Charging rate (C-rate) is a core indicator for measuring fast charging capability. 1C means fully charging to rated capacity in one hour, 4C in 15 minutes, 10C in 6 minutes, and 15C in 4 minutes.
The industry generally defines 4C and above as supercharging. Currently, mainstream power batteries have moved from 4C to 6C and are continuously pushing towards 10C, 12C, and 15C.
The competitive dimension of fast charging has also expanded from “who charges the fastest” to include parameter specifications, technological approaches, and implementation capabilities.
01 How to Understand Fast Charging: Rate and Measurement
To evaluate a fast-charging battery, you need to look at at least three pieces of information: peak rate, charging range, and whether it’s a single cell or a system.
Peak rate refers to the highest instantaneous charging capability, while the equivalent rate is the average charging rate over the entire charging process; these two terms are often used interchangeably. The charging range is equally crucial. 10%-80% is currently the most commonly used comparison range, while “fully charged” usually refers to 97% or 98%, not necessarily 100%.
Therefore, discussing charging time without considering the charging range can be misleading.
02 The Physical Bottleneck of Fast Charging
The core constraint of fast charging lies in the negative electrode. During charging, lithium ions rapidly embed into the negative electrode. If the negative electrode’s absorption speed cannot keep up, lithium ions will precipitate on the surface, forming lithium dendrites. This causes irreversible capacity decay, and in severe cases, it can puncture the separator, causing a short circuit.
Secondly, there are the electrolyte conductivity and electrode internal resistance. Large currents passing through internal resistance generate Joule heating; the higher the charging rate, the more concentrated the heat generation.
Temperature is a critical constraint for fast charging. Lithium hexafluorophosphate (LiPF6), the core material of the electrolyte, begins to decompose at 60°C, and the decomposition accelerates significantly above 70°C. Therefore, the industry has a saying that 70°C is the “golden temperature,” meaning ultra-fast charging must control the temperature below 70°C. However, with technological advancements, LiPF6 may be replaced or can remain stable at higher temperatures.
Furthermore, according to the Arrhenius relation, higher temperatures result in faster reaction rates; the reaction rate may approximately double between 60°C and 70°C. Simultaneously, the starting threshold for the rapid deterioration of SEI film thermal decomposition and electrolyte side reactions is between 80°C and 120°C. This means that higher charging rates correspond to lower safety margins, making precise temperature control a core technological hurdle.
03 2023-2025
During this phase, the charging rate rapidly increased from 4C to 12C, and lithium iron phosphate batteries gradually became the mainstay of fast charging.
04 2026
In 2026, fast charging will enter the “minute level”. Multiple manufacturers broke records in five months, with charging rates jumping from 5C to 12C and 15C.
05 Technical Route
Fast charging is not simply about increasing charging power; it is a systematic engineering process involving voltage platform, cell materials, structural design, and thermal management.
Voltage Platform
Domestic manufacturers generally adopt 800V or even 1000V high-voltage platforms to reduce heat loss by lowering the current; Tesla, on the other hand, insists on a 400V high-current approach. Each path has its trade-offs.
Materials System
Lithium iron phosphate (LFP) has become the mainstay of fast charging due to its cost and safety advantages, achieved by improving compaction density and ionic conductivity. The anode is a key component, with mainstream directions including graphite secondary granulation and carbonization coating, silicon-carbon anodes, and new materials such as black phosphorus. Electrolytes utilize new lithium salts such as LiFSI to improve conductivity and thermal stability.
Structure and Thermal Management
In terms of cell structure, designs such as short blades and full tabs are used to reduce internal resistance and shorten the current path; at the system level, double-sided direct cooling or refrigerant direct cooling is often used to direct cooling to the area with the most concentrated heat generation. This is also a prerequisite for high-rate charging.
07 Summary
Fast charging for power batteries has progressed from 4C to 15C, and is expected to enter the “minute-level” charging stage by 2026, with lithium iron phosphate (LFP) batteries and high-voltage platforms becoming the mainstream approach.
When comparing fast-charging products, it’s crucial to consider peak and equivalent rate, charging range, single-cell or system specifications, and mass production timeline, avoiding judgments based on a single figure.
Further widespread adoption of fast charging depends on the simultaneous advancement of charging infrastructure, grid capacity, and lifespan verification. Which fast-charging metric do you prioritize when choosing a vehicle or model? Feel free to share your thoughts in the comments section.
