High-Nickel Cathode Material With Molybdenum Removal for Low-SOC Output
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Solution Overview
Problem
Lithium-nickel-based complex oxides with high nickel ratios in lithium ion secondary batteries experience reduced performance at low state of charge (SOC) due to nickel reduction, leading to deteriorated output characteristics while maintaining discharge capacity.
Innovation Solution
A method involving the firing of a mixture containing lithium, nickel, and molybdenum compounds to produce lithium transition metal complex oxides with a nickel-to-total metals ratio greater than 0.6 and less than 1, followed by a washing process to remove molybdenum, enhancing the specific surface area and maintaining discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium-nickel-based complex oxide with a high nickel ratio is used to decrease cobalt usage, then charge-discharge capacity per unit weight is improved, but nickel reduction occurs and output deteriorates at low state of charge
Solution Approach 1:
The patent removes molybdenum elements from the surface of lithium transition metal complex oxide particles through washing with water. This extraction of the harmful molybdenum component (which causes nickel reduction) resolves the contradiction by eliminating the root cause of output deterioration while preserving the high nickel ratio structure that provides high charge-discharge capacity
Solution Approach 2:
The patent changes the molybdenum content parameter by controlling the washing process to achieve a specific ratio of molybdenum to total metals other than lithium (0.003 to 0.015). This parameter optimization allows the material to maintain high nickel ratio for capacity while reducing molybdenum-induced nickel reduction that harms output characteristics
2Reliability
If molybdenum compound is added to improve output characteristics at low SOC, then output is improved, but molybdenum remains on the surface and discharge capacity deteriorates
Solution Approach 1:
The patent applies partial action by adding a small, controlled amount of molybdenum compound (0.01 to 1.0 mol% relative to total metals other than lithium) during firing. This partial addition provides enough molybdenum to improve output characteristics through surface effects while limiting the total molybdenum content to prevent discharge capacity deterioration
Solution Approach 2:
The patent converts the potentially harmful effect of molybdenum (causing nickel reduction) into a beneficial effect by controlling its presence as a surface component rather than bulk component. The small amount of molybdenum on the surface improves output characteristics, while the washing process removes excess molybdenum that would cause harm, thus converting molybdenum from a harmful impurity to a beneficial surface modifier
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 method improves output characteristics at low SOC while maintaining discharge capacity by reducing molybdenum content and increasing the specific surface area, thereby promoting lithium ion movement and reducing resistance.
Implementation Method 1
bringing the first particles into contact with a liquid medium in such that a solid content concentration of the first particles is in a range of 20 mass % to 80 mass % to remove a part of molybdenum element contained in the first particles
Data Source
AI summary
A method of manufacturing a positive electrode material for a lithium ion secondary battery includes: firing a mixture containing a lithium compound, a nickel-containing complex compound, and a molybdenum compound, to obtain first particles containing a lithium transition metal complex oxide having a composition in which a ratio of a number of moles of nickel to a total number of moles of metals other than lithium is greater than 0.6 and less than 1; and bringing the first particles into contact with a liquid medium in such that a solid content concentration of the first particles is in a range of 20 mass % to 80 mass % to remove a part of molybdenum element contained in the first particles to obtain second particles.