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The demand for high-energy-density lithium-ion batteries (LIBs) has driven intensive research into cathode materials that exhibit both superior performance and stability over multiple charge–discharge cycles. 

Electrolytes play a critical role in the formation of stable solid electrolyte interphase (SEI) for Si anodes. This study investigates the impacts of five different electrolytes on the specific capacity and cycle stability of Si-based anodes and confirms the advantages of the second-generation (Gen2) electrolyte over the first-generation (Gen1) electrolyte in the first 200 cycles, beyond which the advantages of Gen2 electrolyte disappear. Addition of more FEC and VC additives to Gen2 electrolyte does not offer significant advantages in the cycle stability and specific capacities. However, very high FEC electrolytes with 20 wt% FEC and 80% dimethyl carbonate exhibits strong dependance on the lithiation cutoff voltage. This electrolyte results in durable SEI layers when the lithiation cutoff voltage is at 0.01 V vs Li/Li⁺. Furthermore, lowering the lithiation cutoff voltage from 0.1 V to 0.01 V vs Li/Li⁺has raised the specific capacity of Si-based anodes, leading to higher specific capacities than those of graphite anodes at the electrode level for 380 cycles investigated in this study. The understandings developed here provide unambiguous guidelines for selection of electrolytes to achieve long cycle stability and high specific capacity of Si-based cells simultaneously in the future. 

NaCrO2 is a promising cathode for Na-ion batteries. However, further studies of the mechanisms controlling its specific capacities and cycle stability are needed for real-world applications in the future. This study reveals, for the first time, that the typical specific capacity of ~110 mAh/g reported by many researchers when the charge/discharge voltage window is set between 2.0 and 3.6 V vs. Na/Na+ is actually controlled by the low electronic conductivity at the electrode/electrolyte interface. Through wet solution mixing of NaCrO2 particles with carbon precursors, uniform carbon coating can be formed on the surface of NaCrO2 particles, leading to unprecedented specific capacities at 140 mAh/g, which is the highest specific capacity ever reported in the literature with the lower and upper cutoff voltages at the aforementioned values. However, such carbon-coated NaCrO2 with ultrahigh specific capacity does not improve cycle stability because with the specific capacity at 140 mAh/g the Na deintercalation during charge is more than 50% Na ions per formula unit of NaCrO2 which leads to irreversible redox reactions. The insights from this study provide a future direction to enhance the long-term cycle stability of NaCrO2 through integrating carbon coating and doping. 

Several effective methods have been developed recently to demonstrate simultaneous high energy and high power density in Lithium - carbon fluoride (Li-CFx) batteries. These methods can achieve as high as a 1000 Wh/kg energy density at a 60–70 kW/kg power density (40–50 C rate) in coin cells and a 750 Wh/kg energy density at a 12.5 kW/kg power density (20 C rate) in pouch cells. This performance is made possible by an ingenious nano-architecture design, controlled porosity, boron doping, and electrolyte additives. In the present study, we show that a similarly great performance, a 931 Wh/kg energy density at a 59 kW/kg power density, can be achieved by using a polyacrylonitrile binder and a LiBF4 electrolyte in Li-graphite fluoride coin cells. We also demonstrate that the observed effect is the result of the right combination of the binder and the electrolyte. We propose that the mechanistic origin of the observed phenomena is an electro-catalytic effect of the polyacrylonitrile binder. While our proposed method has a competitive performance, it also offers a simple implementation and a scalable production of high-energy and high-power primary Li-CFx cells.