Lithium-sulfur battery to achieve stable charge-discharge cycle characteristics

JAPAN announced on June 28, 2016 that it has jointly developed a lithium-sulfur battery with the University of Tsukuba to achieve a long-term stable charge-discharge cycle by using a metal-organic framework as a battery separator characteristic. According to reports, the 1C current density (constant current discharge after the end of the discharge current value 1) for 1500 cycles after the test, the lithium-sulfur battery can still maintain up to 900mAh / g charge capacity.

Sulfur as a lithium battery anode lithium-sulfur battery has a positive capacity (theoretical value of 1675mAh / g) features, as a new generation of batteries much anticipated. However, this battery has the problem that the lithium polysulfide, an intermediate product of the discharge reaction, is easily dissolved in the electrolyte. Therefore, as the charge-discharge cycle proceeds, the dissolved polysulfide ions initiate oxidation between the positive electrode and the negative electrode Reduction reaction (shuttling effect), repeated this reaction will lead to battery capacity degradation.

This time, researchers did not take measures to prevent the dissolution of polysulfides. Instead, the "molecular sieve" -metal organic framework, which was previously used for the adsorption and separation of gas molecules, was used to limit the movement of polysulfides toward the negative electrode. Metal-organic framework with sub-nanometer to a few nanometers, dimensional fixed three-dimensional micropores.

Membrane material used in the pore size can not allow polysulfide ions but can pass through the lithium-ion metal organic framework. And by mixing it with the graphene oxide layer, a flexible composite metal organic framework film was synthesized. Because of the crystal, the metal-organic framework has the disadvantage of being easily broken.

Researchers have found that when the composite metal-organic framework film is used as a lithium-sulfur battery separator, it is possible to suppress the shuttling effect which is regarded as a problem, and it is thereby possible to prevent reduction of charge and discharge capacities and reduction of cycle characteristics. After charging and discharging were repeated 1500 times at room temperature, discharge capacity and coulomb efficiency showed almost no deterioration in discharge capacity of 100 to 1500 times except for about 100 charge and discharge performed to perform initial activation, Good cycle characteristics.

Production Research Institute's future goal is to practical as the goal, the development of excellent performance of lithium-sulfur batteries. The research was published online on June 27 (UK time) in the British academic journal NatureEnergy.