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Solid-state Batteries – A Potential Game-Changer in Energy Storage?

4th Apr 2019

The discovery of the reversible “rocking chair” mechanism which allowed for the invention of the lithium-ion (Li-ion) battery in the early 1980’s by Professor John B Goodenough, and the subsequent commercialisation by the Japanese electronics manufacturer Sony in the early 1990’s, led to a boom of portable electronic devices such as mobile phones and laptops, and more recently tablets and wearables.

Latterly, as discussed in our recent blog on The Future of Automotive Powertrains, hybrid and battery electric vehicles have become increasingly important both to reduce emissions and to combat climate change. Although nearly all commercially available hybrids and battery electric vehicles use Li-ion batteries, there are some concerns regarding energy density and safety of Li-ion batteries, especially in the transport sector. Anyone who has had to catch a commercial flight in recent years will know that Li-ion batteries are not supposed to be transported in checked baggage, highlighting those safety concerns.

Replacing the liquid electrolyte (typically a Li-ion containing salt dissolved in a mixture of organic solvents, typically carbonates) with a solid electrolyte is being considered as one of the possible ways to both mitigate the safety concerns and to improve the currently limited energy density.

What is an all solid-state battery?

As the name suggests, all active components in an all solid-state battery (ASSB) are solids, replacing the flammable, volatile, liquid electrolyte in Li-ion batteries with Li-ion conducting solids such as ceramics, glasses, or polymers. Some of the most-researched ceramics and glasses for Li-ion conductive solids include NASICONs, LISICONs, garnets, perovskites, and sulphides. Although many lithium polymer (LiPo) batteries are commercially available, they typically use highly conductive gel polymers as electrolytes, which are beset with the same safety issues as Li-ion batteries.

Not only could solid electrolytes allow for safer batteries by replacing the flammable liquid (or gel) electrolyte, they could also enable the current graphite anodes to be replaced with more energy-dense lithium metal anodes. Using lithium metal anodes in Li-ion batteries can result in the formation of lithium dendrites as the secondary battery is cycled repeatedly, which can cause short circuits and catastrophic cell failure. However, it is hoped that such dendrite formation can be suppressed by using a solid electrolyte.

Why aren’t we all using solid-state batteries then?

Two of the problems stopping the widespread commercialisation of current solid electrolytes are a lower ionic conductivity compared to liquid electrolytes and a limited cycle life as a result of structural changes in the electrolyte material during successive charge and discharge cycles.

Another major problem of solid electrolytes has been found to be the lithium-ion migration and diffusion across the interface between the electrode(s) and the solid electrolyte.

While inorganic glass and ceramic electrolytes show promise, there remain questions regarding ion conductivity across the electrode/electrolyte interface, rigidity, and cycle life. Solid polymer electrolytes on the other hand suffer from narrower stability windows (which limits the energy density of the battery) and insufficient lithium conductivity.

What can the patent landscape tell us about the research and development of solid-state batteries?

Firstly, that the commercialisation of all solid-state batteries is progressing. In the past ten years, the number of patent applications related to ASSBs published worldwide (CPC classification code H01M 10/0562) has risen steadily, from just 337 in 2009 to over 1700 in 2018 (Fig. 1). Whilst this class of patents includes any kind of secondary batteries using an inorganic solid electrolyte, 1696 of the 1766 applications published in 2018 mention lithium-ion.

Figure 1: Worldwide increase in the number of patent applications for secondary solid-state batteries over the past ten years.

Secondly, that the commercialisation of solid-state batteries will probably be led by Asia. The Japanese automobile manufacturer Toyota alone has had 1833 patent applications related to secondary solid-state batteries published between 2009 and 2018 (see Figure 2a). And in 2018, Toyota remained the top filer with 316 published patent applications, far ahead of the second biggest filer Fujifilm (see Figure 2b). Indeed, eight of the top 10 and fifteen of the top 20 filers in 2018 were Asian companies.

Figure 2: Top filers of patent applications for secondary solid-state batteries published a) between 2009 and 2018 and b) in 2018.

So what will the future look like?

Patent publications are not a crystal ball, and the 18-month lag between filing a patent application and it being published always has to be kept in mind, but it seems clear that Asian companies, especially Toyota, are leading the way. They are by far the top filers of patent applications related to solid-state batteries. It therefore seems likely that commercialisation of ASSBs will come from Asia. However, it remains to be seen when (and if) the challenges presented by the commercialisation of solid-state batteries will be overcome.

We are also aware that batteries have a complex supply chain, and there is no reason to believe that this will change with the advancement of ASSBs. As such, there is potential for the protection of intellectual property at many stages in this supply chain. Therefore, there may be a few key innovations protected by patents at various stages in that supply chain which others will have to seek to license if they want to work in this area. And judging by the above patent data, it appears that Asian companies will be well positioned to hold the key patents relating to solid-state batteries.

It seems that European countries are aware of this deficit in battery R&D compared to Asian countries, and have launched various large-scale battery research initiatives such as the UK’s Faraday Challenge (£246m research funding) or the EU’s Horizon 2020 funding (€200m research funding, €800m funding for demonstration facilities). It remains to be seen whether they will help European companies to close the gap to their Asian counterparts.

This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.

Dustin Bauer
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Would you like to know more? You can talk to Dustin Bauer who will be able to help. Call +44 (0)20 7242 0901


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