Nanoscale Ion Transport Enhances Conductivity in Solid Polymer-Ceramic Lithium Electrolytes

Abstract

The predictive design of flexible and solvent-free polymer electrolytes for solid-state batteries requires an understanding of the fundamental principles governing the ion transport. In this work, we establish a correlation among the composite structures, polymer segmental dynamics, and lithium ion (Li + ) transport in a ceramic-polymer composite. Elucidating this structure−property relationship will allow tailoring of the Li + conductivity by optimizing the macroscopic electrochemical stability of the electrolyte. The ion dissociation from the slow polymer segmental dynamics was found to be enhanced by controlling the morphology and functionality of the polymer/ ceramic interface. The chemical structure of the Li + salt in the composite electrolyte was correlated with the size of the ionic cluster domains, the conductivity mechanism, and the electrochemical stability of the electrolyte. Polyethylene oxide (PEO) filled with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium bis(fluorosulfonyl) imide (LiFSI) salts was used as a matrix. A garnet electrolyte, aluminum substituted lithium lanthanum zirconium oxide (Al-LLZO) with a planar geometry, was used for the ceramic nanoparticle moieties. The dynamics of the strongly bound and highly mobile Li + were investigated using dielectric relaxation spectroscopy. The incorporation of the Al-LLZO platelets increased the number density of more mobile Li + . The structure of the nanoscale ion-agglomeration was investigated by small-angle X-ray scattering, while molecular dynamics (MD) simulation studies were conducted to obtain the fundamental mechanism of the decorrelation of the Li + in the LiTFSI and LiFSI salts from the long PEO chain.

CNT Composite β-MnO2 with Fiber Cable Shape as Cathode Materials for Aqueous Zinc-Ion Batteries

“…At present, the materials widely used in AZIBs mainly include: (1) vanadium-based materials that can promote the insertion and removal of Zn 2+ attributed to it having an open layered structure during charging/discharging processes. Nevertheless, they have poor conductivity and low operating voltage. , (2) Prussian blue analogues that possess a high output voltage and stable structure but low theoretical capacity, poor conductivity, and poor rate capability. , (3) Transition metal sulfides that have a high specific area and abundant interior defects, but instability of the material structure affects their electrochemical properties during charging and discharging. , (4) Manganese-based materials that have multiple valence states, adjustable structure, a high operating voltage, and theoretical capacity, but their structures are unstable and tend to collapse in long-term cycles. , Although a manganese-based positive electrode material in AZIBs has become the most widely used positive electrode material because of its high energy density, large capacity as well as long life, its actual application is restricted due to its poor conductivity, relatively low energy density, and incomplete understanding of the electrochemical reaction mechanism. , Therefore, the methods to strengthen the properties of manganese-based positive materials include carbon coating, metal element doping, morphology refinement, defect engineering, nanostructure engineering, and conductive polymer coatings . For example, Wang et al.…”

Development of 2D Framework Structures-Based Solid-State Electrolytes with Fast Ion-Transport Channels Using Ionic Liquids Encapsulated in 2D-LiMNT Frameworks

“…The biggest problem facing SSLMBs is the need to develop SSEs with high ionic conductivity, better processing properties, high electrochemical/thermal stability, and good interfacial contact with electrodes. , Among conventional SSEs, ceramic electrolytes represented by Li 7 La 3 Zr 2 O 12 and Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 are capable of achieving an ionic conductivity of 10 –4 –10 –3 S·cm –1 at room temperature, have a high Li + mobility number (∼1), and a high electrochemical window (>5.0 V vs Li/Li + ). , However, ceramic electrolytes face large interfacial problems and processing bottlenecks. − Polymer electrolytes, represented by poly­(ethylene oxide) (PEO) and polyacrylonitrile (PAN), have better interfacial contact and processing performance, but their room-temperature ionic conductivity is too low (10 –6 –10 –5 S·cm –1 ) to operate at room temperature. , Composite electrolytes prepared from ceramic and polymer electrolytes, such as PEO-Li 7 La 3 Zr 2 O 12 , PEO-Li 0.33 La 0.56 TiO 3 , and PAN-Li 0.33 La 0.56 TiO 3 , also face the problem of low ionic conductivity, which is typically below 10 –3 S·cm –3 . − …”