Advantages of lithium-ion batteries in the field of energy storage

Energy is an important material foundation for human survival and social development, and an important cornerstone for the national economy, national security, and the realization of sustainable development. With the development of human society, mankind’s demand for energy is increasing, but the ecological environment is constantly deteriorating, especially greenhouse gas emissions leading to increasingly severe global climate change. This contradiction has become more severe in recent years. At present, China has become a world energy producer and consumer. China’s demand for energy continues to grow. Therefore, it is urgent to adjust the energy structure: on the one hand, we must develop new energy sources to meet demand, and on the other hand, we must make reasonable and effective use of available energy. renewable energy.

Renewable energy includes: wind energy, solar energy, biomass energy, ocean energy and small hydropower, etc., which are primary energy sources and are usually converted into electrical energy. In the process of developing and utilizing renewable energy, electric energy storage technology plays an important role. As we all know, there are discontinuities and instabilities in the use of wind and solar energy, which need to be stabilized by the energy storage system before being connected to the grid. At the same time, the off-grid power generation mode of wind turbines is also indispensable; on the other hand , There is an imbalance in the use of energy, and the energy storage system can be used for the "peak shaving and valley filling" of the power grid, thereby improving energy utilization. In order to promote the large-scale utilization of renewable energy power generation, improve the efficiency of alternative energy power stations and maintain national energy security, research on energy storage technology has important economic and social significance. Industrial developed countries attach great importance to the research and development of large-scale energy storage systems. For example, the Japanese government’s “New Sunshine Program”, the US’s “DOE Project Program” and the EU’s “Framework Program” all focus on energy storage technology. my country also attaches great importance to the development of energy storage technology. High-efficiency energy conversion and energy storage technology has been listed as the priority development technology field of the future national torch plan. The China Energy Storage Battery Industry-University-Research Technology Innovation Alliance was established in November 2009. In addition, according to the "2000-2015 New Energy and Renewable Energy Industry Development Plan Essentials" issued by the State Economic and Trade Commission, by 2015, the annual production capacity of small wind turbines will reach 50,000 units, and the total output will reach 340,000 units. , With a total installed capacity of 105,000 kW and a total output value of about 900 million yuan, of which the sales of energy storage systems should exceed 100 million yuan, which will surely stimulate the development of the energy storage industry.

Driven by strong social development needs and huge potential markets, new energy storage systems based on new concepts, new materials and new technologies are constantly emerging. Energy storage technology is developing in the direction of large-scale, high efficiency, long life, low cost, and pollution-free.

1. Classification and development trend of energy storage technology

So far, in response to different fields and different needs, people have proposed and developed a variety of energy storage technologies to meet applications. Global energy storage technologies mainly include physical energy storage, chemical energy storage (such as sodium-sulfur batteries, all-vanadium flow batteries, lead-acid batteries, lithium-ion batteries, supercapacitors, etc.), electromagnetic energy storage, and phase-change energy storage.

1. Physical energy storage

Physical energy storage technologies mainly include pumped water storage, compressed air energy storage, and flywheel energy storage. Compared with chemical energy storage, physical energy storage is more environmentally friendly and green, and is realized by using natural resources. Pumped Storage Hydroelectricity (PSH, Pumped Storage Hydroelectricity) is equipped with two upstream and downstream reservoirs. When the load is low, the equipment works in the state of the motor, and the water from the downstream reservoir is pumped to the upstream reservoir for storage, and the equipment works in the state of the generator during the peak load. , Using the water stored in the upstream reservoir to generate electricity, see Figure 1. Due to mature technology, pumped storage power plants have become the most widely used energy storage technology in the power system. Currently, the installed capacity of pumped storage power stations under construction in my country is about 11,400MW. It is estimated that the total installed capacity of pumped storage power stations will reach about 17,500MW by the end of 2010.

Compressed Air Energy Storage (CAES, Compressed Air Energy Storage) is a gas turbine power plant for peak shaving. It mainly uses the surplus power from the grid load to compress air and store it in a high-pressure sealed facility with a typical gas storage pressure of 7.5MPa. It is released during peak electricity consumption to drive gas turbines to generate electricity. The world's first commercial CAES power station was the Huntdorf power station built in Germany in 1978, with an installed capacity of 290MW and an energy conversion efficiency of 77%. It has been started up to more than 7,000 times since its operation, and is mainly used for hot standby and smooth load. Compared with pumped storage power stations, CAES power stations are flexible in site selection. They do not need to build ground reservoirs and the terrain conditions are easily met. At present, compressed air storage power stations have been widely used in some developed countries.

Flywheel energy storage (FW, FlyWheels) realizes charging and discharging through the mutual conversion of mechanical energy and electrical energy. It uses a high-speed rotating flywheel core as a medium for mechanical energy storage, and uses a motor/generator and an energy conversion control system to control energy input and output. Flywheel energy storage requires high raw materials and technology for making flywheels. It was not until the 1990s that it was rapidly developed and used in uninterruptible power supply (UPS)/emergency power supply (EPS), power grid peak shaving and frequency control. my country's research in this area has just started.

Physical energy storage such as pumped water storage and compressed air energy storage have the advantages of large scale, long cycle life, and low operating costs, but they require special geographical conditions and sites, construction limitations, and high one-time investment costs. Not suitable for smaller power off-grid power generation systems. From the perspective of development level and practicality, chemical energy storage has broader application prospects than physical energy storage.