Lithium Composite Oxide Stabilization for Silicon Anode Capacity
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Solution Overview
Problem
Lithium ion secondary batteries using metal-based negative electrodes, such as silicon and tin, face challenges with irreversible capacity and cycle characteristics due to their noble electrode potentials, leading to capacity loss and decreased performance over repeated charge and discharge cycles.
Innovation Solution
A lithium ion secondary battery design incorporating a lithium composite oxide positive electrode with a specific composition, including manganese, nickel, and aluminum, and a metal-based negative electrode, stabilizes the crystalline structure of the oxide, allowing for higher charge capacity and improved cycle characteristics by compensating for irreversible capacity through controlled charge voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal-based negative electrode materials (silicon, tin) are used to achieve high capacity, then battery capacity is improved, but irreversible capacity increases and cycle characteristics deteriorate
Solution Approach 1:
The patent modifies the compositional parameters of the lithium composite oxide positive electrode material by controlling the ratios of Li, Mn, Ni, Co, and Al elements. Specifically, it uses a composition where Li content is 1.05-1.15 times the stoichiometric amount, and Al content is precisely controlled at 0.01-0.05 mol ratio, which stabilizes the crystal structure and reduces irreversible capacity while maintaining high capacity from metal-based negative electrodes
Solution Approach 2:
The patent employs a composite lithium composite oxide material combining multiple transition metals (Mn, Ni, Co) with aluminum doping. This composite structure leverages the high capacity potential of metal-based negative electrodes while the aluminum-doped composite oxide structure provides stability, reducing irreversible capacity and improving cycle characteristics through the synergistic effect of multiple elements
2Quantity of substance
If lithium-rich lithium composite oxide is used to compensate for irreversible capacity, then battery capacity is improved, but cycle characteristics are not sufficiently satisfied
Solution Approach 1:
The patent precisely controls the lithium content parameter to be 1.05-1.15 times the stoichiometric amount (not excessive lithium-rich composition) and critically controls aluminum content at 0.01-0.05 mol ratio. This optimized parameter range provides sufficient lithium to compensate for irreversible capacity while the controlled aluminum content stabilizes the crystal structure to ensure good cycle characteristics, avoiding the problems of excessive lithium-rich compositions
3Reliability
If aluminum is added to stabilize crystalline structure, then cycle characteristics are improved, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the aluminum content parameter to a specific range of 0.01-0.05 mol ratio, which is sufficient to stabilize the crystalline structure and improve cycle characteristics but not so high as to cause excessive aluminum segregation or require complex manufacturing controls. This balanced parameter setting achieves structure stabilization with manageable manufacturing complexity
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 achieves enhanced battery capacity and cycle stability, maintaining high discharge capacity even with metal-based negative electrodes, which have noble potentials compared to carbon materials, by stabilizing the lithium composite oxide and managing irreversible capacity effectively.
Implementation Method 1
a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode contains a lithium composite oxide, and the negative electrode contains a material including at least one of silicon and tin as a constituent element
Implementation Method 2
a lithium ion secondary battery using occlusion and emission of lithium ions has attracted attention
Data Source
AI summary
A lithium ion secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode contains a lithium composite oxide. The negative electrode contains a material including at least one of silicon Si and tin Sn as a constituent element. The lithium composite oxide includes lithium Li having a composition ratio a, a first element having a composition ratio b, and a second element having a composition ratio c as a constituent element. The first element including two kinds or more selected from among manganese Mn, nickel Ni, and cobalt Co, and including at least manganese. The second element including at least one kind selected from among aluminum Al, titanium Ti, magnesium Mg, and boron B. The composition ratios a to c satisfy the relationships of 1.1<a<1.3, 0.7<b+c<1.1, 0<c<0.1, and a>b+c.