Lithium-ion batteries
1. Basic Introduction
A lithium-ion battery is a battery whose electrochemical system contains lithium (including metallic lithium, lithium alloys, lithium ions, and lithium polymers). Lithium-ion batteries can be broadly classified into two categories: lithium metal batteries and lithium-ion batteries. Lithium-ion batteries do not contain metallic lithium and are rechargeable. The fifth generation of rechargeable batteries, the lithium metal battery, was developed in 1996. Its safety, specific capacity, self-discharge rate, and performance-price ratio are all superior to lithium-ion batteries. Due to its high technological requirements, only companies in a few countries currently produce lithium metal batteries.
2. Working principle
(1) Lithium metal batteries:
Lithium metal batteries typically use manganese dioxide as the positive electrode material, lithium metal or its alloy metals as the negative electrode material, and a non-aqueous electrolyte solution.
Discharge reaction: Li + MnO2 = LiMnO2
(2) Lithium-ion batteries:
Lithium-ion batteries typically use lithium alloy metal oxides as the positive electrode material, graphite as the negative electrode material, and a non-aqueous electrolyte.
The reaction that occurs at the positive terminal of the charger is
LiCoO2 == Li(1-x)CoO2 + XLi+ + Xe- (electrons)
The reaction that occurs at the negative terminal of the charger is
6C + XLi + Xe- = LixC6
Overall reaction of the rechargeable battery: LiCoO2 + 6C = Li(1-x)CoO2 + LixC6
1. Lithium batteries have a long lifespan, are lightweight, and are small in size.
Lithium-ion battery electric bicycles currently come from a variety of brands, including Giant, Kaiqi, Jieaobi, and Tuer. The power performance of lithium-ion battery electric bicycles is similar to that of lead-acid battery (basic electric bicycles). Charging takes 6-8 hours, and depending on the battery capacity, they can travel 30-45 kilometers. They weigh only about 1/5 of lead-acid batteries. The biggest advantage of lithium-ion battery electric bicycles is their long lifespan. The high price of lithium-ion batteries globally is only superficially apparent; in reality, the cost is similar to that of lead-acid batteries. Currently, lithium-ion batteries generally have a 2-year warranty, while lead-acid batteries have a 1-year warranty.
2. Lithium batteries have activation-free characteristics.
It's important to note that lithium batteries enter a dormant state after being stored for a period of time, at which point their capacity is lower than normal, and their usage time is shortened. However, lithium batteries are easily activated; just 3-5 normal charge-discharge cycles are sufficient to activate the battery and restore its normal capacity. Due to the inherent characteristics of lithium batteries, they have virtually no memory effect. Therefore, users do not need special methods or equipment to activate new lithium batteries.
3. Lithium batteries have a memory effect.
Consumers have always worried about the memory effect when charging lead-acid and nickel batteries. However, with lithium batteries, everyone can breathe a sigh of relief, as they do not have a memory effect. If some consumers still don't know how to charge lithium batteries, they might want to read the following information.
Disadvantages of lithium battery electric vehicles:
1. The high price of lithium battery electric vehicles is mainly due to lithium batteries.
Currently, lithium battery electric bicycles are generally several hundred to a thousand yuan more expensive than lead-acid battery electric bicycles, making them difficult for consumers to accept in the market. Lithium batteries are lightweight, environmentally friendly, and do not cause pollution after disposal. Once the application technology matures and market sales increase, the price of lithium battery electric bicycles will decrease.
2. Overcharging lithium batteries can be counterproductive.
Lithium batteries and chargers automatically stop charging once the battery is fully charged; there is no "trickle" charging for 10+ hours as claimed by nickel-cadmium chargers. In other words, leaving your lithium battery on the charger after it's fully charged is pointless. Furthermore, no one can guarantee that the battery's charge/discharge protection circuitry will never change or that its quality will be flawless, so your battery will be constantly teetering on the edge of danger. This is another reason why we oppose prolonged charging.
Furthermore, on some electric vehicles, if the charger is not removed after a certain charging time, the system will not only fail to stop charging but will also begin a discharge-charge cycle. While the manufacturer may have its reasons for this practice, it is clearly detrimental to battery life. Therefore, after purchasing a lithium-ion battery electric vehicle, it is essential to consult the manufacturer or dealer to ensure proper battery maintenance.
3. The power performance of lithium batteries needs to be improved.
Lithium batteries are much less resistant to fluctuations in charge and discharge than lead-acid batteries. This is one of the main reasons why lithium batteries cannot be effectively used in high-power vehicles, resulting in reduced durability.
4. Lithium-ion batteries have prominent safety issues.
The safety of lithium batteries still needs improvement. The risk of lithium battery fires, combustion, and even explosions cannot be completely eliminated at present. Vehicle collisions can cause the battery's positive and negative electrode materials to rupture the separator. The instantaneous extremely high current during braking, when energy rapidly recharges into the battery, can also lead to short circuits, increased temperature, and potentially combustion or even explosion. The cause of the fire is the release of lithium ions due to collisions or short circuits, which ignite upon contact with air. Furthermore, the electrolyte in lithium-ion batteries is an organic electrolyte, which is more prone to ignition and combustion upon contact with air.
