Solid Electrolyte Composition for All Solid State Batteries
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Solution Overview
Problem
Lithium phosphorus oxynitride solid electrolytes in all solid state batteries degrade in wet atmospheres, leading to reduced ion conductivity and impaired charge/discharge characteristics due to phosphorus atoms reacting with water, resulting in increased internal impedance.
Innovation Solution
A solid electrolyte composition represented by the formula LiaPbMcOdNe, where M is an element such as Si, B, Ge, Al, C, or S, stabilizes phosphorus in a +5 oxidation state by forming a stronger bond with oxygen, preventing reduction and maintaining ion conductivity even in wet conditions, with specific ranges for parameters a, b, c, d, and e to ensure chemical stability and high ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium phosphorus oxynitride is used as a solid electrolyte to achieve high ion conductivity, then the battery can provide high energy density, but the phosphorus atoms react with water in wet atmosphere causing decomposition and significant decrease in ion conductivity
Solution Approach 1:
Alkali metal atoms (Li, Na, K, Rb, or Cs) are introduced as intermediary elements to form a composite solid electrolyte structure. These alkali metal atoms act as mediators that stabilize the phosphorus atoms in the +5 oxidation state, preventing their direct reaction with water molecules. The alkali metals form a protective structural framework around the phosphorus atoms, reducing their chemical reactivity toward moisture while maintaining the high ion conductivity necessary for battery operation.
Solution Approach 2:
The invention creates a composite solid electrolyte material by combining lithium phosphorus oxynitride with additional alkali metal atoms (forming structures such as Li3-xMxPO3.75N0.25 where M represents alkali metals). This composite approach integrates the high ion conductivity of lithium phosphorus oxynitride with the chemical stability provided by the alkali metal framework, resulting in a material that simultaneously achieves both high performance and moisture resistance.
2Stability of the object's composition
If lithium phosphorus oxynitride is exposed to wet atmosphere, then phosphorus atoms are reduced to lower oxidation state from +5, but this causes decomposition and significantly decreases ion conductivity
Solution Approach 1:
Alkali metal atoms serve as intermediary stabilizers that maintain phosphorus in the +5 oxidation state. By forming a composite structure where alkali metals are positioned within the crystal lattice, they create a chemical environment that prevents phosphorus reduction. This intermediary protection mechanism ensures that phosphorus remains in its high oxidation state, thereby preventing decomposition and maintaining ion conductivity.
Solution Approach 2:
The invention modifies the chemical composition parameters of the solid electrolyte by introducing alkali metal atoms at specific concentrations (represented by the variable x in Li3-xMxPO3.75N0.25, where 0 < x ≤ 3). This parameter change transforms the material from a moisture-sensitive composition to a stable composition that resists phosphorus reduction. The controlled adjustment of alkali metal content allows optimization of both structural stability and ion conductivity.
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 solid electrolyte composition effectively prevents ion conductivity decrease in wet atmospheres, maintaining high ion conductivity and stable charge/discharge characteristics, thus enhancing the performance of all solid state batteries.
Implementation Method 1
stabilizes phosphorus in a +5 oxidation state by forming a stronger bond with oxygen, preventing reduction
Implementation Method 2
stabilizes phosphorus in a +5 oxidation state
Implementation Method 3
phosphorus atoms (P) forming the lithium phosphorus oxynitride react with water molecules present in the wet atmosphere
Data Source
AI summary
A solid electrolyte of the present invention is represented by a general formula: LiaPbMcOdNe, where M is at least one element selected from the group consisting of Si, B, Ge, Al, C, Ga and S, and a, b, c, d and e respectively satisfy a=0.62 to 4.98, b=0.01 to 0.99, c=0.01 to 0.99, d=1.070 to 3.985, e=0.01 to 0.50, and b+c=1.0. The solid electrolyte hardly deteriorates in a wet atmosphere.