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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