Porous Lithium Composite Oxide Cathode Coating for Low Cycle Resistance
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with conventional lithium composite oxides experience increased resistance after repeated charging and discharging.
Innovation Solution
A non-aqueous electrolyte secondary battery design featuring a positive electrode active substance with a lithium composite oxide having a layered structure, where the lithium composite oxide is in the form of a porous particle with an average void ratio of 12% to 50% and coated with lithium tungstate at a surface coverage ratio of 10% to 65%, effectively suppressing resistance increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional lithium composite oxide with layered structure is used as positive electrode active substance, then the battery can achieve basic charge-discharge function, but the resistance increases after repeated charging and discharging
Solution Approach 1:
The patent applies porous materials by constructing the positive electrode active substance with a porous particle structure containing voids. The void ratio is controlled at 12% to 50%, and the porous structure includes voids with diameters of at least 8% of the particle diameter. This porous configuration reduces direct current resistance and suppresses resistance increase during repeated charging and discharging cycles by providing pathways for ion transport and accommodating volume changes.
Solution Approach 2:
The patent employs composite materials by combining lithium composite oxide with a coating layer on the porous particle surface. The coating coverage ratio is controlled at 10% to 65% of the particle surface area. This composite structure integrates the high capacity of lithium composite oxide with the protective and conductive properties of the coating material, thereby improving cycle stability and reducing resistance increase over time.
2Reliability
If the void ratio of porous particle is increased to reduce resistance, then direct current resistance decreases, but the structural stability may be compromised
Solution Approach 1:
The patent applies parameter changes by precisely controlling the void ratio within the range of 12% to 50% and the coating coverage ratio within 10% to 65%. These optimized parameter ranges balance the competing requirements: sufficient void space to reduce resistance and facilitate ion transport, while maintaining enough solid material to ensure structural stability and mechanical strength during cycling.
Solution Approach 2:
The patent implements local quality by creating a non-uniform distribution of voids and coating within the porous particle. The particle contains multiple voids of different sizes and distributions, with the coating applied selectively to the surface at controlled coverage ratios. This local variation in structure optimizes both resistance characteristics and structural stability in different regions of the particle.
Data Source
AI summary
A non-aqueous electrolyte secondary battery is obtained using a lithium composite oxide having a layered structure in a positive electrode active substance. An increase in resistance following repeated charging and discharging is suppressed. The battery includes a positive electrode provided with a positive electrode active substance layer, a negative electrode and a non-aqueous electrolyte. The positive electrode active substance layer contains a porous particle lithium composite oxide having a layered structure. The average void ratio of the porous particle is not less than 12% but not more than 50%, and it contains two or more voids having diameters that are at least 8% of its particle diameter. The surface of the porous particle is provided with a coating of lithium tungstate. The coverage ratio of the surface of the porous particle by the lithium tungstate is not less than 10% but not more than 65%.