One-Pot Synthesis of Lithium-Rich Cathode Material with Hierarchical Morphology.

Kun Luo,Rong Hao,Angus I Kirkland,Christopher S Allen,Niccoló Guerrini,Peter G Bruce,Matthew R Roberts,Emanuela Liberti

doi:10.1021/acs.nanolett.6b03296

Abstract

Lithium-rich transition metal oxides, Li1+xTM1-xO2 (TM, transition metal), have attracted much attention as potential candidate cathode materials for next generation lithium ion batteries because their high theoretical capacity. Here we present the synthesis of Li[Li0.2Ni0.2Mn0.6]O2 using a facile one-pot resorcinol-formaldehyde method. Structural characterization indicates that the material adopts a hierarchical porous morphology consisting of uniformly distributed small pores and disordered large pore structures. The material exhibits excellent electrochemical cycling stability and a good retention of capacity at high rates. The material has been shown to be both advantageous in terms of gravimetric and volumetric capacities over state of the art commercial cathode materials.

Highlights

Lithium-rich transition metal oxides, Li1+xTM1−xO2 (TM, transition metal), have attracted much attention as potential candidate cathode materials for generation lithium ion batteries because their high theoretical capacity
This multistep synthesis requires the precipitate to be combined with the correct amount of Li carbonate followed by high-temperature calcination and despite its widespread application has resulted in different degrees of structural purity and electrochemical response
The precursor was prepared in a single step by first dissolving the Li+, Ni2+, and Mn2+ ions in an aqueous solution to which resorcinol and formaldehyde are added to chelate the ions and a polymerization reaction is initiated between the resorcinol and formaldehyde suspending the ions in an even distribution throughout the formed polymer.[19]

Summary

Nano Letters

LiCoO2 layered structure with alternating Li layers and [Li1/3Mn2/3] layers. By substituting x = 0.2 Ni into Li[Li1/3−2x/3Mn2/3‐x/3Nix]O2, the composition of the material studied here is obtained. Flips of the domains, as well as transition metal-rich defects (arrows in Figure 3b), are observed, which lower the periodicity This lack of long-range order (along the c-direction) is consistent with broad peaks in the 2θ range of 26 to 36° (Fe Kα) observed from the X-ray powder diffraction pattern (Figure 2), and agrees well with previous studies on the local structure of lithium-rich materials.[26,27] we conclude that the composition and crystal structure of Li[Li0.2Ni0.2Mn0.6]O2 synthesized using the one-pot method is in good agreement with those materials prepared previously. The capacity retention on cycling and the rate performance reported for the material synthesized by the one-pot method compares well with some of the best results in the literature of Li rich cathodes. The method reported in this paper can be extended to the synthesis of other electrode materials in batteries

Methods

■ ACKNOWLEDGMENTS

Findings

■ REFERENCES