Surface/Interfacial Structure and Chemistry of High‐Energy Nickel‐Rich Layered Oxide Cathodes: Advances and Perspectives

Abstract

time further and enhance power density during acceleration process so as to perfect its practicality. [1b,3] Electrode materials (cathode and anode) play an important role in the electrochemical properties of LIBs, including energy-density, cycle-life, rate capability, and safety among others. Graphite materials with high capacity greater than 300 mAh g −1 , superior structural stability, as well as low cost are significantly applied as anode electrode in commercialized LIBs. [4] The other anode, graphite/silicon composites that can deliver higher capacity of around 1000 mAh g −1 and that of pure graphite electrode are gradually commercialized to further enhance the energy density of LIBs. [5] The first commercial cathode material, layered oxide LiCoO 2 with O3 structure (in which oxygen anion have a cubic close packing arrangement in the form of ABCABC…), illustrates the unpleasant transformation from hexagonal phase to monoclinic phase, particularly when the Li + deintercalation ratio (x) exceeds 0.5 in Li 1−x CoO 2 . [6] This is in contrast with graphite-based anode with preferred electrochemical performance and low cost. Also, this phase transition derived from the order/disorder transformation of Li + is anticipated to cause rapid decay of reversible capacity. [6d] Consequently, the LiCoO 2 cathode can only deliver around 150 mAh g −1 , which has limi ted the performance promotion of LIBs and the far-ranging applications of LIBs in PHEVs and EVs.Additionally, developing high-capacity (energy-density) cathode materials with desired electrochemical behaviors in place of the conventional LiCoO 2 has been the main motivation behind LIBs in the recent past. Three main groups of cathode materials, layered oxides including lithium-stoichiometric Li[Ni x Co y Mn 1−x−y ]O 2 and lithium-rich Li 1+z M 1−z O 2 (M = Mn, Ni, Co, Ru, Sn, Ir, etc.), spinel LiM 2 O 4 (M = Ni, Mn), together with olive LiMXO 4 (M = Fe, Mn, Co; X = P, Si) as illustrated in Figure 1, are broadly examined as the next-generation cathode materials for LIBs. [3a,6e,7] Among these candidates lithiumrich and manganese-based layered oxides display the highest energy-density of approach 1000 Wh Kg −1 as a result of the large reversible capacity of ≈300 mAh g −1 and high voltage of 3.5 V (vs. Li/Li + ). However, there are various significantThe urgent prerequisites of high energy-density and superior electrochemical properties have been the main inspiration for the advancement of cathode materials in lithium-ion batteries (LIBs) in the last two decades. Nickel-rich layered transition-metal oxides with large reversible capacity as well as high operating voltage are considered as the most promising candidate for next-generation LIBs. Nonetheless, the poor long-term cycle-life and inferior thermal stability have limited their broadly practical applications. In the research of LIBs, it is observed that surface/interfacial structure and chemistry play significant roles in the performance of cathode cycling. This is due to the fact that they are basical...

Realizing Superior Cycle Stability of a Ni‐Rich Layered LiNi0.83Co0.12Mn0.05O2 Cathode with a B2O3 Surface Modification

“…To find more evidence explaining the improved cycle stability and reduced impedance for the 0.5 %‐B sample, XPS was employed to analyze the surface chemical compositions of the cycled electrodes, as shown in Figure . The HF, derived from the electrolyte decomposition, can react with the active material and residual surface compounds to generate LiF and MF (M=Ni, Co, Mn) . Therefore, LiF is usually regarded as the main evidence for reflecting the surface side reactions.…”

A Carbon‐Free Li2TiO3/Li2MTi3O8 (M═Zn1/3Co2/3) Nanocomposite as High‐Rate and Long‐Life Anode for Lithium‐Ion Batteries

“…Note that the average diffusion time ( τ eq ) depends on the diffusivity coefficient ( D ) and the diffusion distance ( L ). According to the equation τ eq = L 2 /2 D , reducing L is more efficient than increasing D . Then, it is expected that these nano‐sized primary grains will remarkably shorten the migration distance of Li + and electrons during redox reactions, which will induce a good rate property.…”

Precise Surface Engineering of Cathode Materials for Improved Stability of Lithium‐Ion Batteries

“…As a matter of fact, protection strategies such as surface coating or elemental doping from surface coating have been well identified as effective protocols to improve the stability of cathode materials and have found broad application in LIBs . The effectiveness of surface coating has been well reviewed by different groups including Cho and Xu . These papers have explicitly demonstrated the critical role played by surface control as well as the antidecay mechanism upon surface modification of different cathode materials.…”