Li2MSiO4 Core-Shell Electrode Material for High Conductivity
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Solution Overview
Problem
Phosphate and silicate compounds with an olivine structure used in lithium-ion secondary batteries have low bulk electrical conductivity, making them unsuitable as effective electrode materials due to insufficient characteristics for high capacity and conductivity.
Innovation Solution
A particulate electrode material with a core containing Li2MSiO4 and a covering layer of LiMPO4, where the covering layer has higher conductivity, is developed, along with a carbon coat layer to enhance electrical conductivity and capacity, and a solid solution material is introduced between the core and the covering layer to improve Li insertion and extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single particle electrode material is used, then the structure is simple, but it is difficult to obtain characteristics sufficient for use as an electrode material due to low conductivity
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where different regions have different properties: the silicate core provides structural stability while the phosphate covering layer provides high conductivity. This allows each part of the particle to optimize its function locally, achieving both structural simplicity and high performance without requiring complex multi-particle assemblies
2Reliability
If the covering layer thickness is increased to improve conductivity, then electrical conductivity improves, but the weight of the covering layer increases relative to the core
Solution Approach 1:
The patent applies partial action by using a thin phosphate covering layer (0.1-10 nm) that is sufficient to provide the necessary conductivity enhancement without excessive weight. The covering layer is thick enough to provide continuous conductive pathways but thin enough to minimize weight penalty, optimizing the trade-off between conductivity improvement and weight addition
Data Source
AI summary
An object is to provide an electrode material with high electrical conductivity and a power storage device using the electrode material. An object is to provide an electrode material with high capacity and a power storage device using the electrode material. Provided is a particulate electrode material including a core containing a compound represented by a general formula Li2MSiO4 (in the formula, M represents at least one kind of an element selected from Fe, Co, Mn, and Ni) as a main component, and a covering layer containing a compound represented by a general formula LiMPO4 as a main component and covering the core. Further, a solid solution material is provided between the core and the covering layer. With such a structure, an electrode material with high electrical conductivity can be obtained. Further, with such an electrode material, a power storage device with high discharge capacity can be obtained.