In the current era of the vigorous development of the new energy vehicle industry, lithium-ion batteries, as the core power source, face the critical challenge of balancing charging efficiency and lifespan. With consumers' increasing demands for longer driving ranges and faster charging speeds, as well as the market's focus on battery lifespan and cost-effectiveness, the charging technology of lithium-ion batteries is undergoing a profound revolution. How to ensure high-efficiency charging while extending battery lifespan has become an urgent issue that the industry needs to address.
I. Fast Charging Technology: The Driving Force for Efficiency Improvement
In recent years, significant progress has been made in the fast charging technology of lithium-ion batteries. Take CATL as an example. Its "Shenxing" ultra-fast charging battery has achieved an ultra-fast charging speed of "10-minute charging for a 400-kilometer driving range". Even in cold environments at -10℃, it can charge to 80% of the capacity within 30 minutes. In April 2024, CATL launched the Shenxing PLUS battery, further enhancing the driving range to 1000 kilometers while maintaining the ultra-fast charging characteristic of charging to 60% of the capacity within 10 minutes. Additionally, CATL and SAIC-GM have collaborated to introduce a 6C ultra-fast charging lithium iron phosphate battery, which is planned to be used in the upgraded Ultium quasi-900V high-voltage battery architecture in 2025. This battery can be fully charged within 10 minutes, adding 200 kilometers of driving range within 5 minutes.
The research team led by Professor Chao-Yang Wang at Pennsylvania State University has also made remarkable achievements. They found that if a battery can be rapidly heated to 60℃ before charging, charged at a fast rate for 10 minutes, and then rapidly cooled to the ambient temperature, thermal degradation of the battery can be avoided, and serious growth of the solid electrolyte interphase (SEI) film can be prevented. After repeated tests, the team conducted isothermal charging tests on three types of power batteries at 40℃, 49℃, and 60℃, using charging at 20℃ as a control. Subsequently, the batteries were disassembled to check for lithium plating. The results showed that after 2500 cycles of extreme fast charging (6C, 4.2V) at 60℃ for 10 minutes, the high-energy-density battery with a capacity of 209 Wh/kg still retained 91.7% of its capacity, with only 8.3% capacity loss. This far exceeded the "500 cycles, 20% capacity loss" target set by the U.S. Department of Energy (DOE), and no lithium plating was observed during the charging process.
Brands such as XPENG and NIO have also achieved breakthroughs in ultra-fast charging. XPENG launched its S4 ultra-fast charging pile, with a maximum output power of 480 kW and a maximum output current of 670 A. This system can provide a 200-kilometer driving range for a car within 5 minutes of charging. According to the official statement, the 4C model can charge from 10% to 80% in less than 15 minutes, which is claimed to be the fastest mass-produced electric vehicle charging speed globally. The 3C model is also equipped with an 800V high-voltage platform, with a peak charging power of around 300 kW. It can add 130 kilometers of driving range within 5 minutes of charging and charge from 10% to 80% in 20 minutes.
II. The Impact of Fast Charging on Battery Lifespan
Although fast charging technology greatly improves charging efficiency, its impact on battery lifespan cannot be ignored. During fast charging, a large current prompts lithium ions to rapidly embed into the anode. If temperature control is inadequate, lithium metal may deposit on the anode surface, forming dendrites that could potentially puncture the separator, leading to internal short circuits and accelerating battery performance degradation. Additionally, the heat generated during fast charging, if not dissipated in time, can accelerate the decomposition of the electrolyte and the aging of electrode materials, shortening the battery's cycle life.
A survey showed that for ride-hailing drivers of pure electric vehicles with an average daily mileage exceeding 100 kilometers, the usage proportion of ultra-fast charging exceeded 70%. The health degree of their on-board power batteries dropped from 100% for new cars to 85% within two years, with an average annual decline of 7.5%. However, the latest research by Professor Ouyang Minggao's team at Tsinghua University revealed that frequent use of ultra-fast charging above 120 kW can shorten the battery's cycle life by 40% compared to slow charging.
Nevertheless, some studies indicate that the impact of fast charging on battery lifespan is not absolute. A tracking study conducted by Recurring Automatic on tens of thousands of Teslas found that the difference in battery lifespan between fast charging and slow charging is actually negligible. Even for commercial ride-hailing vehicles that are fast-charged 1-2 times daily, their battery replacement cycles are similar to those of private cars. This is mainly attributed to the efficient temperature control systems that effectively mitigate the negative impacts of fast charging.
III. Technical Strategies for Balancing Efficiency and Lifespan
To find a balance between fast charging efficiency and battery lifespan, the industry and enterprises have adopted a series of technical strategies.
In terms of material innovation, CATL's ultra-fast charging technology employs an ultra-electron network cathode technology and a second-generation graphite fast ion ring anode technology, further enhancing electrochemical reaction efficiency and charging efficiency. The ultra-electron network, with its fully nanometerized material surface, constructs a well-connected electron network, significantly improving the cathode material's response speed to charging signals and the lithium ion desorption rate. The fast ion ring-modified porous coating layer on the anode material surface provides abundant active sites for lithium ion exchange, greatly increasing the lithium ion charge exchange speed and embedding rate.
In battery structure design, Professor Chao-Yang Wang's team developed an "all-climate" battery. They inserted a 50-micrometer-thick nickel foil inside the battery, which can effectively self-heat. When the current is turned on at low temperatures, it flows through the nickel foil, generating heat. Once the internal temperature of the battery exceeds 60℃, the temperature sensor is triggered to shut off the current flowing through the nickel foil. This battery can self-heat to 60℃ within 30 seconds without compromising its performance and lifespan at normal temperatures. This process does not require the assistance of external heating equipment or the addition of special additives to the electrolyte.
In terms of battery thermal management systems (BMS), some automakers have introduced an "ultra-fast charging protection mode". When the battery charge is below 20%, the charging power is limited to 60 kW to avoid some battery-damaging issues. Others adopt battery pre-heating technology, which improves the fast charging efficiency by 35% in environments at -10℃ while reducing the battery decay rate by 30%.
IV. User Usage Strategies and Industry Outlook
For users, reasonable use of fast charging is crucial for extending battery lifespan. Professor Qilu, director of the New Energy Materials and Technology Laboratory at Peking University, stated that car owners should limit the proportion of ultra-fast charging usage to within 40%. When time permits, slow charging should be used as much as possible. In particular, ultra-fast charging should be avoided when the battery charge is below 10% or above 90%, as using ultra-fast charging in this range can cause greater damage to the battery.
From an industry perspective, through commercial model innovation, such as adopting a battery leasing model, automakers can transition from "selling products" to "selling services". The vehicle-battery separation model can reduce users' sensitivity to battery warranties while also driving enterprises to improve the maturity of fast charging technologies.
In the future, with continuous technological progress, the balance between fast charging efficiency and battery lifespan for lithium-ion batteries will be further optimized. The emergence of new materials and technologies, such as silicon-based anodes and solid-state batteries, is expected to fundamentally solve the lifespan issues caused by fast charging. At the same time, the continuous improvement of intelligent temperature control systems, dynamic power adjustment, and other technologies will provide stronger support for the charging technology revolution of lithium-ion batteries.
In this charging technology revolution, lithium-ion batteries are gradually moving towards a perfect balance between efficiency and lifespan. The industry and enterprises need to continuously innovate, and users also need to use them reasonably to jointly promote the sustainable development of the new energy vehicle industry.
