KIST has developed core technology for aqueous zinc batteries

Most energy storage systems (ESS) have recently adopted lithium-ion batteries (LIBs), with the greatest technological maturity among secondary batteries. However, these are considered unsuitable for ESSs, which store significant amounts of electricity, due to fire hazards. The instability of the international supply of raw materials to build the LIBs also emerged as a critical concern. In contrast, Aqueous Zinc-Ion (AZIB) batteries use water as the electrolyte, which basically prevents battery ignition. Moreover, the price of zinc, the raw material, is only one-sixteenth that of lithium.

The research team led by Dr. Minah Lee from the Energy Storage Research Center of the Korea Institute of Science and Technology (KIST; President Seok-Jin Yoon) announced that they had successfully developed a “High-density zinc metal anode” manufacturing technology. which is essential to the marketing of AZIBs. This manufacturing technology is expected to act as a catalyst for the mass production of AZIB, as high energy density, long life zinc metal anodes can be produced by a simple electroplating process using inexpensive solutions. and environmentally friendly.

In theory, since AZIBs use two electrons per ion, they are advantageous in terms of volumetric energy density over alkaline metal-ion batteries. If the capacity of the metallic zinc used as anode to make the battery does not exceed twice that of the cathode, it is possible to achieve an energy density comparable to that of the LIBs marketed today. Moreover, even though the capacity of zinc metal reaches five times that of the cathode, it is still competitive in that it is similar to that of sodium-ion batteries, which are emerging as the next generation of batteries due to their low cost. and material abundance.

However, zinc metal anodes limit the energy density and lifetime of AZIBs due to irregular nanoparticle growth during battery operation. A low density of metallic zinc particles and a large surface area in the anode accelerate corrosion with the electrolyte, thus depleting the active metallic zinc and the electrolyte. Existing studies have typically used zinc metals that were 20 times thicker than needed to counter lifetime limitations; paradoxically, this led to an inevitable decline in energy density and cost-competitiveness, the greatest strengths of AZIBs.

Thus, the team led by Dr. Minah Lee at KIST controlled the microstructure of zinc metal anodes to reduce the prevalence of side reactions that induce the decline in energy density and lifetime of AZIBs. The team adopted a deep eutectic solvent (DES) solution, which can be easily synthesized at room temperature, to construct the compact zinc anodes. This DES solution is composed of choline chloride and urea mixed at a molar ratio of 1:2; the mixture becomes a liquid complex with a melting point of 12°C. The researchers confirmed that a zincophilic copper-zinc alloy layer forms spontaneously between the zinc and copper current collectors in DES, allowing the growth of high-density zinc particles. The researchers successfully used this discovery to develop an electroplating process that allows zinc metals to grow densely and uniformly in the low-cost, environmentally friendly DES solution.

The application of the fabricated zinc metal anode to an aqueous zinc battery system has shown that the corrosion reactions are effectively suppressed and the capacity is maintained at more than 70% after more than 7000 repeated charging and discharging. This result is exceptional compared to those of similar existing studies that used thin zinc, and the values ​​far exceed the charge and discharge lifetimes (1000 to 2000 times) of commercial LIBs.

Dr Minah Lee of KIST said, “We have been able to develop a core technology for the commercialization of AZIBs that can solve the fire safety problem of ESSs, which is the biggest obstacle to energy supply and expansion. renewable. She added, “We anticipate that this compact zinc anode manufacturing technology will pave the way for mass production of AZIB by combining a particularly economical and environmentally friendly ESD solution with an electroplating process already widely used in industry. .

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