CN114335768A - Waste lithium iron phosphate battery discharging device, discharging method and application - Google Patents
Waste lithium iron phosphate battery discharging device, discharging method and application Download PDFInfo
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- CN114335768A CN114335768A CN202111393808.7A CN202111393808A CN114335768A CN 114335768 A CN114335768 A CN 114335768A CN 202111393808 A CN202111393808 A CN 202111393808A CN 114335768 A CN114335768 A CN 114335768A
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- iron phosphate
- lithium iron
- waste lithium
- discharge
- phosphate battery
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 119
- 239000002699 waste material Substances 0.000 title claims abstract description 103
- 238000007599 discharging Methods 0.000 title claims abstract description 40
- 238000000034 method Methods 0.000 title claims abstract description 34
- 229910052751 metal Inorganic materials 0.000 claims abstract description 53
- 239000002184 metal Substances 0.000 claims abstract description 53
- 238000012360 testing method Methods 0.000 claims abstract description 36
- 239000000843 powder Substances 0.000 claims abstract description 30
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 238000004064 recycling Methods 0.000 claims description 4
- 230000002441 reversible effect Effects 0.000 claims description 4
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 238000005316 response function Methods 0.000 claims description 3
- -1 polytetrafluoroethylene Polymers 0.000 claims description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 2
- 230000001681 protective effect Effects 0.000 claims description 2
- 230000008569 process Effects 0.000 abstract description 9
- 238000001514 detection method Methods 0.000 abstract description 6
- 238000009413 insulation Methods 0.000 description 8
- 230000007423 decrease Effects 0.000 description 6
- 230000002829 reductive effect Effects 0.000 description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 4
- 229910001416 lithium ion Inorganic materials 0.000 description 4
- 229910052493 LiFePO4 Inorganic materials 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- 229910000399 iron(III) phosphate Inorganic materials 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- 238000013508 migration Methods 0.000 description 3
- 230000005012 migration Effects 0.000 description 3
- 239000010926 waste battery Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 229910010710 LiFePO Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002505 iron Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 229910052987 metal hydride Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Secondary Cells (AREA)
Abstract
The invention provides a waste lithium iron phosphate battery discharging device, a discharging method and application. The discharge device includes: the waste lithium iron phosphate battery module is placed in the metal shell when the waste lithium iron phosphate batteries are discharged, so that the waste lithium iron phosphate batteries can be discharged by burying the waste lithium iron phosphate battery module in the conductive powder. Because the metal shell is connected with the test circuit module, the discharge depth can be reflected in real time in the discharge process, the discharge depth of the battery does not need to be artificially sampled and detected, the safety is higher, the discharge condition of the whole battery module can be reflected in real time, and the detection efficiency and the accuracy are higher. This old and useless lithium iron phosphate battery discharge device is applied to old and useless lithium iron phosphate battery and retrieves, can promote the operation safety system, and easily monitors the condition of discharging.
Description
Technical Field
The invention relates to the technical field of waste battery treatment, in particular to a waste lithium iron phosphate battery discharging device, a discharging method and application.
Background
The lithium iron phosphate battery isUsing lithium iron phosphate (LiFePO)4) As the anode material, carbon is used as the lithium ion battery of the cathode material, and the charge and discharge reaction of the lithium iron phosphate battery is in LiFePO4And FePO4Between the two phases. During charging, LiFePO4Gradually separated out lithium ions to form FePO4During discharge, lithium ions are intercalated into FePO4Formation of LiFePO4. The lithium iron phosphate battery has the advantages of high working voltage, high energy density, long cycle life, good safety performance, small self-discharge rate, no memory effect and the like. With the high-speed development of new energy automobiles, lithium iron phosphate batteries are more and more widely applied. Because the lithium iron phosphate battery contains a large amount of metal lithium, the discarded lithium iron phosphate battery is recycled, so that the pollution of the waste battery to the environment can be reduced, and certain economic benefit can be brought. In the traditional method for recovering the waste lithium iron phosphate batteries, the waste lithium iron phosphate batteries are generally discharged, disassembled and crushed, and then the crushed materials of the positive plate are incinerated at high temperature to remove the organic binder, so that the positive active material is separated from the aluminum foil, and the positive active powder is obtained after separation. And dissolving the positive active powder by adopting sulfuric acid, and respectively obtaining iron salt, lithium salt and the like after impurity removal and sorting to complete the recovery of elements such as iron, lithium and the like.
In the conventional discharging method of the waste lithium iron phosphate batteries, the waste lithium iron phosphate batteries are soaked in an electrolyte solution for discharging. The method is generally difficult to measure the residual capacity of the waste lithium iron phosphate battery. In addition, liquid nitrogen is adopted to carry out low-temperature treatment on the waste lithium iron phosphate batteries and then the waste lithium iron phosphate batteries are subjected to forced perforation discharge, but the method has high requirements on equipment and high treatment cost. The short-circuit discharge method is a discharge method of waste lithium iron phosphate batteries which is researched more at present, but because manual sampling is needed when the discharge degree is detected, a single battery is taken and placed, the danger coefficient of operation is higher, and the efficiency and the accuracy of detecting the discharge degree are lower.
Disclosure of Invention
Therefore, a discharge device, a discharge method and an application of the waste lithium iron phosphate battery are needed, wherein the discharge device, the discharge method and the application have high safety and are convenient for detecting the discharge degree.
In one aspect of the present invention, a discharge device for waste lithium iron phosphate batteries is provided, which includes:
the metal shell is used for placing the waste lithium iron phosphate battery module;
the conductive powder is arranged in the metal shell, so that the conductive powder wraps the waste lithium iron phosphate battery module and is connected with the waste lithium iron phosphate battery module and the metal shell;
an insulating assembly connected to an outer surface of the metal shell; and
and the test circuit module is connected with the metal shell.
In some of these embodiments, the test circuit module comprises:
an operational amplifier;
one end of the protection resistor is connected with the metal shell, and the other end of the protection resistor is connected with the reverse input end of the operational amplifier;
one end of the feedback resistor is connected with the reverse input end of the operational amplifier, and the other end of the feedback resistor is connected with the output end of the operational amplifier;
one end of the balance resistor is connected with the positive input end of the operational amplifier, and the other end of the balance resistor is grounded; and
and the oscilloscope is connected with the output end of the operational amplifier and is used for recording the voltage of the output end of the operational amplifier.
In some of these embodiments, the test circuit module further comprises:
the wiring terminal is arranged between the protection resistor and the metal shell and used for connecting the components of the test circuit module with the metal shell; and
and the switch is arranged between the wiring terminal and the protective resistor and used for controlling the state of the test circuit.
In some embodiments, the conductive powder is at least one selected from copper powder and graphite.
In some of these embodiments, the material of the insulating component is polytetrafluoroethylene.
On the other hand, the invention also provides a waste lithium iron phosphate battery discharging method, which comprises the following steps:
and arranging the waste lithium iron phosphate battery module in the waste lithium iron phosphate battery discharging device, wrapping the waste lithium iron phosphate battery module with the conductive powder, and starting the test circuit module to perform short-circuit discharging.
In some embodiments, in the short-circuit discharging step, the temperature of the waste lithium iron phosphate battery module is 25 ℃ to 60 ℃.
In some embodiments, the method for discharging the waste lithium iron phosphate battery further includes: detecting the depth of discharge;
wherein the detecting of the depth of discharge includes:
acquiring leakage current of the metal shell and output voltage of the test circuit;
the depth of discharge is judged according to formula I:
the formula I represents the relation between the self discharge current and the discharge time of the waste lithium iron phosphate battery; i.e. iD(t) represents a discharge current curve, i.e. a function of leakage current and discharge time; c0Representing the geometric capacitance of the waste lithium iron phosphate battery; u shape0Representing an initial output voltage of the test circuit; sigma represents the conductivity of the conductive powder; epsilon0Is a vacuum dielectric constant; and f (t) represents the response function of the waste lithium iron phosphate battery.
In some embodiments, the output voltage of the test circuit module is the voltage of the output end of the operational amplifier;
the leakage current is calculated by formula II:
iD＝U0/Rfformula II;
wherein R isfRepresenting the resistance of the feedback resistor.
On the other hand, the invention also provides application of the waste lithium iron phosphate battery discharging device in recycling of waste lithium iron phosphate batteries.
Above-mentioned old and useless lithium iron phosphate battery discharge device includes: the waste lithium iron phosphate battery module is placed in the metal shell when the waste lithium iron phosphate battery is discharged, so that the waste lithium iron phosphate battery module is buried in the conductive powder, and the waste lithium iron phosphate battery can be discharged. Because metal casing surface is connected with binding post, can be used to connect test circuit, can reflect the depth of discharge in real time at the discharge in-process, need not artificially to carry out the depth of discharge of sample detection battery, therefore the security is higher, and can reflect the condition of discharging of whole battery module in real time, detection efficiency and accuracy are higher.
Drawings
Fig. 1 is a schematic structural diagram of a waste lithium iron phosphate battery discharging device according to an embodiment of the present invention;
fig. 2 is a curve showing the discharge capacity and internal resistance of a waste lithium iron phosphate battery according to the temperature in an embodiment of the present invention;
fig. 3 shows three stages of a physical discharge process of a waste lithium iron phosphate battery according to an embodiment of the present invention;
fig. 4 is a discharge current curve of a waste lithium iron phosphate battery at different temperatures according to an embodiment of the present invention; wherein, the discharge current curves at 60 ℃, 80 ℃, 100 ℃, 120 ℃ and 140 ℃ are respectively from bottom to top;
reference numerals: 110. a metal housing; 120. a conductive powder; 130. an insulating assembly; 200. a test circuit module; 210. an operational amplifier; 220. a protection resistor; 230. a feedback resistor; 240. balancing resistance; 250. an oscilloscope; 260. a wiring terminal; 270. and (4) switching.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate orientations and positional relationships based on those shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be considered as limiting the present invention.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Referring to fig. 1, in an embodiment of the present invention, there is provided a discharge device for a waste lithium iron phosphate battery, including: the testing device comprises a metal shell 110, conductive powder 120, an insulating assembly 130 and a testing circuit module 200.
The metal shell 110 is used for placing the waste lithium iron phosphate battery, and the conductive powder 120 is disposed in the metal shell 110, and is preferably filled with the metal shell 110 in which the waste lithium iron phosphate battery is placed, so as to connect the waste lithium iron phosphate battery and the metal shell 110. Further, the conductive powder 120 completely wraps the waste lithium iron phosphate battery. In some of these embodiments, the conductive powder 120 is selected from at least one of copper powder and graphite. The copper powder and the graphite both have good conductive performance, and the waste lithium iron phosphate battery modules can be short-circuited by being wrapped around the waste lithium iron phosphate battery modules, so that discharging is realized.
An insulation assembly 130 is attached to an outer surface of the metal case 110 for electrically insulating the metal case 110 from the ground. And the insulating member 130 also serves to fix the metal case 110. In some embodiments, the insulating member 130 is made of ptfe, which has excellent insulating properties, heat resistance, cold resistance, acid and alkali resistance, and the like, and can improve the safety of the discharge device when used as the insulating member 130.
The test circuit module 200 is connected to the metal housing 110 for monitoring the discharge process.
Above-mentioned old and useless lithium iron phosphate battery discharge device includes: the metal shell 110, the conductive powder 120 and the insulating assembly 130 are filled with the conductive powder 120 in the metal shell 110, when the waste lithium iron phosphate batteries are discharged, the waste lithium iron phosphate battery modules are placed in the metal shell 110, so that the waste lithium iron phosphate battery modules are buried in the conductive powder 120, and the conductive powder 120 plays a role in connecting the positive electrode and the negative electrode of the waste lithium iron phosphate battery modules and connecting the waste lithium iron phosphate battery modules with the metal shell 110, so that the waste lithium iron phosphate batteries can be discharged. Because the metal shell 110 is connected with the test circuit module 200, the discharge depth can be reflected in real time in the discharge process, and the discharge depth of the battery does not need to be artificially sampled and detected, so that the safety is higher, the discharge condition of the whole battery module can be reflected in real time, and the detection efficiency and the accuracy are higher.
Referring again to fig. 1, in some embodiments, the test circuit module 200 includes: operational amplifier 210, protection resistor 220, feedback resistor 230, balance resistor 240, oscilloscope 250, connection terminal 260 and switch 270.
The operational amplifier 210 is used for amplifying the discharge signal of the waste lithium iron phosphate battery module.
One end of the protection resistor 220 is connected to the connection terminal 260, and the other end of the protection resistor 220 is connected to the inverting input terminal of the operational amplifier 210. The protection resistor 220 is used to protect the test circuit from excessive current.
One end of the feedback resistor 230 is connected to the inverting input terminal of the operational amplifier 210, and the other end of the feedback resistor 230 is connected to the output terminal of the operational amplifier 210.
One end of the balancing resistor 240 is connected to the positive input terminal of the operational amplifier 210, and the other end of the balancing resistor 240 is grounded. The balancing resistor 240 is used to avoid detection errors caused by leakage circuits of the operational amplifier 210.
The oscilloscope 250 is connected to the output terminal of the operational amplifier 210, and is used for recording the voltage at the output terminal of the operational amplifier 210.
The connection terminal 260 is disposed between the protection resistor 220 and the metal housing 110, and is used for connecting the metal housing 110 and the components of the test circuit module 200.
The switch 270 is disposed between the connection terminal 260 and the protection resistor 220, and is used for controlling the state of the test circuit.
In some of these embodiments, the protection resistor 220 has a resistance of 1M Ω. The protection resistor 220 has a high resistance value, so that excessive current passing through the test circuit can be avoided.
In some of these embodiments, the resistance of the balancing resistor 240 is 1M Ω. The high resistance of the balancing resistor 240 prevents the leakage current of the operational amplifier 210 from causing measurement errors.
The invention also provides a discharge method of the waste lithium iron phosphate battery, which comprises the following steps:
the waste lithium iron phosphate battery module is arranged in a metal shell 110 of the waste lithium iron phosphate battery discharging device, so that the waste lithium iron phosphate battery module is wrapped by the conductive powder 120, and the testing circuit module 200 is started to perform short-circuit discharging. The positive electrode and the negative electrode of the waste lithium iron phosphate battery module are connected through the conductive powder 120, and short-circuit discharge occurs.
In the above discharging method for the waste lithium iron phosphate batteries, the conductive powder 120 wraps the waste lithium iron phosphate battery module and is filled in the metal shell 110, and when the waste lithium iron phosphate batteries are discharged, the waste lithium iron phosphate battery module is placed in the metal shell 110, so that the waste lithium iron phosphate battery module is buried in the conductive powder 120, and the waste lithium iron phosphate batteries can be discharged. Because the metal shell 110 is connected with the test circuit module 200, the discharge depth can be reflected in real time in the discharge process, and the discharge depth of the battery does not need to be artificially sampled and detected, so that the safety is higher, the discharge condition of the whole battery module can be reflected in real time, and the detection efficiency and the accuracy are higher.
In some embodiments, in the short-circuit discharging step, the temperature of the waste lithium iron phosphate battery module is 25-60 ℃.
The influence of temperature on the discharge performance is directly reflected on the discharge capacity and the discharge voltage. The temperature is reduced, the internal resistance of the battery is increased, the electrochemical reaction speed is slowed down, the polarization internal resistance is rapidly increased, the discharge capacity and the discharge platform of the battery are reduced, and the output of the power and the energy of the battery is influenced. Taking a nickel-metal hydride battery of 80A · h as an example for discharge, a battery of an electric vehicle is fully charged at normal temperature and discharged at 1C current at different temperatures. The discharge capacity is lower at-20 ℃, the discharge capacity is maximum at 20 ℃, and then the discharge capacity is reduced along with the temperature rise, but the discharge capacity at medium and high temperature is obviously larger than that at low temperature, which indicates that the discharge performance at medium and high temperature is stronger than that at low temperature. The high temperature is favorable for the diffusion of hydrogen atoms in the alloy, the dynamic performance of the alloy is improved, the conductivity of the electrolyte is increased along with the temperature rise, the conductivity of the electrolyte is high at high temperature, the current migration capability is high, the migration internal resistance is reduced, and the current charging and discharging performance is enhanced.
Referring to fig. 2, the applicant studied the discharge of the lithium iron phosphate battery, and it can be seen that, in the case of the lithium iron phosphate battery, the discharge capacity is also sharply decreased at a low temperature, but the discharge capacity is not lower than the normal temperature at a high temperature, and may be slightly higher than the discharge capacity at the normal temperature, which is mainly due to the increased migration rate of lithium ions at the high temperature, and the lithium electrode does not decompose or generate hydrogen gas at a high temperature to decrease the capacity unlike the nickel electrode and the hydrogen storage electrode. When the lithium iron phosphate battery module discharges at low temperature, along with the progress of discharging, the battery temperature rises due to heat generated by the resistor and other reasons, and the voltage rises and gradually drops along with the progress of discharging.
The discharge process of the lithium iron phosphate battery mainly has three stages. The leakage circuit size and depth of discharge are closely related. In the metal case 110 filled with the conductive powder 120, the leakage current is generated due to the overall non-electrical neutrality when the battery is not discharged. If the insulation resistance of the insulation assembly 130 does not vary with voltage, the leakage current to ground from the metal casing 110 may indirectly reflect the degree of battery discharge, but does not result in a reduction or termination of the discharge rate. Referring to fig. 3, three stages of the physical discharge process of the waste lithium iron phosphate battery are shown. Specifically, the discharge process of the lithium iron phosphate battery is divided into a medium-speed discharge area, a fast discharge area and a slow discharge area.
And (3) medium-speed discharge zone: the insulation resistance of the insulation assembly 130 has a significant voltage dependence-the higher the voltage, the lower the insulation voltage of the insulation assembly 130, the significantly increased leakage current shunt fraction of the insulation assembly 130. Therefore, the leakage current during the entire discharge process exhibits the characteristic of the initial medium speed drop, in which the voltage is large, and the leakage current of the insulating member 130 causes the total leakage current to decrease.
A rapid discharge area: as the discharge degree increases, the voltage of the metal case 110 to the ground decreases as a whole, and the leakage current of the insulating member 130 decreases, and the leakage current of the entire metal case 110 to the ground mainly flows through the feedback resistor 230, which is a rapid discharge region. Meanwhile, as the battery discharge proceeds to a certain extent, the temperature in the metal case 110 rises, and the reaction in the electrode accelerates.
A slow discharge area: as the degree of discharge of the battery in the metal case 110 increases and is about to complete, the metal case 110 as a whole tends to be electrically neutral, the voltage to ground decreases, and the leakage current decreases.
In some embodiments, the method for discharging the waste lithium iron phosphate battery further comprises: and detecting the depth of discharge.
Specifically, the step of detecting the depth of discharge includes:
the leakage current of the metal case 110 and the output voltage of the test circuit are obtained.
Then, the depth of discharge is judged according to formula I:
the formula I represents the relation between the self discharge current and the discharge time of the waste lithium iron phosphate battery; i.e. iDRepresenting leakage current, iD(t) represents a discharge currentAs a function of discharge time; c0Representing the geometric capacitance of the waste lithium iron phosphate battery; u shape0Representing an initial output voltage of the test circuit; σ represents the conductivity of the conductive powder 120; epsilon0Is a vacuum dielectric constant; and f (t) represents the response function of the waste lithium iron phosphate battery, and is the inherent property of the battery.
In some embodiments, the output voltage of the test circuit module 200 is the voltage at the output of the operational amplifier 210, and is recorded by the oscilloscope 250.
In some of these embodiments, the leakage current is calculated by equation II:
iD＝U0/Rfformula II;
wherein R isfRepresenting the resistance of feedback resistor 230.
In some of these embodiments, i may be used to simplify the determination of depth of dischargeD(t) judging the depth of discharge by using the curve threshold value. When the current value of a certain average temperature is reduced to a threshold value within a certain time, the discharge is considered to be close to the tail sound. According to the discharge temperature, iDThere are also differences in (t) curve thresholds.
Referring to fig. 4, which is a discharge current curve of the waste lithium iron phosphate battery at different temperatures, when the current value drops below the dotted line in the graph, it is determined that the discharge is close to the end sound.
In one embodiment, the discharge method of the waste lithium iron phosphate battery comprises the following steps:
step S100: the waste lithium iron phosphate battery is placed in the metal shell 110, so that the conductive powder 120 wraps the waste lithium iron phosphate battery.
Step S200: the switch 270 is opened to connect the test circuit and turn on the oscilloscope 250.
Step S300: after turning on the switch 2701 second, the voltage at the output of the operational amplifier 210 is recorded and the leakage current is calculated. Considering the operation overvoltage during the opening of the switch 270, only the output voltage of the operational amplifier 210 after 1 second of the opening of the switch 270is recorded.
Step S400: and obtaining a discharge current curve of the discharge current changing along with time according to the leakage current obtained by calculation in the step S300.
Step S500: and judging the discharge depth of the waste lithium iron phosphate battery according to the current curve threshold value at the measured temperature.
The invention further provides an application of the waste lithium iron phosphate battery discharging device in recycling of waste lithium iron phosphate batteries.
The embodiment of the invention also provides a recovery method of the waste lithium iron phosphate batteries, which adopts the discharge device of the waste lithium iron phosphate batteries to discharge the waste lithium iron phosphate batteries to 0V.
According to the method for recycling the waste lithium iron phosphate batteries, the waste lithium iron phosphate battery discharging device is used for discharging the waste batteries, the operation safety is high, and the discharging degree is convenient to monitor.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, so as to understand the technical solutions of the present invention specifically and in detail, but not to be understood as the limitation of the protection scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. It should be understood that the technical solutions provided by the present invention, which are obtained by logical analysis, reasoning or limited experiments, are within the scope of the present invention as set forth in the appended claims. Therefore, the protection scope of the present invention should be subject to the content of the appended claims, and the description and the drawings can be used for explaining the content of the claims.
Claims (10)
1. The utility model provides a waste lithium iron phosphate battery discharge device which characterized in that includes:
the metal shell is used for placing the waste lithium iron phosphate battery module;
the conductive powder is arranged in the metal shell, so that the conductive powder wraps the waste lithium iron phosphate battery module and is connected with the waste lithium iron phosphate battery module and the metal shell;
an insulating assembly connected to an outer surface of the metal shell; and
and the test circuit module is connected with the metal shell.
2. The waste lithium iron phosphate battery discharging device according to claim 1, wherein the testing circuit module comprises:
an operational amplifier;
one end of the protection resistor is connected with the metal shell, and the other end of the protection resistor is connected with the reverse input end of the operational amplifier;
one end of the feedback resistor is connected with the reverse input end of the operational amplifier, and the other end of the feedback resistor is connected with the output end of the operational amplifier;
one end of the balance resistor is connected with the positive input end of the operational amplifier, and the other end of the balance resistor is grounded; and
and the oscilloscope is connected with the output end of the operational amplifier and is used for recording the voltage of the output end of the operational amplifier.
3. The waste lithium iron phosphate battery discharging device according to claim 2, wherein the testing circuit module further comprises:
the wiring terminal is arranged between the protection resistor and the metal shell and used for connecting the components of the test circuit module with the metal shell; and
and the switch is arranged between the wiring terminal and the protective resistor and used for controlling the state of the test circuit.
4. The discharge device for the waste lithium iron phosphate batteries according to any one of claims 1 to 3, wherein the conductive powder is at least one selected from copper powder and graphite.
5. The waste lithium iron phosphate battery discharging device as claimed in any one of claims 1 to 3, wherein the insulating component is made of polytetrafluoroethylene.
6. A discharging method of a waste lithium iron phosphate battery is characterized by comprising the following steps:
the waste lithium iron phosphate battery module is arranged in the discharge device for the waste lithium iron phosphate batteries according to any one of claims 1 to 5, so that the waste lithium iron phosphate battery module is wrapped by the conductive powder, and the test circuit module is started to perform short-circuit discharge.
7. The discharging method of the waste lithium iron phosphate batteries according to claim 6, wherein in the short-circuit discharging step, the temperature of the waste lithium iron phosphate battery module is 25-60 ℃.
8. The method for discharging the waste lithium iron phosphate batteries according to claim 6, further comprising the following steps: detecting the depth of discharge;
the step of detecting the depth of discharge includes:
acquiring leakage current of the metal shell and output voltage of the test circuit module;
the depth of discharge is judged according to formula I:
wherein iD(t) represents the discharge current curve, i.e. leakage current versus dischargeA function of electrical time; c0Representing the geometric capacitance of the waste lithium iron phosphate battery; u shape0Representing an initial output voltage of the test circuit; sigma represents the conductivity of the conductive powder; epsilon0Is a vacuum dielectric constant; and f (t) represents the response function of the waste lithium iron phosphate battery.
9. The discharging method of the waste lithium iron phosphate batteries according to claim 8, wherein the output voltage of the test circuit module is the voltage of the output end of an operational amplifier;
the leakage current is calculated by formula II:
iD＝U0/Rfformula II;
wherein R isfRepresenting the resistance of the feedback resistor.
10. The use of the discharge device for waste lithium iron phosphate batteries according to any one of claims 1 to 5 in the recycling of waste lithium iron phosphate batteries.
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| CN115084700A (en) * | 2022-06-27 | 2022-09-20 | 中南大学 | Thermosensitive discharge particles and safe discharge method of waste lithium ion battery |
| DE102022203718A1 (en) | 2022-04-13 | 2023-10-19 | Robert Bosch Gesellschaft mit beschränkter Haftung | Device and method for discharging battery units |
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| CN108134154A (en) * | 2018-01-12 | 2018-06-08 | 深圳市比克电池有限公司 | A kind of safe disassembling method of waste and old lithium ion battery |
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