Understanding the effects of surface reconstruction on the electrochemical cycling performance of the spinel LiNi0.5Mn1.5O4 cathode material at elevated temperatures

Ben

et al. 2018

Adv Materials Inter

Self Cite

electric vehicles, hybrid electric vehicles, and plug-in hybrid electric vehicles. [1][2][3][4] High energy density materials for LIBs are strongly desired to further enhance the electrochemical performance, creating the next generation of LIBs. [5] The current market of cathode materials is dominated by LiCoO 2 , which offers limited energy density and suffers from high cost and safety problems. [6] To increase the energy density, high voltage cathode materials for LIBs have received much interest, among which the spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) is well-known for its high operation voltage of ≈4.7 V compared to that of Li + / Li, high specific capacity of 146.7 mAh g −1 , high rate capability, low cost, nontoxicity, and good safety features. [7][8][9][10][11] Despite the advantages, the highvoltage LNMO cathode material still has several issues that need to be solved urgently before commercialization. Particularly, LNMO suffers from a capacity fading issue caused by surface structural distortion and associated dissolution of Mn ions into the electrolyte during electrochemical cycling at elevated temperature. [12,13] In addition, the high operating voltage exceeds the stability window of standard electrolytes, which results in the oxidation of electrolytes and the formation of a cathode electrolyte interface on the surface of the cathode, which consequently increased impedance and decreased columbic efficiency during cycling. [12,13] These issues indicate that a major challenge for the LNMO system is related to the interface stability between the cathode and the electrolyte at high temperatures and high voltages.To further improve the electrochemical performance of LNMO, surface modifications with a small amount of metal oxides for LNMO particles have been studied in several experimental studies. [14][15][16][17][18][19][20][21][22] Wang et al. reported Ru-doped Li 1.1 Ni 0.35 Ru 0.05 Mn 1.5 O 4 and LiNi 0.4 Ru 0.05 Mn 1.5 O 4 enhanced rate capability and cyclic performance by minimizing polarization and improving electrical conductivity. [14] Yi et al. found that Nb doping increased the diffusion coefficient of the lithium ion of LNMO by enlarging the lattice parameter, thus improving the electrochemical performance. [16] Yan et al. reported that a thin Al 2 O 3 coating layer on the surface of Li 1.2 Ni 0.2 Mn 0.6 O 2Surface modification of a high-voltage spinel LiNi 0.5 Mn 1.5 O 4 cathode is a common method to improve its cycling performance for next generation lithium-ion batteries, but the exact surface structural stabilization mechanism is not well-understood. Here, detailed density function theory investigations based on the first-principles calculations of high valence state Ti-/ Ta-surfacedoped LiNi 0.5 Mn 1.5 O 4 are reported. The migration of Ni/Mn ions is simulated into the surface structure of bare and Ti-/Ta-coated LiNi 0.5 Mn 1.5 O 4 . The calculation results suggest that Ti/Ta doping promotes Ni/Mn migration toward the formation of the rocksalt phase. Integrated net spin suggests that the valence...

mentioning

confidence: 99%

mentioning

confidence: 99%

Impact of High Valence State Cation Ti/Ta Surface Doping on the Stabilization of Spinel LiNi_0.5Mn_1.5O₄ Cathode Materials: A Systematic Density Functional Theory Investigation

Ben

et al. 2018

Adv Materials Inter

Self Cite

“…As also suggested by previous studies, the migration of transition-metal, oxygen ions and the existence of antiphase boundaries in the cathode severely affect the electrochemical properties such as cycle ability, rate ability, and battery capacity 8,9 . Atomic scale elemental doping of Ni and/or Mn in LNMO has been widely accepted as a strategy to control the crystallographic properties and stabilize the battery performance of the high-voltage spinel cathodes 35 .…”

Section: Discussionmentioning

confidence: 64%

“…While solid electrolytes have many benefits, there are also drawbacks with respect to battery performance including low ion-conductivity, poor contact between electrode and electrolyte, and grain boundary formation 7 . Besides, the high-voltage LNMO cathode suffers severe problems such as dissolution of Mn ions and capacity degradation at high voltage, which hinders its commercialization 8,9 . As an important issue, the structural evolution during charging in LNMO has been broadly studied since it is directly responsible for the performance of batteries.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Three-dimensional atomic-scale observation of structural evolution of cathode material in a working all-solid-state battery

et al. 2018

Self Cite

Most technologically important electrode materials for lithium-ion batteries are essentially lithium ions plus a transition-metal oxide framework. However, their atomic and electronic structure evolution during electrochemical cycling remains poorly understood. Here we report the in situ observation of the three-dimensional structural evolution of the transition-metal oxide framework in an all-solid-state battery. The in situ studies LiNi0.5Mn1.5O4 from various zone axes reveal the evolution of both atomic and electronic structures during delithiation, which is found due to the migration of oxygen and transition-metal ions. Ordered to disordered structural transition proceeds along the <100>, <110>, <111> directions and inhomogeneous structural evolution along the <112> direction. Uneven extraction of lithium ions leads to localized migration of transition-metal ions and formation of antiphase boundaries. Dislocations facilitate transition-metal ions migration as well. Theoretical calculations suggest that doping of lower valence-state cations effectively stabilize the structure during delithiation and inhibit the formation of boundaries.

Addressing Mn Dissolution in High‐Voltage LiNi_0.5Mn_1.5O₄ Cathodes via Interface Phase Modulation

Han

Jiang

et al. 2022

Adv Funct Materials

Spinel LiNi 0.5 Mn 1.5 O 4 (LNMO), high-voltage and high-power density, is a very promising cathode candidate. Nevertheless, its lack of cycling stability has historically been long accepted as an inherent issue. Based on the above problem, a strategy is initiated to directly address Mn dissolution and unstable interface structure. A beneficial solid-phase reaction occurs at the LNMO interface, transforming the spinel phase into two functional phases. One is the layered phase that provides electrochemical activity and supports charge transport. The other is the rock-salt like phase induced by Li/Mn exchange that can inhibit the dissolution of Mn and provide inert protection. The Li/Mn exchange structure increases the diffusion energy barriers of Mn, which restrains the loss of Mn, proven by the bond valence sum calculation. The two phases are modulated successfully at the LNMO interface to balance the stable material structure and excellent charge transfer, obtaining a sample with excellent electrochemical performance. The capacity retention rate of modified LNMO is 15% higher than that of the pristine sample after 500 cycles. The preparation method does not utilize any dopants or coatings and can play a guiding role in addressing issues regarding structural stability and electrochemical performance for cathode materials.