A chemical battery, or chemical power source, is a device that converts chemical energy into electrical energy. It consists of two electrochemically active electrodes of different compositions, forming the positive and negative electrodes, and a chemical substance that acts as a medium for conduction, serving as the electrolyte. When connected to an external carrier, it provides electrical energy by converting its internal chemical energy.
A physical battery is a device that converts physical energy into electrical energy.
The most significant difference lies in the active materials. The active materials in secondary batteries are reversible, while those in primary batteries are not. Primary batteries have a much lower self-discharge rate than secondary batteries, but their internal resistance is much higher, resulting in a lower load capacity. Furthermore, primary batteries have a higher specific capacity (both gravimetric and volumetric) than typical rechargeable batteries.
Ni-MH batteries use Ni oxide as the positive electrode, hydrogen storage metal as the negative electrode, and alkaline solution (mainly KOH) as the electrolyte. When a Ni-MH battery is charging:
Positive electrode reaction: Ni(OH)2 + OH- → NiOOH + H2O → e-
Negative electrode reaction: M + H2O + e- → MH + OH-
When a Ni-MH battery is discharging:
Positive electrode reaction: NiOOH + H2O + e- → Ni(OH)2 + OH-
Negative electrode reaction: MH + OH- → M + H2O + e-
Positive electrode reaction: LiCoO2 → Li1-xCoO2 + xLi+ + xe-
Negative electrode reaction: C + xLi+ + xe- → CLix
Overall battery reaction: LiCoO2 + C → Li1-xCoO2 + CLix
The reverse reaction occurs during discharge.
Common IEC standards for batteries: The standard for nickel-metal hydride batteries is IEC 61951-2:2003; the lithium-ion battery industry generally follows UL or national standards.
Common 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. Additionally, the Japanese Industrial Standards (JISC) also commonly use battery standards.
IEC, or International Electrotechnical Commission, is a global standardization organization composed of national electrotechnical commissions. Its purpose is to promote standardization in the global electrical and electronic fields. IEC standards are standards developed by the International Electrotechnical Commission.
The main components of a nickel-metal hydride battery are: positive electrode (nickel oxide), negative electrode (hydrogen storage alloy), electrolyte (mainly KOH), separator paper, sealing ring, positive electrode cap, battery casing, etc.
The main components of a lithium-ion battery are: top and bottom covers, positive electrode (active material is lithium cobalt oxide), separator (a special composite membrane), negative electrode (active material is carbon), organic electrolyte, and battery casing (available in steel and aluminum casings).
8. What is battery internal resistance?
Internal resistance refers to the resistance encountered when current flows through the battery during operation. It consists of two parts: ohmic internal resistance and polarization internal resistance. High internal resistance leads to a lower discharge voltage and shorter discharge time. The magnitude of internal resistance is mainly affected by factors such as battery materials, manufacturing process, and battery structure. It is an important parameter for measuring battery performance. Note: Generally, the internal resistance in the charging state is used as the standard.
The internal resistance of a battery must be measured using a dedicated internal resistance meter, not the ohmmeter function of a multimeter. 9. What is nominal voltage? The nominal voltage of a battery refers to the voltage it exhibits during normal operation. The nominal voltage of a secondary nickel-cadmium/nickel-metal hydride battery is 1.2V; the nominal voltage of a secondary lithium battery is 3.6V. 10. What is open-circuit voltage? Open-circuit voltage refers to the potential difference between the positive and negative terminals of the battery when it is not in operation, i.e., when no current flows through the circuit. Operating voltage, also known as terminal voltage, refers to the potential difference between the positive and negative terminals of a battery when it is in operation, i.e., when current flows through the circuit.Battery capacity is divided into rated capacity and actual capacity. The rated capacity of a battery refers to the minimum amount of electricity that the battery should discharge under certain discharge conditions, as specified or guaranteed during the design and manufacturing process. The IEC standard specifies that the rated capacity of nickel-cadmium and nickel-metal hydride batteries, when charged at 0.1C for 16 hours at 20℃ ±5℃ and then discharged at 0.2C to 1.0V, is the amount of electricity discharged, denoted as C5.
For lithium-ion batteries, the rated capacity is defined as the amount of electricity discharged when charged for 3 hours under constant current (1C) — constant voltage (4.2V) conditions at room temperature, followed by discharge at 0.2C to 2.75V. The actual capacity of a battery refers to the actual amount of electricity discharged under specific discharge conditions, primarily affected by the discharge rate and temperature (therefore, strictly speaking, battery capacity should specify the charging and discharging conditions). The units for battery capacity are Ah and mAh (1 Ah = 1000 mAh). 12. What is the residual discharge capacity of a battery?When a rechargeable battery is discharged with a high current (e.g., 1C or higher), due to the "bottleneck effect" caused by the excessive current leading to a high internal diffusion rate, the battery reaches its endpoint voltage before fully discharging its capacity. Discharging can continue with a small current, such as 0.2C, until reaching 1.0V/cell (NiCd and NiMH batteries) and 3.0V/cell (lithium batteries). The capacity discharged at this point is called the residual capacity.
The discharge plateau of a NiMH rechargeable battery typically refers to the voltage range within which the battery's operating voltage is relatively stable under a certain discharge regime. Its value is related to the discharge current; the higher the current, the lower the value.
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