A multi-shelled CoP nanosphere modified separator for highly efficient Li–S batteries

Abstract

Lithium-sulfur batteries are considered to be one of the most promising energy-storage systems because of their high theoretical energy density, as well as low cost, nontoxicity and natural abundance of sulfur. However, their poor cycling stability mostly originates from the shuttling of polysulfides which hinders their future practical applications. Here, multi-shelled CoP nanospheres are designed as a coated separator material for Li-S batteries for the first time. Conductive CoP can efficiently anchor polysulfides not only owing to its polar character but also its partial natural surface oxidation feature as evidenced by XPS results, which further activates Co sites for chemically trapping polysulfides via strong Co-S bonding. Furthermore, the unique multi-shelled structure can capture polysulfides to alleviate the "shuttle effect". Consequently, the battery using a CoP coated separator exhibits outstanding cycling stability with a capacity degradation of 0.078% per cycle over 500 cycles at a current density of 1 C and excellent rate performance (725 mA h g-1 at 5 C). It is also worth noting that a high areal capacity of 3.2 mA h cm-2 can be achieved even with a sulfur loading of 3.24 mg cm-2. Our approach demonstrates the convenient fabrication and application potential for a multi-shelled CoP nanosphere modified separator for highly efficient Li-S batteries.

Separator Modified by Cobalt‐Embedded Carbon Nanosheets Enabling Chemisorption and Catalytic Effects of Polysulfides for High‐Energy‐Density Lithium‐Sulfur Batteries

“…The Co-N x @NPC/G-PP separator possesses excellent robustness and durability, and there is no detectable delamination of Co-N x @NPC/G after either folding or bending ( Figure S8, Supporting Information). [42][43][44] The Li + conductivity of the separators was evaluated by the EIS analyses ( Figure S12, Supporting Information). After Co-N x @NPC/G is coated on the PP separator, the pores in pristine PP are fully covered by Co-N x @NPC/G, and uniform layer is formed on the surface (Figure 4e).…”

A Multifunctional Separator Enables Safe and Durable Lithium/Magnesium–Sulfur Batteries under Elevated Temperature

“…Especially for the CuNWs-GN/PI/LLZO separator, the absorbance for the upper solution is near zero, demonstrating that almost all the polysulfide molecules can be anchored by chemical conversion. [11,14] Also, the high-resolution Cu 2p XPS spectra of the pristine CuNWs-GN/PI/ LLZO separator ( Figure S20, Supporting Information) shows the signals of partial copper oxides and metallic copper. As demonstrated by the high resolution transmission electron microscopy (HRTEM) image in Figure S18 in the Supporting Information, the successful conversion reaction between copper nanowires and soluble polysulfide species is clearly revealed.…”

Multishelled Transition Metal‐Based Microspheres: Synthesis and Applications for Batteries and Supercapacitors

“…In addition to cathode materials, multishelled hollow structures are also used as a coated separator material. Xu and co‐workers successfully fabricated multishelled CoP nanospheres by two‐step annealing and first employed them as coating materials on the separator in Li–S batteries. The shuttle effect can be alleviated depending on a strong adsorption effect for polar CoP and the capture of multishelled hollow structures with more active sites.…”

“…b) discharge capacity of the cell with a functional separator at 1 C. c) comparison illustration of the standard Li–S battery or with a functional separator. a–c) Reproduced with permission . Copyright 2018, Royal Society of Chemistry.…”