Suppressed capacity/voltage fading of high-capacity lithium-rich layered materials via the design of heterogeneous distribution in the composition

Abstract

Lithium-rich layered materials, Li 1+x M 1Àx O 2 (M ¼ Mn, Ni, Co), have been under intense investigation as highperformance cathode materials for lithium ion batteries due to their high discharge capacity, low cost and environmental benignity. Unfortunately, the practical uses of these oxides have so far been hindered by their severe capacity and voltage fading during high voltage cycling (>4.5 V vs. Li/Li + ). In an attempt to overcome these problems, herein, a novel lithium-rich Li 1.14 [Mn 0.60 Ni 0.25 Co 0.15 ] 0.86 O 2 microsphere with heterogeneous distribution in the composition has been reasonably designed and successfully synthesized via a co-precipitation method. The chemical composition in the spherical particle is gradually altered by increasing the Mn concentration while reducing the Co content from the particle center to the outer layer. At the same time, the Ni content remains almost constant throughout the particle. The coin cell with the heterogeneous cathode material delivers a high discharge capacity of over 230 mA h g À1 between 2.0 V and 4.6 V, and shows excellent cyclic stability due to the continuous increase of the stable tetravalent Mn towards the outer surface of the spherical particles, corresponding to 93.8% capacity retention after 200 cycles at 0.5 C. More importantly, the as-prepared material exhibits a significantly lower discharge voltage decay compared with conventional materials, which may mainly be ascribed to the suppression of the layered-to-spinel transformation in the Co-rich/Mn-depleted regions of the spherical particle. The capacity and voltage fading of the lithium-rich layered material are simultaneously suppressed by the special architecturual design, and the results here will shed light on developing cathode materials with special structures and superior electrochemical properties for highperformance lithium ion batteries. Fig. 9 (a) The cycle performance of the Li/HL and Li/CL cells between 2.0 and 4.6 V at a rate of 5 C; the continuous charge/discharge curves of the (b) HL and (c) CL electrodes.This journal is

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

“…10 nm from the surface. As reported by Cho et al, the formation of spinel-like phase is the evidence of structural evolution during cycling [37], and these spinel-like phases are responsible for the poor electrochemcial performance of GLLMO sample. For CLLMO sample, the structural transformation from layered phase to spinel-like is mainly detected on particle surface (Fig.…”

“…[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.…”

“…9g and 9h). The formation of etching area is attributed to oxygen vacancies, which are appeared due to the extensive removal of lattice oxygen at high voltage [37][38][39]. These oxygen vacancies cannot be well maintained upon cycling, leading to densification/shrinkage of the structural lattice.…”

Aluminum and Gallium Substitution into 0.5Li2MnO3·0.5Li(Ni0.375Mn0.375Co0.25)O2Layered Composite and the Voltage Fade Effect

“…[8][9][10] However, this practice requires meticulous attention to avoid misinterpretation of data, especially when the baseline electrode is not optimized, because a depression in the discharge voltage profile can be not only due to voltage fade (thermodynamic parameter) but also a rise in electrode impedance (kinetic parameter). The impedance of LMR-NMC electrodes increases rapidly with cycle number, and the rise becomes more significant compared to that originating from voltage fade at high cycle number.…”

Design and Preparation of a Lithium‐rich Layered Oxide Cathode with a Mg‐Concentration‐Gradient Shell for Improved Rate Capability

“…Our group has also reported as eries of lithium-rich layered oxide materials with core-shell and core-gradient-shells tructures to meet the requirements of ah igh power density and excellent cycling performance. [29][30][31][32] These novel core-shell structures are often employed to integrate two different functions into one entity,f or example, the core can afford high energy density,a nd the shell can provide high structurals tability. [25] The core-shell lithium-rich layered oxide cathode material (CSLM) Li 1.5 …”