Core-Shell NMC Cathode with Al2O3 Coating for High-Ni Stability
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Solution Overview
Problem
High Ni content NMC cathode materials used in lithium ion batteries face stability issues at elevated voltages and temperatures, leading to poor cycle life and safety concerns, particularly in automotive applications.
Innovation Solution
The use of surface-modified lithium nickel manganese cobalt oxide particles with a coating of Al2O3, combined with a nonaqueous liquid electrolyte containing specific additives such as prop-1-ene-1,3-sultone, tris(trimethylsilyl)phosphite, and methylene methanedisulfonate, improves the stability and cycling performance of the batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high Ni content NMC cathode materials are used to achieve high energy density, then the energy density is improved, but the stability at elevated voltages and temperatures deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core maintains high Ni content (0.6-0.8) for high energy density, while the shell provides a different composition (Li1-x-yMxNiyO2 with x=0.05-0.15, y=0.30-0.45) for enhanced stability. This spatial differentiation allows each region to optimize its local properties - the core for capacity and the shell for protection - resolving the contradiction between energy density and stability.
Solution Approach 2:
The patent employs composite materials by combining two distinct NMC phases into a core-shell composite structure. The inner core (Li1-aNiz(Ni1/2Mn1/2)yCoxO2) and outer shell (Li1-x-yMxNiyO2) form a composite cathode material that integrates the high capacity of Ni-rich NMC with the stability of Mn-rich NMC, thereby achieving both high energy density and improved thermal/voltage stability.
2Use of energy by moving object
If high Ni content NMC cathode materials are used to reduce cost and improve energy density, then the cost and energy density are improved, but the cycle life deteriorates
Solution Approach 1:
The core-shell structure enables local quality optimization where the Ni-rich core (0.6≤z<0.8) provides high capacity and cost-effectiveness, while the Mn-rich shell (y=0.30-0.45) provides structural stability for long cycle life. This spatial separation of functions allows the battery to achieve both economic viability and durability simultaneously.
Solution Approach 2:
The Mn-rich NMC shell acts as an intermediary protective layer between the Ni-rich core and the electrolyte environment. This intermediate shell prevents direct exposure of the unstable Ni-rich core to harmful conditions, thereby extending cycle life while preserving the high capacity benefits of the Ni-rich composition.
3Use of energy by moving object
If high Ni content NMC cathode materials are used to achieve high energy density, then the energy density is improved, but the gas generation increases leading to poor storage stability
Solution Approach 1:
The core-shell structure creates local quality differentiation where the Ni-rich core (high energy density) is spatially separated from the electrolyte interface by the Mn-rich shell. This local protection at the critical interface region suppresses gas-generating side reactions while preserving the high capacity of the Ni-rich core material.
Solution Approach 2:
The Mn-rich NMC shell serves as an intermediary barrier that prevents direct contact between the Ni-rich core and the electrolyte. This intermediate layer suppresses parasitic reactions that would otherwise generate gas and compromise storage stability, allowing the high-energy Ni-rich core to function without its usual instability problems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration results in a rechargeable lithium ion battery with reduced capacity fading and enhanced coulombic efficiency, suitable for automotive applications, maintaining performance over 80 cycles with less than 10% capacity reduction and coulombic efficiency greater than 0.998% after 16 cycles.
Implementation Method 1
modifying high Ni NMC materials by surface modification or doping
Implementation Method 2
a nonaqueous liquid electrolyte containing specific additives such as prop-1-ene-1,3-sultone, tris(trimethylsilyl)phosphite, and methylene methanedisulfonate
Data Source
AI summary
A rechargeable lithium ion battery including: a positive electrode including coated particles, wherein each particle includes a core and a coating disposed thereon, wherein the core consists of Li, M, and O, and the coating includes Li, M, O, and AI2O3; wherein: M is (Niz(Ni1/2Mn1/2)yCox)1−kAk; 0.15≤z≤0.50; 0.17≤x≤0.30; 0.35≤y≤0.75; 0<k<0.1; x+y+z=1; and A includes Al and optionally at least one additional metal dopant selected from Mg, Zr, W, Ti, Cr, V, Nb, B, and Ca, and combinations thereof; and wherein the Li and M are present in the core in a molar ratio of Li to M of at least 0.95 and no greater than 1.10; a negative electrode; and a nonaqueous liquid electrolyte including: a lithium salt; a nonaqueous solvent; and an additive mixture including: prop-1-ene-1,3-sultone; at least one compound selected from tris(trimethylsilyl)phosphite, tris(trimethylsilyl)phosphate, tri-allyl phosphate, and combinations thereof; and at least one compound selected from methylene methanedisulfonate, 1,3,2-dioxathiolane-2,2-dioxide, and combinations thereof.