New version page

Charge–discharge stability of graphite anodes for lithium-ion batteries

Upgrade to remove ads

This preview shows page 1-2-3-4-5 out of 14 pages.

Save
View Full Document
Premium Document
Do you want full access? Go Premium and unlock all 14 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 14 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 14 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 14 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 14 pages.
Access to all documents
Download any document
Ad free experience

Upgrade to remove ads
Unformatted text preview:

www.elsevier.nl/locate/jelechemJournal of Electroanalytical Chemistry 497 (2001) 33–46Charge–discharge stability of graphite anodes for lithium-ionbatteriesChunsheng Wanga,*, A. John Applebya, Frank E. LittlebaCenter for Electrochemical Systems and Hydrogen Research, Texas Engineering Experiment Station, Texas A&M Uni6ersity, College Station,Texas77843-3402, USAbCenter for Space Power, Texas Engineering Experiment Station, Texas A&M Uni6ersity, College Station, Texas77843-3118, USAReceived 26 May 2000; received in revised form 6 October 2000; accepted 8 October 2000AbstractA graphite powder disk sandwiched between two nickel screens was used as a lithium-insertion working electrode. Electrochem-ical impedance spectroscopy (EIS), galvanostatic intermittent titration (GIT) using pulsed microcurrent, and in-situ intrinsicresistance measurements were used for the evaluation of kinetics and intrinsic (i.e. physical) resistance changes duringcharge–discharge cycling from room temperature to elevated temperatures. The investigation of the thermal stability of theelectrolyte at elevated temperature used an EIS study of a palladium electrode in the electrolyte. EIS measurements forelectrochemical reaction and intrinsic resistances of a graphite electrode show that the first high-frequency depressed semicircle isdue to the ‘solid electrolyte interphase’ (SEI) film, although it is also influenced by the electrode contact impedance. The growthof the SEI film on the MCMB 10-28 graphite electrode surface with cycling, results in a decline in kinetic rate and a correspondingincrease in contact resistance giving rapid capacity fade. The high stability of the capacity of JM 287 electrodes is due to the slowincrease in SEI film thickness on their surfaces. Although new SEI films were formed on the originals at elevated temperature, thekinetics were still more rapid than at room temperature in the initial cycling. © 2001 Elsevier Science B.V. All rights reserved.Keywords:Electrochemical reaction kinetics; Intrinsic resistance; Electrochemical impedance spectroscopy; Thermal stability1. IntroductionGraphite is the most commonly used anode forlithium-ion secondary cells. Good graphite charge–dis-charge cycle stability is one of the most importantcriteria for reliable and long-lived lithium-ion batteryoperation. It is commonly assumed that the composi-tion and structure of the passivation ‘solid electrolyteinterphase’ (SEI) film are both critical for cycling stabil-ity. This film results from solvent reduction and decom-position products beginning with the first chargeprocess. The SEI film covering the graphite surfaceexposed to the electrolyte must be permeable to Li+cations, and must be electronically insulating to preventfurther electrolyte decomposition during cycling. Fur-ther growth will decrease the conductivity of thegraphite agglomerate, and reduce the reversible capac-ity [1– 3] due to a decrease in the amount of activematerial and in the kinetics of lithium insertion. Hencethe intrinsic resistance change of a graphite electrodecan be used to monitor the formation and growth ofSEI film [4,5]. However, how the SEI film directlyinfluences the thermodynamics and electrochemical ki-netics of absorption of lithium into graphite is not clearat this time.Galvanostatic intermittent titration (GIT) is an effec-tive method of measuring the equilibrium potential–composition– temperature isotherm (PCT) duringlithium insertion and extraction to and from graphite.The extent of lithium absorption into graphite at agiven temperature can be obtained from PCT curves.GIT using pulsed microcurrent can also provide someuseful information on the total reaction resistance [5].One of the more discriminatory methods for measuringelectrochemical reaction kinetics is electrochemicalimpedance spectroscopy (EIS), which can give individ-ual reaction resistances for each step if their timeconstants are resolvable [6].* Corresponding author. Fax: + 1-409-8459287.E-mail address:[email protected] (C. Wang).0022-0728/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.PII: S0022-0728(00)00447-2C. Wang et al./Journal of Electroanalytical Chemistry497 (2001) 33– 4634In this work, the cycling stability and kinetics of alithium– graphite electrode have been studied using in-situ GIT, EIS and in-situ intrinsic resistance measure-ments. Lithium absorption thermodynamics andkinetics into graphite at 25 and 65°C are compared.2. Experimental2.1. Electrode and cell preparationTwo graphite powder samples (MCMB 10-28 andJM 287) were used as anode materials. Their nominalparticle size, BET surface area, and source are shown inTable 1.Composite electrodes were prepared from a mixtureof 92 wt% graphite powder with 8 wt% pure polyvinyli-dene fluoride between two nickel screen current collec-tors using 1-methyl-2-pyrrolidinone as the solvent.After drying overnight at 120°C, the electrode waspressed into a sandwich structure with a geometricsurface area of 2.0 cm2. The configuration of a typicalelectrode was shown in a previous paper [5]. The elec-trodes contained ca. 50 mg of active graphite. Electro-chemical measurements were conducted in a specialfour-electrode PTFE cell. Two lithium foils were usedas both counter and reference electrodes, and a Pd wirewas used as another working electrode to monitor thestability of the electrolyte at elevated temperature. Allpotentials given are versus the Li  Li+reference elec-trode in the experimental electrolyte, which was 1.0 Mlithium hexafluorophosphate (LiPF6) in a 1:1 by vol-ume ethylene carbonate (EC) +dimethyl carbonate(DMC) mixture (High Purity Lithium Battery Grade,Mitsubishi Chemical Company). Cells were assembledin an argon-filled glove box. Charge (lithium intercala-tion) and discharge (lithium extraction) characteristicswere measured between +0.0 and +1.5Vatacon-stant current using an Arbin (College Station, TX)automatic battery cycler.2.2. In-situ intrinsic resistance measurementIn-situ intrinsic (i.e. physical) resistance of graphiteelectrodes was carried out using two potentiostats. Onewas for electrochemical lithium insertion –extraction,and the other was used for measuring intrinsic resis-tance. A constant current (10 mA for JM 287, and 1mA for MCMB 10-28 electrodes) was passed across thegraphite electrode, and the intrinsic resistance was eval-uated from the voltage change between the two sides ofthe working electrodes. The


Download Charge–discharge stability of graphite anodes for lithium-ion batteries
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Charge–discharge stability of graphite anodes for lithium-ion batteries and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Charge–discharge stability of graphite anodes for lithium-ion batteries 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?