Simple Strategy for Synthesizing LiNi_0.8Co_0.15Al_0.05O₂ Using CoAl-LDH Nanosheet-Coated Ni(OH)₂ as the Precursor: Dual Effects of the Buffer Layer and Synergistic Diffusion

Abstract

Ni-rich layered oxide LiNi 0.8 Co 0.15 Al 0.05 O 2 is a promising cathode material for high-power lithium-ion batteries due to its high energy density and low cost. However, obtaining LiNi 0.8 Co 0.15 Al 0.05 O 2 with a large and uniform particle size and without undesired Al-related phases using some conventional synthesis methods is quite difficult. These problems seriously affect the electrochemical performance of LiNi 0.8 Co 0.15 Al 0.05 O 2 , thus impeding its wide application. Here, we propose a simple strategy to synthesize LiNi 0.8 Co 0.15 Al 0.05 O 2 using CoAl-layered double hydroxide (CoAl-LDH) nanosheet-coated Ni-(OH) 2 as the precursor. Compared with LiNi 0.8 Co 0.15 Al 0.05 O 2 synthesized from nickel−cobalt−aluminum hydroxide and Al(OH) 3coated nickel−cobalt hydroxide precursors, LiNi 0.8 Co 0.15 Al 0.05 O 2 produced using the proposed approach showed good sphericity, a large and uniform particle size, a pure phase, and excellent electrochemical performance. The superior properties are attributed to the dual effects of the buffer layer and synergistic diffusion. Specifically, the CoAl-LDH coating layer reacts with LiOH during the lithiation−calcination process to form a Li 1−x (Co 0.75 Al 0.25 ) 1+x O 2 mesophase as the buffer layer, which increases the formation temperature of the layered structure and reduces Li + /Ni 2+ cation mixing, making a well-ordered crystal structure. Moreover, spectroscopic analysis results and density functional theory calculations indicated a synergistic diffusion effect between Co and Al, and the presence of Co on the surface promotes the diffusion of Al during the lithiation−calcination process, thus avoiding the formation of undesired Al-related phases and allowing for a uniform element distribution. KEYWORDS: lithium ion batteries, LiNi 0.8 Co 0.15 Al 0.05 O 2 cathode material, CoAl-LDH nanosheet-coated Ni(OH) 2 , buffer layer, synergistic diffusion

Effects of Oxygen Pressurization on Li+/Ni2+ Cation Mixing and the Oxygen Vacancies of LiNi0.8Co0.15Al0.05O2 Cathode Materials

“…The fabrication of the cathode electrode and the assembly of coin-type half cell (CR2032) were similar to our previous work. 25 The prepared cathode material was blended with acetylene black and polyvinylidene fluoride dissolved in N-methylpyrrolidinone at a weight ratio of 8:1:1. The loading amount of the active material was 3.8−6.3 mg•cm −2 .…”

An MgAl layered double hydroxide as a new transition metal-free anode for lithium-ion batteries

“…[24][25][26] In previous research studies on the application of the LDHs in the LIBs, the LDHs were often used as precursors for the synthesis of transition metal oxide cathodes. [19][20][21] Intriguingly, there are few relevant studies about the LDHs or LDH-based composites that are used as anodes for the LIBs directly. For example, Li et al 22 investigated the application of an NiAl LDH as an anode material for the LIBs, which exhibited an outstanding initial discharge specific capacity of 1324 mA h g À1 at a current density of 50 mA g À1 and good stability in the charge-discharge process.…”

“…14 Apart from the above-mentioned 2D materials, layered double hydroxides (LDHs) with unique characteristics such as variable chemical compositions and the regulation of interlayer anions have also been used in halogen ion batteries, 15,16 oxygen evolution reactions 17,18 and LIBs. [19][20][21][22][23] Generally, the LDHs can be described by the following formula: [M II 1Àx M III x (OH) 2 ] x+ (A nÀ ) x/n ÁmH 2 O, where M II is a divalent metal (such as Mg 2+ , Ni 2+ , and Zn 2+ ), M III is a trivalent metal (such as Al 3+ , Fe 3+ , and Cr 3+ ), x is the adjustable parameter, and A nÀ is the exchangeable interlayer anion (e.g., CO 3 2À , NO 3…”

Protective Nanosheet Coatings for Thiophosphate‐Based All‐Solid‐State Batteries

“…In recent years, some nanosheet materials have already been tested as CAM coatings in LIBs. [26][27][28][29][30] Graphene takes a prominent position owing to its high stability and thoroughly researched properties and processing (including synthesis). Reduced graphene oxide is typically used to produce such carbon coatings due to facile deposition upon reduction, although some authors argue that surface modification or gaseous reducing agents are required, making the techniques experimentally challenging.…”

“…For example, layered double hydroxides were deposited from aqueous dispersions onto NCM and NCA both before and after calcination. [28,38] Graphitic carbon nitride can also be deposited from aqueous dispersions or by chemical vapor deposition (CVD). [39] Transition-metal chalcogenides, such as MoS 2 and WSe 2 , have been shown to increase the stability of CAMs.…”