| 1. |
- Fu, Chaochao, et al.
(författare)
-
Nickel-Rich Layered Microspheres Cathodes: Lithium/Nickel Disordering and Electrochemical Performance
- 2014
-
Ingår i: ACS Applied Materials & Interfaces. - 1944-8252 .- 1944-8244. ; 6:18, s. 15822-15831
-
Tidskriftsartikel (refereegranskat)abstract
- Nickel-rich layered metal oxide materials are prospective cathode materials for lithium ion batteries due to the relatively higher capacity and lower cost than LiCoO2. Nevertheless, the disordered arrangement of Li+/Ni2+ in local regions of these materials and its impact on electrochemistry performance are not well understood, especially for LiNi1–x–yCoxMnyO2 (1–x–y > 0.5) cathodes, which challenge one’s ability in finding more superior cathode materials for advanced lithium-ion batteries. In this work, Ni–Co–Mn-based spherical precursors were first obtained by a solvothermal method through handily utilizing the redox reaction of nitrate and ethanol. Subsequent sintering of the precursors with given amount of lithium source (Li-excess of 5, 10, and 15 mol %) yields LiNi0.7Co0.15Mn0.15O2 microspheres with different extents of Li+/Ni2+ disordering. With the determination of the amounts of Li+ ions in transition metal layer and Ni2+ ions in Li layer using structural refinement, the impact of Li+/Ni2+ ions disordering on the crystal structure, valence state of nickel ions, and electrochemical performance were investigated in detailed. It is clearly demonstrated that with increasing the amount of lithium source, lattice parameters (a and c) and interslab space thickness of unit cell decrease, and more Li+ ions incorporated into the 3a site of transition metal layer which leads to an increase of Ni3+ content in LiNi0.7Co0.15Mn0.15O2 as confirmed by X-ray photoelectron spectroscopy and a redox titration. Moreover, the electrochemical performance for as-prepared LiNi0.7Co0.15Mn0.15O2 microspheres exhibited a trend of deterioration due to the changes of crystal structure from Li+/Ni2+ mixing. The preparation method and the impacts of Li+/Ni2+ ions disordering reported herein for the nickel-rich layered LiNi0.7Co0.15Mn0.15O2 microspheres may provide hints for obtaining a broad class of nickel-rich layered metal oxide microspheres with superior electrochemical performance.
|
|
| 2. |
- Li, Qi, 1990, et al.
(författare)
-
K+-Doped Li1.2Mn0.54Co0.13Ni0.13O2: A Novel Cathode Material with an Enhanced Cycling Stability for Lithium-Ion Batteries
- 2014
-
Ingår i: ACS Applied Materials & Interfaces. - 1944-8252 .- 1944-8244. ; 6:13, s. 10330-10341
-
Tidskriftsartikel (refereegranskat)abstract
- Li-rich layered oxides have attracted much attention for their potential application as cathode materials in lithium ion batteries, but still suffer from inferior cycling stability and fast voltage decay during cycling. How to eliminate the detrimental spinel growth is highly challenging in this regard. Herein, in situ K+-doped Li1.20Mn0.54Co0.13Ni0.13O2 was successfully prepared using a potassium containing α-MnO2 as the starting material. A systematic investigation demonstrates for the first time, that the in situ potassium doping stabilizes the host layered structure by prohibiting the formation of spinel structure during cycling. This is likely due to the fact that potassium ions in the lithium layer could weaken the formation of trivacancies in lithium layer and Mn migration to form spinel structure, and that the large ionic radius of potassium could possibly aggravate steric hindrance for spinel growth. Consequently, the obtained oxides exhibited a superior cycling stability with 85% of initial capacity (315 mA h g–1) even after 110 cycles. The results reported in this work are fundamentally important, which could provide a vital hint for inhibiting the undesired layered-spinel intergrowth with alkali ion doping and might be extended to other classes of layered oxides for excellent cycling performance.
|
|
| 3. |
- Luo, Dong, et al.
(författare)
-
A New Spinel-Layered Li-Rich Microsphere as a High-Rate Cathode Material for Li-Ion Batteries
- 2014
-
Ingår i: Advanced Energy Materials. - 1614-6840 .- 1614-6832. ; 4:11
-
Tidskriftsartikel (refereegranskat)abstract
- Li-rich layered materials are considered to be the promising low-cost cathodes for lithium-ion batteries but they suffer from poor rate capability despite of efforts toward surface coating or foreign dopings. Here, spinel-layered Li-rich Li-Mn-Co-O microspheres are reported as a new high-rate cathode material for Li-ion batteries. The synthetic procedure is relatively simple, involving the formation of uniform carbonate precursor under solvothermal conditions and its subsequent transformation to an assembled microsphere that integrates a spinel-like component with a layered component by a heat treatment. When calcined at 700 °C, the amount of transition metal Mn and Co in the Li-Mn-Co-O microspheres maintained is similar to at 800 °C, while the structures of constituent particles partially transform from 2D to 3D channels. As a consequence, when tested as a cathode for lithium-ion batteries, the spinel-layered Li-rich Li-Mn-Co-O microspheres obtained at 700 °C show a maximum discharge capacity of 185.1 mA h g−1 at a very high current density of 1200 mA g−1 between 2.0 and 4.6 V. Such a capacity is among the highest reported to date at high charge-discharge rates. Therefore, the present spinel-layered Li-rich Li-Mn-Co-O microspheres represent an attractive alternative to high-rate electrode materials for lithium-ion batteries.
|
|
