Li-ion Battery Cathode Material Optimizing Initial Efficiency
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving high capacity, high initial charge-discharge efficiency, and high average discharge voltage due to the high irreversible capacity of Ni—Co—Mn ternary composite oxides and solid solutions, which require excessive counter electrodes, leading to battery capacity deterioration.
Innovation Solution
A positive electrode active material comprising specific compositions such as LiwNix(M1)y(M2)O2 and LitNipCoqMnr(M3)sO2, combined with a second active material like Li1-αVOPO4, where the ratio of the second active material to the total active materials is optimized to enhance charge and discharge efficiency and voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ni—Co—Mn ternary composite oxide or solid solution based material is used as positive electrode active material to increase energy density and discharge capacity, then the quantity of electricity stored per unit mass increases, but the initial charge-discharge efficiency becomes low due to high irreversible capacity
Solution Approach 1:
The patent uses a composite material consisting of a positive electrode active material (Ni-Co-Mn ternary composite oxide or solid solution) and a specific additive material (LiFePO4 or lithium-contained metal oxide containing Ni and Mn). This composite structure allows the base material to provide high capacity while the additive material improves initial charge-discharge efficiency by reducing irreversible capacity, thus resolving the contradiction between quantity of electricity stored and initial charge-discharge efficiency.
2Reliability
If lithium-contained metal oxide containing nickel and manganese and LiFePO4 are included to improve initial charge-discharge efficiency, then the initial charge-discharge efficiency increases, but the average discharge voltage becomes low
Solution Approach 1:
The patent optimizes the composition parameters of the additive material, specifically controlling the Li content (x value in Li1-xFe1-yNiyMn1-yO3) and the ratios of metal elements. By adjusting these parameters, the material achieves a balance where initial charge-discharge efficiency is improved while maintaining relatively high average discharge voltage, resolving the contradiction between these two energy parameters.
3Reliability
If excessive counter electrode is used to compensate for high irreversible capacity, then the initial charge-discharge efficiency problem is addressed, but the battery capacity deteriorates
Solution Approach 1:
The patent extracts and addresses the root cause of high irreversible capacity by introducing a specific additive material (LiFePO4 or lithium-contained metal oxide) to the positive electrode. This additive material actively reduces irreversible capacity through its electrochemical properties, eliminating the need to use excessive counter electrode material. Consequently, both initial charge-discharge efficiency is improved and battery capacity is preserved, resolving the contradiction between these two parameters.
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 proposed solution results in lithium ion secondary batteries with improved capacity, initial charge-discharge efficiency, and average discharge voltage, stabilizing the crystal structure and facilitating effective charge and discharge processes.
Implementation Method 1
the crystal structure of the first active material is partly stabilized by the movement of Li of the first active material to the second active material during mixing or heat treatment of the first active material and the second active material
Implementation Method 2
the capacity, the initial charge-discharge efficiency, and the average discharge voltage are increased because the second active material contributes to the charge and discharge
Data Source
AI summary
To provide an active material with high capacity, high initial charge-discharge efficiency, and high average discharge voltage. An active material according to the present invention includes a first active material and a second active material, wherein the ratio (δ) of the second active material (B) to the total amount by mole of the first active material (A) and the second active material (B) satisfies 0.4 mol %≦δ≦18 mol % [where δ=(B/(A+B))×100].