Advanced Composite Solid Electrolytes for Lithium Batteries: Filler Dimensional Design and Ion Path Optimization

Abstract

organic liquid electrolytes hinder lithium batteries in achieving higher energy density, longer working life, and safer performance. [12,13] Solid electrolytes not only improve the long-term thermal and electrochemical stabilities but also obviate the need for separators and increase the energy density. [14][15][16][17] From these concerns, solid electrolytes are regarded as a potential substituent to improve the cycle performance of lithium batteries.Solid electrolytes are generally categorized as solid polymer electrolytes, inorganic solid electrolytes, and composite solid electrolytes. [16,18,19] Solid polymer electrolytes, such as poly(ethylene oxide) (PEO) and poly(vinylidene fluoride) (PVDF), are favored for their chemical stability, low density, low cost, processability, and wettability. [20][21][22][23] However, the applications are restricted by their low ionic conductivity at room temperature (typically from 10 −6 to 10 −5 S cm −1 ). Therefore, much research has been devoted to synthesizing solid polymer electrolytes with high ionic conductivity via increasing free volume and constructing fast transport paths, such as applying covalent organic framework-based polymer, [24,25] single lithium-ion-conducting polymer, [26,27] crosslinked polymer network, [28,29] and adding plasticizers. [30,31] Inorganic solid electrolytes, such as Li 7 La 3 Zr 2 O 12 (LLZO, garnet-type) and Li 0.33 La 0.56 TiO 3 (LLTO, perovskite-type), are single-ion conductors with superior lithium-ion conductivity (typically from 10 −4 to 10 −2 S cm −1 ). [32][33][34][35] However, inorganic solid electrolytes usually have a defect of high interfacial contact resistance because of the poor wettability at the electrode and electrolyte interface. [36,37] Moreover, recent studies have proved that the ion transport at the interface and the ionic conductivity of electrolytes are both essential to maintain a stable interface between electrode and electrolyte. [38][39][40] Therefore, constructing composite solid electrolytes by utilizing the advantages of both polymeric and inorganic materials is generally viewed as a practicable solution for nextgeneration lithium batteries. [16,41,42] Many recent studies have shown that the ion-conduction behavior is significantly influenced by the filler structures in a polymer/salt matrix, in which the effect is determined by the natural characteristics of the fillers and the interaction Composite solid electrolytes are considered to be the crucial components of all-solid-state lithium batteries, which are viewed as the next-generation energy storage devices for high energy density and long working life. Numerous studies have shown that fillers in composite solid electrolytes can effectively improve the ion-transport behavior, the essence of which lies in the optimization of the ion-transport path in the electrolyte. The performance is closely related to the structure of the fillers and the interaction between fillers and other electrolyte components including polymer matrices and lithium salts. In this rev...

High Ionic Conductivity Motivated by Multiple Ion‐Transport Channels in 2D MOF‐Based Lithium Solid State Battery

“…The loaded Lewis acid sites on the nanosheets act as Li + migration sites, facilitating the creation of rapid ion transport channels. [5,15] The micropore size of Cu-BTC is 6.427 A (Figure S1e, Supporting Information), which can directionally restrict the passage of anionic TFSI − produced by lithium salts, thereby increasing the Li + transfer number (t Li+ ). [16] Based on this, the composite dielectric prepared by the simple solution casting method of CPE is shown in Figure 2a.…”

“…Solid‐state electrolytes (SSEs) can be categorized into inorganic solid electrolytes (ISEs), solid polymer electrolytes (SPEs), and composite polymer electrolytes (CPEs). [ 5 ] ISEs, particularly oxides and sulfides, exhibit remarkable ionic conductivity ranging from 10 −4 to 10 −2 S cm −1 at room temperature (RT), which is comparable to or even higher than that of liquid electrolytes. However, the performance of ISEs can be affected by poor interfacial infiltration and exceedingly high interfacial contact resistance.…”

3D printing of solid polymer electrolytes by fused filament fabrication: challenges towards in-space manufacturing

“…Polymers' semi-crystallinity makes ionic mobility difficult to understand. It could be split in two categories: movements coupled with polymer chain mobility (in amorphous regions, also called free volume theory [52]) and movements decoupled from polymer chain mobility (in crystalline parts also called ion-conduction) [14,47,52]. McLin and Angel [53] introduced a decoupling ratio between the structural and the conductivity relaxation time (equation (3)).…”

Recent Progress on Nanomodification Applied in Anodes of Rechargeable Li Metal Batteries

“…The use of nonflammable organic electrolytes in solid electrolytes enhances the safety of cells. Furthermore, solid electrolytes have a high modulus, which can mechanically inhibit the growth of dendrites in the electrolyte. − However, its widespread use in powerful lithium metal batteries is hampered by its low room-temperature conductivity. − (3) The protection of the lithium metal anode. Making three-dimensional structures to hold plated lithium, reducing the local deposition current density, and minimizing volume changes. − …”