Gradient Cathode Composition for Stable High-Power Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high capacity, power, and stability, particularly under harsh temperature conditions and resistance to penetration-induced failures like short-circuits and explosions, due to limitations in cathode active materials.
Innovation Solution
A lithium secondary battery design incorporating a cathode active material with a first particle having a continuous concentration gradient and a second particle with a constant concentration composition, optimized through specific metal ratios and particle sizes, enhances both electrical and mechanical reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a cathode active material with high capacity is used, then the battery power is improved, but the stability and life-time under harsh conditions deteriorate
Solution Approach 1:
The cathode active material is designed with a concentration gradient structure where the composition varies spatially: the surface region contains more stable elements (Ni-rich) for high power, while the inner region contains more stable elements (Mn-rich) for long-term stability. This local differentiation of composition allows simultaneous optimization of both power and stability without compromise.
Solution Approach 2:
The invention uses a composite cathode active material comprising multiple elements (Ni, Mn, Co, Al) with non-uniform distribution. The composite structure combines the high capacity benefits of Ni-rich regions with the stability benefits of Mn-rich regions, creating a material that exhibits both high power and excellent stability under harsh conditions including high temperature and penetration resistance.
2Quantity of substance
If a cathode active material with high capacity is used, then the battery energy density is improved, but the resistance to penetration-induced failures deteriorates
Solution Approach 1:
The surface region of the cathode particles is enriched with Ni and Co which provide high energy density, while the inner region contains Mn and Al which provide mechanical strength and resistance to penetration-induced failures. This spatial differentiation allows the material to simultaneously achieve high energy density and penetration resistance.
Solution Approach 2:
The stable Mn-rich and Al-rich inner region acts as a cushioning core that prevents catastrophic failure when the cathode is penetrated by external objects. This pre-designed stable core absorbs the mechanical stress of penetration, preventing short-circuits and explosions even when the Ni-rich surface region is compromised.
3Power
If a cathode active material with high power is used, then the charging rate is improved, but the life-time deteriorates
Solution Approach 1:
The surface region with Ni and Co enrichment enables high charging rates through fast ion and electron transport, while the inner Mn-rich region maintains structural integrity during repeated charge-discharge cycles, thereby extending battery life-time. The gradient structure allows both high power and long duration performance.
Solution Approach 2:
The stable Mn-rich and Co-rich inner region serves as a structural buffer that prevents degradation and failure during prolonged cycling. This pre-designed stable core protects the high-performance Ni-rich surface region from degradation, enabling the battery to maintain high charging rates over extended periods.
Data Source
AI summary
A lithium secondary battery comprises 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 separator interposed between the cathode and the anode. The first cathode active material particle includes a lithium metal oxide including a continuous concentration gradient in at least one region between a central portion and a surface portion. The second cathode active material particle includes a constant concentration composition.