Battery life: the inherent anxiety of electric vehicles

The core feature of solid-state batteries is that they replace the liquid electrolytes of traditional batteries with solid-state electrolytes. While ensuring the stability of physical properties, they can improve the energy density, charging efficiency and safety of batteries. Toyota, BMW, Samsung, Volkswagen and other industry giants have invested in the research of solid-state batteries, and power battery giants such as CATL, Panasonic and LG Chem have also laid out their plans in the field of solid-state batteries.

Previously, Samsung demonstrated a high-performance, long-life all-solid-state battery, which for the first time proposed the use of a silver-carbon (Ag-C) composite material layer as the anode, giving the battery a larger capacity, longer cycle life, and improved overall safety. The battery's energy density is increased to 900Wh/L, allowing electric vehicles to have a range of 800 kilometers and a cycle life of more than 1,000 times.

NIO also released a 150kWh solid-state battery with an energy density of up to 360Wh/kg. The range of the NIO ET7 equipped with this battery pack will exceed 1,000km.

As mentioned above, battery energy density can directly affect the endurance, so how to improve the battery energy density? There are two ways to measure the energy density of power batteries: the energy density of battery cells and the energy density of battery systems. Based on these two methods, the energy density of batteries can be increased by increasing the size of the original battery to achieve the effect of expanding the capacity, or by improving the battery grouping efficiency and making the most of every inch of space on the premise of safety, thereby increasing the system energy density. The battery pack can be made lighter in the following ways:

The cost of electric vehicles is generally higher than that of fuel vehicles, even up to 40% or more, and battery costs are a large part of it. The power battery is the "heart" of the electric vehicle. The brakes, power system and other key systems all rely on battery power to operate, and the cost of the battery pack accounts for about a quarter of the total cost of the electric vehicle. Therefore, the development of electric vehicles needs to be driven by the reduction of power battery costs. There are three ways to reduce the cost of power batteries: one is to reduce the cost of raw materials, the second is to improve the production process to form economies of scale, and the third is technological progress and breakthroughs (such as reducing the cost of the Pack link).

Material costs account for about 80% of the cost of power battery systems, of which the four main materials, including positive electrode, negative electrode, electrolyte, and separator, account for about 50%-60% of the total battery cost. Among them, the positive electrode accounts for the largest proportion, with a single GWh investment of 90 million to 100 million yuan, which is twice that of the separator, 6 times that of the negative electrode, and 15 times that of the electrolyte.

At present, the commonly used positive electrode materials include modified lithium manganese oxide, lithium iron phosphate, ternary materials and lithium-rich manganese base, etc. Removing "cobalt" and reducing costs is the direction that the industry has been working hard on. In terms of negative electrode materials, the specific capacity of silicon-based negative electrode materials can reach 4200mAh/g, which is much higher than the theoretical specific capacity of graphite negative electrode 372mAh/g. It is a better choice to replace graphite negative electrode, and using silicon-carbon composite materials to improve battery energy density has been recognized by the industry as one of the development directions of lithium-ion battery negative electrode materials.

The power battery pack in an electric vehicle is an energy storage unit that drives the vehicle after the single cells are connected in series and parallel, plus some management and cooling systems. In the mainstream battery pack structure, an electric vehicle power battery pack is mainly composed of three levels: battery pack → battery module → battery cell. The structural parts and connectors of the module and pack link account for 15%-20% of the power battery cost. Some manufacturers reduce the cost of battery pack modules by using fewer modules or no modules. Among them, BYD's "blade battery" technology and CATL's "CTP" technology are relatively well-known.

CTP (cell-to-package) technology, also known as the module-free solution, greatly reduces the use of redundant components, thereby reducing battery costs and achieving lightweight battery pack design. According to official website information, CATL's CTP technology increases the volume utilization of battery packs by 15% to 20%, reduces the number of parts by 40%, and improves production efficiency by 50% by simplifying the module structure.

In recent years, the cost of power batteries has shown a clear downward trend. According to a research report by Morgan Stanley, the price of electric vehicles is expected to drop to around US$5,000 per vehicle (approximately RMB 32,500) in the next 10 years. It has to be said that this is an attractive price. With the advancement of technology, the three major anxieties surrounding the endurance of electric vehicles will gradually ease or even be completely resolved.