An Ion‐Exchange Promoted Phase Transition in a Li‐Excess Layered Cathode Material for High‐Performance Lithium Ion Batteries

Abstract

batteries crucially relies on electrochemical characteristics of electrode materials, i.e., anode and cathode materials. [ 1 ] Various alternative anode materials have recently been developed, including silicon-based composites, [ 2,3 ] nanoscale transition metal oxides, [ 4,5 ] titanium-based materials, [ 6,7 ] and graphene-based sulfi de, [ 8 ] etc. These materials have demonstrated excellent rate capability and specifi c capacities several times higher than conventional graphite anodes. Since capacities of cathode materials are usually much lower than those of anodes, the cathode is considered as the limiting factor for lithium ion batteries. To a great extent, development of newgeneration lithium ion batteries is limited by the low energy density, low operating voltage, and poor rate capability of cathode materials. [ 9 ] Recently, the emerging Li-excess layered oxides have attracted a great deal of research efforts due to their high capacities. These cathode materials can be cycled over a broad voltage range between 2.0 and 4.8 V versus Li/Li + and deliver specifi c capacities higher than 250 mAh g −1 . They also offer many other advantages such as low cost, environmental benignity, and safety. [ 10 ] A representative example is Li-excess ternary manganese-nickel-cobalt oxide, composed

Gas–solid interfacial modification of oxygen activity in layered oxide cathodes for lithium-ion batteries

“…The influence of the surface oxygen vacancies on the oxygen gas generation is discussed in detail in Supplementary Note 1. The creation of surface oxygen vacancies was previously attempted utilizing a reducing atmosphere2728 and leaching with acid accompanied by heat treatment2930. However, the bulk structure reported in previous work easily transforms from a pure layered phase to spinel- and/or rock-salt phases282930313233, which diminishes the rate capability and cycling stability.…”

Heat‐Treatment‐Assisted Molten‐Salt Strategy to Enhance Electrochemical Performances of Li‐Rich Assembled Microspheres by Tailoring Their Surface Features

“…In addition, ab road peak at 64.58 can be distinguished for LMROa nd MS-LMRO samples after 50 cycles, which shows the formation of some spinel variants. [46] The presence of spinel variants in the electrochemical cycle could result in serious capacity decay.…”

Layered Li1.3Mn0.58Ni0.12Co0.11O2+δ Cathode Material for Lithium‐Ion Batteries with High Reversible Capacity

“…A high capacity of 309.7 mAh g −1 is measured at the second potential plateau, which is significantly higher in comparison with the value reported in literature, indicating that much more lithium has been extracted and more oxygen vacancies have been created simultaneously. In the discharge process, an obvious potential plateau around 2.5 V is attributed to the electrochemical reduction of oxygen, which is different from the Mn 4+ →Mn 3+ plateau of the spinel phase evidenced by the Raman spectra . The d Q /d V curves provide direct evidence of the oxygen reduction peaks at approximately 2.5 V. In addition, it is worth noting that the discharge plateau attributed to oxygen reduction could be still observed at 0.2, 0.5, and 1 C (Figure S4).…”

“…Mn 3 + plateau of the spinel phase evidenced by the Raman spectra. [15,25] The dQ/dV curvesp rovide direct evidenceo ft he oxygen reduction peaks at approximately 2.5 V. In addition, it is worth noting that the discharge plateaua ttributed to oxygen reduction could be still observed at 0.2, 0.5, and 1C ( Figure S4). More interestingly,a ll of these oxygen plateaus between 2.4 and 2.8 Vc orrespond to ac apacity of more than 20.0 mAh g À1 .I ti sk nown that, for conventional Li-rich layered materials, such ad ischarge plateau can be observed only at very low rates below 0.05 C. [8,24] Therefore, the significant improvement in capacity could be ascribed to the enrichment of oxygen in the layered Li 1.3 Mn 0.58 Ni 0.12 Co 0.11 O 2 + d material.…”