For a while, Samsung's flagship smartphone, the Galaxy Note 7, dominated headlines. This wasn't due to its outstanding performance or design (although the Note 7's performance and design were indeed excellent), but rather because, shortly after its release, a major safety hazard was discovered in its built-in battery, with the probability of the phone exploding unexpectedly far exceeding normal levels. This incident dealt a huge blow to Samsung, causing immense financial losses, and consumers of electronic products, as well as people from all walks of life, began to fear the technology. This is evident in the recent absurd behavior of some companies referring to Samsung phones as dangerous goods for civil aviation.
However, in daily life, electronic product explosions are not uncommon. So how do these devices, which are supposed to serve consumers, suddenly turn into "bombs"? Let's take a look at the chemical explanation provided in this article.
They're all lithium-ion batteries, so why are they so different?
Today, most electronic products have entered the "lithium-ion battery era." As a type of battery with considerable application experience, lithium-ion batteries are characterized by long lifespan, large capacity, and low cost, making their widespread popularity entirely understandable. However, although many types of batteries can be called "lithium-ion batteries," are you aware that there are significant differences between different lithium-ion batteries? In fact, lithium-ion batteries can be broadly divided into two categories—traditional lithium-ion batteries and lithium-ion polymer batteries—which differ in many properties:
Traditional lithium-ion batteries: A typical example of this type of battery is the 18650 lithium-ion battery, frequently seen in various "power banks (portable power banks)". This battery is named for its cylindrical shape (18mm in diameter, 65mm in height). Its low cost and durability have made it a top performer in today's lithium-ion battery market. Like other traditional batteries, traditional lithium-ion batteries contain an electrolyte responsible for transferring electrons (because battery charging and discharging are essentially processes of directed electron movement), thus requiring a certain packaging volume (which sometimes makes them less portable) and a hard outer casing to protect the electrolyte.
Lithium-ion polymer batteries: Currently, all portable electronic products such as mobile phones and tablets, as well as the vast majority of laptops, use this type of battery. Because lithium-ion polymer batteries utilize a polymer series battery structure, they require only a small amount of liquid electrolyte. Therefore, these batteries do not require a rigid casing for protection, have no shape restrictions, and their packaging volume can be greatly reduced. Based on these characteristics, lithium-ion polymer batteries are widely used in electronic products that prioritize portability and have requirements for device thickness, and they are showing a strong trend of replacing traditional lithium-ion batteries.
Why have lithium-ion batteries become a "bomb"?
In the Samsung Galaxy Note 7 explosion incident mentioned at the beginning of the article, Samsung subsequently confirmed that the phone's explosion and burning were closely related to a design flaw in its lithium-ion battery. In recent years, all electronic product explosion incidents (such as the Sony laptop explosions in 2006, which ultimately led to a global recall of problematic products) have invariably involved lithium-ion batteries exploding. From a chemical perspective, there are many reasons that can cause lithium-ion battery explosions, a significant portion of which are closely related to design flaws by manufacturers.
As is well known, a major cause of battery explosions is a short circuit (i.e., when there are no electrical appliances in the circuit containing the battery, resulting in an excessive current flowing through the battery in a short period of time). Whether it is a short circuit or overcharging (another important cause of lithium-ion battery explosions, i.e., the battery charging voltage exceeds its set upper limit), both will cause a large amount of heat and gas to accumulate inside the lithium-ion battery in a short period of time (lithium-ion batteries generate gas when they are working). In order to release the pressure, the lithium-ion battery will either activate the internal pressure relief device or directly crack its outer casing. Both of these situations will cause the internal materials of the battery to come into direct contact with the air, thereby causing combustion.
Generally speaking, lithium-ion battery explosions and fires are rarely caused by external circuit failures. This means that the vast majority of lithium-ion battery explosions and fires originate from internal design flaws within the battery. For example, in the aforementioned Sony laptop battery explosion incident, metallic impurities were detected in the electrolyte of the problematic battery. The accident was caused by these impurities creating unexpected conductivity, leading to an internal short circuit and triggering the explosion. Similarly, the Boeing 787 aircraft lithium-ion battery fire incident was also related to the significant degradation of electrolyte performance in aircraft batteries under special conditions, thus inducing an internal short circuit.
Of course, both of these lithium-ion battery explosion and combustion incidents involved traditional lithium-ion batteries, while the "protagonist" in this Samsung Galaxy Note7 explosion incident was a lithium-ion polymer battery. So what's special about lithium-ion polymer batteries in this type of incident? Generally speaking, lithium-ion polymer batteries, because they lack a rigid outer casing, have a significantly reduced likelihood of violent explosions and combustion. When such batteries do explode, their poor impact resistance causes them to burst prematurely, typically resulting in a slow combustion after the explosion. However, the high degree of variability in the shape of lithium-ion polymer batteries gives device manufacturers more design freedom, but it also often requires additional design for the battery pack. This inevitably leads to situations where the battery pack design is inadequate, causing accidents. In this Samsung Galaxy Note7 explosion incident, it has been preliminarily determined that a battery pack with significant manufacturing defects is likely the culprit behind the explosion.
How can we prevent a recurrence of this explosion?
Although Samsung has initiated a recall of products containing the problematic batteries, the severe damage caused by the incident—including the destruction of its brand image, value, and corporate reputation—is irreversible. This incident can be considered one of the major safety accidents in the history of lithium-ion battery development. Given this, what improvements can we make to prevent a recurrence of such an incident?
With the widespread adoption of lithium-ion polymer batteries, the most important task for major lithium-ion battery manufacturers is undoubtedly to strengthen control over battery safety. This requires rigorous product testing before shipment, new product testing, and yield rate control, as well as a strong emphasis on and investment in battery design. After all, theoretically, a perfectly designed and manufactured battery has an extremely low probability of experiencing an accident after long-term use, and even if an accident does occur, it won't damage the manufacturer's reputation. However, if a battery experiences significant problems in these areas, the manufacturer will pay a heavy price.
For consumers, choosing reliable lithium-ion batteries and using them correctly in appropriate environments are crucial to preventing accidents. Some consumers, tempted by lower prices, choose various substandard batteries, which actually creates hidden dangers for future use. Similarly, even with a perfectly qualified lithium-ion battery, accidents can occur if it is not used properly (such as in extreme weather, underwater, or high-temperature environments) or if it is handled inappropriately (such as dropping or scratching the battery).
