Lian Chunyi, an associate professor at the City University of Hong Kong, led Li Hongfei (left) and Tang Zijie (right) to develop a water-based zinc battery. The picture shows three people holding a packaged zinc battery and a dioxide for making two electrodes. Manganese material and zinc flakes. (Picture from Hong Kong media)
For more than 20 years, lithium batteries have become a unique product in the rechargeable battery market, but they cannot be bent and not resistant to high temperatures. They are prone to fire and other safety concerns. They have always been the weakness of lithium batteries. According to Hong Kong media reports, recently, the study of teachers and students of City University of Hong Kong A water-based zinc battery is used as a selling point for softness and safety. It is expected to challenge the status of lithium batteries in some applications such as wearable electronic products.
Zhi Chunyi, an associate professor at the School of Science and Engineering at City University of Hong Kong, said that zinc-based batteries (hereafter referred to as 'zinc batteries') have a history of more than 100 years. They are the second commercialized battery in the world, only slightly more than lead-acid batteries. However, the zinc battery used in the past is mainly used once. In addition, the charge and discharge performance of the conventional zinc battery has been unsatisfactory, and the number of charge and discharge cycles is too small. Until more than three years ago, the water-based zinc battery studied in the university (the electrolyte contains water) ), can only be charged and discharged 100 times to 300 times.
Zhi Chunyi and a group of doctoral students began to study water-based zinc batteries more than three years ago. They encountered many difficulties at the beginning. Two years ago, they abandoned strong alkaline electrolytes, switched to weakly acidic electrolytes, and changed one of the electrodes. With the nanometer manganese dioxide material, a major breakthrough was achieved, and the number of charge and discharge cycles was greatly increased to more than 1000 times; and after 1000 charge and discharge, the storage capacity could still be maintained at the initial 97%.
A few years ago, soft lithium batteries were still not commercially produced. They hope to develop soft water zinc batteries to meet market applications and needs, such as wearable electronics. Because the electrolyte of water zinc batteries is liquid, it is difficult. They are packaged and leaking easily, so they add a 'hydrogel' to make the electrolyte semi-solid, which keeps the soft and flexible properties, and is easier to package. In case of damage to the package, the electrolyte will not leak.
In addition, since the electrolyte of the water-based zinc battery contains water, its essence is not flammable, and it is safer than the organic electrolyte of the lithium battery. After improvement, the water-based zinc battery developed by them is in a very harsh working environment such as impact, cutting, fire, Bending, etc., will not explode or catch fire, and can continue to provide a stable power supply, and the safety is greatly improved.
Zhi Chunyi is optimistic that the water-based zinc batteries they developed have great market potential in wearable electronics, smart clothing, medical products, beauty products, baby products, pet supplies, e-book readers, etc. There are also advantages, because it is not flammable. In theory, there should be no capacity limitation when carrying the aircraft.
According to the US Geological Survey, the world's proven lithium reserves total more than 53 million tons, and lithium reserves are about 14.47 million tons. The global proven zinc resource reserves are about 1.9 billion tons, and zinc reserves are about 230 million tons. The price of zinc is lower than that of lithium. It is used to make batteries. Compared with the same storage capacity, the cost of zinc batteries will be lower than that of lithium batteries.
Zhi Chunyi believes that due to the high requirements on the endurance of electric vehicles and the high energy density of lithium batteries, it is believed that they will still dominate this market. But considering the safety of lithium batteries, the cost and the reserves of lithium metal on the earth, etc. He believes that lithium batteries are unlikely to dominate all rechargeable battery markets in the future.
Li Hongfei and Tang Zijie, Ph.D. students who participated in research and development work, believe that lithium batteries have started in the mobile phone market since 1996. It has only been more than 20 years since its inception. The history of the electric vehicle market is shorter, so there is no problem with the production of lithium. However, with the deadline for some countries to require the production of fuel vehicles, the full conversion to pure electric vehicles may lead to insufficient lithium production and rising prices. Zinc reserves are higher and costs are lower. The future prospects of zinc batteries are worthy of optimism. Must be able to occupy seats in the rechargeable battery market.
In the 2018 "Challenge Cup" National Competition Hong Kong District Selection Competition (Hong Kong Undergraduate Innovation and Entrepreneurship Competition), their research projects won the second prize in the energy and chemical industry category. Now, Zhi Chunyi and his more than 10 doctoral students It is planned that a small amount of water-based zinc batteries developed by them will be trial-produced at the end of this year or early next year, and full commercialization will be in the middle of 2020.
