1. Field of the Invention
This invention generally relates to electrochemical batteries and, more particularly, to a battery anode comprised of antimony (Sb) particles embedded in a layered carbon network.
2. Description of the Related Art
Concerns over the safety of lithium and sodium batteries has led to the pursuit of rechargeable batteries constituting carbonaceous materials and intercalation compounds as electrodes, in which pure lithium or sodium metal foils or thin films have been replaced by coatings of carbonaceous powders as the negative electrode (anode). Conventional carbonaceous materials e.g., graphite and hard carbon, are constrained by a limited charge-storage capacity and low density, yielding small volumetric energy and power density.
Electrochemically active metals such as silicon, germanium, tin, and antimony can accommodate Li or Na ions via alloying reactions, and thus have been considered as alternative systems for anode applications. The reversible formation of Li and Na alloys offers a much higher theoretical capacity than that of carbonaceous materials, and has demonstrated a great potential to radically boost the energy density of Li-ion and Na-ion batteries. However, during charge/discharge reactions, these metallic anode materials suffer from structural instabilities due to drastic volumetric variation of up to 150-300% upon full lithiation or sodiation. Decomposition of the electrolyte then occurs upon contacting the freshly formed surface of pulverized electrodes, resulting in formation of thick and unstable passivation layers. The kinetics of alloying reactions is further hampered by the passivation reactions. This is accompanied with marked consumption of available Li or Na ions in the battery cells, which leads to unsatisfied capacity retention at high charge/discharge rates and long-term cycling.
In order to mitigate mechanical cracking or fracture of the electrode during cycling, current research efforts are concentrated on reducing the domain of active materials or creating nanostructures, while the potential of such nano-sized or nanostructured materials is largely sacrificed by a reduced tap density and low areal mass loading. The high surface area of such electrode materials is not capable of eliminating the irreversible electrolyte decomposition in the initial cycles. Instead, the first cycle capacity loss is rather intensified when nano-sized metal particles are employed in the anode. Incorporating carbonaceous species offers an alternative solution to suppress the detrimental effects of volumetric change as well as isolation of active metal particles from electrical connection due to surface passivation. Nonetheless, widely used carbon additives such as carbon black, carbon fiber, or ketjen black, with small diameter or porous structures, introduce a large irreversible capacity (low coulombic efficiency, CE). The initial CE of such composite materials is typically less than 70%. In addition, the metal particles are conducive to electrochemical sintering. As the material loading increases, the primary metal particles suffer from a stronger tendency to aggregate and separate from conductive components, leaving the issues of long-term cycling stability and inferior CE unresolved.
It would be advantageous if a metal anode and comprehensive battery cell could be fabricated to be compatible with commercial battery configurations and high-throughput manufacturing protocols, particularly for sodium-ion batteries.    1) T. R. Jow, Rechargeable Sodium Alloy Anode, U.S. Pat. No. 4,753,858.    2) D. Larcher, S. Beattie, M. Morcrette, K. Edström, J.-C. Jumas and J.-M. Tarascon, Recent Findings and Prospects in the Field of Pure Metals as Negative Electrodes for Li-Ion Batteries, J. Mater. Chem., 2007, 17, 3759-3772.    3) M. N. Obrovac and L. Christensen, Structural Changes in Silicon Anodes during Lithium Insertion/Extraction, Electrochem. Solid-State Lett., 2004, 7, A93-A96.    4) Y. Oumellal, N. Delpuech, D. Mazouzi, N. Dupré, J. Gaubicher, P. Moreau, P. Soudan, B. Lestriez and D. Guyomard, The Failure Mechanism of Nano-sized Si-Based Negative Electrodes for Lithium Ion Batteries, J. Mater. Chem., 2011, 21, 6201-6208.    5) Y. Xu, Y. Zhu, Y. Liu and C. Wang, Adv. Energy Mater., 2013, 3, 128-133.    6) A. Darwiche, C. Marino, M. T. Sougrati, B. Fraisse, L. Stievano and L. Monconduit, Better Cycling Performances of Bulk Sb in Na-Ion Batteries Compared to Li-Ion Systems: An Unexpected Electrochemical Mechanism, J. Am. Chem. Soc., 2012, 134, 20805-20811.    7) M. He, K. Kravchyk, M. Walter and M. V. Kovalenko, Monodisperse Antimony Nanocrystals for High-Rate Li-Ion and Na-Ion Battery Anodes, Nano Lett., 2014, 14, 1255-1262.    8) L. Xiao, Y. Cao, J. Xiao, W. Wang, L. Kovarik, Z. Nie and J. Liu, High Capacity, Reversible Alloying Reactions in SnSb/C Nanocomposites for Na-Ion Battery Applications, Chem. Commun., 2012, 48, 3321-3323.    9) L. Ji, M. Gu, Y. Shao, X. Li, M. H. Engelhard, B. W. Arey, W. Wang, Z. Nie, J. Xiao, C. Wang, J.-G. Zhang and J. Liu, Controlling SEI Formation on SnSb-Porous Carbon Nanofibers for Improved Na Ion Storage, Adv. Mater., 2014, 26, 2901-2908.    10) J. Qian, Y. Chen, L. Wu, Y. Cao, X. Ai and H. Yang, High capacity Na-storage and superior cyclability of nanocomposite Sb/C anode for Na-ion batteries, Chem. Commun., 2012, 48, 7070-7072.    11) Kefei Li et al., Antimony-Carbon-Graphene Fibrous Composite as Freestanding Anode Materials for Sodium-ion Batteries, Electrochimica Acta, 2015.