Solid-State Lithium Passivation via Phosphorus Agents
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Solution Overview
Problem
Existing methods for surface passivation of lithium metal are inadequate as they often require toxic, corrosive, or gaseous agents, involve high temperatures, or result in undefined organic coatings, posing safety risks and interfering with the pre-lithiation of electrode materials.
Innovation Solution
A method involving the use of a phosphorus-containing passivating agent, specifically lithium (oxalato)phosphate, is applied to lithium metal in the solid state at temperatures below 180°C in an inert, aprotic solvent to form a composite top layer containing lithium carbonate and lithium metaphosphate, avoiding the use of acidic or toxic substances and achieving a stable passivation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium metal is treated with fluorinating agents to stabilize its surface, then the protective effect is improved, but the toxicity and corrosiveness of the process increases
Solution Approach 1:
The invention changes the chemical composition parameters of the passivation layer by using phosphorus-containing compounds instead of fluorinating agents. This substitution maintains protective functionality while eliminating the toxic and corrosive properties associated with fluorine-based treatments.
Solution Approach 2:
The patent employs phosphorus-containing compounds that form effective passivation layers without the persistent environmental and safety hazards of fluorinating agents. These alternative compounds are less hazardous and can be handled more safely in industrial settings.
2Ease of manufacture
If lithium metal is heated above its melting point for coating treatment, then the coating process is improved, but the energy consumption and safety risks increase
Solution Approach 1:
The invention changes the temperature parameter of the treatment process from above-melting-point conditions to below-melting-point conditions. This allows the lithium metal to remain in solid form throughout the process, eliminating the need for high-energy heating while still achieving effective surface passivation.
Solution Approach 2:
The process allows lithium metal to be treated in its native solid state without requiring phase change to liquid. The solid lithium metal undergoes surface reaction with phosphorus-containing compounds directly, eliminating the energy-intensive melting step while maintaining coating effectiveness.
3Reliability
If lithium metal is treated with phosphoric acid to form protective layer, then the passivation effect is improved, but the violent reaction and hydrogen gas production increase
Solution Approach 1:
The patent replaces phosphoric acid with phosphorus-containing compounds that achieve similar passivation effects without the violent reactivity. These alternative compounds do not produce explosive hydrogen gas when reacting with lithium metal, eliminating a major safety hazard.
Solution Approach 2:
The invention converts the potentially harmful violent reaction between phosphoric acid and lithium metal into a controlled, safe surface passivation process. By using phosphorus-containing compounds instead, the reactive phosphorus still forms protective phosphate layers on lithium, but without the dangerous exothermic reaction and hydrogen gas generation.
4Reliability
If lithium metal is coated with wax to protect surface, then the protective effect is improved, but the amount of coating agent required increases
Solution Approach 1:
The invention changes the chemical nature of the coating from organic wax to inorganic phosphorus-containing compounds. This chemical substitution enables more efficient surface coverage and forms a protective layer that is integrated with the lithium surface, reducing the total amount of coating material needed compared to bulkier organic wax coatings.
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
This method creates a stable, composite passivation layer with controlled composition, reducing corrosion and pyrophoric risks, suitable for lithium battery applications, while maintaining the form of lithium metal and avoiding high-energy processes and hazardous handling.
Implementation Method 1
Lithium is passivated below 180° C. with a passivating agent of the general formula Li[P(C2O4)3-x/2Fx]... to form a composite top layer containing or consisting of at least two sparingly soluble lithium-containing components
Data Source
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AI summary
The invention relates to a surface-passivated lithium metal, which has a composite top layer containing or consisting of at least two poorly soluble components containing lithium. The invention further relates to the production of the surface-passivated lithium metal such that lithium metal below 180 °C, thus in the solid state, is transformed into an inert, aprotic solvent with a passivating agent of the general formula Li[P(C2O4)3 - x/2 Fx] where x = 0, 2, or 4.