Factors Influencing the Electrochemical Properties of High-Voltage Spinel Cathodes: Relative Impact of Morphology and Cation Ordering

Abstract

In order to achieve consistent electrochemical properties essential for the commercialization of the high-voltage spinel cathode LiMn 1.5 Ni 0.5 O 4 , a deeper fundamental understanding of the factors contributing to capacity fade is required. Specifically, the relationship between cation ordering, impurity phases present, and particle morphology must be elucidated. We present here a comparison of stoichiometric LiMn 1.5 Ni 0.5 O 4 cathodes with a 3:1 Mn/Ni ratio prepared by different methods with varying morphologies and degrees of cation ordering. Careful structural, chemical, and electrochemical characterizations illuminate the relative influence of the various factors on the electrochemical cycling stability and high-rate performance. It is found that although an increase in the degree of cation ordering decreases the rate capability, the crystallographic planes in contact with the electrolyte have a dominant effect on the electrochemical properties.

Electrochemical Performance and Phase Transitions between 1.5 and 4.9 V of Highly-Ordered LiNi0.5Mn1.5O4with Tailored Morphology: Influence of the Lithiation Method

“…[19][20][21][22][23][24] The reasons of the different processes revealed by electrochemical analysis at low-potentials are currently under investigation and will be the subject of a later communication. From a practical point of view, it is clear that the overall capacity can be controlled by selecting the potential cutoff.…”

Fluorinated Electrolytes for 5-V Li-Ion Chemistry: Probing Voltage Stability of Electrolytes with Electrochemical Floating Test

“…1 To increase the energy density of Li-ion batteries, researchers have developed high capacity cathodes such as the lithium-rich "layered-layered" composite xLi 2 MnO 3 • (1-x)LiMO 2 (M = Ni, Co, Mn) 2 and high voltage cathodes such as the spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) 3,4 and LiCoPO 4 . 5 Of these, the highvoltage spinel LNMO is particularly popular.…”

Phase Component-controllable Synthesis of Layered-Spinel Composite Materials as High-Performance Cathode for Lithium-ion Battery

“…2(e), a few truncated octahedral particles emerge in the microstructure. 28 In Sample S26, the truncated and hexagonal particles retain the same approximate particle size and shape, but the outline becomes blurred, which may be attributed to the longer reaction time [ Fig. 2(f )].…”

“…12 The spinel phase in Samples S6, S10, S18, and S26 consists of truncated particles that reveal a poorer electrochemical performance compared with the octahedral spinel-phase material. 4 In our work, for Sample S2, the spinel and layered primary particles were distributed uniformly in secondary particles, which takes full advantage of the three-dimensional Li ion diffusing path that is beneficial to the rapid diffusion of Li ions from the electrodes into the electrolytes. The existence of an appropriate content of layered phase and the compatibility of different phases protects the structural integrity of composite material during the rapid charge-discharge process.…”

“…1 A layered-structure cathode material can provide increased stability against oxygen loss when charged above 4.7 V, but is electrochemically inactive between 4.5 V and 3.0 V. 2,3 Spinel structures (such as Li 4 Mn 5 O 12 and LiNi 0.5 Mn 1.5 O 4 ) can offer a robust cubic close-packed oxygen array with three-dimensional Li + ion diffusion path, which allows for a fast insertion or removal of Li + ions and provides the spinel-structure materials with excellent performance. The spinel-structure material is active when charging to ³5 V. 4,5 Although the layered-and spinel-type structures have respective advantages, disadvantages are inevitable. The layered cathode material may suffer significant voltage decay and a poor rate performance, and the spinel cathode material shows bad cycle stability and a low capacity during extended cycling.…”