AABC Asia 2014 - LLIBTA Symposium: Large Lithium Ion Battery Technology and Application - Session 2

Since 2007, Automotive Energy Supply Corporation (AESC) has been developing the lithium Ion batteries for xEVs. In 2010, AESC launched mass productions of lithium Ion batteries with laminate structure.

ESC’s batteries have been installed for LEAF, KANGOO, FUGA, SKYLINE, etc. In January 2014, the selling volume of battery pack for LEAF surpassed 100,000 units that is equivalent to 2,400MWh as energy.

Key factors of the lithium Ion batteries for xEVs are as follows:

1. High energy
2. Low cost
3. High reliability
4. Long life

What is the difference between the large batteries for xEVs and the small batteries for consumer use?

Three major points are as follows:

1. LIB system for vehicle application requires about 100 to 200 cells.
2. Requirement for reliability is severer than consumer use.
3. Requirement for life is 5 to 10 years.

This presentation obtained about the laminate cell progress of AESC at this moment and requirements of battery materials which conduct the market expansion of xEV.

Since the introduction of lithium ion batteries in early 1990s there have been continuous improvements in energy densities of the batteries mainly focused on lithium cobalt oxides / graphite systems. On the otherhand lithium ion batteries for automotive application needs not only performance improvement but also cost reduction. To lower $/kWh ratio for automotive cells different type of cathode and anode materials needs to be considered. Among the cell components, the cathode material is the biggest driver for improving performance and choosing the right cathode material platform is the key for future success.

This presentation discusses:

• Presenting Umicore, global leader in active battery materials
• Review on the evolution of energy density of lithium ion batteries
• Update on cathode material developments at Umicore

The anode material plays a critical role in determining the performance of xEV batteries. For meeting the increasing demands of various types of xEV batteries, many different categories of anode materials have been fully developed in Shenzhen BTR New Energy materials Inc. including natural graphite, artificial graphite, MCMB, soft carbon, SiOC, Si-C, LTO, and their composites. The progress of these advanced materials in BTR will be discussed in the conference.

Topics covered:

1. The artificial graphite and MCMB with high energy density applied in xEV.
2. The soft carbon with high power density, low temperature discharge and safety capabilities applied in xEV.
3. Si-based materials with high energy density and good cyclability applied in xEV.

Properties of Si based anode materials; Si , SiO and SiOC

• Structural property
• Chemical property
• Electrical property

Application for high energy density batteries

• Vehicle application

Compared with batteries for consumer electronic market, xEV batteries have much higher performance requirement, especially in cycle life, high temperature storage, low temperature discharge and safety. Electrolyte plays a very important role in determining those battery performances. There are different chemistry applied in xEV batteries aimed at different applications, and the main difference lies in the cathode. Almost all xEV batteries using graphite in anode, but there are several different choices in cathode, and typical solutions are as following:

1. LFP for EV/PHEV batteries
2. LMO+α for EV batteries
3. NMC for HEV/PHEV/EV batteries

These cathode materials have very different performances, especially in cycle and storage. And these differences come from different electrochemical stability of cathode in electrolyte, which including two important aspects:

1. Metal dissolution from cathode
2. Electrolyte decomposition on cathode

For each typical cathode material, the stability of cathode in electrolyte was analyzed and the effect of additives was analyzed and discussed as a key point of electrolyte.

Li-Ion batteries are in constant development with a focus on increasing energy density and reducing cost. Cell materials are more than half of the cell cost and therefore there is pressure on industry to reduce the cost of today’s materials. However, it is not only the cost of an anode or cathode material per kg or per Ah that influences cell cost; it will be shown that other properties are just as important.

Developers of advanced materials for tomorrow’s Li-Ion batteries usually put the emphasis on increasing specific energy and energy density. How the properties of the new active materials affect the battery cost is less often considered. In this presentation the influence of anode and cathode material properties and the influence of some cell design parameters on energy density and cost at the cell level are analyzed using a simple mathematical cell model. The relationship between material properties and electrode design will also be discussed. Some indication of the influence of material properties on cost at battery system level is also given. The following parameters will be examined for both anode and cathode materials:

• Specific capacity of active materials
• Electrochemical potential of active materials
• Active material density
• Electrode density
• Electrode area capacity
• Choice of binder and conductive agent

The results give a direction for the development of active material properties with improved energy density and cost.

We launched our laminated film for automotive LIB market in 2010.
This product is the culmination of our experiences and our studies in mobile LIB market more than 15 years.

Test items for automotive LIB market themselves, e.g. retention period, are not different from that for mobile phone LIB market, but required performance level  is totally different in the point of the hurdles.

For years, several users have made variety of trials and requested a lot.
Based on their requests, we have been providing further insights into our products. The result of these process our products have been commercialized. Now we will present the key factors of our insights and requirements that are needed for the future.

1. How to check the sealing performance and barrier properties
2. Concept of transport vibration intensity and safety valve for heat and pressure
3. Electrical insulation properties which cause corrosion

• Requirement for electrical insulation
• How to check its values

1. Outer Chemical resistance against automotive principal liquid

Li-ion batteries have been used as a power source for a variety kind of applications including electronic devices, automobiles, and energy storage systems. In the Li-ion battery market, cell makers are required to improve their product properties and cost performance in order to meet different specifications and requirements of each application market and so do the material makers. Under these circumstances, Chinese material makers are emerging rapidly and encroaching on the material markets, benefiting from the strong domestic Li-ion battery market and cheap manufacturing costs.

In this presentation, we will take a detailed look at the current trends and future prospects of the Li-ion battery and material markets.

Topics covered:

• Overview of the Li-ion battery market
• Overview of the four major Li-ion battery material markets (cathodes, anodes, electrolytes, and separators)
• Future prospects of the Li-ion battery and material markets