CN114824531B

CN114824531B - Electrode infiltration method, lithium ion battery cell and lithium ion battery

Info

Publication number: CN114824531B
Application number: CN202210601791.8A
Authority: CN
Inventors: 吴德丽
Original assignee: Chongqing Talent New Energy Co Ltd
Current assignee: Chongqing Talent New Energy Co Ltd
Priority date: 2022-05-30
Filing date: 2022-05-30
Publication date: 2023-04-07
Anticipated expiration: 2042-05-30
Also published as: CN114824531A

Abstract

The invention relates to an electrode infiltration method, a lithium ion battery cell and a lithium ion battery. The electrode wetting method of the present invention comprises: injecting electrolyte into the battery cell comprising the positive pole piece and the negative pole piece and sealing; and carrying out charging and discharging on the battery cell after liquid injection so as to realize the electrochemical infiltration step of the battery cell infiltration. The electrode infiltration method of the invention can improve the production efficiency of the battery and reduce the energy consumption on the premise of not influencing the performance of the battery, thereby greatly reducing the manufacturing cost and completely replacing the traditional electrode infiltration method.

Description

Electrode infiltration method, lithium ion battery cell and lithium ion battery

Technical Field

The invention relates to the field of lithium ion batteries, in particular to a method for improving battery cell wettability, a lithium ion battery cell and a lithium ion battery.

Background

The impregnation of the electrodes or cells of lithium ion batteries is a critical step in the battery manufacturing process. The wetting effect of the electrode determines the performance of the cell. Generally, after the battery cell is packaged, electrolyte is injected, and vacuum is continuously pumped in a vacuum box for several times, so that the electrolyte repeatedly flows on the pole piece to soak the electrode.

At present, in order to improve the wettability of the electrode, on one hand, an electrolyte solution optimization scheme is adopted, such as a method of adding an electrolyte additive, selecting a solvent with lower viscosity or reducing the concentration of lithium salt; on the other hand, the wettability of the electrolyte is improved by changing the injection manner, such as vacuum injection, increasing the wetting temperature and the like. Although the above method can improve the wettability of the electrode to some extent, the effect is not good and the productivity is low.

Disclosure of Invention

Problems to be solved by the invention

Based on the above current situation, it is necessary to solve the problems of complicated operation, difficult infiltration, long infiltration time, high cost, etc. of electrode-electrolyte infiltration in the prior art, especially in the thick electrode system.

Means for solving the problems

In the charging process of the lithium ion battery, lithium ions can bring solvent molecules close to the negative electrode, when the voltage continuously rises to reach the lithium intercalation potential, the lithium ions can be desolvated and enter the negative electrode to complete the lithium intercalation process, and on the contrary, in the discharging process, the lithium ions can be desorbed from the negative electrode and return to the positive electrode. The present inventors have conducted extensive studies and found that if pulse charging and discharging are adopted, the above principle can be used, and the voltage and time can be controlled by using a small current, so that the lithium ions tend to bring the solvent close to the negative electrode during pulse charging, which accelerates the wetting of the electrolyte to the negative electrode, and conversely, pulse discharging completes the wetting of the electrolyte to the positive electrode, thereby completing the present invention.

The invention greatly improves the wettability of the electrode-electrolyte, saves time and improves the efficiency of battery preparation by an electrochemical method of pulse charging and discharging, and the method has simple operation and low cost.

The invention provides an electrode infiltration method, which is characterized by comprising the following steps:

a step of injecting an electrolyte into a cell including a positive electrode plate and a negative electrode plate and sealing the same, an

And charging and discharging the battery cell after liquid injection so as to realize the electrochemical infiltration step of the battery cell infiltration.

The electrode wetting method according to the above, wherein in the charging and discharging, the charging current is 0.008C to 0.8C, preferably 0.01C to 0.6C, and the discharging current is 0.008C to 0.6C, preferably 0.01C to 0.2C, where C is a design capacity of the battery.

The electrode impregnation method according to the above, wherein in the charging and discharging, the duration of each of the charging and discharging is 5 to 60s, preferably 10 to 45s;

and carrying out cyclic charge and discharge on the battery cell, wherein the total cyclic charge and discharge time is 0.8-4.0 hours, preferably 1.0-3.5 hours.

The electrode impregnation method described above, wherein in the charging and discharging, the charge cut-off voltage is not less than OCP, which is the open circuit voltage of the cell after the injection, and not more than 1.2V, preferably not less than 0.4V and not more than 1.1V.

The electrode impregnation method described above, wherein in said charging and discharging, a rest time is set after each charging and/or discharging, wherein said rest time is between 1s and 15s, preferably between 2s and 10s.

The electrode infiltration method comprises the following steps of charging and discharging, wherein the charging current is 0.01-0.06C, the discharging current is 0.01-0.04C, the respective duration time of charging and discharging is 20-45 s, the rest time is 1-5 s, and the total time of cyclic charging and discharging is 1.8-2.8 hours.

The electrode infiltration method according to the above, wherein in the charging and discharging, the charging current is 0.1 to 0.6C, the discharging current is 0.04 to 0.2C, the respective durations of the charging and discharging are 10 to 40s, the rest time is 5 to 10s, and the total time of the cyclic charging and discharging is 2.0 to 3.0 hours.

The electrode impregnation method according to the above, wherein the electrochemical impregnation step is performed at room temperature to 55 ℃, preferably at room temperature to 40 ℃.

The electrode wetting method, wherein the charging and discharging is pulse charging and discharging.

The electrode impregnation method comprises a step of placing the battery cell after liquid injection before the step of electrochemical impregnation.

The electrode impregnation method according to the above, wherein in the step of leaving aside, the leaving aside time is 5min to 6 hours, preferably 0.5 hour to 3 hours, and the leaving aside temperature is room temperature to 55 ℃, preferably room temperature to 40 ℃.

The invention also provides a lithium ion battery cell, which is obtained by infiltrating the cell by the electrode infiltration method and then performing a formation process.

The invention further provides a lithium ion battery, which comprises the lithium ion battery cell.

ADVANTAGEOUS EFFECTS OF INVENTION

The technical scheme of the invention has the following beneficial effects:

1) The method has the advantages of no need of high-temperature infiltration, no need of long shelf time, simple process, low cost, strong compatibility and improvement on the production efficiency of the battery;

2) Meanwhile, other performances of the battery are not influenced, and the cycle performance of the battery is almost equal to or even better than that of the battery which is soaked at high temperature and laid aside.

Drawings

FIG. 1 shows a flow chart of the electrode wetting method of the present invention.

Fig. 2 is a schematic diagram showing a pulse charge and discharge process in the electrode wetting of the present invention.

Fig. 3 shows a comparison of cycle performance between example 1 and comparative example 3.

Detailed Description

The embodiments of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims, and embodiments obtained by appropriately combining different embodiments and technical means disclosed in the embodiments are also included in the technical scope of the present invention. All documents described in this specification are incorporated herein by reference.

Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

In the present specification, the numerical range represented by "a value a to B value" means a range including the endpoint value A, B.

In the present specification, "plurality" of "plural", and the like means a numerical value of 2 or more unless otherwise specified.

In this specification, the terms "substantially", "substantially" or "substantially" mean an error of less than 5%, or less than 3%, or less than 1% as compared to the relevant perfect or theoretical standard.

In the present specification, "%" denotes mass% unless otherwise specified.

In the present specification, if "room temperature" or "normal temperature" is mentioned, the temperature may be generally 10 to 37 ℃ or 15 to 35 ℃.

In the present specification, the meaning of "may" or "may" includes both the meaning of the presence or absence of both the aspect and the aspect of performing a certain treatment and the aspect of not performing a certain treatment.

In this specification, "optional" and "optionally" mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not. The terms "comprises" and "comprising," and any variations thereof, in the description and claims of this invention and the above-described drawings are intended to cover non-exclusive inclusions. For example, a process, method, or system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

In the present specification, reference to "some/preferred embodiments", "embodiments", and the like, means that a particular element (e.g., feature, structure, property, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.

Recently, a method for improving the electrode wetting effect by electrochemistry has been attracting attention. For example, the prior art discloses a method for improving the cell wetting effect, which includes: after the lithium ion battery encapsulates the battery core and is injected with liquid, continuously vacuumizing for at least three times; vertically placing the battery cell, and then carrying out micro-charging by using low current; after micro charging is finished, the battery is continuously placed vertically, and the battery core is flapped and rolled in the process; pre-charging the rolled battery cell; and vertically placing the pre-charged battery cell in a high-temperature environment for treatment, and then carrying out high-current formation. The prior art also discloses an electrolyte infiltration method of a lithium ion battery, which comprises high-pressure liquid injection, primary shelving, primary pre-charging, secondary shelving, secondary pre-charging, tertiary shelving and liquid supplementation. The method has the advantages of more steps, complex operation, multiple times of shelving and higher time cost.

In addition, the prior art discloses a method for processing a retired power battery, which includes: injecting electrolyte into a liquid injection hole on a battery core of the power battery; carrying out low-current formation treatment on the battery cell injected with the electrolyte; injecting electrolyte into the battery cell after the undercurrent formation treatment from the liquid injection hole; sealing the liquid injection hole; and carrying out charging and discharging processing of different multiplying powers on the sealed battery cell. However, the charge and discharge treatment is a treatment in a formation stage, and aims to reopen an originally closed pore channel and realize the desorption of lithium ions, rather than realize the infiltration of an electrode or a battery cell.

Although the existing electrochemical infiltration method can improve the wettability of the electrode electrolyte to a certain degree, the existing electrochemical infiltration method has the problems of more operation steps, relative complexity, long infiltration time, low production efficiency, higher cost and the like, and the problems are more prominent particularly for thick electrode systems. Accordingly, the present invention has been made to solve the problems.

< first aspect >

A first aspect of the invention relates to a method for impregnating an electrode or a cell of a lithium ion battery with an electrolyte. As shown in fig. 1, the electrode wetting method of the present invention includes:

step S1: a step of injecting an electrolyte into a cell including a positive electrode plate and a negative electrode plate and sealing the same, an

Step S2: and charging and discharging the battery cell after liquid injection to realize the electrochemical infiltration step of the battery cell.

Battery cell

In the embodiment of the present invention, the battery cell and the method for manufacturing the battery cell are not particularly limited, and a battery cell commonly used in the art and a conventional method for manufacturing a battery cell may be used.

For example, in some embodiments of the present invention, the positive electrode sheet in the battery cell may be obtained by mixing a positive active material, a conductive agent, a binder, a solvent, an optional additive, and the like to obtain a positive electrode slurry, coating the positive electrode slurry on a positive current collector, and then baking, rolling, and slitting to obtain the positive electrode sheet. Similarly, the negative electrode plate in the battery core can be prepared by mixing a negative active material, a conductive agent, a binder, a solvent, an optional additive and the like to obtain a negative slurry, coating the negative slurry on a negative current collector, and then baking, rolling and slitting the negative current collector to obtain the negative electrode plate.

After the positive pole piece and the negative pole piece are manufactured, the positive pole piece, the diaphragm and the negative pole piece are sequentially stacked, wherein the diaphragm completely separates the positive pole piece from the negative pole piece, and the positive pole piece and the negative pole piece are wound and packaged to obtain the battery cell.

In the embodiment of the present invention, there is no particular limitation on the positive electrode active material (hereinafter also simply referred to as "positive electrode material"), the negative electrode active material (hereinafter also simply referred to as "negative electrode material"), the separator, the binder, the current collector, the solvent, the additive, and the like in the battery cell, and those commonly used in the art may be used.

In some embodiments of the invention, examples of the positive electrode material may include one or more of lithium cobaltate, lithium manganate, lithium nickel cobalt aluminate, lithium iron phosphate, lithium hydroxide, lithium oxide, lithium carbonate, lithium halides (e.g., lithium fluoride, lithium chloride, lithium bromide, lithium iodide), and the like. Among them, lithium cobaltate is preferable because the compacted density of lithium cobaltate is large (for example, 4.2 g/cm) in the conventional positive electrode material ³ ) The problem of electrolyte immersion and wetting is more prominent and needs to be solved.

In some embodiments of the invention, examples of the negative electrode material may include graphite, graphite and SiO _x Mixtures of (a), mesocarbon microbeads, and the like.

In some embodiments of the present invention, the material of the separator may be polyethylene, polypropylene, polyethylene terephthalate, polyimide, non-woven fabric, ceramic, or the like.

In some embodiments of the present invention, examples of the conductive agent may include one or more of conductive carbon black, acetylene black, ketjen black, graphene, carbon nanotubes, and the like. Examples of the binder may include polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, acrylonitrile polyblend, styrene butadiene rubber, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and the like. Examples of the current collector may include a stainless steel belt, an aluminum foil, a carbon-coated aluminum foil, a copper foil, a carbon-coated copper foil, a conductive carbon support film, and the like. Examples of the solvent may include water, N-methylpyrrolidone, ethylene carbonate and the like, commonly used solvents, isopropyl alcohol and the like.

In certain embodiments of the present invention, additives may be included in the positive electrode slurry or the negative electrode slurry as needed. Examples of additives may include lithium carbonate, lithium hydroxide, commonly used lithium supplement materials, and the like.

Electrolyte solution

In the embodiment of the present invention, the electrolyte is not particularly limited, and an electrolyte commonly used in the art may be used.

In some embodiments of the invention, the electrolyte comprises a lithium salt, an organic solvent, and optionally additives. Among them, examples of the lithium salt may include lithium hexafluorophosphate (LiPF) ₆ ) Lithium difluorophosphate (LiPO) ₂ F ₂ ) One or more of lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium bis (fluorosulfonyl) imide, lithium trifluoromethyl (sulfonyl) imide and lithium trifluoromethyl (sulfonyl) imide. Examples of the organic solvent may include one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), propyl Propionate (PP), ethyl Methyl Carbonate (EMC), fluoroethylene carbonate (FEC), ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, ethyl butyrate, propyl butyrate, γ -butyrolactone, δ -valerolactone.

In some preferred embodiments of the present invention, additives may be added to the electrolyte as needed. Examples of additives may include one or more of 1,3-Propane Sultone (PS), vinylene Carbonate (VC), adiponitrile (ADN), ethylene glycol bis (propionitrile) ether (done).

Electrochemical wetting of electrodes

In the electrode impregnation method of the present invention, the cell is first injected with the electrolyte and sealed, and then optionally the cell is shelved, followed by electrochemical impregnation. In the present invention, the method of injecting the battery cell is not particularly limited, and a method of injecting a liquid that is conventional in the art may be used.

After injecting the electric core into electrolyte and sealing, the step of shelving or the step of shelving may not be carried out.

When the electrode infiltration method does not comprise a placing step, the battery core is injected with the electrolyte and directly charged and discharged after being sealed, so that the infiltration of the electrode is realized. In this case, the time interval between the sealing of the cell and the charge and discharge may be less than 5min, preferably 3min or less, more preferably 1min or less, in view of practical operation.

When the electrode impregnation method of the present invention includes a standing step, the standing time may be 5min to 6 hours, preferably 0.5 hour to 3 hours, and for example, may be 5min, 15min, 0.5 hour, 1 hour, 1.5 hour, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, or the like. The temperature of the shelf may be from room temperature to 55 deg.C, preferably from room temperature to 40 deg.C, and may be, for example, 25 deg.C, 30 deg.C, 35 deg.C, 40 deg.C, 45 deg.C, 50 deg.C, 55 deg.C, etc.

In the present invention, the step of laying down is preferably performed from the viewpoint of further improving the wettability of the electrode. And it is preferable not to carry out the step of laying aside from the viewpoint of simplicity of operation and time cost saving. In the present invention, even if the electrodes are infiltrated by directly charging and discharging the sealed cell without the step of leaving the cell to stand, the infiltrating effect is excellent.

In some embodiments of the present invention, during charging and discharging, the charging current is 0.008C to 0.8C, preferably 0.01C to 0.6C, and the discharging current is 0.008C to 0.6C, preferably 0.01C to 0.2C, where C is the design capacity of the battery.

In the present invention, it is necessary to set the upper and lower cutoff voltages for charge and discharge. The lower limit voltage may be OCP, where OCP is the open circuit voltage of the cell after liquid injection. The upper limit voltage does not exceed 1.2V. The upper limit is limited to 1.2V, so that the electrode is soaked into low-current charge and discharge, an SEI (solid electrolyte interphase) film is not generated to consume electrolyte so as to prevent the first effect and the capacity of the battery from being reduced, and the steps can be strictly differentiated into working procedures. In the chemical conversion step, a high voltage (1.5V to 3.5V) is reached, and an SEI film is formed, thereby consuming the electrolyte.

Therefore, in the charge/discharge process of the present invention, the charge cut-off voltage is not less than OCP and not more than 1.2V, preferably not less than 0.4V and not more than 1.1V. For example, the charge cut-off voltage may be 0.4V, 0.5V, 0.6V, 0.7V, 0.8V, 0.9V, 1.0V, 1.1V, or the like.

In the charge and discharge of the present invention, the duration of each of the charge and discharge is 5s to 60s, preferably 10s to 45s, and may be, for example, 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, or the like.

In the charge and discharge of the present invention, the battery cell is cyclically charged and discharged, and the total cyclic charge and discharge time, i.e., the total electrode wetting time, may be 0.8 to 4.0 hours, preferably 1.0 to 3.5 hours, and may be, for example, 1.0 hour, 1.5 hours, 1.8 hours, 2.0 hours, 2.2 hours, 2.5 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.5 hours, 3.8 hours, or 4.0 hours.

In the charging and discharging process of the invention, the rest time is set after each charging or discharging. The rest time may be from 1s to 15s, preferably from 2s to 10s, and may be, for example, 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, 11s, 12s, 13s, 14s, 15s. The rest time is set so that solvent molecules brought by lithium ions under the action of current can stay near the pole piece, the infiltration effect of the solvent on the pole piece is increased, and the pole piece is infiltrated through the cyclic reciprocation of charging and discharging.

In actual operation, the total number of charging and discharging times can be converted through the electrochemical soaking time. For example, in example 1, the time of one charge/discharge cycle (i.e., charge time + discharge time + rest time) is 61s, the total cycle time is 2.2h, and the program can select 130 cycles of charge/discharge cycles, and keep the number integer. This allows the programming to be programmed to carry out the charging and discharging process.

In some preferred embodiments of the invention, the charging current is 0.01C to 0.06C, the discharging current may be 0.01C to 0.04C, the charging and discharging time may last 20s to 45s respectively, the rest time may be 1s to 5s, and the total time of the cyclic charging and discharging may be 1.8 hours to 2.8 hours.

In other preferred embodiments of the invention, the charging current may be from 0.1C to 0.6C, the discharging current may be from 0.04C to 0.2C, the charging and discharging times may last from 10s to 40s, respectively, the rest time may be from 5s to 10s, and the total time of the cyclic charging and discharging may be from 2.0 hours to 3.0 hours.

In the present invention, the charge and discharge is preferably pulse charge and discharge. Fig. 2 shows a schematic diagram of the pulse charging and discharging process when the electrode of the present invention is immersed. Although the charging current and the discharging current are shown in fig. 2 as being equal in size and rectangular in pulse shape, this is merely illustrative and not limiting. For example, the pulse shape may be square, rectangular, triangular, trapezoidal, and the like. The charging current and the discharging current may be equal or unequal.

In the present invention, the environmental temperature during the electrochemical infiltration process can be controlled to be room temperature to 55 ℃, preferably, the environmental temperature can be room temperature to 40 ℃, for example, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃ and the like. The temperature is increased and the electrochemical infiltration method is combined to realize the synergistic effect, so that the infiltration of the electrolyte is more facilitated, and the temperature can be properly increased to 40-55 ℃. The impregnation can be carried out at room temperature, taking into account the ease of handling and the energy consumption.

< second aspect >

A second aspect of the invention relates to a lithium ion battery cell and a lithium ion battery.

The lithium ion battery cell of the present invention is obtained by impregnating the cell with the electrode impregnation method of the above < first aspect >, and then performing the formation step.

In the present invention, the conditions in the chemical conversion step are not particularly limited, and chemical conversion conditions generally used in the art can be used.

In some embodiments of the invention, the formation process may include the steps of: charging with small current, charging with large current, primary placement, discharging, secondary placement and constant-current constant-voltage charging.

In the invention, the formation process is carried out by voltage division. Specifically, a film forming stage is mainly performed at 1.5-3.6V, and a small current is adopted at the time, so that the process is continuous current charging; the 3.6V-4.35V is a lithium insertion process, which is characterized by voltage rise and capacity increase, and the charging can be carried out by adopting large current, and the process is continuous current charging. As can be seen from the above, 3.6V is the boundary point between the current levels in the film formation region and the capacity boundary region.

In some embodiments of the present invention, the low-current charging may be continuously charging the battery cell with a current of 0.1 to 0.3C for 20 to 40min to a voltage of 3.6V; the large-current charging may be charging the battery cell with a current of 0.4C to 0.6C to a voltage of 4.35V.

In some embodiments of the invention, the shelf life of one shelf is 3min to 8min, preferably 4min to 6min; the discharge can be from 0.4C to 0.6C to 3.0V; the shelf time of the second shelf can be 3min to 8min, preferably 4min to 6min; the constant current and constant voltage charging can be carried out to 3.8V by using a current of 0.4-0.6C.

The lithium ion battery of the present invention includes a lithium ion battery cell obtained by the above-described cell impregnation step and formation step.

In the present invention, the battery type is not particularly limited, and may be, for example, a cylindrical type, a square case type, a pouch type, or the like. Among them, a soft pack type lithium ion battery is preferably used.

Examples

In order to more clearly and completely show the technical scheme of the invention and to facilitate the understanding of the purpose of the invention and the effect of the gain thereof, the technical scheme of the invention will be described below with reference to specific examples, comparative examples and drawings. It will be understood by those skilled in the art that the following examples are illustrative of the present invention only and should not be taken as limiting the scope of the invention.

The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Preparation of cell

Selecting the compacted density of 4.2g/cm ³ The lithium cobaltate is used as a positive electrode material, and the compaction density is 1.7g/cm ³ As the negative electrode material. The anode material is as follows: the single crystal lithium cobaltate, super-P (carbon black), carbon nanotube and PVDF are 96.5 mass%, 1.3 mass%, 0.2 mass% and 2.0 mass%And (4) mixing the components in proportion. The negative electrode comprises the following materials: the synthetic graphite, super-P, styrene Butadiene Rubber (SBR) and hydroxymethyl cellulose lithium (CMC-Li) are mixed according to the mass percent of 95: 1.5 mass%: 2.5 mass%: mixed at a ratio of 1.0 mass%. Then, NMP solvent was added to the positive electrode material, and ultrapure water was added to the negative electrode material to adjust the viscosity of the positive electrode material to 4000cp and the viscosity of the negative electrode material to 3200cp, thereby obtaining positive and negative electrode slurries, respectively. And then coating the positive electrode slurry on an aluminum foil serving as a positive electrode current collector, coating the negative electrode slurry on a copper foil serving as a negative electrode current collector, baking, rolling and cutting to prepare positive and negative electrode plates respectively, stacking the positive electrode plates, the diaphragm and the negative electrode plates in sequence, completely separating the positive and negative electrode plates by the diaphragm, and winding and packaging to obtain the soft package battery cell.

Preparation of electrolyte

In a drying chamber with a dew point lower than-50 ℃, ethylene Carbonate (EC), propylene Carbonate (PC), propyl Propionate (PP), ethyl Methyl Carbonate (EMC), and fluoroethylene carbonate (FEC) dried after water removal are mixed and shaken in a ratio of EC/PC/PP/EMC/FEC to 5 ₆ ) 0.6wt% lithium difluorophosphate (LiPO) ₂ F ₂ ) The resulting electrolyte solution was prepared by mixing and shaking 2.0wt% of 1,3-Propanesultone (PS), 0.5wt% of Vinylene Carbonate (VC), 1.0wt% of Adiponitrile (ADN), and 1.0wt% of ethylene glycol bis (propionitrile) ether (done) to prepare an electrolyte solution that can be used.

The cells and electrolytes used in examples 1 to 7 and comparative examples 1 to 3 were prepared as described above, and the conditions for electrochemically infiltrating the cells are shown in table 1.

In all the examples, the electrochemical infiltration operation is performed immediately after the cell is sealed by liquid injection. The comparative examples 1 to 3 are soaked by adopting a conventional standing and soaking method, namely, the battery cell is subjected to liquid injection and sealing and then is placed for soaking, wherein the soaking effect of the pole piece is improved by increasing the standing time and increasing the environmental temperature. The shelf conditions of comparative examples 1 to 3 are shown in Table 2.

Table 1 cell wetting conditions for examples 1 to 7

TABLE 2 shelf infiltration conditions for comparative examples 1 to 3

	Shelf life/h	Shelf temperature/. Degree.C
			Comparative example 1	15	/
Comparative example 2	15	25
			Comparative example 3	15	55

And after the electrolyte and the electrode material are soaked according to the respective methods in all the examples and comparative examples, a formation procedure is carried out. All the examples and comparative examples were formed according to a uniform formation system. The formation system is as follows: firstly, charging the battery cell for 30min by using a current of 0.2C, and cutting off the voltage by 3.6V; then, charging the battery cell to 4.35V by 0.5C current; standing for 5min, discharging to 3.0V at 0.5C, standing for 5min, and constant-current and constant-voltage charging to 3.8V to complete the formation process.

The battery performance test method in the present invention is explained below.

Cycle performance

And after the formation of all the battery cores is finished, placing the battery cores in an environment of 25 ℃ for cycle life testing. The charging and discharging system is set aside for 5min, and the constant current and the constant voltage are charged to 4.35V with the current multiplying power of 3C until the current is 0.02C; the mixture was left for 5min and then discharged to 3.0V at a constant current of 1C.

High temperature shelf life

After all the cells are formed, the cells are charged to 4.35V by constant current and constant voltage of 0.5C current, and are placed in a high-temperature oven at the temperature of 45 ℃ for 7 days, and the capacity recovery and retention capability of the cells are tested.

Table 3 shows the capacity retention rate, the high-temperature shelf capacity retention rate and the internal resistance increase rate after 300 cycles at 25 ℃ for all examples and comparative examples.

The calculation method of the circulating capacity retention rate is as follows:

η _{capacity retention rate} ＝(Q ₃₀₀ /Q ₀ )×100％；

The high-temperature shelf capacity retention rate calculation method comprises the following steps:

η _{high temperature capacity retention ratio} ＝(Q _7d /Q _0d )×100％；

Wherein the content of the first and second substances,

Q ₃₀₀ : the capacity of the battery after 300 times of cycling;

Q ₀ : is the initial capacity of the battery;

Q _7d : the capacity of the battery is set aside for 7 days at high temperature;

Q _0d : for the capacity of the battery before high-temperature laying

Table 3 results of cell performance test of examples 1 to 7 and comparative examples 1 to 3

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Through the data of the comparative example and the comparative example, the rapid infiltration of the pole piece can be realized through the electrochemical method provided by the invention.

The electrochemical methods employed in examples 1-7 had substantially the same performance as, and even better than, conventional impregnation methods, both in terms of cell cycle capacity retention and in terms of cell high temperature shelf performance.

As shown in fig. 3, the impregnation by the pulse charge and discharge of the present invention in example 1 is better in cycle stability than the conventional impregnation in comparative example 3.

As can be seen from the above, the impregnation method of the present invention enables rapid and simple impregnation without affecting the battery performance.

Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Industrial applicability

The technical scheme of the invention can completely replace the traditional process at present, and the electrochemical infiltration method does not need to be laid aside on the premise of not influencing the performance of the battery, thereby improving the production efficiency of the battery, reducing the energy consumption and greatly reducing the manufacturing cost.

Claims

1. An electrode wetting method, comprising, prior to formation:

Charging and discharging the battery cell after liquid injection to realize electrochemical infiltration of the battery cell,

during charging and discharging, the charging current is 0.008C to 0.8C, the discharging current is 0.008C to 0.6C, and C is the design capacity of the battery;

wherein in the charging and discharging, the duration time of the charging and the discharging is 5 to 60s;

carrying out cyclic charge and discharge on the battery cell, wherein the total cyclic charge and discharge time is 0.8 to 4.0 hours;

and during the charging and discharging, the charge cut-off voltage is more than or equal to OCP and less than or equal to 1.2V, wherein the OCP is the open-circuit voltage of the battery cell after liquid injection is finished.

2. The electrode impregnation method according to claim 1, wherein in the charging and discharging, the charging current is 0.01 to 0.6C, and the discharging current is 0.01C to 0.2C, wherein C is the design capacity of the battery.

3. The electrode impregnation method according to claim 1, wherein in the charging and discharging, the respective durations of the charging and discharging are 10 to 45s;

and carrying out cyclic charge and discharge on the battery cell, wherein the total cyclic charge and discharge time is 1.0 to 3.5 hours.

4. The electrode wetting method according to any one of claims 1~3, wherein a charge cut-off voltage is 0.4V or more and 1.1V or less in the charging and discharging.

5. The electrode infiltration method of any one of claims 1~3, wherein in said charging and discharging, a rest time is set after each charge and/or discharge, wherein the rest time is 1s to 15s.

6. The electrode infiltration method of any one of claims 1~3, wherein in the charging and discharging, a rest time is set after each charging and/or discharging, wherein the rest time is from 2s to 10s.

7. The electrode infiltration method of any of claims 1~3, wherein in said charging and discharging, the charging current is from 0.01C to 0.06C, the discharging current is from 0.01C to 0.04C, the duration of each of charging and discharging is from 20s to 45s, the rest time is from 1s to 5s, and the total cycle charging and discharging time is from 1.8 hours to 2.8 hours.

8. The electrode infiltration method of any one of claims 1~3, wherein in the charging and discharging, the charging current is 0.1C to 0.6C, the discharging current is 0.04C to 0.2C, the duration of each of charging and discharging is 10s to 40s, the rest time is 5s to 10s, and the total cycle charging and discharging time is 2.0 to 3.0 hours.

9. The electrode infiltration method of any of claims 1~3 wherein the electrochemical infiltration step is performed at room temperature to 55 ℃.

10. The electrode infiltration method of any one of claims 1~3, wherein the electrochemical infiltration step is performed at room temperature to 40 ℃.

11. The electrode wetting method according to any one of claims 1 to 3, wherein the charge and discharge is pulsed.

12. The electrode infiltration method of any one of claims 1-3, further comprising a resting step of resting the cells with completed injection prior to the electrochemical infiltration step.

13. The electrode infiltration method according to claim 12, wherein in the resting step, the resting time is 5min to 6 hours, and the resting temperature is room temperature to 55 ℃.

14. The electrode impregnation method according to claim 12, wherein in the standing step, the standing time is 0.5 to 3 hours, and the standing temperature is room temperature to 40 ℃.

15. A lithium ion battery cell obtained by impregnating a cell by the electrode impregnation method according to any one of claims 1 to 14, followed by a formation process.

16. A lithium ion battery comprising the lithium ion battery cell of claim 15.