Core-Shell Composite Oxide for Battery Electrodes
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Solution Overview
Problem
Current lithium/nickel/cobalt/manganese-containing composite oxides for lithium secondary batteries face challenges in achieving high weight capacity density, packing property, cycle property, discharge rate property, and safety while minimizing free alkalis and preventing gelation during electrode processing.
Innovation Solution
A lithium/nickel/cobalt/manganese-containing composite oxide powder with specific particle size classification and molar ratios, along with controlled specific surface areas and the presence of elements like Al, Ge, or transition metals, is used, where the molar ratio of lithium to nickel, cobalt, manganese, and additional elements is adjusted in small and large particle sizes to optimize properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium/nickel/cobalt/manganese-containing composite oxide with high lithium proportion is used to improve discharge capacity and cycle property, then discharge capacity and cycle property are improved, but the amount of free alkalis increases causing gelation during electrode processing
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region has a different lithium proportion (closer to 1.0) compared to the shell region (1.05-1.15). This spatial differentiation allows the core to provide stable cycling performance while the shell provides high discharge capacity, and the overall structure maintains controlled free alkali content to prevent gelation during processing.
Solution Approach 2:
The patent changes the lithium proportion parameter from a uniform value to a gradient distribution, with the lithium proportion increasing from the core to the shell. This parameter gradient allows optimization of multiple properties simultaneously: the core region ensures structural stability and low free alkali content, while the shell region provides high capacity and improved coating properties.
2Ease of manufacture
If lithium/nickel/cobalt/manganese-containing composite oxide with uniform composition is used, then manufacturing is simplified, but it cannot simultaneously achieve high discharge capacity, high packing density, and excellent cycle property
Solution Approach 1:
The patent implements local quality through a core-shell structure where the core and shell have different compositional characteristics. The core region provides structural stability for excellent cycle property, while the shell region enhances discharge capacity and packing density. This localized differentiation achieves multiple performance goals without significantly complicating the manufacturing process.
3Speed
If small particle size powder is used to improve discharge rate property, then discharge rate property is improved, but packing density and weight capacity density decrease
Solution Approach 1:
The patent uses a composite material approach by combining small particle size powder (improving discharge rate) with large particle size powder (improving packing density). The small particles provide high surface area for fast lithium ion diffusion and excellent discharge rate properties, while the large particles fill voids and provide high packing density, achieving a balance between discharge rate and weight capacity density.
4Power
If high lithium proportion is used to improve discharge capacity, then discharge capacity is improved, but free alkalis increase causing gelation during slurry processing
Solution Approach 1:
The patent applies local quality by concentrating the high lithium proportion (1.05-1.15) in the shell region rather than uniformly throughout the particle. This allows the shell to provide high discharge capacity while the core region maintains lower lithium content, thereby controlling the overall free alkali content and preventing gelation during slurry processing.
Solution Approach 2:
The patent changes the lithium proportion from a uniform parameter to a spatially varying parameter that increases from core to shell. This parameter gradient enables the shell region to contribute high discharge capacity while the core region buffers the overall free alkali content, preventing gelation during electrode manufacturing.
Data Source
AI summary
A lithium/nickel/cobalt/manganese-containing composite oxide powder represented by the formula LipNixCoyMnzMqO2-aFa (wherein M is at least one element selected from the group consisting of Al, Ge, Sn, alkaline earth metal elements and transition metal elements other than Co, Mn and Ni, 0.9≦p≦1.1, 0.2≦x≦0.5, 0.2≦y≦0.5, 0.1≦z≦0.4, 0≦q≦0.5, 1.9≦a≦2.1, p+x+y+z+q=2, and 0≦a≦0.02), characterized in that when the powder is classified into small particle size-classified particles with an average particle size 2 μm≦D50≦8 μm and large particle size-classified particles with an average particle size of 10 μm≦D50≦75 μm, the ratio of (% by weight of the small particle size-classified particles)/(% by weight of the large particle size-classified particles) is from 15/85 to 40/60.