Energy storage device using liquid metal encapsulation and method of manufacture

Abstract

The application discloses a battery encapsulated by liquid metal and a preparation method. The battery comprises an encapsulation shell and an energy storage inner core wrapped in the encapsulation shell. Both the encapsulation shell and the energy storage inner core are flexible and stretchable. Liquid metal is filled into a gap between the encapsulation shell and the energy storage inner core to seal the energy storage inner core. An inner surface of the encapsulation shell is provided with a support array structure facing the energy storage inner core, and / or an outer surface of the energy storage inner core is provided with a support array structure facing the encapsulation shell. The energy storage device encapsulated by the liquid metal has good stability in a stretching process, and has great development potential as a power component of a stretchable electronic device.

Description

Technical Field

[0001] This invention belongs to the field of energy storage device technology, and relates to energy storage devices using liquid metal encapsulation and their preparation methods. Background Technology

[0002] To further expand the application scenarios of wearable electronic products (such as flexible displays, electronic skin, smartphones, and soft medical devices) in real life, there is an urgent need to design and manufacture a universal flexible and stretchable power / energy storage device.

[0003] Currently, research on stretchable battery systems has yielded certain results. To ensure the stretchability of the battery system, elastomers are generally used for sealing and encapsulation. Elastomers have the following characteristics: (1) There are a large number of gaps between the polymer chains, which allow some small molecules such as water molecules and oxygen molecules to pass through effectively; (2) The larger the Young's modulus of the elastomer, the better the sealing performance, but the worse the stretchability.

[0004] Elastomer encapsulation can lead to water and air permeability issues, which severely affect the internal electrochemical stability of power / energy storage devices and cannot meet the requirements for the long-term safe and stable operation of electronic devices under different stretching conditions.

[0005] Although stretchable gas-barrier packaging plays a crucial role in the long-term stability and safe operation of stretchable batteries, it is often overlooked.

[0006] Some research has involved combining materials with good sealing properties but no stretchability, such as metal films and ceramic films, with elastomers after wrinkling. For example, patent CN104716386A discloses a flexible secondary battery comprising: an electrode assembly; and an external material surrounding the electrode assembly and having at least one joint, wherein the external material is bonded to itself at the at least one joint, and the at least one joint extends along the length of the electrode assembly at its edge. It also includes an elastomer located in a separation space, with a first sealing sheet and a second sealing sheet located on a first surface and a second surface of the elastomer, respectively.

[0007] However, the above composite encapsulation materials are not only easily damaged during the stretching process, but their sealing performance also fails to meet the sealing requirements of the battery system.

[0008] Therefore, exploring and designing the sealing structure and fabrication method of flexible stretchable energy storage devices to achieve long-term effective encapsulation of the energy storage core of flexible stretchable energy storage devices is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0009] To address the shortcomings of the existing technology, this invention provides an energy storage device encapsulated in liquid metal and its fabrication method. The flexible and stretchable energy storage device includes an encapsulation shell and an energy storage core encapsulated within the encapsulation shell. Liquid metal fills the gap between the encapsulation shell and the energy storage core, sealing the energy storage core. A support array structure facing the energy storage core is provided on the inner surface of the encapsulation shell, and / or a support array structure facing the encapsulation shell is provided on the outer surface of the energy storage core. The energy storage device encapsulated in liquid metal also exhibits good stability during stretching, and has great development potential as a power component of stretchable electronic devices.

[0010] In a first aspect, the present invention provides an energy storage device using liquid metal encapsulation, comprising: an encapsulation shell and an energy storage core encapsulated within the encapsulation shell, wherein both the encapsulation shell and the energy storage core are made of flexible and stretchable materials.

[0011] Liquid metal is filled into the gap between the packaging shell and the energy storage core to seal the energy storage core. The inner surface of the packaging shell is provided with a support array structure facing the energy storage core, and / or the outer surface of the energy storage core is provided with a support array structure facing the packaging shell.

[0012] The encapsulation shell is designed according to the energy storage core and the actual application requirements to achieve stretchable isolation from water, oxygen, etc. The type, size, capacity, and shape of the energy storage core can all be adjusted according to actual needs.

[0013] The support array set on the inner surface of the packaging shell ensures that the liquid metal maintains a stable seal to the energy storage core under deformation conditions (such as tension, compression, torsion, bending, etc.).

[0014] By combining the outer shell and the energy storage core, and based on the encapsulation of liquid metal (high-boiling-point liquid), a long-term stable and effective stretchable energy storage device can be prepared. This solves the compatibility problem between energy storage devices and wearable electronic devices, as well as the safety and cycle performance problems caused by the loose encapsulation of existing stretchable energy storage devices (such as batteries), and enables its application in wearable electronic devices.

[0015] Furthermore, the energy storage core includes electrodes and a flexible body. The electrodes include a positive electrode and a negative electrode, both of which are adhered to the flexible body.

[0016] Furthermore, the packaging shell includes an upper packaging shell and a lower packaging shell. The inner surfaces of both the upper and lower packaging shells are provided with a support array structure facing the energy storage core. The upper packaging shell is also provided with an inlet for filling liquid metal.

[0017] Furthermore, the material of the encapsulation shell and the flexible body is at least one of rubber and gel, and the liquid metal is one of gallium-based liquid metal, indium-based liquid metal, and bismuth-based liquid metal.

[0018] The stretchability of the packaging shell and the energy storage core depends on the Young's modulus of their respective materials, while the sealing performance depends on the liquid metal filling. By selecting packaging shell and energy storage core materials with different Young's moduli, energy storage devices with different stretchability can be fabricated to meet the stretching requirements of various wearable electronic devices.

[0019] Preferably, the material of the encapsulation shell and flexible body is one of the following: silicone rubber (crosslinked polydimethylsiloxane PDMS, aliphatic aromatic random copolyester Ecoflex), natural rubber, butyl rubber, nitrile rubber, chlorinated butyl rubber, chloroprene rubber, fluororubber, cis-butadiene rubber, polyurethane or other synthetic rubber, ion gel, hydrogel and other stretchable elastic layers.

[0020] The liquid metal is at least one of the following: gallium, gallium-indium alloy, gallium-aluminum alloy, gallium-zinc-gold alloy, gallium-silver alloy, gallium-indium-tin alloy, gallium-indium-tin-zinc alloy or other gallium-based liquid metals, or indium-bismuth alloy, indium-tin alloy, indium-tin-bismuth alloy, bismuth-lead-tin-cadmium alloy, bismuth-lead-tin-cadmium alloy, bismuth-lead-tin-cadmium-indium alloy, etc., which are liquid and have metallic bonds.

[0021] Furthermore, the energy storage core also includes a positive tab and a negative tab, which are connected to the positive and negative plates respectively, and both the positive and negative tabs are deposited with an insulating layer.

[0022] The electrode is connected to the tab and can be used for testing. To prevent short circuits between the positive and negative tabs caused by the liquid metal seal, an insulating layer is pre-deposited in the middle of the positive and negative tabs. The insulating layer can be made of parylene and its thickness can be set to about 10 μm.

[0023] Secondly, the present invention also provides a method for preparing an energy storage device using liquid metal encapsulation, comprising the following steps:

[0024] 1) Fabrication of the energy storage core;

[0025] 2) Fabricate the packaging shell, and fabricate a support array structure on the inner surface of the packaging shell;

[0026] 3) Seal the outer casing and the energy storage core, and inject liquid metal into the gap between the outer casing and the energy storage core to obtain an energy storage device encapsulated with liquid metal.

[0027] 4) Fill the energy storage core with electrolyte.

[0028] Furthermore, step 1) specifically includes the following steps:

[0029] 1.1) Prepare positive and negative electrode sheets separately;

[0030] 1.2) A hydrophilic membrane is used to wrap the positive electrode and the negative electrode separately;

[0031] 1.3) Adhere the positive and negative electrode sheets from step 1.2) to the upper surface of the flexible body;

[0032] 1.4) The upper surface of the flexible body in step 1.3) is encapsulated to prepare the energy storage core.

[0033] A hydrophilic diaphragm is used to make a diaphragm bag to wrap the positive and negative electrode plates separately, preventing short circuits caused by contact between the positive and negative electrode plates inside the battery cell.

[0034] Step 1.4) also includes:

[0035] Prepare positive and negative tabs, and deposit an insulating layer at the edge of the corresponding package shell of the positive and negative tabs; preferably, the thickness of the insulating layer is 10 μm.

[0036] The positive and negative electrode plates are connected to the positive and negative tabs, respectively.

[0037] Prepare a thin tube and connect it to the flexible body in step 1.3) to serve as an electrolyte injection tube.

[0038] Furthermore, step 1.1) specifically includes the following steps:

[0039] The first step is to prepare the positive electrode slurry;

[0040] The second step involves obtaining the precursor of the negative electrode active material using a solvent evaporation method.

[0041] The third step is to dissolve the asphalt in petroleum ether to form an asphalt solution;

[0042] The fourth step is to mix the asphalt solution and the negative electrode active material precursor in a mortar in a certain proportion; preferably, the mass ratio of asphalt to negative electrode active material precursor is 5:10 to 8:10.

[0043] Fifth step: Under the protection of an inert gas, the mixture obtained in the fourth step is heated and carbonized to obtain a carbonized mixture;

[0044] Step 6: Grind the carbonized mixture to obtain negative electrode active material powder;

[0045] Step 7: Prepare negative electrode slurry using the negative electrode active material powder from step 6;

[0046] The negative electrode slurry is prepared by mixing negative electrode active material powder with conductor material and binder material in a certain proportion; preferably, the mass ratio of negative electrode active material powder to conductor material and binder material is 8:1:0.9.

[0047] Step 8: The positive electrode slurry and the negative electrode slurry are uniformly coated onto the current collector in proportion. After drying, rolling and slicing, the positive electrode sheet and the negative electrode sheet are obtained respectively.

[0048] Preferably, the positive electrode slurry and the negative electrode slurry are uniformly coated at a ratio of 2:1 (positive electrode active material to negative electrode active material). Preferably, the current collector is made of stainless steel mesh. Preferably, the size of the positive electrode sheet and the negative electrode sheet is 45×3mm.

[0049] Furthermore, the positive electrode slurry includes lithium manganese oxide powder as an active material, carbon black as a conductor, and carboxymethyl cellulose and styrene-butadiene rubber as binders, with a preferred mass ratio of 8:1:0.3:0.6 to 9.4:0.3:0.1:0.2; the negative electrode slurry includes carbon-coated lithium titanium phosphate powder as an active material, carbon black as a conductor, and carboxymethyl cellulose and styrene-butadiene rubber as binders, with a preferred mass ratio of 8:1:0.3:0.6 to 9.4:0.3:0.1:0.2.

[0050] Furthermore, the preparation of the positive electrode slurry includes: mixing the positive electrode slurry components in the above mass ratio in a homogenizer.

[0051] Furthermore, the precursor of the negative electrode active material is obtained by solvent evaporation, specifically including the following steps:

[0052] Dissolve 1.02 g lithium acetate and 3.45 g ammonium dihydrogen phosphate in 150 mL of deionized water;

[0053] Add the alcohol-ester mixture to the above solution, heat to 60°C, and stir magnetically for 2 hours. The alcohol-ester mixture contains 5.68 g of tetraisopropyl titanate and 45 mL of n-butanol.

[0054] The solution was heated to 100°C and kept constant until all the solvent evaporated, resulting in a dry and uniform lithium titanium carbonate precursor.

[0055] Furthermore, the temperature for dissolving asphalt in petroleum ether is 100-120℃, and the stirring time is 10-20 min; preferably, the dissolution temperature is 100℃, and the stirring time is 15 min.

[0056] Argon is used as the inert gas, and carbonization is carried out in a tube furnace at a temperature of 680-750℃ for 10-12 hours. Preferably, the carbonization temperature is 700℃ and the time is 12 hours.

[0057] Furthermore, a support array structure is fabricated on the inner surface of the packaging shell, specifically including the following steps:

[0058] A) Apply heat release tape to the bottom of the screen, wherein the aperture of a single hole in the screen is larger than the size of the support piece;

[0059] Preferably, the screen is a square-hole screen, and the side length of the square hole is greater than the cross-sectional length of the supporting piece.

[0060] B) Pour the support piece down from the top of the screen, pass it through a single hole in the screen, and adhere it to the heat release tape to form a support array pattern;

[0061] C) Coat the inner surface of the encapsulation shell with adhesive of the same material;

[0062] D) Place the heat release tape from step B) on the inner surface of the encapsulation housing from step C);

[0063] E) Heating the encapsulation shell after step D) until the support array pattern completes the transfer and attachment from the heat-release tape to the inner surface of the encapsulation shell.

[0064] Furthermore, in step E, heating the packaging shell after step D) specifically includes the following steps:

[0065] Curing is carried out in an oven at 60-80℃ for 40-90 minutes, after which the oven temperature is increased to above 100℃. Preferably, the oven temperature is 80℃ and the curing time is 1 hour.

[0066] The energy storage device and its fabrication method using liquid metal encapsulation provided by this invention have at least the following beneficial effects:

[0067] (1) Based on the design of liquid metal gas-proof encapsulation, and integrating a support array structure, it is applied to stretchable energy storage devices. This enables stretchable energy storage devices to maintain long-term stable and safe operation.

[0068] (2) During the liquid metal filling process and in use, energy storage devices are inevitably subjected to local pressure. The support array structure can prevent the packaging shell from sticking to the energy storage core, causing seal failure. The support array set on the inner surface of the packaging shell ensures that the liquid metal maintains a stable seal to the energy storage core under deformation (such as tension, compression, torsion, bending, etc.), thereby ensuring the stretchability of the entire liquid metal-based packaging system. Attached Figure Description

[0069] Figure 1 A structural diagram of an energy storage device using liquid metal encapsulation provided by the present invention;

[0070] Figure 2 A schematic flowchart illustrating the process of preparing the positive and negative electrode sheets in the battery core according to a certain embodiment of the present invention;

[0071] Figure 3 A schematic flowchart illustrating the process of encapsulating a battery core according to one embodiment of the present invention;

[0072] Figure 4 A schematic flowchart illustrating the process of preparing a stretchable battery according to one embodiment of the present invention;

[0073] Figure 5 Figures showing the test results of mass change of stretchable batteries under different strain states in the embodiments and comparative examples provided by the present invention.

[0074] Figure 6 Figures showing the room temperature cycle life test results of stretchable batteries provided in the embodiments and comparative examples of the present invention;

[0075] Figure 7 Graphs showing the electrochemical impedance test results of stretchable batteries provided for embodiments and comparative examples of the present invention;

[0076] Figure 8 Figure 1 shows the charge-discharge test results of a stretchable battery under different strain conditions according to an embodiment of the present invention.

[0077] Figure 9 The graph shows the cyclic test results of the stretchable battery under different strain states according to an embodiment of the present invention.

[0078] Explanation of reference numerals in the attached figures:

[0079] 1-Encapsulation shell, 11-Upper encapsulation shell, 12-Lower encapsulation shell, 111-Liquid inlet, 2-Energy storage core, 21-Electrode, 211-Positive electrode, 212-Negative electrode, 22-Flexible body, 23-Taper, 231-Positive electrode, 232-Negative electrode, 233-Insulating layer, 24-Support array, 25-Stretch sheet, 26-Fine tube, 3-Liquid metal. Detailed Implementation

[0080] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. 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.

[0081] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0082] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0083] Liquid metals possess low gas permeability and flexible mechanical properties, opening up design possibilities for stretchable, gas-tight seals. This facilitates the long-term stable application of stretchable, soft devices (systems) sensitive to various gas permeation, such as flexible electronics, wearable systems, energy generation and storage systems, heat transfer systems, sensing systems, and biomedical systems.

[0084] like Figure 1 As shown, the present invention provides an energy storage device encapsulated using liquid metal 3, comprising: an encapsulation shell 1 and an energy storage core 2 encapsulated within the encapsulation shell 1, both the encapsulation shell 1 and the energy storage core 2 being flexible and stretchable;

[0085] Liquid metal 3 is filled into the gap between the packaging shell 1 and the energy storage core 2 to seal the energy storage core 2. The inner surface of the packaging shell 1 is provided with a support array 24 structure facing the energy storage core 2, and / or the outer surface of the energy storage core 2 is provided with a support array structure 24 facing the packaging shell 1.

[0086] Based on a liquid metal 3-gas-barrier encapsulation design, and integrating a support array 24 structure, it is applied to stretchable energy storage devices (such as batteries). This ensures that stretchable energy storage devices maintain long-term stable and safe operation.

[0087] During the filling process of liquid metal 3 and in use, energy storage devices are inevitably subjected to localized pressure. The support array 24 structure can prevent the packaging shell 1 from sticking to the energy storage core 2, causing seal failure. The support array 24, which is set on the inner surface of the packaging shell 1, ensures that the liquid metal 3 maintains a stable seal on the energy storage core 2 under deformation conditions (such as tension, compression, torsion, bending, etc.), thereby guaranteeing the stretchability of the entire packaging system based on liquid metal 3.

[0088] Energy storage devices include phase change energy storage devices, mechanical energy storage devices, and electrochemical energy storage devices (such as batteries). Batteries can be lithium-ion battery systems, sodium-ion battery systems, silver-zinc battery systems, etc.; the electrolyte of the battery can be an aqueous electrolyte system or an organic electrolyte system. Of course, it also includes fuel cells, supercapacitors, etc.

[0089] When the energy storage device is a battery, the battery system can be an intrinsically stretchable energy storage device in which all functional components such as electrode 21 and current collector are stretchable, or it can be designed as a structure in which the entire energy storage device is stretchable, but some components are not stretchable.

[0090] The energy storage core 2 includes functional components and a flexible body 22. The functional components include a positive electrode 211 and a negative electrode 212, both of which are adhered to the flexible body 22.

[0091] The encapsulation housing 1 includes an upper encapsulation housing 11 and a lower encapsulation housing 12. The inner surfaces of both the upper encapsulation housing 11 and the lower encapsulation housing 12 are provided with a support array 24 structure facing the energy storage core 2. The flexible upper encapsulation housing 11 is also provided with an inlet 111 for filling liquid metal 3.

[0092] The encapsulation shell 1 and the flexible body 22 are made of at least one of rubber and gel, and the liquid metal 3 is one of gallium-based liquid metal 3, indium-based liquid metal 3, and bismuth-based liquid metal 3.

[0093] The encapsulation shell 1 and the flexible body 22 are made of one of the following materials: silicone rubber (crosslinked polydimethylsiloxane PDMS, aliphatic aromatic random copolyester Ecoflex), natural rubber, butyl rubber, nitrile rubber, chlorinated butyl rubber, chloroprene rubber, fluororubber, cis-butadiene rubber, polyurethane or other synthetic rubber, ionogel, hydrogel and other stretchable elastic layers.

[0094] The liquid metal 3 is at least one of the following materials that are in a liquid state and have metallic bonds: gallium, gallium-indium alloy, gallium-aluminum alloy, gallium-zinc-gold alloy, gallium-silver alloy, gallium-indium-tin alloy, gallium-indium-tin-zinc alloy or other gallium-based liquid metals, or indium-bismuth alloy, indium-tin alloy, indium-tin-bismuth alloy, bismuth-lead-tin-cadmium alloy, bismuth-lead-tin-cadmium alloy, bismuth-lead-tin-cadmium-indium alloy, etc.

[0095] The energy storage core 2 also includes a positive tab 231 and a negative tab 232, which are connected to the positive electrode plate 211 and the negative electrode plate 212, respectively. Both the positive tab 231 and the negative tab 232 have an insulating layer 233 deposited on them. The insulating layer 233 can be made of parylene. The positions where the insulating layer 233 is deposited on the positive tab 231 and the negative tab 232 need to correspond to the edge of the packaging shell 1. The thickness of the insulating layer 233 is about 10 μm.

[0096] The stretchability of the packaging shell 1 and the energy storage core 2 depends on the Young's modulus of their respective materials, while the sealing performance depends on the liquid metal 3 used for filling. By selecting packaging shell 1 and energy storage core 2 materials with different Young's moduli, energy storage devices with different stretchability can be fabricated to meet the stretching requirements of various wearable electronic devices.

[0097] The outer casing 1 is designed according to the energy storage core 2 and the actual application requirements to achieve stretchable isolation from water, oxygen, etc. The type, size, capacity, and shape of the energy storage core 2 can all be adjusted according to actual needs.

[0098] By combining the outer shell 1 with the energy storage core 2 and encapsulating it with liquid metal 3 (high-boiling-point liquid), a long-term stable and effective stretchable energy storage device can be prepared. This solves the compatibility problem between energy storage devices and wearable electronic devices, as well as the safety and cycle performance problems caused by the loose encapsulation of existing stretchable energy storage devices (such as batteries), and enables its application in wearable electronic devices.

[0099] Tension sheets 25 are bonded to the upper and lower outer surfaces of the front and rear ends of the energy storage core 2. The tension sheets 25 provide the stress points during the deformation process of the energy storage core 2, and the tension sheets 25 do not affect the sealing performance. The tension sheets 25 can be made of glass. A thin tube 26 is connected to the flexible body 22. The thin tube 26 can be made of thin copper tube. The thin tube 26 extends through the outer edge of the encapsulation shell 1. After the energy storage device is sealed with liquid metal 3, electrolyte is injected into the energy storage core 2.

[0100] The present invention also provides a method for fabricating an energy storage device using liquid metal encapsulation, comprising the following steps:

[0101] 1) Fabrication of the energy storage core;

[0102] 2) Fabricate the packaging shell, and fabricate a support array structure on the inner surface of the packaging shell;

[0103] 3) Seal the outer casing and the energy storage core, and inject liquid metal into the gap between the outer casing and the energy storage core to obtain an energy storage device encapsulated with liquid metal.

[0104] 4) Fill the energy storage core with electrolyte.

[0105] The liquid metal is injected using a vacuum filling method. After the liquid metal is filled through the inlet, the inlet is sealed with the encapsulation shell material.

[0106] Step 1), specifically includes the following steps:

[0107] 1.1) Prepare positive and negative electrode sheets separately;

[0108] 1.2) A hydrophilic diaphragm is used, comprising a positive electrode and a negative electrode.

[0109] 1.3) Adhere the positive and negative electrode sheets from step 1.2) to the upper surface of the flexible body;

[0110] 1.4) The upper surface of the flexible body in step 1.3) is encapsulated to prepare the energy storage core.

[0111] Step 1.4) also includes:

[0112] Prepare positive and negative tabs, and deposit insulating layers at the corresponding edges of the packaging shell for the positive and negative tabs;

[0113] The positive and negative electrode plates are connected to the positive and negative tabs, respectively.

[0114] Prepare a thin tube and connect it to the flexible body in step 1.3) to serve as an electrolyte injection tube.

[0115] Step 1.1) specifically includes the following steps:

[0116] The first step is to prepare the positive electrode slurry;

[0117] The second step involves obtaining the precursor of the negative electrode active material using a solvent evaporation method.

[0118] The third step is to dissolve the asphalt in petroleum ether to form an asphalt solution;

[0119] The fourth step is to mix the asphalt solution and the negative electrode active material precursor in a mortar in a certain proportion; preferably, the mass ratio of asphalt to negative electrode active material precursor is 6:10.

[0120] Fifth step: Under the protection of an inert gas, the mixture obtained in the fourth step is heated and carbonized to obtain a carbonized mixture;

[0121] Step 6: Grind the carbonized mixture to obtain negative electrode active material powder;

[0122] Step 7: Prepare negative electrode slurry using the negative electrode active material powder from step 6;

[0123] The negative electrode slurry is prepared by mixing negative electrode active material powder with conductor material and binder material in a certain proportion; preferably, the mass ratio of negative electrode active material powder to conductor material and binder material is 8:1:0.9.

[0124] Step 8: The positive electrode slurry and the negative electrode slurry are uniformly coated onto the current collector in proportion. After drying, rolling and slicing, the positive electrode sheet and the negative electrode sheet are obtained respectively.

[0125] Preferably, the positive electrode slurry and the negative electrode slurry are uniformly coated at a ratio of 2:1 (positive electrode active material to negative electrode active material). Preferably, the current collector is made of stainless steel mesh. Preferably, the dimensions of the positive electrode sheet and the negative electrode sheet are 45 × 3 mm (length × width).

[0126] The preparation of the positive electrode slurry includes: mixing the positive electrode slurry components in the above mass ratio in a homogenizer.

[0127] The asphalt is dissolved in petroleum ether at a temperature of 100°C and a stirring time of 15 min; preferably, the dissolution temperature is 100°C and the stirring time is 15 min.

[0128] Argon is used as the inert gas, and carbonization is carried out in a tube furnace at a temperature of 700°C for 12 hours. Preferably, the carbonization temperature is 700°C and the time is 12 hours.

[0129] The support array structure is fabricated on the inner surface of the package shell, specifically including the following steps:

[0130] A) Apply heat release tape to the bottom of the screen, wherein the aperture of a single hole in the screen is larger than the size of the support piece;

[0131] Preferably, the screen is a square-hole screen, and the side length of the square hole is greater than the cross-sectional length of the supporting piece.

[0132] B) Pour the support piece down from the top of the screen, pass it through a single hole in the screen, and adhere it to the heat release tape to form a support array pattern;

[0133] C) The inner surface of the encapsulation shell is coated with an adhesive of the same material. For example, the encapsulation shell and the adhesive are based on silicone, and the components can be the same or different.

[0134] D) Place the heat release tape from step B) on the inner surface of the encapsulation housing from step C);

[0135] E) Heating the encapsulation shell after step D) until the support array pattern completes the transfer and attachment from the heat-release tape to the inner surface of the encapsulation shell.

[0136] In step E), heating the packaging shell after step D) specifically includes the following steps:

[0137] Curing is carried out in an oven at 60-80℃ for 40-90 minutes, after which the oven temperature is increased to above 100℃. Preferably, the oven temperature is 80℃ and the curing time is 1 hour.

[0138] Example:

[0139] This embodiment takes the fabrication of a flexible stretchable battery as an example. The stretchable battery is a lithium-ion battery (LIB) with an aqueous electrolyte. The core of the stretchable battery includes electrodes, electrolyte, tabs, and polydimethylsiloxane (PDMS) elastomer, etc. The outer shell is a PDMS shell, the injected sealing material is liquid metal, and the support array structure is a glass bead array.

[0140] In this embodiment, the dimensions of each component in the stretchable battery are as follows:

[0141] The positive and negative electrodes have dimensions of 0.2×3×45mm (thickness×width×length), with a thickness ranging from 0.1-0.3mm, a width of 2-4mm, and a length of 40-50mm. The inner core dimensions are 2.6mm×20×64mm, the inner core cavity dimensions are 1mm×16×60mm, and the overall battery dimensions are 4.2mm×28×72mm. The height of the gap between the outer shell and the inner core is 0.2-1mm, preferably 0.5mm. Furthermore, the glass beads have a diameter of 0.25mm-0.3mm, and the spacing between adjacent glass beads is 0.19-0.22mm, preferably 0.215mm.

[0142] like Figure 2-4 As shown, the method for fabricating a stretchable battery using liquid metal encapsulation specifically includes the following steps:

[0143] Fabricate the battery core, fabricate the encapsulation shell, fabricate a support array structure on the inner surface of the encapsulation shell, and seal the encapsulation shell and the battery core (e.g., Figure 4 As shown in i), liquid metal (such as...) is injected into the gap between the packaging shell and the battery core. Figure 4 As shown in ii), a stretchable battery encapsulated with liquid metal (as shown in ii) is obtained. Figure 4 As shown in iii), the energy storage core can be used after being filled with electrolyte.

[0144] (a) Preparation of battery core.

[0145] Preparation of the negative electrode active material for the battery: 1.02 g of lithium acetate and 3.45 g of ammonium dihydrogen phosphate were dissolved in 150 mL of deionized water; a mixture containing 5.68 g of tetraisopropyl titanate and 45 mL of n-butanol was slowly added to the above solution and heated to 60 °C, and magnetically stirred for 2 h; the above mixed solution was further heated to 100 °C and kept constant until all the solvent evaporated, resulting in a dry and uniform lithium titanium carbonate precursor; asphalt was dissolved in petroleum ether under the following conditions: stirring at 100 °C for 15 min to form an asphalt solution; the asphalt solution and the lithium titanium carbonate precursor were mixed in a mortar at a mass ratio of 6:10; under argon protection, the mixture obtained in the previous step was placed in a tube furnace and heated to carbonize at a temperature of 700 °C for 12 h to obtain a carbonized mixture; finally, the carbonized mixture was ground to obtain carbon-coated lithium titanium carbonate powder.

[0146] Preparation of positive and negative electrode sheets: The positive electrode slurry consists of lithium manganese oxide powder as an active material, carbon black as a conductor, and carboxymethyl cellulose and styrene-butadiene rubber as binders, which are mixed in a homogenizer at a mass ratio of 8:1:0.3:0.6.

[0147] The negative electrode slurry comprises carbon-coated lithium titanium phosphate powder as the active material, carbon black as the conductor, and carboxymethyl cellulose and styrene-butadiene rubber as binders, which are mixed in a mass ratio of 8:1:0.3:0.6.

[0148] The positive electrode slurry and negative electrode slurry are uniformly coated onto the current collector stainless steel mesh (e.g., lithium manganese oxide and lithium titanium carbonate) at a ratio of 2:1 by mass of active materials (i.e., lithium manganese oxide and lithium titanium carbonate). Figure 2 As shown in i), after drying, rolling, and slicing, positive and negative electrode sheets are obtained, with dimensions of 45×3mm (length×width).

[0149] Battery core fabrication: Hydrophilic porous polytetrafluoroethylene (PTFE) is used to wrap the positive and negative electrode sheets (e.g., ...). Figure 2 (As shown in ii); Prepare positive and negative tabs, made of stainless steel, and deposit a layer of parylene insulating layer on the corresponding edges of the packaging shell of the positive and negative tabs. Connect the positive and negative tabs to the positive and negative tabs respectively (as shown in ii). Figure 2 As shown in iii), the connected positive and negative electrode plates are assembled into the PMDS elastomer (e.g., Figure 3 i and Figure 3 As shown in ii), a thin copper tube is prepared and connected to a PMDS elastomer to serve as an injection tube for the aqueous electrolyte, thus obtaining the battery core (as shown in ii). Figure 3 (as shown in iii).

[0150] (ii) Fabrication of a support array on the inner surface of the encapsulation shell.

[0151] A support array structure is prepared on the inner surface of the encapsulation shell: Heat-release tape is attached to the bottom of a square-hole screen, the side length of which is greater than the size of the individual support piece (glass beads are used in this embodiment). In this embodiment, the side length of the square hole in the screen is 0.4 mm, and the diameter of the glass beads is 0.3 mm. The glass beads are poured from the top of the screen, pass through the screen holes, and adhere to the heat-release tape, forming a glass bead array pattern. To transfer the arrayed glass beads to the inner surface of the PDMS shell, a thin layer of uncured PDMS-based adhesive is applied to the inner surface of the PDMS using a scraping process. The heat-release tape with the glass bead array is then attached to the inner surface of the PDMS shell. After curing in an oven at 80°C for 1 hour, the oven temperature is further increased to 100°C to release the glass beads from the heat-release tape, thereby achieving the transfer of the glass beads to the inner surface of the PDMS shell.

[0152] (iii) Filling with liquid metal.

[0153] The liquid metal is injected using a vacuum filling method. After the liquid metal is filled through the inlet, the inlet is sealed with PDMS.

[0154] Comparative example:

[0155] Based on the previous example, the step of "injecting liquid metal into the gap between the PDMS shell and the stretchable battery core" was omitted, and the resulting stretchable battery was not filled with liquid metal.

[0156] Performance testing:

[0157] The stretchable batteries prepared in the above examples and comparative examples were used to test the device performance.

[0158] Quality testing:

[0159] The hermeticity of liquid metal encapsulation systems can be characterized by monitoring the mass change of lithium-ion batteries filled with aqueous electrolyte.

[0160] The lithium-ion batteries prepared in the examples and comparative examples were respectively injected with aqueous electrolyte into the inner core of the lithium-ion battery through copper capillary tubes. After filling, the battery was placed on an analytical balance, which was then placed in a glove box filled with argon gas to monitor the mass change of the lithium-ion battery.

[0161] like Figure 5 The curves shown are: Without LM-based seal-S-0% for the mass change of the control lithium-ion battery in its original state; Without LM-based seal-S-20% for the mass change of the control lithium-ion battery in its 20% stretched state; With LM-based seal-S-0% for the mass change of the lithium-ion battery in its original state; and With LM-based seal-S-20% for the mass change of the lithium-ion battery in its 20% stretched state. During the 24-hour measurement period, the lithium-ion battery with liquid metal encapsulation showed no mass change in either the original or 20% stretched state. In contrast, the control lithium-ion battery without liquid metal encapsulation experienced rapid mass loss in both states, indicating that the electrolyte continuously permeates outward through the PDMS elastomer via water vapor within the control battery. In the 20% stretched state, the increased surface area of ​​the control battery accelerated water vapor permeation, resulting in a greater mass change than the unstretched control sample.

[0162] Battery performance test:

[0163] Battery performance testing without deformation: The lithium-ion batteries prepared in the examples and comparative examples were subjected to cycle life tests at room temperature.

[0164] Figure 6 The cycle life at room temperature was demonstrated for lithium-ion batteries based on liquid metal encapsulation and those without liquid metal encapsulation. Figure 6 In the figures, "Without LM-based Seal" represents the cycle life curve of a lithium-ion battery without liquid metal encapsulation at room temperature, "With LM-based Seal" represents the cycle life curve of a lithium-ion battery with liquid metal encapsulation at room temperature, and "Coulombic efficiency with LM-based Seal" represents the coulombic efficiency curve of the lithium-ion battery with liquid metal encapsulation. The battery with liquid metal encapsulation retains approximately 90% of its reversible capacity after 140 cycles and approximately 72.5% of its reversible capacity after 500 cycles. The coulombic efficiency of the lithium-ion battery with liquid metal encapsulation is approximately 98%.

[0165] In contrast, lithium-ion batteries without liquid metal encapsulation exhibit significant capacity decay during cycling due to the aqueous electrolyte permeating outward through PDMS in the form of water vapor and air permeating inward through PDMS, and eventually fail completely after 160 cycles.

[0166] The reduction in battery capacity in its unstretched state is mainly due to unavoidable side reactions during lithium-ion battery operation, rather than gas permeation.

[0167] The lithium-ion batteries prepared in the examples and comparative examples were subjected to electrochemical impedance spectroscopy tests.

[0168] Figure 7 Comparing the electrochemical impedance spectroscopy (EIS) spectra of the two batteries at 100 cycles, the impedance of the lithium-ion battery with liquid metal encapsulation was significantly lower than that without liquid metal encapsulation. In the figure, "With LM-based seal" represents the impedance curve of the lithium-ion battery with liquid metal encapsulation, and "Without LM-based seal" represents the impedance curve of the lithium-ion battery without liquid metal encapsulation. Due to the lack of a reliable seal provided by liquid metal, the impedance of the control sample continuously increases during battery operation. This indicates that the electrolyte in the control sample is also continuously lost, gradually drying out, and the electrodes are constantly deteriorating, ultimately leading to battery failure.

[0169] Battery performance testing under deformation conditions:

[0170] The lithium-ion batteries prepared in the examples were tested for charge and discharge under different morphological conditions.

[0171] Figure 8 As shown, the constant current charge and discharge of a lithium-ion battery in its undeformed state and under different strain states, in its natural unstretched state ( Figure 8 In the 5% (0%) range, lithium-ion batteries can achieve a high reversible specific capacity of ~105.5 mAh / g, while at 5% (0%)... Figure 8S-5%), 10% Figure 8 S-10% and 20% Figure 8 Under a stretched state (S-20%), its specific capacity can still be maintained at 104.8 mAh / g, 105.8 mAh / g, and 105.0 mAh / g, respectively. The close overlap of these curves indicates that the battery can operate normally even under a 20% stretch.

[0172] The lithium-ion batteries prepared in the examples were subjected to cycle tests under different morphological conditions.

[0173] Under conditions of 20% tensile strain, 60° bending strain, and 90° torsion, at 0.6 mA / cm 2 The current density was subjected to cyclic testing. The battery first ran one cycle in a natural, unstretched state, then five cycles in a stretched, bent, and torsional state, and then five cycles in a natural, unstretched state. Figure 9 This indicates that regardless of the battery's deformation state, its constant current charge-discharge curve and corresponding capacity remain almost unchanged.

[0174] By using an array of glass beads as spacers, the collapse of the PDMS shell encapsulating the liquid metal was prevented during battery deformation, thus achieving a stable seal based on liquid metal. The experimental results demonstrate the excellent stability of lithium-ion batteries encapsulated in liquid metal; therefore, such devices have great potential as power components in stretchable electronic devices.

[0175] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. An energy storage device using liquid metal encapsulation, characterized in that, Includes: a package shell and an energy storage core enclosed within the package shell. Both the package shell and the energy storage core are flexible and stretchable, and the package shell and the energy storage core are made of different Young's moduli. Liquid metal is filled into the gap between the packaging shell and the energy storage core to seal the energy storage core. The inner surface of the packaging shell is provided with a support array structure facing the energy storage core, and / or the outer surface of the energy storage core is provided with a support array structure facing the packaging shell, so that the energy storage device maintains the seal of the liquid metal on the energy storage core in the deformed state. The energy storage core includes electrodes and a flexible body. The electrodes include positive and negative electrode plates, which are both adhered to the flexible body. The encapsulation shell and flexible body are made of at least one of rubber and gel.

2. The energy storage device using liquid metal encapsulation as described in claim 1, characterized in that, Liquid metal is one of gallium-based liquid metal, indium-based liquid metal, or bismuth-based liquid metal.

3. The energy storage device using liquid metal encapsulation as described in claim 1, characterized in that, The energy storage core also includes a positive tab and a negative tab, which are connected to the positive and negative plates respectively. Both the positive and negative tabs have an insulating layer deposited on them.

4. A method for preparing an energy storage device using liquid metal encapsulation as described in any one of claims 1-3, characterized in that, Includes the following steps: 1) Fabrication of the energy storage core; 2) Fabricate the packaging shell, and fabricate a support array structure on the inner surface of the packaging shell; 3) Seal the outer casing and the energy storage core, and inject liquid metal into the gap between the outer casing and the energy storage core to obtain an energy storage device encapsulated with liquid metal. 4) Fill the energy storage core with electrolyte.

5. The method for preparing an energy storage device using liquid metal encapsulation as described in claim 4, characterized in that, Step 1), specifically includes the following steps: 1.1) Prepare positive and negative electrode sheets separately; 1.2) A hydrophilic membrane is used to wrap the positive electrode and the negative electrode separately; 1.3) Adhere the positive and negative electrode sheets from step 1.2) to the upper surface of the flexible body; 1.4) The upper surface of the flexible body in step 1.3) is encapsulated to prepare the energy storage core.

6. The method for preparing an energy storage device using liquid metal encapsulation as described in claim 5, characterized in that, Step 1.1) specifically includes the following steps: The first step is to prepare the positive electrode slurry; The second step involves obtaining the precursor of the negative electrode active material using a solvent evaporation method. The third step is to dissolve the asphalt in petroleum ether to form an asphalt solution; The fourth step is to mix the asphalt solution and the negative electrode active material precursor in a mortar in a certain proportion; Fifth step: Under the protection of an inert gas, the mixture obtained in the fourth step is heated and carbonized to obtain a carbonized mixture; Step 6: Grind the carbonized mixture to obtain negative electrode active material powder; Step 7: Prepare negative electrode slurry using the negative electrode active material powder from step 6; Step 8: The positive electrode slurry and the negative electrode slurry are uniformly coated onto the current collector in proportion. After drying, rolling and slicing, the positive electrode sheet and the negative electrode sheet are obtained respectively.

7. The method for preparing an energy storage device using liquid metal encapsulation as described in claim 6, characterized in that, The temperature for dissolving asphalt in petroleum ether is 100-120℃, and the stirring time is 10-20 minutes. Argon is used as the inert gas, and the heating and carbonization are carried out in a tube furnace at a temperature of 680-750℃ for 10-12 hours.

8. The method for preparing an energy storage device using liquid metal encapsulation as described in claim 4, characterized in that, The support array structure is fabricated on the inner surface of the package shell, specifically including the following steps: A) Apply heat release tape to the bottom of the screen, wherein the aperture of a single hole in the screen is larger than the size of the support piece; B) Pour the support piece down from the top of the screen, pass it through a single hole in the screen, and adhere it to the heat release tape to form a support array pattern; C) Coat the inner surface of the encapsulation shell with adhesive of the same material; D) Place the heat release tape from step B) on the inner surface of the encapsulation housing from step C); E) Heating the encapsulation shell after step D) until the support array pattern completes the transfer and attachment from the heat-release tape to the inner surface of the encapsulation shell.

9. The method for preparing an energy storage device using liquid metal encapsulation as described in claim 8, characterized in that, In step E), the packaging shell from step D) is heated, specifically including the following steps: Cure in an oven at 60-80℃ for 40-90 minutes, then raise the oven temperature to above 100℃.

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