Positive Electrode Particle Coating to Cut Battery Internal Resistance
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Solution Overview
Problem
Conventional secondary batteries experience increased internal resistance due to side reactions, such as reduction and elution of transition metals and electrolyte decomposition, which are not effectively addressed by existing coatings that further increase resistance.
Innovation Solution
A positive electrode comprising first and second active material particles with a phosphorus compound coating, where the first particles are agglomerations of 51 to 20,000 primary particles and the second particles are single or agglomerations of 2 to 50 primary particles, with a controlled mass ratio of phosphorus compound on their surfaces, to suppress side reactions and reduce internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phosphorus compound coating is applied to suppress side reactions, then side reactions are suppressed, but internal resistance increases
Solution Approach 1:
The patent applies different phosphorus compound coatings to different particle size categories. Large particles (51-20,000 primary particles) receive a first phosphorus compound coating, while small particles (1-50 primary particles) receive a second phosphorus compound coating or no coating. This local differentiation allows suppression of side reactions on large particles while maintaining low resistance characteristics of small particles, resolving the contradiction between side reaction suppression and internal resistance reduction.
Solution Approach 2:
The patent controls the mass ratio of phosphorus compound on small particles relative to large particles within a specific range (0-0.5). By adjusting this parameter, the patent optimizes the balance between side reaction suppression (requiring more coating) and internal resistance reduction (requiring less coating), achieving both goals simultaneously through precise parameter control.
2Reliability
If coating is applied to suppress side reactions, then electrolyte decomposition is reduced, but internal resistance increases
Solution Approach 1:
The patent selectively coats large particles with phosphorus compounds while leaving small particles mostly uncoated or lightly coated. Since large particles have greater surface area and are more prone to side reactions, this local coating strategy protects them effectively while minimizing the overall resistance increase, thus improving electrolyte stability without significantly increasing internal resistance.
Solution Approach 2:
The patent controls the mass ratio of phosphorus compound on small particles to that on large particles within 0-0.5, optimizing the coating distribution to balance electrolyte protection and resistance characteristics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The configuration effectively suppresses side reactions and reduces internal resistance while enhancing battery capacity and charge/discharge efficiency.
Implementation Method 1
a phosphorus compound adhered to at least a portion of a surface of the first positive electrode active material particle
Data Source
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AI summary
A positive electrode 10 according to the present disclosure includes first positive electrode active material particles 3, second positive electrode active material particles 4, and a phosphorus compound adhered to at least a portion of a surface of the first positive electrode active material particle 3. The first positive electrode active material particle 3 is a particle formed by agglomeration of 51 to 20,000 first primary particles. The second positive electrode active material particle 4 is one second primary particle or a particle formed by agglomeration of 2 to 50 of the second primary particles. A mass ratio of P contained in a phosphorus compound adhered to surfaces of the second positive electrode active material particles 4 to P contained in the phosphorus compound adhered to the surfaces of the first positive electrode active material particles 3 is 0 or more and 0.5 or less.