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High Ion-Conducting Solid-State Composite Electrolytes with Carbon Quantum Dot Nanofillers.

ABSTRACT: Solid-state polymer electrolytes (SPEs) with high ionic conductivity are desirable for next generation lithium- and sodium-ion batteries with enhanced safety and energy density. Nanoscale fillers such as alumina, silica, and titania nanoparticles are known to improve the ionic conduction of SPEs and the conductivity enhancement is more favorable for nanofillers with a smaller size. However, aggregation of nanoscale fillers in SPEs limits particle size reduction and, in turn, hinders ionic conductivity improvement. Here, a novel poly(ethylene oxide) (PEO)-based nanocomposite polymer electrolyte (NPE) is exploited with carbon quantum dots (CQDs) that are enriched with oxygen-containing functional groups. Well-dispersed, 2.0-3.0 nm diameter CQDs offer numerous Lewis acid sites that effectively increase the dissociation degree of lithium and sodium salts, adsorption of anions, and the amorphicity of the PEO matrix. Thus, the PEO/CQDs-Li electrolyte exhibits an exceptionally high ionic conductivity of 1.39 × 10-4 S cm-1 and a high lithium transference number of 0.48. In addition, the PEO/CQDs-Na electrolyte has ionic conductivity and sodium ion transference number values of 7.17 × 10-5 S cm-1 and 0.42, respectively. It is further showed that all solid-state lithium/sodium rechargeable batteries assembled with PEO/CQDs NPEs display excellent rate performance and cycling stability.

SUBMITTER: Ma C

PROVIDER: S-EPMC5980199 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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High Ion-Conducting Solid-State Composite Electrolytes with Carbon Quantum Dot Nanofillers.

Ma Cheng C Dai Kuan K Hou Hongshuai H Ji Xiaobo X Chen Libao L Ivey Douglas G DG Wei Weifeng W

Advanced science (Weinheim, Baden-Wurttemberg, Germany) 20180301 5

Solid-state polymer electrolytes (SPEs) with high ionic conductivity are desirable for next generation lithium- and sodium-ion batteries with enhanced safety and energy density. Nanoscale fillers such as alumina, silica, and titania nanoparticles are known to improve the ionic conduction of SPEs and the conductivity enhancement is more favorable for nanofillers with a smaller size. However, aggregation of nanoscale fillers in SPEs limits particle size reduction and, in turn, hinders ionic conduc ...[more]

PMID: 29876221

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Project description:Composite polymer electrolytes (CPEs) strike an effective balance between ionic conductivity and mechanical flexibility for lithium-ion solid-state batteries. Long-term performance, however, is limited by capacity fading after hundreds of charge and discharge cycles. The causes of performance degradation include multiple contributing factors such as dendrite formation, physicochemical changes in electrolytes, and structural remodeling of porous electrodes. Among the many factors that contribute to performance degradation, the effect of stress specifically on the composite electrolyte is not well understood. This study examines the mechanical changes in a poly(ethylene oxide) electrolyte with bis(trifluoromethane) sulfonimide. Two different sizes of Li6.4La3Zr1.4Ta0.6O12 particles (500 nm and 5 μm) are compared to evaluate the effect of the surface-to-volume ratio of the ion-conducting fillers within the composite. Cyclic compression was applied to mimic stress cycling in the electrolyte, which would be caused by asymmetric volume changes that occur during charging and discharging cycles. The electrolytes exhibited fatigue softening, whereby the compressive modulus gradually decreased with an increase in the number of cycles. When the electrolyte was tested for 500 cycles at 30% compressive strain, the compressive modulus of the electrolyte was reduced to approximately 80% of the modulus before cycling. While the extent of softening was similar regardless of particle size, CPEs with 500 nm particles exhibited a significant reduction in ionic conductivity after cyclic compression (1.4 × 10-7 ± 2.3 × 10-8 vs 1.1 × 10-7 ± 2.0 × 10-8 S/cm, mean ± standard deviation, n = 4), whereas there was no significant change in ionic conductivity for CPEs with 5 μm particles. These observations -performed deliberately in the absence of charge-discharge cycles -show that repetitive mechanical stresses can play a significant role in altering the performance of CPEs, thereby revealing another possible mechanism for performance degradation in all-solid-state batteries.

Dataset Information

High Ion-Conducting Solid-State Composite Electrolytes with Carbon Quantum Dot Nanofillers.

Publications

High Ion-Conducting Solid-State Composite Electrolytes with Carbon Quantum Dot Nanofillers.

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