Lynntech (United States)

State-of-the-art (SOA) lithium-ion (Li-ion) batteries are approaching their specific energy density limit (~250 Wh kg−1).1 Layered structured, nickel-rich (Ni-rich or high Ni content) lithium transition metal oxides, e.g., LiNi0.8Mn0.1Co0.1O2 (NMC811), have attracted great interests2 owning to their practically deliverable high specific capacity >200 mAh/g. Coupled with high average discharge voltages (~4V vs. Li/Li+), Ni-rich cathode-based lithium batteries possess a great potential to achieve much higher specific energies, e.g., >350 Wh/kg at cell level targeted for electric drive vehicles,3 than SOA Li-ion batteries. In addition, Ni-rich oxides are economically viable as low-cost battery cathode materials due to their low cobalt content. However, Ni-rich cathode-based Li-ion batteries exhibit a quick capacity degradation upon cycling particularly at high charge cutoff voltages (e.g., 4.5V vs. Li/Li+) and at elevated temperatures. Possible degradation mechanisms of Ni-rich based Li cells include structural changes of the material (large c-axis shrinkage at high potentials)4 and parasitic reactions that arise from the interactions between the electrolytes and highly reactive delithiated cathode surface (due to high oxidation state Ni4+ ions).5,6 Therefore, R&D efforts are needed to tackle technical challenges facing the Ni-rick based Li batteries before they become commercially viable.We will present our efforts of developing high voltage electrolytes to afford stable electrochemical performance of Ni-rich cathode-based Li cells. Figure 1 shows the electrochemical performance of NMC-811 cathode, paired Li metal anode, in conventional Li-ion battery electrolyte (Baseline electrolyte) and the high voltage electrolyte developed in this study, evaluated at C/4 rate during the formation and 1 C rate during cycling, between 2.5V and 4.5V, at room temperature. The cell with the high voltage electrolyte maintained ~80% capacity retention after 400 cycles. In contract, the cell with the baseline electrolyte experieced a large capacity fade with only ~25% capacity retention after 400 cycles. The superior cycle stability of the high votage electrolyte, Ni-rich based cell is attributed to the inharently high-voltage stable, multi-functional. Electrolyte chemical structures and their correlation with the electrochemical stability will be discussed. References Chen, W.; Lei, T.; Qian, T.; Lv, W.; He, W.; Wu, C.; Liu, X.; Liu, J.; Chen, B.; Yan, C.; Xiong, J., Advanced Energy Materials 2018, 8 (12).Jiang, M.; Danilov, D. L.; Eichel, R.-A.; Notten, P. H. L., Advanced Energy Materials 2021, 11 (48), 2103005.Gomez‐Martin, A.; Reissig, F.; Frankenstein, L.; Heidbüchel, M.; Winter, M.; Placke, T.; Schmuch, R., Advanced Energy Materials 2022, 12 (8).Cho, D.-H.; Jo, C.-H.; Cho, W.; Kim, Y.-J.; Yashiro, H.; Sun, Y.-K.; Myung, S.-T., Journal of The Electrochemical Society 2014, 161 (6), A920-A926.Chen, C. H.; Liu, J.; Amine, K., Journal of Power Sources 2001, 96 (2), 321-328.Li, J.; Downie, L. E.; Ma, L.; Qiu, W.; Dahn, J. R., Journal of The Electrochemical Society 2015, 162 (7), A1401-A1408. Acknowledgement This material is based upon work supported by the Naval Air Warfare Center Weapons Division, China Lake, CA under Contract No N6893622C0017. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Naval Air Warfare Center Weapons Division, China Lake, CA. Figure 1

Particle size plays an important role in the electrochemical performance of cathodes for lithium-ion (Li-ion) batteries. High energy planetary ball milling of LiNi1/3Mn1/3Co1/3O2 (NMC) cathode materials was investigated as a route to reduce the particle size and improve the electrochemical performance. The effect of ball milling times, milling speeds, and composition on the structure and properties of NMC cathodes was determined. X-ray diffraction analysis showed that ball milling decreased primary particle (crystallite) size by up to 29%, and the crystallite size was correlated with the milling time and milling speed. Using relatively mild milling conditions that provided an intermediate crystallite size, cathodes with higher capacities, improved rate capabilities, and improved capacity retention were obtained within 14 μm-thick electrode configurations. High milling speeds and long milling times not only resulted in smaller crystallite sizes but also lowered electrochemical performance. Beyond reduction in crystallite size, ball milling was found to increase the interfacial charge transfer resistance, lower the electrical conductivity, and produce aggregates that influenced performance. Computations support that electrolyte diffusivity within the cathode and film thickness play a significant role in the electrode performance. This study shows that cathodes with improved performance are obtained through use of mild ball milling conditions and appropriately designed electrodes that optimize the multiple transport phenomena involved in electrochemical charge storage materials.

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for synthesizing nanoscopic VB2 is presented as well as step-by-step procedure for applying a zirconium oxide coating to the VB2 particles for stabilization upon discharge. The process for disassembling existing zinc/air cells is shown, in addition construction of the new working electrode to replace the conventional zinc/air cell anode with a the nanoscopic VB2 anode. Finally, discharge of the completed VB2/air battery is reported. We show that using the zinc/air cell as a test bed is useful to provide a consistent configuration to study the performance of the high-energy high capacity nanoscopic VB2 anode.

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Fullerenes are under intensive study for potential biomedical applications. We have previously reported that a C60 fullerene functionalized with three dimethylpyrrolidinium groups (BF6) is a highly active broad-spectrum antimicrobial photosensitizer in vitro when combined with white-light illumination. We asked whether this high degree of in vitro activity would translate into an in vivo therapeutic effect in two potentially lethal mouse models of infected wounds. We used stable bioluminescent bacteria and a low light imaging system to follow the progress of the infection noninvasively in real time. An excisional wound on the mouse back was contaminated with one of two bioluminescent Gram-negative species, Proteus mirabilis (2.5 × 10(7) cells) and Pseudomonas aeruginosa (5 × 10(6) cells). A solution of BF6 was placed into the wound followed by delivery of up to 180 J/cm(2) of broadband white light (400-700 nm). In both cases there was a light-dose-dependent reduction of bioluminescence from the wound not observed in control groups (light alone or BF6 alone). Fullerene-mediated photodynamic therapy of mice infected with P. mirabilis led to 82% survival compared with 8% survival without treatment (p < 0.001). Photodynamic therapy of mice infected with highly virulent P. aeruginosa did not lead to survival, but when photodynamic therapy was combined with a suboptimal dose of the antibiotic tobramycin (6 mg/kg for 1 day) there was a synergistic therapeutic effect with a survival of 60% compared with a survival of 20% with tobramycin alone (p < 0.01). These data suggest that cationic fullerenes have clinical potential as an antimicrobial photosensitizer for superficial infections where red light is not needed to penetrate tissue.