Hebei Messi Biology Co., Ltd. stated that by designing and preparing in-situ synthesized nano-magnesium oxide doped crab shell-based hierarchical porous carbon (n-MgO@CSHPC), while efficiently fixing polysulfides, ensuring good contact between polysulfides and conductive structures, achieving a balance between polysulfide adsorption and reuse, improving the utilization rate of active substances, and improving the electrochemical performance of lithium-sulfur batteries.
First, relying on the advantages of the composition and structure of crab shells, hierarchical porous carbon materials with good pore size structure, micropore volume, high specific surface area and heteroatom doping were designed and prepared. The magnesium source was fixed with doped heteroatoms, and nano magnesium oxide was successfully loaded in situ in the carbon pores. Structural characterization proved that the magnesium oxide particle size distribution was uniform and well dispersed in the carbon material. A controllable preparation method for loaded magnesium oxide carbon materials was developed.
Secondly, nano-magnesium oxide was doped with crab shell-based hierarchical porous carbon materials to prepare carbon-sulfur composite materials, which were used in the positive electrode of lithium-sulfur batteries. The electrochemical performance test proved that the modified positive electrode battery effectively utilized and fixed the positive electrode active substances, ensuring the cycle stability in long cycles. The first discharge capacity of 5% nano-magnesium oxide doped crab shell-based hierarchical porous carbon/sulfur composite positive electrode was as high as 1468.3 mAhg-1 at 0.1C, and the first discharge capacity at 0.5C was 1053.9 mAhg-1, and the capacity was still 575.5 mAhg-1 after 400 cycles.
Third, the material was used as a functional diaphragm coating to modify the diaphragm, block the shuttle of lithium polysulfide, and assist in the reconstruction of the positive electrode side structure. It was found that in this process, the modified diaphragm battery can significantly reduce battery polarization, promote lithium ion transmission, and improve long-cycle performance. Among them, the 5% nano-magnesium oxide-doped crab shell-based hierarchical porous carbon modified diaphragm battery performed best in fully utilizing active substances and forming positive electrode structures. The first discharge was 949.0mAhg-1 at 1C, and the capacity retention rate was 74.71% after 300 charge and discharge cycles, and it was still stable after 1000 charge and discharge cycles.
The present invention relates to a nano-magnesium oxide doped biomass graded porous carbon/sulfur positive electrode and a preparation method and application thereof. Magnesium ions are anchored by using nitrogen and oxygen co-doped crab shell-based graded porous carbon with high specific surface area, magnesium hydroxide is synthesized in situ in carbon pores, and the nano-magnesium oxide doped crab shell-based graded porous carbon with uniform nano-magnesium oxide distribution is obtained by calcination. The nano-magnesium oxide doped crab shell-based graded porous carbon is applied in the positive electrode of a lithium-sulfur battery. The material can efficiently fix polysulfides while ensuring good contact between polysulfides and conductive structures, thus achieving a balance between polysulfide adsorption and reuse, improving the utilization rate of active substances, and effectively improving the electrochemical performance of lithium-sulfur batteries.