30 minutes makes you half a lithium-ion battery expert
Because more and more people need to understand the energy storage industry, 18650 pack builder and batteries are the core of energy storage, Light technology h...
Because more and more people need to understand the energy storage industry, 18650 pack builder and batteries are the core of energy storage, Light technology has sorted out the relevant information, sorted out a simple information for everyone to learn. I believe that after reading, you will form a more professional knowledge framework about the battery and become a half expert. Wish you a happy study
First, battery family
The professional name "lithium battery" originally refers to lithium metal batteries, battery manufacturing machine which are a battery, but they are no longer used in China because they are explosive. What are now called lithium battery companies are generally through lithium-ion batteries.
The number 7 and 5 batteries we use are dry batteries, the nickel metal hydride batteries used in the early days of brick phones, the lead-acid batteries used in wheelbarrows, four squares stacked on top of each other, and most of the batteries we use in our phones, laptops and even electric cars are lithium-ion batteries.
Comparison of energy storage battery characteristics of main electrochemical batteries
Second, battery terminology analysis
SOX: Full name is state X, battery state description, li ion battery construction H is health, C is capacity, P is power, E is energy, kind of like engine parameters, displacement, power, energy, run time, etc. It's the same idea.
SOC (state of charge) refers to the charge of a battery, like water in a bucket. The amount of available electricity contained in the battery at a certain time is called the SOC of the battery at that time. SOC is 0 for full discharge and 1 for full charge. Available capacity actual capacity.
DOD: (Depth of Discharge) refers to the depth of discharge of the battery, the battery in the case of full DOD is 0, completely different discharge treatment of the DOD is 1, so the normal situation below the DOD through the battery is a problem between 0 and 1 value, DOD and SOC relationship is: DOD+SOC = 1.
Soh: (Health status) refers to the actual battery capacity/initial battery capacity rating, which decreases as the battery ages. It is usually measured in terms of capacity and internal resistance
The most literature defines SOH in terms of battery capacity decay, and the SOH definition is as follows:
Type: Battery current capacity is cage type; The rated battery capacity is cage type.
Third, lithium battery classification
According to practical performance, it is divided into power type (sprint, short-time high-power output) and energy type (long-distance running, high energy storage).
By appearance: cylindrical, square (steel/aluminum shell), soft (aluminum-plastic film)
Pressed electrolyte materials: liquid lithium-ion batteries (Lib) and polymer lithium-ion batteries (PLB).
Liquid lithium-ion batteries use liquid electrolytes (as most batteries do today). Polymer lithium-ion batteries are replaced by solid polymer electrolytes, which can be "dry" or "colloidal," and currently are mainly polymer gel electrolytes. Regarding solid-state batteries, strictly means that the electrodes and electrolytes are solid.
According to the positive electrode material: lithium iron phosphate battery (LFP), lithium cobalt oxide battery (LCO), lithium manganate battery (LMO), (binary battery: lithium nickel manganate u 002 Li-rich nickel cobalt), (ternary battery: lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminate battery (NCA)).
Materials: Lithium titanate battery (LTO), graphene battery, nanocomposite carbon fiber as battery.
The 18650 is a lithium-ion battery model, similar to dry batteries 7, 5, 1, etc.
18650 is the originator of lithium-ion batteries - Japan's SONY company in order to save costs and developed the standard lithium-ion battery model, in which 18 represents the diameter of 18mm, 65 represents the length of 65mm, 0 represents the cylindrical battery. The common 18650 battery is divided into lithium-ion batteries and lithium iron phosphate batteries. The nominal voltage of lithium-ion batteries is 3.7v, the charging cutoff voltage is 4.2v, and the capacity is usually 1200mAh-3350mAh. The nominal voltage of lithium iron phosphate battery is 3.2V, the charging cut-off voltage is 3.6v, and the common capacity is 2200mAh-2600mAh.
Advantages of 18650:
Standardization: The 18650 battery is the oldest, most mature, and most stable lithium-ion battery, and Japanese manufacturers have established a high degree of consistency that can be easily replaced when one battery fails.
Safety :18650 batteries are generally steel housing, which is safer than possible collision problems; And with the continuous improvement of the production process level of 18650 batteries, safety is also improving. The steel shell lithium battery is prone to explosion, but now the 18650 battery is designed with a safety valve, which can not only release too much internal pressure, but also physically disconnect the battery from the outside world, which is equivalent to physically isolating the battery and ensuring the safety of other batteries in the battery pack.
However, compared with other batteries, there are also certain technical advantages, such as the relative safety of polymer lithium batteries, high energy density, low packaging film strength, no explosion, and the worst environment is combustion. It can provide customized product design, but the corresponding enterprise R & D and production costs continue to increase, and the universality is reduced.
Lithium iron phosphate battery
Lithium iron phosphate (molecular formula LiFePO4, lithium iron phosphate, also known as lithium iron phosphate and lithium iron phosphate, abbreviated as LFP) is the cathode material of lithium-ion batteries, also known as lithium iron phosphate batteries, which is characterized by the lack of cobalt and other precious elements, low raw material prices, phosphorus, lithium, iron resources on the earth are rich, there will be no supply problems. Its operating voltage is moderate (3.2V), large capacitance (170mAhu002Fg), high discharge power, fast charging, long cycle life, high stability in high temperature and high thermal environment.
Fourth, lithium battery voltage, capacity
The voltage of a lithium-ion battery varies with discharge current, ambient temperature, and anode and cathode materials.
First of all, during the charging and discharging process, the voltage is constantly changing. Take 490mA as an example. When the battery is fully charged, the open circuit voltage is 4.2V V. With the discharge, the voltage (vertical coordinate) slowly drops, and the discharge (horizontal coordinate) gradually increases, until the voltage begins to drop sharply at 3.5V V... Although the voltage changes throughout the discharge process, for simplicity, only the average 3.7V of the gently discharged part of the curve is labeled as the battery voltage. This voltage is also called the nominal voltage.
The voltage is measured under low current and room temperature operating environment, and will decrease with the increase of discharge current and the increase of temperature.
Another important factor affecting battery voltage is the positive and negative materials, Panasonic batteries use lithium cobalt oxide and graphite as positive and negative materials, which is the standard material for the entire lithium battery industry in the past few years. With the application of new materials in batteries, some 3.6V or 3.8V lithium batteries have appeared in the past two years. They use different cathode materials, both of which increase energy density relative to lithium-cobalt batteries, meaning more energy can be stored per unit weight and volume.
Battery capacity is divided into rated capacity and actual capacity.
1. The actual capacity refers to the actual discharge amount of the battery under certain discharge conditions. The actual capacity is always lower than the theoretical capacity.
2. Rated capacity refers to the minimum amount of electricity that the battery should discharge under certain discharge conditions when designing and manufacturing the battery.
The battery system capacity is generally calculated in AH (ampere-hour, ampere-hour), and we generally mark mAh (milliampere-hour) on the single battery for more convenience. If the rated capacity of the battery is 1300mAh, that is, 130mA of current to discharge the battery, then the battery technology can achieve sustainable development and work for 10 hours (1300mAh/130mA=10h). This is an ideal social state of analysis, digital electronic equipment management in the actual teaching of the current can not always be constant in the enterprise at a specific value.
The capacity of 18650 lithium battery is generally between 1200mah and 3600mah.
The current unit to measure the battery capacity of a mobile phone is mAh. High school taught us that this is a unit of electricity, you need to multiply by a voltage to get a unit of energy.
Wait, how do you measure a phone's energy consumption in one unit of battery life? That's because in portable electronic devices like cell phones, in order to reduce the size of the battery, lithium-ion battery cathodes use lithium cobalt, a highly dense material. Because the positive electrode of the cell phone battery is made of the same material, so the battery voltage is close (3.7V in theory, depending on the battery manufacturer's process), plus the fact that the phone tends to have only one battery (forget that recent phones have two Mach 2000 batteries), you can actually measure the amount of energy stored by the battery just by its capacity.
However, the battery on the computer will show both the capacity (charge) of the battery and the energy. This is because there is not only a single battery in the computer, but many batteries inside the series and parallel together to form a battery pack, so it can not be measured by the capacity of the battery. High school knowledge tells us: After the same type of battery is connected in parallel, the voltage of the battery pack will not change, but the capacity of the battery pack will increase; If the battery is connected in series, the capacity of the battery pack will not change, but the voltage of the battery pack will be increased.