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Analysis of Vehicle Battery: The Achilles' heel of New Energy Vehicle
As long as people have a basic understanding of new energy vehicles, they know that the biggest challenge in electric vehicle technology today lies in the difficulty of making breakthroughs in battery technology. This is because batteries are the core component that determines the performance, range, and cost of an electric vehicle.
Due to the high manufacturing costs of batteries, most electric vehicles cannot significantly improve their driving range within a limited budget, which limits their practical application. Compared to traditional fuel vehicles, this makes them less competitive. Without substantial government subsidies, it's hard for new energy vehicles to gain widespread acceptance.
Therefore, the importance of batteries in new energy vehicles is almost on par with the role of engines and transmissions in traditional cars. In this article, we'll take a closer look at current car batteries, explaining them in simple terms.
What do people care about when it comes to new energy vehicle batteries?
If you live in a first-tier city with restrictions on license plates, you might consider buying a new energy or even a pure electric vehicle. The cost per kilometer for electric vehicles is generally about one-tenth that of petrol vehicles, so power consumption isn't your main concern. Plus, most EVs offer strong acceleration, which is more than enough for daily commuting. However, many people buy cars not just for daily use but also for occasional long trips. That’s when the range on a single charge becomes crucial.
To achieve a longer driving range, you need a battery with as large a capacity as possible. But batteries themselves are bulky, and space inside the car is limited. So, the most important performance metric for a car battery is energy density. Other factors like power output, voltage, efficiency, and lifespan are also essential.
Energy density can be measured in two ways: volume (Wh/L) and mass (Wh/kg). Since electric vehicles typically use battery packs made up of multiple cells connected in series and parallel, and managed by a BMS, it's important to distinguish between the energy density of individual cells and the overall system.
Most manufacturers choose to purchase batteries from suppliers and design their own packaging and systems. This allows them to optimize the layout and performance of the battery pack.
What types of batteries are used in new energy vehicles?
Many people have heard of Tesla’s lithium batteries or BYD’s iron batteries. These are just a few examples of the many types of batteries used in electric vehicles. From a structural perspective, there are three main types: prismatic, pouch, and cylindrical batteries.
However, when considering the materials used, the classification becomes more complex. Common types include lead-acid, nickel-metal hydride, lithium-ion, zinc-air, and supercapacitors. Lead-acid batteries are still used in some low-speed electric vehicles due to their low cost, but they are outdated compared to newer technologies.
Currently, nickel-metal hydride and lithium-ion batteries are the most common. Nickel-metal hydride batteries are often used in hybrid vehicles, such as Toyota’s Camry Hybrid and Corolla Hybrid. They are known for their stability and reliability.
Lithium-ion batteries are now the dominant choice for new energy vehicles. They use compounds containing lithium for the positive electrode, carbon-based materials for the anode, and organic electrolytes. These batteries come in various shapes, including prismatic and cylindrical designs.
The main force behind new energy vehicles—lithium-ion batteries
In the past, lithium batteries were mostly based on binary compounds like lithium manganate, lithium phosphate, and lithium cobalt oxide. Now, the industry has shifted toward ternary lithium batteries, such as NMC (nickel-cobalt-manganese) and NCA (nickel-cobalt-aluminum).
BYD’s iron phosphate (LFP) batteries are known for their safety and lower cost, but they have lower energy density compared to other lithium options. They’re commonly used in passenger cars but are unlikely to be the future direction.
The focus now is on NMC and NCA batteries. NMC is preferred by most automakers due to its stability and cost-effectiveness. It can be further divided into different ratios, such as 111, 523, 622, and 811. The higher the nickel content, the greater the energy density and the lower the cost, making high-nickel batteries a growing trend.
Tesla uses NCA batteries, which have higher energy density but slightly lower stability and cost compared to NMC. Their latest 21700 cells have an energy density of around 300 Wh/kg.
Another key innovation is the use of silicon-carbon anodes, which help increase energy density. Tesla is leading the way in applying this technology in automotive batteries.
Battery Packs
Electric vehicle battery packs consist of many cells connected in series and parallel. The design depends on the type of cells, available space, cooling systems, and other factors. As a result, the same battery chemistry can be packaged in different forms to fit different vehicle layouts.
Typically, battery packs are divided into modules, each with cooling elements and soldered connections. These modules are then enclosed in insulation and frames before being installed in the vehicle. A battery management system (BMS) is included to monitor temperature, voltage, and other parameters, ensuring safe and efficient operation.
In summary, both individual battery cells and complete battery packs are seeing continuous improvements in energy density and cost reduction. This means that future electric vehicles will have longer ranges and lower prices, eventually putting real pressure on traditional fuel vehicles.