Silicon Joule is an advanced bipolar battery technology created by Gridtential Energy. It can turn a standard lead battery into a powerful, fast-charging, long-lasting source of energy for electric vehicles, appliances, homes, and offices. Silicon Joule is a patented AGM battery technology and it incorporates solar wafer processing techniques into a new bipolar battery architecture, while also using existing battery manufacturing and recycling infrastructures. It allows reducing failures, extending life cycle, and improving power performance.
Silicon Joule Technology
As an alternative to lithium-ion based batteries, Silicon Joule is a solar-inspired technology which allows to exploit already available lead-battery technology production facilities. More precisely, Gridtential’s novel technology replaces the metal grids in conventional lead batteries with specially processed silicon wafers and an innovative stacked-cell architecture able to reduce weight, increase power performance and extend cycle life. This results in unprecedented levels of performance, while maintaining lead’s significant cost advantages and its ability to be recycled. Today, most batteries installed on electric and hybrid vehicles, as in many small appliances, tools, and consumer devices, are largely based on lithium-ion technology. Lithium-ion batteries have the advantage of being very light and offering a good level of performance, very important characteristics in electric vehicles where each component contributes to increasing the efficiency and therefore the autonomy of the vehicle. However, there are some disadvantages involved with li-ion batteries, including the need to accurately monitor their temperature and the charging process (in order to avoid the danger of possible explosions), the complexity and costs of the recycling process and the very nature of the required raw materials, such as lithium whose extraction from the subsoil has often been a source of environmental criticism.
On the other hand, Silicon Joule batteries can be recharged in half the time, weigh up to 30% less than conventional lead batteries and feature an excellent thermal stability, simplifying the battery management system. Another significant advantage is their ability to be 99.3% recycled using proven and widely adopted recycling systems. This, in turn, allows to create a clear safety and sustainability advantage over lithium-ion. Since Silicon Joule batteries can be manufactured using existing production equipment, they are able to meet soon the worldwide demand for safe and sustainable energy storage. Some major manufacturers are already fully licensed to mass-produce Silicon Joule batteries, and several manufacturing international partners are piloting this innovative technology, producing batteries off lines in their plants. The first offering is a single-block 24V lead battery optimized for deep-cycle applications, whilst a 12V power version will follow later in Q2 2021, with 48V versions of each appearing in the second half of the year.
Gridtential’s Silicon Joule technology substitutes treated silicon wafers for conventional lead grids and combines them using a patented “stack-and-seal” architecture able to provide a uniform current distribution and efficient thermal management, drastically reducing failure and malfunctions caused by sulfation, corrosion and grid growth. Figure 1 shows the internal structure of Silicon Joule-based 24V battery, with a detail of the “stack-and-seal” architecture.
“What is interesting is our novel material is something that can be made in in solar wafer fabrication facilities. And so, what we’re doing is we’re taking an industry that’s over 100 years old, and we’re leveraging it against a new emerging industry that has had such massive scale and such maturation, that industry already produces in high volume at high quality, very pure materials”, said Collin Mui, Lead Silicon Engineer at Grindtential Energy.
The result is an advanced AGM lead battery that delivers up to 5X the power density, 2X the discharge rate at a 75% lower levelized cost of electricity (LCOE) than conventional lead batteries, offering high-performance at significantly lower weight, creating an attractive alternative to lithium-ion. Thanks to their flexible stacked architecture, Silicon Joule batteries can accommodate a wide range of voltage configurations, including 12V, 24V, 36V and even 48V in a mono-block form factor.
“What we’ve done is to use the walls between the cells of the battery as an electrically conductive element: we put a positive material on one side, and a negative material on the other separator. So, what happens is we are conducting laterally through the entire middle of the battery, which acts as a conduction path. The reason we you can do that is because of the properties of silicon, a conductive material that can remain exposed to sulfuric acid for more than 20 years without being affected”, said Collin Mui.
Unlike lead batteries, which have a limited lifetime due to the occurrence of sulfation, Silicon Joule technology allow a more uniform operation, going from a battery with 100s of cycles to a battery with 1000s of cycles, charging twice as fast and delivering 5 to 10 times more power. The cycle-life outstanding characteristic is shown in Figure 2, where the percent capacity retention of Silicon Joule batteries is compared with traditional lead-acid AGM.
Due to their top-level performance, long duration and high flexibility, batteries based on silicon Joule technology are suitable for a wide range of energy-storage applications, including small hybrid and electrical vehicles, personal mobility, and home energy storage. Market applications can be grouped according to the battery voltage as follows:
- 24V deep-cycle (already available): electric sweepers, scooters, wheelchairs, riding lawn mowers, e-bikes
- 12V power (available starting from Q2 2021): power-sports SLI, automotive start-and-stop and EV auxiliary
- 48V deep-cycle (available in 2H 2021): golf carts, e-tuk-tuks, renewable energy storage, telecom, data center backup, micro-grid
- 48V power: (available in 2H 2021): mild-hybrid, EV auxiliary, ADAS, start-and-stop, infotainment and regenerative braking.