title: Aluminum manganese oxides with mixed crystal structure: high-energy-density cathodes for rechargeable sodium batteries.
abstract: We report a new discovery for enhancing the energy density of manganese oxide (Nax MnO2 ) cathode materials for sodium rechargeable batteries by incorporation of aluminum. The Al incorporation results in NaAl(0.1) Mn(0.9) O2 with a mixture of tunnel and layered crystal structures. NaAl(0.1) Mn(0.9) O2 shows a much higher initial discharge capacity and superior cycling performance compared to pristine Na(0.65) MnO2 . We ascribe this enhancement in performance to the formation of a new orthorhombic layered NaMnO2 phase merged with a small amount of tunnel Na(0.44) MnO2 phase in NaAl(0.1) Mn(0.9) O2 , and to improvements in the surface stability of the NaAl(0.1) Mn(0.9) O2 particles caused by the formation of Al-O bonds on their surfaces. Our findings regarding the phase transformation and structure stabilization induced by incorporation of aluminum, closely related to the structural analogy between orthorhombic Na(0.44) MnO2 and NaAl(0.1) Mn(0.9) O2 , suggest a strategy for achieving sodium rechargeable batteries with high energy density and stability.
authors.affiliation: Energy Storage Group, Samsung Advanced Institute of Technology (SAIT), Samsung Electronics Co., Ltd. Yongin 446-712 (Korea). dongwook.han@samsung.com.
authors.forename: Dong-Wook
authors.initials: DW
authors.lastname: Han
authors.forename: Jun-Hwan
authors.initials: JH
authors.lastname: Ku
authors.forename: Ryoung-Hee
authors.initials: RH
authors.lastname: Kim
authors.forename: Dong-Jin
authors.initials: DJ
authors.lastname: Yun
authors.forename: Seok-Soo
authors.initials: SS
authors.lastname: Lee
authors.forename: Seok-Gwang
authors.initials: SG
authors.lastname: Doo
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D018360:Crystallography, X-Ray; D011211:Electric Power Supplies; D004563:Electrochemistry; D004566:Electrodes; D017895:Manganese Compounds / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry*
chemical_list: D017895:Manganese Compounds; D010087:Oxides; C027424:manganese oxide; D012964:Sodium; D000535:Aluminum
keywords: aluminum; batteries; doping; layered compounds; sodium