Modern research on new lithium battery materials increases capacity by 50% -Lithium - Ion Battery Equipment
Recently, researchers from Hyundai Motor Company found that sulfone-based electrolytes can effectively improve the capacity and reversible capacity retention rate of lithium-sulfur batteries. At the 2014 Society of Automotive Engineers World Congress, Hyundai Motor Company reported in detail the above new findings. Compared with ordinary electrolytes, the capacity of lithium-sulfur batteries can be effectively increased by using sulfone-based electrolytes, with the capacity increased by 52.1% to 715 mAh. hour/g; the reversible capacity retention rate increased by 63.1% to 72.6%.
As a new material battery with energy density exceeding that of lithium-ion batteries, lithium-sulfur batteries have a larger battery capacity, and electric vehicles equipped with this battery will have a longer pure electric range. The theoretical energy density of the lithium-sulfur battery system reaches 2600 Wh/kg, but its low reversible capacity retention rate is a well-known problem. At the same time, lithium-sulfur batteries also have problems such as polysulfide compounds (pS) being dissolved in the electrolyte and solid lithium sulfide and other insoluble precipitates appearing on the cathode during the discharge process.(Lithium - Ion Battery Equipment)
Hyundai Motor Company researcher Shin and others said: The reaction mechanism of lithium-sulfur batteries is that during discharge, the negative electrode metal lithium loses electrons and becomes lithium ions, and the positive electrode sulfur reacts with lithium ions and electrons to form polysulfide (polysulfide pS is polysulfide-containing Ionic compounds, the specific reaction process is S8→Li2S8→Li2S6→Li2S4→Li2S). The potential difference between the positive and negative electrode reactions is the discharge voltage supplied by the lithium-sulfur battery. Under the application of external voltage, the positive and negative electrode reactions of lithium-sulfur batteries proceed in reverse direction, which is the charging process, and a reversible reaction occurs during the charging process. During the reaction of polysulfides, Li2S6 and Li2S4 can dissolve in the electrolyte. Polysulfides play a vital role in improving the sulfur utilization rate of lithium-sulfur batteries to improve the battery's reversible recycling rate.
Ether-type solvents are considered the best electrolyte choice for lithium-sulfur batteries due to their good polysulfide solubility and high chemical stability. In addition, dissolved polysulfides can trigger redox reactions, which will reduce the Coulombic efficiency of the battery, shorten the reversible cycle retention rate, and lead to self-discharge. Therefore, an important purpose of this research and development work is to develop a new electrolyte to reduce the redox reaction and improve the reversible cycle retention rate of the battery.
In the research process of Hyundai Motor Company, researchers used five groups of monoether electrolytes (dimethyl ether DME, diethylene glycol dimethyl ether DEGDME, triethylene glycol Triglyme, triethylene glycol dimethyl ether TEGDME and diethylene glycol dimethyl ether). DIOX), 1 group of dihydric ether electrolytes (mixture of triethylene glycol dimethyl ether TEGDME and dioxane DIOX), and 3 groups of trivalent ether electrolytes (mixing ratios are 1:1:1, 1 respectively : 1:2 and 1:1:3 triethylene glycol dimethyl ether TEGDME: dioxane DIOX: sulfolane Sulfolane mixed electrolyte) were conducted comparative experiments.
The lithium-sulfur battery tested by Hyundai Motor Company researchers used a sulfur cathode and a lithium metal foil anode, with a polyethylene separator between the two electrodes. The electrochemical experiments of lithium-sulfur batteries were conducted at room temperature of 20 degrees Celsius, and the operating voltage was controlled between 1.5 volts and 2.65 volts.
In the monovalent ether electrolyte experiment, the dimethyl ether DME electrolyte system has the highest energy density, reaching 878 mAh/g; the diethylene glycol dimethyl ether DEGDME electrolyte system has the second highest energy density, also reaching 857 mAh. hour/gram. However, the dimethyl ether DME electrolyte system experienced very obvious battery capacity fading after the 6th working cycle; while the diethylene glycol dimethyl ether DEGDME electrolyte system showed very obvious battery capacity fading after the 2nd working cycle. Capacity fading phenomenon. The energy density of the dioxane DIOX electrolyte system reached 1040 mAh/g in the first working cycle, but the energy density quickly dropped to 640 mAh/g in the 12th working cycle. The DIOX electrolyte system has a very high initial energy density. However, its energy density also shows a very obvious battery capacity fading after the 12th working cycle.
As a new material battery with energy density exceeding that of lithium-ion batteries, lithium-sulfur batteries have a larger battery capacity, and electric vehicles equipped with this battery will have a longer pure electric range. The theoretical energy density of the lithium-sulfur battery system reaches 2600 Wh/kg, but its low reversible capacity retention rate is a well-known problem. At the same time, lithium-sulfur batteries also have problems such as polysulfide compounds (pS) being dissolved in the electrolyte and solid lithium sulfide and other insoluble precipitates appearing on the cathode during the discharge process.(Lithium - Ion Battery Equipment)
Hyundai Motor Company researcher Shin and others said: The reaction mechanism of lithium-sulfur batteries is that during discharge, the negative electrode metal lithium loses electrons and becomes lithium ions, and the positive electrode sulfur reacts with lithium ions and electrons to form polysulfide (polysulfide pS is polysulfide-containing Ionic compounds, the specific reaction process is S8→Li2S8→Li2S6→Li2S4→Li2S). The potential difference between the positive and negative electrode reactions is the discharge voltage supplied by the lithium-sulfur battery. Under the application of external voltage, the positive and negative electrode reactions of lithium-sulfur batteries proceed in reverse direction, which is the charging process, and a reversible reaction occurs during the charging process. During the reaction of polysulfides, Li2S6 and Li2S4 can dissolve in the electrolyte. Polysulfides play a vital role in improving the sulfur utilization rate of lithium-sulfur batteries to improve the battery's reversible recycling rate.
Ether-type solvents are considered the best electrolyte choice for lithium-sulfur batteries due to their good polysulfide solubility and high chemical stability. In addition, dissolved polysulfides can trigger redox reactions, which will reduce the Coulombic efficiency of the battery, shorten the reversible cycle retention rate, and lead to self-discharge. Therefore, an important purpose of this research and development work is to develop a new electrolyte to reduce the redox reaction and improve the reversible cycle retention rate of the battery.
In the research process of Hyundai Motor Company, researchers used five groups of monoether electrolytes (dimethyl ether DME, diethylene glycol dimethyl ether DEGDME, triethylene glycol Triglyme, triethylene glycol dimethyl ether TEGDME and diethylene glycol dimethyl ether). DIOX), 1 group of dihydric ether electrolytes (mixture of triethylene glycol dimethyl ether TEGDME and dioxane DIOX), and 3 groups of trivalent ether electrolytes (mixing ratios are 1:1:1, 1 respectively : 1:2 and 1:1:3 triethylene glycol dimethyl ether TEGDME: dioxane DIOX: sulfolane Sulfolane mixed electrolyte) were conducted comparative experiments.
The lithium-sulfur battery tested by Hyundai Motor Company researchers used a sulfur cathode and a lithium metal foil anode, with a polyethylene separator between the two electrodes. The electrochemical experiments of lithium-sulfur batteries were conducted at room temperature of 20 degrees Celsius, and the operating voltage was controlled between 1.5 volts and 2.65 volts.
In the monovalent ether electrolyte experiment, the dimethyl ether DME electrolyte system has the highest energy density, reaching 878 mAh/g; the diethylene glycol dimethyl ether DEGDME electrolyte system has the second highest energy density, also reaching 857 mAh. hour/gram. However, the dimethyl ether DME electrolyte system experienced very obvious battery capacity fading after the 6th working cycle; while the diethylene glycol dimethyl ether DEGDME electrolyte system showed very obvious battery capacity fading after the 2nd working cycle. Capacity fading phenomenon. The energy density of the dioxane DIOX electrolyte system reached 1040 mAh/g in the first working cycle, but the energy density quickly dropped to 640 mAh/g in the 12th working cycle. The DIOX electrolyte system has a very high initial energy density. However, its energy density also shows a very obvious battery capacity fading after the 12th working cycle.
