Engineering topics
Publications and source records attributed to Banerjee, Sanjoy.
Various zinc anodes with increasing calcium zincate (0%, 30%, 70%, 100%) were cycled at 50% theoretical Zn utilization to investigate cycle life and estimated cost. Failure mechanisms of majority 70% Zn/30% CaZn anodes are compared with pure CaZn.
Poster presentation at DOE OE Peer Review 2024 in Bellevue Washington
Achieving high cycle life rechargeableγ-MnO 2 cathodes in alkaline batteries face many challenges. Chief among these is the inability of theγ-MnO 2 polymorph to retain its structural integrity when cycled to high utilization of its theoretical capacity ∼300 mAh g −1 . In this paper, we investigate the root cause of failure of MnO 2 cathodes under deep cycling in the one-electron discharge range and establish a strong link between capacity fade and the amount of birnessite formed. We uncover the underlying cause of failure by cycling industrial scaleγ-MnO 2 cathodes at various levels of theoretical capacity utilization (100%, 50%, and 30%) and in different KOH concentrations (37, 25, and 10 wt%). To determine materials evolution the cycled cathodes were dissected, characterized and analyzed using SEM, XRD, FIB/SEM, EIS, and XPS. Based on our findings, we propose that one major cause of failure of MnO 2 cathodes stems from the solubility of Mn +3 formed during discharge which effectively results in destruction of theγ-MnO 2 phase and amorphization of the cathode. The results show that the bulk of theγ-MnO 2 phase is preserved only in ∼10 wt% KOH, which indicates the attractive range of KOH concentration for cycling of rechargeableγ-MnO 2 cathodes.
Poster presentation at DOE OE Peer Review 2024 in Bellevue Washington
A homogeneous disordered phase separates into ordered structures when quenched into a broken-symmetry phase. The competition of broken-symmetry phases to select an equilibrium state may be studied in terms of coarse-grained order parameters described by a suitable Landau free-energy function. A network of equilibrium-phase domains develops on quenching and coarsens with time with a topology that may be controlled by shear. We use three-dimensional simulations, in which time-dependent models for conserved-order parameters coupled to Navier-Stokes fluid models are solved, to investigate the evolution of such domains, e.g. spinodal decompositions of polymeric materials under shear. The numerical problems are formidable because of the strong nonlinearities inherent in the coupled model, and these are amongst the first 3D calculations undertaken. In linear shear fields we find stable nanostrings, also recently seen in experiments. The affinity of the ordered phases to boundaries plays a role in the form of the structures that develop, with stacked plate-like phase distributions emerging under certain conditions. Such methods appear quite promising for design and analysis of multiphase and complex fluid formulations. The behavior of foams in such conditions is of particular interest in microgravity environments. Additional information can be found in the original extended abstract.