A polyanionic organic cathode for highly efficient K-ion full batteries

Single organic electrode for multi-system dual-ion symmetric batteries

The large void space of organic electrodes endows themselves with the capability to store different counter ions without size concern. In this work, a small-molecule organic bipolar electrode called diquinoxalino[2,3-a:2',3'-c]phenazine-2,6,10-tris(phenoxazine) (DQPZ-3PXZ) is designed. Based on its robust solid structure by the π conjugation of diquinoxalino[2,3-a:2',3'-c]phenazine (DQPZ) and phenoxazine (PXZ), DQPZ-3PXZ can indiscriminately and stably host 5 counter ions with different charge and size (Li+, Na+, K+, PF6- and FSI-). In Li/Na/K-based half cells, DQPZ-3PXZ can deliver the peak discharge capacities of 257/243/253 mAh g-1cathode and peak energy densities of 609/530/572 Wh kg-1cathode, respectively. The Li/Na/K-based dual-ion symmetric batteries can be constructed, which can be activated through the 1st charge process and show the stable discharge capacities of 85/66/72 mAh g-1cathode and energy densities of 59/50/52 Wh kg-1total mass, all running for more than 15000 cycles with nearly 100% capacity retention.

Recent advances in rational design for high-performance potassium-ion batteries

The growing global energy demand necessitates the development of renewable energy solutions to mitigate greenhouse gas emissions and air pollution. To efficiently utilize renewable yet intermittent energy sources such as solar and wind power, there is a critical need for large-scale energy storage systems (EES) with high electrochemical performance. While lithium-ion batteries (LIBs) have been successfully used for EES, the surging demand and price, coupled with limited supply of crucial metals like lithium and cobalt, raised concerns about future sustainability. In this context, potassium-ion batteries (PIBs) have emerged as promising alternatives to commercial LIBs. Leveraging the low cost of potassium resources, abundant natural reserves, and the similar chemical properties of lithium and potassium, PIBs exhibit excellent potassium ion transport kinetics in electrolytes. This review starts from the fundamental principles and structural regulation of PIBs, offering a comprehensive overview of their current research status. It covers cathode materials, anode materials, electrolytes, binders, and separators, combining insights from full battery performance, degradation mechanisms, in situ/ex situ characterization, and theoretical calculations. We anticipate that this review will inspire greater interest in the development of high-efficiency PIBs and pave the way for their future commercial applications.

Small-Molecule Organic Cathodes with Carbon Coating for Highly Efficient Potassium-ion Batteries

Small-molecule organic cathodes face dissolution in potassium-ion batteries (PIBs). For the first time, an interesting and effective strategy is unveiled to resolve this issue by designing a new soluble small-molecule organic compound namely [N,N'-bis(2-anthraquinone)]-1,4,5,8-naphthalenetetracarboxdiimide (NTCDI-DAQ, 237 mAh g-1 ): Through the precise manipulation of carbonization temperature and time, the molecules on the surface of NTCDI-DAQ particles can be transformed into amorphous carbon with controllable thickness. This strategy called surface self-carbonization can form a carbon protective layer on organic cathodes and significantly increase their insolubility against liquid electrolytes without affecting the electrochemical behavior of bulk particles. As a result, the as-obtained NTCDI-DAQ@C sample displays significantly improved cathode performance in PIBs. In half cells, NTCDI-DAQ@C shows superior capacity stability of 84 % compared to 35 % of NTCDI-DAQ during 30 cycles under the same conditions. In full cells with a KC8 anode, NTCDI-DAQ@C delivers a peak discharge capacity of 236 mAh g-1 cathode and a high energy density of 255 Wh kg-1 cathode in 0.1-2.8 V, with 40 % capacity retention during 3000 cycles at 1 A g-1 . To the best of our knowledge, the integrated performance of NTCDI-DAQ@C is among the best of soluble organic cathodes reported in PIBs.

Ultrasonication-aided self-assembly strategy toward PTCDA/RGO film cathode for organic K-ion full batteries

A free-standing PTCDA/RGO film was synthesized by ultrasonication-aided self-assembly strategy to alleviate the solubility of PTCDA in organic electrolyte. The PTCDA/RGO-50% film cathode exhibits a high capacity of 135.1 mA...

A Low-Cost Na-Ion and K-Ion Batteries Using a Common Organic Cathode and Bismuth Anode

Molecule-aggregation organic electrodes in principle have the capability for "single-molecule-energy-storage" in metal-ion rechargeable batteries, which indicates that the same organic electrode can be simultaneously applied to multiple metal-ion rechargeable batteries. In this study, the polyanionic organic compound 9,10-anthraquinone-2,6-disulfonate (Na₂ AQ26DS, 130 mAh g^-1 ) is used as a common cathode and metal bismuth (Bi) as a common anode to simultaneously assemble low-cost Na-ion and K-ion full cells. The Na-ion full cells can deliver the peak discharge capacity of 139 mAh g^-1 _cathode at 0.5-3.0 V, and the K-ion full cells can show the peak discharge capacity of 130 mAh g^-1 _cathode at 0.5-3.0 V. These results are comparable to the best organic-based Na-ion and K-ion full cells reported to date.

Electrolyte Effect on a Polyanionic Organic Anode for Pure Organic K-Ion Batteries

Potassium naphthalene-1,4,5,8-tetracarboxylate (K₄NTC, 117 mAh g^-1) is a new organic anode for K-ion batteries, which possesses four strong K-O ionic bonds within a -4-valent naphthalene-1,4,5,8-tetracarboxylate skeleton (NTC^4-). And thus, K₄NTC is a polyanionic organic salt. Simultaneously, new insights are provided by comparing two typical electrolyte systems (carbonate and ether electrolytes) with KPF₆ as the same solute. Finally, the pure organic K-ion batteries (OKIBs) are fabricated by using perylene-3,4,9,10-tetracarboxydianhydride (PTCDA) as the organic cathode and the reduced state (K₆NTC) of K₄NTC as the anode. And this OKIB can deliver a peak discharge capacity of 121 mAh g^-1_anode and run over 1500 cycles in 0.5-3 V using ether electrolytes.

Bismuth oxychloride anchoring on graphene nanosheets as anode with a high relative energy density for potassium ion battery

In this work, we developed bismuth oxychloride anchoring on graphene nanosheets (BiOCl/G) composite via a simple one-step hydrothermal process for KIBs' anode, which delivers a high reversible specific capacity of 251 mAh g^-1 at 50 mA g^-1 after 50 cycles. Meanwhile, our BiOCl/G composite also exhibits a low voltage plateau during potassiation-depotassiation process, and such low voltage plateau in anode is helpful to improve the energy density of the full battery. In addition, we also provide the energy changes for migration of K-ion of our composite according to the density functional theory calculation and the result shows that the introduction of graphene in BiOCl can reduce the adsorption energy variation, which is in favor of K-ion intercalation process. In consideration of low potential plateau of our composite, we also introduce a new evaluation method, relative energy density (E_R), which not only includes the specific capacity, but also combines the potential plateau of the anode materials during potassiation-depotassiation process. According to the calculation, our BiOCl/G composite obtain an ultra-high E_R of 541 Wh kg^-1 at 50 mA g^-1 after 50 cycles with a relative energy conversion efficiency of 81%.

Molecular Regulation on Carbonyl-Based Organic Cathodes: Toward High-Rate and Long-Lifespan Potassium-Organic Batteries

Organic redox-active molecules have been identified as promising cathodes for practical usage of potassium-ion batteries (PIBs) but still struggle with serious dissolution problems and sluggish kinetic properties. Herein, we propose a pseudocapacitance-dominated novel insoluble carbonyl-based cathode, [2,6-di[1-(perylene-3,4,9,10-tetracarboxydiimide)]anthraquinone, AQ-diPTCDI], which possesses high reversible capacities of 150 mAh g^-1, excellent cycle stability with capacity retention of 88% over 2000 cycles, and fast kinetic properties. The strong intermolecular interactions of AQ-diPTCDI and in situ formed cathode electrolyte interphase films support it against the dissolution problem. The high capacitive-like contribution in capacities and fast potassium-ion diffusion enhance its reaction kinetics. Moreover, a symmetric organic potassium-ion battery (OPIB) based on AQ-diPTCDI electrodes also exhibits outstanding K-storage capability. These results suggest that AQ-diPTCDI is a promising organic cathode for OPIBs and provide a practicable route to realize high-performance K storage.

Organic Electrode Materials for Non-aqueous K-Ion Batteries

The demands for high-performance and low-cost batteries make K-ion batteries (KIBs) considered as promising supplements or alternatives for Li-ion batteries (LIBs). Nevertheless, there are only a small amount of conventional inorganic electrode materials that can be used in KIBs, due to the large radius of K+ ions. Differently, organic electrode materials (OEMs) generally own sufficiently interstitial space and good structure flexibility, which can maintain superior performance in K-ion systems. Therefore, in recent years, more and more investigations have been focused on OEMs for KIBs. This review will comprehensively cover the researches on OEMs in KIBs in order to accelerate the research and development of KIBs. The reaction mechanism, electrochemical behavior, etc., of OEMs will all be summarized in detail and deeply. Emphasis is placed to overview the performance improvement strategies of OEMs and the characteristic superiority of OEMs in KIBs compared with LIBs and Na-ion batteries.