Hitachi mejora el rendimiento de las baterías de litio

Lo esencial es que, si bien las últimas novedades en la química avanzada de las baterías de litio, como las de litio-aire y las de litio-azufre ofrecen una brillante idea del futuro, están aún muy lejos del alcance de los actuales vehículos eléctricos.

Lo más importante, en este momento, es mejorar la tecnología actual con el fin de impulsar la eficiencia. Cuanto mayor sea la eficiencia, más personas estarán dispuestas a ver los vehículos eléctricos no sólo como una alternativa, sino como una sustitución del motor de combustión interna.

La tecnología actual de iones de litio. Es importante ver lo que hace la industria para saber por dónde va el desarrollo de las actuales baterías de litio. La mejora de la eficiencia permitirá masificar la producción de vehículos eléctricos y, en última instancia, reducir el precio.

Hitachi ha anunciado hace unos días que ha creado una nueva cuarta generación de su sistema de baterías que tiene 4.500 W/kg de densidad, aproximadamente 1,7 veces más que las actuales baterías de iones de litio. El promedio de las baterías se encuentra hoy en alrededor de 2.600 W/kg. Hitachi afirma haber desarrollado la batería más potente. ¿Cómo lo consiguen?

Con el fin de reducir la resistencia interna, la batería utiliza cátodos de manganeso y electrodos más delgados, junto con un nuevo método de captación de la electricidad, lo que permite mejorar la eficiencia a través de nuevas configuraciones. La tercera generación de batería de iones de litio, con una densidad energética de 3.000 W/kg, comenzará su producción en masa en 2010.

¿Por qué es importante? En última instancia esto significa es un gran avance en la capacidad de las baterías, como la que Hitachi está a punto de poner en el mercado. Las repercusiones se verán rápidamente, al menos, más de futuro sangrado borde tecnología de litio.

Litium battery performance improved by Hitachi

The latest lithium battery technology development is red hot and can be read on many segment of the news.

The gist is that while the latest developments in high-end advanced lithium chemistry, such as Lithium-Air and Lithium-Sulfur offer a bright glimpse into the future, it is still far away from the reach of current electric vehicles, EVs. What is most important, at this stage is working on improving today’s technology in order to boost efficiency. The more efficiency they have, the more the public will be willing to see them as not only alternatives, but compete replacement of the internal combustion engine, ICE.

Current Lithium-Ion Technology. It is important to see where the industry is going by keeping an eye on the current lithium battery development. This is what will eventually shape the electric vehicles, EV industry and beef up the market. Squeezing more performance out of them will allow for mass production, which should, in theory lower prices and pave the way for even more performance. In the meantime, we need to continue pushing the performance envelop of the curent lithium-ion chemistry.

Hitachi, Squeezing More Power. Hitachi has announced a few day ago that it has created a new fourth generation of its battery system that has 4,500W/kg power density, about 1.7 times the output of its current mass production lithium-ion batteries. The average output today is at around 2,600 W/kg. Hitachi claims it is the world’s highest output. How did they do it?

Technically Speaking. In order to reduce internal resistance, the battery uses manganese cathode and thinner electrodes, along with a new power collection method, they boosted the performance through more effective configurations. A third generation lithium-ion battery that has a power density of 3,000W/kg will go into mass production in 2010.

Why Is This Important? Ultimately what this means is that battery breakthroughs, such as Hitachi’s is something close to being market ready. The repercussions should be quickly felt, at least, more than future bleeding edge lithium technology.

While we can dream of the stuff that will shape tomorrow, we have to continue working on what is currently available, refining it in order to pave the way for the longer term. A battery pack that carries almost twice as much energy density as today’s is something any electric drive aficionado can rejoice with. Hum, a Telsa Roadster than can 480 miles on charge? Nah.

Battery Technology. Last, but not least is the battery technology that has to continue improving if it is to provide propulsion for electric vehicles, EVs. This is a very crowded field where different alchemies fight for relevancy.

Lead Acid Batteries: The history of lead acid could go way back in time, as far as back as the Babylonians. The heavy lead/acid battery has seen transformations through it’s 100 industrial years. From high maintenance flooded types to sealed gel packs, it has grown in energy density and shed some extra weight. Before anyone discards them as too heavy or outdated, I believe they can still play a role for some hybrids and storage facilities, where weight is not as much an issue.

Nickel Based Batteries: The revolution a few decades ago happened with NiCad (nickel cadmium), which were lighter than lead/acid, had better energy density, but were highly toxic, suffered capacity losses from improper charging/discharging procedure. The next phase was the introduction of NiMh (Nickel metal hydride), used in Hybrids such as the Prius. Lighter than lead acid and NiCad they also have a reduced amp/hour capacity compared to lead/acid, as well as being complex in design.

Lithium "Ion": Whether we talk about Lithium Manganese Oxide, Lithium Cobalt Oxide, Lithium Iron phosphate, they are compact, have half the weight of lead/acid batteries and twice their energy density. However, cobalt and manganese modules are prone to thermal problems and need energy management. While Lithium Cobalt Oxide boasts high energy and light weight, it has the highest thermal management issues, with Lithium Iron phosphate having a great thermal stability and power delivery with lower energy density than cobalt. The state-of-the-art Lithium Nano Titanate/ultracapacitors promise fast charging and lightness. They are light and small, and should have better energy density than most other types. If regular lithium is expensive, this is the Cadillac of them all.

Ultracapacitors: This is the preferred "boost" storage power system in hybrid busses and large EVs, which works particularly well well for regenerative braking. It is fast charging, has better power density than most batteries but poor long term charge retention
cycles. None the less, this looks like the most probably "next" step in advanced battery design. It is ideal at short bursts of energy and recoups what it lost as easily as it dispensed it. The best part, is that theoretically, it can take as much charge as you can provide it.

The Others: Other concepts and types that are still in the early development stages, such as Zinc air and lithium-sulfur, among a few mentioned in the media. Only time will tell.

Static Energy Storage Device. When it comes to battery technology, light is not always a requirement. In the French and Swiss Alps, train systems have used static storage to recoup lost energy locomotives generate when coming down those steep mountains, better known as regenerative braking. Instead of the electric motors taking energy from the catenaries, it reverses its polarity and become generators. How does this fit into our smart grids? While wind and solar energy are not constant, having a storage battery pack could help balance the energy load for the grid.

EVs and Plug-In Hybrids As Mobile Storage Units. The use of EVs and now, plug-in hybrids, PHEVs as mobile storage units could greatly enhance the grids capacity to load balance energy transfers, especially during peak demand. It will take some re-educating driving habits and complicated software to determine how much energy is needed for your travel needs and how much can be sent back to the grid.

The Technical Details Pay Off . The last, and probably less talked about revolution is in the details. Current research in lightening electric motors, as well as making them more efficient will probably be the most important factors. Though not as sexy as current buzz words, efficient motors and rolling stocks, as well as lightened aerodynamic body, with robust light materials are where the details are being worked out.

Finally, even though we will continue to use coal, petroleum and gas to generate most of our electricity, alternative energy will slowly shoulder some of our burden, 20% by 2020 in the U.S., more elsewhere, and will gradually become greater. Producing EVs while making them affordable and profitable won’t happen until battery weight versus energy density ratio improves, as well as cost comes down. Alternative energy and EV technology alone will not make all of this come true without finally tackling what we have postponed for decades, revamping our aging grids. This will take many venues, from smart meter systems to smart cars, to better and more efficient power line transmission. All of these are part of the careful balance we need to strive for, while our brightest minds get to work on improving and solving situations. And to think I have only scratched the surface.


Revisiting Lithium-Sulfur Batteries

Advances could at last make the high-energy batteries practical.

Lithium-sulfur batteries, which can potentially store several times more energy than lithium-ion batteries, have historically been too costly, unsafe, and unreliable to make commercially. But they’re getting a fresh look now, due to some recent advances. Improvements to the design of these batteries have led the chemical giant BASF of Ludwigshafen, Germany, to team up with Sion Power, a company in Tucson, AZ, that has already developed prototype lithium-sulfur battery cells.

"Compared to existing technologies used in electric vehicles, the plan is to increase driving distance at least 5 to 10 times," for a given-size battery, says Thomas Weber, CEO of a subsidiary of BASF called BASF Future Business. Other experts say that a threefold improvement is a more reasonable estimate, but that would still be an impressive jump in performance. Weber says that BASF’s expertise in materials will help Sion Power further improve its technology and bring it to market faster. He declined to provide details of the arrangement, however, including how much money is involved and how the companies will share any profits.

Lithium-sulfur batteries have one electrode made of lithium and another made of sulfur that is typically paired with carbon. As with lithium-ion batteries, charging and discharging the battery involves the movement of lithium ions between the two electrodes. But the theoretical capacity of lithium-sulfur batteries is higher than that of lithium-ion batteries because of the way the ions are assimilated at the electrodes. For example, at the sulfur electrode, each sulfur atom can host two lithium ions. Typically, in lithium-ion batteries, for every host atom, only 0.5 to 0.7 lithium ions can be accommodated, says Linda Nazar, a professor of chemistry at the University of Waterloo.

Making materials that take advantage of this higher theoretical capacity has been a challenge. One big issue has been that sulfur is an insulating material, making it difficult for electrons and ions to move in and out. So while each sulfur atom may in theory be able to host two lithium ions, in fact often only those atoms of sulfur near the surface of the material accept lithium ions.

Another problem is that as the sulfur binds to lithium ions, eventually forming dilithium sulfide, it forms a number of intermediate products called polysulfides. These dissolve in the battery’s liquid electrolyte and eventually can settle in other areas of the battery, where they can block charging and discharging. Because of this, the battery can stop working altogether after only a few dozen cycles.

What’s more, the lithium metal electrode presents potential safety problems. For example, during use, the lithium electrode can grow branchlike structures that increase the impedance of the cell, causing it to heat up. Eventually these structures can cause a short circuit. If the battery heats up, the metal can melt. If the molten lithium leaks out of the cell and comes into contact with water, it can start a fire. The battery’s electrolyte can also catch fire.

Although he declined to give specifics, Weber says these safety issues have been solved. BASF’s goal is to further improve the materials to access more of their theoretical capacity, something he says the company has a clear plan for doing.

In terms of addressing safety issues, three advances could account for Weber’s confidence. Methods of chemically treating lithium metal electrodes can prevent at least some dendrite formation, although not all researchers are convinced that this approach will be sufficient. Also, improved polymer and ceramic membranes that separate the two electrodes and resist being pierced by the dendrites could prevent short circuits. The batteries, however, could still be vulnerable to short circuit if they’re damaged. To prevent electrolyte fires, Nazar says that less volatile electrolytes could be used with lithium-sulfur batteries because they have lower voltage than lithium-ion batteries.

Other issues, including low conductivity and a limited number of recharge cycles, seem to have been addressed at least in part by Sion Power. The company has produced cells that store more than twice as much energy as lithium-ion batteries available today, something BASF hopes to improve. And Weber says that the batteries can last the lifetime of a car, although this may be based on projections from Sion Power, rather than measured performance.

John Kopera, Sion Power’s director of commercial operations, says that the company’s current batteries are rated for 50 cycles, and that it has a "comprehensive plan" to reach about 1,000 cycles. (That’s enough for as much as 300,000 miles of driving, with a battery pack that provides a 300-mile range.)

Both companies are keeping details of their advances to themselves. But this week, in the journal Nature Materials, Nazar described one possible approach to solving these problems. In the past, researchers have improved conductivity by combining sulfur with carbon. Nazar went a step further by taking electrodes composed of regularly spaced carbon tubes and making them just a few nanometers wide. (Their structure is different from that of carbon nanotubes.) Nazar’s team then packed sulfur into the nanoscale spaces between these tubes, so that most of the sulfur atoms sit close to conductive carbon, making them accessible to both electrons and lithium ions.

The carbon tubes also helped solve the issue of polysulfides, which can kill a cell prematurely. The carbon tubes effectively trap the polysulfides in place until they are fully converted to dilithium sulfide, which does not poison the battery. Coating the carbon with a polymer that has an affinity for polysulfides also helps keep them in place. But it’s not clear whether BASF might also try a nanostructured electrode to improve Sion’s materials. So far, Sion Power has not used nanostructured materials, Kopera says. One challenge with Nazar’s approach is that it will be difficult to manufacture the carbon tube electrodes in high volumes.

Some issues likely remain. For one thing, the batteries may be costly–lithium metal is the most expensive form of lithium. Also, firm data isn’t yet available on how many recharge cycles the batteries can undergo and how they respond to safety tests. Still, Nazar says, the technology has "certainly come a long way. Our developments and those of a couple of other companies are certainly enabling it to be much closer to reality."


Hitachi develops automotive lithium-ion battery having the world’s highest output*1; sampling set to start in the fall

Tokyo, May 19, 2009 — Hitachi, Ltd. (NYSE:HIT / TSE:6501,hereinafter Hitachi) today announced that Hitachi, Ltd. and Hitachi Vehicle Energy, Ltd. which develops and manufactures lithium-ion batteries for automotive applications, such as hybrid electric vehicles, have developed a lithium-ion battery having the world’s highest power density of 4,500W/kg, 1.7 times the output of the company’s mass-produced, automotive lithium-ion batteries. Sampling of the new battery by domestic and overseas car manufacturers will start in the fall.

To reduce internal resistance, the battery employs a new manganese cathode and an original Hitachi battery structure, in such as thinner electrodes, power collection method and effective configurations to achieve the world’s highest output.

In recent years, lithium-ion batteries have been used for many consumer product applications, including mobile telephones, notebook PCs and digital cameras. For the same energy density, a lithium-ion battery has about half the volume and weight of a nickel-metal hydride battery, and about one-third the volume and weight of a lead acid battery. This makes the lithium-ion battery a small, light, high-energy-density secondary battery that is attracting attention for its applicability to hybrid and electric vehicles.

In 2000, the Hitachi Group used its extensive technological and manufacturing capabilities in fields ranging from materials to battery control systems, to develop and mass-produce the world’s first safe, high-performance, long-operating-life lithium-ion battery for automotive applications.

A second-generation lithium-ion battery with an power density of 2,600 W/kg that currently is being delivered for automotive and railway applications, is the world’s only mass-produced lithium-ion battery for on-board applications. Up to this point, a total of some 600,000 cells have been delivered, mainly to car manufacturers and railway companies.

Moreover, development of a third-generation lithium-ion battery having an even higher power density (3,000 W/kg) has already been completed, and will go into mass-production in 2010, with deliveries scheduled to begin the same year.

The battery set to start sampling this fall has been developed as a fourth-generation lithium-ion battery that is even smaller and lighter yet able to provide the world’s highest output. The high reliability of the new battery, in terms of mass-production and quality, is the culmination of manufacturing technology that Hitachi has built up in the course of its extensive market achievements, and through the feedback from its customers.

Going forward, in addition to this lineup of stand-alone battery cell products, Hitachi will meet customer needs by providing optimal battery system solutions that include control systems.

In line with its long-term "Environmental Vision 2025"*2plan to combat global warming, the Hitachi Group is using the expansion of its systems business, starting with its battery operations, to make a contribution to the future of the global environment, and to strengthen its social innovation business.

The new battery will be on display at the Automotive Engineering Exposition 2009 held at PACIFICO Yokohama from May 20 to May 22.

*1 Lithium-ion battery for on-board applications, as of May 2009.
*2 Announced December 20, 2007 in the press release entitled Hitachi Develops the Long-term Plan "Environmental Vision 2025" to Combat Global Warming.