Basic Understanding of Lithium Power Batteries

Lithium power batteries are a new type of high-energy battery developed successfully in the 20th century. The negative electrode of this battery is metallic lithium, while the positive electrode uses materials such as MnO2, SOCL2, and (CFx)n. They entered practical use in the 1970s. With advantages such as high energy density, high battery voltage, wide operating temperature range, and long storage life, lithium power batteries have been widely used in both military and civilian applications, such as mobile phones, laptops, cameras, and have partially replaced traditional batteries. High-capacity lithium batteries have been tested in electric vehicles and are expected to become one of the main power sources for electric vehicles in the 21st century, as well as being applied in satellites, aerospace, and energy storage.

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1.High working voltage per cell

The voltage is three times that of nickel-cadmium batteries and nickel-metal hydride batteries, and nearly twice that of lead-acid batteries. This is an important reason why lithium power batteries have higher energy density. Therefore, when forming power battery packs with the same voltage, lithium power batteries require significantly fewer cells to be connected in series compared to lead-acid batteries and nickel-metal hydride batteries. If there are more cells in the power battery pack, the consistency requirements of individual cells within the battery pack are higher, making it more difficult to achieve long lifespan. In practical use, when there are issues with the battery pack, it is often traced back to one or two individual cells, highlighting why a 48V lead-acid battery may offer better performance feedback compared to a 36V lead-acid battery. From this perspective, lithium batteries are more suitable for power battery applications. For example, a 36V lithium battery requires only 10 cells, while a 36V lead-acid battery requires 18 cells, equivalent to three sets of 12V batteries, with each 12V lead-acid battery comprising six cells.

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2.Lightweight with high energy density

Up to 150Wh/kg, which is twice that of nickel-metal hydride batteries and four times that of lead-acid batteries. Consequently, the weight of lithium batteries is only one-third to one-fourth of lead-acid batteries with the same energy capacity. From this angle, lithium batteries consume fewer resources, and since lithium manganese oxide, a key component in lithium batteries, is more abundant, the cost of lithium power batteries may decrease further. The weight of lithium batteries for electric bicycles ranges from 2.2 to 4 kilograms, while lead-acid batteries weigh between 12 to 20 kilograms. Lithium batteries weigh approximately one-fourth to one-third that of lead-acid batteries, making lithium batteries about 10 kilograms lighter for the same voltage and capacity (36V, 10Ah battery). This weight reduction in batteries leads to a 70% reduction in overall vehicle weight and at least a 20% reduction in total vehicle weight. Additionally, since lithium electric bicycles are generally lightweight, with battery and vehicle weights reduced, they offer longer travel distances for the same voltage and capacity batteries, making them more suitable for leisure and commuting purposes.

3.Compact size

With energy densities of up to 400Wh/L, lithium batteries occupy only half to one-third of the volume of lead-acid batteries. This provides designers with more flexibility in creating more rational structures and aesthetically pleasing designs. Currently, due to the constraints imposed by the volume and weight of lead-acid batteries, designers’ creativity in electric bicycle design is greatly limited, resulting in a uniform and monotonous appearance of electric bicycles. However, the use of lithium batteries offers designers greater space and opportunities to showcase their design concepts and styles. Nevertheless, the diverse sizes of lithium batteries for electric bicycles present challenges for standardization in the lithium battery industry, which could hinder its development. Therefore, it is essential to establish national standards for lithium batteries used in electric bicycles to accelerate the replacement of lead-acid batteries with lithium batteries in the electric bicycle field. Additionally, as lithium battery technology continues to evolve, there are significant differences in volume among batteries using different materials and manufacturing processes, posing a challenge for standardization.

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4.Long cycle life

Lithium power batteries can withstand up to 1000 cycles, with capacity retention of 60%. A battery pack can achieve over 600 cycles of 100% charge and discharge, with a lifespan of 3 to 5 years, which is two to three times that of lead-acid batteries. With technological advancements and equipment improvements, the lifespan of batteries is expected to increase, resulting in higher cost-effectiveness.

5.Low self-discharge rate

The self-discharge rate of lithium power batteries is less than 5% per month.

Overall, lithium power batteries offer numerous advantages such as high voltage, lightweight with high energy density, compact size, long cycle life, and low self-discharge rate, making them ideal for various applications ranging from small electronic devices to electric vehicles and energy storage systems.

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