Liquid injection method of single battery

Abstract

Some embodiments of the present application provide a liquid injection method for a battery cell, comprising: placing a roll core into a cavity in a housing, the roll core being formed by winding a negative pole piece, a positive pole piece and a diaphragm; the negative pressure process comprises the steps that the cavity is vacuumized to the first pressure P1, the electrolyte is injected, the pressure is maintained for the first time t1, P1 is larger than or equal to-100 kpa and smaller than or equal to-80 kpa, and t1 is larger than or equal to 10 s and smaller than or equal to 100 s; in the positive pressure process, the cavity is pressurized to second pressure P2, pressure maintaining is conducted for second time t2, P2 is larger than or equal to 800 kpa, and t2 is larger than or equal to 390 s and smaller than or equal to 500 s; and circulating the negative pressure process and the positive pressure process. According to the invention, the positive pressure time of a single cycle is prolonged, the negative pressure time of the single cycle is shortened, the time distribution of the liquid injection process is optimized, and the positive pressure process time and the negative pressure process time are reasonably distributed, so that the electrolyte can fully infiltrate the pole piece.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to a method for injecting electrolyte into a battery cell. BACKGROUND

[0002] With the rapid development of battery cells in the new energy field, the requirements for the energy density and fast charging capability of the battery become higher and higher, and thus the requirements for the electrolyte injection process of the battery also become higher and higher. However, the existing electrolyte injection process has a series of problems such as difficulty in fully infiltrating the electrolyte into the electrode. SUMMARY

[0003] Some embodiments of the present application provide a method for injecting electrolyte into a battery cell, comprising: placing a roll core into a cavity in a shell, wherein the roll core is wound by a negative electrode sheet, a positive electrode sheet and a separator; and injecting electrolyte into the cavity, comprising: a negative pressure process: vacuumizing the cavity to a first pressure P1, injecting the electrolyte, and maintaining pressure for a first time t1, wherein -100kpa≤P1≤-80kpa, 10s≤t1≤100s; a positive pressure process: pressurizing the cavity to a second pressure P2, and maintaining pressure for a second time t2, wherein P2≥800kpa, 390s≤t2≤500s; and circulating the negative pressure process and the positive pressure process. The present application optimizes the time distribution of the electrolyte injection process by prolonging the positive pressure time of a single cycle and shortening the negative pressure time of a single cycle, and reasonably distributes the positive pressure and negative pressure process time, so that the electrolyte can fully infiltrate the electrode sheet.

[0004] In some embodiments, the positive electrode sheet has a compaction density in the range of 3.55g / cm 3 -3.62g / cm 3 , and the negative electrode sheet has a compaction density in the range of 1.62g / cm 3 -1.68g / cm 3 .

[0005] In some embodiments, P1≤-85kpa, or 480s≤t1+t2≤600s.

[0006] In some embodiments, the number of times of circulating the negative pressure process and the positive pressure process is ≥3 times.

[0007] In some embodiments, the positive electrode active material of the positive electrode sheet comprises lithium-containing nickel-cobalt-manganese composite metal oxide, and the negative electrode active material of the negative electrode sheet comprises silicon-based material, wherein the chemical formula of the lithium-containing nickel-cobalt-manganese composite metal oxide is Li a Ni b Co c Mn d O e A 2-eWhere 0.8≤a≤1.2, 0.6≤b<1, 0<c<1, 0<d<1, 0<e≤2, b+c+d=1, and A is selected from one or more of N, F, S and Cl.

[0008] In some embodiments, using action time t 11 The cavity is evacuated from atmospheric pressure to the first pressure P1, 25s≤t 11 ≤40s; and utilizing the pressure relief time t 12 The cavity is depressurized from the first pressure P1 to the normal pressure, 10s≤t 12 ≤40s.

[0009] In some embodiments, using action time t 21 The cavity is pressurized from atmospheric pressure to the second pressure P2, 25s≤t 21 ≤40s; and utilizing the pressure relief time t 22 The cavity is depressurized from the second pressure P2 to the normal pressure, 25s≤t 22 ≤40s.

[0010] In some embodiments, the width of the negative electrode active material layer of the negative electrode sheet is 75mm-170mm along the direction of the winding center of the core, and the length of the negative electrode active material layer of the negative electrode sheet is 1300mm-5600mm along the direction perpendicular to the winding center.

[0011] In some embodiments, the total amount of fluid injected in the injection method ranges from 35g to 80g.

[0012] In some embodiments, the battery cell is a cylindrical battery cell, the diameter of the core ranges from 43mm to 46mm, the height of the core ranges from 78mm to 118mm, the width of the negative electrode active material layer of the negative electrode sheet along the direction of the winding center of the core is 75mm to 115mm, and the length of the negative electrode active material layer of the negative electrode sheet along the direction perpendicular to the winding center is 5000mm to 5600mm, and the total amount of liquid injected by the liquid injection method ranges from 35g to 55g. Attached Figure Description

[0013] Various aspects of the invention will be best understood from the following detailed description when read in conjunction with the accompanying drawings.

[0014] Figure 1 A schematic diagram is shown when the electronic device according to an embodiment of this application is a vehicle.

[0015] Figure 2 A battery pack according to an embodiment of this application is shown.

[0016] Figure 3 An exploded view of a battery cell according to an embodiment of this application is shown.

[0017] Figure 4 A schematic diagram of the structure of the positive and negative electrode sheets in a winding core according to some embodiments is shown.

[0018] Figure 5 A graph showing the relationship between immersion time and K value according to Comparative Example 1 of this application is shown, wherein the immersion time represents the time from one injection to the start of low current pre-charge. Detailed Implementation

[0019] The following detailed description of embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely illustrates selected embodiments of the present application. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. Furthermore, the terms "first," "second," "third," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0020] Currently, battery cells are increasingly widely used in the new energy field, such as in electric vehicles and electric bicycles. However, with the wider use of battery cells, the performance requirements for them are also increasing, which in turn places higher demands on the electrolyte injection process. Current injection processes suffer from the problem of insufficient electrolyte wetting of the electrodes. Therefore, this application improves electrolyte wetting by optimizing the injection process. Furthermore, this further reduces the K-value, which is highly correlated with the electrolyte wetting effect. The following detailed description of the battery cell injection method, with specific embodiments, illustrates this process.

[0021] refer to Figure 1 , Figure 1 This is a schematic diagram of an electronic device. The battery cell 1200 of this application can be used in the electronic device 1000, such as... Figure 1 As shown, the electronic device 1000 can be, for example, a vehicle, which may include a body 1100 and a battery pack, the battery pack including one or more battery cells 1200. The battery pack is disposed inside the body 1100 to power the vehicle and ensure its normal operation. In practical applications, the vehicle can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended vehicles, etc. In some other embodiments, the electronic device 1000 can also be, for example, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, and a power tool, etc. This embodiment does not limit the type of the electronic device 1000 described above.

[0022] refer to Figures 2 to 4The battery cell 1200 in this application may include a housing 1210, a top cover 1220, and a winding core 1230. The end of the winding core 1230 is provided with an adapter piece 1221, which is used to perform an electrical path transfer function between the terminals and the winding core 1230. The housing 1210 has an internal accommodating space, and one end of the housing 1210 has an opening. The winding core 1230 can be accommodated in the cavity inside the housing 1210. The top cover 1220 can close onto the opening of the housing 1210 and is fixedly connected to the housing 1210, so that the interior of the housing 1210 is relatively sealed.

[0023] like Figure 4 As shown, the core 1230 can be formed by winding a positive electrode 100a, a negative electrode 100b, and a separator 200. The separator 200 is located between the positive electrode 100a and the negative electrode 100b to isolate the positive electrode 100a and the negative electrode 100b, preventing them from contacting each other and causing a short circuit.

[0024] Some embodiments of this application provide a method for injecting electrolyte into a battery cell 1200, including: placing a core 1230 into a cavity within a housing 1210, as described above, the core 1230 is formed by winding a positive electrode 100a, a negative electrode 100b, and a separator 200; and injecting electrolyte into the cavity. Specifically, injecting electrolyte into the cavity includes: a negative pressure process: evacuating the cavity to a first pressure P1, injecting electrolyte, and holding the pressure for a first time t1, wherein -100kPa≤P1≤-80kPa, 10s≤t1≤100s; a positive pressure process: pressurizing the cavity to a second pressure P2, and holding the pressure for a second time t2, wherein P2≥800kPa, 390s≤t2≤500s; and cyclically combining the negative pressure process and the positive pressure process. In this application, the electrolyte wetting is improved by cycling the negative pressure process and the positive pressure process. Specifically, ① the vacuuming process in the negative pressure process removes air from the pores of the electrode core through negative pressure, allowing the electrolyte to fully wet the electrode; ② the positive pressure process uses external pressure to penetrate the electrolyte into the electrode, allowing the electrolyte to fully wet the electrode, thereby improving electrolyte wetting and reducing the K value.

[0025] Furthermore, in existing electrolyte injection methods, the holding time for negative pressure processes is typically around 470s, while the holding time for positive pressure processes is typically around 10s. This application shortens the holding time for negative pressure processes to t1 (10s≤t1≤100s) and extends the holding time for positive pressure processes to t2 (390s≤t2≤500s). The total holding time is 400s≤t1+t2≤600s, and further, 480s≤t1+t2≤600s. Therefore, this application maintains the overall holding time within a specific range by extending the positive pressure time of a single cycle and shortening the negative pressure time of a single cycle, thus optimizing the time allocation of the electrolyte injection process and rationally allocating the positive and negative pressure process times. This allows the electrolyte to fully wet the electrode, reducing the K value and improving the K value yield. Furthermore, in a further embodiment, P1 ≤ -85 kPa allows for more thorough wetting of the electrode by the electrolyte; or, when the total holding time is 480 s ≤ t1 + t2 ≤ 600 s, optimal production capacity can be maintained. Moreover, the total holding time can be adaptively adjusted based on production capacity requirements, and a longer time results in better wetting. In some embodiments, P2 ≤ 900 kPa, which can be adjusted according to the current equipment capacity.

[0026] In some embodiments, the compaction density of the positive electrode sheet ranges from 3.55 g / cm³. 3 -3.62g / cm 3 The compaction density of the negative electrode sheet ranges from 1.62 g / cm³. 3 -1.68g / cm 3 Due to the high compaction of the positive and negative electrode sheets, the pores in these sheets are small, making electrolyte wetting difficult. The electrolyte injection process significantly impacts this wetting. Currently, improving electrolyte wetting can be achieved by optimizing the battery core design, such as reducing electrode compaction, increasing separator thickness, and reducing group margin. However, these measures reduce the energy density of individual battery cells or increase BOM (Bill of Materials) costs. The electrolyte injection method provided in this application, through optimized injection processes, can improve electrolyte wetting and reduce the K-value without increasing individual battery cell costs or reducing energy density. Specifically, at the aforementioned compaction density of the positive and negative electrode sheets, the electrolyte wetting effect is better utilized, and the guaranteed compaction density ensures higher energy density, meeting industry technological development needs. Therefore, the electrolyte injection method provided in this application is applicable to high-energy-density systems, enabling more thorough electrolyte wetting, a denser and more stable SEI film, and a lower cell K-value.

[0027] In some embodiments, the negative pressure process and the positive pressure process are cycled ≥3 times, which can further improve the wetting effect of the electrolyte.

[0028] In this application, the positive electrode active material of the positive electrode sheet includes a lithium-containing nickel-cobalt-manganese composite metal oxide, and the negative electrode active material of the negative electrode sheet includes a silicon-based material, wherein the chemical formula of the lithium-containing nickel-cobalt-manganese composite metal oxide is Li a Ni b Co c Mn d O e A 2-e Wherein, 0.8≤a≤1.2, 0.6≤b<1, 0<c<1, 0<d<1, 0<e≤2, b+c+d=1, and A is selected from one or more of N, F, S, and Cl. In a high-nickel (0.6≤b<1) ternary cathode and silicon-based anode system, the liquid injection method provided in this application can effectively improve its energy density.

[0029] In some embodiments of this application, the action time t is utilized. 11 The cavity is evacuated from atmospheric pressure to the first pressure P1, 25s≤t 11 ≤40s; utilizing the pressure relief time t 12 Depressurize the cavity from the first pressure P1 to normal pressure, 10s≤t 12 ≤40s; and utilizing the action time t 21 The cavity is pressurized from atmospheric pressure to the second pressure P2, 25s≤t 21 ≤40s; and utilizing the pressure relief time t 22 The cavity is depressurized from the second pressure P2 to the normal pressure, 25s≤t 22 ≤40s. The corresponding action time t 11 t 21 and depressurization time t 12 t 22 Keeping it within the above range can help to further control the wetting of the electrolyte.

[0030] Furthermore, to accommodate the core dimensions of cells such as cylindrical and prismatic battery cells, the total electrolyte injection volume ranges from 35g to 80g. This accommodates the gap requirements of the electrode components within the battery cell core, providing sufficient electrolyte and ensuring effective wetting. In a further embodiment adapting to the aforementioned battery cells, for both prismatic and cylindrical battery cells, the width of the negative electrode active material layer of the negative electrode sheet can range from 75mm to 170mm along the direction of the core winding center, and the length of the negative electrode active material layer of the negative electrode sheet can range from 1300mm to 5600mm along the direction perpendicular to the winding center. This accommodates the total electrolyte volume and ensures effective electrolyte wetting.

[0031] In some embodiments of this application, the battery cell is a cylindrical battery cell, the diameter of which ranges from 43mm to 46mm, and the height of which ranges from 78mm to 118mm. For this cylindrical battery cell, along the direction of the winding center of the winding center, the width of the negative electrode active material layer of the negative electrode sheet can range from 75mm to 115mm, and along the direction perpendicular to the winding center, the length of the negative electrode active material layer of the negative electrode sheet can range from 5000mm to 5600mm. Furthermore, the total amount of electrolyte injected by this method ranges from 35g to 55g. It is evident that the electrolyte injection process provided in this application is suitable for large cylindrical systems, overcoming a series of problems such as poor K-value and lithium plating during cycling caused by the large battery size and high internal stress of cylindrical battery cells with a diameter of 43mm-46mm.

[0032] In some embodiments, the battery cell may be a lithium-ion battery, a sodium-ion battery, a sodium-lithium-ion battery, etc., and this application is not limited thereto. In some embodiments, the battery cell is a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and an electrolyte.

[0033] Positive electrode sheet: This can be prepared using conventional methods in the art. For example, the following method can be used: The corresponding positive electrode active material (containing lithium nickel cobalt manganese composite metal oxide), conductive agent, and binder are mixed at a mass ratio of 96-98:1-2:1-2, a solvent (such as N-methylpyrrolidone) is added, and the mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry; then, the positive electrode slurry is uniformly coated onto a positive electrode current collector; after air drying at room temperature, it is transferred to an oven for further drying, and then cold-pressed, slit, and cut into sheets to obtain the positive electrode sheet. In some embodiments, the chemical formula of the above-mentioned lithium nickel cobalt manganese composite metal oxide is Li a Ni b Co c Mn d O e A 2-eWherein, 0.8≤a≤1.2, 0.6≤b<1, 0<c<1, 0<d<1, 0<e≤2, b+c+d=1, and A is selected from one or more of N, F, S, and Cl. The conductive agent for the positive electrode can be selected from one or more of conductive carbon black (SP), carbon nanotubes (CNT), single-walled carbon nanotubes (SWCNT), Ketjen black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, porous carbon, etc., or a combination of two or more in any proportion. The binder for the positive electrode can be selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), etc. For the current collector of the positive electrode, materials that do not cause chemical changes and have high conductivity can be used without restriction. For example, commonly used materials include stainless steel, aluminum, nickel, titanium, or calcined carbon, or aluminum or stainless steel materials surface-treated with carbon, nickel, titanium, silver, etc. To enhance the adhesion of the positive electrode active material, micro-embossing can be formed on the surface of the current collector. The current collector can be used in various forms, such as films, sheets, foils, meshes, or porous bodies. The compaction density of the aforementioned positive electrode sheet ranges from 3.55 g / cm³. 3 -3.62g / cm 3 .

[0034] Negative electrode sheet: It can be prepared using conventional methods in the art. For example, the following method can be used: after mixing the negative electrode active material (including silicon-based material), binder, conductive agent and optionally thickener in a certain weight ratio, a solvent is added and mixed evenly to obtain a negative electrode slurry; then the negative electrode slurry is uniformly coated on the negative electrode current collector; after drying at room temperature, it is transferred to an oven for further drying, and then cold-pressed, slit and cut to obtain the negative electrode sheet. In the above negative electrode sheet, the negative electrode active material includes silicon-based material, and also includes negative electrode active materials conventionally used in the art to prepare negative electrode sheets, which can be selected from at least one of graphene, artificial graphite, natural graphite, soft carbon, hard carbon, and mesophase carbon microspheres; the binder of the negative electrode can include styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyvinylidene fluoride hexafluoropropylene copolymer (PVDF co HFP), polyvinyl alcohol, polyacrylonitrile, or any other suitable binder, and any one or a mixture of two or more thereof can be used. The conductive agent for the negative electrode can be a carbon-based material, such as carbon black (SP), acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, or carbon fiber; metal powder or metal fiber, such as copper, nickel, aluminum, or silver; conductive whiskers, such as zinc oxide whiskers or potassium titanate whiskers; conductive metal oxides, such as titanium dioxide; or conductive polymers, such as polyphenylene derivatives, etc. Furthermore, a thickener such as carboxymethyl cellulose (CMC) can be used, but there are no specific limitations. For the negative electrode current collector, it can be a current collector conventionally used for negative electrodes in the art, and can be a common current collector or a composite current collector. The negative electrode current collector can be made of a non-chemically reactive and conductive material without limitation. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum-cadmium alloys can be used, or copper, stainless steel, or aluminum-cadmium alloys surface-treated with carbon, nickel, titanium, or silver. In addition, to enhance the adhesion of the negative electrode active material, micro-embossing can be formed on the surface of the negative electrode current collector. The negative electrode current collector can be used in various forms, such as membranes, sheets, foils, meshes, or porous bodies. The compacted density of the aforementioned negative electrode sheet ranges from 1.62 g / cm³. 3 -1.68g / cm 3 .

[0035] Separator: The separator placed between the positive and negative electrode plates uses an insulating film with high ion permeability and high mechanical strength. The separator typically has a thickness of 9 μm-18 μm; a pore size of 5 μm-300 μm; an air permeability of 180 s / 100 mL-380 s / 100 mL; and a porosity of 30% to 50%. As a separator, it is chemically resistant and hydrophobic, and is usually made of sheets or nonwoven fabrics made of: olefin polymers such as polypropylene or polyethylene films; glass fibers; or, further, using the aforementioned sheets or nonwoven fabrics as a base film, coated with a coating.

[0036] Electrolyte: In this application, the electrolyte may be a conventional electrolyte used in lithium-ion batteries, generally including non-aqueous solvents, lithium salts and additives.

[0037] In some embodiments, the non-aqueous solvent may be a conventional non-aqueous solvent in the art, preferably an ester solvent, and more preferably a carbonate solvent. The carbonate solvent may be one or more of ethylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC).

[0038] In some embodiments, the additive may be one or more selected from vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene ethylene carbonate (VEC), vinyl sulfate (DTD), vinylene sulfate, 1,3-propane sulfonyl lactone (PS), propylene sulfonate lactone, and 1,4-butane sulfonate lactone. The conventional amount of the additive in the electrolyte is 1%-4% of the electrolyte, for example, 2%.

[0039] In some embodiments, the lithium salt may be a conventional lithium salt in the art, such as at least one selected from LiPF6, LiBF4, LiN(SO2F)2 (abbreviated as LiFSI), LiClO4, LiAsF6, LiB(C2O4)2 (abbreviated as LiBOB), LiBF2(C2O4) (abbreviated as LiDFOB), LiN(SO2RF)2, and LiN(SO2F)(SO2RF). The concentration of the lithium salt may be conventional in the art, and the lithium salt is preferably present in the electrolyte at a concentration of 5%-20%, typically 1 mol / L-2 mol / L.

[0040] In this application, the preparation method of the electrolyte can be conventional in the art, generally involving mixing a non-aqueous solvent, lithium salt, and additives.

[0041] The preparation of a single battery cell and its complete electrolyte injection process include: winding of the core, assembly of the core and other components such as the casing, primary electrolyte injection, low-current pre-charging, high-temperature wetting, negative pressure formation, secondary electrolyte injection, and SOC adjustment, as shown below:

[0042] (1) Winding to form a core:

[0043] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. Then, they are wound to obtain a core.

[0044] (2) Assembly

[0045] The cavity in which the core is placed;

[0046] (3) One-time injection

[0047] The electrolyte injection process includes: a negative pressure process: evacuating the chamber to a first pressure P1, injecting electrolyte, and holding the pressure for a first time t1, wherein -100 kPa ≤ P1 ≤ -80 kPa, and 10 s ≤ t1 ≤ 100 s; a positive pressure process: pressurizing the chamber to a second pressure P2, and holding the pressure for a second time t2, wherein P2 ≥ 800 kPa, and 390 s ≤ t2 ≤ 500 s; and cyclically performing the negative pressure and positive pressure processes to obtain the battery cell. As above, -100 kPa ≤ negative pressure process ≤ -80 kPa, and positive pressure process ≥ 800 kPa. In some embodiments, the number of cycles is ≥ 3. In some embodiments, the positive pressure process is ≤ 900 kPa.

[0048] The electrolyte injection volume is mainly determined by a combination of the size of the active material layer and the porosity parameters of the core, to ensure that the electrolyte fills the pores of the electrodes and separator. A single injection must meet the gap requirements of the battery's electrode components (electrodes and separator). In this application, for a cylindrical battery cell with a core diameter of 46mm, the single injection volume ranges from 35g to 80g.

[0049] (4) Small current pre-charge

[0050] 1. Let the battery cells stand still for 20-40 seconds;

[0051] 2.0.1C constant current charging for 16 minutes;

[0052] 3. Let stand for 20-40 seconds.

[0053] (5) High-temperature wetting process:

[0054] Soak at 45±5℃ for 24±2 hours.

[0055] (6) Negative pressure formation process:

[0056] 1. Let the battery cells that have been immersed in high temperature stand for 1-2 minutes;

[0057] 2.0.05C constant current charging to 3.0V;

[0058] 3. Let it sit for 2min-3min;

[0059] 4.0.1C constant current charging to 3.5V; and

[0060] 5. Let it sit for 2min-3min.

[0061] (7)Second injection

[0062] 1. The formed battery cell is injected with electrolyte (0g-2g) again under normal pressure to accurately replenish the quantitative amount of electrolyte;

[0063] 2. Seal the opening.

[0064] (8) SOC (State of Charge) adjustment process:

[0065] 1. Let the battery cell stand for 1-2 minutes after the second electrolyte injection;

[0066] 2.0.33C constant current charging to 3.9V; and

[0067] 3. Let stand for 30-35 minutes.

[0068] In this application, the electronic device includes the aforementioned battery cell, and the electronic device can be the vehicle described above, or it can be a mobile phone, portable device, laptop, ship, spacecraft, electric toy, power tool, etc. The vehicle can be a gasoline-powered car, a natural gas-powered car, or a new energy vehicle; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc.; spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. It can also be an energy storage electronic device that stores energy and then discharges it externally. This application does not impose any special limitations on the aforementioned electronic devices.

[0069] The present application is further illustrated below by way of embodiments, but these embodiments are not intended to limit the scope of the present application. Experimental methods not specifically described in the following embodiments are performed according to conventional methods and conditions in the art, or as selected in the product specification.

[0070] Example 1

[0071] Preparation of the positive electrode sheet:

[0072] The corresponding positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1O2, polyvinylidene fluoride (PVDF) binder, and conductive carbon were mixed in a mass ratio of 97:2:1. A solvent (such as N-methylpyrrolidone) was added, and the mixture was stirred under vacuum until homogeneous to obtain a positive electrode slurry. This slurry was then coated onto a positive electrode current collector aluminum foil. After air-drying at room temperature, it was transferred to an oven for further drying. Following cold pressing, slitting, and cutting, the positive electrode sheet was obtained. The compacted density of this positive electrode sheet was 3.58 g / cm³. 3 .

[0073] Preparation of the negative electrode sheet: Artificial graphite (anode active material), silicon-based material (mass ratio 5:1), conductive agent SP, thickener CMC, and binder SBR were mixed with deionized water at a mass ratio of 96:1:1.2:1.8. The mixture was stirred under vacuum until homogeneous to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated onto a copper foil current collector, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing, slitting, and cutting, the negative electrode sheet was obtained. The compacted density of this negative electrode sheet was 1.64 g / cm³. 3 Along the direction of the winding center of the core, the width of the negative electrode active material layer of the negative electrode sheet is 110 mm, and along the direction perpendicular to the winding center, the length of the negative electrode active material layer of the negative electrode sheet is 5300 mm.

[0074] Preparation of electrolyte: Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Finally, 2% VC was added as a film-forming additive.

[0075] Preparation of the separator: A 12μm thick polyethylene film was selected as the separator.

[0076] In this embodiment, the formed battery cell is a cylindrical battery cell with a core diameter of 46mm. The complete electrolyte injection process for this battery cell includes: winding, assembly, primary electrolyte injection, low-current pre-charging, high-temperature wetting, negative pressure formation, secondary electrolyte injection, and SOC adjustment, as shown below:

[0077] (1) Winding to form a core:

[0078] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrode to provide isolation. The electrodes are then wound to obtain a core, which has a diameter of 46 mm and a height of 118 mm.

[0079] (2) Assembly

[0080] The core is placed in the cavity of the housing.

[0081] (3) One-time injection

[0082] The injected electrolyte includes:

[0083] 1. Negative pressure process: utilizing a 30-second action time t 11 The cavity is evacuated from atmospheric pressure to a first pressure (P1) - 85 kPa, and electrolyte is injected. Specifically, the battery cavity is evacuated to remove as much air as possible from inside the cavity and from the micropores of the electrode plates. After reaching the first pressure (P1) - 85 kPa, the injection valve is opened, and the electrolyte is "drawn" into the winding core under the pressure difference between atmospheric pressure and the negative pressure of the cavity. The first pressure holding time t1 is 60 s, and a 20 s pressure release time t is used. 21 Depressurize the chamber from the initial pressure of -85 kPa to atmospheric pressure.

[0084] 2. Positive pressure process: utilizing a 30s action time t 21 The chamber is pressurized from atmospheric pressure to a second pressure (P2) of 800 kPa, and the pressure is maintained for a second time t2 of 420 s. A 30 s depressurization time t is then used. 22 Depressurize the cavity from the second pressure of 800 kPa to atmospheric pressure; and

[0085] 3. Repeat the above negative pressure process and positive pressure process 3 times to obtain the battery cell.

[0086] The relevant parameters are shown in Table 1 below:

[0087] Table 1. Relevant parameters of the injection method in Example 1.

[0088]

[0089] In the above process, for the cylindrical battery cell with a core diameter of 46mm, the total amount of liquid injected at one time is 53.3g.

[0090] (4) Small current pre-charge

[0091] 1. Let the battery cell stand still for 30 seconds;

[0092] 2.0.1C constant current charging for 16 minutes; and

[0093] 3. Let stand for 30 seconds.

[0094] (5) High-temperature wetting process:

[0095] Soak at 45℃ for 24 hours.

[0096] (6) Negative pressure formation process:

[0097] 1. Let the battery cells, after being pre-charged with a small current, stand for 1 minute;

[0098] 2.0.05C constant current charging to 3.0V;

[0099] 3. Let stand for 2 minutes;

[0100] 4.0.1C constant current charging to 3.5V; and

[0101] 5. Let stand for 2 minutes.

[0102] (7)Second injection

[0103] 1. The formed battery cell is injected with 1.3g of electrolyte under normal pressure to accurately replenish the quantitative amount of electrolyte;

[0104] 2. Seal the opening.

[0105] (7) SOC (State of Charge) adjustment process:

[0106] 1. Let the battery cell stand for 1 minute after the second electrolyte injection;

[0107] 2.0.33C constant current charging to 3.9V; and

[0108] 3. Let stand for 30 minutes.

[0109] After undergoing shaping and other processes, lithium-ion cylindrical battery cells are obtained.

[0110] The testing methods for its relevant parameters are as follows:

[0111] Residual electrolyte test: After one electrolyte injection is completed, the battery cell is disassembled, the core is removed, and the residual electrolyte is poured into a beaker and weighed to calculate the weight of the residual electrolyte.

[0112] Length and width of the negative electrode active material layer: After the cell is filled with electrolyte, disassemble it, take out the core, unfold the core, and use a film ruler to measure the length and width of the negative electrode active material layer respectively;

[0113] Unwetting area length test: After the cell is filled with electrolyte, it is disassembled, the core is taken out, the core is unfolded, and the length of the unwetting area on the concave and convex surfaces of the negative electrode active material layer is measured with a film ruler. The surface of the negative electrode active material layer that is close to the winding center of the core is the concave surface, and the surface that is far from the winding center is the convex surface.

[0114] Unwetting area width test: After the cell is filled with electrolyte, it is disassembled, the core is taken out, the core is unfolded, and the width of the unwetting area on the concave and convex surfaces of the negative electrode active material layer is measured with a film ruler.

[0115] K-value test method: After cell formation, age at 45±5℃ for 48±2h. After aging, stand at 25±3℃ for 24±2h and measure OCV1 (initial open-circuit voltage). Then stand at 25±3℃ for 120±2h and measure OCV2 (second open-circuit voltage). K-value = (OCV1 - OCV2) / 120; and

[0116] Compacted density test:

[0117] The compaction density of the electrode sheet in this application can be detected and controlled during electrode preparation using existing process methods. In this embodiment, the following detection method can be used: eight circular active material layer samples with a diameter of 50 mm (total area a1 = 157 cm²) are taken. 2 The material is placed on a balance and weighed to obtain the weight w3 of the double active material layer (including the current collector). The total area a1 is multiplied by the current collector density ρ2 and the current collector thickness h2 to obtain the current collector weight w4. The net weight of the double active material layer w0 = w3 - w4. The surface density of the active material layer (area density of one side) m2 = w0 / (a1×2). The compaction density of one side is m2 / h2.

[0118] Examples 2-9 and Comparative Example 1

[0119] The difference between Examples 2-9 and Comparative Example 1 and Example 1 is that the pressure and holding time of the negative pressure process and positive pressure process in the single injection method, as well as the relevant parameters of the compaction density of the negative electrode and positive electrode, are shown in Table 2 below. Other methods and parameters are the same as in Example 1.

[0120] Table 2 shows the relevant parameters and test results for Examples 1-9 and Comparative Example 1.

[0121]

[0122]

[0123] Comparing Example 1 with Comparative Example 1, it can be seen that the compaction density of the positive electrode sheet is 3.58 g / cm³. 3 The compaction density of the negative electrode sheet is 1.64 g / cm³. 3In this application, by optimizing the electrolyte injection process, the time for a single positive pressure cycle is extended and the time for a single negative pressure cycle is shortened while maintaining the same overall electrolyte injection time. Specifically, the positive pressure process time is extended from 10s to 420s, and the negative pressure process time is shortened from 470s to 60s. The residual electrolyte in the cell is reduced from 2.5g to 1.2g, the length of the unwetted area of ​​the negative electrode active material layer is reduced from 6085mm to 3060mm, the width of the unwetted area is reduced from 35mm to 28mm, and the K-value of the cell is reduced from 0.019mm to 0.015mm. It can be seen that, while maintaining the overall holding time within a specific range, this application optimizes the time allocation of the electrolyte injection process by extending the single positive pressure cycle time and shortening the single negative pressure cycle time. The positive and negative pressure process times are reasonably allocated, allowing the electrolyte to fully wet the electrode and reducing the K-value.

[0124] As can be seen from Comparative Example 1, the existing electrolyte injection process is difficult to wet the electrolyte. Under this process, the battery K value has a significant negative correlation with the wetting time. The shorter the time, the larger the K value, indicating that poor K value is mainly caused by poor wetting. Figure 5 The graph showing the relationship between immersion time and K value in Comparative Example 1 is presented. Figure 5 As can be seen, the shorter the immersion time, the worse the immersion effect, the poorer the SEI film formation, and the higher the K-value self-discharge rate. Therefore, this liquid injection process cannot effectively wet the electrode.

[0125] Comparing Example 1 and Example 2, it can be seen that the compaction density of the positive electrode sheet is 3.58 g / cm³. 3 The compaction density of the negative electrode sheet is 1.64 g / cm³. 3 Under the same overall liquid injection time, the positive pressure process time was extended from 420s to 470s, the negative pressure process time was shortened from 60s to 10s, the residual liquid in the cell was reduced from 1.2g to 1.0g, the length of the unwetted area of ​​the negative electrode active material layer was reduced from 3060mm to 1800mm, the width of the unwetted area was reduced from 28mm to 25mm, and the cell K-value was reduced from 0.015mm to 0.014mm. It can be seen that, under the same overall liquid injection time, the positive pressure process time of a single cycle can be further extended, and the negative pressure process time of a single cycle can be further shortened.

[0126] As can be seen from Examples 1 to 6, when the first pressure P1 of the negative pressure process is controlled to -100kpa≤P1≤-80kpa, the holding time of the negative pressure process is shortened to 10s-100s. When the second pressure P2 of the positive pressure process is controlled to P2≥800kpa, the holding time of the positive pressure process is extended to 390s-500s, and the total holding time is 400s-600s, or even 480s-600s. It can be seen that when the corresponding pressures and the total holding time of the negative pressure process and the positive pressure process are maintained within a specific range, the time of a single cycle of the positive pressure process is extended to the above range (390s-500s), and the time of a single cycle of the negative pressure process is shortened to the above range (10s-100s). This optimizes the time allocation of the electrolyte injection process, allows the electrolyte to fully wet the electrode, reduces the K value, and improves the K value yield. Furthermore, when P1≤-85kPa, the electrolyte can be fully wetted on the electrode, and when the total holding time is 480s≤t1+t2≤600s, the optimal production capacity can be maintained.

[0127] As can be seen from Examples 1 and 7 to 9, the compaction density of the positive electrode sheet ranges from 3.55 g / cm³. 3 -3.62g / cm 3 The compaction density of the negative electrode sheet ranges from 1.62 g / cm³. 3 -1.68g / cm 3 There were no significant differences in the residual electrolyte level, the length of the unwetted area, the width of the unwetted area, or the K-value among the cells. Therefore, the electrolyte injection method provided in this application can improve electrolyte wetting and reduce the K-value without reducing the energy density.

[0128] Examples 10-11

[0129] The difference between Examples 10 and 11 and Example 1 is that the formed battery cell is a cylindrical battery cell, and the relevant parameters of its core diameter and core height are shown in Table 3 below. Other methods and parameters are the same as in Example 1.

[0130] Table 3. Relevant parameters and test results for Examples 10-11

[0131]

[0132]

[0133] As can be seen from Examples 10-11, when the battery cell is a cylindrical battery cell, the corresponding core diameter ranges from 43mm to 46mm, and the core height ranges from 78mm to 118mm. Within this range, along the direction of the core winding center, the width of the negative electrode active material layer of the negative electrode sheet can range from 75mm to 115mm, and along the direction perpendicular to the winding center, the length of the negative electrode active material layer of the negative electrode sheet can range from 5000mm to 5600mm. At this time, when the total amount of electrolyte injected by this injection method is between 35g and 55g, sufficient wetting of the electrolyte can be achieved.

[0134] Examples 12-14

[0135] The difference between Examples 12-14 and Example 1 is that the relevant parameters of the type of battery cell formed, the length and width of the negative electrode active material layer are shown in Table 4 below, while the other methods and parameters are the same as in Example 1.

[0136] Table 4. Relevant parameters and test results for Examples 12-14

[0137]

[0138]

[0139] As can be seen from Examples 12-14, when the battery cell is a cylindrical battery cell or a prismatic battery cell, the width of the negative electrode active material layer of the negative electrode sheet ranges from 75mm to 170mm along the direction of the winding center of the core, and the length of the negative electrode active material layer of the negative electrode sheet ranges from 1300mm to 5600mm along the direction perpendicular to the winding center. The total amount of electrolyte injected ranges from 35g to 80g. When the length and width of the negative electrode active material layer are within the above ranges, the amount of electrolyte injected is guaranteed. The electrolyte injection method provided in this application can achieve full wetting of the electrolyte.

[0140] The foregoing outlines features of several embodiments to enable those skilled in the art to better understand aspects of the invention. Those skilled in the art should understand that they can readily use this invention as a basis to design or modify other processes and structures for implementing the same purposes and / or achieving the same advantages as the embodiments described herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of the invention, and that various changes, substitutions, and modifications can be made to them herein without departing from the spirit and scope of the invention.

Claims

1. A method for injecting electrolyte into a single battery cell, characterized in that, include: The core is placed into the cavity inside the housing, wherein the core is wound together with a negative electrode sheet, a positive electrode sheet, and a diaphragm; and Injecting electrolyte into the cavity includes: Negative pressure process: The cavity is evacuated to a first pressure P1, the electrolyte is injected, and the pressure is maintained for a first time t1, wherein -100kpa≤P1≤-80kpa, 10s≤t1≤100s; Positive pressure process: The cavity is pressurized to a second pressure P2 and held for a second time t2, wherein P2 ≥ 800 kPa, 390 s ≤ t2 ≤ 500 s; and The negative pressure process and the positive pressure process are repeated.

2. The injection method according to claim 1, characterized in that, The compaction density of the positive electrode sheet ranges from 3.55 g / cm³. 3 -3.62g / cm 3 The compaction density of the negative electrode sheet ranges from 1.62 g / cm³. 3 -1.68g / cm 3 .

3. The injection method according to claim 1, characterized in that, P1≤-85kPa, or 480s≤t1+t2≤600s.

4. The injection method according to claim 1, characterized in that, The negative pressure process and the positive pressure process are repeated ≥3 times.

5. The injection method according to claim 1, characterized in that, The positive electrode active material comprises a lithium-containing nickel-cobalt-manganese composite metal oxide, and the negative electrode active material comprises a silicon-based material. The chemical formula of the lithium-containing nickel-cobalt-manganese composite metal oxide is Li. a Ni b Co c Mn d O e A 2-e Where 0.8≤a≤1.2, 0.6≤b<1, 0<c<1, 0<d<1, 0<e≤2, b+c+d=1, and A is selected from one or more of N, F, S and Cl.

6. The injection method according to claim 1, characterized in that, Utilizing action time t 11 The cavity is evacuated from atmospheric pressure to the first pressure P1, 25s≤t 11 ≤40s; as well as Using the pressure relief time t 12 The cavity is depressurized from the first pressure P1 to the normal pressure, 10s≤t 12 ≤40s.

7. The injection method according to claim 1, characterized in that, Utilizing action time t 21 The cavity is pressurized from atmospheric pressure to the second pressure P2, 25s≤t 21 ≤40s; as well as Using the pressure relief time t 22 The cavity is depressurized from the second pressure P2 to the normal pressure, 25s≤t 22 ≤40s.

8. The injection method according to claim 1, characterized in that, Along the direction of the winding center of the core, the width of the negative electrode active material layer of the negative electrode sheet is 75mm-170mm, and along the direction perpendicular to the winding center, the length of the negative electrode active material layer of the negative electrode sheet is 1300mm-5600mm.

9. The injection method according to claim 8, characterized in that, The total amount of liquid injected in the aforementioned injection method ranges from 35g to 80g.

10. The injection method according to claim 1, characterized in that, The battery cell is a cylindrical battery cell, the diameter of the winding core ranges from 43mm to 46mm, and the height of the winding core ranges from 78mm to 118mm. Wherein, along the direction of the winding center of the core, the width of the negative electrode active material layer of the negative electrode sheet is 75mm-115mm, and along the direction perpendicular to the winding center, the length of the negative electrode active material layer of the negative electrode sheet is 5000mm-5600mm, and the total amount of liquid injected by the liquid injection method is in the range of 35g-55g.

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