Double-Layer Cathode Active Materials for Lithium Batteries
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Solution Overview
Problem
Lithium ion secondary batteries face challenges with high price, poor safety, and limited thermal stability due to the instability of current cathode active materials like LiCoO2 and LiNiO2, which lack stable crystal structures and exhibit rapid thermal reactions during charging.
Innovation Solution
A double-layer cathode active material is developed, comprising a nickel-based inner layer with high-capacity characteristics and a transition metal mixture-based outer layer for superior thermal safety, prepared through hydroxide co-precipitation, where the inner layer is Li1+δ[CoaMnbMcNi1−(a+b+c)]O2 and the outer layer is Li1+δ[NixMnx−y/2Co1−2x−zMyNz]O2−aPa or Li1+δ[NixMnx+yCo1−2(x+y)My]O2−aPa, with specific elemental compositions and structural optimizations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiNiO2 is used as cathode material to achieve high discharge capacity, then capacity is improved, but thermal stability deteriorates due to transformation into rocksalt-type structure and oxygen release
Solution Approach 1:
The cathode material is segmented into a core-shell structure with LiNiO2 core for high capacity and LiNi1-xMnxO2 shell for thermal stability. This segmentation allows each component to perform its specialized function: the core provides high discharge capacity while the shell prevents thermal degradation and oxygen release.
Solution Approach 2:
A composite cathode material is formed by combining LiNiO2 and LiNi1-xMnxO2 in a core-shell configuration. The composite structure integrates the high capacity characteristics of LiNiO2 with the thermal stability of LiNi1-xMnxO2, achieving both high discharge capacity and improved thermal safety simultaneously.
2Reliability
If LiCoO2 is used as cathode material to achieve stable charge-discharge characteristics and high electronic conductivity, then electrochemical performance is improved, but cost increases and human toxicity worsens
Solution Approach 1:
The composition parameters of the cathode material are optimized by controlling the manganese content (0.05 ≤ x ≤ 0.50) in the LiNi1-xMnxO2 shell. This parameter adjustment allows achieving sufficient thermal stability and electrochemical performance while reducing cobalt content, thereby lowering cost and toxicity.
Solution Approach 2:
Different regions of the cathode material have different compositions: the core maintains high nickel content for capacity, while the shell has optimized nickel-manganese ratio for stability and safety. This local quality differentiation allows each region to contribute its specific properties to the overall performance.
3Reliability
If nickel atoms are replaced with cobalt atoms to improve charge-discharge characteristics, then electrochemical performance is improved, but thermal safety deteriorates
Solution Approach 1:
The cathode material is divided into core and shell regions with different compositions. The core contains the nickel-rich composition for high capacity, while the shell contains the optimized nickel-manganese composition for thermal safety. This segmentation resolves the contradiction by spatially separating the functions of electrochemical performance and thermal stability.
Solution Approach 2:
The shell region has a specific local quality with controlled manganese content (0.05 ≤ x ≤ 0.50) that provides thermal stability without compromising the overall electrochemical performance. This local quality adjustment allows the material to withstand thermal stress while maintaining good charge-discharge characteristics.
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 double-layer cathode active material achieves high capacity, high charge density, improved cycle characteristics, and superior thermal safety, addressing the limitations of existing materials by stabilizing the structure during charge and discharge cycles and enhancing thermal safety.
Implementation Method 1
a double-layer cathode active material is developed, comprising a nickel-based inner layer with high-capacity characteristics and a transition metal mixture-based outer layer for superior thermal safety, prepared through hydroxide co-precipitation
Data Source
AI summary
Disclosed herein are double-layer cathode active materials comprising a nickel-based cathode active material as an inner layer material and a transition metal mixture-based cathode active material as an outer layer material facing an electrolyte. Since the nickel-based cathode active material as an inner layer material has high-capacity characteristics and the transition metal mixture-based cathode active material as an outer layer material facing an electrolyte has superior thermal safety, the double-layer cathode active materials have high capacity, high charge density, improved cycle characteristics and superior thermal safety.