2014/5/26 OREBA 1.0 SEI Corporation 1

Carbon composite LiFePO4 and the electrode structure for low cost and high performance lithium ion battery

Kazuma HANAI SEI Corporation OREBA 1.0, 2014

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1) Background 2) Conducting carbon additive for LFP 3) Conducting network and CNF dispersion 4) Carbon composited LFP 5) Electrode architecture 6) Performance data of the cell

CONTENTS

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ABOUT SEI CORPORATION

SEI Corporation; SEI is R&D venture company, which was established 14 years ago to develop new battery materials or new electrode architecture and to solve the subject in battery production process. Our purpose is to propose and offer the technologies regarding new materials and electrodes or production process, but not mass production. At present, SEI collaborates with material maker, car maker or car parts maker of over 70 companies in the worldwide. SEI has in view to realize the lithium ion battery world for higher energy, power and regeneration charge, longer calendar life, or higher safety and lower cost.

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Collaboration with Hydro-Québec; SEI Corporation of Japan and Hydro-Québec’s research institute have signed an Intellectual Property Pool Collaboration Agreement for the commercialization of their new co-owned patents for low-cost electrode architecture

Extracted from Hydro-Quebec Press Releases on January 20, 2014

Acknowledgement This research has been partly supported by Hydro-Québec. I appreciate to Dr. Zaghib and the research member of IREQ who took part in this collaboration.

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1. BACKGROUND

TARGET; Start and Stop system on the car Market; 1) Worldwide new car sales in 2013 was 83 million (1%, > 0.8 mill ), 2) Start & Stop car sales is estimated at 23 million@2017 (10% = 2.3 mill) Environmental; 1) Lead-free car electronics, 2) Fuel efficiency and Reduction of CO2 gas emission. Advantage of LFP; Energy density (due to limited cycle life and voltage profile of Lead-acid battery, Start & Stop system needs double or larger size battery), Voltage profile (3.4V LFP/Graphite, 13.4V fits on current car electronic system. Awaiting solutions; 1) Lower resistance and Low temperature working, 2) Long cycle life, 3) Cost performance in rivalry with Lead-acid battery. Solutions; 1) Optimization of the conducting additive for LFP, 2) Robust conducting network, 3) Thicker and shorter electrode.

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2. CONDUCTING CARBON ADDITIVE FOR LFP

Matching LFP with CNF; Model1, CNF (Highway) and CB (Local) Model2, CB (Highway) and CNF (Local) Model3, CNF/CB (Highway) and CNF (Local) High rate discharge; The required current for engine starting is 25-30CA on 20Ah class battery. Model conducting additive CB; DENKA BLACK (DENKA) CNF; MDCNF (MD nanotech)

Unit AB CNF

Diameter nm 48 15-20

Length µm ≤1 0.1-10

Specific surface area m2/g 39 240

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3. CONDUCTING NETWORK AND CNF DISPERSION

Awaiting solutions; Homogeneous distribution of nano-particles 1) Mechanical distribution Dry process; active material, AB and CNF were mixed using mechanochemical mixer 2) Surface modification and dispersion Wet process; Modify the surface condition of CNF to hydrophilic structure using acid treatment and dispersion in suitable solvent for the electrode slurry preparation 3) Conducting network Wt% of conducting carbon additive and suitable AB/CNF ratio

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1) Mechanical distribution

Active material and AB were mixed using mechanochemical mixer

Some micro size of AB agglomerates were found after mixing

ca. 3µm

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Active material, AB and CNF were mixed using mechanochemical mixer

CNF agglomerates were found after mixing. The particle size was larger than AB agglomerate. ---> Dispersant or Chemical treatment

ca. 10µm

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2) Surface Modification and dispersion

COO-

COO- O-

COO- O-

Acid treatment

CNF powder Hydrophilic functional group

Electrode using CNF/NMP dispersion LFP:AB:CNF = 90:8:2(6wt% of PVdF)

Great enhanced distribution

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Compositional dependence of volume resistivity for LFP electrode (wt% of carbon additive)

Electrode sample

Digital Ohmmeter

Electrode resistance decreases with increasing wt% of conducting additive. ---> Model composition; 10wt%

AB:CNF= 2:1 140g/m2, 2.0g/cm3

(6wt% of PVdF, 20µm of Al foil) T=25˚C

LFP : Carbon additive = 98 : 2 94 : 6

3) Conducting network

Surface modification of CNF made the homogeneous distribution on LFP. Next step is decreasing the electrode resistance for high rate discharge.

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Compositional dependence of DC resistance for LFP/Graphite cell (AB/CNF ratio)

Cathode Material LFP AB CNF

wt% 90

10 0 9 1 7 3 6 4

140g/m2, 2.0g/cm3

(6wt% of PVdF, 20µm of Al foil)

Lower resistance was measured at AB:CNF ratio of 9:1 to 8:2. ---> Model composition; AB:CNF=8:2

CNF : AB = 10 : 0 6 : 4

Pouched type cell Specific discharge capacity; 25mAh @1CA, 25˚C DCIR; calculated by IR drop at 3 and 10sec in 0.2-5CA.

Next step is striking a balance between AB/CNF for lower cell resistance. The DCIR of LFP/Graphite cell was measured under different AB/CNF ratio.

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Performance of LFP/Graphite pouch type cell with 10wt% of carbon additive

Decreased ca. 30%

25˚C, SOC50%

90% @10CA

Enhanced cell performance was obtained in10wt% of carbon additive electrode using CNF dispersion.

Pouch type cell, 140g/m2, 2.0g/cm3

(6wt% of PVdF, 20µm of Al foil) Specific discharge capacity; 550-570mAh @1CA, 25˚C

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4. CARBON COMPOSITED LFP

CNF dispersion homogeneous distribution Model composition lower resistance Target; Lower resistance and long cycle life The electrode resistance and cycle stability are limited due to the conduction interrupting Awaiting solution; Carbon additives should adhered by chemical bonding to the surface carbon layer on LFP as carbon coating Key technology; Carbon composited LFP with robust conduction by the chemical bonding Solution idea; Carbon additive and LFP make C-C bonding when the hydrophilic functional group is decomposed during simple heat treatment.

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COO-

COO- O-

COO- O-

Heat treatment

LFP, AB, CNF(dispersion) mixture Carbon composited LFP

LFP

CNF

AB

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Performance of LFP/Graphite pouch type cell using composite LFP

Cell resistance 10% down

25˚C, 3CA /3CA

Pouch type cell, 140g/m2, 2.0g/cm3

(6wt% of PVdF, 20µm of Al foil) Specific discharge capacity; ca. 560mAh @1CA, 25˚C

Carbon composite LFP shows lower resistance and longer cycle life.

Volume resistivity

Electronic resistance 50% down

Longer cycle life

Composite LFP decrease the production cost at mixing the electrode slurry.

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5. ELECTRODE ARCHITECTURE

Target; Approach to Lower cost performance using the electrode architecture Awaiting solution; thicker coating, lower resistance, good adhesion on metallic foil as current collector Projection structure; Projection shows the anchor effect. Hole on the foil supports smooth electrolyte transportation in the call. Key technology; Contamination-less and in-lined production coating system

Projection

Driing

Coating

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3) Projection structure

Projection and hole, The point of the projection covered with electrode

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25˚C, 3CA /3CA

Longer cycle life

Cell resistance 15% down

Pouch type cell, 140g/m2, 2.0g/cm3

(6wt% of PVdF, 20µm of Al foil) Specific discharge capacity; ca. 560mAh @1CA, 25˚C

Carbon composite LFP shows lower resistance and longer cycle life.

Performance of LFP/Graphite pouch type cell using projection foil

Performance of LFP/Graphite pouch type cell for Start and Stop systemc

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2C/2C cycle @50˚C More than 6,000 cycles

-30˚C, 20CA, 19sec

Lead-acid LIB (estimated)

Battery weight 21kg(105D31) 80-90Ah

6-7kg 20-25Ah

Sale price (Production cost)

US$250 (US$70-100)

US$(1000) (US$500-600 )

Calendar life 3-4 years 6-7 years

LIBs shows great potential for Start and Stop system. Now we are focusing on 25CA, 30sec working @-30˚C.

No voltage jumping at higher CA IR drop is restricted by cell resistance (590mAh)

Same slope

6. PERFORMANCE DATA OF THE CELL

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SUMMARY

We proposed new LFP electrode for Start and Stop system on the car. Material; Carbon composite LFP showed great enhanced performance. This concept is not limited to variety of LFP and carbon additive. Electrode architecture; Projection foil affected to raise the performance of LFP electrode. In-lined projection system showed a possibility to decrease the production cost of LFP battery. This application is promising market for LFP battery.