CN110579569A - Method for calculating electrolyte retention in battery - Google Patents

Method for calculating electrolyte retention in battery Download PDF

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Publication number
CN110579569A
CN110579569A CN201910866003.6A CN201910866003A CN110579569A CN 110579569 A CN110579569 A CN 110579569A CN 201910866003 A CN201910866003 A CN 201910866003A CN 110579569 A CN110579569 A CN 110579569A
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active material
material layer
volume
electrode active
positive electrode
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桂亚林
李掌权
占克军
夏小勇
高学友
王恒
朱坤庆
计阳
庞佩佩
楚英
张涛
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Dongguan Weike Battery Co Ltd
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Dongguan Weike Battery Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/389—Measuring internal impedance, internal conductance or related variables
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/392—Determining battery ageing or deterioration, e.g. state of health

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  • Battery Electrode And Active Subsutance (AREA)
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Abstract

The invention relates to a method for calculating the electrolyte retention amount in a battery. The calculation method comprises the following steps: according to the volume V of the positive active material layer on the positive plate in the batteryAVolume V of the negative active material layer on the negative electrode plateCVolume V of the diaphragmSResidual volume V of aluminum plastic filmmAnd electrolyte density ρEcalculating the electrolyte retention mE. The method can more accurately obtain the data of the electrolyte liquid retention amount, and reduces the circulating risk and the safety coefficient of the electric core system; the method provided by the invention overcomes the defect that the prior art can only test a system with a single determined composition, is suitable for different battery systems, and is still suitable for practical life if the used materials, design information and the proportion of positive and negative active substances are changedThe liquid injection amount on the production has certain guiding significance.

Description

Method for calculating electrolyte retention in battery
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a method for calculating the liquid retention amount of electrolyte in a battery.
Background
Because the liquid retention amount of the electrolyte of the soft package lithium battery affects the electrical performance, particularly the cycle performance, the safety performance, the cost and the appearance of the battery, the liquid retention coefficients of the existing soft package lithium battery market are determined by cycle tests, the systems are multiple, the models are multiple, if the liquid retention coefficients of each system and each model are determined by the cycle tests, the cycle test time is long, the occupied resources are multiple, and the market demand of rapid change cannot be met, so a theoretical calculation method is needed for guiding so as to primarily determine the usage amount of the electrolyte.
CN105787140A discloses a method for calculating the liquid retention by testing the porosity of the pole piece and the diaphragm. The method has the main defects that the theoretical liquid retention capacity of each system can be confirmed only by preparing corresponding pole pieces and diaphragms through experiments after each system is basically shaped, the guiding significance is insufficient, and the method can only roughly estimate the liquid retention capacity of the electrolyte.
CN109326764A discloses a method for accurately controlling the remaining amount of electrolyte in a lithium ion battery. The lithium ion battery cell is subjected to the process flows of pretreatment, primary variable liquid injection, secondary variable liquid injection and the like, the influence of different electrolyte demands caused by different coating thicknesses and surface densities is eliminated by measuring the weight of the cell, and the corresponding total electrolyte demand is calculated by using a calculation formula. The method has complex process and cannot be applied industrially.
Therefore, there is a need in the art for a novel method for calculating the electrolyte retention in a battery, which can accurately obtain the data of the electrolyte retention, reduce the circulation risk and safety factor of a battery cell system, and be suitable for different battery systems.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a method for calculating the electrolyte retention amount in a battery, which can more accurately obtain the data of the electrolyte retention amount and reduce the circulation risk and the safety coefficient of an electric core system. The method provided by the invention can be used for overcoming the defect that the prior art can only test a system with a single determined composition, is suitable for different battery systems, and is still suitable if the used materials, design information and the proportion of positive and negative active substances are changed, thereby having guiding significance.
One of the purposes of the invention is to provide a method for calculating the electrolyte retention amount in a battery, which comprises the following steps:
(1) Testing the volume V of the positive active material layer on the positive pole piece in the batteryA；
(2) testing the volume V of the negative active material layer on the negative pole pieceC；
(3) Volume V of test diaphragmSResidual volume V of aluminum plastic filmmAnd electrolyte density ρE；
(4) according to the obtained VA、VC、VS、VmAnd ρECalculating the electrolyte retention mE。
The invention tests the volume V of the positive active material layer on the positive pole pieceAVolume V of the negative active material layer on the negative electrode plateCvolume V of the diaphragmSResidual volume V of aluminum plastic filmmDetermining the bodyThe theoretical liquid retaining capacity of the soft package battery core is further obtained by combining the specific numerical value of the product with the density of the electrolyte, and the theoretical liquid retaining capacity of the electrolyte can be accurately calculated by adopting the method when one or more conditions of the conditions are changed.
The method comprises the calculation of the volume of the electrolyte which can be reserved by the residual volume of the aluminum-plastic film, more comprehensively covers the electrolyte reserving amount, is closer to the reality, and further improves the calculation accuracy; the electrolyte retention amount obtained by the method can guide the injection amount in actual production, can effectively reduce the blind injection of the electrolyte, ensures the cycle performance and the safety performance of the battery, and can effectively reduce the production cost.
the method for calculating the electrolyte retention capacity is suitable for calculating the electrolyte retention capacity in the soft package lithium ion battery.
Preferably, the electrolyte solution retention amount mE＝(VA+VC+VS+Vm)×ρE。
Preferably, the positive electrode active material layer on the positive electrode sheet in the battery comprises a positive electrode active material, a positive electrode binder and a conductive agent.
Preferably, the volume V of the positive active material layer on the positive pole piece in the batteryAThe calculating method comprises the following steps: testing average Density CW of Positive electrode active Material layerACompacted density PD of positive electrode active material layerALength L of positive electrode active material layerAWidth W of positive electrode active material layerAand thickness D of positive electrode active material layerAObtaining the volume V of the positive active material layer on the positive pole pieceA；
Or, testing the positive electrode active material layer for porosity PALength L of positive electrode active material layerAWidth W of positive electrode active material layerAand thickness D of positive electrode active material layerAObtaining the volume V of the positive active material layer on the positive pole pieceA。
The present invention can be used to measure the average density CW of the positive electrode active material layerAThe method of (1) carrying out the volume V of the positive electrode active material layerAThe calculation of (a) is performed,And can be measured by measuring the porosity P of the positive electrode active material layerAThe method of (1) carrying out the volume V of the positive electrode active material layerAThe method has stronger adaptability to different battery systems.
Preferably, the average density CW of the positive electrode active material layerAthe calculating method comprises the following steps: PCT for testing proportion of positive active substance in all powder materials in batteryATrue density ρ of positive electrode active materialAtrue density rho corresponding to conductive agent in positive electrode active material layerCaPCT for the proportion of the conductive agent in all powder materials in the batteryCaTrue density of positive electrode binder rhoBPCT with the proportion of the positive electrode binder in all powder materials in the batteryBTo obtain the average density CW of the positive electrode active material layerA。
Preferably, all powder materials in the battery comprise a positive electrode active material, a negative electrode active material, a conductive agent, a positive electrode binder, a negative electrode binder and a dispersing agent.
Preferably, the average density of the positive electrode active material layer is calculated in the following manner: CWA＝1/(PCTA/ρA+PCTCa/ρCa+PCTB/ρB)。
Preferably, the volume of the positive active material layer on the positive pole piece is calculated in the following manner: vA＝(1-CWA/PDA)×LA×WA×DA；
Or, VA＝PA×LA×WA×DA。
Preferably, the negative active material layer on the negative electrode sheet in the battery includes a negative active material, a negative binder, a conductive agent, and a dispersant.
Preferably, the volume V of the negative active material layer on the negative pole piece in the batteryCThe calculating method comprises the following steps: testing average Density CW of Anode active Material layerCCompacted density PD of negative electrode active material layerCLength L of anode active material layerCWidth W of the negative electrode active material layerCAnd a negative electrode active materialThickness D of the layerCObtaining the volume V of the negative active material layer on the negative pole pieceC；
Or, testing the porosity P of the anode active material layerCLength L of anode active material layerCWidth W of the negative electrode active material layerCAnd thickness D of the anode active material layerCObtaining the volume V of the negative active material layer on the negative pole pieceC。
Preferably, the average density CW of the anode active material layerCThe calculating method comprises the following steps: PCT for testing proportion of cathode active material in all powder materials in batteryCAnd true density ρ of negative electrode active materialCTrue density rho corresponding to conductive agent in negative electrode active material layerCaPCT for the proportion of the conductive agent in all powder materials in the batteryCaTrue density of negative electrode binder rhoRPCT for the proportion of the cathode binder in all powder materials in the batteryRTrue density of dispersant ρDPCT for the proportion of the dispersant in all powder materials in the batteryDTo obtain an average density CW of the negative electrode active material layerC。
Preferably, the average density of the anode active material layer is calculated in the following manner: CWC＝1/(PCTC/ρC+PCTCa/ρCa+PCTR/ρR+PCTD/ρD)。
Preferably, the volume of the negative active material layer on the negative electrode plate is calculated in the following manner: vC＝(1-CWC/PDC)×LC×WC×DC；
Or, VC＝PC×LC×WC×DC。
Preferably, said diaphragm volume VSThe calculating method comprises the following steps: measuring the length L of the diaphragmSWidth W ofSThickness DSAnd the porosity P of the membraneSTo obtain the volume V of the diaphragmS。
Preferably, the diaphragm volume is calculated in the manner of VS＝PS×LS×WS×DS。
Preferably, the residual volume V of the aluminum plastic filmmThe calculation method comprises the following steps: vmVolume in aluminium-plastic film-volume of aluminium foil VAlCopper foil volume VCuDiaphragm volume VSvolume V of positive active material layer on positive pole pieceAVolume V of the layer of negative active material on the negative pole pieceC。
Preferably, the internal volume of the aluminum-plastic film is equal to the length L of the pits in the aluminum-plastic filmmWidth W of x pitmX pit depth Dm。
Preferably, the volume V of aluminum foilAlLength L of aluminum foilAlX width WAlX thickness DAl。
Preferably, the copper foil volume VCuLength L of copper foilCuX width WCuX thickness DCu。
Preferably, the positive electrode active material includes any one of lithium cobaltate, ternary material, lithium iron phosphate, lithium manganate, and lithium-rich manganese or a combination of at least two thereof.
Preferably, the negative active material includes any one of or a combination of at least two of a silicon material, a tin-based material, mesocarbon microbeads, hard carbon, soft carbon, lithium titanate, and lithium metal.
Preferably, the conductive agent includes any one or a combination of at least two of conductive carbon black, carbon nanotubes, graphene and carbon fibers VGCF.
Preferably, the positive electrode binder is polyvinylidene fluoride.
preferably, the negative electrode binder includes any one of styrene-butadiene rubber, polyvinyl alcohol, acrylic resin, polytetrafluoroethylene, polyurethane, fluorinated rubber, polyacrylic acid, LA132, and LA133, or a combination of at least two thereof.
Preferably, the dispersant is carboxymethyl cellulose.
Preferably, the separator is a dry or wet separator.
Preferably, the separator includes any one or a combination of at least two of a base film, a base film coated with a ceramic coating layer, a base film coated with a PVDF coating layer, and a base film coated with a PMMA coating layer.
Preferably, the ceramic coating layer of the base film coated with the ceramic coating layer comprises any one of an aluminum oxide coating layer, a magnesium oxide coating layer and a silicon oxide coating layer or a combination of at least two of the two.
As a preferred technical solution, the method for calculating the electrolyte retention in a battery according to the present invention includes the following steps:
(1) PCT for testing proportion of positive active substance in all powder materials in batteryAtrue density ρ of positive electrode active materialATrue density rho corresponding to conductive agent in positive electrode active material layerCaPCT for the proportion of the conductive agent in all powder materials in the batteryCaTrue density of positive electrode binder rhoBPCT with the proportion of the positive electrode binder in all powder materials in the batteryBTo obtain the average density CW of the positive electrode active material layerA＝1/(PCTA/ρA+PCTCa/ρCa+PCTB/ρB) Then according to the average density CW of the positive electrode active material layerACompacted density PD of positive electrode active material layerALength L of positive electrode active material layerAWidth W of positive electrode active material layerAand thickness D of positive electrode active material layerAObtaining the volume V of the positive active material layer on the positive pole pieceA＝(1-CWA/PDA)×LA×WA×DA；
Or, testing the positive electrode active material layer for porosity PALength L of positive electrode active material layerAWidth W of positive electrode active material layerAAnd thickness D of positive electrode active material layerAObtaining the volume V of the positive active material layer on the positive pole pieceA＝PA×LA×WA×DAAll powder materials in the battery comprise a positive electrode active substance, a negative electrode active substance, a conductive agent, a positive electrode binder, a negative electrode binder and a dispersing agent;
(2) PCT for testing proportion of cathode active material in all powder materials in batteryCAnd true density ρ of negative electrode active materialCThe corresponding of the conductive agent in the negative electrode active material layerDensity pCaPCT for the proportion of the conductive agent in all powder materials in the batteryCaTrue density of negative electrode binder rhoRPCT for the proportion of the cathode binder in all powder materials in the batteryRTrue density of dispersant ρDPCT for the proportion of the dispersant in all powder materials in the batteryDTo obtain an average density CW of the negative electrode active material layerC＝1/(PCTC/ρC+PCTCa/ρCa+PCTR/ρR+PCTD/ρD) Then according to the average density CW of the anode active material layerCCompacted density PD of negative electrode active material layerCLength L of anode active material layerCWidth W of the negative electrode active material layerCAnd thickness D of the anode active material layerCObtaining the volume V of the negative active material layer on the negative pole pieceC＝(1-CWC/PDC)×LC×WC×DC；
Or, testing the porosity P of the anode active material layerCLength L of anode active material layerCWidth W of the negative electrode active material layerCAnd thickness D of the anode active material layerCObtaining the volume V of the negative active material layer on the negative pole pieceC＝PC×LC×WC×DC；
(3) Measuring the length L of the diaphragmSWidth W ofSThickness DSAnd the porosity P of the membraneSTo obtain the volume V of the diaphragmS＝PS×LS×WS×DSThe internal volume of the aluminum-plastic film is equal to the length L of the pits in the aluminum-plastic filmmWidth W of x pitmX pit depth DmVolume V of aluminum foilAlLength L of aluminum foilAlx width WAlX thickness DAlVolume V of copper foilCuLength L of copper foilCuX width WCuX thickness DCuResidual volume V of aluminum plastic filmmVolume in aluminium-plastic film-volume of aluminium foil VAlCopper foil volume VCuDiaphragm volume VSVolume V of positive active material layer on positive pole pieceAVolume V of the layer of negative active material on the negative pole pieceC；
(4) Electrolyte retention amount mE＝(VA+VC+VS+Vm)×ρE。
Compared with the prior art, the invention has the following beneficial effects:
(1) The method fully considers the influence of the change of the use proportion, the use amount and the compaction density of the conductive agent, the dispersing agent, the binding agent and the active substance on the liquid retaining capacity of the battery core, and the influence of the electrolyte reserved in the residual space of the soft package lithium electronic battery except the bare battery core on the liquid retaining capacity of the battery core, determines the theoretical volume by determining the type, the real density, the use proportion, the use amount, the surface density and the compaction density of the positive electrode material, the negative electrode material, the conductive agent, the binding agent and the dispersing agent in the design scheme and the sizes of the foil, the diaphragm and the aluminum plastic film punching pit, further obtains the theoretical liquid retaining capacity of the soft package battery core by combining the density of the electrolyte, more accurately obtains the data of the liquid retaining capacity of the electrolyte, and reduces the circulating risk and the safety coefficient of a battery. If the used materials, design information and the proportion of the positive and negative active substances are changed, the method still has guiding significance.
(2) The method comprises the calculation of the volume of the electrolyte which can be reserved by the residual volume of the aluminum-plastic film, more comprehensively covers the electrolyte reserving amount, and is closer to the reality; the electrolyte retention amount obtained theoretically can guide the injection amount in actual production, can effectively reduce the blind injection of the electrolyte, ensures the cycle performance and the safety performance of the battery, and can effectively reduce the production cost.
Drawings
FIG. 1 is a liquid retention coefficient cycle chart of example 1 of the present invention;
FIG. 2 is a liquid retention coefficient cycle chart of example 2 of the present invention;
FIG. 3 is a liquid retention coefficient cycle chart of example 3 of the present invention.
Detailed Description
For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
The method for calculating the electrolyte retention capacity in the battery in the embodiment 1-5 of the invention adopts the following steps:
(1) PCT for testing proportion of positive active substance in all powder materials in batteryATrue density ρ of positive electrode active materialATrue density rho corresponding to conductive agent in positive electrode active material layerCaPCT for the proportion of the conductive agent in all powder materials in the batteryCaTrue density of positive electrode binder rhoBPCT with the proportion of the positive electrode binder in all powder materials in the batteryBTo obtain the average density CW of the positive electrode active material layerA＝1/(PCTA/ρA+PCTCa/ρCa+PCTB/ρB) Then according to the average density CW of the positive electrode active material layerACompacted density PD of positive electrode active material layerALength L of positive electrode active material layerAwidth W of positive electrode active material layerAAnd thickness D of positive electrode active material layerAObtaining the volume V of the positive active material layer on the positive pole pieceA＝(1-CWA/PDA)×LA×WA×DA；
(2) PCT for testing proportion of cathode active material in all powder materials in batteryCand true density ρ of negative electrode active materialCTrue density rho corresponding to conductive agent in negative electrode active material layerCaPCT for the proportion of the conductive agent in all powder materials in the batteryCaTrue density of negative electrode binder rhoRPCT for the proportion of the cathode binder in all powder materials in the batteryRTrue density of dispersant ρDPCT for the proportion of the dispersant in all powder materials in the batteryDTo obtain an average density CW of the negative electrode active material layerC＝1/(PCTC/ρC+PCTCa/ρCa+PCTR/ρR+PCTD/ρD) Then according to the average density CW of the anode active material layerCCompacted density PD of negative electrode active material layerCLength L of anode active material layerCWidth W of the negative electrode active material layerCAnd a negative electrode active material layerThickness D ofCObtaining the volume V of the negative active material layer on the negative pole pieceC＝(1-CWC/PDC)×LC×WC×DC；
(3) Measuring the length L of the diaphragmSWidth W ofSThickness DSAnd the porosity P of the membraneSTo obtain the volume V of the diaphragmS＝PS×LS×WS×DSThe internal volume of the aluminum-plastic film is equal to the length L of the pits in the aluminum-plastic filmmWidth W of x pitmX pit depth DmVolume V of aluminum foilAlLength L of aluminum foilAlX width WAlX thickness DAlVolume V of copper foilCuLength L of copper foilCuX width WCuX thickness DCuResidual volume V of aluminum plastic filmmVolume in aluminium-plastic film-volume of aluminium foil VAlCopper foil volume VCuDiaphragm volume VSvolume V of positive active material layer on positive pole pieceAVolume V of the layer of negative active material on the negative pole pieceC；
(4) Electrolyte retention amount mE＝(VA+VC+VS+Vm)×ρE。
And (3) performance testing:
(1) testing the capacity of the battery cell: the batteries of the examples and the comparative examples are tested on a Xinwei test cabinet at the temperature of 25 +/-2 ℃, the voltage ranges of the examples 1-2, 4-7 and the comparative example 1 are 3-4.4V, the voltage range of the example 3 is 3-4.2V, and the first-time specific discharge capacity of the batteries is tested;
(2) And (3) testing the liquid retention amount and the liquid retention coefficient of the electrolyte: the batteries of the examples and the comparative examples were placed in a nova test cabinet at 25 ± 2 ℃, the voltage ranges of examples 1-2, 4-7 and comparative example 1 were 3 to 4.4V, the voltage range of example 3 was 3 to 4.2V, and the current density was 0.5C, and the electrolyte solution retention amount and the electrolyte solution retention coefficient were measured, where the electrolyte solution retention coefficient is (cell electrolyte injection amount-cell electrolyte extraction amount)/cell capacity.
The parameters related to the positive electrode active material layer, the negative electrode active material layer, the aluminum foil, the copper foil, the separator, and the aluminum plastic film in the examples and comparative examples of the present invention are shown in tables 1 and 2:
TABLE 1
Positive electrode active material layer negative electrode active material layer Aluminum foil Copper foil Diaphragm Aluminum plastic film
long (mm) 323.2 329.9 370 360 392 91.5
width (mm) 89 90.5 89 90.5 92.3 37.8
Thickness (mum) 52.2 65.3 12 6 12 2.55
TABLE 2
Aluminum foil Copper foil Diaphragm Aluminum plastic film
Volume (mL) 0.40 0.20 0.87 8.82
Example 1 relevant parameters of the positive electrode active material, the conductive agent, the positive electrode binder, the negative electrode active material, the negative electrode binder and the dispersant in the positive electrode active material layer and the negative electrode active material layer are shown in table 3:
TABLE 3
Example 2 relevant parameters of the positive electrode active material, the conductive agent, the positive electrode binder, the negative electrode active material, the negative electrode binder and the dispersant in the positive electrode active material layer and the negative electrode active material layer are shown in table 4:
TABLE 4
Example 3 relevant parameters of the positive electrode active material, the conductive agent, the positive electrode binder, the negative electrode active material, the negative electrode binder and the dispersant in the positive electrode active material layer and the negative electrode active material layer are shown in table 5:
TABLE 5
Example 4 relevant parameters of the positive electrode active material, the conductive agent, the positive electrode binder, the negative electrode active material, the negative electrode binder and the dispersant in the positive electrode active material layer and the negative electrode active material layer are shown in table 6:
TABLE 6
Example 5 relevant parameters of the positive electrode active material, the conductive agent, the positive electrode binder, the negative electrode active material, the negative electrode binder and the dispersant in the positive electrode active material layer and the negative electrode active material layer are shown in table 7:
TABLE 7
The results of calculation of the liquid retention amounts calculated according to examples 1 to 5 are shown in Table 8:
TABLE 8
Fig. 1 to 3 are liquid retention coefficient circulation curves of examples 1 to 3 of the present invention, and it can be seen from fig. 1 that the liquid retention coefficient obtained in example 1 of the present invention is 1.56g/Ah, which is smaller than the difference between the theoretical calculated value of 1.57g/Ah, and a battery (the same as the battery core material of example 1, but liquid retention is performed according to the liquid retention amount of 1.52 g/Ah) with the actual liquid retention coefficient of 1.52g/Ah is selected for performance comparison; the liquid retention coefficient obtained in the embodiment 2 of the invention is 1.56g/Ah, the difference between the liquid retention coefficient and the theoretical calculation value is smaller than 1.58g/Ah, and a battery with the liquid retention coefficient of 1.50g/Ah (the battery core material is the same as that of the embodiment 2, but the liquid retention is carried out according to the liquid retention amount of 1.50 g/Ah) is selected for performance comparison; the liquid retention coefficient obtained in the embodiment 3 of the invention is 1.70g/Ah, the difference between the liquid retention coefficient and the theoretical calculation value is smaller than 1.72g/Ah, and a battery with the liquid retention coefficient of 1.66g/Ah (the battery core material is the same as that of the embodiment 3, but the liquid retention is carried out according to the liquid retention amount of 1.66 g/Ah) is selected for performance comparison; as can be seen from FIGS. 1 to 3, the requirement that the capacity retention rate is more than 80% at 600-700 weeks of normal-temperature 0.5C charge and discharge can be effectively met by controlling the liquid retention of the battery cell near the theoretical calculation, and if the actual liquid retention coefficient is lower than the theoretical liquid retention coefficient by 0.05g/Ah or more, the cycle performance of the battery cell cannot be ensured at all, which proves that the liquid retention coefficient obtained by the theoretical calculation of the invention has sufficient reference significance.
Meanwhile, in examples 4 and 5 of the present invention, the positive electrode conductive agent and the negative electrode binder were adjusted separately from example 1, and it can be seen from the results that the electrolyte solution retention coefficient and the solution retention amount were changed, and it can be seen that the positive electrode active material, the conductive agent, the positive electrode binder, the negative electrode active material, the negative electrode binder, and the dispersant were all factors that were not negligible when the solution retention amount and the solution retention coefficient were calculated.
Example 6
The difference from example 1 is that the electrolyte solutionIn the calculation process of the liquid retention amount, the volume V of the positive active material layer on the positive electrode sheetAThe length × width × height of the positive electrode active material layer is not considered, i.e., the influence of the conductive agent, the binder, and the active material is not considered. The finally obtained electrolyte retention amount mEWhen the weight was 3.10g, the retention coefficient of the electrolyte was 1.63 g/Ah. The electrolyte retention amount and electrolyte retention coefficient obtained in this example were higher than those of example 1, and the amount of electrolyte used was large, which increased the cost.
Example 7
The difference from example 1 is that the volume V of the negative electrode active material layer on the negative electrode sheet in the calculation of the electrolyte retaining amountAThe negative electrode active material layer has a length × width × height, that is, the influence of the conductive agent, the dispersant, the binder, and the active material is not considered. The finally obtained electrolyte retention amount mEThe electrolyte retention coefficient was 1.65g/Ah, which was 3.14 g. The electrolyte retention amount and electrolyte retention coefficient obtained in this example were higher than those of example 1, and the amount of electrolyte used was large, which increased the cost.
Comparative example 1
The difference from the example 1 is that the residual volume V of the aluminum-plastic film is not considered in the calculation process of the electrolyte retention amountmthe influence of (c). The finally obtained electrolyte retention amount mEWhen the weight is 2.8g, the electrolyte retention coefficient is 1.48 g/Ah. The electrolyte retention amount and electrolyte retention coefficient obtained in this example were smaller than those of example 1, and the retention coefficient was low, so that circulation could not be ensured.
The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims (10)

1. A method for calculating the electrolyte retention in a battery, the method comprising the steps of:
(1) Testing the volume V of the positive active material layer on the positive pole piece in the batteryA；
(2) Testing the volume V of the negative active material layer on the negative pole pieceC；
(3) Volume V of test diaphragmSResidual volume V of aluminum plastic filmmAnd electrolyte density ρE；
(4) According to the obtained VA、VC、VS、VmAnd ρECalculating the electrolyte retention mE。
2. The method of claim 1, wherein the electrolyte hold-up m isE＝(VA+VC+VS+Vm)×ρE。
3. The method of claim 1 or 2, wherein the positive electrode active material layer on the positive electrode sheet in the battery comprises a positive electrode active material, a positive electrode binder, and a conductive agent;
preferably, the volume V of the positive active material layer on the positive pole piece in the batteryAThe calculating method comprises the following steps: testing average Density CW of Positive electrode active Material layerACompacted density PD of positive electrode active material layerALength L of positive electrode active material layerAWidth W of positive electrode active material layerAAnd thickness D of positive electrode active material layerAObtaining the volume V of the positive active material layer on the positive pole pieceA；
Or, testing the positive electrode active material layer for porosity PALength L of positive electrode active material layerAWidth W of positive electrode active material layerAAnd thickness D of positive electrode active material layerAObtaining the volume V of the positive active material layer on the positive pole pieceA；
Preferably, the average density CW of the positive electrode active material layerAThe calculating method comprises the following steps: testing positive electrode active materialsPCT in proportion to all powder materials in the batteryATrue density ρ of positive electrode active materialATrue density rho corresponding to conductive agent in positive electrode active material layerCaPCT for the proportion of the conductive agent in all powder materials in the batteryCaTrue density of positive electrode binder rhoBPCT with the proportion of the positive electrode binder in all powder materials in the batteryBTo obtain the average density CW of the positive electrode active material layerA；
Preferably, all powder materials in the battery comprise a positive electrode active material, a negative electrode active material, a conductive agent, a positive electrode binder, a negative electrode binder and a dispersing agent.
4. The method according to any one of claims 1 to 3, wherein the average density of the positive electrode active material layer is calculated by: CWA＝1/(PCTA/ρA+PCTCa/ρCa+PCTB/ρB)；
Preferably, the volume of the positive active material layer on the positive pole piece is calculated in the following manner: vA＝(1-CWA/PDA)×LA×WA×DA；
Or, VA＝PA×LA×WA×DA。
5. The method of any one of claims 1 to 4, wherein the negative active material layer on the negative electrode sheet in the battery comprises a negative active material, a negative binder, a conductive agent, and a dispersant;
Preferably, the volume V of the negative active material layer on the negative pole piece in the batteryCThe calculating method comprises the following steps: testing average Density CW of Anode active Material layerCCompacted density PD of negative electrode active material layerCLength L of anode active material layerCWidth W of the negative electrode active material layerCAnd thickness D of the anode active material layerCObtaining the volume V of the negative active material layer on the negative pole pieceC；
Or, testing the negative active material layerPorosity PCLength L of anode active material layerCWidth W of the negative electrode active material layerCAnd thickness D of the anode active material layerCObtaining the volume V of the negative active material layer on the negative pole pieceC；
Preferably, the average density CW of the anode active material layerCThe calculating method comprises the following steps: PCT for testing proportion of cathode active material in all powder materials in batteryCAnd true density ρ of negative electrode active materialCTrue density rho corresponding to conductive agent in negative electrode active material layerCaPCT for the proportion of the conductive agent in all powder materials in the batteryCaTrue density of negative electrode binder rhoRPCT for the proportion of the cathode binder in all powder materials in the batteryRTrue density of dispersant ρDPCT for the proportion of the dispersant in all powder materials in the batteryDTo obtain an average density CW of the negative electrode active material layerC。
6. The method of any one of claims 1 to 5, wherein the average density of the negative active material layer is calculated by: CWC＝1/(PCTC/ρC+PCTCa/ρCa+PCTR/ρR+PCTD/ρD)；
Preferably, the volume of the negative active material layer on the negative electrode plate is calculated in the following manner: vC＝(1-CWC/PDC)×LC×WC×DC；
Or, VC＝PC×LC×WC×DC。
7. Method according to one of claims 1 to 6, characterized in that the membrane volume VSThe calculating method comprises the following steps: measuring the length L of the diaphragmSwidth W ofSThickness DSAnd the porosity P of the membraneSTo obtain the volume V of the diaphragmS；
Preferably, the diaphragm volume is calculated in the manner of VS＝PS×LS×WS×DS。
8. The method of any of claims 1 to 7, wherein the plastic-aluminum film has a residual volume VmThe calculation method comprises the following steps: vmVolume in aluminium-plastic film-volume of aluminium foil VAlCopper foil volume VCuDiaphragm volume VSVolume V of positive active material layer on positive pole pieceAVolume V of the layer of negative active material on the negative pole pieceC；
Preferably, the internal volume of the aluminum-plastic film is equal to the length L of the pits in the aluminum-plastic filmmWidth W of x pitmX pit depth Dm；
Preferably, the volume V of aluminum foilAlLength L of aluminum foilAlX width WAlX thickness DAl；
preferably, the copper foil volume VCuLength L of copper foilCuX width WCuX thickness DCu。
9. The method according to any one of claims 1 to 8, wherein the positive electrode active material comprises any one of lithium cobaltate, a ternary material, lithium iron phosphate, lithium manganate, and lithium-rich manganese or a combination of at least two thereof;
Preferably, the negative active material comprises any one or a combination of at least two of silicon material, tin-based material, mesocarbon microbeads, hard carbon, soft carbon, lithium titanate and lithium metal;
Preferably, the conductive agent comprises any one or a combination of at least two of conductive carbon black, carbon nanotubes, graphene and carbon fibers VGCF;
Preferably, the positive electrode binder is polyvinylidene fluoride;
Preferably, the negative electrode binder comprises any one or a combination of at least two of styrene-butadiene rubber, polyvinyl alcohol, acrylic resin, polytetrafluoroethylene, polyurethane, fluorinated rubber, polyacrylic acid, LA132 and LA 133;
Preferably, the dispersant is carboxymethyl cellulose;
Preferably, the membrane is a dry or wet membrane;
Preferably, the separator includes any one or a combination of at least two of a base film, a base film coated with a ceramic coating layer, a base film coated with a PVDF coating layer, and a base film coated with a PMMA coating layer;
Preferably, the ceramic coating layer of the base film coated with the ceramic coating layer comprises any one of an aluminum oxide coating layer, a magnesium oxide coating layer and a silicon oxide coating layer or a combination of at least two of the two.
10. The method according to any one of claims 1 to 9, characterized in that it comprises the following steps:
(1) PCT for testing proportion of positive active substance in all powder materials in batteryATrue density ρ of positive electrode active materialATrue density rho corresponding to conductive agent in positive electrode active material layerCaPCT for the proportion of the conductive agent in all powder materials in the batteryCaTrue density of positive electrode binder rhoBPCT with the proportion of the positive electrode binder in all powder materials in the batteryBTo obtain the average density CW of the positive electrode active material layerA＝1/(PCTA/ρA+PCTCa/ρCa+PCTB/ρB) Then according to the average density CW of the positive electrode active material layerACompacted density PD of positive electrode active material layerALength L of positive electrode active material layerAWidth W of positive electrode active material layerAAnd thickness D of positive electrode active material layerAObtaining the volume V of the positive active material layer on the positive pole pieceA＝(1-CWA/PDA)×LA×WA×DA；
Or, testing the positive electrode active material layer for porosity PALength L of positive electrode active material layerAWidth W of positive electrode active material layerAAnd thickness D of positive electrode active material layerAObtaining the volume V of the positive active material layer on the positive pole pieceA＝PA×LA×WA×DAAll powder materials in the battery comprise positive active materials, negative active materials, conductive agents, positive binders and negative electrodesA binder and a dispersant;
(2) PCT for testing proportion of cathode active material in all powder materials in batteryCAnd true density ρ of negative electrode active materialCTrue density rho corresponding to conductive agent in negative electrode active material layerCaPCT for the proportion of the conductive agent in all powder materials in the batteryCaTrue density of negative electrode binder rhoRPCT for the proportion of the cathode binder in all powder materials in the batteryRTrue density of dispersant ρDPCT for the proportion of the dispersant in all powder materials in the batteryDTo obtain an average density CW of the negative electrode active material layerC＝1/(PCTC/ρC+PCTCa/ρCa+PCTR/ρR+PCTD/ρD) Then according to the average density CW of the anode active material layerCCompacted density PD of negative electrode active material layerCLength L of anode active material layerCWidth W of the negative electrode active material layerCAnd thickness D of the anode active material layerCObtaining the volume V of the negative active material layer on the negative pole pieceC＝(1-CWC/PDC)×LC×WC×DC；
Or, testing the porosity P of the anode active material layerCLength L of anode active material layerCWidth W of the negative electrode active material layerCAnd thickness D of the anode active material layerCObtaining the volume V of the negative active material layer on the negative pole pieceC＝PC×LC×WC×DC；
(3) Measuring the length L of the diaphragmSWidth W ofSThickness DSAnd the porosity P of the membraneSTo obtain the volume V of the diaphragmS＝PS×LS×WS×DSThe internal volume of the aluminum-plastic film is equal to the length L of the pits in the aluminum-plastic filmmWidth W of x pitmX pit depth DmVolume V of aluminum foilAlLength L of aluminum foilAlX width WAlX thickness DAlVolume V of copper foilCuLength L of copper foilCuX width WCuX thickness DCuresidual volume V of aluminum plastic filmmPlastic-aluminumIn-film volume-aluminum foil volume VAlCopper foil volume VCuDiaphragm volume VSVolume V of positive active material layer on positive pole pieceAVolume V of the layer of negative active material on the negative pole pieceC；
(4) Electrolyte retention amount mE＝(VA+VC+VS+Vm)×ρE。
CN201910866003.6A 2019-09-12 2019-09-12 Method for calculating electrolyte retention in battery Pending CN110579569A (en)

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