While wet or liquid electrolyte Li-ion batteries form 95 to 99% of commercial batteries used globally, it’s widely accepted that they have severe limitations. The flammable electrolyte (typically ethylene carbonate) raises concerns of explosion or fire and there’s the environmental impact to consider, as demand for high levels of cobalt stretches global reserves and creates humanitarian issues through mining processes in third world countries. Solid-state electrolyte batteries may provide the solution and we’re now seeing a gold rush of patent applications as innovators try to secure the rights to the next game-changing development in battery technology. Given the huge commercial momentum of conventional, liquid electrolyte batteries, it will take something impressive to drive the development of solid-state technology and prompt a massive shift for the industry.
Here, I’ll provide a quick overview of the differences between wet/liquid and solid-state batteries, which gives clues as to possible future patent trends, before looking at the current patent landscape for solid-state battery technology and why innovators should be keeping a close eye on the horizon.
The benefits of wet/liquid batteries
With good energy and power density, liquid electrolyte Li-ion nickel-cobalt-manganese batteries are the battery of choice for two key sectors that are driving battery innovation — automotive and handheld electronics.
Tesla, LG, Samsung and many others have all committed heavily to wet electrolyte cell systems. This isn’t surprising, since Li-ion batteries can now be produced at a low to modest cost and perform well. For electric vehicle (EV) applications, the batteries are simply stacked together in large quantities to provide the required energy and power density. Currently, the Tesla Model S, using Li-ion cells, has an impressive 500km range on a single charge. This could be extended to 1000km in the coming years with incremental improvements across the various internal cell components such as the chemical composition of the electrolyte, the use of additives, interfacial conducting and insulating layers at the electrodes, battery management software, and so forth.
The case for solid-state batteries
However, the battery packs for most fully electric vehicles are bulky and add considerable weight. These limitations are exacerbated for applications such as aerospace where weight and flammability are serious barriers to market acceptance. These problems are precisely those that innovators are looking to solve, and the role of patent protection is a vital one.
A granted patent is a contract under the laws of the local territory in which the applicant on the one hand discloses fully and publicly the details of a new innovation in exchange for the exclusive rights to commercialise in that country. Patents therefore provide a fundamental commercial tool, helping to drive innovation. Research institutions, companies and development consortia around the world are actively looking at solid-state electrolyte batteries as the ‘holy grail’ for sustainable energy storage, powering the vehicles and electronic devices of the future.
John B Goodenough, noble prize laureate for his work on Li-ion battery technology, together with his research team, published a paper in 2017 (‘Alternative strategy for safe rechargeable battery’: Energy Environ. Sci., 2017, 10, 331-336) which describes a non-combustible glass electrolyte having a high energy density, fast charging discharge rate and long cycle life. Since they are generally non-combustible, resistant to self-ignition and thermal runaway and allow for the tight packing of cells which would provide large reductions in size and weight of the overall battery units, solid-state batteries address most of the concerns of liquid electrolyte Li-ion systems.
While this sounds enticing, solid-state batteries have a good distance to go before overtaking conventional liquid cells. Concerns over scalability and production costs have been cited as a major stumbling block. The upscaling challenges arise, in part, due to the coupling of the solid electrolyte with and between the electrodes.
The solid-state battery patent landscape
However, patents are proving to be a very attractive commercial tool, with companies scrambling to secure exclusivity to what might be the next game changing development that could see solid-state systems accelerate and overtake their more bulky, hazardous and less environmentally friendly Li-ion counterparts.
Patent filings worldwide are increasing across all aspects of solid-state cells and batteries, including:
- dendrite-suppressing systems
- interfacial compatibility between the solid electrolyte with the cathode and anode
- configurations to suppress the internal resistance of the cathode and anode active materials.
Some exciting recent developments have been made, in particular:
- JP 2020/038784A — (Tokyo Inst Tech and Toyota Motor Corp) is focused to a promising material for the positive electrode that can generate comparatively higher voltages and simultaneously achieve large capacity, stable cycling and much reduced resistance at the electrolyte/electrode interface. Claim 1 of the patent recites the positive electrode having an underlayer material of SrTiO3 dopped with Nb and a LaAlO3 layer positioned between the SrTiO3 underlayer and the bulk material of the positive electrode.
- US 10,115,999 B2 — (Panasonic IP Man Co Ltd) includes a main claim to an all-solid-state lithium-ion battery having a cathode, an anode, a solid electrolyte between the electrodes and an intermediate layer between the electrolyte and the cathode, with the intermediate layer including elements which form the cathode material and having a lithium ion being less ionic than the lithium ion within the cathode.
- US 10,651,449 B2 — (University Michigan Regents) includes a main patent claim focused to dendrite-suppressing ion conductors formed from aramid nanofibers. In particular, claim 1 is directed to a free-standing film comprising of 5 to 500 alternating layers of aramid nanofibers and polyalkylene oxide. The ion-conducting membranes formed from aramid nanofibers can be prepared via layer-by-layer assembly, sol-gel processing, evaporation or spin coating methods. The batteries incorporating these films have demonstrated resistance to puncture or rupture by dendrites to greatly increase the charge/discharge rates needed for widespread implementation.
Patent literature — a key resource for battery tech innovators
The patent literature is a valuable resource of ‘state of the art’ battery innovation. Being aware of the latest developments in battery technology is important firstly to prompt, validate or redirect R&D efforts but also to ensure new lines of development and commercial offerings don’t infringe existing patent rights.
A patent that protects a significant development in this emerging solid-state sector will be incredibly valuable, as major EV and electronics manufacturers look to ensure they are ‘solid-state ready’ as and when this technology sector is good to go.