LiCoO2 O2 Structure Battery for High Voltage Stability
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving high energy density and maintaining charge-discharge cycle performance due to the instability of crystal structures in LiCoO2 with O2 and O3 structures, particularly when charged to high potentials, leading to irreversible changes and poor capacity retention.
Innovation Solution
A non-aqueous electrolyte secondary battery is developed using a positive electrode active material with a lithium-containing oxide formula Lix1Nay1CoαMnβOγ, where specific compositional ranges for lithium, sodium, cobalt, and manganese ensure a stable O2 structure with high cobalt content, enhancing discharge potential and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiCoO2 with O3 structure is charged to 4.6 V to extract 50% lithium, then capacity is improved, but crystal structure deteriorates and reversibility degrades
Solution Approach 1:
The patent changes the crystal structure parameter from O3 to O2 structure in LiCoO2, which fundamentally alters the material's properties. The O2 structure enables stable charging at 4.6 V with 80% lithium extraction while maintaining crystal structure integrity, resolving the contradiction between capacity and structural stability
Solution Approach 2:
The patent creates a composite positive electrode material containing both LiCoO2 (O2 structure) and Li2MnO3 phases. This composite structure combines the high capacity advantage of Li2MnO3 with the structural stability of O2-LiCoO2, achieving both improved capacity and maintained reversibility at 4.6 V charging potential
2Productivity
If LiCoO2 with O2 structure is produced by ion exchanging at high temperature (>150°C), then ion exchange efficiency is improved, but O3 structure forms instead of O2
Solution Approach 1:
The patent identifies and controls the critical temperature parameter in the ion exchange process, maintaining it below 150°C to preserve the O2 crystal structure while achieving sufficient ion exchange efficiency through optimized process conditions
Solution Approach 2:
The patent prepares Na0.7CoO2 with P2 structure as the starting material before ion exchange, which facilitates the formation of O2-LiCoO2 at lower temperatures during the subsequent lithium ion exchange process
3Quantity of substance
If end-of-charge potential is set at 4.6 V or higher, then capacity is improved, but irreversible crystal structure change occurs and cycle performance degrades
Solution Approach 1:
The patent changes the crystal structure from O3 to O2 type in LiCoO2, which fundamentally alters the voltage-capacity characteristics. The O2 structure enables the material to withstand 4.6 V charging potential without irreversible structural changes, maintaining both high capacity and excellent cycle performance over 500 cycles
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 exhibits improved energy density and charge-discharge cycle performance within the desired potential range, with better stability and capacity retention due to the optimized composition and structure of the positive electrode active material.
Implementation Method 1
The LiCoO2 having an O2 structure can be obtained by preparing Na0.7CoO2 having a P2 structure and ion exchanging the sodium with lithium
Data Source
AI summary
A non-aqueous electrolyte secondary battery has a positive electrode containing a positive electrode active material, a negative electrode, and a non-aqueous electrolyte. The positive electrode active material includes a lithium-containing oxide Lix1Nay1CoαMnβOγ, where 0.66<x1<1.1, 0<y1≦0.02, 0.75≦α<1, 0<β≦0.25, and 1.9≦γ≦2.1.