Development of environment friendly high voltage metal/N-halogen organic cell systems

Development of environment friendly high voltage metal/N-halogen organic cell systems

R Udhayana & Devendra Prakash Bhattb

aKeiyro Commercial (P) Limited, 173,11 Main, Koramanga1a, Bangalore 560 034, India

bCarbon Technology Unit, National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110012, India Received 3 April 1995; accepted 7 July 1995

The employment of orgaqic materials such as dichloroisocyanuric acid (DCIA), trichloroisocyan- uric acid (TCIA), N.N'-dichlorodimethylhydantoin (DDH) and trichloromelamine (TCM) in the ener- gy deijvery devices has been addreSsed in two ways. rnst, these materials have been coupled with magnesium in the presence of aqueous medium of magnesium perchlorate electrolyte. Secondly, on the consideration of, cost, magnesium anodes have been replaced with zinc and zinc! N-halogen or- ganic cells were also constructed using the aqueous ammonium chloride;-zinc chloride solutions. In both the cases, the metal/N-halogen organic cells ascribe to, (a) High open circuit potential (up to 1 V vs Ag/AgCl), (b) High open circuit voltage (up to, 2.67 V), (c) High closed circuit voltage (up to 2.45 V) and (c) High energy density (up to 798 Wh kg-.! of the organic. compound). High melting point of these cathodic materials and their non-toxic properties would supplement the scope of their commercial viability for high temperature applications as well, befitting the environmental require-

ments. ..

Among the several known metallic. electrode ma- commercially available. Replacement of magne- terials in primary battery devices, the research sium by zinc can be done for certain applications and development on zinc or magnesium related where cost is the important criteria. Similarly, battery devices becomes really relevant not only when compared to the conventional inorganic or from the international. view point but also from even the hitherto best known organic cathode ma- the Indian context on the grounds that (i) Magne- terials like meta-dinitrobenzene2,6-8, N-halogen sium is now indigenously. produced from the cyclic ureide organic compounds stand better and readily available sea-bitterns b~sed on CECRI quite exciting iff terms of offering pollution free Technology1 and (ii) it is high time to switch over environments, high electrochemical potential and from the conventional reserve or dry battery de- high current density. It should be noted that the vices2-4 to the emerging systems based on either N-halogen cyclic ureide compounds used in the zinc or preferably magnesium in conjunction with present studies, have certainly no toxicity or pol- certain novel organic cathodes. The high elec- lution problems unlike many other organic mate- trode potential (- 2,37 V vs normal hydrogen elec- rials. This is because of the fact that some of trode compared with -0.76 V for zinc), lower them are used by the industry as the chlorinating electrochemical equivalent (0.45 g A-1 h-1 t:om- agents, disinfectants, industrial deordants, active pared with 1.22 g A -1 h -1 for zinc), greater sta- ingredients in laundry bleaches and diaries and al- bility towards corrosion (shelf life of magnesium so as swimming pool sanitizers9. The' detailed primary batteries \ -5 years) is greater than that' ~f background information on the subject of organic zinc primary batteries (-1 year) and low toxici~ batterles have been reported elsewhere1°-17.

are the-important features of magnesium as a gal- In view of these facts, investigations have been vanic anode5. Presently, it is a common practice under taken on magnesiUIil/or zinc-N-halogen for example to reduce the content of trace ele- cyclic ureide based battery systems for seeking ments .such as heavy metals to stich an extent that the objective of the emergence of a futuristic tech- magnesiu,m alloys become more resistant than nology in the area of primary battery market. This many aluminium alloys and steels. It is only re- paper provides an account of the review especial- cently that rapidly solidified magnesium alloys are ly on the development of Metal! N-halogen organ-

14 INDIAN J. ENG. MATER. SCI., FEBRUARY 1996 -

ic battery systems. Various magnesium salts, viz., thode mix composition was optimised from ca- magnesium chloride, magnesium bromide and pacity measurements as well as from measure- magnesium percl:llorate have been employed as ments of the resistance of the compacted organic

electrolytes 18 -20 and a preferential choice of mag- blend using the four-probe. measurement tech- ~ nesium perchlorate over other electrolytes was nique (Digital Micro-Ohm Meter, Agronic-54C,

made in view of the rea~on that it reduces the India).

corrosion of the battery components considerably. Electrolytes-Solutions of AR grade magnesium The evaluation. of various battery parameters such perchlorate,- ammonium chloride and zinc chlo- as capacit)!, energy density, coulombic efficiency ride were prepared in double distilled water.

and internal resistance has been presented. Stu- Cell assembly- The MgiZn-N-halogen organic dies on the corrosion behaviour of magnesium cells in prismatic configuration were assembled and its alloys in the presence of aqueous magne- using two anodes and a cathode separated by a

sium .salts are also made. The results with respect special synthetic papero. Voltage-time and vol- . to the corrosion rate are explained on the basis of tage-current profiles were obtained, using various r conjugation effect, inductive effect and field effect. discharge rates. Dry cells have also been fabricat-

Cyclic voltammetric (CV) investigations on the ed.

chosen organic compounds have been performed Halfcell potential measurements-In these ex- using NH4CI, MgCl2 and MgBr2 besides periments, the half cell potentials of N-halogen Mg(CIO4)2 solution which are the main electro- organic compounds were measured with reference lytes of metal-organic battery systems21. The to a Ag/ AgCI electrode and a comparative poten- trend of the CV behaviour has been found to be tial-time profile with respect to the meta-dinitro- similar using all these electrolytes. Hence" the re- benzene electrodxe system was also obtained during suIts pertaining to Mg(CIO4)2 solution have been discharge.

discussed. Preliminary X-ray diffraction results of Cyclic voltammetry (CV) measurements-A 0.1 the post-polarised magnesium samples have also M Mg (CIO4)2 aqueous solution containing

been reported. ments. These measurements 1.9608 mM DDH was used for the CV experi-were carried out with ,.

Experimental Procedure a BAS 100 A Electrochemical Analyser (obtained Electrodes-Magnesium metal of 99.8% purity from West Lafayette, Indiana, USA). The cell was obtained from Daupad Chemicals, India and consisted of a platinum working ele~trode (0.0314 magnesium alloy sheets wete supplied by Magne- cm2),.a silver/silver chloride reference electrode sium Elektron limited, UK. Extensive basic in- and a platinum foil auxiliary electrode. The work- vestigations on magnesium and magnesium alloys ing electrode was pretreated electrochemically ili were made using different electrolytes21-23 and it a similar manner as reported elsewhere24. CV was found that the dissolution is more in case of graphs were taken between the potential limits of ' the metal and hence the charge-transfer resistance -0.2 to -0.6 V employing various scan rates has been found to be maximum for Mg AZ31 al- and temperatures.

loy. In this study, the AZ31 alloy anode has been Co"osion measurements-For carrying out the

used in cell fabrications. Commercially pure zinc gasometry measurements, the gasometric set-up "'t-4 sheets as received from Ranveer Metal Industries, was mainta1:ned at a constant temperature. The vo-

Bombay were also employed as anodes. The di- lume of gas evolved was measured at regular inter- mensions of these anodes were 2 x 3 cm. For car- vals over a period of 3 h. The magnesium alloy rying out corrosion studies, the working ele.ctrode sheets were then removed from the. cell and (i.e. magnesium and its alloys) was cloth buffed in cleaned in a boiling solution of 20% H2CrO4 and the presence of pumice and then degreased with 0.02% AgNO3 for 2 min. Weight loss measure- trichloroethylene. The cathodes used were of the ments were then carried out for comparison. Cor:- same dimensions as those of the anodes. The ca'" rosion rate measurements of magnesium have thode mix containing the constant weight, 1.0 g of been carried out with or without using N-halogen N-halogen organic compound (Fluka), various organic compounds.

amounts of acetylene black ranging from 10 to 60 ,l

wt % (commercial grade of Travancore Electro- Results and Discussion

chemicals, India) and an optimum quantity of The current and voltage developed in our elec- 2-3% aqueous carboxymethylcellillose (BDH trochemical primary, energy systems is governed grade) binder was spread over the conducting Ti,. by the reaction of magnesium or zinc metal tanium mesh at an uptimised pressure. The ca- (anode) with the organic cathode. Structures of

the chosen organic compounds are depicted be- gations27-29, it was found that acetylene black is a

low: better conducting material than others because it

possesses more surface area, high conductivity

c~ ~' CI Y CI and more water retention property. Acetylene

CH3-C I-\ 'N~ black also increases the utilisation efficiency of

& C- Z 0 b~ the organic depola~s~rs during red~ction.

0'" ~ I ~ In order to optimise the quantity of acetylene

CI T C~' black, voltage versus tinle behaviour of Mg or Zn

D D H A organic cells have been carried out using different

i ~HCI percentages of acetylene black (Figs 1 and 2).

H'N"'~CI ~c ) These figures show that the working voltage of

b ~ '1 both MgiDCIA and Zll/DCIA cells has increased

0' 'r ~o a HN/~N",C'NHCI as a; function of the amount of aeetylene black.

CI Similarly, the capacity of the cells increased with

DC I A T C M an inerease in the percentage of acetylene black

and then arrived to an optimum value at 50-60%

The reduction of N-halogen compounds (e.g. (Fig. 1} and 30-40% (Fig. 2) ,in ~ase of ~1!(DCIA

DCIA) proceed by taking up the 4 electrons in and Zll/DCIA. systems, respectively. Similar r~-

presence of aqueous electrolytes.. The discharge suIts are obtaIned for other N-halogen organIc

process of the MgiDCIA or Zll/DCIA organic cell systems. These results are further confirmed

cells in the electrolyte media of magnisium perch- b.y voltage-c':lrrent l;11easur~ments and surface re-

lorate or ammonium chloride/zinc chloride are sistance studies. From the lmear curves of voltage-

governed by the following: electrochemical reac- current measurements, internal. resistance .of the

tions: cells have been calculated. The mternal resistance

Anode reactions values for the cells alongwith the surface resist-

2 Mg -2 Mg2+ + 4 e- ance parameters of the DCIA cathode formul-

2Zn -2 Zn2+ + 4 e- ations are furnished in relation to the yarious per-

Cathode reactions centages of acetylene black (Table' 1). Data has,

thus, suggested that the difference in capacity or

R g internal resistance of the cells are negligible be-

CC' N /C, "cc H .., c, "H tween 50-60% (MgiDCIA cell) and 30-40% (Zn/

N 4i N N

I I + 4H+ ~ I I +2HCC DCIA cell) and hence 50% and 30% can be taken

~c c~o ~ c

0 """'N/ o~ , "" ~o

I N

H I

H 2 .3

~ ~~~~~:~~~~

0 0 >~

II 11.1.9'

CC'N/~CC 4' H " C'N""H -IN. M 68

I I + 2¥ --I I +2cI+2OH ~ 1.5

o~C' ~ /40 o...j; ~ /~ 0 1.1 0 75 150 225 300 375 ,SO

H H TltE.. nn

Organic depolarisers are well known for their Fig. I-Influence of th~ ~arious P.ercentage of acetylene black

I . I I d ..2526 d . th h content on the voltage tIme profile of Mg/Mg(ClO4h/DCIA

re ative y ow con ucti~ ' an smce e etero- cell

geneolls electrode processes take place primarily at the surface, more quantity of the supplemen-

tary conducting materials is typically required for 2.1

tne preparation of organic cathode mixes. The> t.t

employment of various conducting materials such .~ t .4

as graphite, carbon black and acetylene black in 1; 4.0

the battery cathodes can facilitate the minimisa- ;

tion of IR voltage losses. In the present investiga- 0.0 0

tion, the N-halogen organic compounds and meta- TIME, min

d}njtrobenzene are tested to be poor conduct?rs Fig. 2~Influence of the va!"~s percentages of acetylene and ~ence they canno~ draw more current durmg black content on the voltage-time profile of Zn/NH4 CV

cell-discharge. After carrying out several investi- DCIA cell

16 INDIAN J. ENG. MATER. SCI., FEBRUARY 1996

as the effective optimum percentage of acetylene m-DNB cathode was -0.52 V. It is, therefore, black for the respective cells systems. imperative that the m-DNB based cell system is Discharge measurements-Concentration de- not discharged at higher currents which indicates

pendence of magnesium perchlorate and ammoni- the limitation of m-DNB cathode for high rate ap- \ urn chloride-zinc chloride with respect to the plications3l. These experiments show that work-

chosen organic cells has been investigated in de- ~ble current density of 20 mA!cm2 can be ob- tail29.30 and the results revealed that. 2 M magne~ tained from DDH based cell system without ad- sium perchlorate and 2 M ammonium chloride versely affecting the cell performance. The elec- + 8 wt % zinc chloride can be considered as the trode potentials for DDH and other N-halogen optimum concentrations for Mf/N-halogen and cathodes are found to be 2.5 times greater than Zn/N'-halogen org:anic cells, respectively. that of m-DNB (- 0.58 V).

Fig. 3 shows t,iie nalf-cell potential of the N -ha- Potential/voltage-time profiles of various Mg/ N-

logen compound (e.g. DDH) against the cell ca- halogen o\ganic cells: are demonstrated in Fig. 4. . pacity at various currents. A comparison of this The open circuit potential of N-halogen organic ~ system with nleta-dinitrobenzene is also shown cell systems has been observed to be around 1 V

under identical conditions at a constant current of vs Ag/ AgCI, which is significantly higher than that 200 mA. Solid lines in the figure alone show the of other well known organic depolarisers, for ex- real capacity of the cells. The real capacity of ample, open circuit potential of m-DNB is 0.12 V Mg/meta-diiiltrobenzene cell was found to be 17 vs Ag/ AgCr8.32. The working potential of DDH, Ah kg-l of m-DNB at the cut-off voltage of 0.75- TCIA and TCM ar~ ()h~erved to be. 0.84, 0.88 0.80 V, the corresponding cut-off potential of the and 0.77 Y vs Ag/f AgCI, respectively. The ob- served parameter~ (ire much higher than those ob- tained from the Mg/m-Dl;-rn cells (open circuit voltage: 1.50 V, working voltage: 1.10 V).

Table 1-Measurements of resistance vs % acetylene black Table 2 gives the data. for the evaluated battery

% Acetylene Resistance values, mQ parameters. The zinc/DCIA cells when activated -'

black in 2 M NH4CI. and 8 Wt % ZrtCI2, have given rise f

Mg/DCIA Zn/DCIA DCIA to the capacity-- value of 142 Ah kg-l of DCIA.

cells cells compacted .

plates The~e values are ve~ much higher than th; co.n- 10 8.6 9.09 7.06 ventlonal aq~eous p~ary battery systetns '. His-

20 5 6 07 togram showmg the influence of current dram on

3 .6. 4.47 the utilisation coulonibic efficiency of a Zn/DCIA 0 4.2 4.06 3.02 cell is shoWJl in Fig. 5. This shows that the cell 40 3.8 3.92 2.94 performs with greater efficiency at low current

50 3.6 -2.50 drains.

60 3.5 -'- 2.48 Cyclic vo/tammetrit measurements-Cyclic vol-

t~etric (CY) studies on a typical N~ha1ogfn or- ganiccompound (e.g. DDH) were obtained on a

900 platinum electrode in magnesium perchlorate. Prior "

~ 800 to the- addition of DDH to the cell, cyclic vol-

"'0. 600 .tammograms were recorded using the blank elec-

; trolyte of 0.1 M Mg (CIO4h. Observation of no

> '00 peaks show~ that the blank. electrolyte is neither

e -

:! -u 0 8!

c -IX!

.! ~

f ~~~=~=~~

0 -515 '... c 2 "5

B. _-3 600 -"" ' >400'. >'~.., .1.9 _>i

: -800 "...' E- ~. 0- )0

a :g 0 TCM DCIA tClA 1.5 i

u -11Xr) ->

0 1 22 i

..-1 l 0 400 800 1200 1600 2000

Capacity, A mn g -ime min

,

Fig. 3-Cathode potential vs capacity prgfiles [( 0) DDH, (8) Fig. 4-Cathode potential/voltage-time profiles of magne- m-DNB1J .sium/N-halogen organic eells at the discharge rate of 10 mA

Table 2-Comparative perforr:nancecharacteristics of various Mg/N-halogen organic cells at the discharge rate of 10 mA

Cathode Mol. wt. OCP, V OCV, V JR, mQ Capacity. Energy density. Utilisation

material Ah kg-c I Wh kg-I efficiency

%

DOH 197.02 0.100 2.50 1.39 350 798 64.0+

TCIA 232.41 0.115 2.67 3,00 300 660. 43.4:i:

DCIA 255.98 0.980 2.45 3.65 200 420 48.0 +

TCM 229.46 0.103 2.51 7.34 50 95 7.1:i:

.Values based on cathode active material w~ight.

+ Values based on 4 e- transfer.

:i: Values based on 6 e -transfer.

~

~ I.O^{~ 30}

~

^E]

c -,"

.~ 20 ~ ,.

::10 '.".",.

...vt,.I..~-'i'0 10 25 50 75 m 125 150 200 la' Current Drain ,mA

Fig. 5-Utilisation coulombic efficiency vs. current drain -0 profiles in respect of Zn/DCIA cell

oxidised nor reduced in the potential range of our

~ interest28. However, in the presence of 2 mM Fig. 6-CV profiles of DOH in 0.1 M Mg (ClO~)~ at various DDH solution to the Mg(Cl°-t)2 well-defined ca- scan rates (a) 5, (b) 10, (c) 20, (~) 40~ (e) 100, (f) 200 and (g) thodic and anodic peaks were obtained at -422 300 mY/S. lnsen plot (a) relatIonshIp of peak current Wllh

V d 357 V

.

m an -m, respectIve y Ig. .e m.

crease of scan rate from 5 to 300 m Vs -1 brings

about the rise in the peak current from 18 to 72 M -M 2 + + 2 - ,uA. Correspondingly, At;p (difference of anodic g g e

and cathodic peak potentials) also increases from 2H.,O + 2 e- -20H- + H., 65 to 121 mY. These values are higher than the :+ + --

values expected fOF a four electron transfer reac- Mg- 20H -Mg(OH)2

tion which indicates that the DDH system is not In contrast to the traditional weight loss meth- completely reversible in Mg(ClO4)2 medium. Plot od, the gasometric technique is a precise and ac- of ip'vs square root of scan rate gives linear be- curate method for determining the kinetics of me- , haviour. Straight lines do not pass through the tal corrosion", When magnesium is immersed in origin which shows that the electr'()chemical be- an aqu~ous electrolyte, hydrogen is evolved in haviour of DDH results from both diffusion and quantities corresponding to the metal dissolved.

kinetic controlled mechanism. The redox behav- The evolved hydrogen has been used as one of iour of DDH is attributed to single stage replace- the important parameter for calculating corrosion

ment of Cl by H, rates,4. The mechanism of maghesium disso!ytion

Co"osion measurements- The. steady-state in acidic and neutral media differs from tha( in al- working potential of magnesium is ~enerally in kaline medium. Magnesium is oxidised to oxide, the order of -1.50 V, This potential deviation hydroxide, or divalent ion in the presence of mag- with respect to the standard potential (i.e, -2,43 nesium perchlorate solution. There arc two hypo- V) has been explained electrochemically du~ to theses, namely:

.0- the formation fil th of inherent tal' magnesium hydroxide.

rf Th f . f h (1) the formatIon and dissolutIon of magnesium

m on e me su ace. e ormatIon 0 y- h d 'd

droxide film is due to the precipitation of Mg2 + y ~OXI e. , ,. , , , h 1 , h

.

d d b th d ti f t d . t h tal may get.separated from the electrode surface.

uce y e re uc..on 0 wa er accor mg 0 t e

~ ^--~._-

following reaction mechanisms: Mg-M:://

l "Y ;)D~~) :~

I"'. .',:" .'\~\

18 INDIAN J. ENG. MATER. SCI.. FEBRUARY 1996 In a second step, the monovalent ion is oxi-

dised by H+ ion: 18

2Mg+ +2H+ -2Mg2+ +H2 16 ~.

or, in contact with water, the conversion takes

place as: 1

2Mg+ +2H 0-2M g2+ +20H- +H ..-

2 2 I

This results in the formation of the stable val- ~ 1 ency of magnesium and the evolution of hydrog- IE en. o.ther side reactions such as the disproportion- C\ 1 ation of Mg + ions into magnesium metal and Mg2 + ..

ions are also possible.

~

.

2Mg+ -Mg+Mg2+ ~

The magnesium atoms thus formed can reduce

in an aqueous magnesium perchlorate solution as )

follows:

Mg+2H2O-Mg(OH)2+H2 20. .-.s

The properties of the magnesium electrode are Concentration Molar related to the existence of an intermediatory com-. ...'

d lik

.

.

poun e magnesIUm y n e .tion profile

Mg+2H+ +2e- -MgH2

lower conductivity in comparison to the bare me-

MgH2 may be oxidised by water in the presence tal itself34. { ,

of Mg(C1O4)2 as follows: OCV vs. time measurements- The open cir-

MgH + 2H 0 -Mg (OH)2 + H2 2 2 measured for several days and the data is re-cuit voltage readings for the different cells were . Relative rates of the above mentioned reactions corded for the continuous time duration of 430 h.

determine the corrosion rate of magnesium alloy. It is interesting to note that these cells give rise to During the gasometry measurements (Fig. 7), the the voltage of more than 2.0 V in contrary to the

formation of a black layer commenced on the conventional zinc or: magnesium based systems. It I electrode surface after 2 h. It is envisaged that is inferred that the open circuit voltage is more or \ this layer could comprise a mixture- of Mg (OH)2 less stabilised during the entire period of the mea-

I film and very fine particles of the metal itself3.6. surement in the free electrolyte. The cells were

The hydroxide, thus formed, i~ not soluble, and dismantled after 430 h and the corrosion rates thereby, could lead to a satu.ration state after 2 h. were calculated.

Thereafter, the gas volume does not rise, as is evi- Determination of the corrosion rate-The mag- .;,..

dent from the gasometry experiments. The gas nesium electrodes were removed from the cell evolution rate ha5 been found to increase with and the weight loss was calculated after suitably

temperature. This behaviour called as disintegra- removing the corrosion products. The values are , tion effect3? could result from co~tinuous damag.e found to be 0.2900, 0.1357,0.2774 and 0.0~34 g j to the film arilJ from the separation of fine partl- for DDH, DCIA, TCIA and TCM, respectively. 1 cles of the metal from the electrode by intergran- The corrosion rate in each case is determined in

ular corrosion leading to an increase in the active mils penetration per year units by using the fol-

surface area of the electrode. lowing formula: ~

The corrosion rate has been calculated from m = 534 W/DTA the measurements of the total volume of gas py

evolved and the results are compared with those where the symbols have their usual meanings. The i.

obtained from weight loss measurements (Table density of the samples is 1.74 g/ cm3 and the ex- 3). It is noticed froI1l the Fig. 7 that corrosion in- posure area of the magnesium sample is 12 cm2.

creases with concentration up to 2 M and then The values of the corrosion rates, thus, calculat- declines which arises from the formation of a ed in the case of DDH, DCIA, TCIA and TCM stable film on the el~ctrode surface that has a are 111.33, 52.07, 106.49 and 35.85 mpy, re-

j

Table 3-Influence of temperature and Mg(CIO4h concentration on corrosion parameters of magnesium AZ 31 alloy

Temp. Conc. Volume of gas Weight Weight Corrosion

°C M evolved loss. loss.. rate.

ml g g g-2h-'

30 0.5 13.4 0.0131 0.0123 5.30511

1.0 17.0 0.0166 0.0163 6.7303

1.5 23.5 0.0230 0.0224 9.3037

2.0 27.5 0.0269 0.0260 10.8873

2.5 8.5 0.0083 0.0081 3.3652

35 0.5 18.0 0.0173 0.0170 7.1262

1.0 21.4 0.0206 0.0200 8.4723

1.5 28.4 0.0269 0.0260 11.0852

2.0 30.7 0.0295 0.0289 12.1541

2.5 14.0 0.0135 0.0131 5.5426

40 0.5 19.8 0.0187 0.0182 7.8388

1.0 25.4 0.0240 0.0239 10.0559

1.5 29.2 0.0276 0.0271 11.5603

2.0 33.8 0.0319 0.1>300 13.3814

2.5 16.7 0.0157 0.0154 6.6115

45 0.5 22.6 0.0211 0.()208 8.9467

1.0 27.2 0.0253 0.0250 10.7685

1.5 31.8 0.0296 0.0289 12.5896

2.0 37.6 0.0350 0.0352 14.8858

2.5 19.4 0.0181 0.0178 7.6805

.Gasometry method ..Weight-ioss method

spectively. The trend of the corrosion rate of corrosion attack of the anode in the case of DDH magnesium alloys is as follows: based cell system. Also the + I effect exhibited DDH>TCIA>DCIA>TCM du~ to the presence of. two methyl groups in DDH structure can partIally reduce the electro- The observation of minimum corrosion rate in philic nature of the neighbouring carbonyl groups.

the case of TCM based system when compared The release of CI is expected to be relatively ea- with the DDH based cell system, could be due to sier for TCIA based cell system in comparison the extensive conjugation of the double bond in with TCM, which is pIlimarily caused because of between the. N and -CNHCI r of the structur'e the loose bonding between Nand CI in the for- of TCM. The supplement to the explanation is mer compound. This is mainly attributed to the envisaged as due to the electron donating ptoper- field effect caused by the influence of the ion ty of -NHCI group by which the entire -NHCI pairs of. the electrons of the two atoms (viz. CI group is tightened towards the cyclic ring and and 0) through space interactions which thereby hence leads to the maximum stability of the com- change the vibrational frequency of both the at- pound. Also, the electron donating property of oms (or groups). In other words, an electrostatic

-NHCI (TCM) is expected to dominate over the repulsioq can take place-between the non-bonding electron with drawing prop.erty of -NCI (DDH). electrons of oxygen and the chlorine atoms which Higher anodic corrosion rate as exhibited by cau.ses change in the hybridisation state of -CO the DDH based cell system in comparison with group enabling it to go away from the plane of

TCM based syst.em may be caused by the reduc: the. doubl6 .bond. Lesser corrosion _rate in case of tion in the conjugation in the case of former coqi- DCIA system in comparison with the TCIA based pound which is responsible for the easy liberation cell. could be obviously explainea'because of the of CI when compared with TCM. This chlorine presence of less number of adjoining Cl atoms to may then form MgCl2 in the resultant solution the N of the ring in the former compound. An- and hence could be responsible for much more other recent studies, based on impedance and

20 INDIAN J. ENG. MATER. sel.,FEBRUARY 1996

Conclusions

Very high potential up to 1 V has been ob-

Seordlmatch G/"qlhic

JDX-Series

60 50 20 70

3:J

I

40

B OP95.Pb

I

Measu~

I

I II

Aer-ment ₁

II II, I I, I

Standard

results of a typical pre-discharged magnesium al- loy sample and the same magnesium alloy sam- ples that are discharged at 10, 25 and 200 mA current drains, respectively. On one hand, it is quite clear to observe the different peaks of dif- ferent D values at each current .drain which. are indifferent from the results of the hlank magne- sium alloy sample. However, on the other side, the appropriate assignment of these peaks is yet to be demonstrated in terms of the surface pro- ducts, viz., magnesium oxide, magnesium hydrox- ide or the combination of both.

rotating disc electrode measurements of the mag- nesium/magnesium perchlorate system, have been reported elsewhere22.23•

In the last phase of tne research programme, the fabrication of Mg/N-hatogen organic dry cells was accomplished2ux wherein extruded magne- sium cylindrical cans in a D-size (height 6.1 em, diameter 3.3 cm) and A-size (height 5 em, diame- ter 1.4 cm) were prepared from magnesium AZ 31 aI.Ioy sheets. Wooden tools have been used to flatten the alloy sheet and to prepare the hollow cylindrical shape. 8 g of N-halogeq organic com- pound, 50% of acetylene black, 3% of barium chromate, 12 mL of magnesium perchlorate and 2% of starch were used for 'making the cathode hobhins. Two typical Mg/N-halogen organic dry cells are shown in Fig. 8.

X-ray -diffraction (XRD) measurements on post- polarised magnesium alloys- The discharged anode samples have been charactensed through XRD analysis. Typical chosen magnesium alloy samples have been obtained from the discharge of mg/DeIA cells at different current drains of 10, 25 and 200 mA up to the cut-off voltage of 1.5 V. Figs 9-10c demonstrate the preliminary XRD

Remain

---

>(L:Iisting *jJ:JCPDS*iC:hard:coPYi S : remain peak; [ES:J Fig. <)~XRD analysis of pre-discharged blank Mg AZ31

alloy

(0)

~h T~/'O

:il ,-

Fig. X-2.5 Volts MglDDH organic dry cells (a) D-size and (b) A-size

20 26 36 44 52 60 68 76

Angle, 2

e

Fig. IO-XRD analysis of post-discharged Mg AZ31 alloy at the discharge rates of (a) 10 mA, (b) 25 mA and (c) 200 mA

served for the N-halogen organic cathodes. In ments and to the Director, CECRI for providing contrast, the well known m-dinitrobenzene ca- the facility for this study. Thanks are also due to thodes possess the potential of 0.12 V. The cell Dr 0 P Bahl, Head, Carbon Technology Unit, systems have given rise to the voltage up to 2.67 NPL, New Delhi and Director, NPL for the en- V, a figure that is con~iderably higher in compari- couragement.

son to other known magnesium cells or any other

traditional aqueous cells. Conventional Zn/carbon References

MnO2 cells or the Mg/meta-dinitrobenzene cells I Kannan K N, Augustin C 0, Srikantan S, Subramanian P, of the recent years are known to perform the vol- Srinivasan K S & Desikan P S, Bull Electrochem, 2

tage 9utput of less than 1.5 V, (1986)473.

In terms of voltage-time relationship, it is found 2 Eul~r J & Dehm~lt K, Z Electrochem, 61 (1957) 1200..

0 0 .3 Lozier G S, Gllcksmann R & Morehouse C K, U5 Pat, that these metal-orgamc batteries have a relatively 874079(1956).

flat discharge profile whereas the conventional ac- 4 Bhatt D P, Leclanche Dry Cells-Indian Scene, Presented idlor alkali based zinc-carbon cells .possess slop- in Workshop on Dry Cell Batteries, Acetylence Black and ing characteristics, and (he other celf systems, vizo, other Battery materials, Madras, 19.88, 2.1.

Mg/MnO or Li/MilO have l~ss of a slope. Pla- 5 Gregory T D, Hoffman R J & WInterton R C, J Electro-

2 2 0 0 I chem Soc, 137 (1990) 775.

teau and stable voltage. charactenStics for .severa 6 Bhatt D P, Muniyandi N, Balasubramanian R & Mathur P months have been obtamed from some typical or- .B, Bull Electrochem, 2 (1986) 27.

ganic cells 16.2°. Keeping in view the constancy and 7 Bhatt D P, Muniyandi N & Mathur P B, Trans SAES7;

stability in the voltage of the fast moving electron- 22 (1987) 13. .."

ic equipmems in the market, the develQpment of 8 Bhatt D P, Murnyandl. N & Mathur P B, m In~em~tlonal b fl od b d 10ho II 39 0 Conferent:e on BatterIes and Fuel Cells, Karalkudl, Ab- car on mono uon ease It lum ce s. IS a stract No. 43 1988.

subject of importance. These cells are claimed to 9 OvchinnikovV K, Ger Pat, 2 550 828 (1975).

be commercially successful non-aqueous primary 10 BlochR, USPat,2556114(1951).

batteries by Japanese in view of their constancy in II Alt H, Binder H, Klempert G, Kochling A & San.o::stede voltage for several years and high reliability. G, Chern Ing !ech, 44 (1972) 195. .

..12 Alt H, Kochlmg A, Sandstede G, Bmder H « Klempert

A vanetles of carbon, fib~es have been deve- G, Ger Offen, 2055 675 (1972).

loped at NPL40.4) ,and there IS a need to develop 13 Knapp'H R & Almerini A L, J Chem Technol, 17 (1963)

the specific indigeneous carbon fibre anodes as a 125. .

substitute to conventional. 14 Yamamoto T & Shoji T, J Appl Electrochem, 20 (1990) 2 Practical current density obtained from N-ha- ^Kl021.c E n

21 A I D 5' C .£ PSC

..-". 15 ent , .roc st nnua .ower ources on),

logen orga~c cells IS .>.20 mA cm -, whereas Pub Com Red Bank,NewJersey (1967)p. 106.

the magneslum/meta-dIDltrobenzene cells and 16 Mathur P B, Balasubramanian R & Muniyandi N, Proc conventional zinc cells, give < 5 mA cm -:! and 12th Seminar on Electrochem, Karaihldi, India, 1972,

< 10 mA cm -2, respectively during their dis- 456.

charge operations, 17 Udhayan R, Muniy~ndi N & Bhatt D P, in 6th SSM Sci Res 3 The trend of the capacities of the organic Seminar in Tamil (Eng Sciences), Bharathiar Univ, Coim-

.'. II batore, 1988.

cells or the corrosion rate of magnesium a oys 18 Udhayan R, Muniyandi N & Mathur P B, Br Corros J, 27 with respect to the chosen organic compounds are (1992)68.

as follows: 19 Udhayan R & Bhatt D P, Corros Sc~ (submitted).

.20 BhattDP&UdhayanR,IndPat,749/DEU91,1991.

DPH>TCIA> DCIA>TCM 21 Udhayan R, Ph D thesis, Madurai Kamaraj University, In-

.0 . ( .dia, 1991.

4 Non-toxIcity of the anodic particularly mag- 22 Udhayan R & Bhatt D P, in International Conference nesium) and cathodic materials is another positive Magnesium Alloys and their Applications, Germisch- parameter for the acceptability of these novel sys- Partenkirchen, Germany, April 1992,59.

terns for practical use and in view of the global 23 Ud~ayan R &: Bhatt D P, in Meeting Electrochemical discussion on environmental pollution these or- SocIety, St Loul~ ~O, Ma~ 1992, 81.

.'.. 24 Mathur P B, Snvldya Ra)agopalan C & Bhatt D p, J Pow-

gallic battery systems have gre~t pote.ntlal. m the erSources,19(1987)269.

market, Replacement of magnesium with zmc can 25 Cahoon N C, Primary Balteries, Vol. 11 (Wiley, New be made in such applications where the users' York),1976.

considerations are based on the cost. 26 Gutman F & Lyons L E, Organic Semiconductors (Wiley, NewYork),1967.

k I d 27 Bhatt D P, Muniyandi N & Mathur P B, Bull Electro-

Ac nowe gement chem,4(1988)643.

Thanks are accorded .to Mr S. Karthikeyan, 28 Udhayan R, Bhatt D P & Mathur P B. J Appl electro- Project ~tudent for assistance in some measure- chem, 22 (1992) 285.

22 INDIAN J. ENG. MATER SCI., FEBRUARY 1996

29 Udhayan R & Bhatt D P, J Power Sources, 39 (1992) .37 Straumains M E & Bhatia B K, J Electrochem Soc, 110

323. (1963) 357.

30 Bhatt D P, Karthikeyan S & Udhayan R, J Electrochem 38 Karthikeyan S, Exploratory Investigations on the N-halog-

Soc,. 139 ( 1992) 3019. en cyclic ureide based magnesium primary cell systems in ~

31 GutJahar M A & Beccu K D, Extended Abstract No. 279, aqueous mediurn, M Sc Dissertation, Bharathidasan Uni- electrochemical Soc Meeting, Los Angels, 1970,678. versity (India), 1991.

32 Udhayan R & Bhatt D P, Electrochim Acta, 37 (1992)₁₉₇₁ 39 N ka aJlma , aglwara .. T H . R M, onya . _{K & "I.}yyatana w _{be N J}, 33 Math~r P B & Vasudevan T, Corros Sci, 38 (1992) 171. Electrochem Sqc, 133 (1986) 1761.

34 Udhayan R & Bhatt D P, J Power Sources, 39 (1992) 107. 40 Donnet J B & Baht 0 P, Carbon Fibres, in Encyclopedia 35 Perrault G G, J Electroanal Chern, 51 (1974) 107. ofPhySciand Techno~ Vol. 2 ()987).515.

36 Zlotowski I & Kolthoff I M, J Phys Chern, 49 (1945) 41 Mathur R B, Mittal J, Bahl 0 P & SandIe N K, Carbon,

386. 32(1994)71.

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