Lithium-Ion Cathode Material with Controlled Crystallite Boundaries
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Solution Overview
Problem
Current lithium ion batteries face limitations in rate performance, capacity, and cycle life due to the diffusion ability of lithium ions in layered ternary materials, particularly in the positive electrode, where the crystallite boundaries within the primary particles affect the battery's overall efficiency.
Innovation Solution
A positive electrode material with a specific formula (Li1+aNixCoyMnzMcM′dO2−bAb) is developed, featuring a controlled number of crystallite boundaries, achieved through a method involving co-precipitation reactions, pH adjustments, and sintering processes, which enhances lithium ion diffusion and maintains crystallinity, thereby improving the battery's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the number of crystallite boundaries in primary particles is increased to improve lithium ion diffusion, then rate performance is improved, but structural integrity may deteriorate leading to microcracks
Solution Approach 1:
The patent applies parameter changes by precisely controlling the number of crystallite boundaries (N) within a specific range (10.5-14.5) through pH adjustment during co-precipitation and controlled sintering. This optimal parameter range enables sufficient lithium ion diffusion pathways while preventing excessive boundary formation that would compromise structural integrity and cause microcracks.
Solution Approach 2:
The patent implements local quality by creating a controlled distribution of crystallite boundaries within primary particles rather than uniform refinement throughout. The specific number of boundaries (10.5-14.5 per particle) provides localized diffusion channels where needed while maintaining overall particle structural coherence, avoiding the microcrack formation that would result from excessive boundary density throughout the entire structure.
2Stability of the object's composition
If pH is increased during co-precipitation to improve crystallinity, then material quality is enhanced, but control precision becomes more difficult
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the pH to a specific range (11.0-12.0) before initiating co-precipitation, and then maintaining it within a narrow window (11.5±0.2) during the reaction. This preliminary pH optimization ensures that crystallinity develops properly while the controlled maintenance range prevents excessive alkalinity that would complicate process control and affect manufacturing precision.
3Quantity of substance
If sintering temperature is increased to improve capacity, then energy density is enhanced, but material stability deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the sintering temperature to a specific range (900-1000°C) rather than using excessively high temperatures. This controlled temperature parameter achieves sufficient capacity (200-220 mAh/g) while preventing thermal degradation and structural collapse that would occur at higher temperatures, thereby maintaining material stability and reliability.
4Speed
If primary particle size is reduced to improve diffusion, then rate performance is enhanced, but surface area increases leading to more side reactions
Solution Approach 1:
The patent implements local quality by controlling the internal structure of primary particles to contain a specific number of crystallite boundaries (10.5-14.5) rather than simply reducing particle size. This approach creates efficient internal diffusion pathways within the particles while maintaining an appropriate external surface area that minimizes side reactions with the electrolyte, avoiding the trade-off that would result from mere size reduction.
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 approach results in improved rate performance and capacity retention, as well as extended cycle life by facilitating rapid lithium ion diffusion and maintaining structural integrity during charge/discharge cycles.
Implementation Method 1
a path for rapid diffusion of lithium ions in the bulk phase is provided, which increases the diffusion coefficient of lithium ions
Implementation Method 2
mixing a first aqueous solution comprising a nickel salt, a cobalt salt and a manganese salt, a second aqueous solution comprising a sodium-containing alkaline compound and/or a potassium-containing alkaline compound, and aqueous ammonia, and adjusting a first pH value of the resultant mixed aqueous solution to from about 9 to about 12, so as to allow a co-precipitation reaction to occur to form crystals
Implementation Method 3
mixing the precursor, a lithium source and a first additive comprising element M, sintering the resultant mixture at a constant temperature of from about 650 to about 900° C. for from about 4 to about 20 hours
Data Source
AI summary
Provided is a positive electrode material for a lithium ion battery, having the following general formula I: Li1+aNixCoyMnzMcM′dO2−bAb general formula I, wherein −0.05≤a≤0.3, 0.8≤x≤1, 0≤y≤0.2, 0≤z≤0.2, 0≤c≤0.01, 0≤d≤0.01, x+y+z+c+d=1, and 0≤b≤0.05; M and M′ are different from each other and each independently selected from at least one of La, Cr, Mo, Ca, Fe, Ti, Zn, Y, Zr, W, Nb, V, Mg, B, Al, Sr, Ba and Ta, A is selected from at least one of F, Cl, Br, I and S, and the number of crystallite boundaries N in primary particles of the positive electrode material is from 10.5 to 14.5, wherein N is calculated according to Equation I: N=DS/DX Equation I, wherein DS is an average size of the primary particles, as measured from scanning electron microscope (SEM) image of cross section of the positive electrode material, and DX is an average size of crystallites in the primary particles of the positive electrode material, as measured by an XRD test and calculated by the Scherrer equation. Also provided is a method for preparing the positive electrode material.