Nickel-Graded Lithium Cobalt Oxide Cathode for High-Capacity Safety
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Solution Overview
Problem
Existing lithium-ion secondary batteries face challenges with high capacity, safety, thermal stability, and cycle performance due to the instability of positive electrode active materials with layered rock-salt crystal structures, particularly lithium cobalt oxide and lithium nickel oxide.
Innovation Solution
A positive electrode active material with a specific composition and structure, including cobalt, nickel, and an additive element such as magnesium, fluorine, or aluminum, is developed, with a controlled nickel content and crystallite size, enhancing stability and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium cobalt oxide with layered rock-salt crystal structure is used to achieve high capacity, then discharge capacity is improved, but safety deteriorates due to crystal structure collapse during charging
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core contains lithium cobalt oxide for high capacity while the outer shell contains a stable layered structure that prevents crystal collapse. This allows the high-capacity material to be protected by a stable protective layer, resolving the contradiction between capacity and safety.
Solution Approach 2:
The patent uses composite materials by combining lithium cobalt oxide particles with a stable layered structure material to form a composite positive electrode active material. The composite structure allows the high-capacity lithium cobalt oxide to be embedded within a protective matrix that maintains structural integrity during charging and discharging, thus improving both capacity and safety.
2Quantity of substance
If lithium nickel oxide is used to increase energy density and reduce cost, then energy density is improved, but thermal stability deteriorates making it less safe
Solution Approach 1:
The patent applies local quality by distributing nickel content non-uniformly within the positive electrode active material, with lower nickel content in regions prone to thermal instability and higher nickel content in regions where it enhances capacity. This localized composition optimization allows energy density improvement while maintaining thermal stability.
Solution Approach 2:
The patent uses parameter changes by precisely controlling the nickel content ratio and crystal structure parameters to achieve optimal balance between energy density and thermal stability. By adjusting compositional parameters and structural parameters, the patent transforms lithium nickel oxide from thermally unstable to thermally stable while maintaining high energy density.
3Ease of manufacture
If cation mixing occurs with nickel substituting lithium sites to reduce manufacturing complexity, then manufacturing is simplified, but discharge capacity deteriorates due to reduced lithium content
Solution Approach 1:
The patent applies local quality by creating regions with different compositional characteristics, where nickel substitution is controlled to occur in specific crystallographic positions or regions rather than uniformly throughout the structure. This localized substitution pattern reduces cation mixing effects while maintaining manufacturing simplicity.
Solution Approach 2:
The patent uses parameter changes by optimizing the nickel-to-lithium ratio and controlling synthesis parameters to minimize cation mixing. By adjusting compositional parameters and processing conditions, the patent achieves low cation mixing without complex manufacturing procedures, thus maintaining both ease of manufacture and high discharge capacity.
Data Source
AI summary
A positive electrode active material with both high capacity and safety is provided. The secondary battery includes a positive electrode. The positive electrode includes a positive electrode active material. The positive electrode active material includes lithium cobalt oxide containing magnesium, nickel, and aluminum. When the positive electrode is analyzed by powder X-ray diffraction using CuKα1 as a radiation source at a charge depth greater than or equal to 0.8, the positive electrode active material has diffraction peaks at 2θ of 19.30±0.20° and 2θ of 45.55±0.10°. The positive electrode active material includes a first region having a surface parallel to a (001) plane and a second region having a surface parallel to a plane intersecting with the (001). A nickel concentration in the first region is higher than a nickel concentration in the second region.