Lithium-ion batteries are divided into single cells, battery packs, battery stacks, and battery stations according to their own scale at work. The three main application areas require the energy and combination of lithium-ion batteries, as shown in Figure 1.1. At the group level, you can focus on pursuing specific characteristics. At this time, you can use new electrode materials and electrolyte systems to a certain degree of “risk”. After the power source energy scale increases, the consistency between single cells becomes very important. The safety and effective capacity of the battery stack / station (this may be solved by electronic circuits to prevent the entire system capacity from being affected by the "worst" battery). "At this time, it is very risky to rush to use a new electrode material / electrolyte system.

   Figure 1.2 is a comparison of the specific characteristics of internal combustion engines and various chemical power sources. The specific power of pure physical capacitors is on the order of 5X105W · h / kg, which is the highest. The basic mechanism of energy storage is the electric double layer charge rearrangement at the interface; electrochemical Capacitors involve the mass-capacitance mechanism. The valence state of some components at the interface will change, so the response speed is slower, and the specific power parameter is smaller than that of a pure physical capacitor. The specific power range of a capacitor is wide. Figure 1.1 shows that the specific power of a lead-acid battery is not as good as that of a lithium-ion battery. It seems to be different from the feeling. It should be larger than a lithium-ion battery in people's perception. This is because the battery (group, stack , Station) under the premise of the total mass, for example, if the car starter battery is changed to a lithium battery, the mass will be reduced by at least 60% to 70%.

Figure 1.1 Requirements for energy and combination of lithium ion batteries in three main areas

Figure 1.2 Specific characteristics of internal combustion engine (in the box in the figure) and various chemical power sources

  In summary, the performance of the internal combustion engine is still the best, while taking into account the specific energy and specific power.