Toyota Solid State Battery Developments

Toyota continues to move forward with Lithium-ion and Lithium-air developments

6/22/14 11:17 am chumakdenis 1

Toyota Motor Corporation has been trying to avoid the use of lithium-ion batteries as much as possible due to their high cost. However, the company does use them for the Prius Plug-in Electric Vehicle and the RAV4 EV. But it has said that it is now betting on solid-state and lithium-air batteries for use in electric vehicles by 2020.

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“As Toyota anticipates the widespread use of electric vehicles in the future, we have begun research in developing next-generation secondary batteries with performance that greatly exceeds that of lithium-ion batteries,” Toyota writes.

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All-solid-state battery. Directly connected cells enables smaller package.

We plan to accelerate our research through collaboration with production technologies. We are currently conducting research and development on two types of batteries, all-solid-state  batteries and lithium-air batteries (see below)

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 Lithium-air battery. Using oxygen in the air for the cathode and lithium metal for the anode allows for a smaller and lighter package.

 

Wide variety of lithium-ion batteries

Lithium-ion” is the name of a family of batteries. There is a wide variety of lithium-ion batteries in existence, and a few are in mainstream use already, including lithium-cobalt, lithium-iron-phosphate, and lithium-polymer batteries. The latter two are commonly used in electric vehicles.

Solid-state batteries utilize a solid electrolyte and solid electrodes, unlike most batteries, which utilize liquid electrolytes.

Benefits of solid-state batteries

The lack of liquid in solid-state battery cells enables them to be connected to each other without being placed in their own individual cases, which enables more compact packaging (cells are just tiny batteries connected to each other to form battery packs, hence the term “packs”)  Solid-state batteries have the potential to outperform lithium-ion batteries (power-to-weight ratio). However their strength is a high energy density, which translates into long range They can be created using thin films They tend to be good conductors of ions, and are insulating towards electrons.

Lithium-ion batteries vs Lithium-air batteries

According to technology review, more than half the bulk of lithium-ion batteries is attributable to materials that don’t even store energy, but insulators and materials designed to protect and cool the components of the batteries. Solid-state batteries reduce that extra material greatly.

Lithium-air batteries, which Toyota is also pursuing, have the theoretical potential to store 50 times more energy than typical li-ion batteries. These batteries “use oxygen in the air as the cathode active material.” The have much better energy density and benefit from weight savings “by changing negative-electrode material into metallic lithium from black lead than solid batteries.”

What's happening now?

Well, engineers from Toyota Motor Corporation weren't wasting their time and a lot of progress is being made to make electric vehicle batteries better.

Representatives from Toyota (including H. Iba from the Battery Research Division of Toyota Motor Corporation) recently participated in 17th International Meeting on Lithium Batteries in Como, Italy from June 10 to 14, 2014.

In their article “Invited Presentation: Innovative Batteries for Sustainable Mobility,” the Japanese company stated that it is developing new batteries with higher densities  - solid state and lithium-air to be more accurate.

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“And now, we are going to develop next-generation vehicles with more energy efficiency; for this reason we need to develop innovative batteries with higher energy densities than traditional batteries.  Figure 1 represents a rough sketch of Ragone plots for traditional Ni-MH and Li-ion batteries together with next-generation batteries such as all-solid-state batteries and Li-air batteries.  Although we have already developed prototype cells of all-solid-state batteries and Li-air batteries with energy densities of 400 Wh/L and 1000 Wh/L, respectively, it is also true that there are still many issues to be overcome until their practical application.  In the presentation, we will overview our recent effort on developing innovative batteries.”

Prototype with extremely low power density

935.gifAs it turns out. the Li-air battery prototypes, which have at least 15-20 years to commercialization, reach energy densities of 1000 Wh/L (yes, we know that they intentionally do not give numbers in kg/L). But more interesting is that solid state lithium batteries achieved 400 Wh/L in the prototype stage and could be commercialized in 6 years. Toyota shows on the graph that this is progress compared to lithium-ion batteries (without solid state electrolyte).

We applaud all developments, but this is pretty strange, because we thought that a level of 400 Wh/L is already behind us. Here is a graph from AESC, which is a joint venture between NEC and Nissan. Li-ions (high capacity cells) are rated from 300-400 Wh/L (not 50-300 Wh/L). And Panasonic’s 18650 cells, at least 5 years ago, had 620 Wh/L in production with 800 Wh/L scheduled for 2013.

This puts us in dismay!

However relying on such data explain to us why executives from Toyota do not hurry up with EVs. And finally, current lithium-ion batteries need higher energy density and lower price, not higher power density.

 

P.S.Maybe some of our readers will tell us what is going on with these numbers from Toyota?=)

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