The fire and explosion caused by out of control battery heat has become the biggest hidden danger that hinders the development of new energy vehicles in China and even in the world. In this regard, ordinary consumers are particularly concerned. Whenever the news of new energy vehicle fire comes out, people will have a wide discussion. “The battery of electric vehicle is not safe” has become the mantra of “electric black”.
On March 29, after a long wait, BYD’s blade battery technology finally appeared. Wang Chuanfu, chairman of the company, said that the biggest breakthrough of blade battery technology compared with other battery technologies is that it has passed the most stringent safety test in the field of power battery, the needle test, and “completely erase the spontaneous combustion from the dictionary of new energy vehicles”. In addition to safety, the blade battery can also improve the space utilization inside the vehicle battery pack, so that the lithium iron phosphate battery pack with low energy density can also reach the level of lithium ternary battery, so as to improve the vehicle range.
For the advantages and effects of blade battery, Wang Chuanfu and he long, chairman of Fudi battery company, the manufacturer of blade battery, had a two-hour “Amway”. But in terms of technical principles, how is this black technology realized? Why is this technology the most important killer for BYD?
(structure principle of BYD blade battery)
The origin of the name “blade battery” is the unique battery shape. Different from the traditional square battery, the positive plate, negative plate and diaphragm of blade battery are made into rectangular sheet structure. The dimensions of the positive and negative plates are shown in the figure, and the aspect ratio exceeds 10:1. After laminating and assembling the cover plate, side plate and spacer ring, the cell is formed by casing. Compared with the nearly 1 meter length and 9 cm width of the whole cell, the cell thickness is only 13.5 mm, so the so-called “blade battery” is also worthy of the name.
There are many reasons for BYD to do so. Its core purpose is to improve the safety of the battery, increase the space utilization of the battery pack, and increase the competitiveness of its main LiFePO4 battery. First of all, on the basis of the laminated structure, BYD also applied high-temperature “ceramic battery” technology on the blade battery, that is, high-temperature ceramic layer with high-temperature resistance and insulation performance (covering the ear and pole) was fully used in the high-risk safety site. These measures make the cell in the event of internal short circuit, will not have the same violent reaction as the ternary lithium battery. In fact, even in the industry’s “most stringent” acupuncture experiment, the highest temperature of blade battery is only about 60 ℃. Combined with LiFePO4 battery material with more stable structure, the probability of spontaneous combustion of blade battery due to thermal runaway is greatly reduced.
(comparison of thermal stability of blade battery)
However, even for the ncm811 ternary lithium battery with the highest energy density, there are not many fire cases caused by the thermal runaway of the battery. In fact, the excessive rendering of the outside world makes the electric vehicle, a new thing, bear too much burden. In fact, at this stage, the biggest reason that hinders it from entering ordinary people’s homes is that people’s anxiety about endurance cannot be solved. Especially for the lithium iron phosphate battery with “natural short board” in energy density, to improve the system energy density of battery pack, we can only start from the perspective of engineering structure. Blade battery is the latest achievement of this route.
As we all know, both ternary lithium batteries and traditional square lithium iron phosphate batteries need to be composed of battery cells, and then the battery pack is composed of modules arranged by modules. Among them, the battery pack also needs to add transverse and longitudinal beams to strengthen the structure. In addition, the modules also need to connect the wiring harness, which takes up the valuable internal space of the battery pack. The blade battery does not need a module and can be directly composed of a battery pack. What’s more, the battery pack of blade battery has better structural strength in both horizontal and longitudinal directions with the help of the structure design of closely arranged battery structure and honeycomb aluminum plate. More importantly, this mode eliminates the transverse rail in the battery pack and improves the overall space utilization. According to reports, the space utilization rate of traditional batteries is about 40%, while that of blade batteries can be increased to 60%.
(comparison between blade battery pack and traditional battery pack)
Finally, in terms of improving the competitiveness of LiFePO4 battery, blade battery is expected to help BYD’s “unique skill” – LiFePO4 battery ushered in glory again. We should know that at present, all the pure electric buses provided by BYD for major cities in China and even the world use lithium iron phosphate batteries. In addition to reducing the vehicle cost, its core purpose is safety. After all, safety is more important than anything for buses that often carry dozens or even hundreds of passengers and run for a long time every day. However, in the field of passenger cars, especially private cars, due to the “baton” effect of high energy density pursued by national and local subsidies for new energy vehicles in the past, automobile enterprises and battery manufacturers are focusing on improving the energy density of batteries. As a result, even BYD, which has previously focused on lithium iron phosphate batteries, has begun to work on ternary lithium batteries.
However, with the decline of subsidies, the blade battery with better battery pack energy density has ushered in a better market prospect. After all, even Tesla is working on cobalt free batteries to reduce vehicle costs. Therefore, LiFePO4 battery, which has gone through market testing, is expected to regain its former glory.
For battery safety and cost control of electric vehicles, BYD has handed over the “hard core” answer of blade battery. According to the company’s plan, this new battery technology will be carried on the new cars launched this year and the most advanced model on BYD’s product line so far – “Han”. It is reported that this is a NEDC car with a driving range of 600 km and a acceleration of 3.9 seconds per 100 km. Obviously, the blade battery will form a combination with the Han model, which has become the core strategy of BYD in 2020.
(preview of BYD’s “Han”
Although China’s government has just announced that the purchase tax and subsidy policy of new energy vehicles will continue until 2022, in the post subsidy era, every automobile enterprise needs to find its core competitiveness in the field of new energy vehicles. After all, the influence of the policy is gradually fading, and the market will become the only standard to test the competitiveness of electric vehicles. As an automobile enterprise that has mastered the core component ability of battery, BYD’s future is obviously more promising.
Editor in charge: WV