Approaches to Improve Both Cycle and Calendar Life of Silicon-Based Lithium-Ion Batteries

Le résumé fourni par la source

During the last few decades, silicon (Si) has been extensively investigated as the next generation of anode material for lithium (Li)-ion batteries (LIBs) due to its high theoretical capacity (~ 4200 mAh g−1) which is more than ten times larger than those of graphite anode materials. However, because of the huge volume changes (~ 300%) of Si during repeated lithiation and delithiation, its lower electrical conductivity, inconsistent kinetics reaction, and relatively low initial Coulombic efficiency (ICE), large-scale application of Si-based LIBs (Si-LIBs) is still limited. The abovementioned intrinsic characteristics of Si trigger the short cycle life of Si-LIBs due to several reasons: 1) pulverization of Si particles; 2) Increasing cell impedance associated with continuous growth of solid electrolyte interphases (SEI) layers, 3) Poor structural integrity of the electrodes. In addition, the calendar life of Si-LIBs is still less than two years, which is far less than the ten-year calendar life required for electric vehicle applications. To improve both cycle life and calendar life, we have developed a low-cost, pitch-based carbon coating approach to synthesize micron-sized porous Si particles. A novel etching method is also developed to prevent overheating and bubbling during the Si etching process. Recently, we have developed a novel electrolyte based on the concept of localized high concentration electrolyte tailored for Si-LIBs. It leads to the formation of stable interphase layers on both the anode and cathode and effectively blocks the crosstalk between the electrodes, minimizing the impedance increase of Si||LiNi0.6Mn0.2Co0.2 (NMC622) batteries during storage at elevated temperature (55°C), therefore largely improves their calendar life. Si||NMC622 batteries using this electrolyte also demonstrated high-capacity retention of 92.4% after 500 cycles at 45°C with well-preserved electrode structures. More details on the development of Si-LIBs in PNNL will be presented in this talk.

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