So you are happy with the large battery in your new iPhone 6 Plus. Finally, Apple listened and put a large, nearly 3,000 mAh, battery in your device. Finally, Apple followed the rest of its Android-based competitors who already had scaled their batteries to sizes between 2,500 and 3,200 mAh. So what do you think these batteries will be in 2015, or even past that, say in 2020! Surely, we must expect batteries with capacity over 4,000 mAh or even 5,000 mAh. Yes, surely you are joking!
Let’s get geeky for just one brief moment. Let’s talk about energy density. That’s the amount of energy that one can pack in a known volume, say a gallon or a liter. Battery energy density is measured in units of Watt-hours per liter (Wh/l). State-of-the-art batteries in the market today boast of an energy density between 600 and 650 Wh/l. Prototypes in the lab are somewhere between 700 and 800 Wh/l depending on whom you choose to believe. Mobile device makers would like to see 1,000 Wh/l. Great, I admire setting ambitious goals, but let’s see how feasible it is.
The present material system uses a special alloy called cobalt-oxide as well as graphite (carbon) for the two electrodes of the battery. This particular material combination has already hit the wall in terms of energy density; somewhere between 600 and 650 Wh/l. So to go past this limit, manufacturers are exploring new types of materials, with silicon or silicon-carbon composites being one such candidate. Early results are promising but scaling the manufacturing remains several years away. Additionally, the cost of building these new high-energy density batteries is rising, driven by more complex manufacturing processes, more expensive materials, more R&D resources, more expensive capital equipment, and more rigorous quality-control steps. Low-cost batteries out of China are now about $0.10 per watt-hour. These new high-energy density batteries can be easily 5 if not 10x more — well, that is if you can find them. They still don’t exist in commercial scale.
So here’s the conundrum for mobile device makers. They want more capacity without making the mobile device bigger. But batteries with such high-energy densities still don’t exist in commercial scale. And if they did, they would be terribly more expensive in a mobile industry where cost pressures are enormous. Then, they are at a point now where their trust in the battery manufacturers is at best shaky. Battery manufacturers have long promised more capacity and better batteries but have struggled to deliver. Instead, several battery vendors chose to play juvenile gimmicks with their battery specifications to cover their shortcomings.
So if you are a mobile device manufacturer, you either recognize you have a serious problem, or if you don’t, it’s time to wake up and smell the coffee!