RESUMEN
Lithium-sulfur (Li-S) batteries are regarded as the most promising next-generation energy storage systems due to their high energy density and cost-effectiveness. However, their practical applications are seriously hindered by several inevitable drawbacks, especially the shuttle effects of soluble lithium polysulfides (LiPSs) which lead to rapid capacity decay and short cycling lifespan. This review specifically concentrates on the shuttle path of LiPSs and their interaction with the corresponding cell components along the moving way, systematically retrospect the recent advances and strategies toward polysulfides diffusion suppression. Overall, the strategies for the shuttle effect inhibition can be classified into four parts, including capturing the LiPSs in the sulfur cathode, reducing the dissolution in electrolytes, blocking the shuttle channels by functional separators, and preventing the chemical reaction between LiPSs and Li metal anode. Herein, the fundamental aspect of Li-S batteries is introduced first to give an in-deep understanding of the generation and shuttle effect of LiPSs. Then, the corresponding strategies toward LiPSs shuttle inhibition along the diffusion path are discussed step by step. Finally, general conclusions and perspectives for future research on shuttle issues and practical application of Li-S batteries are proposed.
RESUMEN
Lithium-sulfur (Li-S) batteries are regarded as one of the most promising next-generation battery technologies owing to their ultrahigh energy density up to 2600 W h kg-1 and low cost. However, major challenges still remain in the application of Li-S batteries, such as shuttle effect and sluggish redox kinetics. Herein, it is demonstrated that phosphorus doping can not only significantly improve the polysulfide adsorption but also enhance the catalysis effects of metal-organic framework-derived CoS2 nanoboxes in Li-S batteries. Consequently, a modified separator integrated with P-CoS2 and carbon nanotubes effectively suppresses the polysulfide shuttle and propels the redox kinetics of polysulfides, thus promising higher specific discharge capacity, better rate, and stable cycle performance. Even under the high sulfur loading condition (4.8 mg cm-2), the areal discharge capacity of the cell with the functional separator can still remain at 4.5 mA h cm-2 after 100 cycles at 0.2 C. More importantly, this work may encourage more effort on anion doping for engineering the polar surface of transition-metal compounds to further mediate the interfacial redox chemistry between transition-metal compounds and polysulfides in Li-S batteries.
RESUMEN
Current commercial Li-based batteries are approaching their energy density limitation, yet still cannot satisfy the energy density demand of the high-end devices. Hence, it is critical to developing advanced electrode materials with high specific capacity. However, these electrode materials are facing challenges of severe structural degradation and fast capacity fading. Among various strategies, constructing defects in electrode materials holds great promise in addressing these issues. Herein, we summarize a series of significant defect engineering in the high-capacity electrode materials for Li-based batteries. The detailed retrospective on defects specification, function mechanism, and corresponding application achievements on these electrodes are discussed from the view of point, line, planar, volume defects. Defect engineering can not only stabilize the structure and enhance electric/ionic conductivity, but also act as active sites to improve the ionic storage and bonding ability of electrode materials to Li metal. We hope this review can spark more perspectives on evaluating high-energy-density Li-based batteries.
RESUMEN
Li-rich layered oxides (LLOs) are promising cathodes for lithium-ion batteries because of their high energy density provided by anionic redox. Although great improvements have been achieved in electrochemical performance, little attention has been paid to the energy density stability during fast charging. Indeed, LLOs have severe capacity fading and voltage decay especially at a high state of charge (SOC), disabling the application of the frequently used constant-current-constant-voltage mode for fast charging. Herein, we address this problem by manipulating the external electric field and tensile strain induced by lattice expansion effect in nanomaterials under the guidance of theoretical calculations, which indicate that LLOs at high SOC have almost a zero band gap and a low oxygen formation energy. This strategy will weaken polarization, stabilize lattice oxygen, and restrict phase transition simultaneously. Thus, the energy density during fast charging can be highly stabilized. Therefore, it may be of great value for the practical application of layered cathodes.
RESUMEN
Spatial confinement is a desirable successful strategy to trap sulfur within its porous host and has been widely applied in lithium-sulfur (Li-S) batteries. However, physical confinement alone is currently not enough to reduce the lithium polysulfide (Li2Sn, 4 ≤n≤ 8, LIPSs) shuttle effect with sluggish LIPS-dissolving kinetics. In this work, we have integrated spatial confinement with a polar catalyst, and designed a three-dimensional (3D) interconnected, Co decorated and N doped porous carbon nanofiber (Co/N-PCNF) network. This Co/N-PCNF film serves as a freestanding host for sulfur trapping, which could effectively facilitate the infiltration of electrolyte and electron transport. In addition, the polar Co species possess strong chemisorption with LIPSs, catalyzing their reaction kinetics as well. As a result of this rational design and integration, the Co/N-PCNF@S cathode with a sulfur loading of 2 mg cm-2 exhibits a high initial discharge capacity of 878 mA h g-1 at 1C, and maintains a discharge capacity of 728 mA h g-1 after 200 cycles. Even with high sulfur loading of 9.33 mg cm-2, the cathode still keeps a stable areal capacity of 7.16 mA h cm-2 at 0.2C after 100 cycles, which is much higher than the current areal capacity (4 mA h cm-2) of commercialized lithium-ion batteries (LIBs). This rational design may provide a new approach for future development of high-density Li-S batteries with high sulfur loading.
RESUMEN
Lattice oxygen activity plays a dominant role in balancing discharge capacity and performance decay of lithium-rich layered oxide cathodes (LLOs). On the basis of density functional theory (DFT) and tight-binding theory, the activity of lattice oxygen can be improved by tensile strain and suppressed by compressive strain. To verify this conclusion, LLOs with large lattice parameters (L-LLOs) were synthesized taking advantage of the lattice expansion effect in nanomaterials. Compared with conventional LLOs with small lattice parameters (S-LLOs), particles in L-LLOs are imposed by tensile strain. L-LLOs show a larger initial discharge capacity and decay faster in the prolonged cycles than S-LLOs. Actually, most of the modified methods in LLOs can come down to strain-induced changes in lattice parameters. We believe this conclusion is a useful guideline to understand and tailor the lattice oxygen activity and may be generalized to other layered oxide cathodes involving anionic redox.
RESUMEN
3D MnO2 nanorod/welded Ag-nanowire-network supercapacitor electrodes were prepared. Welding treatment of the Ag nanowire-network leads to low resistance and long lifetime. Galvanostatic charge/discharge (GCD) induces an ever-lasting morphology changing from flower-like to honeycomb-like for MnO2, which manifests as increasing specific capacitance to 663.4 F g(-1) after 7000 GCD cycles.
