Tungsten-Lithium Surface Compound on Li-Metal Oxide
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Solution Overview
Problem
Existing nonaqueous electrolyte secondary batteries face challenges in achieving high power and capacity while minimizing gas generation, with previous methods often resulting in reduced battery characteristics due to substitution of elements like Mo, W, Nb, and Re with Ni, leading to impaired cycle and capacity performance.
Innovation Solution
A positive electrode active material is developed by forming a compound containing tungsten and lithium on the surface of lithium-metal composite oxide particles, achieved through immersion in an alkaline solution with a tungsten compound followed by solid-liquid separation and heat treatment, ensuring uniform dispersion and reduced reaction resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If different elements such as Mo, W, Nb, Ta, and Re are added to reduce resistance, then high power and low resistance are achieved, but some different elements are substituted with Ni in layers, resulting in reduced battery capacity and cycle characteristics
Solution Approach 1:
The patent applies local quality by concentrating different elements (Mo, W, Nb, Ta, Re) specifically on the surface portions of primary particles rather than uniformly distributing them throughout the entire particle structure. This is achieved by controlling the total atomic ratio of these elements on surface portions to be 5 times or more the atomic ratio of the whole primary particles, ensuring high power performance at the reactive surface while preventing bulk substitution that would harm cycle characteristics.
Solution Approach 2:
The patent segments the particle structure into primary particles with specific surface properties and aggregate secondary particles. By controlling element distribution at the primary particle level and maintaining specific surface area characteristics (0.03 m²/g or more), the invention separates the functions of power delivery (surface) and structural stability (bulk), resolving the contradiction between high power and good cycle characteristics.
2Manufacturing precision
If lithium transition metal compound powder is obtained by pulverizing raw material in liquid medium and spray drying, then uniform dispersion is achieved, but some different elements are substituted with Ni disposed in layers, resulting in reduction in battery characteristics
Solution Approach 1:
The patent changes the critical parameter of element distribution by controlling the total atomic ratio of different elements on surface portions to be 5 times or more the atomic ratio of whole primary particles. This parameter control ensures uniform dispersion of elements on the surface while preventing their substitution into the layered structure, thereby maintaining both manufacturing precision and battery characteristics.
3Use of energy by moving object
If high voltage of 4-V class is obtained using layered or spinel lithium-metal composite oxide, then high energy density is achieved, but resistance reduction is necessary for power enhancement
Solution Approach 1:
The patent uses composite materials by combining lithium-metal composite oxide with specific amounts of different elements (Mo, W, Nb, Ta, Re) on the surface of primary particles. This composite structure maintains the high voltage 4-V class characteristics of the base lithium-metal composite oxide while the surface-added different elements provide the necessary resistance reduction for power enhancement, achieving both high energy density and high power.
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
The solution enables high power and capacity performance with reduced positive electrode resistance, improved lithium ion conductivity, and suppressed gas generation, enhancing the overall battery characteristics.
Implementation Method 1
materials capable of intercalation and deintercalation of lithium ions are used for the active materials of the negative electrode and the positive electrode
Implementation Method 2
immersing a resulting mixture, followed by solid-liquid separation, to obtain a tungsten-containing mixture in which tungsten is uniformly dispersed on the surface of the primary particles
Implementation Method 3
forming a compound containing tungsten and lithium on the surface of the primary particles inside the secondary particles
Implementation Method 4
subjecting the tungsten-containing mixture to heat treatment to thereby form a compound containing tungsten and lithium on the surface of the primary particles
Implementation Method 5
reduced positive electrode resistance, improved lithium ion conductivity
Data Source
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AI summary
Provided is a positive electrode active material for nonaqueous electrolyte secondary batteries which allows high capacity and high power to be obtained when used as a positive electrode material. A method for producing the positive electrode active material for nonaqueous electrolyte secondary batteries, including a first step of mixing a Li-metal composite oxide powder which is represented by the general formula: LizNi1-x-yCoxMyO2 (where 0 ≤ x ≤ 0.35, 0 ≤ y ≤ 0.35, and 0.97 ≤ z ≤ 1.30 are satisfied, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al) and constituted by primary particles and secondary particles formed by aggregation of the primary particles, to an alkaline solution with a W compound dissolved therein at a W concentration of 0.1 to 2 mol/L so that the solid-liquid ratio of the composite oxide powder with respect to the amount of water in the solution falls within the range of 200 to 2500 g/L, and immersing a resulting mixture, followed by solid-liquid separation, to obtain a W mixture with W uniformly dispersed on the surface of the primary particles of the composite oxide, and a second step of heat-treating the W mixture to thereby form a compound containing W and Li on the surface of the primary particles of the composite oxide powder.