WO2021253318A1

WO2021253318A1 - Ultrathin lithium bar preform, composite negative electrode, manufacturing method therefor, and battery

Info

Publication number: WO2021253318A1
Application number: PCT/CN2020/096782
Authority: WO
Inventors: 齐大志; 程滋平; 刘慧芳; 陈强; 牟瀚波; 郇庆娜; 吴春敢; 于坤旺
Original assignee: 天津中能锂业有限公司
Priority date: 2020-06-18
Filing date: 2020-06-18
Publication date: 2021-12-23

Abstract

Provided in the present invention are an ultrathin lithium bar preform, a composite negative electrode, a manufacturing method therefor, and a battery. The ultrathin lithium bar preform is provided with: a supporting layer, the supporting layer being a strip material of which the width is 3-2000 mm; and multiple ultrathin lithium bars arranged on at least one surface of the supporting layer and compounded together with the supporting layer, the multiple ultrathin lithium bars being two or more ultrathin bars extended in the length direction of the supporting layer and separated from each other in the width direction of the supporting layer, the width of the ultrathin lithium bars falling within the range of 1-200 mm, the thickness of the ultrathin lithium bars being consistent and falling within the range of 0.5-15 micrometers, individual ultrathin lithium bars being provided with a through hole of which the aperture is 5-1000 micrometers and a porosity of 50% or less, and adjacent ultrathin lithium bars being provided with a spacing of 0.5-10 mm.

Description

Ultra-thin lithium strip preform, composite negative electrode, preparation method thereof and battery

Technical field

The invention relates to the technical field of energy storage, in particular to an ultra-thin lithium strip preform that can be used in secondary batteries, a composite negative electrode and a preparation method thereof.

Background technique

Lithium batteries are widely used in aerospace, computers, mobile communication equipment, robots and electric vehicles due to their advantages of high energy density, long cycle life and wide applicable temperature range. With the development of society and the advancement of science and technology, the energy density and cycle life requirements of lithium batteries are getting higher and higher. At present, lithium-ion batteries that use graphite as the negative electrode cannot meet the expectations of the society. Therefore, it is necessary to develop new types with higher ratios. Capacity of positive and negative materials. For the negative electrode material, the pre-lithiation work can effectively increase the specific energy of the battery and increase the battery life. Lithium metal has a high specific capacity (3860mAh/g, 10 times that of graphite anode) and the lowest redox potential (-3.04V vs standard hydrogen potential). The use of lithium metal to pre-lithiation of the traditional graphite negative electrode can improve the first coulombic efficiency of the battery and increase the specific energy of the battery on the one hand, and on the other hand can effectively extend the cycle life of the battery, which makes lithium-ion batteries have a broader application field.

Although pre-lithiation (replenishment of lithium) has such advantages, it is necessary to precisely control the amount of it in the battery, which puts forward higher requirements for the pre-lithiation of the negative electrode. At present, the current cathode materials used in lithium-ion batteries are all lithium-containing materials (such as lithium cobalt oxide, lithium iron phosphate, ternary materials, etc.). The lithium contained in the positive electrode can meet the charging and discharging needs of lithium-ion batteries, while the negative electrode only needs A small amount of lithium (the thickness of lithium is 0.5-10 microns) can supplement the lithium lost in the formation of the solid electrolyte interface (SEI) film. In the Chinese patent application CN201610102992.8 of Ningde Times New Energy, lithium powder is sprinkled on the surface of the pole piece during the process of replenishing lithium, and pre-lithiation is performed after rolling. However, the method for supplementing lithium cannot yet achieve precise control of the amount of supplementing lithium, and the process is complicated, the cost is high, and more importantly, the safety is difficult to control.

In view of this, there is a need for a technology that can accurately control the amount of replenishment of lithium and realize the high energy density of the battery.

Summary of the invention

The inventor unexpectedly discovered that for the lithium film used in the prelithiation of the negative electrode, if the lithium film has through holes, the presence of the holes can not only make the electrolyte easier to enter the contact interface between the lithium film and the negative electrode film, and improve the The lithiation speed, and the gas generated during the pre-lithiation can be released from the through hole to avoid the separation of the lithium film from the negative electrode film. Therefore, compared with a complete lithium film, a lithium film with through holes can achieve a better pre-lithiation effect. Furthermore, ultra-thin lithium strips with smaller spacing are used for prelithiation of the negative electrode, and this advantage is even more obvious.

In addition, the inventor also found that ultra-thin lithium strips (0.5-15 microns thick, or even 1-5 microns thick) with through holes can be produced in a roll-to-roll manner by rolling, and the through-hole can be controlled by controlling the rolling pressure. The adhesion between the ultra-thin lithium strips of the holes and the supporting layer is at an appropriate level, which can not only ensure that the ultra-thin lithium strips can be compounded on the supporting layer, but also can be easily transferred from the supporting layer to other substrates. For example, on the negative electrode of a lithium battery. In view of these findings, the present invention has been completed.

Therefore, one aspect of the present invention aims to provide an ultra-thin lithium bar preform, the ultra-thin lithium bar preform having: a supporting layer, the supporting layer is a strip with a width of 3-2000 mm; and A plurality of ultra-thin lithium strips on at least one surface of the supporting layer and composited with the supporting layer, and the plurality of ultra-thin lithium strips extend along the length direction of the supporting layer and are arranged on the supporting layer. Two or more ultra-thin lithium bars separated from each other in the width direction of the carrier layer, the width of each ultra-thin lithium bar is in the range of 1-200mm, and the thickness of each ultra-thin lithium bar is consistent in the range of 0.5-15 microns And a single ultra-thin lithium strip has through holes with a diameter of 5-1000 microns, the porosity is less than 50%, and the distance between adjacent ultra-thin lithium strips is 0.5-10 mm.

The ultra-thin lithium strip preform of the present invention is a product that supports a continuous, through-hole, and adjustable width and thickness (to control the size and pressure of the lithium film) ultra-thin lithium strip on a supporting layer (film base material). A composite strip with spaces between adjacent ultra-thin lithium strips.

In the present invention, the ultra-thin lithium strip is a uniform film, which means that the ultra-thin lithium strip has a complete film shape (without obvious wrinkles and deformation) and has a uniform thickness. Preferably, the ultra-thin lithium strip has through holes that are relatively uniform throughout the lithium film.

Optionally, the lithium strip surface of the ultra-thin lithium strip preform is bright, metallic silver-white, the lithium content is 99.90～99.95%, the thickness of the lithium film is in the range of 0.5-15 microns, preferably 1-10 microns, and the thickness tolerance is ±1μm .

Optionally, the lithium bar of the ultra-thin lithium bar preform is a metal lithium alloy product (for example: lithium magnesium alloy, lithium aluminum alloy, lithium boron alloy, lithium silicon alloy, lithium boron alloy, lithium indium alloy), and the lithium content is 10 ~99.9%.

Optionally, the ultra-thin lithium strip has uniformly distributed through holes with a pore diameter of 100-500 microns.

Optionally, the porosity of the ultra-thin lithium strip is 0-50%, preferably 0.5%-10%, more preferably 1%-5%.

Optionally, there are at least two or more ultra-thin lithium bars, and there is a distance between adjacent ultra-thin lithium bars of 0.5-10 mm, preferably 1-5 mm.

Optionally, the width of the ultra-thin lithium strip is 1-200mm, preferably 1-50mm, more preferably 2-10mm.

Optionally, the width of the ultra-thin lithium strip preform is 3-2000 mm, preferably 100-300 mm.

Optionally, the material of the supporting layer is a polymer or an anti-adhesive film composed of it: for example, high-strength filmed polyolefin (polyethylene, polypropylene, polystyrene), polyester, biaxially oriented polypropylene (BOPP) Anti-adhesion film, etc.; inorganic oxides: such as aluminum oxide; inorganic conductors: such as graphite, carbon nanotubes, graphene; metal current collectors: such as copper, aluminum; the supporting layer is a single layer or a multilayer composite.

Optionally, the thickness of the supporting layer is 1-500 micrometers, preferably 5-100 micrometers, more preferably 10-50 micrometers.

Another aspect of the present invention provides a composite negative electrode comprising: a current collector; a negative electrode coating on the surface of the current collector; and an ultra-thin lithium strip compounded on the side of the negative electrode coating away from the current collector, The ultra-thin lithium strip is obtained by removing the supporting layer of the aforementioned ultra-thin lithium strip preform.

Optionally, the ultra-thin lithium strips covering the surface of the negative electrode coating layer include at least two or more, and the distance between adjacent ultra-thin lithium strips is 0.5-10 mm, preferably 2-5 mm.

Another aspect of the present invention aims to provide a method for preparing the above-mentioned ultra-thin lithium strip preform. The method is a roll-to-roll continuous production method that uses a metal lithium strip with a thickness of 5 to 200 μm as a raw material. The bump release base material is attached, and the other side is attached to the supporting layer and enters the roll together. After rolling, the bump release base material and the metal lithium tape are peeled off to obtain an ultra-thin lithium tape supported by the carrier layer. Part of the metal lithium is removed from the ultra-thin lithium belt supported by the belt supporting layer to form an ultra-thin lithium strip with intervals, to obtain the ultra-thin lithium strip preform.

Optionally, the thickness of the rolled raw metal lithium strip is 1 to 200 μm, preferably 5 to 150 μm.

Optionally, the side of the bump release substrate in contact with the metal lithium is provided with a release coating, and the bump release film or the release coating is provided with a number of uneven dot-shaped protrusions.

Optionally, the bump release substrate is a single-layer or multi-layer film prepared from the following materials, which are selected from polymers, including polyolefins (polyethylene, polypropylene, polystyrene), polystyrene Esters; metals, including steel, aluminum, and copper.

Optionally, the adhesive force of the ultra-thin lithium strip and the supporting layer can be controlled by adjusting the rolling pressure.

Optionally, the process for providing the bump release substrate with a number of point-shaped bumps includes sandblasting on the back of the substrate and a mechanical rolling process.

Optionally, a scraper is used for scraping to remove part of the metallic lithium belt from the ultra-thin lithium belt supported by the belt supporting layer to form an ultra-thin lithium strip with intervals.

Optionally, the scraper is a flat scraper or a rotary scraper. Flat scraper means that the scraper moves relative to the ultra-thin lithium belt, and the rotating scraper means that the scraper can rotate around its own axis.

Another aspect of the present invention provides a method for preparing the above composite negative electrode, characterized in that: the method is a roll-to-roll continuous production method, using the ultra-thin lithium strip preform made above as a raw material, and composite by pressure The transfer method transfers the ultra-thin lithium strip from the supporting layer to the negative electrode coating.

Optionally, the raw material for preparing the composite negative electrode is an ultra-thin lithium strip preform with a release film as a supporting layer.

Another aspect of the present invention provides a battery comprising a positive electrode and a negative electrode disposed oppositely, wherein the negative electrode includes the above-mentioned ultra-thin lithium strip preform or the above-mentioned composite negative electrode.

Optionally, the battery includes a lithium metal battery, an all-solid-state battery, a lithium sulfur battery, or a lithium air battery.

By controlling the thickness and width of the ultra-thin lithium strip, the present invention can accurately control the lithium loading per unit area, so that the ultra-thin lithium strip preform or the composite negative electrode can accurately control the replenishment amount of lithium when it is used to replenish the lithium battery, and effectively improve the battery The first cycle efficiency greatly improves the cycle life of lithium batteries. Moreover, the ultra-thin lithium strip of the present invention may have through holes, which not only make it easier for the electrolyte to enter the contact interface between the lithium film and the negative electrode film, and increase the pre-lithiation speed, but also the gas generated during the pre-lithiation It can be released from the through hole to avoid the separation of the lithium film from the negative electrode film. Therefore, a lithium film with through holes can achieve a better prelithiation effect.

Description of the drawings

Fig. 1 is a top view of the ultra-thin lithium strip preform product of the present invention.

Fig. 2 is a side view of the ultra-thin lithium strip preform product in Fig. 1.

Fig. 3 is a schematic diagram of the composite negative electrode of the present invention.

Figure 4 is a process diagram of the preparation of ultra-thin lithium strip preform products.

Figure 5 is a process diagram of the preparation of composite anode products.

FIG. 6 is a diagram of the negative electrode of the battery after pre-lithiation and disassembly using the ultra-thin lithium strip preform in Example 1. FIG.

Figure 7 is a diagram of the negative electrode of the battery after prelithiation and disassembly using an ultra-thin lithium strip with a relative thickness of 2.6 microns without micropores.

Figure 8 is a diagram of the negative electrode of the battery after pre-lithiation and disassembly using a 5 micron ultra-thin lithium foil.

detailed description

In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not used to limit the present invention.

Fig. 1 and Fig. 2 show the product schematic diagram of the ultra-thin lithium strip preform of the present invention. As shown in Figure 1 and Figure 2, the ultra-thin metal lithium strips L and the supporting layer P are attached together; there is a certain distance between adjacent ultra-thin lithium strips.

The preparation method of the ultra-thin lithium strip preform is described in detail with reference to FIG. 4. The coil of metal lithium belt L is mounted on the lithium belt unwinding shaft 10, passes through the support roller 101 and enters the roll 13. The supporting layer P coil is mounted on the unwinding shaft 11 and is attached to the lower side of the lithium ribbon L (in the upper direction in the figure) and enters the roll 13 together with the lithium ribbon L. The bump release base material P2 is mounted on the unwinding shaft 12, and is attached to the upper side of the lithium belt L (in the upper direction in the figure) after passing through the support roller 121, and enters the roll 13 together with the lithium belt L and the supporting layer P. After rolling by the roller 13, the bump release substrate P2 is peeled off to obtain the ultra-thin lithium foil supported by the supporting layer P; then a scraper 16 (assisted by the support roller 15) is used to remove part of the metal lithium to form an ultra-thin lithium strip prefabricated Pieces PL. After passing through the rollers, the bump release substrate P2 passes through the support roller 141 and then is wound by the winding shaft 14; the prepared ultra-thin lithium strip preform PL is wound by the winding shaft 17.

A method for preparing the bump release substrate P2 is: coating a common substrate with release material to prepare a film substrate with release function; then use a mechanical method on the side where the release material is not coated Apply pressure to make a number of dot-like protrusions appear on the side coated with the anti-sticking material. After the dot-shaped protrusions enter the rolls together with the lithium belt and the supporting layer, micropores will be formed on the positions corresponding to the protrusions on the lithium belt. Therefore, the diameter, height and distribution density of the dot-shaped protrusions determine the diameter and porosity of the micropores in the ultra-thin lithium rod preform. The mechanical method for preparing the protrusions can be: sandblasting or rolling. The sandblasting process is as follows: use pressure spraying fine particles on the side of the prepared release film substrate that is not coated with the release material, so that the particles are hit to form pits on the surface of the substrate, and the corresponding release material is coated. Bumps are formed on one side; the density of bumps on the substrate is controlled by controlling the moving speed of the release film substrate and the amount of fine particles sprayed. The method of rolling is: use at least one roll with bumps to roll the anti-adhesive substrate, so that the anti-adhesive substrate is coated with anti-adhesive material on the side of the anti-adhesive material, the diameter of the bumps The sum density is determined by the diameter and distribution density of the bumps on the roll.

Figure 3 shows a schematic diagram of a composite negative electrode provided by the present invention. The composite negative electrode includes a current collector C, a negative electrode coating N, and an ultra-thin lithium strip L compounded on the side of the negative electrode coating N away from the current collector C.

The preparation method of the composite negative electrode is described in detail with reference to FIG. 5. The negative electrode assembly CN coated with the negative electrode coating N is mounted on the unwinding shaft 22 for unwinding, so that the side of the negative electrode coating is opposite to the ultra-thin lithium strip preform PL. The ultra-thin lithium strip preform PL enters the rolling mill after being unrolled by the unwinding shaft 20, so that the side of the ultra-thin lithium strip preform PL compounded with the ultra-thin lithium strip L is arranged opposite to the negative electrode assembly CN. The ultra-thin lithium strip preform PL and the negative electrode assembly CN enter the rolling mill together. After the pressure composite transfer by the roller 23 and the roller 24, the ultra-thin lithium strip L on the ultra-thin lithium strip preform PL is transferred to the negative electrode assembly CN, thus forming The composite negative electrode CNL of the present invention; the ultra-thin lithium strip preform PL after removing the ultra-thin lithium strip, only the supporting layer P remains. The supporting layer at the exit end of the rolling mill is reeled by the winding shaft 26; the composite negative electrode CNL prepared at the exit end of the rolling mill is wound by the winding shaft 27 after passing through the supporting roller 25.

Hereinafter, using the above-mentioned process method, the present invention will be explained more specifically through examples. The various product parameters and process conditions used in the following embodiments are all typical examples and should not be construed as limiting the present invention.

Example 1: Preparation of an ultra-thin lithium strip preform with a support layer made of PET using lithium tape as a raw material.

Use a metal lithium tape with a width of 100mm and a thickness of 30μm as the raw material; the thickness of the bump release film made of PET is 60μm, the width is 120mm, the peeling force is 5-10g, the diameter of the bump is 30-100μm, and the area ratio of the bump is about It is 5%; the supporting layer used is a PET film with a release layer, with a thickness of 30 μm, a width of 120 mm, and a peeling force of 10-20 g.

Referring to FIG. 4, the coil of lithium metal strip L is mounted on the lithium strip unwinding shaft 10, and the lithium metal strip L passes through the support roller 101 and then enters the roll. The coil of the supporting layer P is installed on the unwinding shaft 11 so that the side of the supporting layer P with the anti-adhesion layer is arranged opposite to the metal lithium belt L, and directly enters the roll after unwinding. The bump release film P2 is installed on the unwinding shaft 12, and the side with the bumps and the release layer is opposite to the metal lithium belt L. The bump release film P2 passes through the support roller 121 and then interacts with the metal lithium belt L and the supporting layer. P enters the roll 13 together. The rolling pressure is controlled to 30 MPa for rolling; after rolling, the bump anti-adhesive film P2 is separated, and the separated bump anti-adhesive film P2 bypasses the support roller 141 and then the winding shaft 14 completes the winding process; after the separation, the super The preform formed by the thin lithium foil and the supporting layer uses a scraper 16 to remove half of the strip metal lithium with an interval of 3mm to form an ultra-thin lithium strip preform PL. The ultra-thin lithium strip preform is reeled by a reel 17 .

The total thickness of the ultra-thin lithium strip preform PL obtained above was measured to be about 35.2μm, the thickness of the pure lithium layer was about 5.2μm after the thickness of the supporting layer was removed; the pore diameter was about 30-100μm, and the porosity was 4.5%. The width of the lithium strip is 2 mm, the distance between adjacent lithium strips is 2 mm, and the relative thickness of the ultra-thin lithium strip preform PL is 2.6 μm.

Example 2: Preparation of an ultra-thin lithium strip preform with a copper foil as the supporting layer using lithium tape as a raw material.

Use a metal lithium tape with a width of 80mm and a thickness of 30μm as the raw material; the thickness of the bump release film made of PET is 60μm, the width is 100mm, the peel force is 3-5g, the diameter of the bump is 30-100μm, and the area ratio of the bump is about It is 5%; the supporting layer used is a copper foil with a thickness of 8 μm and a width of 120 mm.

Referring to FIG. 4, the coil of lithium metal strip L is mounted on the lithium strip unwinding shaft 10, and the lithium metal strip L passes through the support roller 101 and then enters the roll. The copper foil P coil is installed on the unwinding shaft 11, and directly enters the roll after unwinding. The bump release film P2 is installed on the unwinding shaft 12, and the side with the bumps and the release layer is opposite to the lithium metal tape L. The bump release film P2 passes through the support roller 121 and then interacts with the lithium metal tape L and the copper foil P. Enter the roll 13 together. The rolling pressure is controlled to 10MPa for rolling; after rolling, the bump anti-adhesive film P2 is separated, and the separated bump anti-adhesive film P2 bypasses the supporting roller 141 and then the winding shaft 14 completes the winding process; The preform formed of thin lithium foil and copper foil is then used to remove part of the strip-shaped metal lithium using a scraper 16 to form an ultra-thin lithium strip preform PL, which is wound using a winding shaft 17.

The total thickness of the ultra-thin lithium strip preform PL obtained above is measured to be about 37.2μm. After removing the thickness of the copper foil, the thickness of the pure lithium layer is about 29.2μm; the pore diameter is about 30-100μm, and the porosity is 4.5%. The strip width is 2mm, and the distance between adjacent lithium strips is 2mm.

Example 3: The ultra-thin lithium strip preform prepared in Example 1 was used as a raw material to prepare an ultra-thin lithium strip preform whose supporting layer was made of copper foil.

The ultra-thin lithium strip preform prepared in Example 1 was used as a raw material; the supporting layer used was a copper foil with a thickness of 8 μm and a width of 120 mm.

5, the ultra-thin lithium strip preform PL is mounted on the unwinding shaft 20 so that the side with the ultra-thin lithium strip is opposite to the copper foil, and the ultra-thin lithium strip preform PL enters the roll after passing through the support roller 21 . The copper foil coil material CN is installed on the unwinding shaft 22, and directly enters the roll after unwinding. The rolling pressure is controlled to 8MPa for rolling; after rolling, the original supporting layer P of the ultra-thin lithium strip preform PL is separated, and the separated supporting layer P is completed by the winding shaft 26 to complete the winding process; the super thin formed after the separation The new preform formed of thin lithium strips and copper foil is wound using a winding shaft 17.

The total thickness of the new ultra-thin lithium strip preform obtained above is about 13.1μm. After removing the thickness of the copper foil, the thickness of the pure lithium layer is about 5.1μm; the pore diameter is about 30-100μm, and the porosity is 4.5%. The width of the lithium strip is 2mm, and the distance between adjacent lithium strips is 2mm.

Example 4: Using the ultra-thin lithium strip preform prepared in Example 1 as a raw material, a composite negative electrode was prepared.

Using the ultra-thin lithium strip preform prepared in Example 1 as the raw material, the total thickness is about 35.2 μm, the supporting layer width is 120 mm, and the ultra-thin lithium strip width is 100 mm; the total thickness of the negative electrode assembly used is about 100 μm, and the total width is 120 mm. The coating width is 100mm.

5, the ultra-thin lithium strip preform PL is mounted on the unwinding shaft 20, and the ultra-thin lithium strip preform PL enters the roll after passing through the support roller 21. The CN coil of the negative electrode assembly is mounted on the unwinding shaft 22, and directly enters the roll after unwinding. The side of the ultra-thin lithium strip preform PL provided with the ultra-thin lithium strip is opposite to the side provided with the negative electrode coating on the negative electrode assembly CN. The rolling pressure is controlled to 8MPa for rolling; after rolling, the original supporting layer P of the ultra-thin lithium strip preform PL is separated, and the separated supporting layer P is completed by the winding shaft 26 to complete the winding process; the ultra-thin lithium after separation The strip is compounded with the negative electrode assembly CN to obtain a composite negative electrode CNL, and the formed composite negative electrode CNL is wound using a winding shaft 17.

The total thickness of the composite negative electrode CNL obtained above was measured to be about 105.1 μm.

The above embodiments and preparation process are all for describing the intention of the present invention more clearly, and the preparation process and equipment can be simplified, complicated or improved according to specific requirements on this basis. For example, by improving the equipment, two or more rolls of ultra-thin lithium strip preforms can be produced at the same time. For another example, by improving and integrating the preparation process and method of the composite negative electrode, it can be integrated and connected with lithium battery negative electrode coating or other related equipment. These similar improvements and integrations should be regarded as part of the present invention.

The ultra-thin lithium strip preform and the composite negative electrode provided by the present invention enable the adjacent ultra-thin lithium strips to have spacing by removing materials, thereby reducing the relative thickness, achieving the purpose of more accurately controlling the lithium load per unit area, and achieving It meets the requirement of accurately controlling the amount of lithium replenishment at the negative electrode of the battery.

The actual effect of the microporous ultra-thin lithium strip preform of the present invention will be described in detail below with reference to specific embodiments.

Example 5: Prepare a battery by prelithiating the negative electrode with an ultra-thin lithium strip with a relative thickness of 2.6 microns with micropores

With lithium cobalt oxide as the positive electrode, the thickness of the active layer is 80 microns; the separator is a polypropylene microporous film (Celgard2500); the electrolyte is LiPF ₆ -EC:DMCC (volume ratio 1:1, EC: ethylene carbonate, DMC: carbonic acid) Dimethyl, Dongguan Shanshan Battery Material Co., Ltd.), electrolyte additive: 10wt% FEC (FEC: fluoroethylene carbonate, Rongcheng Qingmu Advanced Materials Co., Ltd.); negative electrode is silicon carbon negative electrode, active layer thickness is 50 microns , Composite the ultra-thin lithium strip preform prepared in Example 1 on its surface. A lamination process is used to prepare a soft pack battery with a capacity of 1Ah. The composed battery cells are put aside for 12h, and the current of 0.05C is used for volumetric formation.

Comparative Example 1: Prepare a battery by prelithiating the negative electrode with an ultra-thin lithium strip with a relative thickness of 2.5 microns

With lithium cobalt oxide as the positive electrode, the thickness of the active layer is 80 microns; the separator is a polypropylene microporous film (Celgard2500); the electrolyte is LiPF ₆ -EC:DMCC (volume ratio 1:1, EC: ethylene carbonate, DMC: carbonic acid) Dimethyl, Dongguan Shanshan Battery Material Co., Ltd.), electrolyte additive: 10wt% FEC (FEC: fluoroethylene carbonate, Rongcheng Qingmu Advanced Materials Co., Ltd.); negative electrode is silicon carbon negative electrode, active layer thickness is 50 microns , The composite thickness on its surface is an ultra-thin lithium strip with a relative thickness of 2.6 microns (the preparation method is the same as that in Example 1, except that the anti-adhesive film used in the preparation does not have bumps). A lamination process is used to prepare a soft pack battery with a capacity of 1Ah. The composed battery cells are put aside for 12h, and the current of 0.05C is used for volumetric formation.

Comparative Example 2: Prepare a battery by prelithiating the negative electrode with a 5 micron ultra-thin lithium tape

With lithium cobalt oxide as the positive electrode, the thickness of the active layer is 80 microns; the separator is a polypropylene microporous film (Celgard2500); the electrolyte is LiPF6-EC:DMCC (volume ratio 1:1, EC: ethylene carbonate, DMC: dicarbonate) Methyl ester, Dongguan Shanshan Battery Material Co., Ltd.), electrolyte additive: 10wt% FEC (FEC: fluoroethylene carbonate, Rongcheng Qingmu Advanced Materials Co., Ltd.); the negative electrode is a silicon carbon negative electrode, the thickness of the active layer is 50 microns, An ultra-thin lithium belt with a thickness of 5 microns is compounded on its surface (the preparation method is the same as that of Comparative Example 1, except that the material is not removed with a scraper after the ultra-thin lithium belt is prepared). A lamination process is used to prepare a soft pack battery with a capacity of 1Ah. The composed battery cells are put aside for 12h, and the current of 0.05C is used for volumetric formation.

The batteries of Example 5 and Comparative Example 1 and Comparative Example 2 were disassembled, and the negative electrode of the battery after disassembly is shown in Figure 6-8. It can be seen that the negative electrode pre-lithiated using the ultra-thin lithium strip preform prepared in Example 1, did not observe the presence of metallic lithium on the surface; the ultra-thin lithium strip with a relative thickness of 2.6 microns without micropores was used for pre-lithiation. There is a small amount of metal lithium on the surface of the negative electrode; the negative electrode pre-lithiated with 5 micron ultra-thin lithium tape still has obvious metal lithium on the surface. If the content is too high, all lithium cannot be consumed.

It should be understood that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in this invention. Within the scope of protection of the invention.

Claims

An ultra-thin lithium strip preform, characterized in that the preform has:

The supporting layer, the supporting layer is a strip with a width of 3-2000mm; and

A plurality of ultra-thin lithium bars located on at least one surface of the supporting layer and compounded with the supporting layer, the plurality of ultra-thin lithium bars extending along the length direction of the supporting layer and in There are two or more ultra-thin lithium strips separated from each other in the width direction of the supporting layer, the width of each ultra-thin lithium strip is in the range of 1-200mm, and the thickness of each ultra-thin lithium strip is the same, in the range of 0.5-15 μm A single ultra-thin lithium strip has through holes with a pore diameter of 5-1000 μm, the porosity is less than 50%, and the distance between adjacent ultra-thin lithium strips is 0.5-10 mm.
The ultra-thin lithium strip preform according to claim 1, wherein the single ultra-thin lithium strip satisfies at least one of the following conditions:

The aperture of the through hole is 100-500 microns;

The porosity is 0.5-10%, preferably 1%-5%;

The width is 1-50mm;

The thickness is 1-10 microns.
The ultra-thin lithium strip preform according to claim 1, wherein the ultra-thin lithium strip is a metal lithium or lithium alloy product, preferably, the lithium alloy includes lithium aluminum alloy, lithium magnesium alloy, lithium boron alloy, Lithium indium alloy, lithium silicon alloy.
The ultra-thin lithium strip preform according to claim 1, wherein the supporting layer is a single layer or multiple layers made of the following materials, and the materials are selected from:

Polymers, including polyolefins (polyethylene, polypropylene, polystyrene), polyester;

Inorganic oxides, including aluminum oxide;

Inorganic conductors, including graphite, carbon nanotubes, graphene;

Metals, including copper and aluminum.
A composite negative electrode, characterized in that: the composite negative electrode comprises:

Current collector

The negative electrode coating on the surface of the current collector; and

The ultra-thin lithium strip compounded on the side of the negative electrode coating away from the current collector,

The ultra-thin lithium strip is obtained by removing the supporting layer of the ultra-thin lithium strip preform according to any one of claims 1-4.
A method for preparing the ultra-thin lithium strip preform according to any one of claims 1 to 4, characterized in that: the method is a roll-to-roll continuous production method, using a metal lithium strip with a thickness of 5 to 200 μm The material is the raw material, one side is attached to the bump release base material, and the other side is attached to the supporting layer and then enters the roll together. After rolling, the bump release base material and the metal lithium tape are peeled off to obtain the support of the supporting layer. Ultra-thin lithium belt, and then remove part of the metal lithium belt from the ultra-thin lithium belt supported by the belt supporting layer to form an ultra-thin lithium strip with intervals to obtain the ultra-thin lithium strip preform.
The method according to claim 6, wherein the surface of the bump release substrate in contact with the metal lithium is provided with a release coating, and the bump release film is provided with a number of uneven dot-shaped protrusions.
The method according to claim 6, wherein the bump release substrate is a single-layer or multi-layer film prepared from the following materials, and the materials are selected from:

Polymers, including polyolefins (polyethylene, polypropylene, polystyrene), polyester;

Metals, including steel, aluminum, and copper.
8. The method according to claim 7, wherein the process of providing the bump release substrate with a plurality of dot-shaped protrusions includes sandblasting on the back of the substrate and a mechanical rolling process.
8. The method according to claim 6, wherein a scraper is used for scraping to remove part of the metallic lithium ribbon from the ultra-thin lithium ribbon supported by the tape supporting layer to form an ultra-thin lithium strip with intervals.
The method according to claim 10, wherein the scraper is a flat scraper or a rotary scraper.
A method for preparing the composite negative electrode according to claim 5, characterized in that: the method is a roll-to-roll continuous production method, and the ultra-thin lithium strip preform according to any one of claims 1-4 is used as Raw material, the ultra-thin lithium strip is transferred from the support to the negative electrode coating through the method of roller pressure composite transfer.
A battery comprising a positive electrode and a negative electrode arranged oppositely, wherein the negative electrode comprises the ultra-thin lithium strip preform according to any one of claims 1 to 4 or the composite negative electrode according to claim 5.
The battery according to claim 13, wherein the battery comprises a lithium metal battery, an all-solid-state battery, a lithium sulfur battery, or a lithium air battery.