Secondary battery, battery pack, vehicle, and stationary power supply
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Solution Overview
Problem
Lithium secondary batteries using aqueous electrolytes face instability due to water electrolysis at the negative electrode, leading to hydrogen generation and separation of active materials from the current collector, which hinders satisfactory charge-and-discharge operations.
Innovation Solution
A secondary battery design incorporating an aluminum-containing negative electrode current collector, a titanium-containing oxide active material, and an aqueous electrolyte containing zinc ions and a heterocyclic compound with aromatic rings and heteroatoms, forming films on the current collector and active material surface to suppress water electrolysis, enhancing charge-and-discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an aqueous electrolyte is used in a lithium secondary battery, then safety is improved and manufacturing cost is reduced, but water electrolysis occurs at the negative electrode leading to hydrogen generation and active material separation from the current collector
Solution Approach 1:
The patent introduces zinc ions as an intermediary substance in the aqueous electrolyte. These zinc ions form a protective film on the negative electrode surface, mediating between the aqueous electrolyte and the active material to prevent direct water electrolysis while maintaining ionic conductivity. This resolves the contradiction by enabling aqueous electrolyte use without the harmful water splitting reaction.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by adding zinc ions and heterocyclic compounds, and adjusts the potential range parameters to avoid water electrolysis. This modifies the electrolyte's properties to suppress water splitting while maintaining lithium ion transport, thus improving safety without sacrificing charge-and-discharge stability.
2Stability of the object's composition
If the potential range is limited to prevent water electrolysis, then water stability is improved, but the electromotive force and energy density are reduced
Solution Approach 1:
Zinc ions act as a mediator that enables the system to operate at higher potentials without direct water electrolysis. The zinc-containing protective film formed on the electrode surface allows the battery to achieve electromotive forces of 2.6-2.7V while maintaining water stability, thus resolving the contradiction between potential range limitation and energy density.
3Use of energy by moving object
If a nonaqueous electrolyte is used, then electromotive force and energy density are improved, but safety is reduced due to combustibility of organic solvents
Solution Approach 1:
The patent fundamentally changes the electrolyte's chemical composition from organic-based to aqueous-based, altering the safety parameter from combustible to non-combustible. By adding zinc ions and heterocyclic compounds, the electrolyte maintains the necessary ionic conductivity and electrochemical stability to achieve high electromotive forces (2.6-2.7V) while being inherently safe due to the water-based formulation.
4Reliability
If zinc ions and heterocyclic compounds are added to the aqueous electrolyte, then water electrolysis is suppressed through film formation, but device complexity increases
Solution Approach 1:
The patent modifies the electrolyte composition parameters by adding zinc ions and heterocyclic compounds in specific concentrations. These compositional changes enable automatic film formation on the electrode surface that suppresses water electrolysis. The complexity increase is minimal as these are simple additive components that self-organize into protective films without requiring complex device structures.
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 design effectively suppresses water electrolysis, enabling stable charge-and-discharge reactions and high discharge capacity by forming films that elevate hydrogen overvoltage and maintain lithium ion conductivity.
Implementation Method 1
At least a part of the surface of the negative electrode active material-containing layer has a film containing an aluminum-containing compound
Implementation Method 2
The aqueous electrolyte contains zinc ions, and a heterocyclic compound... forming films on the current collector and active material surface to suppress water electrolysis
Implementation Method 3
maintain lithium ion conductivity
Implementation Method 4
enabling stable charge-and-discharge reactions and high discharge capacity
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
According to one approach, a secondary battery is provided. The secondary battery includes a negative electrode, a positive electrode, and an aqueous electrolyte. The negative electrode includes a negative electrode active material-containing layer containing a titanium-containing oxide. At least a part of the surface of the negative electrode active material-containing layer has a film containing an aluminum-containing compound. The aqueous electrolyte contains zinc ions, and a heterocyclic compound containing aromatic ring(s) and heteroatom(s). The weight ratio of zinc ions to the heterocyclic compound in the aqueous electrolyte is within the range from 0.4 to 250.