A look inside the world of batteries

08Apr 2019

Let’s say you love to ride your bicycle and that you want to measure speed without using fancy computers and GPS. What would you do?

High-school physics to the rescue! All we need is the circumference of the wheel then count the number of rotations the wheel makes in a certain amount of time that we can measure with our stopwatch. The speed, v, is calculated as the number of rotations, N, multiplied by the circumference, L — that’s the total distance traveled by the wheel — divided by the measured time, T. Put in one simple equation:

We replace the circumference with the radius, R, because it is easier to measure the radius of the wheel:

The speed equation becomes:

Therefore, measure the wheel radius, then count the number of rotations, and clock them with a watch…et voila, you can measure speed.

You quickly realize that you have an approximation of speed because it fails to take into account other factors that can introduce errors, for example temperature. On a hot day, the wheel expands a little making the radius longer.  Then you realize that the thickness of the rubber tire is not exact — it varies across manufacturers. With aging, the rubber gets worn out. It becomes thinner and consequently the radius is a little smaller. You may think these are small effects but if you are racing, they can make the difference between winning and losing.

So what is the relevance of a bicycle wheel to a battery?

Scientists understand the electrochemistry inside a battery.  They represent this science with many complex equations — like Fick’s law, Tafel’s equation, and several other mathematical forms. Yet, these equations remain insufficient to describe batteries in real life. 

Much like the wheel, there are significant variations in manufacturing across batteries from the same manufacturer or from different manufacturers. Temperature dependence, aging, presence of defects…etc. are significant additional considerations that impact the performance and safety of the battery.

Capturing these “real-life” considerations is what makes a model of the battery useful.  By “model” I mean a sufficiently accurate representation of the battery that one can use to make meaningful conclusions. For example, a good model can be used to predict the end of life of the battery. It can be used to identify counterfeit batteries or find defective batteries before they become a fire hazard.

Developing the model entails collecting data — millions of measurements — to capture manufacturing variations, temperature dependence, defects…etc. It takes a long time to collect statistically meaningful data across different types of batteries, from different manufacturers and across a board range of operating conditions.

The battery model is not static — it must improve over time or it becomes obsolete. One must keep updating it so it learns and adapts to newer battery materials, newer battery designs and manufacturing processes. This learning process can be in the test lab, or it can be in the field — in other words, intelligent algorithms can learn from batteries deployed in smartphones or other devices already in the hands of users.

Possessing intelligent algorithms and useful battery models is a powerful combination to make key predictions about the battery’s health and safety…that can make the difference between a safe battery and a fire.

19Feb 2019

Some time in August of 2013, hackers breached Yahoo! servers and stole private account information for up to 3 billion users. Verizon Communications received a $350 million discount in the price of its acquisition of Yahoo! in 2017, exemplifying the staggering costs of one single encounter with cyber risk.

The concept of risk and risk management is not new. In 1688, Edward Lloyd set up what would become today Lloyd’s of London to contain the emerging risks of the new and growing maritime trans-Atlantic trade. Since then, the business world has worked diligently to contain such risk in everything from food to the Internet.

Actually, almost everything. One such modern risk that remains inadequately addressed is battery safety, specifically the safety of lithium-ion batteries that are so ubiquitous. To be fair, industry has recognized long time ago the safety hazards surrounding the lithium-ion battery. Battery fires in the early 2000s caused expensive recalls. But they were largely treated as one-off events. These were times when the annual volume of batteries was a few hundred millions. These fires were not treated as an on-going risk. They were seen as failures in manufacturing that could be eliminated by improvements in factories or designs.

Today’s battery shipments have skyrocketed to billions of units and counting. Even a minuscule chance of battery fire becomes a real problem when multiplied by the sheer volume of batteries. Battery failures are an ongoing risk that needs to be contained.

Estimates place the risk of battery fire in the range of a few to tens of parts-per-million (or ppm). One ppm means that for every one million units shipped, there is a risk that one of them will catch fire. It does not mean that one *will* catch fire. It just means that statistically speaking, the probability of a fire is one in a million. Now that seems like a small number. You might tell a precious love that they are “one in a million.” In an industry that ships two billion smartphones annually, that translates to several thousand battery fires annually! Not acceptable! We need to bring this figure down by a factor of 100 or 1,000.

Edward Lloyd’s business was possible because it had its underpinnings in the mathematical advances of probability pioneered by Blaise Pascal and Pierre de Fermat early in the 17th century. In that same vein it is possible to make great improvements in battery safety because it leverages the advances in computation of the past 50 years.

Every smartphone is a miracle device. It contains a processor that is infinitely more powerful than the computer that landed Apollo 11 on the moon. It also contains sophisticated electronics that can measure minute voltages and currents, and in turn it is very telling of the chemical reactions inside the battery. Merge it all with intelligent software, and we can now predict what the battery’s health will be in the future.

But why can’t we just manufacture the perfect battery that will never catch fire? Simply put, it is prohibitively expensive. Consider this: nearly every person with a smartphone is also an amateur photographer. Despite the fact their camera lens is optically deficient, software allows them to take incredible photographs.

The same goes for batteries. Manufacturing batteries in large volumes means that some will have defects. That’s just the balance between quality and cost when it comes to battery manufacturing in large scale. To make matters more challenging, every person will use or abuse their battery in unpredictable ways. It becomes essential to catch and screen these few bad batteries in the field before they become a hazard. Naturally, this is not meant to supersede good manufacturing practices, but rather to complement them in our quest to reduce battery fires to zero.

So how does it work? I talked in the past about electrochemical impedance spectroscopy (EIS). It is a workhorse test instrument in battery laboratories around the world. It is capable of measuring the chemical processes that are taking place inside the battery. Now imagine if you had such a similar tool inside your device. With some expertise, you can now start making smart decisions about your battery. This is not a new concept; a similar concept, for instance, allows glucose measuring devices to save the lives of millions of diabetics.

It’s high time we get serious about battery health and safety. Let’s address this risk before it escalates. The spread between device capabilities and battery threats is only growing — let’s get smart and manage potential incidents before they blow up into something bigger.

15Feb 2019

Everyone’s excited about 5G. And with good reason. All the great things we have been able to do on our smart phones with 4G LTE will multiply into bigger and better things in the 5G Era. We’ll be able to send and receive huge text and image files in the blink of an eye. Entire movies will download in seconds. In short, 5G will make our smart phones vastly more useful as business productivity tools and as entertainment platforms. I don’t know about you, but I can’t wait.

There’s just one thing. The excellent experiences of 5G can’t happen without battery power.

Unfortunately, batteries are a major stumbling block of the smart phone era. Explosions and fires, although rare, are a serious problem. One such mishap is too many.

A little history: Introduced commercially in 1991, lithium-ion batteries are a tremendous advance over previous-generation technology, such as nickel-cadmium and nickel-metal hydride, and they have made the 4G LTE era possible. But in the 5G era, lithium-ion batteries risk being exposed as the weakest link in the chain of 5G-enabling technologies.

This looming catastrophe is no secret. Smart phone manufacturers and network operators I speak with are concerned about 5G and the demands that will be placed on handsets. They know something must be done. But what?

Researchers are working night and day to come up with breakthrough battery technology, such as solid-state batteries or batteries using nano materials. But battery breakthroughs often take a decade or more, and billions of dollars in investments. Much more work needs to be done before these next-generation batteries are ready to be deployed in large volumes. Realistically, we need to accept the fact that 5G will dawn on smart phones equipped with lithium-ion batteries. The only sensible approach is to get those batteries as ready as they can be for the new era.

Briefly, here’s the issue: Every battery has a cathode and an anode, in a substance called the electrolyte. During charging, ions move from the cathode to the anode through the electrolyte. In lithium-ion batteries, tiny tree-like growths called dendrites may form on the anode over repeated charging cycles. These dendrites can grow so large that they eventually reach through, touching the cathode and causing an electrical short, possibly leading to an explosion or fire. Dendrite formation is accelerated by factors that stress the battery, such as rapid charging or overcharging. Damage caused by these stresses accumulates over time.

5G will put stress on batteries as never before, thanks to several factors:

  • The higher-frequency bands of 5G require more power. 5G encompasses new frequency bands of 3 GHz to 6 GHz and above 24 GHz. Power consumption increases linearly with frequency, so going from 900 MHz to 6 GHz, for example, incurs a 5x increase in power demand all else being equal.
  • Data traffic will increase substantially. Even though 5G is highly efficient, throughput rates will be higher and displays will be larger. More bits will be streaming at rates exceeding 1 Gbit per second, requiring additional power.
  • 5G apps will require low latency, about one millisecond. For example, streaming video on a larger screen will sharply reduce idle time for the processor and battery. That means greater power consumption.
  • 5G will require denser placement of antennas across the landscape, and until carriers add more antennas, handsets and their batteries will have to work harder.

In all, network operators estimate 25% to 50% increase in power demand.

Preparedness

There is hope, however, if intelligent battery management software is implemented. The first step is to reduce the stress on the battery; the second is to monitor battery health so that danger is spotted before problems occur. These twin tasks are simple in principle but challenging in practice.

To measure the chemical processes at work, it is possible to utilize the electrical current that charges the battery as a kind of messenger. By applying principles similar to sonar, it is possible to retrieve information from the electrical current’s echo about the chemical reactions within the battery. Based on that information, the reactions can be tuned to make them better performing. These same signals also relay information as to any problems that are developing, such as the dendritic formations that produce electrical shorts.

By lessening battery stress and monitoring battery health, doubling battery longevity is a reasonable expectation. Most phone batteries are rated at 500 charging cycles, but that can be increased to 1000. And battery life isn’t the only thing that can be improved. As a battery charges and recharges, it enlarges in size, gaining perhaps 10 percent in volume. Intelligent battery management can cut that swelling in half.

Simply put, intelligent battery management is a must-have for all smart phones. Nothing else does a better job ensuring battery health and safety. As we await the arrival of 5G, there is no need to despair or to become impatient with the slow progress of battery chemistry technology, when intelligent battery management is here today.

17Jan 2019

Ted Miller, senior manager of energy storage at Ford Motor Co., recently stated:  We don’t see another way to get there without solid-state technology.” The statement is in regard to more powerful batteries for electric vehicles. Mr. Miller goes on clarifying: “What I can’t predict right now is who is going to commercialize it.”

So what is a solid state battery and why is it so difficult to commercialize? 

First, let’s clarify some misconceptions. 

A polymer battery, known as a LiPo, is a lithium-ion battery. 

A cylindrical battery, like an 18650 cell (used in the early Tesla models) is also a lithium-ion battery.

A prismatic battery is too a lithium-ion battery with a hard shell.

And so is a solid-state battery. It involves newer manufacturing processes, but it is a lithium-ion battery. 

All of these variances of lithium-ion batteries have one physical principle in common: the lithium ions contribute to storing the electrical energy.

Simplistically, a lithium-ion battery operates with lithium ions shuffling back and forth between two electrical layers: an anode and a cathode. When the ions are at the cathode, the battery is discharged. When they move to the anode, then the battery is charged. The cathode and anode are called electrodes.

The motion of the ions between these two electrodes is facilitated by an intermediate medium called electrolyte. It is a solution that is electrically conductive: it permits ions to travel through it with little impediment. One key property is called conductivity: it is a scientific measure of the ease at which ions can travel through the electrolyte. High conductivity means the ions can travel easily and quickly. Low means the opposite.

In a lithium-ion battery, the two electrodes are immersed in an electrolyte solution. Today’s batteries use a liquid or gel-like electrolyte. Battery manufacturers go to great lengths to formulate unique electrolytes for their batteries. The formulations do have an impact on many of the battery’s specifications, in particular cycle life (the number of times a battery can be charged and discharged). 

In a solid-state battery, the liquid or gel electrolyte disappears. It is instead replaced by a “solid-state” layer sandwiched between the two electrodes. “Solid-state” means this layer is not a liquid, but a physical solid. The material can consist of a ceramic, glass, or even a plastic-like polymer, or some type of mixture of all three.

So why use a solid electrolyte? There are two major reasons. First, a battery with solid electrolyte occupies a lot less space than one with liquid electrolyte. That means one can pack more energy in the same volume. Consequently, energy density — an important metric of batteries — goes up.

The second reason is safety. Liquid or gel electrolytes are more prone to catching fire than a solid electrolyte.

Traditionally, the primary challenge with solid electrolytes is poor conductivity especially at room temperature (25 °C or 77 °F). A liquid or gel electrolyte has a conductivity that is about 1,000 times better than that of solid electrolyte. In other words, solid electrolytes exhibit a far higher resistance to the flow of lithium ions. This results in several performance challenges, starting with poorer cycle life and inability to charge at fast rates. 

Some companies proposed operating their solid-state batteries at elevated temperatures (> 80 °C) to improve conductivity. But this is not practical under most use scenarios.

Therefore the quest for solid electrolyte materials continues to be a much active field of exploration and discovery. There is confidence in the industry better materials will be discovered, yet, we really can’t predict when a breakthrough will be widely adopted. 

Another challenging aspect is the surface stability and manufacturability of solid electrolytes.  Unlike liquid solutions, glass and ceramic electrolytes are not deformable. They must be assembled with the two electrodes using high external pressure, equivalent to about 1,000 atmospheres. It becomes questionable whether existing battery manufacturing factories can be retooled for this purpose. If not, the economics of solid-state batteries will undoubtedly suffer as is the present case.

In a nutshell, there is much promise in breakthrough material innovations to make solid-state batteries a reality. Yet, many challenges remain ahead. I personally do not expect to see solid-state batteries in commercial scale for several years to come. We will continue to see evolutionary progress with traditional lithium-ion batteries especially as prices continue to decline.

But in all cases, solid-state batteries are subject to the same physical principles that govern traditional lithium-ion batteries. Consequently, many of the battery management solutions developed for traditional lithium-ion batteries will evolve and continue to apply. And that is good news.

14Nov 2018

Geoffrey Fowler at the Washington Post recently published an article observing that phone battery life is getting worse. I enjoyed my conversations with Geoffrey as he researched the topic. But why is the phone battery life getting worse? Why are batteries not keeping up with the new crop of smartphones? 

Like so many things in life, it is all about energy balance. Our doctors tell us that we need to balance our calories: Calories we eat versus the calories we expand on exercise. And so the smartphone needs to balance its energy stored in the battery versus the energy it spends on use. So I distill this to two simple questions on energy demand and supply:

  1. Why is the energy demand growing with increased use of our smartphones?
  2. Why can’t we have a bigger battery to supply our growing energy needs in a smartphone?

So let’s tackle the first question by examining the sources that drive energy consumption in a smartphone. There are three parts in your smartphone that are energy hogs:

  • Your screen….ok, I am sure you all know that ;
  • Your processor….some of you probably know that too ;
  • Your radios. Not your FM radio! Radios means the cellular connection, WiFi connection, bluetooth, GPS….anything that communicates with the outside world using radio waves.

Energy consumption for each of these parts depends on the nature of the hardware and you, the user — that’s the length of time you spend on the device. 

The energy used by a screen is quite large, even with the new OLED screens. Screens are getting a bigger numbers of pixels. Each pixel consumes energy. More pixels means more energy.  Every time you turn the screen on, it’s more energy that the battery has to supply.  And that adds up rapidly. 

If you follow various chatrooms, you probably know that “screen time”, meaning the total amount of available battery time with your screen on, is probably about 6 hours, give or take – regardless of what the smartphone maker advertises about all day use or more.

Next is the processor. Fortunately, that piece of hardware used to be a major energy hog but with the new generation of processors from Qualcomm or Apple or Samsung, they have become quite efficient. How much efficient? About twice more efficient than the previous generations from a few years back. All good news, right? well, not quite.

You see, processors have become efficient indeed, but now they are running a lot more frequently than they ever did. Think about an SUV parked in the garage versus a Honda Civic used for Ubering. Which one uses more energy?

A few years ago, we used our smartphones for texting and emailing….now, we stream videos. So while these processors are efficient, they are being taxed by video and social media. Net net, they are consuming more energy from the battery. How can you tell? watch how hot your smartphone becomes when you stream videos or take 4k movies on your device. That’s your processor getting hot.

Let’s talk now about radios. That’s a growing problem for the battery, so much that carriers like AT&T and Verizon in the US, or DoCoMo in Japan are really worried about it.

On one hand, carriers love that you use more and more data…that’s how they make money. But data use means your cellular connection is on, a lot more than before. 

But you say wait, isn’t 5G cellular connection better than LTE? Think of 5G as adding more lanes on the internet superhighway as compared to LTE. It means more cars, a lot more cars, will use the highway. It means more energy will be consumed. And the battery needs to supply this energy.

The FCC is just auctioning a new range of frequencies between 24 GHz and 47 GHz for the future 5G spectrum. By comparison, LTE runs at frequencies between 0.5 GHz and 2 GHz. Why is this important? Energy use goes up with frequency. So by going to the new 5G frequency, energy consumption will grow with it, worsening the burden on the battery. In other words, the future will tax the battery even more!

Bottom line: our smartphones and our user behavior mean our appetite for more energy will continue to grow.

Now we can tackle the second question: Why can’t the device manufacturer put a bigger battery in the smartphone? 

It is simple: Bigger battery capacity means a physically bigger battery. Batteries are improving so slowly such that the only way to give users more battery capacity is by making the device larger or thicker. The recent iPhone XS, XR and XS Max show a clear trend to making larger devices that can hold larger batteries.

Will that be enough for the future? not really. Smartphone sizes can’t get any bigger. At 6 in or greater screen sizes, they are already too large to hold in one hand. They may get a little thicker but not by much. Our human hands determine the optimal physical form for a smartphone.

So what gives? I don’t know yet, but most likely, our behavior and expectations. It is quite likely that users may charge their smartphones more frequently in one day…perhaps charge twice instead of once. Some users might be happy with fewer pixels in their devices. Others may turn off their Facebook and social media apps. 

Regardless of how we adapt to the future of smartphones, the battery will continue to be the weakest link, and the one in most need for innovation.