Avita 11 battery pack technology interpretation: the best in mass production

The Avita 11 ( parameters | inquiry ) jointly built by Changan Automobile, Huawei, and CATL will soon begin delivery.

Since it is the "own son" in which CATL has invested, it is natural for CATL to give it the best technology.

The Avita 11 is equipped with CATL's most advanced battery system CTP2.0 (Cell to Pack, module-free) that has been mass-produced, and it has been carefully designed to adapt to the battery life and fast charging capabilities required by the Avita 11.

To ensure the optimal design of the Avita battery pack, CATL conducted a large number of simulations during the development phase to find the optimal battery cell chemistry system; and through material modifications, further improved the safety, life and fast charging performance of the battery cells; and finally, through system-level structural design, further improved the safety and reliability of the battery system.

The carefully designed CTP2.0 system is in no way inferior to CATL's Kirin battery, which has not yet been mass-produced, in terms of performance and safety.

01

Development stage: simulation platform locks in the optimal solution

Why is “King Ning” so skilled?

Previously, everyone generally agreed that CATL had talented people. Some people joked that half of China's PhDs in battery research were in CATL.

Now, talent alone is not enough, Ning Wang also has data.

As the world's largest battery manufacturer, CATL has ranked first in global power battery shipments for five consecutive years. It is estimated that one out of every four electric vehicles on the road is powered by a CATL battery.

CATL established a battery data collection and tracking system very early on, and has therefore accumulated a massive amount of actual application data on power batteries - more than 5 million vehicles, 280GWh of batteries, and 1 trillion pieces of data.

One of the uses of this data is to feed back to CATL’s research and development. Previously, based on electrochemical principles and laboratories, battery companies were able to give their best combinations of battery materials, packaging modes, and battery packs.

However, the performance of this solution in application is often unexpected. It is also possible that the designed performance does not match the actual application scenario. For example, previous research and development emphasized the cycle life under full charge and discharge conditions, but actual application data shows that basically all car owners use the battery in the middle of the remaining battery. Therefore, what should be strengthened is the relatively shallow charge and discharge cycle life.

With the data feedback from these practical applications, we can better judge which combination is the optimal solution, and also provide guarantees for the success rate of R&D and the accuracy of improvements.

Based on these data, CATL established a high-throughput computing platform.

Xiang Yanhuo, President of CATL's Passenger Vehicle Solutions Division in China, introduced that CATL's computing platform can cross-integrate the material gene database platform with product development and application, and combine some process characteristics in the production and manufacturing process to provide the best product design plan, so that the product can be fast, accurate, and have excellent performance.

When developing the battery pack for the Avita 11, CATL not only drew on its rich experience in battery design, development, and production, but also applied big data accumulation, high-power computing, and artificial intelligence technology to assist in analysis. CATL will first use the simulation computing platform for calculation and optimization to screen out the most promising formulas and compounds.

The results of simulation calculations, verified by accumulated data, greatly reduce the probability of error in the Avita battery system.

It can be said that in terms of R&D methodology, the Avita 11 battery pack won at the starting line.

02

Battery cells: Material modification to balance safety, life and fast charging

From the beginning of the design of the Avita 11, the goal of the battery system was to increase the range by 200 kilometers with a 10-minute charge.

It is not difficult to achieve this goal alone, but the difficulty lies in supporting fast charging while also ensuring safety and long life, which requires optimized design at the material level of the battery cell.

Generally speaking, the negative electrode tube is fast charged; the positive electrode tube has energy.

For the negative electrode, CATL has improved the charging capacity of the graphite negative electrode by constructing a fast channel for lithium ion transmission on the surface of the graphite material, while taking into account high energy density and good life.

For the positive electrode, CATL uses nano-riveting point technology to connect the microscopic materials together like rivets, ensuring the stability of the material and safety under high energy density.

Specifically for the positive electrode material system, CATL has achieved a cell energy density of 245Wh/kg for the typical medium-nickel formula NCM523 through a series of optimizations. At the same time, its intrinsic safety is better than that of NCM811 batteries.

The electrolyte is the path for lithium ions to migrate between the positive and negative electrodes. This path must be wide and straight, otherwise it will affect the speed of lithium ion migration - that is, the speed of charging and discharging, and may also cause excessive temperature rise, posing a safety hazard.

CATL uses a new type of electrolyte in the battery cells used for Avita. This electrolyte can build an efficient three-dimensional conductive network inside the electrode, which is equivalent to a highway for lithium ions, reducing the internal resistance and heat generation of the battery cell, improving the charge and discharge rate, and making the material more stable.

On the premise of ensuring safety, CATL has created the first mass-produced high-voltage ternary system 2.2C fast-charging battery in China for Avita, which is nearly twice as fast as the mainstream 1.2C fast-charging battery. At normal temperature, it can be charged for 10 minutes and has a range of 200 kilometers, and its low-temperature performance is also excellent.

According to Xiang Yanhuo, this battery can be quickly charged from zero to full power in 60 minutes even in a low-temperature environment, such as minus 10 degrees Celsius in the northern environment.

From a design perspective, the CATL team has developed a good product for Avita 11.

However, to implement this series of sophisticated designs, stable mass production capabilities are required. In terms of quality control, CATL has set up more than 6,000 quality control points and uploaded the data to the platform in real time, which can meet the traceability of more than 20 years, and the product quality is trustworthy.

In terms of battery manufacturing, CATL has crossed the PPM (parts per million) level defect threshold and is striving towards PPB (parts per billion) level extreme manufacturing.

At the battery cell level, the battery cells used in Avita 11 have no shortcomings in terms of energy density, fast charging performance and safety, and its comprehensive capabilities can challenge all competitors.

03

System: NP technology supports and further improves safety

CTP has no modules. The battery cell does its job and the rest of the work is left to the battery system.

The Avita 11 model uses CATL's CTP2.0 battery system technology, which is the most technologically advanced, mature and stable battery pack mass-produced by CATL.

The most prominent point is the thermal management system designed to ensure safety.

In order to meet the fast charging speed of 2.2C, CATL has specially built the cooling system of the Avita battery pack and developed a multi-channel, intelligent thermal management platform. During the operation of the battery system, the overall temperature can be controlled within a temperature difference of 3 degrees.

With more flow channels, the heat dissipation efficiency will naturally be higher, the temperature rise will be similar, the battery consistency can be maintained, and the life of the battery pack will be long. Intelligence uses sensors and monitoring systems to monitor the temperature of the battery cells, control the water cooling system for precise cooling, and keep the temperature between the battery cells stable at the most appropriate level, which helps to eliminate safety hazards and also helps to extend the life of the battery pack.

What if thermal runaway still occurs?

The battery pack of Avita 11 also has a heat spread control strategy for unexpected situations.

CATL adopts a double-layer insurance strategy of isolation first and then guidance.

Aviation-grade insulation material is used between the battery cells, which can withstand temperatures of nearly 1000 degrees. Even if a single battery cell fails, it will not trigger a chain reaction in the surrounding battery cells, greatly improving the safety of the overall battery pack.

At the same time, through 3D simulation of the gas diffusion path when the battery cell fails, an optimized exhaust channel is designed in the battery pack, and a large-capacity pressure relief valve design is adopted. In the event of an accident, the high-temperature airflow can be quickly discharged to reduce the risk of battery pack explosion caused by increased internal pressure.

During the high-temperature airflow discharge process, the design of the commutation channel needs to be very clever. It must be able to control the heat flow to flow along a predetermined trajectory, and also control the heat flow to be distributed as evenly as possible in different structural channels, so as to reduce the thermal shock to adjacent batteries and avoid causing secondary thermal runaway.