CN109030567B - Method for judging internal water content of lithium ion battery cell - Google Patents
Method for judging internal water content of lithium ion battery cell Download PDFInfo
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- CN109030567B CN109030567B CN201810733680.6A CN201810733680A CN109030567B CN 109030567 B CN109030567 B CN 109030567B CN 201810733680 A CN201810733680 A CN 201810733680A CN 109030567 B CN109030567 B CN 109030567B
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Abstract
The invention discloses a method for judging the water content in a lithium ion battery cellThe method comprises the following steps: selecting the same non-injected liquid cell to perform grouping treatment to obtain each test group Z with different degrees of internal water contentN(ii) a For each test group ZNTesting the internal water content by sampling the cell to obtain the corresponding internal water content grade W of each groupN(ii) a Injecting and soaking the residual battery cells after the selective examination of each group, then charging the battery cells by using constant current, stopping after the charging cut-off condition is reached, and obtaining constant-current charging energy QN‑nAnd obtaining the constant current charging energy grade Q corresponding to each groupN(ii) a With corresponding WN、QNA detection mechanism is established in a contrast interval, and the same type of battery cells to be detected are charged for the first time according to the same charging requirement to obtain constant-current charging energy QXCharging constant current to energy QXThe internal water content W of the electric core to be detected can be judged by contrasting the detection mechanismXAnd if not, the product is qualified. Through the established interval comparison relationship, the constant-current charging energy is directly read for the first charging of the battery cell to be tested, and the water content condition in the battery cell can be obtained through contrast and reverse deduction.
Description
Technical Field
The invention relates to lithium ion cell detection, in particular to a method for judging the water content in a lithium ion cell.
Background
The lithium ion battery cell has the advantages of high energy density, long cycle life, no memory effect and the like, and is widely applied to the digital and power energy industries. However, as the application range of the composite material is continuously expanded, the use performance of the composite material is more and more emphasized. In the manufacturing process of the lithium ion battery cell, the control of the moisture of the pole piece inside the battery cell has an important influence on the cycle life and the safety of the battery cell, and the moisture inside the battery cell can react with lithium salt in electrolyte to generate gas in the charging and discharging process, so that various problems such as battery cell gas expansion, polarization increase, cycle performance attenuation and the like are caused. Therefore, in the manufacturing process of the lithium ion battery cell, the water content in the battery cell must be strictly controlled, and the stability and consistency of the performance of the battery cell are ensured.
At present, the water content in the battery cell is generally tested by adopting a Karl Fischer moisture tester, the repeatability and the accuracy of the test method are higher, but the electrode plate position is tested after the battery cell is disassembled by destroying, so that whether the water content in the battery cell is qualified or not is generally judged by adopting a spot inspection mode on batch products, and whether the water content of each battery cell is qualified or not can not be accurately monitored.
Disclosure of Invention
The purpose of the invention is as follows: in view of the above problems, the present invention provides a method for conveniently and rapidly determining the water content in a lithium ion battery, which can perform a full inspection on a batch of products.
The technical scheme is as follows: a method for judging the internal water content of a lithium ion battery cell comprises the following steps:
the method comprises the following steps: selecting a plurality of non-injected battery cells produced under the same material system and the same conditions, grouping and carrying out differentiation treatment to obtain test groups Z with different degrees of internal water contentN；
Step two: for each test group ZNTesting the internal water content by sampling the cell to obtain each test group ZNCorresponding internal water content class WN；
Step three: for each test group ZNAnd (4) carrying out normal liquid injection and infiltration on the residual battery cells after sampling inspection according to the same liquid injection amount and standing time, then charging the battery cells by using constant current, and stopping after the charging cut-off condition is reached so as to obtain constant-current charging energy QN-nAnd obtaining each test group ZNCorresponding constant current charging energy level QN；
Step four: at the corresponding internal water content grade WNConstant current charging energy level QNForming a comparison interval, establishing a detection mechanism, and carrying out primary charging on the battery cells to be detected produced under the same material system and the same conditions according to the charging requirement of the step three to obtain constant-current charging energy QXCharging constant current to energy QXThe internal water content W of the electric core to be detected can be judged by contrasting the detection mechanismXAnd if not, the product is qualified.
Specifically, in the step one, the differentiation treatment refers to baking each group of battery cells to different degrees, so as to obtain each test group Z with different degrees of internal water contentNTest group ZNAt least an unbaked group, a normal baking group and a high-temperature baking group are arranged. In which a high temperature bake group was used as a scale-up test.
Most preferably, in step two, each test group ZNThe number of the sampling inspection electric cores is at least 2 pcs. The number of the random inspection electric cores is increased, the test quantity of the water content test in the random inspection electric cores can be increased, and the internal water content grade W is realizedNAnd is more accurate.
Further, in the third step, the constant current for charging the battery cell is 0.02-0.1C, and the charge cut-off condition is 1% -5% SOC.
Preferably, in the third step, the difference of the ambient temperature for charging each battery cell is not more than +/-3 ℃.
Specifically, in step two, the internal water content is graded as WNThe average value of the internal water content tested by the random inspection cell and the detection point thereof or the grade value optimally set by the average value is used.
Specifically, in the third step, the constant-current charging energy level QNRefers to the constant current charging energy Q of the residual battery cell after sampling inspectionN-nIs measured.
The principle of the invention is as follows: the electric core is at the charging process for the first time, on the one hand can carry out chemical reaction and form SEI film and consume the electric quantity, on the other hand if the inside water content of electric core is on the high side, water decomposition also can additionally consume the electric quantity, finally all can audio-visually reflect on the charging voltage curve, voltage platform is less than normal level, then the constant current energy of charging is in inverse proportion relation with the inside water content of electric core, promptly the inside water content of electric core is higher more, the constant current energy of charging is less, consequently can differentiate whether the inside water content of electric core is unusual according to the constant current energy of the initial stage of charging in the charging process for the first time of.
Has the advantages that: compared with the prior art, the invention has the advantages that: through establishing the interval contrast relation between the different inside water content of electric core and the constant current energy of charging for the first time, to the electric core that awaits measuring through the first time charge directly read the constant current energy of charging and can contrast the back-stepping and draw the inside water content condition of electric core, do not break and tear the electric core and can conveniently carry out the inside water content of electric core fast and differentiate, can realize examining entirely to batch products, carry out inside water content state control to all electric cores in the manufacturing process.
Drawings
FIG. 1 shows test group Z in the example1～Z5Constant current charging energy level Q1～Q5A boxline graph;
FIG. 2 shows test group Z in the example1Two of the cells, test group Z4The first charging voltage curve of two of the cells.
Detailed Description
The invention will be further elucidated with reference to the drawings and specific examples, which are intended to illustrate the invention and are not intended to limit the scope of the invention.
The method for judging the internal water content of the lithium ion battery core is described by taking a lithium iron phosphate 40Ah lithium ion battery core as an example, and specifically comprises the following steps.
The method comprises the following steps: selecting a plurality of non-injected battery cores produced under the same condition and in a 60pcs same material system, dividing the battery cores into 5 groups, baking the battery cores of each group to different degrees to obtain a test group Z with different degrees of internal water contentNI.e. test group Z1(not baked), test group Z2(baking 8h), test group Z3(baking for 16h), test group Z4(baking time for 24h and normal production of the cell), test group Z5(baking 32h), in which test group Z5As a scale-up test.
Step two: in test group Z1～Z5In each group, 2pcs of cells are respectively extracted, 4 detection points are respectively selected for each cell to carry out internal water content testing, the testing method comprises but is not limited to Karl Fischer water content testing, in order to ensure the accuracy of testing data, the detection points of the selective inspection cells are the same, and testing personnel and equipment are fixed. As shown in Table 1 below, the water content in each test group Z was obtained by averaging the water content in each group of the spot test cellsNCorresponding internal water content class WNI.e. test group Z1Internal water content class W1900ppm, test group Z2Internal water content class W2650ppm, test group Z3Internal water content class W3500ppm, test group Z4Internal water content class W4420ppm, test groupZ5Internal water content class W5Was 400 ppm. Internal water content class WNThe internal water content detection standard (such as enterprise mark, row mark and the like) of the battery core of the model can also be referred, and the grade value optimally set by the mean value is taken as the internal water content grade WN。
TABLE 1
Step three: for test group Z1～Z5After the selective inspection, the remaining 10pcs of each group of battery cells are normally injected and soaked in the same injection amount and standing time, then the battery cells enter a formation cabinet to be charged for the first time, the difference of the ambient temperature for charging the battery cells is not more than +/-3 ℃, the battery cells are charged at a constant current of 0.05 ℃, and the battery cells respectively obtain a constant current charging energy Q under the condition that 2.5% of SOC is taken as a charging cut-off conditionN-nI.e. test group Z1The constant current charging energy obtained by the 10pcs battery cells is respectively Q1-1、Q1-2、…、Q1-10Test group Z2The constant current charging energy obtained by the 10pcs battery cells is respectively Q2-1、Q2-2、…、Q2-10…, then constant current charging energy Q for each group of 10pcs cellsN-nTaking the average value as the constant current charging energy level QNI.e. test group Z1Constant current charging energy level Q1Test group Z2Constant current charging energy level Q2…. FIG. 1 shows test group Z1～Z5Constant current charging energy level Q1～Q5And (6) box line graph.
C represents the multiplying power of the rated capacity of the charge-discharge current of the cell, and the 40Ah cell is charged with a constant current of 0.05C, which means that the charge current is 40 × 0.05 ═ 2A; SOC refers to the state of charge of the cell, and a 40Ah cell has a charge cutoff condition of 2.5% SOC, which means that the cell energy is 1Ah at 40 × 2.5%; and (3) carrying out constant current charging on the battery cell at 0.05C, wherein the charging time is 0.5h instead of 1 Ah/2A. Constant current energy QN-nThe energy formula Q is UIt, and I, t indicates charging current and charging current of constant current charging, respectivelyElectric time, U refers to the average voltage during constant current charging, constant current charging energy QN-nCan be directly read by the device.
As can be seen from the SOC definition, the charge cut-off condition may also be selected as time or cell voltage corresponding to the SOC, and for convenience of description, the SOC is uniformly used as the charge cut-off condition because of different charging currents and different cell material systems.
The electric core is at the charging process for the first time, on the one hand can carry out chemical reaction and form SEI film and consume the electric quantity, on the other hand if the inside water content of electric core is on the high side, water decomposition also can additionally consume the electric quantity, finally all can audio-visually reflect on the charging voltage curve, voltage platform is less than normal level, then the constant current energy of charging is in inverse proportion relation with the inside water content of electric core, promptly the inside water content of electric core is higher more, the constant current energy of charging is less, consequently can differentiate whether the inside water content of electric core is unusual according to the constant current energy of the initial stage of charging in the charging process for the first time of. FIG. 2 shows test group Z1Two of the cells, test group Z4The first charging voltage curve of two of the cells.
Step four: the internal water content grade W1-constant current energy charging grade Q1 and the internal water content grade W2Constant current charging energy level Q2…, forming a comparison interval in a one-to-one correspondence manner to establish a detection mechanism, performing first charging on a certain to-be-detected battery cell produced under the same material system and the same conditions as the lithium iron phosphate 40Ah lithium ion battery cell in the embodiment according to the charging requirement of the third step, and obtaining a constant current charging energy QXComparing with the interval range of the detection mechanism, and correspondingly performing back-stepping to obtain the internal water content W of the battery cell to be detectedXWithin the range, whether the internal water content of the battery cell to be tested is qualified or not can be rapidly judged, namely whether the internal water content of the battery cell is qualified or not can be judged by directly comparing and comparing the constant-current charging energy.
Claims (5)
1. A method for judging the internal water content of a lithium ion battery cell is characterized by comprising the following steps:
the method comprises the following steps: selecting the same material systemA plurality of non-injected liquid battery cores produced under the same condition are grouped for differentiation treatment to obtain each test group Z with different degrees of internal water contentN；
The differentiation treatment means that each group of battery cells are baked to different degrees, so that each test group Z with different degrees of internal water content is obtainedNTest group ZNAt least setting an unbaked group, a normal baking group and a high-temperature baking group;
step two: for each test group ZNTesting the internal water content by sampling the cell to obtain each test group ZNCorresponding internal water content class WN；
Step three: for each test group ZNAnd (4) carrying out normal liquid injection and infiltration on the residual battery cells after sampling inspection according to the same liquid injection amount and standing time, then charging the battery cells by using constant current, and stopping after the charging cut-off condition is reached so as to obtain constant-current charging energy QN-nAnd obtaining each test group ZNCorresponding constant current charging energy level QN；
The constant current for charging the battery cell is 0.02-0.1C, and the charge cut-off condition is 1% -5% SOC;
step four: at the corresponding internal water content grade WNConstant current charging energy level QNForming a comparison interval, establishing a detection mechanism, and carrying out primary charging on the battery cells to be detected produced under the same material system and the same conditions according to the charging requirement of the step three to obtain constant-current charging energy QXCharging constant current to energy QXThe internal water content W of the electric core to be detected can be judged by contrasting the detection mechanismXAnd if not, the product is qualified.
2. The method of claim 1, wherein: in step two, each test group ZNThe number of the sampling inspection electric cores is at least 2 pcs.
3. The method of claim 1, wherein: in the third step, the difference of the ambient temperature for charging each battery cell is not more than +/-3 ℃.
4. The method of claim 1, wherein: in step two, the internal water content is graded as WNThe average value of the internal water content tested by the random inspection cell and the detection point thereof or the grade value optimally set by the average value is used.
5. The method of claim 1, wherein: in the third step, constant-current energy charging grade QNRefers to the constant current charging energy Q of the residual battery cell after sampling inspectionN-nIs measured.
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| CN109830761A (en) * | 2019-02-11 | 2019-05-31 | 中兴高能技术有限责任公司 | The method for detecting battery core internal structure |
| CN110470702A (en) * | 2019-07-10 | 2019-11-19 | 深圳市比克动力电池有限公司 | A kind of lithium-ion battery electrolytes and battery core determination of moisture method |
| CN110514724B (en) * | 2019-08-22 | 2022-04-12 | 中车青岛四方车辆研究所有限公司 | Method for detecting micro-water content in soft package lithium ion capacitor core |
| CN115184418A (en) * | 2022-07-13 | 2022-10-14 | 万向一二三股份公司 | Method and system for analyzing water content of lithium ion battery |
| CN115615181A (en) * | 2022-09-30 | 2023-01-17 | 广东利元亨智能装备股份有限公司 | Moisture detection method and baking device |
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