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Park et al. Energy Mater 2023;3:300005 https://dx.doi.org/10.20517/energymater.2022.65 Page 5 of 13

Figure 3. Schematic illustration of battery components, equivalent circuit model and Nyquist plot of the internal resistance of a Li-ion
battery. The diameters of the green and blue circles indicate R SEI and RCT, respectively. The yellow line indicates the Warburg
impedance in the low-frequency region.

conductivities of 6.0 × 10 -5.2 × 10 , 6.7 × 10 , 10 -10 and 1.2 × 10 S cm , respectively. The nature of the
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SEI can provide clues to achieving insights into dendritic Li growth. Table 1 summarizes the experimental
and theoretical values of the Li-ion conductivity of the SEI layer derived from various additives. The organic
phases of the SEI can accommodate part of the electrolyte, thereby enhancing the Li-ion conductivity.
STRATEGIES FOR MINIMIZING DENDRITIC LITHIUM GROWTH
Electrolyte additives
During Li plating and stripping, an organic electrolyte is decomposed into Li O, Li CO , LiF, LiOH and so
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on. These components have poor Li-ion conductivity at the interface with Li metal. These components
affect cell performance due to their low ionic conductivity. Instead of the natural SEI, a new strategic,
artificial SEI with high ionic conductivity is required to suppress dendritic Li growth. In addition, it is also
capable of inhibiting dendritic Li growth with high mechanical strength .
[12]
Interestingly, high ionic conductivity at the Li metal interface decreases the overpotential during Li plating
and stripping, thereby stabilizing the SEI. For this purpose, stable SEI components, such as Li N, lithium
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sulfide (Li S), lithium aluminate (LiAl O ), lithium phosphide (Li P) and ternary lithium aluminum fluoride
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(Li AlF ), have been developed using various combinations of Li additives. In particular, Li salts, including
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lithium nitrate (LiNO ) and Li S , are widely used to improve the interfacial stability of Li metal anodes in
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x y
ether-based electrolytes . In detail, LiNO decomposes into Li N and Li O, and Li N is the key component
[67]
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due to its high ionic conductivity (1.2 × 10 S cm ) for this purpose. Lithium bis(fluorosulfonyl)imide
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(LiFSI)-LiNO in a dimethyl ether electrolyte was found to minimize the dendritic Li growth. This is
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strongly related to the high ionic conductivity of the LiF- and Li N-rich SEI layers. Moon and co-workers
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reported a correlation between SEI thickness and ionic conductivity, as shown in Figure 4A. Regardless of
the thickness of the SEI, the Li N-rich SEI layer introduced a small potential change, resulting in uniform Li
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growth . In addition, a thicker Li N SEI layer causes higher ionic conductivity, although the LiNO
[37]
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additive has the feature of low solubility in carbonate-based electrolytes . Moreover, carbonate-based
[68]
electrolytes have stronger reactivity than ether-based ones toward Li metal.
Recently, significant efforts to use LiNO additives in carbonate-based electrolytes have been made to enable
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the adoption of high-voltage batteries. Even if LiNO is incompletely dissolved in a carbonate-based
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electrolyte, the highly concentrated LiNO additive in ethylene carbonate and diethyl carbonate yielded a
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stable SEI and outstanding cell performance during Li plating and stripping. Figure 4B summarizes the
solubility of the LiNO additive in different carbonate-based electrolytes . The maximum concentration of
[69]
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NO was investigated in different carbonate-based electrolytes through colorimetry by cadmium reduction
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