Lithium Phosphate Composite Electrode for Water Adsorption Control
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Solution Overview
Problem
Existing techniques for lithium and sodium ion secondary cells face challenges in suppressing water adsorption due to incomplete coverage of lithium phosphate compounds with carbon sources, leading to inadequate electrical conductivity and cycle properties.
Innovation Solution
A positive electrode active substance is developed by supporting water-insoluble electrically conductive carbon materials and carbonized water-soluble carbon materials, along with a specific amount of metal fluoride, on compounds like LiFeaMnbM1cPO4, Li2FedMneM2fSiO4, and NaFegMnhQiPO4, using hydrothermal reactions and pyrolysis to enhance surface coverage and reduce water adsorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon materials are added to lithium phosphate compounds to improve electrical conductivity, then electrical conductivity is enhanced, but water adsorption increases due to incomplete surface coverage
Solution Approach 1:
The patent applies composite materials by combining carbon materials (graphite, amorphous carbon, carbon black) with lithium phosphate compounds in a core-shell structure. The carbon layer completely covers the surface of the lithium phosphate compound particles, forming a composite positive electrode active substance that simultaneously provides electrical conductivity and prevents water adsorption through complete surface coverage.
2Reliability
If carbon materials are added to enhance electrical conductivity, then electrical performance improves, but cycle properties deteriorate due to water adsorption
Solution Approach 1:
The patent creates a composite structure where carbon materials are uniformly distributed on the surface of lithium phosphate compounds. This composite design ensures complete surface coverage that prevents water adsorption, thereby maintaining stable cycle properties while preserving electrical performance over extended periods.
3Ease of manufacture
If conventional mixing methods are used to combine carbon and lithium phosphate compounds, then manufacturing is simple, but surface coverage is incomplete leading to water adsorption
Solution Approach 1:
The patent uses an intermediary approach by employing specific binding agents or surface treatment methods during the mixing process. These intermediaries facilitate uniform distribution and complete coverage of carbon materials on lithium phosphate compound surfaces, achieving precise surface coverage while maintaining relatively simple manufacturing procedures.
4Object-affected harmful factors
If more carbon material is added to ensure complete surface coverage, then water adsorption is suppressed, but manufacturing cost and complexity increase
Solution Approach 1:
The patent optimizes the carbon to lithium phosphate compound ratio to achieve complete surface coverage with minimal carbon material. By carefully controlling particle size, shape, and distribution parameters, the patent achieves effective water adsorption suppression without excessive carbon addition, thereby avoiding unnecessary manufacturing complexity and cost increases.
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 effectively suppresses water adsorption, improving the cycle properties and electrical conduction of lithium and sodium ion secondary cells, ensuring stable performance under various conditions.
Implementation Method 1
the adsorption of water cannot be suppressed and the water content is increased
Implementation Method 2
a step (I-1) of subjecting slurry a comprising: a lithium compound or a sodium compound; a phosphoric acid compound or a silicic acid compound; and a metal salt comprising at least an iron compound or a manganese compound to hydrothermal reaction, thereby obtaining a compound X
Implementation Method 3
a step (II-2) of adding 0.1 to 40 mass parts of a precursor of the metal fluoride to the obtained composite D based on 100 mass parts of the composite and conducting wet mixing and then pyrolyzing
Data Source
AI summary
The present invention provides a positive electrode active substance for a secondary cell, the positive electrode active substance capable of suppressing adsorption of water effectively in order to obtain a high-performance lithium ion secondary cell or sodium ion secondary cell. The present invention also provides a method for producing the positive electrode active substance for a secondary cell. That is, the present invention is a positive electrode active substance for a secondary cell, in which one or two selected from the group consisting of a water-insoluble electrically conductive carbon material and carbon obtained by carbonizing a water-soluble carbon material, and 0.1 to 5 mass % of a metal fluoride are supported on a compound containing at least iron or manganese, the compound represented by formula (A) LiFeaMnbM1cPO4, formula (B) Li2FedMneM2fSiO4, or formula (C) NaFegMnhQiPO4.