Selection of Sodium Salt Electrolyte Compatible with Na_0.67Ni_0.15Fe_0.2Mn_0.65O₂ Cathode for Sodium‐Ion Batteries

Abstract

The construction of an optimized electrolyte system compatible with layered transition metal (TM) oxides is of great importance to advanced sodium‐ion batteries (SIBs). Herein, a low‐cost iron‐containing manganese‐based layered cathode material of Na0.67Ni0.15Fe0.2Mn0.65O2 (N‐NFM) is prepared through an improved coprecipitation method. Then, the chemical properties of interfaces between the N‐NFM cathode and organic liquid electrolytes based on NaClO4 and NaPF6 are investigated, respectively. Results show that the cathode electrolyte interphase (CEI) film formed in the NaPF6‐based electrolyte is dense and uniform, which inhibits the dissolution of TM ions effectively and provides a low energy barrier for the transport of Na+. Apart from that the CEI film formed in the NaClO4‐based electrolyte contains more organic but less inorganic compounds, resulting in an increase in impedance. In addition, it is believed that the stability of the CEI film is susceptible to the perchlorate with strong oxidizing property. In this role, a small part of the CEI film falls from the cathode surface, accelerating the dissolution of TM ions and leading to the reactivation of electrolyte decomposition.

Cathode material stability enhancement for layered manganese-based sodium-ion batteries by doping titanium

“…The peak around 781 (002 plane) is significantly enhanced after 100 cycles for both samples, representing a characteristic peak of AI. 29 The XRD characterizations concluded that the cathode material structure is more stable for the doped titanium sample (NNM-Ti0.02) than the NNM sample. Fig.…”

“…It demonstrated that doping the titanium can be conducive to the migration of Na + . 29 In order to verify the contribution of titanium doping to the capacity of the batteries, a cyclic voltammetry test was performed. The peak area of NNM-Ti0.02 was the largest, which indicates that the material contributed the most capacity among other batteries under similar conditions.…”

A Hexafluorophosphate‐Based Ionic Liquid as Multifunctional Interfacial Layer between High Voltage Positive Electrode and Solid‐State Electrolyte for Sodium Secondary Batteries

“…X-ray photoelectron spectroscopy (XPS) disclosed the existence of a CEI on the NVPF surface (Figure S11, Supporting Information). This included prospective inorganic components such as fluoride and fluorophosphate derived from [PF 6 ] − , as well as organic compounds comprising C-C/C-H, C-O, C=O, and C-N. [8,50] It is crucial to mention that the sole source of N-containing constituents is [DEME] + , which underscores the advantageous nature of the IL. However, no associated component was evident on the BASE's surface, signifying that a redox reaction regarding passivation layer formation did not take place on it.…”

CEI Optimization: Enable the High Capacity and Reversible Sodium‐Ion Batteries for Future Massive Energy Storage

“…This resulted in more organic compounds and fewer inorganic compounds, with a decrease in the stability of the CEI. [87] Local high-concentration electrolytes have been extensively studied for lithium-ion batteries. [111,112] By contrast, relatively little research has been conducted on using local high-concentration electrolytes in sodium-ion batteries.…”

“…The NaPF 6 ‐based electrolyte was found to be more compatible with the cathode material, facilitating Na + transference. [ 87 ] A study by Ma et al showed that PC/EMC served as an optimized electrolyte formula. When combined with various additives, this optimized electrolyte could inhibit the chemical dissolution of transition metal ions in dehydrogenated (charged) NFM.…”