Systems, methods, and products for prelithiating lithium-ion battery electrodes with molten lithium

Abstract

The present application provides systems, methods and products for pre-lithiating lithium-ion battery electrodes using molten lithium. The system is used to prepare a pre-lithiated battery anode, the system comprising: a coating device for coating molten lithium metal onto a surface of a current collector to form a lithium layer composed of pure lithium metal on the surface of the current collector, without an intervening conductive layer between the lithium layer and the current collector. The method for pre-lithiating lithium-ion battery electrodes using molten lithium comprises: coating the metal lithium: coating molten lithium metal onto a surface of a current collector; post-coating treatment: cooling the molten lithium on the surface of the current collector to form a lithium layer, and passivating the lithium layer; and transfer printing: transferring a negative active material to a surface of the lithium layer to form a pre-lithiated battery anode. The product provided by the present application is a pre-lithiated battery anode prepared by the aforementioned system or method. The product provided by the present application is a battery comprising a pre-lithiated battery anode prepared by the aforementioned system or method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and in particular relates to systems, methods, and products for prelithiating lithium-ion battery electrodes using molten lithium. BACKGROUND

[0002] With the continuous development of the battery industry, high-energy-density batteries are becoming increasingly important. Among various batteries, lithium-ion batteries have become a research focus due to their high energy density and environmental friendliness. However, in the first charge-discharge process of ordinary commercial lithium-ion batteries, a solid electrolyte interface is formed on the surface of the negative electrode material, consuming lithium from the positive electrode and causing a decrease in initial coulombic efficiency and energy density. This problem is not only present in mainstream commercial graphite negative electrodes, but is even more severe in silicon and silicon-carbon negative electrodes, which are considered to be the next generation of negative electrode materials. Prelithiation can improve the overall performance of lithium-ion batteries by making up for the excessive consumption of lithium in the reaction. Several prelithiation methods have been proposed, including:

[0003] Patent CN115050927A uses an external power source, with lithium metal as the anode and negative electrode sheet as the cathode, to prelithiate under electrolyte immersion conditions. This method is relatively complex and difficult to produce continuously, requiring an electrolyte spraying device, and subsequent negative electrode sheet cleaning and drying.

[0004] Patent CN114974939A uses a lithium metal sheet as a lithium source and combines the negative electrode sheet and the lithium metal layer through pressing. The preparation and transfer of a relatively thin lithium layer are difficult, and the existing lithium layer used for pressing is relatively thick. Controlling the pressing pressure alone cannot accurately control the amount of lithium supplementation, which may lead to excessive lithium supplementation and the growth of lithium dendrites in the battery, affecting the safety of the battery in use.

[0005] Patent CN115020653A deposits a lithium metal layer on the current collector and makes the lithium layer and the negative electrode active material directly contact by dissolving the polymer protective layer between them in the electrolyte. This method is relatively complex, requires the preparation of a polymer protective layer, and may contaminate the negative electrode if the reaction is incomplete. In addition, this method also requires subsequent negative electrode sheet cleaning and drying.

[0006] Patent CN115101710A supplements lithium on the current collector through electrodeposition, and the current collector after electrodeposition of lithium metal needs to be cleaned and dried, which is a relatively complex process.

[0007] The patent with publication number CN115249787A coats a conductive material on a current collector and solidifies, prelithiates the conductive layer using a prelithiation material, and then coats a negative active material slurry on the prelithiated conductive layer and solidifies. The prelithiation of the conductive layer includes coating molten lithium onto the conductive layer and cooling to form a lithium layer. However, the cost of setting up the conductive layer is high, and the operability is not strong. In the prelithiated conductive layer, the molten lithium is likely to infiltrate into the gap between the granular conductive material of the conductive layer, forming a mixed layer of lithium and conductive material doping. The mixed layer cannot accurately control the content of lithium metal, the formed coating is thicker, the amplitude of the energy density improvement of prelithiation is reduced, and the preparation process is more complex. In addition, the slurry system that can be selected in the step of directly coating the negative active material slurry on the prelithiated conductive layer will be very limited. Most of the slurries will react with the prelithiation lithium source material, the slurry selection requirement is high, the applicable scene is less, and the economic benefit is relatively poor.

[0008] Therefore, there is still room for improvement in the existing prelithiation technology. SUMMARY

[0009] To improve the prelithiation scheme, the present application provides a system, method and product for prelithiating lithium ion battery electrodes using molten lithium.

[0010] The system for prelithiating lithium ion battery electrodes using molten lithium provided by the embodiments of the present application is used for preparing a prelithiated battery negative electrode, and the system comprises a coating device for coating molten lithium metal onto the surface of a current collector to form a lithium layer composed of pure metal lithium on the surface of the current collector, and no conductive layer is arranged between the lithium layer and the current collector.

[0011] In at least one embodiment, the coating device comprises a first coating roller and a second coating roller, and the first coating roller and / or the second coating roller can contact the molten lithium metal. As the first coating roller and the second coating roller rotate, the molten lithium metal is transferred by a transfer roller to the surface of the current collector between the first coating roller and the second coating roller. The tangential direction of the rotation direction of the first coating roller and the second coating roller at the current collector is the same as the movement direction of the current collector.

[0012] In at least one embodiment, the system for prelithiating lithium ion battery electrodes using molten lithium further comprises a cooling device for cooling the molten lithium metal on the current collector to form a lithium layer.

[0013] In at least one embodiment, the system for prelithiating lithium ion battery electrodes using molten lithium further comprises a transfer device for transferring the negative active material of a pre-prepared negative electrode to the outside of the lithium layer to form a prelithiated battery negative electrode.

[0014] In at least one embodiment, the transfer device comprises: a pre-prepared negative electrode unwinding device for unwinding the pre-prepared negative electrode, the pre-prepared negative electrode comprising a pre-prepared negative electrode carrier and the negative electrode active material; a pre-prepared negative electrode carrier winding device for winding the pre-prepared negative electrode carrier after the transfer is completed; and a first transfer roller, a second transfer roller, the surface of the negative electrode active material of the pre-prepared negative electrode is opposite to the surface provided with the metallic lithium of the current collector and is subjected to the roller pressure of the first transfer roller and the second transfer roller, so that the negative electrode active material is transferred to the outside of the lithium layer.

[0015] In at least one embodiment, the system for pre-lithiating lithium ion battery electrodes with molten lithium further comprises: a current collector unwinding device for unwinding the current collector; a cleaning and activating device for cleaning and activating the unwound current collector, the cleaning and activating device being arranged upstream of the coating device; and a passivation device for passivating the lithium layer arranged on the current collector.

[0016] In at least one embodiment, the system for pre-lithiating lithium ion battery electrodes with molten lithium further comprises: a roller pressing device for roller pressing the pre-lithiated battery negative electrode formed after the transfer is completed; and a pre-lithiated battery negative electrode winding device for winding the pre-lithiated battery negative electrode after the roller pressing.

[0017] The method for pre-lithiating lithium ion battery electrodes with molten lithium provided by the embodiments of the present application applies the aforementioned system for pre-lithiating lithium ion battery electrodes with molten lithium, and the method comprises: preliminary processing: providing the current collector, cleaning and activating the current collector; preparing a pre-prepared negative electrode, the pre-prepared negative electrode comprising a negative electrode active material; preparing molten lithium metal; coating the metallic lithium: coating the molten lithium metal to the surface of the current collector; post-coating processing: cooling the molten lithium on the surface of the current collector to form the lithium layer, and passivating the lithium layer; and transfer: transferring the negative electrode active material to the surface of the lithium layer to form a pre-lithiated battery negative electrode.

[0018] In at least one embodiment, the surface of the current collector is activated by at least one of surface high-temperature oxidation, coating an organic layer, and coating an inorganic layer.

[0019] The product for pre-lithiating lithium ion battery electrodes with molten lithium provided by the embodiments of the present application is a pre-lithiated battery negative electrode prepared according to the aforementioned system or a pre-lithiated battery negative electrode prepared according to the aforementioned method.

[0020] The product for pre-lithiating lithium ion battery electrodes with molten lithium provided by the embodiments of the present application is a battery, the battery comprising a pre-lithiated battery negative electrode prepared according to the aforementioned system or a pre-lithiated battery negative electrode prepared according to the aforementioned method.

[0021] The application can accurately control the thickness of the lithium layer by coating the surface of the current collector with lithium metal, thereby accurately controlling the lithium supplement amount. The application avoids the problems of adhesive swelling, weakening of the mechanical properties of the electrode sheet, and subsequent cleaning and drying of the electrode sheet caused by the immersion of the electrode sheet in the electrolyte in the existing electrolyte spraying electrode sheet lithium supplement scheme. Compared with the existing electrodeposition lithium supplement scheme, the application eliminates the need for cleaning and drying the current collector after lithium supplement, and the process is simpler. No conductive layer is provided between the lithium layer and the current collector, and the lithium layer is a pure metal layer, so that the content of lithium metal can be accurately controlled, the coating layer is thinner, the amplitude of the energy density improvement of the pre-lithiation is improved, and the preparation process is relatively simple. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A structural schematic diagram of a system for pre-lithiating a lithium ion battery electrode using molten lithium according to an embodiment of the application is shown.

[0023] Figure 2 A structural schematic diagram of a current collector and a lithium layer prepared by the system for pre-lithiating a lithium ion battery electrode using molten lithium in Figure 1

[0024] Figure 3 A structural schematic diagram of a pre-lithiated battery negative electrode prepared by the system for pre-lithiating a lithium ion battery electrode using molten lithium in Figure 1

[0025] Figure 4 A structural schematic diagram of a system for pre-lithiating a lithium ion battery electrode using molten lithium according to another embodiment of the application is shown.

[0026] Figure 5 A structural schematic diagram of a current collector and a lithium layer prepared by the system for pre-lithiating a lithium ion battery electrode using molten lithium in Figure 4

[0027] A structural schematic diagram of a pre-lithiated battery negative electrode prepared by the system for pre-lithiating a lithium ion battery electrode using molten lithium in Figure 6 Figure 4

[0028] BRIEF DESCRIPTION OF DRAWINGS

[0029] 1 current collector unwinding device; 11 current collector;

[0030] 2 cleaning and activating device;

[0031] 3 coating device; 31 first coating roller; 32 second coating roller; 33 lithium layer;

[0032] 4 cooling device;​​​​

[0033] 5. Passivation device;

[0034] 6. Transfer device; 61. Pre-formed negative electrode unwinding device; 62. Pre-formed negative electrode carrier winding device; 63. First transfer roller; 64. Second transfer roller; 65. Negative electrode active material;

[0035] 7. Roller pressing device;

[0036] 8. Pre-lithiated battery negative electrode winding device Detailed Implementation

[0037] Exemplary embodiments of this application are described below with reference to the accompanying drawings. It should be understood that these specific descriptions are for teaching those skilled in the art how to implement this application only, and are not intended to exhaustively describe all possible methods of this application, nor to limit the scope of this application.

[0038] This application provides systems, methods, and products utilizing molten lithium pre-lithiated lithium-ion battery electrodes.

[0039] See Figure 1 , Figure 4 A system utilizing molten lithium pre-lithiated lithium-ion battery electrodes may include a current collector unwinding device 1, a cleaning and activation device 2, a coating device 3, a cooling device 4, a passivation device 5, a transfer device 6, a rolling device 7, and a pre-lithiated battery negative electrode winding device 8.

[0040] The current collector unwinding device 1 is used to unwind the current collector 11. The current collector 11 can be a double-sided electrode current collector or a single-sided electrode current collector. Its unwinding speed is set to be controllable, thereby allowing control over the amount of lithium metal subsequently applied to the current collector 11. The material of the current collector 11 can be copper.

[0041] The cleaning and activation device 2 is located downstream of the current collector unwinding device 1. The cleaning and activation device 2 is used to clean and modify the surface of the current collector 11, improving its wettability. Modification and activation can be achieved through heating activation, i.e., heating the current collector 11 to approximately 300°C to generate some oxides on its surface; alternatively, modification and activation can be achieved through coating, i.e., coating the surface of the current collector 11 with a nanoscale polymer layer. This polymer layer can include a series of polymers such as PVDF (polyvinylidene fluoride), or coating the surface of the current collector 11 with an inorganic material having the same effect. Compared to the existing technology of setting a conductive layer to aid molten lithium wetting, the cleaning and activation method is lower in cost, more operable, and suitable for large-scale industrial production.

[0042] The coating device 3 is located downstream of the cleaning and activation device 2. The coating device 3 is used to coat molten lithium metal onto the surface of the current collector 11.

[0043] In one embodiment of the present application, referring to Figure 1 , Figure 2 , the current collector 11 is a double-sided current collector, and the coating device 3 can include a first coating roller 31 and a second coating roller 32. The first coating roller 31 can be partially immersed in the container containing the molten lithium, and the molten lithium can change position along with the rotation of the first coating roller 31, and then be coated on one side of the current collector 11. Further, the container containing the molten lithium can touch the surface of the second coating roller 32, so that the molten lithium is poured on the surface of the second coating roller 32, and the molten lithium changes position along with the rotation of the second coating roller 32, and then is coated on the other side of the current collector 11. The current collector 11 is conveyed between the first coating roller 31 and the second coating roller 32, and is pressed and coated by the two rollers, so that the molten lithium is covered on both sides of the current collector 11 to form a lithium layer 33.

[0044] By controlling the distance between the first coating roller 31 and the second coating roller 32 and the thickness of the current collector 11, the unwinding speed of the current collector unwinding device 1 can control the thickness of the lithium layer 33, so as to accurately control the lithium supplement amount. Compared with the prior art of pressing the formed lithium layer and the negative electrode sheet to supplement lithium, the present application sets the molten lithium on the current collector 11 by coating, and the thickness of the lithium layer 33 formed after the solidification of the molten lithium can be relatively thin, for example, reaching 20 μm or less, or even 1.5-10 μm, so as to avoid the problems of excessive lithium supplement and lithium dendrite growth in the battery caused by the thick lithium layer.

[0045] In another embodiment of the present application, referring to Figure 4 , the current collector 11 is a single-sided current collector, and the surface of the second coating roller 32 does not contact the molten lithium, so that the molten lithium is only set on one side of the current collector 11 by the first coating roller 31.

[0046] In the present application, the tangential direction of the rotation direction of the first coating roller 31 and the second coating roller 32 at the current collector 11 can be the same as the movement direction of the current collector 11, so as to facilitate the transmission of the current collector 11 and realize the thin coating effect of the molten lithium.

[0047] Of course, the coating process of the molten lithium can also be realized by other forms, and the present application does not limit the specific equipment used in the coating process. For example, the molten lithium can be coated on the current collector 11 by a scraper, a mechanical arm or the like.

[0048] The present application does not limit the contact mode of the coating roller and the molten lithium. For example, the container containing the molten lithium can also touch the first coating roller 31, so that the molten lithium is poured on the first coating roller 31.

[0049] The container containing molten lithium can have a heating function, or the container containing molten lithium can be heated by a heating device to make the lithium metal molten.

[0050] The cooling device 4 is located downstream of the coating device 3. The cooling device 4 is used to cool the molten lithium metal on the current collector 11 to form a lithium layer 33 composed of pure metallic lithium. No conductive layer is provided between the lithium layer 33 and the current collector 11. The lithium layer 33 is a pure metallic layer, which allows for precise control of the lithium metal content, resulting in a thinner coating, improving the energy density increase of pre-lithiation, and making the preparation process relatively simple.

[0051] The passivation device 5 is located downstream of the cooling device 4. The passivation device 5 uses a gas to react with the lithium metal surface, thereby passivating the lithium layer 33. For example, carbon dioxide or hydrogen fluoride gas can be used to passivate the lithium layer 33, preventing the highly reactive lithium metal from reacting with the active atmosphere. Of course, if the preparation environment of the pre-lithiated battery electrode has a good protective gas atmosphere, the passivation device 5 and the corresponding passivation step can be omitted.

[0052] The transfer device 6 is located downstream of the passivation device 5. The transfer device 6 may include a pre-formed negative electrode unwinding device 61, a pre-formed negative electrode carrier winding device 62, a first transfer roller 63, and a second transfer roller 64. The transfer device 6 is used to transfer the negative electrode active material 65 onto the current collector 11 on which the lithium layer 33 is provided, to form a pre-lithiated battery negative electrode.

[0053] The pre-formed negative electrode unwinding device 61 unwinds the pre-formed negative electrode, which includes a pre-formed negative electrode carrier and a negative electrode active material 65. The negative electrode active material 65 is disposed on one side of the pre-formed negative electrode carrier. The pre-formed negative electrode is conveyed between the first transfer roller 63 and the second transfer roller 64, with the side of the pre-formed negative electrode containing the negative electrode active material 65 facing the lithium layer of the current collector 11. The pre-formed negative electrode and the current collector 11 are subjected to rolling pressure by the first transfer roller 63 and the second transfer roller 64, and the negative electrode active material 65 is transferred onto the surface of the current collector 11 to form a pre-lithiated battery negative electrode. The pre-formed negative electrode carrier is wound up by the pre-formed negative electrode carrier winding device 62.

[0054] See Figure 3 , Figure 6 After the transfer, the lithium layer 33 is located inside the negative electrode active material 65 (i.e., the side closer to the current collector 11), which can overcome the problems of lithium dendrite precipitation and impedance increase that may be caused by surface pre-lithiation materials obtained by traditional pre-lithiation methods. In this application, the cured negative electrode active material 65 is transferred to contact the lithium layer 33. Compared with the scheme of coating the negative electrode active material with a slurry, this expands the selection space of the slurry system for the pre-fabricated negative electrode and has better economic benefits. Of course, after the transfer, the pre-fabricated negative electrode carrier can be replenished with new negative electrode active material for recycling.

[0055] A rolling device 7 is arranged downstream of the transferring device 6, and is used to roll the pre-lithiated battery negative electrode after the transferring, so as to improve the flatness and tap density of the electrode.

[0056] A pre-lithiated battery negative electrode winding device 8 is arranged downstream of the rolling device 7, and is used to collect the pre-lithiated battery negative electrode.

[0057] The method for pre-lithiating lithium ion battery electrode by using molten lithium provided in the application can include the following steps:

[0058] (1) preliminary treatment: cleaning and activating the current collector 11; preparing the pre-prepared negative electrode by using a traditional coating method or dry method; and preparing the molten lithium metal.

[0059] (2) coating the lithium metal: coating the molten lithium onto the current collector 11.

[0060] (3) post-coating treatment: cooling the current collector 11 with the lithium metal coated on the surface to form a lithium layer 33, and then passivating the lithium layer 33.

[0061] (4) transferring: rolling the negative electrode active material 65 of the pre-prepared negative electrode against the lithium layer 33 of the current collector 11, so that the negative electrode active material 65 is transferred to the surface of the lithium layer 33 due to the stronger binding force between the lithium metal and the negative electrode active material 65 than the binding force between the negative electrode active material 65 and the pre-prepared electrode carrier, and a pre-lithiated battery negative electrode is formed.

[0062] (5) post-transferring rolling: rolling the pre-lithiated battery negative electrode after the transferring, so as to improve the tap density of the battery negative electrode.

[0063] In step (1), the material of the current collector 11 can be copper, and the thickness of the current collector 11 can be 5-20 μm; the activation process of the current collector 11 can use methods including but not limited to "surface high-temperature oxidation treatment", "coating an organic layer (at the nanometer level)", "coating an inorganic layer (at the nanometer level)", etc. to change the wettability of the surface of the current collector 11, so that the current collector 11 can be easily wetted with the molten lithium; the material of the pre-prepared electrode carrier of the pre-prepared negative electrode can be stainless steel, and the thickness of the pre-prepared electrode carrier can be 5-30 μm; the container containing the lithium metal can be heated by a heating device, and the heating temperature can be 180℃-400℃, so that the lithium metal is in a molten state.

[0064] In step (4), the negative electrode active material of the pre-prepared negative electrode can be one or more of graphite, hard carbon, silicon, silicon monoxide, tin, phosphorus, etc. lithium ion battery negative electrode active materials; the over-rolling pressure and the transferring speed of the current collector and the pre-prepared negative electrode can be adjusted according to the composition of the negative electrode active material and the amount of the coated lithium metal; the rolling temperature used in the transferring process is -40℃-200℃.

[0065] The pre-lithiated negative electrode can be formed by an electrode coating process or a stand-alone film-to-foil process.

[0066] In step (5), the number of rolling times can be 1-10, for example, multiple rolling devices 7 are provided, i.e., multiple rollers repeatedly roll the pre-lithiated negative electrode, so as to improve the flatness and tap density of the electrode.

[0067] The application also provides a product obtained by the above system or method for pre-lithiating a lithium ion battery electrode using molten lithium, the product comprising a pre-lithiated negative electrode and a battery. The battery can be a lithium ion battery, and the battery can comprise the pre-lithiated negative electrode as described above.

[0068] The pre-lithiated negative electrode comprises a current collector 11, a lithium layer 33, and a negative active material 65 outside the lithium layer 33. The lithium layer 33 is composed of pure metal lithium, and the negative active material 65 is mainly active material, which can also be doped with other substances.

[0069] Exemplarily, the application provides some embodiments.

[0070] Embodiment 1

[0071] A pre-lithiated negative electrode was prepared using artificial graphite, conductive carbon black, and PVDF (polyvinylidene fluoride) dispersed in NMP (N-methyl pyrrolidone) as a slurry, and using 30 μm-thick stainless steel as a pre-lithiated negative electrode carrier. A 20 μm-thick copper was used as the current collector 11. The solvent used to activate the surface of the current collector 11 was NMP, and the solute was PVDF. The mass fraction of PVDF was 6.25%. The temperature of the molten lithium was 300°C. The thickness of the lithium layer obtained by coating was 5 μm. The initial coulombic efficiency of the pre-lithiated electrode half-cell obtained was 99%. The initial coulombic efficiency of the half-cell of the comparative example without pre-lithiation was 83%.

[0072] Embodiment 2

[0073] A pre-lithiated negative electrode was prepared using silicon-carbon, conductive carbon black, PVDF, and PAA (polyacrylic acid) dispersed in NMP as a slurry, and using 30 μm-thick stainless steel as a pre-lithiated negative electrode carrier. A 20 μm-thick copper was used as the current collector 11. The solvent used to activate the surface of the current collector 11 was NMP, and the solute was PVDF. The mass fraction of PVDF was 6.25%. The temperature of the molten lithium was 300°C. The thickness of the lithium layer obtained by coating was 5 μm. The initial coulombic efficiency of the pre-lithiated electrode half-cell obtained was 99%. The initial coulombic efficiency of the half-cell of the comparative example without pre-lithiation was 86%.

[0074] Embodiment 3

[0075] A pre-prepared negative electrode was prepared using artificial graphite, conductive carbon black, and PVDF dispersed in NMP as the slurry of the pre-prepared negative electrode, and using 30 μm-thick stainless steel as the pre-prepared negative electrode carrier. A 20 μm-thick copper was used as the current collector 11. The solvent used to activate the surface of the current collector 11 was NMP, and the solute was PVDF. The mass fraction of PVDF was 6.25%. The temperature of the molten lithium was 300℃. The thickness of the obtained lithium layer was 5 μm. The obtained pre-lithiated electrode was assembled into a full battery with an NCM111 positive electrode, and the initial coulombic efficiency of the full battery was 90%, while the initial coulombic efficiency of the full battery of the comparative example without pre-lithiation was 80%. The specific capacity of the pre-lithiated full battery was increased by 19.3 mAh / g.

[0076] Example 4

[0077] A pre-prepared negative electrode was prepared using artificial graphite, conductive carbon black, and PVDF dispersed in NMP as the slurry of the pre-prepared negative electrode, and using 30 μm-thick stainless steel as the pre-prepared negative electrode carrier. A 20 μm-thick copper was used as the current collector 11. The solvent used to activate the surface of the current collector 11 was NMP, and the solute was PVDF. The mass fraction of PVDF was 6.25%. The temperature of the molten lithium was 300℃. The thickness of the obtained lithium layer was 5 μm. The obtained pre-lithiated electrode was assembled into a full battery with an NCM111 positive electrode, and the initial coulombic efficiency of the full battery was 89%, while the initial coulombic efficiency of the full battery of the comparative example without pre-lithiation was 80%. The specific capacity of the pre-lithiated full battery was increased by 16 mAh / g.

[0078] It can be seen that the pre-lithiation of the lithium ion battery electrode using molten lithium can improve the initial coulombic efficiency of the battery and increase the specific capacity.

[0079] Compared with the prior art, the system, method and product for pre-lithiating a lithium ion battery electrode using molten lithium provided by the present application have the following beneficial effects:

[0080] (1) The pre-prepared electrode and the roll-to-roll process adopted by the present application are already very popular in industrial mass production, and the method is simple and low in cost, and is easy to realize large-scale production compared with other pre-lithiation methods.

[0081] (2) The present application sets lithium metal on the surface of the current collector by roll-to-roll coating, which can accurately control the thickness of the lithium layer 33 and thus accurately control the lithium supplement amount. For example, the lithium layer thickness can be easily changed by adjusting the distance between the first coating roller 31 and the second coating roller 32, matching various pre-lithiation requirements.

[0082] (3) The present application avoids the problems of adhesive swelling, weakening of the mechanical properties of the electrode sheet, and subsequent cleaning and drying of the electrode sheet caused by the electrode sheet being immersed in the electrolyte.

[0083] (4) In the present application, the lithium metal is placed under the active material, avoiding the lithium metal being on the surface of the pre-lithiated battery negative electrode, avoiding the problem of lithium dendrite precipitation and impedance rise.

[0084] (5) The present application, relative to the scheme of electrodeposition of lithium supplement, eliminates the requirement of cleaning and drying of the lithium supplement of the current collector, and the process is simpler.

[0085] In the present application, the aforementioned interval a~b includes both end point values a and b. For example, the thickness of the lithium layer 33 is 1.5~10 μm, which means that the thickness of the lithium layer 33 includes both end point values 1.5 μm and 10 μm and any value between the two end points. The same applies to other intervals.

[0086] In one embodiment of the present application, the thickness of the current collector 11 can be 10~20 μm, the thickness of the lithium layer 33 is below 5 μm, and the thickness of the negative electrode active material 65 is 100~200 μm. Figure 2 Figure 3 Figure 5 Figure 6 Only for exemplarily expressing the positional relationship of the above-mentioned substances, and does not represent that the above-mentioned substances have the thickness corresponding relationship as shown in the figure.

[0087] The above is the preferred embodiment of the present application, it should be pointed out that for those skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.​​​

Claims

1. A system for prelithiating lithium-ion battery electrodes with molten lithium, characterized in that, The system for preparing a pre-lithiated battery negative electrode comprises a coating device (3) for coating molten lithium metal to the surface of a current collector (11), forming a lithium layer (33) composed of pure metal lithium between the current collector (11) and the lithium layer (33) without setting an electrically conductive layer, The system further comprises a cleaning and activating device (2) for cleaning and activating the unwound current collector (11), which is arranged upstream of the coating device (3) and performs cleaning and modified activation on the surface of the current collector (11), the modified activation being performed by coating a nanoscale polymer layer on the surface of the current collector (11), and the polymer layer comprising PVDF. The coating device (3) comprises a first coating roller (31) and a second coating roller (32), which can contact the molten lithium metal, and as the first coating roller (31) and the second coating roller (32) rotate, the molten lithium metal is transferred and pressed by a roller between the first coating roller (31) and the second coating roller (32) on the surface of the current collector (11), and the tangential direction of the rotation of the first coating roller (31) and the second coating roller (32) at the current collector (11) is the same as the movement direction of the current collector (11).

2. The system for prelithiating lithium-ion battery electrodes with molten lithium according to claim 1, wherein, The system for pre-lithiating lithium ion battery electrodes with molten lithium further comprises a cooling device (4) for cooling the molten lithium metal on the current collector (11) to form a lithium layer (33).

3. The system for prelithiating a lithium-ion battery electrode with molten lithium of claim 1, wherein, The system for pre-lithiating lithium ion battery electrodes with molten lithium further comprises a transfer device (6) for transferring the negative electrode active material (65) of the pre-prepared negative electrode to the outside of the lithium layer (33) to form a pre-lithiated battery negative electrode.

4. The system for prelithiating lithium-ion battery electrodes with molten lithium according to claim 3, wherein, The transfer device (6) comprises: a pre-prepared negative electrode unwinding device (61) for unwinding the pre-prepared negative electrode, the pre-prepared negative electrode comprising a pre-prepared negative electrode carrier and the negative electrode active material (65); a pre-prepared negative electrode carrier winding device (62) for winding the pre-prepared negative electrode carrier after the transfer is completed; and a first transfer roller (63) and a second transfer roller (64), the surface of the negative electrode active material (65) of the pre-prepared negative electrode being opposite to the surface of the current collector (11) provided with metal lithium and being pressed by the first transfer roller (63) and the second transfer roller (64), so that the negative electrode active material (65) is transferred to the outside of the lithium layer (33).

5. The system for prelithiating a lithium-ion battery electrode with molten lithium of claim 1, wherein, The system for pre-lithiating lithium ion battery electrodes with molten lithium further comprises: a current collector unwinding device (1) for unwinding the current collector (11); and a passivation device (5) for passivating the lithium layer (33) provided on the current collector (11).

6. The system for prelithiating a lithium-ion battery electrode with molten lithium according to claim 3 or 4, characterized in that, The system for pre-lithiating lithium ion battery electrodes with molten lithium further comprises: a roller pressing device (7) for pressing the pre-lithiated battery negative electrode formed after the transfer is completed; and A pre-lithiated battery negative electrode winding device (8) is used to wind the pre-lithiated battery negative electrode after rolling.

7. A method of prelithiating a lithium-ion battery electrode with molten lithium, characterized by, The method comprises the steps of: Pre-treatment: providing the current collector (11), cleaning and modifying the surface of the current collector (11), and modifying and activating the surface of the current collector (11) by coating method, coating a nanoscale polymer layer on the surface of the current collector (11), and the polymer layer comprises PVDF; preparing a pre-prepared negative electrode, the pre-prepared negative electrode comprises a negative active material (65); preparing molten lithium metal; Coating of metal lithium: coating the molten lithium metal to the surface of the current collector (11); Post-treatment: cooling the molten lithium on the surface of the current collector (11) to form the lithium layer (33), and passivating the lithium layer (33); and Transfer: transferring the negative active material (65) to the surface of the lithium layer (33) to form a pre-lithiated battery negative electrode.

8. The method for prelithiating a lithium-ion battery electrode with molten lithium according to claim 7, wherein, The surface of the current collector (11) is activated by at least one of high-temperature oxidation, coating an organic layer, and coating an inorganic layer.

9. A product for prelithiating a lithium-ion battery electrode with molten lithium, characterized in that, The product is a pre-lithiated battery negative electrode prepared by the system according to any one of claims 1 to 6 or a pre-lithiated battery negative electrode prepared by the method according to claim 7 or 8.

10. A product for prelithiating a lithium-ion battery electrode with molten lithium, characterized in that, The product is a battery, and the battery comprises a pre-lithiated battery negative electrode prepared by the system according to any one of claims 1 to 6 or a pre-lithiated battery negative electrode prepared by the method according to claim 7 or 8.

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