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Recently, a research team led by Professor He Xiangming and Professor Wang Li of Tsinghua University successfully synthesized phosphor carbon anode materials for the first time, and won a multinational core invention patent. Phosphorus carbon anode material has injected new impetus for the development of sodium-ion batteries with its excellent performance parameters.
With an embedded sodium specific capacity of up to 1200mAh/g, four times that of conventional hard carbon anode materials, this breakthrough is expected to increase the weight energy density of sodium-ion batteries to 180Wh/kg and beyond, paving the way for lighter and more efficient energy storage solutions.
The bottleneck of sodium electricity development
Limited by the scarcity of mineral resources, the price of lithium products has continued to rise in recent years, resulting in power batteries based on elemental lithium, and the price has also skyrocketed. The battery material system that does not contain lithium, such as sodium-ion batteries, has attracted more and more attention from the industry.
Sodium-ion batteries mainly use hard carbon material as the negative electrode of the battery, hard carbon due to its low gram capacity and low real density characteristics, can not be processed into high capacity density electrodes, become the main bottleneck restricting the energy density of sodium-ion batteries to improve the pace of promotion and application of sodium-ion batteries.
The development of new energy vehicles (NEVs) is a strategic plan for China's automobile industry to overtake the developed countries on the curve, and mileage anxiety is the main challenge in its application. The existing technical solutions of various car companies and battery companies mainly improve the mass energy density, and the space in the car is actually more important to the volume energy density of the power battery.
The battery pack consists of a large number of individual cells connected by a circuit, and its energy density depends on the characteristics of the individual and the integration efficiency. In recent years, new concepts such as blade battery, magazine batteries and chocolate batteries have improved the volume energy density of battery packs by improving the space utilization of battery integration, and although the improvement is limited, it is still conducive to the technological development of electric vehicles.
Through the application of new materials to achieve battery system innovation, the specific energy of the battery can be significantly increased. The industry urgently needs more innovative new material systems to solve this problem.
Why does sodium ion battery use phosphorus carbon as a negative electrode material
The energy density of phosphor carbon is 25% higher than that of hard carbon, and the full battery energy density can reach 200 Wh/kg. This feature significantly increases the energy storage capacity of the battery, making it more competitive in electric vehicles and other energy storage applications. Phosphorus carbon fast charging speed is 2-3 times that of hard carbon, and stable.
Phosphorus carbon gram capacity can exceed 1200 mAh/g, which is more than four times that of hard carbon, with better charge transport characteristics and lower electrochemical impedance. In addition, the charging stability of phosphorus carbon is also excellent, and it can maintain good cycle battery performance at high charging rates. The first effect of phosphorus carbon can reach more than 90%.
The post-production cost of large-scale phosphorus carbon is less than 30,000 yuan/ton, compared to the cost of a single use of hard carbon materials is about 50,000 yuan/ton. When 20% phosphorus carbon is added to the battery, not only the energy density is increased by about 10%, but the overall cost can be reduced by 49%, significantly improving the economy.
Why does sodium ion battery not use silicon carbon?
Crystalline silicon: crystalline silicon has almost no reaction with sodium, and its high sodium-silicon alloy formation energy and sodium ion diffusion barrier in the silicon lattice make its activity in the process of sodium ion intercalation very low. The stability and structural integrity of crystalline silicon prevents it from embedding sodium ions effectively, which limits its feasibility in sodium-ion battery applications.
Amorphous silicon: Amorphous silicon has a large number of defects inside, these defects provide sodium ion adsorption sites, theoretically capable of forming NaSi compounds, theoretical capacity up to 954 mAh/g. However, the effective capacity in actual tests is often much lower than 40 mAh/g, reflecting the deficiency of the material in the dynamic behavior of sodium ions. Although amorphous silicon has certain advantages in structure, its performance in electrochemical activities has not met expectations, resulting in its application potential has not been fully developed.
Expanded silicon: Expanded silicon exhibits good Na-Si interaction and can provide appropriate lattice space for the intercalation of sodium ions. However, in order to achieve the combination with sodium, the original crystal structure of silicon is destroyed, resulting in a decrease in the mechanical strength and stability of the material. This structural change makes the expanded silicon show fatigue and performance decline in a long cycle, and it is difficult to maintain long-term electrochemical performance.
The versatility of the material is also remarkable. It is not only suitable for sodium-ion batteries, but also plays an excellent performance in lithium-ion batteries. More importantly, phosphorus carbon anode material can be used alone, but also can be mixed with other materials such as graphite, hard carbon, which not only broadens its application range, but also breaks the limitation that silicon carbon anode materials must be mixed with graphite, providing greater flexibility and innovation space for battery design. With the continuous progress of new energy technology and the growing market demand, the commercial application of phosphorus carbon anode materials has a broad prospect.
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Market application prospect
Around 2030, the world's major economies or large car companies have plans to completely ban the sale of fuel vehicles. At present, the penetration rate of the entire new energy vehicle is less than 20%, which means that there is a huge demand for power batteries at home and abroad in the next 10-20 years. Because it can save valuable space in the car, the power battery with phosphorus carbon as a negative electrode material with high volume energy density will be more popular in the end market, and the related new material technology will be applied in large numbers.
In addition, with the implementation of the national smart grid strategy, electrochemical energy storage power station due to the convenience of installation and construction, will develop rapidly on the power side, the power grid side and the user side, according to the prediction of relevant institutions, the compound growth rate of the annual installed capacity of electrochemical energy storage power station will reach more than 50%, and the total installed capacity is expected to exceed the demand for new energy vehicle batteries. As there is no shortage of scarce mineral resources, sodium-ion batteries will be quickly applied in related markets.
Conclusion
As lithium becomes increasingly scarce, sodium-ion batteries are becoming increasingly important as an emerging and sustainable energy storage solution. Compared with traditional hard carbon materials, phosphor carbon materials will play a key role in power batteries and energy storage systems.
Its high volume energy density and good economics will make it occupy an important position in the market, and the battery type not only improves the performance of the battery, but also provides greater flexibility for the battery design, and promotes the development of new energy vehicles and electrochemical energy storage systems.
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