Abstract
Polyanionic Na3V2(PO4)2F3 with a NASICON‐type structure is heralded as a promising cathode material for sodium‐ion batteries due to its fast ionic conduction, high working voltage, and favorable structural stability. However, a number of challenging issues remain regarding its rate capability and cycle life, which must be addressed to enable greater application compatibility. Here, a facile and effective approach that can be used to overcome these disadvantages by introducing an aqueous carboxymethyl cellulose (CMC) binder is reported. The resulting conductive network serves to accelerate the diffusion of Na+ ions across the interface as well as in the bulk. The strong binding force of the CMC and stable solid permeable interface protect the electrode from degradation, leading to an excellent capacity of 75 mA h g−1 at an ultrahigh rate of 70 C (1 C = 128 mA g−1) and a long lifespan of 3500 cycles at 30 C while sustaining 79% of the initial capacity value. A full cell based on this electrode material delivers an impressive energy density as high as 216 W h kg−1, indicating the potential for application of this straightforward and cost‐effective route for the future development of advanced battery technologies.
Highlights
Energy storage plays an important role conduction, high working voltage, and favorable structural stability
The strong binding force of the carboxymethyl cellulose (CMC) and stable solid permeable interface protect the electrode from degradation, leading to an excellent capacity of 75 mA h g−1 at an ultrahigh rate of 70 C (1 C = 128 mA g−1) and a long lifespan of teries (LIBs), which are currently the storage technology of choice for portable electronic devices and electric vehicles; cost and safety issues remain two major obstacles that limit the use of LIBs in the smart grid
We have demonstrated a facile and effective route to improve both the rate capability and cycle stability of NVPF by using an aqueous CMC binder
Summary
The phase purity of pristine NVPF was first examined by powder X-ray diffraction followed by a Rietveld refinement analysis, as shown in Figure S1 (Supporting Information). SEM and TEM were used to observe the morphologies of different NVPF electrodes prepared by mixing together the active material, conductive carbon, and CMC or PVDF binders (denoted NVPF– CMC or NVPF–PVDF, respectively). The NVPF–CMC electrode shows a loose and porous structure (Figure 1a), which can favor electrolyte infiltration and the realization of sufficient electrochemically available interfaces and abundant ionic pathways;[8a] in contrast, the NVPF–PVDF electrode shows a more smooth and compact structure (Figure 1d). The stability of the cathode material with CMC was confirmed, as shown in Figure S4 (Supporting Information)
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