PVDF/Palygorskite Nanowire Composite Electrolyte for 4 V Rechargeable Lithium Batteries with High Energy Density.
basic_science · Level V
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- Record sourced from PubMed, PMID 30169958.
- Also identified by DOI 10.1021/acs.nanolett.8b01421.
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Abstract
Solid electrolytes are crucial for the development of solid state batteries. Among different types of solid electrolytes, poly(ethylene oxide) (PEO)-based polymer electrolytes have attracted extensive attention owing to their excellent flexibility and easiness for processing. However, their relatively low ionic conductivities and electrochemical instability above 4 V limit their applications in batteries with high energy density. Herein, we prepared poly(vinylidene fluoride) (PVDF) polymer electrolytes with an organic plasticizer, which possesses compatibility with 4 V cathode and high ionic conductivity (1.2 × 10<sup>-4</sup> S/cm) at room temperature. We also revealed the importance of plasticizer content to the ionic conductivity. To address weak mechanical strength of the PVDF electrolyte with plasticizer, we introduced palygorskite ((Mg,Al)<sub>2</sub>Si<sub>4</sub>O<sub>10</sub>(OH)) nanowires as a new ceramic filler to form composite solid electrolytes (CPE), which greatly enhances both stiffness and toughness of PVDF-based polymer electrolyte. With 5 wt % of palygorskite nanowires, not only does the elastic modulus of PVDF CPE increase from 9.0 to 96 MPa but also its yield stress is enhanced by 200%. Moreover, numerical modeling uncovers that the strong nanowire-polymer interaction and cross-linking network of nanowires are responsible for such significant enhancement in mechanically robustness. The addition of 5% palygorskite nanowires also enhances transference number of Li<sup>+</sup> from 0.21 to 0.54 due to interaction between palygorskite and ClO<sub>4</sub><sup>-</sup> ions. We further demonstrate full cells based on Li(Ni<sub>1/3</sub>Mn<sub>1/3</sub>Co<sub>1/3</sub>)O<sub>2</sub> (NMC111) cathode, PVDF/palygorskite CPE, and lithium anode, which can be cycled over 200 times at 0.3 C, with 97% capacity retention. Moreover, the PVDF matrix is much less flammable than PEO electrolytes. Our work illustrates that the PVDF/palygorskite CPE is a promising electrolyte for solid state batteries.