Inside Green Innovation: Progress Report - Third Edition highlights:
- Over the last decade there has been steady and strong growth in new patent applications for polymer electrolyte innovations in battery technologies.
- Non-lithium battery technologies involving alternative metals are gaining traction, in particular sodium, and zinc. Sodium batteries have gained significant attention in wider news media in recent times, all pointing to this area as one to watch.
- There has been dramatic growth in filings directed to flow battery technology over the last decade. Recent examples of successful commercialisation of the technology suggests that more widespread commercial activity could be on the horizon.
- Innovators in South Korea and Japan continue to lead in new filings in this sector, followed closely by the US.
- Compared to other similar industries, patent filings in these areas remain relatively low, indicating that these sectors remain emergent, but that further R&D and investment could spark dramatic progression once fundamental hurdles are overcome.
Innovation in battery technology is a fundamental requirement for continued sustainable economic development and to ensure effective energy storage in the future.
Applications in portable electronics, electric vehicles, renewables, and storage – at both the local and grid levels as well as innovations in wireless charging and wearables – continue to drive demand for improvements in energy density, battery lifespan, charging speed and alternative utility. Consumers have consistently shown their preference for batteries made of sustainable materials to power next-generation technologies, which will likely continue.
Therefore, it is no surprise that strong growth is predicted in the global market for batteries. A recent Research and Markets (July 2023) report forecast a compound annual growth rate of 12 percent – more than doubling from USD 119bn in 2022 to an estimated USD 297bn by 2030.
As discussed in our Inside Green Innovation: Progress Report 2021 and 2022, improvements in existing liquid lithium-ion battery technology tend to drive innovation in the sector, which is expected for a mature industry. However, this year, we explore innovation in relatively new sectors of battery science that could herald a new generation of energy systems.
Although liquid lithium-ion batteries are presently unrivalled in their success, there is space for technological improvements, creating a significant driving force for research and development from alternative sectors. This report measures patent activity and associated development trends in:
- Polymer electrolyte batteries – do polymers offer a route to safer and more environmentally friendly batteries?
- Non-Li ion batteries – can other metals replace, or at least compete with, lithium?
- Redox flow batteries – is there an electrochemical solution to long-term energy storage at scale, which appears unlikely using liquid lithium-ion technology?
From our analysis, it is clear most alternative technologies are nascent compared to liquid lithium-ion technologies. As research and development continues, these alternative technologies are likely to see growing commercialisation and widespread usage.
Polymers
Polymeric materials have long been a crucial component in modern battery cells. They are applied as binders for electrode slurries, in separators and membranes and as active materials in polymer electrolytes, where charge can be stored in organic moieties. Polymer electrolytes can be divided into different categories, depending on the applied electrolyte solvent, salt, and polymer backbone, such as:
- Gel polymer electrolyte (GPE) – a polymer swollen in an electrolyte solution, forming a stable gel
- Solid polymer electrolyte (SPE) – a polymer film comprising an electrolyte salt and no electrolyte solvent (optionally comprising plasticizers)
- Ionic-liquid-based polymer electrolyte (IL-PE) – a polymeric separator containing an ionic liquid as electrolyte
- Single-ion conducting polymers (SICP) – a class of polymers where either the backbone itself or a side-chain or pendant group carries a charge
Examining priority filings directed to polymer electrolytes over the past fifty years (Figure 1) reveals an initial interest in the 90s, followed by strong and sustained growth since the end of the 00s.
Figure 1: Forty-year trend - global priority filings - secondary batteries and polymeric materials (gel or solid type)
(Priority filing = the first time a patent application for a unique invention has been filed (the first filing))
Polymers that have high affinity for solvents and plasticizers rank among the most popular polymers used to produce polymer electrolytes, including poly(ethylene oxide) (PEO), poly(vinylidene fluoride) (PVDF), poly(methyl methacrylate) (PMMA), polyacrylonitrile (PAN), and poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP).
Examining the patent filings related to these polymer technologies (Figure 2) reveals that polyacrylonitrile (PAN) is leading innovations in this field, whilst complex copolymers like PVDF-HFP have gained traction during the last decade.
Figure 2: Forty-year trend - global priority filings by material - secondary batteries and polymeric materials (gel or solid type)
Top innovators in this field (Figure 3) include electronics companies LG, Samsung, Toyota, Panasonic, and the speciality chemical giant Zeon Corp. In terms of territory, South Korea, Japan, and the US show the most innovation related to polymer electrolytes (Figure 4).
Figure 3: Ten-year trend - top filers - polymer electrolytes
Figure 4: Ten-year trend - global priority filings by territory – polymer electrolytes
Non-lithium-ion batteries
The success of conventional lithium-ion batteries is due to their characteristics, which include high energy density, extended cycle life and minimal self-discharge. However, researchers are endeavouring to make further improvements. In addition, lithium metal is scarce, relative to other metallic elements, and the mining and processing of lithium poses significant environmental and economic challenges.
As such, research and development continue worldwide into alternative metal ion battery technologies using more relatively abundant elements which could offer pathways to cost-effective and greener batteries. However, these filings still significantly lag behind those for lithium-ion related batteries. In this section, we focus on sodium, zinc, manganese, iron, and magnesium.
To understand the growth of lithium alone and establish a present best-mode baseline, Figure 5 shows patent filings directed to lithium battery technologies whilst excluding filings relating to the other most common alternate metals (Zn, Na, Mg, Fe, Mn).
Figure 5: Forty-year trend - global priority filings - lithium-ion batteries
Clearly, filings relating to lithium technology have grown at a steady and impressive pace since the mid-1980s. Evaluating the five alternative metal technologies in a similar way reveals interesting insights (Figure 6).
Figure 6: Forty-year trend – global priority filings by material – non-lithium-ion batteries
Patent filings relating to manganese, iron and magnesium battery technologies have risen steadily but slowly over the past two decades. In contrast, sodium and zinc have enjoyed more attention, with a notable spike in filings in the early 90s and resurging interest over the past decade.
Significantly, there was a large spike in filings regarding sodium-related battery technology, between 2013 and 2015. Sodium is one thousand times more abundant than lithium and is widely available across most continents, whereas lithium is mined mainly in China and Argentina. Some market commentary claims that sodium-ion batteries charge faster than lithium-ion, have a higher lifecycle and a lower cost. Zinc shares many similar benefits, which likely explains the increased filings directed to zinc battery technology. The spike in zinc-related filings was not maintained, but recent filing levels remain at historic highs.
Key innovators in these non-Li technologies are Toyota, Sumitomo, NGK Insulators, Research Institute of Industry, Science and Technology, LG and Resonac (Hitachi Chemical) (Figure 7). Japan is the epicentre of innovation in this area, followed by South Korea and the United States (Figure 8).
Figure 7: Ten-year trend - top filers - non-lithium-ion
Figure 8: Ten-year trend - global priority filings by territory - non-lithium-ion batteries
Flow batteries
Batteries capable of storing large quantities of energy produced by intermittent renewable energy sources – like solar and wind – are necessary for on-demand release. We first discussed the topic of long-term storage in Inside Green Innovation: Progress Report 2021.
One promising technology is redox flow batteries, which has lagged behind metal ion battery technology. A redox flow battery is an electrochemical device that captures electrical energy in the form of chemical potential energy. It operates by using two electrolyte solutions with different chemical redox pairs (reduction-oxidation reactions), allowing the transfer of electrons between them through an electrochemical cell. This converts chemical energy into electrical energy, and vice versa, when needed. Because they are considered relatively safe, flow batteries may be promising for large scale applications. Unlike Li-ion batteries, which use flammable liquid electrolytes, redox flow batteries generally use a water-based or less combustible organic material.
In addition, redox flow batteries can easily be scaled by increasing the volume of their tanks, have a longer asset life (theoretically unlimited lifecycles with no capacity degradation) and can operate at ambient temperatures (not requiring the ventilation/climate control necessary for utility-scale Li-ion solutions). However, despite these advantages, patent filings for flow battery technology only began to gain momentum around 2010 (Figure 9), likely due to significant R&D challenges in the technology, for example, in its energy density, efficiency and cost.
Figure 9: Forty-year trend – global priority filings – flow battery technology
The data shows this technology is in its infancy, and continued research and development over the next decade will surely result in more growth in this emerging area. Looking at specific subject areas of the patent filings reveals significantly more filings from developments in electrical engineering versus chemical engineering, even though redox flow batteries are somewhat more chemical than mechanical in nature (Figure 10).
Figure 10: Forty-year trend - patent families by technology - flow battery technology
(Patent family = A set of patent applications and/or granted patents across multiple countries that protect the same invention and were filed by a common applicant.)
Examples of recent innovations in chemical aspects of flow batteries include optimisation of metal ion components of electrolyte solutions, whereby metals including copper, zinc and aluminium can be used to offset more expensive vanadium ions without detrimental impact on functionality (WO2019181982A1, Showa Denko). Organic polyaromatic hydrocarbons are highly tuneable and often exhibit interesting electronic characteristics, and a recent filing by Mitsubishi (WO2023008548A1) reveals that anthraquinone and aza-anthraquinones derivatives are promising materials for flow battery electrolytes. Electrode design and optimisation rank highly amongst the filing topics, a technology at the interface of chemical and electrical engineering, for example, improving carbon electrodes in flow batteries for decreased cell resistance (WO2020184451A1, Sumitomo Electrical).
Key innovators in this area (Figure 11) include Sumitomo, LG, Lotte Chemical Corporation, and Showa Denko, highlighting how South Korea and Japan are leading patent filings in this technology (Figure 12). The US is the third highest filing territory and includes notable filers such as Lockheed Martin, which has begun to offer its commercial, large-scale implementation of redox flow system GridStar® Flow.
In 2022, Lockheed Martin was contracted to build the first megawatt-scale of its flow system by the US Department of Defence.
Figure 11: Ten-year trend - top filers - flow battery technology
Figure 12: Ten-year trend - global priority filings by territory - flow battery technology
Implications for innovation and future patent filings
With their potential to enhance the performance, safety and environmental friendliness of energy storage systems, these alternatives offer a more sustainable future. The search for alternative battery technologies represents a commitment to a greener and more efficient energy landscape. These areas may hold the promise of revolutionizing electric transportation, renewable energy integration and grid stability, ushering in a cleaner and more resilient energy future.
Although alternative technologies to replace or augment lithium-ion batteries remain relatively emergent, companies continue to pursue sustainable energy solutions. Strong upward trends in patent filings in all developing technologies in this field confirm that interest and investment are growing year-on-year. This will hopefully, in time, lead to next-generation materials and engineering solutions able to challenge the status quo and offer solutions to the critical limitations of Li-ion batteries.
As the world embraces alternative technologies, it can look forward to energy storage systems that meet the demands of a growing global population sustainably. However, there are fundamental challenges to overcome in research and development to ensure their successful implementation. Continued investment should lead to technological breakthroughs and accelerate widespread adoption of alternative technologies. These advances will be highly valuable intellectual property assets which we expect to see reflected in the number of future patent filings.
