Novel sodium-ion battery anode design of Sn4P3 nanoparticles loaded on biomass-derived carbon

Abstract

Tin phosphide (SnxPy) is an anode for sodium-ion batteries resulting from its exceptionally high theoretical capacity in future. Nevertheless, its application will be hindered by significant volume expansion during charge-discharge cycles and poor electrical conductivity. This study employs a Sn-based metal-organic framework (Sn-MOF) as a precursor for synthesizing tin phosphide nanoparticles. Then Solidago Canadensis L., commonly known as Canadian Goldenrod, is utilized as a biomass carbon carrier to form a composite with tin phosphide nanoparticles. The biomass-derived porous carbon provides additional sodium ion storage sites and serves as a structural scaffold that constrains the volumetric expansion of tin phosphide, thereby enhancing the material’s stability. The fabricated composite exhibits superior electrode electrochemical performance for sodium-ion batteries. It retains a high capacity (489.5 mA·h/g) after 100 cycles at 0.2 A/g. Even after 500 cycles at a high current density of 2 A/g, it still maintains a stable reversible capacity. This study offers a comprehensive exploration of innovative design strategies essential for the development of novel anode materials, paving the way for more sustainable and efficient sodium-ion-based energy storage systems.

1. Introduction

As the new energy vehicle industry burgeons and the era of smart grids dawns, the demand for affordable electricity storage systems is escalating [1−5]. Sodium-ion batteries (SIBs), distinguished by their low-cost and abundant raw resources, demonstrate significant potential for development and are emerging as a feasible alternative soon [6−8]. A critical factor influencing SIBs’ application is the selection of anode materials. Graphite anode materials, known for their excellent electrical conductivity and stable chemical properties, are among lithium-ion batteries’ most widely used anode materials. However, the small interlayer spacing of graphite does not effectively accommodate the larger radius of Na+, which limits its application in sodium-ion batteries [9]. Consequently, there is an urgent need to develop a new high-performance anode material for sodium-ion batteries that can adequately host sodium ions. Transition metal phosphides like FeP [10, 11], Cu3P [12, 13], CoP [14, 15], and MnP4 [16] have garnered attention for their superior electrochemical properties, making them focal points in SIBs’ anode material research [17−19].

Amongst various metal phosphides, tin phosphide (Sn4P3) represents a prominent anode choice for SIBs, ascribed to the joint sodium storage reactions of Sn and P elements. This synergy endows Sn4P3 with a remarkably high theoretical capacity (1132 mA·h/g). Compared to tin oxides and tin sulfides, Sn4P3 offers a lower redox potential [20−22]. However, the repeated sodiation/desodiation cycles during charging and discharging lead to substantial volumetric expansion and material pulverization, severely diminishing its capacity over time. Additionally, the intrinsic poor conductivity of pure Sn4P3 hinders its electrochemical performance [23, 24].

To address these challenges, current research focuses on the nanostructural design of Sn4P3, including the development of nano hollow spheres and nano boxes [25, 26]. Recent research also reports compositing Sn4P3 with carbon materials to enhance its conductivity and mitigate volumetric expansion. Carbonaceous materials not only effectively restrict the volumetric expansion of Sn4P3 but also significantly boost the conductivity of the electrode materials [27, 28]. Recently, ZHANG et al [29] proposed a bamboo-like carbon nanotube composite of phosphorus-doped tin, designated as BLCNTs@Sn4P3@C. This composite electrode demonstrates a stable reversible capacity of 275 mA·h/g after 2000 cycles at a current density of 0.2 A/g and superior rate capability in SIBs. ZHAO et al [30] employed electrospinning to attach Sn4P3@C nanospheres to one-dimensional carbon nanofibers, creating a distinctive chain-like structure. This configuration exhibited exceptional electrochemical performance and longevity in sodium-ion batteries. However, the experimental pathways for structural design are complex and pose significant challenges in structural control, which substantially impacts the electrochemical properties of the composites. This study utilized an Sn-based metal-organic framework (Sn-MOF) as a precursor for synthesizing Sn4P3 nanoparticles. Recently, among various carbon materials, biomass-derived carbon has stood out due to its low cost, readily available raw materials, and straightforward preparation process [31−33].