Core tip: A power supply charges the battery. At this time, the electron e on the positive electrode runs from the external circuit to the negative electrode, and the positive lithium ion Li+ "jumps" into the electrolyte from the positive electrode, and "climbs" over the small twists and turns on the diaphragm. The hole, "swimming" to the negative pole, is combined with the electrons that have run over long ago.
1. Positive structure
LiFePO4 (lithium iron phosphate) + conductive agent + binder (PVDF) + current collector (aluminum foil)
2. Negative structure
Graphite + conductive agent + thickener (CMC) + binder (SBR) + current collector (copper foil)
3. Working principle
3.1 Charging process: A power supply charges the battery. At this time, the electron e on the positive electrode runs from the external circuit to the negative electrode. The positive lithium ion Li+ "jumps" into the electrolyte from the positive electrode, and "climbs" over the diaphragm. The small hole, "swimming" to the negative pole, combines with the electrons that have run over long ago.
3.2 Battery discharge process
Discharge has constant current discharge and constant resistance discharge. Constant current discharge is actually adding a variable resistance to the external circuit that can change with the voltage. The essence of constant resistance discharge is to add a resistance to the positive and negative electrodes of the battery to allow electrons to pass. It can be seen that as long as the electrons on the negative electrode cannot run from the negative electrode to the positive electrode, the battery will not discharge. Both electrons and Li+ act at the same time, with the same direction but different paths. When discharging, the electrons run from the negative electrode to the positive electrode through the electronic conductor, and the lithium ion Li+ "jumps" from the negative electrode into the electrolyte and "climbs" over the diaphragm. "Swimming" to the positive pole in the small hole, combined with the electrons that ran over.
Two technological process
1. Preparation of positive pole piece
1.1 Drying of raw materials
(1) Lithium iron phosphate: vacuum baking. (2) Conductive agent: baking at atmospheric pressure. (3) Adhesive: Bake at atmospheric pressure.
1.2 Slurry mixing
a) Pour NMP into a vacuum mixer, and add PVDF to it; b) Add the positive electrode dry material in an average of four times. c) Stir at high speed under vacuum for 3-5 hours; d) Discharge and prepare for coating.
a) Coat the slurry evenly on the surface of the aluminum foil on the precision coating machine, and the coating thickness can be adjusted according to different requirements.
2. Preparation of negative pole piece
2.1 The raw materials do not need to be dried.
2.2 Slurry preparation
a) Pour purified water into the vacuum mixer. B) Add CMC, stir, and dissolve completely; c) Add SBR and deionized water, and stir for 60 minutes; d) The negative electrode dry material is added to the mixer in an average order of four times. e) High-speed vacuum stirring for 3-5 hours; f) Discharge and prepare for coating
a) Coat the slurry evenly on the surface of the copper foil on the precision coating machine, and the coating thickness can be adjusted according to different requirements.
3. Pole piece rolling
The coated pole piece is rolled once on the roll mill to reach the thickness required by the process.
4. Pole piece punching
The rolled pole piece is cut into the required small pieces on the die-cutting machine, ready to be laminated.
The positive electrode, negative electrode, and separator are laminated on the automatic stacking machine in a certain order, and the number of layers is in accordance with the process requirements.
6, battery shell welding
The positive electrode and the negative electrode are respectively welded on the positive and negative electrodes of the cap, and then put into the aluminum shell. The interface between the cap and the aluminum shell is welded by a laser welding machine.
7. Battery injection
Inject a certain amount of electrolyte.
8. Battery formation and capacity division