陶瓷涂层的无纺布隔膜- 特性及其优势

Ceramic coated nonwoven separator "NanoBaseX"
characteristics and its benefit
I. Fujita, K. Kato, N. Kasai, H. Watanabe,M.Kato,K. Hyodo, ,
Battery Separator Group
Mitsubishi Paper Mills Limited
e-mail:libsepa@mpm.co.jp
The nonwoven separator with ceramic coating (NanoBaseX) is designed to meet potential demands of the Li-ion battery industry for safer and affordable Li-ion battery. The wet laid nonwoven process is not only suitable for mass production but also advantageous for uniform and thin nonwoven fabric production. The ceramic coating with fine aluminum oxide particle can improve nonwoven's relatively large pore size and wider pore size distribution resulting in sufficient performance as physical barrier between an anode and a cathode. Thanks to excellent heat resistance of PET
nonwoven, NanoBaseX shows excellent heat resistance even at 220 degree Celsius promising the higher margin of safety. The mechanical strength has been improved by coating. In addition to it, because of rich contents of ceramic particle, NanoBaseX shows excellent protection against foreign particle. The inherent advantages of
nonwoven, such as electrolyte wettability and ion conductivity can be kept even after the ceramic coating resulting in longer cycle life than that in microporous membrane separator.
In this report, we will demonstrate characteristic of this newly developed nonwoven separator and the battery performance with it.
Abstract
Classification of battery based on its applications
ÿ R eproduced based on Roadmap for secondly battery technology by NEDO ÿ M ay 2010ÿ
100
200300
1,000
2,000
3,000
P o w e r d e n s i t y (W /k g )
Gravimetric Energy Density ÿ W h/Kgÿ
Cycle life oriented
Rate oriented
Energy density oriented
Type $`
Type $a
Type $b
Type $c
Type $d
Type $e
Type $f 0ûEV
0ûE -bike
0ûF orklift
0ûG olf buggy
0ûW elding machine
0ûP C
0ûM obile phone
0ûD igital camera
0ûH EV/PHEV 0ûR ailroad vehicle 0ûH EV construction machine 0ûP ower tool
UPS
Back-up battery system for ATM security system
0ûb ack-up system for
wireless base station
ESSÿ s olar energy 0 windmill,
factory and home use ESS)
Challenge in micro porous membrane
Change to another type of separator
may provide a dramatic performance improvement !
Higher safety
Better performance
ÿ Higher capacity0 rate performance0
cycle performance0
Low temperature performance )
Lower Cost
1)heat resistance layer coating 2)triple layers ;thicker than 30 ¼m 3)improÿV e d material
ÿ h igher MW0 modified MS ÿ
4)thermal hysteresis
5)three dimensional pore structure
ÿ d endritic growth control ÿ
1)improved pore structure 2)better electrolyte affinity 3)less thickness
1)Higher productivity
Comparison between
micro porous membrane and nonwoven micro porous membrane nonwoven
Advantage Disadvantage
0ûS mall and uniform pore ÿ 0.06 ¼mÿ
0ûH igher mechanical strength
0ûT hin and smooth film
0ûL ow heat resistance
0ûP oor electrolyte permeability
0ûC ost
0ûH igher heat resistance
0ûL ow cost
0ûG ood electrolyte permeability
0ûH igher thickness
0ûL arge and nonuniform pore
0ûP oor uniformity
0ûL ower mechanical strength
Challenge in nonwoven separator is to realize
small and uniform pore with thickness of lower than 40 micron meter
Wet-laid nonwoven manufacturing method
Drying
Winding
Paper making and
Dewatering
Dispersion of short fiber
Advantagesÿ
(1) Suitable for thin and uniform nonwoven fabric production (2) Flexibility in the selection of different type of fiber material (3) Established process for mass production at low cost
Good dispersion of fibers is very important to realize thin and uniform unwoven fabric.
poor dispersion
Key issue in Wet-laid nonwoven process
good dispersion
general outline of NanoBase
FPC2515
FPC3018
0ûMean Pore Size of less than 1 ¼m
0ûG ood balance between thinness and Submicron pore size
ÿ b y combination of ultrafine PET and cellulose nano fiber )0ûH eat resistance 0ûE xpected to be solo use
NanoBase ÿ
ÿ NB2)
OZ-S
0ûCeramic coating on NanoBase0
0ûM ean Pore Size of less than 1 ¼m 0ûS ufficient mechanical strength with submicron pore size 0ûGood heat resistance and heat conductivity
NanoBaseX
ÿ NBX)
FPB1510FPB1812
0ûMean Pore Size ÿ ÿ ¼mÿ^ÿ ÿ ¼m
or ÿ ÿ ¼mÿ^ÿ ¼m 0ûN on-woven fabric with ultrafine PET fiber 0ûH eat resistance, high tensile strength 0ûU sed as substrate for additional functional layer
NanoBase ÿ
ÿ NB0)
Product Name
Features
NanoBase is series of Mitsubishi's non-woven fabric for battery separator that brings great improvement in battery quality and low cost .
Conventional nonwoven NanoBase2
NanoBase0
top view
20kV 10 ¼ÿM
×1,000
cross-
section
NanoBase2
%ÏThe non-woven separator made of PET fiber and
nano-size cellulose fiber.
%ÏThe mean pore size is less than 1 ¼m at the thickness of less than 40 ¼m.
Successful result:
(1) Small mean pore size less than 0.5 ¼m
(2) Thickness 40 ¼m or less
(3) Excellent heat resistance higher than 180 !
(4) Excellent wettability and cycle performance
Further challenges remained:
(1) Reduction of absorbed moisture
(2) Higher mechanical strength
NanoBaseX(NBX):
-Ceramic coating nonwoven separator -
Expected improvement :
(1) Smaller amount of absorbed moisture contents
(2) Higher mechanical strength than NanoBase2
PET with ceramic coating
<3.0
<5.00.88.3551814.52701,6000.903128OZ-S35
Properties
Unit
Dire-ction
NanoBase0
NanoBase2NanoBaseX FPB1510
FPC2515
FPC3018
Basic Wight(Wj ‘Ï)g/m 2
101518Thickness(Sš0•)¼m
172330Density([Æ^¦)
g/cm 30.59
0.650.60Tensile Strength(_ _5_7^¦)
N/m MD 880490700N/m
CD 150353490Tensile Elongation(_ _5O80s)
%MD 1964%
CD
2033Porosity(zz–™s‡)
%
575359Gurley Permeability(ÿv ÿžÿp ÿš•l ^¦)sec/100cc 0.2 4.77.0Mean Pore Size(^sWG ÿŽÿŸÿq _…)¼m
4.6
0.60.5Heat Resistance(€ q±`')%MD <5.0<3.0<3.0< after 180! / 30mini. >%
CD
<5.0
<3.0
<3.0
Composition(}Db )
PET
PET
Cellulose
PET Cellulose
Characteristics of NanoBase
Surface SEM image
Cross section SEM image
SEM observation of NanoBase-X
anode
cathode
coated side
positive electrode negative
electrode
Comparison of surface roughness of nonwoven separator
traditional nonwoven NanoBase2NanoBaseX
Pouch cell setup
and
battery performance measurement
30mAh
theoretical capacity
of single cell
1M LiPF 6/EC:DEC (3:7)
electrolyte MCMBÿ 30mm ×50mmÿ negative electrode
LiMn 2O 4ÿ 30mm ×50mmÿ positive electrode Experimental condition ÿ
Charge ÿ 1C, 4.2V, cc-cvÿ 1/10ÿ#cut off)Discharge ÿ 0.2, 0.5, 1, 3, 5C,2.8V,cc
;Conditioning ÿ R ate performance of cell was measured after 3 cycle at ÿ ÿ#. ;PP membrane : mono layer PP , 25 ¼m thickness, basic weight 14.3g/m20
air permeability 570sec/100ml
Celgard24002.52.72.93.13.33.53.73.94.14.30510152025e>–û[¹‘Ï(mAh)
–ûW 'ÿÿ6ÿ1C
2C
3C
5C
oz-30S(8th-44)2.52.72.93.13.33.53.73.94.14.30510152025e>–û[¹‘Ï(mAh)
–ûW 'ÿÿ6ÿ1C
2C
3C
5C
Comparison of rate property between micro porous membrane and NanoBaseX
Test Condition Charge ÿ 1C, 4.2V, cc-cv(1/10C cut off)
Discharge ÿ 0.2C, 0.5C, 1C, 3C, 5C, 2.8V cut off
PP monolayer 25 ¼m
NanoBaseX (OZ-S30)
Cycle performance of NanoBaseX 707580859095100
20
40
60
80
100
Cycle Number
D i s c h a r g e C a p a c i t y ÿÿÿPP membrane (25 ¼m)NanoBase-X (35 ¼m)
Cycle condition
Charge at 1C from 2.8V to 4.2V
Discharge at 1C from 4.2V to 2.8V
Comparison of hole shape by a needle with Æ1mm peak.
Dry process
25 ¼m
PP single layer Wet-laid nonwoven
30 ¼m
NanoBase2
Ceramic coating
nonwoven separator
NanoBaseX
NB2 and NBX have less damage by a hole-piercing than pp membrane.
Wettability of separator material to various electrolyte solvent Penetration degree of solvent
into a separator was observed
after one minute of solvent drop.
Excellent Wettability
0.5
1
1.5
2
2.5
0246
time (min)
H e i g h t ÿÿC
ÿM ÿÿ.ÿ"ÿ ÿÿÿÿÿ+ÿ
ÿ#ÿ4ÿ&ÿÿÿÿÿ#ÿE ÿL ÿG ÿA ÿR
ÿD PP monolayer 25 ¼m NanoBaseX
NanoBase210mm
0»0Ñ0ì0ü0¿rG
20mmX 200mm 10mm
PC
PC
0»0Ñ0ì0ü0¿0nT8m²• ^¦n,[šL /cm
Experimental method
separator slip 20mmx200mm
Electrolyte absorption property of NanoBaseX
Time (min)
7PP/PE/PP Dry process 18¼m 8PP
Dry process 25 ¼m 16
NBX Nonwoven 35¼m
ÿ,ÿI ÿ0ÿ&ÿ /
ÿ%ÿ#ÿ ÿ$ÿ%ÿ#ÿ ÿÿÿÿ(g /10 micron0ûm 2)
OÝm²s ‡0n n,[še¹lÕ
0»0Ñ0ì0ü0¿0’–û‰ãm²0k 1m i n •“mx m²0Y 0‹Drain off excess electrolyte by
hanging separator for 1 min.
e l e c t r o l y t e
s e p a r a t o r
s e p a r a t o r
Normalized Electrolyte Absorption (NEA)of separator
Soaking separator in electrolyte for 1 min.
Measurement method of NEA
Separator
NEA
Excellent electrolyte retention ability
NanoBaseX
PP microporous membrane
(25 ¼m+2 ¼m ceramic coating on both side)
5cmÿX 12cm separator slip is hooked at both ends with 5g load on its center,then the specimen was stored at 220! environment.
30minutes later
25seconds later
Heat resistance of N anoBsse X
$`NanoBaseX
$a30 ¼mPPÿ dual-side ceramic coating $b27 ¼mPPÿ single-sideceramic coating $c25 ¼mPPÿ dual-side ceramic coating
$`
$a
$b $c
250! 0 30min
NanoBaseX could be unfolded after the test.
heated up to 250! for 30miniteus in crucible
Heat resistance of N anoBsse X
ÿ ÿ 0!
300!
270! 500!
600!
250!
420!
520!
250!
420!
PETÿ Cellulose
PP
PET
Cellulose
Thermal decomposition of separator material under oxygen-free condition
-12.0
-10.0-8.0-6.0
-4.0-2.00.02.0
2
4
6
8
10
Time (min)
A m o u n t o f e l i m i n a t e d w a t e (%)
100200300
400500600700
T e m p e r a t u r e (!)
$` N a n o B a s e X $a A l l c l l u l o s e $b c e l g a r d 240
T e m p .(! )
T e m p e r a t u r e
$a
$b $`
TGA analysis of release process of adsorbed water.
ÿ ÿ ÿThe rate of temperature elevation was 2.0! /min.
0.0
1.02.03.04.05.06.07.08.09.010.00
20
40
60
80
100
Time 0 (min)
A m o u n t o f w a t e r a d s o r p t i o n (ÿ)
N a n o B a s e X A l l c e l l u l o s e
Moisture re-adsorption behavior on the cellulose contain nonwoven separator.
Each separator was dried at 140 ! for 5 hours first.
Then the weight change was measured as a separator was placed on an electronic balance under the condition of 23 ! and 50 %.
Two different opinion about the shutdown function of separator (1) Shutdown function is still very important.
Although it is not perfect solution for large power battery in
some conditions, shutdown is still best way and indispensable.
(2) There is not strong reason to insist shutdown function
for large power battery.
Then, heat resistance of separator can be alternative
strategy against shutdown function.
Delivery of separator and storage
Assembly of battery and drying of cell
vacuum drying
Storage at room temperature /open humidity
dry room strage
Dry room
vacuum drying
electrolyte filling
electrolyte filling
electrolyte filling
ÿ A)
(B)
(C)
Battery assembly and heat drying process
Dry room
Dry room
battery assembly
battery assembly
battery assembly
dry room strage
Dried at 80!
Dried at 110!
Benefit of higher cell drying temperature
LiMn2O4/ graphite laminated cell
Capacity retention of 20Ah battery after cycle test at room temperature
8,000
12,000
16,000
20,000
1
201
401
601
801
1,001
1,2011,401
Cycle number
D i s c h a r g e C a p a c i t y （m A h ）
NanoBaseX
after 1,450 cycle test retantion rate :74%
PP/PE micro porous membrane
after 1,000 cysle test retention rate :46%
LiMn2O4/ graphite laminated cell
Nail penetration test on 10Ah
battery with NanoBaseX.
0û2 cell were tested resulting in no fire for both cells
0ûS urface temperature of the cell stayed at below 100! after a nail penetration 0ûN o leakage of electrolyte through the hole was recognized .
0ûN o remarkable expansion of the hole was found in the disassembled cell.
LiMn2O4/ graphite laminated cell
<test condition>
nail diameter : 4.5 mm
penetration speed : 20 mm/s
Nail penetration for first 3 cells of 5 series of10 Ah battery
0ûinflation of lamination at first top cell followed by gas releasing
0ûb ut no fire was observed
Model estimation of foreign particle resistance
of battery separator
<Experiment Setup>
model foreign object : short copper wire
(Load)
0.2mm
5mm
brass cylinder
plate electrode
pressure censor
Separator with model foreign object
on the surface
0500
1,000
1,500
2,000
2,500
10
20
30
40
50
Separator thickness ( µm )
W i t h s t a n d l o a d ( N
0)NB2 separator
Paper separator
Microporous membrane
NanoBaseX
<Result>
Model estimation of foreign particle resistance
of battery separator
NanoBaseX has more tolerance
to foreign particles than the other separators.
Estimation of foreign particle resistance
ÿ
2ÿ : merits in battery properties
0ûHeat resistance ÿ =>for higher safetyÿ
0ûG ood electrolyte absorption ability ÿ =>long cycle lifeÿ
ÿ 3ÿ : merit in the manufacturing process 0ûH igher speed in electrolyte absorption
ÿ =>reduction of process time ÿ
0ûL ow contents of adsorbed water and excellent mechanical strength
ÿ 1ÿ : achievement in this study
0ûC eramic coated nonwoven separator (NanoBaseX) has
mean pore size of less than 1 ¼m.
SUMMERY
Battery Separator Group // Mitsubishi Paper Mills Ltd.Ryogoku City Core,2-10-14 Ryogoku, Sumida-ku, Tokyo 130-0026, JAPAN
TEL +81-3-5600-1471// FAX +81-3-5600-1419
0 130-0026
gqN¬•ýX¨u0S:N!Vý2-10-14 N!Vý0·0Æ0£0³0¢N ƒñˆý} h*_ O y>j_€ýgP N‹im •èBSN‹im [¤TEL:03-5600-1471 //FAX:03-5600-1419
Thank you for your attention !
libsepa@mpm.co.jp。