| Energy problems are global focus and hot issues of common concern. High efficient and environmental lithium ion battery as a significant energy storage device has been successful applied in mobile portable electronic devices, electric cars, and other applications. However, low reversible capacity is current existed problem for lithium anode material (commercial graphite) in the prolonged charge/discharge process which is crucial to the entire battery performance. Transition metal oxides generally have high specific capacities, which may compensate for the shortcoming of low irreversible capacity, thus have been widely researched in recent years. Usually, poor cycle stability and agglomeration are common weakness that exsited in monocomponent transition metal oxide. One effective way to solve above problem were composite with high conductive carbon and electrochemical inactive metal oxide. However, traditional preparation methodes are usually complex. Therefore, it is great challenge for synthesis lithium anode material through a simple and efficient method which can improve the synergistic effect of each component. As a kind of important multifunctional layered materials, hydrotalcites has been developed rapidly in many fields of theoretical research and practical application in the past few years. Herein, we successfully prepared two kinds of composite metal compounds (CoO/Co3O4/N-C/Al2O3> Co2SnO4/Co3O4/Al2O3/C) via high temperature pyrolysis hydrotalcite precursors, which can significantly enhance the lithium ion battery anode electrochemical performance. The main content and the innovation points of the paper are as follows:(1) Preparation of CoO/Co3O4/N-C/Al2O3 composite and its lithium storage research:Firstly, precursor was prepared from nucleation crystallization, and then by calcination of CoAl-LDH/melamine mixture, CoO/Co3O4/N-C/Al2O3 composite was obtained. When used as anode material, the resulting composite electrode delivers a higher reversible capacity and better cycle stability compared with the bi-active CoO/Co3O4 mixtures with and without non-active Al2O3 (mCoO/Co3O4 and mCoO/Co304/Al203). The resulting composite bundles the advantages expected to boost electrochemical performances:(ⅰ) bi-active CoO/Co3O4, (ⅱ) highly conductive N-doped carbon, and (ⅲ) N-doped carbon and high-content non-active Al2O3 as buffering reagents, as well as (ⅳ) good distribution of bi-and non-active components resulted from the lattice orientation and confinement effect of the LDH layers.(2) Preparation of Co2SnO4/Co3O4/Al2O3/C composite and its lithium storage research:Based on the versatility in chemically designing the surfactant interlayer anions of LDH precursors, we prepared CoAlSn-LA"-LDH by intercalation lauric acid sodium instead of CO32-into CoAlSn-LDH. Then a multi-component Co2SnO4/Co3O4/Al2O3/C composite was obtained by first calcination and further oxidation procedure of CoAlSn-LA--LDH precursor. The resultant Co2SnO4/Co3O4/Al2O3/C electrode delivers a highly enhanced reversible capacity of 1170 mA h g-1 at 100 mA g-1 after 100 cycles, compared with the bi-active composites designed without Al2O3 or carbon which are easily derived through the same protocol by choosing LDH precursors without Al cation or surfactant intercalation. The distinctly different cycling stability and rate capability of Co2SnO4/Co3O4/Al2O3/C among the different composite electrodes suggests that the high enhancement could result from the following synergistic features:(ⅰ) the combined multi-electron conversion and alloying reaction of bi-active Co2SnO4/Co3O4 during cycling; (ⅱ) slight non-active Al2O3 can buffer volume expansion instead of reduce the specific capacity; at the same time, the self-generated carbon matrix can not only improve conductivity, but also buffer stress changes.The LDH precursor-based approach can be extended to design and synthesis various multi-component transition metal oxides、 sulfides and phosphides nanocomposite materials for synergistic lithium storage. |
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