LIFE+ GLEE Technology
The Innovative Idea
High-performance, high-capacity Cathode Active battery Materials (CAM), including Nickel Cobalt Aluminum (NCA), Lithium Iron Phosphate (LFP), Cobalt-based lithium-ion (LCO) and Nickel Cobalt Manganese (NCM), are a critical core component of Li-Ion batteries. That’s why the rush in the industry to develop the next generation’s Li-Ion batteries, with even higher power and more energy densities, has normally focused on the investigation of new and higher performing CAM. These developments, however, are impeded by the sensitivity of CAM to moisture and their inability to resist harsh environments.
The technology at the basis of the LIFE+ GLEE project addresses and brilliantly solves this issue by providing an easy way to coat the active material with a protection layer.
The immediate advantage of the protected CAM is to allow the usage of water-based formulations in the production process of Cathode slurry. In addition, during battery operation, the protection coating enhances CAM resistance toward the electrolyte.
The Technological Challenge
Problem: Water-borne cathode electrodes cannot be manufactured due to low stability of active materials when in contact with water.
Solution: Protective coating on active material surface prevents interaction with water and maintains good battery performance.
Protecting a water-sensitive material with a coating is not a difficult task. The unique challenge of shielding cathode materials is preserving the essential process of intercalation and deintercalation of Li-Ions within their structure to retain the full functionality in Li-Ion battery operation. To that purpose, the LIFE+ GLEE technology developed a coating that is permeable to Li-Ions and is also impermeable to water and other aggressive media. This innovation is achieved by close control of coating deposition and layer thickness.
The LIFE+ GLEE Protection Process of CAM
Powders of active materials are coated using an electroless deposition process.
This is composed of three steps:
- Activation: the surface of the particles need to be activated. This is done by the adsorption of a catalyst; the powders are dispersed in an aqueous solution containing, for instance, Palladium ions. Clusters of Pd atoms will be created after adsorption on the surface of the particles, and they will act as active sites where the reduction of metal ions will take place during the deposition process. This preparatory action is fundamental to achieve an efficient deposition in the following step.
- Deposition of protection layer. The protective layer is plated by a controlled chemical reduction of metal ions, dispersed in an aqueous solution, on the surface of the powders. The activated particles from previous are immersed in the deposition bath. The aqueous solution into which powders are dispersed contains metal ions and a reducing agent. The latter is able to provide the electrons needed to complete the metal ion-reduction process. The progressive reduction of metal ions will create a continuous layer on the surface of the dispersed particles.
- Final coating formation with subsequent annealing. In order to allow their use in manufacturing electrodes for Li-ion batteries, at the end of the process powders have to be dried. Once the deposition process is completed, the particles are separated from the plating bath and dried at high temperature in contact with air.
Now the powders are protected and ready to be used in manufacturing a Li-ion battery.
What is Electroless?
- Metallization process based on autocatalytic metal ion reduction
- Can coat conductive and non-conductive substrates
- Produces conformal coatings
- Substrate can be of any geometry and shape
The electroless deposition (ELD) is an electrochemical plating technique that allows the reduction of metal ions from an aqueous solution, without the need of an external power source. ELD is also known as autocatalytic deposition, since the reduced metal acts as catalyst for the reduction of metal ions dispersed in the plating solution.
The most important components of an aqueous ELD plating bath are the salt of the metal to be deposited (source of metal ions) and the reducing agent (source of electrons). The redox reaction that is established in the system is composed by the oxidation of the reducing agent, that generates electrons necessary for the reduction of metal ions dispersed in the plating bath.
Among the metals that can be deposited using this technique there are gold, silver, copper, nickel. Substrates made of glass, metals, polymers and oxides can be coated using ELD, with few limitations on its geometry, since deposition takes place wherever the plating solution is wetting the substrate.
Lithium ion Batteries Configuration
In the classical configuration a Li-Ion battery is made of a cathode, an anode and a separator which divides the two.
The battery operating mechanism consists in the cyclic migration of lithium ions among the two electrodes (cathode and anode).
CAMs are coated with a binder, usually Polyvinylidene Fluoride (PVDF), and a conductive additive (CA), generally carbon black or graphite to improve the electrical conductivity of the electrode, on thin metal foils that act as current collectors (typically Al and Cu).
Lithium ions move in the electrolyte interacting with cathodes and anodes: active materials have to intercalate and de-intercalate lithium ions in their molecular structure or have to react reversibly with lithium ions.
Located inside the battery, the electrolyte is typically a liquid with dissolved salts which increases the ionic conductivity. The electrolyte needs to have a good ionic conductivity but no electrical conductivity because this could cause an internal short circuit.
In a standard battery, a separator is used to physically separate the anode and cathode in the electrolyte solution to prevent an internal short circuit. However, the separator is permeable to the electrolyte in order to maintain the desired level of ionic conductivity.
Carbon-based materials (conductive additives) are used to improve the electrode’s electrical conductivity and create a continuous network of filling the pores between the CAM particles.
The function of the polymeric binder in the electrode is to link together the different components in order to create a mechanically and chemically stable network.
The most widely used binder for cathodes is PVDF. It is a high performance partially-fluorinated polymer with excellent thermal, chemical and electrical stabilities.
This polymer grants good electrochemical performance and excellent adhesion among the materials which forms the electrode and the current collector.