| Developing high-performance energy conversion technology is an important way to achieve the“carbon peak and carbon neutrality”strategic target.At present,lithium-ion battery（LIB）is the most widely used energy storage device.However,limiting by theoretical specific capacity of cathode materials,the energy density of commercialized LIB is less than 300 Wh kg-1,making it difficult to satisfy the present and future requirements.Lithium-sulfur（Li-S）battery,with ultra-high theoretical specific capacity(1672 m Ah g-1),theoretical energy density(2600 Wh kg-1)and low cost,is expected to be the next potential electrochemical energy storage technology Nonetheless,the non-uniform nucleation of anode Li+causes the formation of lithium dendrites,resulting in the failure of Li-S batteries and hindering its commercial process.To address these issues,this project constructs a lithiuphilic and sulfophobic protection layer to improve interface stability.Benefiting from the three-dimensional network structure/lithiophilic component introduced,the Li+transfer rate is accelerated,interface current density is homogenized,and the growth of lithium dendrites is effectively inhibited.Furthermore,designing the micro mesoporous structure for the protective layer is also proposed in this project to regulate the transfer behavior of Li+/polysulfide(Sn2-),and achieve uniform deposition of Li+.The main research results are as follows:（1）Due to the nucleation rate of Li+is much higher than the diffusion rate,lithium dendrites are easily caused,leading to the low utilization of lithium.In order to solve the above problems,a 3D flexible self-supported oxygen vacancy-enriched P-Mn3O4-xprotection layer is prepared in this paper.Oxygen vacancy-enriched P-Mn3O4-x has good lithiophile,which can effectively adsorb lithium ions in electrolyte,accelerating its transfer rate in SEI and improving the matching degree of Li+deposition rate and diffusion rate at the anode interface.Meanwhile,the 3D network structure of the protection layer can provide transfer channels for lithium ion to achieve uniform distribution,and reduce the concentration of charge in the local area of the negative electrode.Through the regulation of Li+deposition uniformity and deposition rate,the lithium symmetric cell matched the P-Mn3O4-x layer maintains flat voltage plateaus with an ultralong lifespan（≈5000 h）and keeps an ultralow overpotential of 20 m V without any sign of short-circuiting at high surface capacity of 10 m Ah cm-2.（2）During cycling,the polysulfide generated at the sulfur cathode easily diffuses to the anode and react with exposed lithium to form insulated Li2S/Li2S2,causing Li+uneven deposition.Generally,the lithium deposition/dissolution prefers to occur at the region without Li2S/Li2S2,causing the uneven distribution of electric field and ion concentration field to induce lithium dendrites.On the basis of the previous work,this project uses the size difference between lithium ion and polysulfide ion to design and prepare P-Co/Mn O1-xprotection layer with micro mesoporous structure through ion doping method.The transmembrane diffusion of polysulfide ions is effectively separated,which significantly reduce the chemical corrosion for lithium anode.In addition,the rich micro-pore structure is beneficial to buffer electrolyte,effectively shorten the transfer path of lithium ions and inhibit the lithium dendrites.The experimental results show that the Li||Cu cell matched P-Co/Mn O1-x protection layer achieves very stable and highly reversible with an average CE of 97.6%after 100 cycles at 1 m A cm-2.Even under the ultra-high current density and area capacity of 20 m A cm-2 and 20 m Ah cm-2,the cycling life of assembled lithium symmetrical battery is still over 300 h.Importantly,the lithium-sulfur full battery assembled with P-Co/Mn O1-x demonstrates a specific capacity of up to 658 m Ah g-1 at high charge/discharge rate of 5 C. |
