The scientists from the University of Antioquia and the Technological University of Chocó in Colombia have developed a technology to create cathodes for lithium-ion batteries and assembled fully functional 18650 batteries used in electronics and electric vehicles. For this, they worked with two types of materials: carbon-coated lithium iron phosphate and lithium-rich nickel manganese oxide. Cathode can add up to half the cost of a battery and largely determines its performance and service life, making this development highly significant.
The main idea of the research was the cathode optimization not only at the chemical but also at the structural and assembly levels. The cathode is made from a special suspension – a mixture of an active material, a binder polymer, and conductive additives, which essentially become a working layer of the battery. If the balance in this mixture is out of order, the electrode performance deteriorates: an excess binder or carbon additive can clog the pores and impede the movement of lithium ions. A too-loose structure, on the contrary, impairs the contact among the particles and reduces conductivity.
Therefore, the scientists selected not only the composition but also such physical parameters as a layer thickness and its density after compression. They tested 13 different composition variants and demonstrated that the optimal structure should be dense enough for the particles to be well interconnected but still able to maintain porosity allowing ions to pass freely. This balance allows the battery to efficiently store and release energy.
Then, the researchers manufactured complete electrodes and began testing their performance under real-world conditions. First, they assessed their mechanical properties: how strong they were, whether they cracked when bent, and how well they adhered to the metal base to which they were applied. This is important because in the finished battery, the layers are constantly under stress and should not peel or deteriorate.
Then, they assembled 18650 batteries from these electrodes and tested them under various charging and discharging conditions: from slow to more intense.
The results showed a significant difference between the two types of materials. The cathodes based on lithium-rich nickel manganese oxide provided a higher initial capacity, up to 260 mAh per gram, which means they were able to store more energy than lithium iron phosphate. However, with repeated charging and discharging cycles, these batteries degraded more quickly. Meanwhile, performance of the cathodes based on carbon-coated lithium iron phosphate was much more reliable and their lifespan was longer.
In prospect the scientists plan to focus on improving the stability of lithium-rich nickel manganese oxide and propose several approaches: modifying its composition by adding other elements, applying protective coatings to the particles, and selecting new electrolyte compositions that reduce structural degradation during operation.
