Pre-lithiation device, pre-lithiation method, pre-lithiation negative plate and lithium ion battery

Abstract

The invention provides a pre-lithiation device, a pre-lithiation method, a pre-lithiation negative plate and a lithium ion battery, the pre-lithiation device comprises a pre-lithiation unit, the pre-lithiation unit comprises a tubular lithium ion solid electrolyte, the negative plate to be pre-lithiated is wound on the surface of the outer wall of the tubular lithium ion solid electrolyte, and the negative plate to be pre-lithiated is wound on the surface of the outer wall of the tubular lithium ion solid electrolyte. A lithium source material is accommodated in a tube of the tubular lithium ion solid electrolyte; the pre-lithiation device further comprises an external heating unit; the negative plate to be pre-lithiated comprises a current collector, a negative active material layer on the surface of at least one side of the current collector and a bonding layer, the negative active material layer comprises an oily binder, and the bonding layer comprises an aqueous binder. According to the pre-lithiation device, simple, convenient and accurate pre-lithiation is carried out by adopting the tubular lithium ion solid electrolyte to separate the lithium source material and the negative plate to be pre-lithiated, and meanwhile, the specific pre-lithiation negative plate is matched with the pre-lithiation device, so that the pre-lithiation effect of the negative plate is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of pre-lithiation, and relates to a pre-lithiation device, a pre-lithiation method, a pre-lithiation negative electrode sheet and a lithium ion battery. Background Art

[0002] With the rapid development of new energy vehicles and energy storage markets, the demand for lithium-ion batteries has shown explosive growth. During the first charging process of lithium-ion batteries, the organic electrolyte will be reduced and decomposed on the surface of the electrode material to form a solid electrolyte interface layer, which will cause a large amount of lithium loss, and this loss is irreversible. In order to ensure the capacity of the battery, it is necessary to replenish the lost lithium through pre-lithiation to improve the battery's initial coulombic efficiency and cycle stability.

[0003] Several pre-lithiation methods proposed in the prior art are as follows: (1) Using stable lithium metal powder as a pre-lithiation additive, which reacts with the negative electrode active material after electrolyte penetration, this method has been proven to be a simple and direct pre-lithiation method suitable for large-scale production. However, this method has the disadvantages of high cost in the production and dispersion of stable lithium metal powder, potential safety hazards of lithium powder, and the need to use toxic and hazardous solvents such as toluene on a large scale to disperse lithium powder.

[0004] (2) Adding a piece of lithium metal foil to the negative electrode is another common method for pre-lithiation of the negative electrode. In commercial lithium batteries, the loss of active lithium is less than 1 mAh cm -2 , indicating that precise lithium replenishment requires extremely thin lithium metal foil (thickness < 5 μm). However, self-supporting lithium metal foil with a thickness below 20 μm is beyond the scope of traditional extrusion technology due to its mechanical brittleness, so this method is difficult to achieve.

[0005] (3) Pre-lithiation of the negative electrode by electrochemical methods such as electroplating charge and discharge or sacrificial negative electrode short circuiting. These methods can precisely adjust the degree of lithiation of the negative electrode. However, this method requires a temporary half-cell or a complex reassembly process, and the negative electrode must be cleaned and reassembled after being immersed in the electrolyte of the lithium battery.

[0006] (4) Chemical pre-lithiation by immersing the anode in a lithium-containing solution (such as lithium biphenyl / tetrahydrofuran, lithium naphthalene / methoxymethane) is also a promising approach. However, typical pre-lithiation solutions cannot react with graphite anodes due to their higher redox potential than graphite.

[0007] In addition, both electrochemical and chemical pre-lithiation methods are difficult to link with the roll-to-roll process battery assembly currently used. Although some attempts have been made in the prior art to combine pre-lithiation with roll-to-roll processing, these methods are limited due to their complexity, low feasibility or lack of universality.

[0008] Based on the above research, it is necessary to provide a pre-lithiation device, which can not only combine pre-lithiation with the roll-to-roll process, but also can accurately pre-lithiate, reduce the pre-lithiation cost, shorten the pre-lithiation process, and improve the pre-lithiation efficiency. Summary of the invention

[0009] The object of the present invention is to provide a pre-lithiation device, a pre-lithiation method, a pre-lithiation negative electrode sheet and a lithium ion battery. The pre-lithiation device adopts a tubular lithium ion solid electrolyte to separate the lithium source material and the negative electrode sheet to be pre-lithiation, so that it can not only be connected with a roll-to-roll process battery assembly, but also can utilize the highly selective permeability of the lithium ion solid electrolyte to lithium ions to perform simple and accurate pre-lithiation. At the same time, a specific pre-lithiation negative electrode sheet is used to match the pre-lithiation device, thereby avoiding the problem that the negative electrode sheet is not compatible with the pre-lithiation device due to poor heat resistance and poor flexibility, thereby ensuring the pre-lithiation effect of the negative electrode sheet.

[0010] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a pre-lithiation device, the pre-lithiation device comprising a pre-lithiation unit, the pre-lithiation unit comprising a tubular lithium ion solid electrolyte, a negative electrode sheet to be pre-lithiated is wound on the outer wall surface of the tubular lithium ion solid electrolyte, and a lithium source material is contained in the tube of the tubular lithium ion solid electrolyte, wherein the negative electrode sheet to be pre-lithiated serves as a cathode, and the lithium source material serves as an anode, which are connected to a power supply device accordingly;

[0012] The pre-lithiation device further comprises an external heating unit for heating the lithium source material to make the lithium source material liquid;

[0013] The pre-lithiation negative electrode sheet comprises a current collector, a negative electrode active material layer on at least one surface of the current collector, and a bonding layer on a surface of the negative electrode active material layer away from the current collector. The negative electrode active material layer comprises an oily bonding agent, and the bonding layer comprises an aqueous bonding agent.

[0014] Preferably, the thickness ratio of the negative electrode active material layer to the bonding layer is 1:(0.8-1.25).

[0015] Preferably, the lithium source material includes a molten salt lithium source and / or an alloy lithium source.

[0016] Preferably, the pre-lithiation device further comprises a conveying unit for conveying the negative electrode sheet to be pre-lithiated to the pre-lithiation unit.

[0017] In a second aspect, the present invention provides a pre-lithiation method, wherein the pre-lithiation method uses the pre-lithiation device as described in the first aspect to perform pre-lithiation, and the pre-lithiation method comprises the following steps:

[0018] S1: placing a lithium source material in the tube of the tubular lithium ion solid electrolyte, and then preheating the lithium source material using an external heating unit to make the lithium source material liquid;

[0019] S2: Winding the negative electrode sheet to be pre-lithiated on the outer wall surface of the tubular lithium-ion solid electrolyte, using the negative electrode sheet to be pre-lithiated as the cathode and the lithium source material as the anode, and after electrically connecting them to a power supply device, starting the power supply device for pre-lithiation.

[0020] Preferably, the method for preparing the negative electrode sheet to be pre-lithiated in step S2 comprises the following steps:

[0021] S21: coating the negative electrode active material layer slurry on at least one side of the current collector surface, and obtaining a negative electrode active material layer on at least one side of the current collector surface after drying, thereby obtaining an intermediate electrode sheet;

[0022] S22: coating the adhesive layer slurry on the surface of the negative electrode active material layer, and drying the adhesive layer slurry to obtain the negative electrode sheet to be pre-lithiated;

[0023] The negative electrode active material layer slurry includes an oily binder, and the binding layer slurry includes an aqueous binder.

[0024] Preferably, before performing step S22, the intermediate electrode is first left to stand in a humid environment.

[0025] Preferably, before performing step S22, the intermediate electrode is first placed in a humidity environment with a humidity of 55%-70% and a temperature of 15°C-30°C for 12h-24h.

[0026] Preferably, the negative electrode active material layer slurry in step S21 further includes a negative electrode active material, a conductive agent and an oily solvent.

[0027] Preferably, the bonding layer slurry in step S22 also includes an aqueous solvent.

[0028] Preferably, the mass ratio of the negative electrode active material, the conductive agent, the oily binder and the oily solvent in the negative electrode active material layer slurry is (20-50):(1-5):(5-10):(30-100).

[0029] Preferably, the mass ratio of the aqueous binder to the aqueous solvent in the bonding layer slurry is 1:(6-12).

[0030] Preferably, in step S1, an external heating unit is used for preheating to raise the temperature of the pre-lithiation unit to 150°C-350°C.

[0031] Preferably, in step S2, the negative electrode sheet to be pre-lithiated is wound on the outer wall surface of the tubular lithium-ion solid electrolyte by a conveying unit.

[0032] In a third aspect, the present invention provides a pre-lithiation negative electrode sheet, wherein the pre-lithiation negative electrode sheet is obtained by pre-lithiation using the pre-lithiation method described in the second aspect.

[0033] In a fourth aspect, the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the pre-lithiation negative electrode sheet as described in the third aspect.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention allows lithium ions of a lithium source material to enter a negative electrode sheet to be pre-lithiated through a tubular lithium ion solid electrolyte to achieve pre-lithiation of the negative electrode sheet. This not only avoids the influence of the purity of the lithium source material itself on the pre-lithiation quality of the negative electrode sheet, but also has higher safety and a simplified process flow compared to the method of adding lithium powder or lithium foil to the negative electrode. The pre-lithiation device provided by the present invention can accurately control the amount of metallic lithium pre-lithiated by controlling the current and time parameters, thereby achieving a more uniform pre-lithiation effect and significantly improving the pre-lithiation efficiency, and is well matched with the traditional roll-to-roll battery manufacturing process.

[0036] (2) The present invention adopts a specific negative electrode sheet to be pre-lithiated to match the pre-lithiation device, thereby improving the heat resistance and flexibility of the negative electrode sheet to be pre-lithiated, making it difficult for the active material to fall off during the high-temperature pre-lithiation process, and making it more closely attached to the surface of the solid electrolyte tube during pre-lithiation, thereby ensuring the effect of pre-lithiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a front view of the pre-lithiation device described in Example 1 of the present invention;

[0038] Figure 2 This is a cross-sectional view of the pre-lithiation device described in Example 1 of the present invention;

[0039] Among them, 1-negative electrode sheet to be pre-lithiated, 2-tubular lithium-ion solid electrolyte, 3-lithium source material, 4-transfer roller. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the implementation methods are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0041] In a first aspect, a pre-lithiation device is provided in a specific embodiment of the present invention, wherein the pre-lithiation device comprises a pre-lithiation unit, wherein the pre-lithiation unit comprises a tubular lithium ion solid electrolyte, wherein a negative electrode sheet to be pre-lithiated is wound on the outer wall surface of the tubular lithium ion solid electrolyte, and a lithium source material is contained in the tube of the tubular lithium ion solid electrolyte, wherein the negative electrode sheet to be pre-lithiated serves as a cathode, and the lithium source material serves as an anode, which are connected to a power supply device;

[0042] The pre-lithiation device further comprises an external heating unit for heating the lithium source material to make the lithium source material liquid;

[0043] The negative electrode sheet to be pre-lithiated comprises a current collector, a negative electrode active material layer on at least one side of the current collector, and a bonding layer on a side of the negative electrode active material layer away from the current collector, wherein the negative electrode active material layer comprises an oily binder, and the bonding layer comprises an aqueous binder;

[0044] The pre-lithiation device provided by the present invention uses a tubular lithium ion solid electrolyte to separate the lithium source material and the negative electrode sheet to be pre-lithiated, and the negative electrode sheet to be pre-lithiated serves as the cathode and the lithium source material serves as the anode. The highly selective permeability of the lithium ion solid electrolyte to lithium ions is utilized to allow lithium ions to pass through the solid electrolyte into the interior of the negative electrode sheet to be pre-lithiated, thereby realizing the pre-lithiation of the negative electrode sheet. On the one hand, direct contact between the lithium source material and the electrode sheet to be pre-lithiated is avoided, so that the purity of the anode lithium source material will not affect the quality of the electrode sheet pre-lithiation, and the step of washing the electrode sheet due to direct contact with the lithium source material is omitted. On the other hand, the present invention performs electrochemical pre-lithiation through power supply control, without adding lithium powder or lithium foil to the negative electrode, so that the safety is higher and the process is simpler, and the current and time of the power supply can be controlled to accurately control the pre-lithiation process, thereby realizing accurate and uniform pre-lithiation.

[0045] In addition, since the pre-lithiation device described in the present invention includes an external heating unit, the purpose is to convert the lithium source material into liquid for smooth pre-lithiation, and the negative electrode sheet to be pre-lithiated is wound on the surface of the tubular lithium ion solid electrolyte, therefore, in order to match the pre-lithiation device, the present invention adopts a specific pre-lithiation negative electrode sheet with high heat resistance and high flexibility, thereby avoiding the problem that when the pre-lithiation device described in the present invention is used for pre-lithiation, the negative electrode sheet to be pre-lithiated cannot fit the tubular lithium ion solid electrolyte, and the poor heat resistance causes the active material to fall off, thereby affecting the pre-lithiation effect.

[0046] Specifically, the present invention adopts an oily binder in the negative active material layer of the pre-lithiation negative electrode sheet, so that the oily binder and the current collector establish a strong bonding force, and powder loss is not easy to occur during the high-temperature pre-lithiation process. However, due to the limited flexibility of the oily binder, the bonding effect between the pre-lithiation negative electrode sheet and the tubular lithium ion solid electrolyte will be reduced, resulting in uneven and insufficient pre-lithiation. Therefore, the present invention arranges a bonding layer on the surface of the negative active material layer, and the bonding layer includes an aqueous binder to improve the flexibility of the pre-lithiation negative electrode sheet, so that the pre-lithiation negative electrode sheet can be bonded to the surface of the tubular lithium ion solid electrolyte, thereby ensuring the pre-lithiation effect.

[0047] When the current collector of the negative electrode sheet to be pre-lithiated of the present invention has the negative electrode active material layer and the bonding layer disposed on only one side, the side on which the negative electrode active material layer and the bonding layer are disposed is directly attached to the tubular lithium ion solid electrolyte.

[0048] In some embodiments, the thickness ratio of the negative electrode active material layer to the bonding layer is 1:(0.8-1.25), for example, it can be 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2 or 1:1.25, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] The thickness ratio of the negative electrode active material layer and the bonding layer of the present invention is within a specific range, which can further improve the heat resistance and flexibility of the pre-lithiation negative electrode sheet.

[0050] The tubular lithium ion solid electrolyte of the present invention can contain lithium source materials inside the structure, and is provided with an opening as a feeding port for loading the lithium source materials into the tubular lithium ion solid electrolyte.

[0051] In some embodiments, the tubular lithium-ion solid electrolyte comprises Li7La3Zr2O 12 , Li 6.4 La3Ta 0.6 Zr 1.4 O 12 、LiTi2(PO4)3、Li 14 Any one of Zn(GeO4)4, Li2S-P2S5, LiBH4, LiI, Li3PO4, Li2B4O7, lithium nitride phosphate, polymer-containing lithium ion solid electrolyte or β-Al2O3-doped lithium ion solid electrolyte, or a combination of at least two thereof.

[0052] The preparation method of the tubular lithium-ion solid electrolyte described in the present invention can be found in Chinese Patent 202211720049.5.

[0053] In some embodiments, the lithium source material includes a molten salt lithium source and / or an alloy lithium source; the molten salt lithium source includes a lithium salt and a combination of a lithium salt and other metal salts, wherein the lithium salt includes any one of LiF, LiCl, LiBr, LiI or LiNO3 or a combination of at least two, and the other metal salts include any one of KF, NaF, RbF, CsF, BaF2, KCl, NaCl, RbCl, CsCl, BaCl2, KBr, NaBr, RbBr, CsBr, BaBr2, KI, NaI, RbI, CsI, BaI2, KNO3 or NaNO3 or a combination of at least two; the alloy lithium source includes an alloy formed by lithium and metal such as Li-Zn, Li-Sn, Li-Bi, Li-Pb, Li-Cu or Li-Al.

[0054] The lithium source material used in the present invention is a lithium source material that can form a liquid state when heated, such as the above-mentioned molten salt lithium source and / or alloy lithium source. The "liquid state" mentioned in the present invention includes a full liquid state and a solid-liquid coexistence state (molten state), that is, the lithium source material contains a solid phase component when pre-lithiation is allowed.

[0055] In some embodiments, the mass ratio of the molten salt lithium source to the alloy lithium source is 1:(1-5), for example, it can be 1:1, 1:3 or 1:5, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] In some embodiments, the pre-lithiation device further includes a conveying unit for conveying the negative electrode sheet to be pre-lithiated to the pre-lithiation unit.

[0057] The conveying unit of the present invention comprises at least two conveying rollers, which are arranged on both sides of the tubular lithium-ion solid electrolyte and are used for receiving and placing the negative electrode sheet.

[0058] The negative electrode sheet to be pre-lithiated in the present invention serves as a cathode, and the lithium source material serves as an anode, which are connected to a power supply device. Specifically, conductive components are provided on the side of the negative electrode sheet to be pre-lithiated away from the lithium ion solid electrolyte, and inside the lithium source material, that is, a conductive structure is connected to the outside of the cathode, and a lead, a pole piece or a pole is inserted into the anode to realize electrical connection between the cathode and the power supply device.

[0059] In a second aspect, a specific embodiment of the present invention provides a pre-lithiation method, wherein the pre-lithiation method uses the pre-lithiation device as described in the first aspect to perform pre-lithiation, and the pre-lithiation method comprises the following steps:

[0060] S1: placing a lithium source material in the tube of the tubular lithium ion solid electrolyte, and then preheating the lithium source material using an external heating unit to make the lithium source material liquid;

[0061] S2: Winding the negative electrode sheet to be pre-lithiated on the outer wall surface of the tubular lithium-ion solid electrolyte, using the negative electrode sheet to be pre-lithiated as a cathode and the lithium source material as an anode, and electrically connecting them to a power supply device, and starting the power supply device for pre-lithiation;

[0062] In some embodiments, the method for preparing the negative electrode sheet to be pre-lithiated in step S2 comprises the following steps:

[0063] S21: coating the negative electrode active material layer slurry on at least one side of the current collector surface, and obtaining a negative electrode active material layer on at least one side of the current collector surface after drying, thereby obtaining an intermediate electrode sheet;

[0064] S22: coating the adhesive layer slurry on the surface of the negative electrode active material layer, and drying the adhesive layer slurry to obtain the negative electrode sheet to be pre-lithiated;

[0065] The negative electrode active material layer slurry includes an oily binder, and the binding layer slurry includes an aqueous binder.

[0066] In some embodiments, before performing step S22, the intermediate electrode is first left to stand in a humid environment.

[0067] After the negative electrode active material layer slurry is coated on the surface of the current collector and dried, the present invention is allowed to stand in a humid environment, thereby enhancing the bonding force between the negative electrode active material layer and the current collector. At the same time, a pore structure can be formed on the surface of the negative electrode active material layer, and the slurry portion of the bonding layer is embedded in the pore structure, further improving the flexibility of the negative electrode sheet and avoiding powder loss during high-temperature pre-lithiation.

[0068] Preferably, before performing step S22, the intermediate electrode is first placed in a humidity environment with a humidity of 55%-70%, for example, 55%, 60%, 65% or 70%, and a temperature of 15°C-30°C, for example, 15°C, 20°C, 25°C or 30°C, for 12h-24h, for example, 12h, 14h, 16h, 18h, 20h, 22h or 24h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0069] In some embodiments, the oily binder includes PVDF (polyvinylidene fluoride)

[0070] In some embodiments, the aqueous binder includes SBR (styrene butadiene rubber) and / or PAA (polyacrylic acid).

[0071] In some embodiments, the negative electrode active material layer slurry in step S21 further includes a negative electrode active material, a conductive agent and an oily solvent.

[0072] In some embodiments, the negative electrode active material includes any one of graphite material, silicon-carbon material or silicon-oxygen material, or a combination of at least two of them; the conductive agent includes any one of acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene or carbon nanofibers, or a combination of at least two of them; the oily solvent includes N-methylpyrrolidone.

[0073] In some embodiments, in the negative electrode active material layer slurry described in step S21, the mass ratio of the negative electrode active material, the conductive agent, the oily binder and the oily solvent is (20-50):(1-5):(5-10):(30-100), for example, it can be 30:3:7:50, 20:5:5:30 or 50:1:10:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0074] In some embodiments, the drying temperature in step S21 is 100°C-120°C, for example, 100°C, 110°C or 120°C, and the drying time is 20min-40min, for example, 20min, 30min or 40min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0075] In some embodiments, the thickness of the negative electrode active material layer slurry coating in step S21 is 0.18 mm-0.22 mm, for example, 0.18 mm, 0.19 mm, 0.20 mm, 0.21 mm or 0.22 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0076] In some embodiments, the bonding layer slurry in step S22 further includes an aqueous solvent; wherein the aqueous solvent includes water.

[0077] The negative electrode active material layer slurry of the present invention includes negative electrode active material, conductive agent, oily binder and oily solvent, wherein the oily binder matches the oily solvent; the binder layer slurry includes aqueous binder and aqueous solvent, wherein the aqueous binder matches the aqueous solvent.

[0078] In some embodiments, in the bonding layer slurry described in step S22, the mass ratio of the aqueous binder to the aqueous solvent is 1:(6-12), for example, it can be 1:6, 1:8, 1:10 or 1:12, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0079] In some embodiments, the thickness of the adhesive layer slurry coating in step S22 is 0.18 mm-0.22 mm, for example, it can be 0.18 mm, 0.19 mm, 0.20 mm, 0.21 mm or 0.22 mm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0080] In some embodiments, step S1 uses an external heating unit for preheating to raise the temperature of the pre-lithiation unit to 150°C-350°C, for example, 150°C, 200°C, 250°C, 300°C or 350°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0081] The purpose of preheating by the external heating unit of the present invention is to melt the molten salt lithium source and / or alloy lithium source by heat to form a liquid lithium source.

[0082] In some embodiments, in step S2, the negative electrode sheet to be pre-lithiated is wound on the outer wall surface of the tubular lithium-ion solid electrolyte by a conveying unit.

[0083] In a third aspect, a specific embodiment of the present invention provides a pre-lithiation negative electrode sheet, wherein the pre-lithiation negative electrode sheet is pre-lithiationed by the pre-lithiation method described in the second aspect.

[0084] In a fourth aspect, a specific embodiment of the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the pre-lithiation negative electrode sheet as described in the third aspect.

[0085] The technical solution of the present invention is further illustrated by specific embodiments below.

[0086] Example 1

[0087] This embodiment provides a pre-lithiation device, the front view of which is as follows: Figure 1 As shown, the cross-sectional view is Figure 2 As shown, it includes a pre-lithiation unit, an external heating unit and a conveying unit, wherein the conveying unit includes two conveying rollers 4, which are respectively arranged on both sides of the pre-lithiation unit for conveying the negative electrode sheet to be pre-lithiated; the pre-lithiation unit includes a tubular lithium ion solid electrolyte 2, the outer wall surface of the tubular lithium ion solid electrolyte 2 is wound with a negative electrode sheet to be pre-lithiated 1, and the tubular interior of the tubular lithium ion solid electrolyte 2 contains a lithium source material 3, wherein the negative electrode sheet to be pre-lithiated 1 serves as a cathode, and the lithium source material 3 serves as an anode, the outer side of the cathode is connected to a conductive structure, and a lead is inserted into the anode to realize electrical connection between the cathode and the power supply device;

[0088] The outer tube of the tubular lithium-ion solid electrolyte has a diameter of 2 cm and a length of 10 cm, and is made of LLZTO; the lithium source material is a LiBr-KBr-CsBr (mass fractions are 42.75%, 39.08% and 18.17% respectively) mixed molten salt and Li-Zn (Li is 60%, Zn is 40%) alloy combination system, and the mass ratio of the mixed molten salt to the alloy is 1:3;

[0089] The negative electrode sheet to be pre-lithiated comprises a copper foil, a negative electrode active material layer on one surface of the copper foil, and a bonding layer on the surface of the negative electrode active material layer away from the current collector, wherein the thickness ratio of the negative electrode active material layer to the bonding layer is 1:1, the negative electrode active material layer comprises a graphite material, SP and PVDF, and the bonding layer comprises SBR;

[0090] This embodiment further provides a pre-lithiation method, wherein the pre-lithiation method uses the pre-lithiation device of this embodiment to perform pre-lithiation, and the pre-lithiation method comprises the following steps:

[0091] S1: adding a lithium source material into the tubular lithium ion solid electrolyte through a feeding port, and then starting an external heating unit for preheating, so that the pre-lithiation unit is heated to 300° C., so that the lithium source material is in a liquid state;

[0092] S2: Start the conveying unit and the pre-lithiation unit. Driven by the conveying unit, the negative electrode sheet to be pre-lithiated is wound around the outer wall of the tubular lithium-ion solid electrolyte. At the same time, the cathode conductive structure and the anode lead are adjusted to ensure that the pre-lithiation unit is electrically connected. The negative electrode sheet to be pre-lithiated is electrolyzed under the Land test system. The pre-lithiation process is constant current electrolysis with a current of 100mA, a voltage of 0.3V, and a time of 12 minutes.

[0093] The method for preparing the negative electrode sheet to be pre-lithiated in step S2 comprises the following steps:

[0094] S21: Graphite material, SP, PVDF and N-methylpyrrolidone in a mass ratio of 35:3:6:80 are mixed to obtain a negative electrode active material layer slurry, and the negative electrode active material layer slurry is coated on one side of the copper foil with a coating thickness of 0.2 mm, and then dried at 110° C. for 30 min to obtain a negative electrode active material layer on one side of the current collector to obtain an intermediate electrode sheet;

[0095] S22: placing the intermediate electrode in step S21 in a humidity environment with a humidity of 60% and a temperature of 20° C. for 20 hours;

[0096] S23: After standing, SBR and water in a mass ratio of 1:8 are mixed to obtain a bonding layer slurry, and the bonding layer slurry is coated on the surface of the negative electrode active material layer with a coating thickness of 0.2 mm, and then dried at 80° C. for 5 hours to obtain the negative electrode sheet to be pre-lithiated.

[0097] Example 2

[0098] The present embodiment provides a pre-lithiation device, which includes a pre-lithiation unit, an external heating unit and a conveying unit, wherein the conveying unit includes two conveying rollers, which are respectively arranged on both sides of the pre-lithiation unit and are used to convey the negative electrode sheet to be pre-lithiated; the pre-lithiation unit includes a tubular lithium ion solid electrolyte, the outer wall surface of the tubular lithium ion solid electrolyte is wound with the negative electrode sheet to be pre-lithiated, and the tube of the tubular lithium ion solid electrolyte contains a lithium source material, wherein the negative electrode sheet to be pre-lithiated serves as a cathode, and the lithium source material serves as an anode, the outer side of the cathode is connected to a conductive structure, and a lead is inserted into the anode to realize electrical connection between the cathode and the power supply device;

[0099] The outer tube of the tubular lithium-ion solid electrolyte has a diameter of 2 cm and a length of 10 cm, and is made of LLZTO; the lithium source material is a mixed molten salt of LiBr-KBr-CsBr (mass fractions are 42.75%, 39.08% and 18.17% respectively);

[0100] The negative electrode sheet to be pre-lithiated comprises a copper foil, a negative electrode active material layer on one surface of the copper foil, and a bonding layer on the surface of the negative electrode active material layer away from the current collector, wherein the thickness ratio of the negative electrode active material layer to the bonding layer is 1:1.22, the negative electrode active material layer comprises a graphite material, SP and PVDF, and the bonding layer comprises SBR;

[0101] This embodiment further provides a pre-lithiation method, wherein the pre-lithiation method uses the pre-lithiation device of this embodiment to perform pre-lithiation, and the pre-lithiation method comprises the following steps:

[0102] S1: adding a lithium source material into the tube of the tubular lithium-ion solid electrolyte through a feeding port, and then starting an external heating unit for preheating, so that the pre-lithiation unit is heated to 250° C., so that the lithium source material is in a liquid state;

[0103] S2: Start the conveying unit and the pre-lithiation unit. Driven by the conveying unit, the negative electrode sheet to be pre-lithiated is wound on the outer wall of the tubular lithium-ion solid electrolyte. At the same time, the cathode conductive structure and the anode lead are adjusted to ensure that the pre-lithiation unit is electrically connected. The negative electrode sheet to be pre-lithiated is electrolyzed under the Land test system. The pre-lithiation process is constant current electrolysis with a current of 100 mA, a voltage of 0.3 V, and a time of 12 minutes.

[0104] The method for preparing the negative electrode sheet to be pre-lithiated in step S2 comprises the following steps:

[0105] S21: Graphite material, SP, PVDF and N-methylpyrrolidone in a mass ratio of 50:5:8:100 are mixed to obtain a negative electrode active material layer slurry, and the negative electrode active material layer slurry is coated on one side of the copper foil with a coating thickness of 0.18 mm, and then dried at 120° C. for 20 min to obtain a negative electrode active material layer on one side of the current collector to obtain an intermediate electrode sheet;

[0106] S22: placing the intermediate electrode in step S21 in a humidity environment with a humidity of 70% and a temperature of 15° C. for 12 hours;

[0107] S23: After standing, SBR and water in a mass ratio of 1:12 are mixed to obtain a bonding layer slurry, and the bonding layer slurry is coated on the surface of the negative electrode active material layer with a coating thickness of 0.22 mm. After drying at 80° C. for 5 hours, the negative electrode sheet to be pre-lithiated is obtained.

[0108] Example 3

[0109] The present embodiment provides a pre-lithiation device, which includes a pre-lithiation unit, an external heating unit and a conveying unit, wherein the conveying unit includes two conveying rollers, which are respectively arranged on both sides of the pre-lithiation unit and are used to convey the negative electrode sheet to be pre-lithiated; the pre-lithiation unit includes a tubular lithium ion solid electrolyte, the outer wall surface of the tubular lithium ion solid electrolyte is wound with the negative electrode sheet to be pre-lithiated, and the tube of the tubular lithium ion solid electrolyte contains a lithium source material, wherein the negative electrode sheet to be pre-lithiated serves as a cathode, and the lithium source material serves as an anode, the outer side of the cathode is connected to a conductive structure, and a lead is inserted into the anode to realize electrical connection between the cathode and the power supply device;

[0110] The outer tube of the tubular lithium-ion solid electrolyte has a diameter of 2 cm and a length of 10 cm, and is made of LLZTO; the lithium source material is LiCl-LiBr-KBr-CsBr (with mass fractions of 10.15%, 31.54%, 13.93% and 44.38% respectively);

[0111] The negative electrode sheet to be pre-lithiated comprises a copper foil, a negative electrode active material layer on one surface of the copper foil, and a bonding layer on the surface of the negative electrode active material layer away from the current collector, wherein the thickness ratio of the negative electrode active material layer to the bonding layer is 1:0.81, the negative electrode active material layer comprises a graphite material, SP and PVDF, and the bonding layer comprises SBR;

[0112] This embodiment further provides a pre-lithiation method, wherein the pre-lithiation method uses the pre-lithiation device of this embodiment to perform pre-lithiation, and the pre-lithiation method comprises the following steps:

[0113] S1: adding a lithium source material into the tube of the tubular lithium-ion solid electrolyte through a feeding port, and then starting an external heating unit for preheating, so that the pre-lithiation unit is heated to 250° C., so that the lithium source material is in a liquid state;

[0114] S2: Start the conveying unit and the pre-lithiation unit. Driven by the conveying unit, the negative electrode sheet to be pre-lithiated is wound on the outer wall of the tubular lithium-ion solid electrolyte. At the same time, the cathode conductive structure and the anode lead are adjusted to ensure that the pre-lithiation unit is electrically connected. The negative electrode sheet to be pre-lithiated is electrolyzed under the Land test system. The pre-lithiation process is constant current electrolysis with a current of 100 mA, a voltage of 0.3 V, and a time of 12 minutes.

[0115] The method for preparing the negative electrode sheet to be pre-lithiated in step S2 comprises the following steps:

[0116] S21: Graphite material, SP, PVDF and N-methylpyrrolidone in a mass ratio of 20:1:5:30 are mixed to obtain a negative electrode active material layer slurry, and the negative electrode active material layer slurry is coated on one side of the copper foil with a coating thickness of 0.22 mm, and then dried at 100° C. for 40 min to obtain a negative electrode active material layer on one side of the current collector to obtain an intermediate electrode sheet;

[0117] S22: placing the intermediate electrode in step S21 in a humidity environment with a humidity of 55% and a temperature of 30° C. for 24 hours;

[0118] S23: After standing, SBR and water in a mass ratio of 1:6 are mixed to obtain a bonding layer slurry, and the bonding layer slurry is then coated on the surface of the negative electrode active material layer with a coating thickness of 0.18 mm, and then dried at 80° C. for 5 hours to obtain the negative electrode sheet to be pre-lithiated.

[0119] Example 4

[0120] This embodiment provides a pre-lithiation device, which is the same as that of Embodiment 1 except that the thickness ratio of the negative electrode active material layer to the bonding layer is 1:0.5.

[0121] This embodiment further provides a pre-lithiation method, which is the same as that of Embodiment 1 except that the pre-lithiation device described in the embodiment is used for pre-lithiation and the thickness of the adhesive layer coating is 0.1 mm.

[0122] Example 5

[0123] This embodiment provides a pre-lithiation device, which is the same as that of Embodiment 1 except that the thickness ratio of the negative electrode active material layer to the bonding layer is 1:1.5.

[0124] This embodiment further provides a pre-lithiation method, which is the same as that of Embodiment 1 except that the pre-lithiation device described in the embodiment is used for pre-lithiation and the thickness of the adhesive layer coating is 0.3 mm.

[0125] Example 6

[0126] This embodiment provides a pre-lithiation device, which is the same as that of Embodiment 1 except that the negative electrode sheet to be pre-lithiated in the pre-lithiation device is changed.

[0127] This embodiment further provides a pre-lithiation method, which is the same as that of Embodiment 1 except that the pre-lithiation device described in the embodiment is used for pre-lithiation and step S22 is not performed during the preparation of the negative electrode sheet to be pre-lithiated.

[0128] Comparative Example 1

[0129] This comparative example provides a pre-lithiation device, in which the negative electrode sheet to be pre-lithiation in the pre-lithiation device is a commercially available negative electrode sheet (the commercially available negative electrode sheet manufacturer is CROOD, model number is SM0206), and the rest is the same as Example 1.

[0130] This comparative example also provides a pre-lithiation method, which is the same as Example 1 except that the pre-lithiation device of the comparative example is used for pre-lithiation and the negative electrode sheet to be pre-lithiated is not prepared.

[0131] Comparative Example 2

[0132] This comparative example provides a pre-lithiation device. In the pre-lithiation device, there is no bonding layer in the negative electrode sheet to be pre-lithiated, and the rest is the same as Example 1.

[0133] This comparative example also provides a pre-lithiation method, which is the same as Example 1 except that the pre-lithiation device of the comparative example is used for pre-lithiation and step S23 is omitted during the preparation of the negative electrode sheet to be pre-lithiated.

[0134] Comparative Example 3

[0135] This comparative example provides a pre-lithiation device, in which the negative electrode sheet to be pre-lithiated does not include a bonding layer, and the binder in the negative electrode active material layer is PVDF and SBR, and the rest is the same as Example 1.

[0136] This comparative example also provides a pre-lithiation method, which is the same as Example 1 except that the pre-lithiation device described in the comparative example is used for pre-lithiation, and when preparing the pre-lithiation negative electrode sheet, the SBR in step S23 is added to the negative electrode active material layer slurry prepared in step S21.

[0137] The pre-lithiation negative electrode sheet prepared by the pre-lithiation method described in the above embodiments and comparative examples was assembled into a battery with the electrode sheet with ternary material as the positive electrode, and the charge and discharge test was carried out using a blue electric system. The charging was constant current charging with a current of 20mA and a capacity cutoff of 2mAh. The discharging was constant current discharge with a discharge current of 20mA and a voltage cutoff of 2.75V.

[0138] The test results are shown in Table 1, wherein the deviation rate = |first theoretical discharge capacity - first actual discharge capacity| / first theoretical discharge capacity × 100%.

[0139] Table 1

[0140]

[0141] From Table 1 we can see that:

[0142] (1) It can be seen from Example 1 and Comparative Example 1 that the pre-lithiation device of the present invention needs to correspond to a specific negative electrode sheet. The binder in the conventional negative electrode sheets on the market is not resistant to high temperatures. During pre-lithiation, the active material will fall off. The negative electrode sheet obtained by pre-lithiation cannot be assembled into a battery for charge and discharge testing; It can be seen from Example 1 and Comparative Example 2 that the present invention uses an aqueous binder to prepare the bonding layer, which can ensure the flexibility of the negative electrode sheet, while the negative electrode sheet obtained in Comparative Example 2 has poor flexibility and poor adhesion with the tubular lithium ion solid electrolyte during pre-lithiation, resulting in a large difference between the pre-lithiation amount and the theoretical amount, which is reflected in the large difference between the first theoretical discharge capacity and the actual discharge capacity; It can be seen from Example 1 and Comparative Example 3 that the aqueous binder of the present invention is added when preparing the negative electrode active material layer, and the obtained negative electrode sheet has poor high temperature resistance. Part of the active material falls off during the pre-lithiation process, resulting in a decrease in the first discharge efficiency.

[0143] (2) It can be seen from Examples 1 and 4-5 that the thickness of the adhesive layer of the negative electrode sheet to be pre-lithiated in the present invention will affect the effect of pre-lithiation. If the adhesive layer is too thin, the negative electrode sheet will not be flexible enough, which will affect the bonding effect with the tubular lithium-ion solid electrolyte, resulting in insufficient and uneven pre-lithiation. However, if it is too much compared to the negative electrode active material layer, the surface layer of the pre-lithiated negative electrode sheet will fall off, which will also lead to insufficient pre-lithiation. It can be seen from Examples 1 and 6 that after the negative electrode active material layer is prepared, the present invention is still allowed to stand in a specific environment, which can improve the high temperature resistance of the negative electrode sheet to be pre-lithiated, thereby improving the performance of the negative electrode sheet.

[0144] In summary, the present invention provides a pre-lithiation device, a pre-lithiation method, a pre-lithiation negative electrode sheet and a lithium ion battery. The pre-lithiation device adopts a tubular lithium ion solid electrolyte to separate the lithium source material and the negative electrode sheet to be pre-lithiated, so that it can not only be connected with a roll-to-roll process battery assembly, but also can utilize the highly selective permeability of the lithium ion solid electrolyte to lithium ions to perform simple and accurate pre-lithiation. At the same time, a specific pre-lithiation negative electrode sheet is used to match the pre-lithiation device, thereby avoiding the problem that the negative electrode sheet is not compatible with the pre-lithiation device due to poor heat resistance and poor flexibility, thereby ensuring the pre-lithiation effect of the negative electrode sheet.

[0145] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A pre-lithiation device, characterized in that: The pre-lithiation device comprises a pre-lithiation unit, and the pre-lithiation unit comprises a tubular lithium ion solid electrolyte, and a negative electrode sheet to be pre-lithiated is wound on the outer wall surface of the tubular lithium ion solid electrolyte, and a lithium source material is contained in the tube of the tubular lithium ion solid electrolyte, wherein the negative electrode sheet to be pre-lithiated serves as a cathode, and the lithium source material serves as an anode, which are connected to a power supply device accordingly; The pre-lithiation device further comprises an external heating unit for heating the lithium source material to make the lithium source material liquid; The pre-lithiation negative electrode sheet comprises a current collector, a negative electrode active material layer on at least one surface of the current collector, and a bonding layer on a surface of the negative electrode active material layer away from the current collector. The negative electrode active material layer comprises an oily bonding agent, and the bonding layer comprises an aqueous bonding agent.

2. The pre-lithiation device according to claim 1, characterized in that: The thickness ratio of the negative electrode active material layer to the bonding layer is 1:(0.8-1.25).

3. The pre-lithiation device according to claim 1 or 2, characterized in that: The lithium source material includes a molten salt lithium source and / or an alloy lithium source; Preferably, the pre-lithiation device further comprises a conveying unit for conveying the negative electrode sheet to be pre-lithiated to the pre-lithiation unit.

4. A pre-lithiation method, characterized in that: The pre-lithiation method uses the pre-lithiation device according to any one of claims 1 to 3 to perform pre-lithiation, and the pre-lithiation method comprises the following steps: S1: placing a lithium source material in the tube of the tubular lithium ion solid electrolyte, and then preheating the lithium source material using an external heating unit to make the lithium source material liquid; S2: Winding the negative electrode sheet to be pre-lithiated on the outer wall surface of the tubular lithium-ion solid electrolyte, using the negative electrode sheet to be pre-lithiated as the cathode and the lithium source material as the anode, and after electrically connecting them to a power supply device, starting the power supply device for pre-lithiation.

5. The pre-lithiation method according to claim 4, characterized in that: The method for preparing the negative electrode sheet to be pre-lithiated in step S2 comprises the following steps: S21: coating the negative electrode active material layer slurry on at least one side of the current collector surface, and obtaining a negative electrode active material layer on at least one side of the current collector surface after drying, thereby obtaining an intermediate electrode sheet; S22: coating the adhesive layer slurry on the surface of the negative electrode active material layer, and drying the adhesive layer slurry to obtain the negative electrode sheet to be pre-lithiated; The negative electrode active material layer slurry includes an oily binder, and the binding layer slurry includes an aqueous binder.

6. The pre-lithiation method according to claim 5, characterized in that: Before performing step S22, the intermediate electrode is first placed in a humid environment; Preferably, before performing step S22, the intermediate electrode is first placed in a humidity environment with a humidity of 55%-70% and a temperature of 15°C-30°C for 12h-24h.

7. The pre-lithiation method according to claim 5 or 6, characterized in that: Step S21: the negative electrode active material layer slurry further includes a negative electrode active material, a conductive agent and an oily solvent; Preferably, the bonding layer slurry in step S22 further includes an aqueous solvent; Preferably, the mass ratio of the negative electrode active material, the conductive agent, the oily binder and the oily solvent in the negative electrode active material layer slurry in step S21 is (20-50):(1-5):(5-10):(30-100); Preferably, the mass ratio of the aqueous binder to the aqueous solvent in the bonding layer slurry in step S22 is 1:(6-12).

8. The pre-lithiation method according to any one of claims 4 to 6, characterized in that: In step S1, an external heating unit is used for preheating to raise the temperature of the pre-lithiation unit to 150° C.-350° C.; Preferably, in step S2, the negative electrode sheet to be pre-lithiated is wound on the outer wall surface of the tubular lithium-ion solid electrolyte by a conveying unit.

9. A pre-lithiation negative electrode sheet, characterized in that: The pre-lithiation negative electrode sheet is obtained by pre-lithiation using the pre-lithiation method according to any one of claims 4 to 8.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the pre-lithiation negative electrode sheet as claimed in claim 9.

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