Analysis of the technical bottleneck of 3.7v 2200mah 18650 lithium battery and the technical route of lithium battery

　　Analysis of the technical bottleneck of 3.7v 2200mah 18650 lithium battery and the technical route of lithium battery. The development of electric vehicles requires better batteries. The specific energy, lifespan, safety and price of power lithium batteries are crucial to the development of pure electric vehicles. For now, lithium battery pack technology is relatively mature, and bottlenecks are inevitable. How to break the bottleneck and achieve further development of battery technology is the topic discussed in this article.

　　Technical bottleneck of 3.7v 2200mah 18650 lithium battery

　　1. Short range: With the continuous development of technology, the range of electric vehicles using lithium batteries as power source has increased from less than 100 kilometers to about 300 kilometers, and the range of a single model has exceeded 400 kilometers. However, there is still a certain distance compared with the 500 kilometers of mainstream trekking journey of fuel vehicles.

　　2. Slow charging speed: Compared with the short journey, the slow charging of lithium battery packs is a greater restriction for electric vehicles. At normal speed, it takes 4 to 8 hours for an electric vehicle's power lithium battery to be fully charged. There are also quick-rechargeable lithium batteries that can be fully charged within 1 to 2 hours, but their negative effects are huge. The lifespan will be reduced to 1/3 of the original, and the battery performance will be significantly reduced. Fuel vehicles do not have these problems. The refueling time does not exceed 5 minutes, and safety and stability can be guaranteed.

　　3. Safety functions need to be improved: Since the birth of lithium battery packs, safety issues have always puzzled consumers. From mobile phones and laptops to now electric vehicles, safety accidents continue to occur.

　　Lithium battery material technology

　　●Positive and negative electrode materials

　　There are very rich cathode and cathode material systems for lithium batteries. At present, research on cathode materials such as lithium cobalt oxide, lithium manganate, lithium iron phosphate, and lithium nickel cobalt manganese has become mature. The specific capacity of lithium cobalt oxide material is 200-210mA·h/g. Its material true density and electrode plate compacted density are the highest among existing cathode materials. The charging voltage of commercial lithium cobalt oxide/graphite system can be increased by 4.40V. It can already meet the demand for high-volume energy-density soft-pack batteries for smartphones and tablets. Lithium manganate has low raw material cost, simple production process, high thermal stability, good overcharge resistance, high discharge voltage platform and high safety. It is suitable as a low-cost battery for light electric vehicles, but it has problems such as relatively low theoretical capacity, and the possible dissolution of manganese during the cycle, which affects the battery life in high-temperature environments.

　　●Anode material

　　Anode materials that can be used in power batteries include graphite, hard/soft carbon, and alloy materials. Graphite is currently a widely used anode material, and its reversible capacity can reach 360mAh/g. Amorphous hard carbon or soft carbon can meet the needs of batteries for higher rate and lower temperature applications and is beginning to be used, but it is mainly mixed with graphite. However, due to the volume expansion caused by lithium being embedded in silicon, the problem of reduced cycle life during actual use needs to be further solved.

　　●Electrolyte

　　The electrolyte of lithium-ion batteries is generally a mixture of cyclic carbonate with high dielectric constant and linear carbonate with low dielectric constant. Generally speaking, the electrolyte of lithium batteries should meet the requirements of high ionic conductivity, low electronic conductivity, wide electrochemical window, and good thermal stability. Lithium hexafluorophosphate and other new lithium salts, solvent purification, electrolyte preparation, and functional additive technology continue to advance. The current development direction is to further increase its operating voltage and improve the high and low temperature performance of the battery. Safe ionic liquid electrolytes and solid electrolytes are under development.

　　Lithium battery technology route analysis

　　Currently, there are four main technical routes in terms of power sources for transportation: lithium-ion batteries, hydrogen fuel cells, supercapacitors and aluminum-air batteries. Among them, lithium-ion batteries, supercapacitors and hydrogen fuel cells are widely used, while aluminum-air batteries are still in the laboratory research stage. In terms of energy supply, lithium-ion batteries and supercapacitors are suitable for pure electric vehicles, but they require external charging, while hydrogen fuel cell vehicles require external hydrogen filling, and aluminum-air batteries require replenishing aluminum plates and electrolytes.

　　There are many technical routes for lithium batteries, and energy storage pays more attention to safety and long-term cost. Compared with power lithium batteries, lithium batteries for energy storage have looser requirements on energy density, but have higher requirements on safety, cycle life and cost. From this perspective, lithium iron phosphate batteries are a more suitable technical route for energy storage among various types of lithium-ion batteries at this stage. Most of the lithium battery energy storage projects that have been built currently also use this technology. In addition, lithium titanate batteries have also received widespread attention due to their ultra-long cycle life. As technology costs decrease in the future, they are expected to achieve large-scale applications in the energy storage field. The main advantage of ternary batteries is their high energy density, but their cycle life and safety are relatively limited, making them more suitable for use as power batteries.

　　For a long time in the future, lithium battery packs will still be the most suitable electric vehicle batteries, including lithium manganate cathode materials, ternary system cathode materials, lithium iron phosphate cathode materials, composite carbon anode materials, ceramic coating separators, electrolyte salts The development of functional electrolyte technology supports the progress of battery technology and industrial development. As battery system technology advances in application, safety and reliability will be further improved in the coming years.

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