Abstract
Sodium-ion batteries (SIBs) have been heralded as the most promising “beyond lithium” energy storage technology. This proclamation is based on recent technological trends and the outstanding performance of the state-of-the-art prototype 18650 and pouch cells. However, improving the design and performance of SIBs requires an in-depth understanding of the electrochemical behavior of the electrodes from both an experimental and physics-based modeling perspective. In this contribution, experimental characterizations of SIB electrode materials based on Na3V2(PO4)2F3 (NVPF) cathode and hard carbon (HC) anode are presented. The goal of this experimental investigation is to understand the individual electrode behavior and further elucidate relevant parameters for physics-based models. As a result, geometric, thermodynamic, and kinetic parameters are deduced from the two SIB electrodes. Based on the analyses of Na//NVPF and Na//HC half-cells, diffusion mass transport limitations and Ohmic losses are identified for both electrodes. These overpotential losses are equally present in full cell SIBs composed of NVPF and HC electrodes. These results are useful in the setup of SIB physics-based models.
Highlights
Sodium-ion batteries (SIBs) are an emerging class of rechargeable batteries, which have been proclaimed as the most viable complementary technology to the ubiquitous lithium-ion batteries (LIBs) [1,2,3]
Scanning electron microscopy (SEM) micrographs obtained on Quanta FEG 650 (FEI, USA) environmental Scanning Electron Microscopy (SEM) operated at a voltage of 20 kV were used to analyze the morphology of the Na3V2(PO4 )2F3 (NVPF) and hard carbon (HC) electrodes as well as the 25 μm FS 3005–25 separator (Freudenberg Viledon)
The subscript θ symbolizes the phase of the variable, which can either be in the solid phase (θ = 1) or in liquid/electrolyte phase (θ = 2) and the subscript m symbolizes the cell domain, which can either be the positive NVPF electrode (m = p), the negative HC electrode (m = n) or the separator (m = s)
Summary
Sodium-ion batteries (SIBs) are an emerging class of rechargeable batteries, which have been proclaimed as the most viable complementary technology to the ubiquitous lithium-ion batteries (LIBs) [1,2,3]. Na3V2(PO4)2F3 (NVPF) cathode and HC anode [13] This battery was first developed via the collaboration of the French National Center for Scientific Research (CNRS), Alternative Energies and Atomic Energy Commission (CEA), and the Collège de France, under the umbrella of the French network for electrochemical energy storage (RS2E) [10]. Eq (1) is a general electrochemical half-reaction showing the reversible exchange of 2 Na+ per formula unit in NVPF This results in a theoretical capacity of 128 mAh g−1, which makes NVPF one of the most stable and high energy dense SIB cathode materials [2]. HC achieves an impressively high specific capacity of about 300 mAh g−1 which approximates to that of graphite in LIBs. In this work, the experimental methods applied to both NVPF and HC electrodes are described, in order to derive parameters for physics-based, pseudo-two-dimensional (P2D) modeling. Because battery manufacturers do not typically provide the requisite extensive parameter set, these experimental characterizations are necessary complementary tools to enable accurate P2D modeling
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