A monoclinic polymorph of sodium birnessite for ultrafast and ultrastable sodium ion storage

Abstract

Sodium transition metal oxides with layered structures are attractive cathode materials for sodium-ion batteries due to their large theoretical specific capacities. However, these layered oxides suffer from poor cyclability and low rate performance because of structural instability and sluggish electrode kinetics. In the present work, we show the sodiation reaction of Mn3O4 to yield crystal water free NaMnO2−y−δ(OH)2y, a monoclinic polymorph of sodium birnessite bearing Na/Mn(OH)8 hexahedra and Na/MnO6 octahedra. With the new polymorph, NaMnO2−y−δ(OH)2y exhibits an enlarged interlayer distance of about 7 Å, which is in favor of fast sodium ion migration and good structural stability. In combination of the favorable nanosheet morphology, NaMn2−y−δ(OH)2y cathode delivers large specific capacity up to 211.9 mAh g–1, excellent cycle performance (94.6% capacity retention after 1000 cycles), and outstanding rate capability (156.0 mAh g–1 at 50 C). This study demonstrates an effective approach in tailoring the structural and electrochemical properties of birnessite towards superior cathode performance in sodium-ion batteries.

Layered Birnessite Cathode with a Displacement/Intercalation Mechanism for High-Performance Aqueous Zinc-Ion Batteries

“…Besides, the tremendous electrostatic interaction between zinc ions and host materials usually leads to sluggish diffusion of zinc ions, limiting the development of ZIBs [19]. Fortunately, alkali metal ions of Na + , K + , and Li + , and crystal water could serve as pillars to stabilize the layered structure and improve the interlayer distance and, hence, benefit the diffusion of guest ions in electrode materials [34][35][36][37][38][39]. For example, Mai et al [40] demonstrated a Na 0.33 V 2 O 5 cathode, in which the sodium ions stabilized the layered structure and improved the electronic conductivity for high-performance ZIBs.…”

Uniform Na+ Doping‐Induced Defects in Li‐ and Mn‐Rich Cathodes for High‐Performance Lithium‐Ion Batteries

“…And it is clearly witnessed that the Na + ions are deep-doped into inner lattices (marked by the white arrows in Figure 2b) not forming a coating layer on the surface. [42] The two types stacking faults that insertion layer like sequence CAB A CAB and the deletion layer like sequence ABC AB ABC are vividly shown in Figure 3d and Figure 3e, respectively; [43] furthermore, the pictures in the upper left corner of Figure 2g are the HRTEM images of micro-sized secondary particles for Na-LMR. [42] The two types stacking faults that insertion layer like sequence CAB A CAB and the deletion layer like sequence ABC AB ABC are vividly shown in Figure 3d and Figure 3e, respectively; [43] furthermore, the pictures in the upper left corner of Figure 2g are the HRTEM images of micro-sized secondary particles for Na-LMR.…”

Recent Advances on Boosting the Cell Voltage of Aqueous Supercapacitors

“…Taking manganese oxide (MnO 2 ) as a typical case, due to its charming properties of high specific capacitance, luxuriant reserves, environmental friendliness, low OER activity, and well-established fabrication methods, MnO 2 is regarded as an ideal pseudocapacitive electrode for aqueous SCs [37,38]. When alkali cations are inserted into MnO 2 framework, they can stabilize the polymorph structure, enhance cyclic stability, offer extra capacitance, and facilitate the ion diffusion process [39][40][41][42]. More importantly, alkali cations can also efficiently inhibit the electrocatalytic activity of MnO 2 electrode in aqueous electrolyte because of the competitive relationship between alkali cations intercalation process and OER [31,43].…”