The "blade battery" developed by BYD looks like a neatly arranged paper cutter.

Each "blade battery" contains multiple "blades". Each blade is divided into many holding cavities, each containing an electric cell, and the whole blade is a module made up of multiple pole cores in series. On the whole, it gives the impression that it is very frivolous, but it is full of cells in the limited space.

For a long time, the mature power battery is composed of battery unit (CELL), battery module (Battery Module) and battery pack (Pack), which appear bulging when stacked together, while the blade battery ignores the inherent module concept of the traditional battery and directly lengthens the single battery and is fixed on the frame of the battery package. In the blade battery, the battery unit becomes a part of the structure, which is not only the power supply component, but also the beam of the battery package.

Although the blade battery is essentially a lithium iron phosphate battery and has not made a breakthrough in the battery structure, through the relayout, the volume energy density of the blade battery has increased by 50% compared with the traditional iron lithium battery-the equivalent of a car that used to run 400 kilometers. Now it can run 600 kilometers in one breath.

More powerful than iron lithium battery

Nowadays, most of the power batteries used in pure electric vehicles are lithium-ion batteries, which can be divided into ternary lithium batteries, lithium iron phosphate batteries, lithium manganate batteries, lithium cobalt batteries and so on. Among them, the most mainstream are the ternary lithium battery used by Tesla, Inc. and the lithium iron phosphate battery (referred to as lithium iron battery) used by BYD.

Compared with ternary lithium battery, iron lithium battery has many advantages:

Iron-lithium batteries generally have a cycle life of more than 3000 times, while ternary lithium batteries generally have a cycle life of more than half. Iron-lithium batteries are chemically stable and begin to decompose at 700800 ℃, while ternary lithium batteries decompose in less than 300 ℃. Iron-lithium batteries are cheap, while ternary lithium batteries use rare metal cobalt, which is becoming more and more expensive.

However, high-quality and inexpensive iron-lithium batteries have a fatal drawback. Due to differences in chemical properties, the energy density of ternary lithium batteries is about 70% higher than that of iron lithium batteries, so models with ternary lithium batteries generally run farther and faster.

The appearance of blade battery gives hope to iron-lithium battery.

The traditional lithium iron phosphate battery consists of a three-layer structure: cell, module and battery pack, in which the supporting and fixing structure of the cell and module will occupy a large part of the space.

On the other hand, the "blade battery" omits the module and most of the supporting structure, and is directly packaged by the battery, so the space utilization rate is greatly improved. In the same battery volume, you can now hold a lot more cells than before. According to data from BYD, the remodeling of the battery pack has increased the energy density per unit volume of the blade battery by 50%, which is equivalent to that of an electric car with a full capacity of 400 km, which can now run 600 km.

Safer than ternary lithium batteries

Although the ternary lithium battery is full of power for a long time, "thermal out of control" has always been a lingering nightmare.

In 2013, the chassis of a Tesla, Inc. Model S in Tennessee hit the fallen trailer hook, the battery pack at the bottom of the car was punctured by the hook, and the battery short-circuited and caught fire; in the same year, a Model S in Seattle hit a metal object in the middle of the road, the battery pack was damaged and the car began to ignite spontaneously.

In real life, the situation of piercing and piercing the battery occurs from time to time, and in the event of this situation, nine times out of ten, there will be a big problem with the ternary lithium battery.

The blade battery is far safer than the ternary lithium battery. In the words of Wang Chuanfu, chairman of BYD, "the new energy vehicle with blade battery will completely erase the word 'spontaneous combustion' from the dictionary of new energy vehicles."

To prove this, BYD released a video of the needle penetration test of the blade battery at the launch of the blade battery.

Acupuncture penetration test is recognized as the most stringent testing method for the safety of battery cells in the industry. This test requires a steel needle to pierce the battery cell, causing a large area of short circuit inside the cell.

In the test video, the ternary lithium battery experienced a sharp temperature change at the moment of acupuncture, the surface temperature quickly exceeded 500℃, and the eggs placed on the surface of the battery were blown up. After the traditional bulk lithium iron phosphate battery was pierced, there was no open flame, but there was smoke, and the surface temperature of the battery reached 200-400 ℃, and the eggs on the surface of the battery were scorched.

However, after the blade battery was pierced, the surface temperature remained at a stable level of 30-60 ℃, there was no smoke or fire, and the eggs on the battery surface were still flowing.

The blade battery can pass the needle test, which is inseparable from the stability of the iron-lithium battery itself.

Laboratory data show that the spontaneous combustion temperature of ternary lithium battery is 200℃. At this temperature, the cathode material of ternary lithium battery will begin to decompose to produce oxygen. Oxygen meets the flammable electrolyte inside the battery and is easy to self-ignite and explode at high temperature. The lithium iron phosphate battery has a spontaneous combustion temperature of 500-800 ℃ and does not release oxygen during charge and discharge, so it will only emit smoke and no open fire when it is punctured.

In terms of the stability of the iron-lithium battery itself, the blade battery is made into a thin strip with a larger heat dissipation area, and the battery circuit is long, so the heat is not easy to concentrate on the circuit, so it can maintain a stable temperature after being pierced, and the safety performance is greatly improved.

Although the blade battery looks beautiful, its battery life and safety still need to be tested in practical application.