Lithium Secondary Battery Electrolyte Additives for Stable Cathode Cycling
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high energy density while improving cycling performance, kinetic performance, and storage life due to issues such as Li/Ni mixing, H2-H3 phase transition, and side reactions at the electrode interfaces, which affect cycle stability and longevity.
Innovation Solution
Incorporating specific doping elements like aluminum, zirconium, boron, magnesium, zinc, and titanium into the positive electrode active material, along with a silane-based first additive and lithium fluorosulfonate or lithium tetrafluoroborate second additive in the electrolyte solution, to enhance SEI and CEI membrane formation, thereby stabilizing the electrodes and reducing side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high energy density positive electrode active material is used, then energy density is improved, but structural stability deteriorates due to Li/Ni mixing and H2-H3 phase transition
Solution Approach 1:
The patent applies parameter changes by doping the positive electrode active material with specific elements (Al, Zr, B, Mg, Zn, Ca, or Ti) at controlled concentrations (0.01-5 wt%). This doping modifies the crystal structure parameters and electronic properties of the material, stabilizing the lattice against phase transitions while preserving high capacity. The doping elements occupy specific sites in the crystal structure, preventing Li-Ni mixing and stabilizing the H3 phase structure during cycling.
Solution Approach 2:
The patent creates a composite material system by combining the high-energy-density positive electrode active material (such as LiNi0.8Co0.1Mn0.1O2) with doping elements. This composite approach allows the base material to maintain its high energy density characteristics while the doping elements provide structural stabilization, effectively resolving the contradiction between energy density and structural stability.
2Ease of manufacture
If conventional electrolyte is used, then manufacturing simplicity is maintained, but cycling performance deteriorates due to SEI membrane instability and side reactions
Solution Approach 1:
The patent introduces silane-based additives (containing C2-C8 alkenyl groups) as intermediary substances in the electrolyte. These additives act as mediators that preferentially react with electrode surfaces to form stable protective films (SEI on negative electrode and CEI on positive electrode). These intermediary films prevent direct contact between the conventional electrolyte and electrode materials, thereby reducing side reactions and improving cycling performance while maintaining manufacturing simplicity.
Solution Approach 2:
The patent modifies the electrolyte composition by adding small concentrations (0.01-5 wt%) of silane-based additives to the conventional electrolyte system. This parameter change in electrolyte composition fundamentally alters the interface chemistry between electrolyte and electrodes, leading to formation of stable protective membranes that enhance cycling performance without complicating the manufacturing process.
3Stability of the object's composition
If doping element content is increased, then structural stability is improved, but energy density deteriorates due to replacement of active material
Solution Approach 1:
The patent optimizes the doping element content parameter within a specific range (0.01-5 wt%). This controlled parameter change ensures sufficient doping to stabilize the crystal structure and prevent Li-Ni mixing, while limiting the doping amount to preserve the majority of active material and maintain high energy density. The optimal doping level balances structural stabilization with capacity retention.
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 solution improves cycling performance, kinetic performance, and extends the storage life of lithium secondary batteries by stabilizing the electrode structures and inhibiting the dissolution of doping elements, thus enhancing the overall battery performance.
Implementation Method 1
When the lithium secondary battery is formed, such a first additive participates in the membrane formation reaction of an SEI membrane (Solid Electrolyte Interface Membrane) on one side of a negative electrode plate
Implementation Method 2
Such a second additive can participate in and promote the formation of a CEI membrane on one side of a positive electrode plate to inhibit the dissolution of doping elements in a positive electrode active material
Implementation Method 3
the positive electrode active material includes at least one doping element selected from aluminum, zirconium, boron, magnesium, zinc, calcium and titanium
Data Source
AI summary
A lithium secondary battery and an electrical apparatus. The lithium secondary battery includes a positive electrode plate and an electrolyte solution, where the positive electrode plate includes a positive electrode active material layer containing a positive electrode active material, and the positive electrode active material includes at least one doping element selected from aluminum, zirconium, boron, magnesium, zinc, calcium and titanium; the electrolyte solution includes a silane-based first additive containing C2-C8 alkenyl and a second additive, and the second additive is selected from at least one of lithium fluorosulfonate, lithium bis(fluorosulfonyl)imide and lithium tetrafluoroborate; and the ratio of the mass percentage content W1 of the first additive in the electrolyte solution to the mass percentage content W2 of the second additive in the electrolyte solution to the mass percentage content W3 of the doping element in the positive electrode active material satisfies 1:(0.2-2):(0.1-0.5).