CN116780005A - Battery formation method - Google Patents
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- CN116780005A CN116780005A CN202310921647.7A CN202310921647A CN116780005A CN 116780005 A CN116780005 A CN 116780005A CN 202310921647 A CN202310921647 A CN 202310921647A CN 116780005 A CN116780005 A CN 116780005A
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- 230000015572 biosynthetic process Effects 0.000 title claims abstract description 83
- 238000000034 method Methods 0.000 title claims abstract description 41
- 238000007600 charging Methods 0.000 claims abstract description 47
- 238000004519 manufacturing process Methods 0.000 claims abstract description 35
- 238000010277 constant-current charging Methods 0.000 claims abstract description 29
- 238000010280 constant potential charging Methods 0.000 claims abstract description 18
- 238000007599 discharging Methods 0.000 claims abstract description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical group [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 claims description 16
- 230000008569 process Effects 0.000 claims description 15
- DOCYQLFVSIEPAG-UHFFFAOYSA-N [Mn].[Fe].[Li] Chemical compound [Mn].[Fe].[Li] DOCYQLFVSIEPAG-UHFFFAOYSA-N 0.000 claims description 13
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical group [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 12
- 229910052744 lithium Inorganic materials 0.000 claims description 12
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 claims description 10
- 239000000463 material Substances 0.000 claims description 10
- 229910000616 Ferromanganese Inorganic materials 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 7
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 claims description 4
- 230000000452 restraining effect Effects 0.000 claims description 3
- 230000001603 reducing effect Effects 0.000 abstract description 5
- 208000028659 discharge Diseases 0.000 description 20
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 12
- 230000000694 effects Effects 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 8
- 238000007789 sealing Methods 0.000 description 7
- 239000010439 graphite Substances 0.000 description 6
- 229910002804 graphite Inorganic materials 0.000 description 6
- 239000007788 liquid Substances 0.000 description 5
- 238000000354 decomposition reaction Methods 0.000 description 4
- 238000002347 injection Methods 0.000 description 4
- 239000007924 injection Substances 0.000 description 4
- 230000008439 repair process Effects 0.000 description 4
- 238000007086 side reaction Methods 0.000 description 4
- 238000001311 chemical methods and process Methods 0.000 description 3
- 239000011572 manganese Substances 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 238000005086 pumping Methods 0.000 description 3
- 230000008961 swelling Effects 0.000 description 3
- 230000002159 abnormal effect Effects 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- QXZUUHYBWMWJHK-UHFFFAOYSA-N [Co].[Ni] Chemical compound [Co].[Ni] QXZUUHYBWMWJHK-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910000398 iron phosphate Inorganic materials 0.000 description 1
- AWKHTBXFNVGFRX-UHFFFAOYSA-K iron(2+);manganese(2+);phosphate Chemical compound [Mn+2].[Fe+2].[O-]P([O-])([O-])=O AWKHTBXFNVGFRX-UHFFFAOYSA-K 0.000 description 1
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- PEUPIGGLJVUNEU-UHFFFAOYSA-N nickel silicon Chemical compound [Si].[Ni] PEUPIGGLJVUNEU-UHFFFAOYSA-N 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 239000011163 secondary particle Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000012876 topography Methods 0.000 description 1
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- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a battery formation method, which comprises the following steps: constant-current charging is carried out at 0.02-0.05C until the voltage corresponding to the end of the first-stage gas production is at least twice, constant-voltage charging is carried out at 0.002-0.005C until the voltage corresponding to the end of the first-stage gas production is at the end of the first-stage gas production, and the first-stage charging is completed; constant-current charging at 0.3-0.6C is adopted between the corresponding voltage of the gas production ending of the first stage and the corresponding voltage of the gas production starting of the second stage, so that the charging of the second stage is completed; in the voltage range corresponding to the gas production of the second stage, constant-current charging is carried out by adopting 0.05-0.1C, then constant-voltage charging is carried out to 0.004-0.005C by using the gas production ending voltage of the second stage, and the charging of the third stage is completed; constant-current discharging to 2.5-3.0V at 0.3-0.5C; the charge and discharge cycle is at least 1.5 circles, the charge and discharge current is 0.4-0.6 ℃, the charge cut-off voltage is 4.1-4.35V, and the discharge cut-off voltage is 2.5-2.8V. The battery manufactured by the formation method can obviously improve the stability and mechanical elasticity of the interface film, and has important significance for reducing the air expansion degree of the battery and expecting to obtain good-product shipment batteries with qualified sizes.
Description
Technical Field
The invention belongs to the technical field of battery formation, and particularly relates to a battery formation method.
Background
The statements herein merely provide background information related to the present disclosure and may not necessarily constitute prior art.
The lithium iron manganese phosphate anode is modified by manganese element based on lithium iron phosphate, and Mn is used for 2+ /Mn 3+ The existence of the redox active pair has an average voltage plateau exceeding 3.9V, so that the energy density of the lithium iron manganese phosphate is improved by 20 percent compared with that of the lithium iron phosphate. The appearance of the positive electrode of the lithium iron manganese phosphate (hereinafter referred to as lithium iron manganese) further widens the energy density advantage of the positive electrode of the olivine structure on the basis of maintaining good structural stability.
Currently, the main film forming stage of the lithium iron phosphate battery is 3.25V earlier, so that the commercial lithium iron phosphate battery forming process adopts stepwise sectional charging to 40-60% of SOC electric quantity at high temperature. For Mn modified ferromanganese lithium batteries, the formation process of directly using lithium iron phosphate in actual production seems to be not applicable to a ferromanganese lithium system, the manufactured batteries have high bulging deformation rate, serious cyclic gas production, capacity abnormal attenuation, excessively rapid DCR growth and other problems, and the performance advantages of the materials are difficult to be highlighted. The lithium iron manganese positive electrode is greatly different from the lithium iron phosphate positive electrode in that the particle size is one order of magnitude smaller (the average particle size of the lithium iron manganese is only 200-400 nm), a large number of pores (shown in figure 1) exist between primary particles and in secondary particles, so that the water content of the material is higher, the material is difficult to bake out, the working voltage interval is wider (or the charging cut-off voltage is higher), the consumed electrolyte amount is more, the side reaction activity is also larger, the moisture difficult to bake out is converted into a large amount of HF, SEI is repeatedly destroyed, and the SEI is required to have good mechanical elasticity and stability due to the fact that the high charging cut-off voltage is higher. The excessive water in the electrode cannot be removed directly by the formation process of the lithium iron phosphate battery, the SEI film formed for the first time repeatedly expands and contracts in an excessively wide working voltage range, the plasticity and the impact resistance are insufficient, the continuous film damage and repair are easy to be caused, the problems of rapid consumption of active lithium, abnormal increase of internal resistance and the like in the circulation process are caused, and the commercialization popularization of the lithium iron manganese anode is severely restricted.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide a battery formation method.
In order to achieve the above object, the present invention is realized by the following technical scheme:
a battery formation method comprising the steps of:
constant-current charging is carried out at 0.02-0.05C until the voltage corresponding to the end of the first-stage gas production is at least twice, constant-voltage charging is carried out at 0.002-0.005C until the voltage corresponding to the end of the first-stage gas production is at the end of the first-stage gas production, and the first-stage charging is completed;
constant-current charging at 0.3-0.6C is adopted between the corresponding voltage of the gas production ending of the first stage and the corresponding voltage of the gas production starting of the second stage, so that the charging of the second stage is completed;
in the voltage range corresponding to the gas production of the second stage, constant-current charging is carried out by adopting 0.05-0.1C, then constant-voltage charging is carried out to 0.002-0.005C by using the gas production ending voltage of the second stage, and the charging of the third stage is completed;
constant-current discharging to 2.5-3.0V at 0.3-0.5C;
the charge and discharge cycle is at least 1.5 circles, the charge and discharge current is 0.3-0.6 ℃, the charge cut-off voltage is 4.1-4.35V, and the discharge cut-off voltage is 2.5-2.8V.
The purpose of adopting two-step constant current charging in the first stage of formation charging is to repeatedly decompose H in the battery under the specific potential of the negative electrode 2 O is H 2 Is released in the form of a (c).
The purpose of the small current and constant voltage charging process in the first stage of formation charging is to lengthen decomposition H as much as possible 2 O and the reaction time of initial film formation, H 2 O is fully electrolyzed and a denser SEI film is formed.
The formation current of the second formation charge stage is 0.3-0.6C, so that the whole formation time is shortened, a stable lithium rapid migration channel is formed, and the electrochemical activity of the material is activated, and the process can be rapidly carried out, because the battery hardly generates gas in the interval.
The third stage of formation charging aims to utilize the strong oxidizing property of the positive electrode and the strong reducing property of the negative electrode to activate the shuttle crosstalk reaction between the two electrodes under high SOC to construct the positive electrode CEI and repair the negative electrode SEI film layer, thereby achieving the purpose of shielding the interface side reaction of the electrode of the battery leaving the factory. The low current charging and constant voltage at this stage is to prolong the reaction time of inter-electrode crosstalk reaction, so that the gas generated in the battery can be fully pumped away by the vacuum pumping system, and the low current is favorable for obtaining a compact interface film.
Constant current discharge of 0.3-0.5C to 2.5-3.0V to prevent SEI decomposition caused when discharge is to a lower voltage.
The purpose of the charge-discharge cycle is to increase the anti-telescoping property of the interfacial film by using deep charge and deep discharge with medium current to form SEI and CEI films with good reversibility and stability.
In some embodiments, the positive electrode of the battery is a lithium iron manganese or a lithium iron manganese and ternary nickel cobalt manganese blended positive electrode.
The working voltage range of the ferromanganese lithium battery is generally 2.5-4.30V or even 4.35V, and if the ferromanganese lithium battery is matched with a ternary nickel-cobalt-manganese material to form a mixed anode, the charging cut-off voltage can be higher. The cathode has stronger oxidability and anode reducibility under high voltage, so the solid interface electrolyte membrane with stability, good electronic insulation and good electronic insulation is formed, and has important significance for inhibiting the continuous decomposition of the solvent.
To obtain an ideal solid electrolyte membrane, it is sought to eliminate the H introduced from the outside and generated from the inside of the cell during the first formation 2 O, while the existing formation process easily causes insufficient removal of moisture in the battery, moisture residues seriously deteriorate the stability of the SEI film.
The inventors found that the water can be decomposed into H as much as possible by controlling the formation current, voltage interval and formation time 2 Therefore, the film is pumped out by the pumping system, and in addition, the film formed by the unsuitable formation cut-off SOC is damaged due to repeated expansion and contraction in the later capacity division and earlier cycle process. Therefore, should be communicatedThe SEI has good stability and anti-telescoping performance through the adjustment of the formation process.
The lithium iron manganese anode has the characteristics of easy water absorption, difficult drying out of water, small particle size, large specific surface area, high charging cut-off voltage and the like, so that the lithium iron manganese anode is quite different from a lithium iron phosphate battery in terms of formation film formation gas production, is different from the lithium iron phosphate battery in that the formation gas production of the lithium iron phosphate battery is mainly concentrated in one section (before 3.25V), the formation gas production of the lithium iron manganese battery is concentrated in two sections (before 3.0V and after 4.05V, see figure 2), and H in the gas production components in the two sections of concentrated gas production stage 2 All occupy a larger proportion (3.0V front-end to 42%,4.05V rear to 60%, see FIG. 3). According to the existing pair production H 2 By the mechanism of H 2 On the one hand, the water is decomposed by externally introduced water, such as electrode adsorption water, and water generated by internal reaction of the battery cell; on the other hand, the oxidation-reduction shuttle crosstalk reaction between the positive electrode and the negative electrode can happen continuously.
Therefore, in order to obtain an anode-cathode interface film with excellent stability, the excessive water in the battery cell should be removed as much as possible, so that the conversion into HF with great hazard is avoided, and a CEI and SEI film with high stability should be formed to shield shuttle crosstalk reaction with high reactivity under high SOC.
The formation method of the invention fully decomposes excessive water or HF in the battery core in the first stage of formation charging by controlling the formation current, the formation time and the formation cut-off voltage, and forms a film with priority by using a film forming additive under the high potential of the negative electrode; the second stage of formation charging is charged to a proper cut-off voltage with a large current, which aims to shorten the formation time; in the third stage of formation charging, the battery is guided to utilize the strong oxidizing property of the positive electrode and the strong reducing property of the negative electrode to activate the shuttle crosstalk reaction between the two electrodes in the high SOC section by adjusting the proper current to construct the positive electrode CEI and repair the negative electrode SEI film layer so as to shield the high-activity side reaction of the battery under the high SOC after leaving a factory; after three-step charging, the battery is discharged to a proper voltage, and the SEI film is prevented from being decomposed due to the excessively low voltage. And then circulating for 1.5 circles in a battery working voltage interval under a large current, fully utilizing deep charging and deep discharging to increase the anti-telescoping property and mechanical elasticity of the interface film, and forming an SEI and CEI film with good reversibility and stability.
Preferably, the positive electrode of the battery is lithium iron manganese.
In some embodiments, when the positive electrode of the battery is lithium iron manganese, the first-stage gas production end corresponding voltage is 3-3.25V.
Preferably, the initial corresponding voltage of the gas production in the second stage is 4-4.05V.
Preferably, the corresponding voltage of the gas production end of the second stage is 4.2-4.35V.
In some embodiments, the method further comprises the step of vacuum baking and drying the cells prior to forming the cells.
Preferably, the water content of the positive electrode of the pure ferromanganese lithium bare cell after baking and drying is less than 300-450ppm.
Preferably, the water content of the positive electrode of the battery core made of the mixed material after baking and drying is less than 200-350ppm.
In some embodiments, the cell formation process is in a vacuum environment.
Preferably, the restraining force in the battery formation process is 100-300Kgf.
In some embodiments, the first stage of charging, the interval between constant current charging is 10-30min (the interval is set to eliminate polarization effects from charging).
In some embodiments, the interval between two adjacent charging phases is 5-10min (the interval is set to eliminate the polarization effect of charging).
In some embodiments, the battery is aged at 35-45 ℃ for 40-50 hours after the cycle charge is completed.
The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:
the invention has good formation film forming effect on the pure manganese iron phosphate lithium-graphite battery, can improve the cycle stability of the manganese iron phosphate lithium battery and widen the service life of the manganese iron phosphate lithium battery, but the application range of the invention is not limited to the above, and the invention can be expanded into various material system batteries such as manganese iron phosphate lithium and ternary nickel cobalt manganese mixed anode-graphite, iron phosphate lithium-graphite, ternary nickel cobalt manganese-graphite, high nickel-silicon carbon-graphite, cobalt-free anode-graphite and the like (different material systems have consistent formation thought related to the operation according to the invention and do not need to be changed).
By controlling the formation current, the formation time and the formation cut-off voltage, excessive water or HF inside the battery core is fully decomposed in the first stage of formation charging, and a film is formed by utilizing a film forming additive under the high potential of the negative electrode; the second stage of formation charging is charged to a proper cut-off voltage with a large current, which aims to shorten the formation time; in the third stage of formation charging, the battery is guided to utilize the strong oxidizing property of the positive electrode and the strong reducing property of the negative electrode to activate the shuttle crosstalk reaction between the two electrodes in the high SOC section by adjusting the proper current to construct the positive electrode CEI and repair the negative electrode SEI film layer so as to shield the high-activity side reaction of the battery under the high SOC after leaving a factory; and discharging the battery to a proper voltage after three-step charging, so as to avoid the decomposition of the SEI film caused by the excessively low voltage.
And then circulating for 1.5 circles in a battery working voltage interval under a large current, fully utilizing deep charging and deep discharging to increase the anti-telescoping property and mechanical elasticity of the interface film, and obtaining the SEI and CEI film with good reversibility and stability. After the circulation is finished, the battery is aged for 48 hours at high temperature so as to optimize the self-discharge performance of the battery and fully infiltrate the electrode, and the electrochemical activity of the electrode is fully exerted.
The lithium iron manganese phosphate battery manufactured by the formation method can obviously improve the stability and mechanical elasticity of an interfacial film, and has important significance for reducing the swelling degree of the battery and expecting to obtain good product shipment batteries with qualified sizes.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is an SEM topography of a pure lithium iron manganese phosphate anode (1500X);
FIG. 2 is a graph showing internal pressure changes during the first closed formation of a pure lithium iron manganese phosphate battery (100 Ah);
FIG. 3 shows total volume of internal gas and H of pure lithium manganese iron phosphate soft-packed battery (4 Ah) in primary formation process 2 A volume change map;
FIG. 4 shows the swelling of a lithium iron manganese phosphate cell after 10 cycles of different chemical process cycles versus A) the inventive chemical process with no air bag swelling; b) The formation method of the lithium iron phosphate battery has obvious air bag bulge.
Detailed Description
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the invention. 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 invention is further illustrated below with reference to examples.
Example 1
1. And (3) baking the 100Ah Fang Ke pure ferromanganese lithium bare cell opening in high vacuum until the water content of the positive electrode is less than 450ppm and the water content of the mixed sample is less than 350ppm.
2. The battery is filled with liquid and inserted with a liquid filling nail, and the battery is kept stand for 12 hours at 45 ℃.
3. After the standing, the battery is formed into a cabinet, and a restraining force of 100Kgf is applied to the center of the large surface, and the battery is formed into a full-range negative pressure pumping state through a liquid injection port.
4. Battery formation charging first stage: constant current charging to 3.0V at 0.05C; standing for 20min; constant current charging to 3.0v at 0.05C and constant voltage charging to 0.005C at 3.0 v.
5. Battery formation charging second stage: constant current charging to 4.05V at 0.5C; and standing for 5min.
6. And a third stage of battery formation and charging: constant current charging of 0.1C to 4.35V and constant voltage charging of 4.35V to 0.005C; standing for 5min;
7. constant current discharge stage: constant current discharge of 0.3C to 2.5V.
8. Charge-discharge cycle 1.5 turns:
1) Constant-current and constant-voltage charging to 4.30V at 0.5C; standing for 5min;
2) Constant current discharge of 0.5C to 2.5V; standing for 5min;
3) Constant-current and constant-voltage charging to 4.1V at 0.5C; and standing for 5min.
9. And (5) ending the formation.
Disconnecting the battery on a formation cabinet, and standing for 48 hours at 45 ℃; after standing, sequentially completing secondary injection sealing of the battery cells, and testing the volume V0 of the battery at normal temperature before capacity division; the battery cell is subjected to capacity division in a voltage interval of 2.5-4.30V at 25 ℃, and the volume V1 of the battery is tested after capacity division; v0 and V1 are compared, and the two are not obviously different.
Example 2
1. 4Ah pure ferromanganese lithium soft package bare cell (cell reserved air outlet bag) opening high vacuum baking until the water content of the positive electrode is less than 350ppm and the water content of the mixed sample is less than 250ppm;
2. the battery is completed with vacuum liquid injection sealing, two clamps are arranged, the restraint force is set to be 100Kgf, and the links of normal and high Wen Jinrun are sequentially completed;
3. battery formation charging first stage: constant current charging to 3.25V at 0.05C; standing for 10min; constant current charging to 3.25V at 0.05C; 3.25V constant voltage charging to 0.002C; and standing for 5min.
4. Battery formation charging second stage: constant current charging to 4.05V at 0.6C; and standing for 5min.
5. And a third stage of battery formation and charging: constant current charging to 4.35V at 0.1C and constant voltage charging to 0.002C at 4.35V; and standing for 5min.
6. Constant current discharge stage: constant current discharge of 0.5C to 2.5V.
7. Charge-discharge cycle 1.5 turns:
1) Constant-current and constant-voltage charging to 4.35V at 0.5C; standing for 5min;
2) Constant current discharge of 0.5C to 2.5V; standing for 5min;
3) Constant-current and constant-voltage charging to 4.1V at 0.5C; and standing for 5min.
8. And (5) ending the formation.
Disconnecting the battery on a formation cabinet, and standing for 48 hours at 45 ℃; after the standing is finished, the clamp is removed, the air bag is cut off, the vacuum sealing is carried out, and after the battery returns to normal temperature before circulation, the volume V0 of the soft package battery is tested.
The battery cell circulates for 10 circles in a voltage interval of 2.5-4.30V at 25 ℃, and the volume V1 of the soft package battery after the circulation is tested. V0 and V1 are compared, and the two are not obviously different.
Example 3
1. 4Ah pure ferromanganese lithium soft package bare cell (cell reserved air outlet bag) opening high vacuum baking until the water content of the positive electrode is less than 350ppm and the water content of the mixed sample is less than 250ppm;
2. the battery is completed with vacuum liquid injection sealing, two clamps are arranged, the restraint force is set to 150Kgf, and the links of normal and high Wen Jinrun are sequentially completed;
3. battery formation charging first stage: constant current charging to 3.0V at 0.05C; standing for 10min; constant current charging to 3.0V at 0.05C; 3.0V constant voltage charging to 0.005C; and standing for 5min.
4. Battery formation charging second stage: constant current charging of 0.4C to 4.05V; and standing for 5min.
5. And a third stage of battery formation and charging: constant current charging is carried out to 4.2V at 0.05C, and constant voltage charging is carried out to 0.005C at 4.2V; and standing for 5min.
6. Constant current discharge stage: constant current discharge of 0.3C to 2.5V.
7. Charge-discharge cycle 1.5 turns:
1) Charging to 4.3V at constant current and constant voltage of 0.5C; standing for 5min;
2) Constant current discharge of 0.5C to 2.8V; standing for 5min;
3) Constant-current and constant-voltage charging to 4.1V at 0.5C; and standing for 5min.
8. And (5) ending the formation.
Disconnecting the battery on a formation cabinet, and standing for 48 hours at 45 ℃; after the standing is finished, the clamp is removed, the air bag is cut off, the vacuum sealing is carried out, and after the battery returns to normal temperature before circulation, the volume V0 of the soft package battery is tested.
The battery cell circulates for 10 circles in a voltage interval of 2.5-4.30V at 25 ℃, and the volume V1 of the soft package battery after the circulation is tested. V0 and V1 are compared, and the two are not obviously different.
Performance testing
Setting A, B two groups of material systems, batches and lithium iron manganese phosphate soft package batteries with the same capacity (4 Ah), and keeping all working procedures consistent before the formation;
group A uses the chemical process method of the invention: see example 2;
the closed formation process of the group B using the lithium iron phosphate battery comprises the following steps: charging for 20min at 0.1C; charging at 0.2C for 120min; charging at 0.1C for 10min;
the two groups of batteries are formed by reserving air bags with the same volume and size by adopting an upper clamping force (as shown in figure 4);
after the formation is finished, a small opening is cut at one corner of the air bag, the air generated in the formation stage of the soft bag is exhausted by vacuum air suction, sealing is finished, sealing positions of two groups of batteries are kept consistent, and the volume of the residual air bag of the sealed batteries is kept consistent.
The two groups of batteries circulate for 10 circles in a voltage interval of 2.5-4.30V by adopting 1C current under the environment of 45 ℃; as shown in fig. 4, the air bag area of the battery a is not inflated, and the air bag area of the battery B is inflated obviously. The formation method provided by the invention has good formation effect on the manganese iron lithium battery.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A battery formation method, characterized in that: the method comprises the following steps:
constant-current charging is carried out at 0.02-0.05C until the voltage corresponding to the end of the first-stage gas production is at least twice, constant-voltage charging is carried out at 0.002-0.005C until the voltage corresponding to the end of the first-stage gas production is at the end of the first-stage gas production, and the first-stage charging is completed;
constant-current charging at 0.3-0.6C is adopted between the corresponding voltage of the gas production ending of the first stage and the corresponding voltage of the gas production starting of the second stage, so that the charging of the second stage is completed;
in the voltage range corresponding to the gas production of the second stage, constant-current charging is carried out by adopting 0.05-0.1C, then constant-voltage charging is carried out to 0.004-0.005C by using the gas production ending voltage of the second stage, and the charging of the third stage is completed;
constant-current discharging to 2.5-3.0V at 0.3-0.5C;
the charge and discharge cycle is at least 1.5 circles, the charge and discharge current is 0.4-0.6 ℃, the charge cut-off voltage is 4.1-4.35V, and the discharge cut-off voltage is 2.5-2.8V.
2. The battery formation method according to claim 1, characterized in that: the positive electrode of the battery is a lithium iron manganese phosphate, a lithium iron manganese phosphate or a mixed positive electrode of lithium iron manganese phosphate and ternary nickel cobalt manganese;
preferably, the positive electrode of the battery is lithium iron manganese phosphate or lithium iron manganese.
3. The battery formation method according to claim 2, characterized in that: when the anode of the battery is lithium ferromanganese, the corresponding voltage for ending the gas production in the first stage is 3-3.25V;
preferably, the initial corresponding voltage of the gas production in the second stage is 4-4.05V;
preferably, the corresponding voltage of the gas production end of the second stage is 4.2-4.35V.
4. The battery formation method according to claim 1, characterized in that: the method further comprises the step of drying the battery cells by vacuum baking before the battery cells are formed.
5. The battery formation method according to claim 4, wherein: the water content of the positive electrode of the pure ferromanganese lithium bare cell after baking and drying is less than 300-450ppm.
6. The battery formation method according to claim 4, wherein: the water content of the positive electrode of the battery core made of the mixed materials after baking and drying is less than 200-350ppm.
7. The battery formation method according to claim 1, characterized in that: the cell formation process is in a vacuum environment.
8. The battery formation method according to claim 7, characterized in that: the restraining force in the battery formation process is 100-300Kgf.
9. The battery formation method according to claim 1, characterized in that: and in the first stage of charging, the interval between the two constant current charging is 10-30min.
10. The battery formation method according to claim 1, characterized in that: the interval between two adjacent charging stages is 4-10min.
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| CN116995318A (en) * | 2023-09-25 | 2023-11-03 | 成都特隆美储能技术有限公司 | 3.2V formation process of lithium iron phosphate battery |
| CN116995318B (en) * | 2023-09-25 | 2023-12-01 | 成都特隆美储能技术有限公司 | 3.2V formation process of lithium iron phosphate battery |
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