Change in characteristic FTIR peaks assigned to acrylic C=C bonds cm−1) of UV-polymerizable monomers in SSE. Structural characterization of SSE. a) SEM image of the SSE cross-section on the Li metal anode. Rheological properties of SSE paste (ie before UV curing) for multi-step printing. a) Viscosity as a function of shear rate (b) Viscoelastic properties (G′ and G″) as a function of shear stress.
Conceptual illustration depicting the ion transport phenomena of the control samples (C1, C2 and C3) and SSE. a) Room temperature ionic conductivity () and Li-ion transfer number (tLi+) of the SSE and control samples (C1, C2 and C3). Rheological properties of the NCM811 cathode paste (i.e. before the UV curing) for multi-stage printing. -temperature performance of the S-ASSLMBs. a) Charge/discharge voltage profiles of the S-ASSLMB as a function of operating temperature (−10 ~ 10°C).
Mechanical flexibility of the S-ASSLMBs. a) Photographs showing the bending (bending radius = 5 mm and strain rate = 30 mm min−1), winding and multiple folding of the SSE. Bipolar configuration of the S-ASSLMBs. a) Conceptual representation of the bipolar S-ASSLMBs with in-series configuration (1 → 4 cells).
Introduction
The three main concerns facing all-solid-state metal batteries: (1) low ionic conductivity, (2) electrode/electrolyte and particle interface, and (3) inhomogeneous metal deposition. Soft single-ion conducting electrolytes for solid-state lithium metal batteries operating at ambient conditions.
Single-ion conducting soft electrolytes for all-solid-state lithium metal batteries operating under
Research background
13.sulfonyl)imide (DADMA-TFSI)) and titanium/silica modified alumina nanoparticles (Ti-SiO2@Al2O3) in which ETPTA and DADMA-TFSI provide structural integrity and electrophoresis-driven ionic rectification (i.e. . anion trapping) effect 27-29 and Ti-SiO2@Al2O3. The matched electrolyte is 4M lithium bis(fluorosulfonyl)imide (LiFSI) in propylene carbonate (PC)/fluoroethylene carbonate (FEC), which exhibits electrochemical stability with Li metal anodes and high-voltage cathodes along with non-flammability30. The resulting SSE exhibits high ionic conductivity, a Li-ion transfer number close to unity (tLi+ = 0.91), a wide window of electrochemical stability (~ 6 V (compared to Li+/Li)), nonflammability, and mechanical flexibility.
To develop high-energy density ASSLMBs, a thin Li metal anode is coupled to a high-capacity/high-voltage LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode in the presence of SSE31. The soft feature of the SSE alleviates the concerns about grain boundary resistance and the interfacial instability of electrolyte electrodes that have long posed challenges in conventional ISEs. In addition, the single-ion conductivity of the SSE contributes to the stabilization of the interface of Li metal anodes with NCM811 cathodes.
Driven by the chemical/structural uniqueness of the SSE and monolithic full cell architecture described above, the ASSLMB (Li-metal anode/SSE/NCM811 cathode) exhibits reliable electrochemical performance, cyclic retention, speed capabilities, and bipolar configurations with tunable operating voltages (16.8) . V for 4-stacked cells) under ambient conditions. Furthermore, low-temperature performance, foldability, and safety far exceed those achievable with conventional inorganic electrolyte-based ASSLMBs.
Experimental section
- Synthesis of SSEs and fabrication of S-ASSLMBs at ambient conditions
- Physicochemical/electrochemical characterization of SSEs
- Electrochemical performance, flexibility, and safety of s-ASSLMBs
The rheological properties of NCM811 cathode paste and SSE paste were investigated using a rheometer (Haake MARS 3, Thermo Electron GmbH). The morphologies of the SSEs and their components were characterized using field emission scanning electron microscopy (S-4800, Hitachi) equipped with energy dispersive X-ray spectroscopy (EDS). The EIS of the Li||Li cells was recorded using a potentiostat (Classic VSP, Bio-Logic) in the frequency range 10−2 to 106 Hz.
After the cycling test, the surface morphology of the Li metal anode was analyzed using FE-SEM (S-4800, HITACHI). The morphology of the CEI layers on the NCM811 cathode was characterized by high-resolution transmission electron microscopy (HR-TEM) (JEM-2100F, JEOL). Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) was performed using a TOF-SIMS 5 (ION TOF) with a Bi32+ gun at 50keV to analyze NCM811 cathode byproducts.
A focused ion beam (FIB, Helios Nano Lab450, FEI) was used to analyze the cross-sectional structure of the NCM811 particles. The safety of the S-ASSLMB has been investigated under various harsh conditions (including horizontal cutting and exposure to flame).
Results and discussion
- Fabrication of the SSEs at ambient conditions
- Interfacial stability of the SSE with Li metal at ambient conditions
- Electrochemical performance of SSE-embedded ASSLMBs at ambient conditions
- Beyond conventional ASSLMBs
The ionic conductivity of SSE was evaluated as a function of temperature (varying from room temperature to 100°C). The beneficial effect of SSE was verified by analyzing the resistance of the cell after the cycle test (Figure 2.11d). Li (c) loading/undressing profiles and (d) EIS spectra of symmetric Li||Li cells with SSE and C1. e) SEM image (surface view) of the cycled Li metal (SSE vs.
We explored potential applications of the SSE on ASSLMBs under ambient conditions, focusing on the single-ion conduction characteristic. The obtained S-ASSLMB was characterized by the seamless integration of the Li metal anode, printed SSE and printed NCM811 cathode (Figure 2.12a). The cyclic NCM811 particles of the S-ASSLMB showed the formation of a thin cathode-electrolyte interphase (CEI) layer (~ 7 nm), compared to those of the control ASLMB which showed a thick CEI layer (~ 18 nm) (Figure 2.16a and 2.16b).
The cyclic NCM811 particles from S-ASSLMB maintained structural integrity, whereas those from control ASSLMB were severely cracked and disrupted (Figures 2.19 and 2.20). This SSE-driven beneficial effect on the NCM811 cathode, in combination with the stabilization of the Li metal anode (shown in Figure 2.11), enabled the improvement of the cycling performance of the S-ASSLMB. The faster rate performance of S-ASSLMB was verified by galvanostatic intermittent titration technique (GITT) analysis.
In addition, S-ASSLMB showed higher Li+ ion diffusion coefficients than control ASSLMB over the entire range of state of charge (SOC) and depth of discharge (DOD)38 (Figures 2.21c and 2.21d). TOF-SIMS mapping images (control ASLMB with C1 vs. S-ASSLMB with SSE) of the cycled NCM811 particles (after 100 cycles). The result of S-ASSLMB was compared with the results of previously reported ASSLMB whole cells (Table 2.3).
This excellent cell performance at low temperatures was verified by analyzing the EIS profiles of the cells. To investigate the mechanical flexibility of the S-ASSLMB, a pocket-type cell (length x width mm/mm) was fabricated. This exceptional safety of the S-ASSLMB is attributed to the non-flammable SSE (Figure 2.25c and 2.25d) made possible by the coordinated electrolyte (4M LiFSI in PC/FEC)31.
We investigated the feasibility of ASSLMB in bipolar cell configurations39 that can provide higher cell voltages.
Conclusions
High-energy long-cycling fully charged lithium metal batteries powered by silver-carbon composite anodes. Review of polymeric single lithium ion conductors as an organic route to all solid state lithium ion and metal batteries. Nonflammable lithium metal full cells with ultrahigh energy density based on coordinated carbonate electrolytes.
Construction of Silica-Oxygen-Borate Hybrid Networks on Al2O3-Coated Polyethylene Separators Realizing Multifunction for High-Performance Lithium-Ion Batteries. Revealing the correlation between structural evolution and Li+ diffusion kinetics of nickel-rich cathode materials in Li-ion batteries. Elucidation of the role of dopants in the critical current density for dendrite formation in garnet electrolytes.
Infiltration of solution-processable solid electrolytes into conventional Li-Ion battery electrodes for fully solid Li-Ion batteries. Slurry-fabricable Li+ conductive polymeric binders for practical all-solid lithium-ion batteries enabled by solvate ionic liquids. Behavior of lithium metal anodes under different capacity utilization and high current density in lithium metal batteries.
Low-temperature all-solid-state lithium-ion batteries based on a di-cross-linked starch solid electrolyte. Towards garnet electrolyte-based Li-metal batteries: an ultrathin, highly efficient artificial solid electrolyte/metallic Li interface.
Acknowledgements
