Nonaqueous Electrolyte Battery Tungsten Positive Electrode Low-Temperature Output
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Solution Overview
Problem
Lithium ion secondary batteries, as described in PTL 1, face insufficient output power at low temperatures.
Innovation Solution
A nonaqueous electrolyte secondary battery with a positive electrode containing tungsten and a phosphate compound, and a separator with higher oxidation resistance and a pore distribution peak sharpness index of 40 or more, allowing for the formation of a low-resistance surface film on the negative electrode, thereby improving low-temperature output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a positive electrode containing tungsten and phosphate compound is used to improve low-temperature output characteristics, then low-temperature output characteristics are improved, but heat generation at overcharging may increase
Solution Approach 1:
The patent applies local quality by creating a covering layer with specific composition (tungsten, phosphate compound, and oxide) on the positive electrode surface. This localized modification provides different functional properties: the covering layer promotes tungsten dissolution at low temperatures to improve output characteristics, while the oxide component (particularly W6+ with high oxidation resistance) suppresses heat generation during overcharging by resisting oxidation reactions.
Solution Approach 2:
The patent uses composite materials by combining multiple components in the covering layer: tungsten (for dissolution and low-temperature performance), phosphate compound (for structural stability), and oxide containing W6+, Mo6+, or Zr4+ (for oxidation resistance). This composite structure allows the positive electrode to simultaneously achieve improved low-temperature output characteristics and suppressed heat generation during overcharging.
2Reliability
If a separator with higher oxidation resistance than polyethylene is used to prevent oxidation, then oxidation resistance is improved, but low-temperature output characteristics may deteriorate
Solution Approach 1:
The patent applies parameter changes by optimizing the pore distribution characteristics of the separator. By controlling the pore distribution peak sharpness index to be 40 or more in the 0.01-10 μm range, the separator achieves optimal balance between oxidation resistance and low-temperature performance. This parameter optimization allows sufficient ion transport at low temperatures while maintaining high oxidation resistance through the material composition (polypropylene or aramid).
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 low-temperature output characteristics by inhibiting the increase in negative electrode resistance, ensuring effective film formation and maintaining performance in cold environments.
Implementation Method 1
changing the rate of dissolution of tungsten in a nonaqueous electrolyte with a positive electrode containing tungsten and a phosphate compound
Implementation Method 2
formation of a good (low-resistance) surface film containing tungsten originating from the positive electrode on a negative electrode
Implementation Method 3
the separator contains a material having higher oxidation resistance than a polyethylene
Implementation Method 4
the separator contains a material having higher oxidation resistance than a polyethylene and has a pore distribution peak sharpness index of 40 or more in the range of 0.01 μm to 10 μm
Data Source
AI summary
It is an object of the present invention to improve the low-temperature output characteristics of a nonaqueous electrolyte secondary battery. A nonaqueous electrolyte secondary battery according to an embodiment includes an electrode assembly having a structure in which a positive electrode and a negative electrode are stacked with a porous separator provided therebetween. The positive electrode contains tungsten and a phosphate compound. The separator contains a material having higher oxidation resistance than a polyethylene and has a pore distribution peak sharpness index of 40 or more in the range of 0.01 μm to 10 μm as calculated using formula 1: formula 1: pore distribution peak sharpness index=(peak value of Log differential pore volume)/(difference between maximum pore size and minimum pore size at position corresponding to ½ peak value of Log differential pore volume).