TAP CHI HOA HOC T.51(1)55-58 THANG 2 NAM 2013
NGHIEN CU'U OAC TJNH VA CO CH^ NAP - PHONG OIEN HE OIEN e y e Ag/AgzO, AgO TRONG DUNG DICH OIEN LY KI^M
Sl> DUNG TRONG BO N G U 6 N OIEN BAC - KEM
Tran Qu6c Tfiy, Bui Dire Cumig
Vi?n Hda hgc- Vgi lieu, Vi?n Khoa hgc vd Cdng nghe Qudn su Den Tda soan 25-9-2012
Abstract
Characteristic and mechanism of charge-discharge process of electrode Ag/Ag20, AgO in KOH electrolyte were studied in this paper. The charge process have been studies by galvanometry and the discharge ability by discharge method with resistance constant. It was found that characteristic and mechanism of the charge-discharge process of silver electrode in KOH electrolyte defend on current density and environment temperature. In this article results on influrence of internal resistance in charge-discharge process of electrode were presented.
Keywords: Charge-discharge process, electrode Ag/Ag20, AgO, silver zinc batteries.
1. MO DAU
Do tinh chat ben hda va cd dg dan rieng, tinh khir, tinh thuan nghich dien hda cao, dien eye bgc va bgc oxit dugc sir dung rdng rai trong cdng ngh? che tao ngudn dien hda hgc, dac biet la ngudn dien dac chiing vdi nang Iugng rieng, cdng suat rieng Idn su dung trong ky thuat quan su [1, 2]. Ben canh cac edng trinh nghien cuu cai tien edng nghe che tgo dien cue bac cd chat lugng cao sir dyng trong ngudn di?n, cdn cd cac cdng trinh nghien ciru ca ban ve tinh chat dien hda ciia nd trong dung djch dien ly kiem [3-6]. Tuy nhien cho den nay viec nghien cuu dgc tinh va ca che ve phan ung oxi hda khir di?n hda ciia dien eye he Ag/Ag20, AgO trong dung dich dien ly kiem cdn it de cap va tbilu su thdng nhat.
Trong cac cdng trinh nghien cuu trudc day [7, 8]
chung tdi da gidi thieu mgt sd ket qua ve nghien cuu thilt kl chi tgo dien eye bac va mgt so tinh nang dien hda cua nd sir dung trong h? ngudn di?n hda bgc kem. Trong khudn khd bai bao nay, chung tdi di sau nghien cuu dgc tinh, ban chit ciia qua trinh ngp - phdng ciia dien eye, cac ylu to anh hudng cung nhu su biln thien dien trd ngi toan phin trong qua trinh ngp - phdng.
2. THUC NGHIEM 2.1. Mlu nghien ciru
+ Chit hogt dgng dien eye la bgt bgc tinh khiet 99,9% cd kich thudc thudc < 100 pm dugc che tgo bing phuang phap khir hda hgc AgCI bing bgt kem.
+ Trpng lugng bdt bgc la 8 g duge ep tren ludi ddng mg bac kich thudc 40x70 mm dudi ap lye 30 tan. Ludi ddng dudng kinh 0,1 mm dan each nhau 1 mm.
f Dien eye anot la la kem mac Uo day 0,l±0,01mm kich thudc 40x70 mm dugc dap gan de tang dien tich be mat boat dgng va kha nang khuech lan ciia dung djch dien ly.
+ Dung djch dien ly la KOH ly irpng 1,40 g/cm^
cd do tinh khiet PA.
2.2 Phuang phap nghien ciru
+ Qua trinh tich dien (ngp dien) su dung phuang phap tich dien ganvanoslat.
+ Qua trinh phdng dien bang tai khdng ddi thuc hi?n tren thiet bi khao sat ngudn di^n HL-07.
+ Dien trd ndi loan phan (r) dugc xac djnh bang cdng thuc djnh luat 6m trong qua trinh phong nap:
1 = ^ 1) R + r
Trong do: I la cudng do ddng di?n (A); U la dien the nap-phdng (V); R = const - Tai (Cl).
3. KET QUA v A THAO LUAN 3.1. Dac tinh nap dien
TCHH, T. 51(0,2013 3 1. L Anh hudng mgt do ddng
Ddng ngp cd anh hudng den dgc tinh phan cucanot ciia dien eye. Tuy nhicn de khao sat anh hudng ciia mgt dg ddng den dgc tinh lich di?n chiing tdi lien hanh d cac che dg ngp ddng khdng doi d cac che dg khac nhau (hinh 1).
Tren dudng cong tich dien theo thdi gian (E-t) cho thay ton tai hai viing di^n the nim ngang kha rd net. Viing dien the thap (vimg thir nhit) ung vdl dign Ihl thay ddi lir 1.60 V den 1,75 V; cdn vimg dign Ihl cao (vung thir hai) dien thi lit 1,92 V din 1,96 V.
Biii Dire Cuang vd congs^
Hmh 1: Dudng cong tich di^n E-t phy thudc vao mat dg ddng,
Gia tri va do dai cac nac dien the phy thugc vao tdc dp phan cue anot (ddng ngp). Q viing the thir nhat ddng ngp cang ldn, khoang dien thi nim ngang cang be Vdi dong nap cang nhd viing dien thi nim ngang cang ro net va keo dai. C) viing dien thi nay xay ra qua trinh oxi hda chuyen Ag vl Ag*, theo phan ung:
2Ag + 20H" = AgsO + H2O + 2e Tuy nhien trong cdng nghe che tgo dien eye bac cho nguon dien ngudi ta quan tam chu ylu din nac the thir hai, do la qua trinh xay ra phan irng oxi hda Ag'' —• Ag ' hoac oxi hda tryc tiep Ag" —* Ag'' tiiy thugc vao ddng phan cue theo phan irng di?n eye;
Ag20 + 20H' = 2AgO + H2O + 2e Hoac Ag -I- 20H' = AgO + HjO + 2e
Cung nhu phan irng anot xay ra d vimg di?n thi thIp (viing 1) gia trj va dp dai vimg thi thir hai phy thugc vao tdc dp phan eye. Ddng ngp cang Idn vting the cang ddc va ngan. Tren hinh 1 ta thIy ring khi phan cue vugt qua +2,0 V, dp ddc dudng E-t cang ldn. Day la vimg dien thi xay ra phan irng giai phdng O2 do phan hiiy nudc, theo phan limg:
40H" ^ 2H3O + O2 + 4e
Trong qiia trinh thyc hi?n tich dien cho dipn eye can han chi toi da qua trinh giai phdng O2 tren di?n
eye vi day la qud trinh tieu hao nang lugng khong can thiet. M$t khac, qua trinh phan hiiy nudc kem theo giai phdng O2 tren di^n eye se lam giam tinh nSng v^ dg ben ciia ngudn di$n do nhiet dg tang dong thdi pha buy la each xelophan cua ngudn di|n.
Do vgy Irong qud trinh ngp di^n cho nguon dien bgc- kCm tuy?t doi khdng dugc ngp qua dign thi ph&i hiiy ciia nudc cung nhu khdng ngp di?n vdi dong qua Idn.
3.1.2. Anh hudng ciia nhi?t dg den qud trinh tich di?n cita dien cue
Anh hudng cua nhipt dg din qua trinh tich di^n cua di?n eye dugc md ta d hinh 2,
Hinh 2 cho thay nhiet dg anh hudng din dudng d^c trung lich dien ciia dign eye. Vdi ddng ngp 0,3A tir nhiet dp 20°C den 40°C d nic ngp thir nhit (viing chuyin Ag vl Ag20) nhiet dg cang cao dien thi n^p cang thap va viing the cang h?p. Vdi ddng ngp tren, dien thi ngp ban dau ciia dien eye d 20''C, SO^C va 40"C lln lugt la 1,64; 1,62 va 1,6IV va sau hai gia tich dien dien thi lan lugt tang lt;n la 1,71; 1,70 va 1,69 V. Mat khac tir dudng dac trung ti'ch dien cho thay khi tang nhiet do thdi gian de dien ap dgt gia tri dien the giai phdng Oj cang riit ngin nen kha nang tich dien cho di?n eye cang thap. Do vay dl nang cao hieu qua tich dien cho dien eye khdng ngp dien d nhiet dg qua cao.
Hinh 2: Anh hudng nhiet dg den dudng cong tich dien. Ddng ngp I = 0,3 A
17.3. Anh hudng cua di?n trd ngi todn phdn den qud trinh tich di?n
Di?n trd npi toan phin (r) ciia ngudn dien la yen td quan trpng ciia ngudn dign hda hgc. Sy bien doi ciia no anh hudng den qua trinh phdng-ngp cua ngudn dien. Dign trd toan phin dugc bilu thi bSng bieu thirc:
'• = ^6.+^ = rs„-^r,. (2
TCHH, T. 51(1), 2013
Trong dd: Ep^ la dien thi phan eye (V); rfi^ la dien trd 6m ciia ngudn dien (£2); rp Ja dien trd phan eye (H); I la ddng phan cue (A).
Dien trd dm cita ngudn dien chu ylu phy thugc vao muc do tich dien ciia dien eye va nhiet dg mdi trudng. Dien trd phan eye phy thugc vao cudng dg ddng, trang thai tich dien va nhiet dQ mdi trudng. Sy phu thugc dien trd ngi toan phin vao qua trinh tich dien dugc md ta d hinh 3.
Hinh 3 cho thay dien trd ngi toan phan bien doi trong qua trinh nap dien. Khi bit dIu tich dien, dien trd ngi toan phin cd gia trj 0,15 fi va tang khdng dang kl trong khoang 2 gid dau sau dd tang nhanh va dgt cue dgi d viing dien the oxi hda Ag^ din Ag^^
(r = 0,95 Ci). Sau dd giam nhanh va gan nhu khdng thay ddi hogc thay ddi rlt it d thdi gian ngp dien tilp theo.
Nghien ciru ddc tinh vd ca che . 2AgO + 2e = AgjO + 20H'
Hinh 3: Sy bien ddi dien trd ndi loan phan trong qua trinh ngp dien (Lgp = 0,5A) Gia tri eye dgi cua r dugc ly giai bang sy tgo ldp AgO ben virng lam tang dien trd dm ciia ngudn dien, ddng thdi d dien the phan cue tren dien trd phan eye cung cd gia trj Idn nhat. Sy bien ddi dien trd ngi toan phan qua gia tri eye dai d viing dien the phan eye chuyen tiep tir viing thir nhat sang viing thir hai eho phep phdng doan ve ca che tich dien d cac vimg dien Ihl phan cue khac nhau.
3.2. Dac ti'nh phong dien
3.2.1. Anh hudng cua mdt dg ddng phdng Dung lugng cung nhu dac ti'nh phdng dien ciia dien cue duang trong nguon dien bac - kem phu thugc vao mat dg ddng phdng (hinh 4).
Hinh 4 cho thay khi phdng dien vdi mat dg ddng thap, tren dudng cong phdng dien (E-t) tdn tai 2 nac di^n thi kha ro net. Nac thir nhit dien thS thay ddi khoang tir 1,75 V din 1,5 V chilm khoang 20-30%
dung Iugng tiiy thudc vao mgt dQ ddng phdng. Mat dp ddng phdng cang ldn dien the phdng dien cang giam va viing thi cang thu hep- LTng vdi vimg dien thi nay xay ra phan irng khir catot bgc(II) oxit vl bgc(I) oxit:
V
5A 02A
/
IA ' 0 4A
Hmh 4: Dudng dac trung phdng dien phy thugc vao mat dg ddng
Vimg dien the thii hai ciia dudng (E-t) tuang ddi phang. Gia trj dien Ihl va dg dai nac the thir hai phu thugc vao mat dg ddng phdng. Day la vitng xay ra phan irng khir catot ciia Ag20 ve Ag kim logi:
AgjO + H2O + 2e - 2Ag + 20H- Khi phdng dipn vdi ddng Idn khdng thay xuat hien vimg the thir nhat ma chi cd viing the thir hai cd nghTa la phdng dien true tiep ve bac kim loai.
Sy tdn tgi nac thir nhat khi phdng dien ngudn dien bgc-kem diem bat lgi can phai logi bd. Ngay nay cac nha khoa hgc lap trung nghien ciiu de loai trir sy tdn tgi nac the nay khi phdng dien bang nhieu each khac nhau. Mdt trong nhung hudng nghien cuu la dua them cac chat phu gia vao dien eye duang, dien eye am hoac vao dung djch dien ly. Tuy nhien nhDng ed gang theo hudng tren khdng phai bao gid cung dua den ket qua mong mudn bdi vi tuy cd the thay ddi hoac lam triet tieu nac the nay song cd the dan den giam chi tieu ky thugt dien eye hoac tang kha nang ty phdng va giam thdi gian cat gift ngudn dien. Vi vgy viec nghien ciru tgo dugc tinh dn djnh ma van giii dugc tinh nang ky thugt ciia ngudn dien la dieu het sue cd y nghTa va la hudng di can thiet trong nghien cuu ngudn dien bgc-kem. Trong nhirng nam gan day ngudi ta iing dyng kha hieu qua de dn djnh dien the khi phdng dien la su dung ddng xoay chieu bat ddi xiing de nap dien eho ngudn dien bgc-kem.
3.2.2. Anh hudng ciia nhiet dg
Qua trinh phdng dien ciia dien eye bgc phy thugc vao nhiet dg mdi trudng (hinh 5).
Tren hinh 5 cho thay d nhiet dg tu 20-40°C khi tang nhiet dg mdi trudng dudng cong phdng dien phang ban, dung lugng dien eye cung it nhilu tang 57
TCHH, T. 51(1), 2013
len. C) ddng phdng I = 0,15A, dien thi ban dau d 2 0 T , SO^C, 40"C lln lugt la 1,68; 1,72; 1,74 V, dp dai ciia viing thi thii 2 cung tang len klid ro. Tuy nhien nhiet dp mdi trudng cung khdng the qua cao vi khi dd se Iam giam dung lugng cat giu* nguon dien lien quan din qua trinh ty phdng dien va cac phan irng phy xay ra tren dien eye.
Hmh 5: Dudng dac trung phdng dien phy thugc vao nhieldg(I-0,15A)
3.2.3. Anh hudng di?n trd ngi todn phdn den qud trinh phdng dien
Hinh 6 md ta sy biln thien dien trd ngi loan phin ciia ngudn dien h? bgc-kem dung lugng l,5Ah phdng dien ddng I ^ 0,I5A.
Htnh 6: Bien thien dien trd ngi toan phin din qua trinh phdng dien
Tir hinh 6 cho thay cd su bicn thien dien trd ndi toan phan dang ke trong qua trinh phdng dien. Dien trd ndi toan phan ciia nguon dien bgc-kem khao sat phdng dien I = 0,15A bit dau tir 0,15^ tang dan khi phdng dien va dat eye dgi 0,85ii irng vdi vimg thi khir AgjO ve Ag sau dd giam nhanh din gia trj ban dau. Hien tugng thay ddi dien trd npi toan phin khi phdng dien tuang ly nhu qua trinh ngp dien. Qua sy thay ddi dien trd ndi loan phan vao vimg dien thi d cac nac phdng dien khac nhau cho phep ta phdng Lien he: Biii Dire Circng
Vien Hda hgc-Vat lieu, Vien Khoa hpc va Cdng ngh? Quan sy 17 Hoang Sam, Clu Gily, Ha Ndi
Email; [email protected].
Bill Dire Cuang vd cgng s{c doin ve ca chi khir catot cung nhu sy tgo sin phini phan tirng cua phSn iimg di^n eye. Tir cac ket qui nghien cii'u anh hirdng ciia bien thien dien trd npi toan phan den dudng d$c trung phdng dign cho thay muon cd dien eye cd d$c trung phdng dien tot can che tgo nguon dien cd dien trd ngi toan phan nho nhat.
4. KET LUAN
D^c Irung va ca che ngp-phdng dien dien eye h^
Ag/Ag20, AgO trong dung djch dien ly kiem sii dyng trong nguon dien bgc-kem phy thugc vao m^t dg ddng dien va nhiet dg mdi trudng. Chdng minh ring vdi mgt dg ddng be qua trinh oxi hda va khii dien hda xly ra d hai vimg dien the khac nhau, gia trj va chieu dai nac the phy thugc vao mgt dp dong.
Cdn khi phdng dien vdi ddng Idn qua trinh khir dien hda tryc tiep ve Ag kim logi.
Dien trd ngi toan phan bien ddi trong qua trinh phdng - ngp va dgt gia trj eye dgi tgi vimg dien the chuyen tiep bgc oxit hda trj thap den hda trj cao trong qua trinh ngp va ngugc lai tir bgc oxit hda trj cao ve bgc oxit hda trj thap khi phdng dien.
TAI LIEU THAM KHAO
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2. Raymond Jasinski. High-energy Batteries. 268-270, Plenum Pres, New York (1971).
3 A. Fleischer, J. Lander. Zinc-Silver Oxide Batteries, lr99-l53,NewYork(1971).
4. H. A. Kiehne. Batteries Technology Hand book, Tr 457-463. Germany Marcel Dekker. INC (2003).
5 B Hariprakash, S. K. Martha, A. K. Shukla.
Galvanostatic non-destructive characterization of alkaline silver-zinc cells. Joumai of Power Sources, 117,242-248(2003).
6, Xianbo Jin, Juntao Lu. The potential valleys of silver oxide electrodes during pulse discharge, 104, 253- 259 (2002).
'. Trin Quic Tuy. Nghien cuu ihiit ki che thir pin dif trir bgc-kem su dung cho ten lira Hdi qudn. Bio cio tdng kit dl tai d p BQP/Vien KH-CNQS (2009).
8. Nguyen VSn Tu, Trin QuIc Tiiy, Mai VSn Phirac, DuQfng Chi Quan. Nghien cuu chi tgo dien cue b(fc oxit sir dung cho bg nguon dien dif tru bgc-kem. T^p chi H6a hgc, 47(5), 231-236 (2009).
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