Why does battery capacity decrease quickly at low temperatures?

　　Many friends have experienced situations where batteries are not disabled at low temperatures compared to normal temperatures. Batteries are easily discharged at low temperatures, especially in northern regions where it is more evident that batteries are more prone to running out of battery in severe cold and low temperatures. So why does battery capacity decrease quickly at low temperatures? This involves a complex situation. Below, the editor will provide a brief explanation of several key factors.

　　1. In terms of battery properties

　　In terms of battery properties, batteries can be divided into conventional batteries used at room temperature and specialized low-temperature batteries used at low temperatures. Conventional batteries are generally batteries that can discharge about 90% of their power at temperatures above -15 ℃. If the temperature is lower, the discharge capacity will decrease linearly, and it will be very obvious that the battery is not disabled or cannot be used (such as basically not discharging at -40 ℃), Of course, it can discharge 100% of the electricity at room temperature; Low temperature batteries designed specifically for use at low temperatures can generally operate at temperatures between -40 ℃ and 60 ℃, or in other words, batteries that can operate at temperatures between -50 ℃ and 50 ℃; This type of battery can generally discharge about 85% of its electricity at -50 ℃, about 90% at -40 ℃, and over 95% at -30 ℃ or above.

　　That is to say, if the battery wants to release more electricity in low temperature and severe cold, it needs to use specialized low-temperature batteries, because the raw materials used in the production and manufacturing of low-temperature batteries may differ from those used in conventional batteries.

　　Take the polymer lithium battery that we are familiar with and familiar with as an example. It also includes conventional batteries used at room temperature and specialized low-temperature batteries used at low temperatures. The main raw materials used in their production and manufacturing are generally similar, but the electrolyte formula used is different. The electrolyte used in room temperature batteries is not frost resistant, which means that at low temperatures, the activity of the electrolyte will decrease, and the conductivity will also decrease. If the performance is poor, at lower temperatures, it will cause damage to the internal chemical structure of the raw materials due to freezing, and the discharge performance of the battery will be severely damaged, resulting in a serious decrease in discharge volume and even inability to discharge. The electrolyte formula used in low-temperature polymer lithium batteries is relatively frost resistant. Even at low temperatures of -50 ℃, the internal chemical structure of the battery is still relatively stable and maintains a certain degree of activity, with good conductivity, so the discharge performance can maintain a certain level of performance.

　　So if you feel a significant decrease in the discharge of the battery you are using at low temperatures, then the battery you are using is likely not a low-temperature battery (low-temperature is a new battery or a recently used one).

　　2. In terms of battery types

　　The different types of batteries have different discharge performance at low temperatures (the size of discharge current and the amount of discharged electricity will also vary), mainly due to the chemical properties of the battery's raw materials, which are relatively difficult to improve. Below, let's briefly introduce the basic charging and discharging performance of different types of low-temperature lithium batteries

　　(1) Low temperature lithium iron phosphate battery

　　Low temperature lithium iron phosphate batteries can operate within the temperature range of -40 ℃ to 55 ℃, and if discharged at a current rate of 0.2C at -20 ℃, the discharge capacity exceeds 85%, 70% at -30 ℃, and 55% at -40 ℃. At the same time, they can achieve charging performance at -20 ℃.

　　(2) Low temperature polymer lithium battery

　　The working temperature range of low-temperature polymer lithium batteries is -50 ° C to 50 ° C, and they discharge at a current rate of 0.2C at extremely low temperatures of -50 ° C, with an efficiency of over 60% in discharge capacity; At -40 ℃, discharge at 0.2C with a discharge capacity of over 80%; At the same time, it can also achieve the performance of charging at -20 ℃ low temperature.

　　From the above data, it is evident that the low-temperature charging and discharging performance of low-temperature polymer lithium batteries is better than that of low-temperature iron phosphate lithium batteries, which also indicates that different types of batteries have different discharge performance at low temperatures.

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