Structure/Interface Coupling Effect for High‐Voltage LiCoO₂ Cathodes

Abstract

LiCoO2 (LCO) is widely applied in today's rechargeable battery markets for consumer electronic devices. However, LCO operations at high voltage are hindered by accelerated structure degradation and electrode/electrolyte interface decomposition. To overcome these challenges, co‐modified LCO (defined as CB‐Mg‐LCO) that couples pillar structures with interface shielding are successfully synthesized for achieving high‐energy‐density and structurally stable cathode material. Benefitting from the “Mg‐pillar” effect, irreversible phase transitions are significantly suppressed and highly reversible Li+ shuttling is enabled. Interestingly, bonding effects between the interfacial lattice oxygen of CB‐Mg‐LCO and amorphous CoxBy coating layer are found to elevate the formation energy of oxygen vacancies, thereby considerably mitigating lattice oxygen loss and inhibiting irreversible phase transformation. Meanwhile, interface shielding effects are also beneficial for mitigating parasitic electrode/electrolyte reactions, subsequent Co dissolution, and ultimately enable a robust electrode/electrolyte interface. As a result, the as‐designed CB‐Mg‐LCO cathode achieves a high capacity and excellent cycle stability with 94.6% capacity retention at an extremely high cut‐off voltage of 4.6 V. These findings provide new insights for cathode material modification methods, which serves to guide future cathode material design.

Fundamental Understanding of Nonaqueous and Hybrid Na–CO2 Batteries: Challenges and Perspectives

“…Lithium-ion batteries (LIBs), as one of the most amazing modern electrochemical energy storage technologies, are limited by low theoretical specific energy densities (usually lower than 700 Wh kg −1 ) and even lack sufficient durability and affordability to fulfill practical demands. [6,7] Therefore, it is imperative to develop new secondary battery systems with higher energy densities to cope with future large-scale power storage and transportation power utilization.…”

Enabling interfacial stability of LiCoO2 batteries at an ultrahigh cutoff voltage ≥ 4.65 V via a synergetic electrolyte strategy

“…Among them, structural doping and surface coating are the mainstream and effective methods. 8,22,23 For instance, Zhang et al realized stable cycling of LCO by introducing trace amounts of Ti, Mg, and Al dopants to collaboratively stabilize bulk layered structures and material interfaces, which sets a milestone of high-voltage LCO up to 4.6 V. 24 We have previously proposed and designed Mgdoped and Se-coated LCO, in which the Mg dopant served as a 'pillar' to strengthen the layered structure, while the Se surface layer with low electrical conductivity acted as a functionalized barrier to eliminate the corrosion of the LCO surface and suppress the decomposition of electrolytes at a high charge cutoff of 4.65 V. 25 From the viewpoint of convenient interfacial stabilization of the electrodes, the rational design and optimization of the electrolyte recipe with functional additives are efficient and easily scalable, which can effectively reduce side reactions on electrodes and improve the cycling performance of LIBs. [26][27][28][29][30] For example, Zhang et al developed a new all-uorinated electrolyte (1 M LiPF 6 in FEC/FEMC/TTE + 2 wt% TMSB, FEC: uoroethylene carbonate; FEMC: 2,2,2-triuoroethyl methyl carbonate; TTE: 1,1,2,2-tetrauorethyl-2,2,3,3-tetrauorpropyl ether; TMSB: tris(trimethylsilyl) borate) to form a robust cathode electrolyte interface (CEI) enriched with inorganic species, promoting the high-voltage reversibility of the LCO cathode.…”

“…Among them, structural doping and surface coating are the mainstream and effective methods. 8,22,23 For instance, Zhang et al realized stable cycling of LCO by introducing trace amounts of Ti, Mg, and Al dopants to collaboratively stabilize bulk layered structures and material interfaces, which sets a milestone of high-voltage LCO up to 4.6 V. 24 We have previously proposed and designed Mg-doped and Se-coated LCO, in which the Mg dopant served as a ‘pillar’ to strengthen the layered structure, while the Se surface layer with low electrical conductivity acted as a functionalized barrier to eliminate the corrosion of the LCO surface and suppress the decomposition of electrolytes at a high charge cutoff of 4.65 V. 25…”

Reducing Co/O Band Overlap through Spin State Modulation for Stabilized High Capability of 4.6 V LiCoO2

“…In LCO with such characteristics, only half of Co 3+ could be reversibly oxidized to Co 4+ . With oxidizing more than 50% Co 3+ to Co 4+ , O anion redox (OAR) is ubiquitously triggered. , Although OAR elevates the overall capacity of LCO, severe structural degradation and sharp capacity decay are inevitably aroused. − These problems originate from the intrinsic OAR issues in thermodynamics and kinetics. First of all, OAR shows inferior thermodynamics.…”