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The mystery of lithium-air batteries: Why are they hailed as the future star of electric vehicles?
As the demand for electric vehicles and renewable energy increases, lithium-air batteries (Li-air) have quickly become the focus of the industry due to their theoretically high energy density. Lithium-air batteries are metal-air electrochemical cells that generate electrical current through the oxidation of lithium at the anode and the reduction of oxygen at the cathode. The battery, which uses lithium to react with oxygen from the environment, is said to have the potential to have an energy density comparable to that of gasoline in internal combustion engines.
Theoretically, the energy density of lithium-air batteries can reach about 40.1 MJ/kg, or 11.14 kWh/kg, which gives it unparalleled potential for use in electric vehicles.
According to existing research, the actual energy density of lithium-air batteries is also quite impressive, ranging from about 6.12 MJ/kg (1.7 kWh/kg). This data far exceeds the current commercial lithium-ion batteries and can theoretically support an electric vehicle weighing up to 2,000 kg to travel about 500 kilometers. However, to achieve commercialization, lithium-air batteries still need to address major challenges such as practical power and cycle life.
History
The concept of lithium-air batteries first emerged in the 1970s, when they were primarily seen as a potential source of battery power for electric and hybrid vehicles. Nevertheless, technological challenges kept the concept dormant for decades, but advances in materials science led to a resurgence of interest in the technology in the 2000s.
While technological advances in lithium-air batteries have been impressive, challenges such as battery charging time, moisture sensitivity, and poor conductivity of the Li2O2 material remain significant barriers to commercialization.
Design and Operation
Lithium-air batteries usually consist of an anode, a cathode and an electrolyte. During discharge, lithium ions move between the anode and cathode through the electrolyte, and electrons travel through an external circuit to perform electrical work. During charging, lithium metal is deposited on the anode and oxygen is released at the cathode.
Anode
Compared with other metal materials, lithium metal is the mainstream anode choice in lithium-air batteries. The high specific capacity of lithium anodes (3,840 mAh/g) when conditions are good is undoubtedly one of their advantages, but they also face challenges such as reactions between lithium metal and electrolyte and the risk of lithium dendrites, which may reduce the battery's Performance and lifespan.
Currently, many parties are seeking to address the negative impacts of these dendritic lithium through new electrolyte materials or improved interface design.
Cathode
Cathode gassing is one of the core technologies of lithium-air batteries, and the oxygen reduction reaction is crucial to battery efficiency. The study pointed out that mesoporous carbon-coordinated metal catalysts can effectively enhance the reduction kinetics and specific capacity performance of the cathode, which enables it to provide better performance in practical applications.
Electrolyte Diversity
Currently, there are four main paths for the electrolyte design of lithium-air batteries: aqueous acidic electrolyte, aqueous alkaline electrolyte, non-aqueous proton electrolyte and anaqueous electrolyte. Each electrolyte has its advantages and disadvantages. For example, aqueous electrolytes can avoid cathode clogging, but the reaction of lithium metal to water will bring new safety risks.
The hybrid aqueous-anaqueous electrolyte design attempts to combine the advantages of both to create a safer and more efficient lithium-air battery.
Future Prospects and Challenges
In addition to technical issues, the challenges facing lithium-air batteries include reliability, economy, and market acceptance. As the demand for higher energy density batteries continues to increase, the scientific research community and related companies are working hard to solve these problems. \
ConclusionThe theoretical potential and practical application prospects of lithium-air batteries are attractive, but many technical and market barriers still need to be overcome to make them successful in the electric vehicle market. Whether lithium-air batteries can become the mainstream choice for electric vehicles in the future, and how to realize this ideal, still needs time to prove.
