Progress in Gel Polymer Electrolytes for Sodium-Ion Batteries

Sodium-ion battery is a potential application system for large-scale energy storage due to the advantage of higher nature abundance and lower production cost of sodium-based materials.However,there exist inevitably the safety problems such as flammability due to the use of the same type of organic liquid electrolyte with lithium-ion battery.Gel polymer electrolytes are being considered as an effective solution to replace conventional organic liquid electrolytes for building safer sodium-ion batteries.In this review paper,the authors present a comprehensive overview of the research progress in electrochemical and physical properties of the gel polymer electrolyte-based sodium batteries.The gel polymer electrolytes based on different polymer hosts namely poly(ethylene oxide),poly(acrylonitrile),poly(methyl methacrylate),poly(vinylidene fluoride),poly(vinylidene fluoride-hexafluoro propylene),and other new polymer networks are summarized.The ionic conductivity,ion transference number,electrochemical window,thermal stability,mechanical property,and interfacial issue with electrodes of gel polymer electrolytes,and the corresponding influence factors are described in detail.Furthermore,the ion transport pathway and ion conduction mechanism are analyzed and discussed.In addition,the advanced gel polymer electrolyte systems including flame-retardant polymer electrolytes,composite gel polymer electrolytes,copolymerization,single-ion conducting polymer electrolytes,etc.with more superior and functional performance are classified and summarized.Finally,the application prospects,development opportunities,remaining challenges,and possible solutions are discussed.

以p,V_(m)为参数的范德华气体的焦耳-汤姆逊系数及μJ-T-p-T图像

现有主要物理化学参考资料中较少讨论状态参数对范德华气体节流膨胀的影响,因此本文以压力和体积(p,V_(m))为参数初步讨论了范德华气体的焦耳-汤姆逊系数μ_(J-T),并在此基础上,以氮气为例,利用范德华方程将p,V_(m)参量转变为p,T参量,得到了μ_(J-T)-p-T三维图像和二维等高图,更直观地反映了状态参数p,T对μ_(J-T)的影响。

Facile synthesis of hierarchical Na2Fe(SO4)2@rGO/C as high-voltage cathode for energy density-enhanced sodium-ion batteries

Fe-based sulfates are ideal cathode candidates for sodium-ion batteries(SIBs) owing to their high operating voltage and low cost but suffer from the nature of poor power performance. Herein, a hierarchical porous Na2Fe(SO4)2@reduced graphene oxide/carbon dot(Na2Fe(SO4)2@rGO/C) with low carbon content(4.12 wt%) was synthesized via a facile homogeneous strategy benefiting for engineering application,which delivers excellent sodium storage performance(high voltage plateau of 3.75 V, 85 m Ah g-1 and330 Wh kg-1 at 0.05 C;5805 W kg-1 at 10 C) and high Na+diffusion coefficient(1.19 × 10-12 cm2 s-1).Moreover, the midpoint voltage of assembled full cell could reach 3.0 V. The electron transfer and reaction kinetics are effectively boosted since the nanoscale Na2Fe(SO4)2 is supported by a robust crosslinked carbon matrix with rGO sheets and carbon dots. The slight rGO sheets sufficiently enhance the electron transfer like a current collecter and restrain the aggregation, as well as ensure smooth ion channels. Meanwhile, the carbon dots in the whole space connect with Na2Fe(SO4)2 and help rGO to promote the conductivity of the electrode. Ex-situ X-ray powder diffraction and X-ray photoelectron spectrometry analysis confirm the high reversibility of this sodiation/desodiation process.

Green synthesis of novel conjugated poly(perylene diimide)as cathode with stable sodium storage

Conjugated polymers of organic carbonyl compounds are promising electrode materials for energy storage devices owing to the renewable development prospects,structural variability,and better insolubility in electrolyte.However,the synthesis methods in solution are cumbersome and complicated in separation and purification,and require the introduction of functional groups and use of expensive catalysts.In this work,a novel conjugated poly(3,4,9,10-perylenetetracarboxylic diimide)(PPI)with superior thermal stability and lower solubility was prepared successfully by a green facile mechanical ball milling strategy.The PPI exhibits enhanced electrochemical dynamics performance,preferable rate capability,higher discharge capacity,and excellent cycling stability of 450 cycles at 0.2 C with higher capacity retention of 85.7%when used as cathode material for sodium-ion battery.Furthermore,the in-situ X-ray diffraction(XRD)and in-situ Raman investigations combined with the Fourier transform infrared(FT-IR)and X-ray photoelectron spectroscopy(XPS)were carried out to investigate the sodium storage mechanism.The results indicate that only two sodium ions are bound to two opposite carbonyl groups of PPI monomer to form sodium enolates during normal charging and discharging and to deliver available reversible capacity.

Hierarchical porous onion-shaped LiMn204 as cathode material for lithium ion batteries

Spinel niMn2O4 is a widely utilized cathode material for Li-ion batteries. However, its applications are limited by its poor energy density and power density. Herein, a novel hierarchical porous onion-like LiMn204 （LMO） was prepared to shorten the Li diffusion pathway with the presence of uniform pores and nanosized primary particles. The growth mechanism of the porous onion-like LiMn204 was analyzed to control the morphology and the crystal structure so that it forms a polyhedral crystal structure with reduced Mn dissolution. In addition, graphene was added to the cathode （LiMn2Odgraphene） to enhance the electronic conductivity. The synthesized LiMn2O4/graphene exhibited an ultrahigh-rate performance of 110.4 rnAh.g-1 at 50 C and an outstanding energy density at a high power density maintaining 379.4 Wh.kg-1 at 25,293 W.kg-L Besides, it shows durable stability, with only 0.02% decrease in the capacity per cycle at 10 C. Furthermore, the （LiMn2O4/graphene）/graphite full-cell exhibited a high discharge capacity. This work provides a promising method for the preparation of outstanding, integrated cathodes for potential applications in lithium ion batteries.