An integrated preparation of safety‐reinforced poly(propylene carbonate)‐based all‐solid polymer electrolyte is shown to be applicable to ambient‐temperature solid polymer lithium batteries. In contrast to pristine poly(ethylene oxide) solid polymer electrolyte, this solid polymer electrolyte exhibits higher ionic conductivity, wider electrochemical window, better mechanical strength, and superior rate performance at 20 °C. Moreover, lithium iron phosphate/lithium cell using such solid polymer electrolyte can charge and discharge even at 120 °C. It is also noted that the solid‐state soft‐package lithium cells assembled with this solid polymer electrolyte can still power a red light‐emitting diode lamp without suffering from internal short‐circuit failures even after cutting off one part of the battery. Considering the aspects mentioned above, the solid polymer electrolyte is eligible for practical lithium battery applications with improved reliability and safety. Just as important, a new perspective that the degree of amorphous state of polymer is also as critical as its low glass transition temperature for the exploration of room temperature solid polymer electrolyte is illustrated. In all, this study opens up a kind of new avenue that could be a milestone to the development of high‐voltage and ambient‐temperature all‐solid‐state polymer electrolytes.
A renewable and superior thermal-resistant cellulose-based composite nonwoven was explored as lithium-ion battery separator via an electrospinning technique followed by a dip-coating process. It was demonstrated that such nanofibrous composite nonwoven possessed good electrolyte wettability, excellent heat tolerance, and high ionic conductivity. The cells using the composite separator displayed better rate capability and enhanced capacity retention, when compared to those of commercialized polypropylene separator under the same conditions. These fascinating characteristics would endow this renewable composite nonwoven a promising separator for high-power lithium-ion battery.
A sustainable, heat-resistant and flame-retardant cellulose-based composite nonwoven has been successfully fabricated and explored its potential application for promising separator of high-performance lithium ion battery. It was demonstrated that this flame-retardant cellulose-based composite separator possessed good flame retardancy, superior heat tolerance and proper mechanical strength. As compared to the commercialized polypropylene (PP) separator, such composite separator presented improved electrolyte uptake, better interface stability and enhanced ionic conductivity. In addition, the lithium cobalt oxide (LiCoO2)/graphite cell using this composite separator exhibited better rate capability and cycling retention than that for PP separator owing to its facile ion transport and excellent interfacial compatibility. Furthermore, the lithium iron phosphate (LiFePO4)/lithium cell with such composite separator delivered stable cycling performance and thermal dimensional stability even at an elevated temperature of 120°C. All these fascinating characteristics would boost the application of this composite separator for high-performance lithium ion battery.
Battery separators have drawn considerable attention due to their vital roles for the safety and electrochemical performance of lithium-ion batteries. In this paper, the cellulose/polysulfonamide composite membrane was successfully fabricated from a mixture of microfibrillar cellulose and polysulfonamide via a facile papermaking process. And its potential application was explored as a high performance lithium-ion battery separator by characterizing their electrolyte wettability, heat tolerance, and electrochemical properties. Lithium cobalt oxide/graphite cells using the separator displayed better capacity retention ratios of 85% after 100 cycles and superior rate capability compared with those of a commercial polypropylene separator. Furthermore, the lithium iron phosphate/lithium half cell using cellulose/ polysulfonamide separator exhibited stable charge−discharge capability even at 120°C. It was demonstrated that the composite separator possessed an enhanced thermal dimensional stability. This research provides a promising new strategy for large-scale fabrication of high performance lithium-ion battery membranes.
Interface stability between cathode and electrolyte is closely related to the interface resistance and electrochemical performance of all-solid-state lithium ion batteries (LIBs). However, the significant interface issues between cathode and all-solid-state polymer electrolyte have been researched rarely. Here, we demonstrate that severe interface decomposition reactions occur continually and deteriorate the cycling life of high voltage LiCoO 2 /cellulose-supported poly(ethylene oxide) (PEO)-lithium difluoro(oxalato)borate (LiDFOB)/Li battery between 2.5 and 4.45 V vs. Li/Li + . To improve the interface stability between LiCoO 2 and PEO-LiDFOB electrolyte, we modify the LiCoO 2 surface by a thin layer of high ionic conducting and electrochemical oxidation resistant poly(ethyl cyanoacrylate) (PECA) through in-situ polymerization method. The PECA coating layer significantly suppresses the continuous decomposition of lithium difluoro(oxalato)borate (LiDFOB) salt in PEO electrolyte. As a result, the PECA-coated LiCoO 2 /PEOLiDFOB/Li battery shows decreased interface resistance and enhanced cycling stability. This work will enlighten the understanding of interface stability and enrich the modification strategy between cathode and polymer electrolyte as well as boost the further development of all-solid-state LIBs. Polymer electrolyte-based all-solid-state lithium ion batteries (LIBs) with the merits of flexibility, high energy density and high safety have been researched for a long time.1-5 Nevertheless, their applications are still challenged by the interface issues between electrode and solid-state electrolyte. The thorny interface issues mainly refer to the inherent space charge layer and detrimental chemical reactions at the electrode and electrolyte interface, which lead to large interface impedance and then deteriorate the fast charging/discharging ability and cycling stability of all-solid-state LIBs. [6][7][8][9] Polyethylene oxide (PEO) electrolyte with high ion conductivity and good interface stability with Li metal has been successfully used in commercial polymer LIBs, in which the cathode material is LiFePO 4 instead of LiCoO 2 . The failure application of PEO electrolyte in LiCoO 2 -based high energy density LIBs is mainly due to the interface decomposition reactions of PEO at high voltage. Shiro Seki et al. have proposed that the oxidation decomposition of PEO electrolyte takes place from 4.0 V vs. Li/Li + , which leads to continuous increasing of LiCoO 2 /PEO interfacial resistance and results in poor cycle performance at 4.4 V vs. Li/Li + . 10 Moreover, during high voltage charging of LiCoO 2 , the highly oxidized Co 4+ ions will accelerate the oxidation decomposition of PEO electrolyte.11 It can be concluded that the cathode/polymer electrolyte interface characteristic is quite essential to the electrochemical performance of all-solid-state LIBs, especially for the high voltage cathode LiCoO 2 and PEO electrolyte. However, the interface oxidation decomposition products and reaction mechanism between ...
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