Gravediggers of Lithium-ion batteries: Dual-Ion Batteries

wallpapers Innovation 2020-08-05

Current Status of Lithium-Ion Batteries

Relying on the advantages of high energy density and long life, lithium-ion batteries have achieved great success in the field of consumer electronics. In recent years, with the rapid development of the electric vehicle industry, lithium-ion batteries have begun to conquer cities in the field of new energy. However, under the boundless scenery, the crisis has quietly appeared. As the cruising range of electric vehicles continues to increase, the requirements for indicators such as power battery energy density and cost have gradually increased. For lithium-ion batteries, the current energy density has reached a bottleneck period. Researchers generally believe that 350Wh/kg is the limit of lithium-ion batteries. To continue to increase energy density, a new system is required. And in recent years: the price of raw materials such as lithium, cobalt, and nickel has risen, causing the cost of lithium-ion batteries to also bear great pressure, and there is limited room for continued cost reduction.

Dual-Ion Battery Becomes the Dark Horse Among the Successors

Faced with these crises, early deployment of new technologies and new products is the only option. With the efforts of the majority of scientific researchers, the successors of lithium-ion batteries are also eager to try, and dual-ion batteries are more like a dark horse. The speed of development is very rapid, the front foot has already stepped on the face of the lithium-ion battery, and the strength must not be underestimated. The dual-ion battery is called dual-ion battery because it is not a single-ion that participates in the electrochemical reaction in the dual-ion battery system. We know that in lithium-ion batteries, only Li+- ions shuttle between the positive and negative electrodes.  The anions in the electrolyte (such as PF6-) do not participate in the reaction. This is not the case in dual-ion batteries. Not only can the cations undergo intercalation reactions, but the anions in the electrolyte can also undergo intercalation reactions.

Characteristics That the Electrolyte of Dual-Ion Battery Needs to Meet

In general, the electrolyte of a dual-ion battery needs to meet the following characteristics:(1)Good high voltage stability.(2)It has good compatibility with the active materials and inactive materials in the battery, and helps the negative electrode to form a good SEI film. (3)In a dual-ion battery, the concentration of the electrolyte decreases with the increase of SoC and increases with the decrease of SoC.  Therefore, it is necessary to ensure good conductivity in the entire concentration range, and excessive electrolyte is required. (4) The ability of anions to be embedded in graphite directly affects the capacity of dual-ion batteries. Therefore, we prefer small anions. However, due to the agglomeration of anions and the formation of ion pairs, small ions may not perform the best Performance, therefore, also need to cooperate with the electrolyte solvent for comprehensive selection. At the same time, the electrolytes that can meet the above characteristics are only ionic liquids and high-concentration electrolytes. Especially high-concentration electrolytes can not only improve the stability of the electrolyte under high voltage, but also reduce the corrosion of Al foil, and Concentrated electrolyte is also conducive to increasing the capacity of the graphite cathode, which is currently a better choice.