High-Performance Poly(1-naphthylamine)/Mesoporous Carbon Cathode for Lithium-Ion Batteries with Ultralong Cycle Life of 45000 Cycles at -15 °C

Intramolecular Hydrogen Bonds Weaken Interaction Between Solvents and Small Organic Molecules Towards Superior Lithium-Organic Batteries

The strong interaction between organic electrode materials (OEMs) and electrolyte components induces a high solubility tendency of OEMs, thus hindering the practical application of lithium-organic batteries. Herein, we propose an efficient strategy for intramolecular hydrogen bonds (HBs) to redistribute the charge of OEMs to weaken the interaction with electrolyte components, thereby suppressing their dissolution. For the designed 2,2',2''-(2,4,6-trihydroxybenzene-1,3,5-triyl) tris (1H-naphtho[2,3-d]imidazole-4,9-dione) (TPNQ) molecule, the intramolecular HBs (O-H⋅⋅⋅N and N-H⋅⋅⋅O) reduce the charge density of active sites and alter the charge distribution on the molecular skeleton. As a result, TPNQ shows significantly reduced solubility in both ether- and ester-based solvents. In situ measurements and theoretical calculations indicate that the O-H⋅⋅⋅N dominated HB interaction strengthening during the discharging process, which can continuously suppress dissolution. Therefore, the TPNQ cathode displays high cycling stability (no capacity fading over 100 cycles at 0.1 A g-1; 88.4 % capacity retention over 1000 cycles at 1 A g-1), fast Li+-storage kinetics (211 mAh g-1 at 2 A g-1), and surprising low-temperature performances (stability cycles 500 times at -60 °C). Our results offer evidence that the intramolecular HBs strategy is promising in developing robust organic electrode materials for rechargeable batteries.

A Porphyrin-Phenylalkynyl-Based Conjugated Organic Polymer as a High-Performance Cathode for Rechargeable Organic Batteries

Organic electrode materials (OEMs) have attracted much attention for rechargeable batteries due to their low cost, environment friendliness, flexibility, and structural versatility. Despite the above advantages, high solubility in electrolyte and low electronic conductivity remain critical limitations for the application of OEMs. In this work, the conjugated organic polymer (COP) poly([5,10,15,20-tetrakis(4-phenylalkynyl)porphyrin]Cu(II)) (PCuTPEP) is proposed as a cathode for high performance in organic lithium batteries. The polymerization inhibits the dissolution of the organic electrodes in the electrolyte, and the porphyrin and ethynyl-phenyl groups greatly expand the conjugated system and result in a high average discharge plateau at 4.0 V (vs Li+/Li). The PCuTPEP cathode exhibits a reversible discharge capacity of 119 mAh g-1 at a current of 50 mA g-1. Even at a high current density of 2.0 A g-1, excellent cycling stability up to 1000 cycles is achieved with capacity retentions of 88.5 and 90.4% at operating temperatures of 25 and 50 °C in organic lithium batteries, respectively. This study provides the approach for the development of organic cathodes for electrochemical energy storage.

Ferrocene-Based Polymer Organic Cathode for Extreme Fast Charging Lithium-Ion Batteries with Ultralong Lifespans

To meet the growing demand for energy storage, lithium-ion batteries (LIBs) with fast charging capabilities has emerged as a critical technology. The electrode materials affect the rate performance significantly. Organic electrodes with structural flexibility support fast lithium-ion transport and are considered promising candidates for fast-charging LIBs. However, it is a challenge to create organic electrodes that can cycle steadily and reach high energy density in a few minutes. To solve this issue, accelerating the transport of electrons and lithium ions in the electrode is the key. Here, it is demonstrated that a ferrocene-based polymer electrode (Fc-SO3Li) can be used as a fast-charging organic electrode for LIBs. Thanks to its molecular architecture, LIBs with Fc-SO3Li show exceptional cycling stability (99.99% capacity retention after 10 000 cycles) and reach an energy density of 183 Wh kg-1 in 72 seconds. Moreover, the composite material through in situ polymerization with Fc-SO3Li and 50 wt % carbon nanotube (denoted as Fc-SO3Li-CNT50) achieved optimized electron and ion transport pathways. After 10 000 cycles at a high current density of 50C, it delivered a high energy density of 304 Wh kg-1. This study provides valuable insights into designing cathode materials for LIBs that combine high power and ultralong cycle life.

Electropolymerized Bipolar Poly(2,3-diaminophenazine) Cathode for High-Performance Aqueous Al-Ion Batteries with An Extended Temperature Range of -20 to 45 °C

Achieving reversible insertion/extraction in most cathodes for aqueous aluminum ion batteries (AAIBs) is a significant challenge due to the high charge density of Al3+ and strong electrostatic interactions. Organic materials facilitate the hosting of multivalent carriers and rapid ions diffusion through the rearrangement of chemical bonds. Here, a bipolar conjugated poly(2,3-diaminophenazine) (PDAP) on carbon substrates prepared via a straightforward electropolymerization method is introduced as cathode for AAIBs. The integration of n-type and p-type active units endow PDAP with an increased number of sites for ions interaction. The long-range conjugated skeleton enhances electron delocalization and collaborates with carbon to ensure high conductivity. Moreover, the strong intermolecular interactions including π-π interaction and hydrogen bonding significantly enhance its stability. Consequently, the Al//PDAP battery exhibits a large capacity of 338 mAh g-1 with long lifespan and high-rate capability. It consistently demonstrates exceptional electrochemical performances even under extreme conditions with capacities of 155 and 348 mAh g-1 at -20 and 45 °C, respectively. In/ex situ spectroscopy comprehensively elucidates its cation/anion (Al3+/H3O+ and ClO4 -) storage with 3-electron transfer in dual electroactive centers (C═N and -NH-). This study presents a promising strategy for constructing high-performance organic cathode for AAIBs over a wide temperature range.

Long Cycle Life for Rechargeable Lithium Battery using Organic Small Molecule Dihydrodibenzo[c,h][2,6]naphthyridine-5,11-dione as a Cathode after Isoindigo Pigment Isomerization

Sustainability and adaptability in structural design of the organic cathodes present promises for applications in alkali metal ion batteries. Nevertheless, a formidable challenge lies in their high solubility in organic electrolytes, particularly for small molecular materials, impeding cycling stability and high capacity. This study focuses on the design and synthesis of organic small molecules, the isomers of (E)-5,5'-difluoro-[3,3'-biindolinylidene]-2,2'-dione (EFID) and 3,9-difluoro-6,12-dihydrodibenzo [c, h][2,6]naphthyridine-5,11-dione (FBND). While EFID, characterized by a less π-conjugated structure, exhibits subpar cycling stability in lithium-ion batteries (LIBs), intriguingly, another isomer, FBND, demonstrates exceptional capacity and cycling stability in LIBs. FBND delivers a remarkable capacity of 175 mAh g-1 at a current density of 0.05 A g-1 and maintains excellent cycling stability over 2000 cycles, retaining 90% of its initial capacity. Furthermore, an in-depth examination of redox reactions and storage mechanisms of FBND are conducted. The potential of FBND is also explored as an anode in lithium-ion batteries (LIBs) and as a cathode in sodium-ion batteries (SIBs). The FBND framework, featuring extended π-conjugated molecules with an imide structure compared to EFID, proves to be an excellent material template to develop advanced organic small molecular cathode materials for sustainable batteries.

Ultrastable Dendrite-Free Potassium Metal Batteries Enabled by Weakly-Solvated Electrolyte

Potassium (K) metal is considered one of the most promising anodes for potassium metal batteries (PMBs) because of its abundant and low-cost advantages but suffers from serious dendritic growth and parasitic reactions, resulting in poor cyclability, low Coulombic efficiency (CE), and safety concerns. In this work, we report a localized high-concentration electrolyte (LHCE) consisting of potassium bis(fluorosulfonyl)imide (KFSI) in a cosolvent of 1,2-dimethoxyethane (DME) and 1,1,2,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) to solve the problems of PMBs. TTE as a diluent not only endows LHCE with advantages of low viscosity, good wettability, and improved conductivity but also solves the dendrite problem pertaining to K metal anodes. Using the formulation of LHCE, a CE of 98% during 800 cycles in the K||Cu cell and extremely stable cycling of over 2000 h in the K||K symmetric cell are achieved at a current density of 0.1 mA cm-2. In addition, the LHCE shows good compatibility with a Prussian Blue cathode, allowing almost 99% CE for the K||KFeIIFeIII(CN)6 full cell during 100 cycles. This promising electrolyte design realizes high-safety and energy-dense PMBs.