Silicon Anode Electrolyte Composition for Lower Irreversible Capacity Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with silicon-based negative electrode materials face challenges in achieving high initial charge/discharge efficiency due to irreversible capacity losses, particularly with SiOx, which limits their performance in high-energy density applications.
Innovation Solution
A non-aqueous electrolyte secondary battery design incorporating a negative electrode active material with a lithium silicate phase and dispersed silicon particles, where the lithium silicate phase has an atomic ratio of O/Si greater than 2 and less than 4, and an electrolyte solution containing a halogenated benzene, such as fluorobenzene, to enhance lithium ion conductivity and reduce irreversible reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SiOx is used as negative electrode active material, then lithium ion absorption capacity per unit volume is increased, but irreversible capacity loss increases and initial charge/discharge efficiency decreases
Solution Approach 1:
The invention changes the chemical composition parameters of the negative electrode active material by using a lithium silicate phase with controlled O/Si atomic ratio (greater than 2 and less than 4) instead of conventional SiOx. This parameter change reduces the irreversible reaction between lithium ions and the matrix material, thereby reducing irreversible capacity loss while maintaining high lithium ion absorption capacity.
Solution Approach 2:
The invention uses a composite material structure consisting of a lithium silicate phase with dispersed fine silicon particles. The lithium silicate phase (Li2zSiO2+z) serves as the matrix, and fine silicon particles are dispersed within it. This composite structure combines the advantages of both materials: the lithium silicate phase reduces irreversible reactions, while the dispersed silicon particles provide high lithium ion absorption capacity through alloying reactions.
2Stability of the object's composition
If SiO2 matrix is used to disperse silicon particles, then structural stability is improved, but lithium ions absorbed during charge are not released during discharge due to irreversible reaction
Solution Approach 1:
The invention changes the stoichiometric composition of the silicate matrix by controlling the O/Si atomic ratio to be greater than 2 and less than 4. This compositional parameter change transforms the matrix from SiO2 (O/Si = 2) to a lithium silicate phase (Li2zSiO2+z) that exhibits reduced chemical reactivity with lithium ions, thereby reducing irreversible reactions while maintaining structural stability.
Solution Approach 2:
The invention extracts lithium ions from the conventional Li-ion battery system and incorporates them into the negative electrode active material itself by using a lithium silicate phase (containing Li2zSiO2+z). This eliminates the need for lithium ions to be extracted from the positive electrode during charge, as the lithium silicate phase already contains lithium, thereby reducing irreversible capacity loss.
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 battery exhibits improved initial charge/discharge efficiency and reduced irreversible capacity loss, achieving a balance between high capacity and structural stability through the controlled use of halogenated benzene in the electrolyte solution.
Implementation Method 1
a material containing silicon that can be alloyed with lithium is expected to be used as a negative electrode active material that has a high theoretical capacity density
Implementation Method 2
the negative electrode active material is capable of electrochemically absorbing and desorbing lithium
Implementation Method 3
The reaction represented by the above formula (ii) is an irreversible reaction. That is, lithium ions absorbed in the SiO2 matrix during charge are unlikely to be released during discharge
Implementation Method 4
the electrolyte solution contains a halogenated benzene, and the amount of the halogenated benzene contained in the electrolyte solution is 1 ppm or more and 500 ppm or less
Data Source
Figure 1
AI summary
Disclosed is a non-aqueous electrolyte secondary battery including: a positive electrode; a negative electrode; and an electrolyte solution. The negative electrode contains a negative electrode active material that is capable of electrochemically absorbing and desorbing lithium. The negative electrode active material contains a lithium silicate phase and silicon particles that are dispersed in the lithium silicate phase. The lithium silicate phase is an oxide phase that contains lithium, silicon, and oxygen. The atomic ratio O/Si of oxygen relative to silicon in the lithium silicate phase is greater than 2 and less than 4. The electrolyte solution contains a halogenated benzene. The amount of halogenated benzene contained in the electrolyte solution is 1 ppm or more and 500 ppm or less.