Non-aqueous Battery Electrolyte Film Formation
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries experience significant degradation in charge/discharge cycle characteristics, particularly at high temperatures, due to side reactions between the electrolyte and positive electrode active material, which are exacerbated by the use of highly reactive materials.
Innovation Solution
A non-aqueous electrolyte secondary battery design incorporating a positive electrode with a composite oxide active material represented by LiNixM1-x-yLyO2 and a non-aqueous electrolyte containing vinyl ethylene carbonate, where 0.3≦x≦0.9 and 0≦y≦0.1, which promotes the formation of a polymer-like protective film on the positive electrode through 1,3-butadiene polymerization, suppressing side reactions and enhancing thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a highly reactive positive electrode active material is used to improve energy density, then the energy density is improved, but the cycle characteristics in a high-temperature environment deteriorate due to violent side reactions with the electrolyte
Solution Approach 1:
A polymer-like protective film is introduced as an intermediary layer between the highly reactive positive electrode active material and the electrolyte. This film acts as a mediator that prevents direct contact and violent side reactions while allowing lithium ion transport, thereby enabling the use of high-energy-density materials without sacrificing cycle stability at high temperatures
Solution Approach 2:
The chemical composition and structure parameters of the positive electrode active material are optimized by controlling the Ni content (0.3≦x≦0.9) and doping with element L (0≦y≦0.1) to adjust reactivity. Additionally, the electrolyte composition is modified by adding vinyl ethylene carbonate (0.01-5 wt%) to change the properties of the protective film formed on the electrode surface, thereby balancing energy density and cycle characteristics
2Reliability
If vinylene carbonate or vinyl ethylene carbonate is added to the electrolyte to suppress side reactions on the negative electrode, then the charge/discharge characteristics are improved, but violent side reactions still occur on the positive electrode in high-temperature environments
Solution Approach 1:
Different protective film-forming agents are used for different electrodes: vinylene carbonate or vinyl ethylene carbonate for the negative electrode, and specifically vinyl ethylene carbonate for the positive electrode. This local differentiation allows optimization of protection for each electrode, with vinyl ethylene carbonate on the positive electrode providing superior high-temperature stability by forming a more robust protective film
Solution Approach 2:
The electrolyte uses a composite approach by combining vinylene carbonate or vinyl ethylene carbonate with vinyl ethylene carbonate in specific proportions. This composite electrolyte formulation creates complementary protective films on both electrodes, where vinyl ethylene carbonate specifically addresses the high-temperature side reaction problem on the positive electrode while maintaining the benefits of the original additives
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 charge/discharge cycle characteristics and thermal stability, maintaining capacity retention even after repetitive high-temperature cycling, with optimal performance within the specified Ni and element L content ranges.
Implementation Method 1
when vinyl ethylene carbonate decomposes on the negative electrode, 1,3-butadiene is produced
Implementation Method 2
1,3-butadiene produced by the decomposition of vinyl ethylene carbonate on the negative electrode causes a polymerization reaction on the surface of the positive electrode active material
Implementation Method 3
a positive electrode capable of absorbing and desorbing lithium
Implementation Method 4
a non-aqueous electrolyte includes a main solvent, a solute and vinyl ethylene carbonate
Data Source
AI summary
A non-aqueous electrolyte secondary battery includes: a positive electrode capable of absorbing and desorbing lithium; a negative electrode capable of absorbing and desorbing lithium; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte. The positive electrode includes a composite oxide represented by formula (1): LiNixM1-x-yLyO2 as an active material. The formula (1) satisfies 0.3≦x≦0.9 and 0≦y≦0.1. The element M is at least one selected from the group consisting of Co and Mn, and the element L is at least one selected from the group consisting of Mg, Al, Ti, Sr, Zn, B, Ca, Cr, Si, Ga, Sn, P, V, Sb, Nb, Ta, Mo, W, Zr, Y and Fe. The non-aqueous electrolyte includes a main solvent, a solute and vinyl ethylene carbonate.