LITHIUM ION - SILICON ANODE BATTERIES

BY : ASHIMA GUPTA

ECE 2

12310102811

CONTENTS

1. INTRODUCTION

2. STANDARD LITHIUM BATTERY

3. SPECIFICATIONS AND WORKING OF LITHIUM ION BATTERY

4. NEED FOR SILICON ANODE

5. SILICON ANODE BATTERY

6. SILICON NANOWIRES

7. APPLICATION OF LI-ON SI ANODE BATTERY

INTRODUCTION

Lithium-ion batteries are common in consumer electronics. They are one of the most popular types of rechargeable batteries for portable electronics, with a high energy density, no memory effect, and only a slow loss of charge when not in use. Beyond consumer electronics, LIBs are also growing in popularity for military, electric vehicle and aerospace applications.

Thus with such wide applications, it was felt the need for the lithium ion battery to have a higher capacity and longer cycle life and hence the lithium battery with silicon anode was developed .

Further , silicon anode was used as silicon nanowires for better performance.

STANDARD LITHIUM ION BATTERIES• A lithium-ion battery (sometimes Li-ion battery or LIB) is a member of a family

of rechargeable battery types in which lithium ions move from the negative

electrode to the positive electrode during discharge and back when

charging.

• Li-ion batteries use an intercalated lithium compound as one electrode

material, compared to the metallic lithium used in a non-rechargeable

lithium battery. The electrolyte which allows for ionic movement, and the two

electrodes are the consistent components of a lithium-ion cell.

• These are rechargeable batteries for portable electronics, with a high energy

density, no memory effect, and only a slow loss of charge when not in use. Li-

ion batteries provide lightweight, high energy density power sources for a

variety of devices. Lithium-ion batteries are in smart phones, laptops, most

other consumer electronics, and the newest electric cars.

SPECIFICATIONS AND WORKINGOF LITHIUM ION BATTERY

• Specific energy density: 360 to 900 kJ/kg

• Volumetric energy density: 900 to 1900 J/cm³

• Specific power density: 300 to 1500 W/kg

• During charging, an external electrical power source (the charging circuit) applies an over-voltage (a higher voltage but of the same polarity) than that produced by the battery, forcing the current to pass in the reverse direction. The lithium ions then migrate from the positive to the negative electrode, where they become embedded in the porous electrode material in a process known as intercalation.

• During discharge, lithium ions Li+ carry the current from the negative to the positive electrode, through the non-aqueous electrolyte

NEED FOR SILICON ANODE

• In a lithium-ion battery, charge moves from the cathode to the anode, a critical component for storing energy. There was a need for developing rechargeable lithium batteries with higher energy capacity and longer cycle life for applications in portable electronic devices, electric vehicles and implantable medical devices.

• Silicon is an attractive anode material for lithium batteries because it has a low discharge potential and the highest known theoretical charge capacity (4,200 mAh) .It absorbs eight times the lithium of current designs, and has maintained its greatly increased energy capacity.

• Silicon is a promising anode material to replace graphite for high capacity lithium ion cells since its theoretical capacity is ~10 times of graphite and it is an abundant element on earth.

‘structured’ silicon in the form of

micron-dimension pillars

SILICON - ANODE BATTERY• Design variations of the lithium-ion battery have been announced, in which

the traditional graphite anode is replaced by a silicon anode .It potentially improves battery performance.

• Silicon stores ten times more lithium than graphite, offering increased energy density. The large surface area increases the anode's power density, allowing for fast charging and high current delivery. The anode was invented at Stanford University in 2007.

• Silicon expands during charging and disintegrates after a small number of cycles.

SILICON - NANOWIRES• Initially , the people kind of gave up on using silicon because the capacity wasn't

high enough and the cycle life wasn't good enough. And it was just because of the shape they were using. It was just too big, and they couldn't undergo the volume changes. Silicon anodes had been dismissed because they tended to crack and become unusable, because it swelled by 400% intercalating lithium during charging . This degrades the performance of the battery. So researchers concentrated on finding ways to use silicon, maintaining anode conductivity.

• Silicon nanowire battery electrodes circumvent these issues as they can accommodate large strain without pulverization, provide good electronic contact and conduction, and display short lithium insertion distances. The theoretical charge capacity for silicon anodes was achieved and the discharge capacity close to 75% of this maximum, with little fading during cycling was maintained.

• Silicon nanowires also provide enhanced mass support.

Silicon Nanowire

• A nanowire battery uses nanowires to increase the surface area of one or both of its electrodes.

• The lithium is stored in a forest of tiny silicon nanowires, each with a diameter one-thousandth the thickness of a sheet of paper. The nanowires inflate four times their normal size as they soak up lithium. But, unlike other silicon shapes, they do not fracture. The nanowires were grown on a stainless steel substrate, providing an excellent electrical connection.

Fabrication of

graphene sheet

wrapped nano-Si

• One approach mixes silicon particles in a flexible polymer binder, adding carbon to the mix to conduct electricity. Unfortunately the repeated swelling and shrinking of silicon as it acquires and releases lithium ions eventually push away the carbon particles. What’s needed is a flexible binder that can conduct electricity by itself, without added carbon.

• Thus , a tailored polymer that conducts electricity and binds closely to lithium-storing silicon particles, even as they expand to more than three times their volume during charging and then shrink again during discharge was fabricated. Anodes made from these conducting polymers have low-cost materials and are compatible with standard lithium-battery manufacturing technology.

Silicon nanoparticles and graphene

Scaffolding combine to give two

patents pending.

• At left , the traditional approach to

composite anodes using silicon ( blue

spheres ) for higher energy capacity has a

polymer binder (light brown) plus added

particles of carbon to conduct electricity.

• Silicon swells and shrinks while acquiring

and releasing lithium ions. Repeated

swelling and shrinking eventually break

contacts among the conducting carbon

particles . At night ,the new Berkley Lab

polymer ( purple) is itself conductive and

continues to bind tightly to silicon particles

despite repeated swelling and shrinking.

APPLICATIONS OF LI-ON SI ANODE BATTERIES

• Canonical announced on July 22, 2013, that its Ubuntu Edge smartphone would contain a silicon-anode lithium-ion battery.

• Hybrid and Electric vehicle ( EV ) applications . Nissan is one such company involved in the manufacturing.

• They could also be used in homes or offices to store electricity, generated by rooftop solar panels.

• To power laptops, iPods, video cameras, cell phones, and countless other devices.

• “GEN3” lithium-ion battery : The GEN3 battery is largely based on Argonne’s provisionally patented silicon-graphene battery anode process . CalBattery says that it can produce the GEN3 battery in the United States at a cost reduction of 70 percent.

…THANK YOU…

* BY: ASHIMA GUPTA *

ROLL NO.: 12310102811

ECE-2