Conductive Polymer Positive Electrode for High Energy Density Batteries
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges with low power density due to the large specific gravity of lithium-containing transition metal oxides and require a large amount of electrolyte solution, leading to low energy density and size limitations.
Innovation Solution
A nonaqueous electrolyte secondary battery design featuring a positive electrode composed of an electrically conductive polymer and a lithium salt formed by substituting part of a polyanionic acid with lithium, maintaining a specific molar ratio to ensure lithium ion concentration stability during charge/discharge, allowing for a cation migration type reaction without reducing lithium ion concentration in the electrolyte solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a lithium-containing transition metal oxide is used as a positive electrode active material, then the battery can be charged and discharged, but the power density is low due to lower electrochemical reaction rate and large specific gravity
Solution Approach 1:
The patent changes the chemical composition parameters of the positive electrode material by incorporating electrically conductive polymers with specific dopants (polyanionic acid or polyvinyl sulfonate) to achieve both high power density and reduced specific gravity compared to conventional lithium-containing transition metal oxides
Solution Approach 2:
The patent uses composite materials combining electrically conductive polymer matrices with specific dopants (polyanionic acid or polyvinyl sulfonate) to create a positive electrode material that exhibits both high electrochemical reaction rate and reduced specific gravity, resolving the contradiction between power density and weight
2Power
If an electrically conductive polymer with polyanionic acid dopant is used as positive electrode material, then power density is improved, but a large amount of electrolyte solution is required leading to low energy density
Solution Approach 1:
The patent changes the dopant parameter from conventional polyanionic acids to specifically selected dopants (polyanionic acid with specific molecular weight range or polyvinyl sulfonate) to achieve cation migration type reaction that reduces electrolyte solution requirement while maintaining high power density
Solution Approach 2:
The patent introduces local quality differentiation by selecting specific dopant types (polyanionic acid or polyvinyl sulfonate) with particular properties to create localized cation migration zones in the positive electrode, enabling high power density with reduced electrolyte solution volume
3Stability of the object's composition
If a cation migration type reaction is implemented using electrically conductive polymer with polymer anion dopant, then ion concentration change in electrolyte solution is reduced, but lithium ion concentration decreases requiring large electrolyte solution amount
Solution Approach 1:
The patent changes the dopant parameter to specifically selected polymer anions (polyanionic acid or polyvinyl sulfonate) with appropriate molecular weights and structures that enable cation migration while maintaining lithium ion concentration, achieving both ion concentration stability and reduced electrolyte solution requirement
Solution Approach 2:
The patent uses polymer anion structures (polyanionic acid or polyvinyl sulfonate) that can be doped and dedoped reversibly, copying the charge/discharge mechanism in a way that maintains lithium ion concentration in the electrolyte solution while achieving stable ion concentration without requiring large electrolyte solution volumes
4Quantity of substance
If the amount of electrolyte solution is increased to obtain higher battery capacity, then battery capacity is improved, but volume energy density decreases due to battery size increase
Solution Approach 1:
The patent changes the positive electrode material composition parameters to use electrically conductive polymers with specific dopants that enable high battery capacity with reduced electrolyte solution volume, thereby improving volume energy density while maintaining high battery capacity
Solution Approach 2:
The patent employs composite materials (electrically conductive polymer with specific dopant) in the positive electrode that provide high battery capacity in a compact form factor, resolving the contradiction between battery capacity and volume energy density by reducing the volume occupied by electrolyte solution
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 design achieves excellent weight energy density and low dependency on electrolyte solution amount, enabling higher battery capacity and volume energy density while minimizing battery size increase.
Implementation Method 1
the polymer of the positive electrode is doped with an anion in a charge period and dedoped with the anion in a discharge period
Implementation Method 2
a negative electrode prepared by using a carbonaceous material capable of lithium ion insertion/desorption
Implementation Method 3
an electrolyte solution containing a supporting salt having ionic conductivity
Data Source
AI summary
A nonaqueous electrolyte secondary battery is provided, which includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and negative electrode, and an electrolyte solution containing a supporting salt having ion conductivity, wherein the positive electrode comprises a composition containing components (a) and (b) below and satisfying a requirement (α) below, and wherein the negative electrode contains metal lithium and at least one selected from materials capable of lithium ion insertion/desorption:(a) an electrically conductive polymer;(b) a lithium salt formed by substituting a part of a polyanionic acid with lithium; and(α) a molar ratio of a lithium element content in the component (b) to a content of an element involved in a charge/discharge reaction in the component (a) is 0.1 to 1.0. Consequently, the nonaqueous electrolyte secondary battery has an excellent weight energy density and can reduce dependency on electrolyte solution amount.