What are the core parameters of rechargeable lithium batteries?

Core indicators of rechargeable batteries 1. Safety performance A battery with unqualified safety performance indicators is impossible to accept. The most influential ones are explosions and liquid leakage. Explosion and leakage are mainly related to the internal pressure, structure and process design of the battery (such as safety valve failure, lithium battery without protection circuit, etc.) and improper operation that should be prohibited (such as throwing the battery into a fire). 2. Capacity refers to the total amount of electricity that a battery can release under certain discharge conditions. According to the IEC standard and the national standard, nickel-cadmium and nickel-metal hydride batteries are charged at 0.1C for 16 hours and discharged at 0.2C to 1.0V under the condition of 20±50C, which is the rated capacity of the battery, denoted by C; lithium battery The battery’s rated capacity is the battery’s rated capacity when charged at room temperature, constant current (1C), and constant voltage (4.2V) for 3 hours and then discharged at 0.2C to 2.75V. The unit of battery capacity is mah and Ah (1Ahu003d1000mAh). Taking the AA2300mAh Ni-MH rechargeable battery as an example, it means that when the battery is charged at 230mA (0.1C) for 16 hours and then discharged at 460mA (0.2C) to 1.0V, the total discharge time is 5 hours, and the discharged power is 2300mAah. Correspondingly, if it is discharged with a current of 230 mA, the discharge time is about 10 hours. 3. Internal resistance The internal resistance of a battery refers to the resistance encountered when current flows through the battery. The internal resistance of the rechargeable battery is very small, and a special instrument can be used to measure more accurate results. The internal resistance of the battery generally known is the internal resistance of the charged state, even if the internal resistance of the battery is fully charged (corresponding to the internal resistance of the discharged state, it refers to the internal resistance of the battery after fully discharged. Generally speaking, the internal resistance of the discharged state is more than The internal resistance in the charged state is large and not very stable). The greater the internal resistance of the battery, the more energy the battery consumes, and the lower the efficiency of the battery. A battery with a large internal resistance generates a lot of heat during charging, causing the battery's temperature to rise sharply. The impact on the battery and the charger is great. As the number of times the battery is used increases, the internal resistance of the battery will increase to varying degrees due to the consumption of the electrolyte and the decrease in the activity of the internal chemical substances in the battery. The lower the quality of the battery, the faster the rise. 4. Cycle life Cycle life is the number of times the battery can be repeatedly charged and discharged. The battery life and capacity are in an inverse relationship. Generally, the cycle life of a Ni-MH battery can reach more than 500 times. The life of a high-capacity battery is shorter, but it can reach more than 200 times. The cycle life is also closely related to the charging and discharging conditions. Generally, the larger the charging current (the faster the charging speed), the shorter the cycle life. 5. Charge retention capability The charge retention capability, which is usually referred to as self-discharge, refers to the retention capability of the stored power of the battery under certain environmental conditions in an open circuit state. Self-discharge is mainly determined by various factors such as battery materials, manufacturing processes, and storage conditions. Generally, the higher the temperature, the greater the self-discharge rate. A certain degree of self-discharge of rechargeable batteries is normal. Take nickel-metal hydride batteries as an example. The IEC standard stipulates that after the battery is fully charged, at a temperature of 20±5°C and a humidity of 65±20%, the battery should be left open for 28 days, and the 0.2C discharge time shall not be less than 3 hours (that is, the remaining power Greater than 60%). The self-discharge of lithium batteries and dry batteries is much smaller. Parameters of rechargeable batteries 1. Energy density per unit volume or unit weight. For the same power requirements, batteries with high energy density can be smaller in size and lighter in weight. 2. C current refers to the amount of current required to discharge a fully charged battery or fully charge an exhausted battery within one hour. In fact, it is the numerical value of the ampere-hour capacity. For a battery with a capacity of 1800mA, the C current is 1800mA. For a battery with a capacity of 2000mA, the C current is 2000mA. 3. Open circuit voltage refers to the potential difference between the two poles of the battery. 4. The new battery with memory effect has fine crystal grains of the electrode material, and the largest electrode surface area can be obtained. The battery content is crystallized due to use. After the crystallization is formed, the crystal grains increase, which is also called (passivation), which reduces the usable electrode area, and the grown crystal grains will increase the self-discharge and make the battery The capacity is reduced and the performance is impaired. This is the memory effect. The memory effect occurs because the battery is partially charged and discharged repeatedly incompletely. 5. Self-discharge rate A charged battery will gradually lose its power even when it is not in use. Generally, the higher the temperature, the more significant the self-discharge. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous post: Which is better for lithium ion batteries or graphene batteries?