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Shipitsyn et al. Energy Mater 2023;3:300038 https://dx.doi.org/10.20517/energymater.2023.22 Page 19 of 37

Table 10. Nitrogen-containing additives

Chemical name Ethoxy(pentafluoro)cyclotriphosphazene Acetamide (N, O-bis(trimethylsilyl) Diamondoid (bis-N,N’-propyl-4,9-
of the additive (EFPN) trifluoroacetamide (BSTFA) dicarboxamidediamantane (DCAD)
Chemical
structure of
additive

additive for carbonaceous anode additives. Compatibility testing of the EFPN with metallic sodium showed
no reactions. Oxidation current starts at 4.8V vs. Na/Na for 5% EFPN-added electrolyte in coin cells with
+
Na/stainless steel electrode.

[89]
Acetamide (N, O-bis(trimethylsilyl) trifluoroacetamide (BSTFA, Table 10) was found by Jiang et al. as a
promising additive for SIBs with a sodium metal anode. The main purpose of this additive is to scavenge HF
and H O. This additive was introduced into an ultra-low concentrated electrolyte of 0.3M NaPF + EC/PC
2
6
(1/1) to improve Na V (PO ) /Na cells. 2 wt.% BSTFA decreases the impedance of Na/Na symmetric cells
4 3
3
2
and keeps it constant even after 100 h of cycling. BSTFA helps to protect the sodium metal anode from
dendrite growth by creating a uniform and dense SEI. Moreover, this additive improves the electrochemical
performance by decreasing impedance and increasing capacity retention and CE of the Na V (PO ) /Na
4 3
3
2
cells.
Bis-N,N’-propyl-4,9-dicarboxamidediamantane (DCAD, Table 10) was used as an additive to avoid the
dendrite formation in SIBs with a sodium metal anode. Kreissl et al. showed that 2.5 mg/mL of DCAD
[90]
improves the performance of Na/Na symmetric cells and Na/O cells by stabilizing the surface of metallic
2
sodium.
Sulfur-containing additives
Sulfur-containing electrolytes were found to improve the sodium metal anode reversibility by forming
sulfur-containing SEI species (e.g., Na S, Na SO ). Diphenyl disulfide (DPDS, Table 11) is an organic
2
2
3
compound with a structure of di-Ph-S, which was tested by Zhu et al. as an additive to form a stable SEI
[91]
film and suppress the dendrite growth. They showed that an addition of 1% DPDS additive can maintain a
stable overpotential of Na/Na symmetric cells for more than 200 h of cycling. SEM data showed that DPDS
decomposes to Ph-S-Na and participates in the formation of a uniform and smooth SEI layer. Moreover,
Prussian blue/Na cells show a stable cycling performance with a 1% DPDS additive.

Tetramethylthiuram disulfide (TMTD, Table 11) was investigated by Zhu et al. as a film-forming additive
[92]
with organic sulfide salts. It was stated that the overpotential of Na/Na symmetric cells remains stable for
600 h of cycling in an electrolyte with 2 wt.% TMTD. Moreover, the electrolyte with 2 wt.% TMTD
improved the electrochemical performance of Prussian blue/Na full-cells with a high CE of 94.25% and
capacity retention of 80% after 600 cycles at 4C-rate.

[93]
DTD [Table 11] was used by Zhu et al. as an additive to form an SEI with the function of preventing
sodium dendrite growth. Na/Na symmetric cells keep a stable performance for > 1,350 h of cycling in an