Ten key technologies about lithium batteries

　　01What are the differences between primary batteries and secondary batteries?

　　The main difference is the difference in active materials. The active materials of secondary batteries are reversible, while the active materials of primary batteries are not reversible. The self-discharge of primary batteries is much smaller than that of secondary batteries, but the internal resistance is much larger than that of secondary batteries, so the load capacity is lower. In addition, the mass specific capacity and volume specific capacity of primary batteries are greater than general rechargeable batteries.

　　02What is battery internal resistance?

　　It refers to the resistance to current flowing through the interior of the battery when the battery is working. It consists of two parts: ohmic internal resistance and polarization internal resistance. A large internal resistance of the battery will cause the battery discharge working voltage to decrease and the discharge time to shorten. The internal resistance is mainly affected by factors such as battery materials, manufacturing processes, and battery structure. It is an important parameter to measure battery performance. Note: Generally, the internal resistance in the charging state is used as the standard. To measure the internal resistance of the battery, you need to use a special internal resistance meter to measure it, rather than using the ohm range of a multimeter.

　　03What is the nominal voltage?

　　The nominal voltage of the battery refers to the voltage displayed during normal operation. The nominal voltage of the secondary nickel-cadmium nickel-hydrogen battery is 1.2V; the nominal voltage of the secondary lithium battery is 3.6V.

　　04What is open circuit voltage?

　　Open circuit voltage refers to the potential difference between the positive and negative electrodes of the battery when the battery is not working, that is, when no current flows through the circuit. Working voltage, also called terminal voltage, refers to the potential difference between the positive and negative electrodes of the battery when the battery is in working condition, that is, when there is current in the circuit.

　　05What is the capacity of the battery?

　　The capacity of the battery is divided into rated capacity and actual capacity.

　　The rated capacity of the battery refers to the stipulation or guarantee that the battery should discharge the minimum amount of electricity under certain discharge conditions when designing and manufacturing the battery.

　　The actual capacity of the battery refers to the actual amount of electricity released by the battery under certain discharge conditions, which is mainly affected by the discharge rate and temperature (so strictly speaking, the battery capacity should specify the charge and discharge conditions).

　　The units of battery capacity are Ah and mAh (1Ah=1000mAh).

　　06What is the discharged residual capacity of the battery?

　　When a rechargeable battery is discharged with a large current (such as 1C or above), due to the "bottleneck effect" of the internal diffusion rate caused by the excessive current, the battery has reached the end voltage before the capacity is fully discharged. If the battery is discharged with a small current, such as It can continue to discharge at 0.2C until the capacity released at 1.0V/unit (nickel-cadmium and nickel-hydrogen batteries) and 3.0V/unit (lithium battery) is called residual capacity.

　　07What is a discharge platform?

　　The discharge platform of nickel-metal hydride rechargeable batteries usually refers to the voltage range in which the battery's operating voltage is relatively stable when the battery is discharged under a certain discharge system. Its value is related to the discharge current. The greater the current, the lower the value. The discharge platform of lithium-ion batteries is generally the discharge time when the voltage is 4.2V and the current is less than 0.01C. The battery is then left aside for 10 minutes and discharged to 3.6V at any rate of discharge current. It is an important standard to measure the quality of the battery.

　　When testing inventory

　　08What are the commonly used standards for batteries?

　　Commonly used IEC standards for batteries: The standard for nickel-metal hydride batteries is IEC61951-2:2003; the lithium-ion battery industry generally follows UL or national standards.

　　Commonly used national standards for batteries: the standards for nickel-metal hydride batteries are GB/T15100_1994, GB/T18288_2000; the standards for lithium batteries are GB/T10077_1998, YD/T998_1999, GB/T18287_2000.

　　In addition, common standards for batteries also include Japanese Industrial Standards JISC standards for batteries.

　　IEC, the International Electrical Commission, is a worldwide standardization organization composed of electrotechnical committees from various countries. Its purpose is to promote standardization in the world's electrical and electronic fields. IEC standards are standards developed by the International Electrotechnical Commission.

　　09What are the main structural components of nickel-metal hydride batteries?

　　The main components of nickel-metal hydride batteries are: positive electrode sheet (nickel oxide), negative electrode sheet (hydrogen storage alloy), electrolyte (mainly KOH), diaphragm paper, sealing ring, positive electrode cap, battery shell, etc.

　　10What is the electrochemical principle of nickel-metal hydride batteries?

　　Ni-MH batteries use Ni oxide as the positive electrode, hydrogen storage metal as the negative electrode, and alkali solution (mainly KOH) as the electrolyte. When charging the nickel-hydrogen battery:

　　Positive electrode reaction: Ni(OH)2+OH-→NiOOH+H2O–e-

　　Negative reaction: M+H2O+e-→MH+OH-

　　When nickel metal hydride batteries are discharged:

　　Positive electrode reaction: NiOOH+H2O+e-→Ni(OH)2+OH-

　　Negative reaction: MH+OH-→M+H2O+e-

　　11What are the main structural components of lithium-ion batteries?

　　The main components of a lithium-ion battery are: upper and lower battery covers, positive electrode sheet (the active material is lithium cobalt oxide), separator (a special composite film), negative electrode (the active material is carbon), organic electrolyte, and battery case (divided into Steel shell and aluminum shell) etc.

　　12What is the electrochemical principle of lithium-ion batteries?

　　The main component of the positive electrode of lithium-ion battery is LiCoO2, and the negative electrode is mainly C. When charging,

　　Positive electrode reaction: LiCoO2→Li1-xCoO2+xLi++xe-

　　Negative reaction: C+xLi++xe-→CLix

　　Total battery reaction: LiCoO2+C→Li1-xCoO2+CLix

　　The reverse reaction of the above reaction occurs during discharge.

　　Real 8-10

　　13What is charging efficiency?

　　Charging efficiency refers to a measure of the degree to which the electrical energy consumed by a battery during charging is converted into chemical energy that the battery can save. It is mainly affected by the battery process and the working environment temperature of the battery. Generally, the higher the ambient temperature, the lower the charging efficiency.

　　14What is discharge efficiency?

　　Discharge efficiency refers to the ratio of the actual amount of electricity released to the rated capacity when discharging to the end voltage under certain discharge conditions. It is mainly affected by factors such as discharge rate, ambient temperature, internal resistance, etc. Generally speaking, the higher the discharge rate, the higher the discharge rate. The lower the discharge efficiency. The lower the temperature, the lower the discharge efficiency.

　　15What is the output power of the battery?

　　The output power of a battery refers to the ability to output energy per unit time. It is calculated based on the discharge current I and the discharge voltage, P=U*I, and the unit is watts.

　　The smaller the internal resistance of the battery, the higher the output power. The internal resistance of the battery should be smaller than the internal resistance of the electrical appliance. Otherwise, the power consumed by the battery itself will be greater than the power consumed by the electrical appliance, which is uneconomical and may damage the battery.

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