Brief analysis of all vanadium redox flow battery

Brief analysis of all vanadium redox flow battery

Lithium-ion batteries is very hot in energy storage industry in recent years. According to statistics, in new installed capacity of energy storage technology in 2014, lithium-ion batteries accounted for up to 74%. Tesla's super battery factory chose lithium-ion battery technology for R&D and production. They also launched Powerwall for the small energy storage market, which widely welcome by the market. However, in fact, depending on requirements of the energy storage technology in the application field, various energy storage technologies have suitable application fields. When dealing with large-scale energy storage applications, lithium-ion batteries have encountered rivals. According to foreign media reports, the US Department of Energy is supporting the United States UniEnergy Technologies to implement a new flow battery energy storage project, the goal is to be able to liquid flow battery and Tesla battery-based lithium when the project reaches large-scale and grid integration. Ion batteries were compared and compared.

Energy storage technology, everyone will feel that Japan, the United States is the most cattle, but in the field of flow batteries, China can be said to be No.1 in the world. At present, the world's largest all-vanadium flow battery energy storage system is developed by Chinese companies, and the international standard for liquid flow batteries is also researched and developed by Chinese scientists. Can Dou visit the head of the standard system and was also the chief engineer of the world's largest all-vanadium flow battery system project, Professor Zhang Huamin.

Professor Zhang is currently the Principal Investigator of Dalian Institute of Chemical Physics, Director of the National Key Laboratory of Energy Flow Battery Energy Storage Technology, and Deputy General Manager and Chief Engineer of Dalian Rongke Energy Storage Technology Development Co., Ltd. Professor Zhang Huamin was a talented person of the Chinese Academy of Sciences in 2000 and returned to China to work at the Dalian Institute of Chemical Physics. He studied in Japan and worked on fuel cell research. After returning to China, Professor Zhang Huamin served as the director of the Fuel Cell Research Center, assistant to the director, and minister of the energy storage technology department.

Why did Professor Zhang Huamin switch from a fuel cell to a flow battery? Since 2000, what happened to China's energy storage in 15 years? What is the future of energy storage technology development? Please pay attention to the omnipotent 2015 summit. Energy talker, Professor Zhang Huamin as a special guest will share his wonderful experience and his judgment on the future blue ocean of energy storage technology.

Today, I can take you in advance with the science of what is a flow battery, and see why the future of large-scale energy storage is here.

Flow battery ABC

1. What is a flow battery?

A flow battery is a secondary battery technology in which an active material is present in a liquid electrolyte. The electrolyte is placed outside the stack, flows through the stack under the push of the circulation pump, and an electrochemical reaction occurs to convert the chemical energy and the electric energy, thereby realizing the storage and release of the electric energy.

2. What are the characteristics of the flow battery?

1 The energy storage capacity is easy to adjust the scale. The output power of the battery depends on the size and number of the stack. The energy storage capacity depends on the electrolyte capacity and concentration. Therefore, the scale design of the flow battery is very flexible: as long as the area of the stack and the number of stacks are increased, the output can be increased. Power; if the volume of the electrolyte is increased, the energy storage capacity can be increased.

2 The flow cell has a high degree of freedom in site selection. The system can be fully automatic closed operation, no pollution, simple maintenance and low operating cost.

3 high security. The electrolyte solution is an aqueous solution, and the battery system has no potential explosion or fire hazard and is highly safe.

3. Type of flow battery

According to the different active substances, the flow battery can be divided into various technical routes such as vanadium, zinc/bromine, sodium polysulfide/bromide and iron/chromium. Up to now, the total installed capacity of liquid flow batteries worldwide is about 68MW, of which all vanadium redox flow batteries account for 40%. From the current technology maturity and engineering application effects, all vanadium redox flow battery technology has entered the stage of engineering application and market development, and commercialization has begun; zinc-bromine flow battery technology has entered the application demonstration and market development stage; other flow batteries are still at Research phase.

The positive electrode pair of all vanadium redox flow energy storage battery is VO2+/VO2+, and the negative electrode pair is V2+/V3+. The electrode has the following electrochemical reaction:

4. Technical characteristics of all vanadium flow battery

1 Long cycle life: The charge and discharge cycle life of all vanadium redox energy storage batteries can reach more than 13,000 cycles, and the calendar life is over 15 years.

2Charging and discharging characteristics are good: The all-vanadium flow battery energy storage system has the characteristics of fast, deep charge and discharge without affecting the service life of the battery, and the uniformity of each single cell is good. In addition, vanadium ions have high electrochemical reversibility and small electrochemical polarization, which is very suitable for rapid charging and discharging of large currents.

3 Power and capacity independent design: The power of the all-vanadium flow battery is determined by the size and quantity of the stack, and the capacity is determined by the concentration and volume of the electrolyte. Therefore, the power expansion can be achieved by increasing the power of the stack and increasing the number of stacks, and the increase in capacity can be achieved by increasing the volume of the electrolyte.

4Safety and environmental protection: The all-vanadium flow battery energy storage system works under normal temperature and normal pressure conditions, which not only prolongs the service life of battery components, but also shows very good safety performance. In addition, the electrolyte solution can be recycled and recycled, which is environmentally friendly and saves resources. Most of the battery components are inexpensive carbon materials, engineering plastics, long service life, rich material sources, mature processing technology and easy recycling.

In general, all vanadium redox flow batteries have a capacity of hundreds of kilowatts to hundreds of megawatts, and energy storage capacity is hundreds of kilowatt hours to hundreds of megawatts. It has obvious advantages and is one of the preferred technologies for large-scale and efficient energy storage technology.

5. What are the challenges faced by all vanadium redox flow batteries?

1 ion exchange membrane technology. The ion exchange membrane can affect the mutual ion permeability between the positive and negative electrolytes, thereby affecting the energy efficiency of the flow battery and the life of the battery. It is necessary to research and develop a highly selective and highly conductive ion exchange membrane for a liquid flow battery.

2 high concentration and high stability electrolyte preparation technology. Previously, electrolyte costs accounted for nearly 50% of the total cost. At present, due to the decrease in battery cost, the proportion of electrolyte cost is greater.

3 The energy density is low and the volume is large. The battery system needs to be equipped with many auxiliary components such as pipelines, valve components, electrolyte circulation pumps, heat exchangers, etc., which makes the flow battery more complicated and puts higher requirements on the reliability of the battery system.

6. What is the current status and prospects of flow battery development?

The all-vanadium flow battery is suitable for energy storage in peak shaving power systems, large-scale photovoltaic power systems, wind power generation systems, and uninterruptible power supplies or emergency power systems.

The world's all-vanadium flow battery manufacturers mainly include: Sumitomo Electric Company of Japan, Dalian Rongke Energy Storage Technology Development Co., Ltd. (hereinafter referred to as: Rongke Energy Storage Company), UniEnergy Technologies of the United States and Gildemeister of Austria.

Sumitomo Electric Co., Ltd. began research and development of all-vanadium flow battery technology in the 1990s. It has leading system integration and engineering application technology, but its key functional materials and components depend on outsourcing, and the cost is high. UniEnergy Technologies of the United States has the world's leading mixed-acid all-vanadium flow battery technology, and is responsible for the construction of the first megawatt-class all-vanadium flow battery energy storage power station in the United States. Gildemeister has been developing all-vanadium liquid storage energy storage batteries since 2002. The products are mainly used in solar photovoltaic cells for power supply in remote areas and electric vehicle charging stations.

China's all-vanadium liquid energy storage technology and industrial development are at the world's leading level. At present, Rongke Energy Storage Company has realized an installed capacity of all vanadium redox flow batteries exceeding 12MW, accounting for 40% of the world's total installed capacity. In 2013, the world's largest 5MW/10MWh all-vanadium flow battery energy storage system jointly developed by Rongke Energy Storage Company and Dalian Institute of Chemical Industry successfully passed the acceptance of the owner. This is the world's first 5MW that is connected to the grid. The large-scale industrial energy storage devices, all indicators are at the international leading level.

In 2014, Rongke Energy Storage Co., Ltd. cooperated with Bosch Group (BOSCH) to build a 250kW/1MWh all-vanadium flow battery energy storage system in northern German wind farm. The system is currently the largest all-vanadium flow battery system in Europe, and its performance and stability are highly valued by overseas customers. Rongke Energy Storage Co., Ltd. also cooperated with UniEnergy Technologies of the United States to build the first megawatt all-vanadium liquid energy storage battery power station in the United States.

The page contains the contents of the machine translation.