Types and Introduction of Electric Vehicles

In the electric bicycle market, the most commonly used are lead-acid maintenance free batteries, including AGM type batteries using glass fiber partition adsorption technology, and GEL type colloidal batteries using colloidal electrolyte technology.

The working principle of lead-acid batteries is that the anode (PbO2) and cathode (Pb) inside the lead-acid battery are immersed in the electrolyte (dilute sulfuric acid), and 2V of electricity is generated between the two poles. The chemical change during discharge is that dilute sulfuric acid will react with the active substances on the cathode and anode plates, generating a new compound called lead sulfate. The sulfuric acid component is released from the electrolyte through discharge, and the longer the discharge, the thinner the sulfuric acid concentration. The consumed components are proportional to the discharge amount. As long as the concentration of sulfuric acid in the electrolyte is measured, i.e. its specific gravity, the discharge amount or residual amount can be determined. The chemical change during charging is that the lead sulfate produced on the anode and cathode plates during discharge is decomposed and reduced to sulfuric acid, lead, and lead peroxide during charging. Therefore, the concentration of the electrolyte in the battery gradually increases, that is, the specific gravity of the electrolyte increases, and gradually returns to the concentration before discharge. This change indicates that the active substance in the battery has been reduced to a state where it can be re powered, When the lead sulfate at both poles is reduced to its original active substance, it is equivalent to the end of charging, and the cathode plate produces hydrogen, while the anode plate produces oxygen. At the final stage of charging, almost all of the current is used for water electrolysis, so the electrolyte will decrease. At this time, pure water should be used to supplement it.

AGM type batteries are batteries filled with dilute sulfuric acid, which is absorbed in ultra-fine glass fiber partitions and plates, with almost no flowing electrolyte. Most electric bicycle batteries sold on the market are AGM type batteries.

GEL gel battery has no free electrolyte after the electrolyte gel, so the probability of acid leakage is much lower than that of the previous battery; Its infusion amount is 10-15% more than dilute sulfuric acid, and it has less water loss, so the colloidal battery will not fail due to water loss; The injection of colloids increases the strength of the separator, protects the electrode plate, and compensates for the defect of the separator shrinking when encountering acid, making the assembly pressure not significantly reduced, which is one of the reasons why it has the ability to extend battery life; Colloids fill the gap between the separator and the electrode, reducing the internal resistance of the battery and improving its charging acceptance. So the over discharge, Shaanxi recovery capacity, and low-temperature charging and discharging performance of colloidal batteries are superior to AGM type batteries; The consistency of colloidal batteries is much better than that of similar AGM type batteries. There are four types of colloids that have been mass-produced domestically: gas-phase gel, silica sol, mixed sol, and organosilicon polymer gel.

The working principle of lithium-ion batteries is that during battery charging, lithium in the positive electrode material comes out, passes through the separator, and enters the negative electrode graphite; When the battery is discharged, lithium ions detach from the negative graphite and pass through the separator back into the positive electrode material. As charging and discharging progress, lithium ions continuously embed and detach from the positive and negative electrodes.

Lithium ion batteries are a type of secondary battery, which have many advantages such as high energy density, high current charging and discharging, no memory effect, low raw material cost, and environmental friendliness. Therefore, their sales have increased rapidly year by year since their introduction, and they will definitely become the winner in the future of secondary batteries. Since its inception in the 1990s, button batteries in electronic products, lithium batteries in mobile phones and DC digital products have also been applied to electric bicycles. However, the cost of lithium-ion batteries accounts for one-third to half of the cost of electric vehicles, far exceeding the proportion of lead-acid batteries in the entire vehicle. Moreover, due to the high specific energy and poor material stability of lithium batteries, they are prone to safety issues. With the development and maturity of technology, lithium-ion batteries will become the development trend of high-quality electric vehicles.