Spinel-Layered Intergrowth Composite Cathodes for Sodium-Ion Batteries

Abstract

The vital challenge of a layered manganese oxide cathode for sodium-ion batteries is its severe capacity degradation and sluggish ion diffusion kinetics caused by irreversible phase transitions. In response to this problem, the spinel-layered manganese-based composite with an intergrowth structure is ingeniously designed by virtue of an interesting spinel-to-layered transformation in the delithiated LiMn 2 O 4 under Na + insertion. This unique spinel-layered intergrowth structure is strongly confirmed by combining multiple structure analysis techniques. The layered component can provide more reversible capacity, while the spinel component is crucial for the stabilized crystal structure and accelerated ion diffusion kinetics. As an appealing cathode for sodium-ion batteries, the layered-spinel composite delivers a high reversible capacity of 180.9 mAh g −1 , excellent cycling stability, and superior rate capability with 55.7 mAh g −1 at 12 C. Furthermore, the reaction mechanism upon Na + extraction/ insertion is revealed in detail by ex situ X-ray diffraction and X-ray photoelectron spectroscopy, indicating that Na + ions can be accommodated by the layered structure at a low voltage and by the spinel at a high voltage. This study will provide a new idea for the rational design of an advanced cathode for sodium-ion batteries.

Tracking Electrochemical-Cycle-Induced Surface Structure Evolutions of Cathode Material LiMn2O4 with Improved Operando Raman Spectroscopy

“…The spectra are normalized for better comparison. For pristine LiMn 2 O 4 , the percentage of Mn 4+ (49.5%) is almost identical to that of Mn 3+ (50.5%), which is consistent with previous studies . When the sample is charged to 1 V vs Ag/AgCl, the Mn 4+ content (68.4%) is dominant on the surface, while there is still 31.6% Mn 3+ present.…”

“…For pristine LiMn 2 O 4 , the percentage of Mn 4+ (49.5%) is almost identical to that of Mn 3+ (50.5%), which is consistent with previous studies. 51 When the sample is charged to 1 V vs Ag/AgCl, the Mn 4+ content (68.4%) is dominant on the surface, while there is still 31.6% Mn 3+ present. Considering that the Li content is ∼0.1 per formula unit in the charged state, the corresponding Mn 4+ and Mn 3+ contents are 95 and 5% on average, respectively.…”

Electrochemically induced catalytic adsorption sites in spent lithium-ion battery cathodes for high-rate vanadium redox flow batteries

“…The formation of mixed-valent transition metals in a higher oxidation state was attributed to charge compensation arising from Li-ion extraction during LiET. 45 Fig. 3d–f illustrate the O 1s core level representing the four states of oxygen, denoted as O 1 , O 2 , O 3 , and O 4 .…”

“…The formation of mixed-valent transition metals in a higher oxidation state was attributed to charge compensation arising from Li-ion extraction during LiET. 45 56,57 Oxygen vacancies were estimated from the ratio of the relative area (O 2 /O 1 ), 46,53,55,58 and this ratio is plotted in Fig. 3d-f.…”

Layered Oxide Cathode‐Electrolyte Interface towards Na‐Ion Batteries: Advances and Perspectives

“…Xia et al prepared spinel-layered composite NaMnO 2 cathode for NIBs through an electrochemical Li + /Na + exchange. [146] Insertion of Na into the de-lithiated spinel phase expands the diffusion layer and drive Mn from octahedral 16d to 16c to form an layered structure. Meanwhile, a few amount of spinel NaMn 2 O 4 was preserved to form a composition with the layered phase.…”