Battery Report 2025: Li-S and Zinc Start to Materialise

The Volta Foundation have just released the 2025 edition of their annual Battery Report. These open-access reports are well-renowned in the battery world and provide a comprehensive analysis of developments in battery research, industry and regulations. We at Mewburn Ellis were delighted to participate in this year’s report, as Senior Associate Chloe Flower co-authored and contributed to the policy section.

This is the second article in our 2025 Report series, following on from Sophie Chua’s take on Watt’s New for this year, tracking how eVTOLs, BESS, sodium-ion and solid-state technology have moved forward over the past twelve months.

In today’s article, we take a look at lithium-sulfur (Li-S) and zinc-based batteries, which are particular chemistries that the Battery Report spotlights. These technologies are maturing and starting to compete with established battery chemistries. The report discusses the promise and current challenges associated with these types of batteries – in a world demanding high-performance electrochemical storage, it is necessary to consider factors such as the cost, energy density, safety, and design flexibility.

Lithium-Sulfur: Lightweight Chemistry Meets Aerospace Technology

Li‑S batteries are a particularly promising area of battery innovation. They are relatively lightweight, and have remarkably high theoretical energy densities, which the 2025 Battery Report notes as being key to aerospace electrification (see page 360 of the report). The high abundance and decentralised distribution of sulfur globally represent further advantages (see page 364 of the report).

Uniquely, Li-S batteries use lithium polysulfides to store charge, facilitating multiple electron transfers per molecule and high gravimetric capacity. However, this mechanism also introduces challenges, such as polysulfide shuttling, dendrite formation, and poor cathode conductivity. These limit effective energy densities and have so far held Li-S batteries back from widespread commercialisation.

It is hoped that some of these issues may be solved through the development of all-solid-state lithium sulphur batteries (ASSLSBs). While the kinetics and conductivity of ASSLSB cathodes still require improvement, the Battery Report identifies two strands of ongoing academic research in this area, involving compositing metal materials into Li-rich sulfur cathodes. First is the use of in-electrode catalysts such as SnS₂, as demonstrated by a group at the Austrian Institute of Technology. Meanwhile, scientists at the University of Waterloo in Canada recently published a paper about new core‑shell electrode particles, specifically LiVS₂‑coated Li₂S, which demonstrate improved redox kinetics at the cathode interface (see page 623 of the report). Innovation in this area has seen a step change in pace in 2025.

Building on such research, adoption in industry has also grown. Companies including Theion and Gelion advanced commercial agreements and secured significant additional funding in 2025, driven primarily by aerospace markets where mass efficiency and low‑temperature operation are of critical importance. Lyten also demonstrated a 3-hour autonomous drone flight utilising their US-made Li-S battery (see page 361 of the report).

Looking forward, refining cathode and electrolyte chemistry as a unified system will be key to continue Li-S’s momentum. The University of Cambridge spinout Molyon are looking to do just that, as they scale up their metallic molybdenum disulfide cathode technology with proprietary quasi-solid-state electrolytes.

Zinc Batteries: Safe, Abundant, and Surging into Market Deployment

While Li-S focuses on specialist lightweight applications, zinc batteries are taking aim at the other end of the market – focusing on low cost and low maintenance.

Zinc batteries exploit the Zn/Zn²⁺ redox couple, benefiting from aqueous electrolytes that are non‑flammable and leverage an abundant, low‑cost supply chain. Compared to Li‑ion, zinc systems sacrifice some energy density but offer high levels of safety and long cycle lifetimes (see page 407 of the Battery Report 2025).

Zinc batteries encompass a broad range of different technologies – including zinc air batteries, which have good potential for energy density and long-term storage of 24+ hours, and zinc bromine (Zn-Br) batteries, which have developed commercial traction for short-term energy storage (e.g., 3-12 hours).

Notable research in 2025 included progress in dendrite suppression and electrode architecture optimisation. For example, researchers based in China demonstrated that predisposing zinc electrodes with lead in Zn-Br flow batteries can enable dendrite-free zinc growth, which is crucial for long-term performance (see page 625 of the report).

Zn‑ion batteries (ZIBs) have also seen remarkable recent innovation in cathode materials, electrolyte engineering and electrode-electrolyte interface design (see page 409 of the report). Within cathode materials research, there has been a focus on easing manufacturability. Data-driven approaches have been employed to refine hydrothermal synthesis and ion exchange processes, as well as model failure modes – all with an eye on making ZIBs cost-competitive with large-scale LFP lithium-ion cell manufacturing.

Although energy densities are lower compared to market-leading Li-ion batteries, pioneers of ZIBs hope their sustainability, safety, and the promise of sub-$50/kWh cells will make them a realistic contender for the mass market.

In industry, the Battery Report highlights companies including Eos Energy, who secured a major project to provide a US naval base with zinc energy storage, and Gold Peak, who announced a $150 million investment in their nickel zinc platform for powering data centres. Also, ZincFive were recognised by Time Magazine as a top Greentech company of 2025 and recently secured $30 million in funding, allowing further increases in manufacturing capacity to supply data centres.

Protecting Emerging Technologies

As well as the progress in the Li-S, zinc and sodium-ion systems discussed above, the Battery Report also delves into other chemistries with interesting potential, including vanadium, lithium titanium oxide, niobium oxide, and potassium batteries.

Patent applications for developments in these and other battery materials are constantly being filed, as inventors seek to protect and commercialise their R&D. We expect that innovation in these technologies will continue to grow in 2026 and beyond, driven by sensible and strategic IP considerations. With our knowledge and experience in battery technology, the Mewburn Ellis team understand the importance of a strong IP position and are well equipped to provide support and advice – so contact us if you want to develop a commercially relevant IP strategy to maximise your technology’s potential.

Read the full Battery Report 2025 series here.