Energy storage battery competition

Introduction: with the development of renewable energy industry and electric vehicle industry, energy storage technology and industry are highly valued by all countries. Research and development of a variety of new electrochemical energy storage battery technology have made continuous progress. Among them, the more representative liquid flow battery, lithium sulfur battery and lithium air battery, etc., but their technological development are facing some practical challenges.

At present, the main international chemical energy storage technologies include sodium sulfur battery, lithium battery, liquid flow battery, lead-acid battery, lithium iron phosphate battery, etc. Zhang huamin, a researcher at the dalian institute of chemical physics of the Chinese academy of sciences, said that with the development of the renewable energy industry and electric vehicle industry, energy storage technology and industry have been highly valued by all countries, and the research and development of various new electrochemical energy storage battery technology has made continuous progress. Among them, the more representative liquid flow battery, lithium sulfur battery and lithium air battery, etc., but their technological development are facing some practical challenges.

Liquid flow battery energy storage technology

Liquid-flow battery is an electrochemical energy storage device which can realize the mutual conversion of electric energy and chemical energy through the REDOX reaction of the liquid active substance. Because of its independent power and capacity, depth of charge and discharge, good security and other outstanding advantages, has become one of the best choice in the field of energy storage.

Since the invention of liquid flow battery in the 1970s, it has gone through hundreds of projects from laboratory to enterprise, from prototype to standard product, from demonstration application to commercial promotion, from small to large scale, from single to comprehensive function, with a total installed capacity of about 40 mw.

The total vanadium flow battery with a installed capacity of 35 mw is the most widely used liquid flow battery. With the technical support of Dalian institute of chemical physics, Chinese academy of sciences, dalian rongke energy storage technology development co., LTD. (hereinafter referred to as rongke energy storage) cooperated with dalian institute of chemical physics to realize the localization and large-scale production of key materials of all-vanadium liquid flow battery. Electrolyte products have been exported to Japan, South Korea, the United States, Germany and the United Kingdom. The high selectivity, high durability and low cost of the developed non-fluorinated ion conduction membrane is better than the perfluorinated sulfonic acid ion exchange membrane, and the price is only 10% of the latter, truly breaking through the "cost bottleneck" of the all-vanadium flow battery.

Through structural optimization and application of new materials, vanadium flow batteries electric pile rated current density has increased from the original 80 ma/c ㎡ to 120 ㎡ and ma/c keep the same performance, electricity costs plunged nearly 30%, single pile specification of 32 kw, has been exported to the United States and Germany. In May 2013, the world's largest 5 megawatt /10-megawatt hour full vanadium flow battery energy storage system was successfully connected to the grid in guodian longyuan niushi 50 megawatt wind farm. Since then, the 3 mw /6 mw hour energy storage project for wind power grid connection in jinzhou and the 2 mw /4 mw hour energy storage project for guodian and wind are also important cases for China to explore the energy storage business model.

Another leader in the field of all-vanadium flow batteries is sumitomo electric. The company restarted the liquid-flow battery business in 2010, and will build a 15-megawatt / 60-megawatt hour all-vanadium liquid-flow battery power station in 2015 to solve the peak load regulation and power quality pressure caused by the large-scale solar power station grid-connection in Hokkaido. The successful implementation of this project will be another milestone in the field of all-vanadium liquid-flow battery. In 2014, UniEnergyTechnologies, LLC(UET) established a 3 mw /10 mw full vanadium flow battery energy storage system with support from the U.S. department of energy and the Washington clean energy foundation. In this project, UET will apply its mixed acid electrolyte technology for the first time, which will increase the energy density by about 40%, broaden the temperature window and voltage range of all-vanadium flow batteries, and reduce energy consumption in thermal management.

At present, it is an important task to improve the energy efficiency and system reliability of liquid flow battery and reduce its cost. Developing high-performance battery materials, optimizing battery structure design and reducing internal resistance are the key technologies. Recently, zhang hua and his team through the battery material innovation and structure innovation, make the total vanadium flow batteries of the single battery in 80 ma / / c ㎡ working current density, charge and discharge energy efficiency increased to 93% from 81% a few years ago, fully prove that it has a broad space for development and prospects.

Lithium - sulfur battery technology

In recent years, the traditional lithium-ion battery technology has made continuous progress, but the specific energy of the battery still cannot meet the requirements of the application, and battery technology is still the biggest bottleneck in the development of portable electronic devices and electric vehicles. In order to realize the innovative breakthrough of high specific energy battery technology, researchers choose the breakthrough direction as lithium sulfur battery with higher energy density, lithium air battery and other metal air battery, and have made some progress. Some new battery technologies are already showing promise.

Lithium sulfur battery is a kind of battery with sulfur element as the positive electrode and lithium metal as the negative electrode. Its theoretical specific energy density can reach 2600Wh/kg, and the actual energy density can reach 450Wh/kg. At the same time, sulfur is cheap, abundant and environmentally friendly, which is the closest to industrialization of high specific energy battery technology.

Internationally, the representative research and development manufacturers for lithium and sulfur batteries include SionPower, Polyplus, Moltech from the United States, Oxis from the United Kingdom and Samsung from South Korea, etc., among which, SionPower is the most representative. In 2010, SionPower applied lithium sulfur battery to unmanned aerial vehicle (uav). The battery was charged by solar cells in the daytime and discharged at night to provide power, which set a record of 14 consecutive days of flight for uav. It is a successful application example of lithium sulfur battery. In China, the research on lithium - sulfur battery is mainly concentrated in dalian institute of chemical compounds of Chinese academy of sciences, China institute of chemical prevention and research, Beijing institute of technology and other research institutions. At present, the lithium sulfur battery developed in China has been in a leading position in the world in terms of energy density (>450Wh/kg), but after dozens of normal charging and discharging times, the energy density has been greatly reduced, and its cycle life needs to be improved urgently.

Lithium - sulfur battery is one of the most advanced technologies in the world. How to improve the cycle life and safety of the battery will be the key to the industrial development of li-sulfur battery.

Metal air battery technology

At present, metal air batteries, especially lithium - air batteries, have attracted great attention and made great progress.

Lithium - air battery takes lithium metal as the negative electrode and oxygen in the air as the positive electrode active material. The theoretical energy density of the battery is about 3500Wh/kg, 10 times that of lithium-ion batteries and close to that of gasoline. With an eye to the potential application prospects of lithium-air batteries, many countries in the world have carried out relevant research work. IBM has been working on the "battery 500" project, which aims to give electric cars a range of 500 miles on a single charge. The addition of enterprises such as Japan's asahi chemical will promote the research of diaphragm and electrolyte.

The concept of the lithium-air battery is not entirely new and was first proposed by lockheed researchers in 1976. In 1996, Abraham et al. proposed the organic electrolyte system, which initiated a new situation in the study of lithium-air batteries. At present, the study of li-air battery mainly focuses on the positive electrode, which directly determines the performance of the battery. In terms of energy density, the most representative material is graphene. Researchers at the Pacific northwest national laboratory in the United States have developed a layered graphene material with a bubble-like structure that achieves a discharge specific capacity of about 15,000 mah /g, far exceeding that of existing lithium-ion batteries.

However, the oxygen-containing intermediate products generated in the charging and discharging process of lithium-air battery will have chemical reactions with carbon materials and electrolytes, resulting in the generation of a large number of by-products (such as lithium carbonate, etc.), which greatly affects the battery cycle and is the bottleneck problem restricting its development. Bruce et al. applied porous gold and titanium carbide to the positive electrode, which can effectively inhibit side reactions, and the retention rate of 100 cycles is greater than 95%.

High energy density is the main advantage of li-air battery, and the cycling stability is the key and difficult problem for its development. On the other hand, purification of lithium metal, protection of lithium anode and dendrite inhibition during charging and discharging, development of highly active positive catalytic components and selective oxygen permeable membrane, and integration technology of battery structure design are all problems that need to be effectively solved in the practical process.

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