CN113178633A - Formation method of pre-lithiation battery, lithium ion battery and preparation method of lithium ion battery - Google Patents
Formation method of pre-lithiation battery, lithium ion battery and preparation method of lithium ion battery Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/44—Methods for charging or discharging
- H01M10/446—Initial charging measures
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2220/00—Batteries for particular applications
- H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention provides a formation method of a pre-lithiation battery, a lithium ion battery and a preparation method thereof, wherein the pre-lithiation battery is provided with a negative electrode pre-lithiation layer, and the formation method comprises the following steps: vacuumizing the pre-lithiation battery assembled with the pre-lithium core, and injecting electrolyte in multiple times; pre-sealing edges, pressurizing and standing in an environment with the temperature of-20-15 ℃, wherein the pressure is 0.01-5 Kgf/cm2(ii) a Charging to 5-30% SOC at a current of 0.01-0.1C in an environment with a temperature of 15-35 ℃, and discharging the battery cell to 4-6% SOC after charging is finished; charging by adopting segmented current under the environment of 15-35 ℃, wherein the current is charged to 100% SOC from small to large. The formation method of the pre-lithiation battery is simple and convenient to operate, and can form a stable SEI film, so that the cycle performance of the lithium ion battery can be improved。
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a formation method of a pre-lithiation battery, a lithium ion battery and a preparation method of the lithium ion battery.
Background
With the wide use of lithium ion batteries, electrochemical energy storage puts higher requirements on the cost, energy density, cycle life and safety of the lithium ion batteries. In the production flow of the lithium ion battery, after the preparation of the battery core is finished, continuous processes of liquid injection, formation and aging are required, the liquid injection, formation and aging processes are long-time and high-cost processes, and the processes have important influence on the performance and service life of the lithium ion battery. One important factor is the electrode wetting process, and sufficient and uniform cell wetting is particularly important in the formation/aging process. After the electrolyte fully infiltrates the electrode, an SEI film at the interface of the electrode/the electrolyte is formed in a formation stage and is further subjected to chemical rearrangement adjustment in an aging stage. In the process, a plurality of technical parameters such as temperature, external mechanical pressure, charge and discharge current, charge and discharge voltage, charge state, electrolyte composition and property, battery chemical characteristics and the like influence the formation effect of the battery, so that the difference between the formation time and the performance of the battery is caused, and the production cost of the battery is directly determined.
The formation is to charge the battery cell for the first time after the battery is injected with liquid, activate active substances in the battery and activate the lithium ion battery. In the formation process, along with the intercalation of lithium ions in a negative electrode, the components of an electrolyte solution generate a reduction reaction at the negative electrode to form a stable solid electrolyte interface film (SEI film) so as to prevent the irreversible consumption of the electrolyte solution and the lithium ions in the subsequent circulation process, so that the significance of the technology on the battery performance is remarkable, and the formation effect directly influences the subsequent performance of the lithium ion battery, including storage performance, cycle life, rate capability, safety and the like. A plurality of charge-discharge cycles are required for a complete formation process, and research shows that 10-20% of the initial capacity of the lithium ion battery is used as irreversible capacity loss to form an SEI film in the first charge-discharge cycle, and a small amount of SEI film is continuously formed in the subsequent cycles. Since lithium ions from the positive electrode are consumed in the formation process and cannot become active lithium capable of providing effective capacity for the battery cell, various lithium supplement technologies have been paid attention. The existing lithium supplementing method using metal lithium does not consider that the metal lithium is accurately used for supplementing lithium ions, the metal lithium is directly attached to a negative electrode plate and is waited to be oxidized into lithium ions, so that a lot of dead lithium can be caused, the effect is equivalent to that of lithium dendrites, and even potential safety hazards can be caused. Particularly, as the requirement of people on the energy density of the battery is higher and higher, the high-nickel ternary cathode material and the silicon cathode are used on a large scale, the gas generation in the lithium ion battery is further aggravated, and the SEI film generation condition in the formation process is very important.
The conventional formation process is to perform charge and discharge after the battery subjected to liquid injection and pre-sealing is kept stand for a period of time to form an SEI film, and then the battery is kept stand for a period of time to realize the stabilization of the SEI film. Different forms of SEI films formed by different formation processes have different forms. In order to obtain an SEI film with good uniformity and stability, the traditional formation process adopts a low-current formation process, which is beneficial to the formation of the stable SEI film, but the resistance of the formed SEI film is increased by the process, so that the cycle and rate performance of a battery are poor; the other mode is a high-temperature large-current formation mode, but the electrolyte solvent or additive is unstable at high temperature, and the film formation of the electrolyte on the negative electrode is also influenced, so that the electrochemical performance of the lithium ion battery is reduced.
Therefore, there is a need to develop a method for forming a pre-lithiated battery with simple operation and good SEI interface to improve the cycle performance of a lithium ion battery.
Disclosure of Invention
Therefore, a formation method of a pre-lithiation battery, a lithium ion battery and a preparation method thereof are needed, wherein the formation method is simple and convenient to operate, and can form a stable SEI film so as to improve the cycle performance of the lithium ion battery.
A formation method of a prelithiation battery provided with a negative electrode prelithiation layer, the formation method comprising the steps of:
(1) vacuumizing the pre-lithiation battery assembled with the pre-lithium core, and injecting electrolyte in batches;
(2) after pre-edge sealing, adding the mixture in a vacuum environment at the temperature of-20 to 15 DEG CStanding under a pressure of 0.01 to 5Kgf/cm2；
(3) Charging to 5-30% SOC at a current of 0.01-0.1C in an environment with a temperature of 15-35 ℃, and discharging the battery cell to 4-6% SOC after charging is finished;
(4) charging by adopting segmented current under the environment of 15-35 ℃, wherein the current is charged to 100% SOC from small to large.
In one embodiment, in the step (1), the injection coefficient is 2-4, the injection is performed for 2-5 times, the vacuum degree is-40 kPa-60 kPa, and the battery is kept still for 5-30 min after each injection.
In one embodiment, in the step (2), the edge is pre-sealed under the environment of vacuum degree of-80 kPa to-90 kPa and the pressure is 0.1 to 5Kgf/cm2And standing for 24-120 h at the temperature of-10-5 ℃.
In one embodiment, in the step (3), the battery is charged to 5% -30% SOC with a current of 0.02-0.05C, and after the charging is finished, the battery is kept still for 2-12 h and is discharged to 5% SOC.
In one embodiment, step (4) includes the following steps:
applying 5-40 Kgf/cm to the pre-lithiation battery under the environment with the temperature of 20-30 DEG C2Charging to 30-50% SOC at a current of 0.02-0.05C, and standing for 5-15 min;
and charging to 100% SOC by a constant current and constant voltage method at a current of 0.2-0.5 ℃.
In one embodiment, the thickness of the negative electrode pre-lithiation layer is 1 to 5 μm.
A preparation method of a lithium ion battery is provided, wherein the lithium ion battery is a pre-lithiation battery provided with a negative electrode pre-lithiation layer, and the preparation method comprises the following steps:
assembling a pre-lithium battery core;
the formation method is adopted for formation;
and after the formation is finished, secondary sealing exhaust, aging and capacity grading are carried out on the battery core.
In one embodiment, after the two air-discharging and before the aging, the method further comprises the step of standing for 24-72 hours at the temperature of 20-30 ℃.
The lithium ion battery prepared by the preparation method.
An electric vehicle comprises the lithium ion battery.
The invention has the following beneficial effects:
the formation method of the pre-lithiation battery can improve the amount of lithium transferred between the positive electrode and the negative electrode, utilizes the active lithium of the negative electrode lithium supplement layer to compensate lithium ions consumed by the SEI film, reduces the loss of the active lithium from the positive electrode, and optimizes the formation steps, so that the SEI film formed by the formation method has higher stability, can effectively reduce polarization, reduces self-discharge, and achieves the purpose of improving the first efficiency, multiplying power and cycle performance of the lithium ion battery. The formation method of the pre-lithiation battery is carried out under the condition of normal temperature or low temperature in the whole process, a series of problems caused by high-temperature formation are avoided, energy consumption can be reduced, and a brand new thought is provided for developing a high-efficiency and convenient formation process of the pre-lithiation battery.
Drawings
FIG. 1 is a flow chart of a chemical synthesis method according to an embodiment of the present invention;
fig. 2 is a first-cycle charge-discharge graph of the batteries of example 1 and comparative example 1, in which a solid line 1 represents example 1 and a dotted line 2 represents comparative example 1.
Detailed Description
In order that the invention may be more fully understood, a more particular description of the invention will now be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all 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. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
One embodiment of the invention provides a formation method of a pre-lithiation battery, and the pre-lithiation battery is provided with a negative electrode pre-lithiation layer.
The lithium ion battery is provided with the negative electrode pre-lithiation layer, and in the negative electrode, lithium in the lithium metal layer is diffused and moved to the negative electrode active material layer below the lithium metal layer in a lithium ion form through pre-lithiation and is combined with the negative electrode active material, so that lithium ions consumed by forming an SEI film can be compensated, the loss of active lithium from the positive electrode is reduced, and the realization of the purposes of all steps of the method is facilitated.
The prelithiation battery of the present invention is provided with a negative electrode prelithiation layer, and the negative electrode prelithiation layer can be prepared by using the existing prelithiation layer material and preparation process, which are not specifically limited herein, and should be understood as all falling within the protection scope of the present invention. For example: the lithium metal layer may be formed by adding and dispersing lithium metal powder and a binder in an organic solvent, and then uniformly applying the solution onto the formed anode active material layer, or by placing a lithium metal foil on the anode active material layer and pressing.
In some embodiments, the negative pre-lithiation layer has a thickness of 1 to 5 μm; further, the thickness of the negative electrode pre-lithiation layer is 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, or 4.5 μm.
The technicians of the invention find in the research that: in the prior art, a pressure is applied to the battery during the charging and discharging processes, and the gas generated during the charging and discharging processes of the battery core is discharged, so as to form a uniform SEI film. However, the wettability of the electrolyte before charging and discharging and the standing of the battery after charging and discharging have a great influence on the compactness and stability of the SEI film. With the increase of the energy density of the battery, the coating amount of the positive and negative active materials is increased, and even if the standing time before and during charge and discharge is prolonged, the wettability of the electrolyte and the stability and compactness of an SEI film cannot be ensured.
Based on this, the present inventors designed a method for forming a prelithiation battery according to the present invention:
1) a negative electrode lithium supplement layer is arranged, and active lithium of the negative electrode lithium supplement layer is used for compensating lithium ions consumed by SEI film formation, so that the loss of active lithium from the positive electrode is reduced;
2) the whole operation steps of each formation are optimized, and a method of vacuum fractional liquid injection, pre-sealing and low-temperature pressurization standing is adopted firstly to reduce the side reaction of the negative electrode pre-lithiation layer and the electrolyte, reduce instant heat release, accelerate the permeation of the electrolyte to an electrode, fully infiltrate a battery cell, slowly release lithium ions from the lithium supplement layer and perform a preliminary pre-lithium intercalation reaction with a negative electrode material. And then, pre-lithium intercalation formation is carried out, and the low-current charging is adopted to the SEI film forming voltage stage, so that active lithium of the pre-lithium layer is further consumed, the side reaction of the negative electrode, the pre-lithium layer and the electrolyte interface is fully carried out, a stable and compact SEI film is formed, the battery cell is activated, and the subsequent gas production risk is reduced. Then, on the basis of improving the pressure of the clamp, the segmented current charging is adopted, so that the inside of the battery cell has better electrode contact, the lithium deposition is reduced, the generation and the distribution of gas are reduced, the battery cell bulging is avoided, the formation interface is improved, and an SEI film formed after the formation has the best ionic conductivity and stability, so that the purposes of improving the first efficiency, the multiplying power and the cycle performance of the lithium ion battery are achieved.
Specifically, as shown in fig. 1, the formation method of the prelithiation battery of the present invention includes the following steps:
s110: liquid injection: and vacuumizing the pre-lithiation battery assembled with the pre-lithium core, and injecting electrolyte in multiple times.
By adopting the method of injecting the electrolyte into the pre-lithiation battery in vacuum in a fractional manner, the side reaction between the negative electrode pre-lithiation layer of the pre-lithiation battery and the electrolyte can be reduced, active lithium in the lithium supplement layer is consumed, instant heat release is reduced, the permeation of the electrolyte to an electrode is accelerated, and the performance of the battery is improved.
In some embodiments, in the step S110, the liquid injection coefficient is 2-4, the liquid injection is performed for 2-5 times, the vacuum degree is-40 kPa-60 kPa, and the battery is kept still for 5-30 min after each liquid injection; further, the liquid injection coefficient is 2.3-3.5, liquid injection is carried out for 2-3 times, and the battery stands for 5-15min after each liquid injection.
In some embodiments, in step S110, the injection is divided into 2, 3, 4, or 5 times.
In some embodiments, in step S110, the vacuum level is-40 kPa, -42kPa, -45kPa, -48kPa, -50kPa, -52kPa, -55kPa, -58kPa, or-60 kPa.
In some embodiments, the battery resting time after each injection is 5min, 6min, 8min, 10min, 12min, 14min, 15min, 18min, 20min, 23min, 25min, 28min, or 30 min.
S120: pre-sealing and standing: pre-sealing edges, pressurizing and standing in an environment with the temperature of-20-15 ℃, wherein the pressure is 0.01-5 Kgf/cm2。
After pre-sealing, pressurizing and standing to fully soak the battery cell, so that the pre-lithium layer is gradually diffused to the surface of the negative electrode, and the battery cell can be fully and uniformly wetted. After the electrolyte fully infiltrates the electrode, an SEI film at the interface of the electrode/the electrolyte is formed in a formation stage and is further subjected to chemical rearrangement adjustment in an aging stage, so that the problem caused by more gas production in the formation process due to insufficient infiltration of the electrolyte can be effectively avoided, for example: the gas causes the swelling of the battery core, the infiltration of the pole piece at the side of the air bag and SEI film formation, and the problems of black spots, lithium precipitation and the like are caused because the electrolyte is consumed.
In some embodiments, the clamp pressure is 0.5 to 5Kgf/cm2。
In some embodiments, in step S120, the pre-sealing is performed under an environment with a vacuum degree of-80 kPa to-90 kPa, and then the pre-sealing is performed in a negative pressure clamp under a pressure of 0.1Kgf/cm to 5Kgf/cm2And standing for 24-120 h at the temperature of-10-5 ℃.
In some embodiments, the pre-seal vacuum ranges from-82 kPa, -84kPa, -86kPa, -88kPa, or-90 kPa.
In some embodiments, the clamp pressure ranges from 2 to 3Kgf/cm2(ii) a Further, the range of the jig pressure was 0.1Kgf/cm2、0.5Kgf/cm2、0.8Kgf/cm2、1Kgf/cm2、1.2Kgf/cm2、1.5Kgf/cm2、1.8Kgf/cm2、2Kgf/cm2、2.2Kgf/cm2、2.5Kgf/cm2、2.8Kgf/cm2Or 3Kgf/cm2。
In some embodiments, the temperature is from-10 ℃ to 5 ℃; further, the temperature is-10 ℃, -8 ℃, -6 ℃, -4 ℃, -2 ℃, 0 ℃, 2 ℃, 5 ℃.
In some embodiments, the pressurizing and standing time is 48-72 hours; further, the pressurizing standing time is 28h, 30h, 32h, 34h, 36h, 40h, 44h, 46h, 48h, 50h, 52h, 56h, 60h, 65h, 70h or 75 h.
S130: pre-lithium intercalation: charging to 5-30% SOC at a current of 0.01-0.1C in an environment with a temperature of 15-35 ℃, and discharging the battery cell to 4-6% SOC after charging.
By adding the step of pre-lithium intercalation formation, a pressure is applied to the battery in the charging and discharging process, so that the pre-lithium layer gradually reacts with the electrolyte at a small current to release active lithium, and the active lithium is diffused in a lithium ion form and combined with a negative electrode active material to pre-embed lithium to form an initial SEI film, thereby effectively improving the stability of the SEI film and improving the performance of the battery.
In some embodiments, in step S130, the clamp pressure is in the range of 3 to 5Kgf/cm2。
In some embodiments, the temperature in step S130 is 15 ℃ to 35 ℃; further, the temperature is 20-30 ℃; further, the temperature is 20 ℃, 22 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃ and 30 ℃.
In some embodiments, in step S130, charging to 5% to 30% SOC with a current of 0.02 to 0.05C, and after the charging is finished, standing for 2 to 12 hours, discharging to 5% SOC; further, charging to 5% -20% SOC with a current of 0.02-0.03C, and discharging to 5% SOC after standing for 4-8 h after charging is finished.
S140: negative pressure segmented current formation: under the environment of 15-35 deg.C, the step-by-step current formation method is adopted to charge to 100% SOC.
The charging is carried out by adopting the sectional current with the current from small to large, the charging is carried out by adopting the smaller current, the lithium supplement material which is not completely consumed in the pre-lithium embedding stage in the process further reacts with the electrolyte, the SEI film is formed on the surface of the active material of the negative electrode, the stability of the SEI film is further improved, and after the charging of the small current is finished, the current is increased for charging, the charging speed is improved, and the processing efficiency is improved.
In some embodiments, in step S140, preferably, the clamp pressure is increased, and the clamp pressure is increased during the charging process with the segmented current, so as to perform pressurization formation, so that the contact of the electrode inside the battery cell is better, the lithium deposition is reduced, the gas generation and distribution are reduced, and further, the cycle performance of the battery is effectively improved.
In some embodiments, the clamp pressure is increased to 5 to 40Kgf/cm2(ii) a Further, the pressure is increased to 8 to 20Kgf/cm2. The technical personnel of the invention find that the low mechanical pressure can cause the expansion of the active material and the gas can not be discharged, and the high pressure can cause the deformation caused by the closure of the uneven holes of the diaphragm, so the internal dynamics of the battery is hindered, therefore, the pressure of the clamp needs to be controlled in a proper range, and the battery can be ensured to have better performance.
Further, the pressure range was 6Kgf/cm2、8Kgf/cm2、10Kgf/cm2、12Kgf/cm2、14Kgf/cm2、16Kgf/cm2、18Kgf/cm2、20Kgf/cm2、22Kgf/cm2、24Kgf/cm2、26Kgf/cm2、28Kgf/cm2、30Kgf/cm2、32Kgf/cm2、34Kgf/cm2、36Kgf/cm2、38Kgf/cm2Or 40Kgf/cm2。
In some embodiments, the temperature in step S140 is 15 ℃ to 35 ℃; further, the temperature is 20-30 ℃; further, the temperature is 20 ℃, 22 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃ and 30 ℃.
In some implementations, in step S140, a small current is used to charge for a predetermined time, after standing, the current is increased, and a constant current and constant voltage is used to charge to 100% SOC; further, in step S140, the low current charging is performed for 240-.
In some embodiments, step S140 includes the steps of:
s141: raising the pressure of the clamp to 5-40 Kgf/cm in an environment with a temperature of 20-30 deg.C (preferably 25 deg.C)2Charging to 30-50% SOC at current of 0.02-0.05C, and standing for 5-15 min.
Further, in step S141, the pressure of the jig is raised to 8 to 20Kgf/cm2Charging to 40-50% SOC at current of 0.02-0.03C, and standing for 5-15min (preferably 10 min).
In some embodiments, the clamp pressure is 10Kgf/cm2、12Kgf/cm2、14Kgf/cm2、16Kgf/cm2、18Kgf/cm2Or 20Kgf/cm2。
S142: and charging to 100% SOC by a constant current and constant voltage method at a current of 0.2-0.5 ℃.
Further, in step S142, the current is 0.2C, 0.25C, 0.3C, 0.35C, 0.4C, 0.45C, or 0.5C.
In some embodiments, the pressure of the jig is gradually increased from step S120 to step S140; in some embodiments, the clamp pressure of step S120 is greater than step S130, and the clamp pressure of step S130 is greater than step S140.
An embodiment of the present invention further provides a method for preparing a lithium ion battery, including the following steps:
s210: assembling a pre-lithium battery core;
step S210 may adopt an existing battery cell and an assembly method thereof, and is not particularly limited herein, and should be understood to be within the protection scope of the present invention.
S220: formation;
the formation method of step S220 is as described above, and is not particularly limited herein.
S230: and (4) carrying out secondary sealing exhaust, aging and capacity grading on the battery core.
In some embodiments, in step S230, evacuation is performed at a temperature of 20 ℃ to 30 ℃ (preferably 25 ℃); further, after the step of exhausting, before the aging step, the mixture is left standing for 24 to 72 hours in an environment at a temperature of 20 to 30 ℃ (preferably 25 ℃). After secondary air exhaust, the film is subjected to standing and aging at normal temperature for a long time, so that the formed SEI film has the best ionic conductivity and stability.
It is understood that the existing aging and capacity grading method can be adopted in step S230, and will not be described herein again.
The embodiment of the invention also provides the lithium ion battery prepared by the preparation method. The pre-lithiation forming process can improve the amount of lithium transferred between the positive electrode and the negative electrode, utilize the active lithium of the lithium supplementing layer to compensate lithium ions consumed by the SEI film, reduce the loss of the active lithium from the positive electrode, form a stable SEI film, reduce polarization and reduce self-discharge, so that the lithium ion battery prepared by the method has better first efficiency, multiplying power and cycle performance.
Further, the lithium ion battery also comprises a positive electrode and a negative electrode, wherein the positive electrode comprises a positive active material, and the negative electrode comprises a negative active material, wherein the positive active material comprises but is not limited to lithium iron phosphate (LiFePO)4Lithium cobaltate LiCoO2Lithium manganate LiMn2O4Lithium nickelate LiNiO2Lithium nickel cobalt manganese oxide NCM, lithium nickel cobalt aluminate NCA and lithium manganese phosphate LiMnPO4One or more of; the anode active material includes, but is not limited to, one or more of a carbon-based anode, a silicon-based anode, and an oxide-based anode.
The embodiment of the invention also provides an electric vehicle which comprises the lithium ion battery. The lithium ion battery has high first coulombic efficiency, high energy density and high cycle stability, and the whole process can be carried out at normal temperature, so that the production cost of the lithium ion battery is further reduced.
The present invention will be described below with reference to specific examples.
The lithium ion battery cells used in the following examples and comparative examples were: the designed capacity is 8Ah, the anode of the battery cell is a ternary material, and the cathode is a silicon-oxygen-carbon cathode. The lithium ion battery after liquid injection and pre-sealing is composed of a positive plate, a negative plate, a diaphragm, electrolyte, external positive and negative electrode tabs and a battery core outer packaging film.
Example 1
S1: injecting liquid for several times: after the pre-lithium battery core is assembled, vacuumizing and injecting electrolyte for multiple times; the injection coefficient is 3.2, the times of fractional injection are 2, the vacuum degree is-60 KPa, and the battery is kept still for 15min after each injection.
S2: pre-sealing and standing: after the liquid injection is finished, placing the battery cell in a vacuum pre-sealing cavity, vacuumizing for pre-sealing the edge, wherein the pre-sealing vacuum degree is-90 KPa, pressurizing and standing, and the pressure is 1.5Kgf/cm2Keeping the temperature at 5 ℃ for 48 hours;
s3: pre-lithium intercalation: carrying out small-current pressurization charging on the pre-lithium battery after standing at normal temperature, wherein the charging current is 0.02C, charging to 20% SOC, standing at normal temperature for 4h after charging is finished, and discharging to 5% SOC;
s4: segmented current formation: after the completion of the preliminary formation, the formation pressure was increased to 10Kgf/cm2Charging to 40% SOC at a low current of 0.02C, standing for 10min, charging to 100% at a constant current and a constant voltage at a current of 0.2C, and cutting off the current of 0.02C.
S5: secondary sealing, standing and aging: and after the formation is finished, performing secondary sealing on the lithium battery, vacuumizing, exhausting, aging at normal temperature, standing for 24 hours, and performing volume-divided discharge.
Example 2
S1: injecting liquid for several times: after the pre-lithium battery core is assembled, vacuumizing and injecting electrolyte for multiple times; the injection coefficient is 3.2, the times of fractional injection are 3, the vacuum degree is-60 KPa, and the battery is kept still for 15min after each injection.
S2: pre-sealing and standing: after the liquid injection is finished, placing the battery cell in a vacuum pre-sealing cavity, vacuumizing for pre-sealing the edge, wherein the pre-sealing vacuum degree is-90 KPa, pressurizing and standing, and the pressure is 3Kgf/cm2Standing at 5 deg.C for 64 h;
s3: pre-lithium intercalation: carrying out small-current pressurization charging on the pre-lithium battery after standing at normal temperature, wherein the charging current is 0.02C, charging to 20% SOC, standing at normal temperature for 4h after charging is finished, and discharging to 5% SOC;
s4: segmented current formation: after the completion of the preliminary formation, the formation pressure was increased to 20Kgf/cm2Charging to 40% SOC at low current of 0.02C, standing for 10min, and constant-current and constant-voltage charging to 100 at current of 0.2C% and cutoff current 0.02C.
S5: secondary sealing, standing and aging: and after the formation is finished, performing secondary sealing on the lithium battery, vacuumizing, exhausting, aging at normal temperature, standing for 36 hours, and performing volume-divided discharge.
Example 3
S1: injecting liquid for several times: after the pre-lithium battery core is assembled, vacuumizing and injecting electrolyte for multiple times; the injection coefficient is 3.6, the times of fractional injection are 3, the vacuum degree is-60 KPa, and the battery is kept still for 15min after each injection.
S2: pre-sealing and standing: after the liquid injection is finished, placing the battery cell in a vacuum pre-sealing cavity, vacuumizing for pre-sealing the edge, wherein the pre-sealing vacuum degree is-90 KPa, pressurizing and standing, and the pressure is 3Kgf/cm2The temperature is 0 ℃, and the standing time is 64 hours;
s3: pre-lithium intercalation: carrying out small-current pressurization charging on the pre-lithium battery after standing at normal temperature, wherein the charging current is 0.03C, the charging is carried out until the SOC is 20%, and after the charging is finished, standing at the normal temperature for 4 hours, and discharging until the SOC is 5%;
s4: segmented current formation: after the completion of the preliminary formation, the formation pressure was increased to 20Kgf/cm2Charging to 40% SOC at a low current of 0.03C, standing for 10min, charging to 100% at a constant current and a constant voltage at a current of 0.3C, and stopping at a current of 0.02C.
S5: secondary sealing, standing and aging: and after the formation is finished, performing secondary sealing on the lithium battery, vacuumizing, exhausting, aging at normal temperature, standing for 36 hours, and performing volume-divided discharge.
Example 4
S1: injecting liquid for several times: after the pre-lithium battery core is assembled, vacuumizing and injecting electrolyte for multiple times; the injection coefficient is 4, the times of fractional injection are 5 times, the vacuum degree is-60 KPa, and the battery is kept stand for 5min after each injection.
S2: pre-sealing and standing: after the liquid injection is finished, placing the battery cell in a vacuum pre-sealing cavity, vacuumizing for pre-sealing the edge, wherein the pre-sealing vacuum degree is-90 KPa, pressurizing and standing, and the pressure is 5Kgf/cm2The temperature is minus 10 ℃, and the standing time is 72 hours;
s3: pre-lithium intercalation: carrying out small-current pressurization charging on the pre-lithium battery after standing at normal temperature, wherein the charging current is 0.05C, the charging is carried out until the charging reaches 30% SOC, and the pre-lithium battery is placed for 12 hours at normal temperature after the charging is finished and is discharged until the charging reaches 5% SOC;
s4: segmented current formation: after the completion of the preliminary formation, the formation pressure was increased to 40Kgf/cm2Charging to 40% SOC at a low current of 0.05C, standing for 10min, charging to 100% at a constant current and a constant voltage at a current of 0.5C, and stopping at a current of 0.02C.
S5: secondary sealing, standing and aging: and after the formation is finished, performing secondary sealing on the lithium battery, vacuumizing, exhausting, aging at normal temperature, standing for 72 hours, and performing volume-divided discharge.
Example 5
S1: injecting liquid for several times: after the pre-lithium battery core is assembled, vacuumizing and injecting electrolyte for multiple times; the injection coefficient is 2, the times of fractional injection are 2, the vacuum degree is-60 KPa, and the battery is kept still for 30min after each injection.
S2: pre-sealing and standing: after the liquid injection is finished, placing the battery cell in a vacuum pre-sealing cavity, vacuumizing for pre-sealing the edge, wherein the pre-sealing vacuum degree is-90 KPa, pressurizing and standing, and the pressure is 0.5Kgf/cm2Standing at-5 deg.C for 48 h;
s3: pre-lithium intercalation: carrying out small-current pressurization charging on the pre-lithium battery after standing at normal temperature, wherein the charging current is 0.02C, charging to 5% SOC, standing at normal temperature for 4h after charging is finished, and discharging to 5% SOC;
s4: segmented current formation: after the completion of the preliminary formation, the formation pressure was increased to 10Kgf/cm2Charging to 30% SOC at a low current of 0.02C, standing for 10min, charging to 100% at a constant current and a constant voltage at a current of 0.2C, and stopping at a current of 0.02C.
S5: secondary sealing, standing and aging: and after the formation is finished, performing secondary sealing on the lithium battery, vacuumizing, exhausting, aging at normal temperature, standing for 24 hours, and performing volume-divided discharge.
Comparative example 1
S1: injecting liquid for several times: after the pre-lithium battery cell is assembled, vacuumizing and injecting electrolyte; the injection coefficient is 3.2, the times of fractional injection are 1, the vacuum degree is-60 KPa, and the battery is kept stand for 15min after injection.
S2: pre-sealing and standing: after the liquid injection is finished, placing the battery cell in a vacuum pre-sealing cavity, vacuumizing and pre-sealing edges, wherein the pre-sealing vacuum degree is-90 KPa, and then standing at a high temperature of 55 ℃ for 48 hours;
s3: pre-formation: the static pre-lithium battery is pressurized and charged at high temperature of 55 ℃ by small current, and the formation pressure is increased to 10Kgf/cm2Charging to 20% SOC at charging current of 0.02C, and standing for 15 min;
s4: formation: after the completion of the pre-formation, the pre-lithium battery is continuously charged at a high temperature of 55 ℃, and is charged to 100% at a constant current and a constant voltage with a current of 0.2 ℃ and the current is cut off at 0.02 ℃.
S5: secondary sealing, standing and aging: and after the formation is finished, performing secondary sealing on the lithium battery, vacuumizing, exhausting, aging at high temperature, standing for 24 hours, and performing volume-divided discharge.
Comparative example 2
The same as example 1 except that the liquid coefficient was 3.2, and the injection was performed 1 time.
Comparative example 3
Substantially the same as in example 1 except that the standing step in step S2 was a high-temperature standing at 45 ℃.
Comparative example 4
Substantially the same as in embodiment 1, except that step S3 (i.e., the preliminary formation step) is omitted.
Comparative example 5
The process is substantially the same as example 1, except that, in step S5, after formation is completed, the pre-lithium battery is aged and left standing at 55 ℃.
Table 1 shows the test data for various examples
As can be seen from table 1 and fig. 2, compared with the conventional high-temperature pressurized formation process, the formation process of the lithium ion battery of the present invention has a better technical effect, and can effectively improve the electrochemical performance of the lithium ion battery.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A formation method for a prelithiation battery, wherein the prelithiation battery has a negative electrode prelithiation layer, the formation method comprising the steps of:
(1) vacuumizing the pre-lithiation battery assembled with the pre-lithium core, and injecting electrolyte in batches;
(2) after pre-sealing, pressurizing and standing the blank in an environment with the temperature of-20 to 15 ℃, wherein the pressure is 0.01 to 5Kgf/cm2；
(3) Charging to 5% -30% SOC with 0.01-0.1C current in the environment of 15-35 ℃, and discharging the battery cell to 4% -6% SOC after charging;
(4) charging by adopting segmented current under the environment of 15-35 ℃, wherein the current is charged to 100% SOC from small to large.
2. The chemical synthesis method according to claim 1, wherein in the step (1), the injection coefficient is 2 to 4, the injection is performed in 2 to 5 times, the vacuum degree is-40 kPa to-60 kPa, and the battery is allowed to stand for 5 to 30min after each injection.
3. The chemical conversion method according to claim 1, wherein in the step (2), the degree of vacuum is-80 kPa &Pre-sealing the edge under the environment of 90kPa to the extent that the pressure is 0.1 to 5Kgf/cm2And the mixture is pressurized and kept stand for 24 to 120 hours at the temperature of between 10 ℃ below zero and 5 ℃.
4. The chemical conversion method according to claim 1, wherein in the step (3), the battery is charged to 5% to 30% SOC at a current of 0.02 to 0.05C, and after the charging is finished, the battery is left to stand for 2 to 12 hours and is discharged to 5% SOC.
5. The chemical synthesis method according to claim 1, wherein the step (4) comprises the steps of:
applying 5-40 Kgf/cm to the pre-lithiation battery under the environment with the temperature of 20-30 DEG C2Charging to 30-50% SOC at a current of 0.02-0.05C, and standing for 5-15 min;
and charging to 100% SOC by a constant current and constant voltage method at a current of 0.2-0.5 ℃.
6. The chemical conversion method according to any one of claims 1 to 5, wherein the thickness of the negative electrode prelithiation layer is 1 to 5 μm.
7. A preparation method of a lithium ion battery is characterized in that the lithium ion battery is a pre-lithiation battery provided with a negative electrode pre-lithiation layer, and the preparation method comprises the following steps:
assembling a pre-lithium battery core;
carrying out formation by using the formation method of any one of claims 1 to 6;
and after the formation is finished, secondary sealing exhaust, aging and capacity grading are carried out on the battery core.
8. The preparation method of claim 7, further comprising the step of standing at 20-30 ℃ for 24-72 hours after the secondary degassing and before aging.
9. A lithium ion battery prepared by the preparation method according to any one of claims 7 to 8.
10. An electric vehicle comprising the lithium ion battery of claim 9.
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| CN110224182A (en) * | 2019-05-20 | 2019-09-10 | 合肥国轩高科动力能源有限公司 | A kind of method of lithium ion battery prelithiation |
| CN111769332A (en) * | 2020-06-29 | 2020-10-13 | 合肥国轩高科动力能源有限公司 | Formation method of pre-lithium battery and pre-lithiation lithium ion battery |
| CN111934039A (en) * | 2020-08-11 | 2020-11-13 | 华鼎国联动力电池有限公司 | Formation process of lithium ion battery |
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| CN110224182A (en) * | 2019-05-20 | 2019-09-10 | 合肥国轩高科动力能源有限公司 | A kind of method of lithium ion battery prelithiation |
| CN111769332A (en) * | 2020-06-29 | 2020-10-13 | 合肥国轩高科动力能源有限公司 | Formation method of pre-lithium battery and pre-lithiation lithium ion battery |
| CN111934039A (en) * | 2020-08-11 | 2020-11-13 | 华鼎国联动力电池有限公司 | Formation process of lithium ion battery |
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