Preparation Of Porous Structure Composite And Its Performance For Lithium-sulfur Battery

Rechargeable lithium–sulfur batteries are promising candidates for advanced energy storage areas due to their high energy density and low cost. Nevertheless, commercial applications that utilize lithium–sulfur batteries have not been very successful because of the low electrical conductivity of sulfur, dissolution of lithium polysulfides in organic electrolyte, and volume expansion of sulfur during discharge. Carbon-based sulfur-containing materials prepared by carbon materials and sulfur can improve the performance of sulfur cathodes. However, their cycle stability and rate performance were not satisfactory. To obtain high-performance sulfur cathode materials, porous structure composites were designed and fabricated. The main content were summarized as follows:The amorphous microporous carbon coting on carbon nanotubes composite CNT0@C was synthesized under the hydrothermal reaction of glucose and CNTs. The microporous carbon coating on carbon nanotubes composite CNT@C was synthesized after calcined CNT0@C under the degree of 900?. The role of different glucose concentration in the performance of CNT@C nancomposite had been studied. Both CNT0@C-S and CNT@C-S had better performance of lithium-sulfur battery. We can achieve higher capacity, steady coulombic efficiency and cycle performance when glucose concentration is 0.05 ~ 0.1 mol×L-1.To compare the effect of different pore structure on the performance of the lithium-sulfur battery, CMK-3-S and CMK-8-S nanocomposites were prepared using ordered mesoporous carbon CMK-3(two-dimensional hexagonal structure) and CMK-8(three-dimensional cubic structure) as sulfur matrixes. Use Ti O2 coating on CMK-3-S and CMK-8-S to obtain high-performance sulfur cathode materials. The results indicated that Ti O2/CMK-3-S-2 nanocomposite showed better performance, the second discharge capacity is 1133 m Ah·g-1 at a rate of 800 m A·g-1, and a high coulombic efficiency(98%) was achieved, and for Ti O2/CMK-8-S-2 nanocomposite, the second discharge capacity is 1111 m Ah·g-1 at the same rate, and a high coulombic efficiency(96%) was achieved.We prepared porous spherical carbon PSC using Ti O2 as template, after the load of sulfur, The electrochemical test results showed that this battery can maintain high capacity, but the electrical conductivity of PSC-S nanocomposites is not so good. The electrical conductivity of composites PSC-S can highly improve after the addition of CNT into porous spherical carbon. The results indicated that PSC-CNT-S nanocomposite showed better electrical conductivity, the second discharge capacity is 919 m Ah·g-1 at the same rate, and a high coulombic efficiency(96%) was achieved.Add mesoporous silica SBA-15 into CMK-8/S, SBA-15 can absorb polysulfides to improve the electrochemical performance. The results indicated that, when the load of sulphur is up to 66%, the second discharge capacity of CMK-8-S-SBA-15 nanocomposite is 930 m Ah·g-1 at the rate of 800 m A·g-1,and a high coulombic efficiency(97%) was achieved.