Ni-MH battery packs

　　High Energy Density Lithium Battery Technology

　　High energy density lithium battery technology is currently a research hotspot and key development direction in the field of lithium batteries. The following are some related technologies:

　　1. Improvement of positive electrode material :

　　-High nickel ternary materials: High nickel ternary materials (such as NCM811, NCA, etc.) have high specific capacity and high voltage platform, which can significantly improve the energy density of lithium batteries. By optimizing the synthesis process of materials, improving their crystal structure and surface properties, the performance stability and safety of high nickel ternary materials can be enhanced. For example, high nickel ternary materials with uniform particle size and high crystallinity can be prepared by coprecipitation, sol gel and other synthesis methods; By means of surface coating, doping, and other methods, the cyclic performance and thermal stability of materials can be improved.

　　-Rich lithium manganese based materials: Rich lithium manganese based materials have ultra-high specific capacity, theoretically reaching over 300mAh/g, making them a very promising high-energy density positive electrode material. However, rich lithium manganese based materials have problems such as low initial charge discharge efficiency and voltage decay. The current research focus is on improving the performance of lithium rich manganese based materials by optimizing their composition, structure, and preparation processes. For example, methods such as element doping and surface modification can improve the electrochemical performance of lithium rich manganese based materials; By compounding with other materials such as ternary materials, carbon materials, etc., the conductivity and stability of the material can be improved.

　　2. Innovation in Negative Electrode Materials :

　　-Silicon based negative electrode material: The theoretical specific capacity of silicon is as high as 4200mAh/g, far higher than traditional graphite negative electrode materials (372mAh/g), making it an ideal negative electrode material for improving the energy density of lithium batteries. However, silicon undergoes significant volume expansion (about 300%) during the charging and discharging process, leading to electrode structure damage and affecting the cycling performance of the battery. To solve this problem, researchers have adopted various methods, such as preparing silicon nanowires, silicon carbon composite materials, silicon oxygen composite materials, etc. These materials can effectively alleviate the volume expansion of silicon and improve the cycling performance and stability of negative electrode materials. For example, silicon nanowires have one-dimensional nanostructures that can provide space for the volume expansion of silicon while improving the conductivity of the material; Silicon carbon composite materials combine silicon with carbon materials, utilizing the good conductivity and flexibility of carbon to suppress the volume expansion of silicon.

　　-Metal lithium negative electrode material: Metal lithium is an ideal negative electrode material with the highest theoretical specific capacity (3860mAh/g) and the lowest electrode potential. However, metallic lithium is prone to forming lithium dendrites during the charging and discharging process, leading to battery short circuits and posing safety hazards. At present, researchers use methods such as solid-state electrolytes, three-dimensional current collectors, and surface modifications to suppress the growth of lithium dendrites and improve the safety and cycling performance of metal lithium negative electrode materials. For example, solid electrolytes can prevent the formation of lithium dendrites in liquid electrolytes, improving the safety of batteries; Three dimensional current collectors can provide a uniform electric field for the deposition of metallic lithium and suppress the growth of lithium dendrites.

　　3. Optimization of Electrolytes:

　　-Solid state electrolyte: Solid state electrolyte has high safety, good mechanical strength, and high ion conductivity, and is one of the key technologies for achieving high energy density lithium batteries. At present, researchers are developing various types of solid electrolytes, such as polymer solid electrolytes, inorganic solid electrolytes, composite solid electrolytes, etc. Polymer solid electrolytes have good flexibility and processability, but low ionic conductivity; Inorganic solid electrolytes have high ionic conductivity and mechanical strength, but are brittle; Composite solid electrolytes combine the advantages of polymers and inorganic solid electrolytes, and have good comprehensive performance. For example, combining polymers with inorganic solid electrolytes can improve the ion conductivity and mechanical strength of solid electrolytes while maintaining good flexibility.

　　-High voltage electrolyte: In order to improve the energy density of lithium batteries, it is necessary to increase the operating voltage of the battery. However, traditional electrolytes can decompose at high voltages, affecting the performance and safety of batteries. Therefore, developing high-voltage electrolytes is an important way to improve the energy density of lithium batteries. High voltage electrolytes require high oxidation stability, good conductivity, and low viscosity. At present, researchers are improving the high-voltage performance of electrolytes by using new solvents, additives, and other methods. For example, using fluorinated solvents, sulfone solvents, and other solvents with high oxidation stability can improve the high pressure resistance of electrolytes; Adding additives such as ethylene carbonate (VC) and fluorinated ethylene carbonate (FEC) can form a stable SEI film on the electrode surface, improving the cycling performance and safety of the battery.

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