The creation of the first commercially viable lithium-ion battery (LIB) in 1985 revolutionised the portable electronics market. It was the first battery of its kind; offering high power and high energy efficiency while being lightweight and rechargeable. Today, LIBs can be found in everything from mobile phones, to pacemakers, to electric cars. The 2019 Nobel Prize for Chemistry was awarded to three scientists for developing this field.
LIBs typically rely on a carbon-based anode, a liquid lithium salt electrolyte, and a transition metal oxide cathode. A key area of research is focussed on incorporating silicon into the anode, as this can enable the LIB to store more energy for the same volume than traditional carbon-based materials.
LIB anodes are typically formed from a variety of particulate materials. Consequently, drafting patent claims to cover improved anode materials often requires the use of various parameters associated with the particles, for example the particle size, porosity, pore volume, and surface area. However, the assessment of parameters in claims can be inconsistent between major patent jurisdictions. In the extreme, a form of claim which is acceptable in one jurisdiction can lead to insurmountable problems in another.
Taking the particle size parameter as an example, the European Patent Office (EPO) usually requires the particle size to be specifically defined and for a specific method for measuring that particle size to be provided in the application. If these requirements are not met then a claim defining a particle size may be deemed unclear and/or insufficiently disclosed, sometimes proving fatal for an application.
The problem arises because the EPO commonly considers the term “particle size” to have multiple plausible meanings with different values. For instance, a “particle size” could be understood as a median particle size or a mean particle size and these will likely be different. Moreover, different methods exist for measuring the particle size and these can also give different results. Therefore, to ensure that a particle size parameter is deemed to be clear in Europe, it is essential to define the specific type of particle size that is intended and to define a specific method for measuring that particle size. Both requirements should be met – defining a specific particle size without a measurement method may still lead to problems at the EPO. If this information is not included when the patent application is drafted it makes it significantly more difficult to overcome the EPO’s objection that the particle size is unclear. An unclear parameter is also vulnerable to attack under the ground of insufficiency during opposition.
The same consideration applies to other parameters which may be used in claims directed towards new battery technologies – each parameter should be specifically defined and a specific measurement method given.
The problems associated with parameters in claims are not confined to LIBs; however, they are particularly apparent in this field. LIBs represent a high-value market which is incredibly competitive. There are a number of parties conducting research, publishing numerous patent applications, leading to a significant volume of prior art. As a consequence, innovators may need to rely on parameters, such as particle size, in order to distinguish their innovations. Therefore, understanding the technical and legal nuances relating to the use of such parameters is of key importance when working with patents for LIBs.