(Digital Presentation) Cobalt Free Cathode Synthesized By Sacrificial Template (α-MnOOH) for Rechargeable Lithium Batteries
Authors: Agudelo Arias Hector David , Calderon Jorge , Vasquez Arroyave Ferley Alejandro 
Published: July 2022

LiCoO2 cathode has been used widely for Li-ion batteries (LIBs) for portable applications due to it is compactness, high energy density, excellent cycle life and reliability [1]. Nevertheless, the high cost of cobalt represent some of the limitations of this material [1]. As an alternative, LiNiO2, which iso-structural with LiCoO2, is reported as a stable material for LIB cathodes. Although, the poor thermal stability of this material in operating LIB represents safety risk [2]. On the other hand, LiMnO2 has also been proposed as a low-cost cathode for LIB. However, it is not stable during charging/discharging processes [3]. Ni-rich layer oxide (LiM1-x NxiO2, where M is a transition metal, x > 0.8) appeared as result of much effort dedicated for finding an adequate balance between cost and stability [4]. In comparison to Ni-rich layer, Li-rich layer oxide exhibited better cyclability and safety performance at higher electrode potentials (>4.5 V vs. Li|Li+) [4]. However, the structural and electrochemical properties of the as-prepared materials are determined by the synthesis methods and/or preparation conditions [5]. For instance, the electrochemical performance of Li1.5Ni0.25Mn0.75O2.5 layer material obtained by a simple carbonate coprecipitation method was improved with 240 mAh g-1 and 70.3% of capacity retention after 30 cycles at 0.05C [6].

In this work, we report the feasibility of producing a cobalt free cathode LiNi0.5Mn0.5O2 with high energy density using a sacrificial template α
-MnOOH as precursor with a simple balance between lithium and nickel content. The synthesis strategies performed in this work led to a promising cathode material with high energy density without sacrificing the operating voltage window, by combining our understanding of the factors governing the cation order with a facile synthetic route that ensured good cation mixing.

The LiNi0.5Mn0.5O2 active cathode material was produced by co-precipitated method according to the following procedure:

α-MnOOH sacrificial template was synthesized according to ref. [7].

Then active cathode material was obtained by co-precipitation method using α-MnOOH, lithium acetate and nickel acetate with a molar ratio of 0.5:1.05:0.5 mol at different treatment temperatures (700°C, 800°C and 900°C).

Rate capabilities of all samples are displayed in Fig. 1. The charge-discharge current was increased from 20 mA g-1 (0.1C) to 2000 mA g-1 (10C), and then decreased back to 20 mA g-1. The Li1.05Ni0.5Mn0.5O2 material displayed the best electrochemical performance at 800°C which the initial discharge capacity was 179.9 mAh g-1
. The other samples at 700
°C and 900
°C showed initial discharge capacities of 171.3
mAh g-1
and 156.4
mAh g-1
at 0.1C, respectively. On the other hand, α-MnOOH sacrificial template synthesis showed to be a plausible formation mechanism and the structure–function relationships of LiNi0.5Mn0.5O2.

[1] N. Nitta, F. Wu, J. T. Lee, and G. Yushin, “Li-ion battery materials: present and future,” Mater. Today, vol. 18, no. 5, pp. 252–264, Jun. 2015.

[2] M. Bianchini, M. Roca-Ayats, P. Hartmann, T. Brezesinski, and J. Janek, “There and Back Again—The Journey of LiNiO2 as a Cathode Active Material,” Angew. Chemie Int. Ed., vol. 58, no. 31, pp. 10434–10458, Jul. 2019.

[3] T. Ohzuku and Y. Makimura, “Layered Lithium Insertion Material of LiNi 1/2 Mn 1/2 O 2 : A Possible Alternative to LiCoO 2 for Advanced Lithium-Ion Batteries,” Chem. Lett., vol. 30, no. 8, pp. 744–745, Aug. 2001.

[4] G. Hu et al., “A facile cathode design with a LiNi0.6Co0.2Mn0.2O2 core and an AlF3-activated Li1.2Ni0.2Mn0.6O2 shell for Li-ion batteries,” Electrochim. Acta, vol. 265, pp. 391–399, Mar. 2018.

[5] C. Zhao, X. Wang, R. Liu, F. Xu, and Q. Shen, “β-MnO2 sacrificial template synthesis of Li 1.2Ni0.13Co0.13Mn0.54O2 for lithium ion battery cathodes,” RSC Adv., vol. 4, no. 14, pp. 7154–7159, Jan. 2014.

[6] M. Akhilash, P. S. Salini, K. Jalaja, B. John, and T. D. Mercy, “Synthesis of Li1.5Ni0.25Mn0.75O2.5 cathode material via carbonate co-precipitation method and its electrochemical properties,” Inorg. Chem. Commun., vol. 126, p. 108434, Apr. 2021.

[7] F. A. Vásquez, J. E. Thomas, A. Visintin, and J. A. Calderón, “LiMn1.8Ni0.2O4 nanorods obtained from a novel route using α-MnOOH precursor as cathode material for lithium-ion batteries,” Solid State Ionics, vol. 320, pp. 339–346, Jul. 2018.

Figure 1