USA: Winning in the Gigantic New EV Market (great reference)

Ninety times larger in five years … The Li-ion rechargeable battery market is on the verge of a massive transformation. With their adoption in electric vehicles (EV), the Li-ion rechargeable battery market is expected to surpass three trillion yen in five years. An era of intense competition in technology development has begun, embroiling a host of newly entered companies.

In the fall of 2010, Nissan Motor Co., Ltd. will release its Leaf electric vehicle (EV), implementing an ambitious plan to manufacture 50,000 units in fiscal 2010 and 200,000 in fiscal 2012. Viewed in terms of Li-ion rechargeable battery production volume, this is 24kWh of capacity per Leaf, which works out to 4800MWh for 200,000 units. This alone is far larger than the 3000MWh market for Li-ion batteries in mobile telephones today. In other words, a single car model will totally change the market environment.

“Production Can’t Keep Up”
Nissan Motor is not the only one: Major automotive manufacturers around the world have announced large-scale production plans for EVs mounting Li-ion batteries. General Motors Corp. plans to sell 50,000 to 60,000 plug-in hybrid EVs (PHEV) from the second half of 2010, and 100,000 hybrids a year.

Honda Motor Co., Ltd. will begin manufacture of Li-ion rechargeable batteries at its Blue Energy Co., Ltd. joint venture in Japan with GS Yuasa Power Supply Ltd. from the second half of 2010, and hopes to “boost the percentage of hybrid new car sales in industrialized nations to 50% in 2020.” Battery manufacturers are feeling the pressure of burgeoning demand from automotive companies around the world: “If we booked all those orders, production would never be able to keep up,” says Ken Sawai, Manager, Corporate Strategic Planning Division of GS Yuasa Corporation (Note 1).

Note 1: GS Yuasa is the parent company of Lithium Energy Japan, which supplies Li-ion rechargeable batteries for the i-MiEV electric vehicles for Mitsubishi Motors.

From Mobile Phones to Cars
The massive production of EVs is bringing about significant chance in the Li-ion battery industry. The market for EV Li-ion rechargeable batteries will far surpass the existing market for the same batteries in mobile phones in only a few more years… and they will not be miniature cells, but rather primarily large-size, large-capacity cells.

This change will not only to trigger new investment into manufacturing equipment and facilities, it will also spark new competition to develop technologies for large-capacity Li-ion batteries. Battery and battery materials manufacturers are facing intensifying competition not only from other firms already in the industry, but from a host of new entrants as well.

Fig . 1 Global Investment Competition Heating Up
Battery manufacturers are beefing up production capacity in preparation for future demand increases, and just adding up the major companies shows over one trillion yen earmarked already. Diagram by Nikkei Electronics based on material courtesy of Deutsche Bank Securities and other sources. A diverse selection of companies is taking aim at the EV market, rushing to grab a piece of the large-capacity Li-ion rechargeable battery business.

Sony Corp. is a representative example. In November 2009, the company announced it was entering the automotive and large-capacity storage battery fields, among others, although it had declined to do so in the past (Fig. 1). The firm is quite serious, according to Hiroshi Yoshioka, Executive Deputy President, Corporate Executive Officer, President of Consumer Products & Devices Group of the firm: “We will invest 100 billion yen over the next few years into volume production facilities.”

Sanyo Electric Co., Ltd. has earmarked 80 billion yen for investment into the field by 2015, while Panasonic Corp. has budgeted 123 billion yen by 2012. The three major Japanese Li-ion battery firms will invest a total of 300 billion yen.

Massive Investments by Overseas Firms, Too
Battery manufacturers outside Japan are active, too. In Korea, for example, LG Chem, Ltd. is investing about 100 billion yen, including investment into its US subsidiary, while Samsung SDI Co., Ltd. will invest about 38.5 billion yen by 2015 (Note 2). In China BYD Co. Ltd. and Tianjin Lishen Battery Joint-Stock Co., Ltd. both have plans to boost production capacity to 1000MWh, and recently investment of at least 200 billion yen is expected in China.

Note 2: Samsung SDI and Bosch jointly established SB LiMotive, with total investment of US$600 million.

Existing battery manufacturers are being joined by firms coming from other industries. In Japan, heavy equipment manufacturers Mitsubishi Heavy Industries, Ltd. and IHI Corp. have joined in. Mitsubishi Heavy Industries is investing about 10 billion yen into a pilot plant at its Nagasaki Shipyard, planning to produce 66MWh annually from the fall of 2010.

IHI, meanwhile, does not manufacture its own batteries, but has entered into an agreement with A123 Systems, Inc. of the US, and plans to begin supplying their Li-ion rechargeable batteries to the Japan market.

Overseas, giant chemicals firm Dow Chemical Co. has established a joint venture with Kokam Engineering Co., Ltd. of Korea and other partners. With an investment of US$600 million (about 54 billion yen), the company plans to volume-produce Li-ion rechargeable batteries for EVs and hybrid vehicles at 60,000 units/year.

Automotive Market 90 Times Larger in Five Years
Just the investments that Nikkei Electronics looked into already exceed one trillion yen. The driving application for the Li-ion rechargeable battery market is on the verge of shifting from mobile phones to electric vehicles.

According to Fuji Keizai Co., Ltd. of Japan, the total market for Li-ion rechargeable batteries in 2009 was about 841 billion yen. The company estimates that 97% of that was accounted for by mobile phones, notebook PCs and other portable equipment (Fig. 2). In contrast, the market for EVs was only about 25 billion yen, but this will explode to 300 billion in 2010, and overshadow the portable equipment market in 2012 by reaching a staggering 1,580 billion yen. Estimates beyond that call for continuing growth to 2,250 billion 2014, representing a 90-fold increase in only five years.

Fig. 2 A Three Trillion Yen Market in 2014
The electric vehicle Li-ion rechargeable battery market is expected to exceed two trillion yen in 2014, and the total market for the batteries surpass three trillion yen. Diagram by Nikkei Electronics based on material courtesy of Fuji Keizai.

The capacity of Li-ion batteries used in an EV is enormously larger than that found in a mobile phone. The battery in a mobile phone has a capacity of only 2Wh to 3Wh, while a single hybrid car packs about 1kWh, or roughly 500 times more capacity. An electric vehicle is 20kWh, representing at least 10,000 times more (Fig. 3).

Fig. 3 Far More Capacity in a Single Vehicle
An electric vehicle will mount at least 200 times more capacity than a notebook PC. Diagram based on the standard “18650” batteries used in notebook PCs, measuring 18mm in diameter × 65mm long.
Mobile telephone shipment volume in 2009 reached about 1.1 billion handsets worldwide, putting the scale of the mobile phone Li-ion battery market at about 3000MWh a year. When notebooks PCs and other equipment is added in, the total size for the portable gear market is probably between 10,000MWh and 15,000MWh. The capacity of 150,000 EVs would be roughly equivalent to the market for handsets, or between 500,000 and 750,000 to equal the entire mobile equipment market. Total global new car sales are about 70 million units, and even if only 1% of those are EVs and 20% hybrids, the market scale will be significantly larger than the entire portable equipment market!

Future Expansion into Railroads, Industrial Equipment and More
If large-capacity Li-ion rechargeable batteries for EVs really take off, it seems likely prices will drop significantly (Fig. 4). If new, fully automated manufacturing lines are built, slashing personnel expenses, says a source at one battery manufacturer, “it will be possible to halve the current cost of 200,000 yen per kWh.” There are a number of people in the industry who say prices could drop to 50,000 yen per kWh by 2015 if volume production for EVs gets under way.

Fig. 4 Cost Down to 50,000 yen/kWh by 2015
Automated manufacturing and stable product quality have brought the price of Li-ion batteries down to about 100,000 yen/kWh now, but if EVs enter volume production and boost demand, prices may well drop to about 50,000 yen/kWh by 2015.

If that does happen, it would mean expanded application for large-capacity Li-ion rechargeable batteries in rail carriages, industrial equipment, etc. (Fig. 5). For example, Hitachi, Ltd. recently booked one trillion yen worth of diesel hybrid rail carriages equipped with Li-ion rechargeable batteries for delivery to the UK. Next-generation light-rail transit (LRT), for example, could eliminate some or all of the aerial lines to slash aerial line construction cost and ensure operation even during outages … representing new demand for onboard large-capacity Li-ion batteries.

Fig. 5 Lower-Cost Li-ion Rechargeable Batteries Means More Applications
If the scale of electric vehicle volume production increases, battery cost will drop, and that could lead to rapid and widespread adoption in a host of non-automotive applications such as mobile equipment, industrial machinery, and stationary installations.
In industrial equipment, Li-ion batteries are already being installed in forklifts, unmanned automatic vehicles, harbor cranes, and construction machinery, for example. Mitsubishi Heavy Machinery released a hybrid forklift equipped with the company’s own Li-ion rechargeable battery in October 2009. Sumitomo Heavy Industries Engineering & Services Co., Ltd. of Japan began selling a hybrid crane for harbor freight handling in July 2008 equipped with Li-ion batteries, and has already booked orders from Hong Kong.

A source at one heavy machinery manufacturer reveals, “they aren’t offering Li-ion rechargeable batteries yet, but hybrid shovels with onboard capacitors are selling in China.” The price of a hybrid shovel is about half again more than a standard design, but “fuel expenses are 25% to 40% less,” says a source at Komatsu Ltd. of Japan. In places like China where machinery is operated for prolonged periods of time, this eventually results in lower cost.

Into the Home in 2015 or Beyond
If the manufacture of large-capacity Li-ion rechargeable batteries for EVs, industrial machinery, and other applications expands even more, the price could well drop to 30,000 yen/kWh. At that price, Li-ion batteries could be considered for stationary power storage applications, an extremely cost-critical market.

The output of renewable energy sources such as solar cells and wind power varies greatly with meteorological conditions. Connecting unstable power supplies to the electrical power grid can cause frequency fluctuation, degrading power quality. If the generated power can be stored in large-capacity Li-ion rechargeable batteries, though, it can then be supplied to the grid later with stability. At present, sodium sulfur (NAS) batteries are the only option for such large-capacity electricity storage, but if large-capacity Li-ion rechargeable batteries become available they could make possible medium-sized power storage facilities in power stations, buildings, factories, etc.

For example, ITOCHU Corp. of Japan and others will market a system for condominiums in January 2010 combining Li-ion batteries with solar cells. The batteries are automotive designs manufactured by EnerDel Inc. of the US, with a capacity of 24kWh. They are intended to assist with daytime illumination of public areas in the buildings, reducing building management fees for residents.

Korea, China, and the US Threaten Japanese Industry
The entry of a large number of manufacturers into the promising large-capacity Li-ion rechargeable battery market is likely to intensify the battle for survival. Japanese electrical equipment manufacturers recall the shares they lost to Korean and other firms by falling behind in the investment competition for products such as DRAM and LCD panels.

The Korean manufacturers in particular are champing at the bit. Multiple sources in the battery industry agree that Samsung SDI will probably pull ahead of Sanyo Electric in terms of market share. Japan held close to a 100% share of the Li-ion rechargeable battery market in around 2000, dropping to about 64% in fiscal 2003, and under half in fiscal 2008. Many Japanese materials manufacturers working on batteries say that demand will probably grow more for export than for domestic use within another two or three years.

Korea is not the only rival: China, the United States, and other regions are emerging as serious competitors, too. China in particular, supported by soaring domestic demand, seems likely to develop its own market for Li-ion rechargeable batteries. The automobile market there has grown to match the US as the biggest in the world, with 12 million units sold a year. Environmental measures in major cities like Beijing and Shanghai have fueled demand for an enormous domestic market for Chinese battery manufacturers, such as at least 20 million electric motorcycles.

Already some people in the industry have pointed out that low-priced Li-ion rechargeable batteries from China might take the global market. Part of the reason is that many Chinese battery manufacturers are putting designs using lithium iron phosphate (LiFePO4) cathodes into volume production. The most expensive item in Li-ion batteries is the cathode material (Fig. 6). Manufacturers in other nations including Japan and Korea, on the other hand, are turning to 3-element cathodes composed of Co, Ni, and Mn, hoping to boost capacity. Chinese manufacturers are concentrating on price, abandoning the current lithium cobalt oxide (LiCoO2) standard in favor of LiFePO4, which costs only about one-tenth as much.

Fig. 6　High Cathode Material Cost
In battery cells using 3-element cathodes composed of Co, Ni, and Mn, the cathode material accounts for at least 30% of the total cost. Diagram by Nikkei Electronics based on material courtesy of Deutsche Bank Securities.
In addition, adds one engineer in the Li-ion battery field, even though “manufacturing yield is probably only 20% to 30%,” Chinese manufacturers are making a profit. Battery major BYD is expected to quickly boost production capacity, reaching 1000MWh in 2010 and 4000MWh in 2012. A source in the battery industry reveals, “They are using all the latest, made-in-Japan manufacturing equipment.” If yield rises, Japanese manufacturers will face stiff competition indeed.

Strong US-China Ties
The United States, however, under the Obama administration, has revealed a policy of making everything from materials to battery packs domestically. It is interesting to note that as long as manufacturing is performed in the US, foreign manufacturers can also tap funding. Already companies like LG Chem and Saft Groupe S.A. of France have received financing via their American subsidiaries. Japanese companies include Toda Kogyo Corp., which has received financing and begun volume production of cathode material, while Nissan Motor plans to use separate US federal funding to construct a Li-ion rechargeable battery plant.

Japanese battery manufacturers seem to have no plans to join in, apparently because of the risk entailed in having overseas manufacturing facilities. If Nissan Motor expands its procurement scale and continues its policy of local procurement, then manufacturing in the United States will become almost certain.

The American political strategy goes a bit further, though. In November 2009, the United States announced a comprehensive cooperative agreement with China in energy. Joint projects are already under way in promoting the use of EVs, introducing renewable energy, etc.

In the promotion of EVs, concrete activities include joint standardization and demonstration projects, while in renewable energy the two nations plan to develop a smart grid strategy for the next-generation power grid.

Japan does not have a very effective comprehensive policy in the energy field and almost no cooperative agreements with other nations. A strategic partnership between giant markets China and America can only leave even less room for Japanese manufacturers to squeeze in.

Volume production plans for large-capacity Li-ion rechargeable batteries are being finalized one after another, targeting electric vehicles (EVs) and other applications. Performance is still not sufficient, and the development of a new Li-ion rechargeable battery delivering improvements in capacity and safety would mean significant business opportunity: the worldwide competition to develop the next generation of batteries is on!

High-volume production plans are being budgeted and implemented around the globe, hoping to supply surging demand for large-capacity Li-ion rechargeable batteries. Many battery manufacturers have already made their choices for key components such as cathode and anode materials, separators, and electrolyte. In many cases, the materials chosen have been the ones developed by Japanese manufacturers, who took the lead in Li-ion rechargeable batteries for mobile telephones.

That is not to say that the Japanese materials manufacturers have any assurance for the future, though. Li-ion rechargeable batteries for EVs have only just reached the realm of commercial use, and the real competition for technology development is just heating up.

A source in the automotive industry complains that the performance of Li-ion rechargeable batteries is “still not good enough” to power EVs capable of long-distance driving. Further improvement is needed in a number of areas, including energy density, output density, cost, and safety.

In particular, existing Li-ion rechargeable batteries occupy too much volume and cost for EVs and plug-in hybrid electric vehicles (PHEVs) viewed by the automotive industry as trump cards to slash CO2 emissions. If the materials used in today’s Li-ion rechargeable batteries are the first generation, then the second generation delivering roughly double the energy density (200Wh/kg to 300Wh/kg) needs to be developed, with a target implementation of 2015 to 2020 (Fig. 1).

Fig. 1 Targeting 500Wh/kg in 2030
R&D first hopes to achieve Li-ion rechargeable batteries with energy densities of 200Wh/kg to 300Wh/kg through changes in cathode, anode, and other materials. Entirely new rechargeable batteries are also being developing, with a target energy density of 500Wh/kg in 2030.

Basic research is also underway around the world to develop post-Li-ion rechargeable batteries―solid-state batteries, Li-metal batteries, Li-S batteries or Li-air batteries, for example―all with commercial roll-out in about 2030.

Li-ion rechargeable batteries are composed as cathode and anode materials, electrolyte, separators, and other parts, and their characteristics as batteries must be carefully balanced. In many cases, merely selecting a high-performance cathode material and combining it with a high-performance anode material does not result in a high-performance battery. The electrode materials and the electrolyte may not work well with each other, for example. Or it may simply be difficult to establish a volume production technology for new materials.

In fact, there is not a very wide range of commercial choice for cathode and anode material, electrolyte, etc., for use in consumer electronics. That’s exactly why the development of a new and promising combination of materials could represent enormous business opportunity.

Directions for the Second Generation
At present, large-capacity Li-ion rechargeable batteries for EVs and other applications use 3-element† (Li(Ni-Mn-Co)O2), lithium manganese oxide (LiMn2O4) or lithium iron phosphate (LiFePO4) cathodes, with graphite-based anodes (Note 1). Development will probably be guided by three key factors, namely higher energy density, better safety and lower materials cost (Fig. 2).

† 3-element: Some of the Co in lithium cobalt oxide (LiCoO2) is replaced with Ni or Mn.

Note 1: LiCoO2 is not used for high-capacity Li-ion rechargeable batteries in EVs because of safety concerns, and because they are unsuitable for high-output applications.

Fig. 2 Developing Materials to Resolve Specific Issues
Cathode material development will probably concentrate on lower cost and higher voltage, while anode materials need to be safer. In electrolytes, researchers are especially interested in ionic liquid solutions to boost voltage and improve safety.

The issues involved in selecting candidates for cathode materials are quite different from those of anode materials. Compared to anode materials, there just aren’t any new candidates for high-capacity cathode materials (Fig. 3). It looks now that capacity simply doesn’t increase unless sulfur, air, or other materials are used, and they are being eyed as post-Li-ion rechargeable batteries (Li-S or Li-air cells, for example). These batteries face a host of unresolved problems, and commercial application will still take time. As a result, development of cathode material is concentrating on boosting cell voltage to obtain higher output.

Fig. 3 Diverse Range of Candidates for Cathodes
Compared to anode materials, few cathode materials offer large capacity. There are, however, anode materials that can deliver very high capacity, such as Si or Sn alloys. The difference in potential between the cathode and anode determines the voltage of the battery cell. Diagram by Nikkei Electronics based on material courtesy of various manufacturers, NEDO, etc.
There are high-capacity candidates for anodes, but they suffer from excessive expansion and contraction during charge/discharge, causing physical breakdown and excessively short charge/discharge cycle life. In addition, the graphite now used in almost all designs has a low electrical potential relative to Li. This can cause Li deposition on the surface of the graphite electrode, and electrolyte decomposition.

Development of the improved (second generation) Li-ion rechargeable batteries is likely to combine a cathode material supporting higher voltage to boost output, with an anode material delivering better capacity and safety. A flame-resistant electrolyte with a potential window† capable of withstanding high voltages will also have to be developed.

Searching for New Cathode Materials
Cathodes in Li-ion rechargeable batteries today use layered LiMO2 materials like 3-element designs or lithium cobalt oxide (LiCoO2), spinels such as LiM2O4, or LiMPO4 olivine materials. They all have average discharge voltages of a bit over 3V, however. There are cathode materials, though, with an electrical potential of about 5V relative to Li. If one of these 5V cathode materials is used, it becomes possible to increase the average discharge voltage. Energy density is the product of specific capacitance and voltage, so a higher voltage means more battery capacity.

Olivine materials are especially intriguing from the aspects of both safety and cost. In olivines, elements P and O are tightly bonded, and oxygen is not released even at high temperature. This makes thermal runaways† less likely, improving safety. Olivines, however, have low electrical conductivity, and people in the industry expressed doubt that they can be used in batteries for several years. Recently the Massachusetts Institute of Technology (MIT), A123 Systems, Inc. of the US and others have found a way to make practical Li-ion rechargeable batteries for use in high-output applications by using smaller LiFePO4 particles and sheathing them in carbon (Fig. 4).

† Thermal runaway: Excessive heating inside the cell, caused by internal shorts or other factors, leading to smoking, ignition, rupture, etc.

Fig. 4 Improving Cathode Materials through Finer Particles, Carbon Sheathes
Olivine cathodes made of LiFePO4 and other low-conductivity materials can be modified to output higher voltage by using finer particles with carbon sheathes (a, b).
The finer particles and carbon sheathing makes it possible to use the material, formerly suffering from low electrical conductivity, in cathodes, rapidly increasing the number of candidates in the running. Recognizing that olivines offer higher voltages, development of lithium manganese phosphate (LiMnPO4) is accelerating.

The electrical potential of LiFePO4 to Li is only about 3.4V, but this can be increased to 4.2V with LiMnPO4. Unfortunately, LiMnPO4 has lower electrical conductivity than LiFePO4, demanding the use of smaller particles and better carbon sheathes.

Solid Solution Materials Promising
Work is also under way to develop 5V cathode layered materials layered and spinel materials, and a solid solution material (Li2MnO3-LiMO2) has been gaining attention rapidly. It has a layered structure, but is especially interesting because it could well surpass the theoretical ceiling of 275mAh/g accepted for layered materials.

For example, the Li-ion and Excellent Advanced Batteries Development Project being advanced by Nissan Motor jointly with New Energy and Industrial Technology Development Organization (NEDO) is now developing a solid material using Li(Ni0.17Li0.2Co0.07Mn0.56)O2 (Fig. 5). According to a source at Nissan Motor, the material has a Li layer, and various transition metal layers (Co, Mn, etc.), but the initial charge causes Mn, Co, and other elements to migrate into the Li layer, changing its structure into a new and stable form. Ni in transition metal does not migrate, say Nissan Motor researchers.

Fig. 5 Solid Solution Materials Promise Higher Capacity
Nissan Motor is developing a solid solution material Li(Ni0.7Li0.2Co0.07Mn0.56)O2　expected to deliver higher capacitance. The material itself has a layered structure, but after initial charging, the structure changes (a). It has been verified that the new structure exhibits a capacitance above the theoretical value for a layered cathode material of 280mAh/g (b). Diagram by Nikkei Electronics, based on a paper presented by Nissan Motor at the 50th Battery Symposium in Japan organized by NEDO.
In addition to the oxidation reduction reaction of Mn and Co, larger capacity is thought to be due to charge compensation (O2- to O-).

R&D is also active into fluoride phosphate olivine (Li2MPO4F), silicate (Li2MSiO4) and other materials offering high specific capacitances exceeding 300mAh/g.

Larger Capacity with Si-Alloy Composites
Unlike cathode materials, where specific capacitance is generally low, there are a good number of anode materials offering the potential for larger capacity, such as Si and Sn. Si in particular has a theoretical capacity at least 10 times higher than graphite, the most commonly used anode material today. Li ion intercalation, however, causes a change in volume of 400%, and the structure can be easily destroyed by repeated charge/discharge, making the extension of cycle life a key problem.

Some ideas being tried out include mixing with conventional graphite to create air gaps, thereby controlling volumetric expansion to some extent, and alloying with SiO or other materials, then mixing in graphite to create a SiO-C composite. The first battery cells using this Si composite for the anode are expected to appear in another year or two, as Li-ion rechargeable batteries for mobile phones.

Safer Anode Materials
When it comes to large-capacity Li-ion rechargeable batteries, where many cells are connected together for use, improving safety becomes more important than in conventional mobile phone applications. The most commonly used anode material, graphite, has a low electrical potential relative to lithium metal, which means problems such as Li deposition and the formation of chemical compounds at the interface of the anode and the electrolyte are common. Toshiba Corp. has developed a new material attracting attention in the industry: lithium titanium oxide, or LTO (Li4Ti5O12).

LTO has a high potential relative to Li, and delivers excellent safety because of its freedom from interface reactions with the electrolyte or Li deposition, for example. The electrical potential of LTO is about 1.5V above Li, however, which means if used with existing cathode materials would drop the cell discharge voltage to about 2.4V. The theoretical capacitance is about the same as graphite, which means there are limits to how high the cell energy density can be raised.

It seems likely that the cell energy density, however, can be boosted to at least 200Wh/kg by using LTO with a 5V cathode material to increase battery discharge voltage, or using it in a composite with high-capacity Si allow or similar material, for example.

LTO already has a competitor, too: Sanyo Electric Co., Ltd. is developing an anode material with a theoretical volumetric capacitance double that of LTO, with an electrical potential on a par with that of Li (Fig. 6). The company optimized the oxygen composition ratio of MoOx, and succeeded in creating single-phase molybdenum oxide (MoO2) with excellent reversibility. A prototype coin-type battery (6.8mm diameter × 1.4mm high) made with a LiCoO2 cathode and a MoO2 anode achieved a capacity of 2.9mAh, 1.3 times the level of the same design with an LTO anode. The firm is continuing research into MoO2 as a promising candidate for battery anodes.

　
Fig. 6 MoO2: Higher Capacitance that LTO
A coin-type cell prototype made with a MoO2 anode exhibited 1.3 times more capacitance that the same design with an LTO anode. The cathode was LiCoO2, cell charge was 100µA, and discharge between 100µA and 5µA. Diagram by Nikkei Electronics based on material courtesy of Sanyo Electric.

Basic Research for
Innovative New Batteries
It seems likely that efforts will develop Li-ion rechargeable batteries with energy densities of 200Wh/kg or higher, utilizing new materials, will accelerate in the future. At the same time, basic research is underway around the world into brand new types of batteries surpassing 500Wh/kg. Some promising candidates are Li-metal, all solid-state, Li-S, and Li-air batteries.

In June 2009, IBM Corp. announced it was developing post-Li-ion rechargeable batteries, including Li-air designs. IBM hosted an international conference on this subject in August 2009, with invited researchers from the global community.

In Japan, Toyota Motor Corp. is actively engaged in basic research, establishing the Battery Research Division in June 2008 specifically for basic research into new battery technologies. Researchers there are working on fundamental themes such as interface reactions between particles, and between electrodes and electrolytes, with the goal of developing new Li-ion rechargeable battery materials, all solid-state batteries, Li-air batteries, and more. At the 50th Battery Symposium in Japan held from Nov. 30 to Dec. 2, 2009, Toyota Motor presented nine papers on basic research, demonstrating the firm’s strong interest in the field.

Of the candidate post-Li-ion rechargeable batteries, Toyota Motor appears to be especially interested in all solid-state batteries. An ideal all solid-state battery, says theory, would achieve a Li diffusion speed higher than that possible with a liquid electrolyte, making higher output possible. It would also be safer than organic electrolytes, which combust at high temperatures, and because there is no contained liquid, it seems likely that the exterior casing could be simplified. At present, though, reaction products form at the interface between solid electrolyte and electrode, significantly degrading battery performance.

A source at Toyota Motor has disclosed that the reaction products formed at the interface between electrode and solid electrolyte (Li7P3S11) vary with cathode material. Concretely, layered LiCoO2 results in mutual diffusion of cathode Co, and solid electrolyte S and P. When the cathode is LiMn2O4 spinel, however, oxygen from the LiMn2O4 diffuses into the solid electrolyte, creating very high interface resistance.

Researchers at Toyota are working on clarifying each phenomenon individually, and if they can improve characteristics such as Li-ion and electrode conductivity, they believe it will be possible to develop a safe, large-capacity battery.

Preventing Dendrites
Other leading contenders for the position of post-Li-ion rechargeable battery are Li-metal and Li-air batteries, and research is hot here as well. Li-metal batteries were actually commercialized back in the ‘80s, before commercial Li-ion rechargeable batteries appeared, but following ignition accidents in 1989 they are ronly used as primary batteries today.

Read more at
Source: nikkeibp.co.jp

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