CN112540297B - Method for researching overcharge safety redundancy boundary of lithium ion battery - Google Patents
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 149
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 149
- 238000000034 method Methods 0.000 title claims abstract description 23
- 230000008859 change Effects 0.000 claims abstract description 37
- 239000000463 material Substances 0.000 claims abstract description 21
- 238000002474 experimental method Methods 0.000 claims abstract description 20
- 238000011056 performance test Methods 0.000 claims abstract description 20
- 238000012512 characterization method Methods 0.000 claims abstract description 17
- 230000007246 mechanism Effects 0.000 claims abstract description 14
- 238000004458 analytical method Methods 0.000 claims abstract description 12
- 238000004519 manufacturing process Methods 0.000 claims abstract description 4
- 238000007600 charging Methods 0.000 claims description 12
- 238000002441 X-ray diffraction Methods 0.000 claims description 8
- 238000010277 constant-current charging Methods 0.000 claims description 6
- 238000004364 calculation method Methods 0.000 claims description 5
- 239000013078 crystal Substances 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 5
- 238000007599 discharging Methods 0.000 claims description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 3
- 229910052744 lithium Inorganic materials 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 230000003213 activating effect Effects 0.000 claims description 2
- 238000007781 pre-processing Methods 0.000 claims description 2
- 238000002203 pretreatment Methods 0.000 claims description 2
- 238000011076 safety test Methods 0.000 abstract description 2
- 239000007773 negative electrode material Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 5
- 206010000369 Accident Diseases 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
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- 239000010405 anode material Substances 0.000 description 2
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- 230000004048 modification Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
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Abstract
The invention belongs to the technical field of safety test of lithium ion batteries, and relates to a method for researching an overcharge safety redundant boundary of a lithium ion battery, which comprises the following steps: step 1: pretreating a selected battery; step 2: performing an overcharge thermal runaway experiment on the selected first lithium ion battery, recording the temperature, voltage, capacity and the like of the first lithium ion battery at different moments, and determining the safety protection boundary of the battery; step 3: disassembling the selected second lithium ion battery to manufacture half batteries respectively comprising the anode and the cathode of the second lithium ion battery, wherein one anode half battery and one cathode half battery are grouped, and each group of half batteries is respectively overcharged to an overcharge SOC point and a thermal runaway SOC point which are more than 100 percent of SOC; step 4: disassembling the positive and negative half batteries overcharged in the step 3, and carrying out battery material characterization analysis; step 5: and analyzing a battery change mechanism by combining the half-battery material characterization result and the first lithium ion battery basic performance test result to jointly determine the performance protection boundary of the battery.
Description
Technical Field
The invention belongs to the technical field of safety test of lithium ion batteries, and particularly relates to a method for researching a safety redundancy boundary of overcharge of a lithium ion battery.
Background
The lithium ion battery has the advantages of high energy density, long service life and the like, and is widely applied to the fields of electric automobiles and energy storage power stations. But in recent years, electric automobiles have endless thermal runaway accidents; according to incomplete statistics, tens of electric automobile fire accidents occur in succession in China only in 2020; after analysis of the fire accident, the proportion of the fire accident caused by the overcharge is found to be larger. In order to better prevent the occurrence of the overcharge thermal runaway accident of the lithium ion battery, the overcharge protection of the battery is necessary. The research of the overcharge protection of the battery is focused on the research of the risk tolerance degree of the battery under different grades of the battery so as to analyze the risk tolerance degree of the battery under a specific scene when a BMS (battery management system), a charger and the like in the battery system are in faults, and most importantly, the determination of the overcharge safety redundancy boundary of the lithium ion battery can provide safety guidance for the use of the lithium ion battery and ensure the safe use of the battery.
Most of the existing lithium ion battery overcharge boundary research methods only consider the establishment of a safety protection boundary and a thermal model under the condition of battery thermal runaway, neglect the performance protection boundary and lack the analysis of the change mechanism of the battery under different overcharge degrees.
Disclosure of Invention
In view of the problems and drawbacks described in the background above, an object of the present invention is to: while considering the safety protection boundary, the half batteries with different overcharging degrees are disassembled for X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) analysis, and the mechanism change of the lithium ion battery is analyzed by combining the results of a reference performance test RPT (Reference Performance Test), so that the performance protection boundary of the lithium ion battery is determined, and the specific technical scheme is as follows:
a method of studying a lithium ion battery overcharge safety redundancy boundary comprising the steps of:
step 1: firstly, randomly selecting two lithium ion batteries in the same type of lithium ion batteries, and then preprocessing the two selected lithium ion batteries;
the two selected lithium ion batteries are respectively determined as follows: a first lithium ion battery and a second lithium ion battery;
step 2: selecting a plurality of SOC (state of charge) points, selecting an overcharge rate, and carrying out an overcharge thermal runaway experiment on the first lithium ion battery;
the SOC, the voltage change rate and the temperature change rate in thermal runaway are determined to be the safety protection boundary of the lithium ion battery;
the number of SOC points includes: an overcharge SOC point and a thermal runaway SOC point SOC max;
wherein, the overcharge SOC point of more than 100% SOC is x-1;
Step 3: firstly discharging the second lithium ion battery to a discharge cut-off voltage, and then disassembling the second lithium ion battery to obtain positive and negative pole pieces of the second lithium ion battery;
manufacturing x positive half batteries and x negative half batteries in a glove box by utilizing the obtained positive and negative pole pieces of the second lithium ion battery;
the positive electrode of the positive electrode half battery is the positive electrode of the second lithium ion battery, the negative electrode of the negative electrode half battery is the negative electrode of the second lithium ion battery, and the positive electrode is the metal lithium;
Grouping a positive half-cell and a negative half-cell into a group;
Overcharging each group of half batteries to a plurality of overcharging SOC points which are more than 100% of the SOC and a thermal runaway SOC point SOC max selected in the step 2 respectively by the overcharging rate in the step 2;
Step 4: disassembling each group of positive half batteries and negative half batteries which are overcharged to different SOC points, and carrying out characterization analysis on lithium ion battery materials;
step 5: analyzing the change mechanism of the lithium ion battery by combining the result of characterization analysis of the lithium ion battery material and the result of overcharge thermal runaway experiment of the first lithium ion battery, jointly determining the performance protection boundary of the lithium ion battery, and combining the safety protection boundary determined in the step 2 to determine the overcharge safety redundancy boundary of the lithium ion battery;
The performance protection boundary includes: an overcharge start boundary, a voltage change rate performance protection boundary and a voltage maximum boundary V max;
The overcharge starting boundary is a charge cut-off voltage;
The voltage change rate performance protection boundary is 0.001V/s;
The voltage maximum boundary V max is the voltage maximum during the overcharge thermal runaway experiment.
Based on the technical scheme, the pretreatment method in the step1 is as follows:
and activating the two lithium ion batteries with 1/3C current, and circulating for 3 times to ensure the stable state of the lithium ion batteries.
Based on the technical scheme, the method for the overcharge thermal runaway experiment in the step 2 is as follows:
And selecting a plurality of SOC points for reference performance test, recording the temperature, voltage, battery capacity, SOC, direct current internal resistance, polarized internal resistance and polarized capacitance of the first lithium ion battery at different moments, and determining the safety protection boundary of the lithium ion battery.
Based on the above technical solution, the method for performing the reference performance test through the overcharge thermal runaway experiment in step 2 is as follows:
selecting an overcharge rate, and determining a charging current I charge;
After the first lithium ion battery is discharged to a discharge cut-off voltage, constant-current charging is carried out with a determined charging current I charge, constant-current charging is continued until the lithium ion battery is in thermal runaway, parameters such as the capacity, SOC, voltage, temperature, direct-current internal resistance, polarized capacitance and the like of the lithium ion battery from the beginning of an experiment to the thermal runaway are recorded, and the safety protection boundary of the lithium ion battery is determined jointly by combining the voltage change rate and the temperature change rate;
performing reference performance test RPT (Reference Performance Test) on the lithium ion battery every n% of SOC, wherein n represents the interval of SOC and the value is a natural number greater than 1;
Among them, in the reference performance test, only the mixed pulse power performance test (HPPC) at one specific SOC point is included.
On the basis of the technical scheme, the overcharge rate is selected according to the practical application condition of the lithium ion battery, and the charging current is determined according to the selected overcharge rate and the capacity of the lithium ion battery.
Based on the technical proposal, the calculation formula of x in the step 2 and the step 3 is shown as the formula (1),
Wherein, SOC max is the thermal runaway SOC point, n is the SOC interval selected in step 2,To round the symbol up.
Based on the technical scheme, the step 4 for carrying out characterization analysis of the lithium ion battery material comprises the following steps:
After the positive half-cell and the negative half-cell of each group which are overcharged to different SOC points are disassembled, the internal materials are subjected to material characterization such as X-ray diffraction (XRD) and Scanning Electron Microscope (SEM), and the crystal structure of the lithium ion battery is analyzed by combining with fine modification calculation.
Based on the technical scheme, the specific steps of the step 5 are as follows:
Combining the lithium ion battery material characterization result of the same SOC point with the direct current internal resistance, the polarized internal resistance and the polarized capacitance result of the first lithium ion battery, analyzing the variation mechanism of the lithium ion battery, defining different stages according to the characteristic performances such as voltage, voltage variation rate, temperature and temperature variation rate in the overcharge thermal runaway experiment of the first lithium ion battery, summarizing the mechanism variation of the different stages, and jointly determining the performance protection boundary of the lithium ion battery;
And finally, combining the performance protection boundary with the result of the safety protection boundary determined in the step (2) (namely, the SOC value, the voltage change rate and the temperature change rate of the first lithium ion battery in the stage before thermal runaway) to determine the overcharge safety redundancy boundary of the lithium ion battery.
The invention has the following beneficial technical effects:
The invention can determine the overcharge safety redundant boundary of the lithium ion battery. According to the method provided by the invention, the parameters such as the voltage change rate, the temperature change rate, the SOC and the like in the previous stage of thermal runaway in the full battery test can be used as the overcharge safety protection boundary of the lithium ion battery, the positive half battery and the negative half battery which are overcharged to different SOC points are disassembled, the mechanism evolution rule in the overcharge process of the lithium ion battery is analyzed by combining the test result of the reference performance test RPT through X-ray diffraction XRD and scanning electron microscope SEM analysis and the overcharge thermal runaway test, and the parameters such as the battery voltage and the voltage change rate and the like are selected as the lithium ion battery performance protection boundary, so that important basis is provided for the state monitoring and the thermal runaway protection design of the battery overcharge process in practical application.
Drawings
The invention has the following drawings:
FIG. 1 is a schematic flow chart of the method of the present invention.
Fig. 2 is a schematic diagram of a lithium ion battery in an overcharge thermal runaway experiment according to an embodiment of the invention.
Fig. 3 is a schematic view of scanning of a negative electrode material of a negative electrode half cell under a scanning electron microscope according to an embodiment of the present invention.
Fig. 4 is a schematic diagram showing the X-ray diffraction result of the anode material of the anode half cell according to the embodiment of the present invention.
Fig. 5 is a schematic view of a crystal structure of a negative electrode material of a negative electrode half cell according to an embodiment of the present invention.
Detailed Description
The steps of the present invention will be described in further detail with reference to the accompanying drawings and test examples.
As shown in fig. 1, the flow chart of the method for researching the overcharge safety redundancy boundary of the lithium ion battery is implemented according to the following steps:
step 1: the selected lithium ion battery is pre-treated.
Two lithium ion batteries are selected randomly from the lithium ion batteries of the same model, then the two lithium ion batteries are activated by 1/3C current, and the cycle is performed for 3 times, so that the state stability of the lithium ion batteries is ensured.
The two selected lithium ion batteries are respectively determined as follows: a first lithium ion battery and a second lithium ion battery.
Step 2: carrying out an overcharge thermal runaway experiment on a first lithium ion battery;
In the experimental process of overcharge thermal runaway, a plurality of SOC points are selected for reference performance test, the temperature, voltage, battery capacity (simply referred to as capacity), SOC, direct current internal resistance, polarized internal resistance and polarized capacitance of the first lithium ion battery at different moments are recorded, and the safety protection boundary of the lithium ion battery (simply referred to as battery) is determined, wherein the specific steps are as follows:
And selecting an overcharge rate according to the actual application condition of the lithium ion battery, determining a charging current I charge by combining the capacity of the lithium ion battery, discharging the first lithium ion battery to a discharge cut-off voltage, performing constant-current charging by using the selected charging current I charge, and continuously performing constant-current charging until the lithium ion battery is subject to thermal runaway, recording parameters such as the capacity, the SOC, the voltage, the temperature, the direct-current internal resistance, the polarized capacitance and the like of the battery from the beginning of an experiment to the thermal runaway, and determining the safety protection boundary of the lithium ion battery by combining the voltage change rate and the temperature change rate.
Performing reference performance test RPT (Reference Performance Test) on the lithium ion battery every n% of SOC;
wherein the RPT test comprises only a mixed pulse power performance test (HPPC) at a specific SOC point.
In the example, the charging current I charge is determined as 1c, the interval n=5 of the SOC, from 0% SOC to 167% SOC (thermal runaway SOC point), and the reference performance test is performed every 5% SOC. As shown in fig. 2, at the point of reaching the maximum SOC, namely the thermal runaway SOC point SOC max, the voltage starts to decrease rapidly, the temperature of the lithium ion battery starts to rise rapidly, and finally the SOC >167%, the voltage change rate dV/dT < -1V/s, and the temperature change rate dT/dT >1 ℃/s are taken as the safety protection boundary of the lithium ion battery.
Step 3: firstly discharging the second lithium ion battery to a discharge cut-off voltage, and then disassembling the second lithium ion battery to obtain positive and negative pole pieces of the second lithium ion battery (namely half batteries respectively comprising the positive and negative poles of the selected second lithium ion battery);
manufacturing x positive half batteries and x negative half batteries in a glove box by utilizing the obtained positive and negative pole pieces of the second lithium ion battery;
the positive electrode of the positive electrode half battery is the positive electrode of the second lithium ion battery, the negative electrode of the negative electrode half battery is the negative electrode of the second lithium ion battery, and the positive electrode is the metal lithium;
The number x of half cells is shown in the formula (1),
Wherein, SOC max is the thermal runaway SOC point, n is the SOC interval selected in step 2, i.e. n=5,Rounding up the symbol;
And (3) classifying one positive half battery and one negative half battery into one group, and respectively overcharging each group of half batteries to a plurality of overcharging SOC points greater than 100% SOC and thermal runaway SOC points selected in the step (2) according to the overcharging rate in the step (2).
In the example where x=14, the thermal runaway SOC point SOC max is 167% and 14 half-cells are overcharged to 105%, 110%, …,165% and 167% SOC, respectively, every 5% SOC.
Step 4: and disassembling each group of positive half batteries and negative half batteries (namely positive half batteries) with different overcharge SOC points, and carrying out characterization analysis on lithium ion battery materials, wherein the specific steps are as follows:
After the positive half-cell and the negative half-cell of each group which are overcharged to different SOC points are disassembled, the internal materials are subjected to material characterization such as X-ray diffraction (XRD) and Scanning Electron Microscope (SEM), and the crystal structure of the lithium ion battery is analyzed by combining with fine modification calculation.
In the example, the negative half-cell of each SOC point is disassembled, and a scanning electron microscope is used for carrying out material characterization on the negative material of the negative half-cell, so that the result shown in the figure 3 is obtained;
then, carrying out X-ray diffraction on the negative electrode material to obtain a result shown in fig. 4;
Subtracting the calculated value from the observed value to obtain a difference value, and judging the collapse condition of the anode material according to the difference value and the difference value position;
Finally, a crystal structure diagram of the negative electrode material is derived according to the results shown in fig. 3 and 4, as shown in fig. 5.
Step 5: and analyzing the change mechanism of the lithium ion battery by combining the result of characterization analysis of the lithium ion battery (i.e. half battery) material and the result of the first lithium ion battery overcharge thermal runaway experiment (i.e. basic performance test result), and jointly determining the performance protection boundary of the lithium ion battery. The method comprises the following specific steps:
And combining the lithium ion battery material characterization result of the same SOC point with the direct current internal resistance, the polarized internal resistance and the polarized capacitance result of the first lithium ion battery, analyzing the change mechanism of the lithium ion battery, defining different stages according to the characteristic performances such as voltage, voltage change rate, temperature change rate and the like in the overcharge thermal runaway experiment of the first lithium ion battery, summarizing the mechanism changes of the different stages, and jointly determining the performance protection boundary of the lithium ion battery.
The performance protection boundary includes: an overcharge start boundary, a voltage change rate performance protection boundary and a voltage maximum boundary V max;
The overcharge start boundary is a charge cutoff voltage, which in the example is 4.2V;
The voltage rate performance guard boundary is 0.001V/s, in the example, the boundary of phase 1 (see below): the voltage change rate dV/dt is more than 0.001V/s;
The voltage maximum boundary V max is the voltage maximum during the overcharge thermal runaway experiment, and in the example, is the boundary of phase 2 (see below): the voltage reached a maximum value V max, a value of 5.1V.
By adopting the method, the example study is carried out to summarize the mechanism changes of different stages of the lithium ion battery, and the overcharging process is divided into the following 3 stages:
Stage 1: starting when the charging voltage of the first lithium ion battery exceeds the charging cut-off voltage of the first lithium ion battery, and ending when the rate of change of the charging voltage of the battery is more than 0.001V/s, wherein lithium ions of the positive electrode of the battery remain at the stage, the lithium ions are separated from the positive electrode, and then are inserted into the negative electrode material through the diaphragm, so that the temperature change is small;
Stage 2: the positive electrode voltage and the temperature are continuously increased at the stage from the time that the voltage change rate is larger than 0.001V/s to the time that the voltage reaches the maximum value, the electrolyte starts to decompose, the side reaction in the battery is aggravated, a large amount of gas and heat are generated, meanwhile, the SEI film of the negative electrode starts to decompose at a high temperature, the negative electrode material and the electrolyte undergo a reduction reaction, gas and heat are also generated, the temperature rise rate is increased, and the temperature rise is faster;
stage 3: the method comprises the steps that from the time when charging voltage reaches the maximum value to the time when the battery is triggered to generate heat and is out of control, the positive electrode material of the battery is subjected to structural collapse, voltage is reduced, temperature is rapidly increased until a battery diaphragm is contracted, large-scale internal short circuit is caused, a large amount of heat is released, and the occurrence of thermal runaway is caused;
And finally, combining the performance protection boundary with the result of the safety protection boundary determined in the step (2) (namely, the SOC value, the voltage change rate and the temperature change rate of the first lithium ion battery in the stage before thermal runaway) to determine the overcharge safety redundancy boundary of the lithium ion battery.
The above embodiments are described in detail with respect to the technical solution of the present invention. It is obvious that the invention is not limited to the described embodiments. Based on the embodiments of the present invention, those skilled in the art can make various changes thereto, but any changes equivalent or similar to the present invention are within the scope of the present invention.
What is not described in detail in this specification is prior art known to those skilled in the art.
Claims (2)
1. A method for studying the overcharge safety redundancy boundary of a lithium ion battery, comprising the steps of:
step 1: firstly, randomly selecting two lithium ion batteries in the same type of lithium ion batteries, and then preprocessing the two selected lithium ion batteries;
the two selected lithium ion batteries are respectively determined as follows: a first lithium ion battery and a second lithium ion battery;
step 2: selecting a plurality of SOC points, selecting an overcharge rate, and carrying out an overcharge thermal runaway experiment on the first lithium ion battery;
the SOC, the voltage change rate and the temperature change rate in thermal runaway are determined to be the safety protection boundary of the lithium ion battery;
the number of SOC points includes: an overcharge SOC point and a thermal runaway SOC point SOC max;
wherein, the overcharge SOC point of more than 100% SOC is x-1;
Step 3: firstly discharging the second lithium ion battery to a discharge cut-off voltage, and then disassembling the second lithium ion battery to obtain positive and negative pole pieces of the second lithium ion battery;
manufacturing x positive half batteries and x negative half batteries in a glove box by utilizing the obtained positive and negative pole pieces of the second lithium ion battery;
the positive electrode of the positive electrode half battery is the positive electrode of the second lithium ion battery, the negative electrode of the negative electrode half battery is the negative electrode of the second lithium ion battery, and the positive electrode is the metal lithium;
Grouping a positive half-cell and a negative half-cell into a group;
Overcharging each group of half batteries to a plurality of overcharging SOC points which are more than 100% of the SOC and a thermal runaway SOC point SOC max selected in the step 2 respectively by the overcharging rate in the step 2;
Step 4: disassembling each group of positive half batteries and negative half batteries which are overcharged to different SOC points, and carrying out characterization analysis on lithium ion battery materials;
step 5: analyzing the change mechanism of the lithium ion battery by combining the result of characterization analysis of the lithium ion battery material and the result of overcharge thermal runaway experiment of the first lithium ion battery, jointly determining the performance protection boundary of the lithium ion battery, and combining the safety protection boundary determined in the step 2 to determine the overcharge safety redundancy boundary of the lithium ion battery;
The performance protection boundary includes: an overcharge start boundary, a voltage change rate performance protection boundary and a voltage maximum boundary V max;
The overcharge starting boundary is a charge cut-off voltage;
The voltage change rate performance protection boundary is 0.001V/s;
The voltage maximum boundary V max is the voltage maximum in the overcharge thermal runaway experiment process;
the method for the overcharge thermal runaway experiment in the step 2 is as follows:
selecting a plurality of SOC points for reference performance test, recording the temperature, voltage, battery capacity, SOC, DC internal resistance, polarized internal resistance and polarized capacitance of the first lithium ion battery at different moments, and determining the safety protection boundary of the lithium ion battery;
The method for determining the safety protection boundary of the lithium ion battery in the step 2 is as follows:
selecting an overcharge rate, and determining a charging current I charge;
After the first lithium ion battery is discharged to a discharge cut-off voltage, constant-current charging is carried out with a determined charging current I charge, constant-current charging is continued until the lithium ion battery is in thermal runaway, parameters of lithium ion battery capacity, SOC, voltage, temperature, direct-current internal resistance, polarized internal resistance and polarized capacitance from the beginning of an experiment to the thermal runaway are recorded, and the safety protection boundary of the lithium ion battery is determined jointly by combining the voltage change rate and the temperature change rate;
performing Reference Performance Test (RPT) on the lithium ion battery every n% of SOC, wherein n represents the interval of the SOC, and the numerical value is a natural number larger than 1;
The reference performance test only comprises a mixed pulse power performance test under a specific SOC point;
the calculation formula of x in the step 2 and the step 3 is shown as formula (1),
x=⌈100*(SOCmax-100%)/n⌉ （1）
Wherein, SOC max is the thermal runaway SOC point, n is the SOC interval selected in step 2,Rounding up the symbol;
the step 4 of carrying out characterization analysis of lithium ion battery materials comprises the following steps:
after the positive half-cell and the negative half-cell which are overcharged to different SOC points are disassembled, carrying out X-ray diffraction and scanning electron microscope material characterization on the internal materials, and analyzing the crystal structure of the lithium ion battery by combining with fine calculation;
The specific steps of the step 5 are as follows:
Combining the lithium ion battery material characterization result of the same SOC point with the direct current internal resistance, the polarized internal resistance and the polarized capacitance result of the first lithium ion battery, analyzing the variation mechanism of the lithium ion battery, defining different stages according to the characteristic performances of voltage, voltage variation rate, temperature and temperature variation rate in the overcharge thermal runaway experiment of the first lithium ion battery, summarizing the mechanism variation of the different stages, and jointly determining the performance protection boundary of the lithium ion battery;
And finally, combining the performance protection boundary with the result of the safety protection boundary determined in the step 2 to determine the overcharge safety redundancy boundary of the lithium ion battery.
2. The method for studying lithium-ion battery overcharge safety redundancy boundaries of claim 1, wherein: the pretreatment method in the step 1 is as follows:
and activating the two lithium ion batteries with 1/3C current, and circulating for 3 times to ensure the stable state of the lithium ion batteries.
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