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[Energy] Electrochemical energy storage as a common energy storage technology

At present, electrochemical energy storage mainly includes lead-acid batteries, flow batteries, sodium-sulfur batteries, lithium-ion batteries, etc. At present, lithium batteries and lead batteries are the main ones.

1. Lead-acid battery energy storage

A lead-acid battery is a battery whose electrodes are mainly made of lead and its oxides, and the electrolyte is a sulfuric acid solution. Now it is widely used in the world, the cycle life can reach about 1,000 times, the power can reach 80%-90%, and it is cost-effective. It is often used in emergency power or backup power in power systems.

Disadvantage: Assuming deep, rapid and high-power discharge, the available capacity will decrease. It is characterized by low energy density and short life span. This year, lead-acid batteries have greatly improved their cycle life by adding super-active carbon materials to the negative plates of lead-acid batteries.

2. Li-ion battery energy storage

Lithium-ion batteries are a type of batteries that use lithium metals or lithium alloys as negative electrode materials and use non-aqueous electrolyte solutions. Mainly used in portable mobile devices, its power can reach more than 95%, the discharge time can reach several hours, the number of cycles can reach 5000 times or more, and it responds quickly. It is the most practical battery with the highest energy in the battery. Used the most. In recent years, the technology has also been continuously upgraded, and the positive and negative electrode materials are also used in a variety of ways.

The mainstream power cone batteries on the market are divided into three categories: drill acid batteries, manganese acid hammer batteries and iron phosphate batteries. The former has high energy fragmentation, but the safety is slightly worse. On the contrary, domestic electric cars such as BYD now mostly use potassium iron phosphate batteries. But it seems that foreigners are playing with ternary batteries and iron phosphate batteries?

Lithium-sulfur batteries are also very popular. They use sulfur as the positive electrode and metal carp as the negative electrode. The theoretical specific energy density can reach 2600wh/kg, and the practical energy density can reach 450wh/kg. But how to greatly improve the charge-discharge cycle life and safety of the battery is also a big problem.

Disadvantages: There are safety issues such as high quotations, overcharging causing heat, burning, etc., and charging maintenance is required

3. Sodium-sulfur battery energy storage

A sodium-sulfur battery is a secondary battery that uses metallic sodium as the negative electrode, sulfur as the positive electrode, and a ceramic tube as the electrolyte diaphragm. The cycle can reach 4500 times, the discharge time is 6-7 hours, the cycle efficiency is 75%, the energy density is high, and the response time is fast. Today, more than 200 such energy storage power stations have been built in Japan, Germany, France, the United States and other places, mainly for load leveling, peak shifting and power quality improvement

Disadvantages: Due to the use of liquid sodium, it runs at high temperature and is easy to burn. And if the grid is out of power, diesel generators are needed to help maintain the high temperature, and perhaps help meet the conditions for cooling the battery.

4. Flow battery energy storage

The flow battery is a high-performance battery that separates the positive and negative electrolytes and circulates them separately. The power and energy of the battery are irrelevant, and the stored energy depends on the size of the storage tank, so energy can be stored for hours to days, and the capacity can reach MW level. This battery has multiple systems, such as iron-chromium system, zinc-aluminum system, sodium polysulfide-aluminum system and all-vanadium system, among which vanadium batteries are the most popular.

Disadvantages: the battery volume is too large; the battery requires too high ambient temperature; the quotation is expensive.