A New Silica-Based Anode Using Three-Dimensional Nanostructured Copper As a Current Collector for Lithium Ion Batteries

Introduction

Lithium ion batteries are widely used high energy density rechargeable energy storage devices, but there is great demand for batteries with higher energy densities. Consequently, new electrodes (or active materials) with improved capacities have been developed to replace current electrodes. Silicon and silica are promising candidates to replace the conventional graphite anode since their theoretical capacities (4200 mAhg^-1 and 1965 mAhg^-1, respectively ¹⁾) are high compared to that of graphite (372 mAhg^-1). Unfortunately, these active materials exhibit low cyclability due to degradation and separation of the silicon and silica from the current collector, caused by volumetric changes during alloying/de-alloying with lithium ions. Nanosized active materials have been examined as a means of mitigating this effect, and a three-dimensional (3D) network current collector has also been investigated to enhance the cyclability of lithium ion batteries using a silicon-based anode²⁾. We previously reported a new and simple method of fabricating a 3D nanostructured copper layer by electrodeposition³⁾.

Herein, we propose 3D nanostructured copper as a current collector using silica nanoparticles as the anode material for lithium ion batteries

Experimental

The composition of the 3D nanostructured copper plating bath was 0.85 M CuSO₄�{0.55 M H₂SO₄+3´10^-4M polyacrylic acid (M.W. 5000). Electrodeposition was carried out under galvanostatic conditions at 25°C. A pure copper plate and a phosphorous copper plate were used as the cathode and anode, respectively. Silica nanoparticles were synthesized by the sol-gel method. 3D nanostructured copper was immersed into a solution of ethanol and tetraethyl orthosilicate. Ammonia water was added to this solution and silica nanoparticles were fabricated on/in the 3D nanostructured copper layer.

Electrochemical studies of the fabricated anode were carried out with coin cells assembled in an Ar-filled glove box. Each coin cell consisted of lithium foil as the counter and reference electrode and the fabricated anode as the working electrode. The electrolyte was 1 M LiPF₆ in ethylene carbonate (EC) and diethyl carbonate (DEC) (1:1 vol%). Cycling tests were performed between 0 - 3 V (vs. Li/Li⁺) at a constant temperature of 25°C.

Results and Discussion

 Figure 1 presents a cross-sectional SEM image of the fabricated anode and clearly shows uniform 200-300 nm diameter silica nanoparticles inside the 3D nanostructured copper layer.

Charge-discharge without conductive additive and binder was confirmed. The electrochemical performance of the anode will be discussed in detail at the meeting.

References

1)Young-Kuk Kim*, Jong-Woo Moon, Jung-Goo Lee, Youn-Kyung Baek, Seong-Hyun Hong, Journal of Power Sources, 272(2014) 689-695

2)Y. Liu, K. Huang, Y. Fan, Q. Zhang, F. Sun, T. Gao, L. Yang, J. Zhong, Electrochimica Acta, 88(2013) 766.

3) S. Arai, T. Kitamura, ECS Electrochemistry Letters, 3(5) (2014) D7.