Secondary Battery Silicon Negative Electrode High Temperature Cycle
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Solution Overview
Problem
Lithium ion secondary batteries using silicon or silicon oxide as negative electrode active materials experience significant capacity reduction and deteriorated cycle characteristics when charged or discharged at high temperatures, due to insufficient studies on essential components like binders, electrolytic solutions, and electrode structures.
Innovation Solution
A secondary battery design featuring a planar laminate structure with a negative electrode composed of metals capable of alloying with lithium and metal oxides, using polyimide or polyamide-imide as binders, and an electrolytic solution containing phosphazene compounds, which helps in maintaining high capacity and cycle performance even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon or silicon oxide is used as negative electrode active material, then battery capacity is improved, but cycle characteristics deteriorate at high temperature
Solution Approach 1:
The patent uses a composite negative electrode structure combining silicon particles (for high capacity) with carbon coating (for stability) and polyimide binder (for thermal stability). This composite approach allows the battery to maintain high capacity from silicon while the carbon and polyimide components provide structural stability and resistance to thermal degradation, resolving the contradiction between capacity and high-temperature cycle characteristics.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolytic solution by introducing phosphazene compounds, which form protective films on the silicon surface. This parameter change prevents direct degradation reactions at high temperature while maintaining lithium ion transport, thus improving cycle characteristics without sacrificing the high capacity benefit of silicon.
2Use of energy by moving object
If silicon is used as negative electrode active material, then energy density is improved, but volume expansion occurs at high temperature
Solution Approach 1:
The patent employs a carbon coating shell around silicon particles and a polyimide binder matrix that can accommodate volume changes. The carbon shell acts as a flexible container that prevents uncontrolled expansion while allowing the silicon core to expand and contract during cycling. The polyimide binder provides a compliant matrix that absorbs volume changes, preventing structural collapse and maintaining electrode integrity at high temperature.
Solution Approach 2:
The patent implements a nested structure where silicon particles are coated with carbon, which is then embedded in a polyimide binder matrix. This nested arrangement allows the inner silicon to expand while being contained by the carbon shell, which in turn is accommodated by the outer polyimide matrix, thus managing volume expansion at multiple levels while maintaining high energy density.
3Ease of manufacture
If conventional binders and electrolytes are used with silicon, then manufacturing is simplified, but high-temperature performance is insufficient
Solution Approach 1:
The patent modifies the electrolyte composition by adding phosphazene compounds to conventional carbonate-based electrolytes. This parameter change enables the formation of stable protective films on silicon surfaces at high temperature, improving performance without significantly complicating the manufacturing process, as the phosphazene compounds are mixed into the existing electrolyte formulation.
Solution Approach 2:
The patent uses polyimide as a binder material that combines organic polymer flexibility with high-temperature stability. While polyimide requires specific processing conditions, it can be applied using conventional coating and drying processes, maintaining relative manufacturing simplicity while providing the necessary high-temperature performance that conventional binders like PVDF cannot achieve.
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 provides a lithium ion secondary battery with improved high-temperature cycle characteristics and capacity retention, effectively addressing the capacity reduction and volume expansion issues associated with silicon-based electrodes.
Implementation Method 1
the electrolytic solution contains a phosphazene compound
Implementation Method 2
a metal particle capable of alloying with lithium
Implementation Method 3
an active material layer containing an oxide particle capable of absorbing and releasing lithium ions
Implementation Method 4
a carbon material particle capable of absorbing and releasing lithium ions
Data Source
AI summary
A secondary battery having high capacity and satisfactory high-temperature cycle characteristics is provided. A secondary battery according to the exemplary embodiment has an electrode element in which a positive electrode and a negative electrode are arranged so as to face each other, an electrolytic solution and an outer package packaging the electrode element and the electrolytic solution, wherein the negative electrode is formed by binding a negative electrode active material containing at least one of a metal (a) capable of forming an alloy with lithium and a metal oxide (b) capable of absorbing and releasing lithium ions, to a negative electrode collector, with a polyimide or a polyamide-imide serving as a negative electrode binder; and the electrolytic solution contains a phosphazene compound.