Fast-Charging Electrodes by Crystal Structure Control Towards High-Performance Lithium-Ion Batteries
Jie Zheng is a PhD student in the department Inorganic Materials Science. Promotors are prof.dr.ir. M. Huijben and prof.dr.ir. G. Koster from the faculty Science & Technology.
Fast-charging lithium-ion batteries (LIBs) that deliver high energy and high-power performance play a significant role in our daily life. Electrodes with fast-charging ability are essential components, allowing efficient ionic and electronic conductivity. The commonly used fast-charging electrodes, such as the spinel LiMn2O4 cathode and titanium/niobium oxide anode, possess three-dimensional interconnected channels or an open crystal framework for efficient Li+ diffusion. However, they often fail to achieve the predicted performance due to crystal structural instability or sluggish ionic/electronic transfer kinetics. Therefore, controlling the crystal structure is necessary to enhance the practical behavior of fast-charging electrodes. In this PhD project, various control strategies for fast-charging electrodes at both the nanoscale and microscale were developed and comprehensively investigated
The nanoscale control involved the construction of a two-dimensional (2D) titanoniobate-titanium carbide nanohybrid anode and an epitaxial LiMn2O4 thin film cathode system. In particular, the combined exfoliation-flocculation process resulted in the 2D hybrid configuration, exhibiting a pseudocapacitive-dominated lithium storage mechanism that enabled enhanced ionic/electronic transfer kinetics compared to the bulk counterpart. Regarding the epitaxial LiMn2O4 cathode, a hetero-interfacial lattice strain was proposed to stabilize the crystal structure during the overlithiation process. This approach would provide double capacity with improved structural stability and Li+ diffusivity
On the other hand, microscale control involved the incorporation of alien elements through doping/substitution in micro-sized titanium/niobium-based oxide anodes. In the doping case, the optimal ruthenium doping in the dual-phase TiO2 was demonstrated to simultaneously enhance lithium transfer kinetics and stabilize the dual-phase configuration. The mechanism was revealed to involve expanded lattice structures and suppressed phase separation. Regarding the substitution case, fast and durable lithium storage in titanium-niobium oxide was achieved by entropy tuning through the partial substitution of titanium with iron. This entropy increase successfully reduced the grain size along the diffusion channel direction and stabilized the crystal facets
The strategies proposed in this thesis were demonstrated to effectively enhance ionic/electronic transfer kinetic and structural stability for both nanoscale and microscale fast-charging electrode, providing more insight into achieving high-performance LIBs.