The blade battery developed by BYD looks like a bunch of neatly arranged paper cutters.
Each blade battery contains multiple blades. Each blade is further divided into multiple housing cavities, and each housing cavity contains a battery cell. The entire blade is a module composed of multiple cells connected in series. Overall, it gives the impression of being very thin and light, yet packed with battery cells in a limited space.
The blade battery is like a set of neatly arranged paper cutters. Traditionally, mature power lithium batteries consist of three parts: battery cells, battery modules, and battery packs, stacked together to create a bulky appearance. The blade battery, however, disregards the traditional module concept, directly elongating the individual battery cells and fixing them to the edge of the battery pack. In the blade battery, the battery cell becomes part of the structure, serving as both a power supply component and a beam of the battery pack.
Although the Blade Battery is essentially a lithium iron phosphate battery and has not made any breakthroughs in battery structure, through redesign, the volumetric energy density of the Blade Battery is 50% higher than that of traditional lithium iron phosphate batteries. This means that a car that could previously travel 400 kilometers can now travel 600 kilometers in one go.
More powerful than lithium iron phosphate batteries
Currently, most pure electric vehicles use lithium batteries, which can be further divided into ternary lithium batteries, lithium iron phosphate batteries, lithium manganese oxide batteries, and lithium cobalt oxide batteries, depending on the cathode material. Among these, the most mainstream are the ternary lithium batteries used in the TSLA and the lithium iron phosphate batteries (referred to as lithium iron phosphate batteries) used by BYD.
Compared with the two mainstream power lithium batteries and ternary lithium batteries, lithium iron phosphate batteries have many advantages:
Lithium iron phosphate (LiFePO4) batteries generally have a cycle life of over 3000 cycles, while ternary lithium batteries have only half that number. LiFePO4 batteries are chemically stable, only beginning to decompose at 700-800℃, while ternary lithium batteries decompose at less than 300℃, making them extremely flammable. LiFePO4 batteries are cheaper to manufacture, while ternary lithium batteries require the rare metal cobalt, making them increasingly expensive.
However, the cost-effective lithium iron phosphate battery has a fatal flaw. Due to differences in chemical properties, the energy density of ternary lithium batteries is about 70% higher than that of lithium iron phosphate batteries. Therefore, vehicles equipped with ternary lithium batteries generally travel farther and faster.
A comparison of the two types of batteries: The emergence of the blade battery has given hope to lithium iron phosphate batteries.
Traditional lithium iron phosphate batteries consist of a three-layer structure: cells, modules, and battery packs, with the supporting and fixing structures for the cells and modules occupying a significant portion of the space.
Traditional lithium iron phosphate batteries, while blade batteries eliminate the need for modules and most of the supporting structures, directly assembling the cells into a pack, significantly improving space utilization. Much more cells can now be packed into the same battery volume. According to data from BYD, the redesign of the battery pack increases the energy density per unit volume of the blade battery by 50%, meaning that an electric vehicle that previously had a range of 400 kilometers on a full charge can now travel 600 kilometers.
Safer than ternary lithium batteries
Despite the long range and powerful performance of ternary lithium batteries, thermal runaway has always been a persistent nightmare for them.
In 2013, a TSLA Model S in Tennessee, USA, crashed into a tow hook that had fallen onto the road. The tow hook punctured the battery pack under the car, causing a short circuit and a fire. That same year, a Model S in Seattle struck a metal object in the middle of the road, damaging the battery pack and causing the car to spontaneously combust. In real life, incidents of batteries being punctured or penetrated are not uncommon, and in such cases, ternary lithium batteries are almost always in serious danger.
The TSLA battery is known for its spontaneous combustion, but the blade battery is far safer than ternary lithium batteries. In the words of BYD Chairman Wang Chuanfu, new energy vehicles equipped with blade batteries will completely erase the word "spontaneous combustion" from the dictionary of new energy vehicles.
To demonstrate this, BYD released a video of a needle penetration test of the Blade Battery at the launch event.
The needle penetration test is recognized in the industry as the most stringent safety testing method for battery cells. This test requires piercing the battery cell with a steel needle, causing a large-area short circuit inside the cell.
In the test video, the ternary lithium battery exhibited a dramatic temperature change upon being punctured, with its surface temperature rapidly exceeding 500°C, causing an egg placed on its surface to explode. In contrast, a traditional block-shaped lithium iron phosphate battery, when punctured, did not produce an open flame, but emitted smoke, and its surface temperature reached 200-400°C, charring the egg placed on its surface.
However, even after the blade battery was punctured, its surface temperature remained stable at 30-60°C, without smoke or fire, and the egg on the battery surface remained liquid.
The fact that the blade battery can pass the needle penetration test is inseparable from the inherent stability of the lithium iron phosphate battery itself.
Laboratory data shows that the auto-ignition temperature of ternary lithium batteries is 200℃. At this temperature, the positive electrode material of ternary lithium batteries begins to decompose, releasing oxygen. This oxygen, when it comes into contact with the flammable electrolyte inside the battery, can easily ignite and explode at high temperatures. In contrast, the auto-ignition temperature of lithium iron phosphate batteries is 500-800℃. They do not release oxygen during charging and discharging, so when punctured, they only emit smoke without open flame.
In terms of the stability of lithium iron phosphate batteries, the blade battery is made into a thin and long strip shape, with a larger heat dissipation area. At the same time, the battery circuit is long, and heat is not easy to concentrate on the circuit. Therefore, it can maintain a stable temperature even after being punctured, greatly improving safety performance.
Although the blade battery looks appealing, its battery life and safety still need to be tested in real-world applications.
