The practical application of lithium-sulfur batteries is hampered by the sluggish redox reaction kinetics and severe lithium polysulfide (LiPS) migration, especially under high sulfur loading and lean electrolyte scenarios. Strategies to catalyze the sulfur liquid/solid conversion within a "hermetic" nano-container have been proposed, where the LiPS migration and sluggish reaction kinetics can be simultaneously addressed. Herein, to realize rapid LiPS conversion and slow LiPS migration, the sulfur species are packed by a hermetic catalytic interface, constructed by the phosphorene/graphene heterostructure. The 2D phosphorene/graphene stacking has two unique benefits: 1) a direct electron transfer avoiding any insulating media, resulting in an exceptional catalytic effect on LiPS conversion; ii) favorable charge rearrangement that enhances chemisorption toward LiPS and limits LiPS crossover. The proposed highly flexible hermetic interface with strong van der Waals serves as a bifunctional nano-container to pack sulfur species and promote sulfur redox reactions, which gives rise to excellent battery performances: a high areal capacity of 5.57 mAh cm −2 under a low electrolyte/sulfur ratio of 5.7 mL g −1 . This work affords a coupling strategy that embraces interfacial and structural engineering to promote kinetic reactions of sulfur conversions under electrolyte-lean conditions.
and a light mass density of 0.53 g cm −3 , is considered as the "Holy Grail" anode to realize a breakthrough for above limitation. [3] When Li metal anode (LMA) is used as a substitute for graphite anode and equipped with traditional cathodes (e.g., LiCoO 2 ), the energy density of batteries can be enhanced from ≈260 Wh kg −1 to ≈500 Wh kg −1 . [4] Given the dramatically improved theoretical energy density, advanced Li metal batteries (LMBs), such as Li-oxygen (Li-O 2 ) (≈3505 Wh kg −1 ) and Li-sulfur (Li-S) (≈2600 Wh kg −1 ) batteries, are in the spotlight. [5][6][7][8][9][10] So far, practical gravimetric energy densities of Li-lithium transition-metal oxide (Li-LMO), Li-S, and Li-O 2 batteries can achieve ≈440 Wh kg −1 , ≈650 Wh kg −1 and ≈950 Wh kg −1 , respectively, surpassing that of commercialized LIBs.Notably, the Li-O 2 batteries owning a high volumetric energy density (≈1100 Wh L −1 ) is on a par with petrol (≈1200 Wh L −1 ) (Figure 1a). [11] Since 2010s, chasing higher energy density boosts the rapid development of LMAs (Figure 1b) and exponentially increasing scientific researches (Figure 1c).Nevertheless, the practical implementation of LMAs is confronted with some intrinsic obstructions. Li metal with low electrochemical potential is highly reactive with organic components of electrolyte, leading to the generation of side products and formation of heterogeneous and unstable solid electrolyte interphase (SEI) on LMAs surface. [16][17][18][19] In heterogeneous SEI, formed "hotspots", namely the bulges on the surface of Li metal which own higher surface exchange current density and local temperature compared with other flat region, are harnessed to induce faster conduction of partial Li ions and drastically enhance the deposition of Li ions, which is the critical factor of Li dendrites forming. [20] Besides, the poor robustness of SEI may trigger the continuously alternating processes of destruction and reconstruction, vastly consuming the fresh Li and electrolyte. [21,22] Furthermore, the large volume change of LMAs during the continuous Li plating/stripping is detrimental due to the formation of "dead" Li and porous Li. [23,24] These uncontrollable processes are pernicious to Li cycling efficiency and electrochemical performance of LMBs. Some valid strategies have been proposed, including electrolyte engineering, [25][26][27] Li metal hosts, [28][29][30] protective layers (PLs), [31][32][33][34][35] and so forth.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smtd.202201177.
Lewis‐base sites have been widely applied to regulate the properties of Lewis‐acid sites in electrocatalysts for achieving a drastic technological leap of lithium‐oxygen batteries (LOBs). Whereas, the direct role and underlying mechanism of Lewis‐base in the chemistry for LOBs are still rarely elucidated. Herein, we comprehensively shed light on the pivotal mechanism of Lewis‐base sites in promoting the electrocatalytic reaction processes of LOBs by constructing the metal–organic framework containing Lewis‐base sites (named as UIO‐66‐NH2). The density functional theory (DFT) calculations demonstrate the Lewis‐base sites can act as electron donors that boost the activation of O2/Li2O2 during the discharged‐charged process, resulting in the accelerated reaction kinetics of LOBs. More importantly, the in situ Fourier transform infrared spectra and DFT calculations firstly demonstrate the Lewis‐base sites can convert Li2O2 growth mechanism from surface‐adsorption growth to solvation‐mediated growth due to the capture of Li+ by Lewis‐base sites upon discharged process, which weakens the adsorption energy of UIO‐66‐NH2 towards LiO2. As a proof of concept, LOB based on UIO‐66‐NH2 can achieve a high discharge specific capacity (12 661 mAh g−1), low discharged‐charged overpotential (0.87 V) and long cycling life (169 cycles). This work reveals the direct role of Lewis‐base sites, which can guide the design of electrocatalysts featuring Lewis‐acid/base dual centers for LOBs.
Dendritic growth of lithium (Li) is well-known to originate from deposition on rough and inhomogeneous Li-metal surfaces, and has long been a central problem in charging lithium metal batteries. Herein, a universal strategy is proposed for dendrite suppression by both in situ and ex situ electrochemical polishing of Li metal from the corrosion science perspective. This polishing technique greatly smoothens the surface of the Li and dynamically regenerates a homogeneous solid electrolyte interphase film simultaneously during cell cycling, which suppresses the nucleation sites for dendritic Li and establishes an ideal matrix for even deposition of Li. As a result, the polished Li presents a stable voltage profile and high Li utilization in both the symmetric cells and the full cells coupled with LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) or LiFePO 4 . The long cycle life of polished Li electrodes clearly demonstrates a uniform dendrite-free deposition of Li. This strategy shows a new direction to realize a uniform deposition of Li by providing a regenerative homogeneous Li-surface during repeated cycling.
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