New solid state zinc battery with superb cycle performance

Researchers in Australia have developed a new class of solid electrolytes for rechargeable aqueous zinc-iodine batteries, which has allowed for extended lifespan and high-efficiency. Symmetric cells employing this electrolyte have demonstrated excellent cycle performance, maintaining stability for approximately 5,000 hours at room temperature, while all-solid-state ZnI2 batteries exhibit over 7,000 cycles with a capacity retention exceeding 72.2%

Schematic of the battery

Image: University of Queensland

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From pv magazine ESS News site

Rechargeable zinc-iodine (ZnI2) batteries have received a lot of attention due to their inherent advantages, including natural abundance, low cost, safety, and high theoretical capacity. However, their limited cycle life remains a major challenge for practical applications.

Namely, the thermodynamic instability of the zinc electrode in an aqueous electrolyte always leads to the release of hydrogen, which causes the battery to swell and eventually fail. In addition to that, ZnI2 batteries are also susceptible to dendrite growth, which can damage the separator and cause battery failure.

Now, researchers at the University of Queensland in Australia have developed a new class of fluorinated block copolymers as solid electrolytes for all-solid-state ZnI2 batteries with extended lifespan.

Their results demonstrate the formation of a solid electrolyte interphase (SEI) layer on zinc, promoting horizontal zinc growth, mitigating dendrite penetration, and enhancing battery cycle life.

Symmetrical cells employing this electrolyte demonstrate excellent cycle performance, maintaining stability for approximately 5,000 hours at room temperature, while solid-state ZnI2 batteries exhibit over 7,000 cycles with a capacity retention exceeding 72.2%.

The complete ZnI2 battery has a nearly 100% Coulombic efficiency for more than 7,000 cycles (over 10,000 hours).

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Furthermore, the electrolyte exhibits excellent rate performance, delivering a reversible capacity of 79.8 mAh g-1 even at ultra-high current densities of 20 C.

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