EN 
ZH 
In recent years, the fire safety issue of lithium iron phosphate battery energy storage has attracted much attention.
Although the risk of thermal runaway of lithium iron phosphate batteries is lower than that of ternary lithium and other batteries, it is only relatively safe, not absolutely safe, and the safety issue pursues “safety”.
Due to its chemical combustion reaction mechanism, lithium iron phosphate batteries are highly complex and technically difficult.
In particular, how to suppress the re-ignition of batteries is a difficult point in the industry, and there is no absolutely effective fire prevention method at home and abroad.
Due to the difficulty of fire extinguishing, the lack of standards related to fire safety is a pain point that plagues the development of the industry, especially the lack of reference basis in engineering design, equipment manufacturing, fire acceptance and other links, resulting in certain “disorder” and safety risks.
At present, the lithium battery energy storage industry generally adopts the concept of “prevention first, combining prevention and elimination”, and suppressing the probability of battery fires is the top priority.
For fires that occur after batteries run out of control, the industry generally uses fire-fighting media such as heptafluoropropane, perfluorohexanone, fine water mist, and aerosols to suppress battery fires, and at the same time uses water fire-fighting as a means of protection.
The release of the national standard “Safety Regulations for Electrochemical Energy Storage Power Stations” (hereinafter referred to as “safety national standard”) has aroused widespread concern in the industry, and its fire extinguishing media and fire protection configuration methods have attracted much attention.
It is understood that the national safety standard has not yet proposed specific fire extinguishing media requirements. Only the need for fire suppression and sustained suppression of re-ignition is mentioned.
For the fire protection configuration scheme, the safety national standard proposes that the automatic fire extinguishing system of the battery room should be a battery module, and each battery module can be equipped with a fire extinguishing medium nozzle or a fire detection tube independently.
Although the relevant standards have not yet put forward specific requirements for fire-fighting media, it is undeniable that the release of national safety standards provides a major reference for the specification and guidance of the fire safety configuration of lithium iron phosphate batteries, and provides guidance for later-stage engineering design, equipment manufacturing, and fire acceptance.
It is an important basis for promoting the overall safety of lithium battery energy storage power stations.
By studying the thermal runaway mechanism of battery fires, after the thermal runaway of a single battery is induced by external factors such as external overheating
overcharging, overdischarging, impact, extrusion, short circuit or its own manufacturing defects, the internal temperature of the battery rises rapidly, and the internal temperature of the battery rises rapidly.
Reactions such as SEI film decomposition and electrode material decomposition occur, and combustible combustion-supporting gases such as H2, CO, and alkanes are released, eventually causing fire or even explosion.
At the same time, because the energy storage unit is composed of a large number of single cells connected in series and parallel, and the thermal runaway is generally caused by the thermal runaway of the single cells after a fire, and gradually expands.
When the thermal runaway of the single cells occurs, the heat is transferred to the The surrounding batteries are transmitted, which in turn triggers a fire in the surrounding batteries, causing the scope of the accident to expand.
By observing the thermal runaway mechanism of lithium batteries, it can be seen that how to identify the occurrence of thermal runaway in the early stage of thermal runaway of a single battery and suppress the spread of accidents is an important part of prevention. In combination with the requirements of national safety standards, adopting a module-level automatic fire extinguishing scheme can effectively improve Safety level of energy storage system.
Generally speaking, the module-level fire extinguishing scheme is based on battery modules, equipped with combustible gas detectors and fire extinguishing medium nozzles.
The early thermal runaway state of the battery is identified by combustible gas detectors, temperature sensors and battery management systems. After the thermal runaway of the single battery, the fire extinguishing medium is sprayed through the fire extinguishing medium nozzle configured on the battery module to prevent the spread of the fire.
The module-level fire extinguishing scheme poses a challenge to the structure of the energy storage system due to the configuration of relevant detectors and fire extinguishing medium nozzles in the battery module, especially the liquid-cooled energy storage system.
Due to the high protection level and high integration density of the battery module, the industry Energy storage products of some manufacturers do not yet meet the requirements for module-level fire extinguishing.
At the same time, the cost of fire protection at the module level is relatively high, especially in conjunction with the widely used perfluorohexanone fire extinguishing medium, resulting in a sharp increase in the cost of energy storage equipment.
It is understood that if a single energy storage battery cabin adopts the perfluorohexanone module-level fire protection scheme, the cost will be around 200,000-300,000 yuan, compared with the cost of about 30,000 yuan for full flooding with heptafluoropropane.
Taking a 100MW/200MWh energy storage power station as an example, the storage The procurement cost of energy storage equipment has increased by about 10 million yuan, and at the same time, the later maintenance cost has also increased to a certain extent.
Under the current background of winning bids at low prices and lack of profit means in the industry, it brings considerable challenges to the construction and operation costs of energy storage power stations.
Taking effective fire-fighting measures to break through the safety problem of lithium-ion battery energy storage is one of the key factors for the sustainable and long-term development of its technical route.
For the thermal runaway mechanism of lithium-ion battery energy storage, identify and take effective early warning in the early stage of the accident In the event of a fire, it can quickly and accurately extinguish the fire and prevent re-ignition, and establish multiple lines of defense to ensure the safety level of the lithium-ion battery energy storage power station.
