Degradation and Structural Evolution ofxLi₂MnO₃·(1–x)LiMn_1/3Ni_1/3Co_1/3O₂during Cycling

Abstract

In the present work, the electrochemical degradation and structural evolution of xLi 2 MnO 3 • (1-x)LiMn 1/3 Ni 1/3 Co 1/3 O 2 (x = 0.3, 0.5, and 0.7) materials and the role of Li 2 MnO 3 component during electrochemical cycling are systematically studied through careful analysis of electrochemical data, ex-situ XRD, and HR-TEM observations. The materials consisting of higher Li 2 MnO 3 content show better cyclic performance with more significant voltage decay compared to that of xLi 2 MnO 3 • (1-x)LiMn 1/3 Ni 1/3 Co 1/3 O 2 electrodes with low Li 2 MnO 3 content. The electrochemical degradation of xLi 2 MnO 3 • (1-x)LiMn 1/3 Ni 1/3 Co 1/3 O 2 electrodes upon cycling not only results from the remarkably increase in impedance caused by the damage of the electrode surface, in particular for low Li 2 MnO 3 content; but also arises from structural rearrangement, especially for high Li 2 MnO 3 content. Upon cycling, high Li 2 MnO 3 content in the crystal structure of lithium-rich transition metal oxides can stabilize the electrode\electrolyte interface at high potentials, facilitates the rapid formation of cracks and porosity in the cycled electrodes, and promotes the distortions and breakdown of the original well-layered lattice.

High-performance lithium-rich layered oxide materials: Effects of chelating agents on microstructure and electrochemical properties

“…[36][37][38][39], the evolution of a redox reaction in 3.0V region (Fig 6d) represents the layer-to-spinel transition. The reduction peaks of the GLLMO electrodes continuously shift to a lower voltage of 2.8 V after 100th cycle, suggesting the increasing formation of the spinel phase within the electrode structure.…”

“…All the profiles show the characteristics of the lithium-rich layered oxide, comprising a sloping curve below 4.5 V and a long plateau around 4.5 V in the first charge process and continuous sloping curve in the discharge process[33][34][35][36][37]. During the initial charge, the sloping curve below 4.5 V corresponds to lithium extraction from LiNi 0.5 Co 0.2 Mn 0.3 O 2 component, while the plateau around 4.5 V relates to the removal of lthium from the crystal structure accompanied by oxygen evolution [6,9-11, 22, 23].…”

Solution combustion synthesis and enhanced electrochemical performance Li1.2Ni0.2Mn0.6O2 nanoparticles by controlling NO3–/CH3COO– ratio of the precursors

“…Therefore, lithium-rich layered oxides based on xLi 2 MnO 3 Á(1-x) LiMO 2 (M = Co, Ni, Mn, etc. ), are undoubtedly becoming appealing as cathode materials for high-energy LIBs due to their high capacity (>200 mA h g À1 ) [11][12][13][14][15].…”

“…Despite the outstanding advantages of lithium-rich layered oxides, these materials are plagued with problems like large initial irreversible capacity [11][12][13] and capacity decay during chargedischarge cycles [11,16]. In addition, the achievement of high-rate capability is hindered by the kinetic barriers such as intrinsic poor electronic conductivity and low lithium-ion diffusion because the flow of electrons and diffusion of lithium-ions in the lithium-rich layered oxides are blocked by the occupancy of the excess lithiumions in the transition metal layer [13][14][15][16][17].…”

“…In addition, the achievement of high-rate capability is hindered by the kinetic barriers such as intrinsic poor electronic conductivity and low lithium-ion diffusion because the flow of electrons and diffusion of lithium-ions in the lithium-rich layered oxides are blocked by the occupancy of the excess lithiumions in the transition metal layer [13][14][15][16][17]. Some efforts have been tried to solve these problems.…”