Stable Cycling of All-Solid-State Lithium Batteries Enabled by Cyano-Molecular Diamond Improved Polymer Electrolytes
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-06-17 |
| Journal | Nano-Micro Letters |
| Authors | Yang Dai, Mengbing Zhuang, Yi-Xiao Deng, Yuan Liao, Jian Gu |
| Institutions | Shanghai University, Beijing Institute of Technology |
| Citations | 16 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThe research details the use of 1-adamantanecarbonitrile (ADCN) as a novel cyano-molecular diamond additive to significantly enhance the performance and interfacial stability of poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) for all-solid-state lithium metal batteries (ASSBs).
- Enhanced Ionic Performance: ADCN acts as a plasticizer, weakening the Li+-EO coordination and improving Li+ conductivity to 1.44 x 10-4 mS cm-1 at 45 °C, a 7-fold increase over the baseline SPE.
- Interfacial Stabilization: The additive promotes the formation of dense, LiF-rich solid electrolyte interphases (SEI and CEI) on both the lithium anode and the high-voltage cathode, crucial for long-term cycling stability.
- Mechanical and Dendrite Suppression: The rigid C10H15 âdiamond blockâ structure of ADCN crosslinks the polymer matrix, increasing the tensile strength to 5.1 MPa and effectively suppressing lithium dendrite growth.
- Anode Longevity: Li/Li symmetric cells using the optimized ADCN-SPE demonstrated stable lithium plating/stripping for over 2000 hours, with a high critical current density (CCD) of 1.1 mA cm-2.
- High-Voltage Cycling: The resulting ASSBs coupled with high-voltage NMC811 cathodes achieved stable cycling for 1000 times at 4.3 V and 45 °C, maintaining an impressive 80% capacity retention.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Optimal ADCN Loading | 5 | wt% PEO | LiTFSI/P(EO)14/ADCN-2 SPE |
| Ionic Conductivity (45 °C) | 1.44 x 10-4 | mS cm-1 | ADCN-2 SPE (7x higher than baseline) |
| Li+ Transference Number (tLi+) | 0.38 | N/A | ADCN-2 SPE (vs. 0.25 baseline) |
| Electrochemical Stability Window | 5.0-5.5 | V vs. Li/Li+ | ADCN-based SPEs (vs. 4.5 V baseline) |
| Critical Current Density (CCD) | 1.1 | mA cm-2 | Li/SPE/Li symmetric cell (ADCN-2) |
| Li/Li Symmetric Cycling Stability | >2000 | h | At 45 °C |
| Tensile Strength (Optimal) | 5.1 | MPa | ADCN-2 SPE (vs. 1.3 MPa baseline) |
| LFP/Li Cycling Performance | 1000 | cycles | 85% capacity retention at 0.3 C, 45 °C |
| NMC811/Li Cycling Performance | 1000 | cycles | 80% capacity retention at 0.3 C, 4.3 V, 45 °C |
| LiTFSI F- Dissociation Energy | Reduced from 9.33 to 8.83 | eV | Promoted by ADCN (DFT calculation) |
| Cathode Degradation Indicator (I003/I104) | 1.312 | N/A | Cycled ADCN-2 cathode (vs. 0.619 baseline) |
Key Methodologies
Section titled âKey Methodologiesâ-
SPE Membrane Preparation:
- PEO (Mw â 600,000) and LiTFSI (EO:Li ratio of 14:1) were dissolved in anhydrous acetonitrile (AN).
- ADCN was added at various concentrations (1, 5, and 10 wt% PEO).
- Membranes were formed via solvent-casting onto a polytetrafluoroethylene (PTFE) plate and dried under vacuum at 80 °C for 36 h.
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Electrochemical Characterization:
- Ionic conductivity was measured using Stainless Steel (SS) symmetric cells via Electrochemical Impedance Spectroscopy (EIS) across a temperature range (20 to 80 °C).
- Electrochemical stability was determined by Linear Sweep Voltammetry (LSV) at 1 mV s-1, scanning from 2.5 V to 6 V.
- Li/Li symmetric cells were tested for long-term plating/stripping stability and Critical Current Density (CCD).
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ASSB Assembly and Testing:
- Cathode slurries (LFP or NMC811, conductive carbon, SPE, and PVDF binder) were cast onto aluminum foil.
- ASSBs were assembled in 2032 coin cells using the cathode, ADCN-SPE, and lithium metal anode.
- Cycling performance was evaluated at 45 °C, primarily at 0.3 C, with a high cut-off voltage of 4.3 V for NMC811 cells.
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Interfacial and Structural Analysis:
- Structural properties were analyzed using X-ray Diffraction (XRD) and Fourier-Transform Infrared Spectroscopy (FTIR).
- Interfacial composition (SEI/CEI) was studied post-cycling using X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) to map species like LiF2- and C10H15-.
- Solid-state 6Li MAS NMR spectra were used to quantify the mobile Li+ content within the SPE.
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Computational Modeling:
- Density Functional Theory (DFT) calculations (CP2K program, MNDO method) were performed to model the dissociation energy of LiTFSI molecules, both alone and in the presence of ADCN, to elucidate the mechanism of LiF formation.
Commercial Applications
Section titled âCommercial ApplicationsâThe development of high-performance, stable solid polymer electrolytes capable of operating with high-voltage cathodes and lithium metal anodes is critical for next-generation battery technology.
- High-Energy Electric Vehicles (EVs): The ability to cycle NMC811 (4.3 V) for 1000 cycles at 45 °C enables the use of high-nickel cathodes, significantly increasing the energy density and range of EVs while improving safety compared to liquid electrolytes.
- Grid and Stationary Energy Storage: The exceptional long-term stability (1000 cycles, 85% retention for LFP/Li) and inherent safety of ASSBs make this technology ideal for large-scale, reliable energy storage systems.
- Flexible and Wearable Electronics: PEO-based SPEs offer excellent flexibility and processability, allowing for the design of safer, non-flammable batteries for flexible devices.
- Advanced Lithium Metal Anodes: The use of the C10H15 âdiamond blockâ structure provides a robust, mechanically strong SEI, addressing the primary challenge of lithium dendrite growth in high-current lithium metal batteries.
- High-Voltage Battery Components: This methodology provides a general strategy for stabilizing PEO electrolytes against oxidative degradation, opening pathways for coupling them with other high-voltage cathode materials (e.g., lithium-rich or spinel structures).
View Original Abstract
Abstract The interfacial instability of the poly(ethylene oxide) (PEO)-based electrolytes impedes the long-term cycling and further application of all-solid-state lithium metal batteries. In this work, we have shown an effective additive 1-adamantanecarbonitrile, which contributes to the excellent performance of the poly(ethylene oxide)-based electrolytes. Owing to the strong interaction of the 1-Adamantanecarbonitrile to the polymer matrix and anions, the coordination of the Li + -EO is weakened, and the binding effect of anions is strengthened, thereby improving the Li + conductivity and the electrochemical stability. The diamond building block on the surface of the lithium anode can suppress the growth of lithium dendrites. Importantly, the 1-Adamantanecarbonitrile also regulates the formation of LiF in the solid electrolyte interface and cathode electrolyte interface, which contributes to the interfacial stability (especially at high voltages) and protects the electrodes, enabling all-solid-state batteries to cycle at high voltages for long periods of time. Therefore, the Li/Li symmetric cell undergoes long-term lithium plating/stripping for more than 2000 h. 1-Adamantanecarbonitrile-poly(ethylene oxide)-based LFP/Li and 4.3 V Ni 0.8 Mn 0.1 Co 0.1 O 2 /Li all-solid-state batteries achieved stable cycles for 1000 times, with capacity retention rates reaching 85% and 80%, respectively.