In January, Zhiji Auto, a high-end intelligent pure electric vehicle brand jointly created by SAIC Motor, Zhangjiang Hi-Tech Park and Alibaba Group, launched two mass-produced prototype vehicles for the first time globally.
The biggest highlight of this high-end electric vehicle is that it will be equipped with a battery developed jointly by SAIC and CATL using "silicon-doped lithium-ion battery cell" technology, with a maximum range of over 1,000 kilometers. The new vehicle is expected to achieve mass production and delivery in the fourth quarter of 2021.
What is "silicon-doped lithium supplementation"? Why can this technology support an electric vehicle's range of over 1000 kilometers?
By definition, the "silicon-doped lithium-ion" technology launched by Zhiyi Auto is not fundamentally different from the "inorganic pre-lithiated carbon silicon anode" used in NIO's solid-state batteries. In essence, both increase the silicon content in the anode while increasing the lithium content to compensate for the increased lithium loss during charging and discharging caused by the increased silicon content.
Regarding "silicon doping," it actually involves adding silicon to the negative electrode material. The reason is that the limiting factor for the energy density of power batteries is no longer the positive electrode material, because with the application of positive electrode materials such as NCM and NCA, the energy density of positive electrode materials has been greatly improved.
In contrast, the specific capacity of the more commercially available anode material, which uses carbon (graphite) as the main material, is already close to its limit. In order to meet the requirements of high driving range for new energy vehicles and improve the overall energy density of batteries, silicon materials have emerged and are considered an ideal alternative to carbon anode materials.
Data shows that silicon materials have a maximum specific capacity of 4200 mAh/g, far exceeding the 372 mAh/g of carbon materials, making it the material with the highest theoretical specific capacity known for use as an anode. Furthermore, silicon is advantageous due to its low lithium intercalation potential, low atomic mass, high energy density, environmental friendliness, abundant reserves, and low cost.
Regarding "lithiation replenishment," its necessity is built upon the foundation of "silicon doping." To address the capacity loss caused by the SEI film in carbon anode materials, the current common method is pre-lithiation of the anode material. Simply put, pre-lithiation replenishes lithium to the electrode material in advance, offsetting the irreversible lithium loss caused by the formation of the SEI film, thereby improving the battery's overall capacity and energy density.
By "doping silicon with lithium", the energy density of the power battery can be increased and the cycle life can be improved, thus enabling electric vehicles to have a range of more than 1,000 kilometers.
However, the preparation process of silicon-based anodes is complex, lacks standardized processes, and has high technical barriers. The main difficulty lies in the nano-sizing of silicon materials and the preparation process of silicon-carbon composite materials, which are core technologies for each company.
