Tungsten-Modified Positive Electrode Suppresses IV Resistance
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries with lithium-titanium composite oxide and carbon materials experience increased IV resistance during high-temperature storage, leading to decreased power characteristics due to the formation of coatings on the negative electrode.
Innovation Solution
Incorporating tungsten into the positive electrode, either as a solid solution or a surface compound, to form a coating on the negative electrode, which reduces IV resistance by precipitating tungsten on the negative electrode during charge and discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative electrode containing lithium-titanium composite oxide and carbon material is combined with a positive electrode containing lithium transition metal oxide, then discharge cut-off is regulated by the negative electrode, but the IV resistance of the battery increases due to high-temperature storage
Solution Approach 1:
The patent changes the chemical composition parameters of the positive electrode by incorporating tungsten element and specific metal elements (Ni, Co, Mn, Zn, Al, Ti, V, Mo, Hf, Ta, Nb, Zr) in controlled ratios. This compositional parameter change modifies the electrode's chemical stability and electrochemical properties, preventing the formation of high-resistance coatings during high-temperature storage while maintaining discharge cut-off regulation.
Solution Approach 2:
The patent creates a composite positive electrode material by combining lithium transition metal oxide with tungsten element and other metal elements. This composite structure leverages the synergistic effects of different elements: tungsten provides structural stability and prevents coating formation, while the transition metal elements maintain electrochemical activity. The composite material resolves the contradiction by achieving both reliable discharge cut-off regulation and resistance stability.
2Power
If tungsten is added to the positive electrode to suppress IV resistance increase, then power characteristics are maintained, but the complexity of electrode composition increases
Solution Approach 1:
The patent specifies precise compositional parameters: tungsten content at 0.01-3.0 mole percent and transition metal elements at 30-80 mole percent of total metal elements excluding Li. These controlled parameter ranges optimize power characteristics while preventing excessive complexity. The quantified composition guidelines provide a clear formulation framework that balances performance enhancement with manufacturing feasibility.
Solution Approach 2:
The patent applies local quality by concentrating tungsten addition specifically in the positive electrode rather than uniformly across the battery system. This localized modification targets the specific problem of IV resistance increase at the positive electrode interface during high-temperature storage, maintaining simplicity in other battery components while achieving power characteristic improvement where needed.
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 introduction of tungsten in the positive electrode effectively suppresses the increase in IV resistance and maintains power characteristics by forming a coating on the negative electrode, thereby enhancing the battery's performance during high-temperature storage.
Implementation Method 1
Incorporating tungsten into the positive electrode, either as a solid solution or a surface compound, to form a coating on the negative electrode, which reduces IV resistance by precipitating tungsten on the negative electrode during charge and discharge cycles.
Implementation Method 2
The nonaqueous electrolyte contains a substance reduced on the negative electrode at a potential of 0.5 V to 1.5 V (vs. Li/Li+).
Data Source
AI summary
The present invention provides a nonaqueous electrolyte secondary battery capable of suppressing the increase in IV resistance of a battery in a combination of a negative electrode containing a lithium-titanium composite oxide and a carbon material and a positive electrode containing a lithium transition metal oxide. A nonaqueous electrolyte secondary battery according to the present invention includes a positive electrode, a negative electrode, a separator placed between the positive electrode and the negative electrode, and a nonaqueous electrolyte. The positive electrode contains a lithium transition metal oxide in which Ni accounts for 30 mole percent or more of the total molar amount of metal elements excluding Li and also contains tungsten element. The negative electrode contains a lithium-titanium composite oxide and a carbon material. The nonaqueous electrolyte contains a substance reduced on the negative electrode at a potential of 0.5 V to 1.5 V (vs. Li/Li+).