Nonpolar Alkanes Modify Lithium‐Ion Solvation for Improved Lithium Deposition and Stripping

Huo

et al. 2021

Adv Funct Materials

Developing solid‐state electrolytes with good compatibility for high‐voltage cathodes and reliable operation of batteries over a wide‐temperature‐range are two bottleneck requirements for practical applications of solid‐state metal batteries (SSMBs). Here, an in situ quasi solid‐state poly‐ether electrolyte (SPEE) with a nano‐hierarchical design is reported. A solid‐eutectic electrolyte is employed on the cathode surface to achieve highly‐stable performance in thermodynamic and electrochemical aspects. This performance is mainly due to an improved compatibility in the electrode/electrolyte interface by nano‐hierarchical SPEE and a reinforced interface stability, resulting in superb‐cyclic stability in Li||Li symmetric batteries (>4000 h at 1 mA cm−2/1 mAh cm−2; >2000 h at 1 mA cm−2/4 mAh cm−2), which are the same for Na, K, and Zn batteries. The SPEE enables outstanding cycle‐stability for wide‐temperature operation (15–100 °C) and 4 V‐above batteries (Li||LiCoO2 and Li||LiNi0.8Co0.1Mn0.1O2). The work paves the way for development of practical SSMBs that meet the demands for wide‐temperature applicability, high‐energy density, long lifespan, and mass production.

Section: Resultsmentioning

confidence: 99%

In‐Built Quasi‐Solid‐State Poly‐Ether Electrolytes Enabling Stable Cycling of High‐Voltage and Wide‐Temperature Li Metal Batteries

Huo

et al. 2021

Adv Funct Materials

“…The improved reductive stabilities lead to improved lithium metal cycling, 12 , 13 and ether solvents such as 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) can increase Coulombic efficiencies to 93.5% and 98.4%, respectively. 14 , 15 However, the challenges of ether solvents remain as they have very poor oxidative stability. 1 , 9 , 16 At potentials greater than 3.9–4 V Li , they are oxidized significantly and cannot be used with traditional cathodes such as LiCoO 2 .…”

Section: Introductionmentioning

confidence: 99%

Effect of Building Block Connectivity and Ion Solvation on Electrochemical Stability and Ionic Conductivity in Novel Fluoroether Electrolytes

Mirmira

Amanchukwu

2021

ACS Cent. Sci.

Self Cite

Novel electrolytes are required for the commercialization of batteries with high energy densities such as lithium metal batteries. Recently, fluoroether solvents have become promising electrolyte candidates because they yield appreciable ionic conductivities, high oxidative stability, and enable high Coulombic efficiencies for lithium metal cycling. However, reported fluoroether electrolytes have similar molecular structures, and the influence of ion solvation in modifying electrolyte properties has not been elucidated. In this work, we synthesize a group of fluoroether compounds with reversed building block connectivity where ether moieties are sandwiched by fluorinated end groups. These compounds can support ionic conductivities as high as 1.3 mS/cm (30 °C, 1 M salt concentration). Remarkably, we report that the oxidative stability of these electrolytes increases with decreasing fluorine content, a phenomenon not observed in other fluoroethers. Using Raman and other spectroscopic techniques, we show that lithium ion solvation is controlled by fluoroether molecular structure, and the oxidative stability correlates with the “free solvent” fraction. Finally, we show that these electrolytes can be cycled repeatedly with lithium metal and other battery chemistries. Understanding the impact of building block connectivity and ionic solvation structure on electrochemical phenomena will facilitate the development of novel electrolytes for next-generation batteries.

Advanced Energy Materials

“…Similar approaches utilizing nonpolar alkane solvents have also been investigated, demonstrating analogous improvements to the desolvation energy of Li + cations. [ 60 ] Importantly, the use of meticulously designed solvents in conjunction with rational design of the ionic coordination state of lithium‐ions in solution seems to be a highly promising and necessary approach moving forward.…”

Section: Low‐temperature Lithium‐metal Batteriesmentioning

confidence: 99%

Designing Advanced Lithium‐Based Batteries for Low‐Temperature Conditions

Gupta

Manthiram

2020

294

193

requirements over the time of use, including variable rates, and pressures, and often most critical, temperatures. [2-4] The required low-temperature capabilities, shown in Figure 1, can present a critical roadblock toward the use of lithium-ion batteries. Commercial state-of-the-art batteries see noticeable drops in capacity retention and rate capability below 0 °C, and will rarely be recommended for use below −20 °C. [5] This limitation is defined by the kinetics of ion-transfer in solution; at low-temperatures, every stage of charge-transfer, from ion diffusion within the electrolyte and electrode materials to charge-transfer across the electrode-electrolyte interfaces, is significantly impeded. Low-temperature conditions, in which the environment itself has relatively limited thermal kinetic energy available, can present significant energetic hurdles within the chemical reaction pathway normally followed during charge and discharge at room temperature. In applications with recurring exposure to low-temperature conditions, particularly electric-vehicles and space applications, there is currently heavy reliance on secondary heating solutions coupled with thermal management systems in order to ensure consistent power delivery during operation. [6] Thermal management solutions can generally be classified as either internal, with thermal management elements integrated directly within the cell itself, or external, where thermal management solutions are applied to an entire pack or module. Internal solutions, including cells with integrated AC self-heating [7] or other internal self-heating structures, [8] are generally not feasible or practical to integrate within every cell used in an application given the added weight and complexity of such systems. [9] More commonly, external heating solutions are applied including thermal heating jackets or heating elements, warm-air heating, or liquid heat-transfer approaches. While these strategies may be more feasible to implement in practice than internal solutions, they also are accompanied by added weight, greater complexity, and reduced overall energy efficiency. [7,9] In space applications, there is often a reliance on radioisotope thermal generators (RTGs), which pair a thermoelectric generator with a decaying radioactive material to ensure consistent and reliable power generation energy. The waste heat from such systems is utilized to heat secondary systems, such Energy-dense rechargeable batteries have enabled a multitude of applications in recent years. Moving forward, they are expected to see increasing deployment in performance-critical areas such as electric vehicles, grid storage, space, defense, and subsea operations. While this at first glance spells great promise for conventional lithium-ion batteries, all of these usecases, unfortunately, share periodic and recurring exposures to extremely low-temperature conditions, a performance constraint where the lithiumion chemistry can fail to perform optimally. Next-generation chemistries employing alternative anodes...