Cathode Composition for Lithium Primary Battery Gas Management
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Solution Overview
Problem
Lithium primary batteries used in medical devices face issues with gas formation due to excess lithium reacting with the organic electrolyte after the cathode's active material is consumed, leading to increased battery size and reduced packing density.
Innovation Solution
Incorporating metal oxide and/or metal fluoride into the cathode, which allows the lithium to react with these materials instead of the electrolyte, reducing gas production and maintaining structural integrity by consuming excess lithium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If excess lithium is used in the anode to increase discharge capacity, then the battery can deliver higher energy, but gas is formed when the lithium reacts with the organic electrolyte after the cathode active material is consumed, leading to increased battery size and reduced packing density
Solution Approach 1:
The patent converts the harmful gas-forming reaction between excess lithium and organic electrolyte into a beneficial process by replacing the organic electrolyte with an aqueous electrolyte. The excess lithium now reacts with water to form hydrogen gas and hydroxide ions, which are then consumed by the metal oxide or metal fluoride in the cathode to form water or hydrogen gas, respectively. This converts the harmful side reaction into a controlled process that eliminates gas accumulation problems while maintaining high discharge capacity.
Solution Approach 2:
The patent changes the chemical composition parameter of the electrolyte from organic to aqueous, fundamentally altering the reaction pathways. This parameter change transforms the nature of the side reactions involving excess lithium, converting them from gas-forming reactions with organic electrolytes to controlled reactions with water that can be further managed by the metal oxide/fluoride components, thereby reducing overall gas formation and battery swelling.
2Object-generated harmful factors
If metal oxide and/or metal fluoride is added to the cathode to consume excess lithium, then gas formation is reduced, but the cathode composition becomes more complex
Solution Approach 1:
The metal oxide or metal fluoride in the cathode serves multiple functions: it acts as a cathode active material for electrochemical reactions, serves as a gas-scavenging agent to consume hydrogen gas produced from lithium-water reactions, and maintains structural integrity of the cathode. This multi-functionality reduces the need for separate gas management components, thereby limiting the increase in device complexity while effectively reducing gas formation.
Solution Approach 2:
The cathode is designed as a composite material combining metal oxide or metal fluoride with other cathode components. This composite structure integrates the gas-consuming function directly into the cathode material itself, eliminating the need for separate gas management systems and minimizing the increase in device complexity while effectively addressing gas formation issues.
3Reliability
If the battery housing is made larger to accommodate gas formation, then structural integrity is maintained, but packing density decreases
Solution Approach 1:
The patent converts the harmful effect of gas formation into a beneficial outcome by using the metal oxide or metal fluoride to consume the hydrogen gas produced from lithium-water reactions. This eliminates the need for additional housing volume to accommodate gas, maintaining compact battery dimensions and high packing density while ensuring structural integrity through controlled chemical reactions.
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 approach reduces gas formation within the battery housing, enabling a smaller device size and increased packing density by ensuring lithium reacts with the cathode materials before the electrolyte, thus maintaining the battery's structural integrity and efficiency.
Implementation Method 1
a primary battery comprising a cathode comprising at least one active material and at least one of a metal oxide and metal fluoride... an anode comprising a metal as an electron source... the metal reacts with the electrolyte below a third discharge capacity at a voltage lower than the second discharge capacity to form a gas
Implementation Method 2
the metal reacts with the active material at the first discharge capacity, and, following the consumption of the active material of the cathode, the metal reacts with the at least one of metal oxide and metal fluoride of the cathode prior to reacting with the electrolyte below the third discharge capacity
Data Source
AI summary
In some examples, a primary battery comprising a cathode comprising at least one active material and at least one of a metal oxide and metal fluoride, wherein the active material exhibits a first discharge capacity and the at least one of metal oxide and metal fluoride exhibits a second discharge capacity at a voltage lower than the first discharge capacity; an anode comprising a metal as an electron source; and an electrolyte between the cathode and anode. The metal reacts with the electrolyte below a third discharge capacity at a voltage lower than the second discharge capacity to form a gas, where the metal reacts with the active material at the first discharge capacity, and, following the consumption of the active material of the cathode, the metal reacts with the at least one of metal oxide and metal fluoride of the cathode prior to reacting with the electrolyte below the third discharge capacity.