In recent years, Li-polymer batteries have been widely used as a high energy density power source. However, the safety of Li-polymer batteries has been a major concern. This paper will discuss the principles of safety issues of Li-polymer batteries and the factors that may lead to safety issues during the production process. In addition, the testing standards and methods for the safety performance of lithium batteries will be introduced to improve the safety of lithium batteries. There is also how we should use lithium batteries properly to avoid lithium battery damage and fire problems.
The principle that Li-polymer batteries are prone to fire
The main principle behind the tendency of lithium polymer batteries to catch fire is the thermal runaway reaction caused by overheating. Thermal runaway is caused by the fact that the rate of heat generation is much higher than the rate of heat dissipation, and that a large amount of heat accumulates and is not dissipated in time. This reaction is caused by a combination of factors, including the thermal decomposition of the polymer electrolyte: the polymer usually decomposes thermally at ~100 to 300°C. The decomposition temperature is related to the chemical structure of the monomer, the degree of polymerisation, the length of the polymerisation chain, the crystallinity and the atmosphere; the oxidation of the electrode material: the electrolyte is usually an organic solution of alkyl carbonate, which is flammable. And the positive electrode material is usually transition metal oxide, which has strong oxidation in the charging state, and is easy to decompose and release oxygen at high temperature, and the released oxygen reacts with the electrolyte in oxidation, and then releases a large amount of heat; the generation of lithium metal, etc. The internal resistance of the electric cell is too high in the charging and discharging process is prone to high temperature, once the thermal runaway, it will catch fire and explode. When the internal temperature of the battery exceeds a certain threshold, these reactions will rapidly amplify and generate a large amount of heat and flammable gases, resulting in a battery fire or explosion.
Factors in the production process that may lead to safety problems
Test standards and methods for the safety performance of lithium batteries
To ensure the safety performance of lithium batteries, a series of tests are required. Generic testing standards generally classify safety testing items into the following four categories: electrical testing, mechanical testing, thermal runaway temperature testing and environmental testing.
Thermal Runaway Temperature (Tc) Test: The thermal runaway temperature of a battery is determined by testing the battery's performance in a high temperature environment to assess the thermal stability of the battery.
Electrical tests include: short circuit test: simulates the internal short circuit of the battery to assess the short circuit resistance of the battery; overcharge test: charges the battery to over the rated voltage and observes its performance to assess the overcharge safety of the battery; over discharge test: discharges the battery to too low a voltage and observes its performance to assess the over discharge safety of the battery.
Environmental tests include impact tests: simulate the battery being impacted during use to assess the battery's impact resistance; flame tests: expose the battery to an open flame and observe its performance to assess the battery's flame resistance, etc.
Mechanical testing involves subjecting the battery to a range of extreme behaviours such as crushing, pinning, shock, vibration and dropping to test how the battery will react under extreme behaviour. Mechanical testing is carried out using a professional battery testing machine.
Through the above tests, the safety performance of lithium batteries can be fully assessed, providing an important reference for the design and production of batteries.
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How should we properly use lithium batteries and how should we as consumers properly extinguish a fire when the battery is on fire
When we talk about the proper use of lithium batteries, we usually mean in terms of small applications, i.e. consumer electronics, such as home beauty devices, smartphones and laptops. Medium and large applications are much more complex, usually medium-sized applications are in new energy vehicles, which we generally call power batteries; large applications are usually in base stations, which are generally called energy storage batteries. Therefore, when we talk about "how to use lithium batteries", we limit lithium batteries to small applications in line with people's customary understanding.
Charging
1. Original
Mismatched current and voltage when charging can damage the circuit system, shorten the life of the battery and even bring about safety hazards, so be sure to use the charger exclusively.
2. Moderate charging and discharging
Overcharging and discharging will greatly damage the battery, so do not wait for the power to be completely exhausted before charging, and do not charge for too long (avoid charging all night), generally keep the charger for 1-2 hours after the green light is on.
3. Pay attention to the charging environment
Charging in a humid environment of rain and snow can easily short circuit the circuit; charging in the summer under the hot sun can easily lead to spontaneous combustion. To ensure safety, you should choose to charge in a dry, ventilated and cool environment.
Storage
1. The best storage temperature is between 4°C and 35°C. Do not expose the battery to high temperature or cold. A lithium battery that has been used is usually in a shelved state for at least half of the time, so a suitable temperature has the most frequent and important significance for lithium battery maintenance.
2. Lithium batteries not used for a long time should be charged and discharged once a month, similar to "activation", to do a power calibration. This is because the battery electrodes will be passivated if the battery is not used for a long time, and the electrons in the battery should be kept in a flowing state. Of course, the best case scenario is to keep it in a semi-charged state.
Any method is effective under certain conditions. The measure of lithium battery maintenance is not to extend the life of the lithium battery, but to extend the life of the lithium battery within the effective cycle of the lithium battery design. Therefore, it is necessary to position the meaning of lithium battery maintenance on not making it reduce the life.
When the lithium battery fire, due to the lithium battery in the thermal runaway temperature will rise to 800-1000 ℃ in a short period of time, and thermal runaway has a transmission, so for the lithium battery fire, the conventional practice is to immediately disconnect the power, use a lot of water to extinguish the fire and cool down, and the most critical is to monitor in real time, in the early stage of thermal runaway fire is the most effective.
The safety of lithium polymer batteries has been a major concern. Understanding the principles of lithium polymer batteries catching fire and the factors that may lead to safety problems during the production process is crucial to improving the safety of lithium batteries. At the same time, the safety performance of lithium batteries can be comprehensively assessed through reasonable testing standards and methods, providing reference and guidance for the design and production of batteries. Only by ensuring the safety performance of lithium batteries can we better promote their application in various fields.
Our company, Ufine New Energy, specialises in the production and development of lithium batteries. We attach great importance to the safety of lithium batteries and ensure the safety and reliability of our products by strictly controlling the production process and implementing production monitoring. Our products undergo multiple tests and quality controls to ensure that they meet the highest safety standards. We are ready to provide you with high quality lithium battery products to ensure your safety and peace of mind during use. At the same time, we are constantly upgrading our technology and processes to meet the ever-changing and growing demands of the market. We are committed to providing our customers with the best products and the most satisfactory service.
Thank you for reading. If you would like to buy some Ufine battery products and learn more about batteries, please click on the links below.
UFX 104964 4950mAh 3.7V
UFX 102040 750mAh 3.7V
UFX 375678 2500mAh 3.7V
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