Font Size: a A A

Preparation And Characterization Study Of Cellulose And Cellulose Derivatives Composite Lithium Ion Battery Separator

Posted on:2017-12-11Degree:MasterType:Thesis
Country:ChinaCandidate:C T LiuFull Text:PDF
GTID:2381330623954635Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
Nowadays environmental friendly battery materials have received widespread attention for oil resources shortage,energy crisis and serious pollution.In our study,we choose cellulose and its derivatives as constituent materials to prepare Lithium-ion battery composite membrane for its excellent properties,such as abundance,high dielectric,lyophilic,etc.The composite separator was got through phase separation method.Carboxymethyl cellulose-lithium(CMC-Li)is a kind of polymer polyelectrolyte,belongs to the ionic cellulose ethers.CMC-Li can ionize into long anion ionization chain of-OCH2COO~-and Li~+.CMC-Li is soluble in water,just like poly(vinyl alcohol)(PVA).PVA/CMC-Li composite membrane was successfully fabricated through phase separation method.The separator has uniform pore structure.Porosity is about 60%.The electrolyte uptake is about 2.3.The addition of CMC-Li has no side effect of membrane pores,electrolyte uptake.The more CMC-Li added in membrane,the better dimensional stability,ionic conductivity,interfacial stability and electrochemical stability we get.On the one side,it belongs to CMC-Li's large polarity.On the other side,CMC-Li increases the content in battery system to some extent.It helps inhibit the formation of lithium dendrite which increases the safety of the battery system.However,the poor mechanical properties limit its application.Inspired by CMC-Li,cellulose nanofibers-lithium(CNFs-Li)was successfully achieved in our study.It has large length to diameter ratio and group of-COO-Li,which makes it has excellent properties of both cellulose nanofibers and ionic cellulose ethers CMC-Li.PVA/CNFs-Li composite membrane with good hole structure was successfully prepared.CNFs-Li's big polarity has positive effect on ionic conductivity,electrolyte wettability.Besides,CNFs-Li increase the content of Li~+in battery system.It opens a new way to transport Li~+,which improves the transmission efficiency,reduces the capacity loss.The solvent used during the preparation process is water and anhydrous ethanol which is environmentally and friendly.The separator can be a high-performance alternative battery material for its good performance and friendly processing method.Cyanoethyl cellulose(CEC)has excellent mechanical properties,thermal properties,good electrochemical stability and high dielectric constant.The cyanoethyl group in separator can be beneficial to membrane's ionic conductivity.In our study,we selected poly(vinylidene fluoride)(PVDF)as the backing material for its good electrochemical stability and film-forming performance.PVDF/CEC composite membrane with good pore structure was successfully prepared.CEC's good polarity dielectric properties increased electrolyte invasive,largely keeped the electrolyte,which is beneficial to promote the dissolution of lithium salt well.It helps increase the carrier concentration,inhibit the formation of lithium dendrite to some extent.The security and the comprehensive performance of the battery system improved a lot.
Keywords/Search Tags:carboxymethyl cellulose-lithium, cellulose nanofibers-lithium, cyanoethyl cellulose, phase separation, lithium-ion, separator, environmentally and friendly
PDF Full Text Request
Related items