CN-122025924-A - Method for constructing lithium battery heating safety boundary in low-temperature environment

Abstract

A method for constructing a lithium battery heating safety boundary in a low-temperature environment includes the steps of carrying out a battery thermal runaway experiment in the low-temperature environment to obtain a thermal runaway trigger boundary temperature of a large battery surface, carrying out a battery heating temperature rise experiment in the low-temperature environment to obtain temperature change difference characteristics of the large battery surface and tabs, constructing a battery temperature rise simulation model in a low-temperature polar-speed heating condition by utilizing experimental data, analyzing the battery temperature rise characteristics in different boundary conditions, calculating to obtain corresponding tab temperatures in different environment temperatures and at different heating rates during thermal runaway trigger based on the thermal runaway trigger boundary temperature of the large battery surface in the thermal runaway experiment, and fitting to construct the battery safety temperature boundary. The method is based on experimental means and finite element simulation, obtains the rule of influence of different low-temperature environment temperatures and different lug heating rates on the temperature rise of the battery, constructs a safe temperature boundary model of the battery, is used for guiding the heating process, and can effectively avoid the phenomenon of thermal runaway.

Inventors

• WANG FACHENG
• ZHANG YANG
• GAO SHEN
• LI XINGGANG
• LIU HUAYUAN
• LUO YULIN
• WANG LEI
• CHEN YADONG
• Zang Weihong
• TONG YUQI
• WANG TIANZE

Assignees

• 中国北方车辆研究所

Dates

Publication Date

20260512

Application Date

20251202

Claims (6)

1. 1. The method for constructing the lithium battery heating safety boundary in the low-temperature environment is characterized by comprising the following steps of: s1, carrying out a battery thermal runaway experiment at a low temperature to obtain a battery thermal runaway boundary temperature; s2, carrying out a battery heating temperature rise experiment at low temperature to obtain the temperature change difference characteristic of a large surface of the battery and the electrode lugs; s3, constructing a battery temperature rise simulation model under the low-temperature and rapid heating condition by using experimental data; And S4, analyzing the temperature rise characteristics of the battery under different boundary conditions to obtain the rule of influence of the external heating rate on the temperature rise of the battery under low temperature, and constructing the safety temperature boundary of the battery tab.
2. 2. The method according to claim 1, wherein said step S1 comprises the steps of: placing the battery to be tested in a low-temperature environment for cooling; Obtaining the maximum power limit which can be born by the battery heating film; Gradually heating the cooled battery cell to thermal runaway based on the maximum power which can be born by the battery heating film; And taking the battery large-surface temperature at the earliest abnormal occurrence as the boundary temperature triggered by thermal runaway as the temperature boundary for subsequent tests and analysis according to the obtained large-surface and tab temperature change curve.
3. 3. The method according to claim 1, wherein said step S2 comprises the steps of: placing the battery to be tested in a low-temperature environment for cooling; heating the battery cell until the large-area temperature reaches a set temperature, wherein the set temperature is lower than the boundary temperature obtained in the step S1, and recording temperature data in the temperature rise process of the battery; respectively adopting different heating rates to obtain the temperature change conditions of the large surface and the polar lugs under different temperature rise rates; And analyzing the battery heating temperature rise experiment result to obtain the temperature rise rates of the large surface and the electrode lugs under different heating currents, wherein the temperature rise rate of the electrode lugs is far lower than the large surface under the working condition of high-power heating, and the temperature difference between the large surface and the electrode lugs is gradually increased along with the increase of the temperature rise rate.
4. 4. The method according to claim 1, wherein said step S3 comprises the steps of: s31, establishing a battery temperature rise finite element model; s32, setting boundary conditions of the finite element model, wherein the boundary conditions comprise one or more of material setting, heating capacity setting, external environment temperature setting and initial temperature setting; S33, performing simulation analysis based on the established model, and comparing the simulation analysis with experimental results to verify the correctness of the simulation model.
5. 5. The method according to any one of claims 1-4, wherein said step S4 comprises the steps of: S41, researching temperature rise characteristics of the battery at different environmental temperatures: extracting tab temperature values before thermal runaway occurs on the large surface of the battery cell under different low-temperature environment temperatures, fitting the values by using a fitting tool to obtain a change expression of tab temperature f (x) along with the environment temperature x under constant heating power, and determining that the tab temperature and the environment temperature are approximately in a linear relation; s42, researching the temperature rise characteristics of the battery at different heating rates: Extracting the values of the temperature of the electrode lug before thermal runaway occurs on the large surface of the battery cell under different temperature rising rates, fitting the values by using a fitting tool to obtain a change expression of the temperature f (x) of the electrode lug along with the temperature rising rate x under constant environmental temperature, and determining the relationship of the temperature of the electrode lug and the temperature rising rate to be quadratic; S43, constructing a tab safety temperature boundary: analyzing the law of influence of different low-temperature environments under fixed heating rates and different heating rates under the same environment temperature on the temperature rise of the battery, extracting the tab temperature condition when the large-surface temperature under each working condition reaches the trigger thermal runaway boundary, taking the tab temperature condition as the lithium battery heating safety boundary temperature, and fitting to obtain the variation expression of the lithium battery heating safety boundary temperature f (x, y) along with the environment temperature x and the temperature rise rate y under constant environment temperature.
6. 6. The method according to claim 5, wherein the change expression of the lithium battery heating safety boundary temperature f (x, y) with the ambient temperature x and the temperature rise rate y obtained in the step S43 is: the R-square value of the fitting result was 0.9993.

Description

Method for constructing lithium battery heating safety boundary in low-temperature environment Technical Field The invention relates to the technical field of heat management of new energy power batteries, in particular to a method for constructing a lithium battery heating safety boundary facing a low-temperature environment, which can be widely applied to the fields of electric automobiles, energy storage systems, power supplies of special equipment and the like. Background With the increasing application demands of batteries in cold regions, especially in the fields of electric automobiles, energy storage systems and the like in cold environments, the low-temperature performance and the safety of the batteries become important points of research. The low temperature environment has remarkable influence on the battery, and the charge and discharge performance, capacity fading speed and safety of the battery at low temperature are all affected, especially when the battery is heated at a high speed in the low temperature environment, the temperature change of the battery is rapid and severe, and the occurrence of thermal runaway phenomenon can be possibly caused, so that serious potential safety hazards are caused. Thermal runaway of a battery is a self-enhanced reaction caused by an excessively high internal temperature, which is manifested in a severe temperature rise of the internal reaction of the battery, which may cause the battery to fire or even explode. In general, thermal runaway is caused by an excessively high temperature, an excessively large charging current, and the like during charge or discharge. However, in a low temperature environment, the electrochemical reaction inside the battery is retarded, and the heating rate of the battery has a greater influence on the change in temperature. An excessively fast external heating rate may cause the internal temperature of the battery to rise sharply, and thus a thermal runaway phenomenon may be induced. Meanwhile, due to the limitation of the internal structure of the battery pack, the temperature sensor is more conveniently arranged at the position of the lug. Considering that the temperature rise characteristics of the large-surface center of the battery and the tab are different in the heating process, the tab temperature can be monitored only in the actual use process, so that the construction of the heating safety boundary is greatly influenced. Therefore, how to control the heating rate at low temperature, and by judging the temperature of the tab, the battery is prevented from triggering thermal runaway in the external heating process, is a key problem in the cold region battery rapid heating technology. Disclosure of Invention The invention provides a lithium battery heating safety boundary construction method under a low-temperature environment, which aims to reproduce the phenomenon that a battery triggers thermal runaway under a rapid heating condition through a battery thermal runaway experiment under the low-temperature environment, further acquire thermal runaway triggering temperature data of a large battery surface in the thermal runaway experiment, take the thermal runaway triggering temperature data as the thermal runaway triggering boundary condition, further construct a battery temperature rise simulation model under the low-temperature rapid heating condition through the battery heating temperature rise experiment under the low-temperature rapid heating condition by utilizing experimental data, discuss a generating mechanism of battery temperature rise in the low-temperature rapid heating process, study an influence rule of an external heating rate under the low temperature on the battery temperature rise through simulation data analysis, reveal the effect of the heating rate on the battery safety, and simultaneously take the large battery surface thermal runaway triggering temperature as the boundary, extract the tab temperature when the large battery surface temperature reaches the triggering boundary according to a simulation result, take the tab temperature as the thermal runaway boundary temperature, construct the battery safety temperature rise boundary, ensure that a tab temperature sensor does not exceed the upper limit in practical use, provide scientific basis and safety guidance for a battery rapid heating technology in a cold region, promote the optimal design of a battery heating system under the low-temperature environment, and ensure the safety and reliability of the battery under the low-temperature environment. The method for constructing the lithium battery heating safety boundary in the low-temperature environment mainly comprises the following steps: s1, carrying out a battery thermal runaway experiment at a low temperature to obtain a battery thermal runaway boundary temperature; s2, carrying out a battery heating temperature rise experiment at low temperature to obtain the temperature change difference ch