How did the byd blade battery develop?
- What is a byd blade battery?
- Manufacturing process of byd blade battery
- Sandwich structure design of byd blade battery pack
- Test and evaluation method of byd blade battery system
- Six key characteristics of blade batteries
At present, the key performance indicators of power batteries mainly include six aspects: safety, life, low temperature, charging, power and energy. In 2020, ternary batteries have developed rapidly. And here is a list of top 10 ternary power battery manufacturers in China for you to refer to.
However, the stability of the ternary battery is much worse than that of the lithium iron phosphate battery (the thermal runaway temperature is above 500 ℃), so BYD began to launch the byd blade battery. Blade batteries have begun to enter the public.
What is a byd blade battery?
Byd blade battery refers to the flat and long battery cell like a blade, and is very similar to the shape of chewing gum. Although the byd blade battery has not made major innovations in materials, the positive electrode material is lithium iron phosphate, and the negative electrode material is artificial graphite. But the byd blade battery is a world first in construction and engineering.
Byd blade battery is a long cell solution (battery based on square aluminum shell), based on the size of BYD’s original cell (BYD used more 173 and 148 before) , by thinning the thickness of the cell and increasing the length of the cell, the cell is designed to be elongated and thinned.
Compared with the traditional technical battery system, the number of parts of the battery system using the byd blade battery is reduced by more than 40%. Although the specific energy density is only increased by 9%, the VCTP volume energy density can be increased by more than 50%, and the cost can be reduced by more than 30%.
So far, there have been at least 400 patents on byd blade battery layouts. Nowadays, there are three types of blade batteries: single-series blade batteries, multi-car blade batteries and multi-series square batteries, with high flexibility and a variety of lengths and thicknesses to choose from.
The internal structure of the multi-string byd blade battery is mainly composed of 1-cell aluminum shell, 2-pole core, 3-sampling wire harness, 4-protective film (inner), 5/7/8-insulator, 6-bottom cover, 9- Top cover plate and 10-protective film (outer).
Manufacturing process of byd blade battery
In terms of manufacturing process, there are generally two manufacturing processes for battery cells: winding and lamination processes. The byd blade battery adopts advanced high-speed lamination process, the length of the lamination pole piece can reach about 1000mm, the lamination tolerance is within ±0.3mm, and the single lamination efficiency is 0.3s/pcs.
The lamination process of the byd blade battery is to cut the positive and negative pole pieces and the diaphragm into a specified size, and then stack the positive pole piece, the diaphragm and the negative pole piece into a small cell unit, and then stack the small cell unit.
A large cell is formed in parallel, and then the cover plate, side plate, spacer etc. and sleeve are assembled to form a single byd blade battery cell. Compared with the winding process, the battery produced by the lamination process has better cycle characteristics and safety characteristics, which means longer life and better safety.
Generally speaking, the lamination process mainly consists of stirring, coating, roll-to-roll, die-cutting, lamination, welding, top sealing, liquid injection, preconditioning, air extraction and sealing, forming, forming and testing. However, each battery manufacturer can properly optimize the production process to be more suitable for their own production.
Due to the particularity of the large size of the byd blade battery, it can only be produced by the lamination process, and the large-scale high-speed lamination technology is even more difficult for all power battery manufacturers. This also reflects the advanced nature of BYD technology. According to BYD’s introduction, the production process of BYD blade batteries is mainly divided into several steps, such as batching, coating, rolling, lamination, assembly, baking, liquid injection and testing.
In addition to the high-speed lamination process, the byd blade battery also uses wide-width coating, wide-width rolling and ultra-thin aluminum shell manufacturing technologies, which are basically the first in mass production.
The maximum coating width of wide coating is 1300mm, the detection system accuracy is within ±0.5mm, the high speed is 70m/min, and both sides are coated at the same time. The maximum rolling width of wide rolling is 1200mm, the thickness tolerance is controlled within 2μm, and the high speed is 120m/min.
The ultra-thin aluminum shell manufacturing technology breaks through the constraints of the traditional deep drawing/extrusion process, and the innovative technology realizes the ultra-long aluminum shell manufacturing technology with a thickness of 0.3mm.
Sandwich structure design of byd blade battery pack
In terms of system integration, the sandwich structure design is innovatively used, and the structural concept of SVOLT panel is used for reference. The SVOLT panel has the characteristics of light weight, high strength and high rigidity.
The battery system based on the byd blade battery uses the battery array as the skeleton, and the upper cover, the bottom plate and the battery array are bonded into a whole through high-performance adhesives to achieve ultra-high integration efficiency, ultra-high strength and rigidity.
Test and evaluation method of byd blade battery system
The reliability evaluation of the battery system is a difficult problem. The current method is generally characterized by multiple experiments of vibration, cycle, temperature shock, high temperature and high humidity, but it is often found that the experimental results cannot match the test results of the whole vehicle. The multiple experiments, could not simulate the actual usage conditions.
The byd blade battery innovatively combines several factors of temperature, humidity, vibration and cycle. By studying the actual use conditions of multiple typical areas and combining the accelerated life test theory, a new set of reliability test evaluation methods is proposed. At present, simulation It takes about 2 months for the whole set of verification of 20W kilometers of the whole vehicle.
Six key characteristics of blade batteries
The byd blade battery proposes six key characteristics of super safety, super strength, super endurance, super low temperature, super life and super power.
In terms of material safety, the cathode material of the byd blade battery adopts lithium iron phosphate with better stability and lower cost. Since the start-up temperature of ternary NCM (thermal runaway temperature is 205°C-210°C) is much lower than that of lithium iron phosphate LFP (thermal runaway temperature is above 500°C), material decomposition is more likely to occur, and oxygen is generated when NCM material decomposes. The heat release rate of NCM is much greater than that of LFP, the decomposition rate is fast, and the total heat release of NCM is greater than that of LFP.
In terms of cell safety, based on the LFP material system and the unique structure of the byd blade battery, the byd blade battery can achieve no smoke or fire in the acupuncture test, the highest temperature is only about 60°, extrusion test, furnace temperature test and overcharge.
The test only emits smoke, no fire, no explosion, and its safety performance far exceeds the national standard in terms of furnace temperature and overcharge. At the same time, the byd blade battery system adopts a lightweight and high-strength SVOLT structure composite material protection board, which can effectively protect the bottom damage.
Based on the blade system, the modal can reach more than 80Hz, and the vibration life is more than 3 million km. The simulated collision can easily meet the 60g-level collision acceleration requirements, which is equivalent to 45km/h collision with a rigid barrier.
In terms of extrusion, the maximum extrusion force is 100-800kN, the battery pack is only slightly deformed, there is no smoke or fire. In terms of compressive strength, the current battery system based on blade batteries can withstand a pressure of 445kN, which is equivalent to the weight of a 45-ton truck.
Super battery life
The byd blade battery based battery system can easily achieve high endurance. The maximum power of the package body can exceed 100KWh (car). The A-Class sedan uses 60kWh of electricity and can achieve a cruising range of 500km. The B-class sedan uses 80kWh of electricity and can achieve a cruising range of 600km. The C-Class sedan uses 100kW of power and can achieve a cruising range of 700km.
Super low temperature
The charging time of LFP at 0°C is 2% better than that of NCM. The charging time of LFP at -10℃ is 1% different from that of NCM. The low-temperature discharge capacity of the byd blade battery can be maintained at 90% of normal temperature.
Super life is divided into storage life and cycle life, which are far greater than the service life requirements of the whole vehicle. The storage life is stored at 100% SOC, LFP is better than NCM811, and the LFP voltage window is lower, the electrolyte is more stable, and the capacity recovery rate of LFP during storage is much greater than that of NCM811. Cycle life 1C/1C, 100% DOD, LFP is better than NCM811, because LFP material structure, better stability, LFP cycle life > vehicle service life requirements.
Low temperature and low SOC, LFP has better power performance than NCM. At room temperature and low SOC, the performance of LFP is comparable to that of NCM. NCM dominates at high SOC, but LFP fully meets the demand. The instantaneous maximum power is 363kW, about 500 horsepower, and supports acceleration from 100 km/h in 3.9 seconds.
In general, blade batteries are recognized by users in the market due to their excellent performance. Major OEMs are also adopting byd blade battery solutions one after another, including major automakers such as Toyota and Ford. It is believed that in the future, the byd blade battery will develop more perfect.