Abstract
Multielectronic reaction electrode materials for high energy density lithium-ion batteries (LIBs) are severely hindered by their inherent sluggish kinetics and large volume variations, leading to rapid capacity fade. Here, a simple method is developed to construct low-carbon and nanosheathed ZnCo2O4 porous spheroids (ZCO@C-5). In this micro/nanostructure, an ultrathin amorphous carbon layer (~2 nm in thickness) is distributed all over the primary nanosized ZCO particles (~20 nm in diameter), which finally self-assembles into porous core (ZCO)-shell(carbon) micron spheroids. The nanoencapsulation and macro/mesoporous architecture can not only provide facile electrolyte penetration and rapid ion/electron transfer but also better alleviate volumetric expansion effect to avoid pulverization of ZCO@C-5 spheroids during repeat charge/discharge processes. As expected, the three-dimensional porous ZCO@C-5 composites exhibit high reversible capacity of 1240 mAh g−1 cycle at 500 mA g−1, as well as excellent long-term cycling stability and rate capability. The low-carbon and nanoencapsulation strategy in this study is simple and effective, exhibiting great potential for high-performance LIBs.
Highlights
Lithium-ion batteries (LIBs) as important energy storage devices are widely applied in various fields, such as portable electronic devices and electric vehicles, and so on [1,2,3]
We develop a facile route to fabricate low-carbon and nanoencapsulation ZCO porous spheroids (ZCO@C-5) via hydrothermal reaction combined with subsequent high-temperature treatment, as shown in Scheme 1
The crystal structure and chemical composition of materials were characterized by X-ray diffraction (XRD), XPS, FTIR, Raman, and TG tests (Figure 1; Figures S1-S7, Supplementary Materials)
Summary
Lithium-ion batteries (LIBs) as important energy storage devices are widely applied in various fields, such as portable electronic devices and electric vehicles, and so on [1,2,3]. It is necessary to exploit alternative anode materials with high energy density, long cycling stability, and low cost for highperformance LIBs [6, 7]. In addition to conversion reaction (Zn2+ + 2e− ←→ Zn) during charge storage, the alloying reaction can be performed between Zn and Li (Zn + Li+ + e− ←→ LiZn) [17, 18] As a result, it can produce a very high reversible capacity. Different from the insertiontype anode materials, low conductivity, huge volume expansion/contraction effect, and severe self-aggregation of spinel ZCO during lithiation/delithiation cycling will lead to unsatisfactory electrochemical performances [19]. A variety of nanostructures for ZCO have been reasonably designed toward overcoming the above issues, such as 2D ultrathin ZCO nanosheets [20], orange-shaped ZCO [21], hollow ZCO nanocages [13], ZCO-urchins-on-carbon-fibers
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