Phosphorous Compound Additive for Nonaqueous Battery Life
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Solution Overview
Problem
Nonaqueous electrolyte batteries with lithium titanium composite oxide active materials face reduced battery life due to water adsorption and the subsequent production of free acids, leading to increased surface resistance and capacity loss.
Innovation Solution
Incorporating a phosphorous compound, such as AxH3-xPO4 or A′yH(6-2y)(PO4)2, into the nonaqueous electrolyte or negative electrode to react with fluoric acid and suppress the dissolution of active material constituents, thereby reducing resistance and improving life performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium titanium composite oxide is used as active material, then cycle characteristics are improved and lithium metal deposition is prevented, but water adsorption increases leading to free acid production and surface resistance increase
Solution Approach 1:
A phosphorous compound is introduced as an intermediary substance that reacts with free acid to form a protective coating on the lithium titanium composite oxide surface. This coating acts as a barrier that prevents water adsorption and subsequent free acid generation, thereby resolving the contradiction between maintaining cycle characteristics and preventing surface resistance increase.
Solution Approach 2:
The phosphorous compound converts the harmful free acid into a beneficial protective coating through chemical reaction. The free acid that would normally dissolve active material and increase resistance is instead transformed into a protective layer that prevents further degradation, turning the harmful factor into a beneficial protective mechanism.
2Productivity
If lithium titanium composite oxide is used as active material, then high current charging capability is achieved, but free acid dissolves active material leading to capacity loss
Solution Approach 1:
The phosphorous compound serves as an intermediary that intercepts and neutralizes free acid before it can attack and dissolve the active material. This protective mechanism allows high current charging to proceed without the detrimental effects of active material dissolution, maintaining both charging rate and material integrity.
Solution Approach 2:
The phosphorous compound performs preliminary protection by forming a protective coating on the active material surface before free acid can cause dissolution. This pre-established protective barrier prevents subsequent active material loss during high current charging operations.
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 use of phosphorous compounds effectively suppresses the precipitation of transition metal ions on the negative electrode, enhancing the battery's resistance and life performance by maintaining lower surface resistance and capacity.
Implementation Method 1
Incorporating a phosphorous compound, such as AxH3-xPO4 or A′yH(6-2y)(PO4)2, into the nonaqueous electrolyte or negative electrode to react with fluoric acid
Implementation Method 2
nonaqueous electrolyte batteries including a lithium titanium composite oxide (about 1.5 V vs. Li/Li+) having a lithium absorption-release potential higher than that of the carbonaceous material as an active material
Implementation Method 3
the amount of water adsorbed on the surface of the lithium titanium composite oxide is large, and a hydroxyl group is present on the surface
Data Source
AI summary
According to one embodiment, a nonaqueous electrolyte battery includes a positive electrode, a negative electrode and a nonaqueous electrolyte. The negative electrode contains an active material having a lithium absorption potential of not lower than 0.4 V vs. Li/Li+. The nonaqueous electrolyte contains a fluorine-containing lithium salt and a phosphorous compound. The phosphorous compound is at least one selected from the group consisting of AxH3-xPO4 (wherein A is at least one element selected from Na and K, and x is from 0 to 3) and A′yH(6-2y)(PO4)2 (wherein A′ is at least one element selected from Mg and Ca, and y is from 0 to 3).