Kim, Haegyeom — Page 3 | Engineering Papers

DOE OSTI2020

A High-Energy NASICON-Type Cathode Material for Na-Ion Batteries

Over the last decade, Na-ion batteries have been extensively studied as low-cost alternatives to Li-ion batteries for large-scale grid storage applications; however, the development of high-energy positive electrodes remains a major challenge. Materials with a polyanionic framework, such as Na superionic conductor (NASICON)-structured cathodes with formula Na x M 2 (PO 4 ) 3 , have attracted considerable attention because of their stable 3D crystal structure and high operating potential. Herein, a novel NASICON-type compound, Na 4 MnCr(PO 4 ) 3 , is reported as a promising cathode material for Na-ion batteries that deliver a high specific capacity of 130 mAh g –1 during discharge utilizing high-voltage Mn 2+/3+ (3.5 V), Mn 3+/4+ (4.0 V), and Cr 3+/4+ (4.35 V) transition metal redox. In addition, Na 4 MnCr(PO 4 ) 3 exhibits a high rate capability (97 mAh g –1 at 5 C) and excellent all-temperature performance. In situ X-ray diffraction and synchrotron X-ray diffraction analyses reveal reversible structural evolution for both charge and discharge.

25 ENERGY STORAGE↗

DOE OSTI2019

Correction to: Investigation of Alkali-Ion (Li, Na, and K) Intercalation in K x VPO 4 F( x ~ 0) Cathode

This work compares the intercalation of K, Na, and Li in K x VPO 4 F (x~0). The K x VPO 4 F (x~0) cathode delivers reversible capacities of ≈90-100 mAh g -1 in K, Na, and Li cells, at an average voltage of ≈4.33 V for K, ≈3.98 V for Na, and ≈3.96 V for Li. This is so far the highest average voltage known for a K-intercalation cathode. The lower voltage of Li insertion compared to Na is attributable to undercoordinated Li ions in the K x VPO 4 F (x~0) framework. While the material shows high rate capability for all the alkali ions, Li migration in K x VPO 4 F (x~0) is more difficult than with Na and K. Here, this work suggests that a large cavity is not always good for insertion of alkali ions and cathode materials need to be suitably tailored to each intercalating ion species.

25 ENERGY STORAGE↗

DOE OSTI2019

Investigation of Alkali-Ion (Li, Na, and K) Intercalation in K x VPO 4 F( x ~ 0) Cathode

This work compares the intercalation of K, Na, and Li in K x VPO 4 F (x~0). The K x VPO 4 F (x~0) cathode delivers reversible capacities of ≈90-100 mAh g -1 in K, Na, and Li cells, at an average voltage of ≈4.33 V for K, ≈3.98 V for Na, and ≈3.96 V for Li. This is so far the highest average voltage known for a K-intercalation cathode. The lower voltage of Li insertion compared to Na is attributable to undercoordinated Li ions in the K x VPO 4 F (x~0) framework. While the material shows high rate capability for all the alkali ions, Li migration in K x VPO 4 F (x~0) is more difficult than with Na and K. Here, this work suggests that a large cavity is not always good for insertion of alkali ions and cathode materials need to be suitably tailored to each intercalating ion species.

25 ENERGY STORAGE↗