Boosting the Ion Mobility in Solid Polymer Electrolytes Using Hollow Polymer Nanospheres as an Additive

Abstract

Solid polymer electrolytes (SPEs) possess improved thermal and mechanical stability as safe energy storage devices. However, their low ion mobilities and poor electrochemical stabilities still hinder the wide industrial application of SPEs. Herein, we introduce an SPE design that provides an enormous number of electrochemically stable pathways and space for lithium-ion transport, blending polymer (polydopamine) hollow nanospheres with an inactive inorganic template into a poly­(ethylene oxide) (PEO) and lithium bis­(trifluoromethanesulfonyl)­imide (LiTFSI) based SPE. Hollow silica acts as a template for polydopamine processing a large contact area with the polymer electrolyte, and the interface between the polymer electrolyte and hollow composite fillers provides amounts of ion transport channels. In addition, theoretical calculations reveal a strong adsorption between polydopamine and TFSI–, which suppresses the TFSI– motion and meanwhile facilitates the selective Li+ transport. The hollow polydopamine can serve as a versatile platform for anion trapping and has large compatible and stable depression for a well-defined ion transfer interface layer, forming a three-in-one nanocomposite for the enhancement of ionic conductivity with no sacrifice of the mechanical properties. Experimental data confirmed the high mobility of ions within the composite electrolyte with an ionic conductivity of 0.189 mS cm–1 in comparison to the SPE without additives (0.105 mS cm–1) at 60 °C. The mobility of the Li+ increases after adding the polymer-coated inorganic additives, associated with a noticeable enlargement of the electrochemical window. Furthermore, an all-solid-state Li/LiFePO4 battery with a hollow polydopamine nanoparticle–polymer composite electrolyte shows long life, high reversible capacity (134.9 mAh g–1), and high capacity retention (97.2%) after 205 cycles at 0.2 C.

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

“…Li et al [ 100 ] prepared HPDA fillers, as shown in Fig. 2 a, in which hollow silica was used as a template and covered with a layer of polydopamine.…”

“…Adapted with permission from Ref. [ 100 ]. c Schematic of dopamine on the surface of LLZTO particles; d Arrhenius log 1000/ T of LLZTO@PDA-PEO and LLZTO/PEO CPEs.…”

“…Facilitating the dispersion of fillers in polymers is an effective method for forming percolation networks [99]. Li et al [100] prepared HPDA fillers, as shown in Fig. 2a, in which hollow silica was used as a template and covered with a layer of polydopamine.…”

“…Thus, the Fe-MOFs-PEO Adapted with permission from Ref. [100]. e Schematic representation of the lithium-ion route within LLZO (5-50 wt%)-PEO (LiTFSI).…”

Interface Manipulation of Composite Solid Polymer Electrolyte with Polydopamine to Construct Durable and Fast Li+ Conduction Pathways

“…Moreover, the inorganic fillers can establish a rigid and interfacial cross-linked skeleton of PEO matrices, which is able to improve the mechanical and thermal stability of CPEs. Apart from the structural features (e.g., size and morphology), the surface characteristic of the fillers plays a crucial role in the homogeneous interface properties and kinetic transport behaviors of CPEs. , It is highly desirable to design and synthesize inorganic fillers that can afford rich types of Lewis acid–base interactions with either PEO chains or Li salt, including hydrogen-bond interaction, positive vacancy-salt interaction, and dipole–dipole interaction . For example, Wieczorek et al elucidated the Lewis acid–base theory that the acidic surface sites of the Al 2 O 3 filler have strong affinity with ClO 4 – and promote the dissociation of LiClO 4 to release Li + .…”