Patent Application: US-201715462216-A

Abstract:
xanthan gum has been found to be a superior binder for binding an electrode , especially an anode , in a lithium - ion or lithium - sulfur battery , being able to accommodate large volume changes and providing stable capacities in batteries tested with different types of anode materials .

Description:
cyclic voltammetry and cell cycling were carried out on half cells using 2325 - type coin cells assembled in an argon - filled glove box . cyclic voltammograms were recorded using a biologic ™ vmp3 potentiostat / galvanostat . the potential of the working electrode was swept at 0 . 1 mv s − 1 from open - circuit potential down to 5 mv ( or 10 mv ) versus li / li + , then swept up to 1 . 5 v ( or 2 v or 3 v ) versus li / li + ; afterwards cells were cycled between 1 . 5 v ( or 2 v or 3 v ) and 5 mv ( or 10 mv ) versus li / li + . capacity measurements were performed by galvanostatic experiments carried out on a multichannel arbin battery cycler . the working electrode was first charged down to 5 mv ( or 10 mv ) versus li / li + at different c - rates and then discharged up to 1 . 5 v ( or 2 v or 3 v ) versus li / li + . the mass of active material used in the calculation is the mass of the material used in the active electrode . working electrodes were prepared as follows . active material ( e . g . carbon graphite ( mcmb ), nano - sno 2 / c , sn — co , znmn 2 o 4 or si ) was mixed with 5 wt % of super carbon ( timcal ) and 5 or 10 wt % of binder . electrode films were made by spreading the material onto a high purity copper foil current collector ( cleaned using a 2 . 5 % hcl solution in order to remove the copper oxide layer ) using an automated doctor - blade and then dried overnight at 85 ° c . in a convection oven . individual disk electrodes ( 0 = 12 . 5 mm ) were punched out , dried at 80 ° c . under vacuum overnight and then pressed under a pressure of 0 . 5 metric ton . a lithium metal disk ( 0 = 16 . 5 mm ) was used as a negative electrode ( counter electrode and reference electrode ). 70 μl of a solution of 1 m lipf 6 in ethylene carbonate / dimethyl carbonate ( 1 : 1 , v / v ) was used as electrolyte and spread over a double layer of microporous propylene separators ( celgard ™ 2500 , 30 μm thick , = 2 . 1 mm ). the cells were assembled in an argon - filled dry glove box at room temperature . referring to fig1 , it is evident that for half batteries comprising meso carbon microbead ( mcmb ) anodes , the use of xanthan gum as the anode binder leads to significantly higher and more stable discharge capacity over 100 charging cycles than all of the use of any of the other binders , including pvdf . referring to fig2 , it is evident that this result is consistent across a broad range of c - rates . for half batteries comprising nano - sno 2 / c anodes , the use of xanthan gum as the anode binder leads to significantly higher and more stable discharge capacity over tens of charging cycles than with the use of pvdf , and the use of xanthan gum is comparable to the use of nacmc ( see fig4 ). for half batteries comprising sn — co anodes , the use of xanthan gum as the anode binder leads to significantly higher and more stable discharge capacity over tens of charging cycles than with the use of pvdf , albeit a somewhat lower discharge capacity than with the use of nacmc ( see fig5 ). for half batteries comprising znmn 2 o 4 spinel anodes , the use of xanthan gum as the anode binder leads to higher and more stable discharge capacity over tens of charging cycles than with the use of pvdf , although the use of xanthan gum led to somewhat lower discharge capacity than the use of licmc or nacmc ( see fig6 ). for half batteries comprising silicon anodes , the use of xanthan gum as the anode binder leads to higher discharge capacity retention at cycle # 2 than pvdf ( 45 % vs . 21 %) but lower discharge capacity retention than either licmc ( 87 %) or nacmc ( 95 %) ( see fig7 ). results demonstrate that the use of xanthan gum as an anode binder provides higher and more stable discharge capacity than polyvinylidene fluoride over a broad range of anode materials , while in some cases being comparable to carboxymethylcellulose . references : the contents of the entirety of each of which are incorporated by this reference . beattie s d , larcher d , morcrette m , simon b , tarascon j m . 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