Internal and External Co‐Engineering of Stable Cathode Interface Improves Cycle Performance of Polymer Sodium Batteries

Abstract

The development of polymer sodium batteries requires cathode materials with stable interfaces to avoid poor interfacial contact and interfacial side reactions during cycling. Here, a co‐engineering strategy is deployed to tailor the cathode internal structure and improve the cathode interface stability through bonding interactions. Internally, the effect of low‐cost Fe substitution in the obtained Na0.67Mn2/3Fe1/3O2 cathode material renders favorable effects in several aspects. First, the increased lattice constant facilitates Na+ intercalation and thereby lowers the diffusion barrier of Na+ ions. Second, it increases the electronic conductivity, thereby improving the reaction reversibility. Third, the MnO bond length is shortened, which alleviates the Jahn‐Taylor effect and improves structural stability. In addition to these internal effects, the FeOB bond interactions due to Fe substitution promote the decomposition of the tris(trimethylsilane)borate additive and the formation of a dense and uniform cathode electrolyte interface film, leading to improved cycling stability. Owing to the co‐engineering of both internal structure and surface modification, the polymer solid‐state sodium battery with a stable interface exhibits a specific capacity of 85.2 mAh g‐1 after 800 cycles at 1 C.

Unlocking Charge Transfer Limitation in NASICON Structured Na3V2(PO4)3 Cathode via Trace Carbon Incorporation

“…Large electrochemical polarization of NVP (Figure 4a) and NVP/C (Figure 4b) is exhibited, and that of NVP/NCDs could be greatly restrained after carbon dot incorporation (Figure 4c). In addition, sodium-ion diffusion coefficient could be calculated based on the CV curves under different scan rates (Figure 4d; Table S6, Supporting Information) [49] and galvanostatic intermittent titration technique (GITT; Figure 4e,f; Figure S17, Supporting Information), [50][51][52] respectively. The sodium-ion diffusion coefficient of NVP/NCDs is much higher than that of NVP and NVP/C, confirming the much-improved electrochemical kinetics of NVP/NCDs after carbon dot incorporation.…”

Robust Artificial Interlayer with High Ionic Conductivity and Mechanical Strength toward Long‐Life Na‐Metal Batteries

“…Compared to lithium batteries, sodium (Na) batteries present a lot of advantages, including the costeffective and plenty of the raw materials. [14][15][16][17] Among the various anode candidates for Na batteries, the Na metal anode is considered as the eventual material, owing to its high theoretical capacity and low redox potential. [18][19][20][21] However, the metallic Na with high reactivity can react with the electrolyte to form a solid electrolyte interphase (SEI) on the Na surface.…”