Safety

17May 2018

I googled the question “ should I charge my phone to 100”. Google returned 467 million results. From folks offering opinions on “how to properly charge” to others calling on “science”, there seems no obvious consensus in the media. Yet,  unlike views on more socially charged topics, this question ought to be a lot simpler and ought to have a clear cut answer. Let’s explore.

I start with an easy experiment. Take two batteries. Charge one of them continuously to 100% and discharge it back to zero. Repeat. Take the second battery and charge it only to 90%. Discharge it. Repeat. Now compare the two batteries.  Are there differences? the answer is yes, there is difference. The battery that was charged to 100% will age considerably faster. 

What do I mean by aging? The technical term is “cycle life.” In practice, it means that the battery charged to 100% will lose its ability to store electric charge faster than the other battery. The difference between the two batteries can vary between 100 and 300 charge cycles.

So is that good? Well, it depends on what your use is. The definition of “good” is relative.

For a smartphone, my answer is “I really don’t care.” 

For an electric vehicle, my answer is “yes, it is better, but may be only marginally.”

For energy storage batteries used by electric utilities, my answer is “yes, absolutely.”

Now, let’s dive into the details.

A smartphone battery usually lives about 500 to 800 cycles. By cycles, I mean the number of times you will be able to charge it (to 100%) and discharge it before it becomes old and useless. Some smartphone manufacturers do better than others. Apple’s and Samsung’s batteries tend to be closer to 500 cycles. Others like LG, Sony and Huawei tend to be closer to 800 cycles. 

Let’s convert cycles to real-life years. Most smartphones are charged once a day. So 800 cycles is about 2 years of use before your battery becomes old. That corresponds well with the average time for consumers to upgrade. But wait, you might say you plan to keep your smartphone for longer than 2 years. What should you do?

Naturally, one option is to spend $30 to $50 once your battery is depleted and get your phone serviced after 2 years. The other option is to charge your phone to only 80% or 90% instead of 100%. That exercise will probably get you an extra year of usage.

But that is not the only way to get more longevity. You probably don’t know that if you use a small AC adapter instead of a bigger one, you will probably get the same benefit. For this method, look for an AC adapter that is rated 5 Watts, or use the USB port in your PC to charge you handset. And that applies to iPhones or Android phones. What do you give up? You are giving up fast charging. If you charge your handset overnight, then you really don’t care.

A self-serving plug for Qnovo: Smartphones with intelligent charging algorithms will take care of longevity issues for you so you really don’t have to think about this question and its answer. 

Now, let’s talk about electric vehicles. Should you top off the battery in your electric vehicle (EV)? First, it is important to know that EV manufacturers (from GM and Tesla to Nissan and VW) already limit the charging of the car battery to somewhere near 80%. The 100% that you read in your dashboard is actually 80% of the what the battery is rated for. That figure usually is sufficient to meet the warranty terms of the vehicle, often 100,000 miles or 10 years.

If you are leasing your car, then you really don’t care. Your lease will expire long before any meaningful battery aging sets in. But if you purchased your EV and plan to keep for a long time, then you may have an incentive to not top off your battery.

But wait, that is also not the only way to get more longevity. Every time you use a supercharger or DC fast-charging, you are causing serious damage to the battery. So instead, try to avoid using superchargers. This is particularly acute for the Panasonic batteries used in some of the Tesla models.

Lastly, I will add a few final words about electric utilities and batteries they use. These are complex systems that are slated to operate for at least 20 years! They are also very expensive assets that cost millions of dollars. So longevity is a serious matter. Naturally, users have no say in how these batteries get charged. Utilities and battery manufacturers do watch over these batteries so that they can last for a long time.

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.

24Jan 2017

Samsung announced this week the results of their investigations regarding the Galaxy Note 7 fires. Samsung hired three independent test laboratories, Exponent, TUV Rheinland and UL to perform the analyses. The result was three full reports and presentations with technical details, mostly written by engineers for engineers. Vlad Savov at The Verge called the reports “humble and nerdy.” I can hear many in the audience screaming: “Translation, please!” I will try in this post to simplify and summarize the findings.

Of the three reports, the one written by Exponent is the one that offers the most useful pointers into what went wrong with the Note 7 batteries.  Here’s what it said, in simple terms.

First, Samsung Electronics (the maker of the Note 7) used batteries from two battery manufacturers: Manufacturer A is Samsung’s sister company, Samsung SDI; Manufacturer B is China-based Amperex Technology Limited, also known as ATL. In the sequence of events, the batteries made by Samsung SDI were the first to catch fires. Samsung Electronics decided to replace all SDI batteries with those made by ATL, but these too caught fire. Two different battery designs made by two different manufacturers, both catching fires..ouch! If you are a gambler, this is equivalent to winning the jackpot! But as we will see next, the published reports pointed instead to sloppy designs and poor manufacturing.

Let’s start with the Samsung SDI cells and what went wrong with them. I have shared in past posts the basic structure of a lithium-ion battery. It is made of alternating layers of conducting electrodes separated by an insulating layer called the separator. The #1 edict of battery safety is that the two electrodes, the anode and cathode, cannot touch. If they do, they form an electric short and cause a fire. It is common practice among battery experts that the root cause of most battery fires is an electric short. So what caused the electric short in the batteries from Samsung SDI?

The Samsung reports (as well as our own internal investigations) show that there was sufficient force on the edge of the battery during the manufacturing process that damaged the battery, effectively damaging the insulating separator or the graphite anode. When the separator gets damaged, it can no longer hold the anode and cathode physically apart; the two electrodes touch resulting in an electric short.

The second failure mode is more subtle but equally deadly. If you recall from previous posts, I have spoken about the need of a “balance” between the anode and cathode to prevent the formation of metallic lithium, also known as lithium plating. The presence of physical damage in the graphite layer breaks this balance creating the seeds for lithium metal. With use, lithium metal dendrites begin to form and ultimately grow to form a direct electric short inside the battery. The Exponent report illustrates this effect well in the following diagram. In other words, lithium plating is a dangerous culprit in the Note 7 fires.

I cannot over-emphasize the dangers of lithium metal plating! It is a lurking hazard that leads to unexpected fires. It is a risk that develops without visible manifestation. No amount of X-Ray inspection at the manufacturing site will detect the presence of lithium metal plating. And when these dendrites grow slowly in time, your battery will catch fire. In this particular case, the physical damage to the battery edge was the catalyst that led to lithium metal plating. But as I have mentioned repeatedly, many other reasons including aggressive battery designs can lead to lithium metal plating.

exponent

Now let’s talk about what went wrong with the ATL cells. The batteries made by ATL did not suffer from physical damage. Instead, the reports point to defects during the welding process of the electrical tabs (where one makes a connection to the battery). As the battery swelled and contracted during charging/discharging, these weld defects came apart and caused an electric short. In other words, this was pure and simple sloppy manufacturing by ATL in their rush to manufacture millions of batteries for Samsung.

Is there any hidden good news here or is it all bad news? The good news is that Samsung came clean. The Exponent report is credible and matches our own internal findings on the SDI battery. The good news is that the manufacturing defects during welding of the ATL batteries are relatively easy to address. I am reasonably certain that ATL and Samsung have now implemented proper procedures to eliminate welding defects. I am also reasonably certain that Samsung and SDI have implemented procedures to minimize physical damage to the battery edges.

But the bad news is that none of the new procedures address the elephant in the room: Lithium metal plating! We applaud all the additional inspection steps that Samsung is implementing, but the sad reality is that none of them will detect or prevent the formation of lithium metal plating. As I have observed in several prior posts, lithium metal plating can occur for many different reasons. Eliminating physical damage during manufacturing is good but is not sufficient and is not addressing a root cause of safety failures. Be prepared to see more battery fires in the industry!

17Jan 2017

It was the best of times, it was the worst of times. It was the age of innovation, it was the age of imitation. It was the epoch of the battery, it was the epoch of lithium. It was the season of Japan, it became the season of China. It was the spring of hope for batteries, it was the winter of despair from safety. Charles Dickens will forgive me for contorting his famous novel into a Tale of Two Geographies: China vs. the world, that is in lithium-ion batteries, of course.

The credit goes to Sony for being the first to commercialize the lithium-ion battery in 1991 for use in their handheld video cameras. Twenty five years later, Sony Energy Devices (or SEND), as the business came to be known, was sold to Murata Manufacturing Co. Ltd., epitomizing the massive changes that swept through the lithium-ion battery industry. An icon and a giant in the evolution of lithium-ion batteries, SEND had estimated revenues in 2016 of $1.2B, and its rumored sale price was approximately $150m. What happened?

Several factors came into play as the lithium-ion battery industry grew and matured. As our society turned mobile and demanded portable power sources, demand for rechargeable batteries grew from 3 GWh in 1990 to 58 GWh in 2015, with a forecast exceeding 400 GWh in 2025. Initial demand came from laptop PCs which was soon surpassed with smartphone use. The forecasted demand from electric vehicles is already eclipsing that of consumer devices.

Growth invites competition and increasing pricing pressures. The first to compete with the early Japanese manufacturers were the large Korean conglomerates LG Chem and Samsung SDI. By the early 2000s, the quality of the Korean batteries improved significantly and came to match that of the Japanese makers. Consumer device OEMs began to switch their supply chain from Japanese to Korean manufacturers. Sanyo, once a dominant supplier to laptop PCs, saw its market share dwindle. Panasonic suffered the same fate in consumer devices, and ultimately bet its future on Tesla Motors.

By 2010, China was rising to compete with LG Chem and Samsung SDI….but competing with these giants was no small feat. The quality of Chinese batteries was no match to their Korean or Japanese counterparts. Samsung SDI was effectively a sole supplier to Samsung Electronics. LG Chem offered great quality and supplied Samsung’s nemesis, Apple’s iPhones. Life was Good!

China is big. China is patient. China is focused…and China can be ruthless to foreign suppliers. As the smartphone industry grew competitive and Android opened up swathes of new customers in developing countries for inexpensive mobile devices, OEMs began to seriously consider lower cost batteries from lower tier Chinese suppliers…but only for smartphones aimed for China or developing countries in Asia, Africa or South America. The high-end market was still off-limits to Chinese battery suppliers, which meant LG Chem and Samsung SDI continued to enjoy dominance and profits.

Then Apple disrupted the landscape! Early in the current decade, Apple began to cultivate a little known Chinese battery manufacturer. This company’s name is Amperex Technology Limited, often abbreviated as ATL. It came to compete with LG Chem, Sony Energy and Samsung SDI for Apple’s iconic and fast growing iPhone business. TDK of Japan had acquired ATL a few years earlier in 2005. ATL was the opening salvo for Chinese manufacturers to take direct aim at the incumbents, namely LG Chem, Samsung SDI, Sony Energy, and to a lesser extent Hitachi Maxell of Japan. It is not known what fraction of the iPhone batteries are sourced from ATL but it is considered to be quite substantial judging from TDK’s public financial disclosures over the past years. ATL became a growth engine for TDK and a model for Chinese battery suppliers to expand outside of China.

August of 2016 was another aha moment. The batteries in the Samsung Galaxy Note 7 came into focus revealing that Samsung Electronics was now sourcing batteries from both Samsung SDI and ATL. Not only ATL was aggressively chasing its usual competitors, it was also going after Samsung SDI’s stronghold: the Samsung Galaxy series. ATL, by now, was making quality batteries at a substantial discount over LG Chem, Samsung SDI and Sony Energy. ATL was winning market share at a fast rate and enjoyed a very special position: no other Chinese battery manufacturer was yet able to break into the smartphone market outside of China.

With raging price wars in consumer batteries, LG Chem and Samsung SDI began to turn their sight to more profitable applications. Their financials for 2016 were far from exemplary. Guided by Panasonic’s successful model with Tesla Motors, they increasingly focused their resources and investments into the growing xEV market (including both hybrid and pure electric vehicles). LG Chem became the supplier of choice for the Chevy Volt and the Bolt. Samsung SDI supplies many of the German-built xEVs.

China map

In 2017, we see rising competitive pressures from additional Chinese battery suppliers that until recently were household names only in remote Chinese towns. Tianjin Lishen has grown to be a large player in China and increasing willing to supply top-tier OEMs around the world. Small players including Coslight, BAK and SCUD are emerging with prices attractive for the low-end and mid-tier smartphone market segments. It is estimated that there are nearly 100 such battery vendors throughout China….but for now, their questionable quality will keep many of them out of the race.

It takes very little in this historical examination to recognize that China is on its way to become a dominant supplier of lithium-ion batteries, at the very least for consumer electronic devices including smartphones. Quality is still not at par with batteries from Korea or Japan, but their aggressive pricing strategies will surely maintain momentum as they continue to improve their manufacturing. Barring unforeseen safety disasters that are uniquely attributed to Chinese manufacturers, this trend will continue if not accelerate. Chinese vendors will increase their market share in consumer devices as the large traditional vendors, in particular LG Chem, SDI, and Panasonic continue to shift their positions to xEVs.

From the view of the smartphone OEMs, this increasing shift in the supply chain disrupts the historic relationships between them and the battery vendors. Samsung Electronics’ cozy relationship with Samsung SDI cannot and will not be replicated with ATL. Same goes with LG Electronics and LG Chem. If you are an OEM, it is becoming imperative to take ownership of your “battery destiny.” Failing to do so will carry serious safety implications with disastrous financial consequences. Samsung Electronics is sufficiently large to weather the Note 7 fiasco, but other small OEMs may not have this luxury.

21Dec 2016

This year has been one of heightened awareness regarding battery safety. Smartphone manufacturers now realize that battery fires are real and recalls from the field are enormously expensive. Along with this education comes a deeper realization that battery quality and the presence of hidden defects are very serious matters.

Today’s post sheds light onto the challenges of battery manufacturing and ensuing defects. These discussions are not useless academic conversations. We see manufacturing defects in batteries especially those sourced from Chinese manufacturers. We observe them more frequently in batteries with high energy density where manufacturing tolerances are challenging.

We analyzed recently a family of batteries from a China-based manufacturer that shall remain unnamed. The battery in question is in serious consideration for a possible release in a smartphone in 2017. Our analysis revealed that the battery was potentially unsafe exhibiting an elevated risk of lithium metal plating; this can lead to electrical shorts. A post-mortem dissection showed regular horizontal bands of lithium metal deposited on the surface of the graphite anode. The scary part was that this battery was quite new….it had only been used for a few days with less than 10 charge-discharge cycles. So what’s happening?

img_5145_1920px

Let’s go back to basics. This previous post recaps the basic structure of a lithium-ion battery. There are two electrodes that face each other with a porous insulating layer in between meant to keep these two electrodes apart. The anode has a coating of carbon (in the form of graphite) on top of a copper layer. The cathode has a coating of a specialized metal oxide, often lithium cobalt oxide abbreviated as LCO.

The design of the battery dictates that the amount of graphite compared to the amount of LCO must be balanced. This balance, which in technical jargon is called the A to C ratio, requires that there is a small amount of excess graphite relative to LCO. Usually, in a good design, there is about 5% more graphite material than LCO.

If, for some reason, there is less graphite than there is LCO, then this creates a condition where excess lithium ions cannot be absorbed by the anode, leading to lithium metal forming on the surface of the graphite….this is called lithium metal plating. As I said before and I will say again, lithium metal is a NO NO. It is a risk for electrical shorts and it is highly flammable in the presence of water vapor or oxygen; both are precursors for poor safety.

In a good manufacturing environment, the graphite anode layer is uniform in thickness and density. In other words, anywhere along the large anode surface, the graphite maintains the proper balance with the cathode layer that sits on the opposite side.

But now imagine a scenario where the manufacturing is not well controlled such that regions of the anode (or the cathode) are not uniform — for example the thickness or the density of graphite particles vary. Now remember that this need not be a huge variation: only a mere 5% change in particle density is sufficient to create an imbalance between the two electrodes. That is precisely what happened in this Chinese battery. The figure below illustrates how these bands are related to the defects in the electrode layer.

scalloping

When the manufacturer coated the anode and cathode layers, their machines created small ripples in the density and/or thickness. So when the battery was first powered, lithium metal began to form…and that was what we observed in our laboratory.

So now you will say, “Well, that was a cheap Chinese factory. Surely the more reputable incumbents do not have this problem.” True, but that is not good enough. The economics are not in their favor. I will explain.

The tolerances of manufacturing high-energy-density batteries are becoming very tight. This drives the need for newer state-of-the-art manufacturing equipment, such as machines that can coat the electrodes more uniformly. The cost of equipping new manufacturing facilities therefore increases, driving up the cost of manufacturing these batteries.

Compare this to manufacturing silicon integrated circuits. Moore’s Law makes it possible to spend billions of dollars on manufacturing facilities and yet amortize this cost over a rapidly increasing number of electronic chips. The result is the amortized cost per chip actually goes down.  Sadly, there is no equivalent of Moore’s Law in batteries. More expensive manufacturing means more expensive batteries, and consequently, a loss of market share to the low-cost Chinese battery manufacturers. It is no surprise therefore that the reputable incumbents in lithium-ion batteries like LG Chem and Samsung SDI have their sights set on the electric vehicle market where they get to build the power train, not just a battery. This is a big invitation to low-cost  and low-quality battery makers in China to continue expanding.

The combination of increasing energy density along with the enormous pricing pressures from second-tier battery manufacturers in China are invariably leading to increased incidence of manufacturing defects — and that is something smartphone and device OEMs ought to be thinking about very seriously.