Progress in phase field research of dead lithium in lithium batteries

In recent years, as people's demand for energy has increased, the development of secondary batteries has been driven, and lithium metal has emerged as the preferred negative electrode material for high-energy density batteries due to its high theoretical capacity and low electrochemical potential, which has the potential for a huge energy storage technology revolution. However, the practical application of lithium metal anodes faces major challenges, mainly due to the inevitable formation of lithium dendrites and dead lithium during the charge-discharge cycle. These problems greatly reduce the coulomb efficiency and service life of lithium metal batteries, and constitute a substantial obstacle to the development and wide application of lithium metal batteries.Lithium dendrites are tree-like structures formed by uneven lithium deposition during charging of lithium metal. These dendrites can penetrate the diaphragm and reach the cathode, causing a short circuit and potentially catastrophic battery failure.Dead lithium refers to lithium that is separated from the anode during the cycle and therefore no longer participates in the electrochemical reaction. The accumulation of dead lithium reduces the inventory of active lithium, causing battery capacity and efficiency to decline over time.Addressing these challenges requires a deep understanding of the formation mechanisms of lithium dendrites and dead lithium, and this paper focuses on analyzing these mechanisms from the perspective of the phase field, a powerful computational method for modeling the evolution of microstructures, which provides insights into the complex dynamics of lithium deposition and the conditions under which dendrites and dead lithium form. The latest research progress on the inhibition of dead lithium by temperature, pressure, diaphragm, bubble and high active electrolyte was reviewed. Firstly, the influence of temperature and pressure on the formation of dead lithium is discussed, and the effect of two coupling fields on dead lithium is also discussed. Secondly, starting from the diaphragm and electrolyte, the results of researchers in recent years are reviewed. For example, selecting a diaphragm with appropriate pore size can promote the uniform deposition of lithium, prevent the penetration of dendrites better, and promote the resurrection of dead lithium; The highly active electrolyte can enhance the smooth deposition of lithium and inhibit the formation of dead lithium. These factors can regulate the deposition form of lithium to a certain extent, slow down or avoid the formation of lithium dendrites and dead lithium.By optimizing these factors, researchers can better control the deposition morphology of lithium, alleviating or even avoiding the formation of dendrites and dead lithium. The phase-field method is also used to study how the formation of dead lithium affects the overall life of the battery. The phase field is used to simulate the long-term behavior of lithium metal anodes to predict the battery life under various operating conditions.Finally, this paper discusses and summarizes the shortcomings of the existing phase field method in the study of the radical elimination of dead lithium, and prospects the future development.