What are the factors that limit the charge and discharge rate performance of lithium-ion batteries?

The charge-discharge rate performance of lithium-ion batteries is directly related to the migration ability of lithium ions at the positive and negative electrodes, electrolyte, and the interface between them. All factors that affect the migration speed of lithium ions (these influencing factors can also be equivalent to battery The internal resistance) will affect the charge-discharge rate performance of lithium-ion batteries. In addition, the heat dissipation rate inside the battery is also an important factor affecting the rate performance. If the heat dissipation rate is slow, the heat accumulated during high rate charging and discharging cannot be transferred out, which will seriously affect the safety and life of the lithium ion battery. Therefore, to study and improve the charge-discharge rate performance of lithium-ion batteries, it is important to start from two aspects: improving the migration speed of lithium ions and the heat dissipation rate inside the battery. 1. The internal resistance of lithium-ion batteries generally adds a conductive agent inside the positive active material to reduce the contact resistance between the active materials, the active material and the positive electrode matrix/current collector, and improve the conductivity of the positive electrode material (ionic and electronic conductivity) ) To improve the magnification performance. Conductive agents of different materials and shapes will all have an impact on the internal resistance of the lithium-ion battery, thereby affecting its rate performance. The current collectors (tabs) of the positive and negative electrodes are the carrier for the lithium ion battery to transfer electric energy to the outside world. The resistance value of the current collector also has a great influence on the rate performance of the battery. Therefore, by changing the material, size, extraction method, connection process, etc. of the current collector, the rate performance and cycle life of the lithium-ion battery can be improved. In addition, the liquid absorption and porosity of the separator also have a greater impact on the passability of lithium ions, and will also affect the rate performance (relatively small) of the lithium ion battery to a certain extent. The degree of infiltration between the electrolyte of the lithium ion battery and the positive and negative materials will affect the contact resistance at the interface between the electrolyte and the electrode, thereby affecting the rate performance of the battery. The total amount of electrolyte, viscosity, impurity content, and the pores of the positive and negative materials will change the contact impedance between the electrolyte and the electrode, which is an important research direction for improving the rate performance. 2. The ionic conductivity of the electrolyte The ionic conductivity of the electrolyte is the same as the resistance of water, and it has a very large impact on the swimming speed of lithium ions. At present, the organic electrolytes used in lithium-ion batteries, whether liquid electrolytes or solid electrolytes, have low ionic conductivity. The resistance of the electrolyte has become an important part of the overall battery resistance, and its impact on the high-rate performance of lithium-ion batteries cannot be ignored. In addition to improving the ionic conductivity of the electrolyte, the chemical stability and thermal stability of the electrolyte should also be emphasized. When charging and discharging at a high rate, the electrochemical window of the battery has a very wide range. If the chemical stability of the electrolyte is not good, it is easy to oxidize and decompose on the surface of the positive electrode material, which affects the ionic conductivity of the electrolyte. 3. The diffusion capacity of positive and negative lithium-ion batteries. The rate at which lithium-ion batteries are deintercalated and embedded in the positive/negative active material, which is the speed at which lithium ions escape from the positive/negative active material, or from the positive/negative electrode How fast can the surface enter the active material to find a place to settle down? This is an important factor that affects the charge and discharge rate. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Is the lithium-ion battery of electric vehicles safe?