The Critical Role of Fillers in Composite Polymer Electrolytes for Lithium Battery

Abstract

With excellent energy densities and highly safe performance, solid-state lithium batteries (SSLBs) have been hailed as promising energy storage devices. Solid-state electrolyte is the core component of SSLBs and plays an essential role in the safety and electrochemical performance of the cells. Composite polymer electrolytes (CPEs) are considered as one of the most promising candidates among all solid-state electrolytes due to their excellent comprehensive performance. In this review, we briefly introduce the components of CPEs, such as the polymer matrix and the species of fillers, as well as the integration of fillers in the polymers. In particular, we focus on the two major obstacles that affect the development of CPEs: the low ionic conductivity of the electrolyte and high interfacial impedance. We provide insight into the factors influencing ionic conductivity, in terms of macroscopic and microscopic aspects, including the aggregated structure of the polymer, ion migration rate and carrier concentration. In addition, we also discuss the electrode–electrolyte interface and summarize methods for improving this interface. It is expected that this review will provide feasible solutions for modifying CPEs through further understanding of the ion conduction mechanism in CPEs and for improving the compatibility of the electrode–electrolyte interface.

Recent progress and strategic perspectives of inorganic solid electrolytes: fundamentals, modifications, and applications in sodium metal batteries

“…Although the bilayer or sandwich structures of polymers and inorganic SEs have demonstrated a much more stable interface during cycling, the additional interfaces between these layered structures can impede the fast ion diffusion and increase the total resistance of the SEs. By adding inorganic fillers in the polymer matrix, composite SEs should exhibit merits from both highly conductive ISEs and interfacial compatible polymer SEs, [796][797][798][799][800] which deserve future in-depth research for all-solid-state SMBs.…”

Effect of Residual Solvents on Properties of Composite Solid Electrolytes

“…CSE can combine the advantages of SPE and ISE and show better performance through the combination of organic−inorganic components. 21,22 By adding fast ion conductors to the solid polymer electrolyte, the chain segment transport ability of SPE will be significantly improved and new Li + transport channels can be provided. Moreover, the mechanical properties and stability can also be improved.…”

“…SPEs including poly­(vinylidene difluoride) (PVDF), , PPC, poly­(ethylene oxide) (PEO), , and polyacrylonitrile (PAN) perform better in flexibility and safety. , However, they often suffer from poor oxidation stability and low ionic conductivity. CSE can combine the advantages of SPE and ISE and show better performance through the combination of organic–inorganic components. , By adding fast ion conductors to the solid polymer electrolyte, the chain segment transport ability of SPE will be significantly improved and new Li + transport channels can be provided. Moreover, the mechanical properties and stability can also be improved .…”

Softening of PEO–LiTFSI/LLZTO Composite Polymer Electrolytes for Solid-State Batteries under Cyclic Compression

“…Solid electrolytes in batteries are safer than the more common organic liquid electrolytes, which are subject to concerns such as flammability and overheating. – Poly­(ethylene oxide) (PEO), which complexes with lithium salts, is one of the most widely considered materials for polymer electrolytes. – Solid polymers have favorable toughness but suffer from limited ionic conductivity. Accordingly, composite polymer electrolytes (CPEs) incorporate filler particles for enhancing ionic conductivity. – Active fillers with lithium, such as Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) and Li 6.4 La 3 Zr 1.4 O 12 (LLZO), have been among the most widely investigated in recent years. – Despite rapid advances in the development of CPEs, attention regarding the effects of compressive stress has predominantly been from the perspective of porous electrodes, electrode–electrolyte interfaces, or combined effects throughout an entire cell. – Much less is known about the mechanical behavior of composite polymer electrolytes, particularly for long-term cycling. Stress distribution within a composite electrolyte can result in a variety of failure modes, including detachment or delamination between active materials and surrounding polymer electrolytes .…”