Abstract Lithium–sulfur (Li–S) batteries, with high theoretical energy density, promise to be the optimal candidate of next‐generation energy‐storage. Rapid development in materials has made a major step forward in Li–S batteries. However, a big gap in cycle life and efficiency for practical applications still remains. Reasonable design of materials/electrodes a is significant aspect that must be addressed. The rising metal‐organic frameworks (MOFs) are a new class of crystalline porous organic–inorganic hybrid materials. Abundant inorganic nodes and designable organic linkers allow tailored pore chemistry at a molecular‐scale, which enables tunable interaction with electroactive components in Li–S batteries. In this review, the interaction between basic component/structure of MOFs and electroactive components in Li–S batteries is clarified to guide precise function‐driven design of MOFs. First, the reaction mechanisms and issues in Li–S batteries are briefly summarized. Second, the structural advantages of MOFs in pore chemistry and morphology are highlighted. Based on the above two aspects of understanding, a bridge between issue‐structure‐function is proposed. The interaction between MOFs with transport and reaction of electroactive components are discussed. Finally, a perspective on the future development of MOFs based materials in Li–S batteries are given. It is believed that the tunable interaction will boost the frontier interdiscipline of MOFs based electrochemical systems.
In article number 1903843, Feng Li and co-workers provide an anion-tuned strategy to regulate the electrolyte chemistry of a Li+ solvation sheath, which not only facilitates fast Li+ desolvation kinetics, but significantly reduces the energy barrier during Li+ diffusion through the solid electrolyte interphase, subsequently contributing to uniform Li+ deposition with high cycling stability.
Delocalized CS decorated carbon materials (CS/HCSs) promote spatial π-electron conjugation and the formation of spatial C–C hybridization. The CS/HCSs delivered fast 3D charge transfer for superior performance in rechargeble batteries.
Abstract Sluggish evolution of lithium ions’ solvation sheath induces large charge‐transfer barriers and high ion diffusion barriers through the passivation layer, resulting in undesirable lithium dendrite formation and capacity loss of lithium batteries, especially at low temperatures. Here, an ion‐dipole strategy by regulating the fluorination degree of solvating agents is proposed to accelerate the evolution of the Li + solvation sheath. Ethylene carbonate (EC)‐based fluorinated derivatives, fluoroethylene carbonate (FEC) and di‐fluoro ethylene carbonate (DFEC) are used as the solvating agents for a high dielectric constant. As the increase of the fluorination degree from EC to FEC and DFEC, the Li + ‐dipole interaction strength gradually decreases from 1.90 to 1.66 and 1.44 eV, respectively. Consequently, the DFEC‐based electrolyte displays six times faster ion desolvation rate than that of a non‐fluorinated EC‐based electrolyte at −20 °C. Furthermore, LiNi 0.8 Co 0.1 Mn 0.1 O 2 ||lithium cells in a DFEC‐based electrolyte retain 91% original capacity after 300 cycles at 25 °C, and 51% room‐temperature capacity at −30 °C. By bridging the gap between the ion‐dipole interactions and the evolution of Li + solvation sheath, this work provides a new technique toward rational design of electrolyte engineering for low‐temperature lithium batteries.
Owing to anionic oxygen redox, cathode materials containing lithium-rich oxides (LROs) exhibit a large discharge capacity exceeding 300 mAh/g. This makes them viable choices for fabrication of cathode materials for future development of lithium-ion batteries with an energy density exceeding 500 Wh/kg. However, O redox is irreversible, resulting in voltage/capacity fade with precipitation of lattice oxygen during cycling. In this work, we review the mechanism of O redox, the role of intrinsic microstrains and potential defects in O redox, and strategies to achieve a reversible O redox through artificial engineering of these intrinsic microstrains and defects. We also evaluate facile and simple methods that are effective to modify these microstrains through engineering of phase distribution, phase structure, and morphology, as well as methods for modification of intrinsic defects, so that discharge capacity can also be improved. This work provides routes to achieve high-performance LROs with a long lifespan.
In article number 2100935, Zhenhua Sun, Feng Li and co-workers demonstrate an ion-dipole strategy in which the fluorination degree of solvating agents is altered to accelerate the evolution of the Li+ solvation sheath. This ensures fast Li+ desolvation kinetics at the electrode/electrolyte interface during the discharging/charging process, but also produces a stable interface at cathode/anode interfaces and enables stable cycling of low-temperature lithium metal batteries.
Heterostructure materials with different band gaps, which can accelerate interfacial electronic/ionic conduction via the formation of a built-in electric field (E-field) and thus promote energy/power outputs of batteries, have been regarded as an alternative anode material candidate for sodium-ion batteries. Nevertheless, being functional in both discharge and charge processes under such a unidirectional E-field is difficult. Accordingly, constructing a heterostructure with a bidirectional E-field is the central issue, but challenging. In this contribution, ZnS/Sn2S3 and ZnS/SnS heterostructures with a close intrinsic energy gap serve as a model system to produce a similar thermodynamic-induced E-field to promote the discharging process. Taking advantage of the reversibility difference of ZnS, Sn2S3, and SnS, a stronger dynamic-induced E-field for the ZnS/Sn2S3 heterostructure is derived from its preferential release of Na+ in the charging process. Benefiting from the synergistic effect of thermodynamic- and dynamic-induced E-field, the interfacial charge transfer is improved in both charging and discharging processes. Consequently, the ZnS/Sn2S3@C anode exhibits a stable and higher capacity of 413 mAh g–1 after 100 cycles at a current density of 0.5 A g–1 current density, which is 2.4-fold higher than that of the ZnS/SnS@C anode. This finding not only deepens the understanding on the E-field but also sheds light on the design of heterostructure anode materials.
Fabricating electrochemical power sources with both high specific energy and power is highly desirable but remains challenging. In this work, a kind of self-charging hybrid electric power device (HEPD) is created with an intrinsic combination of polymer electrolyte membrane fuel cells and supercapacitors on the electrode level. Because of the unique processes of electrocatalytic reactions boosted by the fast pseudocapacitive discharge, remarkably high specific energy (1550 Wh kg–1) and power (4080 W kg–1) can be delivered by the hybrid device. The working mechanism of HEPD is proposed and demonstrated by in situ characterization and extensive electrochemical investigations. The self-charging HEPD with its synergistic electrochemical processes will broaden the applications of electrochemical power sources.
Abstract Non-dissociative chemisorption solid-state storage of hydrogen molecules in host materials is promising to achieve both high hydrogen capacity and uptake rate, but there is the lack of non-dissociative hydrogen storage theories that can guide the rational design of the materials. Herein, we establish generalized design principle to design such materials via the first-principles calculations, theoretical analysis and focused experimental verifications of a series of heteroatom-doped-graphene-supported Ca single-atom carbon nanomaterials as efficient non-dissociative solid-state hydrogen storage materials. An intrinsic descriptor has been proposed to correlate the inherent properties of dopants with the hydrogen storage capability of the carbon-based host materials. The generalized design principle and the intrinsic descriptor have the predictive ability to screen out the best dual-doped-graphene-supported Ca single-atom hydrogen storage materials. The dual-doped materials have much higher hydrogen storage capability than the sole-doped ones, and exceed the current best carbon-based hydrogen storage materials.
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