PVDF/Palygorskite Nanowire Composite Electrolyte for 4 V Rechargeable Lithium Batteries with High Energy Density

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 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)SiO(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 from 0.21 to 0.54 due to interaction between palygorskite and ClO ions. We further demonstrate full cells based on Li(NiMnCo)O (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.

Li+‐Containing, Continuous Silica Nanofibers for High Li+ Conductivity in Composite Polymer Electrolyte

“…The Li 2 SO 4 ‐doped SiO 2 CPEs demonstrates lower E a values than that of the Li 2 SO 4 ‐free one, indicating improved Li + conduction behaviors by Li‐salt introducing. The Li + transference number ( t Li+ ) of the SiO 2 /Li 2 SO 4 /PEO CPEs was evaluated by the potentiostatic polarization (PP) method . As shown in Figure S9 (Supporting Information), the Li 2 SO 4 ‐doped SiO 2 CPEs yield higher t Li+ values (0.25, 0.32, 0.45, and 0.52 for 0, 0.05, 0.10, and 0.15 g Li 2 SO 4 , respectively) than the reported bare PEO/LiTFSI electrolyte (0.12) .…”

“…The enhanced t Li+ could be assigned to two reasons. First, the incorporating of mesoporous SiO 2 /Li 2 SO 4 nanofibers into the PEO/LiTFSI matrix, promotes the anions absorption and relaxation of polymer local chains for more free Li + ; second, in situ introduced Li salt within the nanofibers affords considerable intrinsic Li + conduction. Besides, time‐related ionic conduction was investigated to determine the composite electrolyte stability over duration.…”

“…As illustrated in Figure S1a (Supporting Information), the classical CPE using low‐aspect‐ratio nanoparticle fillers, presents relatively low Li + conductivity due to the short and isolated Li + transport pathways . When using higher‐aspect‐ratio nanorod or nanowire fillers (Figure S1b, Supporting Information), the Li + paths are comparatively prolonged but still discontinuous . A latest study shows that the capability to suppress Li dendrites highly relies on the mechanical strength of CPEs, while the above two categories of CPEs demonstrate poor mechanical strength due to the absence of strong skeleton.…”

Recent progress on flexible nanogenerators toward self‐powered systems

“…53,54 According to the previous reports, various structures of PVDF and its copolymers have been developed, including fiber arrays, nanowires, thin film, and nanotube arrays. [55][56][57][58][59][60] Thin film poly(vinylidene fluoride-co-trifluoroethylene) (P[VDF-TrFE]) owns a significant value for large-area deposition, excellent uniformity, and remarkable surface morphology. 61 However, the piezoelectric constant of the fiberbased composites exhibits about four times greater than the controlled thin film-based ones.…”

Composition Modulation and Structure Design of Inorganic‐in‐Polymer Composite Solid Electrolytes for Advanced Lithium Batteries

“…As mentioned above, these liquid organics were also termed as plasticizers. For example, Yang and co‐workers investigated the influence of the content of DMF solvent residue in PVDF‐based composite solid electrolyte on the ionic conductivity. They observed that the ionic conductivity increased with the increment of DMF residue by adjusting the vacuum‐dried temperature.…”