Anatomy of electric vehicle safety
1. Battery safety
Among the core components of electric vehicles, the safety of batteries is undoubtedly the focus of the most attention. Batteries, as carriers of energy, can have catastrophic consequences if they fail. It is not difficult to recall those heart-wrenching news reports that an electric car suddenly caught fire while driving, and the occupants of the car were unable to escape and were killed. The root cause behind this is often thermal runaway of the battery.
Thermal runaway refers to a sharp increase in the temperature inside the battery due to various reasons, which in turn triggers a series of uncontrollable chemical reactions, which eventually leads to the combustion of battery components. There are many causes of thermal runaway, such as short circuit, overcharge and overdischarge, mechanical extrusion damage, etc. Once thermal runaway begins to spread within a single battery module, it can quickly lead to a "domino effect" of the entire battery pack, where temperatures can exceed 500 degrees Celsius within minutes, releasing large amounts of heat and toxic gases.
In order to prevent problems before they occur, electric vehicle manufacturers have put a lot of effort into battery design. First of all, the battery management system (BMS) undertakes the important task of monitoring and protection, always detecting the temperature, voltage, current and other parameters of the battery, and once an abnormality is found, it will immediately trigger protection measures, such as cutting off the power supply, forced refrigeration, etc. The modular design of the battery can also isolate the thermal runaway diffusion to a certain extent. The structural design of the battery pack is also very important, and it needs to be strong enough to resist crushing and impact, and avoid thermal runaway caused by battery damage.
Second, the safety of the whole vehicle
In addition to the safety of the battery itself, the design concept of the whole vehicle is also related to safety. In terms of collision safety, electric vehicles are fundamentally different from traditional fuel vehicles. Without the volume and weight of the engine and fuel tank, electric vehicles can place the battery pack on the underbody, which not only lowers the center of gravity to improve handling, but more importantly, the battery pack is less likely to be hit head-on in the event of a collision.
Although the location of the battery pack is relatively safe, it also brings new challenges to the design of the body structure. In order to protect the occupants in the event of a side or rear collision, the vehicle must be strong enough to maintain an escape space. The application of new materials and processes, such as aluminum alloys, carbon fibers and thermoforming processes, has contributed to improving the rigidity of the body.
In addition to passive safety, active safety is also a key direction for the development of electric vehicles. The reliability of automated driving assistance systems is directly related to driving safety. We've all heard of Tesla's "stall gate" incident, which was caused by a malfunction of the autopilot system, which caused the vehicle to accelerate out of control on the highway, which eventually led to a tragedy. There is still a long way to go in terms of artificial intelligence algorithms, hardware sensors, etc.
3. Navigation capacity
For electric vehicle owners, range is undoubtedly the most important concern. Compared with fuel vehicles with gas stations, the charging infrastructure of electric vehicles is still thin, and long-distance driving will inevitably encounter "fan anxiety". The determining factor of the sailing capacity mainly depends on the energy density of the battery.
At present, the mainstream electric vehicle batteries mainly use ternary lithium batteries, and their energy density is about 200-300Wh/kg, which is much higher than the 100-150Wh/kg of lithium iron phosphate batteries. This means that ternary lithium batteries can store more power at the same weight, so they have a longer range. For example, Volkswagen's all-electric SUV "ID4 X", with its large 83.4 kWh battery version, has an all-electric range of up to 550 km.
The increase in energy density often comes at the expense of some safety. The thermal stability of ternary lithium batteries is relatively poor, and once thermal runaway occurs, the consequences will be unimaginable. Therefore, there is a trade-off between safety and battery life in battery selection. The advent of new batteries such as solid-state batteries is expected to have breakthroughs in both safety and energy density.
In addition to the battery itself, the design of the vehicle will also affect the flight capability. Volkswagen's MEB platform is a good example of this, with a high battery capacity of 83.4 kWh by optimizing the layout of the battery modules and maximizing the use of chassis space. The lightweight design of the vehicle also reduces energy consumption, which in turn extends the range.
Fourth, development prospects
Throughout the development of electric vehicles, it is not difficult to find that battery technology has always been a key factor restricting its development. From lead-acid batteries, nickel-metal hydride batteries, to today's lithium-ion batteries, every iteration of technology has injected new vitality into electric vehicles. And in the foreseeable solid-state battery will likely become the next revolutionary technology.
The biggest advantage of solid-state batteries is safety, and the use of solid-state electrolytes can effectively avoid the risk of leakage from traditional liquid electrolytes. At the same time, the energy density of solid-state batteries will also be further improved, and it is expected to break through the ceiling of 300Wh/kg. The commercialization process of solid-state batteries is not smooth, and there are still many technical problems to be overcome, such as the ionic conductivity of electrolyte materials and the interface compatibility between electrodes and electrolytes. With the continuous increase in scientific research investment, it is believed that solid-state batteries will eventually come out.
In addition to the battery technology itself, the development of electric vehicles is also inseparable from the construction of infrastructure. The layout density and charging efficiency of charging piles will directly affect the user's experience. At present, the mainland has started the construction of new energy vehicle charging piles, and by 2025, it plans to build more than 6 million new public charging piles. The development of electric vehicles also needs strong policy support, such as purchase subsidies, exemption from vehicle and vessel tax and other preferential measures, in order to further expand the popularization.
Although there are still some shortcomings in terms of safety and flight capability, the development prospects of electric vehicles are bright. With the continuous emergence of new technologies and the full support of infrastructure and policies, we have reason to believe that electric vehicles will eventually become the mainstream force in the automotive industry.