In the energy storage industry, a quiet revolution is taking place. Once, graphite, as the king of lithium battery anode materials, supported the operation of various electronic devices with its stable performance. However, with the rapid development of science and technology, especially the urgent need for long-range battery life of electric vehicles, and the continuous challenge of battery energy density by smart phones and AI devices, the theoretical specific capacity of graphite of 372mAh/g can no longer meet the market demand.
Why is It Necessary to Develop Silicon-Carbon Anode
At this time, silicon, an element with abundant reserves in the earth’s crust, has become a new research object in the eyes of scientists with its theoretical capacity of up to 4200mAh/g. The theoretical gram capacity of silicon anode is 10 times that of graphite. The cruising range is one of the biggest pain points in the development of new energy vehicles, and energy density is the most critical factor restricting the cruising range. Battery energy density is affected by the specific capacity of positive and negative electrodes. Improving the specific capacity of negative electrode materials on the basis of current positive electrode materials still makes a great contribution to improving the energy density of the entire battery.
From the structural point of view, the fast charging performance of silicon anode is better than that of graphite. When lithium-ion batteries are charged, lithium ions migrate to the negative electrode. In fact, the most important technical difficulty of fast charging cells is the embedding of lithium ions in the negative electrode. Silicon provides channels for lithium ion embedding and extraction from all directions, while graphite can only provide channels for lithium ion embedding and extraction from the layered end face direction, so the silicon negative electrode has better fast charging performance. Silicon negative electrode is safer than graphite. Silicon negative electrode avoids the problem of lithium dendrites that may appear in graphite negative electrode during charging, which further improves the safety during fast charging.
Innovative Technology of Silicon-Carbon Composite Materials
However, the characteristics of silicon are a headache: during the charging and discharging process, the volume of silicon will expand by 300%, and this drastic volume change often leads to the collapse of the electrode structure. In order to solve this problem, scientists began to explore the combination of silicon and carbon, and this combination quickly became a hot topic in the field of materials science.
Silicon-carbon composite materials embed silicon particles into the carbon matrix, which not only utilizes the high capacity characteristics of silicon, but also alleviates the volume expansion problem of silicon with the help of the flexibility and conductivity of carbon. Innovative technologies such as core-shell structure, yolk-shell design and porous silicon-carbon continue to emerge, allowing silicon-carbon composite materials to achieve significant breakthroughs in energy density and cycle stability.
Commercialization of Silicon-Carbon Anodes
From the laboratory to commercialization, the journey of silicon-carbon anodes is full of challenges and opportunities. The consumer electronics field took the lead in testing the waters, and many mobile phone manufacturers have successively launched smartphones equipped with silicon-carbon batteries, which not only greatly increased the battery capacity, but also became thinner and charged faster. In the field of power batteries, Tesla’s 4680 large cylindrical battery has pushed the application of silicon-carbon anodes to a new height, and the improvement in battery life has effectively alleviated the battery life anxiety of electric vehicles.
The application map of silicon-carbon batteries is still expanding. In the field of electric vehicles, it has become a new way to improve battery life. In the field of consumer electronics, it is a necessary condition for the era of thinness. In the field of energy storage and aerospace, it is a new way of energy revolution. The characteristics of high energy density, fast charging performance and long cycle life allow silicon-carbon batteries to show great potential in many fields.
Technical Difficulties of Silicon-Carbon Anode
However, the development of silicon-carbon anode is not smooth sailing. Three technical difficulties, such as expansion stress, first effect problem and cost, still lie ahead. Scientists are constantly overcoming these difficulties by developing self-healing materials, optimizing silicon/carbon ratio and innovating CVD process. Innovative concepts such as bionics and AI empowerment also provide new ideas for the future development of silicon-carbon anode.
When we use mobile phones, drive electric cars, wear AI glasses and other electronic products in our daily life, we may not realize the technological innovation behind these conveniences. The evolutionary history of silicon-carbon anode is a microcosm of human beings’ continuous pursuit and exploration of energy limits.
