The significance of the Li2MnO3 component in ‘composite’ xLi2MnO3 · (1 − x)LiMn0.5Ni0.5O2 electrodes

Abstract The electrochemical behavior of 0.3Li 2 MnO 3  · 0.7LiMn 0.5 Ni 0.5 O 2 ‘composite’ electrodes, when charged to potentials ⩾4.5 V in lithium cells, has been compared with the behavior of electrodes that were preconditioned by acid treatment. When charged to 5 V, all the lithium can be extracted from 0.3Li 2 MnO 3  · 0.7LiMn 0.5 Ni 0.5 O 2 in two distinct steps to yield a Mn 0.65 Ni 0.35 O 2 product, the first step corresponding predominantly to lithium extraction from the electrode structure with the concomitant oxidation of Ni 2+ to Ni 4+ , and the second to the electrochemical removal of Li 2 O from the structure. The electrode delivers a rechargeable capacity >250 mAh/g when cycled between 5.0 and 2.0 V vs. Li 0 ; the high capacity and cycling stability are attributed to the high manganese (IV) content in the electrode over this voltage range. Acid-treatment significantly reduces the coulombic inefficiency of the initial charge/discharge cycle of the cells. The electrochemical behavior of 0.3Li 2 MnO 3  · 0.7LiMn 0.5 Ni 0.5 O 2 is compared with that of standard Li 2 MnO 3 electrodes. The advantage of using the two-component notation x Li 2 MnO 3  · (1 −  x )LiMn 0.5 Ni 0.5 O 2 instead of the equivalent layered notation Li[Li x /(2 +  x ) Mn (1 +  x )/(2 +  x ) Ni (1− x )/(2 +  x ) ]O 2 to monitor the compositional changes that occur in the electrode during electrochemical charge and discharge is highlighted.

[1]  Christopher S. Johnson,et al.  Lithium and Deuterium NMR Studies of Acid-Leached Layered Lithium Manganese Oxides , 2002 .

[2]  S. Yamanaka,et al.  Preparation and electrochemical properties of layered lithium–cobalt–manganese oxides , 1999 .

[3]  M. Thackeray,et al.  Lithium manganese oxides from Li2MnO3 for rechargeable lithium battery applications , 1991 .

[4]  John T. Vaughey,et al.  Structural Characterization of Layered LixNi0.5Mn0.5O2 (0 < x ≤ 2) Oxide Electrodes for Li Batteries , 2003 .

[5]  S. Gopukumar,et al.  Lithium metal rechargeable cells using Li2MnO3 as the positive electrode , 1999 .

[6]  K. Amine,et al.  Synthesis and electrochemical properties of Li[Li(1−2x)/3NixMn(2−x)/3]O2 as cathode materials for lithium secondary batteries , 2002 .

[7]  C. Delmas,et al.  Optimization of the Composition of the Li1 − z Ni1 + z O 2 Electrode Materials: Structural, Magnetic, and Electrochemical Studies , 1996 .

[8]  Peter G. Bruce,et al.  Synthesis of layered LiMnO2 as an electrode for rechargeable lithium batteries , 1996, Nature.

[9]  Christopher S. Johnson,et al.  Electrochemical and Structural Properties of xLi2M‘O3·(1−x)LiMn0.5Ni0.5O2 Electrodes for Lithium Batteries (M‘ = Ti, Mn, Zr; 0 ≤ x ⩽ 0.3) , 2004 .

[10]  C. Delmas,et al.  A new variety of LiMnO2 with a layered structure , 1996 .

[11]  Jeff Dahn,et al.  Structure and electrochemistry of Li1±yNiO2 and a new Li2NiO2 phase with the Ni (OH)2 structure , 1990 .

[12]  Michael M. Thackeray,et al.  Improved capacity retention in rechargeable 4 V lithium/lithium- manganese oxide (spinel) cells , 1994 .

[13]  H. Kanoh,et al.  Preparation of plate-form manganese oxide by selective lithium extraction from monoclinic Li2MnO3 under hydrothermal conditions , 2000 .

[14]  P. Bruce,et al.  New intercalation compounds for lithium batteries: layered LiMnO2 , 1999 .