The invention of graphite anode facilitated the successful commercialization of lithium-ion batteries (LIBs) in history. The charging rate, cycle lifespan and energy density of LIBs play key roles in determining its applications. However, the slow electrochemical reaction at the graphite interface brings a significant challenge to the realization of fast-charging LIBs without sacrificing the energy density, cycle life, and safety, where slow Li+ desolvation and its diffusion at solid-electrolyte interphase (SEI) at graphite anode are two determining factors. Exploring new interphase chemistry on this very “old” graphite could offer many practical avenues for rapidly achieving practical fast-charging LIBs, and directly bring positive impacts for various applications.
Recently, Professor Yongming Sun’s group investigated the effect of different SEI components on the Li+ ions desolvation. This work revealed that Li3P exhibited a high affinity for Li+ ions, facilitating the kinetic transport of Li+ ions at the anode interface. Inspired by the above results, the authors employed the “bridging“ effect of sulfur (S) on phosphorus (P) molecules to construct an ultrathin P-coating on the surface of graphite, resulting in a P-S-graphite (namely “blue graphite”). During the initial cycle of the battery, the “blue graphite” anode in situ generated a continuously crystalline Li3P-based SEI with high ionic conductivity. When it paired with LiNi0.6Co0.2Mn0.2O2(NCM622), NCM622||“blue graphite” pouch cells exhibited excellent fast-charging capabilities (achieving 91.2% and 80% charge within 10 minutes and 6 minutes, respectively) and stable cycling performance under fast-charging conditions (at 6 C rate), maintaining ~82.9% capacity after 2000 cycles. Furthermore, a ~3 Ah laminated NCM622||“blue graphite” pouch cell assembly for mobile phones, which, when charged for 10 minutes, achieved a charge of 90.3%, further demonstrating that “blue graphite” is a high-performance anode for fast-charging LIBs. Considering the superior electrochemical performance, facile synthesis, and low cost of the raw materials, “blue graphite” is potentially cost-effective and thus is promising for the battery industry.
Figure 1. Theoretical Simulation of Li+ solvation structures at different SEI component surfaces.
Figure 2. Preparation and characterization of “blue” graphite.
Figure 3. Morphology, composition, and kinetic properties of SEIs on different graphite (conventional graphite, “blue” graphite) anodes.
Figure 4. Electrochemical performance of NCM622||“blue” graphite and NCM622||graphite pouch cells, and structural and morphological characterization of the graphite anodes after fast-charge cycling.
Figure 5.Electrochemical performance of laminated NCM622||“blue” graphite pouch cells.
Related work has been published on Nature Energy (https://www.nature.com/articles/s41560-023-01387-5) on October 30, 2023, with the title Fast-charging capability of graphite-based lithium-ion batteries enabled by Li3P-based crystalline solid-electrolyte interphase. The first unit for this research is the Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, and it has been funded by the National Natural Science Foundation of China.
