Coated Polyanionic Positive Electrode Material for Battery Conductivity
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries using polyanionic compounds as positive electrode active materials face challenges with electron conductivity and Li ion insertion/extraction, leading to deteriorated rate characteristics and charge-discharge capacity, especially when coated with carbon materials that do not contribute to Li ion conductivity.
Innovation Solution
A positive electrode material is developed with core particles of LiaMbPO4 (where M represents Fe, Mn, or Ni) coated with a material capable of Li ion insertion and extraction, enhancing electron conductivity and charge-discharge capacity while maintaining safety and cycle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyanionic compounds are used as positive electrode active material, then safety and cycle stability are improved, but electron conductivity deteriorates
Solution Approach 1:
The patent uses composite materials by coating polyanionic compound particles with a specific compound (LiaMbPO4) that has both high electron conductivity and high Li ion conductivity. This composite structure allows the core polyanionic compound to provide safety and cycle stability while the coating layer provides the necessary electron conductivity without using traditional carbon coatings.
2Loss of energy
If carbon material is coated on polyanionic compound to improve electron conductivity, then electron conductivity is improved, but Li ion conductivity deteriorates
Solution Approach 1:
The patent changes the material parameter by selecting LiaMbPO4 compounds (where M is Fe, Mn, Co, or Ni) as the coating material. These compounds have different electronic and ionic conductivity parameters compared to carbon materials, providing both high electron conductivity and high Li ion conductivity simultaneously, thus resolving the contradiction between electron conductivity improvement and Li ion conductivity preservation.
3Loss of energy
If carbon material is excessively coated on polyanionic compound, then electron conductivity is improved, but rate characteristics deteriorate
Solution Approach 1:
The patent applies local quality by using a thin coating layer of LiaMbPO4 compound on the surface of polyanionic compound particles. This localized coating provides sufficient electron conductivity at the particle surface where electron transport is needed, while maintaining high Li ion conductivity pathways through the coating layer, thus preserving rate characteristics without excessive coating thickness.
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 solution improves electron conductivity and charge-discharge capacity of the battery, ensuring high rate characteristics and cycle stability while reducing the risk of ignition and explosion, with the coating material contributing to increased battery capacity and safety.
Implementation Method 1
the coating material contributes to Li ion insertion and extraction
Implementation Method 2
A positive electrode active material coated with a carbon material has excellent electron conductivity
Data Source
AI summary
A positive electrode material for non-aqueous electrolyte secondary batteries having high rate characteristics and high energy density, and a battery using the same are provided. The non-aqueous electrolyte secondary battery includes a positive electrode containing a positive electrode material, a conductive agent and a binder; a negative electrode; a separator; and a non-aqueous electrolyte, in which the positive electrode material contains core particles and a coating material that covers from 10% to 90% of the surfaces of the core particles, the core particles are formed of a compound represented by LiaMbPO4 (wherein M represents at least one element selected from Fe, Mn, Co and Ni, and satisfies the relations: 0<a≦1.1 and 0<b≦1), and the coating material part is formed of a compound which is capable of insertion and extraction of Li ions in the potential range exhibited by the core particles at the time of charge and discharge.