C14H6O4Na2/graphene composite as a high performance sodium storage cathode

Nine-Electron Transfer of Binder Synergistic π-d Conjugated Coordination Polymers as High-Performance Lithium Storage Materials

To solve the problems such as the dissolution and the poor conductivity of organic small molecule electrode materials, we construct π-d conjugated coordination polymer Ni-DHBQ with multiple redox-active centers as lithium storage materials. It exhibits an ultra-high capacity of 9-electron transfers, while the π-d conjugation and the laminar structure inside the crystal ensure fast electron transport and lithium ion diffusion, resulting in excellent rate performance (505.6 mAh g^-1 at 1 A g^-1 after 300 cycles). The interaction of Ni-DHBQ with the binder CMC synergistically inhibits its dissolution and anchors the Ni atoms, thus exhibiting excellent cycling stability (650.7 mAh g^-1 at 0.1 A g^-1 after 100 cycles). This work provides insight into the mechanism of lithium storage in π-d conjugated coordination polymers and the synergistic effect of CMC, which will contribute to the molecular design and commercial application of organic electrode materials.

Advanced 1D Metal-Organic Coordination Polymer for Lithium-Ion Batteries: Designing, Synthesis, and Working Mechanism

Anthraquinone (AQ) and its derivatives have been attracting more attention as promising electrode materials for lithium storage because of their high specific capacity, structural diversity, and environmental friendliness. The dissolution and poor electrical conductivity of AQ, however, limit its practical application. Here, a novel metal-organic coordination polymer with a one-dimensional (1D) chain ([C₁₄H₆O₄Cu]_n denoted as Cu-DHAQ; DHAQ, 1,5-dihydroxyl anthraquinone) and its composite with graphene (Cu-DHAQ/G; G, graphene) are developed by the introduction of graphene and copper ion into DHAQ. The fabricated polymer with a 1D chain not only well inhibits the dissolution of DHAQ in organic electrolytes but also facilitates lithium-ion insertion/extraction on carbonyl groups and shortens the migration path of lithium ions. Furthermore, the addition of the conductive network of graphene provides fast transfer rates of electrons. As a result, Cu-DHAQ/G delivers a high discharge capacity, long cycle life, and excellent rate capability. The lithium storage mechanism shows lithium ion insertion/extraction on two carbonyl groups of Cu-DHAQ in the range of 1.6-2.0 V and the redox reaction of Cu⁺/Cu²⁺ between 2.8 and 3.0 V, and Cu²⁺ and Cu⁺ coexist in the Cu-DHAQ/G electrode during the charge/discharge process. This study provides meaningful guidance to develop metal-organic coordination polymer electrodes for high-performance Li-ion batteries.

Facile Synthesis of a LiC15H7O4/Graphene Nanocomposite as a High-Property Organic Cathode for Lithium-Ion Batteries

Organic electrode materials face two outstanding issues in the practical applications in lithium-ion batteries (LIBs), dissolution and poor electronic conductivity. Herein, we fabricate a nanocomposite of an anthraquinone carboxylate lithium salt (LiAQC) and graphene to address the two issues. LiAQC is synthesized via a green and facile one-pot reaction and then ball-milled with graphene to obtain a nanocomposite (nr-LiAQC/G). For comparison, single LiAQC is also ball-milled to form a nanorod (nr-LiAQC). Together with pristine LiAQC, the three samples are used as cathodes for LIBs. Results show that good cycling performance can be obtained by introducing the -CO₂Li hydrophilic group on anthraquinone. Furthermore, the nr-LiAQC/G demonstrates not only a high initial discharge capacity of 187 mAh g^-1 at 0.1 C but also good cycling stability (reversible capacity: ∼165 mAh g^-1 at 0.1 C after 200 cycles) and good rate capability (the average discharge capacity of 149 mAh g^-1 at 2 C). The superior electrochemical properties of the nr-LiAQC/G profit from graphene with high electronic conductivity, the nanorod structure of LiAQC shortening the transport distance for lithium ions and electrons, and the introduction of the -CO₂Li hydrophilic group decreasing the dissolution of LiAQC in the electrolyte. Meanwhile, density functional theory calculations support the roles of graphene and -CO₂Li groups. The fabrication is general and facile, ready to be extended to other organic electrode materials.

Graphene-Supported Naphthalene-Based Polyimide Composite as a High-Performance Sodium Storage Cathode

Electroactive acid anhydride with multicarbonyl is highly promising for electrochemical energy storage because of its high specific capacity and environmental benignity. Its low electrical conductivity and high dissolution in organic electrolyte, however, result in poor cycling and rate capabilities. Here, we report a naphthalene polyimide derivative (NPI) synthesized by using anhydride under condensation polymerization conditions, along with its composite with graphene (NPI-G) fabricated via in situ polymerization. The composite delivers a high reversible capacity and outstanding cycling stability and rate capability as a cathode for sodium-ion batteries (SIBs) owing to the formation of a polymer, the improvement in the electrical conductivity brought about by the highly dispersed graphene sheets, and the enhancement of structural stability resulting from the π-π stacking interaction between the phenyl groups of NPI and the six-member carbon rings of graphene. This investigation sheds light on the development, design, and screening of next-generation organic electrode materials with high performance for SIBs.