Solid-Solution Cathode Optimizing Spinel Ratio for Capacity
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Solution Overview
Problem
Lithium ion batteries using certain cathode compositions struggle to achieve high discharge capacity and capacity retention rates.
Innovation Solution
A non-aqueous electrolyte secondary battery with a transition metal oxide containing solid-solution lithium as the positive electrode, featuring a specific compositional formula and structural changes between layered and spinel structures during charge-discharge cycles, optimizing the spinel structure change ratio for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional cathode composition is used, then the battery structure is simple, but the discharge capacity and capacity retention rate are low
Solution Approach 1:
The patent uses a composite cathode material with a core-shell structure where the core is Li2MnO3 and the shell is LiMn1-xNixO4 spinel structure. This composite structure combines the high capacity of Li2MnO3 with the high conductivity and stability of the spinel shell, achieving both high discharge capacity and good capacity retention without excessive complexity
Solution Approach 2:
The patent applies local quality by creating a core-shell structure where different regions of the cathode material have different compositions and functions. The core region (Li2MnO3) provides high capacity while the shell region (spinel structure) provides conductivity and structural stability, allowing each region to optimize its local properties for its specific function
2Quantity of substance
If the spinel structure change ratio is increased to improve capacity, then the discharge capacity increases, but the capacity retention rate deteriorates
Solution Approach 1:
The patent optimizes the spinel structure change ratio parameter to a specific range (0.2-0.4) during charge-discharge cycles. This parameter optimization allows the material to transform between layered and spinel structures in a controlled manner, achieving high discharge capacity while maintaining capacity retention through reversible structural transformation
Solution Approach 2:
The patent utilizes dynamic structural transformation between layered and spinel structures during charge-discharge cycles. The material can reversibly change its crystal structure in response to electrochemical conditions, allowing it to adapt its properties during operation to maintain both high capacity and good retention
3Quantity of substance
If the battery uses conventional materials for high capacity, then the initial discharge capacity is high, but the charge-discharge efficiency is low
Solution Approach 1:
The composite core-shell structure combines Li2MnO3 core with LiMn1-xNixO4 spinel shell, where the spinel shell provides high ionic and electronic conductivity that enhances charge-discharge efficiency while the core provides high capacity, achieving both high initial discharge capacity and high productivity
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 battery achieves high initial discharge capacity, capacity retention, and charge-discharge efficiency, making it suitable for vehicle power sources and other applications.
Implementation Method 1
a site which changes to a spinel structure by performing a charge or a charge-discharge in a predetermined electric potential range
Data Source
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Figure 1B
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AI summary
Provided is a transition metal oxide containing solid-solution lithium which can realize high initial discharge capacity and capacity retention rate. The transition metal oxide containing solid-solution lithium is represented by the compositional formula: Li1.5[NiaMbMnc[Li]d]O3 (in the formula, Li represents lithium, Ni represents nickel, M represents at least one kind of element selected from the group consisting of silicon, phosphorus and metal elements (but excluding Ni, Mn and Li), Mn represents manganese, and O represents oxygen, and a, b, c and d satisfy the relationships of 0 < a < 1.4, 0 < b ≤ 0.2, 0 < c < 1.4, 0.1 < d ≤ 0.4, a + b + c + d = 1.5 and 1.1 ≤ [a + b + c] < 1.4, and n, which is the valence of M, is in a range of 3 ≤ n ≤ 6 (when M consists of two or more elements, n is the average value of the valence of each element)). The oxide has a layered structure site and a site which changes to a spinel structure by performing a charge or a charge-discharge in a predetermined electric potential range, and a spinel structure change ratio k of the transition metal oxide containing solid-solution lithium is in a range of 0.25 ≤ k < 1.0 when the spinel structure change ratio is assumed to be 1 in a case where Li2MnO3 of the layered structure in the transition metal oxide containing solid-solution lithium completely changes to LiMn2O4 of the spinel structure.