lithium 18650 li ion battery technology has made new progress

OFweek Lithium Network Comprehensive Report: At present, the main chemical energy storage technologies in the world include sodium-sulfur batteries, lithium batteries, flow batteries, lead-acid batteries, lithium iron phosphate batteries, etc. A researcher from the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, said that with the development of the renewable energy industry and the electric vehicle industry, energy storage technology and industry have been highly valued by various countries, and the research and development of various new electrochemical energy storage battery technologies have made continuous progress. Among them, the more representative ones are flow batteries, lithium-sulfur batteries and lithium-air batteries, but their technological development faces some practical challenges.

Flow battery energy storage technology

Flow batteries are generally electrochemical energy storage devices that realize the mutual conversion of electrical energy and chemical energy through the redox reaction of liquid active substances, thereby realizing the storage and release of electrical energy. Because of its outstanding advantages such as independent power and capacity, deep charging and discharging, and good safety, it has become one of the best choices in the field of energy storage.

Since its invention in the 1970s, flow batteries have gone through a process from laboratory to enterprise, from prototype to standard product, from demonstration application to commercial promotion, from small to large scale, from single to comprehensive functions. More than 100 projects of various types have been implemented, with a cumulative installed capacity of about 40 megawatts.

With an installed capacity of 35 megawatts, all-vanadium flow batteries are currently the most widely used flow batteries. Dalian Rongke Energy Storage Technology Development Co., Ltd. (hereinafter referred to as Rongke Energy Storage), which is technically supported by the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences, has cooperated with the Dalian Institute of Chemical Physics to achieve the localization and large-scale production of key materials for all-vanadium flow batteries. Among them, electrolyte products have been exported to Japan, South Korea, the United States, Germany and the United Kingdom in large quantities. The highly selective, highly durable, and low-cost non-fluorine ion conductive membrane developed has better performance than perfluorosulfonic acid ion exchange membranes, and its price is only 10% of the latter, which truly breaks through the "cost bottleneck" of all-vanadium flow batteries.

Through structural optimization and application of new materials, the rated operating current density of the all-vanadium liquid flow battery stack has been increased from the original 80mA/c㎡ to 120mA/c㎡ while maintaining the same performance. The stack cost has dropped by nearly 30%, and the single stack specification has reached 32 kilowatts, which has been exported to the United States and Germany. In May 2013, the world's largest 5MW/10MWh all-vanadium liquid flow battery energy storage system designed and built was successfully connected to the grid at the Guodian Longyuan Woniu Stone 50MW wind farm. The subsequent implementation of the 3MW/6MWh energy storage project for wind power grid connection in Jinzhou and the Guodian Hefeng 2MW/4MWh energy storage project are also important cases for my country to explore energy storage business models.

Another leading company in the field of all-vanadium liquid flow batteries is Japan's Sumitomo Electric Industries. The company restarted its flow battery business in 2010 and will build a 15MW/60MWh all-vanadium flow battery power station in 2015 to solve the peak load regulation and power quality pressure brought by the grid connection of large-scale solar power stations in local areas of Hokkaido. The successful implementation of this project will be another milestone in the field of all-vanadium flow batteries. In 2014, UniEnergyTechnologies, LLC (UET) of the United States established a 3MW/10MWh all-vanadium flow battery energy storage system with the support of the U.S. Department of Energy and the Washington Clean Fund. In this project, UET will apply its mixed acid electrolyte technology for the first time, which will increase the energy density by about 40%, and can broaden the temperature window and voltage range of all-vanadium flow batteries, and reduce thermal management energy consumption.

At present, improving the energy efficiency of flow batteries and the reliability of the system and reducing their costs are important issues for the large-scale popularization and application of flow batteries. Developing high-performance battery materials, optimizing battery structure design, and reducing battery internal resistance are technical keys. Recently, Zhang Huamin and his research team have improved the charge and discharge energy efficiency of all-vanadium liquid flow battery from 81% a few years ago to 93% at a working current density of 80mA//c㎡ through battery material innovation and structural innovation, which fully proves that it has broad development space and prospects.

lithium 18650 li ion battery technology

In recent years, traditional lithium-ion battery technology has continued to improve, but the specific energy of the battery still cannot meet the requirements of application. Battery technology is still the biggest bottleneck in the development of portable electronic devices and electric vehicles. In order to achieve innovative breakthroughs in high-specific-energy battery technology, researchers have chosen lithium-sulfur batteries and metal-air batteries such as lithium-air batteries with higher energy density, and have made certain progress. Some new battery technologies have seen the dawn of practical application.

According to the latest news, American scientists have recently broken through the main obstacle currently facing lithium-sulfur batteries-the problem of electrolyte dissolution, and solved the problem of rapid failure of lithium-sulfur batteries. This technological breakthrough is expected to greatly enhance the market competitiveness of lithium-sulfur batteries. In a paper published in the Royal Society of Chemistry journal Nanoscale, researchers at the University of California, Riverside's Burns School of Engineering announced that they have recently successfully developed a nanoscale sulfur particle. The cathode material formed by combining it with silicon dioxide can prevent the dissolution of lithium 18650 li ion battery electrolytes and significantly improve battery performance.

lithium 18650 li ion battery is a battery with sulfur as the positive electrode and metallic lithium as the negative electrode. Its theoretical specific energy density can reach 2600Wh/kg and its actual energy density can reach 450Wh/kg. At the same time, elemental sulfur is cheap, abundant in output, and environmentally friendly. It is currently the most industrialized high-specific energy battery technology.

Internationally, representative R&D manufacturers of lithium-sulfur batteries include SionPower, Polyplus, Moltech in the United States, Oxis in the United Kingdom, and Samsung in South Korea. Among them, the results of SionPower are the most representative. In 2010, SionPower applied lithium-sulfur batteries to drones, which were charged by solar cells during the day and discharged at night to provide power, creating a record of 14 consecutive days of drone flight, which is a relatively successful application example of lithium-sulfur batteries. In China, the research on lithium-sulfur batteries is mainly concentrated in scientific research units such as the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences, the China Institute of Special Chemicals, and the Beijing Institute of Technology, and has achieved rapid development in recent years. At present, the lithium-sulfur batteries developed in China are already in the world's leading position in energy density (>450Wh/kg), but after dozens of normal charge and discharge, the energy density will be greatly reduced, and its cycle life needs to be improved urgently.

Lithium-sulfur batteries are cutting-edge technologies that countries around the world are competing to develop, and their industrialization prospects are generally optimistic. How to significantly improve the charge and discharge cycle life and safety of the battery will become the key to the industrial development of lithium-sulfur batteries.

Metal-air battery technology

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

Lithium-air batteries use metallic lithium as the negative electrode and oxygen in the air as the positive electrode active substance. Through the electrochemical reaction between lithium and oxygen, the mutual conversion of electrical energy and chemical energy is realized. The theoretical energy density of this battery can reach about 3500Wh/kg, which is 10 times that of lithium-ion batteries and close to gasoline. Focusing on the potential application prospects of lithium-air batteries, countries around the world have carried out related research work. IBM has been committed to the "Battery 500" project, hoping to achieve the goal of 500 miles of electric vehicle range on a single charge; and the participation of Japanese companies such as Asahi Kasei will promote the research of diaphragms and electrolytes.

Lithium-air batteries are not a new concept. They were first proposed by researchers at Lockheed in 1976. In 1996, Abraham et al. proposed an organic electrolyte system, which opened up a new situation for lithium-air battery research. At present, the research on lithium-air batteries is mainly focused on the positive electrode, which directly determines the various performance indicators of the battery. In terms of energy density, the most representative is graphene-based materials. Researchers at the Pacific Northwest National Laboratory in the United States have prepared a layered graphene material with a bubble-like structure, achieving a discharge specific capacity of about 15,000 mAh/g, far exceeding existing lithium-ion batteries.

However, the oxygen-containing intermediate products generated during the charge and discharge process of lithium-air batteries will react chemically with carbon materials, electrolytes, etc., resulting in the generation of a large number of byproducts (such as lithium carbonate, etc.), which greatly affects the battery cycle process and is a bottleneck problem restricting its development. Bruce et al. used porous gold and titanium carbide for the positive electrode, which can effectively inhibit side reactions, and the capacity retention rate after 100 cycles is greater than 95%.

High energy density is the main advantage of lithium-air batteries, while cycle stability is the key to its technological development and the difficulty it faces. On the other hand, the purification of metallic lithium and the protection of lithium negative electrodes and the suppression of dendrites during charge and discharge, the development of highly active positive electrode catalytic components and selective oxygen permeable membranes, and the battery structure design integration technology are all problems that need to be effectively solved in its practical process.

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