How to design a zero-degradation battery

Loss of lithium inventory (LLI) caused by side reactions in lithium-ion cells is one of the major reasons behind their capacity fade and shorter cycle life. Research in academia and industry has explored additives such as Lithium Iron oxide (Li₅FeO₄) in LFP-based battery chemistries that sacrifice their lithium inventory to compensate for LLI. Over the last ~15 years, research has proven that LFO can compensate for LLI and help maintain stable cell performance, and more recently, CATL & Rimac announced its commercial-level usage claiming to have achieved zero degradation for extended periods. However, the specifics behind achieving such excellent performance are neither fully disclosed by them nor much explored in the literature. This work advances and broadens the existing theoretical understanding of employing sacrificing agents and demonstrates how exactly LFO can be employed in commercial large LFP cells with LFP/LFO positive electrode (PE) and Graphite negative electrode (NE) using simulations run by building a full-cell physics-based model in PyBaMM. The work digs deeper into the science behind releasing lithium inventory from LFO, and its impact on cell degradation, discharge capacity, and cell life. The work also attempts to find the optimal methods to control lithium release from LFO and the optimum weight fraction of LFO to minimize cell degradation and achieve long-lasting, zero-degradation batteries. Model results reveal that the slow lithium release maintains the cell balancing and keeps the degradation rates of SEI formation and lithium plating under control, while rapid lithium release and excessive LFO content can accelerate their degradation rates resulting in faster pore-clogging in the NE and lower cycle life. This work shows that merely adding lithium-rich additives does not promise high-performance batteries; instead depends on using them in optimal amounts and ensuring the controlled release of lithium inventory through appropriate control methods