrode of the thin-film pressure sensor. The side serving as the negative electrode composite current collector is still connected to other negative electrode composite current collectors via tabs for conduction, while the side serving as the sensing electrode does not need to be connected to other current collectors using tabs, ensuring insulation between it and other current collectors. In addition, the other three battery schemes do not use a negative electrode composite current collector as the sensing electrode. Since the separately fabricated sensing electrode's substrate (PI) itself has good insulation properties from the external environment, and there are no electronic conduction paths inside the battery, no separate insulation treatment is required.

[0069] It should also be noted that for different battery forms, as long as the innermost layer of the outer packaging structure is made of polymer material, it can be used as the substrate for the functional material layer. For example, for pouch-type liquid electrolyte lithium batteries, aluminum-plastic film pouch packaging is typically used, as described in detail above; for prismatic and cylindrical liquid electrolyte lithium batteries, the outer packaging structure is usually a metal shell, and the innermost layer is usually an insulating polymer film such as PE / PP / epoxy coating; for semi-solid electrolyte batteries, the outer packaging structure is also mainly aluminum-plastic film pouch; for solid electrolyte batteries, the outer packaging structure is usually a composite packaging, and the innermost layer can also be a polymer film. In other words, this invention is applicable to most lithium batteries, utilizing the innermost layer of the lithium battery's outer packaging structure as the substrate for the functional material layer.

[0070] This invention involves doping organic electrolyte materials from within a battery with a polymer matrix, preparing a homogeneous mixture through stirring and other methods, and then solidifying it into a functional membrane material. Furthermore, this material can be directly fabricated inside the lithium battery's encapsulation layer, achieving integrated fabrication of the sensor's functional materials and the battery's encapsulation structure. Since these materials are inherent to lithium batteries and possess corrosion-resistant properties, they can remain stable within the lithium battery. Therefore, even in the electrolyte environment inside the lithium battery, the mechanical properties of the thin-film pressure sensor will not be affected.

[0071] In summary, the fabrication process of the thin-film pressure sensor proposed in this invention is highly compatible with the aluminum-plastic film fabrication process and the negative electrode composite current collector fabrication process of lithium batteries, enabling excellent integration of the two processes and achieving integrated fusion at the process level. The thin-film pressure sensor embedded within the lithium battery can respond to pressure changes during charging and discharging. Because it is embedded inside the lithium battery, the influence of rigid packaging on pressure transmission is avoided, allowing for more accurate and sensitive acquisition of pressure and pressure distribution changes. The integrated smart battery with the embedded thin-film pressure sensor, through real-time acquisition and analysis of pressure and pressure distribution, can monitor early dendrite formation in lithium-ion batteries, provide early warning of thermal runaway, and perform quantitative analysis of aging and battery health.

[0072] Finally, it should be noted that although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art, guided by this specification, can make many other forms without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. An implantable thin-film pressure sensor, comprising a functional material layer and an electrode layer adjacent to the functional material layer, the electrode layer comprising a flexible substrate and a metal electrode formed on the flexible substrate; characterized in that, The functional material layer includes a polymer substrate and a functional film formed on the polymer substrate; the functional film is composed of an ion-conducting material and a polymer matrix, and has multiple arrayed microstructures on its surface. The ion-conducting material is a material that can exist stably inside a lithium battery or a material used in the manufacturing process of a lithium battery. The polymer matrix is ​​a polymer material or polymer precursor that is compatible with ion-conducting materials and has the ability to form gels or polymer networks.

2. The implantable thin-film pressure sensor as described in claim 1, characterized in that, When the lithium battery is a liquid electrolyte battery, the ion-conducting material is composed of an organic electrolyte system. The organic electrolyte includes a combination of a carbonate organic solvent and a soluble lithium salt, wherein the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, and lithium trifluoromethanesulfonate; and the carbonate organic solvent is selected from one or a mixture of methyl carbonate, ethyl carbonate, and ethyl methyl carbonate. When the lithium battery is a semi-solid electrolyte battery, the ion-conducting material is selected from the gel electrolyte material in the semi-solid electrolyte battery system; the gel electrolyte material is formed by a polymer matrix and an organic electrolyte. When the lithium battery is a solid-state electrolyte battery, the ion-conducting material is selected from polymer solid-state electrolytes or inorganic solid-state electrolyte materials in the solid-state electrolyte battery system; the polymer solid-state electrolyte includes a complex formed by polyethylene oxide or polymethyl methacrylate and lithium salt; the inorganic solid-state electrolyte material includes sulfide materials, oxide materials and halide materials.

3. The implantable thin-film pressure sensor as described in claim 1, characterized in that, The polymer in the polymer material is a polymerized synthetic polymer, including any one of polyurethane, polyvinyl alcohol, polyvinylidene fluoride, and polyacrylate. The polymer precursor is one or more composites of epoxy resin and organosilicon resin; the polymer precursor can form a flexible film or gel structure after treatment.

4. The implantable thin-film pressure sensor as described in claim 1, characterized in that, The polymer substrate is any one of PET, PI, PP, CPP, and PDMS; the thickness is 50–150 μm.

5. The implantable thin-film pressure sensor as described in claim 1, characterized in that, The metal electrode is made of copper; the flexible substrate is made of PI or PDMS; and the surface of the metal electrode is also provided with a gold plating layer.

6. The implantable thin-film pressure sensor as described in claim 1, characterized in that, The implantable thin-film pressure sensor has a sandwich electrode structure or an interdigitated electrode structure; correspondingly, the electrode layer includes a positive electrode layer and a negative electrode layer, or the electrode layer is a single-layer interdigitated electrode layer.

7. A lithium battery, comprising an outer encapsulation structure and an electrolyte, a positive electrode, a negative electrode, and a separator for separating the positive and negative electrodes disposed within the outer encapsulation structure; characterized in that, It also includes an implantable thin-film pressure sensor as described in any one of claims 1 to 6; the implantable thin-film pressure sensor is disposed between the outer encapsulation structure and the outermost positive or negative electrode adjacent to the outer encapsulation structure.

8. A lithium battery, comprising an outer encapsulation structure and an electrolyte, a positive electrode, a negative electrode, and a separator for isolating the positive and negative electrodes disposed within the outer encapsulation structure, wherein the inner side of the outer encapsulation structure is a polymer material; characterized in that, It also includes an implantable thin-film pressure sensor as described in any one of claims 1 to 6; the implantable thin-film pressure sensor has an interdigitated electrode structure and is disposed between the outer encapsulation structure and the outermost positive or negative electrode adjacent to the outer encapsulation structure; the polymer material inside the outer encapsulation structure constitutes the polymer substrate of the implantable thin-film pressure sensor.

9. A lithium battery, comprising an outer encapsulation structure and an electrolyte, a positive electrode, a negative electrode, and a separator for separating the positive and negative electrodes disposed within the outer encapsulation structure; characterized in that, It also includes an implantable thin-film pressure sensor as described in any one of claims 1 to 6; the implantable thin-film pressure sensor is disposed between an outer encapsulation structure and an outermost negative electrode adjacent to the outer encapsulation structure; the positive electrode and / or negative electrode of the implantable thin-film pressure sensor is made of copper foil on the side of the composite current collector in the outermost negative electrode near the outer encapsulation structure, and the side of the composite current collector in the outermost negative electrode near the outer encapsulation structure is insulated from the other side of the composite current collector in the outermost negative electrode and other electrodes.

10. A lithium battery, comprising an outer encapsulation structure and an electrolyte, a positive electrode, a negative electrode, and a separator for isolating the positive and negative electrodes disposed within the outer encapsulation structure, wherein the inner side of the outer encapsulation structure is a polymer material; characterized in that, It also includes an implantable thin-film pressure sensor as described in any one of claims 1 to 6; the implantable thin-film pressure sensor has an interdigitated electrode structure and is disposed between an outer encapsulation structure and an outermost negative electrode adjacent to the outer encapsulation structure; the polymer material inside the outer encapsulation structure constitutes the polymer substrate of the implantable thin-film pressure sensor; the electrode of the implantable thin-film pressure sensor is made of copper foil on the side of the composite current collector in the outermost negative electrode near the outer encapsulation structure, and the side of the composite current collector in the outermost negative electrode near the outer encapsulation structure is insulated from the other side of the composite current collector in the outermost negative electrode and other electrodes.

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