多孔Mn3O4微米立方体/rGO修饰的新型锂硫电池隔膜及其电化学性能研究

Novel Lithium-Sulfur Battery Separators Modified with Porous Mn3O4 Micrometer Cubes/rGO and Their Electrochemical Properties

摘要:

锂硫电池（LSBs）因高的理论比容量（1 675 mAh?g^-1）和能量密度（2 567 Wh?kg^-1）及丰富的硫资源，被视为极具发展潜力的新一代储能器件。然而，LSBs在充放电过程中产生的多硫化物穿梭效应、硫及硫化锂的导电性差、硫利用率低等问题，极大地制约了其广泛应用。基于此，采用水浴法合成了具有立方体结构的MnCO₃前驱体，通过煅烧制备了具有丰富孔结构的多孔Mn₂O₃微米立方体，利用引入的氧化石墨烯（GO）和采用二次退火，得到了具有丰富孔结构的多孔Mn₃O₄微米立方体/还原氧化石墨烯（Mn₃O₄/rGO）复合材料，并将其用于修饰改性商用隔膜，以提高锂硫电池的电化学性能。Mn₃O₄/rGO复合材料在锂硫电池隔膜应用中表现出更为优异的电化学性能，在0.1 C下其可逆容量为1 090 mAh?g^-1，即使在1 C的高电流密度下可逆容量仍有877 mAh?g^-1，在1 C下经400次循环后可逆容量仍然保持为422 mAh?g^-1，证明Mn₃O₄/rGO纳米材料具有优异的电化学性能。实验结果表明，内层孔隙丰富的Mn₃O₄微立方体为多硫化锂（LiPSs）的催化转化提供了丰富的活性位点，其与多硫化物之间的强相互作用和优异的催化性能可以极大地削弱多硫化物的穿梭效应，外层相互交联具有高导电率的三维rGO网络为锂离子的穿梭提供了天然的通道，并且从物理层面限制了极性LiPSs的穿梭，两者协同限制了LiPSs的穿梭效应，提高了LSBs的循环稳定性。本研究为解决锂硫电池中多硫化锂的穿梭问题提供了新思路。

Abstract:

Lithium-sulfur batteries are regarded as a new generation of energy storage devices with great potential for development due to their high theoretical specific capacity （1 675 mAh?g^-1） and energy density （2 567 Wh?kg^-1）， as well as the abundance of sulfur resources. However， the shuttle effect of polysulfides generated during charging and discharging， the poor conductivity of sulfur and lithium sulfide， and the low sulfur utilization rate have greatly restricted the wide application of lithium-sulfur batteries. In this study， a team of researchers successfully produced porous Mn₃O₄ micrometer cubes with abundant pore structure. The process involved preparing the MnCO₃ precursor using the water bath method， followed by calcination. The addition of GO and secondary annealing led to the creation of porous Mn₃O₄ micrometer cube/reduced graphene oxide （Mn₃O₄/rGO） composites， which were then used to modify commercial diaphragms to enhance the electrochemical performance of lithium-sulfur batteries. The study's results were auspicious， as the composite structure demonstrated excellent electrochemical performance in lithium-sulfur battery diaphragm applications. Specifically， it exhibited a reversible capacity of 1 090 mAh?g^-1 at 0.1 C and 877 mAh?g^-1 even at a high current density of 1 C. After 400 cycles at 1 C， the capacity remained at 422 mAh?g^-1， further attesting to the outstanding electrochemical performance of Mn₃O₄/rGO nanomaterials. The researchers found that the inner pore-rich Mn₃O₄ micro boxes provided abundant active sites for the catalytic conversion of lithium polysulfides， while the outer interconnected three-dimensional rGO network with high electrical conductivity provided a natural channel for lithium-ion shuttling and restricted the shuttling effect of polysulfides. Together， these two components limited the shuttling effect of LiPSs， leading to improved cycling stability of LSBs and providing valuable insights into addressing the issue of lithium polysulfide shuttling in lithium-sulfur batteries.