Comprehensive Review of Polymer Architecture for All-Solid-State Lithium Rechargeable Batteries

Abstract

Solid-state batteries are an emerging option for next-generation traction batteries because they are safe and have a high energy density. Accordingly, in polymer research, one of the main goals is to achieve solid polymer electrolytes (SPEs) that could be facilely fabricated into any preferred size of thin films with high ionic conductivity as well as favorable mechanical properties. In particular, in the past two decades, many polymer materials of various structures have been applied to improve the performance of SPEs. In this review, the influences of polymer architecture on the physical and electrochemical properties of an SPE in lithium solid polymer batteries are systematically summarized. The discussion mainly focuses on four principal categories: linear, comb-like, hyper-branched, and crosslinked polymers, which have been widely reported in recent investigations as capable of optimizing the balance between mechanical resistance, ionic conductivity, and electrochemical stability. This paper presents new insights into the design and exploration of novel high-performance SPEs for lithium solid polymer batteries.

Keywords: SPE; lithium; lithium bis(trifluoromethanesulfonyl)imide (LiTFSI); poly(ethylene oxide) PEO; polymer.

Figure 1

Ragone plot of some energy storage devices.

Figure 2

Illustration of all solid-state lithium polymer batteries (ASSLPB) composition.

Figure 3

Ion transport mechanism in non-ionic polymer.

Figure 4

Synthesis of oxyethylene-grafted polyphosphazenes (MEEPs).

Figure 5

Temperature dependence of ionic conductivity of (a) LiTFSI/PEO polymer electrolytes with a molar ratio EO/Li⁺ = 20 [66]; (b) LiTFSI/poly-PEGMEM with a molar ratio EO/Li⁺ = 18 [65]; (c) LiTFSI/polymethacrylate-graft-poly(ethylene glycol) monomethyl ether (Poly(MA)-g-PEGME) with a molar ratio EO/Li⁺ = 16 [67]. Reproduced with permission from [65]. Copyright 2019, The Chinese Ceramic Society; [66]. Copyright 2014, Elsevier E. V.; [67]. Copyright 2019, American Chemical Society.

Figure 6

Structure of hyper-branched star polymer HBPS-(PMMA- b-PPEGMA)_x (a) and photograph of HBPS-(PMMA- b-PPEGMA)₄₆/LiTFSI electrolyte film (b) [83]. Reproduced with permission from [83]. Copyright 2016, Elsevier E. V.

Figure 7

Synthesis of hbPPEGMA_m-s-PS_n hyperstar polymers; (a) synthetic route; (b) schematic of hyper-branched hbPPEGMA_m and hbPPEGMA_m-s-PS_n polymers with different average chain lengths of branched PEO (m) and linear PS (n); (c) digital photograph of hbPPEGMA₅₀-s-PS₂₉₉ SPE membrane [85]. Reproduced with permission from [85]. Copyright 2019, American Chemical Society.

Figure 8

Dependence of ideal morphology factor (f_ideal) on morphology. The blue and red regions represent conducting and non-conducting micro-phases, respectively [93]. Reproduced with permission from [93]. Copyright 2015, American Chemical Society.

Figure 9

Synthesis route of polymer electrolyte membrane (a) and ionic conductivity of membranes with varying LiTFSI contents (b) [95]. Reproduced with permission from [95]. Copyright 2017, Elsevier B.V.

Figure 10

(a) Diagram of PTT–SPE inter-crosslinking structure; (b,c) SEM images of PTT–SPE membrane; (d,e) Photographs of PTT–SPE (2:1:2) film in stretching mode [97]. Reproduced with permission from [97]. Copyright 2019, Elsevier B.V.

Figure 11

(a) Glass transition temperature as a function of poly(ethylene glycol) dimethacrylate (PEGDMA) fraction (Φ) in the membranes. The red line is the Gordon-Taylor fit to the experimental results; (b) Tensile analysis of the crosslinked membrane at various PEGDMA content. The oscillatory tensile measurement was done on thin films at a low strain rate of 0.1% in the frequency range of 100–10 Hz. The plateau modulus is plotted as a function of PEGDMA content in the inset [98]. Reproduced with permission from [98]. Copyright 2019, Springer Nature Limited.

Figure 12

Preparation schemes of comb-like network polymer electrolyte [106]. Reproduced with permission from [103]. Copyright 2005, Elsevier B.V.

Figure 13

Effect of polymer architecture on electrolyte properties.

Figure 14

(Top) Chemical structures of aliphatic imidazolium-based backbone and pendant PILs and varying counter anions; (Bottom) (a) conductivity profiles of B-PILs and P-PILs from DRS shown as a function of temperature (TFSI⁻ = bis(trifluoromethane)sulfonimide anion; NfO⁻ = nonafluorobutanesulfonate anion; CPFSI⁻ = 1,1,2,2,3,3-hexafluoropropane-1,2-disulfonimide anion) and (b) scaled to each material’s corresponding glass transition temperature [120]. Reproduced with permission from [120]. Copyright 2019, American Chemical Society.