Abstract Highly fluorinated electrolytes have proved effective in improving electrochemical stability of lithium metal batteries. However, excessive fluorination not only detrimentally impacts the electrolyte ionic conductivity, but also inevitably forms the over‐fluorinated interphases with sluggish ion diffusivity. Herein, a strategy on remodeling Li+ solvation structure in highly fluorinated electrolyte aided is proposed by fluorinated amide (FDMA), which denoted as “shielding agent”. Benefitting from FDMA's high donor number (DN) value (22.1), the Li+‐dipole (fluoroethylene carbonate (FEC) or trans‐4,5‐Difluoroethylenecarbonate (DFEC)) interaction is interrupted and the participation of FDMA in primary solvation sheath fructify the solid‐electrolyte interphase without scarifying the privilege of fluorinated electrolyte on interphase chemistry. Eventually, the optimal high‐fluorinated electrolyte (FDMA/DFEC + 1.0 mol L−1 LiTFSI) with this unique shielding effect displays high ionic conductivity and rapid Li+ desolvation behavior, enabling Li||LiNi0.6Co0.2Mn0.2O2 (Li||NCM622) to achieve an ultralong cycle‐life of 2000 cycles at 1C with 84.7% capacity retention. Even under extreme conditions (NCM622: 10 mg cm−2; electrolyte: 20 µL; Li: 50 µm), the Li||NCM622 displays excellent electrochemical performance. Additionally, 447 Wh kg−1 Li||LiNi0.8Co0.1Mn0.1O2 (Li||NCM811) pouch cells have been successfully fabricated and demonstrate an exceptional cycle‐life over 150 cycles. The proposed “shielding” strategy to modulate the solvation structure paves the way for developing practical LMBs with fluorinated electrolytes.

Solid-state electrolytes (SSEs) are essential materials in all -solid-state lithium -metal batteries. However, a comprehensive SSE possessing high ionic conductivity, broad electrochemical window, and high thermal stability remains elusive. In this work, a novel bi-phase SSE featuring a shape memory effect is developed by in -situ thermal cross -linking of 2 -ethyl cyanoacrylate (CA), polyethylene glycol methyl ether acrylate (PEGMEA), succinonitrile (SN), and fluoroethylene carbonate (FEC) additives. Due to the phase separation phenomenon and interfacial Li -ion conduction, the bi-phase SSE exhibits a room -temperature ionic conductivity of 1.9 mS cm( -1). Meanwhile, the bi-phase SSE exhibits a high oxidation potential of 4.9 V (vs Li/Li+), and a lithium -ion transference number (t(Li+)) of 0.56. Coupling with LiNi0.8Co0.1Mn0.1O2 (NCM 811) cathode and 11 mu m bi-phase SSE, solid-state lithium metal batteries (SSLMBs) demonstrate long-term cycling stability (capacity retention > 92% after 250 cycles), excellent rate performance (126 mA h g(-1) at 2 C, and high -voltage stability (208 mA h g(-1) at 4.5 V). This investigation demonstrates the potential of bi-phase SSEs as a promising material for the development of high-performance SSLMBs.

High Li+ transference number electrolytes have long been understood to provide attractive candidates for realizing uniform deposition of Li+. However, such electrolytes with immobilized anions would result in incomplete solid electrolyte interphase (SEI) formation on the Li anode because it suffers from the absence of appropriate inorganic components entirely derived from anions decomposition. Herein, a boron-rich hexagonal polymer structured all-solid-state polymer electrolyte (BSPE+10% LiBOB) with regulated intermolecular interaction is proposed to trade off a high Li+ transference number against stable SEI properties. The Li+ transference number of the as-prepared electrolyte is increased from 0.23 to 0.83 owing to the boron-rich cross-linker (BC) addition. More intriguingly, for the first time, the experiments combined with theoretical calculation results reveal that BOB− anions have stronger interaction with B atoms in polymer chain than TFSI−, which significantly induce the TFSI− decomposition and consequently increase the amount of LiF and Li3N in the SEI layer. Eventually, a LiFePO4|BSPE+10% LiBOB|Li cell retains 96.7% after 400 cycles while the cell without BC-resisted electrolyte only retains 40.8%. BSPE+10% LiBOB also facilitates stable electrochemical cycling of solid-state Li-S cells. This study blazes a new trail in controlling the Li+ transport ability and SEI properties, synergistically.

Boosting the energy density and safety issue of lithium-ion batteries (LIBs) have become ever more important to satisfy the diverse applications. Herein, we present a new high voltage polyether-based electrolyte (HVPEE) by molecular design that can endure high-voltage operations and also present non-flammable features. Especially, HPVEEs show better compatibility and stability with electrode than conventional electrolyte. We find that the solvent separated ion pair (SSIP) and contact ion pair (CIP) dominate the ion-solvent structure of HPVEEs, rather than the free solvent and ions. In this way, the oxidative decomposition of HPVEE on the cathode interface can be suppressed significantly due to the lower highest occupied molecular orbital of SSIP complex structure than that of free TFSI - . As a result, the oxidation voltage can achieve as high as 5.35 V when the ether group/Li is optimized at 10/1 in the HVPEE, enabling the LiFePO 4 //Li full cell deliver a capacity of 165 mA h g -1 with a capacity retention of 98 % after 200 cycles. Moreover, when the cut-off voltage is 4.4 V, the discharge capacity of the LiNi 0.6 Mn 0.2 Co 0.2 O 2 //Li full cell can still reach 143 mA h g -1 after 80 cycles.

Superior to conventional liquid electrolytes, incombustible ionic liquids (ILs) with wide electrochemical stability windows show privilege to endow quasi-solid-state electrolyte (QSE) with benign interfacial contact with both metallic Li and high-voltage cathode, which bodes well for implementation of high-performance solid-state Li metal battery. But regardless of its merits, the inherent high-viscosity and frail interphase chemistry of IL towards cathodes still jeopardize ionic conductivity within QSE and even crossing the interface, and should be overcame. Herein, we creatively introduce N, N-Dimethyltrifluoroacetamide (FDMAC) into QSE fabrication, design a quasi-solid-state electrolyte (QSE-EF) by hybridizing FDMAC/EMImFSI-based IL mixture and nano-LLZTO@PVDF-HFP. This FDMAC with well compatibility to IL, significantly decreases the viscosity but without sacrificing noncombustible feature. With the aid of FDMAC, QSE-EF exhibits fast ion-conducting and high Li+ transference number. More importantly, FDMAC also contributes to tuning interphase chemistry, and therefore, the high compatibilities of both QSE-EF|Li and QSE-EF|NCM622 interfaces are fulfilled involving profitable CEI&SEI establishment. Consequently, the assembled NCM622|QSE-EF|Li cell delivers outstanding electrochemical behaviors even at 4.4 V high voltage. 1.0 Ah NCM811||Li pouch cell also shows satisfactory energy density (350 Wh center dot kg(-1)) with negligible capacity loss. This work provides a feasible strategy to circumvent inherent defect of ionic liquid in QSE, and emphasizes the importance of tuning compatible interfacial chemistry in further QSE design.

Solid-state polymer electrolytes are outstanding candidates for next-generation lithium metal batteries in the realm of high specific energy densities, high safeties and tight contact with electrodes. However, their applications are still hindered by the limitations that no single polymer is electrochemically stable with the oxidizing high-voltage cathode and the highly reductive Li anode, simultaneously. Herein, a bilayer asymmetric polymer electrolyte (SL-SPE) without accessional interface resistance that using poly (ethylene glycol) diacrylate (PEGDA) as a “bridge” to connect the sulfonyl (OS = O)-contained oxidation-tolerated layer and polyether-derived reduction-tolerated layer (SPE), is proposed and synthesized by sequential two-step UV polymerizations. SL-SPE can provide widened electrochemical stability window up to 5 V, while simultaneously deploying a stable Janus interface property. Eventually, the superior high-voltage (4.4 V) cycling durability can be displayed in LiNi0.6Co0.2Mn0.2O2|SL-SPE|Li batteries. This finding provides a bran-new idea for designing multifunctional polymer electrolytes in the application of solid-state batteries.

Solid‐state batteries (SSBs) with addition of liquid electrolytes are considered to possibly replace the current lithium‐ion batteries (LIBs) because they combine the advantages of benign interfacial contact and strong barriers for unwanted redox shuttles. However, solid electrolyte and liquid electrolyte are generally (electro)‐chemically incompatible and the resistance of the newly formed solid–liquid electrolyte interphase (SLEI) appears as an additional contribution to the overall battery resistance. Herein, a boron, fluorine‐donating liquid electrolyte (B, F‐LE) is introduced into the interface between the high‐voltage cathode and ultrathin composite solid electrolyte (CSE), which is fabricated by adhering a high content of nanosized Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) with poly(vinylidene fluoride‐ co ‐hexafluoropropylene) (PVDF‐HFP), to generate a low resistance and high stable SLEI in situ, giving a stable high‐voltage output with a reinforced cathode|CSE interface. B, F‐LE, consisting of a highly fluorinated electrolyte with a lithium bis(oxalato)borate additive, exhibits good chemical compatibility with CSE and enables rapid and uniform transportation of Li + , with its electrochemically and chemically stable interface for high‐voltage cathode. Eventually, the B, F‐LE assisted LiNi 0.6 Co 0.2 Mn 0.2 O 2 |Li battery displays the enhanced rate capability and high voltage cycling stability. The findings provide an interfacial engineering strategy to turn SLEI from a “real culprit” into the “savior” that may pave a brand‐new way to manipulate SLEI chemistry in hybrid solid–liquid devices.