Battery pre-lithiation method

Abstract

The present invention provides a method for prelithiation of a battery, which includes the following steps: Step 1: provide a lithium source half-cell, the lithium source half-cell including a single electrode, an electrolyte, and a housing sealing the single electrode and the electrolyte, the housing being provided with an external conduit communicating with the fluid inside the housing, and a microfluidic pump controlling the flow of the fluid in the external conduit; Step 2: provide a battery to be prelithiated, and drill a hole on the battery to be prelithiated to form a prelithiation channel; Step 3: connect the external conduit to the prelithiation channel, turn on the microfluidic pump, and realize the circulation between the lithium source half-cell and the electrolyte of the battery to be prelithiated; Step 4: connect the electrode of the lithium source half-cell and the negative electrode of the battery to be prelithiated to an external power source, and prelithiate the battery to be prelithiated; Step 5: after prelithiation, remove the external conduit, seal the prelithiation channel, and obtain a prelithiated battery. The prelithiation method of the present invention is simple to operate, has high safety, and is highly applicable.

Description

[Technical Field]

[0001] The present invention relates to the field of lithium battery technology, and in particular to a method for prelithiation of batteries. [Background technology]

[0002] Lithium-ion batteries (LIBs) have become a widely applied electrochemical energy storage system due to their high energy density, high operating voltage, and no memory effect. However, the commonly used graphite anode has a relatively low capacity (372 mAh g -1 ), which means they cannot fully meet the market demand for high-energy density batteries. Researchers are seeking new anode materials with advantages such as an ideal potential range, higher capacity, excellent rate characteristics, and long cycle life. However, these materials all suffer from the drawback of large loss of initial active lithium. Therefore, research into prelithiation technology has become an important research direction.

[0003] Conventional prelithiation methods include adding a lithium source to the negative electrode, adding a lithium source to the positive electrode, the sacrificial electrode method, and adding an additional lithium source. The method of adding a lithium source to the negative electrode requires strict conditions, inevitably increasing manufacturing costs. Furthermore, negative electrodes with pre-loaded lithium present safety issues due to their high reactivity, making large-scale application difficult. After releasing lithium ions, the lithium source material added to the positive electrode becomes inactive and, ultimately, insulating, which is detrimental to improving the overall battery energy density. The additional lithium source added during the negative electrode paste homogenization process is typically stabilized lithium metal powder (SLMP) manufactured by FMC Corporation (USA). However, this method is prone to short circuits, and lithium metal powder poses significant safety risks. While the sacrificial electrode method is relatively practical, it requires an additional metal foil assembly step during battery assembly. During prelithiation, a working voltage is applied between the metallic lithium electrode and the negative electrode, and the metallic lithium electrode does not contribute to battery operation during normal battery operation. After prelithiation is complete, the metallic lithium electrode is not removed, resulting in a decrease in the energy density of the battery.

[0004] Therefore, there is a need to provide a battery pre-lithiation method that is simple to operate, highly safe, and highly applicable. Summary of the Invention [Problem to be solved by the invention]

[0005] In contrast to the shortcomings of the prior art, the present invention provides a prelithiation method that is safer and more applicable. [Means for solving the problem]

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for prelithiating a battery, comprising the steps of: Step 1: Providing a lithium source half-cell, the lithium source half-cell including a single electrode, an electrolyte, and a housing sealing the single electrode and the electrolyte, the housing being provided with an external conduit communicating with the fluid inside the housing and a microfluidic pump controlling the flow of the fluid in the external conduit, the electrode active material of the single electrode being a lithium-containing metal or a lithium-containing oxide. The lithium source half-cell housing is provided with two external conduits. ; Step 2: providing a battery to be prelithiated, and drilling holes on the battery to be prelithiated to form prelithiated channels; Step 3: Connect the external conduit to the prelithiation channel, and turn on the microfluidic pump to realize circulation between the lithium source half-cell and the electrolyte of the battery to be prelithiated; Step 4: connecting the electrode of the lithium source half-cell and the negative electrode of the battery to be prelithiated to an external power source, and prelithiating the battery to be prelithiated; Step 5: After prelithiation, remove the external conduit and seal the prelithiation channel to obtain a prelithiated battery.

[0008] In some embodiments, the lithium-containing oxide includes lithium iron phosphate, lithium iron manganese phosphate, lithium titanate, lithium cobalt oxide, lithium manganate (LiMnO), LiMnO, lithium nickel oxide, lithium nickel-manganese oxide, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, and perlithiation materials, and the lithium-containing metal includes metallic lithium and an alloy of lithium with at least one element selected from Ag, Al, Au, Ba, Be, Bi, B, C, Ca, Cd, Co, Cr, Cs, Fe, Ga, Ge, Hf, Hg, In, Ir, K, Mg, Mn, Mo, N, Na, Nb, Ni, Pt, Pu, Rb, Rh, S, Se, Si, Sn, Sr, Ta, Te, Ti, V, Y, Zn, Zr, Pb, Pd, Sb, and Cu.

[0009] In some embodiments, the prelithiated channel is located at the top and / or bottom of the battery and has a channel diameter of 1 mm to 10 mm.

[0010] In some embodiments, In step 4 The prelithium The transformation , controlled by adjusting the inter-electrode current, environmental temperature, prelithiation time and the rotation speed of the microfluidic pump.

[0011] In some embodiments, the current applied in step 4 is 1 mA to 5000 mA.

[0012] In some embodiments, the prelithiation temperature is between 35°C and 65°C. be .

[0013] In some embodiments, the prelithiation time is from 1 hour to 240 hours.

[0014] In some embodiments, the rotational speed of the microfluidic pump is between 1 rpm and 30 rpm.

[0015] In some embodiments, the electrolytes in the lithium source half-cell and the battery to be prelithiated are the same or different (preferably different), and are each selected from an ester-based electrolyte or an ether-based electrolyte.

[0016] In some embodiments, the ester-based electrolyte includes ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and the like.

[0017] In some embodiments, the ether-based electrolyte includes diphenyl ether, ethylene glycol bispropionitrile ether, ethylene glycol dimethyl ether (DME), dioxolane (DOL), methyl nonafluoro-n-butyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and the like.

[0018] In some embodiments, the negative electrode active material of the battery to be prelithiated includes a carbon material (such as graphite, hard carbon, soft carbon, or graphene), silicon, silicon monoxide, lithium titanate, a metal-organic framework material, a covalent organic framework material, or a composite thereof. [Effects of the Invention]

[0020] The prelithiation method of the present invention has at least the following advantages. 1. The operation process of the prelithiation method is simple and convenient. 2. The materials used in the prelithiation process are stable and safe. 3. The pre-lithiation method employs an external lithium source, which is equivalent to "infusing" the battery to be pre-lithiated, and has strong applicability. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of the prelithiation process using a lithium source half-cell in the present invention. [Figure 2] FIG. 2 is a graph showing the charge / discharge capacity of the battery D1 of Example 1 of the present invention. [Figure 3] FIG. 3 is a graph showing the charge / discharge capacity of the battery D2 of Example 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] As shown in FIG. 1, the prelithiation method of the present invention first provides a lithium source half-cell. The lithium source half-cell includes a single electrode 2, an electrolyte 3, and a housing (sealing material) 1 that seals the single electrode and the electrolyte. The housing 1 is provided with an external conduit 4 that communicates with the internal fluid of the housing and a microfluidic pump 5 that controls the flow of fluid through the external conduit. Next, a prelithiation channel is drilled at the upper and / or lower ends of the battery 6 to be prelithiated, and the lithium source half-cell and the battery are connected by the external conduit. After the connection points of the external conduit are sealed, the lithium source half-cell and the battery to be prelithiated become a single communicating device, and the flow of electrolyte between the batteries is controlled by controlling the microfluidic pump, thereby achieving electrolyte circulation. The electrodes of the lithium source half-cell and the negative electrode of the battery to be prelithiated are connected to an external power source 8 by lead wires 7, allowing the battery to be prelithiated.

[0023] Fabrication of lithium source half-cell The lithium-copper composite tape is used as the single electrode of the lithium source half-cell, and a common ester-based electrolyte (specifically, the lithium salt is lithium hexafluorophosphate and the solvent is ethylene carbonate) is used as the electrolyte of the lithium source half-cell. An aluminum plastic film is used to seal the single electrode and the electrolyte, and an external conduit is provided on the aluminum plastic film.

[0024] Preparation of positive electrode sheet Lithium cobalt oxide is used as the positive electrode active material, polyvinylidene fluoride (PVDF) as the binder, and conductive carbon (SP) as the conductive agent. These are dissolved in N-methylpyrrolidone (NMP) in a ratio of positive electrode active material:PVDF:SP=95:3:2 (mass ratio), and the mixture is stirred uniformly to form a positive electrode paste. This is then uniformly applied to copper foil and dried to obtain a positive electrode sheet.

[0025] Preparation of lithium-refilled negative electrode sheet: Conductive carbon (SP) is used as the electronic conductive material, silicon-carbon composite material (silicon monoxide:carbon = 55:45 (mass ratio), silicon-carbon composite material has a low initial charge / discharge efficiency of about 65%) as the ion conductive material, and carboxymethyl cellulose (CMC) as the polymer. These materials are dissolved in deionized water and stirred uniformly to form a paste, with a mass ratio of SP:silicon-carbon composite:CMC = 8:85:7. The paste is then uniformly spread on copper foil and dried. The moisture content of the negative electrode sheet is less than 200 ppm. After hot pressing and slicing, a negative electrode sheet to be replenished with lithium is obtained.

[0026] The positive electrode sheet, the negative electrode sheet to be refilled with lithium, and a ceramic-coated separator are stacked together. The stacking process must be carried out in a dry room with a dew point of -50°C. After stacking is complete, the cell is placed in an aluminum plastic bag and the sides are sealed. An electrolyte (lithium hexafluorophosphate (LiPF6) concentration of 1 mol / L, solvent ratio of ethylene carbonate: ethyl methyl carbonate: diethyl carbonate = 1:1:1) is poured in, and the top is sealed to obtain the battery to be prelithiated. Six batteries are assembled and numbered D1 to D6, respectively.

[0027] Example 1 Take the battery D1 and perform a charge / discharge test, record the charge capacity and discharge capacity of the battery, and calculate the coulomb efficiency of the battery.

[0028] Example 2 Taking battery D2, prelithiation channels were drilled at the top and bottom of the battery and connected to the lithium source half-cell. The microfluidic pump was turned on to circulate the electrolyte between the two batteries. The current between the lithium source half-cell and the negative electrode of the battery to be prelithiated was 50 mA, the ambient temperature was 45°C, the microfluidic pump rotation speed was 10 rpm, and the prelithiation time was 60 min.

[0029] Example 3 Taking battery D3, prelithiation channels were drilled at the top and bottom of the battery and connected to the lithium source half-cell. The microfluidic pump was turned on to circulate the electrolyte between the two batteries. The current between the lithium source half-cell and the negative electrode of the battery to be prelithiated was 50 mA, the ambient temperature was 45°C, the microfluidic pump rotation speed was 10 rpm, and the prelithiation time was 120 min.

[0030] Example 4 Taking battery D4, prelithiation channels were drilled at the top and bottom of the battery and connected to the lithium source half-cell. The microfluidic pump was turned on to circulate the electrolyte between the two batteries. The current between the lithium source half-cell and the negative electrode of the battery to be prelithiated was 50 mA, the ambient temperature was 45°C, the microfluidic pump rotation speed was 20 rpm, and the prelithiation time was 60 min.

[0031] Example 5 Taking battery D5, prelithiation channels were drilled at the top and bottom of the battery and connected to the lithium source half-cell. The microfluidic pump was turned on to circulate the electrolyte between the two batteries. The current between the lithium source half-cell and the negative electrode of the battery to be prelithiated was 50 mA, the ambient temperature was 55°C, the microfluidic pump rotation speed was 10 rpm, and the prelithiation time was 60 min.

[0032] Example 6 Taking battery D6, prelithiation channels were drilled at the top and bottom of the battery and connected to the lithium source half-cell. The microfluidic pump was turned on to circulate the electrolyte between the two batteries. The current between the lithium source half-cell and the negative electrode of the battery to be prelithiated was 200 mA, the ambient temperature was 45°C, the microfluidic pump rotation speed was 10 rpm, and the prelithiation time was 10 min.

[0033] The prelithiation conditions for the batteries of each example were statistically calculated and shown in Table 1, and the coulombic efficiency of the batteries of each example was calculated.

[0034] [Table 1]

[0035] As can be seen from Table 1, the Coulombic efficiency of Battery D1, which was not pre-lithiated, was 64.7%. The charge / discharge capacity graph of Battery D1 is shown in Figure 2. As can be seen from the graph, there was a large difference between the charge and discharge capacities of Battery D1. This is because the lithium ions in the positive electrode were consumed during the first discharge due to the formation of a solid electrolyte film on the negative electrode surface. After pre-lithiation, the discharge capacity of Battery D2 was significantly improved. The charge / discharge graph of Battery D2 is shown in Figure 3. As can be seen from the graph, after pre-lithiation, Battery D2 had a charge capacity of 290 mAh, a discharge capacity of 238 mAh, and a Coulombic efficiency of 81%. This indicates that pre-lithiation replenished the lithium ions consumed during the first discharge due to the formation of a solid electrolyte film on the negative electrode surface, improving the Coulombic efficiency of Battery D2 and demonstrating the effectiveness of the pre-lithiation method. After the pre-lithiation time was extended from 60 min to 120 min, the coulombic efficiency of battery D3 was 100%, indicating that under these pre-lithiation conditions, the lithium ions consumed during the first discharge of battery D3 were completely replenished, and the first charge / discharge of the battery no longer consumed lithium ions in the positive electrode material.

[0036] Increasing the rotational speed of the microfluidic pump and the ambient temperature contribute less to improving the Coulombic efficiency than extending the prelithiation time. This is mainly because increasing the rotational speed of the microfluidic pump and the ambient temperature favors the diffusion of lithium ions in the electrolyte, but makes little contribution to battery capacity. As can be seen from battery D6, after increasing the prelithiation current, the prelithiation of the battery can be completed in a short time.

[0037] In the examples of the present invention, the prelithiation method according to the present invention is described in detail in connection with specific positive and negative electrode active materials, current collectors, electrolytes, separators, binders, and conductive agents, but it should be understood that these are merely descriptions to satisfy legal requirements, and the present invention is not limited to the examples described above. Those skilled in the art can complete the replication of the prelithiation method by appropriate operations based on the disclosure and teachings of the specification.

[0038] Based on the disclosure and teachings of the above specification, a person skilled in the art to which the present invention pertains can appropriately change and modify the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and any modifications and variations to the present invention should also be included within the scope of the claims of the present invention. Although some specific terms are used in this specification, these terms are for the convenience of explanation and do not impose any limitations on the present invention.

Claims

1. A method for prelithiating a battery, comprising the steps of: Step 1: Providing a lithium source half-cell, the lithium source half-cell including a single electrode, an electrolyte, and a housing sealing the single electrode and the electrolyte, the housing being provided with an external conduit communicating with the fluid inside the housing and a microfluidic pump controlling the flow of the fluid in the external conduit, the electrode active material of the single electrode being a lithium-containing metal or a lithium-containing oxide, the housing of the lithium source half-cell being provided with two external conduits; Step 2: Providing a battery to be prelithiated, and drilling holes on the battery to be prelithiated to form prelithiated channels; Step 3: Connect the external conduit to the prelithiation channel and turn on the microfluidic pump to achieve circulation between the lithium source half-cell and the electrolyte of the battery to be prelithiated; Step 4: Connecting the electrode of the lithium source half-cell and the negative electrode of the battery to be prelithiated to an external power source, and prelithiating the battery to be prelithiated; Step 5: After prelithiation, the external conduit is removed and the prelithiation channel is sealed to obtain a prelithiated battery.

2. The lithium-containing oxides include lithium iron phosphate, lithium iron manganese phosphate, lithium titanate, lithium cobalt oxide, and lithium manganese oxide (LiMn ２ O ４ ), LiMnO ２ , lithium nickel oxide, lithium nickel-manganese oxide, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, and perlithiation materials, and the lithium-containing metal includes metallic lithium and an alloy of lithium and at least one element selected from the group consisting of Ag, Al, Au, Ba, Be, Bi, B, C, Ca, Cd, Co, Cr, Cs, Fe, Ga, Ge, Hf, Hg, In, Ir, K, Mg, Mn, Mo, N, Na, Nb, Ni, Pt, Pu, Rb, Rh, S, Se, Si, Sn, Sr, Ta, Te, Ti, V, Y, Zn, Zr, Pb, Pd, Sb, and Cu.

3. 2. The method for pre-lithiation of a battery according to claim 1, wherein the pre-lithiation channel is located at the upper end and / or the lower end of the battery, and the channel diameter is 1 mm to 10 mm.

4. A battery prelithiation method as described in claim 1, characterized in that in step 4, the prelithiation is controlled by adjusting the inter-electrode current, ambient temperature, prelithiation time and rotation speed of the microfluidic pump.

5. 5. The method for pre-lithiation of a battery according to claim 4, wherein the current applied in step 4 is 1 mA to 5000 mA.

6. 5. The method for prelithiation of a battery according to claim 4, wherein the prelithiation temperature is 35° C. to 65° C., and the prelithiation time is 1 hour to 240 hours.

7. 5. The method for prelithiation of a battery according to claim 4, wherein the rotation speed of the microfluidic pump is 1 rpm to 30 rpm.

8. 2. The method for prelithiation of a battery according to claim 1, wherein the electrolytes in the lithium source half-cell and the battery to be prelithiated are the same or different, and are selected from an ester-based electrolyte and an ether-based electrolyte, respectively.

9. The battery prelithiation method according to claim 1, characterized in that the negative electrode active material of the battery to be prelithiated includes a carbon material, silicon, silicon monoxide, lithium titanate, a metal-organic framework material, a covalent organic framework material, and a composite thereof.

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