Products for batteries

Industry information 2244

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Contents

1 Introduction Description of diff erent battery types 3

2 Electrolyte 42.1. AEROSIL® for lead acid gel batteries 42.2 Dynasylan® for (Li-ion) batteries 5

3 Separators 63.1. Separators in lead acid batteries (SIPERNAT®) 63.2. Separators for Li-ion batteries (AEROSIL®, AEROXIDE®) 7

4 Electrodes 94.1. Electrodes for Li-ion batteries (AEROXIDE®) 94.2. Titania as precursor material for lithium titanate 9

5 Global presence 10

6 Literature of Evonik 11

7 Product recommendation 11

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1. IntroductionThe world of rechargeable batteries is changing. For the last decades, lead acid starter batteries have been the most prominent type of battery on the market. But since the greenhouse eff ect and global warming are regarded as global threats and since energy costs are increasing signifi cantly, scientists and technicians are looking for new energy concepts worldwide. Battery technology plays an important role in solving the current problems and in making energy available in a better way.

Renewable energy sources, like wind and solar ener-gy, are becoming more and more important and the necessity for effi cient intermediate energy storage is increasing. This can be solved, for example, by lead acid gel batteries (LAB) or lithium-ion batteries (Li-ion ).

Nowadays, high-energy and high-power Li-ion bat-teries play an important role for new energy storage concepts in automobiles. Hybrid electric vehicles (HEV) as well as full electric vehicles (EV) are reliant on these battery technologies, which are currently developed intensively.

Additionally, the new electric bike generation (e-bikes) requires an effi cient rechargeable battery system based on advanced lead acid (gel, AGM / SiO2) or Li-ion technologies.

These few examples demonstrate the growing demand for new materials and technologies for effi cient and environmentally friendly batteries.

Evonik Industries, as one of the most important chemical suppliers to the battery industry, provides many sophisticated solutions for present and future battery systems.

In gel batteries fumed silica is applied as thickening agent in the electrolyte. Precipitated silica is used as fi ller in separators for LAB while fumed products are used as fi ller and as well for coatings in Li-ion separator technology. Fumed titania is suitable as precursor material for the production of lithium tita-nate Li4Ti5O12 – an anode active material for Li-ion batteries. These are just a few examples from the extensive portfolio of Evonik for the battery industry. Ask us, challenge us – we will fi nd the right solution for your application. Our applied technology experts will provide optimum solutions for your advanced battery technology.

Description of diff erent battery typesIn general, batteries can be classifi ed using the concept of physical and chemical batteries. The class of physical batteries consists of thermal cells and solar power batteries, while their chemical analogues include primary (non-rechargeable) and secondary (rechargeable) batteries.

Various types of rechargeable batteries are known, including the four most common ones:• Lead acid batteries• Nickel cadmium batteries• Nickel metal hydride batteries• Lithium-ion batteries

Primary battery(not rechargeable)

Rechargeable battery

Lead acid battery

Lithium-ion battery

Lithium polymer battery

Nickel cadmium battery

Nickel metal hydride battery

Other rechargeable batteries

Physical battery

Solar battery

Thermal cell

Chemical battery

Battery

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General principle of a rechargeable battery

e-

e-

Discharge and Charge

ANODE

CATHODE

Both, lead acid and Li-ion batteries consist of the same major components – the two electrodes (anode and cathode), a separator in between them and fi nally an electrolyte, which is responsible for the ion transfer during charge and discharge processes.

Evonik products are present in the following battery components

Electrode material Separator Electrolyte

Lead acid battery

– SIPERNAT® AEROXIDE®

AEROSIL®

Lithium ion battery

AEROXIDE® AEROSIL®AEROXIDE®

Dynasylan®

2. Electrolyte2.1. AEROSIL® for lead acid gel batteries

Lead acid batteries are one of the oldest types of rechargeable batteries. Even though their energy-to-weight ratio is low, the ability of the cells to supply a high surge current results in a high power-to-weight ratio.

Due to their low costs, lead acid batteries are still gaining market shares, especially in these fi elds, where new battery systems are either too expen-sive or too demanding, particularly with regard to maintenance.

Lead acid batteries are still the most cost eff ective battery type for the following applications:

• Starter batteries for automotive engines • Traction batteries for golf caddies, fork-li s, wheelchairs, cleaning machines

• Stationary batteries as power back-up for tele-communication and data centers, power plants, hospitals, renewable energy systems, emergency lighting, green energy plants

History of lead acid gel batteries

Conventional fl ooded cell lead acid batteries are problematic in view of safety, due to their liquid acidic electrolyte. Therefore, they should be used only in an upright position in order to prevent leaking or spilling of the highly corrosive sulphuric acid.

In the late fi ies, a new class of advanced lead acid battery based on gel technology was introduced.

The gel battery is a type of valve-regulated lead-acid battery (VRLA). In VRLA batteries no water needs to be added during their lifetime and the battery is sealed with valves. The acidic electrolyte is either fi xed in the form of a gel or is absorbed in a glass fl eece.

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The advantages of gel batteries are:

• Almost maintenance-free • Spillage-free • Can be used in diff erent positions / no need to be kept upright / operation irrespective of its position

• Possibility of high discharge currents • Resistance to vibration, shock, extreme temperatures

• No acid stratifi cation • Deep discharge

Fumed silica is used to gelify the sulfuric acid.The requirements for gel forming agents are challenging:

• High purity • Chemical stable towards sulphuric acid, lead oxide, and lead

• Thickening and thixotropic behavior • Medium to high surface area

AEROSIL® fumed silica fulfi lls these demands and provides our customers with the following benefi ts:

• Highly eff ective thickening • Thixotropic behavior • Electrochemically and chemically inert • Stable viscosity • High purity • Prevention of acid stratifi cation

2. 2. Dynasylan® for Li-ion batteriesDue to their special properties, organofunctional silanes act as highly effi cient surface modifi ers, as water and HF scavengers, and as solvents. Hence, they can act as additives for electrolytes in lithium ion batteries. In addition to increased reliability due to higher thermal stability and the lower risk of hydro-gen and oxygen formation, increased durability and a higher number of load cycles can also be expected.

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3. Separators3.1. Separators in lead acid batteries (SIPERNAT®)

The function of the separator is to prevent the physi-cal contact of cathode and anode from eachother to avoid a short-circuit. Additionally, it must be permeable for ions, which move freely between the electrodes.

To fulfi ll those contradicting properties, the separa-tor has to be mechanical stable and porous at the same time.

Due to the high porosity, protons can migrate from one electrode to the other and close the electrical circuit. Because of the non-conducting separator the electrodes are not in direct contact with each other.

Separators for lead acid batteries can be made up of diff erent polymers, such as polyethylene (PE), polyvinylchloride (PVC), resins or rubber. They vary regarding design (thickness, ribs), porosity, and composition of the ingredients. In comparison to the other polymers, the polyethylene based separa-tors show a high fl exibility and weld ability, making PE suitable for a preferred application in starter batteries.

The main raw materials are PE (UHMW-PE), silica and oil. Selected additives are used, such as lubricants, wetting agents, carbon black.

Benefi ts of the PE separator compared to other materials are: puncture resistance, fl exibility, ability to be folded and sealed, oxidation resistance and low acid displacement.

The function of silica is to make the separator porous. This is achieved by mixing the raw materials and by extruding the mixture to form a sheet. The oil is extracted from the sheet and the sheet becomes porous. The silica remains in the porous sheet and makes the surface of the PE separator hydrophilic and wettable for sulfuric acid – allowing the protons to pass through the separator.

The silica for battery separators needs to be tailor-made to achieve the following properties: low electrical resistance of the separator material, good processing properties for the manufacturing process, specifi c morphology to control the separator shrink-age behavior during manufacturing and in service, and specifi c requirements for purity and trace elements.

The Evonik grades SIPERNAT® 325 C, SIPERNAT® 325 AP, SIPERNAT® BG–2, SIPERNAT® 325 E and possibly new grades fulfi ll these market requirements excellently.

Materials for separators in lead acid batteries

PE PVC Rubber Rubber / PE Phenolic resin

Strength Excellent Good Fair Excellent Good

Flexibility Flexible Rigid Flexible Flexible Rigid

Mean pore diameter (µm)

0.100.07

0.220.15

0.06 0.10 0.500.34

Pore Volume (%) 55 – 65 60 – 70 45 – 55 50 – 60 60 – 70

ER (Ωcm²) 0.120 0.130 0.250 0.110 0.140

Oxidation resistance

Excellent Excellent Good Good Excellent

Resists to Antimony transfer

No No Yes Yes No

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3. 2. Separators for Li-ion batteries (AEROSIL®, AEROXIDE®)

Similar to lead acid batteries, the basic function of the separator in Li-ion batteries is to prevent physical contact of anode and cathode from each other, while allowing lithium ions to move freely between the electrodes.

Therefore, the separator is made of electrically insu-lating materials, exhibiting a high porosity. The basis of all micro porous membranes is a thermoplastic material, that prevents short circuiting by separating the electrodes and blocking ionic conductivity in case of thermal runaway. The separator itself does not participate in the chemical reaction.

The performance of the battery, including energy and power density, cycle life and safety is directly aff ected by the separator. Various separator types are known for Li-ion batteries, including:

1 Micro porous membranes 2 Solid ion conductors 3 Gel polymer electrolytes

The application of Li-ion batteries as energy storage systems in HEVs and full EVs requires an improve-ment of the currently used separators in order to increase the safety function signifi cantly.

Modifi cation of these micro porous membranes with inorganic nanostructured particles, e.g. silica or alumina as fi llers or coatings, results in an improved inorganic-organic hybrid membrane with a high porosity and enhanced thermal stability. Further-more, the mechanical strength and electrolyte wet-ability is signifi cantly increased.

These inorganic fi llers can either be integrated directly into the thermoplastic material or into a separate layer that is coated, laminated or coextruded on top of the membrane.

Such a ceramic modifi ed separator enhances enhanc-es the mechanical stability and, therefore, leads additionally to an advanced protection against lithium dendrite growth inside the cell.

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Requirements for Li-Ion battery separators

Parameter Goal

Thickness < 25 µm

Porosity > 40 %

Pore size < 1 µm

Electrical resistance 2 ohms · cm–2

Wettability Complete wetting by typical electrolytes

Puncture strength > 300 g · mil–1

Shrinkage < 5 % @ 90 °C for 1 h

High-temperature melt integrity

> 150 °C

Shutdown temperature ~ 130 °C

Dimensional stability Should lay flat and not curl on the edges

Inorganic fi llers like AEROSIL® and ceramic layers with AEROXIDE® greatly infl uence the characteristics and properties of the micro porous separator:

• Improve thermal stabiliy (high temperature melt integrity)

• Enhance mechanical strength • improve electrolyte wettability • Increase porosity

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4. Electrodes4. 1. Electrodes for Li-ion batteries

(AEROXIDE®)

The two electrodes of a Li-ion battery act as host materials for the insertation of small Li+ ions. Upon charge / discharge of the battery Li ions start to migrate out of one electrode active material, diff use through the electrolyte fi lled separator, to fi nally insertate into the other electrode.

As appropriate anode materials a huge variety of dif-ferent carbonaceous compounds (natural & artifi cial graphite, hard and so carbons) were used as hosts for the reversible storage of Li ions in between the carbon sheets.

In general, the electrodes are formulated from the following materials:

1 Current collector2 Electrode active material3 Conductive material (e.g. carbon black)4 Binder5 Additives

4.2. Titania as precursor material for lithium titanate

Carbon based anode materials exhibit a disadvan-tage: the formation of an (irregular) solid electro-lyte interface (SEI) and the subsequent irreversible capacity decline upon fi rst-time battery cycling. This phenomenon can lead to a decreased cycle life of the battery and represents additionally a safety risk, because of the potentially growth of lithium dendrites. Therefore, other types of anode active materials, especially for those batteries, which are designed for HEVs and full EVs, are currently devel-oped intensively.

Lithium titanate Li4Ti5O12 seems to be an appropri-ate anode active material, mainly due its high safety. During the charge / discharge, i.e. lithiation and deli-thiation process, a signifi cant volume change of the host material is not observed (zero-strain material), resulting in a stable anode structure.

Furthermore, the formation of a SEI between the anode material and the electrolye does not occur, avoiding the irreversible capacity decline upon fi rst-time battery cycling.

Li titanate can be synthesized from diff erent Ti sources like Ti(OR)4, TiCl4 or TiO2 and the use of a variety of Li salts (see table below). Two types of AEROXIDE® materials – AEROXIDE® P 25 and AEROXIDE® P 90 – are recommended precursor compounds for the synthesis of Li4Ti5O12.

Different synthesis methods for the production of Li4Ti5O12

Method Ti sourceLi source (examples)

Sol-gel Ti(OR)4, TiCl4 Li2CO3, Li(COOR), Li(OR)

Electrochemical insertion

TiO2 LiClO4, LiAsF6, LiCF3SO3

Solid-state reaction TiO2 Li2CO3, LiOH, Li2O

Electrochemical TiO2 LiCl (molten)

Hydrothermal TiO2 LiOH

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5. Sites for production and applied technologies (AT) of SIPERNAT®, AEROSIL® and AEROXIDE®

Wesseling, Germany

Ta Yuan, Taiwan

Map Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, ThailandMap Ta Phut, Thailand

Zubillaga-Lantaron, SpainZubillaga-Lantaron, SpainZubillaga-Lantaron, SpainZubillaga-Lantaron, SpainZubillaga-Lantaron, SpainZubillaga-Lantaron, SpainZubillaga-Lantaron, SpainChester, PA, USAChester, PA, USAChester, PA, USA Akoh, JapanAdapazari, TurkeyAdapazari, TurkeyAdapazari, TurkeyAdapazari, TurkeyAdapazari, TurkeyAdapazari, TurkeyAdapazari, TurkeyAdapazari, TurkeyAdapazari, TurkeyAdapazari, TurkeyAdapazari, Turkey

AT-Center, Shanghai, AT-Center, Shanghai, AT-Center, Shanghai, ChinaAT-Center, Shanghai, ChinaAT-Center, Shanghai,

AT-Center, Piscataway, USAAT-Center, Piscataway, USAAT-Center, Piscataway, USA

Rheinfelden, Germany Rheinfelden, Germany Rheinfelden, Germany Leverkusen, Germany Leverkusen, Germany Roussillon, FranceRoussillon, FranceRoussillon, FranceRoussillon, FranceRoussillon, France

Antwerpen, BelgiumAntwerpen, BelgiumAntwerpen, BelgiumAntwerpen, BelgiumAntwerpen, BelgiumAntwerpen, BelgiumAntwerpen, Belgium

Yokkaichi, JapanYokkaichi, JapanYokkaichi, Japan(Production, AT-Center)Yokkaichi, Japan(Production, AT-Center)Yokkaichi, Japan

Waterford, USAWaterford, USAWaterford, USAWaterford, USAWaterford, USAWaterford, USAWaterford, USAPortland, USA

AT-Center, Hanau-Wolfgang, GermanyAT-Center, Hanau-Wolfgang, GermanyAT-Center, Hanau-Wolfgang, Germany

Mobile, USAMobile, USAMobile, USANanping, ChinaNanping, ChinaNanping, ChinaGajraula, Indien

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6. Literature of Evonik • Specialty Silica, Product Overview • AEROSIL® Product Overview • Dynasylan® Product Range • Technical Overview: AEROSIL® - Fumed silica

7. Product recommendation

Lead acid batteries

AEROSIL® SIPERNAT®

Separator SIPERNAT® 325 CSIPERNAT® 325 APSIPERNAT® BG–2SIPERNAT® 22 S

Electrolyte (gel) AEROSIL® 200AEROSIL® 200 VAEROSIL® 200 VS*

*Regionally restricted availability

Li-ion batteries

AEROSIL®/ AEROXIDE® Dynasylan®

Precursors for elec-trode active materials

AEROXIDE® TiO2 P 25AEROXIDE TiO2 P 90AERODISP® W 740 X

Separator AEROSIL®AEROXIDE® Alu CAEROXIDE Alu 65AEROXIDE Alu 130AEROXIDE C 805

AEROXIDE® TiO2 P 25AERODISP® W 740 XAERODISP® W 630

Dynasylan® VTMO

Electrolyte Dynasylan®(aminofunctional silanes as HF scavengers)

5. Sites for production and applied technologies (AT) of SIPERNAT®, AEROSIL® and AEROXIDE®

Europe / Middle-East / Africa / Latin AmericaEvonik Resource Effi ciency GmbHBusiness Lines Silica & SilanesRodenbacher Chausse 463457 Hanau-WolfgangGermany +49 6181 59-12532 +49 6181 59-712532ask-si@evonik.com

www.evonik.com

North America

Evonik CorporationBusiness Lines Silica & Silanes299 Jeff erson RoadParsippany, NJ 07054-0677USA +1 800 233-8052 +1 973 929-8502ask-si-na a@evonik.com

Asia / Pacifi c

Evonik (SEA) Pte. Ltd.Business Lines Silica & Silanes3 International Business Park#07-18 Nordic European CentreSingapore 609927 +65 6809-6877 +65 6809-6677ask-si-asia@evonik.com

This information and any recommendations, technical or otherwise, are presented in good faith and believed to be correct as of the date prepared. Recipients of this information and recommendations must make their own determination as to its suitability for their purposes. In no event shall Evonik assume liability for damages or losses of any kind or nature that result from the use of or reliance upon this information and recommendations. EVONIK EXPRESSLY DISCLAIMS ANY REPRESENTATIONS AND WARRANTIES OF ANY KIND, WHETHER EXPRESS OR IMPLIED, AS TO THE ACCURACY, COMPLETENESS, NON-INFRINGEMENT, MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE (EVEN IF EVONIK IS AWARE OF SUCH PURPOSE) WITH RESPECT TO ANY INFORMATION AND RECOMMENDATIONS PROVIDED. Reference to any trade names used by other companies is neither a recommendation nor an endorsement of the corresponding product, and does not imply that similar products could not be used. Evonik reserves the right to make any changes to the information and/or recommendations at any time, without prior or subsequent notice.

AEROSIL®, AEROXIDE®, AERODISP®, SIPERNAT® and Dynasylan® are registered trademark of Evonik Industries or its subsidiaries.

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