Energy Focus: Sponge electrode architecture provides safe, high-performance Ni-3D Zn battery
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esearch team relied on an aqueous mixture of potassium and lithium hydroxides as the electrolyte, along with insoluble calcium hydroxide that was deposited on specific surface locations of the metallic Zn sponge. The Ni-3D Zn cells were cycled in primary (singleuse) and secondary (multiple charge/discharge cycles) configurations. A full discharge of the battery allowed 91% of the zinc sponge to oxidize and yielded 1.2 kilowatt-hours of energy per kilogram of the anode material. When the cells cycled repeatedly (reversibly tapping 40% of the total amount of zinc present in the battery), the energy densities reached single-cell Li-ion capacity for over 100 cycles. EnZinc implemented the NRL results into their multicell stack design and found that weight and volumetric advantages accrue for Ni-3D Zn; the new technology minimizes the added weight/volume of system components necessary to manage safety concerns with Li-ion stacks. The sponge-like structure of the anodes demonstrated a vital microstructural advantage: repeated cycling, including both high and low power loads, did not allow for significant dendrite growth. The anodes endured 54,000 charge/discharge cycles using a duty cycle typical of start–stop batteries, which requires high power pulses, but low utilization of zinc per cycle. The Ni-3D Zn performance demonstrates that it can viably compete against advanced lead-acid batteries in microhybrid electric vehicles. “By demonstrating extreme capacity in single-use mode, cyclability to high Zn-normalized depths-of-discharge, and tens-of-thousands of short-duration duty cycles,” Parker says, “we can now offer a technologically relevant alternative to fire-prone Li-ion batteries in multiple fields-of-use.” A novel battery configuration is only as good as its large-scale production viability. To that end, the Ni-3D Zn approach presents important advantages because its raw materials are abundant and its balance of plant requirements (e.g., thermal management, electronic controls, and structural protection) is
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NEWS & ANALYSIS MATERIALS NEWS minimal. Furthermore, the battery can be effectively scaled up from small electronics (3000 m2/g) gives rise to more efficient electrochemical reactions at the electrode–electrolyte interface (i.e., lower overpotential), while reasonable conductivity resulting from GNR provides sufficient bulk conduction. Use of asphalt is important as it forms the necessary high-surface-area backbone structure. Additionally, it has very low levels of graphitization, which in turn reduces the propensity for Li intercalation in the host material, and promotes Li deposition at the surface. This intercalation-free approach also favors ultrafast operation, as sluggish solid-state diffusion—which is a characteris
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