Lithium Battery Cathode Gradient Structure for Power and Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high capacity, power output, and stability, particularly at extreme temperatures and against penetration, due to limitations in cathode active materials.
Innovation Solution
A lithium secondary battery design incorporating a cathode active material blend of first and second particles, where the first particle has a concentration gradient and secondary particle structure, and the second particle has a single crystalline structure, with a specific composition and mixing ratio to enhance capacity, power output, and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a cathode active material with high nickel content is used to achieve high capacity and power output, then the battery capacity and power output are improved, but the thermal stability and penetration resistance deteriorate
Solution Approach 1:
The cathode active material is designed with a concentration gradient structure where nickel content varies spatially: high nickel concentration at the core for high capacity/power, and lower nickel concentration at the surface for thermal stability. This local variation in composition resolves the contradiction between high power output and thermal stability.
Solution Approach 2:
The cathode active material is formulated as a composite with multiple metal elements (nickel, cobalt, manganese, and other metals) in specific ratios. This composite structure combines the high capacity benefits of nickel-rich regions with the stability benefits of nickel-poor regions, achieving both high power output and thermal stability.
2Quantity of substance
If a cathode active material with high nickel content is used to achieve high capacity, then the battery capacity is improved, but the life-span deteriorates
Solution Approach 1:
The concentration gradient structure provides high nickel content at the core to maximize battery capacity while maintaining lower nickel content at the surface to ensure structural stability and long cycle life. This spatial differentiation resolves the contradiction between high capacity and long life-span.
Solution Approach 2:
The nickel concentration parameter is changed spatially within the particle structure, creating a gradient from high nickel at the core to low nickel at the surface. This parameter variation allows the material to simultaneously achieve high capacity (from core nickel) and long life-span (from surface stability).
3Power
If a cathode active material with high nickel content is used to achieve high power output, then the battery power output is improved, but the penetration stability deteriorates
Solution Approach 1:
The surface region with lower nickel content provides enhanced penetration stability and mechanical strength, while the core region with high nickel content delivers high power output. This local composition differentiation resolves the contradiction between power output and penetration stability.
4Quantity of substance
If a cathode active material with high nickel content is used to achieve high capacity, then the battery capacity is improved, but the stability in harsh conditions deteriorates
Solution Approach 1:
The concentration gradient creates a stable surface composition that resists degradation in harsh conditions (high temperature, penetration), while the nickel-rich core maintains high capacity. This spatial composition variation resolves the contradiction between high capacity and stability in harsh conditions.
Data Source
AI summary
A lithium secondary battery includes a cathode formed from a cathode active material including a first cathode active material particle and a second cathode active material particle, an anode and a separation layer interposed between the cathode and the anode. The first cathode active material particle includes a lithium metal oxide including a concentration gradient and has a secondary particle structure formed from an assembly of primary particles. The second cathode active material particle includes a lithium metal oxide having a single particle structure. The first and second cathode active material particles each includes at least two metals except from lithium, and an amount of nickel is the largest among those of the metals in each of the first and second cathode active material particles.