depositing/stripping process because of the unstable solid electrolyte interphase (SEI) layer, [2,3,6,7] leading to low Coulombic efficiency (CE), short life span, and in the worst cases, explosion. [8,9] To avoid this scenario, a high-quality SEI layer is essential.In recent reports, various strategies have been employed to enable LMB performance. Substantial attempts have been made to form a stable SEI layer on the Li anode, such as adding additives, [10][11][12][13][14] using a high-concentration electrolyte (HCE) and localized high concentration, [3,6,[15][16][17][18] combining multiple lithium salts, [1,15,19,20] and employing new organic solvents or lithium salts. [21][22][23][24] Recently, HCEs have been regarded as advanced LMB electrolytes. In HCEs, salt anions enter the solvation sheath to form associated states such as contact ion pairs (CIPs) and aggregates (AGGs) because of the scarcity of solvent molecules; hence, a stable and conductive SEI layer is mainly derived from the decomposition of Li salts. [6,25] The high concentration (10.0 m) lithium bis(fluorosulfonyl) imide (LiFSI) in dimethyl carbonate (DMC) enables interphases with high fluorine (F) content on both the Li metal anode and LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622) cathode surfaces. [3] Consequently, the 10.0 m LiFSI-DMC electrolyte exhibits a high Li CE of 99.3%, effectively suppressing the Li dendrite formation and stabilizing the carbonate molecules against oxidation at high cut-off voltages of 4.6 V on the surface of NMC622. A new class of "solvent-in-salt" was developed containing a high concentration of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) (>7.0 mol per liter of solvent) in 1,3-dioxolane (DOL)/1,2-dimethoxyethane (DME) (1:1 by volume) that inhibits the dissolution of polysulfide in Li-S batteries and also protects the Li metal anode by preventing the growth of Li dendrites. [18] Yu et al. proposed a concentrated electrolyte with lithium difluoro(oxalate)borate (LiODFB) in DME, which enables good cycling of Li metal anode at high CEs (up to 98.1%) without dendrite growth. [26] Jiao et al. developed an ether-based electrolyte system composed of concentrated dual lithium salts (LiTFSI and LiODFB) and DME, which forms a stable SEI layer on both the Li metal anode and the LiNi 1/3 Mn 1/3 Co 1/3 O 2 cathode, resulting in a capacity retention of 90% after 300 cycles (at a high voltage of 4.3 V). [1] Our group developed an ether-based electrolyte system composed of concentrated bisalt Lithium metal is a promising anode material for lithium metal batteries (LMBs). However, dendrite growth and limited Coulombic efficiency (CE) during cycling have prevented its practical application in rechargeable batteries. Herein, a highly concentrated electrolyte composed of an ether solvent and lithium bis(fluorosulfonyl)imide (LiFSI) salt is introduced, which enables the cycling of a lithium metal anode at a high CE (up to ≈99%) without dendrite growth, even at high current densities. Using 3.85 m LiFSI in tetrahydrofuran (THF) as the electr...

Lithium metal batteries (LMBs) have the potential to deliver a greater specific capacity than any commercially used lithium battery. However, excessive dendrite growth and low Coulombic efficiencies (CEs) are major hurdles preventing the commercialization of LMBs. In this study, two different salts, lithium difluorophosphate (LiDFP) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), are chosen for use in concentrated electrolytic systems. By mixing salts with vastly different cation–anion interaction energies, the ion solvation structures in the electrolyte can be modulated to enhance the physical/electrochemical properties and suppress Li dendrite growth in LMBs. Among the investigated electrolyte systems, 2.2 m LiDFP + 1.23 m LiTFSI in 1,2‐dimethoxyethane is proposed as a highly promising electrolyte system because of its high conductivity (6.57 mS cm−1), CE (98.3%), and the formation of an extremely stable solid–electrolyte interface layer. The bisalt electrolyte presented herein, as well as the associated concepts, provide a new avenue toward commercial LMBs.

Next-generation highenergy-density battery systems require improvement to handle this market gap. On the anode side, lithium (Li) metal is considered an ideal anode material for high-energy-density rechargeable batteries because of its ultrahigh theoretical specific capacity (3860 mAh g −1 ) and considerably low standard electrochemical redox potential (−3.040 V vs standard hydrogen electrode). [2] On the cathode side, the state-of-the-art high-voltage Ni-rich LiNiare the most promising cathodes because of their high specific capacities, low costs, and low Co contents. [4][5][6][7][8] NMC811 exhibits a specific capacity of over 200 mAh g −1 , considerably higher than those of LiFePO 4 (LFP, 170 mAh g −1 ) or other NMC cathode materials, such as NMC333 (160 mAh g −1 ) and NMC622 (185 mAh g −1 ). Hence, a Li metal battery (LMB) system comprising Li metal as the anode and NMC811 as the cathode is expected to possess specific energy, exceeding 500 Wh kg −1 on the cell level, practically 1.5 times higher than those of LIBs currently applied in electric vehicles. [4] The development of these high-voltage LMBs is challenging because of the high reactivity of electrolytes with the Li metal anode and NMC cathode.Regarding the anode, a solid electrolyte interphase (SEI) is formed on the surface of the Li anode by reactions between the Li metal and organic electrolyte and acts as a protective barrier. However, the SEI can break during cycling, leading to several issues: 1) "dead Li" formation, 2) volume expansion and morphological changes, 3) dendritic growth, 4) low coulombic efficiency (CE), and 5) short lifespan. [1,3,9,10] Therefore, a stable SEI layer is required to enhance LMBs. Regarding the cathode, highly reactive transition-metal ions (particularly Ni-rich cathodes) formed in a delithiated state at high voltages can cause severe unwanted reactions with electrolytes. [7,8,11] These reactions are considered to be the main cause of the degradation of NMC cathodes. [12] The cathode electrolyte interphase (CEI) layer plays a crucial role in suppressing unwanted reactions between the catalytically active cathode and organic electrolytes. To deal with the aforementioned issues, extensive strategies have been recently devoted to forming stable SEI/CEI layers Li metal batteries (LMBs) are ideal candidates for future high-energy-density battery systems. To date, high-voltage LMBs suffer severe limitations because of electrolytes unstable against Li anodes and high-voltage cathodes. Although ether-based electrolytes exhibit good stability with Li metal, compared to carbonate-based electrolytes, they have been used only in ≤4.0 V LMBs because of their limited oxidation stability. Here, a high concentration electrolyte (HCE) comprising lithium bis(fluorosulfonyl)imide (LiFSI) and a weakly solvating solvent (1,2-diethoxyethane, DEE) is designed, which can regulate unique solvation structures with only associated complexes at relatively lower concentration compared to the reported HCEs. This effectively suppresses dendrites on t...

Inverted type perovskite solar cells (PSCs) have recently emerged as a major focus in academic and industrial photovoltaic research. Their multiple advantages over conventional PSCs include easy processing, hysteresis‐free behavior, high stability, and compatibility for tandem applications. However, the maximum power conversion efficiency (PCE) of inverted PSCs still lags behind those of conventional PSCs because suitable charge‐selective materials for inverted PSCs are limited. In this study, excellent hole‐selective materials for inverted PSCs are introduced. A series of tricyclic aromatic rings containing O, S, or Se, respectively, as a core heteroatom, along with a phosphonic acid anchor, form a self‐assembled monolayer (SAM) that directly contacts the perovskite absorber. The influence of heteroatoms in the aromatic structure on the molecular energetics and operating characteristics of the corresponding inverted PSCs is investigated using complementary experimental techniques as well as density functional theory (DFT) calculations. It is found that all of the SAMs formed an energetically well‐aligned interface with the perovskite absorber. The interaction energy between the Se‐containing SAM and perovskite absorber is the strongest among the series and it reduces the interfacial defect density, in turn leading to an extended charge carrier lifetime. As a result, PSCs incorporating the Se‐containing SAM achieves a PCE of 22.73% and retains ≈96% of their initial efficiency after a maximum power point tracking test of 500 h without encapsulation under ambient conditions. All of the SAMs are then employed in organic solar cells (OSCs). Again, the Se‐containing SAM‐based OSCs demonstrates the highest PCE of 17.9% among the three molecular SAM‐based OSCs. This study demonstrates the great potential for precisely engineered SAMs for use in high‐performance solar cells.

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