Positive Electrode Composite Oxide for Battery Cycle Stability
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Solution Overview
Problem
Conventional non-aqueous electrolyte secondary batteries require improvement in charge-discharge cycle characteristics for on-board and power storage applications, as existing positive electrode active materials do not adequately achieve both high capacity and good cycle performance.
Innovation Solution
A positive electrode active material comprising a first lithium-transition metal composite oxide (LixNi1-y-zCoyMzO2) and a second lithium-transition metal composite oxide with a specific diffraction peak range in X-ray diffraction, along with additional components like carbon nanotubes, inorganic particles on the separator, and sulfonylimide salts in the electrolyte, enhances cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive electrode active materials are used, then battery capacity can be maintained, but charge-discharge cycle characteristics are insufficient
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region contains lithium-rich composite oxide (LixMO2 where x>1) providing high capacity, while the outer shell region contains lithium-deficient composite oxide (LiyMO2 where y<1) providing stable cycle characteristics. This spatial differentiation of material properties within the particle enables simultaneous achievement of high capacity and good cycle performance.
Solution Approach 2:
The patent uses composite materials by combining two different lithium-transition metal composite oxides with distinct compositional characteristics into a single positive electrode active material system. The first lithium-rich composite oxide (LixNi1-y-zCoyMzO2 where x>1) and second lithium-deficient composite oxide (LiyNi1-a-bCoaMbaO2 where y<1) work synergistically to resolve the contradiction between capacity and cycle stability.
2Productivity
If lithium-rich composite oxide is used to increase capacity, then battery capacity improves, but cycle stability deteriorates
Solution Approach 1:
The patent segments the positive electrode active material into two distinct compositional regions: a core region with lithium-rich composition (x>1) for high capacity and a shell region with lithium-deficient composition (y<1) for stability. This segmentation allows each region to perform its specialized function without compromising the other.
Solution Approach 2:
The patent changes the lithium content parameter spatially within the particle structure. The core region has elevated lithium content (x>1) to provide high capacity, while the shell region has reduced lithium content (y<1) to provide structural stability during cycling. This parameter gradient resolves the contradiction between capacity and stability.
3Reliability
If lithium-deficient composite oxide is used to improve cycle stability, then charge-discharge cycle characteristics improve, but battery capacity decreases
Solution Approach 1:
The patent applies preliminary action by forming a lithium-deficient shell layer around the lithium-rich core before the particle undergoes charge-discharge cycling. This pre-formed protective shell prevents degradation of the high-capacity core material during cycling, enabling the core to maintain its capacity over many cycles.
Solution Approach 2:
The lithium-deficient composite oxide shell acts as an intermediary protective layer between the electrolyte and the lithium-rich core material. This intermediary shell prevents direct harmful interactions between the electrolyte and the capacity-providing core, thereby preserving both capacity and cycle stability.
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 significantly improves charge-discharge cycle characteristics by protecting the surface of the first lithium-transition metal composite oxide, maintaining stable crystal structure, and enhancing battery capacity and longevity.
Implementation Method 1
protecting the surface of the first lithium-transition metal composite oxide, maintaining stable crystal structure
Implementation Method 2
a second lithium-transition metal composite oxide having at least one diffraction peak having a peak top at a diffraction angle (2θ) of greater than or equal to 21.40° and less than or equal to 21.65° in a radiation X-ray diffraction
Data Source
AI summary
A positive electrode active material for nonaqueous electrolyte secondary batteries according to one embodiment of the present invention contains: a first lithium transition metal composite oxide that is represented by general formula LixNi1-y-zCoyMzO2 (wherein 0.8≤x≤1.2, 0≤y≤0.2, 0<z≤0.5, and M represents at least one metal element excluding Li, Ni and Co); and a second lithium transition metal composite oxide that has at least one diffraction peak which has a peak top at a diffraction angle (2θ) of from 21.40° to 21.65° in radiation X-ray diffraction (with a light energy of 16 keV).