What is the difference between the positive and negative materials of lithium batteries?

The negative electrode is mainly graphite, which is a kind of C, and the transition metal oxide used in the positive electrode, such as lithium cobalt oxide or lithium manganate, lithium iron phosphate, etc. The potential of the positive electrode is higher than that of the negative electrode, and the potential difference between the two constitutes the voltage of the battery. Lithium battery cathode material The cathode material is one of the key materials that determine the performance of lithium batteries, and is also an important source of lithium ions in the current commercial lithium batteries. Its performance and price have a greater impact on lithium batteries. Currently, the positive electrode materials that have been successfully developed and applied include lithium cobalt oxide, lithium iron phosphate, lithium manganate, ternary materials such as lithium nickel cobalt manganate (NCM) and lithium nickel cobalt aluminate (NCA). 1. Lithium cobalt oxide Lithium cobalt oxide is the first to be commercialized due to its simple processing technology and stable electrochemical performance. At the same time, because lithium cobalt oxide has the advantages of high working voltage, stable charging and discharging voltage, suitable for high current charging and discharging, high specific energy, and good cycle performance, it has important applications in the field of small rechargeable batteries. The disadvantage of lithium cobalt oxide cathode material is that it is expensive, and the actual specific capacity is only about 50% of its theoretical capacity of 274mAh/g; the cycle life of lithium cobalt oxide has reached 1,000 times, but it still needs to be further improved; in addition, lithium cobalt oxide The anti-overcharge performance is poor, and the specific capacity decreases rapidly at a higher charging voltage. 2. Ternary materials In recent years, the layered lithium-intercalating multiple transition metal composite cathode materials have developed rapidly, especially the new transition metal lithium-intercalating oxide composite materials containing three elements of cobalt, nickel and manganese. 3. Compared with lithium cobalt oxide and lithium nickel oxide, lithium manganate has the advantages of good safety, good overcharge resistance, abundant raw material manganese resources, low price and non-toxicity, and it is very promising. A cathode material. The disadvantage of using layered lithium manganate as a positive electrode material for lithium batteries is that although it has a high capacity, it is unstable at high temperatures, and is easy to transform into a spinel structure during charge and discharge, resulting in excessive capacity decay. 4. Lithium iron phosphate With the development of power lithium-ion batteries, most domestic manufacturers tend to use lithium iron phosphate materials. It is a new type of cathode material for lithium batteries. This type of material has the characteristics of high energy density, low price, excellent safety, etc., and is especially suitable for power lithium-ion batteries. Its appearance is a major breakthrough in lithium battery materials, and it has now become a hot spot for competing research in various countries. At present, lithium iron phosphate is considered to be the most promising cathode material for power lithium-ion batteries. Due to the high threshold of lithium iron phosphate processing technology, it is difficult for most manufacturers to guarantee the stability of their products during batch processing. Its disadvantage is that the resistivity is relatively large, and the utilization rate of electrode material is low. Therefore, the research work is mainly focused on solving the problem of its conductivity. In addition, the patent problem of lithium iron phosphate is also a problem to be solved in its industrial process. Anode materials for lithium batteries Important anode materials for lithium batteries include tin-based materials, lithium-based materials, lithium titanate, carbon nanomaterials, and graphene materials. The energy density of lithium battery anode materials is one of the important factors affecting the energy density of lithium batteries. 1. Carbon nanotube Carbon nanotube is a kind of carbon material with graphitized structure. It has excellent electrical conductivity. At the same time, because of its small depth and short stroke when releasing lithium, it is used as a negative electrode material for polarization during high-rate charging and discharging. Smaller, can improve the battery's high-rate charge and discharge performance. However, when carbon nanotubes are directly used as anode materials for lithium batteries, there will be problems such as high irreversible capacity, voltage lag, and unobvious discharge platform. For example, Ng and others have prepared single-walled carbon nanotubes by simple filtration and used them directly as negative electrode materials. The first discharge capacity is 1700mAh/g, and the reversible capacity is only 400mAh/g. 2. Graphene In 2004, researchers at the University of Manchester in the United Kingdom discovered graphene for the first time and won the Nobel Prize. Graphene is a new type of carbon material formed by carbon six-membered ring. It has many excellent properties, such as large surface area, high thermal conductivity, high electronic conductivity and good mechanical properties. It has attracted much attention as a lithium battery material. . 3. Lithium titanate spinel-type lithium titanate is used as a negative electrode material that has attracted much attention, because it has the following advantages: 1) Lithium titanate has almost zero strain before and after lithium extraction; 2) Lithium insertion potential is relatively high ( 1.55V), prevent the appearance of lithium dendrites, and have high safety; 3) have a very flat voltage platform; 4) high chemical diffusion coefficient and Coulomb efficiency. 4. Silicon-based material Silicon as an ideal negative electrode material for lithium batteries has the following advantages: 1) Silicon can form a Li4.4Si alloy with lithium, and the theoretical lithium storage capacity is as high as 4200mAh/g (more than 10 times the specific capacity of graphite); ：Some pictures and content of articles published on this site are from the Internet. 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