A New Spinel‐Layered Li‐Rich Microsphere as a High‐Rate Cathode Material for Li‐Ion Batteries

Abstract

rate capability. [ 12,13 ] In contrast, spinel cathodes exhibit a high-rate capability due to the effi cient 3D diffusion of lithium ions, nevertheless the discharge capacity is low, only about 130 mA h g −1 . [ 14,15 ] Then, a highly interesting, but also challenging question appears: can the rate capability be much improved by introducing spinel component into the layered oxides? Previous investigations have shown that the cubic close-packed oxygen arrays in both the layered and spinel oxides are structurally compatible. [ 16 ] Therefore, it is possible to integrate the Li-rich layered and spinel oxides into a composite, which might show both a high capacity and an excellent rate capability.Much effort has been devoted to the preparation of composites that intergrate both layered Li-rich oxides and spinel oxides (i.e., spinel-layered materials), which have led to several high-energy and power electrodes, [17][18][19][20] such as the outstanding cathode materials of spinel/ layered heterostructure, [ 17 ] [ 18 ] Unfortunately, most synthetic methods still suffer from several shortcomings. For instance, it is diffi cult to obtain a homogeneous mixture of layered and spinel oxides. The preparation procedures are always tedious, which may introduce uncertain factors in reproducing the electrochemical performance. On the other hand, metal-ion impurities, such as K + , were inevitably introduced into the fi nal products. In particular, the synthetic methods ever reported cannot allow the control over the morphology to give microspheres of spinellayered materials, due to the multiple transition metal ions and phases involved. As a consequence, spherical spinel-layered cathode materials are highly necessary, which expect to impose a signifi cant impact on electrochemical performance (especially for rate capability) of Li-ions batteries.Here, we report on the preparation of a spinel-layered Lirich Li-Mn-Co-O microsphere using a solvothermal-precursor method. This method is an extension of ther oxalate-precursor method, [ 21 ] which has been successfully applied to prepare Lirich layered composite cathodes. This new method has the advantages of the oxalate-precursor method where lithium ions and transition metal ions are precipitated simultaneously in the absence of alkali metal ions to form uniform precursors, and provides the possibility for regulation of spherical morphology and dimension. Based on previous results, [ 16,22 ] we 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...

Controllable oxygenic functional groups of metal-free cathodes for high performance lithium ion batteries

“…3 problems such as dissolution of transition metals occur at the electrode-electrolyte interface after long-term cycling, resulting in uncontrolled voltage changes and limited cycling stability 13,14 . As a result, the research on lithium-ion batteries has been directed mainly towards the design of high capacity, good cycling stability and low cost cathode materials, which emerges a surging demand to develop environmentally friendly green cathode materials to replace the current several non-renewable and not environment-friendly cathodes.…”

Comparative Investigation of 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 Cathode Materials Synthesized by Using Different Lithium Sources

“…Sample A composed of 200–300 nm primary particles and the distance of the lattice fringes of particles is calculated to be 0.204 nm, matching well with the d (104) planes, which attributed to layer structure R-3m (Yang et al, 2016). Figures 3C,D show that sample B composed of 300–400 nm primary particles and the lattice spacing are 0.273 and 0.368 nm, corresponding to the planes d (111) and d (−111) of Li 2 MnO 3 phase (C2/m) (Luo et al, 2014). As illustrated in Figures 3E,F, Sample C has severe aggregation although it possesses small primary particles from some regions owing to the destruction of released gas.…”

Microstructurally Composed Nanoparticle Assemblies as Electroactive Materials for Lithium-Ion Battery Electrodes

“…Lithium rich layered oxides are promising cathode materials on account of their, typically, much higher capacity (>250 mAh g −1 ) and potential for reduced cost [81]. Despite these advantages, they suffer from intrinsic poor rate capability and cycle stability, primarily because lithium extraction is accompanied with Li 2 O oxidation in the initial charge followed by substantial transition metal ion migration into the lithium sites [82]. This oxidation and subsequent irreversible migration event is stabilized by surface structural rearrangement that effectively impedes Li-ion transport [83].…”