No abstract

High-nickel layered oxide cathode materials are the most promising candidates for developing lithium-metal batteries (LMBs) because of their high energy density and low cost. Herein, we present a localized saturated electrolyte (LSE) based on readily available, low-cost LiPF6 salt with limited solubility in carbonate solvents for developing LiNiO2 cathodes. Compared to the conventional electrolyte that retains only 55% of the initial capacity after 200 cycles, the LSE retains a record 81% of the initial capacity after 600 deep cycles at 4.4 V (versus Li/Li+). The LSE protects the LiNiO2 surface from degrading into rock-salt and spinel phases during cycling and helps form a robust Li morphology on the Li-metal anode that is covered by an inorganic-rich solid-electrolyte interphase. The drastically enhanced cycling stability with LSE demonstrates the importance of developing robust electrolytes compatible with both high-Ni cathodes and Li-metal anodes.

Electrolytes play a critical role in stabilizing highly reactive lithium‐metal anodes (LMAs) and high‐voltage cathodes for rechargeable lithium‐metal batteries (LMBs). Localized high concentration electrolytes (LHCEs) have achieved remarkable success in the context of LMBs. However, the state‐of‐the‐art LHCEs are based on LiFSI salt, which is prohibitively expensive. Here, the utility of low‐cost LiPF6 salt in localized saturated electrolytes (LSEs) with a series of solvents and diluents in LMBs with cobalt‐free LiNiO2 cathode is systematically explored. Experimental and theoretical analyses reveal that the unique solvation structure formed not only changes the distribution of solvents and anions but also alters the atom–atom distances within them, leading to different reduction and oxidation stabilities compared to low‐concentration electrolytes. In addition, LSEs help form LiF‐rich interphase layers on the LMA and LiNiO2 cathode, protecting the electrodes from degradation during cycling. Different LSEs also lead to differences in lithium plating morphology and impedance buildup during cycling, impacting the performance of LMBs. The solvent and diluent must be carefully selected for compatibility with a lithium salt when developing LHCEs and LSEs for LMBs.

without altering their natural mechanics. [5] These batteries should be compliant and deformable so that they can conform to rounded and irregularly shaped surfaces, such as the contours the human body, and be capable of supplying stable voltage and current under mechanical strain, bending, and dynamic motions. Recent studies have successfully fabricated highly deformable lithium-ion batteries, zinc-air batteries, and supercapacitors. [6][7][8][9][10] However, further progress requires advancements in materials selection and design to address challenges of existing battery technologies: (i) eliminate dependency on rigid electrodes so that batteries can be stretchable rather than only flexible, and (ii) reduce the potential for battery failure/explosion caused by dendrite growth.Metal electrodes that are commonly used in batteries, such as lithium, zinc, aluminum metal anode, or copper current collectors, are rigid and can interfere with the mechanical compliance of soft devices that are designed to be flexible and stretchable. [11,12] One approach to overcoming this challenge is to pattern the metal anode into thin flexible sheets or stretchable spring-like coils or nanowires, which allow batteries to exhibit a strain limit of up to 30%. [13][14][15] Such a deterministic approach to obtain stretchable functionality has been extended to island-bridge architectures. However, such architectures require complex fabrication steps, such as electron beam evaporation and photolithography, that can be time consuming or require expensive equipment. [16,17] Moreover, batteries with wavy structures obtained by prestretching the surrounding substrate could exhibit a reduction in internal conductivity during stretching, which may lead to a decrease in electrochemical performance. [18][19][20][21] Another obstacle to the practical application of metal anode batteries is the formation of dendrites during charging, which can penetrate the separator and result in an internal shortcircuit that causes safety issues. [22,23] Even though dendrites do not penetrate the separator, they hasten adverse reactions between the electrolyte and metal anode, leading to fast electrolyte decomposition, for example, low current efficiency ascribed to hydrogen evolution reaction during zinc-air battery charging process. [24] Modifying the anode, electrolyte, and their interface can suppress dendrite growth. For example, electrolytic additives have been introduced to help form a stable artificial solid electrolyte interface (SEI); [25,26] rigid/elastic layer can A rechargeable, stretchable battery composed of a liquid metal alloy (eutectic gallium-indium; EGaIn) anode, a carbon paste, and MnO 2 slurry cathode, an alkaline electrolytic hydrogel, and a soft elastomeric package is presented. The battery can stably cycle within a voltage range of 1.40-1.86 V at 1 mA cm −2 while being subject to 100% tensile strain. This is accomplished through a mechanism that involves reversible stripping and plating of gallium along with MnO 2 chemical conversion. Mor...

Anode-free lithium-metal batteries (LMBs) are ideal candidates for high-capacity energy storage as they eliminate the need of a conventional graphite electrode or excess lithium-metal anode. Current anode-free LMBs suffer from...