Electrochemical Performance and Elevated Temperature Properties of the TiO₂-Coated Li[Ni_0.8Co_0.1Mn_0.1]O₂ Cathode Material for High-Safety Li-Ion Batteries

Abstract

Nowadays, the LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode material has attracted great research interest due to its high energy density and less usage of costly raw materials. However, the high nickel content of NCM811 brings about an extremely unstable interface between the electrode and electrolyte and therefore inferior cyclic stability. Herein, we have proposed a straightforward method to deliver 1, 2, and 4 wt % of TiO 2 nanoparticles (NPs) on the surface of the NCM811 cathode material and to improve its properties at room and high temperatures. Based on scanning electron microscopy and transmission electron microscopy observations, the coating thickness varies from 10 to 35 nm and the 2 wt % TiO 2 -coated cathode is provided with uniformly distributed NPs that could result in an improved structural stability and electrochemical performance. In detail, at 25 and 55 °C and 1 C, the 2 wt % TiO 2 -coated cathode shows capacity retentions of 90.0 and 80.5% after 100 cycles, higher than those of pristine and coated cathodes. Under a high current rate of 10 C at 25 and 55 °C, the discharge capacities of the 2 wt % TiO 2 -coated cathode were 135.9 and 141.4 mA h g −1 , which are significantly higher than those of the pristine cathode material (128.3 and 89.1 mA h g −1 ). Results of the dissolution test at 55 °C reflect the effectiveness of the TiO 2 coating in maintaining the structural integrity of the cathode material and protecting it from HF attack and deleterious side reactions. Also, the differential scanning calorimetry result proves the enhanced safety after surface modification; the TiO 2 coating shifts the exothermic peak of the electrode from 231.1 to 242.9 °C. Therefore, surface modification with TiO 2 NPs can be proposed as a practical and cost-effective method for the commercial application of the high energy density NCM811 cathode at room and high temperatures. KEYWORDS: LiNi 0.8 Co 0.1 Mn 0.1 O 2 , nanocoating, TiO 2 , safety, cathode, lithium-ion batteries

Enhancing the Electrochemical Properties of Nickel-Rich Cathode by Surface Coating with Defect-Rich Strontium Titanate

“…The fitted Nyquist curves are demonstrated in Figure a, the equivalent circuit model is shown in Figure b, and the corresponding data are listed in Table S2. All the fitting curves comprise two semicircles: the first semicircle at the high frequency is related to the resistance of the CEI film generated at the cathode surface ( R s ), and the second semicircle in the medium frequency is associated with the charge-transfer resistance ( R ct ) . Furthermore, the calculation of D (Li + ) for NCA and NCA-STOx is based on eq D = R 2 T 2 2 A 2 n 4 F 4 C 2 σ 2 where R is the gas constant, T denotes the absolute temperature ( RT = 298.15 K), A is the surface area of the cathode (circular cathode sheet with a diameter of 1.4 cm), n stands for the number of electrons per molecule ( n = 1) during the electrochemical reactions, F is the Faraday constant, C signifies the Li + concentration in the cathode ( C ≈ 0.0235 mol/cm 3 ), and σ is the Warburg coefficient (or Weber factor), which obeys eq Z ′ = R normale + R normalc normalt + σ ω − 1 / 2 where Z′ denotes the real part of impedance, R e is the electrolyte resistance, and ω is the angular frequency (ω = 2π f ).…”

“…All the fitting curves comprise two semicircles: the first semicircle at the high frequency is related to the resistance of the CEI film generated at the cathode surface (R s ), and the second semicircle in the medium frequency is associated with the charge-transfer resistance (R ct ). 42 Furthermore, the where R is the gas constant, T denotes the absolute temperature (RT = 298.15 K), A is the surface area of the cathode (circular cathode sheet with a diameter of 1.4 cm), n stands for the number of electrons per molecule (n = 1) during the electrochemical reactions, F is the Faraday constant, C signifies the Li + concentration in the cathode (C ≈ 0.0235 mol/cm 3 ), and σ is the Warburg coefficient (or Weber factor), which obeys eq 5…”

Li0.33La0.56TiO3, a novel coating to improve the electrochemical properties and safety of NCM523 cathode materials for Li-ion batteries

“…This can be explained by the effect of LLTO coating on maintaining the structural integrity of the cathode lattice and inhibiting formation of the SEI layer. 42…”

“…This could be because of the high LLTO content that leads to a strong interaction between coating particles and considerable agglomeration. 23,42 This phenomenon can reduce the effectiveness of the LLTO coating since small particles interact with each other to form larger particles, instead of covering the cathode surface. The distribution of the constituent elements of the 5-A sample is shown in Fig.…”

Challenges and Strategies towards Single‐Crystalline Ni‐Rich Layered Cathodes

“…Particularly, surface coating has been regarded as the most common and effective strategy to increase surface/interface stability and charge transportation. The coating materials can be categorized as metal compounds with electrochemical passivation (e.g., Al 2 O 3 , [ 76 ] ZrO 2 , [ 77 ] B 2 O 3 , [ 78 ] TiO 2 , [ 79 ] Y 2 O 3 , [ 80 ] MoO 3 , [ 81 ] SiO 2 , [ 82 ] CuO, [ 83 ] AlPO 4 , [ 84 ] FePO 4 , [ 85 ] Co x B [ 5c ] etc. ), electrical conductors (e.g., carbon, [ 86 ] graphene, [ 87 ] polyaniline, [ 88 ] polypyrrole, [ 89 ] RuO 2 [ 90 ] etc.…”