Abnormal Excess Capacity of Conjugated Dicarboxylates in Lithium-Ion Batteries

Abstract

Lithium-ion batteries (LIBs) are considered to be key energy storage systems needed to secure reliable, sustainable, and clean energy sources. Redox-active organic compounds have been proposed as interesting candidates for electrode materials for the next-generation LIBs because of their flexible molecular design, recyclability, and low production cost. Despite wide interest, a molecular-level understanding of the electrochemical lithiations/delithiations of those materials remains rudimentary. We synthesized a set of π-conjugated dicarboxylates and discovered unprecedented excess capacities for inverse-Wurster-type nonfused aromatic compounds (dilithium terephthalate and dilithium thiophene-2,5-dicarboxylate). Molecular structural investigations based on solid-state CP/MAS (13)C NMR combined with the stable isotope labeling method and ex situ X-ray diffraction were carried out to elucidate the origin of the excess reversible capacity. Interestingly, an open-chain-type dilithium muconate did not show an analogous behavior, signifying the key role played by the cyclic moiety in the electrochemical reaction.

Organic Thiocarboxylate Electrodes for a Room‐Temperature Sodium‐Ion Battery Delivering an Ultrahigh Capacity

“…[24] Thec harge-discharge curves show that the discharge capacities at acurrent density of 50 mA g À1 for the four samples are increasing when the number of sulfur atoms increases.C onsidering the low average voltage plateau and capacity,m olecule b is ac ompetitive material for the sodium-ion battery.T he molecule with one phenyl group and four sulfur atoms (c)s hows the highest capacity of 567 mAh g À1 which is also the highest capacity of an organic sodium battery electrode reported in literature (Table S4). In contrast, the curves for the molecules with one or two oxygen atoms (a and b)show asignificant plateau around 0.5 V. Theslope-like discharge plateau for the molecules with four sulfur atoms can possibly be attributed to the low crystallinity after initial discharge.…”

“…Herein, for the first time,wereport afamily of sodiumion battery electrodes obtained by replacing stepwise the oxygen atoms with sulfur atoms in the carboxylate groups of sodium terephthalate whichi mproves electron delocalization, electrical conductivity and sodium uptake capacity.T he versatile strategy based on molecular engineering greatly enhances the specific capacity of organic electrodes with the same carbon scaffold. [21,22] In the case of alithium-ion anode,far more than two Li + ions can be stored in the carboxylate molecule under deep discharge, [23,24] which leads to the high capacity of organic lithium anodes.H owever,f or sodium-ion battery cells,there is no evidence of super-sodiation. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Generally,o rganic electrodes accommodate redox centers and alkali-metal ions by functional groups such as carboxylate, [16] carbonyl, [17] organodisulfide, [18] thioether [19] and nitroxyl radicals, [20] while the aromatic cores donate or accept electrons during the redox process.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Generally,o rganic electrodes accommodate redox centers and alkali-metal ions by functional groups such as carboxylate, [16] carbonyl, [17] organodisulfide, [18] thioether [19] and nitroxyl radicals, [20] while the aromatic cores donate or accept electrons during the redox process. [21,22] In the case of alithium-ion anode,far more than two Li + ions can be stored in the carboxylate molecule under deep discharge, [23,24] which leads to the high capacity of organic lithium anodes.H owever,f or sodium-ion battery cells,there is no evidence of super-sodiation. [21,22] In the case of alithium-ion anode,far more than two Li + ions can be stored in the carboxylate molecule under deep discharge, [23,24] which leads to the high capacity of organic lithium anodes.H owever,f or sodium-ion battery cells,there is no evidence of super-sodiation.…”

Organic Thiocarboxylate Electrodes for a Room‐Temperature Sodium‐Ion Battery Delivering an Ultrahigh Capacity

“…[19] Carboxylate groups are usually applied as lithium/sodium anodes which reversibly store/release Li + /Na + ions through at wo-electron process. [21,22] In the case of alithium-ion anode,far more than two Li + ions can be stored in the carboxylate molecule under deep discharge, [23,24] which leads to the high capacity of organic lithium anodes.H owever,f or sodium-ion battery cells,there is no evidence of super-sodiation. Thesodium ion is larger and less electronegative than the lithium ion.Even though the organic sodium-ion battery has al ower specific capacity than the lithium-ion battery,the sodium-ion battery is attractive because of the less rigid lattice compared with metal-oxide lattices,w hich can accommodate the large sodium ions so that the rate capability and cycle stability are advantageous.…”

Carbonyl‐Based π‐Conjugated Materials: From Synthesis to Applications in Lithium‐Ion Batteries

“…Investigating excess capacity in π-conjugated carboxylates, Lee et al studied also compounds 94 and 96. [58] In addition, to support the effect of the cyclic structure on the excess capacity the di-lithium thiophene-2,5-di-carboxylate (Li 2 TDC) 98, was considered as heterocyclic di-carboxylate. The synthesis of the two compounds 94 and 96 were achieved following the procedure reported by Armand et al [12e] For its part, Li 2 TDC 98 was prepared from thiophene-2,5-di-carboxylic acid 97 by deprotonation reaction with LiOH·H 2 O in water at 90°C for 5 h in 74 % yield (Scheme 21, reaction c).…”