Polyanionic Compound Particle Carbon Coating Conductivity
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Solution Overview
Problem
Lithium-ion secondary batteries using polyanionic compounds as positive electrode active materials face challenges with low electronic conductivity, leading to insufficient capacity and rate characteristics due to inadequate contact between the polyanionic compound and carbon particles.
Innovation Solution
A method involving a compound particle covered with a carbon layer and carbon particles to enhance electronic conductivity, where the compound particle is synthesized through a hydrothermal process and firing step, ensuring a high contact area and improved lithium diffusing capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyanionic compound is combined with carbon particles to improve electronic conductivity, then electronic conductivity is enhanced, but contact area between polyanionic compound and carbon is insufficient due to particle size mismatch
Solution Approach 1:
The patent applies the nesting principle by forming compound particles where the polyanionic compound is embedded within or coated on the carbon particles. This nested structure ensures intimate contact between the polyanionic compound and carbon, resolving the particle size mismatch issue and providing sufficient contact area for effective electron transfer while maintaining high electronic conductivity.
Solution Approach 2:
The patent applies local quality by creating a composite structure where carbon is concentrated at specific locations (on or around the polyanionic compound particles) rather than uniformly distributed. This localized carbon placement ensures optimal contact areas where needed most, enhancing electronic conductivity at the interface between polyanionic compound and carbon while maintaining overall particle integrity.
2Quantity of substance
If polyanionic compound is used as positive electrode active material, then battery capacity is improved, but rate characteristic is reduced due to low electronic conductivity
Solution Approach 1:
The patent applies composite materials by combining polyanionic compound with carbon to form a composite active material. The carbon component provides high electronic conductivity to compensate for the inherently low electronic conductivity of polyanionic compounds, enabling both high battery capacity (from the polyanionic compound's lithium storage capability) and high rate characteristics (from the carbon's electron transport capability) to coexist.
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 approach significantly enhances the discharge capacity and rate characteristics of lithium-ion secondary batteries by improving the electronic conductivity and lithium diffusing capability of the active material.
Implementation Method 1
heating a mixture including a lithium compound, a first compound containing one species selected from the group consisting of Fe, Mn, Co, Ni, and V, a second compound containing one species selected from the group consisting of P, Si, S, V, and Ti, an organic compound, a carbon particle, and water under pressure
Implementation Method 2
a firing step of firing the mixture after the heating under pressure in the hydrothermal synthesizing step
Data Source
AI summary
An active material capable of forming an electrochemical device excellent in its discharge capacity and rate characteristic is provided. The active material in accordance with a first aspect of the present invention comprises a compound particle containing a compound having a composition represented by the following chemical formula (1), a carbon layer covering the compound particle, and a carbon particle. The active material in accordance with a second aspect of the present invention comprises a carbon particle and a compound particle having an average primary particle size of 0.03 to 1.4 μm, being carried by the carbon particle, and containing a compound represented by the following chemical formula (1):LiaMXO4 (1)where a satisfies 0.9≦a≦2, M denotes one species selected from the group consisting of Fe, Mn, Co, Ni, and VO, and X denotes one species selected from the group consisting of P, Si, S, V, and Ti.