The consumer electronics industry is witnessing a lithium - battery revolution: Is the combination of silicon - carbon anodes and semi - solid batteries about to make a full - scale breakthrough?

The war of foldable smartphones is entering a "millimeter - level" precision close - combat.

The successive launches of the vivo X Fold5 and the Honor Magic V5 have not only raised the hardware ceiling of large foldable flagship phones but also amazed people once again at the performance limits under the premise of thinness and lightness. Especially in the area of the battery, which is often considered a "weak point", these two models have remarkably achieved a balance - they are not only thinner but also have larger capacities.

More specifically, the vivo X Fold5 packs an equivalent 6000mAh Blue Ocean battery into a foldable body with an unfolded thickness of 4.3mm and a folded thickness of 9.2mm. Meanwhile, the Honor Magic V5 fits a 6100mAh "Qinghai Lake Blade Battery" into a foldable body with an unfolded thickness of 4.35mm and a folded thickness of 8.8mm.

These figures are still quite incredible even when compared to a year ago when silicon - carbon anode battery technology had just started to be applied. The common secret behind them lies in a newly emerged material technology combination: silicon - carbon anode and semi - solid electrolyte.

Image/ vivo

As we all know, the internal space of smartphones has been continuously encroached upon by camera modules, chip modules, and heat dissipation structures. The battery, being the most space - consuming component, cannot compromise on capacity, as that would become a pain point for users. Therefore, to make smartphones thinner and lighter without sacrificing battery life, the rules of the game must be rewritten at the material level.

Leikeji reported in mid - 2024 on the revolution in mobile phone batteries triggered by "silicon - carbon anodes" and predicted that silicon - carbon anodes would spread from some mid - range models to flagship models. However, it was still unexpected that Honor would so quickly increase the silicon content from 10% a year ago to 25% in the Magic V5, pushing the battery energy density to 901 Wh/L.

What's even more surprising is the application speed of semi - solid batteries in the mobile phone field. After introducing semi - solid battery technology for the first time in the previous generation, the vivo X Fold5 continues to adopt the second - generation semi - solid battery technology, also increasing the battery energy density to 866 Wh/L.

These technical terms may sound complicated, but the core behind them is actually quite simple: this is a quiet revolution led by "material innovation". The end - point of this revolution may not only be thinner and lighter foldable screens but also the answer for the next version of the entire consumer electronics industry.

The "comeback" of lithium batteries depends entirely on material upgrades

The improvement in the battery life of foldable smartphones, with larger and thinner batteries, may seem like an overnight "magic trick", but the real change actually started quietly from the battery material side. To understand the underlying logic of this change, we need to start with the basic structure of a lithium battery.

A typical lithium - ion battery mainly consists of three key elements:

- Cathode material: Usually a lithium - containing metal oxide, such as ternary (NCM) or lithium iron phosphate (LFP), which is responsible for releasing lithium ions;

- Anode material: Traditionally graphite, which is responsible for adsorbing lithium ions;

- Electrolyte: It conducts lithium ions between the cathode and the anode. Traditionally, it is a liquid lithium salt solution.

The charging and discharging process of a lithium battery, Image/ US Department of Energy

During charging, lithium ions "move" from the cathode to the anode and embed themselves. During discharging, they migrate in the opposite direction, releasing energy. This process may sound simple, but what determines the usability of a battery is often "how much electricity it can store per unit volume/weight" - that is, what we commonly refer to as energy density (Wh/kg or Wh/L).

To increase the energy density of a battery, the core lies in: electrode materials with higher capacity + a more compact structural design + a safer electrolyte system.

In the past, most lithium batteries used graphite as the anode material. Its advantages are stability, safety, and low cost. However, its performance has almost been fully exploited, with a theoretical specific capacity of only 372 mAh/g, almost reaching the "ceiling". In contrast, silicon has a theoretical capacity as high as 4200 mAh/g, more than ten times that of graphite.

There are challenges, though. Silicon is too "aggressive". During the charging and discharging process, its volume can expand by up to 300%, which can easily cause pulverization and capacity attenuation, making it difficult for mass production. Therefore, the key to the silicon - carbon anode is to "strike a balance": encapsulate nano - sized silicon particles in a carbon - based framework to form a structure that "has both high capacity and elasticity".

In the vivo X Fold5, vivo uses the fourth - generation silicon - carbon anode material. While maintaining stability, it achieves a silicon content of up to 12%, significantly increasing the specific capacity of the battery. Honor Magic V5 goes even further, directly raising the silicon content to 25%, setting a new record in the mobile phone industry. This is one of the core reasons why they can accommodate large batteries of over 6000mAh in ultra - thin and light bodies.

Image/ Honor

In addition to the upgrade of the anode, the evolution of the electrolyte is also crucial.

Although traditional liquid electrolytes have strong conductivity, they have problems such as poor safety, easy leakage, and flammability. Moreover, they take up a relatively large space, which is not conducive to making the device thinner and lighter. Solid electrolytes, on the other hand, are safer and can be arranged more compactly, but their current conductivity and mass - production processes are not yet mature.

At this time, the semi - solid electrolyte becomes an ideal "intermediate solution". By introducing some solid components (such as polymers or inorganic oxides) into the traditional liquid electrolyte, it not only retains the conductivity but also improves the safety and structural support ability. More importantly, it allows for a more compact and thinner encapsulation of the entire battery cell, creating space for high - energy - density batteries.

Vivo uses the second - generation semi - solid battery structure in the X Fold5. The electrolyte extends from the cathode to the anode, forming a "bipolar solid - state protection" structure. This enables the battery to discharge stably even at a low temperature of - 30°C and increases the energy density to 866 Wh/L, achieving a technological breakthrough that allows for coexistence in extremely cold environments, thin stacking, and large capacity.

From cars to phones to glasses, is semi - solid the future?

In the past year, the "practical performance" of silicon - carbon anode technology has been quite well - verified. All major mobile phone brands have introduced silicon - carbon anode batteries in their models, achieving a "collective upgrade" of mobile phone battery capacities. From this perspective, silicon - carbon anode battery technology has proven to the entire market that the new generation of high - energy - density materials can indeed be implemented in the extremely compressed internal space of mobile phones.

In contrast, the popularization curve of semi - solid batteries is significantly steeper. Vivo is currently the only manufacturer that has continuously used semi - solid batteries in mass - produced mobile phones - from the first - generation technology in the X Fold3 Pro to the second - generation upgrade in this year's X Fold5. Continuously advancing this technological path is not easy. However, at the same time, the potential and value of semi - solid batteries have become even clearer.

vivo X Fold5, Image/ Leikeji

Both the silicon - carbon anode and semi - solid battery technologies have a common "past" - they both evolved from new - energy vehicle batteries.

In the field of electric vehicles, the demand for increasing energy density is straightforward: to travel farther, more electricity needs to be stored. Players such as CATL, BYD, and Tesla started researching silicon - based anodes many years ago and later also began to experiment with introducing solid components into the battery cell structure. Although consumer electronics products are much smaller in size, the core problems are the same: limited space, increasing power consumption, and persistent range anxiety.

Therefore, when the mobile phone and electric vehicle industries "reach the same goal through different paths" in the face of battery bottlenecks, the spread of new technologies becomes a natural result. However, the mobile phone is not the end of this spread. If we broaden our perspective, we will find that more and more emerging product categories - such as smart glasses, headphones, and other wearable devices - are also moving towards the path of "high - performance + small size", which is exactly the scenario where traditional liquid lithium batteries are the least adaptable.

Take smart glasses as an example. They not only need to control weight but also support multiple high - power - consumption components such as AI computing, Bluetooth connection, and camera modules. The internal space of glasses is extremely limited, and the wearing scenario involves facial skin and periorbital nerves, which places higher safety requirements than mobile phones.

Thunderbird V3 AI - enabled shooting glasses, Image/ Leikeji

In this context, although the silicon - carbon anode provides a significant leap in energy density, due to factors such as volume expansion and cyclic stress, its application in extremely small - sized products still faces certain thresholds. Semi - solid batteries, on the other hand, have advantages such as high safety, stable structure, and resistance to high and low temperatures. They also have higher adaptability in terms of mild flexibility and irregular - shaped encapsulation.

In other words, they are more suitable for products like smart glasses than silicon - carbon anode battery technology. This trend is already emerging. When Leikeji communicated with several smart glasses manufacturers, they all mentioned the challenges in battery life and batteries. Manufacturers generally regard semi - solid batteries as "the key" and even said that they may be seen in products to be launched as early as next year.

All of this points to a possibility: semi - solid batteries may not only be the next "version answer" after mobile phones but also the new starting point for the upgrade of all consumer electronics products. Just as battery technology has penetrated from cars to mobile phones, in the future, it will continue to penetrate from mobile phones to smaller and more precise product forms.

Conclusion

If the chip determines what a device can do, then the battery determines how long it can do it and to what extent. In the past few years, we have witnessed the leapfrog development of mobile phone imaging, screens, and AI computing capabilities, but battery life has always seemed like an overlooked variable, constantly hovering between "sufficient" and "insufficient".

However, the gradual maturity and mass production of silicon - carbon anode and semi - solid battery technologies are redefining this variable. Whether for smart glasses, AI headphones, or other computing terminals, these changes in batteries are expected to bring significant improvements in user experience. For users, it also means that personal devices will become more long - lasting, reliable, and in line with the rhythm of life.

This article is from the WeChat official account "Leikeji", author: Leikeji. Republished by 36Kr with permission.