Ampere-Hour-Scale Soft-Package Potassium-Ion Hybrid Capacitors Enabling 6-Minute Fast-Charging
Authors: Li Huanxin 
Published: December 2024

Extreme fast charging of Ampere-hour (Ah)-scale electrochemical energy storage devices has emerged as a crucial target for advancing their widespread adoption in various applications, ranging from portable electronics to electric vehicles. The ability to recharge energy storage systems rapidly enhances convenience, productivity, and efficiency, driving the demand for technologies capable of achieving charging times of less than 10 minutes. However, conventional lithium-ion (Li-ion) batteries, ubiquitous in many electronic devices and electric vehicles, face significant challenges in meeting this demand due to their inherent reaction mechanisms and safety concerns associated with high current densities. Our work focuses on addressing the pressing need for extreme fast charging by introducing 1 Ah soft-package potassium-ion hybrid supercapacitors (PIHCs). These PIHCs are designed to leverage the combined merits of high-energy density from battery-type negative electrodes and high-power density from capacitor-type positive electrodes, offering a promising solution to the challenges posed by conventional Li-ion batteries. The architecture of the PIHCs is meticulously engineered to optimize performance while maintaining safety and reliability. The positive electrode of the PIHCs is composed of defect-rich, high specific surface area N-doped carbon nanotubes, facilitating efficient ion adsorption and desorption processes. On the other hand, the negative electrode incorporates MnO quantum dots inlaid within spacing-expanded carbon nanotubes, which provide ample active sites for potassium-ion storage and promote rapid charge transfer kinetics. Crucially, the electrolyte chosen for the PIHCs is a carbonate-based non-aqueous solution, carefully selected to ensure compatibility with the electrode materials and enable high ionic conductivity. Furthermore, the PIHCs feature a binder- and current collector-free cell design, reducing the overall weight and improving the energy density of the devices. Through systematic optimization of the cell configuration, electrode materials, and electrolyte composition, we have achieved remarkable performance metrics for the PIHCs. The full cells (1 Ah) exhibit a cell voltage of up to 4.8 V, enabling efficient energy storage and utilization. Importantly, the PIHCs demonstrate a high full-cell level specific energy of 140 Wh kg−1, calculated based on the entire mass of the device. Moreover, the extreme fast charging capability of the PIHCs is demonstrated through their remarkable charging time of only 6 minutes for a full 1 Ah capacity. This exceptional charging speed significantly enhances the usability and practicality of the PIHCs in various real-world applications, where rapid energy replenishment is essential. In addition to fast charging, the PIHCs exhibit excellent cycling stability and voltage retention under high current conditions. After 200 cycles at 10 C (corresponding to a discharge current of 10 A), the PIHCs maintain an impressive 88% capacity retention, highlighting their robustness and durability. Furthermore, the voltage retention of the PIHCs remains at 99% at a stable temperature of 25 ± 1 °C, underscoring their reliability and consistency over extended usage periods. Overall, the development of 1 Ah soft-package potassium-ion hybrid supercapacitors represents a significant advancement towards meeting the growing demand for extreme fast charging in electrochemical energy storage devices. By combining the advantages of battery-type and capacitor-type electrodes, along with innovative cell design and electrolyte selection, the PIHCs offer a compelling solution to the challenges posed by conventional Li-ion batteries, paving the way for the next generation of extreme fast charging energy storage technologies.[1]

Ref. 1 H. Li etal. Nature Communications 14 (1), 6407

Figure 1