Electroless plating of a Sn-Ni/graphite sheet composite with improved cyclability as an anode material for lithium ion batteries

Abstract

A Sn-Ni/graphite sheet composite is synthesized by a simple electroless plating method as an anode material for lithium ion batteries (LIBs). The microstructure and electrochemical properties of the composite are characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), and AC impedance spectroscopy. The results show that the as-prepared composite has Sn-Ni nanoparticles around 100 nm in size, where metallic Ni acts as an "anchor" to fix metallic Sn. The reunion phenomenon of Sn is alleviated by adding metallic Ni between the metallic Sn and graphite sheets. The Sn-Ni/graphite sheet electrode exhibits a good rate performance with a capability of 637.4, 586.3, 466.7, 371.5, 273.6, 165.3 and 97.3 mA h g^-1 at a current density of 0.1, 0.2, 0.5, 1.0, 2.0, 5.0 and 10 A g^-1, respectively. The good electrical conductivity of Ni, high specific capacity of Sn and excellent cycling capability of the graphite sheets have a synergistic effect and are the main reasons behind the superior electrochemical performance. Furthermore, the as-prepared composite exhibits excellent lithium storage capacity and the reversible capacity increased as the cycle number increased.

Fig. 1. SEM images of flake graphite (a) and oxidized graphite sheets (b).

Fig. 2. SEM images of the Sn/graphite sheet sample before sintering (a) and after sintering at 600 °C (b), the Ni/graphite sheet sample before sintering (c), and the Sn–Ni/graphite sheet sample before sintering (d) and after sintering at 600 °C (e).

Fig. 3. TEM images of the Sn–Ni/graphite sheet sample with the corresponding SAED patterns (inset) (a) and the nano-phases dispersed in the Sn–Ni/graphite sheets (b), EDS spectrogram of the Sn–Ni/graphite sheet sample and elemental distribution for C, O, Ni, Sn (c), and TGA curves of Ni/graphite sheets and Sn–Ni/graphite sheets (d).

Scheme 1. The formation mechanism of the Sn–Ni/graphite sheet composite material.

Fig. 4. The first three CV curves of the Sn–Ni/graphite sheets (a), the Sn/graphite sheets (b) and the Ni/graphite sheets (c) with a scan rate of 0.1 mV s⁻¹ between 1.0 mV and 3.0 V.

Fig. 5. The 1st, 2nd and 10th discharge–charge curves of the Sn–Ni/graphite sheets (a), the Sn/graphite sheets (b) and the Ni/graphite sheets (c).

Fig. 6. The rate capability and cycling performance of the graphite sheets, Ni/graphite sheets, Sn/graphite sheets and Sn–Ni/graphite sheets (a), and the electrochemical impedance spectra of the graphite sheets, Ni/graphite sheets, Sn/graphite sheets and Sn–Ni/graphite sheets (b).