During the pre-launch hype period for the Xiaomi 11 Pro/Xiaomi 11 Ultra, Xiaomi officially released promotional materials stating that both phones would use a brand-new silicon-oxygen anode battery. This left many netizens confused: "Is it too hard to follow the latest news these days? Our knowledge can't keep up with Xiaomi's rapid pace of technological advancements!" In this article, we'll provide a comprehensive analysis of what exactly this silicon-oxygen anode battery technology used in Xiaomi's flagship models is.
01 Silicon-oxygen anode batteries cannot be considered a new technology.
First, silicon-oxygen anode batteries are not exactly a new technology. This technology is already used in electric vehicle power systems; for example, NIO's recent announcement of solid-state battery technology innovations included the use of silicon-carbon anode technology.
There are three main ways to increase battery capacity: replacing the positive electrode material with one that improves energy storage density, adopting new battery separator technology, and replacing the negative electrode material with one that improves energy storage density. Currently, the most important innovation in rechargeable battery positive electrode materials is graphene, which is used to improve charging speed but cannot effectively increase energy density. Modifications to battery separator technology mainly focus on making the separator thinner and thinner; however, excessively thin separators can easily pose a safety hazard. Therefore, replacing the negative electrode material with a completely new one is the most cost-effective way to increase battery capacity.
Using silicon-carbon anode materials can effectively improve the energy storage density of batteries. This is mainly because traditional battery anode materials are carbon materials. Carbon materials, as battery anodes, are characterized by a small coefficient of expansion (about 10%) and a low energy density (theoretical specific capacity 372 mAh/g). Although they are ideal battery anode materials, the energy density of batteries of the same volume is relatively low. Silicon materials have a theoretical specific capacity of about 4200 mAh/g, but a high coefficient of expansion (about 300%). In contrast, silicon oxide has a theoretical specific capacity of 2615 mAh/g and a coefficient of expansion of about 160%. In simpler terms, silicon-oxygen anode materials achieve a balance between battery energy density and coefficient of expansion.
Using silicon-oxygen anode batteries significantly improves smartphone performance. This means that batteries of the same size can have a larger capacity, or the phone can be made thinner and lighter by controlling the battery capacity. The Xiaomi 11 Pro/Xiaomi 11 Ultra chose the former, achieving a 5000mAh battery to ensure long battery life.
Therefore, silicon-oxygen anode batteries are not a new technology. However, mass production of silicon-oxygen anode materials is not an easy task.
02 Silicon-oxygen anode batteries are difficult to mass-produce
In the previous section, we compared the theoretical specific capacity and expansion coefficient of carbon, silicon, and silicon oxide as battery anode materials. We found that carbon materials have the lowest expansion coefficient at 10%; while silicon anode batteries, although having high energy density, are prone to bulging during charging. The safety ranking of the three battery anode materials is: carbon > silicon > silicon oxide. To summarize the problems with silicon oxide anode batteries: the most important issue is their tendency to expand during charging, which is unsafe; secondly, they have short battery life and a rapid decrease in energy density.
The key technical challenge of silicon-oxygen anode batteries lies in controlling the expansion of the anode material. This requires breakthroughs in encapsulation materials, processing techniques, and adhesives, all of which affect the final cost of the entire battery. Furthermore, to ensure safer charging, Xiaomi opted for 67W fast charging instead of 120W to guarantee charging safety.
Summarize
Finally, let's summarize the advantages and disadvantages of silicon-oxygen anode batteries. Advantages: High capacity per unit volume, allowing for larger battery capacity in the same battery volume in mobile phones; Disadvantages: High coefficient of thermal expansion of the anode material, requiring careful control of charging safety.
Applying electric vehicle technology like silicon-oxygen anode batteries to smartphones shows that Xiaomi has put considerable effort into it. It's important to note that electric vehicle batteries and mobile phone batteries are two distinct technologies, so this cannot be considered a direct transfer of technology. While silicon-oxygen anode batteries aren't exactly new technology, they undeniably improve the user experience of smartphone batteries. Although major breakthroughs in battery technology are currently unlikely, we still look forward to a revolution in battery technology as soon as possible.
