INVESTIGATION OF CAPACITY FADING IN

LITHIUM-ION COIN CELLS

MUHAMMAD RASHID

DEPARTMENT OF MECHANICAL ENGINEERING

INDIAN INSTITUTE OF TECHNOLOGY DELHI

OCTOBER 2016

©Indian Institute of Technology Delhi (IITD), New Delhi, 2016

INVESTIGATION OF CAPACITY FADING IN

LITHIUM-ION COIN CELLS

by

MUHAMMAD RASHID

Department of Mechanical Engineering

Submitted

In fulfillment of the requirements of the degree of Doctor of Philosophy

to the

INDIAN INSTITUTE OF TECHNOLOGY DELHI

OCTOBER 2016

Dedicated to my grandparents (Dada, Dadi, Nana and Nani)

i

CERTIFICATE

This is to certify that the thesis entitled “Investigation of Capacity Fading in Lithium-ion Coin

Cells” being submitted by Mr. Muhammad Rashid to the Indian Institute of Technology, Delhi

for the award of the degree of Doctor of Philosophy is a bonafide record of original research work

carried out by him under my supervision in conformity with rules and regulations of the institute.

The results contained in this thesis have not been submitted, in part or in full, to any other

University or Institute for the award of any Degree or Diploma.

Date: October 20, 2016 Dr. Amit Gupta

Assistant Professor

Department of Mechanical Engineering,

Indian Institute of Technology Delhi,

New Delhi-110016, India.

ii

ACKNOWLEDGEMENTS

This work could not have been possible without the prolific guidance, intellectual counsel and

incessant encouragement of my supervisor, Dr. Amit Gupta. I am extremely obliged and indebted

to him for considering me capable enough to develop the first experimental facility in IIT Delhi to

conduct research on Li-ion battery. He supported me in various stages of my PhD and his relentless

inspiration was the backbone that paved way to deliver my best to accomplish the desired

objectives.

I would also like to extend my gratitude to the members of my dissertation committee, Prof. PMV

Subbarao, Dr. Subhra Datta and Dr. Anuj Dhawan, for their positive criticism and valuable

comments while evaluating my research plan, progress and synopsis of my dissertation.

I am also thankful to my department colleagues, particularly K. B. Sutar, Aamir Hayat, Dilshad

Khan, Abdul Rahman, Nipun Arora, Kuldeep Singh, Salahuddin Ahamd, Rattandeep Singh and

Nitin Baliyan who assisted me directly and indirectly to complete my research work at IIT Delhi.

I also appreciate and cherish the companionship of my friends Jarrar Ahmad, Viqar Baig, Abdul

Quiyoom, Danish Iqbal, Mehnaz Rasool that helped me to relieve stress during hard times in my

doctoral research.

I will always be indebted to Abbu and Ammi, who have given many sacrifices and worked

extremely hard to provide me resources and facilities to pursue my highest academics degree. The

efforts made by my grandparents, Rahmatullah, Akib, sisters and relatives, especially, my maternal

uncles are priceless.

iii

I would like to thank my wife for her love, support and immolation in the last two years of my

dissertation. Lastly, I am grateful to Allah for blessing me with daughter Maseera and neice Zainab,

whose cute smiles and innocent crying kept me energized during the last year of my doctoral

tenure.

Muhammad Rashid

iv

ABSTRACT

Due to higher gravimetric and volumetric energy density than other battery technologies, Lithium-

ion batteries (LIBs) are proved as a portable energy systems to power electronic devices such as

mobiles and laptops. However, the implementation of LIBs to power automotive vehicles is limited

due to their high cost, low cycle life and rapid capacity loss at high discharge rates. The capacity

degradation of LIBs is caused by formation of SEI (solid-electrolyte interface) film and gas

evolution at anode and dissolution at cathode. The SEI film formation at anode is a result of

electrolyte reduction which forms alkyl carbonate and ethylene. The capacity loss due to SEI

formation is studied with relaxation of cell after each charge and discharge for 1000 cycles. A

longer relaxation of cell after discharge is shown to lead to an improved cell performance with

lower loss in cyclable lithium as compared to the relaxation after charge.

A numerical model capable of considering concurrent effect of SEI film and gas formation on the

capacity degradation of LIBs is developed. Using this model, cycle life of mesocarbon microbead

(MCMB) - LiMn2O4 (LMO) cells has been estimated at 1C, 2C and 4C-rates. Moreover, the SEI

film thickness, volume of gas and reduction in electrolyte volume fraction are quantified as a

function of cycle number and a thicker SEI film is observed in case of cell cycled at 1C current

due to the longer duration of the cell operation in this case. The developed model is further

implemented to investigate the capacity degradation of layered MCMB anode with LMO cathode.

The anode has three layers each consisting of dissimilar size particle i.e. 0.7 R, R and 1.3 R which

results in different interfacial area in the electrode sections. Simulations conducted for the cells

with different morphological anodes show that the cells having smaller size particles in the middle

v

layer of the anode loses the least amount of initial capacity with the thinnest SEI film and lowered

gas generation after completing 1000 cycles at 1C-rate.

The electrochemical performance of MCMB-LMO cells is gauged by various electrochemical

techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS),

galvanostatic charge and discharge. Capacity loss in full-cells are contributed by occurrences of

parasitic reaction based degradation at cathode and anode. The contribution of each electrode in

full-cell degradation is gauged by testing of MCMB and LMO half-cells. For this purpose, cells

are cycled with similar current as it is done in full-cells and is observed that MCMB half-cells have

faster rate of degradation as compared to LMO. Lithium diffusion coefficient of MCMB and LMO

electrodes are calculated using galvanostatic intermittent titration technique (GITT) at various

stages of cycling. The diffusivity is shown to vary with state of lithiation during charging and

discharging phase. The computed diffusion coefficient together with other experimental

measurable, i.e., electrode thicknesses, porosity and solid phase volume fraction are used as input

in numerical simulations of MCMB and LMO half-cells. The derived cycling performance and

cell potential vs. discharge capacity through numerical simulation show excellent agreement with

experimentally obtained data for MCMB and LMO half-cells. The half-cell simulation reveals that

loss in discharge capacity occurs due thickening of SEI film, increase in gas formation and loss in

cyclable lithium caused by electrolyte reduction at MCMB electrode. Simulation of LMO half-

cells shows that capacity loss with cycling is a result of reduction in active material, increase in

surface resistance with inactive material deposition caused by manganese dissolution and loss in

cyclable lithium at LMO electrode.

vi

TABLE OF CONTENTS

CERTIFICATE........................................................................................... i

ACKNOWLEDGEMENTS ...................................................................... ii

ABSTRACT ............................................................................................. iv

TABLE OF CONTENTS ......................................................................... vi

LIST OF FIGURES ................................................................................... x

LIST OF TABLES ................................................................................. xvi

NOMENCLATURE .............................................................................. xvii

CHAPTER ONE: INTRODUCTION ....................................................... 1

1.1 Introduction ..........................................................................................1

1.2 Electric Vehicles in India .....................................................................2

1.3 Why Li-ion Battery? .............................................................................3

1.4 Li-ion Cells ...........................................................................................5

1.4.1 Cathode (Positive Electrode) .................................................................. 6

1.4.2 Anode (Negative Electrode).................................................................... 6

1.4.3 Separator ................................................................................................. 7

1.4.4 Electrolyte ............................................................................................... 7

1.5 Li-ion Battery .......................................................................................7

vii

1.5.1 Serial Connection of Battery ................................................................... 8

1.5.2 Parallel Connection of Battery ................................................................ 9

1.5.3 Mixed Connection of Battery .................................................................. 9

1.6 Working Principle of Li-ion Cell .......................................................10

1.7 Motivation ..........................................................................................11

1.8 Outline of the report ...........................................................................13

CHAPTER TWO: LITERATURE REVIEW ......................................... 15

2.1 Introduction ........................................................................................15

2.2 Negative Electrode .............................................................................15

2.3 Positive electrode ...............................................................................18

2.4 Capacity Degradation in Li-ion Cells ................................................20

2.4.1 Experimental Studies ............................................................................21

2.4.2 Numerical Studies .................................................................................25

2.5 Status of knowledge ...........................................................................30

2.6 Conclusions from literature review ....................................................31

2.7 Scope of the present work ..................................................................33

CHAPTER THREE: APPROACH ......................................................... 34

3.1 Introduction ........................................................................................34

3.2 Experimental Approach ......................................................................35

3.2.1 Development of the Experimental Facility ...........................................35

viii

3.2.2 Experimental Procedure ........................................................................36

3.2.3 Characterization ....................................................................................38

3.2.3.1 X-ray Diffraction ....................................................................................... 38

3.2.3.2 Electrochemical Impedance Spectroscopy ................................................ 39

3.2.3.3 Cyclic Voltammetry ................................................................................... 42

3.2.3.4 Scanning Electron Microscopy .................................................................. 43

3.2.3.5 Galvanostatic charge/discharge ................................................................. 44

3.2.3.6 Galvanostatic intermittent titration technique (GITT) ............................... 44

3.2.4 Testing of the Assembled Cells ............................................................45

3.3 Numerical Approach ..........................................................................46

3.3.1 Experimentally determined parameters ................................................46

3.3.2 Ideal cell model .....................................................................................49

3.3.3 SEI growth and gas evolution model ....................................................52

3.3.4 Manganese dissolution model ...............................................................54

3.3.5 Solution techniques ...............................................................................55

CHAPTER FOUR: RESULTS ............................................................... 56

4.1 Performance improvement through relaxation ..................................56

4.1.1 Applied current with relaxation ............................................................56

4.1.2 Model validation ...................................................................................58

4.1.3 Parametric study ....................................................................................60

4.1.4 Effect of Discharge Rate .......................................................................71

4.2 SEI formation and gas evolution in anode .........................................76

ix

4.2.1 SEI formation with gas evolution .........................................................76

4.2.2 Effect of layered anode .........................................................................81

4.3 Electrochemical testing of MCMB and LMO electrodes ..................92

4.3.1 Characterization ....................................................................................92

4.3.2 MCMB-Lithium manganese oxide full cells ........................................94

4.3.2.1 Effect of applied current ............................................................................ 99

4.3.3 MCMB electrode .................................................................................103

4.3.3.1 Rate dependence on degradation ............................................................. 107

4.3.3.2 Li-ion diffusion in MCMB electrode ....................................................... 110

4.3.3.3 Numerical simulation of MCMB half-cell .............................................. 112

4.3.4 LMO electrode ....................................................................................116

4.3.4.1 Role of applied current ............................................................................ 121

4.3.4.2 Li-ion diffusion in LMO electrode .......................................................... 123

4.3.4.3 Numerical simulation of LMO electrode ................................................. 125

4.4 Summary .......................................................................................... 128

CHAPTER FIVE: CONCLUSIONS .................................................... 131

CHAPTER SIX: FUTURE WORK ...................................................... 135

REFERENCES ...................................................................................... 137

LIST OF PUBLICATIONS .................................................................. 150

BIO-DATA OF THE AUTHOR ........................................................... 151

x

LIST OF FIGURES

Figure 1.1: Comparison of different battery technologies in terms of volumetric and gravimetric

energy density (adapted from Ref [12]). ......................................................................................... 4

Figure 1.2: Schematic diagram of Li-ion cell. ................................................................................ 6

Figure 1.3: Serially connected cells. ............................................................................................... 8

Figure 1.4: Parallel connection of cells........................................................................................... 8

Figure 1.5: Mixed connection of cells. ........................................................................................... 9

Figure 1.6: Pseudo-two-dimensional representation of Li-ion batteries. ...................................... 10

Figure 1.7: 3-D schematic representation of rechargeable Li-ion batteries. ................................. 11

Figure 3.1: The instruments of the experimental facility in their sequence of application. ......... 36

Figure 3.2: Sequential arrangement of components for cell assembly.` ....................................... 38

Figure 3.3: Nonlinear behavior of Potential vs. current plot with pseudo-linearity (Inset) in a small

segment. ........................................................................................................................................ 41

Figure 3.4: Nyquist plot with demonstration of different losses associated with Li-ion cells. ..... 42

Figure 3.5: Potential ramp for CV measurement of (a) MCMB and (b) LMO electrodes. .......... 43

Figure 3.6: Intermittent current and potential profile for the diffusion measurement of electrodes.

....................................................................................................................................................... 44

Figure 3.7: 1C current profile applied to cycle cells. .................................................................... 45

Figure 3.8: OCP of MCMB against Li-metal at C/30 current. ..................................................... 48

xi

Figure 3.9: OCP of LMO against Li-metal at C/30 current. ......................................................... 48

Figure 3.10: Schematic representation of anode before and after cycling. ................................... 52

Figure 4.1: Profile of applied current for 1 cycle.......................................................................... 57

Figure 4.2: Variation of electrolyte salt concentration across the cell domain for various grid

spacing. ......................................................................................................................................... 58

Figure 4.3: Comparison of the pseudo 2-D model with single particle model for 100th cycle. .... 59

Figure 4.4: (a) Variation of cell potential with time during discharge for different trest,1 with

constant trest,2 (b) Variation of lithium concentration across the negative electrode at the end of

relaxation period after discharge. .................................................................................................. 62

Figure 4.5: (a) Variation of cell potential with time during discharge for different trest,2 with

constant trest,1 (b) Variation of lithium concentration across the negative electrode at the end of

relaxation period after charge. ...................................................................................................... 62

Figure 4.6: Comparison of the effect of relaxation at EOD on cell potential for different depth of

discharge at 1000th cycle with trest,2 = 5 min. The capacities of 5.83, 8.75 and 11.67 Ah/m2 shown

are obtained for DOD corresponding to 33, 50 and 67%, respectively. ....................................... 64

Figure 4.7: Comparison of effect of relaxation on cell potential with CC and CC-CV charging at

1C-rate (inset shows the zoomed view of cell potential after 1000 cycles). ................................. 64

Figure 4.8: Variation of lithium concentration across the positive electrode (a) at the end of

relaxation period after discharge (b) at the end of relaxation period after charge. ....................... 65

Figure 4.9: Variation of electrolyte salt concentration across the cell domain (a) at the end of

relaxation period after discharge (b) at the end of relaxation period after charge. ....................... 66

Figure 4.10: Lithium concentration for ,1 120 minrestt and ,2 5 minrestt at EOD and EORD of

500th cycle (a) across the particle radius at current collector/anode interface (b) at anode/separator

xii

interface (c) across the negative electrode (d) across the particle radius at separator/cathode

interface (e) at cathode/current collector interface (f) across the positive electrode. ................... 69

Figure 4.11: Variation of film thickness across the negative electrode for various relaxation periods

after 1000 cycles. .......................................................................................................................... 70

Figure 4.12: Comparison of effect of relaxation over cell potential for different C-rates with trest,2

= 5 min (the potential drop for 2C-rate is high due to higher kinetic overpotential). ................... 72

Figure 4.13: 1st and last cycle lithium concentration in solid matrix at EORD for 1C and 2C-rates

(a) in anode (b) in cathode. ........................................................................................................... 72

Figure 4.14: Comparison of lithium concentration at the beginning and end of cycling in the solid

phase of (a) anode and (b) cathode at EORC for 1C and 2C-rates. .............................................. 73

Figure 4.15: Last cycle lithium concentration at surface and center of the electrode particle at EOD

and EORD for 1C and 2C-rates across the (a) anode and (b) cathode. ........................................ 74

Figure 4.16: Variation of SEI film across the anode for the last cycle at 1C and 2C-rates. ......... 75

Figure 4.17: Applied current profile for cycling fo MCMB-LMO at 1C-rate. ............................. 77

Figure 4.18: Voltage vs. capacity for different cycling rates. The inset shows a comparison of

results considering (i) only SEI, and (ii) SEI with gas formation when almost 80% capacity is lost

due to degradation. ........................................................................................................................ 78

Figure 4.19: Current and cell potential for 1C-rate for different number of cycles. The abscissa has

been shifted so that the beginning of discharge for each cycle corresponds to 0 seconds. .......... 81

Figure 4.20: Different possible combinations of particle orientation of anode. ........................... 82

Figure 4.21: Representation of negative electrode with B-A-C orientation of different particle at

fresh and cycled stage. .................................................................................................................. 83

Figure 4.22: Variation of cell potential with cycle number for different anode based cells. ........ 83

xiii

Figure 4.23: Cell voltage vs. capacity for different morphological anode based cell. Inset shows

the enlarged view of the cell voltage at the end of the life for visual clarity. ............................... 85

Figure 4.24: Variation of space averaged lithium concentration with respect to cycle number (a)

across the negative electrode (b) across the positive electrode, at EOD. ..................................... 87

Figure 4.25: Variation of lithium concentration for different morphologies corresponding to (a) A-

B-C, (b) A-C-B, (c) B-A-C, (d) B-C-A, (e) C-A-B and (f) C-B-A shown at EOC and EOD. ..... 89

Figure 4.26: Representation of Li-ion and electron movement inside the negative electrode for B-

A-C morphology at (a) EOC and (b) EOD. .................................................................................. 91

Figure 4.27: X-ray diffraction pattern of the MCMB electrode. .................................................. 93

Figure 4.28: X-ray diffraction pattern of the LMO electrode. ...................................................... 94

Figure 4.29: SEM images of fresh (a) MCMB and (b) LMO electrodes. ..................................... 94

Figure 4.30: Cyclic voltammogram of LMO / MCMB cell at scan rate of 0.1 mV/s................... 96

Figure 4.31: Variation in cell capacity with cycle number for MCMB-LMO cells. .................... 97

Figure 4.32: Variation in discharge capacity with cycle number for cell 1. ................................. 98

Figure 4.33: EIS spectra of cell 1 at fresh and 100th cycle. .......................................................... 98

Figure 4.34: Comparison of loss in discharge capacity at 1C and 2C-rates. ................................ 99

Figure 4.35: Cell potential vs. discharge capacity at various stages of cycling at 1C and 2C-rates.

..................................................................................................................................................... 100

Figure 4.36: Cell impedance of at different stages of cycling at (a) 1C-rate and (b) 2C-rate. ... 101

Figure 4.37: SEM images of the disassembled electrodes of cell cycled at 1C-rate and 700 cycles

for (a) MCMB (b) LMO, at 2C-rate and 500 cycles for (c) MCMB and (d) LMO. ................... 102

xiv

Figure 4.38: Cyclic voltammogram of MCMB electrode against Li-metal at fresh stage. The inset

shows a minute reduction peak at 0.65 V. .................................................................................. 104

Figure 4.39: Cycling performance of MCMB between 2-0.005V at 1C-rate. ............................ 105

Figure 4.40: Potential vs. capacity at 1st and 100th cycle of MCMB for cell 3. .......................... 105

Figure 4.41: Nyquist impedance at different stages of cycling of cell 3. ................................... 106

Figure 4.42: SEM image of cycled MCMB electrode for 100 cycles at 1C-rate........................ 107

Figure 4.43: Variation in cell capacity with respect to cycle number at 1C and 2C-rates. ......... 108

Figure 4.44: Cell potential vs. discharge capacity at different stages of cell cycled at (a) 1C-rate

and (b) 2C-rate. ........................................................................................................................... 108

Figure 4.45: Impedance of MCMB half-cells at different stages of cycling when cycled at (a)1C

and (b) 2C-rates........................................................................................................................... 109

Figure 4.46: Cell potential vs. time for MCMB duirng charge and discharge recorded through

GITT at C/15. .............................................................................................................................. 110

Figure 4.47: Diffusion coefficient of Li-ions in MCMB electrode at different stages of cycling

during (a) charge and (b) discharge. ........................................................................................... 111

Figure 4.48: Discharge capacity of MCMB half-cells for 100 cycles derived through experiments

and simulation at 1C-rate. ........................................................................................................... 113

Figure 4.49: Variation in cell potential with discharge capacity for 1st, 50th and 100th cycle. ... 113

Figure 4.50: Variation in electrode porosity and SEI film resistance for 100 cycles. ................ 114

Figure 4.51: Space averaged lithium concentration in MCMB electrode at EOC and EOD...... 115

Figure 4.52: 1st, 50th and 100th cycle lithium concentration across the MCMB electrode at (a) EOC

and (b) EOD. ............................................................................................................................... 116

xv

Figure 4.53: Cyclic voltammogram of a fresh Li-LMO half cell. .............................................. 117

Figure 4.54: Cycling performance of LMO between 4.2-3.0V at 1C-rate. ................................ 118

Figure 4.55: Potential vs. discharge capacity at 1st and 100th cycle of cell 1. ............................ 119

Figure 4.56: Impedance of cell 1 at different stages of cycling. ................................................. 120

Figure 4.57: SEM image of LMO electrode after 100 cycles at 1C-rate. ................................... 120

Figure 4.58: Discharge capacity vs. cycle number at different C-rates. ..................................... 121

Figure 4.59: 1st and 100th cycle cell potential vs. discharge capacity at different C-rates. ......... 122

Figure 4.60: Cell impedance at fresh and charged stage of 100th cycle at different C-rates. ..... 123

Figure 4.61: Cell potential vs. time for LMO duirng charge and discharge recorded through GITT

at C/15. ........................................................................................................................................ 124

Figure 4.62: Diffusion coefficient of Li-ions in LMO electrode at different stages of cycling during

(a) charge and (b) discharge. ....................................................................................................... 125

Figure 4.63: Cycling performance of LMO for 100 cycles at 1C-rate. ...................................... 126

Figure 4.64: Potential vs. discharge capacity at 1st and 100th cycle of LMO. ............................ 127

Figure 4.65: Variation of lithium concentration across the LMO electrode at (a) EOD and (b) EOC.

..................................................................................................................................................... 128

xvi

LIST OF TABLES

Table 3.1: Cut-off voltages used for cycling of cells. ................................................................... 46

Table 3.2: Experimentally measured parameters for cell modeling. ............................................ 47

Table 3.3: Ideal Cell Model .......................................................................................................... 50

Table 4.1: Parameters used in simulation of cell relaxation. ........................................................ 61

Table 4.2: Various output properties of the cell at the end of discharge as a function of the ongoing

cycle number (N) for various rates. For instance, N=500 will mean that cycle 499 is complete and

cycle 500 is underway. .................................................................................................................. 79

Table 4.3: Number of cycles completed before the end of life and corresponding space-averaged

film thickness, resistance and gas volume. ................................................................................... 85

Table 4.4: Parameters used in numerical simulation of MCMB half-cells................................. 112

Table 4.5: Parameters used in numerical simulation of LMO half-cells. ................................... 125

Table 4.6: Various output properties of of LMO half-cells obtained at diefferent stages of cycling

..................................................................................................................................................... 127

xvii

NOMENCLATURE

as specific interfacial area of the electrode (m-1)

A surface area (m2)

c concentration (mol/m3)

C specific capacity (Ah/g)

d lattice spacing (Aº)

D diffusion coefficient (m2/s)

E intermittent potential (V)

Ea activation energy (kJ/mol)

F Faraday’s constant (96,487 C/mol)

f± mean molar activity coefficient

i current (A/m2)

ie ionic current (A/m2)

J current density (A/m3)

k rate constant of lithium intercalation/deintercalation (m2.5/(mol0.5.s))

kdiss dissolution reaction constant (1/s)

m loading of the electrode (g)

M molecular weight of solid deposit (kg/mol)

n number of electrons

r particle radius (m)

Rsei film resistance (Ω/m2)

xviii

Ru universal gas constant (J/ (mol K))

t time (s)

0t cation transference number

T temperature (K)

U equilibrium potential of porous electrode (V)

V volume (m3)

x state of charge

Xa dissolution reaction rate

a anodic transfer coefficient

c cathodic transfer coefficient

δsei SEI film thickness (m)

s volume fraction of solid phase

e volume fraction of electrolyte

ηint overpotential of an electrochemical reaction (V)

ηpara overpotential of parasitic reaction

angle of incidence (º)

ionic conductivity of electrolyte (S/m)

sei film conductivity (S/m)

λ wavelength of the incident ray (Aº)

v molar volume (m3/mol)

ρel electrode density (kg/m3)

ρb bulk density of material (kg/m3)

xix

electronic conductivity of solid phase (S/m)

potential (V)

Subscript

a anodic

c cathodic

diss dissolution

e electrolyte

fl filler

g gas

int intercalation

is inactive solid material

n negative electrode

p positive electrode

para parasitic

ref reference

rest,1 relaxation after discharge

rest,2 relaxation after discharge

s solid

sd solid deposit

Superscripts

0 initial

eff effective

xx

Abbreviation

CC-CV constant current- constant voltage

CV cyclic voltammetry

DMC dimethyl carbonate

DOD depth of discharge

EC ethylene carbonate

EIS electrochemical impedance spectroscopy

EOC end of charge

EOD end of discharge

EORC end of relaxation after charge

EORD end of relaxation after discharge

EVs electric vehicles

GITT galvanostatic intermittent titration technique

HEVs hybrid electric vehicles

LIBs Li-ion batteries

LMO lithium manganese oxide (LiMn2O4)

MCMB mesocarbon microbeads

SEI solid-electrolyte interface

SEM scanning electron microscopy

SOC state of charge