1.Lithium metal battery
Lithium metal batteries generally use manganese dioxide as the positive electrode material, metal lithium or its alloy as the negative electrode material, and use a non-aqueous electrolyte solution. Its basic principle and basic component technical parameters of typical products are shown in Figure 1.
(1) Basic principles of lithium-ion batteries.
Lithium-ion batteries generally use lithium alloy metal oxide as the positive electrode material, graphite as the negative electrode material, and use a non-aqueous electrolyte.
The total reaction of the rechargeable battery is: LiCoO2+6C=Li(1-x)CoO2+LixC6
The reaction that occurs on the positive electrode of the charge is: LiCoO2→Li(1-x)CoO2+xLi+xe– (electron)
The reaction on the negative electrode of the charge is: 6C+xLi+xe–=LixC6
There are many cathode materials available for this type of battery, and most mainstream products use lithium iron phosphate. The voltage and specific power [V/(mA·h/g)] of different cathode materials are compared as follows: LiCoO2 (3.7/140); Li2Mn2O4 (4.0/100); Li2FePO4F (3.6/115).
Positive electrode reaction: Lithium ions are deintercalated during charging, and lithium ions are intercalated during discharging.
When charging: LiFePO4→Li(1-x) FePO4+xLi++xe–.
When discharging: Li(1-x)FePO4+xLi++xe–→LiFePO4.
Graphite is mostly used as the anode material, and new research has found that titanate may be a better material.
Negative reaction: Lithium ions are deintercalated during discharge, and lithium ions are intercalated during charging.
When charging: xLi+xe-+6C→LixC6.
When discharging: LixC6→xLi++xe–+6C.
(2) The basic components of lithium batteries.
The basic element is a single small battery, which has two types: cylindrical and square. The technical parameters of cylindrical lithium batteries are shown in Figure 2. It can be seen from the figure that its size is very small, its mass is very small, its voltage is very low, and its current is not large. Therefore, many series and parallel connections are necessary to achieve the required current and voltage.
(3) Examples of large-scale lithium battery components.
Lithium battery components can be large or small, as small as button batteries used in watches or meters, or square lithium batteries used in mobile phones and cameras (usually 6V/mA level). The car power battery is much larger. It uses a lot of lithium batteries in series and parallel to output a certain voltage, current and power as shown in Figure 3. The two batteries in the picture are lithium iron phosphate batteries with relatively large mass-to-energy ratio (w·h/kg) and volume-specific energy (w·h/L). In particular, the output voltage and power of THE352100 are high, which is suitable for higher power electric cars. Multiple modules can be connected in series and parallel to obtain different output voltages and output powers, which can be used to drive electric cars.
The new research uses carbon nanotubes, nanometer titanium dioxide or nanometer silicon and graphene to add to the electrode, which can greatly increase the storage energy, which is a new development direction.
(4) Operating characteristics of lithium batteries.
Compared with the main performance of lead-acid batteries, lithium batteries have the following characteristics: ①The specific energy is 6-7 times; ②The service life is more than 4 times; ③The working voltage is 3.7V or 3.2V; ④With high power tolerance, such as phosphoric acid Ferrous Lithium-ion battery can reach 15~30C charge and discharge capacity; ⑤Self-discharge rate can be as low as 0.5%~1% per month; ⑥Quality is 1/5~1/6 of lead-acid products; ⑦High and low temperature Adaptability increased by 20C; ⑧No metal lithium, no memory effect; ⑨Environmental protection, production, use and scrapping process, no toxic and hazardous substances; ⑩Basically no water consumption in production; ⑪Quick charge, using constant current and constant voltage charger, It can be fully charged in 1.5~2.5h, and the new type of phosphorus iron lithium battery can be fully charged in 35 minutes. All kinds of storage batteries have their own characteristics but the laws are roughly the same. The operating characteristics of lithium iron phosphate batteries commonly used in electric cars are shown in Figure 4. It can be seen from the figure that the voltage will drop rapidly after running with batteries of different capacities for a certain period of time and must be charged before. In addition, the capacity retention rate will decrease as the cycle life increases. When used at a certain capacity retention rate, the temperature decrease will reduce the output voltage and the capacity retention rate quickly. This is something that must be paid attention to in the use of lithium batteries. The degree of decrease also symbolizes the difference in battery performance and quality.