Abstract
Biomass-derived approaches have been accepted as a practical way for the design of transitional metal phosphides confined by carbon matrix (TMPs@C) as energy storage materials. Herein, we successfully synthesize P/N-co-doped carbon nanosheets encapsulating Cu3P nanoparticles (Cu3P@P/N-C) by a feasible aqueous reaction followed by a phosphorization procedure using sodium alginate as the biomass carbon source. Cu-alginate hydrogel balls can be squeezed into two-dimensional (2D) nanosheets through a freeze–drying process. Then, Cu3P@P/N-C was obtained after the phosphorization procedure. This rationally designed structure not only improved the kinetics of ion/electron transportation but also buffered the volume expansion of Cu3P nanoparticles during the continuous charge and discharge processes. In addition, the 2D P/N co-doped carbon nanosheets can also serve as a conductive matrix, which can enhance the electronic conductivity of the whole electrode as well as provide rapid channels for electron/ion diffusion. Thus, when applied as anode materials for sodium-ion batteries, it exhibited remarkable cycling stability and rate performance. Prominently, Cu3P@P/N-C demonstrated an outstanding reversible capacity of 209.3 mAh g−1 at 1 A g−1 after 1,000 cycles. Besides, it still maintained a superior specific capacity of 118.2 mAh g−1 after 2,000 cycles, even at a high current density of 5 A g−1.
Highlights
In recent years, lithium-ion batteries (LIBs) have been widely applied from portable electronic devices to electric vehicles (Zou et al, 2017, 2019; Qiu et al, 2019)
When compared with LIBs, sodium-ion batteries (SIBs) are Biomass-Derived P/N-Co-Doped Carbon Nanosheets still an immature technology that is confronted with a lot of challenges, such as low specific energy, poor cycleability, and low power density (Wessells et al, 2011; Lotfabad et al, 2014; Li and Zhou, 2018)
Scheme 1 exhibits the typical synthesis of Cu3P@P/N-C
Summary
Lithium-ion batteries (LIBs) have been widely applied from portable electronic devices to electric vehicles (Zou et al, 2017, 2019; Qiu et al, 2019). In recent years, red phosphorus has been regarded as one of promising SIB anode materials owing to its comparatively low redox potential (∼0.4 V vs Na/Na+) and extremely high theoretical specific capacity (2,596 mAh g−1) (Kim et al, 2013; Qian et al, 2013; Zhou et al, 2017; Hu et al, 2018; Wu Y. et al, 2018). The 2D carbon nanosheet structure can shorten the Na+ diffusion path, provide more active sites of Na+, as well as enhance the electronic conductivity of the entire electrode Benefiting from these advantages mentioned above, Cu3P@P/N-C exhibited a long cycle life and outstanding rate performance when applied as anode for SIBs. Cu3P@P/N-C anode materials demonstrated a long cycle life (209.3 mAh g−1 at 1 A g−1 after 1,000 cycles) and excellent rate performance (118.2 mAh g−1 even at a high current density of 5 A g−1 after 2,000 cycles). Cyclic voltammetry behavior was studied by the CHI 650d electrochemical workstation at a scan rate of 0.1 mV s−1
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