The cost is equivalent to that of the cheapest aqueous electrolyte at present. The
new electrolyte may solve the problem of large-scale application of rechargeable zinc batteries.
In the new electrolyte composed of hydrated zinc tetrafluoroborate and ethylene glycol solvent, the high boiling point of ethylene glycol itself and the strong interaction between the components in the electrolyte make the electrolyte not easy to volatilize and freeze, and can simultaneously Withstands the extreme heat and cold, which greatly broadens the scope of application of zinc batteries.
◎Reporter Chen Xi, correspondent Zhang Hua
Rechargeable zinc battery is a new type of electrochemical energy storage device, which is safer and more reliable than lithium battery, and the cost is also lower.
However, the limitation of using water as the electrolyte solvent of zinc batteries severely restricts the industrialization of zinc batteries.
The reporter learned from Tianjin University on December 13 that the Advanced Carbon and Nano Energy Laboratory of the university, in conjunction with the Advanced Energy Materials Team of the Shenzhen International Graduate School of Tsinghua University and the Advanced Carbon Materials Research Department of the Institute of Metals, Chinese Academy of Sciences, successfully developed a new type compatible with metallic zinc. The new low-cost non-flammable aqueous organic electrolyte.
Related results were published online in the international journal "Nature·Sustainability".
Aqueous electrolyte makes zinc batteries face dendrite and corrosion challenges
How to achieve the goal of "carbon peak and carbon neutrality" has become a global focus and topic, and increasing the green development and efficient use of renewable energy has become a global consensus.
The vigorous development of green and safe large-scale energy storage technology is the necessary technical support for the full development and utilization of renewable energy.
Rechargeable zinc battery is a promising green and safe energy storage technology. It uses a similar working principle to lithium batteries and uses the reciprocating shuttle of zinc ions in the electrolyte between the positive and negative electrodes to store and release electrical energy.
However, unlike lithium batteries that use highly flammable organic electrolytes, rechargeable zinc batteries mainly use water as the electrolyte solvent, so there are no problems such as flammability and explosion of lithium batteries, and it is safer to use.
"Moreover, because of the abundant raw material reserves of zinc batteries and the relatively simple assembly, storage, transportation and maintenance of batteries, they are considered to have broader application prospects in the field of large-scale energy storage and have received extensive attention in recent years." School of Chemical Engineering, Tianjin University Professor Yang Quanhong introduced.
However, metal zinc as a negative electrode has serious dendrite and corrosion problems in aqueous electrolytes that need to be resolved urgently.
"The so-called dendrites refer to the non-uniform deposition of zinc ions in the electrolyte on the zinc negative electrode during the charging process, resulting in the appearance of dendritic metallic zinc." Yang Quanhong explained that this kind of dendrites continue to grow during battery charging and discharging, and finally It will pierce the separator and contact the positive electrode, causing the battery to fail due to an internal short circuit.
The corrosion problem is mainly due to the fact that zinc metal is more active and will spontaneously chemically react with water, which will continue to consume the metal zinc negative electrode and electrolyte, resulting in a significant reduction in battery life.
"It can be said that the dendrite and corrosion problems of the metal zinc anode seriously restrict the industrialization and large-scale application of zinc batteries." Yang Quanhong said.
The new electrolyte is composed of hydrated zinc tetrafluoroborate and ethylene glycol
In order to overcome the two major problems faced by rechargeable zinc batteries, the project team developed a new electrolyte composed of hydrated zinc tetrafluoroborate and glycol solvent.
Using ethylene glycol instead of water as the electrolyte solvent can greatly inhibit the corrosion problem of the metal zinc anode. At the same time, the tetrafluoroborate anion and a small amount of water molecules (from the bound water in the hydrated zinc tetrafluoroborate) in the electrolyte will interact with The metal zinc negative electrode reacts and spontaneously forms a dense and stable zinc fluoride solid electrolyte interface layer on the surface of the zinc negative electrode. This interface layer can block the direct contact between the electrolyte and the zinc negative electrode while allowing zinc ions to pass through, thereby further inhibiting The formation of zinc dendrites and the occurrence of corrosion side reactions have greatly increased the service life of zinc batteries.
"Although ethylene glycol is also a flammable organic solvent, hydrated zinc tetrafluoroborate is a widely used flame retardant." Yang Quanhong introduced. Therefore, this type of The electrolyte composed of glycol still maintains the same non-flammability as the water-based electrolyte, and is safe and reliable.
Not only that, the high boiling point of ethylene glycol itself and the strong interaction between the components in the electrolyte make the electrolyte not easy to volatilize and freeze, and can withstand both extreme heat (40°C) and severe cold (-30°C). It is currently unattainable with water-based electrolytes, which greatly broadens the scope of application of zinc batteries.
"Due to the mature industrial application of hydrated zinc tetrafluoroborate and ethylene glycol, and the low cost, the cost of the new electrolyte developed by us is comparable to the current cheapest aqueous electrolyte." Yang Quanhong said.
The successful research and development of the electrolyte is expected to further drive the current research boom in zinc batteries and promote the industrialization process of zinc batteries.
"Nature·Sustainability" issued a special article review at the same time. It is believed that this work uses cheap and environmentally friendly electrolyte to solve several key problems in the process of zinc battery industrialization, and provides a reliable and cost-effective way to build a sustainable future. Battery solutions.