Lithium-ion batteries are a new type of high-energy battery. 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 application in the 1970s. Due to their advantages such as high energy density, high battery voltage, wide operating temperature range, and long shelf life, they are widely used in military and civilian small electronic devices, such as mobile phones, portable computers, camcorders, and cameras, partially replacing traditional batteries. High-capacity lithium-ion batteries are now used in electric vehicles.
Features of lithium-ion batteries
1. The working voltage of a single lithium-ion battery is as high as 3.7V, which is three times that of nickel-cadmium and nickel-metal hydride batteries, and nearly twice that of lead-acid batteries. This is a major reason for the high energy density of lithium-ion batteries. Therefore, when forming a power battery pack with the same voltage, the number of lithium-ion batteries used in series is much less than that of lead-acid and nickel-metal hydride batteries. The more individual cells in a power battery pack, the higher the consistency requirements for the individual cells, and the more difficult it is to achieve a long lifespan. In actual use, after analyzing battery pack problems, it is generally found that one or two individual cells malfunction, leading to problems with the entire pack. Therefore, it is not difficult to understand why 48V lead-acid batteries have higher feedback rates than 36V lead-acid batteries. From this perspective, lithium-ion batteries are more suitable for power battery applications.
2. Lightweight and high energy density: Up to 150Wh/kg, twice that of nickel-metal hydride batteries and four times that of lead-acid batteries. Therefore, lithium batteries weigh one-third to one-quarter of the energy of lead-acid batteries of the same capacity. From this perspective, lithium batteries consume fewer resources. Furthermore, because lithium manganese oxide batteries use more abundant elements, their price may increase further compared to lead-acid and nickel-metal hydride batteries, while the cost of lithium-ion batteries will actually decrease. The weight of lithium batteries used in electric bicycles is 2.2-4 kg, while lead-acid batteries weigh 12-20 kg. Lithium batteries weigh approximately one-quarter to one-third of lead-acid batteries, about 10 kg lighter than lead-acid batteries (36V, 10Ah battery), a 70% reduction in battery weight and at least a 20% reduction in the overall weight of the vehicle. In addition, most lithium-ion electric bicycles are simple electric bicycles. Because the battery and the whole vehicle are light, the driving range is longer with the same voltage and capacity battery. Ordinary electric bicycles weigh more than 40 kilograms, while lithium-ion electric bicycles weigh between 7 and 26 kilograms. Women and the elderly can easily move them. They are also very convenient to ride by hand, making them suitable for both sports and leisure.
3. Compact Size: Reaching up to 400Wh/L, its volume is one-half to one-third that of lead-acid batteries. This provides more rational structural design and a more aesthetically pleasing appearance, offering greater design space and possibilities. Currently, the size and weight limitations of lead-acid batteries severely restrict designers' ideas, resulting in electric bicycles that are structurally and aesthetically homogenous, lacking originality and appearing uniform. The use of lithium batteries provides designers with greater space and conditions to showcase their design ideas and styles. However, this also leads to a wide variety of sizes for lithium-ion batteries used in electric bicycles, which is detrimental to the development of the lithium-ion battery industry. The lithium-ion battery industry needs to quickly formulate national standards for lithium-ion batteries used in electric bicycles to accelerate the replacement of lead-acid batteries by lithium-ion batteries in the electric bicycle sector. Of course, lithium-ion batteries are constantly evolving, and the different materials and processes used result in significant differences in battery size, making standardization a challenge.
4. Long cycle life: Up to 1000 cycles. With 60% capacity retained, the battery pack can withstand over 600 charge-discharge cycles, providing a service life of 3-5 years, approximately two to three times that of lead-acid batteries. With technological innovation and equipment improvements, battery life will continue to increase, and cost-effectiveness will become increasingly better.
5. Low self-discharge rate: less than 5% per month.
6. Wide operating temperature range and good low-temperature performance: Lithium-ion batteries can operate between -20℃ and +55℃, making them especially suitable for low-temperature use. In contrast, aqueous batteries (such as lead-acid batteries and nickel-metal hydride batteries) experience a significant performance reduction at low temperatures due to the decreased fluidity of the electrolyte.
7. No memory effect: Unlike nickel-cadmium and nickel-metal hydride batteries, it does not need to be discharged before each charge and can be charged anytime, anywhere. The depth of charge and discharge has little impact on the battery's lifespan; it can be fully charged and fully discharged. Our cycle test involved fully charging and fully discharging the battery.
8. Particularly suitable for power batteries: In addition to the high voltage of lithium batteries, the protection board of lithium power battery packs can perform high-precision monitoring of each individual cell, low-power intelligent management, and has complete overcharge, over-discharge, temperature, overcurrent, short circuit protection, lockout self-recovery functions, and reliable equalization charging functions, which greatly extends the battery's lifespan. Other types of batteries (such as lead-acid batteries) are prone to overcharging and over-discharging problems during use due to issues such as battery consistency and chargers (due to cost and other reasons, lead-acid battery packs cannot monitor and protect each individual cell).
9. Pollution-free: Lithium-ion batteries do not contain toxic substances, hence they are called "green batteries" and receive strong government support. Lead-acid and nickel-cadmium batteries, on the other hand, contain harmful substances like lead and cadmium, leading to stricter government regulation and control (e.g., the cancellation of export tax rebates for lead-acid batteries, the increase in lead resource tax, and restrictions on the export of lead-acid electric bicycles), thus increasing costs for related companies. Although lithium-ion batteries are pollution-free, from a resource conservation perspective, the recycling of lithium-ion batteries, the safety during recycling, and the cost of recycling also need to be considered.
10. Safety Hazards: Due to the high energy density and poor material stability of lithium-ion batteries, they are prone to safety issues. World-renowned manufacturers of mobile phone and laptop batteries (using lithium cobalt oxide and ternary lithium-ion batteries as cathode materials), such as Sanyo and Sony of Japan, require battery explosion rates to be controlled below 40 ppb (parts per billion). Domestic companies achieving ppm (parts per million) is considered good. However, the capacity of power batteries is hundreds of times that of mobile phone batteries, thus placing extremely high safety requirements on lithium-ion batteries. Although lithium cobalt oxide and ternary lithium-ion batteries have advantages such as lighter weight and smaller size, they are unsuitable for use as power batteries in electric vehicles.
11. High Price: Lithium-ion batteries with the same voltage and capacity are 3-4 times more expensive than lead-acid batteries. However, with the expansion of the lithium-ion battery market, cost reductions, performance improvements, and the increasing price of lead-acid batteries, the cost-effectiveness of lithium-ion batteries may eventually surpass that of lead-acid batteries.
