Aegle Technology

Our mission is to advance the development of innovative advanced material solutions

Electronics

Ultra long-life batteries – thanks to nanoparticles!

by

Batteries power much of our modern day life – from our phones, laptop computers, cars and may other devices we use every day and take for granted.

Yet the lifespan of current battery technology is disappointingly short – at best giving us a few years of reliable service and at worst catching fire or even exploding. Apart from the obvious inconvenience of our devices running out of power, this short lifespan creates major environmental issues with the need to source increasingly large amounts of raw materials, and the disposal of growing mountains of defunct batteries.

Much of our current battery technology is based on lithium-ion technology. Electrochemical lithium insertion and extraction often severely alters the electrode crystal chemistry, and this contributes to degradation with electrochemical cycling. Moreover, electrodes do not act in isolation, and this can be difficult to manage, especially in all-solid-state batteries. Therefore, discovering materials that can reversibly insert and extract large quantities of the charge carrier (Li+), that is, high capacity, with inherent stability during electrochemical cycles is necessary. 

In a recent paper published in Nature Materials (Konuma, I., Goonetilleke, D., Sharma, N. et al. A near dimensionally invariable high-capacity positive electrode material. Nat. Mater. (2022).) the authors examined lithium-excess vanadium oxides with a disordered rocksalt structure as high-capacity and long-life positive electrode materials. 

Nanosized Li8/7Ti2/7V4/7O2 in optimized liquid electrolytes delivered a large reversible capacity of over 300 mAh g−1 with two-electron V3+/V5+ cationic redox, reaching 750 Wh kg−1 versus metallic lithium.

Critically, highly reversible Li storage and no capacity fading for 400 cycles were observed in all-solid-state batteries with a sulfide-based solid electrolyte. X-ray diffraction combined with high-precision dilatometry reveals excellent reversibility and a near dimensionally invariable character during electrochemical cycling, which is associated with reversible vanadium migration on lithiation and delithiation.

This work demonstrates an example of an electrode/electrolyte couple that produces high-capacity and long-life batteries enabled by multi-electron transition metal redox with a structure that is near invariant during cycling.

In plain English, in future batteries based on this technology could have an almost infinite life, extending the useful life of our devices and reducing the need to mine new materials or dispose of old worn-out batteries!

Aegle Technology – Nanoparticles for Printed Electronics

by

Authors: Martí Busquets-Fité, Christopher W. Young

The field of printed electronics is advancing rapidly, changing the current paradigm of electronic devices and circuit boards from hard structures and rigid sheets to flexible thin layers, which will lead to the emergence of a plethora of new devices and technological possibilities such as disposable electronics, smart labels, and a further step in the ongoing process of miniaturization of devices. 

printed electronics

One of the main driving forces to achieve this is the development of nanoparticle-based “functional” inks.

Functional inks are used to create printed and flexible circuits and offer a cost-effective alternative to conventional methods such as etched copper flex circuits and printed circuit boards (PCBs). Functional inks make it possible for manufacturers to print on flexible substrates for mass-scale circuit manufacturing. Functional inks can be applied to a broad range of rigid and flexible surfaces using different printing processes:

  • screen printing (sheet-fed and roll-fed), 
  • aerosol jet printing, 
  • and gravure printing.

The choice of the printing technique depends on the ink type and ultimate product use. Functional inks are generally more environmentally friendly than traditional methods because etching copper on PCBs requires the use of acid baths, while the process of employing functional inks generates no waste and uses no harmful chemicals. 

Inks which conduct electricity have a wide range of uses, including:

  • capacitive and membrane switches, 
  • RFID tags, 
  • touch screens, 
  • biological and electrochemical sensors, 
  • Positive Temperature Coefficient (PTC) heaters, 
  • electromagnetic interference/radio frequency interference (EMI/RFI) shielding, 
  • wearable electronics (stretchy conductive inks).

The use of specific metal nanoparticles produced to tightly controlled specifications in the production of high-performance functional inks, such as required for printed electronics, helps to achieve the desired properties.

Nanoparticles (NPs) are usually defined as particles of matter that are between 1 and 100 nanometres (nm) in diameter. Because of their extremely small size (they cannot be seen even using an ordinary optical microscope) they exhibit very different physical and chemical properties, including the way they behave in a solution as well as optical effects and electric properties.

A wide variety of metals, including silver (Au), gold (Ag), platinum (Pt) and palladium (Pd), are used in nanoparticle form. 

Of all the metal nanoparticles, silver nanoparticles (AgNPs) possess the highest electrical and thermal conductivity which, along with other properties and factors (e.g., lower cost, resistance to oxidation, interesting plasmonic and antibacterial properties), has put silver nanoparticle (AgNP) based inks as the most widespread nanoparticles-based ink product with the better-established technology and the highest production and sales volumes. 

However, most of the currently available AgNP inks contain a remarkably broad distribution of sizes with specifications describing cut-off sizes rather than detailing mean sizes and size distribution. In practice, this reduces the effectiveness of these inks for many applications. 

Nanoparticles-based inks for printed electronics

Printed electronics requires inks with certain levels of viscosity and surface tension to be operable (achievable with the use of organic solvents, dispersing agents and humectants to avoid inks drying too quickly on the nozzles). Such general requirements depend on several factors: printing technique, requirements of the printing equipment and the desired functional properties of the ink as a final product. 

Of all the inks requirements, probably the most relevant and restrictive is their viscosity. For instance, aerosol jet printers can only operate with viscosities below 15 cP, piezoelectric printheads require viscosities between 5 and 20 cP and thermal printheads inks must have even lower viscosities (1-5 cP). 

Particle size is another restrictive requirement. For aerosol jet printers, particle size must be below 100nm to avoid clogging of the nozzles. That is why well-defined NPs below 100nm are clearly preferred for this technique and all printing techniques requiring an aerosolization step. 

Historically, noble metals (specially Au, Ag) and copper have monopolised the field of printed electronics, as are their nano-sized equivalents. Other materials such as nickel, brass, chromium, iron and iron oxides and even intrinsically conductive polymers and carbon-based materials have proved to yield to conductive nanotechnology-based inks and are worth mentioning, although attracting a significant lower deal of attention. 

In all the aforementioned cases, the nanoscale counterparts offer remarkable advantages in contrast to the bulk materials due to their scale: stable colloidal suspensions easy to manipulated and use in microfluidics and printing; high surface/volume ratio; collective electron resonances, the so-called plasma waves enabling surface plasmon resonance (SPR), and interactions with the electromagnetic field; a huge enhancement of diffusivity of the surface atoms; and above all, strikingly low sintering (melting) temperatures. 

Amongst all of them Ag possesses the highest electrical and thermal conductivity, which along with other properties and factors (e.g. lower cost than Au, Pt and Pd, resistance to oxidation, interesting plasmonic and antibacterial properties, etc.), has put the silver nanoparticles (AgNPs) based inks as the indisputable most widespread nanoparticles-based ink product with the better established technology and the highest production and sales volumes. 

3D Printing 

Apart from using nanotechnology-based conductive inks for printed electronics, other applications for inks based on NPs of different compositions are emerging. 

nanoparticle 3D printing

As already mentioned, AgNP inks (as well as AuNP and CuNP) used for printed electronics can be used for sensing, surface-enhanced Raman spectroscopy (SERS) and photonics, taking advantage of their unique electrical and optical properties. Nanoparticles-based inks are also being used in the thriving field of 3D printing.

Many promising materials have been developed, especially focused on metal oxides NPs with exceptional properties such as:

  • magnetic -including paramagnetic- inks (Fe3O4NPs); 
  • inks for printing intricate prosthesis and implants or other functional materials with antibacterial (with AgNPs), antifungal (with Cu2O, CuO and even Cu(0) NPs) and anti-inflammatory or pro-inflammatory (with the very promising CeO2NPs) properties; 
  • or the more complex hydrogels-based bioactive scaffolds that promote tissue growth around them (using “bio-inks” based on hydrogels including nano silicates).

Aegle Technology 

Aegle technology designs and manufactures a wide range of nanoparticles, including metal nanoparticle solutions (colloids) with highly uniform particle sizes (highly monodisperse) at distinctively high concentrations. Our AgNP colloids have a level of sphericity and mono-dispersity unmatched in the market, potentially providing superior and more robust electrical and physicochemical properties to inks (check our catalogue at https://aegle-technology.es/shop).

Specifically, our AgNP (and AuNP) colloids provide: 

  1. high morphological control and narrow size distribution 
  2. high colloidal stability (essential to avoid aggregation and clogging of the nozzles) 
  3. A range in sizes: 5, 20 and 50nm are our standard mean sizes but we can adapt to our clients preferred sizes – 60, 70, 80 , 90 or 100nm as mean size with <10% SD

We are experts in the design and production of NPs colloids for a broad range of applications, including for the formulation of functional inks. Our knowledge in this field comes from our direct experience interacting with clients in the conductive inks sector. 

Our experience includes different degrees of involvement in the preparation of the ink formulation:

  1. Supplying AgNP and AuNP colloids dispersed in aqueous media (2-5mM sodium citrate for concentrations up to 2mg Au/mL and + PVP of certain MWs and concentrations for concentrations as high as 50mg/mL) and our clients use them as core ingredients of their ink formulations. 
  2. Preparing highly concentrated inks following our client’s formulations using mixtures of water, ethanol and ethylene glycol, coupled with the use of dispersing and stabilizing agents such as PVP, methylcellulose, ethanolamine and other more specific dispersing agents. 

For more information, please see https://aegle-technology.es or contact us at sales@aegle-technology.es to discuss your requirements.