CN114759277A - Low-temperature discharge method of lithium ion battery - Google Patents

Low-temperature discharge method of lithium ion battery Download PDF

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Publication number
CN114759277A
CN114759277A CN202210519176.2A CN202210519176A CN114759277A CN 114759277 A CN114759277 A CN 114759277A CN 202210519176 A CN202210519176 A CN 202210519176A CN 114759277 A CN114759277 A CN 114759277A
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battery
lithium ion
temperature
low
ion battery
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刘小红
暴旭
纪影
刘峰
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Tianjin EV Energies Co Ltd
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Tianjin EV Energies Co Ltd
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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
    • H01M10/443—Methods for charging or discharging in response to temperature
    • 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
    • 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
    • H01M10/448—End of discharge regulating 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
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/61—Types of temperature control
    • H01M10/615—Heating or keeping warm
    • 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
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/62—Heating or cooling; Temperature control specially adapted for specific applications
    • H01M10/625—Vehicles
    • 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
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/63—Control systems
    • H01M10/633—Control systems characterised by algorithms, flow charts, software details or the like
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Automation & Control Theory (AREA)
  • Secondary Cells (AREA)

Abstract

The invention provides a low-temperature discharge method of a lithium ion battery. The low-temperature discharge method comprises the following steps: s1: monitoring the working state of the lithium ion battery, and starting a lithium ion battery heating control system to heat the battery when the lithium ion battery is in an unconventional working state; s2: when the surface of the battery is heated to reach the normal working state, the heating is stopped. According to the invention, the working state of the battery is monitored in the discharging process of the battery in the low-temperature environment, so that the battery can be heated in time, the excessive loss of the capacity of the battery in the low-temperature environment is avoided, and the purpose of simply and conveniently improving the low-temperature discharging performance of the lithium ion power battery is realized.

Description

Low-temperature discharge method of lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion batteries, and relates to a low-temperature discharge method of a lithium ion battery.
Background
Under the dual promotion of energy safety and green traffic, the electric automobile develops rapidly in recent years. Lithium ion batteries are the main power source for electric vehicles because of their advantages of high energy density, high power density, long cycle life, etc. However, the lithium ion battery still faces some difficulties and challenges in practical application due to the dependence of battery parameters and use conditions. Under the low-temperature environment, the available capacity of lithium ions is greatly reduced, and the endurance mileage of the electric automobile is directly influenced. Meanwhile, the internal resistance of the battery is sharply increased along with the temperature reduction, so that the output power of the battery is sharply reduced, and safety accidents may be caused in severe cases. The long-term output of high power of the lithium ion battery in a low-temperature environment increases the risk of aging, and the limitation of the power output affects the driving experience. Therefore, it is very important to heat the lithium ion battery at low temperature, improve the service performance and prolong the cycle life.
Particularly, in a low-temperature environment, the endurance mileage of the new energy automobile is obviously shortened and is far lower than the nominal mileage, which is determined by the material system of the lithium ion power battery. At low temperature, the viscosity of the electrolyte of the lithium ion power battery is increased, the ionic conductivity is poor, and the dynamic performance of the lithium ion power battery is affected, so that the low-temperature performance of the battery is greatly reduced.
In order to solve the problem of mileage shortening of a new energy automobile in a low-temperature environment, the current solution idea mainly has three aspects: on one hand, the optimization is carried out at the battery end, the low-temperature performance improvement is mainly carried out on electrolyte or positive and negative active materials, on the other hand, the optimization is carried out at the battery pack end, the whole large-area foam package or other similar materials are carried out on the battery module, and on the third condition, the adjustment is carried out at the charge-discharge mechanism end, and charging and discharging are carried out by adopting different mechanisms according to the non-use of the battery voltage.
The above discharge mechanisms all have certain disadvantages. (1) For the adjustment of the battery end, the lifting space of the current material system is limited; (2) the improvement of module end needs extra increase outer wrapping material, and the material needs to verify the selection, and the volume energy density of module also makes the extranal packing that increases moreover reduce, must not repay. Therefore, the most simple and effective way is to improve the charge and discharge mechanism by adjusting the charge and discharge mechanism, but most of the existing charge and discharge mechanisms for improving low-temperature discharge are complicated, and most of the existing charge and discharge mechanisms need to set a plurality of voltage intervals and then carry out charge and discharge with different multiplying powers.
Therefore, how to solve the problem of the tedious mechanism of the low-temperature charge and discharge is a urgent need to be considered at present.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a low-temperature discharge method of a lithium ion battery. According to the invention, the working state of the battery is monitored in the discharging process of the battery in a low-temperature environment, so that the battery can be heated in time, the excessive loss of the capacity of the battery in the low-temperature environment is avoided, and the purpose of simply and conveniently improving the low-temperature discharging performance of the lithium ion power battery is realized.
In order to achieve the purpose, the invention adopts the following technical scheme:
in one aspect, the present invention provides a low temperature discharge method for a lithium ion battery, including the steps of:
s1: monitoring the working state of the lithium ion battery, and starting a lithium ion battery heating control system to heat the battery when the lithium ion battery is in an abnormal working state;
s2: when the surface of the battery is heated until the battery reaches a normal working state, the heating is stopped.
In a preferred embodiment of the present invention, in step S1, the abnormal operation state is set as a condition that the battery surface temperature is 0 ℃ or less or the battery SOC is 10% to 50%, for example, the battery surface temperature may be 0 ℃, -5 ℃, -10 ℃, -15 ℃, -20 ℃, -25 ℃, -30 ℃, or-35 ℃, and the battery SOC may be 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, or 50%, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned value range may be applied.
In a preferred embodiment of the present invention, the abnormal operation condition is a battery surface temperature of-30 to 0 ℃ or a battery SOC of 10 to 30%, and the battery surface temperature may be, for example, 0 ℃, -3 ℃, -5 ℃, -8 ℃, -10 ℃, -13 ℃, -15 ℃, -18 ℃, -20 ℃, 23 ℃, -25 ℃, -28 ℃, or-30 ℃, and the battery SOC may be, for example, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, or 30%, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.
As a preferred embodiment of the present invention, in step S2, the condition of the normal operation state is that the battery surface temperature is >0 ℃ or the battery SOC is > 50%, for example, the battery surface temperature may be 3 ℃, 5 ℃, 10 ℃, 13 ℃, 15 ℃, 20 ℃ or 25 ℃, and the battery SOC may be 52%, 55%, 60%, 65%, 70%, 75%, 80% or 90%, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
As a preferred technical solution of the present invention, the method further comprises:
and after the heating is stopped, continuously discharging the battery until the voltage of the battery reaches a discharge cut-off voltage.
As a preferred technical solution of the present invention, after the heating is stopped, the working state of the lithium ion battery is continuously monitored while the battery is continuously discharged, and when the battery is in the unconventional working state again, the heating control system is continuously started to heat the battery until the battery reaches the conventional working state, and the heating is stopped again.
As a preferred technical solution of the present invention, the heating control system includes a heating resistor and a controller.
As a preferred technical solution of the present invention, the heating resistor and the lithium ion battery operating circuit are connected in parallel.
In a preferred embodiment of the present invention, the discharge current of the lithium ion battery in the operating state is 0.3C to 1C, for example, 0.3C, 0.4C, 0.5C, 0.6C, 0.7C, 0.8C, 0.9C, 1C, etc., but the discharge current is not limited to the above-mentioned values, and other values not listed in the above-mentioned range of values are also applicable.
As a preferred embodiment of the present invention, the low-temperature discharge method includes the steps of:
s1: monitoring the working state of the lithium ion battery, and starting a lithium ion battery heating control system to heat the battery when the surface temperature of the lithium ion battery is-30-0 ℃ or the SOC of the battery is 10-30%;
s2: when the surface of the battery is heated until the surface temperature of the battery reaches more than 0 ℃ or the SOC of the battery is more than 50%, stopping heating, and continuing discharging the battery after the heating is stopped until the voltage of the battery reaches the discharge cut-off voltage;
the discharge current of the lithium ion battery in the working state is 0.3-1C.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, the working state of the battery is monitored in the discharging process of the battery in a low-temperature environment, so that the battery can be heated in time, the process is simple, the low-temperature discharging performance of the lithium ion battery is improved without adopting a complex charging and discharging mechanism, the excessive loss of the capacity of the battery in the low-temperature environment is avoided without repeatedly regulating and controlling the current and voltage values, the purpose of simply and conveniently improving the low-temperature discharging performance of the lithium ion power battery is realized, the capacity retention rate of the battery after low-temperature discharging is improved, and the battery can be more suitable for working in the low-temperature environment. After the low-temperature discharge method of the lithium ion battery provided by the invention is adopted, the ratio of the discharge capacity of the battery to the discharge capacity of the lithium ion battery at normal temperature can reach more than 60%, and the ratio of the discharge capacity at low temperature to the discharge capacity at normal temperature can reach more than 65% when the surface temperature of the battery is-30-0 ℃ or the SOC of the battery is 10-30% under the unconventional working condition is further regulated and controlled; and the discharge capacity ratio of the lithium ion battery under the NCM system at low temperature and normal temperature can reach more than 83 percent.
Drawings
Fig. 1 is a schematic flow chart of a low-temperature discharging method of a lithium ion battery according to an embodiment of the present invention.
Fig. 2 is a detailed flow chart of a low-temperature discharging method of a lithium ion battery according to an embodiment of the present invention.
Fig. 3 is a low-temperature discharge curve diagram obtained by the low-temperature discharge method of the lithium ion battery provided in example 1 according to the present invention.
Fig. 4 is a low-temperature discharge graph obtained by the low-temperature discharge method of the lithium ion battery provided in comparative example 1 according to the present invention.
Fig. 5 is a normal temperature discharge curve diagram of the lithium ion battery provided in embodiment 1 of the present invention.
Detailed Description
The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
In one embodiment, the present invention provides a low-temperature discharge method of a lithium ion battery, and fig. 1 shows a schematic flow chart thereof, where the low-temperature discharge method includes the following steps:
s1: monitoring the working state of the lithium ion battery, and starting a lithium ion battery heating control system to heat the battery when the lithium ion battery is in an abnormal working state;
s2: when the surface of the battery is heated until the battery reaches a normal working state, the heating is stopped.
The method for monitoring the surface of the battery in the present invention can be performed by conventional techniques, for example, the temperature can be monitored by a heating control system, or the SOC or voltage state of the battery can be monitored by SOC capacity display technique or a voltmeter structure.
In the invention, the low-temperature discharge performance of the lithium ion battery is improved without adopting a complicated charge-discharge mechanism, and the discharge process of the battery is normal without repeatedly regulating and controlling the current and voltage values.
According to the invention, the working state of the battery is monitored in the discharging process of the battery in the low-temperature environment, so that the battery can be heated in time, the excessive loss of the capacity of the battery in the low-temperature environment is avoided, the purpose of simply and conveniently improving the low-temperature discharging performance of the lithium ion power battery is realized, the capacity retention rate of the battery after low-temperature discharging is improved, and the battery can be more suitable for working in the low-temperature environment.
If the lithium ion battery is not subjected to any treatment in the low-temperature discharging process, the lithium ion battery is directly discharged until the discharge is cut off, the discharge capacity of the battery is sharply reduced, and the effect of obviously shortening the endurance mileage on the electric vehicle is shown.
Specifically, the working state of the battery in the present invention is a discharge process in a low temperature environment, and for example, the simulation of the low temperature environment may be performed in a low temperature box, that is, the battery is placed in the low temperature environment for low temperature discharge.
Further, the temperature of the low temperature environment is 0 ℃ to-30 ℃, for example, -30 ℃, -28 ℃, -25 ℃, -23 ℃, -20 ℃, -18 ℃, -15 ℃, -13 ℃, -10 ℃, -8 ℃, -5 ℃, or 0 ℃, but the temperature is not limited to the values listed, and other values not listed in the range of the values are also applicable.
And the battery is placed in the low-temperature environment at the temperature, so that the real low-temperature working environment of the battery can be effectively simulated.
Further, the battery is placed in a low temperature environment for 4-8 hours, and then low temperature discharge is performed, for example, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours, but the battery is not limited to the recited values, and other values not recited in the range of the values are also applicable.
After the battery is placed for 4-8 hours in a low-temperature environment, the uniformity of the internal and external temperatures of the battery is realized, if the placing time is too short, the internal temperature of the battery is not favorably reduced to be consistent with the surface temperature, and if the placing time is too long, electrolyte stagnation is caused, the internal resistance is obviously increased, and even lithium precipitation occurs, so that the service life of the battery is irreversibly influenced.
In the invention, the normal working state of the battery in the discharging process is that the surface temperature of the battery is more than 0 ℃ or the SOC of the battery is more than 50%, the discharging cut-off voltage is 1.8-3.0V, and the condition which does not meet the normal working state is the non-normal working state.
Fig. 2 shows a detailed flow diagram of a low-temperature discharging method of a lithium ion battery in an embodiment, as shown in fig. 2:
specifically, in step S1, the abnormal operation condition is that the battery surface temperature is 0 ℃ or less or the battery SOC is 10% to 50%, for example, the battery surface temperature may be 0 ℃, 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃, or 35 ℃, or the like, and the battery SOC may be 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, or 50%, but is not limited to the enumerated values, and other values not enumerated within the numerical range may be similarly applied.
In the conditions of the unconventional working state provided by the invention, the surface of the battery needs to be heated by using the heating control system as long as the battery reaches any one of the conditions in the discharging process.
In the invention, when the surface temperature of the battery is higher than 0 ℃, if the surface of the battery is heated, the internal temperature of the battery is increased quickly, and even the problems of the SEI film falling and decomposition and other safety aspects can be caused;
similarly, if the battery is heated when the SOC is more than 50%, the safe use of the battery is also influenced, and the battery is electrochemically unstable in a high-temperature and high-power state, so that internal decomposition reaction is easily caused, and potential safety hazards are caused.
Further, the conditions of the abnormal operation state are that the battery surface temperature is-30 to 0 ℃ or the battery SOC is 10 to 30%, for example, the battery surface temperature may be 0 ℃, -3 ℃, -5 ℃, -8 ℃, -10 ℃, -13 ℃, -15 ℃, -18 ℃, -20 ℃, 23 ℃, -25 ℃, -28 ℃ or-30 ℃, and the battery SOC may be 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28% or 30%, but not limited to the values listed, and other values not listed in the range of the values are also applicable.
Specifically, in step S2, the condition of the normal operating state is that the battery surface temperature is >0 ℃ or the battery SOC is > 50%, for example, the battery surface temperature may be 3 ℃, 5 ℃, 10 ℃, 13 ℃, 15 ℃, 20 ℃, or 25 ℃, and the battery SOC may be 52%, 55%, 60%, 65%, 70%, 75%, 80%, or 90%, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
In the invention, after the battery meets any one of the conditions, the battery is in a normal working state.
Specifically, the low temperature aspect method further comprises:
after the heating is stopped, the battery continues to be discharged until the battery voltage reaches a discharge cut-off voltage.
And (4) selecting discharge cut-off voltage, and adaptively adjusting according to different battery systems.
Further, after the heating is stopped, the working state of the lithium ion battery is continuously monitored in the process of continuously discharging the battery, when the battery is in the unconventional working state again, the heating control system is continuously started to heat the battery until the battery reaches the conventional working state, and the heating is stopped again.
If the battery is in the abnormal working state again, the battery is heated continuously, and the low-temperature discharge performance of the battery can be improved.
Specifically, the heating control system includes a heating resistor and a controller.
Further, the heating resistor is connected in parallel with the lithium ion battery working circuit.
The heating control system in the battery surface can monitor the temperature of the battery surface and heat the battery surface in time, and the control system can control the heating of the battery surface, and the connection between the system and the battery can refer to a battery heating control device in the prior art, for example, the method and the structure provided by the publication number CN110752418A, and other structures and methods which can monitor, control and heat the battery surface, and the invention is also applicable.
Specifically, the discharge current of the lithium ion battery in the operating state is 0.3C to 1C, for example, 0.3C, 0.4C, 0.5C, 0.6C, 0.7C, 0.8C, 0.9C, 1C, or the like, but is not limited to the enumerated values, and other unrecited values within the numerical range are also applicable.
Too high low temperature discharge current can increase the polarization of the battery at low temperature, thereby affecting the exertion of the battery discharge capacity.
Specifically, the low-temperature discharge method comprises the following steps:
s1: monitoring the working state of the lithium ion battery, and starting a lithium ion battery heating control system to heat the battery when the surface temperature of the lithium ion battery is-30-0 ℃ or the SOC of the battery is 10-30%;
s2: when the surface of the battery is heated until the surface temperature of the battery reaches more than 0 ℃ or the SOC of the battery is more than 50%, stopping heating, and continuing discharging the battery after the heating is stopped until the voltage of the battery reaches the discharge cut-off voltage;
the discharge current of the lithium ion battery in the working state is 0.3-1C.
The lithium ion battery in the present invention may be a liquid lithium ion battery or a solid lithium ion battery, and is not particularly limited.
When the lithium ion battery is a liquid lithium ion battery, the lithium ion battery comprises a negative pole piece, a positive pole piece, a diaphragm and electrolyte.
The positive pole piece, the diaphragm and the electrolyte in the liquid lithium ion battery are all known and easily obtained by the technical personnel in the field, and the corresponding substances and the preparation method which can be assembled to obtain the complete lithium ion battery are all applicable.
When the lithium ion battery is a solid lithium ion battery, the lithium ion battery comprises a negative pole piece, a positive pole piece and a solid electrolyte layer.
The positive pole piece and the solid electrolyte layer in the solid lithium ion battery are both easily known and available by the technical personnel in the field, and the corresponding substances which can be assembled to obtain the complete lithium ion battery and the preparation method are both applicable.
Example 1
The embodiment provides a low-temperature discharge method of a lithium ion battery, based on the low-temperature discharge method provided by the above specific embodiment:
the lithium ion battery provided in this embodiment is a lithium iron phosphate-graphite system, and the tab is located on a 30Ah soft-package lithium ion power battery (in a discharge system, the initial voltage is 3.65V, and the discharge cut-off voltage is 1.8V) on the opposite side of the battery. The battery is produced by laminating a negative plate, a diaphragm and a positive plate, and is wrapped by an aluminum plastic film and then injected with electrolyte to complete heat sealing;
arranging a heating control system on the surface of a lithium ion battery of a lithium iron phosphate-graphite system, arranging a heating resistor on the surface of a battery main body, connecting the heating resistor with positive and negative lugs of the lithium ion battery, arranging a controller at the top ends of the lugs, and arranging a temperature sensing system in the controller;
s1: the lithium ion battery is subjected to low-temperature discharge under the current of 1C in a low-temperature box at the temperature of minus 20 ℃, and is firstly placed in the low-temperature box for 4 hours, and when the surface temperature of the battery reaches minus 10 ℃, the lithium ion battery is heated by a heating control system through a heating resistor;
s2: and when the temperature of the surface of the battery reaches 5 ℃, stopping heating the heating resistor, then continuously discharging the lithium ion battery in the low-temperature box until the lithium ion battery is discharged to reach a discharge cut-off voltage of 1.8V, and finishing the discharge.
Example 2
The difference between this example and example 1 is that in this example, heating was performed when the surface temperature of the battery was monitored to be-15 ℃ in S1, and the heating was stopped when the surface temperature of the battery reached 10 ℃ in S2.
The remaining low temperature discharge methods and parameters were in accordance with example 1.
Example 3
The present example is different from example 1 in that heating was performed when the surface temperature of the battery was monitored to be 1 ℃ in S1, and heating was stopped when the surface temperature of the battery reached 10 ℃ in S2.
The remaining low temperature discharge methods and parameters were in accordance with example 1.
Example 4
The embodiment provides a low-temperature discharge method for a lithium ion battery, which is based on the low-temperature discharge method provided by the above specific embodiment and includes:
wherein the lithium ion battery and its heating control system were kept the same as in example 1.
In the low-temperature discharge method, the heating is carried out when the SOC of the battery is 30% in the unconventional working state of S1, the heating is stopped when the SOC of the battery reaches 60% in S2, then the discharging of the lithium ion battery is continued in the low-temperature box until the discharging of the lithium ion battery reaches the discharging cut-off voltage of 1.8V, and the discharging is finished.
Example 5
The present embodiment is different from embodiment 4 in that, when it is detected in step S1 that the SOC of the battery is 10%, heating is performed.
The remaining low temperature discharge methods and parameters were in accordance with example 4.
Example 6
The present embodiment is different from embodiment 4 in that heating is performed when the SOC of the battery is detected to be 50% in S1, and heating is stopped when the SOC of the battery is detected to be 75% in S2.
The remaining low temperature discharge methods and parameters were in accordance with example 4.
Example 7
The present embodiment is different from embodiment 4 in that heating is performed when the SOC of the battery is detected to be 51% in S1 of the present embodiment.
The remaining low temperature discharge methods and parameters were in accordance with example 4.
Example 8
The embodiment provides a low-temperature discharging method of a lithium ion battery, which is based on a low-temperature power generation method provided by a specific embodiment and comprises the following steps:
the lithium ion battery provided by the embodiment is an NCM811 system, and a 30Ah soft-package lithium ion power battery with tabs located on the same side of the battery (the initial voltage in a discharge system is 4.35V, and the discharge cut-off voltage is 3.0V).
The low-temperature discharge method of the lithium ion battery comprises the following steps:
arranging a heating control system on the surface of a lithium ion battery of an NCM811 system, arranging a heating resistor on the surface of a battery main body, connecting the heating resistor with positive and negative lugs of the lithium ion battery, connecting the lugs with a controller, and arranging a temperature sensing system in the controller;
s1: placing the lithium ion battery with the heating control system on the surface in a low-temperature environment at the temperature of-15 ℃, discharging at the current of 0.5 ℃, and heating the lithium ion battery by using the heating control system through a heating resistor when the surface temperature of the lithium ion battery is monitored to reach-5 ℃;
s2: and stopping heating the heating resistor when the monitored temperature of the surface of the battery reaches 10 ℃, then discharging the lithium ion battery until the lithium ion battery is discharged to reach the discharge cut-off voltage of 3.0V, and finishing the discharge.
Example 9
The embodiment provides a low-temperature power distribution method of a lithium ion battery, which is based on a low-temperature discharge method in a specific embodiment and comprises the following steps:
the lithium ion battery and the heating control system were the same as in example 8.
In the low-temperature discharge method, the battery SOC is monitored to be 20% in S1, and heating is carried out;
in S2, after the battery SOC reaches 55%, the heating is stopped.
Comparative example 1
The difference between the comparative example and the example 1 is that the lithium ion battery provided by the comparative example is not provided with a heating control system, and the low-temperature discharge method comprises the following steps:
and (3) placing the lithium ion battery in a low-temperature box at the temperature of-20 ℃ for 8h, and discharging the battery by a 1C and 1.8V discharge mechanism.
Fig. 3 shows a low-temperature discharge curve obtained by the low-temperature discharge method of the lithium ion battery provided in example 1, fig. 4 shows a low-temperature discharge curve obtained by the low-temperature discharge method of the lithium ion battery provided in comparative example 1, and fig. 5 shows a normal-temperature discharge curve of the lithium ion battery provided in example 1, and it can be seen from fig. 3, fig. 4, and fig. 5 that, if no measures are taken, the discharge capacity of the lithium ion battery is very poor when the lithium ion battery is directly discharged at low temperature, and it is difficult to achieve normal operation at low temperature.
Comparative example 2
The difference between the comparative example and the example 8 is that the lithium ion battery provided by the comparative example is not provided with a heating control system, and the low-temperature discharge method comprises the following steps:
and (3) placing the lithium ion battery in a low-temperature box at the temperature of-15 ℃ for 8h, and discharging the battery by a 0.5C and 3V discharge mechanism.
And (3) low-temperature discharge test:
(1) the battery systems provided in examples 1 and 8 were first charged and discharged at room temperature:
lithium iron phosphate: under the normal temperature environment, the battery is charged in the following way: 1C, 3.65V, 0.05C, cut off; then, the discharge was performed as follows: 1C, 2.0V, and determining the normal-temperature initial capacity C of the lithium ion power battery0A normal-temperature discharge curve diagram of the battery provided in example 1 can be obtained;
the NCM811 system: under the normal temperature environment, the battery is charged in the following way: 1C, 4.35V, 0.05C, cut off; the discharge was then carried out as follows: 1C, 3.0V, and also the initial discharge capacity C0；
(2) The discharge capacities of the lithium ion batteries after low-temperature discharge provided in examples 1 to 9 and comparative examples 1 to 2 were denoted as C1To obtain the capacity retention rate R of the batteries provided in examples 1 to 9 and comparative examples 1 to 21＝C1/C0The results are shown in Table 1.
Figure BDA0003640994800000131
Figure BDA0003640994800000141
From the data results of examples 1-2 and 3, it can be seen that when the battery starts to be heated at a surface temperature of more than 0 ℃ in the abnormal working state of the battery, the active lithium is irreversibly lost at a low temperature, and the capacity retention rate is reduced.
From the data results of examples 4 to 6, it is understood that in the abnormal operation state of the battery, the SOC of the battery is 30% or less, and then the battery is heated, so that the reversible lithium in the battery can be sufficiently activated to contribute more capacity.
From the data results of examples 4-6 and example 7, it is clear that during the abnormal operation of the battery, when the battery is heated with the SOC of more than 50%, the thermal runaway problem in the high charge state occurs.
From the data results of examples 1-2 and examples 4-6, it can be seen that the improvement of the low-temperature discharge performance of the battery can be achieved by monitoring the surface temperature of the battery or monitoring the SOC of the battery.
From the data results of the embodiments 1 and 8, and the embodiments 4 and 9, it can be seen that the low-temperature discharge method provided by the present invention is suitable for lithium ion batteries under various systems.
Compared with the comparative data of examples 1-2, 4-6 and comparative example 1, and 8-9 and comparative example 2, the low-temperature discharge method provided by the invention is used for low-temperature discharge of the lithium ion battery, so that the capacity loss of the battery in a low-temperature environment can be effectively reduced, and the low-temperature discharge performance of the battery can be improved.
In conclusion, the working state of the battery is monitored in the discharging process of the battery in the low-temperature environment, so that the battery can be heated in time, the process is simple, the low-temperature discharging performance of the lithium ion battery is improved without adopting a complex charging and discharging mechanism, the excessive loss of the capacity of the battery in the low-temperature environment is avoided without repeatedly regulating and controlling the current and voltage values, the aim of simply and conveniently improving the low-temperature discharging performance of the lithium ion power battery is fulfilled, the capacity retention rate of the battery after low-temperature discharging is improved, and the battery can be more suitable for working in the low-temperature environment. After the low-temperature discharge method of the lithium ion battery provided by the invention is adopted, the ratio of the discharge capacity of the battery to the discharge capacity of the lithium ion battery at normal temperature can reach more than 60%, and the ratio of the discharge capacity at low temperature to the discharge capacity at normal temperature can reach more than 65% when the surface temperature of the battery is-30-0 ℃ or the SOC of the battery is 10-30% under the unconventional working condition is further regulated and controlled; and the discharge capacity ratio of the lithium ion battery under the NCM system at low temperature and normal temperature can reach more than 83 percent.
The applicant states that the present invention is illustrated by the above examples of the process of the present invention, but the present invention is not limited to the above process steps, i.e. it is not meant that the present invention must rely on the above process steps to be carried out. It will be apparent to those skilled in the art that any modification of the present invention, equivalent substitutions of selected materials and additions of auxiliary components, selection of specific modes and the like, which are within the scope and disclosure of the present invention, are contemplated by the present invention.

Claims (10)

1. A low-temperature discharge method of a lithium ion battery is characterized by comprising the following steps:
s1: monitoring the working state of the lithium ion battery, and starting a lithium ion battery heating control system to heat the battery when the lithium ion battery is in an abnormal working state;
s2: when the surface of the battery is heated to reach the normal working state, the heating is stopped.
2. The method of claim 1, wherein in step S1, the condition of the abnormal operation state is that the surface temperature of the battery is less than or equal to 0 ℃ or the SOC of the battery is 10-50%.
3. The method of claim 2, wherein the non-normal operating condition is a surface temperature of the battery of-30 to 0 ℃ or a SOC of the battery of 10 to 30%.
4. The method for low-temperature discharge of lithium ion batteries according to any of claims 1 to 3, wherein in step S2, the condition of the normal operating state is that the battery surface temperature is >0 ℃ or the battery is SOC > 50%.
5. The method of any of claims 1-4, further comprising:
and after the heating is stopped, continuously discharging the battery until the voltage of the battery reaches a discharge cut-off voltage.
6. The low-temperature discharge method of the lithium ion battery according to claim 5, wherein after the heating is stopped, the working state of the lithium ion battery is continuously monitored while the battery is continuously discharged, and when the battery is in the unconventional working state again, the heating control system is continuously started to heat the battery until the battery reaches the conventional working state, and the heating is stopped again.
7. The method of any of claims 1-6, wherein the heating control system comprises a heating resistor and a controller.
8. The method according to claim 7, wherein the heating resistor is connected in parallel with the lithium ion battery operating circuit.
9. The method for discharging a lithium ion battery at a low temperature according to any one of claims 1 to 8, wherein the discharge current of the lithium ion battery in an operating state is 0.3C to 1C.
10. The method for low-temperature discharge of a lithium ion battery according to any one of claims 1 to 9, wherein the method for low-temperature discharge comprises the steps of:
s1: monitoring the working state of the lithium ion battery, and starting a lithium ion battery heating control system to heat the battery when the surface temperature of the lithium ion battery is-30-0 ℃ or the SOC of the battery is 10-30%;
s2: when the surface of the battery is heated until the surface temperature of the battery reaches more than 0 ℃ or the SOC of the battery is more than 50%, stopping heating, and continuously discharging the battery after the heating is stopped until the voltage of the battery reaches a discharge cut-off voltage;
wherein the discharge current of the lithium ion battery in the working state is 0.3-1C.
CN202210519176.2A 2022-05-12 2022-05-12 Low-temperature discharge method of lithium ion battery Pending CN114759277A (en)

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Publication number Priority date Publication date Assignee Title
US20120094152A1 (en) * 2009-06-18 2012-04-19 Guanglin Wu Method and device for controlling battery heating
CN210040468U (en) * 2019-07-01 2020-02-07 江苏智航新能源有限公司 Low-temperature heating device for lithium ion battery
CN210881696U (en) * 2019-09-11 2020-06-30 郑州宇通客车股份有限公司 Hybrid vehicle and battery heating system thereof
CN113782872A (en) * 2021-09-15 2021-12-10 珠海冠宇电源有限公司 Lithium battery pack and heating method thereof
CN114464928A (en) * 2022-01-27 2022-05-10 安徽维德电源有限公司 Heating control method for battery pack of lithium electric forklift

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120094152A1 (en) * 2009-06-18 2012-04-19 Guanglin Wu Method and device for controlling battery heating
CN210040468U (en) * 2019-07-01 2020-02-07 江苏智航新能源有限公司 Low-temperature heating device for lithium ion battery
CN210881696U (en) * 2019-09-11 2020-06-30 郑州宇通客车股份有限公司 Hybrid vehicle and battery heating system thereof
CN113782872A (en) * 2021-09-15 2021-12-10 珠海冠宇电源有限公司 Lithium battery pack and heating method thereof
CN114464928A (en) * 2022-01-27 2022-05-10 安徽维德电源有限公司 Heating control method for battery pack of lithium electric forklift

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