Juicelet

REVYVE - WristBank: an interesting take on a common problem — battery life

The perpetual back and forth between smartphone performance upgrades and the resulting increased power consumption calls for a new approach.

Studies in the US show so many people not getting the performance they need from batteries and yet so little of us are using current solutions.

The problem is practicality — wires leaves confined to outlets and lugging a bulky portable charger in 2020 is simply way too impractical for day-to-day life. In June of 2019, I decided to tackle this problem in interest of taking on a unique yet scalable idea, So, I got designing.

Very quickly 3 major obstacles became very apparent; lithium ion batteries can’t be curved easily, the batteries need to have a connection through the hinge, and a reasonable amount of mAh in a battery to get through the day can get pretty big. The best way to get through this was the solution to every modern problem; graphene… in the form of lithium-ion batteries, along with some optimized circuitry to make a respectable amount of battery not look like house arrest on your wrist.

After several iterations and starting over from scratch. What seemed like my final design had finally come after investigating into tons of factors such as wrist curvature, sizing, hinge geometries, types of PCB’s, accelerometers, connectors, optimal materials, manufacturing processes, cost, and much, much more. However, nothing could teach more than getting my hands at working and making it. The inital designs were named “Juicelet”, then later renamed to the “REVYVE WristBank”.

Although the end product seemed great with 1000mAh, I still hadn’t reached my goals yet. The design was able to pack a decent amount without the use of any of the nanotechnology or modern design approaches I had in plan. The goal always was over 50% charge on over 99% of phones, and there was clearly room for much more, but the main issue was, funding. With some extra money and my university laboratory I could incorporate a fluorinated graphene cell with folded composite film anodes in my cells, plus a MEMS or even NEMS accelerometer to provide fitness tracking with minimal internal volume losses due to the circuitry.

The graphene is perfect for this application for 2 main reasons:

First, graphene is incredibly light, strong, and flexible, making the battery bendable when stacked in thin modules; this removes the need to rely on the less superior lithium polymer and the extra costs due to the special tooling to make the custom curvature.

Second, graphene provides superior conductivity; with which improves two major flaws of my concept; recharging times and safety. Graphene is notoriously known for its especially high conductivity of 5.8 times more than copper by weight, meaning charging and discharging in less than half the time compared to graphite electrode cells, and because the cell generates much less heat it's safer too, with cycles reported as high as 250’000; up to a thousand times more.

The folding of the graphene is a solution proven to work in tackling the problem of wasted voids of space within a battery by increasing effective surface area and thus improving areal capacity. In fact, one paper showed a 67% increase in energy density from 271Wh/kg to 452Wh/kg when compared to a standard LiCoO2 cathode cell. Not only will this extra ‘room’ contribute to more battery per Juicelet, but a thinner, larger filleted design which will compete with the fitness bracelet market by also using some of that extra space for features such as pulse monitoring with an optical heart rate sensor.

In additon, in the past 10 years the cost of graphene has gone down by nearly 10’000X as of 2020 thanks to advancements especially in chemical vapor deposition (CVD) techniques. Plus, graphene is relatively cheap due to how little is needed for battery applications. Estimates show that graphene batteries cost only add about 30% extra cost compared to traditional lithium ion batteries and this number will only go down further; the major issue is supply in scaling this.

UPDATE: due to COVID we pushed back our kickstarter date to early 2021, in the meantime adjustments to the 3D printed plastic enclosures, PCB’s, UI, and curved touch panel have been made.