TY - JOUR
T1 - Stabilized Octahedral Frameworks in Layered Double Hydroxides by Solid-Solution Mixing of Transition Metals
AU - Lee, Ji Hoon
AU - Lee, Hyeon Jeong
AU - Lim, Soo Yeon
AU - Chae, Keun Hwa
AU - Park, Sung Hyeon
AU - Chung, Kyung Yoon
AU - Deniz, Erhan
AU - Choi, Jang Wook
N1 - Publisher Copyright:
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2017/2/17
Y1 - 2017/2/17
N2 - Pseudocapacitors have received considerable attention, as they possess advantages of both rechargeable batteries and electric double layer capacitors. Among various active materials for pseudocapacitors, α-layered double hydroxides (α-TM(OH)2, TM = transition metal) are promising due to their high specific capacities. Yet, irreversible α-to-β phase transitions of α-TM(OH)2 hinder their long-term cyclability, particularly when the TM is nickel. Here, it is reported that binary TM ion mixing can overcome the limited cycle lives of α-TM(OH)2 by stabilizing the octahedral frameworks of α-TM(OH)2. In particular, an α-TM(OH)2 with equal amounts of nickel and cobalt exhibits long-term capacity retention (89.0% after 2000 cycles) and specific capacity (206 mA h g−1), which are better than those of individual TM counterparts. A series of analyses reveals that the improved performances originate from the synergistic effects between the TM ions; the preferred trivalent state of cobalt ions stabilizes the octahedral framework by accommodating the detrimental Jahn–Teller distortion of Ni3+. The stabilized framework also widens the redox swing range of the nickel up to 4+, thus, increasing the specific capacity of the corresponding α-TM(OH)2. This study indicates that proper mixing of TMs is a prolific approach in enhancing the vital properties of α-TM(OH)2, a promising family of pseudocapacitor materials.
AB - Pseudocapacitors have received considerable attention, as they possess advantages of both rechargeable batteries and electric double layer capacitors. Among various active materials for pseudocapacitors, α-layered double hydroxides (α-TM(OH)2, TM = transition metal) are promising due to their high specific capacities. Yet, irreversible α-to-β phase transitions of α-TM(OH)2 hinder their long-term cyclability, particularly when the TM is nickel. Here, it is reported that binary TM ion mixing can overcome the limited cycle lives of α-TM(OH)2 by stabilizing the octahedral frameworks of α-TM(OH)2. In particular, an α-TM(OH)2 with equal amounts of nickel and cobalt exhibits long-term capacity retention (89.0% after 2000 cycles) and specific capacity (206 mA h g−1), which are better than those of individual TM counterparts. A series of analyses reveals that the improved performances originate from the synergistic effects between the TM ions; the preferred trivalent state of cobalt ions stabilizes the octahedral framework by accommodating the detrimental Jahn–Teller distortion of Ni3+. The stabilized framework also widens the redox swing range of the nickel up to 4+, thus, increasing the specific capacity of the corresponding α-TM(OH)2. This study indicates that proper mixing of TMs is a prolific approach in enhancing the vital properties of α-TM(OH)2, a promising family of pseudocapacitor materials.
KW - Jahn–Teller effects
KW - crystal field theory
KW - layered double hydroxides
KW - octahedral coordination
KW - solid-solution mixing
UR - http://www.scopus.com/inward/record.url?scp=85007481133&partnerID=8YFLogxK
U2 - 10.1002/adfm.201605225
DO - 10.1002/adfm.201605225
M3 - Article
AN - SCOPUS:85007481133
SN - 1616-301X
VL - 27
JO - Advanced Functional Materials
JF - Advanced Functional Materials
IS - 7
M1 - 1605225
ER -