In-situ Electrochemical AFM Observations of SEI Film Formation on Graphite Anodes

Abstract

Solid Electrolyte Interphase (SEI) films play an important role in lithium ion battery. SEI films form on graphite anode surfaces during early lithium intercalation process. SEI films prevent further solvent decomposition during charge and discharge in the battery. Morphological study of SEI film formation is very important to understand the function of SEI film in lithium ion battery system. Simultaneous in-situ electrochemical Atomic Force Microscopy (AFM) and Friction Force Microscopy (FFM) were successfully introduced to monitor SEI film formation in real time. Topographic and frictional changes on the surface of a Highly Oriented Pyrolytic Graphite (HOPG) electrode in 1 mol/dm3 LiC104 EC/EMC (1:1) electrolyte were examined during charge and discharge. SEI film formation commenced at approximately 2V vs. Li/Li+ and stable film formation with an island-like morphology was observed below approximately 0.9V vs. Li/Li+. Further experiments on a composite electrode made of synthetic graphite powder and polyvinylidene difluoride (PVDF) binder showed similar phenomena. KEYWORDS: Lithium ion battery, Graphite Intercalation Compound, Anodes, SEI, in-situ electrochemical AFM 1.ƒŠ ƒ` ƒEƒ€ ƒCƒI ƒ" "d 'r ‚AE •• ‰" •‰‹É •@‹ß "N,ƒr ƒf ƒI ƒJ ƒ• ƒ‰,OEg 'Ñ"d ˜b,PHS,ƒm •[ ƒgOE^ ƒp •[ ƒ\ ƒi ƒ‹ ƒR ƒ"ƒs ƒ… •[ ƒ^•[ "™OEg 'Ñ-p •¬OE^"dŽq‹@Ší ‚Ì ‹} '¬ ‚È•• ‹y ‚É"º ‚¢ •‚-e-Ê •¬OE^2ŽŸ "d'r ‚Ì Žù-v ‚ª ‹} '• ‚µ ‚Ä‚¢ ‚é•B ƒŠƒ`ƒŠƒ`ƒEƒ€ƒCƒI ƒ"2ŽŸ"d 'r ‚Í ‚± ‚ê ‚Ü‚ÅŽå-¬ ‚Å‚ ‚Á‚½ƒj ƒbƒPƒ‹ ƒJ ƒhƒ~ƒEƒ€"d'r ‚â ƒj ƒbƒP ƒ‹ •…'f "d 'r ‚É"ä ‚× •½‹Ï "dˆ³ ‚ª-ñ3"{ ‚AE ƒGƒl ƒ‹ ƒM •[-§ "x ‚ª •‚ ‚-, ‚ae ‚蕬 ‚³ ‚-‚ae ‚èOEy‚¢ "d'r ‚ª ‚Å ‚« ‚é ‚½‚ß1991"N ‚Ì •ã ŽsˆÈŽsˆÈ-ˆ •L ‚Ñ'± ‚¯,OE» •Ý‚Å ‚Í ‰" "d'r,ƒj ƒbƒPƒ‹ ƒJ ƒhƒ~ƒEƒ€"d'r ‚AE ƒj ƒbƒPƒ‹ •…'f "d'r ‚ðŠÜ‚Þ 'S2ŽŸ "d'r ‚Ì ' † ‚Å•Å'å ‚Ì • ¶ ŽY Šz ‚ð •è ‚ß ‚é ‚Ü‚Å •¬ '· ‚µ‚½•B ƒŠƒ`ƒŠƒ`ƒEƒ€ƒCƒI ƒ""d 'r ‚Í ‚» ‚Ì-¼'O‚© ‚ç ‚à ‚í ‚©‚é 'Ê ‚è,•‰ ‹É ‚É ‹à '® ƒŠƒ`ƒŠƒ`ƒEƒ€ ‚ð Žg-p ‚¹ ‚¸'‚¸'Y'f •‰ ‹É ' † ‚É ƒŠƒ`ƒŠƒ`ƒEƒ€ ‚ð ƒCƒI ƒ"•ó 'Ô ‚Å'~ ‚¦ ‚é ‚± ‚AE‚© ‚ç-½-¼‚³ ‚ê ‚½ ‚à‚Ì ‚Å‚ ‚é •B1980"N 'ã ‚Ì OEã"¼ ‚Ɉê "Ê-¯ • ¶-p‚AE‚µ‚Ä•‰‚ß ‚ÄŽs "Ì ‚³ ‚ê ‚½‹à '® ƒŠƒ`ƒŠƒ`ƒEƒ€•‰‹É ‚ð-p ‚¢ ‚½‰~ "› OE^ƒŠƒ`OE^ƒŠƒ`ƒEƒ€2ŽŸ"d'r ‚Í "-‰ÎŽ-OEÌ‚ð ‹N‚± ‚µ ‚½‚½‚ß Žs •ê ‚© ‚ç‰ñ Žû ‚³ ‚ê ‚½•B ‚±‚Ì OE´ˆö ‚Í ‹à '® ƒŠƒ`ƒŠƒ`ƒEƒ€•‰‹É•ã ‚Å•[ •ú "d ‚É Šî ‚à ‚-ƒŠƒ`ƒŠƒ`ƒEƒ€ ‚Ì-n ‰ð•E•Í •o ‚ª ‹N‚± ‚é •Û,ƒŠ ƒ` ƒEƒ€‚ª ƒf ƒ" ƒh ƒ‰ ƒC ƒg•¬ '· ‚µ‚â ‚· ‚¢ ‚½‚ß ƒŠƒ`ƒŠƒ`ƒEƒ€ƒf ƒ" ƒhƒ‰ ƒC ƒg‚ª ƒZƒp ƒOE •[ ƒ^ ‚ð"Ë ‚«"j ‚è'Z-•‚µ ‚½OE‹‰Ê,"-‰ÎŽ-OÊɂ‚Ȃª ‚Á‚½ ‚AE •l ‚¦ ‚ç‚ê ‚Ä‚¢ ‚é •B ‚» ‚ê ‚ð-h ‚®•û-@‚Ì ‚ЂAE ‚ ‚AE‚µ‚ăŠƒ`‚AE‚µ‚ăŠƒ`ƒEƒ€ ƒCƒI ƒ"‚ð ‰Â ‹t "I ‚É‹z ' •E •ú •o ‰Â "\ ‚Å‚©‚ ƒŠƒ`ƒŠƒ`ƒEƒ€ ƒCƒI ƒ" ‚ð‹z ' ‚µ‚½Žž‚Ì ‰» Šwƒ| ƒe ƒ" ƒVƒƒƒ‹ ‚ª ‹à '® ƒŠƒ`ƒŠƒ`ƒEƒ€‚Ì ‰» Šwƒ| ƒe ƒ"ƒVƒƒƒ‹ ‚É‹ß ‚¢ 'Y'f •Þ-¿‚𠕉 ‹É ‚AE‚µ,‹ó ‹C ' † ‚Å‚àˆÀ'è ‚ÈLiCoO2‚ð •³ ‹É ‚AE‚µ‚Ä-p ‚¢ ‚½‚Ì ‚ª OE» •Ý‚Ì ƒŠƒ`ƒŠƒ`ƒEƒ€ƒCƒI ƒ""d 'r ‚Å‚ ‚é1)•B •• ‰" 'wŠÔ‰» • ‡ •¨(GIC,Graphite Intercalation Compound)2) ‚ª •Å•‰‚É• ‡ •¬ ‚³ ‚ê ‚½‚Ì ‚Í1841"N ‚Å‚ ‚Á‚½‚ª,OE» •Ý ƒŠƒ`ƒŠƒ`ƒEƒ€ ƒC ƒI ƒ""d 'r ‚Ì •‰‹É ‚É-p‚¢ ‚ç ‚ê ‚Ä‚¢ ‚é ƒŠƒ`ƒŠƒ`ƒEƒ€•• ‰" 'w ŠÔ‰» • ‡ •¨ (Li-GIC)‚Ì • ‡ •¬ ‚Ì ŽŽ‚Ý‚Í1955"N ‚ÉH6rold‚É ‚ae ‚Á‚Ä•Å•‰‚É•ñ •• ‚³ ‚ê ‚Ä‚¢ ‚é •BLi-GIC‚𠃊ƒ`ƒŠƒ`ƒEƒ€‹à '®‚É•Ï ‚¦ ‚ăŠƒ`‚ăŠƒ`ƒEƒ€2ŽŸ "d 'r-p •‰ ‹É ‚É-p ‚¢ ‚é •l ‚¦ •û ‚Í1976"N ‚ÌBesenhard‚ç ‚Ì˜_‚̘_ • ¶3) ‚É‚· ‚Å‚É•q ‚× ‚ç‚ê ‚Ä‚¢ ‚é ‚ª.ŽÀ •Û‚Ì ƒŠƒ`ƒŠƒ`ƒEƒ€2ŽŸ"d 'r ‚AE‚µ‚Ä‚Ì ‰ž-p ‚Í1980"N ‚É•Ä•' ƒx ƒ‹OE¤‹ † •Š ‚ÌBasu‚É ‚ae ‚èLiCl+KCl"™ ‚Ì •‚ ‰·-n-Z ‰-‚ð "d‰ð Ž¿ ‚AE‚µ‚ÄŽg-p ‚· ‚é •‚ ‰·ƒ^ƒCƒv‚Ì ƒŠƒ`ƒŠƒ`ƒEƒ€2 ŽŸ"d 'r "Á‹-‚ª •‰‚ß ‚Ä‚Å‚ ‚é4)•B•í ‰·ƒ^ƒCƒv‚Í1981"N ‚ÉŽO-m "d ‹@ ‡Š ‚Ì 'r "c ‚ç5),1982"N ‚Ƀx ƒ‹OE¤‹ † •Š ‚ÌBasu6)‚É ‚ae ‚è"AE-§‚É Li-GIC‚𠕉‹É ‚ÉŽg-p‚µ‚½ƒŠƒ`p‚µ‚½ƒŠƒ`ƒEƒ€2ŽŸ"d'r "Á‹-‚ª •o Šè ‚³ ‚ê ‚Ä ‚¢ ‚é •B ‚± ‚ê ‚ç ‚Ì "Á‹-‚Å‚Í ‚ ‚ç ‚© ‚ ¶‚ß •‚ ‰·‚Å ƒŠƒ`ƒŠƒ`ƒEƒ€‹à '®‚É•Ú •G ‚³ ‚¹ ‚é ‚È ‚Ç ‚µ‚ÄLi-GIC‚ð • ‡ •¬ ‚µ,‚± ‚ê ‚ð•‰ ‹É ‚AE‚µ ‚Ä,ƒv ƒ• ƒs ƒOEƒ"ƒJ •[ ƒ{ ƒl •[ ƒg‚AEƒW ƒ• ƒgƒLƒVƒGƒ^ƒ"•¬• ‡-n "} ‚â1,3-ƒW ƒI ƒL ƒ\ ƒ‰ ƒ"‚ð-n "} ‚AE‚µ ‚ÄŽg-p‚µ ‚½"d ‰ð ‰t' † ‚Å•³ ‹É ‚AE‚Ì 'g ‚Ý• ‡ ‚í ‚¹ ‚é ‚± ‚AE‚É ‚ae ‚è2ŽŸ"d 'r ‚AE ‚· ‚é ‚à‚Ì ‚Å‚ ‚Á‚½‚ª,Li-GIC‚Í ‚± ‚ê ŽO •H‰» Šw ‡Š•â •o Ž-‹AE•Š‹Z•p ŠJ"-•":•• •ì OE § •â •oŽs"Ô‚Ì •B '¬1"Ô'n