Pre-lithiation module and pre-lithiation device

Abstract

The utility model relates to the technical field of lithium ion battery manufacturing, and provides a pre-lithiation module and a pre-lithiation device.The pre-lithiation module is applied to the pre-lithiation device of a negative plate and comprises a pre-lithiation cavity, a supporting guide roller, a metal lithium deposition body and a rotating shaft; the metal lithium deposition body, the negative plate and the electrolyte are positioned in the pre-lithiation cavity; the partial area of the negative plate and the metal lithium deposition body are immersed in the electrolyte; the rotating shaft is detachably connected with the metal lithium deposition body, and the rotating shaft and the metal lithium deposition body share the same rotating axis; the peripheral surface of the metal lithium deposition body and the peripheral surface of the supporting guide roller are in contact with the surface of the negative plate in a tensioned state; a potential difference exists between the metal lithium deposition body immersed in the electrolyte and the negative plate, so that lithium ions in the metal lithium deposition body are transferred to the negative plate. The pre-lithiation module is used for carrying out continuous, safe and controllable pre-lithiation treatment on a negative plate.

Description

Technical Field

[0001] This utility model relates to the field of lithium-ion battery manufacturing technology, and in particular to a pre-lithiation module and a pre-lithiation device. Background Technology

[0002] During the initial charge and discharge cycle of a lithium-ion battery, the formation of a solid electrolyte interphase (SEI) film on the negative electrode surface and irreversible lithium consumption lead to the loss of active lithium, thereby reducing battery capacity and energy density. To compensate for this loss of active lithium, pre-lithiation technology is widely used in the lithium-ion battery manufacturing process.

[0003] Traditional negative electrode lithium replenishment technology involves mixing lithium powder or lithium alloy into the negative electrode slurry. However, lithium powder has high activity and poor dispersibility, posing safety hazards. Electrochemical pre-lithiation requires additional equipment, making the process complex and costly. Therefore, there is an urgent need for a pre-lithiation module and device to improve these problems. Utility Model Content

[0004] The purpose of this invention is to provide a pre-lithiation module and a pre-lithiation device, wherein the pre-lithiation module is used to perform continuous, safe and controllable pre-lithiation treatment on negative electrode sheets.

[0005] According to a first aspect of the present invention, a pre-lithiation module is provided, applied to a pre-lithiation device for a negative electrode sheet, comprising: a pre-lithiation chamber, a support guide roller, a lithium metal deposit, and a rotating shaft; the lithium metal deposit, the negative electrode sheet, and an electrolyte are located in the pre-lithiation chamber; a portion of the negative electrode sheet and the lithium metal deposit are immersed in the electrolyte; the rotating shaft is detachably connected to the lithium metal deposit, and the rotating shaft and the lithium metal deposit have a common axis of rotation; the outer peripheral surface of the lithium metal deposit and the peripheral surface of the support guide roller are both in contact with the surface of the negative electrode sheet in a tensioned state; a potential difference exists between the lithium metal deposit immersed in the electrolyte and the negative electrode sheet, so that lithium ions in the lithium metal deposit are transferred to the negative electrode sheet.

[0006] Optionally, the bulk density of the negative electrode is less than 1.45 g / cm³. 3 .

[0007] Optionally, the thickness of the lithium metal deposit is greater than 50 μm.

[0008] Optionally, the negative electrode sheet is further used to control the potential of the lithium metal deposit to 0.1~0.6V; or the support guide roller is used to control the movement speed of the negative electrode sheet so that the total time for the negative electrode sheet to fully contact the lithium metal deposit is 1min~1h, wherein the total time is the time for a single lithium metal deposit to contact the negative electrode sheet multiplied by the number of lithium metal deposits.

[0009] Optionally, the lithium metal deposit is cylindrical; the outer peripheral surface of the lithium metal deposit rolls and rubs against the negative electrode sheet; the outer peripheral surface is parallel to the axis of rotation.

[0010] Optionally, the number of the rotating shaft and the number of the lithium metal deposits are both several, and the rotating shaft and the lithium metal deposits are detachably connected in a one-to-one correspondence; the number of the lithium metal deposits is a positive even number; and the rotation axes of each lithium metal deposit are parallel to each other.

[0011] Optionally, the lithium metal deposit has a peripheral side facing the electrolyte surface and a peripheral side facing away from the electrolyte surface; the lithium metal deposits are arranged along a first direction; the peripheral side of the odd-numbered lithium metal deposits contacts the first surface of the negative electrode, and the peripheral side of the even-numbered lithium metal deposits contacts the second surface of the negative electrode; the first surface and the second surface are opposite each other; the first direction is parallel to the electrolyte surface and perpendicular to the rotation axis of the lithium metal deposits.

[0012] Optionally, the number of lithium metal deposits is several, and the outer diameter of each lithium metal deposit is D, where D is a positive value; the distance between the rotation axes of adjacent lithium metal deposits is L, where L is greater than D.

[0013] Optionally, the axis of the support guide roller is parallel to the rotation axis of the lithium metal deposit; the number of support guide rollers is at least 2, wherein 2 of the support guide rollers are located on both sides of the lithium metal deposit.

[0014] Optionally, the distance from the axis of the support guide roller to the axis of rotation of the nearest lithium metal deposit is L.

[0015] According to a second aspect of the present invention, a pre-lithiation device is provided, comprising a pre-lithiation module as described in any one of the first aspects, and further comprising: a cleaning module near a first outlet end of the pre-lithiation chamber; the negative electrode sheet being removed from the pre-lithiation module from the first outlet end; the cleaning module comprising a cleaning chamber containing an organic solvent for cleaning residual electrolyte on the negative electrode sheet; the cleaning module further comprising a plurality of cleaning rollers immersed in the organic solvent; the negative electrode sheet passing through the cleaning chamber around the plurality of cleaning rollers.

[0016] Optionally, the pre-lithiation device further includes a baking module near the second outlet end of the cleaning chamber; the negative electrode sheet is removed from the cleaning chamber from the second outlet end; the baking module includes a heating section facing the negative electrode sheet, the heating section being used to heat the negative electrode sheet to evaporate the residual organic solvent on the negative electrode sheet; the baking module further includes a drying roller, the periphery of which is tangent to the surface of the negative electrode sheet.

[0017] Optionally, the pre-lithiation device further includes a feeding guide roller, a discharging guide roller, and at least one marking section; the feeding guide roller and the discharging guide roller are located on opposite sides of the pre-lithiation chamber; the feeding guide roller is loaded with a negative electrode sheet that has not passed through the pre-lithiation chamber; the discharging guide roller is loaded with a negative electrode sheet that has passed through the pre-lithiation chamber; the negative electrode sheet loaded on the feeding guide roller is pulled by the discharging guide roller and passes through the pre-lithiation chamber; the marking section is electrically connected to the discharging guide roller; when the discharging guide roller stops rotating, a portion of the negative electrode sheet is marked by the marking section; the marked portion is removed when the negative electrode sheet is cut.

[0018] Compared with existing technologies, the advantages of this invention are as follows: By setting the outer peripheral surface of the lithium metal deposit to contact the surface of the tensioned negative electrode sheet, lithium ions in the lithium metal deposit migrate directionally through the electrolyte and embed into the negative electrode sheet, thereby achieving pre-lithiation treatment of the negative electrode sheet. Compared with traditional technologies that use highly active lithium powder or lithium alloys for lithium replenishment, this invention avoids the safety hazards caused by uneven lithium powder dispersion and violent reactions, significantly improving the safety and stability of the production process. Furthermore, by using a support guide roller to pull the tensioned negative electrode sheet around the lithium metal deposit, allowing it to continuously pass through the pre-lithiation chamber, continuous pre-lithiation treatment of the negative electrode sheet is achieved. This not only improves production efficiency but also simplifies the process flow, reduces equipment and operational complexity, and helps save costs. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a pre-lithiation module according to an exemplary embodiment.

[0020] Figure 2 This is a schematic diagram of the structure of a cleaning module according to an exemplary embodiment.

[0021] Figure 3 This is a schematic diagram of the structure of a baking module according to an exemplary embodiment.

[0022] Figure 4 These are schematic diagrams of voltage differential capacity curves for Examples 1-4 and Comparative Examples 1-3.

[0023] Figure 5 These are the 25°C 1C cycle curves for Examples 1-4 and Comparative Examples 1-3.

[0024] Explanation of the reference numerals in the figure:

[0025] 1. Negative electrode sheet; 2. Rotating shaft; 3. Lithium metal deposit; 31. Rotation axis; 4. Supporting guide roller; 41. Cleaning roller; 42. Drying roller; 5. Electrolyte; 51. Organic solvent; 6. Exhaust section; 7. Heating section; 8. Pre-lithiation chamber; 81. First outlet end; 82. First inlet end; 83. Cleaning chamber; 84. Second outlet end; 9. Pre-lithiation module; 91. Cleaning module; 92. Baking module. Detailed Implementation

[0026] Unless otherwise defined, the technical or scientific terms used in this specification shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. Specific embodiments of this invention will be described below with reference to the accompanying drawings. It should be noted that, in order to provide a concise description, this specification cannot provide a detailed description of all features of the actual embodiments. Without departing from the spirit and scope of this invention, those skilled in the art can make modifications and substitutions to the embodiments of this invention, and the resulting embodiments are also within the protection scope of this invention.

[0027] like Figure 1 As shown, this utility model provides a pre-lithiation module 9, applied to a pre-lithiation device for a negative electrode 1, comprising: a pre-lithiation chamber 8, a support guide roller 4, a lithium metal deposit 3, and a rotating shaft 2; the pre-lithiation chamber 8 is used to accommodate the lithium metal deposit 3, the negative electrode 1, and an electrolyte 5; a portion of the negative electrode 1 and the lithium metal deposit 3 are immersed in the electrolyte 5; the rotating shaft 2 carries the lithium metal deposit 3 and is used to position the rotation axis 31 of the lithium metal deposit 3; the support guide roller 4 is used to pull the negative electrode 1 to tension and pass around the lithium metal deposit 3 through the pre-lithiation chamber 8; there is a potential difference between the lithium metal deposit 3 immersed in the electrolyte 5 and the negative electrode 1, so that lithium ions in the lithium metal deposit 3 are transferred to the negative electrode 1.

[0028] In some embodiments, the bulk density of the negative electrode 1 is less than 1.45 g / cm³. 3 The applicant noted that when the bulk density of the negative electrode 1 is too high, its pore size decreases and its porosity reduces, making it difficult for the electrolyte 5 to penetrate. This results in difficulty for the negative electrode 1 to absorb liquid, which in turn affects the lithium ion transport efficiency and distribution uniformity during the pre-lithiation process, ultimately reducing the consistency and reliability of the pre-lithiation effect. This embodiment, by controlling the bulk density of the negative electrode 1 within a reasonable range, helps to improve its liquid absorption performance, thereby ensuring the uniformity and stability of the pre-lithiation reaction.

[0029] Specifically, the negative electrode 1 is at least one of graphite negative electrode, silicon-carbon negative electrode, nano-silicon negative electrode, and silicon suboxide negative electrode.

[0030] In other specific embodiments, the negative electrode is composed of an active material, a conductive agent, a binder, etc.

[0031] In some examples, the active material includes at least one of natural graphite, artificial graphite, mesophase carbon microspheres, nano-silicon, and silicon suboxide; the conductive agent includes at least one of conductive carbon black (Super P Conductive Carbon Black, abbreviated as SUPER P), acetylene black, conductive graphite, carbon nanotubes, graphene, and carbon fiber; and the binder includes at least one of thermoplastic resin, acrylic resin, and styrene-butadiene rubber.

[0032] The thermoplastic resin includes at least one selected from polyvinylidene fluoride, copolymers of polyvinylidene fluoride, polytetrafluoroethylene, copolymers of polyvinylidene fluoride and hexafluoropropylene, copolymers of tetrafluoroethylene and hexafluoropropylene, copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ethers, copolymers of ethylene and tetrafluoroethylene, copolymers of polyvinylidene fluoride and tetrafluoroethylene, copolymers of polyvinylidene fluoride and trifluoroethylene, copolymers of polyvinylidene fluoride and trichloroethylene, copolymers of polyvinylidene fluoride and fluorinated ethylene, copolymers of polyvinylidene fluoride, hexafluoropropylene and tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene.

[0033] In some specific embodiments, the electrolyte 5 is composed of a solvent, a lithium salt, and additives. The solvent is an ester solvent or an ether solvent.

[0034] In some examples, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), and lithium tetrafluoroborate (LiBF4). The ester solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene methyl carbonate (EMC), and methyl propyl carbonate (MPC).

[0035] In another example, the solvent in the ether electrolyte 5 includes at least one of tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4-MeDOL), dimethylmethane (DMM), 1,2-dimethoxyethane (DME), 1,2-dimethoxypropane (DMP), and diethylene glycol dimethyl ether (DG).

[0036] Lithium salts include at least one of lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethylsulfonyl)imide lithium salt (LiTFSI), lithium bis(fluorosulfonyl)imide lithium salt (LiFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiODFB), and lithium hydroxide (LiOH).

[0037] The additives include at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), and 1,3-propanesultone (PS).

[0038] In some embodiments, the thickness of the lithium metal deposit 3 is greater than 50 μm. A thicker lithium metal deposit 3 has higher strength, lower cost, and is easier to use in production; with the same amount of lithium replenishment, a thicker lithium metal deposit 3 is consumed more slowly, which can reduce the number of times the lithium metal deposit 3 can be replaced in a long production process.

[0039] It is worth noting that if the contact time between the negative electrode 1 and the lithium metal deposit 3 is too short, or if the potential of the negative electrode 1 relative to the lithium metal deposit 3 is controlled too high during the pre-lithiation process, the amount of lithium replenishment will be insufficient, making it difficult to effectively improve the first coulombic efficiency of the battery. Conversely, if the contact time between the negative electrode 1 and the lithium metal deposit 3 is too long, or if its lithium potential is controlled too low, excessive lithium replenishment may occur, leading to excessive lithium intercalation of the negative electrode 1. This can easily cause lithium plating during subsequent battery assembly and use, thereby affecting the cycle performance and safety of the battery.

[0040] In some embodiments, the first pre-lithiated negative electrode sheet in the same batch is verified. The speed at which the first pre-lithiated negative electrode sheet passes through the lithium metal deposit is recorded. The first pre-lithiated negative electrode sheet, separator, and lithium metal are packaged into a button cell. The positive and negative electrode voltages of the button cell are tested and determined to be between 0.1V and 0.6V. When the positive and negative electrode voltages of the button cell are greater than 0.1V and less than 0.6V, the first pre-lithiated negative electrode sheet is confirmed as a good product. The negative electrode sheet is kept passing through the lithium metal deposit at the current speed, and the pre-lithiation of subsequent negative electrode sheets continues. When the positive and negative electrode voltages of the button cell are less than 0.1V or greater than 0.6V, the first pre-lithiated negative electrode sheet is a defective product.

[0041] This embodiment verifies that the potential of the negative electrode 1 to the lithium metal deposit 3 is 0.1~0.6V, which can avoid insufficient lithium replenishment or excessive lithium intercalation of the negative electrode 1.

[0042] In other embodiments, the support guide roller 4 is used to control the movement speed of the negative electrode 1 so that the total time for the negative electrode 1 to fully contact the lithium metal deposit 3 is 1 min to 1 h. The total time is the time for a single lithium metal deposit 3 to contact the negative electrode 1 multiplied by the number of lithium metal deposits 3. The time for a single lithium metal deposit 3 to contact the negative electrode 1 is the time for the lithium metal deposit 3 to rotate half a revolution.

[0043] In this embodiment, the movement speed of the negative electrode 1 is controlled by the support guide roller 4 so that the total contact time between the negative electrode 1 and the lithium metal deposit 3 is 1 min to 1 h, which can also avoid insufficient lithium replenishment or excessive lithium intercalation of the negative electrode 1.

[0044] In some embodiments, the lithium metal deposit 3 is cylindrical; the outer peripheral surface of the lithium metal deposit 3 rolls and rubs against the negative electrode 1; the outer peripheral surface is parallel to the rotation axis 31. The rotation axis 31 is perpendicular to the X and Z directions, with the Z direction perpendicular to the horizontal plane, and the negative electrode 1 passes through the pre-lithiation cavity 8 along the X direction.

[0045] In some examples, the cylindrical lithium metal deposit 3 has an annular cross-section. The cross-section is a vertical plane formed by the X and Z directions.

[0046] In other examples, the lithium metal deposit 3 is formed by spreading a section of lithium foil roll onto the outer peripheral surface of an inert support. The inert support is cylindrical, and its inner peripheral surface is detachably connected to the shaft. The inert support does not participate in the chemical reaction in the electrolyte 5.

[0047] In this embodiment, the outer peripheral surface of the lithium metal deposit 3 is used to roll and rub against the negative electrode 1, which can avoid the sliding friction between the lithium metal deposit 3 and the negative electrode 1, and is conducive to improving the surface flatness of the negative electrode 1 to ensure its electrochemical performance.

[0048] In some specific embodiments, the width of the lithium metal deposit 3 is greater than the width of the negative electrode 1, and the width is along the extension direction of the rotation axis 31.

[0049] In some examples, the width of the lithium metal deposit 3 is at least 1 mm larger than the width of the negative electrode 1.

[0050] In other examples, the rotating shaft is configured as an air shaft, a mechanical shaft, or a magnetic powder clutch. The air shaft expands after being inflated to load the lithium metal deposit 3, and contracts after being deflated to unload the lithium metal deposit 3; the mechanical shaft locks or releases the lithium metal deposit 3 through a mechanical structure; the magnetic powder clutch controls the tension applied to the lithium metal deposit 3 by means of electric current to achieve loading or unloading of the lithium metal deposit 3.

[0051] In some embodiments, the number of the rotating shaft 2 and the lithium metal deposit 3 are both several, and the rotating shaft 2 and the lithium metal deposit 3 are detachably connected in a one-to-one correspondence; the number of lithium metal deposits 3 is a positive even number; in the example shown in the figure, the number of lithium metal deposits 3 and the number of rotating shafts 2 are both set to 8. The rotation axes 31 of each lithium metal deposit 3 are parallel to each other.

[0052] In some specific embodiments, the lithium metal deposit 3 has a peripheral side facing the liquid surface of the electrolyte 5 and a peripheral side facing away from the liquid surface of the electrolyte 5; the lithium metal deposits 3 are arranged along a first direction; the peripheral side of the odd-numbered lithium metal deposits 3 contacts the first surface of the negative electrode 1, and the peripheral side of the even-numbered lithium metal deposits 3 contacts the second surface of the negative electrode 1; the first direction is parallel to the liquid surface of the electrolyte 5 and perpendicular to the rotation axis 31 of the lithium metal deposits 3. The first direction is the X direction, and the liquid surface of the electrolyte 5 is located in the Z direction of the lithium metal deposits 3.

[0053] In this embodiment, the upper edge of the odd-numbered lithium metal deposit 3 contacts the first surface of the negative electrode 1, and the lower edge of the even-numbered lithium metal deposit 3 contacts the second surface of the negative electrode 1, thereby achieving bi-sided lithium replacement of the negative electrode 1, which is beneficial to improving the uniformity of lithium replenishment of the negative electrode 1.

[0054] In some embodiments, the number of lithium metal deposits 3 is several, and the outer diameter of each lithium metal deposit 3 is D, where D is a positive value; the distance between the rotation axes 31 of adjacent lithium metal deposits 3 is L, where L is greater than D.

[0055] In some specific embodiments, L equals D+h, where h is the thickness of the negative electrode 1; the rotation axis 31 of each of the lithium metal deposits 3 in this embodiment is located on the same horizontal plane, the negative electrode 1 is sandwiched between adjacent lithium metal deposits 3, and the negative electrode 1 appears as a continuous wave shape from a horizontal perspective, which can save the space occupied by the pre-lithiation cavity 8 and is beneficial to shortening the production line.

[0056] In other specific embodiments, L is greater than D+h; in this embodiment, the rotation axis 31 of the odd-numbered lithium metal deposits 3 is located on the first horizontal plane, and the rotation axis 31 of the even-numbered lithium metal deposits 3 is located on the second horizontal plane, which extends the spacing of the negative electrode 1 bending along the outer peripheral surface of the lithium metal deposit 3. The negative electrode 1 has a tooth shape composed of alternating arcs and line segments when viewed from a horizontal perspective, which helps to reduce the damage to the negative electrode 1 caused by bending. Both the first and second horizontal planes are parallel to the liquid surface of the electrolyte 5.

[0057] In some embodiments, the lithium metal deposits 3 are arranged in two rows in the Z direction, with the first row consisting of odd-numbered lithium metal deposits and the second row consisting of even-numbered lithium metal deposits. The rotation axis 31 of the odd-numbered lithium metal deposits and the rotation axis 31 of the even-numbered lithium metal deposits are spaced L1 apart in the X direction. This design ensures that the two opposing surfaces of the negative electrode can contact lithium metal deposits of equal area, which is beneficial to improving the consistency and stability of the pre-lithiation effect.

[0058] In some embodiments, the axis of the support roller 4 is parallel to the rotation axis 31 of the lithium metal deposit 3; the number of support rollers 4 is at least 2, wherein 2 of the support rollers 4 are located on both sides of the lithium metal deposit 3.

[0059] In this embodiment, there are at least two support guide rollers 4, providing sufficient support points to maintain stable transmission of the negative electrode sheet 1. This reduces the risk of production interruption due to failure or wear of a single support guide roller 4, and enhances the reliability and durability of the entire system. The parallel arrangement of the support guide rollers 4 ensures that the negative electrode sheet 1 maintains constant tension throughout the pre-lithiation process, avoiding the problem of loosening or overstretching of the negative electrode sheet 1 due to uneven tension, and improving the stability of the pre-lithiation process.

[0060] In some examples, the first support guide roller 4 is located at the beginning of the transport direction of the eight lithium metal deposits 3, and the second support guide roller 4 is located at the end of the transport direction of the eight lithium metal deposits 3. The transport direction is perpendicular to the rotation axis 31 of the lithium metal deposits 3 and parallel to the surface of the electrolyte 5. The transport direction is along the X direction.

[0061] In some embodiments, the distance from the axis of the support guide roller 4 to the rotation axis 31 of the nearest lithium metal deposit 3 is L.

[0062] In this embodiment, the distance between the support roller 4 and the lithium metal deposit 3 is the same, ensuring that the negative electrode 1 obtains consistent electrochemical reaction conditions when passing through each lithium metal deposit 3, thereby improving the uniformity and consistency of lithium-ion intercalation. This not only improves the initial coulombic efficiency of the battery but also enhances its overall electrochemical performance.

[0063] This utility model also provides a pre-lithiation device, including the pre-lithiation module 9 as described in any of the above embodiments, and further including: a cleaning module 91 near the first outlet end 81 of the pre-lithiation chamber 8; the negative electrode 1 is removed from the pre-lithiation module 9 from the first outlet end 81. Figure 2 and Figure 3 As shown, the cleaning module 91 includes a cleaning chamber 83, which is used to contain an organic solvent 51 for cleaning the residual electrolyte 5 on the negative electrode 1.

[0064] Specifically, the cleaning module 91 further includes a plurality of cleaning rollers 41, which are immersed in the organic solvent 51; the negative electrode 1 passes through the cleaning chamber 83 around the plurality of cleaning rollers 41.

[0065] In other specific embodiments, the pre-lithiation chamber 8 is further provided with a first inlet end 82; the first inlet end 82 and the first outlet end 81 are located at opposite ends of the pre-lithiation chamber 8; the negative electrode 1 is moved into the pre-lithiation module 9 from the first inlet end 82.

[0066] In some examples, the organic solvent 51 includes at least one of propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,3-dioxolane, and ethylene glycol dimethyl ether.

[0067] In other examples, the organic solvent 51 is the same as the solvent in the electrolyte 5.

[0068] like Figure 3 As shown, in some embodiments, the pre-lithiation device further includes a baking module 92 near a second outlet end 84 of the cleaning chamber 83; the negative electrode 1 is removed from the cleaning chamber 83 from the second outlet end 84; the baking module 92 includes a heating section 7 directly opposite the negative electrode 1, the heating section 7 being used to heat the negative electrode 1 to evaporate the residual organic solvent 51 on the negative electrode 1. In some examples, the cleaning module 91 is located between the pre-lithiation module 9 and the baking module 92.

[0069] Specifically, the heating part 7 adopts at least one of electric heating, microwave heating or infrared heating.

[0070] In some examples, the baking temperature of each region of the negative electrode 1 by the baking module 92 is 50~150℃, and the baking time is 1min~1h.

[0071] In some embodiments, the baking module 92 further includes an exhaust section 6, which is used to accelerate the removal of the evaporated organic solvent 51 from the negative electrode 1.

[0072] In some embodiments, the baking module 92 further includes a drying roller 42, the periphery of which is tangent to the surface of the negative electrode 1; the drying roller 42 is used to carry the negative electrode 1 and drive the negative electrode 1 through the heating section 7.

[0073] like Figure 3 As shown, the two heating elements 7 are symmetrically distributed on the top and bottom sides of the drying roller 42. The exhaust element 6 is located on the top side of the drying roller 42. In some examples, the heating element 7 is a hot air blower with its air outlet facing the negative electrode 1, and the exhaust element 6 is a cold air blower with its air outlet facing away from the negative electrode 1.

[0074] In other embodiments, the baking module 92 further includes a gas recovery device for recovering evaporated organic solvent 51.

[0075] In some embodiments, the pre-lithiation device further includes a feeding guide roller, a discharging guide roller, and at least one marking section; the feeding guide roller and the discharging guide roller are located on opposite sides of the pre-lithiation chamber 8; the feeding guide roller is loaded with a negative electrode sheet 1 that has not passed through the pre-lithiation chamber 8; the discharging guide roller is loaded with a negative electrode sheet 1 that has passed through the pre-lithiation chamber 8; the negative electrode sheet 1 loaded on the feeding guide roller is pulled by the discharging guide roller and passes through the pre-lithiation chamber 8; the marking section is electrically connected to the discharging guide roller; when the discharging guide roller stops rotating, a portion of the negative electrode sheet 1 is marked by the marking section; the marked portion is removed when the negative electrode sheet is cut.

[0076] Specifically, the marking section is a marking machine used to apply marking tape to the stationary negative electrode sheet 1 when the feeding guide roller stops rotating. When the negative electrode sheet 1 is cut, the area where the marking tape is applied and its adjacent areas are removed. The adjacent areas include the area where the stationary negative electrode sheet 1 is in contact with the lithium metal deposit 3.

[0077] In other specific embodiments, the number of marking machines is two, and the two marking tapes and the area between them are discarded. The area between them includes the region where the stationary negative electrode 1 contacts the lithium metal deposit 3.

[0078] In some other specific embodiments, the feeding guide roller is located on the side of the baking module 92 away from the pre-lithiation module 9.

[0079] This utility model also provides Embodiments 1-4 and Comparative Examples 1-3.

[0080] Example 1

[0081] 1) Preparation of pre-lithiated anode sheets

[0082] Artificial graphite, a conductive agent, and a negative electrode binder were mixed in a mass ratio of 95:2:3, and then dispersed in deionized water to obtain a negative electrode slurry. The negative electrode binder consisted of sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in a mass ratio of 1.5:1.5. The slurry was coated on both sides of a copper foil and dried to obtain a negative electrode sheet. The bulk density of the negative electrode sheet at this point was measured to be 1.12 g / cm³. 3 .

[0083] The negative electrode sheet is introduced into the pre-lithiation chamber, where it is first immersed in an electrolyte. The electrolyte solvent consists of 30% ethylene carbonate and 70% methyl ethyl carbonate, with a lithium hexafluorophosphate concentration of 1.0 M. Electrolyte additives include fluoroethylene carbonate (FEC) and vinylene carbonate (VC). The FEC comprises 10% FEC and the VC comprises 1% VC. The negative electrode sheet is then passed around an air-expanded shaft containing lithium metal to bring it into contact with the lithium metal for pre-lithiation, maintaining a lithium potential of 0.2V. The pre-lithiated negative electrode sheet is then introduced into a cleaning chamber to remove residual electrolyte. Finally, the cleaned pre-lithiated negative electrode sheet is introduced into a baking area and heated to 100°C for 30 minutes using electric heating. The obtained pre-lithiated anode sheet is rolled for later use.

[0084] 2) Preparation of positive electrode sheet

[0085] Lithium iron phosphate (LFP), conductive carbon black, and polyvinylidene fluoride (PVDF) binder were mixed uniformly at a mass ratio of 96:2:2. The mixture was then dispersed in N-methyl-2-pyrrolidone (NMP) solvent to obtain a positive electrode slurry. This slurry was uniformly coated on both sides of an aluminum foil, and after drying and calendering, a positive electrode sheet was obtained.

[0086] 3) Preparation of electrolyte

[0087] Ethylene carbonate and diethyl carbonate were mixed in a 1:1 mass ratio, and then lithium hexafluorophosphate was added until the molar concentration was 1.0 mol / L.

[0088] 4) Preparation of lithium-ion batteries

[0089] The pre-lithiated negative electrode, positive electrode, electrolyte, and polyethylene porous separator prepared above are assembled into a soft-pack battery.

[0090] Example 2

[0091] This embodiment is basically the same as Embodiment 1, except that the lithium potential of the pre-lithiated negative electrode is controlled differently, specifically, the lithium potential of the pre-lithiated negative electrode is controlled to be 0.1V.

[0092] Example 3

[0093] This embodiment is basically the same as Embodiment 1, except that the lithium potential of the pre-lithiated negative electrode is controlled differently, specifically, the lithium potential of the pre-lithiated negative electrode is controlled to be 0.6V.

[0094] Example 4

[0095] This embodiment is basically the same as Embodiment 1, except that the density of the negative electrode sheet before pre-lithiation is controlled to be 1.4 g / cm³. 3 .

[0096] Comparative Example 1

[0097] This comparative example is basically the same as Example 1, except that the lithium potential of the pre-lithiated negative electrode is controlled differently, specifically, the lithium potential of the pre-lithiated negative electrode is controlled to be 0.05V.

[0098] Comparative Example 2

[0099] This comparative example is basically the same as Example 1, except that the lithium potential of the pre-lithiated negative electrode is controlled differently, specifically, the lithium potential of the pre-lithiated negative electrode is controlled to be 0.8V.

[0100] Comparative Example 3

[0101] This embodiment is basically the same as Embodiment 1, except that the density of the negative electrode sheet before pre-lithiation is controlled to be 1.55 g / cm³. 3 .

[0102] The lithium-ion batteries prepared in each embodiment and comparative example were subjected to performance testing according to the following methods:

[0103] Note: The current involved in the following test methods is expressed as xC, where x is a number and C represents the nominal capacity of the battery. For example, the charging current of a battery with a nominal capacity of 1Ah is 0.5C, which means 0.5×1=0.5A, and 6C means 6×1=6A.

[0104] First charge / discharge efficiency

[0105] Formation steps: 0.05C charging with constant current for 60 min; 0.1C charging with constant current for 60 min; 0.2C charging with constant current for 120 min;

[0106] Capacity testing steps: Charge at 0.33C constant current and constant voltage to 3.8V, cut off at 0.05C; Discharge at 0.33C to 2.0V;

[0107] First charge / discharge efficiency = 0.33C discharge capacity / (0.05C charging capacity + 0.1C charging capacity + 0.2C charging capacity + 0.33C constant current constant voltage charging capacity) × 100%.

[0108] 25℃ 1C cycle test

[0109] ① Place the soft-pack battery in a 25℃ environment for 3 hours;

[0110] ② Charge at 1C constant current and constant voltage until 3.65V, then cut off at 0.05C; let stand for 30 minutes;

[0111] ③ Discharge at a constant current of 1C to 2.5V; let stand for 30 minutes;

[0112] Repeat steps ② to ③;

[0113] This process is repeated, recording the discharge capacity of the first cycle and the discharge capacity of the last cycle. The capacity retention rate during the cycle is calculated using the following formula:

[0114] Battery capacity retention rate (%) = (last discharge capacity / first discharge capacity) × 100%.

[0115] The performance test results of each embodiment and comparative example are shown in Table 1 and Table 2.

[0116] Table 1. Experimental comparison of lithium potential with different pre-lithiationd anodes

[0117]

[0118] As can be seen from the test results of Examples 1-3 and Comparative Examples 1-2 in Table 1, as the lithium potential of the pre-lithiated negative electrode decreases, the higher the degree of pre-lithiation, the higher the initial charge-discharge efficiency of the battery. The pre-lithiated negative electrode of this invention, when the lithium potential of the pre-lithiated negative electrode is controlled at 0.1~0.6V, produces a lithium-ion battery with high initial charge-discharge efficiency and good cycle performance. As can be seen from the test results of Comparative Examples 1-2, when the lithium potential of the pre-lithiated negative electrode is less than 0.1V, the initial charge-discharge efficiency of the lithium-ion battery is high, but the cycle performance deteriorates. This is because too high a degree of pre-lithiation leads to an insufficient negative / positive capacity ratio (N / P), ultimately resulting in deterioration of the battery's lithium plating performance; when the lithium potential of the pre-lithiated negative electrode is greater than 0.6V, the initial charge-discharge efficiency of the battery is low. Figure 4 The differential capacity voltage curves (dQ / dV) of Examples 1-4 and Comparative Examples 1-3 show that the lower the lithium potential of the pre-lithiated anode, the lower the film formation reaction peak during the formation process, indicating that the pre-lithiated anode has already formed a stable SEI film in the pre-lithiation stage.

[0119] Table 2. Experimental comparison of anode sheet bulk density before different pre-lithiation

[0120]

[0121] As can be seen from the test results of Examples 1 and 4 and Comparative Example 3 in Table 2, the pre-lithiated negative electrode of this invention, when the bulk density of the negative electrode before pre-lithiation is controlled to be less than 1.45 g / cm³, achieves the desired effect. 3 When the lithium-ion battery is prepared, it exhibits high initial charge-discharge efficiency and good cycle performance. As can be seen from the test results of Comparative Example 3, when the bulk density of the negative electrode sheet before pre-lithiation is controlled to be greater than 1.45 g / cm³, the battery achieves this. 3 At this stage, the initial charge-discharge efficiency and cycle performance of the prepared lithium-ion battery deteriorate. From Figure 4 As can be seen from the dQ / dV curves of Examples 1, 4 and Comparative Example 3, the smaller the density of the negative electrode before pre-lithiation, the lower the film formation reaction peak during the formation process, indicating that the smaller the density of the negative electrode sheet, the more uniform the pre-lithiation of the electrode sheet.

[0122] like Figure 5 As shown, the capacity retention rates of Examples 1-4 are higher than those of Comparative Examples 1-3, illustrating the importance of precisely controlling the pre-lithiation potential and rationally adjusting the bulk density of the anode sheet during the preparation of the pre-lithiation anode. These optimization measures work together to significantly improve the cycle stability and lifespan of the battery.

[0123] In this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0124] The above description of the embodiments is intended to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope and spirit of the present invention are within the scope of the present invention.

Claims

1. A pre-lithiation module, applied to a pre-lithiation device for a negative electrode sheet, characterized in that, include: Pre-lithiation chamber, support guide roller, lithium metal deposit, and rotating shaft; The lithium metal deposit, the negative electrode, and the electrolyte are located in the pre-lithiation chamber; A portion of the negative electrode and the lithium metal deposit are immersed in the electrolyte; The rotating shaft is detachably connected to the lithium metal deposit, and the rotating shaft and the lithium metal deposit have a common axis of rotation; The peripheral surface of the support guide roller and the outer peripheral surface of the lithium metal deposit are both in contact with the surface of the tensioned negative electrode sheet. There is a potential difference between the lithium metal deposit immersed in the electrolyte and the negative electrode, so that lithium ions in the lithium metal deposit are transferred to the negative electrode.

2. The pre-lithiation module according to claim 1, characterized in that, The bulk density of the negative electrode is less than 1.45 g / cm³. 3 .

3. The pre-lithiation module according to claim 1, characterized in that, The thickness of the lithium metal deposit is greater than 50 μm.

4. The pre-lithiation module according to claim 1, characterized in that, The lithium metal deposit is cylindrical; the outer peripheral surface of the lithium metal deposit rolls and rubs against the negative electrode sheet; the outer peripheral surface is parallel to the axis of rotation.

5. The pre-lithiation module according to claim 1, characterized in that, The number of rotating shafts and lithium metal deposits is several, and each rotating shaft and lithium metal deposit is detachably connected in a one-to-one correspondence; the number of lithium metal deposits is a positive even number; the rotation axes of each lithium metal deposit are parallel to each other.

6. The pre-lithiation module according to claim 5, characterized in that, The lithium metal deposit has a peripheral side facing the electrolyte surface and a peripheral side facing away from the electrolyte surface. Each of the lithium metal deposits is arranged along a first direction; The odd-numbered lithium metal deposits are in contact with the first surface of the negative electrode on their upper and lower sides, and the even-numbered lithium metal deposits are in contact with the second surface of the negative electrode on their lower and lower sides; the first surface and the second surface are opposite to each other. The first direction is parallel to the surface of the electrolyte and perpendicular to the axis of rotation of the lithium metal deposit.

7. The pre-lithiation module according to claim 1 or 6, characterized in that, The number of lithium metal deposits is several, and the outer diameter of each lithium metal deposit is D, where D is a positive value; the distance between the rotation axes of adjacent lithium metal deposits is L, where L is greater than D.

8. The pre-lithiation module according to claim 7, characterized in that, The axis of the support guide roller is parallel to the axis of rotation of the lithium metal deposit; The number of the support guide rollers is at least 2, with 2 of the support guide rollers located on both sides of the lithium metal deposit.

9. The pre-lithiation module according to claim 7, characterized in that, The distance from the axis of the support guide roller to the axis of rotation of the nearest lithium metal deposit is L.

10. A pre-lithiation device, comprising the pre-lithiation module according to any one of claims 1 to 9, characterized in that, Also includes: A cleaning module near the first outlet end of the pre-lithiation chamber; the negative electrode sheet is removed from the pre-lithiation module from the first outlet end; The cleaning module includes a cleaning chamber containing an organic solvent, which is used to clean the residual electrolyte on the negative electrode sheet. The cleaning module further includes several cleaning rollers, which are immersed in the organic solvent; the negative electrode sheet passes through the cleaning chamber around the several cleaning rollers.

11. The pre-lithiation device according to claim 10, characterized in that, It also includes a baking module near the second outlet end of the cleaning chamber; the negative electrode sheet is removed from the cleaning chamber from the second outlet end; The baking module includes a heating section facing the negative electrode sheet, the heating section being used to heat the negative electrode sheet to evaporate the residual organic solvent on the negative electrode sheet; The baking module also includes a drying roller, the periphery of which is tangent to the surface of the negative electrode sheet.

12. The pre-lithiation device according to claim 10, characterized in that, It also includes a feeding guide roller, a discharging guide roller, and at least one marking section; The feeding guide roller and the unloading guide roller are located on opposite sides of the pre-lithiation chamber; The feeding guide roller is loaded with negative electrode sheets that have not passed through the pre-lithiation chamber; the unloading guide roller is loaded with negative electrode sheets that have passed through the pre-lithiation chamber. The negative electrode sheet loaded on the feeding guide roller is pulled by the unloading guide roller and passes through the pre-lithiation chamber; the marking part is electrically connected to the unloading guide roller; When the feeding guide roller stops rotating, a portion of the negative electrode sheet is marked by the marking part, and the marked portion is removed when the negative electrode sheet is cut.

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