Boron-Doped Ni-Rich Cathode Material for Crack-Resistant Battery Cycling
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Solution Overview
Problem
Current lithium secondary batteries face challenges in achieving high-capacity, long-life, and stable performance, particularly in minimizing life-span shortening and crack generation due to charge/discharge cycles, which are exacerbated by high nickel concentrations.
Innovation Solution
A positive active material composed of nickel, lithium, and oxygen with boron doping, where the nickel concentration is 59 mol% or more, and the average angle between particle orientation lines is 12.2° or less, is developed. This material includes a secondary particle structure with primary particles agglomerated in a specific orientation, allowing for stress relaxation and reduced impurity phase formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel concentration (59 mol% or more) is used in the positive active material, then capacity is improved, but crack generation and life-span shortening occur during charge/discharge cycles
Solution Approach 1:
The patent applies parameter changes by precisely controlling the nickel concentration at 59 mol% or more while simultaneously controlling the average particle diameter to 6 μm or more. These parameter adjustments optimize the balance between capacity and structural stability during charge/discharge cycles, preventing crack generation while maintaining high nickel content for improved capacity.
Solution Approach 2:
The patent applies local quality by creating a specific particle size distribution where larger particles (6 μm or more average diameter) provide structural stability and crack resistance, while the high nickel concentration regions provide high capacity. This spatial differentiation of properties resolves the contradiction between capacity and reliability.
2Productivity
If high nickel concentration is used to increase capacity, then charge/discharge efficiency is improved, but crack generation increases reducing stability
Solution Approach 1:
The patent changes physical parameters by setting the average particle diameter to 6 μm or more, which provides sufficient structural stability to prevent cracks during charge/discharge cycles. Simultaneously, the nickel concentration is maintained at 59 mol% or more to ensure high charge/discharge efficiency. This dual parameter control resolves the contradiction between productivity and stability.
3Ease of manufacture
If particle orientation is randomized, then manufacturing is simpler, but stress relaxation is reduced leading to increased crack generation
Solution Approach 1:
The patent applies local quality by creating specific oriented regions within the particle aggregate where primary particles are arranged with their c-axes oriented at angles of 45° or less relative to the radial direction. This localized orientation provides stress relaxation pathways and crack resistance in critical regions while allowing other regions to maintain simpler structures, thus resolving the contradiction between ease of manufacture and reliability.
Data Source
AI summary
A positive active material includes a secondary particle in which a plurality of primary particles is agglomerated. The positive active material is composed of, in which a compound containing nickel, lithium, and oxygen. An average angle between a reference line connecting a center portion of the secondary particle and a center portion of the primary particle provided at the outermost portion of the secondary particle and a particle orientation line penetrating the center portion of the primary particle provided at the outermost portion of the secondary particle and extending in parallel to an orientation direction of the primary particles is 12.2° or less. A concentration of the nickel in the compound is 59 mol % or more. The compound further includes an added metal composed of a different element from the nickel and the lithium. The added metal includes one or more of boron (B) and tungsten (W).