High‐Performant All‐Organic Aqueous Sodium‐Ion Batteries Enabled by PTCDA Electrodes and a Hybrid Na/Mg Electrolyte

Abstract

Aqueous sodium-ion batteries (ASIBs) are aspiring candidates for low environmental impact energy storage, especially when using organic electrodes.I nt his respect, perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) is apromising anode active material, but it suffers from extensive dissolution in conventional aqueous electrolytes.Asaremedy, we here present anovel aqueous electrolyte,whichinhibits the PTCDAdissolution and enables their use as all-organic ASIB anodes with high capacity retention and Coulombic efficiencies.F urthermore,t he electrolyte is based on two,h ence "hybrid", inexpensive and non-fluorinated Na/Mg-salts,i t displays favourable physico-chemical properties and an electrochemical stability window > 3V without resorting to the extreme salt concentrations of water-in-salt electrolytes.A ltogether,t his paves the wayf or ASIBs with both relatively high energy densities,i nexpensive total cell chemistries,l ong-term sustainability,a nd improved safety.

Sustainability and Technical Performance of An All‐Organic Aqueous Sodium‐Ion Hybrid Supercapacitor

“…92 mAh g À 1 , which is ca. 30 % more than in our previous study [55] and this is attributed to the here lower (ca. 1/3) electrode mass loading.…”

“…Sodium sulfate (Na 2 SO 4 ) (� 99 % anhydrous) and magnesium sulfate (MgSO 4 ) (� 99.5 % anhydrous), both purchased from Sigma-Aldrich, were used to create a "hybrid electrolyte" (1.9 m Na 2 SO 4 + 2.4 m MgSO 4 ), as introduced in our previous study. [55] This was done by first dissolving Na 2 SO 4 to saturation in ultra-pure water (Millipore® Direct-Q® Purification, 18.2 MΩ cm at 25 °C), before adding MgSO 4 , all made in magnet stirred vials.…”

“…The PTCDA (Sigma-Aldrich) based electrodes employed herein were similar to those used in Ref. [55] but had a lower loading. They were made by first preparing a solution of 3 wt % cmC (Sigma-Aldrich) in ultra-pure water until complete dissolution by stirring.…”

“…[19] All of the above as well as the either glass fibre or polyolefin based (oil-derived) separators needed to complete the cell are laden with large environmental footprints, not the least green-house gas emissions. [20] Therefore, a truly sustainable ESD should rather be assembled from inexpensive and very simple inorganic salts, [21,22] combined with for example cellulose-based binders and separators, [23,24] and carbon-based CCs. [25][26][27] Furthermore, the active materials should not require complicated synthesis protocols, one of the most critical factors for cost and energy use.…”

“…Therefore, a truly sustainable ESD should rather be assembled from inexpensive and very simple inorganic salts, [21,22] combined with for example cellulose‐based binders and separators, [23,24] and carbon‐based CCs [25–27] . Furthermore, the active materials should not require complicated synthesis protocols, one of the most critical factors for cost and energy use.…”