Nexeon Technology
Nexeon has patented a unique way of structuring silicon so that it delivers extended cycle life and significantly increases battery capacity. In contrast to carbon, Nexeon’s silicon anode materials have a much higher capacity for lithium and as a result are capable of almost ten times the gravimetre capacity per gram (mAh/g).
Product Details
At the carbon anode: 6C + Li+ + e- ↔ LiC6 ⇒ 372 mAh/g
At the silicon anode: 4Si + 15Li+ + 15e- ↔ Li15Si4 ⇒ 3580 mAh/g
Nexeon’s patented silicon structures overcome the previous problems of poor cycle life encountered when using silicon by mitigating the volume expansion issue. These uniquely structured silicon anode materials deliver extended cycle life without degradation of capacity:
Nexeon is developing a range of materials with differing morphologies and capacities.
The first commercially available material is a low cost silicon capable of capacities up to 1000mAh/g.
A commercial 2600 mAh 18650 Li-ion cell today uses around 10g of graphite anode material. Just 2.6g of Nexeon’s unique first generation structured silicon can replace graphite.
Second generation material has a different morphology and has been optimised for even higher capacities, i.e up to 3600 mAh/g.
Nexeon has designed its technology for easy adoption in existing Li-ion battery production lines. The graphite currently used can simply be replaced with Nexeon materials and used in combination with conventional polymer binders and current collectors as part of the standard battery manufacturing process. In this way, Nexeon technology truly offers a ‘drop-in’ approach.
About Li-ion batteries
Lithium ion (Li-ion) batteries are a commonly used type of rechargeable battery with a global market estimated at $11bn and predicted to grow to $60bn by 2020.
The popularity of the Li-ion battery is due to the advantages offered over other secondary (or rechargeable) batteries:
- Lighter than other rechargeable batteries for a given capacity
- Li-ion chemistry delivers a high open-circuit voltage
- Low self-discharge rate (about 1.5% per month)
- Do not suffer from battery memory effect
- Environmental benefits: rechargeable and reduced toxic landfill
However Li-ion batteries have also struggled with issues such as:
- Poor cycle life, particularly in high current applications
- Rising internal resistance with cycling and age
- Safety concerns if overheated or overcharged
- Applications demanding more from Li-ion battery capacity
In Li-ion batteries, lithium ions move from the anode to cathode during discharge, and from cathode to anode when charged. The materials used for the anode and cathode can dramatically affect a number of aspects of the battery’s performance, including capacity.
New higher capacity materials are urgently required in order to address the need for greater energy density, cycle life and charge lifespan, among other issues faced by Li-ion batteries.
Graphite has traditionally been the anode of choice for commercial use, with typical first generation Li-ion chemistry working as follows:
Overall reaction on a Li-ion cell: C + LiCoO2 ↔ LiC6 + Li0.5CoO2
At the cathode: LiCoO2 – Li+ – e- ↔ Li0.5CoO2 ⇒ 143 mAh/g
At the anode: 6C + Li+ + e- ↔ LiC6 ⇒ 372 mAh/g
Materials other than graphite have been investigated, with silicon offering the highest gravimetric capacity (mAh/g).
The volumetric capacity of silicon (Wh/cc), i.e. the capacity of silicon taking into account volume increases resulting from lithium insertion, is still significantly higher than that associated with carbon anode materials.
The potential contained within silicon holds great promise for the future of Li-ion batteries, if it can be used without compromising the battery cycle life.
When charging a lithium ion battery, lithium is inserted into the silicon, causing a dramatic increase in volume (up to 400%). On discharge, lithium is extracted from the silicon which returns to a smaller size. Repeated expansion and contraction places great strain on the silicon, causing silicon material to fracture or pulverise. This, in turn, leads to the electrical isolation of silicon fragments from nearest neighbours and a loss of conductivity in the anode of the battery. For this reason, charge-discharge cycle life for conventional silicon-based anodes is typically short.
Nexeon’s technology solves the cycle life problem posed by silicon, thus enabling its greater energy density properties to be harnessed for the next generation of Li-ion batteries.
Benefits of Nexeon Technology
Nexeon’s silicon anode Li-ion battery technology has numerous applications, and the ‘drop-in’ approach offers significant benefits to battery manufacturers and end users:
Capacity
- Allows cell capacity to be increased by 30-40% using a standard cathode
- Provides far higher capacity than any other battery system
Cycle Life
- Increased longevity of battery
- Consistent performance over 300+ cycles
Cost
- Lower cost to manufacture using less material
- Low switching cost through simple integration of Nexeon’s silicon anode into existing manufacturing processes
Form Factor
- Smaller, lighter cells allowing innovative product design potential
Safety
- Successful performance in thermal exposure, overcharge and external short circuit tests on prototype Li-ion cells
- Delivers a higher safety margin at a given capacity for silicon material (buffer capacity)
Compatibility With Current Manufacturing Processes
- ‘Drop-in’ approach minimises disruption to existing manufacturing process
- Silicon anode batteries operate at the same voltage as existing Li-ion batteries
- Compatibilty with present electronic device designs
- Using less material within the battery future-proofs the technology providing the opportunity for manufacturers to make improvements to the design of the cell
Sustainable Energy
- Lighter batteries with more power and less charging required will overcome a key limitation of electric transport
- Nexeon’s increased Li-ion battery capacity represents a huge leap forward in providing excellent energy storage systems to increase the effectiveness of sustainable energy such as wind or photovoltaics
The benefits for end users of this technology are potentially huge, with applications across a vast range of industries and products.
Licensing
Nexeon continues to build Intellectual Property (IP) around structured silicon materials and lithium-ion battery technology, and is interested to talk with potential customers, users, and suppliers throughout the value chain. Initial discussions are already being held with battery manufacturers who see the potential for major competitive advantage as a result of adopting Nexeon anode technology.
As part of these discussions, Nexeon provides data from cells made at its own facility using standard cathodes. Following this, test cells or material samples are provided under a Material Evaluation Agreement so that the materials may be evaluated.
Nexeon will grant non-exclusive licenses to patents along with a package of technology which describes the fabrication of electrodes and the general optimised formulations of anodes.
Nexeon will help licensees implement this technology in their manufacturing plants through Technology Transfer projects, Joint Development Agreements, and R&D contracts. The materials will be available from Nexeon.
Patent information
Nexeon has a growing portfolio of patent families relating to silicon materials and batteries, for which non-exclusive licences can be negotiated. Our patent grants and applications protect various technologies focusing on, but not limited to, the use of high capacity silicon material as an active agent in the negative electrode of a lithium-ion battery.
Example technologies covered by our portfolio include:
- Structured silicon particles (e.g. pillared particles, fibres or porous particles), their use and methods of manufacture.
- Electrodes comprising silicon nanowires/fibres coupled to a substrate or as part of an interconnected conducting network in a composite.
- Electrodes where the active material comprises silicon or tin inside carbon nanotubes.
- Binders and electrolytes for Li-ion battery composites.
- A method of making a multiple electrode stacked cell with a continuous folded separator or polymer electrolyte layer.
- A process of making a thin solvated polymer membrane with controlled porosity.
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