What is the most effective way to increase the energy density of lithium batteries?

What is the most effective way to increase the energy density of lithium batteries? The optimized porosity of graphite electrodes is generally controlled at 20% to 40%, while the performance of silicon-based electrodes becomes poor after compaction. The porosity of these electrodes is generally 60% to 70%. High porosity can expand the volume of silicon-based data, buffer the sharp deformation of particles, and slow down pulverization and decline. However, the high-porosity silicon-based anode limits the volumetric energy density. Silicon-based cathode is one of the most effective ways to increase the energy density of lithium batteries because it has a high specific capacity and volume specific capacity. However, as an active material, silicon inserts and releases lithium during charge and discharge cycles, and its volume changes as much as 270%, resulting in poor cycle life. The reasons for this volume swelling are: (1) the destruction of silicon particles and the separation of the plating layer in the copper collection solution; (2) the solid electrolyte (SEI) film is unstable during the cycle, and the volume expansion causes the SEI to break repeatedly, leading to the failure of the lithium battery . The compaction process will make the solid contact more tightly and improve the electronic transmission function of the pole. However, low porosity will increase lithium ion transfer resistance and electrode/electrolyte interface charge transfer resistance, resulting in poor multiplier function. The optimized porosity of graphite electrodes is generally controlled at 20%-40%, while the performance of silicon-based electrodes becomes worse after compaction. The porosity of these electrodes is generally 60% to 70%. High porosity can expand the volume of silicon-based data, buffer the sharp deformation of particles, and slow down pulverization and decline. However, the high-porosity silicon-based anode limits the volumetric energy density. So, how to prepare silicon-based cathode plates for lithium batteries? KarkarZ et al. studied the preparation of silicon electrodes. First, they prepared 80wt% silicon, 12wt% graphene and 8wt% CMC electrode paste using two mixing methods: (1) SM: conventional ball mill relaxation technology; (2) RAM: two-step ultrasonic dispersion process. The first step is to disperse silicon and CMC in PH3 buffer (0.17m citric acid + 0.07mKOH). The second step is to add graphene flakes and water, and continue ultrasonic dispersion. As shown in Figure 1a and d, the incoherent RAM related to graphite sheets and ultrasonic graphene adheres to the original tracking table. The length of the table is greater than 10×m, and the distributed parallel collection of liquid, the coating with higher porosity, and the SM mixing leads to The length of the graphene sheet and the graphene sheet is only a few microns. The porosity of the uncompacted RAM electrode is about 72%, which is greater than 60% of the SM electrode. Regarding silicon, there is no difference between the two mixing methods. Nanosheet graphene has excellent electronic conductivity, RAMslack adheres to the integrity of the graphene sheet, and the battery has a good cycle function (Figure 3a and Figure b). Then they studied the effects of compaction on electrode porosity, density and electrochemical function. As shown in Figure 1, after compaction, the graphene sheet and the silicon tracer did not change significantly, but the coating became denser. The electrode sheet was made into a half-cell, and its electrochemical performance was tested. It can be seen from Figure 2: (1) As the compaction pressure increases, the electrode porosity decreases, the density increases, and the volume specific capacity increases. (2) For the uncompacted electrode sheet, the porosity of RAM is about 72%, which is greater than 60% of SM electrode. In addition, RAM electrode compaction is more difficult, reaching a porosity of 35%. RAM electrode needs 15T/cm2 pressure, SM electrode only needs 5T/cm2 pressure. This is because the graphene sheet is difficult to deform, and the RAM sheet is attached to the graphene sheet structure, making it more difficult to compact. (3) Calculate the volume specific capacity based on the volume expansion of complete lithium silicon by 193%. Under the density of 20T/cm2, the volume specific capacity is the largest. The porosity of RAM and SM electrodes are 34% and 27%, respectively, and the corresponding volumetric specific capacities are 1300mAh/cm3 and 1400mah/cm3, respectively. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete it.