A new lithium battery with ultra-thin metal casing

Abstract

The present invention provides a novel lithium battery with an ultra-thin metal shell, comprising an ultra-thin metal shell and a bare cell located inside the ultra-thin metal shell, wherein the bare cell comprises a positive electrode sheet, a negative electrode sheet, a separator, a positive electrode tab, a negative electrode tab, and an electrolyte, wherein a thermoplastic polymer sealing layer is provided between the positive electrode tab, the negative electrode tab and the ultra-thin metal shell, and the ultra-thin metal shell comprises an ultra-thin metal plate layer, and the surface of the ultra-thin metal plate layer is coated with a high thermal conductivity insulating coating. The power battery made with the ultra-thin metal shell has the advantages of high energy density, good heat dissipation effect, high safety, high packaging strength and high electrolyte corrosion resistance, good long-term reliability and lower cost.

Description

Technical Field

[0001] The invention relates to the technical field of lithium batteries, and in particular to a novel lithium battery with an ultra-thin metal shell. Background Art

[0002] In recent years, with the increasing environmental pollution, the new energy industry has received more and more attention. As an important component of electric vehicles, lithium-ion power batteries have a direct impact on the promotion and use of electric vehicles due to their safety performance, energy density and cycle life, thus attracting widespread attention.

[0003] At present, there are three main types of shell structures for lithium-ion power batteries on the market, namely cylindrical steel shell, square aluminum shell or steel shell, and aluminum-plastic composite film soft packaging. The commonly used model of cylindrical steel shell power battery is 18650. This type of battery shell is of standard size and is easy to mass-produce, thereby reducing the manufacturing cost of a single battery. However, due to the small capacity of a single 18650 battery, an electric car requires a large number of single batteries for series and parallel combination, which greatly increases the complexity and cost of subsequent battery module assembly and power management system (BMS); square aluminum shell or steel shell power battery is a commonly used shell structure at present. Since square aluminum shell or steel shell power battery generally has a large single cell capacity, and the heat transfer and thermal conductivity of the metal shell is relatively good, the difficulty and cost of subsequent battery module and BMS assembly are lower than those of cylindrical steel shell power batteries. At present, most domestic power battery factories use this type of structure, but the shell thickness of square aluminum shell or steel shell is difficult to make thin, and is lower than 100mm. Aluminum shells with a thickness of 0.6mm cannot be used because of various problems that are difficult to solve during use. Therefore, the shell occupies a large volume space, and the energy density of the single battery cell is lower than the previous year, resulting in limited improvement in the capacity density of the entire battery pack; aluminum-plastic composite film soft-package battery, as the name suggests, is a power battery that uses aluminum-plastic composite film as the battery cell shell material. Its biggest feature is that its shell material is very thin (0.1mm or even as thin as 0.06mm) and the volume of the single battery cell can be made very large, so the energy density of the single battery cell is the highest. At the same time, due to the aluminum-plastic composite film soft packaging, when gas is produced inside the battery cell due to other safety abnormalities such as overcharging or internal short circuit, the shell will only swell slightly when gas is produced inside. When a large amount of gas is produced, it will only break through the edge thermal composite packaging port to exhaust and reduce pressure. Generally, there will be no explosion. It is the safest of the three shell structures. However, the processing and manufacturing technology threshold of aluminum-plastic composite film materials is relatively high, and the market has long been dominated by Showa Denko and DNP of Japan, and the cost is also high. In addition, since the inner and outer layers of the aluminum-plastic composite film are polymers, its heat transfer and heat conduction effect is poor. Therefore, it is generally necessary to add a heat conduction plate or a cooling plate in the module structure of the soft-package battery, which takes up a lot of space and reduces the module assembly efficiency. Therefore, although the energy density of a single cell of a soft-package power battery is the highest, the overall capacity density of the battery pack after assembly has no advantage. Therefore, the three existing shell structures have their own advantages and disadvantages, and each has its own trade-offs. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a new type of lithium battery with an ultra-thin metal shell. The power battery made using this ultra-thin metal shell has the advantages of high energy density, good heat dissipation effect, high safety, high packaging strength and high resistance to electrolyte corrosion, good long-term reliability and lower cost.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A novel lithium battery with an ultra-thin metal shell comprises an ultra-thin metal shell and a bare battery cell located inside the ultra-thin metal shell, wherein the bare battery cell comprises a positive electrode sheet, a negative electrode sheet, an isolation film, a positive electrode tab, a negative electrode tab, and an electrolyte, and a thermoplastic polymer sealing layer is provided between the positive electrode tab, the negative electrode tab and the ultra-thin metal shell; the ultra-thin metal shell comprises an ultra-thin metal plate layer, and the surface of the ultra-thin metal plate layer is coated with a high thermal conductivity insulating coating.

[0007] Furthermore, the thermoplastic polymer sealing layer includes a positive electrode tab hot-melt sealing layer and a negative electrode tab hot-melt sealing layer, the positive electrode tab hot-melt sealing layer includes a bonding layer between the positive electrode tab and the thermoplastic polymer, a bonding layer between the thermoplastic polymer and the ultra-thin metal shell, and a hot-melt fusion layer between the positive electrode tab and the ultra-thin metal shell; the negative electrode tab hot-melt sealing layer includes a bonding layer between the negative electrode tab and the thermoplastic polymer, a bonding layer between the thermoplastic polymer and the ultra-thin metal shell, and a hot-melt fusion layer between the negative electrode tab and the ultra-thin metal shell.

[0008] Furthermore, the high thermal conductivity insulating coating includes the high thermal conductivity coating and the electronic insulating coating, the high thermal conductivity coating is a graphite thermal conductive film or a thermal conductive silicone thermal conductive film, and the electronic insulating coating is a thermal conductive film with a resistivity greater than 10 10 Ω·m inorganic substance or polymer. Further, the high thermal conductivity insulating coating is a high thermal conductivity insulating composite coating, and the high thermal conductivity insulating composite coating is a graphite thermal conductive composite film or a graphene thermal conductive composite film with PET coated on the outer surface.

[0009] Furthermore, the thickness of the ultra-thin metal shell is 0.02-0.2 mm.

[0010] Furthermore, the thickness of the ultra-thin metal shell is 0.05-0.15 mm.

[0011] Furthermore, the ultra-thin metal plate layer is made of stainless steel or aluminum alloy, the stainless steel is any one of austenitic stainless steel, ferritic stainless steel, and austenitic-ferritic duplex stainless steel, and the aluminum alloy is any one of 1 series pure aluminum, 1 series aluminum alloy, 3 series aluminum-manganese alloy, 5 series aluminum-magnesium alloy, and 6 series aluminum-silicon alloy.

[0012] Furthermore, it is characterized in that the non-positive pole tab and negative pole tab of the bare battery cell are packaged with the ultra-thin metal shell by welding.

[0013] Furthermore, the thermoplastic polymer sealing layer includes at least one of PP and CPP, which are prepared by extruding the thermoplastic polymer sealing layer in an extruder.

[0014] The above technical solution has the following technical effects:

[0015] 1. The novel lithium battery with an ultra-thin metal shell of the present invention adopts an ultra-thin metal shell, so that the novel lithium battery has both the high sealing and mechanical strength of a square aluminum shell battery shell, which is beneficial to the reliability and durability of the power battery during long-term operation, and also has the safety and ultra-thin thickness of an aluminum-plastic composite film soft-package battery shell, thereby reducing the space occupied by non-effective battery components;

[0016] 2. The new lithium battery with an ultra-thin metal shell of the present invention has good thermal conductivity, which can further reduce the space occupied by the heat-conducting components during the module assembly process, taking into account the improvement of energy density and the heat dissipation performance of the battery. At the same time, the cost of the shell material is also relatively advantageous compared with the existing battery shell materials;

[0017] 3. The novel lithium battery of the present invention has an ultra-thin metal shell, wherein the positive electrode tab, the negative electrode tab and the ultra-thin metal shell are electronically isolated by a thermoplastic polymer sealing layer to prevent the positive electrode tab and the negative electrode tab from being connected through the ultra-thin metal shell to form a short circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of the novel lithium battery with an ultra-thin metal shell of the present invention before packaging;

[0019] Figure 2 It is a schematic diagram of disassembling multiple layers of the ultra-thin metal housing of the present invention;

[0020] Figure 3 It is a schematic diagram of the structure of the new lithium battery with an ultra-thin metal shell after packaging of the present invention;

[0021] In the figure: ultra-thin metal shell -10; ultra-thin metal plate layer -11; high thermal conductivity coating -12; electronic insulation coating -13; bare battery cell -20; positive electrode tab -21; negative electrode tab -22; positive electrode tab hot-melt sealing layer -31; negative electrode tab hot-melt sealing layer -32. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0023] Combination Figure 1-3The present invention provides a novel lithium battery with an ultra-thin metal shell, comprising an ultra-thin metal shell 10 and a bare cell 20 located inside the ultra-thin metal shell, wherein the bare cell comprises a positive electrode sheet, a negative electrode sheet, a separator, a positive electrode tab 21, and a negative electrode tab 22, wherein a thermoplastic polymer sealing layer is provided between the positive electrode tab 21, the negative electrode tab 22 and the ultra-thin metal shell 10; the ultra-thin metal shell 10 comprises: the surface of the ultra-thin metal plate layer 11 is coated with a high thermal conductivity insulating coating; the thermoplastic polymer The sealing layer includes a positive electrode tab hot-melt sealing layer 31 and a negative electrode tab hot-melt sealing layer 32. The positive electrode tab hot-melt sealing layer 31 includes a bonding layer between the positive electrode tab and the thermoplastic polymer, a bonding layer between the thermoplastic polymer and the ultra-thin metal shell, and a hot-melt fusion layer between the positive electrode tab and the ultra-thin metal shell; the negative electrode tab hot-melt sealing layer 32 includes a bonding layer between the negative electrode tab and the thermoplastic polymer, a bonding layer between the thermoplastic polymer and the ultra-thin metal shell, and a hot-melt fusion layer between the negative electrode tab and the ultra-thin metal shell.

[0024] The novel lithium battery with an ultra-thin metal shell of the present invention has the following advantages:

[0025] 1. The thickness of the bare cell shell can be compressed to the limit, so that the volume energy density of the power battery is higher; preferably, the thickness of the ultra-thin metal shell is 0.02-0.2mm; more preferably, the thickness of the ultra-thin metal shell is 0.05-0.15mm;

[0026] 2. The ultra-thin metal plate layer of the ultra-thin metal shell is made of stainless steel or aluminum alloy. The thermal conductivity of stainless steel or aluminum itself is better than that of aluminum-plastic composite film or steel-plastic composite film. In addition, the stainless steel surface is sprayed with a high thermal conductivity insulation composite coating, such as a graphene thermal conductive film. The thermal conductivity of the battery cell plane is super high, and the heat is directly transferred to the bottom water cooling plate or radiator. The thermal conductive aluminum plate between the battery cells in the soft pack module can be eliminated, further improving the energy density of the power battery pack;

[0027] 3. The packaging of ultra-thin aggregates is achieved by using pre-punching, bag making, heat sealing and welding processes. The packaging strength and electrolyte corrosion resistance are significantly better than those of aluminum-plastic composite films.

[0028] 4. Low cost of raw materials. In view of the three key issues currently faced by power batteries, namely, energy density improvement, battery heat dissipation and cost reduction, the use of ultra-thin metal shells, a non-traditional battery outer packaging material, can take into account both energy density improvement and battery heat dissipation performance. At the same time, the cost of the outer packaging material and the existing outer packaging material structure also have certain advantages.

[0029] In this embodiment, the high thermal conductivity insulating coating includes a high thermal conductivity coating 12 and an electronic insulating coating 13. The high thermal conductivity coating 12 is a graphite-based thermal conductive film or a thermal conductive silicone-based thermal conductive film, and the electronic insulating coating 13 is a thermal conductive film with a resistivity greater than 10 10Ω·m inorganic substance or polymer; alternatively, the high thermal conductivity insulating coating is a high thermal conductivity insulating composite coating, and the high thermal conductivity insulating composite coating is a graphite thermal conductive composite film or a graphene thermal conductive composite film with PET coated on the outer surface.

[0030] Preferably, the ultra-thin metal plate layer 11 is made of stainless steel or aluminum alloy, the stainless steel is austenitic stainless steel, ferritic stainless steel or austenitic-ferritic duplex stainless steel, and the aluminum alloy is 1 series pure aluminum, 1 series aluminum alloy, 3 series aluminum-manganese alloy, 5 series aluminum-magnesium alloy, and 6 series aluminum-silicon alloy.

[0031] In the present embodiment, the non-positive pole tab and the negative pole tab of the bare battery cell 20 are packaged with the ultra-thin metal shell by welding, and the welding can be performed by laser penetration welding, electromagnetic welding or ultrasonic welding.

[0032] In this embodiment, the thermoplastic polymer sealing layer includes at least one of PP and CPP, which are prepared by extruding them together through an extruder.

[0033] Preferably, the ultra-thin metal shell sheet is pre-punched according to the design size of the battery cell to prevent the thermoplastic polymer from overflowing during heat sealing.

[0034] Using the above technical solution, the manufacturing process of the new lithium battery with ultra-thin metal shell is as follows:

[0035] Preparation of bare battery cell: stack the positive electrode sheet, separator and negative electrode sheet in a Z-shaped stacking manner, so that the separator is between the positive and negative electrode sheets to play an isolating role. After the stacking is completed, wrap the separator with a circle and fix it with adhesive tape to obtain a bare battery cell;

[0036] Preparation of ultra-thin metal shell: The ultra-thin metal shell sheet with a thickness of 0.1mm is punched and stretched multiple times to form a punching hole of preset size. A double-pit structure is adopted, and two small air bag holes are pre-punched at the air bag position at the same time. In addition, a step is pre-punched at the battery cell tab to facilitate the subsequent heat sealing of the tab position;

[0037] Battery cell packaging: place the prepared bare battery cell in the pre-punched pit of the above-mentioned ultra-thin metal shell, wrap it in a stacked manner and clamp it, use laser welding to weld the non-ear edge of the outer packaging material and the non-ear part of the ear edge, and use heat sealing to melt the thermoplastic polymer PP material pre-made on the ear and bond it to the ultra-thin metal shell and the ear, and at the same time, the upper and lower ultra-thin metal shells are separated from the ear by electronic insulation.

[0038] Air bag welding and vacuum liquid injection: The edge of the air bag close to the battery body is also welded by laser welding, leaving a small opening for electrolyte filling and exhaust after formation. Then vacuum liquid injection is carried out in a drying room. After liquid injection, it is left to stand in vacuum (vacuum degree -50KPa), and then the outer edge of the air bag is completely sealed by laser welding.

[0039] Hot pressing formation and degassing bag: The hot pressing formation fixture on the battery cell is hot pressed at a formation temperature of 80°C and a pressure of 900Kgf. After the formation, the reserved liquid injection port on the fixture is sealed with a laser spot to completely block the formation gas in the air bag. Then, the battery is shaped using a hot and cold pressing fixture and the side of the air bag is finely sealed. Finally, the air bag is directly cut off with a cutter to obtain a formed battery.

[0040] A high thermal conductivity insulating composite film is pasted on the battery surface: After the battery performance test is completed, the surface of the battery is wrapped and pasted with a graphene thermal conductive film. The graphene thermal conductive film is a multi-layer composite film, the part in contact with the battery is an adhesive layer, followed by a graphene thermal conductive layer, and the outer layer is a PET insulating film; it can also be that after all electrical performance tests are completed on the formed battery, a layer of high thermal conductivity epoxy resin with a thickness of 0.005mm is sprayed on its surface. After the high thermal conductivity insulating composite film or high thermal conductivity epoxy resin is added to the outer layer of the battery, the battery has a good heat dissipation effect, and the thermal conductivity plate between the battery cells can be eliminated when the battery module is assembled, saving the space occupied by the heat dissipation components.

[0041] The above are only preferred embodiments of the present invention, and the scope of rights of the present invention cannot be limited thereto. Therefore, equivalent changes made according to the patent scope of the present invention still fall within the scope covered by the present invention.

Claims

1. A new type of lithium battery with an ultra-thin metal shell, characterized in that: The invention comprises an ultra-thin metal shell and a bare battery cell located inside the ultra-thin metal shell, wherein the bare battery cell comprises a positive electrode sheet, a negative electrode sheet, a separator, a positive electrode ear, and a negative electrode ear, wherein the positive electrode ear and the negative electrode ear extend out of the ultra-thin metal shell respectively, and a thermoplastic polymer sealing layer is provided between the positive electrode ear, the negative electrode ear and the ultra-thin metal shell; the ultra-thin metal shell comprises an ultra-thin metal plate layer, and the surface of the ultra-thin metal plate layer is coated with a high thermal conductivity insulating coating; The thickness of the ultra-thin metal shell is 0.02-0.2 mm; The thermoplastic polymer sealing layer includes a positive electrode tab hot-melt sealing layer and a negative electrode tab hot-melt sealing layer, wherein the positive electrode tab hot-melt sealing layer includes a bonding layer between the positive electrode tab and the thermoplastic polymer, a bonding layer between the thermoplastic polymer and the ultra-thin metal shell, and a hot-melt fusion layer between the positive electrode tab and the ultra-thin metal shell; the negative electrode tab hot-melt sealing layer includes a bonding layer between the negative electrode tab and the thermoplastic polymer, a bonding layer between the thermoplastic polymer and the ultra-thin metal shell, and a hot-melt fusion layer between the negative electrode tab and the ultra-thin metal shell; The new lithium battery with ultra-thin metal casing is made as follows: Preparation of bare battery cells: stack the positive electrode sheet, separator, and negative electrode sheet in a Z-shaped stack, so that the separator is between the positive and negative electrode sheets to play an isolating role. After stacking, wrap the separator with a circle and fix it with adhesive tape; Preparation of ultra-thin metal shell: The ultra-thin metal shell sheet with a thickness of 0.1mm is punched and stretched multiple times to form a punching hole of preset size. A double-pit structure is adopted, and two small air bag holes are pre-punched at the air bag position at the same time. In addition, a step is pre-punched at the battery cell tab to facilitate the subsequent heat sealing of the tab position; Cell packaging: placing the prepared bare cell in the pre-punched pit of the ultra-thin metal shell, stacking and wrapping it and clamping it, using laser welding to weld the non-ear edge of the outer packaging material and the non-ear part of the ear edge, and using heat sealing to heat-melt the thermoplastic polymer PP material pre-made on the ear and bond it with the ultra-thin metal shell and the ear, and at the same time, the upper and lower ultra-thin metal shells are separated from the ear by electronic insulation; Air bag welding and vacuum liquid injection: The edge of the air bag close to the battery body is also welded by laser welding, leaving a small opening for electrolyte filling and exhaust after formation. Then vacuum liquid injection is carried out in a drying room. After liquid injection, it is left to stand in vacuum, and then the outer edge of the air bag is completely sealed by laser welding. Hot pressing formation and degassing bag: The hot pressing formation fixture on the battery cell is hot pressed at a temperature of 80°C and a pressure of 900Kgf; after the formation, the reserved liquid injection port on the fixture is sealed with a laser spot to completely block the formation gas in the air bag, and then the battery is reshaped using a hot and cold pressing fixture, and the side of the air bag is finely sealed; finally, the air bag is directly cut off with a cutter to obtain the formed battery; A high thermal conductivity insulating composite film is pasted on the battery surface: after the battery performance test is completed, the surface of the battery is wrapped and pasted with a graphene thermal conductive film. The graphene thermal conductive film is a multi-layer composite film, the part in contact with the battery is an adhesive layer, followed by a graphene thermal conductive layer, and the outer layer is a PET insulating film; alternatively, after all electrical performance tests are completed on the formed battery, a layer of high thermal conductivity epoxy resin with a thickness of 0.005mm is sprayed on its surface. After the high thermal conductivity insulating composite film or high thermal conductivity epoxy resin is added to the outer layer of the battery, the battery has a good heat dissipation effect, and the thermal conductivity plate between the battery cells can be eliminated when the battery module is assembled, saving the space occupied by the heat dissipation components.

2. The novel lithium battery with an ultra-thin metal casing according to claim 1, characterized in that: The high thermal conductivity insulating coating includes the high thermal conductivity coating and the electronic insulating coating. The high thermal conductivity coating is a graphite thermal conductive film or a thermal conductive silicone thermal conductive film. The electronic insulating coating is an inorganic substance or a polymer with a resistivity greater than 1010Ω·m.

3. The novel lithium battery with an ultra-thin metal casing according to claim 1, characterized in that: The high thermal conductivity insulating coating is a high thermal conductivity insulating composite coating, and the high thermal conductivity insulating composite coating is a graphite thermal conductive composite film or a graphene thermal conductive composite film with PET coated on the outer surface.

4. The novel lithium battery with an ultra-thin metal casing according to claim 1, characterized in that: The thickness of the ultra-thin metal shell is 0.05-0.15 mm.

5. The novel lithium battery with an ultra-thin metal casing according to claim 1 or 4, characterized in that: The ultra-thin metal plate layer is made of stainless steel or aluminum alloy, the stainless steel is austenitic stainless steel, ferritic stainless steel, austenitic ferritic double stainless steel, and the aluminum alloy is 1 series pure aluminum, 1 series aluminum alloy, 3 series aluminum-manganese alloy, 5 series aluminum-magnesium alloy, and 6 series aluminum-silicon alloy.

6. The novel lithium battery with ultra-thin metal casing according to claim 1, characterized in that: The positive pole tab and the negative pole tab of the bare battery cell are packaged with the ultra-thin metal shell by welding.

7. The novel lithium battery with an ultra-thin metal casing according to claim 1, characterized in that: The thermoplastic polymer sealing layer includes at least one of PP and CPP, and is prepared by extruding the thermoplastic polymer sealing layer in an extruder.

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