Source: Yuanchuan Technology Review Author: He Luheng At the beginning of this year, after releasing the 14 Ultra and introducing its imaging function for more than an hour, another protagonist, "Jinshajiang Battery," arrived late. Xiaomi 14 Ultra's super-large camera module is 20% larger than the previous generation, but the whole machine is 3g lighter and the battery life is improved by 17%. [1] The hero behind the scenes is "Jinshajiang Battery." In recent years, domestic mobile phone brands, such as vivo's "Blue Sea Battery," oneplus's "Glacier Battery," honor's "Qinghai Lake Battery," and Xiaomi's "Jinshajiang Battery," have suddenly risen to prominence. Behind these famous mountains and rivers is actually the underlying technology from the next new energy ships-silicon-carbon batteries. Before the emergence of "Dongting Lake Battery" and "Qinghai Lake Battery," it may be necessary to clarify what silicon-carbon batteries are and what technology can make both the new energy vehicle and consumer electronics industries flock to them.
Source: Yuanchuan Technology Review Author: He Luheng The weather is good today The weather is good today.

Please use your Futubull account to access the feature.$XIAOMI-W (01810.HK)$After releasing the 14 Ultra and introducing its imaging function for more than an hour at the beginning of this year, another protagonist, "Jinshajiang Battery," arrived late.

Xiaomi 14 Ultra's super-large camera module is 20% larger than the previous generation, but the whole machine is 3g lighter and the battery life is improved by 17%. The hero behind the scenes is "Jinshajiang Battery."

From domestic mobile phone brands such as vivo's "Blue Sea Battery," oneplus's "Glacier Battery," honor's "Qinghai Lake Battery," and Xiaomi's "Jinshajiang Battery," suddenly gaining popularity.

Behind these famous mountains and rivers is actually the underlying technology from the next new energy ships-silicon-carbon batteries.

Before domestic mobile phone manufacturers named their products after Chinese topography, Tesla's self-produced 2170/4680 batteries and CATL's Kirin batteries both applied silicon-carbon battery solutions.

Before the emergence of "Dongting Lake Battery" and "Qinghai Lake Battery," it may be necessary to clarify what silicon-carbon batteries are and what technology can make both the new energy vehicle and consumer electronics industries flock to them.

The "escape" of electrons.

Before understanding silicon-carbon batteries, it is first necessary to understand the principle of battery life.

Whether it is a mobile phone or a car, the essence of battery charging is the "escape" of electrons: the atomic nucleus carries a positive charge, the electron carries a negative charge, the two sides have the same number, and the positive and negative charges of the atoms are balanced. However, under certain conditions (such as voltage application, electrolysis), electrons will break away from atoms and generate current.

The work of the battery can be simply understood as creating conditions for electrons to break away from atoms, flowing into the designed circuit to form a current, and delivering power to electronic devices. The two major components that determine the battery life are the cathode and the anode.

The cathode is the "cell" that "imprisons" electrons, and is generally a metallic compound. Due to its negligence, the lithium element makes it easier for electrons to escape and has become the choice of most batteries, which is what we usually call "lithium batteries."

The anode is the "safe house" for electrons: after the electrons escape, they go to the anode along the circuit, and in this process, they will generate current to supply the electronic device. At this time, the lithium ions that discovered the electron escape will quickly rush through the electrolyte and head towards the anode to catch the electron and maintain the positive and negative balance.

The charging and discharging of batteries is an infinite cycle of electrons constantly breaking free and lithium ions constantly capturing electrons.

The core of battery life is, on the one hand, the cathode playing the role of prison can provide how much organization and accommodate lithium in charge, and on the other hand, the anode playing the role of a safe house can provide how many beds to accommodate escaping electrons.

In recent years, battery manufacturers' technological investments have been mostly on cathode materials. It can be understood that after determining the main position of lithium elements, what materials to use as auxiliary police to cooperate with lithium ions to capture electrons.

"Ternary lithium batteries" are batteries with three kinds of lithium element compounds as cathode materials. For example, NCM811 is a mixture of nickel (N) lithium, cobalt (C) lithium, and manganese (M) lithium, and 811 represents the molar ratio of the three elements. NCM522 is another ratio.

"LFP batteries" are batteries with iron phosphate as the cathode material. Although its ability to capture electrons is not as good as ternary lithium batteries, it is cheaper because it does not require rare metals.

In the past decade, battery factories have been focusing on the cathode, from "ternary lithium vs. lithium iron phosphate" to "cobalt-containing vs. cobalt-free" and "low-nickel vs. high-nickel". The energy density has continuously improved, and the driving range of electric vehicles has increased from 300km to over 700km. In recent years, many battery factories have turned their attention to the anode, and are researching and developing construction plans for the transformation of safe rooms.

Carbon has always been the mainstream choice for the anode material, and graphite is the side branch brother (isomer) of carbon. Another side branch brother we are more familiar with is diamond.

In the face of the pressure to increase the driving range, engineers opened the periodic table of elements and found that silicon was just below carbon, belonging to the "same family brother", meaning that the two have similar chemical properties and are both suitable for the "sanctuary" of lithium electrons. Therefore, the so-called "silicon-carbon battery" is a battery that uses silicon and carbon as the anode material, but how much silicon to add into carbon is an art that repeatedly jumps in the shackles of cost and technology.

Therefore, the so-called "silicon-carbon battery" is a battery that uses silicon and carbon as the anode material. However, how much silicon should be added to carbon is an art that repeatedly jumps in the shackles of cost and technology.

$Tesla (TSLA.US)$

After years of investment, the progress of cathode materials has gradually touched the ceiling, unable to release more employed positions. Therefore, many battery factories have turned their attention to the anode, and are researching and developing construction plans for the transformation of safe rooms. The "fine lines" in the unclear background image announced on the official website in Battery Day are actually silicon nanowires, a new anode technology that has accumulated a lot of momentum in the industry in the past few years.

Musk early realized that the cathode mainly composed of carbon would become a barrier to upgrading energy density. Therefore, Tesla has already turned its attention to the anode. When Model S was launched in 2015, Tesla equipped one of them with the "ludicrous mode" and claimed that it only took 2.8 seconds to accelerate to 100 kilometers per hour. However, this more powerful model had a 6% increase in driving range compared to other models. Musk secretly boasted on Twitter that he added some "spices" to the battery anode-which is silicon.

Compared with carbon elements, silicon elements have the advantage of larger space, which is convenient for lithium ions to completely capture electrons:

Six carbon atoms can accommodate one lithium ion, while one silicon atom can accommodate four lithium ions. Theoretically, the ability of silicon material to "capture" lithium ions is more than 10 times that of carbon material [3], making it the best choice to replace graphite material as the anode material.

From the perspective of materials, directly replacing carbon with silicon as the battery anode material can bring an explosive improvement in driving range.

However, silicon has a fatal weakness-its volume expands severely during charging and discharging, and the expansion rate of lithium-ion entering the silicon can reach as high as 300% (compared to a 16% expansion rate of carbon)[4], and it contracts when lithium-ion exits, which results in the material breaking and powdery after expansion and contraction. In practical use, it will cause the battery to decay quickly and the number of charging cycles is extremely low.

According to international standards, power batteries must be able to cycle more than 1000 times, which temporarily seals the road of pure silicon negative electrodes.

Tesla's solution is to draw on the strengths and mix a small amount of silicon into the graphite negative electrode, which can improve battery life and ensure cycle times. The Panasonic 2170 battery negative electrode used in the Model S contains 5% silicon.

Materials scientists have broken through along another path by changing the presentation of silicon atoms.

Because the smaller the particle size, the less likely it is to break, so if silicon materials can be reduced to tens of nanometers in size (carbon materials are generally hundreds of nanometers or even microns), it can perfectly avoid silicon's chemical weaknesses. This is the extremely radical technology route of 'silicon nanowires' introduced at Tesla's 2020 Battery Day.

According to Tesla's idea, the size of silicon materials can be reduced to 10nm, and they can be coated externally with silicon dioxide, which is 100% silicon material[3], without a drop of carbon, foolproof.

However, four years have passed, and 'silicon nanowires' still lies quietly in Musk's pancake army. It may be that Musk's pancakes have drawn too much, so everyone has forgotten about this pancake.

Tesla's technological development philosophy has always been 'if it's not forbidden by physics textbooks, it's possible'. Compared with spending billions of dollars to challenge the laws of physics, most battery factories will choose a more 'pragmatic' approach - adding some silicon to the graphite negative electrode, which has led to silicon-carbon battery sets appearing in various forms.

However, in the application of electric vehicles, there is a cost issue: on the one hand, the existing battery technology is basically sufficient for fast charging piles and the range is adequate; on the other hand, even if the range needs to be increased, it may be more cost-effective to install a larger battery pack than to use methods like silicon-carbon negative electrodes to improve 'unit energy density'.

But for smartphones, adding silicon to the negative electrode has become urgent.

High-end smartphones don't have to make a choice.

In 2015, China's smartphone shipments fell below 10% for the first time[5], the high-growth period ended, and the inventory game era began.

Thereafter, 'material stacking' became the main theme of smartphone iterations. Major smartphone brands spared no expense in upgrading hardware such as cameras and processors, while high-end product lines were the culmination of 'material stacking', with smoke everywhere. But the biggest impact on the smartphone experience is actually the battery.

PhoneArena's 2015 survey found that 64% of consumers were most concerned about improving battery life[6].

Compared with electric vehicles, the reason why smartphone manufacturers are pursuing silicon-carbon batteries is an important one: internal space inside the phone is extremely valuable.

In the past few years, with the popularity of functions such as triple cameras and facial recognition, the area of the lens module and face recognition module inside the phone has increased rapidly, eroding the already scarce internal space. The battery capacity of the iPhone 15 Pro is actually lower than the iPhone 15, because an extra camera forces the battery to compromise for the larger lens module.

Smartphones cannot have larger battery packs like electric vehicles, so the silicon-carbon battery, which can increase 'unit energy density', has entered the vision of smartphone manufacturers.

In 2019, Xiaomi first used a nano-silicon battery on the concept phone MIX Alpha. Due to the attractive surround screen design of MIX Alpha, everyone paid little attention to the rather radical technical proposal of the nano-silicon battery.

Two years later, Xiaomi 11 Ultra replaced nano silicon with silicon oxide in the negative electrode and brought silicon carbon batteries into mass production models for the first time. Although the energy density improvement effect of silicon oxide is not as good as that of nano silicon, it is better in terms of number of cycles and relatively controllable cost. Due to the contribution of silicon carbon negative electrode, Xiaomi 11 Ultra enters the "5000mAh Club". At the same time, the volume of the battery module is almost unchanged and the thickness of the body is maintained in the comfortable zone of 8.38mm.

Because of the contribution of silicon carbon negative electrode, Xiaomi 11 Ultra enters the "5000mAh Club". At the same time, the volume of the battery module is almost unchanged and the thickness of the body is maintained in the comfortable zone of 8.38mm.

Since then, silicon carbon negative electrode has become a standard configuration of various high-end product lines. The emergence of folding screen mobile phones has added fuel to the silicon carbon battery.

The screen is the most power-consuming component in mobile phones. Most "big folding" mobile phones essentially increase the screen area three times, becoming real "power monsters". Samsung Z Fold 3 was criticized as "full power before going to bed and 3% after getting up". On the other hand, due to the form of "folding", the whole machine has higher requirements for lightness and thinness, and higher requirements for the unit energy density of the battery.

With the high-end mobile phones of "extreme stacking" and the "both-need" folding screen, the battery life of mobile phones has reached a new height of 6000mAh. In comparison, the capacity of iPhone 15, which has only 3349mAh, is somewhat embarrassing.

A few years ago, in an interview, Apple executive Greg Joswiak made the confusing statement "iOS+3000mAh > 5000mAh". Go next door to Tesla now and learn something, maybe it's not too late.

Reference material

[1] Xiaomi 14 Ultra Heavy Release | Professional Image Flagship, Making Real Layers, Lei Jun

[2] Tesla's Silicon Nanowire Battery Negative Material, What are the Highlights? Huabao Securities

[3] Product Introduction, Amprius official website

[4] Overcoming "Expansion", Silicon-Carbon Negative Electrode Battery Has Small Body and Large Energy, Science Popularization Times

[5] 2015 China Smartphone Annual Report, Strategy Analytics

[6] Going into 2016, battery life is still the number one concern with our readers, Phone Arena

Editor/Somer