30 November 2022

Patenting battery technologies in Europe – Growth and challenges

Just over 30 years ago, in 1991, Sony launched a camcorder containing the first commercial rechargeable lithium ion battery. Rechargeable batteries have come a long way since then – in awarding the 2019 Nobel Prize in Chemistry to the inventors of the original lithium ion battery, the awarding committee noted that lithium ion batteries have “revolutionised our lives.” Today rechargeable batteries are ubiquitous in portable electronic devices and are a crucial part of the move to cleaner and more efficient energy, from electric vehicles to domestic energy storage.

The growth and spread of rechargeable batteries are reflected in an increase in patent applications in battery technologies, which have grown at a much faster rate than patent applications overall (Figure 1). Battery patent applications originating in Japan show a particularly marked increase over the last two decades (Figure 2).

Figure 1

Figure 2

Figure 3: EP A publications with IPC code B60L50/00 – Electric propulsion with power supplied within the vehicle

Figure 4: EP A publications with IPC code B60L53: Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles

Figure 5: EP A publications with IPC code B60L58 – Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles

Figure 6

A range of different types of rechargeable batteries (for example, metal ion, metal, metal-air, and redox flow) are being developed for a range of different fields of application. Each of these fields has its own battery requirements driving battery research and associated patent filings. For example, the challenges in research and development of smartphone batteries are quite different to those of electric vehicle batteries. A specific example is solid vs. liquid electrolytes for the automotive sector, discussed in more detail by our colleague Jack Rogan.

Therefore, it is informative to look at not only the overall trend for battery filings but also trends within specific sectors.

Focusing on the automotive sector, there has been an increase in patent applications classified under International Patent Classification (IPC) codes for electric vehicles and charging, monitoring, and controlling batteries for electric vehicles (see Figures 3-5 for the numbers of published European patent applications).

Until about five years ago, at least one-third of all European patent applications published in these areas were attributed to Japanese applicants. While the most recent figures still show that Japanese applicants are filing roughly between one in four and one in six applications, what is noticeable is the step change in the number of applications being filed by Chinese applicants. The number of applications published in the name of Chinese applicants in some areas has trebled in successive years.

These trends in the automotive sector are within the disciplines of electrical engineering and software. Growth of patent filings in other disciplines can be seen by comparing changes in the technology classifications for Patent Cooperation Treaty applications over the last ten years in the broad field of secondary batteries (Figure 6).

Increases are particularly pronounced in the following areas, encompassing a diverse range of technical disciplines:

  • H01M10/052 – Lithium accumulators
  • H01M10/42 – Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
  • H01M4/62 – Selection of inactive substances as ingredients for active masses, for example binders, fillers.

Commercially successful technologies are often accompanied by extensive patent litigation. Examples include the recent patent infringement claims filed by Moderna against Pfizer and BioNTech in relation to the mRNA technology used in COVID-19 vaccines, and the so-called smartphone patent wars that accompanied the rise in popularity of smartphones. In the case of battery technology, however, the range of different battery types and fields of application set out above point to a possible future of sector-specific battery patent litigation or sector-specific patent pooling.

This makes it all the more important for patent applicants to draft patent applications in a way that maximise the chances of success during patent prosecution and any subsequent litigation. For patent applicants with an interest in patent protection in Europe this is illustrated by recent case law for battery inventions which highlight pitfalls specific to European patent law.

In the chemistry and materials area, T 0144/20 relates to a polymeric battery separator containing, inter alia, the presence of microfibres for high tensile strength. The Board of Appeal found that although microfibres can be selected so as to improve tensile strength, the “mere presence” of microfibres as recited in the claim at issue was not enough to achieve this effect. Consequently, the claim was found to lack an inventive step in the absence of the feature or features necessary to solve the problem of achieving a high tensile strength across the scope of the claim.

This decision is in line with long-established case law of the Boards of Appeal that if inventiveness of a claimed invention is based on a given technical effect, then that technical effect should be achievable over the whole area claimed. These precedents are from outside the area of battery technology – indeed, for chemical inventions, much of the case law comes from the field of pharmaceuticals – but this decision demonstrates that legal principles developed in these other fields will be applied to the field of batteries unless there is a good reason not to do so.

Similarly, in the field of battery charging in T 2787/19, a claim to a system for recharging of a robot cleaning system was refused based on long-established case law on the strict requirement for amendments to a claim to find “direct and unambiguous” in the disclosure of the application as filed. In this case, the application disclosed a robot cleaner using sound as a basis for triangulation for the cleaner to find its way back to a charging base when the cleaner battery charge falls below a pre-set value. The Board of Appeal found that the amended claim recited a general triangulation using sound whereas the basis relied on for this amendment discloses a specific form of sound-source localisation. The amendment was therefore found to be an unallowable “intermediate generalisation” in line with established case law.

Applicants also need to take care with terminology, especially when translating into English, and interpretation of features. For example, in T 2696/18 , the applicant/appellant argued that a claim was distinguished over the prior art because the claim recited a “charging station” implying that it was stationary, such as a charging station for an electric vehicle, whereas the prior art disclosed a “charging circuit.” The Board of Appeal did not agree with the appellant.


Patent applications for rechargeable batteries are growing at a significantly faster rate than patent applications as a whole, and as rechargeable batteries become ever more widespread, it can be expected that patent litigation will follow as patent owners seek to establish and protect their positions within their market sector. Patent applicants filing in this space and with an interest in the European market should be mindful of the patent validity issues that are in some cases unique to Europe.