Interfacial Speciation Determines Interfacial Chemistry: X-ray-Induced Lithium Fluoride Formation from Water-in-salt Electrolytes on Solid Surfaces.
Angewandte Chemie (International ed. in English)
Super-concentrated "water-in-salt" electrolytes recently spurred resurgent interest for high energy density aqueous lithium-ion batteries. Thermodynamic stabilization at high concentrations and kinetic barriers towards interfacial water electrolysis significantly expand the electrochemical stability window, facilitating high voltage aqueous cells. Here we investigated LiTFSI/H 2 O electrolyte interfacial decomposition pathways in the "water-in-salt" and "salt-in-water" regimes using synchrotron X-rays, which produce electrons at the solid-electrolyte interface to mimic reductive environments, and simultaneously probe the structure of surface films using X-ray diffraction. We observed the surface-reduction of TFSI - at super-concentration, leading to lithium fluoride interphase formation, while precipitation of the lithium hydroxide was not observed. The mechanism behind this photoelectron-induced reduction was revealed to be concentration-dependent interfacial chemistry that only occurs among closely contact ion-pairs, which constitutes the rationale behind the "water-in-salt" concept.
View details for DOI 10.1002/anie.202007745
View details for PubMedID 32881197
- Enabling Deformable and Stretchable Batteries ADVANCED ENERGY MATERIALS 2020
- Molecular design for electrolyte solvents enabling energy-dense and long-cycling lithium metal batteries NATURE ENERGY 2020
- Electrode Design with Integration of High Tortuosity and Sulfur-Philicity for High-Performance Lithium-Sulfur Battery MATTER 2020; 2 (6): 1605–20
Stretchable electrochemical energy storage devices.
Chemical Society reviews
The increasingly intimate contact between electronics and the human body necessitates the development of stretchable energy storage devices that can conform and adapt to the skin. As such, the development of stretchable batteries and supercapacitors has received significant attention in recent years. This review provides an overview of the general operating principles of batteries and supercapacitors and the requirements to make these devices stretchable. The following sections provide an in-depth analysis of different strategies to convert the conventionally rigid electrochemical energy storage materials into stretchable form factors. Namely, the strategies of strain engineering, rigid island geometry, fiber-like geometry, and intrinsic stretchability are discussed. A wide range of materials are covered for each strategy, including polymers, metals, and ceramics. By comparing the achieved electrochemical performance and strain capability of these different materials strategies, we allow for a side-by-side comparison of the most promising strategies for enabling stretchable electrochemical energy storage. The final section consists of an outlook for future developments and challenges for stretchable supercapacitors and batteries.
View details for DOI 10.1039/d0cs00035c
View details for PubMedID 32483575
- Tortuosity Effects in Lithium-Metal Host Anodes JOULE 2020; 4 (4): 938–52
Decoupling of mechanical properties and ionic conductivity in supramolecular lithium ion conductors.
2019; 10 (1): 5384
The emergence of wearable electronics puts batteries closer to the human skin, exacerbating the need for battery materials that are robust, highly ionically conductive, and stretchable. Herein, we introduce a supramolecular design as an effective strategy to overcome the canonical tradeoff between mechanical robustness and ionic conductivity in polymer electrolytes. The supramolecular lithium ion conductor utilizes orthogonally functional H-bonding domains and ion-conducting domains to create a polymer electrolyte with unprecedented toughness (29.3 MJ m-3) and high ionic conductivity (1.2*10-4 S cm-1 at 25°C). Implementation of the supramolecular ion conductor as a binder material allows for the creation of stretchable lithium-ion battery electrodes with strain capability of over 900% via a conventional slurry process. The supramolecular nature of these battery components enables intimate bonding at the electrode-electrolyte interface. Combination of these stretchable components leads to a stretchable battery with a capacity of 1.1 mAh cm-2 that functions even when stretched to 70% strain. The method reported here of decoupling ionic conductivity from mechanical properties opens a promising route to create high-toughness ion transport materials for energy storage applications.
View details for DOI 10.1038/s41467-019-13362-4
View details for PubMedID 31772158
- A Dynamic, Electrolyte-Blocking, and Single-Ion-Conductive Network for Stable Lithium-Metal Anodes JOULE 2019; 3 (11): 2761–76
An Electrochemical Gelation Method for Patterning Conductive PEDOT:PSS Hydrogels.
Advanced materials (Deerfield Beach, Fla.)
Due to their high water content and macroscopic connectivity, hydrogels made from the conducting polymer PEDOT:PSS are a promising platform from which to fabricate a wide range of porous conductive materials that are increasingly of interest in applications as varied as bioelectronics, regenerative medicine, and energy storage. Despite the promising properties of PEDOT:PSS-based porous materials, the ability to pattern PEDOT:PSS hydrogels is still required to enable their integration with multifunctional and multichannel electronic devices. In this work, a novel electrochemical gelation ("electrogelation") method is presented for rapidly patterning PEDOT:PSS hydrogels on any conductive template, including curved and 3D surfaces. High spatial resolution is achieved through use of a sacrificial metal layer to generate the hydrogel pattern, thereby enabling high-performance conducting hydrogels and aerogels with desirable material properties to be introduced into increasingly complex device architectures.
View details for DOI 10.1002/adma.201902869
View details for PubMedID 31414520
- Designing polymers for advanced battery chemistries NATURE REVIEWS MATERIALS 2019; 4 (5): 312–30
Electrochemical patterning of tissue-mimetic conductive hydrogels
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000478861205318
- A Dual-Crosslinking Design for Resilient Lithium-Ion Conductors ADVANCED MATERIALS 2018; 30 (43)
- Concentrated mixed cation acetate "water-in-salt" solutions as green and low-cost high voltage electrolytes for aqueous batteries ENERGY & ENVIRONMENTAL SCIENCE 2018; 11 (10): 2876–83
A Dual-Crosslinking Design for Resilient Lithium-Ion Conductors.
Advanced materials (Deerfield Beach, Fla.)
Solid-state electrolyte materials are attractive options for meeting the safety and performance needs of advanced lithium-based rechargeable battery technologies because of their improved mechanical and thermal stability compared to liquid electrolytes. However, there is typically a tradeoff between mechanical and electrochemical performance. Here an elastic Li-ion conductor with dual covalent and dynamic hydrogen bonding crosslinks is described to provide high mechanical resilience without sacrificing the room-temperature ionic conductivity. A solid-state lithium-metal/LiFePO4 cell with this resilient electrolyte can operate at room temperature with a high cathode capacity of 152 mAh g-1 for 300 cycles and can maintain operation even after being subjected to intense mechanical impact testing. This new dual crosslinking design provides robust mechanical properties while maintaining ionic conductivity similar to state-of-the-art polymer-based electrolytes. This approach opens a route toward stable, high-performance operation of solid-state batteries even under extreme abuse.
View details for PubMedID 30199111
- Crosslinked Poly(tetrahydrofuran) as a Loosely Coordinating Polymer Electrolyte ADVANCED ENERGY MATERIALS 2018; 8 (25)