High-yield carbon nanofibers derived from nanoporous Cu catalyst alloyed with Ni for sodium storage with high cycling stability

Abstract

High-performance and low-cost anode materials are critical for superior sodium-ion batteries (SIBs). Herein, high-yield porous carbon nanofiber (CNF) anode materials (named CNFs@Cu–Ni) are prepared by chemical vapor deposition using a specialized nanoporous Cu–Ni alloy catalyst. Density functional theory calculations indicate that Ni incorporation results in a shift of the d-band center of the catalyst from −2.34157 to −1.93682 eV. This phenomenon elucidates the remarkable adsorption capacity of the Cu–Ni catalyst toward C2H2, thereby facilitating the catalytic growth of high-performance CNFs. With this approach, a superior yield of 258.6% for deposited carbon is reached after growth for 1 h. The CNFs@Cu–Ni anode presents an outstanding discharge capacity of 193.6 mAh·g−1 at 1.0 A·g−1 over 1000 cycles and an exceptional rate capability by maintaining a capacity of 158.9 mAh·g−1 even at 5.0 A·g−1 in an ether-based electrolyte. It also exhibits excellent performance in the CNFs@Cu–Ni//NVP full battery attributed to the presence of abundant Na+ adsorption sites on its surface. This study presents a new concept for the advancement of high-performance carbonaceous electrodes for SIBs.

1. Introduction

The limited lithium sources hinder the development of lithium-ion batteries (LIBs) [1]. As a promising alternative to LIBs, sodium-ion batteries (SIBs) have received increasing attention due to the abundance of sodium resources [2]. However, the large radius of Na+ (0.95 Å) affects the de-embedding kinetics of ions, which poses a major challenge for the development of new SIB electrodes [3]. Carbonaceous materials, such as hard carbon, carbon nanofibers (CNFs), soft carbon, and graphite [4–8], feature the merits of excellent electrical conductivity, mechanical strength, and corrosion resistance and are considered to be the most promising key anode materials for SIBs [9]. However, the industrial application of carbonaceous anode materials in SIBs still encounters several challenges, such as low cyclic stability [10], slow transport kinetics of Na+ [11], and high commercialization costs [12]. Intelligent auxiliary agents, such as catalysts in chemical vapor deposition (CVD), can effectively boost the yield of carbonaceous anode materials, offering a promising solution to these challenges. Taking into account the yield and incorporating appropriate interlayer spacing and defects, a tailored design of carbonaceous materials has the potential to substantially enhance their sodium storage capacity and improve the cyclic stability of SIBs.

Among carbonaceous materials, one-dimensional (1D) CNFs have high porosity, large specific surface area, and excellent sodium storage performance [13]. Emerging as the preferred technique for fabricating carbon nanostructures, low-cost CVD allows for the tailored synthesis of carbon nanomaterials with diverse and intricate 3 dimensional (3D) conformations [14]. In growing CNFs by CVD, the lattice orientation and chemical composition of the catalyst profoundly influence the produced CNFs because the carbon source is initially decomposed, diffused, and nucleated on the catalyst’s surface while growing [15]. Therefore, catalyst optimization represents a crucial strategy for the generation of high-yield, high-performance CNF electrodes for SIBs.