The technology of lithium-ion battery systems for vehicles has become a bottleneck for the popularization of electric vehicles. It is necessary to explore and break through in many aspects, including material development, battery design, processing and manufacturing, system integration, and business models.
1. Classification of power lithium batteries for new energy vehicles
New energy vehicle power lithium batteries can be divided into two main categories: storage batteries and fuel cells. Storage batteries are used in pure electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); fuel cells are used in fuel cell vehicles (FCVs).
1.1 Storage Battery
Batteries are the sole power source for the drive system in pure electric vehicles, and important types include nickel-metal hydride (NiMH) and lithium-ion batteries. Currently, lithium-ion batteries are in a phase of rapid development and are used in new energy vehicles such as the Nissan Leaf, Toyota Prius plug-in, Tesla Model S, GM Volt, Ford Focus EV, and BMW i3. Furthermore, lithium resources are relatively abundant and inexpensive, making lithium-ion batteries arguably the most promising power lithium battery type currently on the market. A performance comparison of the four types of batteries is shown in Figure 1.
1.2 Fuel Cell Power Battery
Fuel cell batteries are devices that directly convert the chemical energy of fuel and oxidant into electrical energy through an electrode reaction. Fuel cell batteries do not require recharging and have advantages such as high energy density, long lifespan, low maintenance, and the ability to provide continuous high-power supply. Furthermore, fuel cell vehicles can achieve the same driving range as gasoline-powered vehicles.
Based on the different electrolytes, fuel cell batteries can be divided into five categories: alkaline fuel cell batteries, phosphoric acid fuel cell batteries, proton exchange membrane fuel cell batteries, molten carbonate fuel cell batteries, and solid oxide fuel cell batteries. Currently, proton exchange membrane fuel cell batteries are widely used in fuel cell vehicles and are a highly competitive battery type in the future field of lithium-ion batteries for new energy vehicles.
2. Overview of New Energy Power Lithium Battery Industry Technology
Because the usage of lithium-ion batteries for vehicles differs significantly among different types of new energy vehicles, their performance requirements also vary considerably. HEVs, powered by gasoline engines, emphasize acceleration and hill-climbing capabilities, thus prioritizing battery specific power (requiring a high specific power of 800-1200 W/kg); PHEVs and EVs, powered entirely by batteries, emphasize range after charging, thus focusing on battery specific energy (requiring a specific energy of 100-160 Wh/kg) (see Table 1).
Due to significant differences in performance, materials, and cost, different types of power lithium batteries have different application prospects. Currently, nickel-metal hydride power lithium batteries are the most technologically mature, but lithium-ion batteries have achieved the most commercial success, while fuel cell power batteries are widely regarded as a long-term goal.
