High-rate lithium carbon fluoride soft package battery cell and preparation method thereof

Abstract

The invention discloses a high-rate lithium carbon fluoride soft package battery cell which comprises a plurality of cell units which are stacked repeatedly and separated by heat-conducting fins, each cell unit comprises two layers of carbon fluoride positive plates provided with positive tabs and a metal lithium negative plate provided with negative tabs, the two layers of carbon fluoride positive plates and the metal lithium negative plates are separated by diaphragms, the positive tabs are welded with external positive tabs, and the negative tabs are welded with external negative tabs. In addition, the invention further provides a preparation method of the high-rate lithium carbon fluoride soft package battery cell, the carbon fluoride positive plate and the metal lithium negative plate are prepared respectively and then assembled into the cell unit, and then the cell unit is assembled into the soft package battery cell. According to the high-rate lithium carbon fluoride soft package battery, the heat conducting sheets are designed between the battery cell units, and the structures of the battery cell units are controlled, so that a heat transfer path is increased, the rate discharge capability and the safety of the high-rate lithium carbon fluoride soft package battery are remarkably improved, and the high-rate lithium carbon fluoride soft package battery has the characteristics of good rate capability, high process compatibility and easiness in industrialization.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery manufacturing, and particularly relates to a high-rate lithium carbon monofluoride soft-pack battery cell and a preparation method thereof. Background Art

[0002] Lithium-carbon monofluoride has advantages such as high energy density, stable voltage, and long storage life, and has important application values in the fields of national defense, military, aerospace, etc. However, due to the poor conductivity of the carbon monofluoride cathode material, the polarization of the carbon monofluoride electrode is relatively serious, and there is an obvious voltage lag at the initial stage of discharge; in addition, due to the low conductivity of the carbon monofluoride material, the temperature rise during high-current discharge of the lithium carbon monofluoride battery is too high, resulting in limitations in the engineering application of the lithium carbon monofluoride battery.

[0003] The lithium-carbon monofluoride battery has poor rate performance, especially when discharging at high rates, the heat generation is very serious, and the temperature can usually reach above 80 degrees, which has a serious impact on the safety performance and largely limits the further application of the power-type lithium-carbon monofluoride battery. However, there is no effective method to solve this problem at the material level. Therefore, through the optimization of the battery structure design, reducing the internal resistance, reducing the discharge polarization, controlling the heat generation during high-rate discharge, and at the same time significantly improving the heat dissipation capacity of the battery, it is of great significance for improving the safety of the lithium-carbon monofluoride battery, further expanding the application scenarios, and promoting the application of the power-type lithium-carbon monofluoride battery in the military and civilian fields.

[0004] In summary, there is a need to provide a high-rate lithium carbon monofluoride soft-pack battery cell and a preparation method thereof. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-rate lithium carbon monofluoride soft-pack battery cell in view of the above-mentioned deficiencies of the prior art. By designing a heat conducting sheet between the cell units and controlling the structure of the cell units, this soft-pack battery cell is beneficial to reducing the internal resistance, reducing the polarization, quickly conducting the heat generated inside the battery during the discharge process to the outside of the battery, increasing the heat conduction area in the width direction, effectively improving the heat dissipation capacity of the battery itself, avoiding thermal runaway caused by excessive temperature rise during high-rate discharge, and significantly improving the rate discharge capacity and safety of the high-rate lithium carbon monofluoride soft-pack battery, and has the characteristics of good rate performance, high process compatibility, and easy industrialization.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: a high-rate lithium carbon monofluoride soft-pack battery cell, characterized in that the soft-pack battery cell comprises a plurality of repeatedly stacked cell units, and adjacent cell units are separated by heat-conducting sheets. Each cell unit comprises upper and lower layers of carbon monofluoride positive electrode sheets and a lithium metal negative electrode sheet located between the two layers of carbon monofluoride positive electrode sheets. The two layers of carbon monofluoride positive electrode sheets and the lithium metal negative electrode sheet are separated and wrapped by diaphragms. Each carbon monofluoride positive electrode sheet is provided with a positive electrode tab, and all the positive electrode tabs in the plurality of repeatedly stacked cell units are ultrasonically welded to the positive external tab. Each lithium metal negative electrode sheet is provided with a negative electrode tab, and all the negative electrode tabs in the plurality of repeatedly stacked cell units are ultrasonically welded to the negative external tab. The outside of the plurality of repeatedly stacked cell units is heat-sealed and packaged with a packaging shell.

[0007] For the above-mentioned high-rate lithium carbon monofluoride soft-pack battery cell, it is characterized in that the number of the cell units is 2 to 25.

[0008] For the above-mentioned high-rate lithium carbon monofluoride soft-pack battery cell, it is characterized in that the length of the heat-conducting sheet is the same as that of the carbon monofluoride positive electrode sheet, and the width is 1.2 to 2.0 times the width of the carbon monofluoride positive electrode sheet. Adhesive layers are provided on both the upper and lower surfaces of the part of the heat-conducting sheet that extends beyond the carbon monofluoride positive electrode sheet. Pole ear adhesives are provided on the upper part of the uppermost heat-conducting sheet and the lower part of the lowermost heat-conducting sheet. The carbon monofluoride positive electrode sheet and the lithium metal negative electrode sheet have the same size.

[0009] For the above-mentioned high-rate lithium carbon monofluoride soft-pack battery cell, it is characterized in that the carbon monofluoride positive electrode sheet is composed of a current collector and a surface coating layer, specifically, a graphene coating layer and a carbon monofluoride coating layer are sequentially coated on one side surface of the current collector. One end of the carbon monofluoride positive electrode sheet reserves an area without a surface coating layer as the positive electrode tab. The lithium metal negative electrode sheet is composed of a copper foil and a lithium layer, specifically, metal lithium layers are coated on both sides of the copper foil. The area of the copper foil without lithium coating at one end of the lithium metal negative electrode sheet is used as the negative electrode tab. The widths of the positive electrode tab and the negative electrode tab are both the same as the widths of the carbon monofluoride positive electrode sheet and the lithium metal negative electrode sheet. The positive electrode tab and the negative electrode tab in the cell unit are distributed on opposite sides.

[0010] For the above-mentioned high-rate lithium carbon monofluoride soft-pack battery cell, it is characterized in that the packaging shell comprises an upper aluminum-plastic shell and a lower aluminum-plastic shell. The upper aluminum-plastic shell and the lower aluminum-plastic shell are both provided with grooves matching the plurality of repeatedly stacked cell units. The upper aluminum-plastic shell and the lower aluminum-plastic shell are respectively provided with an upper aluminum-plastic shell sealing edge and a lower aluminum-plastic shell sealing edge.

[0011] In addition, the present invention also provides a method for preparing a high-rate lithium carbon monofluoride soft-pack battery cell, characterized in that the method comprises the following steps:

[0012] Step 1. Preparation of carbon fluoride positive electrode sheet: Add carbon fluoride, conductive agent, and binder into a solvent and stir well until it is uniform and stable to obtain a carbon fluoride slurry. Then coat the carbon fluoride slurry on a current collector with a graphene coating, and then perform baking, rolling, and punching in sequence to obtain a carbon fluoride positive electrode sheet;

[0013] Step 2. Preparation of metallic lithium negative electrode sheet: Cover both the upper and lower surfaces of a copper foil with a double-sided lithium layer with a release film, and then perform punching and remove the release film to obtain a metallic lithium negative electrode sheet;

[0014] Step 3. Preparation of battery cell unit: Stack one carbon fluoride positive electrode sheet obtained in Step 1, one metallic lithium negative electrode sheet obtained in Step 2, and one carbon fluoride positive electrode sheet obtained in Step 1 in sequence, and separate and wrap them with a separator in the middle, where the sides coated with the carbon fluoride slurry of the two carbon fluoride positive electrode sheets both face the metallic lithium negative electrode sheet to obtain a battery cell unit;

[0015] Step 4. Preparation of soft-pack battery cell: Stack multiple battery cell units obtained in Step 3, place heat-conducting sheets in them, set adhesive layers and tab adhesives, then perform hot pressing and welding on all the heat-conducting sheets, ultrasonically weld all the positive tabs of multiple battery cell units to the positive external tab, ultrasonically weld all the negative tabs of multiple battery cell units to the negative external tab, then put the upper aluminum-plastic shell and the lower aluminum-plastic shell on both sides of multiple battery cell units respectively, and perform hot-melt packaging on the tab adhesives, the edges of the upper aluminum-plastic shell, and the edges of the lower aluminum-plastic shell to obtain a high-rate lithium-carbon fluoride soft-pack battery cell.

[0016] The present invention uses a current collector with a graphene coating, and the graphene coating therein plays a role in reducing the contact impedance between the active material in the carbon fluoride slurry and the current collector and improving the coating adhesion strength, enhancing the rate performance of the high-rate lithium-carbon fluoride soft-pack battery; meanwhile, by utilizing the high thermal conductivity of graphene, the heat generated during the battery reaction process can be quickly conducted through the current collector, improving the heat conduction ability of the battery.

[0017] When preparing the carbon fluoride positive electrode sheet in the present invention, the carbon fluoride slurry is coated on a current collector with a graphene coating to obtain a carbon fluoride coating, and the carbon fluoride coating is firmly combined with the current collector with a graphene coating through baking and rolling, and the required specification size is obtained through punching; when preparing the metallic lithium negative electrode sheet, the lithium layer is prevented from sticking by covering a release film, ensuring the performance of the battery, and the required specification size is obtained through punching.

[0018] The present invention forms a packaging shell through hot-melt packaging of the tab adhesives, the edges of the upper aluminum-plastic shell, and the edges of the lower aluminum-plastic shell to protect the internal structure and improve the service life.

[0019] The above method is characterized in that in step one, the conductive agent is Ketjen black and carbon fiber, the binder is polyvinylidene fluoride, the solvent is N-methylpyrrolidone, the mass content of carbon fluoride in the carbon fluoride slurry is 85% - 95%, the mass content of the conductive agent is 2.5% - 10%, and the balance is the binder. In the present invention, the composite of Ketjen black and carbon fiber is used as the conductive agent, which has both conductive and heat-conducting functions. Among them, the nanoscale 0D Ketjen black conductive agent enhances the short-range electron conductivity ability around the carbon fluoride particles. At the same time, by using the high specific surface area of Ketjen black, the liquid absorption ability of the electrode is increased, and the ion conductivity ability is improved. The 1D carbon fiber is used to achieve long-range conductivity in the electrode structure. By using its whisker-like structure and high graphitization degree, efficient heat conduction inside the electrode is realized.

[0020] The above method is characterized in that in step one, the current collector with a graphene coating is obtained by coating graphene with a thickness of 0.5 μm - 2 μm on the surface of an aluminum foil current collector with a thickness of 8 μm - 20 μm. In the present invention, by controlling the thicknesses of the current collector and graphene, the performance of the carbon fluoride positive electrode sheet is ensured.

[0021] The above method is characterized in that in step two, the thickness of the copper foil is 5 μm - 12 μm, the thickness of the lithium layer is 40 μm - 100 μm, the thickness of the release film is less than 50 μm, and the material is PET, PTFE, PP or PE. In the present invention, by controlling the thicknesses of the copper foil and the lithium layer, the performance of the lithium metal negative electrode sheet is ensured. By controlling the parameters of the release film, adhesion during punching is ensured not to occur.

[0022] The above method is characterized in that in step three, the separator is a porous membrane with a thickness of 10 μm - 30 μm, and the material is polyethylene or polypropylene; in step four, the thickness of the heat-conducting sheet is 10 μm - 50 μm, and the material is aluminum, copper or nickel. In the present invention, by controlling the parameters of the separator and the heat-conducting sheet, the performance of the high-rate lithium carbon fluoride soft-pack battery cell is effectively ensured.

[0023] The present invention has the following advantages compared with the prior art:

[0024] 1. In the present invention, a heat-conducting sheet is designed between the battery cell units, and by controlling the structure of the battery cell units, it is beneficial to reduce the internal resistance and polarization. The heat-conducting sheet is close to the carbon fluoride positive electrode sheet, and the heat generated inside the battery during discharge is quickly conducted to the outside of the battery. Efficient heat dissipation is carried out through the multi-layer heat dissipation fins extending to the outside of the battery. Moreover, the multi-layer heat-conducting sheet design increases the heat transfer path and the heat-conducting area in the width direction, effectively improving the heat dissipation ability of the battery itself, avoiding thermal runaway caused by excessive temperature rise during high-rate discharge, and significantly improving the rate discharge ability and safety of the high-rate lithium carbon fluoride soft-pack battery. It has the characteristics of good rate performance, high process compatibility, and easy industrialization.

[0025] 2. The core structure of the high-rate lithium-carbon monofluoride soft-pack battery of the present invention greatly improves the internal electrical conductivity and thermal conductivity. Heat dissipation is carried out through the external ear, the battery surface, and the heat sink respectively, and at the same time, multi-path external heat dissipation is realized, which is beneficial to improving the rate discharge capacity, solving the problems of aggravated polarization and serious heating existing in the high-rate discharge of the current power-type lithium-carbon monofluoride battery. Improvements have been made in terms of electrode construction and single-cell design, greatly enhancing the heat dissipation performance and rate discharge capacity of the lithium-carbon monofluoride battery.

[0026] 3. The positive electrode tab and the negative electrode tab of the present invention are distributed on opposite sides in the length direction. The widths of the positive electrode tab and the negative electrode tab are the same as the widths of the carbon monofluoride positive electrode sheet and the metallic lithium negative electrode sheet, which improves the current-carrying capacity of the tabs and also increases the heat conduction area. The heat inside the battery can be conducted to the external tabs through the current collector for heat dissipation, which is beneficial to reducing the temperature rise during discharge, reducing the internal temperature gradient, and improving the high-rate discharge capacity of the battery.

[0027] 4. In the structure of the carbon monofluoride positive electrode sheet of the present invention, a graphene bottom-coated aluminum foil current collector is used, which plays a role in reducing the contact impedance between the active material coating and the current collector and improving the coating adhesion strength, enhancing the rate performance of the lithium-carbon monofluoride battery. At the same time, using the high thermal conductivity of the graphene material, the heat generated during the reaction process can be quickly conducted through the current collector to improve the heat conduction ability. The metallic lithium negative electrode sheet uses a lithium-copper composite tape with lithium coated on both sides. The contact area between lithium and copper is large, which improves the electron conductivity and current-carrying capacity. At the same time, using the high thermal conductivity of copper, the heat conduction and heat dissipation capabilities of the negative electrode are improved.

[0028] 5. In the carbon monofluoride positive electrode sheet of the present invention, a Ketjen black and carbon fiber composite conductive agent is introduced, which has both electrical conductivity and thermal conductivity functions. The nanoscale 0-dimensional Ketjen black conductive agent is used to enhance the short-range electron conductivity around the carbon monofluoride particles. At the same time, using the high specific surface area of Ketjen black, the liquid absorption capacity of the electrode is increased, and the ion conductivity is improved. The 1-dimensional carbon fiber is used to achieve long-range conductivity in the electrode structure. Using its whisker-like structure and high graphitization degree, efficient heat conduction inside the electrode is realized.

[0029] The technical solutions of the present invention will be further described in detail below with reference to the drawings and embodiments. Brief Description of the Drawings

[0030] Figure 1 It is a schematic structural diagram of the core of the high-rate lithium-carbon monofluoride soft-pack battery of the present invention.

[0031] Figure 2 It is an exploded view of the core of the high-rate lithium-carbon monofluoride soft-pack battery of the present invention.

[0032] Figure 3 It is an assembly schematic diagram of the carbon monofluoride positive electrode sheet, the metallic lithium negative electrode sheet, and the separator in the core of the high-rate lithium-carbon monofluoride soft-pack battery of the present invention.

[0033] Figure 4 This is a schematic structural view of the carbon fluoride positive electrode sheet in the high-rate lithium carbon fluoride soft-pack battery cell of the present invention.

[0034] Figure 5 This is an exploded view of the carbon fluoride positive electrode sheet in the high-rate lithium carbon fluoride soft-pack battery cell of the present invention.

[0035] Figure 6 This is a schematic structural view of the metallic lithium negative electrode sheet in the high-rate lithium carbon fluoride soft-pack battery cell of the present invention.

[0036] Figure 7 This is an exploded view of the metallic lithium negative electrode sheet in the high-rate lithium carbon fluoride soft-pack battery cell of the present invention.

[0037] Figure 8 This is the curve of the surface temperature change during rate discharge of the soft-pack battery prepared from the battery cells obtained in Example 2, Comparative Example 1 and Comparative Example 2 of the present invention.

[0038] Figure 9 This is the voltage-capacity curve during rate discharge of the soft-pack battery prepared from the battery cells obtained in Example 2, Comparative Example 1 and Comparative Example 2 of the present invention.

[0039] Description of reference numerals:

[0040] 1 - battery cell unit; 2 - heat conducting sheet; 3 - carbon fluoride positive electrode sheet;

[0041] 4 - metallic lithium negative electrode sheet; 5 - separator; 6 - positive electrode tab;

[0042] 7 - positive electrode external tab; 8 - negative electrode tab; 9 - negative electrode external tab;

[0043] 10 - packaging case; 11 - adhesive layer; 12 - graphene coating;

[0044] 13 - carbon fluoride coating; 14 - current collector; 15 - lithium layer;

[0045] 16 - copper foil; 17 - upper aluminum-plastic case; 18 - lower aluminum-plastic case;

[0046] 19 - upper aluminum-plastic case sealing edge; 20 - lower aluminum-plastic case sealing edge. Detailed description of the specific implementation mode

[0047] A high-rate lithium carbon fluoride soft-pack battery cell of the present invention is described in detail through Example 1.

[0048] Example 1

[0049] As Figures 1 to 3As shown in the figure, a high-rate lithium carbon monofluoride soft-pack battery cell of this embodiment includes a plurality of repeatedly stacked cell units 1. The adjacent cell units 1 are separated by heat-conducting sheets 2. Each cell unit 1 includes upper and lower layers of carbon monofluoride positive electrodes 3 and a lithium metal negative electrode 4 located between the two layers of carbon monofluoride positive electrodes 3. The two layers of carbon monofluoride positive electrodes 3 and the lithium metal negative electrode 4 are separated and wrapped by a separator 5. Each carbon monofluoride positive electrode 3 is provided with a positive electrode tab 6, and all the positive electrode tabs 6 in the plurality of repeatedly stacked cell units 1 are ultrasonically welded to the positive external tab 7. Each lithium metal negative electrode 4 is provided with a negative electrode tab 8, and all the negative electrode tabs 8 in the plurality of repeatedly stacked cell units 1 are ultrasonically welded to the negative external tab 9. The outside of the plurality of repeatedly stacked cell units 1 is heat-sealed with a packaging case 10.

[0050] It should be noted that by designing the heat-conducting sheet 2 between the cell units 1 and controlling the structure of the cell units 1, the heat-conducting sheet 2 is made to be close to the carbon monofluoride positive electrode 3, so that the heat generated inside the battery during discharge is quickly conducted to the outside of the battery, and efficient heat dissipation is carried out through the multi-layer heat sinks extending to the outside of the battery. Moreover, the design of the multi-layer heat-conducting sheet 2 increases the heat transfer path and the heat-conducting area in the width direction, effectively improving the heat dissipation capacity of the battery itself.

[0051] It should be noted that by controlling the structure of the high-rate lithium carbon monofluoride soft-pack battery cell, the conductivity and heat conductivity inside the high-rate lithium carbon monofluoride soft-pack battery cell are greatly improved. At the same time, multi-path heat dissipation outside the battery is realized, and heat dissipation is carried out respectively through the external tabs, the battery surface, and the heat sinks, which is beneficial to improving the rate discharge capacity. The battery preparation process is simple, has good compatibility, and is easy to industrialize.

[0052] In this embodiment, the number of cell units 1 is 2 to 25. By calculating according to the thickness of each component in the cell, a relatively reasonable range of the number of cell units 1 is given. Among them, 25 cell units 1 are basically close to the thickness limit of the aluminum-plastic shell packaged battery. The thickness of the soft-pack battery with aluminum-plastic packaging is usually within 12 to 13 mm, limited by the depth of the punching pit.

[0053] Such as Figure 1 and Figure 2As shown, in this embodiment, the length of the heat conductive sheet 2 is the same as the length of the carbon fluoride positive electrode sheet 3, and the width is 1.2 to 2.0 times the width of the carbon fluoride positive electrode sheet 3. The upper and lower surfaces of the heat conductive sheet 2 that exceeds the carbon fluoride positive electrode sheet 3 are both provided with a glue layer 11, and the upper part of the uppermost heat conductive sheet 2 and the lower part of the lowermost heat conductive sheet 2 are both provided with a lug glue. The carbon fluoride positive electrode sheet 3 and the metal lithium negative electrode sheet 4 have the same size. By making the width of the heat conductive sheet 2 1.2 to 2.0 times the width of the carbon fluoride positive electrode sheet 3, the heat conductive sheet 2 is extended out of the battery cell unit 1, which is convenient for the rapid heat extraction. By setting the glue layer 11, multiple heat conductive sheets 2 are bonded together to play a sealing role. The heat conductive sheets 2 are stacked between the battery cell units 1, and finally fixed by heat sealing with the packaging shell 10. The lug glue is provided to facilitate the cooperation with the packaging shell 10 to achieve sealing.

[0054] like Figures 4 to 7 As shown, in this embodiment, the carbon fluoride positive electrode sheet 3 is composed of a current collector 14 and a surface coating, specifically, a graphene coating 12 and a carbon fluoride coating 13 are sequentially coated on a single side surface of the current collector 14, and an area without a surface coating is reserved at one end of the carbon fluoride positive electrode sheet 3 as a positive electrode tab 6, and the metal lithium negative electrode sheet 4 is composed of a copper foil 16 and a lithium layer 15, specifically, a metal lithium layer 15 is coated on both sides of the copper foil 16, and an area of ​​the copper foil 16 without lithium coating at one end of the metal lithium negative electrode sheet 4 is used as a negative electrode tab 8, and the width of the positive electrode tab 6 and the width of the negative electrode tab 8 are the same as the width of the carbon fluoride positive electrode sheet 3 and the metal lithium negative electrode sheet 4, and the positive electrode tab 6 and the negative electrode tab 8 in the battery cell unit 1 are distributed on opposite sides. By using a current collector 14 coated with a graphene coating 12 and a carbon fluoride coating 13, the graphene coating 12 reduces the contact impedance between the carbon fluoride coating 13 and the current collector 14, improves the bonding strength of the carbon fluoride coating 13, and improves the rate performance of the high-rate lithium carbon fluoride soft-pack battery. At the same time, by utilizing the high thermal conductivity of the graphene coating 12, the heat generated during the reaction process can be quickly conducted through the current collector 14, thereby improving the thermal conductivity. By using a copper foil 16 with a lithium layer 15 on both sides, the contact area between lithium and copper is large, thereby improving the electron conductivity. The positive electrode tab 6 and the negative electrode tab 8 are distributed on opposite sides of the length direction, and the width of the positive electrode tab 6 and the negative electrode tab 8 is the same as the width of the carbon fluoride positive electrode sheet 3 and the metal lithium negative electrode sheet 4, which improves the current capacity of the tab and also increases the thermal conductivity area. The heat inside the battery can be transferred to the external tab through the current collector 14 for heat dissipation, which is beneficial to reduce the discharge temperature rise, reduce the internal temperature gradient, and improve the high-rate discharge capability of the battery.

[0055] It should be noted that the material of the positive electrode external tab 7 is aluminum, and the material of the negative electrode external tab 9 is nickel.

[0056] like Figure 1and Figure 2 As shown, in this embodiment, the packaging shell 10 includes an upper aluminum-plastic shell 17 and a lower aluminum-plastic shell 18, and the upper aluminum-plastic shell 17 and the lower aluminum-plastic shell 18 are both provided with grooves matching the multiple repeatedly stacked battery core units 1, and the upper aluminum-plastic shell 17 and the lower aluminum-plastic shell 18 are respectively provided with an upper aluminum-plastic shell edge seal 19 and a lower aluminum-plastic shell edge seal 20. By providing the upper aluminum-plastic shell 17 and the lower aluminum-plastic shell 18 and matching the grooves, the multiple repeatedly stacked battery core units 1 are coated, and by providing the upper aluminum-plastic shell edge seal 19 and the lower aluminum-plastic shell edge seal 20, it is convenient to seal.

[0057] The preparation method of a high-rate lithium fluoride carbon soft-pack battery cell of the present invention is described in detail through Examples 2 to 6.

[0058] Example 2

[0059] This embodiment includes the following steps:

[0060] Step 1: Preparation of carbon fluoride positive electrode sheet 3: Add carbon fluoride, Ketjen black, vapor-grown carbon fiber, and polyvinylidene fluoride to N-methylpyrrolidone at a mass ratio of 91:3:2:4 and stir until uniform and stable to obtain a carbon fluoride slurry with a viscosity of 9000 Pa·s to 11000 Pa·s, and then coat the carbon fluoride slurry on one side of the current collector 14 with graphene coating 12, and control the surface loading to 8 mg / cm 2 , wherein the current collector 14 with the graphene coating 12 is a current collector 14 with a thickness of 15 μm, on which a graphene with a thickness of 1 μm is coated, and then baked at 80° C. to 90° C. for 20 minutes, and then rolled to control the thickness to 95±2 μm, and finally punched with a special die to obtain a carbon fluoride positive electrode sheet 3;

[0061] Step 2, preparation of the metal lithium negative electrode sheet 4: a layer of PET release film with a thickness of 25 μm is covered on the upper and lower surfaces of the lithium copper composite tape, wherein the lithium copper composite tape is a 5 μm copper foil 16 with a thickness of 80 μm lithium on both sides, and then a special die is used to punch and remove the release film to obtain the metal lithium negative electrode sheet 4;

[0062] Step 3, preparation of battery cell unit 1: stacking a carbon fluoride positive electrode sheet 3 obtained in step 1, a metal lithium negative electrode sheet 4 obtained in step 2 and a carbon fluoride positive electrode sheet 3 obtained in step 1 in sequence and separating and wrapping them with a polypropylene porous membrane with a thickness of 25 μm, wherein one side of the two carbon fluoride positive electrode sheets 3 coated with carbon fluoride slurry faces the metal lithium negative electrode sheet 4, to obtain a battery cell unit 1;

[0063] Step 4, preparation of soft-pack battery cells: stack the five battery cell units 1 obtained in step 3, and place an aluminum thermal conductive sheet 2 with a thickness of 15 μm therein, and set a glue layer 11 and a pole ear glue, and the width of the aluminum thermal conductive sheet 2 is 1.5 times the width of the carbon fluoride positive electrode sheet 3, then hot-press and weld all the aluminum thermal conductive sheets 2, ultrasonically weld all the positive electrode tabs 6 and the aluminum positive electrode external tab 7, and ultrasonically weld all the negative electrode tabs 8 and the nickel negative electrode external tab 9, and then respectively put the upper aluminum plastic shell 17 and the lower aluminum plastic shell 18 on both sides of the five battery cell units 1, and hot-melt package the pole ear glue, the upper aluminum plastic shell edge sealing 19 and the lower aluminum plastic shell edge sealing 20 to obtain a high-rate lithium carbon fluoride soft-pack battery cell.

[0064] Comparative Example 1

[0065] The difference between this comparative example and Example 2 is that: in step 4, no aluminum heat conductive sheet 2 is provided.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 2 is that the conductive agent used in step one is superconducting carbon black, the mass ratio of carbon fluoride, superconducting carbon black and polyvinylidene fluoride is 91:5:4, and no thermal conductive sheet 2 is provided in step four.

[0068] The cells obtained in Example 2, Comparative Example 1 and Comparative Example 2 were injected with liquid, prevented from discharge, aged and repackaged to finally obtain soft-pack batteries. Then, the surface temperature rise and discharge capacity of different soft-pack batteries at 3C rate discharge were compared and tested. Figure 6 and Figure 7 As shown, the test results show that under the same rate conditions, the soft-pack battery obtained in Example 2 has a longer discharge time, a slower battery temperature rise, and a lower surface temperature. Therefore, the high-rate lithium carbon fluoride soft-pack battery cell and preparation method of the present invention are beneficial to enhancing heat dissipation capacity, reducing the temperature rise rate, and greatly improving the rate discharge capacity of the lithium carbon fluoride battery.

[0069] Example 3

[0070] This embodiment includes the following steps:

[0071] Step 1: Preparation of carbon fluoride positive electrode sheet 3: Add carbon fluoride, Ketjen black, vapor-grown carbon fiber, and polyvinylidene fluoride to N-methylpyrrolidone at a mass ratio of 85:5:5:5 and stir until uniform and stable to obtain a carbon fluoride slurry with a viscosity of 12000 Pa·s to 15000 Pa·s. Then, the carbon fluoride slurry is coated on one side of the current collector 14 having a graphene coating 12, and the surface loading is controlled to be 10 mg / cm 2, wherein the current collector 14 with the graphene coating 12 is obtained by coating graphene with a thickness of 0.5 μm on the surface of an aluminum foil current collector 14 with a thickness of 15 μm, then baking at 70 °C to 80 °C for 25 min, then rolling to control the thickness to 115 ± 2 μm, and finally punching with a special knife die to obtain the carbon fluoride positive electrode sheet 3;

[0072] Step 2. Preparation of the metallic lithium negative electrode sheet 4: Cover a layer of PET release film with a thickness of 25 μm on the upper and lower surfaces of the lithium copper composite tape. The lithium copper composite tape is a copper foil 16 with a thickness of 5 μm and a lithium layer with a thickness of 100 μm on both sides. Then, after punching with a special knife die, the release film is removed to obtain the metallic lithium negative electrode sheet 4;

[0073] Step 3. Preparation of the battery cell unit 1: Stack one carbon fluoride positive electrode sheet 3 obtained in Step 1, one metallic lithium negative electrode sheet 4 obtained in Step 2, and one carbon fluoride positive electrode sheet 3 obtained in Step 1 in sequence, and separate and wrap them with a polypropylene porous film with a thickness of 25 μm in the middle. Both sides of the two carbon fluoride positive electrode sheets 3 coated with the carbon fluoride slurry face the metallic lithium negative electrode sheet 4 to obtain the battery cell unit 1;

[0074] Step 4. Preparation of the soft-pack battery cell: Stack 2 battery cell units 1 obtained in Step 3, place an aluminum heat-conducting sheet 2 with a thickness of 20 μm in the middle, set the adhesive layer 11 and the tab glue. The width of the aluminum heat-conducting sheet 2 is 1.5 times the width of the carbon fluoride positive electrode sheet 3. Then, thermally press and weld all the aluminum heat-conducting sheets 2, ultrasonically weld all the positive electrode tabs 6 to the aluminum positive external tab 7, ultrasonically weld all the negative electrode tabs 8 to the nickel negative external tab 9, then respectively put the upper aluminum plastic shell 17 and the lower aluminum plastic shell 18 on both sides of the 2 battery cell units 1, and perform hot-melt encapsulation on the tab glue, the edge sealing 19 of the upper aluminum plastic shell and the edge sealing 20 of the lower aluminum plastic shell to obtain the high-rate lithium-carbon fluoride soft-pack battery cell.

[0075] Example 4

[0076] This example includes the following steps:

[0077] Step 1. Preparation of the carbon fluoride positive electrode sheet 3: Add carbon fluoride, Ketjen black, vapor-grown carbon fiber, and polyvinylidene fluoride in a mass ratio of 95:1:1.5:2.5 to N-methylpyrrolidone and stir well until uniform and stable to obtain a carbon fluoride slurry with a viscosity of 7000 Pa·s to 9000 Pa·s. Then, coat the carbon fluoride slurry on one side of the current collector 14 with the graphene coating 12, and control the areal loading to 6 mg / cm 2, wherein the current collector 14 with a graphene coating 12 is obtained by coating a graphene layer with a thickness of 2 μm on the surface of an aluminum foil current collector 14 with a thickness of 15 μm, baking at 80 °C to 90 °C for 20 min, then rolling to control the thickness to 75 ± 2 μm, and finally punching with a special knife die to obtain the carbon fluoride positive electrode sheet 3;

[0078] Step 2. Preparation of the lithium metal negative electrode sheet 4: Cover the upper and lower surfaces of the lithium-copper composite tape with a PTFE release film with a thickness of 20 μm. The lithium-copper composite tape is a copper foil 16 with a thickness of 5 μm coated with lithium with a thickness of 40 μm on both sides. Then, after punching with a special knife die, the release film is removed to obtain the lithium metal negative electrode sheet 4;

[0079] Step 3. Preparation of the battery cell unit 1: Stack one carbon fluoride positive electrode sheet 3 obtained in Step 1, one lithium metal negative electrode sheet 4 obtained in Step 2, and one carbon fluoride positive electrode sheet 3 obtained in Step 1 in sequence, and separate and wrap them with a polypropylene porous film with a thickness of 25 μm. The sides coated with the carbon fluoride slurry of the two carbon fluoride positive electrode sheets 3 face the lithium metal negative electrode sheet 4 to obtain the battery cell unit 1;

[0080] Step 4. Preparation of the soft-pack battery cell: Stack 20 battery cell units 1 obtained in Step 3, place an aluminum heat-conducting sheet 2 with a thickness of 20 μm among them, set an adhesive layer 11 and an ear glue. The width of the aluminum heat-conducting sheet 2 is 1.5 times the width of the carbon fluoride positive electrode sheet 3. Then, hot-press and weld all the aluminum heat-conducting sheets 2, ultrasonically weld all the positive electrode ears 6 to the aluminum positive external ear 7, ultrasonically weld all the negative electrode ears 8 to the nickel negative external ear 9. Then, put the upper aluminum plastic shell 17 and the lower aluminum plastic shell 18 on both sides of the 20 battery cell units 1 respectively, and perform hot-melt encapsulation on the ear glue, the edge sealing 19 of the upper aluminum plastic shell and the edge sealing 20 of the lower aluminum plastic shell to obtain the high-rate lithium carbon fluoride soft-pack battery cell.

[0081] Example 5

[0082] This example includes the following steps:

[0083] Step 1. Preparation of the carbon fluoride positive electrode sheet 3: Add carbon fluoride, Ketjen black, vapor-grown carbon fiber, and polyvinylidene fluoride in a mass ratio of 95:1:1.5:2.5 to N-methylpyrrolidone and stir well until uniform and stable to obtain a carbon fluoride slurry with a viscosity of 7000 Pa·s to 9000 Pa·s. Then, coat the carbon fluoride slurry on one side of the current collector 14 with a graphene coating 12, and control the areal loading to 6 mg / cm 2, wherein the current collector 14 with the graphene coating 12 is a current collector 14 with a thickness of 8 μm, on which a graphene with a thickness of 1 μm is coated, and then baked at 80° C. to 90° C. for 20 minutes, and then rolled to control the thickness to 68±2 μm, and finally punched with a special die to obtain a carbon fluoride positive electrode sheet 3;

[0084] Step 2, preparation of the metal lithium negative electrode sheet 4: a layer of 40 μm thick PP release film is respectively covered on the upper and lower surfaces of the lithium copper composite strip, wherein the lithium copper composite strip is a copper foil 16 with a thickness of 10 μm and lithium with a thickness of 60 μm on both sides, and then a special die is used for punching and then the release film is removed to obtain the metal lithium negative electrode sheet 4;

[0085] Step 3, preparation of battery cell unit 1: stacking a carbon fluoride positive electrode sheet 3 obtained in step 1, a metal lithium negative electrode sheet 4 obtained in step 2 and a carbon fluoride positive electrode sheet 3 obtained in step 1 in sequence and separating and wrapping them with a polyethylene porous membrane with a thickness of 10 μm, wherein two carbon fluoride positive electrode sheets 3 coated with carbon fluoride slurry are both facing the metal lithium negative electrode sheet 4, to obtain a battery cell unit 1;

[0086] Step 4, preparation of soft-pack battery cells: stack 25 battery cell units 1 obtained in step 3, and place a copper thermal conductive sheet 2 with a thickness of 50 μm, and set a glue layer 11 and a pole ear glue therein, and the width of the copper thermal conductive sheet 2 is 1.2 times the width of the carbon fluoride positive electrode sheet 3, and then hot-press and weld all the copper thermal conductive sheets 2, ultrasonically weld all the positive electrode tabs 6 and the aluminum positive electrode external tab 7, and ultrasonically weld all the negative electrode tabs 8 and the nickel negative electrode external tab 9, and then respectively put the upper aluminum-plastic shell 17 and the lower aluminum-plastic shell 18 on both sides of the 25 battery cell units 1, and hot-melt package the pole ear glue, the upper aluminum-plastic shell edge sealing 19 and the lower aluminum-plastic shell edge sealing 20 to obtain a high-rate lithium carbon fluoride soft-pack battery cell.

[0087] Example 6

[0088] This embodiment includes the following steps:

[0089] Step 1: Preparation of carbon fluoride positive electrode sheet 3: Add carbon fluoride, Ketjen black, vapor-grown carbon fiber, and polyvinylidene fluoride to N-methylpyrrolidone at a mass ratio of 95:1:1.5:2.5 and stir until uniform and stable to obtain a carbon fluoride slurry with a viscosity of 7000Pa·s to 9000Pa·s, and then coat the carbon fluoride slurry on one side of the current collector 14 with graphene coating 12, and control the surface loading to 6mg / cm 2, wherein the current collector 14 with the graphene coating 12 is obtained by coating a graphene layer with a thickness of 1 μm on the surface of an aluminum foil current collector 14 with a thickness of 20 μm, baking it at 80 °C to 90 °C for 20 min, then roll-pressing to control the thickness to 80 ± 2 μm, and finally punching with a special knife die to obtain the carbon fluoride positive electrode sheet 3;

[0090] Step 2: Preparation of the lithium metal negative electrode sheet 4: Cover a 30-μm-thick PE release film on the upper and lower surfaces of the lithium-copper composite tape. The lithium-copper composite tape is a 12-μm-thick copper foil 16 with 80-μm-thick lithium coated on both sides. Then, after punching with a special knife die, the release film is removed to obtain the lithium metal negative electrode sheet 4;

[0091] Step 3: Preparation of the battery cell unit 1: Stack one carbon fluoride positive electrode sheet 3 obtained in Step 1, one lithium metal negative electrode sheet 4 obtained in Step 2, and one carbon fluoride positive electrode sheet 3 obtained in Step 1 in sequence, and separate and wrap them with a 30-μm-thick polypropylene porous membrane in the middle. The sides of the two carbon fluoride positive electrode sheets 3 coated with the carbon fluoride slurry face the lithium metal negative electrode sheet 4 to obtain the battery cell unit 1;

[0092] Step 4: Preparation of the soft-pack battery cell: Stack 10 battery cell units 1 obtained in Step 3, place a 10-μm-thick nickel heat-conducting sheet 2 in the middle, set the adhesive layer 11 and the tab glue. The width of the nickel heat-conducting sheet 2 is 2.0 times the width of the carbon fluoride positive electrode sheet 3. Then, thermally press and weld all the nickel heat-conducting sheets 2, ultrasonically weld all the positive tab 6 to the aluminum positive external tab 7, ultrasonically weld all the negative tab 8 to the nickel negative external tab 9. Then, put the upper aluminum plastic shell 17 and the lower aluminum plastic shell 18 on both sides of the 10 battery cell units 1 respectively, and perform hot-melt encapsulation on the tab glue, the upper aluminum plastic shell edge 19 and the lower aluminum plastic shell edge 20 to obtain the high-rate lithium-carbon fluoride soft-pack battery cell.

[0093] The above is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change, and equivalent change made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A high-rate lithium carbon fluoride soft pack battery cell, characterized in that: The soft-pack battery cell comprises a plurality of repeatedly stacked cell units (1), wherein adjacent cell units (1) are separated by a heat conductive sheet (2), each cell unit (1) comprises an upper and lower carbon fluoride positive electrode sheet (3) and a metal lithium negative electrode sheet (4) located between the two layers of carbon fluoride positive electrode sheets (3), the two layers of carbon fluoride positive electrode sheets (3) and the metal lithium negative electrode sheet (4) are separated and wrapped by a diaphragm (5), and each of the carbon fluoride positive electrode sheets (3) is provided with a heat conductive sheet (2). Each carbon positive electrode sheet (3) is provided with a positive electrode tab (6), and all the positive electrode tabs (6) in the multiple repeatedly stacked battery cell units (1) are ultrasonically welded to the positive electrode external tab (7), each of the metal lithium negative electrode sheets (4) is provided with a negative electrode tab (8), and all the negative electrode tabs (8) in the multiple repeatedly stacked battery cell units (1) are ultrasonically welded to the negative electrode external tab (9), and the multiple repeatedly stacked battery cell units (1) are externally hot-melt-sealed with a packaging shell (10).

2. A high-rate lithium carbon fluoride soft pack battery cell according to claim 1, characterized in that: The number of the battery core units (1) is 2 to 25.

3. A high-rate lithium carbon fluoride soft pack battery cell according to claim 1, characterized in that: The length of the heat conductive sheet (2) is the same as that of the carbon fluoride positive electrode sheet (3), and the width is 1.2 to 2.0 times the width of the carbon fluoride positive electrode sheet (3). The upper and lower surfaces of the portion of the heat conductive sheet (2) that exceeds the carbon fluoride positive electrode sheet (3) are both provided with a glue layer (11). The upper part of the uppermost heat conductive sheet (2) and the lower part of the lowermost heat conductive sheet (2) are both provided with a lug glue. The carbon fluoride positive electrode sheet (3) and the metal lithium negative electrode sheet (4) are the same size.

4. A high-rate lithium carbon fluoride soft pack battery cell according to claim 1, characterized in that: The carbon fluoride positive electrode sheet (3) is composed of a current collector (14) and a surface coating, specifically, a graphene coating (12) and a carbon fluoride coating (13) are sequentially coated on a single side surface of the current collector (14); an area without a surface coating is reserved at one end of the carbon fluoride positive electrode sheet (3) as a positive electrode tab (6); the metal lithium negative electrode sheet (4) is composed of a copper foil (16) and a lithium layer (15); specifically, a metal lithium layer (15) is coated on both sides of the copper foil (16); an area of ​​the copper foil (16) without lithium coating at one end of the metal lithium negative electrode sheet (4) is used as a negative electrode tab (8); the width of the positive electrode tab (6) and the width of the negative electrode tab (8) are both the same as the width of the carbon fluoride positive electrode sheet (3) and the metal lithium negative electrode sheet (4); and the positive electrode tab (6) and the negative electrode tab (8) in the battery cell unit (1) are distributed on opposite sides.

5. A high-rate lithium carbon fluoride soft pack battery cell according to claim 1, characterized in that: The packaging shell (10) comprises an upper aluminum-plastic shell (17) and a lower aluminum-plastic shell (18), wherein the upper aluminum-plastic shell (17) and the lower aluminum-plastic shell (18) are both provided with grooves matching a plurality of repeatedly stacked battery cell units (1), and the upper aluminum-plastic shell (17) and the lower aluminum-plastic shell (18) are respectively provided with an upper aluminum-plastic shell edge seal (19) and a lower aluminum-plastic shell edge seal (20).

6. A method for preparing a high-rate lithium fluoride carbon soft-pack battery cell as claimed in any one of claims 1 to 5, characterized in that: The method comprises the following steps: Step 1, preparation of a carbon fluoride positive electrode sheet (3): adding carbon fluoride, a conductive agent, and a binder into a solvent and stirring them thoroughly until they are uniform and stable to obtain a carbon fluoride slurry, then coating the carbon fluoride slurry on a current collector (14) having a graphene coating (12), and then baking, rolling, and punching in sequence to obtain a carbon fluoride positive electrode sheet (3); Step 2, preparation of a metal lithium negative electrode sheet (4): a layer of release film is covered on the upper and lower surfaces of a copper foil (16) covered with a lithium layer (15) on both sides, and then the release film is removed after punching to obtain a metal lithium negative electrode sheet (4); Step 3, preparation of a battery cell unit (1): stacking a carbon fluoride positive electrode sheet (3) obtained in step 1, a metal lithium negative electrode sheet (4) obtained in step 2, and a carbon fluoride positive electrode sheet (3) obtained in step 1 in sequence and separating and wrapping them with a separator (5), wherein the two carbon fluoride positive electrode sheets (3) coated with carbon fluoride slurry are both facing the metal lithium negative electrode sheet (4), to obtain a battery cell unit (1); Step 4, preparation of soft-pack battery cells: stack multiple battery cell units (1) obtained in step 3, place a heat conductive sheet (2) therein, and set a glue layer (11) and a tab glue, then perform hot-pressing welding on all the heat conductive sheets (2), ultrasonically weld all the positive pole tabs (6) of the multiple battery cell units (1) to the positive external tab (7), and ultrasonically weld all the negative pole tabs (8) of the multiple battery cell units (1) to the negative external tab (9), then respectively cover the upper aluminum-plastic shell (17) and the lower aluminum-plastic shell (18) on both sides of the multiple battery cell units (1), and perform hot-melt sealing on the tab glue, the upper aluminum-plastic shell edge sealing (19) and the lower aluminum-plastic shell edge sealing (20), to obtain a high-rate lithium fluoride carbon soft-pack battery cell.

7. The method according to claim 6, characterized in that In step one, the conductive agent is Ketjen black and carbon fiber, the adhesive is polyvinylidene fluoride, the solvent is N-methylpyrrolidone, the mass content of carbon fluoride in the carbon fluoride slurry is 85% to 95%, the mass content of the conductive agent is 2.5% to 10%, and the remainder is the adhesive.

8. The method according to claim 6, characterized in that The current collector (14) with a graphene coating (12) in step 1 is a current collector (14) with an aluminum foil having a thickness of 8 μm to 20 μm and a graphene having a thickness of 0.5 μm to 2 μm coated on its surface.

9. The method according to claim 6, characterized in that In step 2, the thickness of the copper foil (16) is 5 μm to 12 μm, the thickness of the lithium layer (15) is 40 μm to 100 μm, the thickness of the release film is less than 50 μm, and the material is PET, PTFE, PP or PE.

10. The method according to claim 6, characterized in that The diaphragm (5) in step three is a porous membrane with a thickness of 10 μm to 30 μm, and is made of polyethylene or polypropylene; the heat conductive sheet (2) in step four has a thickness of 10 μm to 50 μm, and is made of aluminum, copper or nickel.

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