CATL 4C iron-lithium ultra-fast charging battery, technical speculation

CATL's press conferences are always concise and efficient. At yesterday's press conference, the world's first 4C supercharged battery "Shenxing Supercharged Battery" was launched. This is a plan to expand 4C technology to the field of lithium iron phosphate after the completion of 4C ternary lithium batteries . The 4C battery, which can be charged in 10 minutes and has a range of 400 kilometers, no longer needs to worry about "no power". This battery uses lithium iron phosphate material, which not only charges super fast, but also can achieve a range of more than 700 kilometers.

We have many problems, such as:

● What is the difference between 4C lithium iron phosphate and 4C ternary battery?

● Will the introduction of 4C lithium iron phosphate increase the cost of battery cells ? Does it need to be paired with 800V small-capacity batteries? What is the cost difference with 4C ternary batteries? Since both can achieve a range of 700 kilometers, have ternary 4C batteries become redundant?

● There are many processes for 4C battery cells. Do they need to match Kirin’s pack process?

Part 1. What exactly is Ning Wang’s super skill?

As a lithium iron phosphate battery , this product has an impressive driving range and charging speed, using a series of advanced technologies, including improvements in positive electrode materials, negative electrode materials , electrolytes , separators and safety measures. The main features of this battery include:

● Endurance: At room temperature, this battery can achieve a range of 700 kilometers

● Fast charging capability: At room temperature, only ten minutes of charging is required to provide a range of 400 kilometers.

● Low temperature charging: At -10 degrees Celsius, it only takes half an hour to charge to 80% (30 minutes)

● Positive electrode material: The super electron net positive electrode technology is adopted. Through the nano-sized lithium iron phosphate positive electrode material, the resistance of lithium ion escape is reduced and the fast charging performance of the battery is improved. 5) Negative electrode material: By improving the graphite surface, the embedding channel of lithium ions is increased, and a multi-gradient layered pole piece design is adopted to achieve a balance between fast charging and endurance.

● Electrolyte: Using a new ultra-high conductivity electrolyte formula, the ability of lithium ion desolvation is improved, while the ultra-thin SEI film is optimized to reduce the internal resistance of the battery.

● Diaphragm: The design of the diaphragm has been improved to increase the liquid phase transfer rate of lithium ions, which helps to charge and discharge more efficiently. 8) Safety: An improved electrolyte system and a high-safety coating separator are used, and the internal temperature of the battery is controlled by an intelligent algorithm to ensure the safety performance of the battery. In addition, after certification in multiple scenarios, the safety of the battery under various working conditions is guaranteed.

Of course, the most important point that was not mentioned at the press conference is: Can all the original batteries be directly compatible with 4C after such a transformation?

Part 2: Speculations about 4C and Kirin batteries

In fact, we understand that the battery cell improvement mentioned above mainly solves the problem that the battery cell level can withstand large currents such as 4C fast charging. In other words, assuming the capacity is 100Ah, then when charging with a current of 400A, the battery impedance is low enough.

But here are a few wild guesses:

◎ At 4C, a 200Ah battery must have 800A. In other words, the huge current here brings great system challenges. We can reasonably guess that 4C lithium iron phosphate is actually the LFP version of Kirin battery. In other words, the battery capacity is also small, and 800V is required to reduce the current.

◎ 4C lithium iron phosphate (LFP) needs to be compatible with the design of the Kirin battery. This is also easy to understand. If you want to achieve 4C, the impedance of the battery cell can be low enough, but the heat still needs to be dissipated. The Kirin battery design with double-sided cooling has enough heat dissipation space.

◎ In the design of Ning Wang, there is another idea, which is to directly transform the original battery with an electrochemical system. We understand that 4C is a relatively vague concept at present, that is, the peak value may reach 4C; but because the battery pack design does not change, the fast charging effect is slightly inferior.

Part 3. Refer to the internal structure of Kirin battery

We can find the answer to this question by revisiting the previous "Kirin Battery Disassembly Report".

We boldly speculate that this 4C lithium iron phosphate battery cell needs to be used in conjunction with the Kirin battery system.

Heavy cushioning foam is added to the top of the battery box, and multiple pressure relief valves are set at the front and rear ends to improve safety. The cells are arranged in six rows to maximize the use of space and eliminate redundant horizontal and vertical beams inside the battery. The cooling pipeline arrangement on both sides of the cell and the battery pack helps with thermal management. A cooling plate is used for cooling between the cell and the cooling plate, the groove is filled with thermally conductive foam material, connected by double-sided tape, and the cooling plate is insulated by powder spraying. A pressure relief valve is set at the bottom, the structure is strengthened by structural glue, the bottom glue blocking mechanism prevents the overflow of structural glue, and aerogel is used at the micro-joints. The setting of the pressure relief valve and the smoke exhaust hole help release pressure and smoke in the case of thermal runaway, and the mica board is used to prevent the spread of thermal runaway.

The key innovations of the internal structure of Kirin Battery include a multifunctional elastic interlayer, which uses insulating powder, tape and thermally conductive foam to bond the water-cooling plate to the battery cell to provide support, insulation and cooling. Large-area water-cooling technology places the water-cooling plate on the side of the battery cell to increase the heat dissipation area and improve the charging speed and temperature uniformity in fast-charging scenarios. Active isolation technology for high voltage and flue gas places the explosion-proof valve at the bottom of the battery cell to achieve directional pressure relief and avoid interference between high voltage and flue gas. Mica protective covers are used to prevent high-temperature shock and heat insulation to prevent the spread of thermal runaway.

We have reason to believe that:

Under the balanced price, 4C fast-charged iron-lithium batteries will be slightly more expensive than large-capacity iron-lithium batteries, and Kirin Pack will also increase some costs, so there will be a certain increase overall. Of course, under the current situation, CATL has achieved parity with the original battery cost through 4C fast-charged batteries, which is a technical price war.

Summary: The above is our guess. Without changing the cell structure, CATL has actually optimized the electrochemical system and Pack design. However, we understand that this fast-charging LFP system is more expensive than the ordinary 2C ternary battery. This design may be an initial version of the current 800V vehicle low-power battery and a variant of the 4C ternary battery.

Of course, CATL may use this technology to separate a special battery, the LFP fast-charging battery. Even if it may not be the full 4C, its advantage is that it does not change the Pack design and can be directly replaced, ultimately leading to a price war at the battery level.