Mobile devices

21Apr 2017

T’is the season of new smartphone releases. The Samsung S8 is here and the drums are beating loud ahead of the much anticipated Apple iPhone 8 (or Edition, or whatever they will call it).

These devices and their makers clearly tout their performance features: faster processors, better camera, pretty displays, more memory….etc. But for this year and possibly for many years to come, the #1 feature is look and feel, otherwise known as industrial design, or just plain ID.

Industrial design includes how the device feels in the hand and eliminating or at least reducing the bezel to make the display reach out to the edges. It also includes thickness and profile, often some type of a rounded design that is comfortable in the palm. Invisible to the consumer are the havoc that these aesthetic features wreak on the battery. For example, thin smartphones mean thinner batteries; I mean really thin (less than 3 mm). Round profiles can mean non-planar batteries to maximize space utilization inside the smartphone. Are these batteries difficult and expensive to make? Absolutely. Given that the battery consumes between ½ to ⅔ of the overall space inside the smartphone, pushing the industrial design means serious business as far as the battery is concerned. Today’s post shows how your choice of a smartphone as a consumer impacts the battery and its underlying design.

First, and above all, every consumer wants his or her smartphone to last at least a full day. Now the definition of a “full day” is subjective, but there is broad consensus that it translates to a battery capacity of at least 3,000 mAh, preferably near 3,500 mAh for the top of the line smartphones. Indeed, if we examine the average capacity in smartphones over the past 5 years, we see that it has grown at about 8% annually. A battery in a 2017 smartphone contains about 40 – 50% more capacity (mAh) than it did in 2012.

Capacity

The smartphones are also getting thinner, so lesser volume available for the battery. The chart below shows the thickness of iPhones (in orange) and Samsung Galaxy line (in blue) over the past few years. The trend is clear!

Capacity is increasing. Volume is decreasing. That’s more energy in a smaller volume. In other words, the energy density is rising rapidly thus creating serious headaches because of various implications to safety and quality as well as cost.

If you are a battery vendor and need to increase energy density, what can you do? First, you can pack more material inside the battery to store more of the lithium ions. Second, you can increase the voltage. If you recall from your high-school physics, electrical energy is the product of electrical charge × voltage. More voltage translates to more energy. If we look at the maximum voltage of batteries that have been shipping commercially in the past few years, we immediately notice that the voltage has risen from 4.20 V to 4.40 V for one individual cell. We even see prototypes today at 4.45 V and above. The chart below shows that going from 4.20 V to 4.40 V provides an additional 20% in energy, or the equivalent of four battery generations.

volts

The challenge is that at these elevated cell voltages there is a heightened risk of lithium plating. Operating at 4.40 V is far from obvious or trivial. The margin of error is extremely small at these voltage levels. Manufacturing defects or design fluctuations are sufficient to cause the formation of lithium metal plating thus risking a potential battery fire.

So when you choose your next smartphone, be it a Samsung, Apple or any other brand, keep in mind how your choice as a consumer drives the OEM and in turn it drives the battery technology. The smartphone and its battery are ultimately the responsibility of the OEM, but an informed consumer will make the right and safe choice.

31Mar 2017

We, that’s all of us on this planet, buy every year 1.6 billion smartphones. It works out to one new smartphone every year for every four living human beings on this planet. Cumulatively, we own and use 4 billion smartphones around the world. Every region of the world, rich or poor, is buying smartphones. Many developing nations in the Middle East, Africa, and Asia are growing their smartphone subscriptions at a fast rate. Ericsson reports that by 2021, there will be 6.3 billion smartphone subscriptions, that’s nearly every man, woman and child around the world. Impressive!

Of course, each and every one of these smartphones has a battery in it. Your first reaction is: “that’s a lot of batteries.” Yes, that is true. Sadly, many of these batteries go to landfills after they are exhausted. The easiest way to gauge the size of the market for batteries is to calculate the entire energy supplied by all of them. Of course, that is a large number. It is measured in billions of watt-hours, abbreviated as GWh. As a reference mark, the battery in a top of the line Tesla S is 100 kWh. One GWh = 1 million kWh = 10,000 Tesla S.

 

Screen Shot 2017-03-31 at 9.48.15 AM

 

In 2016, the battery factories around the world manufactured about 50 GWh worth of batteries for consumer devices. That drives an industry and a market worth in excess of $10 billions annually. Forecasts indicate that the consumer market will use about 65 to 70 GWh worth of batteries in 2020. Our appetite for more batteries is insatiable and the numbers show it.

Now let’s look at batteries in electrified vehicles, including both hybrid plug-in cars and pure electric cars (xEVs). This is a relatively new market. The Tesla S first came in 2012. The Nissan Leaf came a little earlier in 2011. Many states in the US or countries around the world haven’t yet experienced or experimented with such vehicles. In 2016, all of these vehicles accounted for a mere 0.9% of all car sales. In total, they amounted to less than 1 m vehicles in 2016.

 

GWh

 

However, in battery lingo, these cars accounted for an increasingly large number of GWh. The year 2016 was the first year that the battery capacity used in xEVs equalled that of all consumer devices, about 50 GWh. By 2020, xEVs will account for ⅔ of all battery production in the world. No wonder Elon Musk and the major car makers pay a lot of attention to their supply chain, including building these Gigafactories.

 

18Oct 2016

State-of-the-art lithium-ion batteries, whether used in smartphones or electric vehicles, all rely on the same fundamental cell structure: two opposing electrodes with an intermediate insulating separator layer, with lithium ions shuffling between the two electrodes.

The positive electrode during charging, usually called the cathode, consists of a multi-metal oxide alloy material. Lithium-cobalt-oxide, or LCO, is by far the most common for consumer electronic applications. NCM, short for lithium nickel-cobalt-manganese oxide, also known as NMC, is gradually replacing other materials in energy storage and electric vehicle applications. LCO and NCM have a great property of storing lithium ions within their material matrix. Think of a porous swiss cheese: the lithium ions insert themselves between the atomic layers.

In contrast, the anode, or negative electrode during charging, is almost universally made of carbon graphite. Carbon historically was and continues to be the material of choice. It has a large capacity to store lithium ions within its crystalline matrix, much like the metal oxide cathode.

So how do manufacturers increase energy density? In some respects, the math is simple. In practice, it gets tricky.

Energy density equals total energy stored divided by volume. The total stored energy is dictated by the amount of active material, i.e., the available amount of metal oxide alloy as well as graphite that can physically store the lithium ions (i.e., the electric charge). So battery manufacturers resort to all types of design tricks to reduce the volume of inactive material, for example, reducing the thickness of the separator and metal connectors. Of course, there are limits with safety topping the list. To a large extent, this is what battery manufacturers did for the past 20 years — amounting largely to about a 5% increase annually in energy density.

But once this extra volume of inactive material is reduced to its bare minimum, increasing energy density gets tricky and challenging. This is the difficult wall that the battery industry is facing now. So what is next?

There are two potential paths forward:

1.  Find a way to pack more ions (i.e., more electric charge) within the electrodes. This is the topic of much research to develop new materials capable of such feat. But any such breakthrough is still several years away from commercial deployment, leaving the second option to….

2.  Increase the voltage. Since energy equals charge multiplied by voltage, increasing the voltage also raises the amount of energy (remember that energy and charge are related but are not commutable). This is the object of today’s post.

The battery industry raised the voltage a few years back from a maximum of 4.2 V to the present-day value of 4.35 V. This was responsible for adding approximately 4 to 5% to the energy density. A new crop of batteries is now beginning to operate at 4.4 V, adding an additional 4 to 5% to the energy density. But that does not come without some serious challenges. What are they?

First, there is the electrolyte. It is a gel-like solvent that imbibes the inside of the battery. Short of a better analogy, if ions are like fish, then the electrolyte is like water. It is the medium within which the lithium ions can travel between the two electrodes. As the voltage rises, it subjects the electrolyte to increasingly higher electric fields causing its early degradation and breakdown. So we are now seeing a new generation of electrolytes that can in principle withstand the higher voltage — albeit, we see in our lab testing that some of these electrolyte formulations are responsible for worse cycle life performance. This is a first example of the compromises that battery designers are battling.

Second, there is the structural integrity of the cathode. Let’s take LCO as an example. If we peer a little closer into the cathode material (see the figure below), we find a crystal structure with layers made of cobalt and oxygen atoms. When the battery is fully discharged, the lithium ions occupy the vacant space between these ordered layers. In fact, there is a proportion of lithium ions to cobalt and oxygen atoms: there is one lithium ion for every one cobalt and two oxygen atoms.

lco

courtesy of visualization for electronic and structural analysis (VESTA)

As the battery is charged, the lithium ions leave the cathode to the anode vacating some of the space between the ordered layers of the LCO cathode. But not all the lithium ions can leave; if too many of them leave, then the crystal structure of the cathode collapses and the material changes its properties. This is not good. So only about half of the lithium ions are “permitted” to leave during charging. This “permission” is determined by, you guessed it, the voltage. Right about 4.5 V, the LCO crystal structure begins to deteriorate, so one can easily see that at 4.4 V, the battery is already getting too close to the cliff.

Lastly, there is lithium plating. High energy-density cells push the limit of the design and tolerances in order to reduce the amount of material that is not participating in the storage. One of the unintended consequences is an “imbalance” between the amount of cathode and anode materials. This creates an “excess” of lithium ions that then deposit as lithium metal, hence plating.

These three challenges illustrate the increasing difficulties that battery manufacturing must overcome to continue pushing the limits of energy density. As they make progress, however, compromises become the norm. Cycle life is often shortened. Long gone are the days of 1,000+ cycles without intelligent adaptive controls. Fast charging becomes questionable. In some cases, safety may be in doubt. And the underlying R&D effort costs a lot of money with expenses that are stretching the financial limits of battery manufacturers without the promise of immediate financial returns in a market that is demanding performance at a the lowest possible price.

It is great to be a battery scientist with plenty of great problems to work on…but then again, may be not.

02Sep 2016

The images of melted Samsung Note 7 smartphones are all over the internet. News of Samsung’s massive recall are headline news. It is embarrassing to Samsung Mobile, its marketing and engineering teams, and most certainly its executives. Consumers are wondering how could Samsung ship units with defective batteries that can catch fire.

It is easy but not right to pick on Samsung or be critical of the company at this moment. Why? because this could happen to anyone…that’s right, anyone. If you are an OEM of smartphone devices or consumer devices with lithium-ion batteries, this is the time for you to pay attention to your products because you could be next.

While this sounds ominous, the intent here is to raise safety awareness in the entire ecosystem that depends on batteries. Samsung happened to be the first unlucky company to exhibit the strains that have been accumulating now for several years. I have covered in several past posts how the battery industry has been hitting the wall. Battery materials are reaching their limits. Battery economics are not favorable. Yet, the performance demands on batteries continue to rise. All of these factors are and continue to be precursors to the situation that Samsung finds itself in.

As is often the case in life, we tend to remain complacent until a crisis hits. The crisis is here, and now. Samsung is first to feel the pain, but each and every company in this ecosystem, from consumer devices to energy storage and electric vehicles, should acknowledge the severity of the situation and participate in its solution. Again, why?

This perfect storm has been brewing for a while, in particular, the drive to increase energy density along with faster charging while making less expensive batteries. Increased energy density and faster charging operate the battery near its physical limits. In other words, the margins for error at these elevated performance levels are really thin. For example, the newest lithium-ion cells now operate at a terminal voltage of 4.4 Volts, up from 4.2 Volts a few years back. This increase in voltage is one of the underlying physical tenants of increased energy density, yet it moves the battery every so close to the edge of the safety abyss. Another example relates to charging speed: it is widely accepted now that charge rates are approaching if not exceeding 1C. Electric vehicle makers are actively exploring very fast charging for EVs. Tesla is deploying their superchargers at a fast pace. These superchargers can charge a Tesla model at up to 1.5C, i.e., put in half a tank in about 20 minutes. Fast charging wreaks havoc inside the cell if not properly managed.

So now add the push for making less expensive batteries. Battery manufacturing, unlike semiconductors, does not scale. There is no equivalent of Moore’s law. In other words, as energy density increases, the cost per Wh (per energy unit) does not decrease…au contraire, it tends to increase because manufacturing tolerances get tighter. As a result, capital expenditures go up. Combine that with low-cost, low-quality batteries coming out of China and at a fundamental level, you can see how the financials of battery companies do not look pretty. This invariably leads to changes in manufacturing processes as companies seek more efficient ways to manufacture. But when the design margin of error is so thin, it does not take much before small variations in manufacturing lead to disastrous consequences. Remember, all it took in the case of Samsung was 35 failing devices out of a total of 2,500,000 shipped to cause a recall. This is a failure rate of 14 ppm (parts per million). It is a small number but, clearly, not small enough.

This is not to say that battery manufacturing and battery technology are doomed. There are countless examples in history where engineers built far more complex systems and structures safely and economically…but usually these include a change in paradigm. For example, pause for a second and compare the first commercial airplanes with the most recent jetliners. The newest Boeing and Airbus commercial airliners are marvels in computation and software. Fly-by-wire and automated systems with redundancy are the norm today, yet these new airplanes are scantily faster than their predecessors. In other words, the industry added so much more intelligence and shifted the burden to computation. The result is that modern planes are vastly safer than ever and far more economical to operate.

This is precisely the opportunity in front of the battery manufacturers and their customers, the OEMs, to think deep and hard on how they are going to implement a lot more intelligence to manage their batteries. Kudos to Sony for recognizing this….the batteries in their smartphones carry a great deal of intelligence, perform incredibly well and are safe. I am biased here…a lot of that intelligence is from Qnovo, but that should not diminish from the importance of the point of needing intelligence to manage the vanishing margins of error that battery designers have to cope with.

19Aug 2016

As I pondered over the past couple of weeks what might be a befitting topic for this 100th post, a group at MIT announced that they discovered how to make batteries with double the energy. Of course, the operative word in the press release was “first-prototype” which means that it might be a long while before, that is if, we see commercial deployment. However this announcement was the catalyst to focus this post on the state of the lithium-ion battery: In other words, if we ignored future inventions, what is the best that we can expect from the lithium-ion battery today across a number of applications.

For the vast majority of modern applications, the lithium-ion battery is capable of delivering the requisite performance. So if you are wondering why is it that most users complain about the battery, I will use an analogy of a jigsaw puzzle. The solution to storing electrical energy involves many pieces, like the pieces of a jigsaw puzzle. These pieces include the battery materials, chemistry and design, which is often provided by one party: the battery manufacturer. But also a critical piece includes the power management of the device and system, in particular the electronics and software needed to monitor how the energy is efficiently used, say by the apps on your smartphone. An equally critical piece is the battery management intelligence, which is what we do here at Qnovo, that is responsible for the integrity and efficient operation of the battery. If water use is to represent energy use, then the battery is the reservoir; power management is akin to water conservation, something we, Californians, are familiar with; and battery management is ensuring the integrity of the reservoir and its contents, making it large and free of toxins.

Separately and individually, each piece of the jigsaw puzzle is today at an exceptional state of the art for consumer electronics, energy storage, and electric vehicles. For example, energy density of batteries in commercial deployment is already near or at 700 Wh/l. This energy density is sufficient to power smartphones comfortably for a full day of use, or power an electric vehicle for 300 miles. Power management has become quite sophisticated, especially in consumer electronics where now the operating systems, e.g., Android OS and iOS, are asserting clever decisions on how apps may use power. Battery management intelligence has also become quite sophisticated, peering deep into the battery in real time and ensuring its continued health and integrity under extreme operating conditions.

But now imagine for a moment trying to build a jigsaw puzzle where multiple players share in putting the puzzle together, or worse yet, each player owns a subset of the puzzle pieces, but not all the pieces. Now you can imagine that putting the puzzle together can get quite complicated. You see, battery vendors know how to build the battery itself but tend to be quite novices in power management and battery management intelligence. System integrators and OEMs tend to have plenty of experience in power management but their knowledge of the battery chemistry tends to be limited. As to battery management, both battery vendors and OEMs have historically under-estimated its need and are playing catch up.

This, for example, begins to explain why Tesla Motors wants to own all these three pieces of the puzzle, beginning with their widely discussed Gigafactory but also their less-advertised efforts in power management and battery management. Apple is also in the same league. While Apple does not manufacture their own batteries, it is widely known that Apple does design their own batteries as well as having growing expertise in both power and battery management. But these tend to be early adopters who have recognized that they need to lead in owning and putting the pieces of the puzzle together. There are other giants who are in need of playing catch up, and they include the likes of Google, Microsoft, Facebook…as well as industrial players who are eyeing batteries for stationary energy storage and electric vehicles. Gradually, they are all beginning to make power and battery management integral to their long-term strategies.

Historically, system integrators and OEMs treated the battery as yet another component they source from suppliers, like the display or other electrical or mechanical components. But this model of outsourcing the battery expertise is beginning to fray. First, battery vendors are hitting the limits of materials and are struggling to meet the increasing demands of their customers without the use of intelligent power and battery management algorithms. Second, there is a growing discomfort, and I might dare say mistrust, between the OEMs and system integrators on one side, and the battery vendors on the other. Third, with the advent of cheap, meaning both inexpensive and lower quality, batteries form China, the business model of the traditional battery vendors, in particular Sony Energy, Samsung SDI, LG Chem is under pressure. A quick evaluation of their financials is sufficient to show they are not healthy. Sony recently announced the sale of their battery business to Murata Manufacturing. These shifting dynamics complicate the necessary tasks required to put together this battery puzzle and are forcing participating companies to seek different alliances.  For example, see the growing alliance between Tesla and Panasonic as well as between GM and LG Chem. In China, witness the growing influence of BYD in making batteries and making electric vehicles. The result is that the optimal battery system that incorporates the right battery, right power management intelligence, and right battery management intelligence is accessible to limited few organizations that either have the means to be vertically integrated or put together the necessary alliances.

As the reader can gather, the challenges in offering a great battery experience is really not technical in nature, but rather have economic and organizational origins. For consumer applications, the technology already exists to build elegant smartphones with battery capacities in excess of 3,000 mAh, charging very fast at 1 to 1.5C, and lasting 800 to 1,000 cycles. These specifications give the average consumer an excellent overall battery experience. For energy storage, the challenge is not the battery chemistry but rather hitting the right price points and building out comfort in the specifications from extensive testing. For electric vehicles, the cost of the battery is rapidly dropping. The Chevy Bolt and the promised Tesla Model 3 are prime examples of vehicles targeting the broader population at an increasingly affordable price. That is not to say that engineering innovations and continued disciplined product improvements are not necessary; they are important. But the perception that the battery industry is in dire need of a large breakthrough in technology and materials is not well founded. Instead, there is a bigger need for all the players around the battery jigsaw to learn to work together and leverage each other’s expertise and technologies. This is happening; in the process, we will continue to see a race to build up intellectual property, patent ownership, expertise, and skills by the various participants.