Traditionally focusing on lead and lead-acid batteries, the biennial ABC and RECYCLE100 conferences provide suppliers and manufacturers with the opportunities to both network and update their industry knowledge. Whilst heavily biased towards lead and lead-acid batteries (LABs), this year’s offerings still made room for alternative technologies, namely sodium recycling and sodium-ion (SIB) battery developments. The first point of note is that compared with lead-acid-based battery conferences of the last 10 years, there was a more sanguine, perhaps even optimistic mood amongst the delegates.
My personal reading of this is that there were two influences: one, the growing feeling that we are actually in a growing market, and two, the undeniable talent of Dr Mark Stevenson in delivering the perfect conference experience. This latter achievement was realised, despite the inclement weather of the rainy season.
As BEST’s technical editor, my interest was mostly in the speakers’ offerings, particularly the technical and R&D presentations. However, I have to pay tribute to some of the commercial talks, in particular that of Dong Li, the charismatic CEO of Leoch Batteries. His message was clear – in order to survive and flourish, you need to be in the largest markets. Diversification into new technology is essential for this. As he put it: “Do you wish to be a small fish in a pond, or a shark in the ocean?”
Regarding battery technology, it was clear that there are markets where lead-acid still provides the best solution, both technically and economically. The newly found interest in ROI and LCOE applied to lead-acid batteries has been a hobby-horse of mine for some years. It’s importance for BESS applications, and the opportunity for LAB solutions in energy storage, is gaining popularity. Equally, the benefits of LAB in EFB and motive power applications are excellent promotion tools. Whilst there are too many excellent presentations to include them all, the following selection for this report reflects my personal interest. It does not in any way reflect on the importance or quality of the other presentations.
Starting with the RECYCLE100 conference, there were three presentations that I wish to include – Dr Mark Stevenson on the antimony dilemma, Farid Ahmed on the progress of Ace Green’s recycling plant and Dr Ola Hekselman on the progress of Solveteq’s pilot scale facility.
Mark Stevenson’s presentation tackled the metallurgical and financial consequences of recovering antimony from LAB scrap and also proposed strategies for LAB manufacturers to reduce or eliminate Sb content in their grid alloys. The latter aspect bore such an uncanny resemblance to my own presentation that we agreed to write a joint paper combing both of our presentations.
This would amount to a ‘How To’ guide and would be of benefit to both the recycling and the LAB industries. Dr Stevenson’s presentation covered extraction difficulties from the various metallic fractions. He also gave advice on secondary element additions to low and no antimony alloys to overcome their casting difficulties. One memorable take-away for me was the slide showing an SEM image of a perfect cubic crystal of PbSe (Se is a grain refiner) alongside a classic grain boundary junction in a low Sb lead alloy (Fig 1).
The other two papers were of interest as they are representative of the alternative, and potentially more environmentally friendly, solvent extraction method for lead and other metals from LAB scrap. Since around 2016 there have been several start-up companies, some with their origins in a university laboratory, that used lead dissolution followed by either electrolytic deposition or precipitation and filtration to extract lead or its compounds from scrap LABs. Compared to conventional methods which use blast furnaces and de-sulphurisation methods to recover lead from the active material paste, they should be cheaper, use less energy and reduce carbon emissions. Oh yes, another major advantage – no blast furnace dross!
Provided the processes can be refined and commercialised, they are a possible route to establishing a true 100% recycling process for lead-acid batteries. In all cases it is the oxide that is treated – the metallic fractions from the battery breaking process are generally destined for the relatively clean refining kettles.
Solveteq, headed by Dr Hekselman, is a breakaway spinout company from Imperial College, London. My first sight of this was at the ABC in Bali. The process, based on Deep Eutectic Solvents (DES) appeared to offer more flexibility than the citric acid versions prevalent at the time.
Fig 2 shows the range of products that can be extracted from the LAB scrap, depending on the processing route. From this you can see that the oxide can be returned to a manufacturer with various opportunities for reuse. The current status is given in Fig 3.
The prototype plant has verified the processes with increased scale from grams to kilograms. The approximate variable costs for the process and the conversion rates have been established. One interesting change of direction is to review the secondary elements such as antimony (presumably in the paste) and develop a solvent-based strategy to reflect the different chemical forms found in solute. The next phase is to scale up to near commercial size to demonstrate the efficiencies, lower cost per kilogram and verify the flexibility, energy reduction and lower environmental impact of the process.
Ace Green’s progress in solvent-based extraction of lead compounds from LAB scrap was presented by the accomplished and well-known metallurgist, Farid Ahmed. In Ace Green’s process, the metallics and plastics are separated and washed post battery breaking, then segregated into two fractions (Fig 4).
The subsequent paste sludge fraction undergoes what appears to be a more complex process of paste de-sulphurisation, precipitation and electrolysis, to provide compressed metallic bricks with no secondary metal losses. This fraction goes straight to the refining kettles. There is also a fair amount of sodium sulphate decahydrates produced. This is recycled back into various industries, e.g. to produce potassium sulphate or ammonium sulphate, widely used in the fertiliser industry.
The other good news is that this process can also handle Li-ion scrap. What’s more, it is chemistry agnostic. The present status of both processes is pre-commercial. However, these recycling facilities are substantial and are already processing many tonnes of material.
The 21ABC presentations were split between LAB enhancement, suitable applications for lead-acid, process improvements and alternative chemistries to lithium – in this case sodium-ion. As often reported in BEST, a disproportionate amount of R&D, new additives and performance improvement solutions were provided by the suppliers to the battery manufacturers. For this reason, I was really pleased to see the submission by Dr Mark Stevenson’s team from Eternity Batteries.
In the presentation by Kalyan Sundaram, the Eternity team showed a redesigned and improved tubular lead-acid cell. In this presentation the performance improvement is heavily weighted towards minimising cell internal resistance through battery redesign and negative plate active material enhancement. The highlights are more and thinner positive tube plates, upgraded separator material and Molecular Rebar carbon nanotubes in the NAM. A breakdown of the design changes and the NAM upgrade is given in Fig 5.
These resistance-reducing modifications increase the charge acceptance, improve the discharge capacity (V = I x R) and substantially improve cycle life. The presentation also showed a comparison between Li-ion performance and that of standard LAB plus the Eternity Quasar range, demonstrating the narrowing gap between the latter and LIB technologies.
Taking in this ambition to improve performance and also the market opportunities for lead-acid, the presentation of the CBI technical road map by Dr Begum Bozkaya was of interest. The CBI focus prioritises auxiliary batteries and ESS applications, followed by industrial, motive power and e-bike applications.
Positive active material (PAM) improvement is under scrutiny, with use of performance enhancers, including silicates and metal oxide additives. The usual carbon additives are being tested for auxiliary lead batteries (ALBA). This is a growing market and another automotive outlet for LAB in addition to SLI in ICE vehicles. The novel approach of additives for positive active material (PAM) is also interesting, as is the partnership choice of Jinkeli Power Technology. This is a company that has grown very rapidly over the last 10 years to become a major player in the additives market.
The last sentence provides a neat segway to the additive suppliers. Long established stalwarts of the industry, such as Hammond and Penox, are now joined by relative newcomers including Black Diamond and Jinkeli. Perhaps even more interesting, from my perspective at least, there appears to be a growing emphasis on inter-company collaboration for lead-acid technology, not least in the additives market. Whatever the reason, be it cost savings by not reproducing the work and products of other companies which results in prices being driven down by competition, or by sharing resources for greater effectiveness, it adds up to the same thing – faster and more targeted battery improvement. That can only be a positive for the lead-acid battery industry.
The Jinkeli presentation highlighted this principle of cooperation. The presentation gave insight to the wide range of additives and different aspects of battery performance in which Jinkeli is currently engaged. Having uprated its R&D labs, the company is embarking on a very comprehensive programme of assessing and developing new additives for both positive and negative active materials.
Taking the trouble to reproduce real-life cyclic conditions rather than simply follow existing test standards, Jinkeli has examined the performance of EFBs in 17.5% DOD cycles as experienced in an automobile with a fixed 14.4V charge regime. It found that even the best products on the market only achieved 700 cycles. To improve this, the company tested a package of PAM and NAM additives. With the right additive blends it found that both active materials could be improved. For NAM a 50% cycle life improvement was found (Fig 6) and for PAM a remarkable 120% improvement was possible for the 17.5% DOD life cycle tests (Fig 7). Jinkeli is also advertising for partners for collaboration.
One problem that should have been put to bed a decade ago is that of negative carbon additives (NCAs) contributing to increased water loss from PBA batteries. As I recall, it was one of the objectives of a CBI programme from the Boris Monahov days? However, Hammond appear to be on the case and the presentation by Enquin Gao explained the company’s approach and its progress in this area.
As we know, water loss is proportional to hydrogen evolution on the negative plate. The hydrogen evolution reaction (HER) is catalysed by the presence of impurities in the lead negative plate which lowers the activation energy for the gas formation. Because carbon additive particles are generally very small, often nano-sized, they have a greater surface area and therefore a greater activation effect because of the higher number of HER activation sites. Hammond demonstrated in its presentation that with a special composite – lignin, another common additive – the active carbon sites can be selectively covered and the HER supressed, causing water loss. Fig 8 shows the conclusions of Hammond following its extensive testing.
Black Diamond’s presentation by Dr Paul-Everill highlighted the company’s progress in reducing high temperature corrosion and enhancing the cost-reducing performance of LABs by incorporating its nano-tube carbon-based additives. Molecular Rebar PbAC and PbLite are products from Black Diamond Structures that use discrete carbon nanotubes to improve lead-acid battery plates. PbAC is a general-application product designed to provide improved plate strength and corrosion resistance. PbLite is a more recent development focused on improving the manufacturing process by increasing paste processability, reducing waste and boosting plate output per batch for battery manufacturers. This is another company benefitting from its associations with other manufacturers. It has formed an additive alliance with three other companies to enable better customer service and improve research capability.
Still with the additives theme, the presentation by Dr Rainer Busar of Penox was of special interest to me as it highlighted the importance of reducing a battery’s energy of formation. The magic ingredient is simply red lead, Pb3O4. However, this is not just any red lead – Penox has developed its RL+. This ensures that the cured AM has a smaller 4BS crystal size. Larger crystals reduce formation efficiency. With this combination the company maintains that with 25% of the RL+ oxide in the paste mix, it can reduce formation energy by 40– 50%. Part of reason for this is the fact that Pb3O4 could be expressed as 2PbO.PbO2.
The PbO2 in the formula means that by adding the RL+ compound, even as little as 10 wt%, we are already part way towards the formed PAM structure of 85% PbO2. This whopping reduction, when applied to the form factor measurement of LAB SLI formation, 19 can reduce this from around 4.5 times a battery’s C20 capacity for standard SLI formation, to near 2.5 times! Bearing in mind the R&D formation work of the development team that includes BEST, I can guarantee we will be closely associating with Rainer Bussar and Penox in the future.
The next presentation that I found interesting was that of Professor Shu-Huei Hsieh, National Formosa University. Whilst carbon fibre sheets are still technically an additive, this research had the novel approach of combining and covering the carbon fibre sheets with the spongy lead of the negative active material. The method of incorporation is not clear to me as the Nano Materials Lab conducting the work specialises in the synthesis of nano rods and electroless plating, but the equipment shown in the presentation included a hot-pressing operation.
However, I did speak to Professor Shu-Huei Hsieh and we will be discussing this and most probably reporting on it in a future edition. I hope to clarify this and other points centred around commercial manufacture in the coming months. Whatever the manufacturing method, the results for 2V cells and 12V battery cycle testing are very encouraging, particularly for charge acceptance and capacity retention when compared to conventional batteries.
The alternative chemistries section was covered by Clause Yi of SIB Paragonage, a company that is now mass-producing sodium-ion batteries (SIBs). Sodium has long been lauded as an alternative to lithium due to the higher safety, along with the abundance and low cost of sodium compared to lithium chemistries. In this presentation, the strengths and weaknesses of SIBs were highlighted with several comparisons to other chemistries, including lithium-ion batteries (LIBs).
On the whole, the present design of SIBs has shortcomings in key areas – the operating voltage window, the present cost, and in my opinion, energy density. The advantages, however, seem real enough. These are: safety, high-rate discharge (HRD) and low temperature performance. Regarding safety, SIBs can be transported at 0 V i.e. 0% SOC compared to LIBs that need to be 30% SOC.
According to Yi, the use of SIBs would ensure that sea and road fires would be a thing of the past. Paragonage has a commercial manufacturing plant with e-bikes as its initial target market. Plans to diversify into outdoor and cold temperature applications, such as fork-lift trucks in the materials handling industry, will require some chemistry tweaking to overcome some of the current technical difficulties.
The final choice of the presentations is the metallurgical response for LAB manufacturers to the high cost of antimony (Sb). This was described in my presentation, representing the consortium of Microtex, UK Powertech, BEST and Ecotech Energy Solutions. In this, strategies for either reducing or eliminating Sb in grid lead alloys, for both component suppliers and LAB manufacturers, were presented.
Using real case studies, the metallurgical consequences and the results of the practical solutions adopted to overcome the problems of Sb removal or reduction were reported (Fig 9). Along with this, the guidelines necessary for processing the new alloys were outlined and discussed. A final word, to the organisers and support staff who enabled, yet again, memorable ABC and RECYCLE100 conferences – many thanks and well done.
