Lithium Secondary BatteriesLithium Secondary Batteries

Lab. of Energy Conversion & Storage MaterialsLab. of Energy Conversion & Storage Materials

Produced by K. Y. ChungProduced by K. Y. ChungProduced by K. Y. ChungProduced by K. Y. Chung

Edited by S. B. MaEdited by S. B. MaEdited by S. B. MaEdited by S. B. Ma

Directed by K. B. KimDirected by K. B. KimDirected by K. B. KimDirected by K. B. Kim

Lab. of Energy Conversion & Storage Materials

전지란전지란전지란전지란 ?

전지는전지는전지는전지는 내부에내부에내부에내부에 들어있는들어있는들어있는들어있는 화학물질화학물질화학물질화학물질((((활물질활물질활물질활물질))))의의의의 화학에너지를화학에너지를화학에너지를화학에너지를 전기전기전기전기

화학적화학적화학적화학적 산화산화산화산화----환원반응에환원반응에환원반응에환원반응에 의해의해의해의해 전기에너지로전기에너지로전기에너지로전기에너지로 변환하는변환하는변환하는변환하는 장치장치장치장치

Lab. of Energy Conversion & Storage Materials

Batteries Compared to Heart…..

Brain

Eye

Heart

Lab. of Energy Conversion & Storage Materials

전지의전지의전지의전지의 종류종류종류종류 (전지전지전지전지 Tree)

Lab. of Energy Conversion & Storage Materials

전지의전지의전지의전지의 발전발전발전발전 방향방향방향방향

Lab. of Energy Conversion & Storage Materials

Volta 전지전지전지전지

Cu2+(aq) + 2e- Cu(s) Zn(s) Zn2+(aq) + 2e-

Zn(s) + CuZn(s) + CuZn(s) + CuZn(s) + Cu2+2+2+2+(aq) Zn(aq) Zn(aq) Zn(aq) Zn2+2+2+2+(aq) + Cu(s)(aq) + Cu(s)(aq) + Cu(s)(aq) + Cu(s)

Lab. of Energy Conversion & Storage Materials

Why Lithium Batteries ?

Large capacity leads to longer use time

Compared to NiCd and NiMH batteries:

1.5 times with same volume

1.5~2 times with same weight

High operating voltage means lighter

weight

Compared to NiCd and NiMH batteries:

3.6V, or approximately 3 times higher

1 Lithium-ion battery = 3 NiCd of NiMH

Longer cycle life leads to low maintenance

The cycle life (number of charge/discharge)

is more that 500 times. Repeated use over a

long period is made possible

Minimal self-discharge

There is little loss of electronics because no

chemical reaction takes places between the

electrolyte and the poles, giving minimal

self-discharge. (less that 10%/month).

No memory effect means battery capacity

is not reduced

There is no memory effect such as that seen

in nickel cadmium batteries, so lithium ion

batteries can be recharged during use.

Accurate remaining capacity display

Detection of remaining capacity is easy

because the discharge characteristics change

gradually and continuously.

Lab. of Energy Conversion & Storage Materials

리튬이온전지의리튬이온전지의리튬이온전지의리튬이온전지의 구조구조구조구조

Lab. of Energy Conversion & Storage Materials

Electrochemical Reactions

Cathode : LiMO2 Li1-xMO2 + xLi+ + xe- ; layered structure

LiM2O4 Li1-xM2O4 + xLi+ + xe- ; spinel structure

Anode : 6C + xLi+ + xe- LixC6

Overall : LiMO2 + 6C Li1-xMO2 + LixC6 ; layered structure

LiM2O4 + 6C Li1-xM2O4 + LixC6 ; spinel structure

charge

charge

charge

charge

charge

discharge

discharge

discharge

discharge

discharge

Lab. of Energy Conversion & Storage Materials

Commercial Batteries

Lab. of Energy Conversion & Storage Materials

전지의전지의전지의전지의 구성구성구성구성 요소요소요소요소

양극과 음극의 물리적 접촉 방지를위한 격리막

(4) 분리막(Separator)

양극의 환원반응, 음극의 산화반응이 화학적 조화를 이루도록 물질이동이 일어나는 매체

(3) 전해질(Electrolyte)

음극 활물질이 산화되면서 도선으로전자를 방출하는 전극

(2) 음극(Anode)

외부 도선으로부터 전자를 받아 양극 활물질이 환원되는 전극

(1) 양극(Cathode)

Lab. of Energy Conversion & Storage Materials

양극양극양극양극 활물질의활물질의활물질의활물질의 종류종류종류종류

~130 mA/h148 mAh/gPoor cycleability

Lower cost

Environmental benignity

Easy preparation

LiMn2O4

(spinel)

~150 mAh/g275 mAh/g

Difficult preparation

Poor thermal

stability

Lower cost and higher

specific capacity

compared to LiCoO2

LiNiO2

(layered)

~140 mAh/g274 mAh/gToxicity

High cost

Easy preparation

High theoretical specific

capacity

LiCoO2

(layered)

Practical

capacity

Theoretical

capacityDisadvantagesAdvantages

Lab. of Energy Conversion & Storage Materials

Layered Structure

MO slabs

Li ions

2

Lab. of Energy Conversion & Storage Materials

Capacity I

� Theoretical Capacity

� “ampere-hour capacity” of a battery is directly associated with the

quantity of electricity obtained from the active material

� The total quantity of electricity involved in the electrochemical

reactions and is defined in terms of coulombs or ampere-hours

� Theoretically, 1 gram-equivalent weight of material will deliver

96,485 C or 26.8 Ah

� gram-equivalent weight : the atomic or molecular weight of the

active material in grams divided by the number of electrons

involved in reaction

Lab. of Energy Conversion & Storage Materials

Capacity II

� Theoretical Capacity (Ah/g or mAh/g) of Voltaic batteries

� 1 gram-equivalent weight : 96485C or 26.8 Ah

Zn(s) + CuZn(s) + CuZn(s) + CuZn(s) + Cu2+2+2+2+(aq) Zn(aq) Zn(aq) Zn(aq) Zn2+2+2+2+(aq) + Cu(s)(aq) + Cu(s)(aq) + Cu(s)(aq) + Cu(s)

Cu2+(aq) + 2e- Cu(s) Zn(s) Zn2+(aq) + 2e-

Atomic weight : 65.4 g

g-equi. weight : 65.4 / 2 = 32.7g

Capacity : 26.8Ah/32.7g = 0.82Ah/g

1.22 g/Ah

Atomic weight : 63.5 g

g-equi. weight : 63.5 / 2 = 31.75g

Capacity : 26.8Ah/31.75g = 0.84Ah/g

1.19 g/Ah

1.19 g/Ah + 1.22 g/Ah = 2.41 g/Ah

0.415 Ah/g

Lab. of Energy Conversion & Storage Materials

Capacity III

� Theoretical Capacity (Ah/g or mAh/g) of LiCoO2

� 1 gram-equivalent weight : 96485C or 26.8 Ah

CoOCoOCoOCoO2222 + Li+ Li+ Li+ Li++++ + e+ e+ e+ e---- LiCoOLiCoOLiCoOLiCoO2222 ; discharge

Molecular weight : 97.871 g

g-equi. weight : 97.871 / 1 = 97.871 g

Capacity : 26.8 Ah / 97.871 g = 0.274 Ah/g

= 274 mAh/g

Lab. of Energy Conversion & Storage Materials

Experimental Setup

� Three electrode cell

� Working electrode : Composite electrode

active material + conducting material + binder

LiCoO2 carbon PVDF

� Counter electrode & reference electrode : lithium foil

� Electrolyte : Li salt in non-aqueous solvent

Li salt : LiPF6, LiBF4, LiClO4…

Solvent : EC, PC, DMC, DME…

Lab. of Energy Conversion & Storage Materials

Typical discharge curve of LiCoO2

Fig. (a) Typical discharge

curve of LiCoO2 and its

(b,c) lattice parameter

change

(a) (b)

(c)

Lab. of Energy Conversion & Storage Materials

Cyclic Voltammogram of LiCoO2

3.2 3.4 3.6 3.8 4.0 4.2 4.4

-60

-40

-20

0

20

40

60

80

current /µA

E / V vs. Li/Li+

Cutoff voltages : 3.2~4.25V

Lab. of Energy Conversion & Storage Materials

Cycle Performance of LiCoO2

Lab. of Energy Conversion & Storage Materials

Seek for New Cathode Materials

~160 mAh/g280 mAh/gNot extensively

studied yet

Lower cost

High theoretical and

practical capacity

Better thermal stability

LiNi0.5Mn0.5O2

~130 mAh/g148 mAh/gPoor cycleability

Lower cost

Environmental

benignity

Easy preparation

LiMn2O4

~150 mAh/g275 mAh/gDifficult preparation

Poor thermal stability

Lower cost and higher

specific capacity

compared to LiCoO2

LiNiO2

~140 mAh/g274 mAh/gToxicity

High cost

Easy preparation

High theoretical

specific capacity

LiCoO2

Practical

capacity

Theoretical

capacityDisadvantagesAdvantages