Heterogeneous intercalated metal-organic framework active materials for fast-charging non-aqueous Li-ion capacitors

Synergistic Effects of Fluorinated Li-Based Metal-Organic Framework Filler on Matrix Polarity and Anion Immobilization in Quasi-Solid State Electrolyte for Lithium-Metal Batteries

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) based electrolyte is a promising alternative to liquid electrolytes in lithium metal batteries. However, its commercial application is limited by high crystallinity and low Li+ ion conductivity. In this study, we synthesized a fluorinated Li-based metal-organic framework (Li-MOF-F) and used it as a filler to address these limitations. The strategy for the Li-MOF-F filler stands out in two main aspects: framework structure for rapid Li+ ion transport and F-functional group with electronegativity. The LiO4 with π-π conjugated dicarboxylate enables the reversible Li intercalation in the lattice structure. The fluorine atoms with electronegativity transform the polymer matrix from non-polar to polar phase and immobilize TFSI- anions by electrostatic interaction. As a result, the PVDF-HFP electrolyte with Li-MOF-F (LMF-PE) achieves the highest polarity and Li transference number. In Li/Li symmetric cell tests, LMF-PE demonstrates stable Li plating/stripping behavior without dendrites. Additionally, we applied lithium nickel manganese cobalt oxide (NCM) with 94 % Ni content as a cathode material in cell test. LMF-PE cell delivers a high initial discharge capacity of 226.9 mAh g-1 and 80 % capacity retention after 150 cycles, highlighting its superior cycling performance. These enhancements are attributed to the structural and electrostatic benefits of Li-MOF-F.

Crystal structure of poly[[aqua-(μ2-pyrazine-κ2 N:N')(μ2-2,3,5,6-tetra-chloro-benzene-1,4-di-car-boxyl-ato-κ2 O 1:O 4)copper(II)] hemihydrate]

The asymmetric unit of the title compound, {[Cu2(C8Cl4O4)2(C4H4N2)2(H2O)2]·H2O} n or {[Cu2(Cl4bdc)2(pyz)2(H2O)2]·H2O} n comprises of a CuII ion, one tetra-chloro-benzene-dicarboxyl-ate ion (Cl4bdc2-), one pyrazine ligand (pyz), and one and a half water mol-ecules. The CuII ion exhibits a five-coordinated square-pyramidal geometry with a CuN2O3 coordination environment comprising two oxygen atoms of the Cl4bdc2- ligands, one oxygen atom of a water mol-ecule, and two nitro-gen atoms of the pyz ligands. The carboxyl-ate group is almost perpendicular to the benzene ring and shows monodentate coordination to the CuII ion. The CuII ions of these units are bridged by both the Cl4bdc2- and pyz ligands to form two-dimensional (2D) layers, which are linked by alternating hydrogen-bonding and C-Cl⋯π inter-actions to yield a three-dimensional network.

Crystal structure of catena-poly[[[tetra-aquacobalt(II)]-μ2-1,5-di-hydroxy-naphthalene-2,6-di-carboxyl-ato] di-methyl-formamide disolvate]

The asymmetric unit of the title compound, {[Co(C12H6O6)(H2O)4]·2C3H7NO} n or {[Co(H2dondc)(H2O)4]·2DMF} n , comprises half of a CoII ion, half of a 1,5-di-hydroxy-naphthalene-2,6-di-carboxyl-ate dianion (H2dondc2-), two water mol-ecules and a di-methyl-formamide (DMF) mol-ecule. The CoII ion, which is located on a crystallographic inversion center, exhibits a distorted six-coord-inated octa-hedral geometry with two oxygen atoms of the H2dondc2- ligand and four oxygen atoms of the water mol-ecules. The carboxyl-ate group is almost coplanar with the naphthalene moiety and shows monodentate coordination to the CoII ion. The CoII ions are bridged by the H2dondc2- ligand to form a one-dimensional chain. The hy-droxy groups of the ligand have intra-chain hydrogen bonding inter-actions with coordinated water mol-ecules. The coordinated water mol-ecules exhibit not only intra-chain hydrogen bonding inter-actions, but also inter-chain hydrogen-bonding inter-actions. The chains are connected by inter-chain hydrogen-bonding inter-actions and are arranged in parallel to form a two-dimensional network. The chains are further connected by inter-chain hydrogen-bonding inter-actions via the DMF mol-ecules and C-H⋯π inter-actions to give a three-dimensional network.

In Situ Construction of Bimetallic Selenides Heterogeneous Interface on Oxidation-Stable Ti3C2Tx MXene Toward Lithium Storage with Ultrafast Charge Transfer Kinetics

Ti3C2Tx (MXene) is widely acknowledged as an excellent substrate for constructing heterogeneous structures with transition metal chalcogenides (TMCs) for boosting the electrochemical performance of lithium-ion storage. However, conventional synthesis strategies inevitably lead to poor electrochemical charge transfer due to Ti3C2Tx-derived TiO2 at the heterogeneous interface between Ti3C2Tx and TMCs. Here, an innovative in situ selenization strategy is proposed to replace the originally generated TiO2 on Ti3C2Tx with metallic TiSe2 interphase, clearing the bottleneck of slow charge transfer barrier caused by MXene oxidation. The construction of bimetallic selenide formed by CoSe2 and TiSe2 generates intrinsic electric fields to guide the fast ion diffusion kinetics in a heterogeneous interface. Additionally, the CoSe2/TiSe2/Ti3C2Tx heterogeneous structure with enhanced structural stability and improved rate performance is confirmed by both experiments and theoretical calculations. The engineered heterogeneous structure exhibits an ultra-high pseudocapacitance contribution (73.1% at 0.1 mV s-1), rendering it well-suited to offset the kinetics differences between double-layer materials. The assembled lithium-ion capacitor based on CoSe2/TiSe2/Ti3C2Tx possesses a high energy density and an ultralong life span (89.5% after 10 000 times at 2 A g-1). This devised strategy provides a feasible solution for utilizing the performance advantages of MXene substrates in lithium storage with ultrafast charge transfer kinetics.

Crystal structure of catena-poly[[di-aqua-di-imida-zole-cobalt(II)]-μ2-2,3,5,6-tetra-bromo-benzene-1,4-di-carboxyl-ato]

The asymmetric unit of the title compound, [Co(C8Br4O4)(C3H4N2)2(H2O)2] n or [Co(Br4bdc)(im)2(H2O)2] n , comprises half of CoII ion, tetra-bromo-benzene-dicarboxylate (Br4bdc2-), imidazole (im) and a water mol-ecule. The CoII ion exhibits a six-coordinated octa-hedral geometry with two oxygen atoms of the Br4bdc2- ligand, two oxygen atoms of the water mol-ecules, and two nitro-gen atoms of the im ligands. The carboxyl-ate group is nearly perpendicular to the benzene ring and shows monodentate coordination to the CoII ion. The CoII ions are bridged by the Br4bdc2- ligand, forming a one-dimensional chain. The carboxyl-ate group acts as an inter-molecular hydrogen-bond acceptor toward the im ligand and a coordinated water mol-ecule. The chains are connected by inter-chain N-H⋯O(carboxyl-ate) and O-H(water)⋯O(carboxyl-ate) hydrogen-bonding inter-actions and are not arranged in parallel but cross each other via inter-chain hydrogen bonding and π-π inter-actions, yielding a three-dimensional network.

Dual-Carbon Phase-Encapsulated Prelithiated SiOx Microrod Anode for Lithium-Ion Batteries

Among silicon-based anode family for Li-ion battery technology, SiOx, a nonstoichiometric silicon suboxide holds the potential for significant near-term commercial impact. In this context, this study mainly focuses on demonstrating an innovative SiOx@C anode design that adopts a pre-lithiation strategy based on in situ pyrolysis of Li-salt of silsesquioxane trisilanolate without the need for lithium metal or active lithium compounds and creates dual carbon encapsulation of SiOC nanodomains by simply one-step thermal treatment. This ingenious design ensures the pre-lithiation process and pre-lithiation material with high-environmental stability. Moreover, phenyl-rich organosiloxane clusters and polyacrylonitrile polymers are expected to serve as internal and external carbon source, respectively. The formation of an interpenetrating and continuous carbon matrix network would not only synergistically offer an improved electrochemical accessibility of active sites but also alleviate the volume expansion effect during cycling. As a result, this new type of anode delivered a high reversible capacity, remarkable cycle stability as well as excellent high-rate capability. In particular, the L2-SiOx@C material has a high initial coulomb efficienc of 80.4% and, after 500 cycles, a capacity retention as high as 97.5% at 0.5 A g-1 with a reversible specific capacity of 654.5 mA h g-1.

Developments in conducting polymer-, metal oxide-, and carbon nanotube-based composite electrode materials for supercapacitors: a review

Supercapacitors are the latest development in the field of energy storage devices (ESDs). A lot of research has been done in the last few decades to increase the performance of supercapacitors. The electrodes of supercapacitors are modified by composite materials based on conducting polymers, metal oxide nanoparticles, metal-organic frameworks, covalent organic frameworks, MXenes, chalcogenides, carbon nanotubes (CNTs), etc. In comparison to rechargeable batteries, supercapacitors have advantages such as quick charging and high power density. This review is focused on the progress in the development of electrode materials for supercapacitors using composite materials based on conducting polymers, graphene, metal oxide nanoparticles/nanofibres, and CNTs. Moreover, we investigated different types of ESDs as well as their electrochemical energy storage mechanisms and kinetic aspects. We have also discussed the classification of different types of SCs; advantages and drawbacks of SCs and other ESDs; and the use of nanofibres, carbon, CNTs, graphene, metal oxide-nanofibres, and conducting polymers as electrode materials for SCs. Furthermore, modifications in the development of different types of SCs such as pseudo-capacitors, hybrid capacitors, and electrical double-layer capacitors are discussed in detail; both electrolyte-based and electrolyte-free supercapacitors are taken into consideration. This review will help in designing and fabricating high-performance supercapacitors with high energy density and power output, which will act as an alternative to Li-ion batteries in the future.

Zinc-copper dual-ion electrolytes to suppress dendritic growth and increase anode utilization in zinc ion capacitors

The main bottlenecks that hinder the performance of rechargeable zinc electrochemical cells are their limited cycle lifetime and energy density. To overcome these limitations, this work studied the mechanism of a dual-ion Zn-Cu electrolyte to suppress dendritic formation and extend the device cycle life while concurrently enhancing the utilization ratio of zinc and thereby increasing the energy density of zinc ion capacitors (ZICs). The ZICs achieved a best-in-class energy density of 41 watt hour per kilogram with a negative-to-positive (n/p) electrode capacity ratio of 3.10. At the n/p ratio of 5.93, the device showed a remarkable cycle life of 22,000 full charge-discharge cycles, which was equivalent to 557 hours of discharge. The cumulative capacity reached ~581 ampere hour per gram, surpassing the benchmarks of lithium and sodium ion capacitors and highlighting the promise of the dual-ion electrolyte for delivering high-performance, low-maintenance electrochemical energy supplies.

Crystal structure of dilithium biphenyl-4,4'-di-sulfonate dihydrate

The asymmetric unit of the title compound, μ-biphenyl-4,4'-di-sulfonato-bis-(aqua-lithium), [Li2(C12H8O6S2)(H2O)2] or Li2[Bph(SO3)2](H2O)2, consists of an Li ion, half of the diphenyl-4,4'-di-sulfonate [Bph(SO3 -)2] ligand, and a water mol-ecule. The Li ion exhibits a four-coordinate tetra-hedral geometry with three oxygen atoms of the Bph(SO3 -)2 ligands and a water mol-ecule. The tetra-hedral LiO4 units, which are inter-connected by biphenyl moieties, form a layer structure parallel to (100). These layers are further connected by hydrogen-bonding inter-actions to yield a three-dimensional network.