Communication—Enhancing the Electrochemical Performance of Lithium-Excess Layered Oxide Li_1.13Ni_0.3Mn_0.57O₂ via a Facile Nanoscale Surface Modification

Abstract

In this work, a facile surface modification with nanoscale equilibrium Li 3 PO 4 -based surface amorphous films (SAFs) has been applied to Lithium-excess layered oxide Li 1.13 Ni 0.3 Mn 0.57 O 2 , which significantly improves the first cycle coulombic efficiency, rate capability, and cycling stability. The nanoscale surface modification can be easily achieved by ballmilling and isothermal annealing. The optimized surface modified Li 1.13 Ni 0.3 Mn 0.57 O 2 is capable of maintaining a high capacity of 201 mAh g −1 after 60 cycles at 55 • C testing with a rate of 1 C. This work provides a facile and scalable surface modification method to improve electrochemical performance of cathode materials for lithium ion batteries. The Lithium-excess layered oxides benefit from an extraordinary high reversible capacity (>280 mAh g −1 ) and is one of the most promising cathode materials for plug-in electric vehicle application. [1][2][3] However, this high-energy-density material suffers from large irreversible capacity in its first electrochemical cycle when it is charged to high voltages, namely more than 4.6 V. In addition, its rate capability is yet unsatisfactory for high power application. Moreover, the gradual voltage and capacity degradation upon electrochemical cycling, especially at elevated temperature when side reactions related to the interactions with the electrolyte occur more prevalently, represent the most serious technical challenge for this material. 4,5 In the past few years, significant amount of surface modification works have been carried out to protect the surfaces of the Li-excess. Most of the reported surface modifications are performed under solution-based reactions.6-8 For example, Bian et al. used LiOH and NH 4 H 2 PO 4 to coat Lithium-excess with Li 3 PO 4 .7 However, the solution based surface modification adds an additional layer of complexity for preparation of Lithium-excess, which will definitely raise the cost of production. Although Konishi coated high voltage spinel LiNi 0.5 Mn 1.5 O 4 with uniform Li 3 PO 4 via pulsed laser deposition (PLD), this technique requires special equipment, which is difficult to realize for large scale production. 9In this work, we modify the surface of Lithium-excess layered oxide Li 1.13 Ni 0.3 Mn 0.57 O 2 via simple mixing and calcination to form Li 3 PO 4 -enriched and nanometer-thick surface amorphous films (SAFs). 10 Our results indicate that the optimized material shows remarkably improved performance. ExperimentalThe synthesis of the Li-excess is described in our previous publications. 3,6 The procedure for preparing Li 3 PO 4 surface modified Li 1.13 Ni 0.3 Mn 0.57 O 2 (LPLNMO) was adapted from work by Huang et al.10 0.06 g Li 3 PO 4 (Alfa Aesar, 99.99%) and 3 g Li 1.13 Ni 0.3 Mn 0.57 O 2 were mixed using a planetary ball mill (PM 100, Retsch). The powder was calcinated at 500• C (LP500), 600• C (LP600), and 700• C (LP700), respectively, for 5 h in air. Electrochemical test, XRD, SEM and HRTEM characterization are described with details in our previous...

Enhancing the Ion Transport in LiMn1.5Ni0.5O4 by Altering the Particle Wulff Shape via Anisotropic Surface Segregation

“…Figure shows the neutron diffraction patterns for the undoped and WO 3 -doped LiMn 1.5 Ni 0.5 O 4 specimens. The Rietveld refinement structure analysis was used to investigate the crystal structure of both samples. − For long-term annealing at 700 °C, LiMn 1.5 Ni 0.5 O 4 intended to become ordered structure, and the ordered structure is disturbed upon further higher heating. , While these samples were annealed at 800 °C and cooled down quickly, both of them retained the fully disordered structure. Both patterns of undoped and doped specimens did not show any superstructure peaks arising from ordered structure ( P 4 3 32 space group), and both were successfully refined according to the Fd 3̅ m space group of a disordered structure.…”

“…The Rietveld refinement structure analysis was used to investigate the crystal structure of both samples. [53][54][55][56] For long term annealing at 700 °C, LiMn 1.5 Ni 0.5 O 4 intended to become ordered structure, and the ordered structure is disturbed upon further higher heating. 57,58 While these samples were annealed at 800 °C and cooled down quickly, both of them retained the fully disordered structure.…”

Multiscale factors in designing alkali-ion (Li, Na, and K) transition metal inorganic compounds for next-generation rechargeable batteries

“…294 For cathode materials which experience severe all above mentioned surface reaction problems at high voltage, it is essential that having a more effective coating with moderate uniformity, coverage and thickness to be conserved from aggressive environments. Therefore, it has been explored with diverse kinds of coating species, notably resulting in improved electrochemical performance and thermal stability results 295 by Al 2 O 3 , 219,[296][297][298][299][300] AlF 3 , 301,302 Li 3 PO 4 , 303,304 AlPO 4 , [305][306][307][308] etc.…”

Constructing High Conductive Composite Coating with TiN and Polypyrrole to Improve the Performance of LiNi0.8Co0.1Mn0.1O2 at High Cutoff Voltage of 4.5 V

“…Among them, surface modification has been proved to be an effective method to solve above problems. Metal oxides (Al 2 O 3 , TiO 2 , MgO,), ,, phosphates (AlPO 4 , Li 3 PO 4 ), − and fluorides (AlF 3 , LiF) , are often used to modify certain properties of the Ni-rich cathode materials. Even though these coatings have played a certain role in improving the electrochemical performance, the limited ionic and the electronic conductivities of these coatings often lead to sacrificing some properties of the material .…”