A two-layer electrode sheet for an electrolyte spill-proof thermal battery and its preparation method

Abstract

This invention discloses a two-layer electrode sheet for an electrolyte overflow-proof thermal battery and its preparation method. The two-layer electrode sheet includes a positive electrode layer, a separator layer, and an insulating ring. The positive electrode layer and the separator layer are cylindrical structures, and the insulating ring is a cylindrical structure with a central hole. The separator layer is surrounded by the insulating ring. The insulating ring and the positive electrode layer have the same outer diameter. The upper surface of the insulating ring has an interlocking interface layer region covered by both the positive electrode layer and the separator layer, preventing the positive electrode layer powder from penetrating downwards through the gaps between the separator layer, the insulating ring, and the mold. On the one hand, the complete wrapping effect of the insulating ring and the positive electrode layer on the side of the separator layer can eliminate the risk of short circuit caused by electrolyte overflow at high temperatures. On the other hand, the preparation of a highly reliable two-layer electrode sheet based on twisting and pre-pressing the powder layer can reduce the phenomena of uneven powder layer, short circuit due to positive electrode layer penetration, and breakage of the separator layer after demolding, thereby improving the yield rate, efficiency, and safety of the thermal battery operation, and possessing engineering application value.

Description

Technical Field

[0001] This application relates to the technical field of thermal batteries, and in particular to a two-layer electrode sheet for an electrolyte spill-proof thermal battery and its preparation method. Background Technology

[0002] A thermally activated battery is a disposable storage battery that is activated by melting solid molten salt using its own heating system. It has the advantages of short activation time, long storage time, and maintenance-free operation.

[0003] With the increasing demands on the specific energy and specific power of thermal batteries, the design of thin and large-size electrode sheet structures has become the mainstream. Figure 1 The two-layer electrode sheet shown consists of a positive electrode layer and an isolation layer (a mixture of halogen eutectic salt electrolyte and MgO). Because the overall safety of a single cell is higher than that of three-layer or four-layer sheets, it is more suitable for long-term high-pulse power supply environments and is therefore increasingly used in current thermal battery products.

[0004] Conventional manual electrode fabrication methods are insufficient for producing thin, large-sized electrode sheets. The thinnest uncompacted powder layer of a two-layer electrode sheet is approximately 1mm. When the electrode sheet size is Φ50mm or larger, manually spreading the powder layer is difficult to ensure uniformity and smoothness, and easily disturbs the already smoothed powder layer, negatively impacting the consistency of the product's physical structure and electrical properties, as well as the molding yield. Furthermore, due to the low strength of thin two-layer electrode sheets, the insulating layer may crack during demolding due to friction with the mold, resulting in defective electrodes. Currently, the yield rate of traditional manual fabrication of two-layer electrode sheets is less than 70%, with an efficiency of less than 2 minutes per sheet, making it difficult to guarantee product consistency.

[0005] When a thermal battery is operating, the temperature can rise to around 500°C. At this temperature, the electrolyte is in a semi-molten state and may overflow under significant mechanical vibration, causing short circuits between adjacent electrode sheets and affecting battery safety. Existing technologies for solving this problem either result in overly complex electrode sheet structures, making electrode sheet leveling difficult, unit assembly challenging, and overall manufacturing efficiency low, hindering engineering applications; or make it difficult to achieve precise dimensional matching between the insulating collar and the separator, and the sides of the separator cannot be completely covered. When using traditional manual leveling-pressing processes, the insulating collar, separator, and mold are not tightly bonded, leaving gaps. During leveling and pressing, positive electrode powder can easily seep in and is difficult to detect. This can range from affecting the electrode sheet yield to causing short circuits during thermal battery operation, introducing new safety risks. Summary of the Invention

[0006] To address the technical problems of high difficulty and low yield in the preparation of thin, large-sized two-layer electrode sheets, and the easy leakage of electrolyte, this invention proposes a two-layer electrode sheet for an electrolyte-proof thermal battery and its preparation method.

[0007] In a first aspect, a two-layer electrode sheet for an electrolyte overflow-proof thermal battery is provided. The two-layer electrode sheet includes a positive electrode layer, an isolation layer, and an insulating ring. Both the positive electrode layer and the isolation layer are cylindrical structures, and the insulating ring is a cylindrical structure with a central hole. The main body of the isolation layer is surrounded by the insulating ring. The positive electrode layer covers the isolation layer and the insulating ring. The outer diameter of the insulating ring is the same as the outer diameter of the positive electrode layer. The positive electrode layer has a chamfer on the side facing the insulating ring. The isolation layer fills the space formed by the chamfer to prevent the material of the positive electrode layer from penetrating downward through the gap between the main body of the isolation layer and the insulating ring.

[0008] In conjunction with the first aspect, in certain implementations of the first aspect, the insulating collar satisfies at least one of the following:

[0009] The insulating collar comprises at least one of the following high-temperature resistant insulating materials: asbestos, aluminum silicate fiber cotton, and mica;

[0010] The thickness of the insulating collar ranges from 0.3mm to 0.5mm, the width from 1mm to 2mm, and the outer diameter is the same as the nominal diameter of the two electrode plates of the electrolyte overflow-proof thermal battery.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, the insulating layer is a powder mixture of one or more halogen eutectic salts and MgO, wherein the halogen eutectic salt includes at least one of the following: LiCl, LiBr, LiF, and KCl.

[0012] In conjunction with the first aspect, in certain implementations of the first aspect, the positive electrode layer satisfies at least one of the following:

[0013] The positive electrode layer is one or more powder mixtures of FeS2, CoS2 and halogen eutectic salts.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the thickness of the two electrode sheets of the electrolyte overflow-proof thermal battery ranges from 1 mm to 2 mm, and the diameter ranges from Φ50 mm to Φ80 mm.

[0015] Secondly, a method for preparing a two-layer electrode sheet for an electrolyte spill-proof thermal battery as described in any of the implementations of the first aspect above is provided, comprising:

[0016] The insulating collar is placed inside the mold, and a limiting sleeve is used to press down the insulating collar around its perimeter. The limiting sleeve has a chamfer at the bottom facing the insulating collar.

[0017] Pour the weighed isolation layer powder into the mold so that the powder fills the insulating ring. Excess powder that does not enter the insulating ring accumulates in the limiting sleeve. Use the screwing head to screw and flatten the isolation layer powder, and then remove the screwing head.

[0018] Place a pre-compression head into the mold and use a press to pre-compress the isolation layer powder, so that the isolation layer powder fills the space formed by the chamfer of the limiting sleeve;

[0019] Remove the mold from the press, and remove the limiting sleeve and pre-pressing head;

[0020] Pour the weighed positive electrode powder into the mold, use the screw press head to screw and flatten the positive electrode powder, and then remove the screw press head.

[0021] A forming head is placed in the mold, and a press is used to press and shape the material. After demolding, the two-layer electrode sheet of the electrolyte anti-overflow type thermal battery as described in claim 1 is obtained.

[0022] In conjunction with the second aspect, in some implementations of the second aspect, the outer diameter of the limiting sleeve is the same as the nominal outer diameter of the insulating collar, the inner diameter is the same as the nominal inner diameter of the insulating collar, the chamfer angle α at the bottom of the inner wall is 45°, and the chamfer height is 0.2mm. <A<0.4mm。

[0023] In conjunction with the second aspect, in some implementations of the second aspect, the diameter of the screw head used for screwing the separator powder is the same as the nominal inner diameter of the limiting sleeve, and the diameter of the screw head used for screwing the positive electrode powder is the same as the nominal diameter of the two electrode sheets of the electrolyte overflow-proof thermal battery. The surface of the screw head is distributed with hemispherical protrusions with a radius of 0.2 mm to 0.5 mm to improve the uniformity of the distribution of viscous electrode powder.

[0024] In conjunction with the second aspect, in some implementations of the second aspect, the rotating pressure head presses against the powder layer and rotates clockwise and counterclockwise once to form one action cycle. When rotating the separator powder, 3 to 5 cycles are rotated, and when rotating the positive electrode powder, 2 to 4 cycles are rotated.

[0025] In conjunction with the second aspect, in certain implementations of the second aspect, the preparation method satisfies at least one of the following:

[0026] The diameter of the preload head is the same as the nominal size of the inner diameter of the limiting sleeve, and the preload pressure is 50kN to 200kN.

[0027] The diameter of the forming head is the same as the nominal diameter of the two electrode sheets of the electrolyte overflow-proof thermal battery, and the forming pressure is 500kN to 2000kN.

[0028] Compared with the prior art, the solution provided in this application has at least the following beneficial technical effects:

[0029] First, an interlocking interface layer of positive electrode layer-insulating collar-separator layer was designed. By completely wrapping the sides of the separator layer with the insulating collar and positive electrode layer, the risk of short circuit between electrode sheets caused by high-temperature electrolyte overflow can be eliminated, improving the working safety of the thermal battery. Second, due to the introduction of the separator layer pre-compression process, the insulating collar and separator layer are shaped, resulting in a tight bond between the insulating collar, separator layer and mold, avoiding the risk of the positive electrode layer penetrating downwards during electrode sheet preparation and operation. Third, the interlocking interface layer can effectively improve the structural strength of the electrode sheet, reduce the risk of damage during demolding, subsequent assembly processes and product use, and improve reliability. Fourth, based on the screw press head to achieve powder layer flatness and the addition of the separator layer pre-compression compaction process, the problems of poor powder layer uniformity, low preparation efficiency and low forming qualification rate of the two-layer electrode sheets of thin and large-size thermal batteries are solved. The preparation efficiency of a single electrode sheet can reach within 60s / sheet, and the forming qualification rate is over 92%, which has engineering application value. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a traditional two-layer electrode structure for a thermal battery.

[0031] Figure 2 This is a schematic diagram of the two-layer electrode structure of the thermal battery of the present invention.

[0032] Figure 3 This is a schematic diagram of the limiting sleeve for auxiliary molding proposed in this invention.

[0033] Figure 4 This is a schematic diagram showing the combined relationship of the insulating collar, the insulating layer, and the limiting sleeve after being screwed and leveled according to the present invention.

[0034] Figure 5 This is a schematic diagram of the rotary press head for leveling powder layers proposed in this invention.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Positive electrode layer, 2. Insulating layer, 3. Insulating collar, 4. Limiting sleeve, 5. Tightening head. Detailed Implementation

[0037] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0038] Figure 2This invention illustrates a two-layer electrode sheet for an electrolyte spill-proof thermal battery. The two-layer electrode sheet includes a positive electrode layer 1, an insulating layer 2, and an insulating ring 3. Both the positive electrode layer 1 and the insulating layer 2 are cylindrical structures, while the insulating ring 3 is a cylindrical structure with a central hole. The main body of the insulating layer 2 is surrounded by the insulating ring 3. The positive electrode layer 1 covers the insulating layer 2 and the insulating ring 3, and the insulating ring 3 and the positive electrode layer 1 have the same outer diameter. The positive electrode layer 1 has a chamfer on the side facing the insulating ring 3, and the insulating layer 2 fills the space formed by the chamfer, thereby forming an interlocking interface layer region on the upper surface of the insulating ring 3, which is jointly covered by the positive electrode layer 1 and the insulating layer 2, to prevent material from the positive electrode layer 1 from penetrating downwards through the gap between the insulating layer 2 and the insulating ring 3.

[0039] Furthermore, the insulating collar 3 includes, but is not limited to, high-temperature resistant insulating materials such as asbestos, aluminum silicate fiber cotton, and mica.

[0040] Furthermore, the thickness of the insulating collar 3 ranges from 0.3mm to 0.5mm, the width from 1mm to 2mm, and the outer diameter is the same as the nominal diameter of the electrode sheet.

[0041] Furthermore, the isolation layer 2 is a powder mixture of one or more eutectic salts of halogens such as LiCl, LiBr, LiF, and KCl with MgO.

[0042] Furthermore, the positive electrode layer 1 is a powder mixture of one or more FeS2, CoS2 and halogen eutectic salts.

[0043] Furthermore, the applicable electrode sheet thickness ranges from 1mm to 2mm, and the diameter ranges from Φ50mm to Φ80mm.

[0044] The present invention also provides a method for preparing a two-layer electrode sheet for an electrolyte spill-proof thermal battery, comprising the following steps.

[0045] Step 1: Place the insulating collar 3 into the mold and use the limiting sleeve 4 to press down the insulating collar 3 around its perimeter. The limiting sleeve 4 has a chamfer at the bottom facing the insulating collar 3.

[0046] Step 2: Pour the weighed powder of the isolation layer 2 into the mold so that the powder of the isolation layer 2 fills the insulating ring 3. The excess powder that does not enter the insulating ring 3 accumulates in the limiting sleeve 4. Use the screwing head 5 to screw and flatten the powder of the isolation layer 2, and then remove the screwing head 5.

[0047] Step 3: Place the pre-pressing head into the mold and use a press to pre-press and compact the powder of the isolation layer 2, so that the powder of the isolation layer 2 fills the space formed by the chamfer of the limiting sleeve 4.

[0048] Step 4: Remove the mold from the press, and remove the limiting sleeve 4 and the pre-pressing head;

[0049] Step 5: Pour the weighed positive electrode layer 1 powder into the mold, use the screw press head 5 to screw and flatten the positive electrode layer 1 powder, and then remove the screw press head 5.

[0050] Step 6: Place the forming head into the mold, use a press to press the electrode sheet into shape, and then demold it through the demolding device to obtain the electrode sheet.

[0051] Furthermore, the outer wall dimension of the limiting sleeve 4 is the same as the outer diameter dimension of the insulating collar 3, and the inner wall dimension of the limiting sleeve 4 is the same as the inner diameter dimension of the insulating collar 3. The chamfer angle α at the bottom of the inner wall is 45°, and the chamfer height is 0.2mm. <A<0.4mm。

[0052] Furthermore, during the twisting process, the diameter of the twisting head 5 corresponding to the isolation layer 2 is the same as the nominal inner diameter of the limiting sleeve 4, and the diameter of the twisting head 5 corresponding to the positive electrode layer 1 is the same as the nominal diameter of the electrode sheet. The surface of the head is covered with hemispherical protrusions with a radius of 0.2mm to 0.5mm to improve the uniformity of the distribution of viscous electrode powder.

[0053] Furthermore, during the twisting process, the twisting head 5 presses the powder layer and rotates clockwise and counterclockwise once each to complete one action cycle. The powder in the isolation layer 2 is twisted 3 to 5 times, and the powder in the positive electrode layer 1 is twisted 2 to 4 times.

[0054] Furthermore, during the pre-compression process, the diameter of the pre-compression head is the same as the nominal inner diameter of the limiting sleeve 4, and the pre-compression pressure is 50kN to 200kN.

[0055] Furthermore, in the pressing and molding process, the diameter of the molding head is the same as the nominal diameter of the electrode sheet, and the molding pressure is 500kN to 2000kN.

[0056] Example 1:

[0057] Step 1: Place the mica insulating collar 3 with a thickness of 0.3mm and a width of 1mm into a mold with a diameter of 65mm, and use a limiting sleeve 4 with a chamfer height of 0.2mm to press down the insulating collar 3 around its perimeter.

[0058] Step 2: Pour the weighed isolation layer 2 powder (a mixture of LiCl-KCl and MgO, weighing 3.20g) into the mold, and use the 63mm diameter screw head 5 to screw it for 3 cycles to flatten the isolation layer 2 powder. The radius of the hemispherical protrusion on the screw head 5 is 0.3mm. Then remove the screw head 5.

[0059] Step 3: Place the pre-compression head into the mold and use a press to pre-compress the powder of the isolation layer 2. The pre-compression pressure is 100kN to compact the powder of the isolation layer 2.

[0060] Step 4: Remove the mold from the press, and remove the limiting sleeve 4 and the pre-pressing head;

[0061] Step 5: Pour the weighed positive electrode layer 1 powder (a mixture of FeS2 and LiCl-KCl, weighing 6.78g) into the mold, and use the 65mm diameter screw head 5 to screw for 2 cycles to flatten the positive electrode layer 1 powder. The radius of the hemispherical protrusion on the screw head 5 is 0.3mm. Then remove the screw head 5.

[0062] Step 6: Place the forming head into the mold, put the mold into the press, and press the electrode sheet into shape with a forming pressure of 1000kN. After demolding, the electrode sheet is obtained by demolding through the demolding device.

[0063] Example 2:

[0064] Step 1: Place the asbestos insulating collar 3 with a thickness of 0.5mm and a width of 2mm into a mold with a diameter of 80mm, and use a limiting sleeve 4 with a chamfer height of 0.4mm to press down the insulating collar 3 around its perimeter.

[0065] Step 2: Pour the weighed isolation layer 2 powder (a mixture of LiCl-LiBr-LiF and MgO, weighing 6.34g) into the mold, and use the 76mm diameter screw head 5 to rotate 5 times to flatten the isolation layer 2 powder. The radius of the hemispherical protrusion on the screw head 5 is 0.5mm. Then remove the screw head 5.

[0066] Step 3: Place the pre-compression head into the mold and use a press to pre-compress the powder of the isolation layer 2. The pre-compression pressure is 200kN to compact the powder of the isolation layer 2.

[0067] Step 4: Remove the mold from the press, and remove the limiting sleeve 4 and the pre-pressing head;

[0068] Step 5: Pour the weighed positive electrode layer 1 powder (a mixture of CoS2 and LiCl-LiBr-LiF, weighing 19.23g) into the mold, and use the 80mm diameter screw head 5 to screw it for 4 cycles to flatten the positive electrode layer 1 powder. The radius of the hemispherical protrusion on the screw head 5 is 0.5mm. Then remove the screw head 5.

[0069] Step 6: Place the forming head into the mold, put the mold into the press, and press the electrode sheet into shape at a forming pressure of 2000kN. After demolding, the electrode sheet is obtained by demolding through the demolding device.

[0070] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. An electrolyte spill-proof type thermal battery two-layer electrode sheet, characterized by, The two-layer electrode sheet comprises a positive electrode layer (1), a separation layer (2), and an insulating sleeve (3). The positive electrode layer (1) and the separation layer (2) are both in a cylindrical structure, and the insulating sleeve (3) is in a middle-hole cylindrical structure. The main body of the separation layer (2) is surrounded by the insulating sleeve (3), the positive electrode layer (1) is above the separation layer (2) and the insulating sleeve (3), and the outer diameter of the insulating sleeve (3) is the same as that of the positive electrode layer (1). The positive electrode layer (1) has a chamfer on the side facing the insulating sleeve (3), and the separation layer (2) is filled in the space formed by the chamfer to prevent the material of the positive electrode layer (1) from penetrating downward through the gap between the main body of the separation layer (2) and the insulating sleeve (3).

2. The electrolyte spill-proof two-layer electrode sheet for a thermal battery according to claim 1, characterized by The insulating sleeve (3) satisfies at least one of the following conditions: The insulating sleeve (3) comprises at least one high-temperature-resistant insulating material, such as asbestos, aluminum silicate fiber cotton, and mica. The thickness of the insulating sleeve (3) is in the range of 0.3mm-0.5mm, the width is in the range of 1mm-2mm, and the outer diameter is the same as the nominal size of the diameter of the electrolyte-overflow-preventing thermal battery two-layer electrode sheet.

3. The electrolyte spill-proof thermal battery two-layer electrode sheet according to claim 1, wherein The separation layer (2) is a mixture of one or more powders of halogen eutectic salt and MgO, and the halogen eutectic salt comprises at least one of LiCl, LiBr, LiF, and KCl.

4. The electrolyte spill-proof thermal battery two-layer electrode sheet according to claim 1, wherein The positive electrode layer (1) satisfies at least one of the following conditions: The positive electrode layer (1) is a mixture of one or more powders of FeS2, CoS2, and halogen eutectic salt.

5. The spill-proof, thermal battery two-layer electrode sheet of claim 1, wherein, The thickness of the electrolyte-overflow-preventing thermal battery two-layer electrode sheet is in the range of 1mm-2mm, and the diameter is in the range of Φ50mm-Φ80mm.

6. A method of producing an electrolyte spill-proof thermal battery two-layer electrode sheet according to any one of claims 1 to 5, characterized by, The method comprises the following steps: The insulating sleeve (3) is placed in a mold, and a limiting sleeve (4) is used to press the insulating sleeve (3) around; The weighed separation layer (2) powder is poured into the mold, and the separation layer (2) powder fills the insulating sleeve (3). The excess powder that does not enter the insulating sleeve (3) is accumulated in the limiting sleeve (4). A screwing pressure head (5) is used to screw and flatten the separation layer (2) powder, and then the screwing pressure head (5) is removed; A pre-pressing pressure head is placed in the mold, and a press machine is used to pre-press and compact the separation layer (2) powder, so that the separation layer (2) powder fills the space formed by the chamfer of the limiting sleeve (4); The mold is taken out of the press machine, and the limiting sleeve (4) and the pre-pressing pressure head are removed; The weighed positive electrode layer powder is poured into the mold, and the screwing pressure head (5) is used to screw and flatten the positive electrode layer (1) powder, and then the screwing pressure head (5) is removed; A forming pressure head is placed in the mold, and a press machine is used for pressing and forming. After demolding, the electrolyte-overflow-preventing thermal battery two-layer electrode sheet of claim 1 is obtained.

7. The production method according to claim 6, wherein The outer wall diameter of the limiting sleeve (4) is the same as the nominal size of the outer diameter of the insulating sleeve (3), the inner wall diameter is the same as the nominal size of the inner diameter of the insulating sleeve (3), the inner wall bottom chamfer angle is α=45°, and the chamfer height is 0.2mm 8. The preparation method according to claim 6, characterized in that, The diameter of the screwing pressure head (5) used for screwing the isolation layer (2) powder is the same as the nominal size of the inner diameter of the limiting sleeve (4), and the diameter of the screwing pressure head (5) used for screwing the positive electrode layer (1) powder is the same as the nominal size of the diameter of the two-layer electrode sheet of the electrolyte anti-overflow thermal battery, and the surface of the pressure head is distributed with semispherical convex points with a radius of 0.2mm-0.5mm, for improving the uniformity of the distribution of the viscous electrode powder.

9. The preparation method according to claim 6, characterized in that, The screwing pressure head (5) presses the powder layer to rotate clockwise and counterclockwise for one cycle as one action cycle, and the isolation layer (2) powder is screwed for 3-5 cycles, and the positive electrode layer (1) powder is screwed for 2-4 cycles.

10. The preparation method according to claim 6, characterized in that, The preparation method satisfies at least one of the following: The diameter of the pre-pressing pressure head is the same as the nominal size of the inner diameter of the limiting sleeve (4), and the pre-pressing pressure is 50kN-200kN; The diameter of the forming pressure head is the same as the nominal size of the diameter of the two-layer electrode sheet of the electrolyte anti-overflow thermal battery, and the forming pressure is 500kN-2000kN.

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