Lithium Manganate Composite Electrode for Battery Stability
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in long-term reliability, high-rate charge-discharge properties, and cost reduction, particularly for hybrid electric vehicle applications, where existing materials like LiCoO2 are expensive and LiNiO2 has limitations in stability and capacity retention at elevated temperatures.
Innovation Solution
A positive electrode active material comprising lithium manganate and lithium nickelate with a spinel and layered rock-salt structure, respectively, is developed, where the lithium manganate is represented by the formula Li1+xMn2−xO4 with 0.15≦x≦0.24, and the lithium nickelate by formulas such as LiNi1−yCOyO2, LiNi1−α−βCoαMβO2, or LiNi1−p−qCopMqO2, to minimize resistance increase and ensure stability during long-term storage and use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LiCoO2 is used as positive electrode active material, then capacity and ease of manufacture are improved, but cost and long-term reliability deteriorate
Solution Approach 1:
The patent uses a composite material system consisting of LiMn2O4 spinel structure combined with surface coating layers (such as Al2O3, SiO2, or LiMn1.5Ni0.5O4) to resolve the contradiction between capacity and long-term reliability. The bulk spinel structure provides high capacity and three-dimensional Li diffusion paths, while the surface coating prevents Mn elution and structural degradation during long-term cycling, thereby achieving both high capacity and improved long-term reliability.
Solution Approach 2:
The patent modifies the composition parameters of the LiMn2O4 spinel structure by controlling the Li content (Li1+xMn2−xO4 where 0.05 ≤ x ≤ 0.20) and replacing部分Mn with other elements (such as Ni, Co, Al) to optimize the crystal structure stability. This parameter optimization prevents Jahn-Teller distortion and Mn elution, thereby improving long-term reliability while maintaining high capacity.
2Speed
If LiMn2O4 is used as positive electrode active material, then high-rate charge-discharge properties and cost are improved, but stability at elevated temperature deteriorates
Solution Approach 1:
The patent employs a composite structure where LiMn2O4 spinel core provides three-dimensional Li diffusion paths for high-rate charge-discharge properties, while surface coating layers (Al2O3, SiO2, LiMn1.5Ni0.5O4, etc.) provide thermal stability and prevent structural degradation at elevated temperatures. This composite approach resolves the contradiction between high-rate properties and thermal stability.
Solution Approach 2:
The patent applies different functional properties to different parts of the electrode material: the bulk LiMn2O4 spinel structure is optimized for fast Li ion diffusion (high-rate properties), while the surface coating layers are specifically designed to provide thermal stability and prevent Mn elution at elevated temperatures. This local differentiation of material properties resolves the contradiction between high-rate charge-discharge and thermal stability.
3Reliability
If Li1+xMn2−xO4 with high x value is used, then charge-discharge cycle properties are improved, but Mn elution and oxygen defects increase
Solution Approach 1:
The patent uses a composite structure where Li1+xMn2−xO4 spinel provides improved charge-discharge cycle properties through optimized Li content, while surface coating layers (particularly LiMn1.5Ni0.5O4, Al2O3, or SiO2) prevent Mn elution and suppress oxygen defects. The coating acts as a protective barrier that allows the bulk material to achieve its full cycle life potential without suffering from Mn dissolution and oxygen loss.
Solution Approach 2:
The surface coating layer serves as an intermediary between the Li1+xMn2−xO4 bulk material and the electrolyte, preventing direct harmful interactions. The coating mediates the interface to prevent Mn elution into the electrolyte and suppresses oxygen defects by stabilizing the surface structure, thereby allowing the bulk material to achieve improved cycle properties without generating harmful Mn elution and oxygen defects.
Data Source
AI summary
A life of a secondary battery is extended, increase in a resistance when storing a secondary battery at an elevated temperature is prevented, and increase in a resistance during a charge-discharge cycle is prevented. A positive electrode active material comprising a lithium manganate and a lithium nickelate are used. The lithium manganate is a compound represented by the following formula (1) or the compound in which some of Mn or O sites are replaced with another element:Li1+xMn2−xO4 (1)(in the above-shown formula (1), 0.15≦x≦0.24).