Development and status quo of cathode materials for lithium batteries

At present, the cathode materials of lithium batteries are mainly lithium cobalt acid, lithium manganese acid, lithium iron phosphate and ternary materials.  

Development of cathode materials for lithium batteries

The first stage of the rise of lithium battery cathode materials was dominated by lithium cobalt oxide (LCO) from 2005 to 2011.  The cathode material market in this phase is driven by consumer batteries.  

Because of its simple production process, LCO has become the first generation of cathode material successfully widely used in the market, and is recognized as the most mature cathode material at present.  This material has excellent cycling properties, high specific energy, can operate at high voltages and maintain a stable voltage when charging and discharging.  However, due to more cobalt content, its price is expensive, and its specific capacity is low, poor overcharge resistance.  Another fatal drawback of this material is that its specific capacity decays rapidly at higher charging voltages.  This is because Li+ needs to be released from LCO during the charging process. Although the structure of the material can remain stable when the amount of Li+ is less than 50%, as long as the amount of Li+ is more than 50%, the material is prone to phase transformation, which will lead to a large change in volume, resulting in the powder of the material particles.  If you continue charging at this point, the Co in the material will dissolve and release O2, and the specific capacity of the battery will decay rapidly.  Despite its high cost, lithium cobaltate is still the preferred cathode material for small lithium batteries.  The energy density of lithium cobalt acid has basically developed to the limit of the current existing chemical system and process equipment, and its specific capacity is limited by the problem of easy decomposition of electrolyte under high pressure, compared with its theoretical capacity there is still a large space for improvement.  If a breakthrough is made in electrolyte technology in the future, the specific capacity of lithium cobalt oxide will be further improved.  

Due to the large volume of new energy vehicle market, lithium battery cathode material ushered in the second stage of development during 2014~2015, and the proportion of lithium iron phosphate cathode material (LFP) in the market increased rapidly.  

Status quo of cathode materials for lithium batteries

LFP has a stable olivine skeleton structure, which is still one of the research hotspots of cathode materials with high energy density, low price, excellent safety, long battery life and other characteristics.  But the voltage of this material is only about 3.3V, which is significantly lower than other positive materials, which means its energy density is also low.  At the same time, the resistivity of this material is relatively high, which makes its electrical conductivity is poor, but this shortcoming can be solved by doping method, material nano or coating, so as to obtain good electrochemical performance.  Lithium iron phosphate is mainly used in power tools and electric vehicles.  Lithium iron phosphate is a promising cathode material for energy storage batteries due to its long battery life and much room for cost reduction.  The future direction is definitely to solve the conductivity problem and patent problem.