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Jurnal Ilmu Pengetahuan dan Teknologi TELAAH Volume 26, November 2009

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The Effect of Milling Time on The Electrolyte Ceramic Composite of Lithium Battery

BAMBANG PRIHANDOKO

Research Center for Physics,LIPI, PUSPIPTEK Serpong-Tangerang E-MAIL :[email protected]

ABSTRACT: Research on The Effect of Milling Time on the Electrolyte Ceramic Composite of Lithium Battery have been done. The electrolyte ceramic composite material is a mixed material from windows glasses or soda lime silica as matrix and Lithium Titanium Aluminum Phosphate (LTAP) as filler. Soda Lime Silica Glasses contain Na2O 11.6%, CaO 8.1% and SiO2 58.7%. LTAP material mixed in the slurry of powder windows glasses with composition of weight procentage 75%. The temperatures process for sintering of samples is above of glass transition at 6000C. Then samples quenched with liquid nitrogen. The variations of millings time are 0, 12, 24, 36 and 48 hour. On the SEM analyses the visual photos of composite surface give the pictures of particle size decreasing from powder materials. Soda lime silica can more good function as glue in the small particle. The other effects are decreasing of porosity and increasing of ionic conductivity. KEYWORDS: soda lime silica, LTAP, lithium battery, electrolyte, composite INTISARI : Penelitian Pengaruh Waktu Milling pada Keramik Komposit Elektrolit Baterai Lithium telah dilakukan. Material komposit elektrolit keramik merupakan bahan campuran dari kacamata jendela atau soda kapur silika sebagai matriks dan Lithium Titanium Aluminium Fosfat (LTAP) sebagai pengisi. Gelas Soda Kapur Silika mengandung 11,6% Na2O, CaO dan SiO2 8,1% 58,7%. Materi LTAP dicampur dalam bubur gelas bubuk jendela dengan komposisi prosentase 75% berat. Proses sintering suhu untuk sampel di atas transisi kaca pada 6000C. Kemudian sampel dipadamkan dengan nitrogen cair. Variasi waktu penggilingan adalah 0, 12, 24, 36 dan 48 jam. Pada analisis SEM foto-foto visual permukaan komposit memberikan foto ukuran partikel penurunan dari bahan bedak. Soda kapur silika dapat berfungsi lebih baik sebagai perekat dalam partikel kecil. Efek lainnya adalah penurunan porositas dan peningkatan konduktivitas ionik. KATA KUNCI: soda kapur silica, LTAP, baterai lithium, elektrolit, komposit 1. INTRODUCTION

Lithium batteries work with a phenomenon of intercalation process from the transfer of lithium ion. This process accour in process of charging and discharging, like in Figure 1[1]. Intercalation work in the electrodes of lithium batteries. A electrolyte deals of lithium battery is a medium for a migration of lithium ion.

Figure 1. Schematics process of charging and discharging in lithium battery[1]. The used electrolyte of lithium batteries is general in a basic of liquids materials in the market lithium

batteries. Lithium per chlorate ( Li4ClO4 ) is common used[2]. In the new development of lithium batteries, solid polymer electrolyte ( SPE ) used as a composite material from ceramic and polymer material[2]. High current capacity of lithium batteries needs high temperature resistant material, because a process of charging and discharging increases batteries temperature that is more quickly with high current capacity. High current batteries is usage in industry of automotive and UPS for communication.

One electrolyte candidate of LiTi2(PO4)3 (LTP) have high enough ionic conductivity which is around 10-7 Scm-1 3. Because LTP has NASICON crystal structure making its cationic free to move among interstitial


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place in the network. NASICON crystal structure is shown by Figure 2[4]. This material LTP is basic structure of LTAP (Li1,3Ti1,7Al0,3(PO4)3 ). In this experiment solid electrolyte is searched for target of above. Solid electrolyte is a composite material from LTAP with glasses metric. The raw material of glasses is windows glasses that are in technical term as Sodium Lime Silica.

Li2O is included solid electrolyte base on lithium and have anti fluorite structure able to yield great

number of cationic vacation. Diffusion Li2O can be done into structure and only causing a little expansion of glasses interface. One theory expresses that pregnant glass more than 5-mole % Li2O can generate rich interface of lithium ionic5. The addition of Li2O is to make glass becoming conductivity materials, because Li-ion can used as ion modified networks on windows glasses. This effect like as Na and Ca ion on silica glass. Structure Li2O crystal form shown by Figure 3[5]. In the previously experiment addition of Li2O give a good interaction within windows glasses6. The conductivity of windows glasses increase more than one thousand times. Great deals of Li2O diffuse on window glasses, and the others react with silica oxide. The optimum addition of Li2O is 7,5% weight.

Commercial glass is silicate, with SiO2 tetrahedral structure added by some modification ion. Crystal silicate structure can be differentiated by between crystalline form with amorphous form or glass. Glass can be considered sometime to be very viscous dilution because a glass is non-crystalline materials or amorphous. At high temperature above Tm, glass represents real dilution. Atoms have freedom move and can shift. When commercial glass in a state of melting to be made cool swiftly, hence decrease of thermal happened because of atoms perform a restructuring and form more efficient heap. This construction (Figure 4) representing the nature of typically from all liquid phases, but with quicker refrigeration happened change of sudden expansion coefficient. Under certain temperature is so-called glass transition temperature, or glass temperature, Tg, where there are not restructuring from atom and decreasing because of small thermal vibration.

Figure 3. Structure of Li2O[5].

Figure 4. Change of dilution volume at quenching[7].

Figure 2. Model of NASICON Structure[4].


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Table 1. Temperature glass transition ( tg) some glass materials[8]

Transition glass material temperature is simply referred as also with temperature, where at that

moment material which is its molecule, have very small mobility. At temperature under Tg materials have the character of brittle and stiff and above Tg materials have the character of more elastic. The elastic character of glasses is useful as glue to make a metric of composite electrolyte from windows glasses. The temperature process of sintering is above Tg of windows glasses in this experiment 2. METHODOLOGY

Li2O obtained from Merck produced carbonate lithium (Li2CO3) through calcinations process at temperature 700oC in 2 hour to discharge CO2. Equation reaction of process mentioned as following: Li2CO3 Li2O + CO2 (1) Li2O added at slurry of windows glasses in weight percentages of 7.5%. Process to make LTAP use powder metallurgy technique. Raw material able to be seen in equation of chemical reaction 2, which produced by Merck, namely Li2CO3, Al2O TiO2 and (NH4)2HPO4. The calcinations temperature is 9000C during 2 hours, then sintering at temperature 11000C during 8 hours[8].

0,65Li2CO3+0,15Al2O3+1,7TiO2+3(NH4)2HPO4 → Li1,3Al0,3Ti1,7(PO4)3+0,65CO2+6NH3+H2O (2) The used raw materials for windows glasses are common or commercial clear glass. The XRF analyses of this glass gift types and content of compound, namely Na2O 11.6%, CaO 8.1%, MgO 3.58%, Al2O3 0.19%, K2O 0.053% and SiO2 58.7%9. Samples are mixture materials from windows glasses, 7,5% weight of Li2O and LTAP with 75% weight. The materials have a mixing and milling in the Ball Mill with time variation of 0, 12, 24, 36 and 48 hours. At former experiment, temperature process sintering above Tg obtained at 6000C10. Samples of mixture materials sintered at temperature 6000C during 1 hour, then quenched in liquid nitrogen. The samples have make with method of tape casting. Samples are in form of palette with the size of diameter 1.5 cm and thick 0.5 cm. The samples analyzed with SEM, EDX, hardness, porosity and density. The samples measured conductivity with method of complex impedance or Electrochemical Impedance Spectroscopy (EIS). This measure use Solartron 1260. A simple electrochemical cell acts like a resistance and a capacitor where make a series or parallel circuit. Rtot represents a resistance from electrolyte and Cdl represents double layers capacitor. Notation for complex impedance is[11]: Z = Z’ + iZ” with 1i (3) and 2/122 "' ZZZ (4) Thus notation of complex impedance equation is for an electrochemical cell: Z = Rtot – i/ .Cdl. (5) To get Rtot value, hence we have to get Z"= 0 by extrapolation form semicircle to X-axis. From Z value = Rtot, we earn to determine conductivity of materials by using equation:

Type Tg(oC) measured Tg (oC)

Silica glass ~1200 -

Pyreks 550 350

Windows glass 550 270


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AlR (6)

with: R = Rtot = resistance from extrapolation (ohm) = specific resistance (ohm.m)

l = thickness of sample (m)

A = square of sample (m2) The size of powder on grinding for 48 hours seem small and almost equally, as in Figure 22 and 23. Pellets can also be seen to connect quite meeting each other. On the other smoothing effect of long milling almost is invisible. Variation of powder size is almost the same.

Figure 5.SEM analysis with 1000X

Figure 6. The measurement results of the powder on the milling time variation

The result of EDX analysis in Figure 24 shows the process of homogenization of soda lime silica bonding function. The longer the process of smoothing with the smaller size of the powder LTAP, the soda

O jam 12 jam

48jam

24 jam 36 jam


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lime silica can reach almost all grains. So the soda lime silica can wrap the whole grain refinement LTAP on for 48 hours. Photos surface of the sample with 48-hour long meeting and terhung rarefaction seen one another.

Figure 7. EDX analysis results from milling time of 48 and 0 hour .

The result of SEM images and EDX analysis can provide a model illustration of soda lime silica in performing its function as a glue. In the great powder and irregular in shape, soda lime silica glue themselves with just a stick. This was evident when the grain in the EDX analysis detected only LTAP compounds. Some soda lime silica powder does not stick to the surface area.

Figure 8. Model gluing of soda lime silica powder LTAP

The condition occurs in powder LTAP blanketed with long grinding 48 hours, while the others occurred in the conditions just stuck. EDX results illustrated difference between the two. Condition A has a very low Si concentrations, and in condition B has a concentration of Si equals the number of P concentration, where the ion Si comes from soda lime silica and P from LTAP. Mechanical properties have profited greatly in condition B. Ionic conductivity should also benefit from the condition B, where the more extensive surface contact and facilitate movement of Li ions, as in Figure 26 .

Figure 9. Conductivity under variation of powder size


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But the value of the sample conductivity with long grinding 48 hours which is equivalent to a large powder can not exceed the order of 10-6. This value is close to the conductivity of conductive glass in the manufacture of glass conductive chapter. LTAP powder as a whole covered by the soda lime silica in a large sample with approximately 1μm. So the soda lime silica to form an intermediate layer between the two powders LTAP. The motion of lithium ions through the LTAP should this intermediate layer. Violence tends to increase with the longer time smoothing or the smaller size of powder, see in Figure 27. At 48 hours smoothing value of hardness and tensile strength seen soaring. This is consistent with the small and dense powder on the SEM photograph. Increasing the value of hardness and tensile strength occurs almost 2.5 times of the sample that is not refined.

Figure 10. The results of hardness and strengthens test .

Porosity and density are not much different from the results - previous results Porosity in Figure 28 shows a decline, but the decline did not occur with drastic. Effect of Ball Mill grinding with a little less strong impact on the reduction of powder granules LTAP.

Figure 11. Porosity and density under variation of powder size

Density showed an increase which is not too strong. Media methanol is still being used in this study, so the compression of powder blocked by liquid methanol.

4. CONCLUSION This experiment gives a good result to produce electrolyte materials and give conclusion as follows 1. Milling time gif positive influence on character of electrolyte ceramic composite. 2. By the process of glue soda lime silica make optimize function with small powder. 3. Conventional milling make powder size only until 1 µm by milling time of 48 hours


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ACKNOWLEDGMENT This experiment is a part of my research for promotion of doctoral degree in Department of Metallurgy and Materials, FTUI. We gratefully acknowledge to Prof. Lilik Hendrajaya and State Ministry of Research and Technology - Republic of Indonesia for financial support of my doctoral study. This research is cooperation between State Ministry of Research and Technology - Republic of Indonesia, Research Center for Physics – Indonesian Institute of Science and Department of Metallurgy and Material – Engineering Faculty of University of Indonesia.

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[Online]. Available: http://www.mater.unimib.it/research.php?article=6 Feb. 2004. [2] P. P. Prosini, R. Mancini, L. Petrucci, V. Contini, P. Villano,Li Ti O as anode in all-solid-state,

plastic, lithium-ion batteries for low-power applications, Solid State Ionics, vol. 144, pp. 185–192, 2001 . Available: http://www.elsevier.com/locate/ssi

[3] Physics and Chemistry of Lithium-Ion-type-Accumulators. [Online]. Available: http://www.solid-energy.com/funktionsweise_eng.html, Nov. 2003. [4] Van Vlack, L.H, Ilmu dan Teknologi Bahan (Ilmu Logam dan Bukan Logam) terjemahan Sriati ,

Edition 5nd, Penerbit Erlangga, Jakarta, 1997. [5] Online Website available : http://www.world.house/wikipidia [6] B. Prihandoko, P. Sardjono, W. Waskitoaji, Pemanfaatan Karakter Gelas dari Sodium Lime Silica

sebagai Matrik untuk Pembuatan Komposit Elektrolit Baterai Lithium, Proceeding of Seminar Kimia Nasional, Sept. 2004 in press.

[7] Online Website: http://www.solartron.com [8] Powder diffraction file, International Centre for diffraction data, USA, 1990. [9] Annual Book of ASTM Standards, ‘testing of Density and Porosity’, ASTM C20-92, West

Conshohochen, PA, USA, vol. 15.02, 1999. [10] Online Website available: http://www.valleydesign.com [11] A. M. George, P. Richet, and J. F. Stebbinsi, Cation Dynamics and premelting in lithium

metasilicate (Li2SiO3) and sodium metasilicate(Na2SiO3): A high-temperature NMR study, American Mineralogist, Vol. 83, pp. 1277–1284, 1998.

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