Phase Transition Induced Synthesis of Layered/Spinel Heterostructure with Enhanced Electrochemical Properties

Abstract

A one‐step synthesis of Li‐rich layered materials with layered/spinel heterostructure has been systematically investigated. The composites are synthesized by a polyol method followed with an annealing process at 500–900 °C for 12 h. A spinel to layer phase transition is considered to take place during the heat treatment, and the samples obtained at different temperatures show diverse phase compositions. An “Li‐rich spinel phase decomposition” phase transition mechanism is proposed to explain the formation of such a heterostructure. The electrochemical properties of the heterostructure are found to be associated with the ratio of spinel to layer phases, the leach out of rock salt phase, and the change of crystallinity and particle size. Product with improved cyclic and rate performance is achieved by annealing at 700 °C for 12 h, with a discharge capacity of 214 mA h g−1 remaining at 0.2 C after 60 cycles and discharge capacity of about 200 mA h g−1 at 1 C.

Uniform Na+ Doping‐Induced Defects in Li‐ and Mn‐Rich Cathodes for High‐Performance Lithium‐Ion Batteries

“…The Fourier transform infrared spectroscopy (FTIR) was used to identify the existence of SDS in carbonate precursors ( Figure S2, Supporting Information). [16] The subsequent mass loss emerged between 181.9 and 389.6 °C would be attributed to the decomposition of TM-CO 3 (NCMCO) and formation of TM-O (NCMO); the endothermic peak presented at 347 °C agrees well with the decomposition temperature of MnCO 3 (347 °C). It is reasonable to speculate that the extra stage may relate to the decomposition of SDS (melting point of 204-207 °C).…”

“…In this context, Li-and Mn-rich (LMR) transition metal (TM) oxides are labeled as one of the most promising candidates for next generation cathode materials of rechargeable LIBs because of their prominent energy density of ≈1000 Wh kg −1 . [11][12][13][14][15][16] Doping is considered as an effective strategy to improve the performance of the LMR cathode materials. [7][8][9][10] For instance, voltage decay and capacity fading resulted from structural degradation and phase transition are major obstacles for nearly all LMR cathodes with chemical formula xLi 2 MnO 3 ·(1−x)LiTMO 2 (transition metal (TM) = Ni, Co, Mn, etc.).…”

Multistage Li1.2Ni0.2Mn0.6O2 Micro‐architecture towards High‐Performance Cathode Materials for Lithium‐Ion Batteries

“…Z′ : the real part of impedance, thus can be obtained from the linear fitting of Z′ vs. w −1/2 in the low frequency range shown in Figure b ,. The slope of two linear equations (the value of the ) are 185.5 J s 1/2 C −2 and 388.46 J s 1/2 C −2 for the cathode material before cycles and after 40 cycles.…”

Composite‐Structure Material Design for High‐Energy Lithium Storage

“…Though the layered–layered composite‐structure materials of LLOs display high capacity, there are still various challenges, low initial CE, voltage, and capacity decay, as well as poor rate performance, which have limited their practical applications . Based on the clear cognition of the average and local structure of LLOs, structural design approach should be considered to further improve the electrochemical properties of LLOs, including increasing the initial CE, suppressing the voltage decay associated with enhance rate performance.…”