CN111957610A - Screening method for improving consistency of lithium iron phosphate battery - Google Patents
Screening method for improving consistency of lithium iron phosphate battery Download PDFInfo
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- CN111957610A CN111957610A CN202010744812.2A CN202010744812A CN111957610A CN 111957610 A CN111957610 A CN 111957610A CN 202010744812 A CN202010744812 A CN 202010744812A CN 111957610 A CN111957610 A CN 111957610A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
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Abstract
A screening method for improving consistency of lithium iron phosphate batteries comprises the following steps: performing constant current discharge of 0.5-1C on the lithium battery, wherein the cut-off voltage is 2500 mV; standing for 5-20 minutes; performing constant current discharge of 0.2-0.3C on the lithium battery again, wherein the cut-off voltage is 2000 mV; standing for 2-5 minutes; charging the lithium battery subjected to constant current discharge twice to 3-8% SOC (state of charge) at a low current of 0.2-0.3 ℃ in a constant current manner; standing for 12-36 h; performing an OCV voltage test on the lithium battery; grading the lithium battery according to the capacity range within 0.5-2 Ah and the pressure difference within 10-30 mV; and adjusting the shipment SOC of the lithium batteries in the same grade to be the same SOC. The invention can effectively improve the tail end pressure difference of the power battery pack during charging and discharging and improve the dynamic consistency of the battery pack.
Description
Technical Field
The invention relates to the technical field of lithium iron phosphate batteries, in particular to a screening method for improving the consistency of lithium iron phosphate batteries.
Background
The lithium ion power battery system for the vehicle is formed by connecting a plurality of single batteries in series and parallel in various modes, and if the difference between the performance of individual single batteries and the performance of other battery cores is large, the performance of the whole battery system is attenuated, and the service life is terminated in advance. Therefore, screening and assembling the single batteries with consistent electrical performance becomes a key item before the battery cells are delivered, and accordingly, an appropriate consistency screening method becomes very important. At present, lithium ion battery manufacturers generally screen single batteries according to static parameters such as capacity, internal resistance and self-discharge rate, and can effectively control the static consistency of battery cells after battery grouping, but cannot simultaneously ensure the dynamic consistency of each battery cell during charging and discharging of a battery pack, and the phenomenon that even if single batteries with good consistency are selected according to static parameters such as capacity, internal resistance and self-discharge rate, the charge and discharge tail ends still show overlarge pressure difference after grouping, namely the phenomenon of poor dynamic consistency is shown.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a screening method for improving the consistency of lithium iron phosphate batteries. A screening method for improving consistency of lithium iron phosphate batteries comprises the following steps:
step 1: performing 0.5-1C constant current discharge on the lithium battery, wherein the cut-off voltage is C;
step 2: the discharged lithium battery is placed aside for 5-20 minutes;
and step 3: performing constant current discharge of 0.2-0.3C on the lithium battery again, wherein the cut-off voltage is D;
and 4, step 4: the discharged lithium battery is placed aside for 2-5 minutes;
and 5: charging the lithium battery subjected to constant current discharge twice to 3-8% SOC at a low current of 0.2-0.3 ℃ in a constant current manner;
step 6: the charged lithium battery is placed aside for 12-36 hours;
and 7: performing an OCV voltage test on the lithium battery;
and 8: grading the lithium battery according to the capacity range difference within A and the pressure difference within B;
and step 9: adjusting the shipment state of the lithium batteries in the same level to be in the same state;
wherein, the range of A is 0.5 Ah-2 Ah, the range of B is 10 mV-30 mV, the range of C is 2500 mV-3000 mV, and the range of D is 2000 mV-2300 mV.
Further comprises the following steps: the C is 2500mV, and the D is 2000 mV.
Further comprises the following steps: the adjustment range of the shipment state of the lithium batteries is 50-100% of SOC, and the initial working states of the lithium batteries are guaranteed to be the same.
The invention has the beneficial effects that: the method comprises the steps of carrying out different current discharging on the lithium battery twice, then carrying out low current charging to a low SOC state, simulating the discharging tail end state of the lithium battery, grading the voltage of the low SOC lithium battery, screening the polarization consistency lithium battery, finally adjusting the lithium battery to the same SOC before delivery, and ensuring the initial SOC consistency. The battery pack is assembled according to the method provided by the invention, after the batteries are connected in series and in parallel to form the battery pack, the voltage difference at the charging and discharging tail ends of the battery pack is obviously reduced compared with the common assembling method through repeated charging and discharging, the charging and discharging curve fitting consistency is better, and the dynamic consistency is obviously improved.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a diagram illustrating the variation of charging and discharging voltages of a conventional assembled battery;
FIG. 3 is a diagram showing the variation of charging and discharging voltages of the assembled battery after the improvement of the present invention.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings. Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative only and should not be construed as limiting the invention. The terms of orientation such as left, center, right, up, down, etc. in the examples of the present invention are only relative to each other or are referred to the normal use state of the product, and should not be considered as limiting.
The first embodiment: a screening method for improving consistency of lithium iron phosphate batteries is shown in figure 1 and comprises the following steps:
step 1: performing constant current discharge at 0.5-1 ℃ on the lithium iron phosphate battery, wherein the cut-off voltage is 2700 mV;
step 2: the discharged lithium battery is placed aside for 5-20 minutes;
and step 3: performing constant current discharge of 0.2-0.3C on the lithium battery again, wherein the cut-off voltage is 2300 mV;
and 4, step 4: the discharged lithium battery is placed aside for 2-5 minutes;
and 5: charging the lithium battery subjected to constant current discharge twice to 3-8% SOC at a low current of 0.2-0.3 ℃ in a constant current manner;
step 6: the charged lithium battery is placed aside for 12-36 hours;
and 7: performing an OCV voltage test on the lithium battery;
and 8: grading the lithium battery according to the capacity range within 2Ah and the pressure difference within 10 mV;
and step 9: and adjusting the shipment state of the lithium batteries in the same grade to 50% SOC.
Second embodiment: a screening method for improving consistency of lithium iron phosphate batteries is shown in figure 1 and comprises the following steps:
step 1: performing 0.5C constant current discharge on the lithium battery, wherein the cut-off voltage is 2500 mV;
step 2: the discharged lithium battery is placed aside for 5 minutes;
and step 3: performing 0.2C constant current discharge on the lithium battery again, wherein the cut-off voltage is 2000 mV;
and 4, step 4: the discharged lithium battery is placed aside for 2-5 minutes;
and 5: charging the lithium battery subjected to constant current discharge twice to 3-8% of SOC (state of charge) at a low current of 0.2C;
step 6: the charged lithium battery is placed aside for 12 hours;
and 7: performing an OCV voltage test on the lithium battery;
and 8: grading the lithium battery according to the capacity range within 1Ah and the pressure difference within 20 mV;
and step 9: and adjusting the delivery state of the lithium batteries in the same gear to 80% SOC.
The third embodiment: a screening method for improving consistency of lithium iron phosphate batteries is shown in figure 1 and comprises the following steps:
step 1: 1C constant current discharge is carried out on the lithium battery, and the cut-off voltage is 3000 mV;
step 2: the discharged lithium battery is placed aside for 15 minutes;
and step 3: performing 0.3C constant current discharge on the lithium battery again, wherein the cut-off voltage is 2300 mV;
and 4, step 4: the discharged lithium battery is placed aside for 2-5 minutes;
and 5: charging the lithium battery subjected to constant current discharge twice to 5% SOC at a low current of 0.3C;
step 6: the charged lithium battery is placed aside for 24 hours;
and 7: performing an OCV voltage test on the lithium battery;
and 8: classifying the lithium battery according to the capacity range difference within 0.5Ah and the pressure difference within 30 mV; the smaller the capacity range and the pressure difference are, the better the battery consistency is, but the more difficult the grouping is, so that the comprehensive consideration is needed during actual grouping, and the screening range can be expanded within an allowable range;
and step 9: and adjusting the shipment state of the lithium batteries in the same grade to be 100% SOC.
The working principle of the invention is as follows: the factors affecting the uniformity of the battery pack are mainly capacity uniformity, initial SOC uniformity, and polarization uniformity. The consistency of the capacity is ensured by controlling the extreme difference of the capacity; the initial SOC consistency of the battery pack is ensured by accurately adjusting the SOC of the single batteries before grouping; because the polarization degree of the battery is different under different SOC, and the polarization of the inside of the single battery is the maximum under the low SOC state, the voltage under the low SOC is graded, and the polarization consistency of the battery is ensured by controlling the voltage range difference under the low SOC; the invention realizes the consistency of the battery pack under the dynamic condition by realizing the key three factors.
Taking 65Ah batteries, 2 batteries in parallel and 100 batteries as an example, and taking the 65Ah batteries as an example, the batteries which are matched and assembled and have the capacity range within 1Ah, the voltage range within 20mV and the initial SOC of 100% as an example, the batteries are assembled into a battery pack, then a charge and discharge test is carried out, and the charge and discharge terminal pressure difference and the battery pack capacity of the battery pack are recorded. As can be seen from the graph, the dynamic end differential pressure and the static differential pressure of the battery pack after screening and improvement using the present invention are significantly lower than those before the improvement, and the capacity is increased accordingly.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (3)
1. A screening method for improving consistency of lithium iron phosphate batteries is characterized by comprising the following steps:
step 1: performing 0.5-1C constant current discharge on the lithium battery, wherein the cut-off voltage is C;
step 2: the discharged lithium battery is placed aside for 5-20 minutes;
and step 3: performing constant current discharge of 0.2-0.3C on the lithium battery again, wherein the cut-off voltage is D;
and 4, step 4: the discharged lithium battery is placed aside for 2-5 minutes;
and 5: charging the lithium battery subjected to constant current discharge twice to 3-8% SOC at a low current of 0.2-0.3 ℃ in a constant current manner;
step 6: the charged lithium battery is placed aside for 12-36 hours;
and 7: performing an OCV voltage test on the lithium battery;
and 8: grading the lithium battery according to the capacity range difference within A and the pressure difference within B;
and step 9: adjusting the shipment state of the lithium batteries in the same level to be in the same state;
wherein, the range of A is 0.5 Ah-2 Ah, the range of B is 10 mV-30 mV, the range of C is 2500 mV-3000 mV, and the range of D is 2000 mV-2300 mV.
2. The screening method for improving the consistency of the lithium iron phosphate battery according to claim 1, characterized by comprising the following steps: the C is 2500mV, and the D is 2000 mV.
3. The screening method for improving the consistency of the lithium iron phosphate battery according to claim 1, characterized by comprising the following steps: the adjustment range of the shipment state of the lithium battery is 50% SOC-100% SOC.
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| US6187479B1 (en) * | 1998-03-06 | 2001-02-13 | Changle Liu | Ambient temperature, rechargeable cells with metal salt-based electrodes and a system of cell component materials for use therein |
| US20140328729A1 (en) * | 2013-05-06 | 2014-11-06 | Liang-Yuh Chen | Apparatus for Preparing a Material of a Battery Cell |
| CN103611692B (en) * | 2013-10-21 | 2017-01-11 | 厦门华锂能源股份有限公司 | Lithium iron phosphate power battery consistency matching screening method |
| CN108993931A (en) * | 2018-05-18 | 2018-12-14 | 中山大学 | A kind of method for separating of power battery |
| CN109459703A (en) * | 2018-12-25 | 2019-03-12 | 山东精工电子科技有限公司 | A kind of self discharge of lithium iron phosphate battery conformity classification method |
| CN109622426A (en) * | 2018-12-27 | 2019-04-16 | 银隆新能源股份有限公司 | A kind of battery consistency screening technique and battery consistency screening plant |
-
2020
- 2020-07-29 CN CN202010744812.2A patent/CN111957610A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6187479B1 (en) * | 1998-03-06 | 2001-02-13 | Changle Liu | Ambient temperature, rechargeable cells with metal salt-based electrodes and a system of cell component materials for use therein |
| US20140328729A1 (en) * | 2013-05-06 | 2014-11-06 | Liang-Yuh Chen | Apparatus for Preparing a Material of a Battery Cell |
| CN103611692B (en) * | 2013-10-21 | 2017-01-11 | 厦门华锂能源股份有限公司 | Lithium iron phosphate power battery consistency matching screening method |
| CN108993931A (en) * | 2018-05-18 | 2018-12-14 | 中山大学 | A kind of method for separating of power battery |
| CN109459703A (en) * | 2018-12-25 | 2019-03-12 | 山东精工电子科技有限公司 | A kind of self discharge of lithium iron phosphate battery conformity classification method |
| CN109622426A (en) * | 2018-12-27 | 2019-04-16 | 银隆新能源股份有限公司 | A kind of battery consistency screening technique and battery consistency screening plant |
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Application publication date: 20201120 |