Kwang Kim

Yonsei University

kbkim@yonsei.ac.kr

Foundations of

Materials Science and Engineering

Lecture Note 10

(Lithium ion battery and Supercapacitor) May 29, 2013

39

Y 88.91

8

O 16.00

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I 126.9

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Se 78.96

7

N 14.01

Battery

A battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy

Batteries compared to heart…

Declared “Low Carbon Green Growth” as the National Vision of Korea (2008.8.15)

Batteries Technologies have been chosen as one of the ten technologies of the “2010 Green Growth Action Plan” by Presidential Committee on Green Growth (’10. 2)

Announced $2.4 billion in grants for batteries and electric cars

(United States)

Global demand increases for Li-ion batteries

HEV, PHEV, and EV

Chevy Volt (General Motors, USA) Plug-in hybrid electrical vehicle (PHEV)

Battery pack – LG Chem., Korea

Module Single cell

Single cell

Electroactive materials + Binder + Conducting Agent

Electrode + Separator + Electrolyte + Counter Electrode

Single Cell

- metal oxide - conducting polymer - particle size, shape

- particle size, shape - current collector - Aqueous or not

- conductivity - size - point or linear

- Electrolyte - Pore size

- potential window - ionic conductivity - ion reaction

- potential window - energy - power - mechanism

- thickness - shape

- staking electrode - shape - formation

Engineering + Science -Thermodynamics -Electrochemistry -Diffusion -Physical chemistry -Mechanical engineering -Electrical engineering and more…

=> We are Material Scientist!!!

Research on battery is…

100 101 102 103 104100

101

102

103

Spec

ific

ener

gy (W

h/kg

)

Specific power (W/kg)

100 h

10 h

1 h 0.1 h 36 s

3.6 s

Li-ion battery

Lead-acid Ni-MH

Supercapacitors

★ EV goal

★ PHEV goal

★ HEV goal

Fuel cells

Acceleration

Dis

tanc

e

Lithium-Ion Battery (LIB)

Lithium-ion battery with high energy density Having the highest energy density among all rechargeable batteries, lithium-ion battery (LIB)

is considered as the best candidate of rechargeable batteries for transportation applications such as PHEV and EV.

*HEV: hybrid electrical vehicle PHEV: plug-in hybrid electrical vehicle EV: electrical vehicle

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Terminology

Ohm’s law I (ampere) = E (volt)/R (ohm)

electrical current= voltage/resistance

Ampere (A) : measure of the amount of electric charge passing a point in

an electric circuit per unit time with 6.241 × 1018 electrons, or one coulomb per

second constituting one ampere ( Coulomb/second)

Capacity: the amount of electric charge (unit: coulomb) it can store

(Specific capacity : mAh/g , Volumetric capacity: Ah/L)

Energy density (Wh/kg or Wh/l) : the amount of energy per unit weight (or volume)

: Distance

Power density (W/kg or W/l): the amount of power per unit weight (or volume)

: Acceleration

Power (W) = J/s = i (A) x E (V)

Energy (Wh=J) = Q(C) x E(V)

Example

Galaxy S4, Samsung

3.8 V Li-ion Battery, 9.88 Wh (energy) ⇒2600 mAh (capacity, unit:coulomb) Wh= Q(C) x E(V)

Lithium-Ion Battery (LIB)

- 비교적 큰 용량 니켈카드뮴 전지 및 니켈수소 전지와 비교시 동일한 부피당 1.5 배 이상, 동일한 무게당 1.5~2배 이상의 용량 발현 - 높은 작동 전압 니켈카드뮴 전지 및 니켈수소 전지와 비교시 3배 이상 높은 작동 전압 (1 리튬이온전지 = 3 니켈카드뮴 전지 또는 니켈수소 전지) - 우수한 수명 특성 500회 이상 충방전이 가능하여 장시간 사용 가능 - 최소화된 자가방전 ★

전해질과 전극 사이에 화학적 반응이 발생하지 않음 1개월에 10 % 미만의 자가방전율 (★ 자가방전: 전지는 내부에 화학물질을 다량 함유하고 있기 때문에 오랫동안 사용하지 않고 방치해 두면 전지 내부 물질들의 화학반응에 의해 자체적으로 방전이 됨)

- 존재하지 않는 기억효과(memory effect) ★ 니켈카드뮴 전지에서 용량의 저하를 초래하는 기억효과가 이차전지에는 없음 (★기억효과: 방전이 충분하지 않은 상태에서 다시 충전하면 전지의 실제 용량이 줄어드는 효과)

납축전지 니켈-카드뮴

전지 니켈-금속수소

전지 리튬이온전지

양극 소재 PbO2 NiOOH NiOOH LiCoO2 등

음극 소재 Pb Cd MH 흑연

작동 전압 2.0V 1.2V 1.2V 3.7V

에너지 밀도(Wh/kg)

30 35 50 100

출력 밀도 (W/kg)

150 200 150 60

수명 특성 500 500 500 500

Lithium-Ion Battery (LIB)

리튬 이온 전지의 역사

- 1976년: Exxon 社와 빙햄턴 대학의 위팅엄 교수에 의해 이황화티타늄을 양극으로, 금속리튬을 음극으로

사용한 최초의 리튬 이차 전지 발명

- 1977년: 펜실베니아 대학의 바수 교수에 의해 음극 소재인 흑연 내부로의 리튬이온의 삽입 확인

- 1979년: 굿이노프 교수와 미쯔시마 연구원에 의해 리튬이온전지 상용화의 혁명적 발견이라 할 수 있는

4 V 영역에서 구동되는 ‘리튬코발트산화물(LiCoO2)’ 발견

- 1980년: 야자미 교수에 의해 음극 소재인 흑연에서의 리튬이온의 가역적인 탈삽입 확인

- 1983년: 테커레이 박사와 굿이노프 교수에 의해 출력특성이 우수한 리튬망간산화물(LiMn2O4) 발견

- 1991년: 일본의 Sony社는 최초의 상용화된 리튬 이차 전지 출시

- 2011년 현재: 전세계 휴대용 기기 전지 시장의 50 % 를 리튬 이차 전지가 담당

- 2012~ : 미래형 수송기계 및 에너지저장 장치용으로 개발 및 상용화 중

LIB consists of two lithium insertion materials, one for the cathode and the other one for anode

Working principle of LIB

Anode: 전지의 방전 (discharge)동안 전극물질의 전기화학적 산화반응 (oxidation, A→ A+ e-)이 일어나며, 이 전극을 산화전극이라 부름. Cathode: 전지의 방전 동안 외부회로를 통해 음극으로부터 전달된 전자에 의해 전극 물질의 환원반응 (reduction, B+ + e- → B) 이 일어나며, 이 전극을 환원전극이라 부름.

Electrochemical Reactions

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

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

Anode : 6C + xLi+ + xe- LixC6 (372mAh/g)

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

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

charge

charge

charge

charge

discharge

discharge

discharge

discharge

charge

discharge

Cathode and Anode materials for LIB

Cell potential change during charge/discharge

(1) Energy density: mostly determined by the material’s intrinsic chemistry

such as electrode potential or Fermi level (related to cell voltage), capable of

accommodating large quantities of lithium per formula unit (related to

capacity).

(2) Rate capability: high electronic and ionic mobilities

(3) Cycling performance: reversible lithium intercalation and deintercalation

without major structural changes

(4) Safety

(5) Cost and environmental friendliness

Criteria for cathode materials

Materials LCO NCM NCA LMO LFP

Formula LiCoO2 LiNi1/3Co1/3Mn1/3O2 LiNi0.8Co0.15Al0.05O2 LiMn2O4 LiFePO4

Structure

Specific capacity

145mAh/g 120mAh/g 160mAh/g 100mAh/g 150mAh/g

Voltage 3.7 V 3.6 V 3.6 V 4.0 V 3.2 V

Safety good relatively good poor good very good

Cyclability high medium high low High

Difficulties easy little difficult difficult little difficult difficult

Application small small, large large large Large

Cost 25~28 $/kg 20~23 $/kg ~21 $/kg 8~9 $/kg ~20 $/kg

Argonne National Laboratory (2011.10)

Cathode materials for LIB

- The layered lithium transition metal oxide (LiMO2, M= Co, Ni, Mn, etc.) materials with the high specific capacity are one of the most attractive cathode material. - Main Problems of layered lithium transition metal oxide materials are cost and safety!!

layered layered layered spinel olivine

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TM

O O

O

O O

O

TM (transition metal)-O6 octahedra

Edge sharing between TM-O6 octahera

TM-O6 layer (or MO2 slab)

Layer-structured LiMO2 (M=Co, Ni, Mn, etc.)

Space group: R-3m

TM layer (TM: 3a site, O: 6c site)

Li layer (Li: 3b site)

Structure of layered LiMO2 cathode material

LiCoO2 and LiNiO2

Sony 18650 Li-ion cell (1st commercial LIB)

-Cathode (positive electrode) - LiCoO2.

-Anode (negative electrode) - MCMB.

-Cell capacity – 1.8 Ah

LiCoO2 -Specific capacity: 145 mAh/g -Voltage: 3.7 V -Safety : good -Cyclability: good -Difficulties: easy -Cost: expensive

LiNiO2 -Specific capacity: 170-190 mAh/g -Voltage: 3.6 V -Safety: bad -Cyclability: bad -Difficulties: difficult --cost: cheap

Safety concerns for LIB

“ There is certainly no need for a “safe” battery that does not perform but also there is no need for a high performance battery that is unsafe”

- A General Discussion of Li ion Battery Safety, Interface, 21, 2012

Safety is a critical performance requirement for applications because it is directly related to people’s lives.

A laptop bursts into flames after the battery overheated during a conference

The heavily burned battery from Boeing 787 planes after it suffered thermal runaway

Three BYD e6 (EV taxi commercialized in China) passengers Killed in fiery crash by explosion of LIB

How do we design safe battery?

Electrochemical performance vs. Cost vs. Safety

LiCoO2 LiNiO2 Specific energy

Specificpower

Safety

Cost

Cyclability

Specific energy

Specificpower

Safety

Cost

Cyclability

Specific energy

Specificpower

Safety

Cost

Cyclability

LiNi0.8Co0.15Al0.05O2 (NCA) LiNi1/3Co1/3Mn1/3O2 (NCM) Specific energy

Specificpower

Safety

Cost

Cyclability

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Criteria for anode materials

음극활물질 기본 역할

-양극으로부터 나온 리튬이온을 가역적으로 흡장/방출하면서

외부회로를 통해 전자 (전류)를 흐르게 하여 전기를 발생시킨다.

음극의 주요 기능

대체 재료

리튬 금속 : 반응이 지속됨에 따라 금속 표면에 수지상

(dendrite) 형성

탄소계 물질 : 리튬 이온을 가역적으로 흡수할 수 있는

layer 구조

안전성 문제 낮은 수명

전지의 안정화

주 : 용량(mAh/g), 표면적(m2/g) 자료 : Argonne National Laboratory(2011.10)

Anode materials for LIB

구분 인조흑연 천연흑연 저결정탄소 금속

구 조

용 량 280~360 360~370 235~315 700~1,000

표면적 1 이하 3~8 2~5 -

수 명 높음 낮음 중간 매우 낮음

가 격 > 15 $/kg 10 $/kg

12 $/kg

> 60 $/kg

국내업체 포스코켐텍 애경유화 GS칼텍스 -

해외업체 히타치화학 JFE Chemical

Shanghai Shanshan

BTR Energy

Nippon carbon JFE Chemical

3M Mitsui

음극 활물질 종류

Graphite Si/Graphite

Oxide/Carbon

200 nm200 nm

Si

SiOx

SiOx

SiOx

SiOx

Si-oxide

Gen.I Gen.II Gen.III

• KMFC/ MCF

• PHS

• Smilion-A

• CZ50 (DAG-A)

• MKL ….

리튬 이온 전지의 기술로드맵

자료: 에코 프로(2011.06)

리튬 이온 전지 4대 핵심 소재별 국내시장 점유율(국가별)

자료: 일본 Institute of Information Technology (2009)

Ideal Energy Storage Devices

Energy storage device with performance characteristics of high energy density and high power density

Ideal Energy Storage Devices

Energy : system’s capability to do work [Wh/kg] Power : the rate at which work is performed or energy is converted [energy/time], [W/kg]

Battery-like Capacitors

Capacitor-like Batteries

Pow

er D

ensi

ty (W

/kg)

Energy Density (Wh/kg)

LIB vs EC

Electrochemical capacitor

- Non-faradaic reaction - Carbon materials with high specific area

Electrical Double Layer Capacitor

metal oxide

Pseudocapacitor

~ 100 F/g

- Pseudocapacitance

- Faradaic redox reaction

- transition metal oxide,

conducting polymer ~ 1000 F/g

F (farad)= C/V =(Ampere x second)/volt

전기이중층 커패시터용 전극소재 의사커패시터용 전극소재 전기이중층/의사커패시턴스

복합소재

그래핀 활성탄 탄소나노튜브 금속산화물 전도성 고분자 금속산화물/

탄소 복합소재 전도성 고분자/탄소 복합소재

초고용량 커패시터용 전극소재

현기술 수준 : 120 F/g 장점 : 고비표면적, 상용화, 고전기전도도

문제점 : 비축전용량 향상의 기술적 한계

장점 : 이론용량 : ~ 1000 F/g 문제점 : 낮은 전기전도도

낮은 전기화학적 활용도

금속산화물소재 활성탄소소재

Electrode Materials for Electrochemical Capacitor

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MnO2 layer reacted

MnO2 core unreacted dead volume

D = 2.8 x 10-13 cm2/s L = (D t)1/2

E. Deiss et al. Electrochim. Acta 46, 4185 (2001)

Nano-sized metal oxides

Improved electrochemical utilization of metal oxide by reducing a particle size

L. Gao et al. Mater. Lett., 61, 1785 (2007) MnO2 nanoparticle

MnO2 nanowire

Nanosize MnO2

Microsize MnO2

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H. Y. Lee et al, Electrochem. Solid-State Lett., 4, A19 (2001)

Metal oxide/Carbon nano-composite materials

Mater. Lett., 62, 3388 (2008) Nano Lett., 7, 281 (2007) J. Power Sources, 125, 85 (2004)

Improved electric conductivity by greater chemical contact and

increased contact area between metal oxide and carbon materials

carbon

MnO2

102~4 S/m

100 S/m

40/26

Porous metal oxides

3D- porous structure for easy access of electrolyte ions to the reaction sites in order to improve the ion transport

ion transport

solid-state diffusion

Science, 276, 926 (1997) Chem. Mater., 18, 5621 (2006)

active site

MnO2

Metal oxide deposited on carbon Nanosized Metal Oxide/Nanocarbon Composite

Energy storage characteristics of Metal oxide/Nanocarbon

1. “each metal oxide nanoparticle in contact with nanocarbon”

→ High electronic conductivity

2. “nanosized metal oxide without agglomeration ”

high SSA and short travel length of ions and electrons

→ High electrochemical utilization

3. “3D nanoporous structure of nanocarbon”

→ Easy access of ions to reaction sites

4. “use of nanocarbon with good mechanical properties

as a support and template for metal oxide nanoparticles”

→ Mechanically stable electrode structure

5. “no binders or conducting additives”

→ Self-supported electrode structure

Electrolytic ions

Metal oxide

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

e- e-

e-

e-

e-

e-

e-

J. Mater. Chem., DOI:10.1039/C1JM13741G J. Mater. Chem., 2011, 21, 1984 J. Mater. Chem., 2011, 21, 680 J Power Sources, DOI : 10.1016/j.jpowsour.2011.08.10 Electrochemistry Communication, 12 (2010) 1768 Electrochimica Acta, 55 (2010) 8056 Microporous and Mesoporous Materials, 130 (2010) 208 Electrochemistry Communication, 11 (2009) 1575