High-Manganese Hydroxide Precursor for Dense Battery Cathodes
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Solution Overview
Problem
The challenge is to enhance the densification of hydroxide precursors for lithium transition metal composite oxides with high Mn/Me ratios, which is hindered by the granular crystalline form of Ni(OH)2 and flaky form of Mn(OH)2, leading to low energy density per unit volume in nonaqueous electrolyte secondary batteries.
Innovation Solution
A method involving the use of a hydroxide precursor with a transition metal hydroxide coprecipitated using a solution containing a complexing agent and reducing agent, where the Mn/Me ratio exceeds 0.5 and Co/Me is 0.15 or less, followed by firing at 800 to 940°C to achieve a high tap density and specific crystal structure, resulting in a lithium transition metal composite oxide with improved discharge capacity per unit volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a hydroxide precursor with high Mn/Me ratio (exceeding 0.5) is used to increase discharge capacity, then the discharge capacity per unit volume is improved, but the crystalline form becomes flaky and tap density decreases
Solution Approach 1:
The patent applies parameter changes by controlling the pH during coprecipitation to be 11.5 or less, which fundamentally alters the crystalline morphology of the hydroxide precursor. This pH control prevents the formation of flaky structures and promotes granular or spherical particles with high tap density (1.00 g/cm³ or more), thereby resolving the contradiction between high Mn/Me ratio and maintainable tap density
Solution Approach 2:
The patent uses composite materials by coprecipitating multiple transition metals (Mn, Ni, Co) together in a controlled pH environment. This coprecipitation process creates a composite hydroxide precursor where the interaction between different metal hydroxides at controlled pH produces a synergistic effect, forming a granular crystalline structure that maintains high tap density even with high Mn content (Mn/Me > 0.5)
2Quantity of substance
If the Mn/Me ratio is increased to improve discharge capacity, then the energy density per unit volume is enhanced, but the crystal structure stability deteriorates due to spinel transformation
Solution Approach 1:
The patent applies parameter changes by controlling the pH during coprecipitation to be 13.0 or less (preferably 11.5 or less), which fundamentally alters the crystalline morphology from flaky to granular/spherical. This pH control maintains the layered crystal structure stability even with high Mn/Me ratios by preventing spinel transformation during charging
Solution Approach 2:
The patent uses composite materials by coprecipitating Mn with Ni and/or Co in specific ratios (Ni/Me: 0.1-0.5, Co/Me: 0.05-0.3). This composite approach creates a layered structure where Ni and Co stabilize the crystal structure against spinel transformation while Mn provides high capacity, achieving both high energy density and structural stability
3Ease of manufacture
If conventional coprecipitation methods are used to produce hydroxide precursor, then the production process is simple, but the tap density remains low due to flaky crystalline form
Solution Approach 1:
The patent applies parameter changes by controlling the pH during coprecipitation to be 11.5 or less, which fundamentally alters the crystalline morphology from flaky to granular or spherical. This single parameter change maintains the simplicity of the coprecipitation process while dramatically improving tap density to 1.00 g/cm³ or more
Solution Approach 2:
The patent applies local quality by controlling the local pH environment during coprecipitation. By maintaining pH at 11.5 or less in the reaction zone, the process promotes granular crystal growth locally while keeping the overall process simple. This local pH control creates nuclei that grow into dense granular particles rather than flaky structures
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 approach results in a lithium transition metal composite oxide with a high tap density and enhanced discharge capacity per unit volume, effectively addressing the low energy density issues in nonaqueous electrolyte secondary batteries.
Implementation Method 1
a transition metal hydroxide precursor for use in production of a lithium transition metal composite oxide, in which a transition metal (Me) includes Mn and Ni, or Mn, Ni and Co in the transition metal hydroxide precursor, a mole ratio Mn/Me of the Mn to the transition metal (Me) is larger than 0.5, and a mole ratio Co/Me of the Co to the transition metal (Me) is 0.15 or less
Implementation Method 2
followed by firing at 800 to 940°C to achieve a high tap density and specific crystal structure
Data Source
AI summary
To provide a hydroxide precursor having a high density, a method for producing a lithium transition metal composite oxide using the precursor, a positive active material having a large discharge capacity per unit volume, which uses the composite oxide, an electrode for nonaqueous electrolyte secondary battery, and a nonaqueous electrolyte secondary battery. A method for producing a transition metal hydroxide precursor for use in production of a lithium transition metal composite oxide, including adding a solution containing a transition metal (Me) into a reaction tank in which a water solvent of dissolution of a complexing agent and a reducing agent has been charged in advance to coprecipitate a transition metal hydroxide that includes Mn and Ni, or Mn, Ni and Co, and has a mole ratio Mn/Me of larger than 0.5 and a mole ratio Co/Me of 0.15 or less. Further, a lithium transition metal composite oxide having an α-NaFeO2-type crystal structure, in which a mole ratio Li/Me is larger than 1, the mole ratios of Mn and Co are as described above, and which has an X-ray diffraction pattern attributable to R3-m, a ratio (FWHM (003)/FWHM (114)) of a full width at half maximum of a diffraction peak of a (003) plane to a full width at half maximum of a diffraction peak of a (104) plane of 0.72 or less, and a peak differential pore volume of 0.50 mm3/(g·nm) or less as determined by a BJH method from an adsorption isotherm using a nitrogen gas adsorption method.