High‐Energy Ni‐Rich Cathode Materials for Long‐Range and Long‐Life Electric Vehicles

Abstract

of the global EV market, Li-ion battery (LIB) technology has progressed to meet the demand for longer driving ranges and extended service lives, while increasing the thermal stability and reducing the cost of the battery. As the performance of LIBs is largely determined by the cathode material, the development of high-performance LIBs for EVs has focused on increasing the capacity of the cathode by usingHowever, cathodes with a high Ni content suffer from inherent structural and chemical instabilities, which lead to rapid capacity fading and thermal instability. [3][4][5][6][7][8][9] In particular, the rapid capacity fading of Ni-rich layered cathodes is largely caused by microcracking and the resultant microstructural instability. [9][10][11][12][13][14][15][16][17][18][19] Microcracks create channels through which the electrolyte can infiltrate the cathode particles, which increases the surface area exposed to electrolyte and worsens parasitic electrolyte attack. The subsequent degradation of the internal surfaces accelerates the accumulation of NiO-like impurity layers at the cathode-electrolyte interface, which hinders electrochemical reactions. [9,[19][20][21][22][23][24][25] As microcracking is caused by abrupt contraction of the unit cells during the H2-H3 phase transition at a high state of charge (SoC), microstructural engineering to facilitate the dissipation of internal mechanical strain and mitigate microcracking in the cathode particles has been extensively investigated. [19,21,[24][25][26][27][28][29][30] One such engineered microstructure is a highly oriented microstructure in which elongated primary particles are aligned along the radial direction in the secondary particle periphery. This radial alignment of rod-shaped primary particles effectively dissipates localized strain by allowing the unit cell to contract and expand uniformly. Microstructural manipulation can be achieved by compositional gradient design of transition metal ions [19,24,25,31] or by doping with various atoms (e.g., B, Ta, Mo, W, and Sb) during lithiation. [18,[26][27][28][29][30]32,33] Furthermore, a reduction in volume deformation and internal stress inside the particle via Al doping can enhance the structural integrity and robustness of cathode. [30,34,35] In addition to microcracking, the time during which highly reactive Ni 4+ ions are exposed to the electrolyte when the cathode is in a highly charged state also affects the deterioration of the cathode. Although the exposure time is not Li-ion batteries (LIBs) in electric vehicles (EVs) are usually operated intermittently and maintained at high states of charge (SoCs) for long periods. Because the internal particles of Ni-rich cathodes are easily exposed to the electrolyte at high SoCs owing to mechanical instability, the electrolyte exposure time-during which highly reactive Ni 4+ ions react with the electrolyte-critically affects the degradation of the cathode. Here, 1 mol% B doping of a core-shell concentration gradient (CSG) Li[Ni 0.88 Co 0.10 Al 0.02 ]O 2 cathode (C...

Stabilizing lattice oxygen and interface chemistry of Ni-rich and Co-poor cathodes for high-energy lithium-ion batteries

“…Trends of R sf and R ct manifested the less structural deterioration and surface side reaction during the electrochemical process. 37,39 Overall, the Al introduction and CeO 2− x coating reinforced the crystal structure and interfacial stability, hindering the irreversible phase transitions and surface evolution during cycling.…”

Micro- and nano-structural design strategies towards polycrystalline nickel-rich layered cathode materials

“…The CSG-NCMA90 cathode displayed a capacity retention of 90.6% and 94.1% aer 1000 cycles at 100% and over 60% depths of discharge, respectively. Namkoong et al 125 introduced 1 mol% B into Li [Ni0 .88 Co 0.10 Al 0.02 ]O 2 CSG (CSG-NCAB87) and studied the effect of exposure time to the electrolyte on the cathode material at a high state of charge (SOC). The result showed that the capacity decay increased with the increase of exposure time.…”

Construction of Planar Gliding Restriction Buffer and Kinetic Self-Accelerator Stabilizing Single-Crystalline LiNi0.9Co0.05Mn0.05O2 Cathode

“…The additional modification that regulates the chemical–mechanical properties of the single-crystalline Ni-rich cathode is necessary to be conducted for enhancing the electrochemical performance of LIBs, such as cation/anion doping and surface coating. , Ionic doping (such as B, F, Mg, Mo, and Nb) can stabilize the internal lattice structure by forming a stable crystal network structure, which effectively suppresses the structure collapse caused by the anisotropic lattice strain during H2–H3 phase transition . Meanwhile, the conductivity of cathode electrons/ions is also enhanced by the introduction of additional elements into the internal lattice structure, beneficial to promoting lithium-ion diffusion.…”