Sponge silicon negative electrode battery + four-in-one electric drive, a brief analysis of the core technical advantages of AION LX Plus

At the 2021 Guangzhou Auto Show, GAC Aion officially launched the successor model of its flagship product AION LX ( parameters | inquiry ) - AION LX Plus. More than two years ago, AION LX became one of the representatives of domestic luxury high-end pure electric vehicles with its strong highlights such as a maximum range of more than 650km and an acceleration time of 3.9 seconds per 100 kilometers. Today, with the technological progress in the three-electric system and intelligence, the new AION LX Plus has once again become a unique high-end luxury smart pure electric SUV in China with a maximum range of more than 1008km (CLTC working conditions), an acceleration time of 2.9 seconds per 100 kilometers, and a three-laser radar assisted driving solution.

Previously, we have conducted a simple static experience of the new car "Here, the 1000km range you wanted is here! Real shots of GAC Aion AION LX Plus at the auto show". This article mainly talks about several highlight technologies of the new car.

Sponge silicon negative electrode battery

Although we have long anticipated that with the development of battery technology, it is no longer a dream for electric vehicles to have a comprehensive range of over 1,000 km, we did not expect it to come so soon.

According to official data, the AION LX Plus has a comprehensive range of up to 1008km under the latest CLTC conditions, making it the fastest mass-produced pure electric vehicle in China with a range of over 1000km, and it is not easy for an SUV to achieve a high range (considering vehicle weight and wind resistance factors). As the key to endurance, the power battery technology of the AION LX Plus is the absolute core, which is also the first technical highlight of the new car that has attracted attention - the "sponge silicon negative electrode" battery technology.

Previously, in order to pursue higher energy density and longer driving range, the domestic pure electric vehicle market tried to increase the proportion of nickel on the basis of ternary lithium cathode materials, and NCM 811 batteries became popular for a while. However, the thermal stability of high-nickel ternary batteries cannot be well controlled, and safety incidents frequently occurred. Since this year, most mainstream electric vehicle companies have returned to the 523 or 622 battery series.

So, in addition to increasing the nickel content of the positive electrode to increase the total energy of the battery, can there be a breakthrough in the negative electrode of the battery? Silicon may be the best answer today.

At present, almost all negative electrode materials of lithium batteries are graphite, which has the advantages of high stability and low price, but the disadvantage is that after a long period of charge and discharge cycle, the capacity and life will drop significantly. Silicon is not a rare element, and its price is similar to that of graphite, but the capacity of silicon negative electrode material can reach more than 10 times that of graphite. In other words, if the same lithium battery uses silicon as the negative electrode, the energy can theoretically exceed that of a graphite battery by 10 times.

However, the biggest problem with silicon negative electrodes is that they are easy to expand. Graphite expands no more than 10% during the battery charge and discharge cycle, while silicon can expand up to 360%, causing the battery cell to deform, which is unacceptable for any product.

Therefore, we came up with a compromise solution, "silicon doping". That is, adding silicon to the graphite negative electrode, that is, the negative electrode is a mixture of graphite and silicon. This not only has the advantages of high capacity of the silicon negative electrode, but also restrains the expansion of silicon through the stability of graphite. GAC Aion uses "nano-composite silicon technology", "self-healing adhesive technology", "gradient conformal coating technology", etc., which can make the silicon negative electrode sheet inside the battery as elastic as a sponge. The expansion and contraction during the charging and discharging process will be buffered and will not break. It will also maximize the advantages of silicon like a sponge absorbing water. In addition, the addition of silicon material will cause a certain amount of lithium loss (about 15-35%) during the first charging process. At this time, lithium foil, lithium powder, and pre-lithiation additives need to be introduced, which is "lithium supplementation".

The silicon sponge negative electrode battery technology can reduce the volume of lithium-ion battery cells by 20% and the weight by 14%. In the future, the volume and weight of the cells can be reduced by more than half. In addition, this technology also has a significant effect on extending the battery life and improving the reliability of lithium-ion batteries.

With the support of sponge silicon negative electrode battery technology, the total energy of the AION LX Plus battery pack is as high as 144.4kWh, and the battery system energy density is 205Wh/kg, which is not inferior to the 811 ternary battery. This high-energy battery pack can provide the new car with the highest range among domestic pure electric vehicles, with a range of 1008km under the new CLTC comprehensive working conditions.

Officials revealed that in the advance highway and urban road tests, the actual range of AION LX Plus can reach more than 600km and more than 1000km respectively.

Two-speed dual-motor "four-in-one" electric drive system

In order to maximize the endurance, in addition to the high-energy battery pack, the technical capabilities of the electric drive system are also crucial, and its comprehensive efficiency directly affects the power consumption of the vehicle. Moreover, the AION LX Plus also needs to accelerate from 0 to 100 km/h in 2.9 seconds, which is 1 second faster than the previous generation.

The solution proposed by GAC Aion this time is a brand-new "four-in-one" electric drive system. This electric drive system is highly integrated with two sets of permanent magnet synchronous motors, two reducers with different speed ratios, and motor controllers, and is coaxially arranged on the rear axle of the vehicle.

The "four-in-one" electric drive system is 30% smaller and 25% lighter than power units of the same level. The motor drive efficiency is as high as 90%, the system has a maximum output power of 340kW, and the wheel-end torque is as high as 6100N·m.

In addition to the data level, in practical application, based on the dual motor and dual reducer configuration, this system enables AION LX Plus to have a variety of rear axle motor drive modes, including single-speed single motor, single-speed dual motor and two-speed dual motor, and can be switched intelligently. High-power motors and high-speed ratio reducers can be selected during starting and rapid acceleration to provide optimal power output. Low-power motors and low-speed ratio reducers can be used during cruising to achieve lower power consumption.

The four-wheel drive version of the AION LX Plus will be equipped with an additional 200kW permanent magnet synchronous motor on the front axle. The front and rear three-motor electric four-wheel drive system can achieve a maximum vehicle power of 540kW and a maximum acceleration time of 2.9 seconds from 0 to 100 km/h.

Three second-generation LiDARs for urban NDA navigation assistance

Nowadays, electric vehicles cannot do without intelligence, and the biggest highlight of intelligence is undoubtedly the assisted driving level. This is a reflection of a car company's cutting-edge technologies in many aspects such as R&D capabilities, computing capabilities and software development capabilities.

The intelligent driving assistance hardware configuration of AION LX Plus is absolutely luxurious. The whole car has a total of 35 sensors, including 3 second-generation intelligent variable-focus laser radars, including: 3 second-generation intelligent variable-focus laser radars, 6 millimeter-wave radars, 12 ultrasonic radars, 8 autonomous driving high-definition cameras, 4 surround-view cameras and 2 independent high-precision positioning modules.

The second-generation intelligent variable-focus LiDAR has an intelligent variable-focus function and an intelligent adjustable resolution of 0.2°-0.05° (the mainstream first-generation is fixed at 0.2°). Compared with the first-generation LiDAR, it can see farther and more clearly.

Left: First generation fixed resolution; Right: Second generation intelligently adjustable resolution

During high-speed driving, the target area can be focused on and the target area resolution can be dynamically increased from 0.2° to 0.1° (or even higher), which means that the vehicle's recognition distance is increased from 120-150 meters to 180-200 meters, and the detection distance for static small obstacles is increased from 85 meters to 160 meters. For smart driving vehicles traveling at a speed of 120km/h, this is a qualitative change from safe braking distance to comfortable braking/lane change distance.

In the urban autonomous driving scene, parallel vehicles, two-wheeled vehicles, pedestrians with different behaviors, and vehicles shuttling sideways make the road conditions complex and change quickly, and obstacles are very close to the vehicle. At this time, the faster the laser radar refresh frame rate, the more it can identify changes in road conditions first, and the more calmly it can deal with emergencies such as cutting in and ghosting. However, the first-generation laser radar has a fixed and low refresh frame rate, slow response, and a large gap between following vehicles, so it is easy to be "cut in line" by other vehicles.