12 research outputs found
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Ultrathin positively charged electrode skin for durable anion-intercalation battery chemistries
The anion-intercalation chemistries of graphite have the potential to construct batteries with promising energy and power breakthroughs. Here, we report the use of an ultrathin, positively charged two-dimensional poly(pyridinium salt) membrane (C2DP) as the graphite electrode skin to overcome the critical durability problem. Large-area C2DP enables the conformal coating on the graphite electrode, remarkably alleviating the electrolyte. Meanwhile, the dense face-on oriented single crystals with ultrathin thickness and cationic backbones allow C2DP with high anion-transport capability and selectivity. Such desirable anion-transport properties of C2DP prevent the cation/solvent co-intercalation into the graphite electrode and suppress the consequent structure collapse. An impressive PF6−-intercalation durability is demonstrated for the C2DP-covered graphite electrode, with capacity retention of 92.8% after 1000 cycles at 1 C and Coulombic efficiencies of > 99%. The feasibility of constructing artificial ion-regulating electrode skins with precisely customized two-dimensional polymers offers viable means to promote problematic battery chemistries
Recommended from our members
Ultrathin positively charged electrode skin for durable anion-intercalation battery chemistries
The anion-intercalation chemistries of graphite have the potential to construct batteries with promising energy and power breakthroughs. Here, we report the use of an ultrathin, positively charged two-dimensional poly(pyridinium salt) membrane (C2DP) as the graphite electrode skin to overcome the critical durability problem. Large-area C2DP enables the conformal coating on the graphite electrode, remarkably alleviating the electrolyte. Meanwhile, the dense face-on oriented single crystals with ultrathin thickness and cationic backbones allow C2DP with high anion-transport capability and selectivity. Such desirable anion-transport properties of C2DP prevent the cation/solvent co-intercalation into the graphite electrode and suppress the consequent structure collapse. An impressive PF6−-intercalation durability is demonstrated for the C2DP-covered graphite electrode, with capacity retention of 92.8% after 1000 cycles at 1 C and Coulombic efficiencies of > 99%. The feasibility of constructing artificial ion-regulating electrode skins with precisely customized two-dimensional polymers offers viable means to promote problematic battery chemistries
Graphene-like Carbon–Nitride Monolayer: A Potential Anode Material for Na- and K‑Ion Batteries
Presently,
great attention is being directed toward the development
of promising electrode materials for non-lithium rechargeable batteries
which have the advantages of low cost, high energy storage density,
and high rate capacity for substantial renewable energy applications.
In this study, we have predicted that the C<sub>3</sub>N monolayer
is a potential electrode material for Na- and K-ion batteries by first-principle
calculations. The diffusion barriers are calculated to be as small
as 0.03 eV for Na and 0.07 eV for K, which could lead to a very fast
diffusion on the C<sub>3</sub>N monolayer surface, implying high mobility
and cycle stability for batteries. The C<sub>3</sub>N monolayer is
predicted to allow a high storage capacity of 1072 mAh/g by the inclusion
of multilayer adsorption with an average voltage of 0.13 V for Na<sub>2</sub>C<sub>3</sub>N and 0.26 V for K<sub>2</sub>C<sub>3</sub>N
systems, which is more promising than previously studied anode materials.
All of these results ensure that the C<sub>3</sub>N monolayer could
serve as an excellent anode material for Na- and K-ion batteries
Hexagonal BC<sub>3</sub> Electrode for a High-Voltage Al-Ion Battery
Recent
progresses in the field of Al-ion batteries have given directions
to look for new electrode materials that can lead toward the enhancement
of battery performance. Using the dispersion-corrected density functional
theory calculations, we have examined the applicability of hexagonal
BC<sub>3</sub> as a cathode material for Al-ion battery by evaluating
its stability, specific capacity, and voltage profile diagram of AlCl<sub>4</sub>-intercalated hexagonal BC<sub>3</sub>. Our results show that
AlCl<sub>4</sub>-intercalated BC<sub>3</sub> compounds are stable.
We have found that there is a significant charge transfer from the
BC<sub>3</sub> system to AlCl<sub>4</sub> indicating toward the oxidation
of BC<sub>3</sub> upon intercalation reaction. Several low-energy
pathways are observed for the diffusion process, and it is observed
that the AlCl<sub>4</sub> diffusion is trouble-free in the two-dimensional
plane of BC<sub>3</sub>, having a diffusion barrier as low as 0.38
eV. Moreover, we have observed that BC<sub>3</sub> can provide a higher
average voltage 2.41 V and specific capacity of 74.37 mAh/g. These
findings suggest that BC<sub>3</sub> could be a promising cathode
material for Al-ion batteries
Pt<sub>3</sub>Ti (Ti<sub>19</sub>@Pt<sub>60</sub>)‑Based Cuboctahedral Core–Shell Nanocluster Favors a Direct over Indirect Oxygen Reduction Reaction
Developing a highly
efficient catalyst with lower Pt content for
the oxygen reduction reaction (ORR) is highly sought for fuel cell
applications. The potential applicability of a cuboctahedral core–shell
(Ti<sub>19</sub>@Pt<sub>60</sub>) nanocluster (NC) toward ORR activity
has been investigated and compared with that of a pure Pt NC (Pt<sub>79</sub>). The energetic stability, thermal stability, and dissolution
limit of Ti<sub>19</sub>@Pt<sub>60</sub> NCs has been investigated
for their possible synthesis and practical usages. Thermodynamic and
kinetic parameters are explored to find out the most favored ORR pathway
and product selectivity on the Ti<sub>19</sub>@Pt<sub>60</sub> NC.
Rate-determining steps (*O<sub>2</sub> activation and *OH formation)
are highly improved over the Ti<sub>19</sub>@Pt<sub>60</sub> NC with
respect to the cuboctahedral Pt NC (Pt<sub>79</sub>), pure metal (Pt,
Pd, and Ag), and alloy (Pt<sub>3</sub>M; M = Ni, Co, Ti) based catalysts.
Our detailed investigation reveals that the *O<sub>2</sub>-induced
structural changes favor direct *O<sub>2</sub> dissociation on the
Ti<sub>19</sub>@Pt<sub>60</sub> NC surface. Further, we find that
a dual mechanism (ligand effect and charge transfer) plays an important
role to improve the ORR activity. The results obtained in this study
provide fundamental insight into the role of a core–shell NC
toward ORR activity
High-energy-density dual-ion battery for stationary storage of electricity using concentrated potassium fluorosulfonylimide
Graphite dual-ion batteries represent a potential battery concept for large-scale stationary storage of electricity, especially when constructed free of lithium and other chemical elements with limited natural reserves. Owing to their non-rocking-chair operation mechanism, however, the practical deployment of graphite dual-ion batteries is inherently limited by the need for large quantities of electrolyte solutions as reservoirs of all ions that are needed for complete charge and discharge of the electrodes. Thus far, lithium-free graphite dual-ion batteries have employed moderately concentrated electrolyte solutions (0.3–1 M), resulting in rather low cell-level energy densities of 20–70 Wh kg^−1. In this work, we present a lithium-free graphite dual-ion battery utilizing a highly concentrated electrolyte solution of 5 M potassium bis(fluorosulfonyl)imide in alkyl carbonates. The resultant battery offers an energy density of 207 Wh kg^−1, along with a high energy efficiency of 89% and an average discharge voltage of 4.7 V.ISSN:2041-172
Cation-selective two-dimensional polyimine membranes for high-performance osmotic energy conversion
Two-dimensional (2D) membranes are emerging candidates for osmotic energy conversion. However, the trade-off between ion selectivity and conductivity remains the key bottleneck. Here we demonstrate a fully crystalline imine-based 2D polymer (2DPI) membrane capable of combining excellent ionic conductivity and high selectivity for osmotic energy conversion. The 2DPI can preferentially transport cations with Na+ selectivity coefficient of 0.98 (Na+/Cl− selectivity ratio ~84) and K+ selectivity coefficient of 0.93 (K+/Cl− ratio ~29). Moreover, the nanometer-scale thickness (~70 nm) generates a substantially high ionic flux, contributing to a record power density of up to ~53 W m−2, which is superior to most of nanoporous 2D membranes (0.8~35 W m−2). Density functional theory unveils that the oxygen and imine nitrogen can both function as the active sites depending on the ionization state of hydroxyl groups, and the enhanced interaction of Na+ versus K+ with 2DPI plays a significant role in directing the ion selectivity
Porous Dithiine-Linked Covalent Organic Framework as a Dynamic Platform for Covalent Polysulfide Anchoring in Lithium-Sulfur Battery Cathodes
Dithiine linkage formation via a dynamic and self-correcting nucleophilic aromatic substitution reaction enables the de novo synthesis of a porous thianthrene-based two-dimensional covalent organic framework (COF). For the first time, this organo-sulfur moiety is integrated as a structural building block into a crystalline layered COF. The structure of the new material deviates from the typical planar interlayer π-stacking of the COF to form undulated layers caused by bending along the C-S-C bridge, without loss of aromaticity and crystallinity of the overall COF structure. Comprehensive experimental and theoretical investigations of the COF and a model compound, featuring the thianthrene moiety, suggest partial delocalization of sulfur lone pair electrons over the aromatic backbone of the COF decreasing the band gap and promoting redox activity. Postsynthetic sulfurization allows for direct covalent attachment of polysulfides to the carbon backbone of the framework to afford a molecular-designed cathode material for lithium-sulfur (Li-S) batteries with a minimized polysulfide shuttle. The fabricated coin cell delivers nearly 77% of the initial capacity even after 500 charge-discharge cycles at 500 mA/g current density. This novel sulfur linkage in COF chemistry is an ideal structural motif for designing model materials for studying advanced electrode materials for Li-S batteries on a molecular level
Covalent Trapping of Cyclic-Polysulfides in Perfluorinated Vinylene-Linked Frameworks for Designing Lithium-Organosulfide Batteries
The strategic combination of redox-active triazine- or quinoxaline-based lithium-ion battery (LIB) mechanisms with the polysulfide ring-mediated lithium-sulfur battery (Li-SB) mechanism enabled the configuration of covalent organic-framework (COF)-derived lithium-organosulfide (Li-OrSB) battery systems. Two vinylene-linked frameworks were designed by enclosing polysulfide rings via postsynthetic framework sulfurization, allowing for the separate construction of triazine-polysulfide and quinoxaline-polysulfide redox couples that can readily interact with Li ions. The inverse vulcanization of the vinylene linking followed by the sulfurization-induced nucleophilic aromatic substitution reaction (SNAr) on the perfluorinated aromatic center of the COFs enabled the covalent trapping of cyclic-polysulfides. The experimentally observed reversible Li-interaction mechanism of these highly conjugated frameworks was computationally verified and supported by in situ Raman studies, demonstrating a significant reduction of polysulfide shuttle in a conventional Li-SB and opening the door for a COF-derived high-performing Li-OrSB