Carboxyl-conjugated phthalocyanines used as novel electrode materials with high specific capacity for lithium-ion batteries

Two Birds One Stone: Graphene Assisted Reaction Kinetics and Ionic Conductivity in Phthalocyanine-Based Covalent Organic Framework Anodes for Lithium-ion Batteries

This work reports a covalent organic framework composite structure (PMDA-NiPc-G), incorporating multiple-active carbonyls and graphene on the basis of the combination of phthalocyanine (NiPc(NH2 )4 ) containing a large π-conjugated system and pyromellitic dianhydride (PMDA) as the anode of lithium-ion batteries. Meanwhile, graphene is used as a dispersion medium to reduce the accumulation of bulk covalent organic frameworks (COFs) to obtain COFs with small-volume and few-layers, shortening the ion migration path and improving the diffusion rate of lithium ions in the two dimensional (2D) grid layered structure. PMDA-NiPc-G showed a lithium-ion diffusion coefficient (DLi + ) of 3.04 × 10-10 cm2 s-1 which is 3.6 times to that of its bulk form (0.84 × 10-10 cm2 s-1 ). Remarkably, this enables a large reversible capacity of 1290 mAh g-1 can be achieved after 300 cycles and almost no capacity fading in the next 300 cycles at 100 mA g-1 . At a high areal capacity loading of ≈3 mAh cm-2 , full batteries assembled with LiNi0.8 Co0.1 Mn0.1 O2 (NCM-811) and LiFePO4 (LFP) cathodes showed 60.2% and 74.7% capacity retention at 1 C for 200 cycles. Astonishingly, the PMDA-NiPc-G/NCM-811 full battery exhibits ≈100% capacity retention after cycling at 0.2 C. Aided by the analysis of kinetic behavior of lithium storage and theoretical calculations, the capacity-enhancing mechanism and lithium storage mechanism of covalent organic frameworks are revealed. This work may lead to more research on designable, multifunctional COFs for electrochemical energy storage.

Graphene composite 3,4,9,10-perylenetetracarboxylic sodium salts with a honeycomb structure as a high performance anode material for lithium ion batteries

In order to address the issues of high solubility in electrolytes, poor conductivity and low active site utilization of organic carbonyl electrode materials, in this work, the 3,4,9,10-perylenetetracarboxylic sodium salt (PTCDA-Na) and its graphene composite PTCDA-Na-G are prepared by the hydrolysis of 3,4,9,10-perylenetetracarboxylic dianhydride and the strategy of antisolvent precipitation. The obtained PTCDA-Na active substance has a porous honeycomb structure, showing a large specific surface area. Moreover, after recombination with graphene, the dispersion and specific surface area of PTCDA-Na are further enhanced, and more active sites are exposed and conductivity is improved. As a result, the PTCDA-Na-G composite electrode materials exhibit superior electrochemical energy storage behaviors. The initial charge capacity of the PTCDA-Na-G electrode is 890.5 mA h g-1, and after 200 cycles, the capacity can still remain at 840.0 mA h g-1 with a high retention rate of 94.3%, which is much larger than those of the PTCDA-Na electrode. In addition, at different current densities, the PTCDA-Na-G electrode also presents higher capacities and better cycle stability than the PTCDA-Na electrode. Compared with PTCDA-Na with a porous honeycomb structure and previously reported sodium carboxylic acid salts with a large size bulk structure, the PTCDA-Na-G composite material prepared in this work shows superior electrochemical energy storage properties due to its large specific surface area, high dispersion, more exposed active sites and large electrical conductivity, which would provide new ideas for the development of high performance organic electrode materials for lithium-ion batteries.

A phthalocyanine-grafted MA-VA framework polymer as a high performance anode material for lithium/sodium-ion batteries

A porous MA-VA-PcNi polymer was prepared by grafting nickel phthalocyanine (PcNi) onto the main chain of a maleic anhydride-vinyl acetate (MA-VA) polymer, and an MA-VA-PcNi electrode is prepared by electrospinning technology to inhibit the agglomeration of the active powder effectively, which produces spherical particles with a diameter of 100-300 nm. The synthesized MA-VA-PcNi polymer is used as the anode for lithium-ion and sodium-ion batteries, exhibiting excellent energy storage behaviors. The MA-VA-PcNi/Li battery displays a high capacity of 610 mA h g-1 and can still remain at 507 mA h g-1 with a retention rate of 83.1% after 400 cycles at a current density of 200 mA g-1. Even at a high current density of 2 A g-1, the specific capacity can remain at 195 mA h g-1. In addition, the MA-VA-PcNi/Na battery displays a high capacity of 336 mA h g-1 and can still remain at 278 mA h g-1 with a retention rate of 82.7% after 400 cycles at a current density of 100 mA g-1. A high specific capacity of 164 mA h g-1 can also be achieved at a high current density of 1 A g-1. After nickel phthalocyanine (PcNi) was grafted onto the MA-VA polymer, aggregation between phthalocyanine rings was effectively prevented, and this exposes more active sites. At the same time, the spherical particles obtained by electrospinning technology further improve the dispersion and increase the number of active sites of the active materials. Finally, the electrode materials show excellent energy storage behavior for lithium-ion and sodium-ion batteries, which provides a new idea for designing high-performance energy storage materials for organic electrodes.

1,4,5,8-Naphthalenetetracarboxylic dianhydride grafted phthalocyanine macromolecules as an anode material for lithium ion batteries

For solving the problems of high solubility in electrolytes, poor conductivity and low active site utilization of organic electrode materials, in this work, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) grafted nickel phthalocyanine (TNTCDA-NiPc) was synthesized and used as an anode material for lithium ion batteries. As a result, the dispersibility, conductivity and dissolution stability are improved, which is conducive to enhancing the performance of batteries. The initial discharge capacity of the TNTCDA-NiPc electrode is 859.8 mA h g^-1 at 2 A g^-1 current density, which is much higher than that of the NTCDA electrode (247.4 mA h g^-1). After 379 cycles, the discharge capacity of the TNTCDA-NiPc electrode is 1162.9 mA h g^-1, and the capacity retention rate is 135.3%, which is 7 times that of the NTCDA electrode. After NTCDA is grafted to the phthalocyanine macrocyclic system, the dissolution of the NTCDA in the electrolyte is reduced, and the conductivity and dispersion of the NTCDA and phthalocyanine ring are also improved, so that more active sites of super lithium intercalation from NTCDA and phthalocyanine rings are exposed, which results in better electrochemical performance. The strategy of grafting small molecular active compounds into macrocyclic conjugated systems used in this work can provide new ideas for the development of high performance organic electrode materials.

Porous diatomite-mixed 1,4,5,8-NTCDA nanowires as high-performance electrode materials for lithium-ion batteries

A porous composite electrode composed of diatomite-mixed 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) is prepared by electrostatic spinning technology. Compared with traditional coated electrodes without diatomite mixing, the obtained composite electrode materials have higher porosity, larger specific surface area and faster lithium ion transport channels, which makes them exhibit better electrochemical performance, such as smaller impedance, higher capacity, and better cycling stability and rate performance. The electrospun diatomite-mixed 1,4,5,8-NTCDA composite (ED-1,4,5,8-NTCDA) electrode shows an initial coulombic efficiency of 77.2%, which is much higher than that of the electrospun 1,4,5,8-NTCA (E-1,4,5,8-NTCDA) electrode without diatomite mixing (63.8%) and the coated 1,4,5,8-NTCA (C-1,4,5,8-NTCDA) electrode (48.3%). Moreover, the ED-1,4,5,8-NTCDA electrode displays an initial discharge capacity of 1106.5 mA h g-1, which is much higher than that of the E-1,4,5,8-NTCDA electrode (546.0 mA h g-1) and the C-1,4,5,8-NTCDA electrode (185.4 mA h g-1). After 200 cycles, the capacity of the ED-1,4,5,8-NTCDA electrode remains at 1008.5 mA h g-1 with a retention ratio of 91.2%, which is also much higher than that of 753.2 mA h g-1 for the E-1,4,5,8-NTCDA electrode and 288.1 mA h g-1 for the C-1,4,5,8-NTCDA electrode. Even at a higher current density of 1500 mA g-1, its capacity remains above 508.9 mA h g-1. The ED-1,4,5,8-NTCDA electrode presents superior performance, which opens up a promising new approach for further utilization of organic materials as electrode materials in rechargeable lithium-ion batteries.

Electrochemical properties of carbonyl substituted phthalocyanines as electrode materials for lithium-ion batteries

Through I₂doping and foam nickel coating technology, the conductivity and electrochemical properties of phthalocyanines (2and3) have been improved obviously.