Battery liquid injection method, battery and electric device

Abstract

The invention belongs to the technical field of batteries, and discloses a battery liquid injection method, a battery and an electric device. The battery comprises a shell and an electrode assembly, the shell defines a containing space, and the electrode assembly is arranged in the containing space. The battery liquid injection method comprises the following steps: (1) vacuumizing the accommodating space to a first negative pressure, keeping the first negative pressure for a first time, and injecting an electrolyte; (2) injecting the residual electrolyte into the accommodating space step by step while performing gradient pressure relief on the accommodating space to second negative pressure; (3) pressurizing the accommodating space until the pressure in the accommodating space is first positive pressure, keeping for second time, and releasing the pressure to normal pressure; and (4) the containing space is vacuumized to third negative pressure, and the third negative pressure is kept for third time. Therefore, sufficient and uniform injection of the electrolyte is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, in particular, relates to a battery liquid injection method, a battery and a power utilization device. BACKGROUND With the rapid development of the market of electronic equipment, electric vehicles, smart home, electric tools, intelligent transportation, etc., the demand for batteries is also increasing. Lithium ion batteries gradually become the most mainstream power battery due to their excellent energy density, high safety performance, low cost and long service life. The market now requires higher specific energy of batteries. To achieve high specific energy, in addition to selecting high-capacity electrode materials and thinner separators, another method is to put more positive and negative active materials into a specific volume of battery shell. This requires the electrode sheet to be pressed tighter by a roller press, that is, to increase the compaction density.

[0002] Although increasing the compaction density of electrode materials can improve the specific energy of batteries to some extent, the internal porosity of electrode materials with excessive compaction density is low and the pore size is small. Traditional atmospheric pressure injection and vacuum injection methods have drawbacks, such as insufficient and uneven injection. Therefore, developing a new battery liquid injection method to solve the infiltration problem of high compaction electrodes is one of the current challenges. SUMMARY

[0003] The present application aims to at least solve one of the technical problems in the related art. To this end, the present application proposes a battery liquid injection method, a battery and a power utilization device. The battery liquid injection method is simple to operate, can realize directional penetration of electrolyte and ensure sufficient and uniform infiltration of electrolyte in the electrode, and the battery obtained by using the liquid injection method has excellent electrochemical performance.

[0004] In a first aspect of the present application, a battery liquid injection method is proposed. The battery includes a shell and an electrode assembly. The shell defines a containing space, and the electrode assembly is arranged in the containing space. The battery liquid injection method includes: (1) vacuumizing the containing space to a first negative pressure, injecting electrolyte after maintaining for a first time; (2) while gradiently releasing the pressure of the containing space to a second negative pressure, injecting the remaining electrolyte into the containing space step by step; (3) pressurizing the containing space to a first positive pressure, maintaining for a second time, and releasing the pressure to atmospheric pressure; (4) vacuumizing the containing space to a third negative pressure, maintaining for a third time.

[0005] The battery liquid injection method in the present application combines gradient negative pressure relief, positive pressure extrusion and micro-negative pressure balance. The gradient negative pressure relief helps to slow down the penetration rate of the electrolyte while ensuring sufficient penetration of the electrolyte; the positive pressure extrusion can realize positive extrusion of the electrolyte inside the electrode, forcing the electrolyte to break through the capillary resistance in the deep small pores of the electrode, and the positive pressure extrusion can further discharge the residual micro-bubbles inside the containing space; the micro-negative pressure balance can stabilize the position of the electrolyte, thereby realizing sufficient injection of the electrolyte.

[0006] In some embodiments, the gradient pressure relief includes at least one-time pressure relief and two-time pressure relief, the pressure difference between the one-time pressure relief and the two-time pressure relief is ≤30KPa, and each pressure relief is maintained for 60s-90s. Thus, it helps to slow down and stabilize the rate of electrolyte entering the deep pores, and it is not easy to have the problem of local over-injection and local under-injection.

[0007] In some embodiments, at least one of the following conditions is met: the one-time pressure relief is -80KPa to -60KPa; the two-time pressure relief is -70KPa to -30KPa; the pressure of the one-time pressure relief is less than the pressure of the two-time pressure relief. Thus, the electrolyte is further penetrated from the surface pores to the deep pores under the driving of capillary action and pressure difference.

[0008] In some embodiments, the step (3) is repeated at least 3 times. Thus, it helps to enhance the uniformity of electrolyte penetration.

[0009] In some embodiments, the third negative pressure is greater than the second negative pressure.

[0010] In some embodiments, at least one of the following conditions is met: the second negative pressure is -40KPa to -30KPa; the third negative pressure is -15KPa to -10KPa. Thus, it helps to balance the distribution of electrolyte inside the containing space, further reducing the probability of local oversaturation or local under-infiltration; at the same time, micro-negative pressure adsorption can further stabilize the position of the electrolyte, avoiding possible phenomena such as liquid backflow before sealing.

[0011] In some embodiments, the battery liquid injection method meets at least one of the following conditions: the first negative pressure is -90KPa to -95 KPa; the first positive pressure is 0.6Mpa to 0.65Mpa; the first time is 90s to 120s; the second time is 60s to 90s; The third time is 60s-90s. In this way, it is helpful to realize uniform injection of the electrolyte.

[0012] In some embodiments, the step (3) is performed using high-pressure nitrogen. Nitrogen is highly stable in chemical properties and does not cause side reactions with the electrolyte, the electrode, etc., and nitrogen is highly safe, low in cost, and widely available.

[0013] In a second aspect of the present application, a battery is provided, which is obtained by the battery liquid injection method described above. In this way, the battery has a high first charge-discharge efficiency, a low internal resistance, excellent rate performance and cycle life, etc.

[0014] In a third aspect of the present application, a power-using device is provided, which includes the battery described above. In this way, the power-using device has excellent performance. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a cross-sectional schematic view of an electrode core in an embodiment of the present application.

[0016] Figure 2 is a structural schematic view of a porous liquid injection head in an embodiment of the present application. DETAILED DESCRIPTION

[0017] Embodiments of the present application are described in detail below. The embodiments described below are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0018] A lithium battery mainly consists of positive and negative electrode materials, positive and negative electrode conductive substrates, a separator, an electrolyte, and an assembly, etc. Processes involved usually include: positive and negative electrode material stirring, positive and negative electrode material coating, rolling, sheet making process and winding or stacking, liquid injection sealing, formation and capacity measurement, etc. As described above, to make a battery with high specific energy, the electrode material needs to simultaneously satisfy the synergistic optimization of high compaction density and high surface density. However, a large compaction density of the electrode (for example: lithium iron phosphate (LFP) ≥ 2.6 g / cm³, graphite ≥ 1.6 g / cm³) and a large surface density (LFP ≥ 200 g / m²) result in low porosity and small pore size in the electrode, and the electrolyte is difficult to fully infiltrate, which leads to certain difficulties in the liquid injection process.

[0019] The inventors conducted in-depth research on the electrolyte injection process in related technologies and discovered that some related technologies first evacuate the battery, then depressurize the electrode interior to atmospheric pressure, while simultaneously drawing the electrolyte back into the electrode interior to complete the injection; or other related technologies depressurize the battery interior to atmospheric pressure, and after the electrolyte enters the battery interior, positive pressure is applied to further ensure sufficient electrolyte wetting. Both of these injection methods involve directly depressurizing the battery to atmospheric pressure to allow the electrolyte to enter the electrode interior. This causes the compressed gas inside the electrode to expand due to the sudden pressure drop, potentially pushing the already permeated electrolyte back into the pores inside the electrode. Ultimately, this may result in the electrode surface being wetted but the deeper layers remaining dry. Even if positive pressure is subsequently applied to the electrode, uniform electrolyte wetting inside the electrode cannot be completely guaranteed.

[0020] Based on the above understanding, the inventors considered injecting a portion of electrolyte after evacuating the battery, and then using a gradient pressure reduction method to allow the remaining electrolyte to enter the electrode in stages, ensuring that the electrolyte gradually penetrates from the surface to the depth inside the electrode. On this basis, positive pressure is then applied to further ensure that the electrolyte is fully wetted. By combining positive and negative pressure for electrolyte injection, the problem of wetting the high-pressure compacted electrode is solved.

[0021] Therefore, in a first aspect, this application proposes a battery electrolyte filling method. The battery includes a casing and an electrode assembly. The casing defines a receiving space, and the electrode assembly is disposed in the receiving space. Specifically, the electrode assembly includes a positive electrode, a negative electrode, and a separator, and the positive electrode, negative electrode, and separator are placed in the receiving space by stacking or winding. The above-mentioned battery electrolyte filling method includes: S10: Evacuate the containment space to a first negative pressure, maintain it for a first time, and then inject electrolyte.

[0022] In this step, the containment space is evacuated to a first negative pressure, maintained for a first time, and a portion of the electrolyte is injected. Specifically, for high-pressure electrodes, there are numerous micron-sized or even nano-sized pores inside, some of which are located deep within the electrode. Under normal pressure, the gas in these deep pores is difficult to escape, thus hindering electrolyte wetting. Evacuating the inside of the electrode (i.e., creating a high negative pressure environment) creates a significant pressure difference between the inside and outside of the electrode, thereby strongly drawing in the gas from the deep pores of the electrode, creating space for subsequent electrolyte filling.

[0023] For example, the containing space can be evacuated to -90 kPa to -95 kPa. Specifically, it can be -90 kPa, -91 kPa, -92 kPa, -93 kPa, -94 kPa, -95 kPa, etc., and the evacuation can be maintained for 90 s, 95 s, 100 s, 105 s, 110 s, 115 s, 120 s, etc. This helps to expel gas from the deep pores of the containing space.

[0024] Furthermore, a portion of the electrolyte is injected. The amount of electrolyte injected here is not limited; an appropriate amount can be injected according to actual needs.

[0025] S20: While the containment space is depressurized to a second negative pressure, the remaining electrolyte is injected into the containment space in stages.

[0026] In this step, the containment space is gradually depressurized until the internal pressure reaches a second negative pressure. After each depressurization, the remaining electrolyte is injected in stages. Specifically, the containment space is gradually depressurized (the negative pressure is gradually reduced) to -40 kPa to -30 kPa, specifically -40 kPa, -38 kPa, -36 kPa, -34 kPa, -32 kPa, -30 kPa, etc. This allows the electrolyte to further permeate from the surface pores to the deeper pores under the drive of capillary action and pressure difference.

[0027] There is no limit to the amount of electrolyte injected in stages. The remaining electrolyte can be divided into multiple portions as needed (consistent with the number of gradient depressurization cycles). The electrolyte is injected after each depressurization cycle.

[0028] During the process of depressurizing the pressure gradient inside the containment space, the pressure difference between the outside and inside of the electrode is gradually reduced, which helps to control the electrolyte injection rate. An excessive pressure difference will cause the electrolyte injection rate to be too high, which may cause the compressed gas in the deep pores of the electrode to expand due to the sudden pressure drop, thus "pushing" the injected electrolyte out of the pores.

[0029] The essence of capillary action described above is the spontaneous penetration force generated by the electrolyte within the deep pores of the electrode due to the combined effects of surface tension and contact angle. Specifically, the capillary action F = 2γcosθ / r, where γ is the surface tension of the electrolyte, θ is the contact angle between the electrolyte and the pore sidewall, and r is the radius of the pores inside the electrode. The larger γ is, the stronger the cohesive force between electrolyte molecules, and the more significant the "traction effect" generated within the pores, equivalent to the electrolyte itself having the power to drive the whole to penetrate deeper into the pores; the smaller r is, the stronger the capillary action. Thus, the tiny pores deep inside the electrode can achieve electrolyte wetting through capillary action.

[0030] Furthermore, while capillary action draws the electrolyte into deep pores, the combined effect of pressure relief can further promote the continuous penetration of the electrolyte.

[0031] In some embodiments, gradient pressure relief includes at least two pressure reliefs. Gradient pressure relief helps to slow down the rate of electrolyte permeation while ensuring sufficient electrolyte permeation. For example, gradient pressure relief may include two pressure reliefs, three pressure reliefs, four pressure reliefs, etc.

[0032] In some embodiments, gradient pressure relief includes primary pressure relief and secondary pressure relief. The pressure difference between the primary and secondary pressure relief is ≤30 kPa. Specifically, the pressure difference between the primary and secondary pressure relief can be 10 kPa, 15 kPa, 20 kPa, 25 kPa, 30 kPa, etc. Controlling the pressure difference of gradient pressure relief within the above range helps to ensure that the electrolyte enters the deep pores slowly and steadily, and avoids the problems of excessive or insufficient local electrolyte injection.

[0033] For example, gradient depressurization includes primary depressurization and secondary depressurization. Primary depressurization is performed to -80 kPa to -60 kPa. Specifically, it can be -80 kPa, -75 kPa, -70 kPa, -65 kPa, -60 kPa, etc. After primary depressurization, the pressure is maintained for 60 to 90 seconds. Specifically, it can be maintained for 60, 70, 80, or 90 seconds. Secondary depressurization is performed to -70 kPa to -30 kPa. Specifically, it can be -70 kPa, -65 kPa, -60 kPa, -55 kPa, -50 kPa, -45 kPa, -40 kPa, -35 kPa, -30 kPa, etc. After secondary depressurization, the pressure is maintained for 60 to 90 seconds. Specifically, it can be maintained for 60, 70, 80, or 90 seconds. This helps the electrolyte to gradually penetrate deep pores and fully wet them.

[0034] In some embodiments, the battery cell typically comprises an electrode assembly, a housing, and a top cover, with the electrode assembly housed within the housing and the top cover covering the housing. (See reference...) Figure 1 The diagram shows a cross-sectional view of the battery cell's top cover, where the positive terminal 1 and negative terminal 4 are located on opposite sides of the aluminum sheet 3, and terminal 2 is the electrolyte injection hole. For details, please refer to... Figure 2 During injection, a porous injection head 21 can be arranged in the injection hole for injection. When using the porous injection head, the electrolyte can be atomized into micro-droplets, reducing the liquid flow pressure in a single hole and achieving three-dimensional permeation.

[0035] In some embodiments, the pore size of the pores in the porous injection head is 75 micrometers to 100 micrometers. Specifically, it can be 75 micrometers, 80 micrometers, 85 micrometers, 90 micrometers, 95 micrometers, 100 micrometers, etc. A pore size within the above range helps to atomize the electrolyte into microdroplets, reduce the liquid flow pressure in a single pore, and achieve three-dimensional permeation.

[0036] S30: Pressurize the containment space until the pressure inside the containment space reaches a first positive pressure, maintain it for a second time, and then depressurize it to normal pressure.

[0037] In this step, the containment space is pressurized until the pressure inside the containment space reaches a first positive pressure, maintained for a second time, and then depressurized to atmospheric pressure. This process of pressurizing the containment space until the pressure inside reaches the first positive pressure, maintaining it for a second time, and then depressurizing to atmospheric pressure again is repeated. By applying positive pressure to the containment space, the electrolyte inside is subjected to positive compression, forcing the electrolyte to overcome the capillary resistance in the deep micropores of the electrode (such as highly tortuous pores and nanoscale gaps). Simultaneously, the positive pressure compression can further expel residual microbubbles from the electrode area. Depressurizing to atmospheric pressure further enhances the uniformity of electrolyte penetration through the reciprocating flow of the electrolyte.

[0038] In some embodiments, the specific operation of pressurizing and then depressurizing to atmospheric pressure is repeated at least three times; for example, it can be repeated three, four, five times, etc. This helps to enhance the uniformity of electrolyte penetration.

[0039] In some embodiments, the first positive pressure is 0.6 MPa to 0.65 MPa, for example, it can be 0.6 MPa, 0.61 MPa, 0.62 MPa, 0.63 MPa, 0.64 MPa, 0.65 MPa, etc. Within the above range, the first positive pressure can essentially enable the electrolyte to overcome the capillary resistance within the deep micropores of the electrode, thereby ensuring that the electrolyte fully penetrates to the deepest part of the electrode; at the same time, it can effectively compress the microbubbles inside the containment space, causing them to be discharged from the pores inside the electrode.

[0040] In some embodiments, the second time is 60s to 90s, specifically 60s, 70s, 80s, 90s, etc. This ensures that the electrolyte sufficiently overcomes the capillary resistance within the deep micropores of the electrode and adequately compresses the microbubbles within the containment space.

[0041] In some embodiments, the containment space can be pressurized using high-pressure nitrogen. Nitrogen is chemically highly stable, does not react with electrolytes, electrodes, etc., and is safe, inexpensive, and widely available.

[0042] S50: Evacuate the containing space to a third negative pressure and maintain it for a third time.

[0043] In this step, the containment space is evacuated to a third negative pressure and maintained for a third time. This third negative pressure is greater than the second negative pressure, meaning it is a micro-negative pressure. This micro-negative pressure helps balance the electrolyte distribution within the containment space, further reducing the probability of local oversaturation or underwetting. Simultaneously, the micro-negative pressure adsorption further stabilizes the electrolyte position, preventing potential backflow of liquid before sealing.

[0044] In some embodiments, the third negative pressure is -15 kPa to -10 kPa, specifically -15 kPa, -14 kPa, -13 kPa, -12 kPa, -11 kPa, -10 kPa, etc. The third negative pressure within the above range can basically balance the distribution of electrolyte inside the containment space and stabilize the position of the electrolyte.

[0045] In some embodiments, the third time is 120s to 150s, specifically 120s, 125s, 130s, 135s, 140s, 145s, 150s, etc. Within the above time range, the electrolyte can be basically guaranteed to remain stable inside the electrode.

[0046] In a second aspect of this application, a battery is proposed. This battery is obtained through the aforementioned liquid injection method. As a result, the battery exhibits high initial charge / discharge efficiency, low internal resistance, excellent rate performance, and long cycle life.

[0047] According to the embodiments of this application, it can be understood that the specific type of battery is not particularly limited, and it can be a primary battery or a secondary battery; the shape of the battery can be a cylindrical battery, a square battery, or other batteries of any shape, and according to the outer packaging, the battery can be a hard-shell battery, a soft-pack battery, etc. In other embodiments, the battery can be a lithium-ion battery, a sodium-ion battery, etc.

[0048] Typically, a battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The positive electrode, negative electrode, and separator are fabricated into electrode assemblies using winding or stacking processes. The electrode assemblies and electrolyte are housed in an outer package. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0049] The positive electrode in the battery may include a positive current collector and a positive active material layer, wherein the positive active material layer is disposed on at least one surface of the positive current collector.

[0050] In some embodiments, the positive current collector can be a metal current collector or a composite current collector. For example, metal current collectors include, but are not limited to, aluminum foil current collectors; composite current collectors may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. Composite current collectors can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0051] In some embodiments, the positive electrode active material layer may include positive electrode active material, binder and conductive agent, and may also include additives with specific functions and effects, such as thickeners, sodium supplements, film-forming additives, flame retardants, high temperature / low temperature stabilizers, etc., as needed.

[0052] As an example, positive electrode active materials may include lithium nickel cobalt manganese oxide (including but not limited to NCM811, NCM613, NCM523, etc.), lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium nickel manganese oxide, lithium-rich manganese-based materials, or positive electrode active materials commonly used in the art.

[0053] As an example, the binder in the positive electrode active material layer may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0054] As an example, the conductive agent in the positive electrode active material layer may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0055] In some embodiments, the electrolyte may include lithium salts and solvents. Furthermore, additives with specific functions, such as film-forming additives, lithium replenishing agents, flame retardants, and thermal stability additives, may be added to the electrolyte as needed. As an example, the electrolyte may include lithium salts, solvents, and additives.

[0056] In some embodiments, the lithium salt may include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate, etc. Lithium salts can provide lithium ions to lithium-ion batteries, support electrolyte stability and electrochemical reactions, help form a protective SEI film, improve conductivity, and enhance the safety of lithium-ion batteries.

[0057] In some embodiments, the solvent may include carbonates, fluorocarbonates, etc. This allows for the thorough dissolution of lithium salts, provides an ion transport medium, and also helps improve the electrochemical and safety performance of lithium-ion batteries.

[0058] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector. As an example, the negative electrode active material layer may include a negative electrode material, a thickener, a conductive agent, and a binder.

[0059] Specifically, the negative electrode current collector can be a metal foil, for example, copper foil. The negative electrode material can include carbon-based materials, silicon-based materials, tin-based materials, etc. The binder in the negative electrode material layer can include, but is not limited to, at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethyl methacrylate (PMAA), and carboxymethyl chitosan (CMCS). The conductive agent in the negative electrode material layer can include, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0060] In a third aspect of this application, an electrical device is proposed, comprising the aforementioned positive electrode or the aforementioned battery. Therefore, the electrical device has high capacity and energy density.

[0061] In some embodiments, the specific type of electrical device is not particularly limited and can be any device that uses a battery as a power source or energy storage unit. Examples of electrical devices include, but are not limited to, electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), mobile terminals (e.g., mobile phones, laptops, game consoles, wearable devices, etc.), drones, aerospace equipment, satellites, ships, energy storage systems, and so on.

[0062] It is understood that, in addition to the battery mentioned above, the electrical device also includes other necessary structures and components, all of which can be made with reference to conventional technologies. For example, an electric vehicle may include a body, chassis, tires, navigation system, radar system, steering system, braking system, lubrication system, cooling system, driving system, etc., which will not be described in detail here.

[0063] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0064] Example 1 Preparation of the positive electrode sheet: The positive electrode active material NCM811, conductive graphite, PVDF, and PMAA were mixed in a mass ratio of 96.8:1.5:1.5:0.2. The mixture was first dry-mixed, then wet-mixed with an appropriate amount of solvent to obtain a positive electrode slurry. The solid content of the positive electrode slurry was controlled to be 65%. Further, the positive electrode slurry was coated onto a 14μm thick carbon-coated aluminum foil (the aluminum foil thickness was 12 μm, with a 1 μm thick carbon layer on each side). It was dried and rolled at 100℃, and finally die-cut according to the cell size to obtain the positive electrode sheet, which was then placed in a nitrogen oven at 100℃ for later use. The double-sided areal density of the positive electrode sheet was 40 mg / cm³. 2 The compacted density is 2.30 g / cm³. 3 .

[0065] Preparation of the negative electrode sheet: A slurry was prepared by mixing hard carbon, carbon nanotubes, and SBR in a mass ratio of 96.5:1.0:2.5. The mixture was first dry-mixed, then wet-mixed with an appropriate amount of solvent to obtain the negative electrode slurry, with a solid content controlled at 55%. The negative electrode slurry was then coated onto a 6μm thick copper foil, dried at 80℃, and rolled. Finally, it was die-cut to the cell dimensions to obtain the negative electrode sheet, which was then placed in a nitrogen oven at 90℃ for later use. The double-sided areal density of the negative electrode sheet was 13 mg / cm³. 2 The compacted density is 1.50 g / cm³. 3 . Electrolyte preparation: LiPF6:EC:EA:VC = 14%wt:70%wt:10%wt:6%wt.

[0066] Lithium-ion battery assembly: A stacking process is used, and one more negative electrode sheet is required than the positive electrode sheet. The number of electrode sheets is calculated based on a design capacity of 1Ah. The electrodes are stacked in the order of separator, negative electrode sheet, separator, positive electrode sheet, separator, negative electrode sheet. After hot pressing, welding tabs, and encapsulation, the moisture content is controlled to be below 400ppm, and electrolyte is injected according to the design capacity.

[0067] The electrolyte filling method according to this application is as follows: (1) Evacuate the battery casing to -90 kPa, hold for 90 seconds, and inject some electrolyte; (2) Depressurize the containment space to -60 kPa, maintain for 60 seconds, and then inject half of the remaining electrolyte; (3) Depressurize the containment space to -30 kPa, maintain for 60 seconds, and then inject the remaining electrolyte; (4) Pressurize the containment space to a pressure of 0.6 MPa, maintain for 60 seconds, and then depressurize to atmospheric pressure. Repeat this process 3 times (pressurizing to 0.6 MPa and then depressurizing to atmospheric pressure constitutes one cycle). (5) Evacuate the containment space to -10 kPa and hold for 90 seconds.

[0068] Example 2 Same as Example 1, except that: (1) Evacuate the battery casing to -95 kPa, hold for 90 seconds, and inject some electrolyte; (2) Depressurize the containment space to -65 kPa, maintain for 70 seconds, and then inject one-third of the remaining electrolyte; (3) Depressurize the containment space to -55 kPa, maintain for 70 seconds, and then inject half of the remaining electrolyte; (4) Depressurize the containment space to -30 kPa, maintain for 80 seconds, and then inject the remaining electrolyte; (5) Pressurize the containment space to a pressure of 0.6 MPa, maintain for 60 seconds, and then depressurize to atmospheric pressure. Repeat this process 5 times (pressurizing to 0.6 MPa and then depressurizing to atmospheric pressure constitutes one cycle). (6) Evacuate the containment space to -10 kPa and hold for 80 seconds.

[0069] Example 3 Same as Example 1, except that: (1) Evacuate the battery casing to -95 kPa, hold for 90 seconds, and inject some electrolyte; (2) Depressurize the containment space to -80 kPa, maintain for 70 seconds, and then inject one-third of the remaining electrolyte; (3) Depressurize the containment space to -60 kPa, maintain for 70 seconds, and then inject half of the remaining electrolyte; (4) Depressurize the containment space to -30 kPa, maintain for 80 seconds, and then inject the remaining electrolyte; (5) Pressurize the containment space to a pressure of 0.62 MPa, maintain for 60 seconds, and then depressurize to atmospheric pressure. Repeat this cycle 5 times (pressurizing to 0.6 MPa and then depressurizing to atmospheric pressure constitutes one cycle). (6) Evacuate the containment space to -10 kPa and hold for 80 seconds.

[0070] Comparative Example 1 Same as Example 1, except that: the containment space of the battery casing is evacuated to -80 kPa, held for 60 seconds, and then all electrolyte is injected.

[0071] Detection methods Twenty batteries were injected with electrolyte using the method described in Example 1. The RSD1 of the electrolyte injection volume for the 20 batteries was calculated by weight method (specifically, the weight of the battery before injection is W1, and the weight after injection is W2, then the injection volume = W2 - W1, and finally the relative standard deviation (RSD) of the electrolyte injection volume for the 20 batteries was calculated). Ten batteries were injected with electrolyte using the method described in Example 2, and the RSD2 of the electrolyte injection volume for the ten batteries was calculated by weight method. Ten batteries were injected with electrolyte using the method described in Example 3, and the RSD3 of the electrolyte injection volume for the ten batteries was calculated by weight method. Twenty batteries were injected with electrolyte using the same method as in Comparative Example 1, and the RSD (Responsible Displacement) of the electrolyte injection volume for each of the 20 batteries was calculated by weight. A smaller RSD value indicates more uniform electrolyte injection.

[0072] 0.1C Initial Efficiency: In an environment of 25℃±2℃, using a calibrated charge / discharge meter, determine the 0.1C current according to the battery's rated capacity, and define the charge / discharge cutoff voltages as 4.2V / 2.5V; first charge at a constant current of 0.1C to the cutoff voltage, then charge at a constant voltage to the 0.01C cutoff current (record the initial charge capacity Ccharge), and let it stand for 0.5h; subsequently discharge at a constant current of 0.1C to the discharge cutoff voltage (record the initial discharge capacity Cdischarge), and finally let it stand for 0.5h. Calculate the initial efficiency as (Cdischarge / Ccharge) × 100%.

[0073] Room temperature cycling: Place the battery in an ambient temperature chamber (25℃) and let it rest for 4 hours. Then perform charge-discharge cycles: discharge at 1 / 3C constant current to 2.0V, rest for 30 minutes; charge at 0.5C constant current to 3.8V, rest for 5 minutes; charge at 0.1C constant current to 3.8V, rest for 30 minutes; discharge at 0.5C constant current to 2.0V, rest for 30 minutes; repeat the above steps until 1000 cycles are completed, and calculate the capacity retention rate. The capacity retention rate is calculated as (discharge capacity after 1000 cycles / initial discharge capacity) × 100%.

[0074] Test results The RSD1 for the electrolyte injection volume of 20 batteries using the injection method of Example 1 was 0.00389; the RSD1 for the electrolyte injection volume of 10 batteries using the injection method of Example 2 was 0.00425; the RSD1 for the electrolyte injection volume of 10 batteries using the injection method of Example 3 was 0.00409; and the RSD for the electrolyte injection volume of 20 batteries using the injection method of Comparative Example 1 was 0.00617. This demonstrates that the electrolyte injection consistency of the batteries obtained using the injection method of this application is high.

[0075] The specific performance parameters of the above batteries are shown in Table 1.

[0076]

[0077]

[0078]

[0079] Note: In Table 1, Example 1-1 represents the first battery sample obtained by the liquid injection method of Example 1, and Example 1-2 represents the second battery sample obtained by the liquid injection method of Example 1. Other similar descriptions have the same meaning.

[0080] Conclusion: Based on the data of the battery's initial efficiency at 0.1C and capacity retention rate at room temperature in Table 1, it can be seen that the battery obtained by the liquid injection method of this application has good performance. Specifically, the initial efficiency at 0.1C is ≥91.79%, and the capacity retention rate at room temperature is ≥99.51%.

[0081] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0082] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0083] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0084] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0085] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0086] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for injecting electrolyte into a battery, characterized in that, The battery includes a housing and an electrode assembly, the housing defining a receiving space, the electrode assembly being disposed within the receiving space, the method comprising: (1) Evacuate the containment space to a first negative pressure, maintain it for a first time, and then inject electrolyte; (2) While the containment space is gradually depressurized to the second negative pressure, the remaining electrolyte is injected into the containment space in stages; (3) Pressurize the containment space until the pressure inside the containment space is a first positive pressure, maintain it for a second time, and then depressurize it to normal pressure; (4) Evacuate the containment space to a third negative pressure and maintain it for a third time.

2. The injection method according to claim 1, characterized in that, The gradient pressure relief includes at least a primary pressure relief and a secondary pressure relief, the pressure difference between the primary pressure relief and the secondary pressure relief is ≤30 kPa, and the pressure is maintained for 60s~90s after each pressure relief.

3. The injection method according to claim 2, characterized in that, At least one of the following conditions must be met: The pressure was initially released to -80 kPa to -60 kPa. The secondary pressure relief is reduced to -70 kPa to -30 kPa; The pressure of the first pressure relief is less than the pressure of the second pressure relief.

4. The injection method according to claim 1, characterized in that, Step (3) is repeated at least 3 times.

5. The injection method according to claim 1, characterized in that, The third negative pressure is greater than the second negative pressure.

6. The injection method according to claim 5, characterized in that, At least one of the following conditions must be met: The second negative pressure is -40 kPa to -30 kPa; The third negative pressure is -15 kPa to -10 kPa.

7. The injection method according to claim 1, characterized in that, At least one of the following conditions must be met: The first negative pressure is -90 kPa to -95 kPa; The first positive pressure is 0.6 MPa to 0.65 MPa; The first time is 90s~120s; The second time is 60s~90s; The third time is 60s~90s.

8. The injection method according to claim 1, characterized in that, Step (3) is performed using high-pressure nitrogen.

9. A battery, characterized in that, It is obtained by the injection method described in any one of claims 1 to 8.

10. An electrical device, characterized in that, Includes the battery as described in claim 9.

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