CN113258152A - Variable frequency pulse formation method based on optimal frequency of lithium ion battery - Google Patents
Variable frequency pulse formation method based on optimal frequency of lithium ion battery Download PDFInfo
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- CN113258152A CN113258152A CN202110511966.1A CN202110511966A CN113258152A CN 113258152 A CN113258152 A CN 113258152A CN 202110511966 A CN202110511966 A CN 202110511966A CN 113258152 A CN113258152 A CN 113258152A
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- frequency
- lithium ion
- ion battery
- formation
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- 230000015572 biosynthetic process Effects 0.000 title claims abstract description 83
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 62
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims abstract description 42
- 238000001453 impedance spectrum Methods 0.000 claims abstract description 9
- 238000010586 diagram Methods 0.000 claims description 8
- 230000000694 effects Effects 0.000 claims description 2
- 230000010287 polarization Effects 0.000 abstract description 5
- 238000009825 accumulation Methods 0.000 abstract description 2
- 238000000157 electrochemical-induced impedance spectroscopy Methods 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 239000008151 electrolyte solution Substances 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 230000002238 attenuated effect Effects 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000004807 desolvation Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
- 238000002847 impedance measurement Methods 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/44—Methods for charging or discharging
- H01M10/446—Initial charging measures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Secondary Cells (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
The invention relates to a variable frequency pulse formation method based on the optimal frequency of a lithium ion battery. Firstly, the electrochemical impedance spectrum of the lithium ion battery is measured off line, and the optimal frequency of the lithium ion battery under different formation voltages is obtained. In the formation process, according to the terminal voltage of the formation battery, selecting the optimal frequency of the battery corresponding to the voltage as the frequency of pulse formation, adjusting the amplitude and the duty ratio of pulse current, and performing variable-frequency pulse formation on the lithium ion battery. The pulse formation method based on the optimal frequency of the lithium ion battery can slow down the polarization in the battery in the formation process, avoid uneven accumulation of reduction products and form a uniform and compact SEI film, thereby improving the cycle stability of the lithium ion battery, particularly the cycle performance at normal temperature and high temperature and prolonging the service life of the lithium ion battery.
Description
Technical Field
The invention relates to a lithium ion battery formation method, in particular to a variable frequency pulse formation method based on the optimal frequency of a lithium ion battery.
Background
Lithium ion batteries are energy storage elements widely used in recent years, and have the characteristics of high specific energy, high power density, high efficiency, environmental protection and the like, so that the lithium ion batteries are widely used in the fields of consumer electronics, electric drive, energy storage power stations and the like. The formation process is a key process of the lithium ion battery. In the first charging process of formation, before lithium ions are inserted into graphite, the electrolyte solution can perform a reduction reaction on the surface of the electrode material to form an SEI film which is insoluble in an organic solution. The SEI film has an important influence on initial capacity loss, safety, cycle life, and the like of the lithium ion battery.
At present, a constant current and constant voltage method is generally adopted for formation of the lithium ion battery, but polarization phenomenon exists in the battery during constant current formation. On the other hand, since lithium ions diffuse in an electrolyte solution much more slowly than electrons are conducted, the slow movement of lithium ions causes the formation of an uneven SEI film. Further, lithium ions reach the negative electrode, desolvate and diffuse inside the negative electrode, and are intercalated into the negative electrode, but problems such as desolvation kinetics and graphite internal diffusion reduce intercalation efficiency, resulting in uneven deposition of metallic lithium at the graphite negative electrode-electrolyte solution interface.
Disclosure of Invention
The invention provides a variable frequency pulse formation method based on the optimal frequency of a lithium ion battery, aiming at relieving the polarization phenomenon of the lithium ion battery in the formation process and forming a uniform and compact SEI film, so as to improve the cycle performance of the lithium ion battery and prolong the service life of the lithium ion battery.
The technical scheme adopted by the invention is as follows: a frequency conversion pulse formation method based on the optimal frequency of a lithium ion battery is characterized in that according to a Bode diagram of the relationship between the impedance and the frequency of an electrochemical impedance spectrum of the lithium ion battery, the frequency corresponding to the impedance with the minimum value is used as the optimal frequency for formation of the lithium ion battery; in the formation process, along with the change of the terminal voltage of the battery, the optimal frequency under the corresponding voltage is determined as the formation frequency, and the lithium ion battery is subjected to variable-frequency pulse formation by adopting positive and negative pulse currents.
Further, the lithium ion battery formation optimum frequency is measured off-line using an electrochemical workstation.
Further, besides changing the formation frequency, the positive and negative pulse amplitudes and duty ratios are adjusted to obtain the optimal formation effect.
Compared with the conventional direct current formation method of the lithium ion battery, the variable frequency pulse formation method adopting the adjustable amplitude and the duty ratio can determine the pulse frequency according to the electrochemical characteristics of the battery and specifically make a pulse formation strategy. The method can slow down the internal polarization of the lithium ion battery in the formation process, avoid the uneven accumulation of reduction products, and form an even and compact SEI film, thereby improving the cycle stability of the lithium ion battery and prolonging the service life of the lithium ion battery.
Drawings
FIG. 1 is a Bode plot of electrochemical impedance spectroscopy impedance versus frequency for a lithium ion battery used to determine optimal frequency in an embodiment of the present invention;
FIG. 2 is a diagram of the formation voltage-optimum frequency relationship of a lithium ion battery in an embodiment of the present invention;
FIG. 3 is a schematic diagram of the relationship between formation current and time of the pulse formation technique in the embodiment of the present invention, wherein ICIs a positive pulse current amplitude; i isDIs the negative pulse current amplitude; t isCThe time for which a positive pulse current is applied; t isDThe time for which the negative pulse current acts; the period T ═ T of the pulse formationC+TD(ii) a The duty cycle has the value: t isD/T；
FIG. 4 is a schematic diagram comparing the relationship between the battery capacity and the voltage in the constant current formation and the pulse formation in the embodiment of the present invention;
fig. 5 shows the capacity change of each experimental battery set after 1500 cycles at 25 ℃ with 28A as the charging and discharging current in the example of the present invention.
Detailed Description
The invention provides a variable frequency pulse formation method based on the optimal frequency of a lithium ion battery, which comprises the following concrete implementation processes: and selecting the frequency corresponding to the impedance with the minimum value in a Bode diagram (see the attached figure 1) of the electrochemical impedance spectrum impedance and frequency relation of the lithium ion battery as the formation optimal frequency of the lithium ion battery. During the formation process, the optimum frequency of a lithium ion battery varies with the terminal voltage of the battery. Therefore, the lithium ion battery formation voltage-optimum frequency relation is obtained through the electrochemical impedance spectrum test (see the attached figure 2). In the pulse formation, according to the formation voltage of the battery, the pulse frequency is adjusted according to the relationship between the formation voltage of the battery and the optimal frequency, the amplitude and the duty ratio of positive and negative pulses are adjusted, the variable-frequency pulse formation of the lithium ion battery is realized, and the pulse current time sequence is shown in an attached figure 3.
The present invention will be described in detail below with reference to examples and drawings of a 28Ah lithium iron phosphate battery, but the present invention is not limited thereto.
The invention provides a variable-frequency pulse forming method based on the optimal frequency of a lithium ion battery, which comprises the following specific steps of:
(1) measuring electrochemical impedance spectrums (EIS spectrums) of the lithium ion battery at different terminal voltages (formation voltages) in the formation process in a constant current mode by using an electrochemical workstation, wherein the frequency range measured by the EIS spectrums is 0.003 Hz-3000 Hz, and the current amplitude is 1000 mA;
(2) acquiring a Bode graph of impedance changing along with frequency according to the EIS graphs of the lithium ion battery under different formation voltages obtained in the step (1), wherein the frequency corresponding to the minimum impedance in the graph is the formation optimal frequency of the lithium ion battery under the voltage;
(3) in the formation process, selecting the optimal frequency corresponding to the battery voltage as the frequency of pulse formation according to the battery voltage;
(4) and adjusting the pulse amplitude and the duty ratio until the formation is finished, wherein the pulse formation duty ratio is 1-20%, the positive pulse amplitude is 0.01C-1C, and the negative pulse amplitude is 0.01C-1C.
Examples
(1) Measuring an electrochemical impedance spectrum (EIS spectrum) of the lithium ion battery at a specific temperature by using an electrochemical workstation under an alternating current impedance measurement mode, wherein the frequency range measured by the EIS spectrum is 0.003 Hz-3000 Hz, and the current amplitude is 1000 mA;
(2) acquiring an EIS map of the lithium ion battery through the step (1), and acquiring a Bode map (shown in figure 1) of which the imaginary part impedance changes along with the frequency, wherein the frequency corresponding to the imaginary part impedance as the minimum value in the map is used as the optimal frequency of the lithium ion battery;
(3) during the formation process, the optimum frequency of a lithium ion battery varies with the terminal voltage of the battery. Therefore, the lithium ion battery is subjected to off-line test of electrochemical impedance spectrum under different battery end voltages to obtain a formation voltage-optimal frequency relation (figure 2);
(4) and another battery is taken and is formed respectively according to two modes of constant current formation and pulse formation. Wherein: the pulsing strategy is set to: the positive pulse amplitude is 5.6A, the negative pulse amplitude is 5.88A, the duty ratio is 10%, the frequency value corresponding to the battery terminal voltage is selected according to the formation voltage-optimal frequency relation shown in figure 2, and the frequency conversion formation is realized in the formation process until the formation is finished;
(5) fig. 4 is a schematic diagram comparing the relationship between the battery capacity and the voltage in the constant current formation and the pulse formation. Compared with the conventional constant-current formation method, the pulse formation method based on the optimal frequency of the lithium ion battery can slow down the polarization in the battery.
(6) Laying the formed battery at normal temperature;
(7) charging the shelved battery at the normal temperature T-25 ℃ (298K) for 0.5C to 3.65V → charging at constant voltage to cut-off current 0.01C → shelving 3h → 0.5C discharging → shelving 3h, and performing constant volume at the normal temperature;
(8) cycling the battery for 1500 weeks at a normal temperature T-25 ℃ (298K) by using 28A as a charging and discharging current, performing the normal-temperature constant volume in the step (7) every 500 weeks, and recording the capacity of the battery;
(9) taking the battery, and circulating for 100 weeks under the condition that T is 40 ℃ (313K) and 28A is used as charging and discharging current;
(10) and (4) carrying out constant volume at normal temperature on the batteries subjected to the circulation in the steps (8) and (9), measuring the circulated capacity, and analyzing and comparing the capacity fading change of the batteries formed by the two formation methods.
Under the temperature of 40 ℃ (313K), the battery capacity of the battery formed by the constant current formation method is attenuated by 5.98% after the battery is cycled for 100 weeks, and the battery capacity is only attenuated by 3.35% after the battery formed by the variable frequency pulse formation method based on the optimal frequency of the lithium ion battery is cycled for 100 weeks.
Under 25 ℃ (298K), the battery capacity of the battery formed by the constant-current formation method decays by 10.02% after circulating for 500 weeks, the decay is increased to 15.45% after circulating for 1000 weeks, and the capacity decay is further increased to 19.84% after circulating for 1500 weeks; the battery formed by the frequency conversion pulse formation method based on the optimal frequency in the invention has the capacity attenuation of 6.59% after 500 cycles, the capacity attenuation rate of 9.79% after 1000 cycles and the capacity of 13% after 1500 cycles. Therefore, the lithium ion battery prepared by the frequency conversion pulse formation method based on the optimal frequency has more excellent cycle stability compared with the battery prepared by constant current formation under the conditions of 25 ℃ (298K) and 40 ℃ (313K).
The above examples are only for illustrating the present invention and do not limit the present invention in any way. Any modification within the spirit of the present invention and the scope of the appended claims is within the scope of the present invention.
Claims (4)
1. A variable frequency pulse formation method based on the optimal frequency of a lithium ion battery is characterized in that: according to a Bode diagram of the relationship between the electrochemical impedance spectrum impedance and the frequency of the lithium ion battery, taking the frequency corresponding to the impedance with the minimum value as the optimal frequency for formation of the lithium ion battery; in the formation process, along with the change of the terminal voltage of the battery, the optimal frequency under the corresponding voltage is determined as the formation frequency, and the lithium ion battery is subjected to variable-frequency pulse formation by adopting positive and negative pulse currents.
2. The variable-frequency pulse formation method based on the optimal frequency of the lithium ion battery according to claim 1, characterized in that: the optimal frequency is the frequency corresponding to the minimum impedance in a Bode diagram of the electrochemical impedance spectrum impedance and frequency relation of the lithium ion battery under different formation voltages.
3. The variable-frequency pulse formation method based on the optimal frequency of the lithium ion battery according to claim 1, characterized in that: the optimum frequency of lithium ion battery formation is measured off-line using an electrochemical workstation.
4. The variable-frequency pulse formation method based on the optimal frequency of the lithium ion battery according to claim 1, characterized in that: besides changing the formation frequency, the positive and negative pulse amplitudes and duty ratios are adjusted to obtain the optimal formation effect.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105305562A (en) * | 2015-11-25 | 2016-02-03 | 成都迅能达电源科技有限公司 | Storage battery inner formation charge and discharge device and inner formation charge and discharge equipment |
| CN109449541A (en) * | 2018-09-26 | 2019-03-08 | 北京交通大学 | Lithium ion battery Converting frequency & amplitude exchanges low temperature self-heating method |
| CN111162332A (en) * | 2019-12-20 | 2020-05-15 | 浙江大学 | Pulse charging method based on characteristic frequency of power lithium ion battery |
| CN111755765A (en) * | 2020-07-30 | 2020-10-09 | 陕西科技大学 | Lithium ion battery variable frequency pulse charging method and system based on real-time detection |
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- 2021-05-11 CN CN202110511966.1A patent/CN113258152A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105305562A (en) * | 2015-11-25 | 2016-02-03 | 成都迅能达电源科技有限公司 | Storage battery inner formation charge and discharge device and inner formation charge and discharge equipment |
| CN109449541A (en) * | 2018-09-26 | 2019-03-08 | 北京交通大学 | Lithium ion battery Converting frequency & amplitude exchanges low temperature self-heating method |
| CN111162332A (en) * | 2019-12-20 | 2020-05-15 | 浙江大学 | Pulse charging method based on characteristic frequency of power lithium ion battery |
| CN111755765A (en) * | 2020-07-30 | 2020-10-09 | 陕西科技大学 | Lithium ion battery variable frequency pulse charging method and system based on real-time detection |
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Application publication date: 20210813 |