Interphases in Sodium‐Ion Batteries

Abstract

search for alternative high energy batteries using abundant and low cost materials is imperative. [2] Sodium ion batteries (SIBs), which as LIBs' close analogy was first explored in the 1980s, have regained substantial spotlights for their great potential as beyond/ post lithium battery chemistry in lowcost electrical energy storage (EES) systems. [3] Being in the same alkaline group with Li, Na chemistry/electrochemistry bears many similarities to Li, hence the SIB development naturally follows the track of success left by LIBs. A variety of cathode/anode pairs and electrolyte have been explored within a short period of time and some of them have been proven to be potentially practical for SIBs. [4] With the understanding deepened, however, it becomes clear that the choice of electrode materials in SIBs and LIBs and their corresponding performance have much less in common than expected, and in many cases even contradictory to each other despite the similarity of the intercalation chemistry between Na-ions and Li-ions.Among the implications ensuing from such differences, the uniqueness of electrode/electrolyte interphases in SIBs profoundly affects the SIBs performances and has not been thoroughly investigated. Such interphases, also known as SEI on anode surface or cathode electrolyte interphase (CEI) on cathode surface, are to a great extent dictated by the chemistry and electrochemistry of Na salts dissolved in aprotic solvent molecules. After the solid electrolyte interphase (SEI)/CEI formation in the initial cycles of SIBs, their chemical/electrochemical reactivity/stability will determine the reversibility and rate of the cell reactions for the rest of the cell life. Solid Electrolyte InterphaseIn battery systems of high voltages such as LIBs, the electrodes operate at potentials outside of the thermodynamic stability limits of the electrolyte. In some cases (but not all), an interphase forms at the interface between electrode (cathode/anode) and electrolyte at the decomposition of the latter, which prevents parasitic reactions and kinetically stabilizes the system. Figure 1A shows a simplified schematic illustration of the anode/cathode surface in LIBs/SIBs with SEI/CEI configuration. The Li/Na ions transport in the bulk electrolyte in the form of solvated ions, and must go through a desolvation process to pass these SEI/CEI into the electrode. Early notions of an ideal SEI layer must possess the general attributes such as: (1) an Sodium-ion batteries (SIBs) as economical, high energy alternatives to lithiumion batteries (LIBs) have received significant attention for large-scale energy storage in the last few years. While the efforts of developing SIBs have benefited from the knowledge learned in LIBs, thanks to the apparent proximity between Na-ions and Li-ions, the unique physical and chemical properties of Na-ions also distinctly differ themselves from Li-ions. It is expected that SIBs have drastically different electrode material structure, solvation-desolvation behavior, electrode-electrolyte interp...

Hard Carbon as Sodium‐Ion Battery Anodes: Progress and Challenges

“…Electrolyte with cyclic carbonate, including propylene carbonate (PC) and ethylene carbonate (EC); linear carbonate, including dimethyl carbonate (DMC), diethylene carbonate (DEC), ethyl methyl carbonate (EMC); and ethers have been thoroughly investigated in LIBs . The electrolyte decomposes on carbon anodes at low voltage and the decomposition product forms a layer termed the SEI, which is a critical prerequisite for high performance in LIBs.…”

“…As shown in Figure c, although TEGDME was found to form very little SEI, it was still only able to achieve an ICE of 72 %. Irreversible defect binding, pore filling, and so forth are responsible for this loss, and hence, a method of compensation it is essential for full‐cell tests . Precycling of the HC electrode for several cycles prior to full‐cell assembly is proven to boost the full‐cell performance .…”

Lithium‐Pretreated Hard Carbon as High‐Performance Sodium‐Ion Battery Anodes

“…[8] Delicate control of the HC defects and surface area is therefore particularly required. [5,10,11] Concerning this, attempts also have been made to tune the SEI coverage, thickness, stability, and ionic conductivity, etc., by developing novel electrolytes or electrolyte additives that decompose preferentially to form SEI or tailoring the surface area and physiochemical properties of the carbon materials. [5,10,11] Concerning this, attempts also have been made to tune the SEI coverage, thickness, stability, and ionic conductivity, etc., by developing novel electrolytes or electrolyte additives that decompose preferentially to form SEI or tailoring the surface area and physiochemical properties of the carbon materials.…”

“…[5,9] It is known that the electrochemical reversibility and the rate and life performance of LIBs and SIBs are to a great extent dictated by the SEI formation and its chemical/electrochemical reactivity and stability. [10][11][12][13] Ether-based electrolyte has been extensively used in lithium-air and lithiumsulfur batteries. [10][11][12][13] Ether-based electrolyte has been extensively used in lithium-air and lithiumsulfur batteries.…”

Enhanced Interfacial Kinetics of Carbon Monolith Boosting Ultrafast Na‐Storage

“…Remarkably, the sodium charge storage performances are mainly limited by the transport of Na + and interfacial kinetics. It ought not to ignore that the formation of solid electrolyte interface (SEI) film and its electrochemical stability influence the ion diffusion rate and thus determine the cyclic stability and rate performance of charge storage . Nevertheless, the correlation between interfacial charge transport behavior and the resulted electrochemical properties of advanced SIB anode in the initial cycle has not been studied in depth until now .…”