Understanding the sodium storage mechanisms of organic electrodes in sodium ion batteries: issues and solutions

132

lithium resources greatly limits the large-scale promotion and application of LIBs. [4-7] As possible candidates, sodium and potassium ion systems are receiving intense attention owing to their low cost and high natural abundant resources. [8-14] Particularly, recent studies indicated that compared with sodium ions, potassium ions exhibited more merits on the basis of its similar intercalation behaviors in graphite and closer redox potential (K/K + , −2.92 V) with Li ions. [15,16] Therefore, potassium ion energy storage system, including potassium ion batteries (PIBs) and potassium ion hybrid capacitors (PIHCs) demonstrates a promising prospect in practical applications, and the corresponding studying upsurge is just beginning. [16,17] In the exploration of potassium electrode materials, porous carbons are highly preferable owing to their elastic framework, rich porosity and good conductivity, which can efficiently alleviate the volume expansion caused by the larger K + (ionic radius, 1.38 Å) intercalation and provides more pathways for fast K + diffusion. [16,18-21] So far, many carbons with various porosities have been successfully used in potassium ion system, exhibiting excellent electrochemical performance. [22,23] In current strategies of producing porous carbons, the template method is considered as one ideal way owing to its good control of porous architectures. [16] Presently, solid-phase templates including salts, SiO 2 nanospheres, and metal foams have been applied widely in constructing porous carbons. [24-26] Besides, gas-phase templates such as gas bubbles and foams are also popular due to their facile and economical process. [23,27] Despite a great process, several challenges still remain. For example, salt or gas-phase templates are simple and scalable, but always create large-size pores, giving rise to the severe decrease of the volumetric capacitance. [28] The nanosized solid-phase templates can lead to small-size pores, but are hindered by high cost and the probability of contamination from the removal process. [29] Therefore, the development of a scalable and green template strategy for the synthesis of carbons with rich nanosized porosity is important. Notably, in contrast to the success of solid-and gas-phase templates, liquid-state templates are rarely reported so far, which might be Template-assistant design and fabrication of porous carbon electrode materials has experienced great progress throughout the past decades and yielded lots of successes via various gas or solid state templates. Nevertheless, liquid-state templates are rather rare in preparing porous carbon materials to date. In this work, melting B 2 O 3 beads are used as both templates and a B dopant, leading to unique B, N co-doping hierarchically porous carbons containing a "bubble pool"-like skeleton built of interconnected carbon nanobubbles. Notably, an interesting amending effect of doped B atoms on the N-doped carbon network can be identified for the first time, which creates a "paddy field"-like hybrid microstructure wi...

Section: Introductionmentioning

confidence: 99%

Liquid‐State Templates for Constructing B, N, Co‐Doping Porous Carbons with a Boosting of Potassium‐Ion Storage Performance

Feng

Liu

et al. 2020

132

“…[9][10][11] Therefore, organic materials as electrodes applied for metal-ion batteries have fascinated researchers gradually in recent years. [8,[12][13][14] Lithium-ion batteries (LIBs) have been widely applied in electron devices and electric vehicles due to its high energy density. [15] Meanwhile, there is also an increasing attention on sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) that are potentially comparable to LIBs due to their low cost and abundant resources.…”

Section: Introductionmentioning

confidence: 99%

“…[ 9–11 ] Therefore, organic materials as electrodes applied for metal‐ion batteries have fascinated researchers gradually in recent years. [ 8,12–14 ]…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Study of Poly(2,6‐Anthraquinonyl Sulfide) as Cathode for Alkali‐Metal‐Ion Batteries

Gao

Fan

et al. 2020

Organic electrode materials are extensively applied for alkali metal (lithium, sodium, and potassium)‐ion batteries (LIBs, SIBs, and PIBs) due to their sustainability and low cost. As a typical organic cathode, poly(2,6‐anthraquinonyl sulfide) (PAQS) shows high theoretical capacity, yet its electrochemical behavior and mechanisms in alkali‐metal‐ion batteries still require clarification. Herein, PAQS microspheres are synthesized and applied as cathodes for LIBs, SIBs, and PIBs. When using traditional low‐concentration electrolytes, the reduction voltage and the initial discharge capacity of PAQS electrode in LIB, SIBs, PIBs are 2.11 V/103 mAh g−1, 1.76/1.30 V/134 mAh g−1, 1.94/1.54 V/198 mAh g−1 at 100 mA g−1, respectively, while the cycling stability of PAQS is in the order of LIBs > SIBs > PIBs. To further promote the practical application of PIBs, a facile method is demonstrated to improve the cycle stability of PAQS for PIBs by using a novel high‐concentration electrolyte. The cycling stability of PIBs with PAQS can be improved significantly to 1200 cycles with a capacity decay of 0.031% per cycle. This work may provide guidelines for developing innovative organic materials used in applicable metal‐ion batteries demonstrates the impact of electrolyte optimization on improving the cycling stability.

“…

…”

mentioning

confidence: 99%

Organic Negative Electrode Materials for Metal‐Ion and Molecular‐Ion Batteries: Progress and Challenges from a Molecular Engineering Perspective

Lakraychi

Dolhem

Vlad

et al. 2021

Thanks to their versatility and flexibility, EOMs have shown broad applicability as bulky solid [3] or dissolved [4,5] active material, in aqueous [6][7][8] or non-aqueous electrolyte, [9][10][11] for portable and stationary batteries, respectively. In practice, OEMs are explored as main active materials in LIBs, [12] beyond Li systems (e.g., hydrogen, [13,14] Na-ion, [15][16][17][18][19] K-ion, [20][21][22][23][24] and multivalent batteries like magnesium, [25,26] zinc, [27] or aluminum [28,29] ) and also redox flow batteries; [30] or as supporting active materials such as redox mediators for Li-O 2 batteries, [31] Li-source sacrificial materials for Li-ion capacitor [32] and redox electrolytes for high-energy supercapacitors. [33] In contrast to the state-of-the-art inorganic materials, whose reactivity is based on redox of transition metal center and consequently Li + de/insertion, [34,35] the redox reaction of EOMs is based on the charge state change of the redox moiety, [12] for which the charge compensation during redox can be either made by cations, referring to n-type systems, or by anions, belonging then to p-type system, according to the proposed Hünig's classification. [36,37] The richness of organic chemistry coupled with molecular modifications have provided thus far a plethora of molecules and architectures operating within a large potential window with high specific capacities, extended cycling stability and high cycling rate. This has enabled building a broad database of electroactive compounds for both positive and negative electrode applications. Organic positive electrode materials (OPEMs) certainly benefit from larger attention since there are more possibilities to explore, for example, conducting polymers, [38,39] nitroxides, and other stable organic radicals, [40][41][42][43] sulfur compounds, [11] as well as conjugated amines, [44][45][46] conjugated sulfonamides, [47] nitro-aromatics, [48] and carbonyls. [49,50] The latter being certainly the most explored category owing to major advances attained so far but also to opportunities for further improvements to attain simultaneously high energy and power densities combined with good cycling stability. [12] On the opposite side, the chemical library is less rich for organic negative electrode materials (ONEMs), primarily due to much focus on positive electrode chemistries, for which many issues and strategies are to be addressed and explored, respectively. Today, the ONEMs database counts fewer redox families as OPEMs one, with also less specific chemistries within each class. To cite some: the most studied conjugated dicarboxylates, [51] Hückel-stabilized Schiff base, [52] nitrogen-redox azo