Synthesis and Characterization of High‐Energy, High‐Power Spinel‐Layered Composite Cathode Materials for Lithium‐Ion Batteries

Abstract

the LiNi 0.5 Mn 1.5 O 4 material is intensively investigated due to its high-voltage electrochemical activity, excellent rate capability as well as cycling stability. [2][3][4][5][6][7] LiNi 0.5 Mn 1.5 O 4 exists mainly in two crystallographic structures according to the oxygen stoichiometry in the material. [ 2,[8][9][10] The cation-ordered spinel (space group P 4 3 32) which is oxygen-stoichiometric, contains all the Mn ions in their tetravalent form. [ 11 ] At the same time in the cation-disordered structure (space group Fd 3 m) , in addition to the tetravalent Mn species, some of the Mn ions exist in the trivalent form as a result of oxygen deficiency from the crystal lattice. [ 12 ] This is mainly associated with the synthesis temperature. According to Pasero et al. [ 10 ] when the synthesis temperature exceeds ≈650 °C, the structure of LiNi 0.5 Mn 1.5 O 4 transforms gradually from the cationordered to cation-disordered. In the cation-ordered structure, the only electrochemically active species is Ni 2+ . The electrochemical reaction takes place at ≈4.7 V with two plateaus corresponding to Ni 2+ / Ni 3+ and Ni 3+ /Ni 4+ reactions, respectively. [ 2,12 ] Meanwhile, in the cation-disordered structure, a slight electrochemical activity is observed around 4.0 V versus Li/Li + as a result of Mn 3+ /Mn 4+ electrochemical reaction. [ 12 ] However, this material offers only a theoretical capacity of ≈148 mAh g −1 in the usual cycling voltage range 3.5-5.1 V. [ 13 ] It is possible to intercalate a second Li + into the material at voltage <3.0 V which in turn increases the capacity delivered. [ 1,14 ] For this purpose a Li excess electrode must be used as the counter electrode during cycling. Moreover, this process is believed to induce Jahn-Teller distortion of the structure due to the existence of excessive amount of Mn 3+ which in turn results in an average oxidation state of Mn less than +3.5. [ 1,14,15 ] The layered lithium-rich (Li-rich) materials with a general composition x Li 2 MnO 3 · (1 -x ) LiMO 2 (M = Mn, Co, Ni) are known to deliver capacities >250 mAh g −1 when cycled within the voltage range 2.0-4.8 V. [ 16 ] This material has a complex structure which is reported either as composites with nanodomains of Li 2 MnO 3 -and LiMO 2 -like features or as their solid solutions. [17][18][19][20] The powder diffraction patterns of this material

Li-Substituted Layered Spinel Cathode Material for Sodium Ion Batteries

“…This hypothesis has been investigated in layered-spinel cathode materials for lithium ion batteries. 48,[50][51][52] The diffusion coefficients of LS-NFM drops when the voltage is near 2.82 V, and recover at 2.93 V, which can be explained by the phase transformation between O3 and P3 phases, 18 consistent with the plateau region in the voltage profiles (Figure 3a). This sluggish electrochemical reaction implies the O3-P3 phase transformation is a kinetically controlled process associated with the complex Na ion/vacancy ordering and host rearrangement.…”

“…One of the advantages of the layered-spinel cathodes used for lithium-ion batteries is the enhanced rate capability due to the shortened diffusion path that is created by the integration of 3D channels (spinel phase), and 2D channels (layered phase). 48,49 We also investigated the rate capability of our layered-spinel cathode for sodium ion batteries (Figure 3d). Both LS-NFM and NFM cathodes were cycled at the rate of 12 mA g -1 , 36 mA g -1 , 120 mA g -1 , 36 mA g -1 , and back to 12 mA g -1 .…”

Surface/Interface Structure Degradation of Ni‐Rich Layered Oxide Cathodes toward Lithium‐Ion Batteries: Fundamental Mechanisms and Remedying Strategies

“…As widely demonstrated, the lattice breathing during the charging process, resulting from the lattice expansion along the c direction and contraction along a and b directions, which is reversed upon discharging, is also largely related to the Ni‐rich cathodes fracture . The microcracks for the Ni‐rich cathodes, to be more precise, can be categorized into intergranular cracks and intragranular cracks depending on the cracking locations . Such strain‐induced intergranular microcracks can not only engender poor grain‐to‐grain connections, resulting in poor electrical conductivity, but also expose fresh surfaces to electrolytes, thus creating new sites for side reactions, which consequently accelerates the cell degradation .…”

High‐Capacity Layered‐Spinel Cathodes for Li‐Ion Batteries

“…[37] In 2015, Bhaskar et al reportedo ns pecific capacities higher than 200 mA hg À1 for multi-phase x Li 2 MnO 3 ·y LiCo 1/3 Mn 1/3 Ni 1/3 O 2 ·z LiNi 0.5 Mn 1.5 O 4 . [38] The list of recent publications on this type of high capacity composite cathodes is long, marking an increasing interest in Li and Mn-rich layered-spinelc athodes for Li-ionbatteries.…”

“…In some cases, layered LiNiO 2 [22] or any other rhombohedral phase (LiMO 2 )i sp resenti nt he layeredspinel cathodes. [27,30,38]…”