Nanostructured Block Polymer Electrolytes: Tailoring Self-Assembly to Unlock the Potential in Lithium-Ion Batteries

Abstract

Metrics & MoreArticle Recommendations CONSPECTUS: Ion-containing solid block polymer (BP) electrolytes can self-assemble into microphase-separated domains to facilitate the independent optimization of ion conduction and mechanical stability; this assembly behavior has the potential to improve the functionality and safety of lithium-ion batteries over liquid electrolytes to meet future demands (e.g., large capacities and long lifetimes) in various applications. However, significant enhancements in the ionic conductivity and processability of BPs must be realized for BP-based electrolytes to become robust alternatives in commercial devices. Toward this end, the controlled modification of BP electrolytes' intra-domain (nanometer-scale) and multi-grain (micrometer-scale) structure is one viable approach; intra-domain ion transport and segmental compatibility (related to the effective Flory−Huggins parameter, χ eff ) can be increased by tuning the ion and monomer-segment distributions, and the morphology can be selected such that the multi-grain transport is less sensitive to grain size and orientation.To highlight the characteristics of intra-domain structure that promote efficient ion transport, this Account begins by describing the relationship between BP thermodynamics (namely, χ eff and the statistical segment length, b, which is indicative of chain stiffness) and local ion concentration. These thermodynamic insights are vital because they inform the selection of synthesis and formulation variables, such as polymer and ion chemistry, polymer molecular weight and composition, and ion concentration, which boost electrolyte performance. In addition to its relationship with local ion transport, χ eff is also an important factor with respect to electrolyte processability. For example, a reduced χ eff can allow BP electrolytes to be processed at lower temperatures (i.e., lower energy input), with less solvent (i.e., reduced waste), and/or for shorter times (i.e., higher throughput) yet still form desired nanostructures. This Account also examines the impact of electrolyte preparation and processing on the ion transport across nanostructured grains because of grain size and orientation. As morphologies with a 3D-connected versus 2D-connected conducting phase show different sensitivities to conductivity losses that can occur because of the fabrication methods, it is necessary to account for electrolyte processing effects when probing ion transport. The intra-domain and micrometer-scale structure also can be tuned using either tapered BPs (macromolecules with modified monomer-segment composition profiles between two homogeneous blocks) or blends of BPs and homopolymers, independent of the BP molecular weight and composition, as detailed herein. The application of TBPs or BP/HP blends as ion-conducting materials leads to improved ion transport, reduced χ eff , and greater availability of morphologies with 3D connectivity relative to traditional (non-tapered and unblended) BP electrolytes. This feature results from the fact...

Are Polymer‐Based Electrolytes Ready for High‐Voltage Lithium Battery Applications? An Overview of Degradation Mechanisms and Battery Performance

“…Owing to the mentioned potential benefits of polymer electrolytes (safety, processability, energy density) and the current attention towards high‐energy lithium batteries, polymer electrolytes are experiencing a renewed interest, with almost one thousand research articles and over 50 reviews published in only the last five years (source Web of Science). Among these, several reviews describe the general progress in SSEs, [ 63–70 ] or in specific classes of polymer electrolytes [ 14,71–81 ]…”

“…Owing to the mentioned potential benefits of polymer electrolytes (safety, processability, energy density) and the current attention towards high-energy lithium batteries, polymer electrolytes are experiencing a renewed interest, with almost one thousand research articles and over 50 reviews published in only the last five years (source Web of Science). Among these, several reviews describe the general progress in SSEs, [63][64][65][66][67][68][69][70] or in specific classes of polymer electrolytes [14,[71][72][73][74][75][76][77][78][79][80][81] Certain reviews have specifically focused on the interfaces in solid-state batteries [82][83][84][85] and, particularly, on the issues related to the use of lithium metal anodes. [39,[86][87][88] Correspondingly, only a few recent reviews are focused on the cathode interface and the possible application in HVLP batteries.…”

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“…Ketkar et al. have recently compiled an account, which includes the research described above [ 72 ] in addition to a detailed review on Li‐ion polymer electrolytes. [ 31 ]…”

“…The combined improvement in conductivity and reduced segregation strength signifies tapering to be a promising factor for developing BPEs and deserves further investigation. Ketkar et al have recently compiled an account, which includes the research described above [72] in addition to a detailed review on Li-ion polymer electrolytes. [31]…”

In situ prepared “polymer-in-salt” electrolytes enabling high-voltage lithium metal batteries

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