I. Different properties.
Power lithium batteries refer to batteries that provide power for transportation vehicles, generally as opposed to small batteries that provide energy for portable electronic devices. Ordinary lithium batteries are primary batteries that use lithium metal or lithium alloy as the negative electrode material and a non-aqueous electrolyte solution; they are different from rechargeable lithium-ion batteries and lithium-ion polymer batteries.
II. Different battery capacity.
When both are new batteries and the battery capacity is tested with a discharge tester, the capacity of power lithium batteries is generally around [value omitted in the original text], while ordinary lithium batteries have a capacity above 2000 mAh, and some can reach 3400 mAh.
III. Different discharge power.
A single 4200 mAh power lithium battery can discharge all its power in just a few minutes, but an ordinary lithium battery cannot do this at all. Therefore, the discharge capability of ordinary lithium batteries cannot compare with that of power lithium batteries at all.
The biggest difference between power lithium batteries and ordinary lithium batteries is their high discharge power and high specific energy. Since power-type lithium batteries are mainly used for vehicle energy supply, they must have higher discharge power than ordinary batteries.
The characteristics of lithium power batteries are described as follows:
- The operating voltage of a single cell is as high as 3.7 V, three times that of nickel-cadmium and nickel-metal hydride batteries, and nearly twice that of lead-acid batteries. This is also an important reason why lithium power batteries have high specific energy. Therefore, when assembling a power battery pack of the same voltage, the number of lithium power batteries connected in series will be much smaller than that of lead-acid and nickel-metal hydride batteries.
- Light weight and high specific energy, up to 150 Wh/kg, twice that of nickel-metal hydride batteries and four times that of lead-acid batteries. Therefore, for the same energy, its weight is one-third to one-quarter that of lead-acid batteries. From this perspective, lithium batteries consume fewer resources. Moreover, because the reserves of elements used in lithium manganese oxide batteries are relatively abundant, while lead-acid and nickel-metal hydride batteries may further increase in price, the cost of lithium power batteries may actually decrease further.
- Small size, up to 400 Wh/L; its volume is one-half to one-third that of lead-acid batteries. This provides design conditions, design space, and possibilities for a more reasonable structure and a more attractive appearance. At present, owing to the limitations of the volume and weight of lead-acid batteries, designers’ design ideas are greatly constrained, causing today’s electric bicycles to be “all alike" in structure and appearance—similar, identical, and monotonous.
- Long cycle life, with up to 1,000 cycles. At a capacity retention of 60%, the battery pack can achieve more than 600 100% charge-discharge cycles, with a service life of 3–5 years, about two to three times that of lead-acid batteries. With technological innovation and improved equipment, battery life will become longer and longer, and cost performance will become higher and higher.
- Low self-discharge rate, less than 5% per month.
- Wide allowable operating temperature range and good low-temperature performance. Lithium power batteries can operate between -20°C and +55°C and are especially suitable for low-temperature use. Aqueous batteries (such as lead-acid and nickel-metal hydride batteries), however, experience greatly reduced performance at low temperatures because the electrolyte’s fluidity deteriorates.
- No memory effect, so before each charge there is no need to discharge as with nickel-cadmium and nickel-metal hydride batteries; they can be charged anytime and anywhere. The depth of charge and discharge has little effect on battery life, so full charge and full discharge are permissible; our cycle tests are carried out with full charge and full discharge.
