Challenges and Modification Strategies of Ni-Rich Cathode Materials Operating at High-Voltage

Abstract

Ni-rich cathode materials have become promising candidates for lithium-based automotive batteries due to the obvious advantage of electrochemical performance. Increasing the operating voltage is an effective means to obtain a higher specific capacity, which also helps to achieve the goal of high energy density (capacity × voltage) of power lithium-ion batteries (LIBs). However, under high operating voltage, surface degradation will occur between Ni-rich cathode materials and the electrolytes, forming a solid interface film with high resistance, releasing O2, CO2 and other gases. Ni-rich cathode materials have serious cation mixing, resulting in an adverse phase transition. In addition, the high working voltage will cause microcracks, leading to contact failure and repeated surface reactions. In order to solve the above problems, researchers have proposed many modification methods to deal with the decline of electrochemical performance for Ni-rich cathode materials under high voltage such as element doping, surface coating, single-crystal fabrication, structural design and multifunctional electrolyte additives. This review mainly introduces the challenges and modification strategies for Ni-rich cathode materials under high voltage operation. The future application and development trend of Ni-rich cathode materials for high specific energy LIBs are projected.

Low-cobalt active cathode materials for high-performance lithium-ion batteries: synthesis and performance enhancement methods

“…In order to maintain the charge neutrality, the lattice O 2− oxidizes and escapes from the NCM lattice. 101 The released singlet oxygen ( 1 O 2 ) further facilitates electrolyte oxidation. 102 Thus, the release of lattice oxygen creates oxygen vacancies in the NCM crystal structure and promotes the migration of TMs from the tetrahedral to the octahedral site of the Li-slab.…”

Near‐Atomic‐Scale Evolution of the Surface Chemistry in Li[Ni,Mn,Co]O2 Cathode for Li‐Ion Batteries Stored in Air

“…[ 9,42,44 ] These cracks are serious concern while operating batteries at higher voltages. Surface coatings of cathode particles have been shown to provide efficient protective layer to hinder the dissolution of the constituent metal from the particles, and enhance the internal structure stability, [ 45,46 ] yet the precise mechanisms by which coatings interact with preexisting or freshly formed cracks cannot yet be discussed without a dedicated future study.…”

Illustration of Capacity Fading Factors on the Example of La2(Li0.5Ni0.5)O4‐Modified High Nickel Layered Oxide Material

“…For layered oxide structure cathode materials, degradation could be caused by bulk structural changes, e. g., undesirable phase transition accompanied by anisotropic volume change, cation disordering, cracking and surface instability effect (gas evolution, metal dissolution, surface impurities from Li-residuals and impedance built up). [1][2][3][4][5] Coating compounds can act as barrier for undesirable process, such as oxygen releasing, transition metal displacement from structure, or as a conductor for lithium ions flux. [6][7][8] Some of them can possess surface structure stabilizing and cracking suppress properties.…”