High-capacity sodium (Na) anodes suffer from dendrite growth due to the high reactivity, which can be overcome through inducing a stable NaF-rich solid electrolyte interphase (SEI). Herein, we propose an additive strategy for realizing the anion-enriched structure of Na + solvation to obtain a NaF-rich SEI. The electron-withdrawing acetyl group in 4-acetylpyridine (4-APD) increases the coordination number of PF 6 À in the Na + solvation sheath to facilitate PF 6 À to decompose into NaF. Thus, the NaF-rich SEI with high mechanical stability and interfacial energy is formed to repress the growth of Na dendrites. With the 4-APD-contained electrolyte, the symmetric Na j j Na cells show excellent cycling performance over 360 h at 1.0 mA cm À 2 . Meanwhile, excellent stability is also achieved for Na j j Na 3 V 2 -(PO 4 ) 2 O 2 F full cells with high Coulombic efficiency (97 %) and capacity retention (91 %) after 200 cycles.

NaF‐rich electrode–electrolyte interphases play crucial roles in determining the cycling stability of sodium metal batteries (SMBs) because of their electronic insulation and mechanical stability. In this work, perfluorobenzene (PFB) is proposed as the additive to contribute the formation of NaF‐rich solid electrolyte interphases (SEI). PFB at the periphery of the solvation layer can pull out a part of the EC with the lowest solvation energy by Van der Waals forces, thus allowing more to participate in the Na+ solvation layer and form an anion‐aggregated solvation sheath, thus promoting the decomposition of to produce NaF. In addition, PFB has a higher highest occupied molecular orbital and lower lowest unoccupied molecular orbital energy level, which also preferentially decomposes to produce NaF at both electrodes. Benefiting from the intensified NaF ratio in SEI, the Na||Na symmetric cells with such an electrolyte achieves a superior cycling life over 350 h at 1 mA cm−2, and the Na||Na3V2(PO4)2O2F batteries also realize ultrahigh cycling performance with 88.8% capacity retention after 500 cycles.

Tailoring inorganic components of cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI) is critical to improving the cycling performance of lithium metal batteries. However, it is challenging due to complicated electrolyte reactions on cathode/anode surfaces. Herein, the species and inorganic component content of the CEI/SEI is enriched with an objectively gradient distribution through employing pentafluorophenyl 4‐nitrobenzenesulfonate (PFBNBS) as electrolyte additive guided by engineering bond order with functional groups. In addition, a catalytic effect of LiNi0.6Mn0.2Co0.2O2 (NCM622) cathode is proposed on the decomposition of PFBNBS. PFBNBS with lower highest occupied molecular orbital can be preferentially oxidized on the NCM622 surface with the help of the catalytic effect to induce an inorganic‐rich CEI for superior electrochemical performance at high voltage. Moreover, PFBNBS can be reduced on the Li surface due to its lower lowest unoccupied molecular orbital , increasing inorganic moieties in SEI for inhibiting Li dendrite generation. Thus, 4.5 V Li||NCM622 batteries with such electrolyte can retain 70.4% of initial capacity after 500 cycles at 0.2 C, which is attributed to the protective effect of the excellent CEI on NCM622 and the inhibitory effect of its derived CEI/SEI on continuous electrolyte decomposition.

Lithium metal batteries (LMBs) comprising Li metal anode and high-voltage nickel-rich cathode could potentially realize high capacity and power density. However, suitable electrolytes to tolerate the oxidation on the cathode at high cut-off voltage are urgently needed. Herein, we present an armor-like inorganic-rich cathode electrolyte interphase (CEI) strategy for exploring oxidation-resistant electrolytes for sustaining 4.8 V Li j j LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) batteries with pentafluorophenylboronic acid (PFPBA) as the additive. In such CEI, the armored lithium borate surrounded by CEI up-layer represses the dissolution of inner CEI moieties and also improves the Li + conductivity of CEI while abundant LiF is distributed over whole CEI to enhance the mechanical stability and Li + conductivity compared with polymer moieties. With such robust Li + conductive CEI, the Li j j NCM622 battery delivered excellent stability at 4.6 V cut-off voltage with 91.2 % capacity retention after 400 cycles. The excellent cycling performance was also obtained even at 4.8 V cut-off voltage.

High-capacity sodium (Na) anodes suffer from dendrite growth due to the high reactivity, which can be overcome through inducing a stable NaF-rich solid electrolyte interphase (SEI). Herein, we propose an additive strategy for realizing the anion-enriched structure of Na + solvation to obtain a NaF-rich SEI. The electron-withdrawing acetyl group in 4-acetylpyridine (4-APD) increases the coordination number of PF 6 À in the Na + solvation sheath to facilitate PF 6 À to decompose into NaF. Thus, the NaF-rich SEI with high mechanical stability and interfacial energy is formed to repress the growth of Na dendrites. With the 4-APD-contained electrolyte, the symmetric Na j j Na cells show excellent cycling performance over 360 h at 1.0 mA cm À 2 . Meanwhile, excellent stability is also achieved for Na j j Na 3 V 2 -(PO 4 ) 2 O 2 F full cells with high Coulombic efficiency (97 %) and capacity retention (91 %) after 200 cycles.