Li[Ni_0.9Co_0.09W_0.01]O₂: A New Type of Layered Oxide Cathode with High Cycling Stability

Abstract

transportation emissions account for nearly one-quarter of all greenhouse gases. [1] However, the current fleet of EVs, mainly powered by lithium-ion batteries (LIBs), still falls short of performance standards, especially in driving range per charge, that are required for broad consumer appeal. A driving range comparable to that of an ICEV requires a substantial increase in the energy density of LIBs, whose capacity is largely limited by the cathode. [2][3][4] Archetypal cathodes for LIBs deployed in current EVs are layered Li[Ni x Co y (Al or Mn) 1−x−y ]O 2 (Al = NCA or Mn = NCM) oxide materials. [4][5][6][7] Both cathodes were derived from LiNiO 2 , which has a high theoretical capacity of 270 mAh g −1 . Multiple phase transitions during delithiation quickly deteriorate the reversible capacity of LiNiO 2 ; this inherent structural instability renders the cathode unsuitable for EV applications. NCA cathodes were developed by introducing Co 3+ and Al 3+ to LiNiO 2 to prevent multistep phase transitions and stabilize the structure, resulting in the Li[Ni 0.8 Co 0.15 Al 0.05 ]O 2 cathode, which currently powers the Tesla Model S. [8] In another example, Ni was partially replaced with Co and Mn to develop Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 ; this cathode exhibited excellent capacity retention and thermal stability but its capacity was limited to 160 mAh g −1 . [9] To compensate for inferior capacity, Ni content was increased to x = 0.6; this cathode is also widely commercialized. Although both NCA and NCM cathodes are adequate, the energy density of 350 Wh kg −1 required to provide a drive range threshold of 300 miles per charge requires a new class of layered oxide cathodes. As Ni content exceeds x = 0.8, NCA and NCM cathodes are plagued by increasingly compromised battery life and thermal safety, due to rapid capacity fading and an abundance of unstable Ni 4+ species, as observed in LiNiO 2 . [4,[10][11][12][13] To overcome the inherent instability of Ni-rich NCM and NCA cathodes, we propose a new type of layered oxide cathode, Li[Ni x Co y W 1−x−y ]O 2 . Previous work indicates that W doping of LiNiO 2 substantially improved its cycling stability without sacrificing energy density. [14,15] In this study, we show that replacement of Al ions with W ions in a Ni-rich NCA layered oxide cathode markedly modifies the cathode microstructure through particle refinement and greatly improves the cycling stability of the cathode. We compare the electrochemical performance of the Li[Ni 0.9 Co 0.09 W 0.01 ]O 2 cathode (NCW90) to the well-characterized Li[Ni 0.885 Co 0.1 Al 0.015 ]O 2 (NCA89) to demonstrate its superior structural and thermal stability compared to the commercialized NCA cathode.Substituting W for Al in the Ni-rich cathode Li[Ni 0.885 Co 0.10 Al 0.015 ]O 2 (NCA89) produces Li[Ni 0.9 Co 0.09 W 0.01 ]O 2 (NCW90) with markedly reduced primary particle size. Particle size refinement considerably improves the cathode's cycling stability such that the NCW90 cathode retains 92% of its initial capacity after 1000 cycles (c...

Pseudo‐Bonding and Electric‐Field Harmony for Li‐Rich Mn‐Based Oxide Cathode

“…Herein, in order to verify the alleviated loss of lattice oxygen after modification, differential scanning calorimetry (DSC) was employed, as displayed in Figure 6A. [37] The distinct exothermic peak for charged 3% LCO is at 291.61 °C while that for the pristine sample is decreased to 284.76 °C along with an increased specific heat release (594.4 and 684.5 J g −1 for 3% LCO and pristine samples, respectively), strongly manifesting the improved thermal stability and the modified stability of lattice oxygen evolution. And it proves that the lattice oxygen evolution of the modified samples is effectively stabilized by the linkage-functionalized modification.…”

Surface/Interface Structure Degradation of Ni‐Rich Layered Oxide Cathodes toward Lithium‐Ion Batteries: Fundamental Mechanisms and Remedying Strategies

“…Doping has been widely demonstrated to be the simplest approach for enhancing the structural and thermal stabilities of the Ni-rich cathodes. Typically, to date, a wide range of dopants including cations doping (Mg, [211,242] Al, [67,129,140,[243][244][245][246] Ti, [209,211] Zr, [208,[247][248][249] Nb, [250] Cd, [251] Ce, [252] Mo, [87] Ca, [253] Ta, [211] V, [254] Na [255,256] W, [257,258] and B, [132,259] ) and anions doping (F, [260,261] Cl, [262] and S, [263] ) have been introduced into the Ni-rich cathodes. The origins for the obviously improved structural stabilities by doping are closely associated with the three aspects as follows: i) the reinforcement of the bonding energy between TM ions and oxygen, ii) the suppression of the detrimental phase distortion from the layered to rocksalt structure, and iii) the promotion of the Li-ion migration thanks to increased Li slab distance by the dopants.…”

Degradation and Aging Routes of Ni-Rich Cathode Based Li-Ion Batteries

“…However, green energy sources are intermittent in nature and their proper utilization demands the use of highly efficient and durable electrochemical energy storage devices [4]. Similarly, xEVs necessities the use of high energy density batteries that are capable of negating the existing "driving range anxiety" [5]. Amid existing electrochemical energy storage devices, lithium-ion batteries (LIBs) have attracted huge attention as one of the most versatile and enabler devices for use in a wide range of applications.…”