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Lithium battery, i.e. lithium metal battery, generally refers to the battery using manganese dioxide as the positive material, lithium metal or its alloy metal as the negative material, and using non-aqueous electrolyte solution. With the rapid development of science and technology, lithium battery packs have gradually become mainstream.
Main materials: positive electrode, negative electrode, electrolyte, diaphragm
Structure: round, square; laminated, coiled
Shape: polymer (flexible package), liquid lithium ion (steel case)
Anode
Positive electrode materials account for 30% - 40% of the cost of lithium-ion batteries, directly affecting the energy density and performance of lithium battery packs.
Negative Electrode
Negative electrode materials need to be composed of materials with lower potential relative to lithium electrode, and have high specific capacity and better charge/discharge reversibility, so as to maintain good dimensional and mechanical stability during lithium embedding.
Electrolyte
Electrolyte plays the role of transporting charge between positive and negative electrodes, which affects the energy density, power density, wide temperature application, cycle life, safety performance and other factors of lithium battery pack.
Diaphragm
The aperture of the diaphragm needs to meet the good ionic throughput, liquid absorption and moisture capacity, to maintain ionic conductivity; at the same time, it has electronic insulation to achieve mechanical isolation of the insulation between the positive and negative electrodes, in addition, it should have sufficient puncture strength, tensile strength and other mechanical properties and corrosion resistance and sufficient electrochemical stability.
Currently more commonly used lithium battery pack materials are lithium cobaltate, lithium nickelate and lithium manganate. The most used material is lithium cobalt, good cycle performance, manufacturing is also convenient, the disadvantage is that the cobalt compound is more expensive.
Lithium battery pack working principle:
Lithium battery is a kind of secondary battery (rechargeable battery), mainly relying on the lithium ion between the positive and negative electrodes back and forth embedded and de-embedded to work, to achieve the storage and release of energy.
1, charging process
Driven by the electric field, lithium ions are dislodged from the positive lattice, pass through the electrolyte and embedded in the negative lattice.
At the beginning of charging, the voltage of the battery to be charged should be detected first, and if the voltage is lower than 3V, it should be pre-charged first, and the charging current is 1/10 of the set current, and about 0.05C is generally chosen. After the voltage rises to 3V, it enters the standard charging process. The standard charging process is: constant current charging with the set current, the battery voltage rises to 4.20V, change to constant voltage charging, keep the charging voltage is 4.20 V. At this time, the charging current gradually decline, when the current drops to 1/10 of the set charging current, charging end.
2, discharge process
The process is just the opposite of the lithium ion returns to the positive pole, the electrons through the electrical appliances from the external circuit to reach the positive pole and lithium ion compound. Battery discharge, at this time the negative electrode on the electron e from the external circuit to run to the positive electrode, positive lithium ion Li + from the negative electrode "jumped into" the electrolyte, "climbed" the diaphragm on the curved small holes, "swimming "Swimming" to reach the positive electrode, with the electrons that have long run over together.
The higher the battery discharge current, the smaller the discharge capacity and the faster the voltage drops.
Lithium battery pack assembly process:
Tools / raw materials: positive pole material, negative pole material, diaphragm paper
Steps/methods
Pulping:
Use special solvents and bonding agents to mix with powdered positive and negative active materials respectively, and then make pulp-like positive and negative materials after high-speed mixing.
Coating:
Coat the made slurry evenly on the surface of the metal foil, dry it, and make positive and negative electrode sheets respectively.
Assembly:
According to the order of positive pole piece - diaphragm - negative pole piece - diaphragm from top to bottom, put them in place, and make the battery core by winding, and then inject electrolyte, sealing and other processes, that is to say, complete the assembly process of the battery, and make the finished battery.
Chemical formation:
Charge and discharge test the finished battery with special battery charging and discharging equipments, test every battery, screen out the qualified finished battery to be shipped.